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Sample records for seismic refraction survey

  1. Seismic refraction survey of the ANS preferred site

    Energy Technology Data Exchange (ETDEWEB)

    Davis, R.K. (Automated Sciences Group, Inc., Oak Ridge, TN (United States)); Hopkins, R.A. (Marrich, Inc., Knoxville, TN (United States)); Doll, W.E. (Oak Ridge National Lab., TN (United States))

    1992-02-01

    Between September 19, 1991 and October 8, 1991 personnel from Martin Marietta Energy Systems, Inc. (Energy Systems), Automated Sciences Group, Inc., and Marrich, Inc. performed a seismic refraction survey at the Advanced Neutron Source (ANS) preferred site. The purpose of this survey was to provide estimates of top-of-rock topography, based on seismic velocities, and to delineate variations in rock and soil velocities. Forty-four seismic refraction spreads were shot to determine top-of-rock depths at 42 locations. Nine of the seismic spreads were shot with long offsets to provide 216 top-of-rock depths for 4 seismic refraction profiles. The refraction spread locations were based on the grid for the ANS Phase I drilling program. Interpretation of the seismic refraction data supports the assumption that the top-of-rock surface generally follows the local topography. The shallow top-of-rock interface interpreted from the seismic refraction data is also supported by limited drill information at the site. Some zones of anomalous data are present that could be the result of locally variable weathering, a localized variation in shale content, or depth to top-of-rock greater than the site norm.

  2. Refraction seismic surveys in the investigation trench TK3 area in Olkiluoto, Eurajoki 2004

    Energy Technology Data Exchange (ETDEWEB)

    Ihalainen, M. [Suomen Malmi Oy, Espoo (Finland)

    2005-03-15

    Posiva Oy submitted an application for the Decision in Principle to the Finnish Government in May 1999. A positive decision was made at the end of 2000 by the Government. The Finnish Parliament ratified the Decision in Principle on the final disposal facility for spent nuclear fuel at Olkiluoto, Eurajoki in May 2001. The decision makes it possible for Posiva to focus the confirming bedrock investigations at Olkiluoto, where in the next few years an underground rock characterisation facility, the ONKALO, will be constructed. As a part of the investigations Suomen Malmi Oy (Smoy) conducted refraction seismic surveys at Olkiluoto site in Eurajoki. The work was ordered by Posiva Oy. The field work was carried out during May and June 2004. On five profiles S70-S74 totally 1002.5 m was surveyed. The purpose of the work was to determine the overburden thickness and to study bedrock properties, e.g. eventual fractured zones. The work consisted of staking, levelling, seismic measurements, interpretation and reporting. Fieldwork and interpretation were concluded by May and June 2004. Previously in 2000 and 2002 Smoy has carried out 33.0 km of seismic surveys in the area. (orig.)

  3. SEISMIC REFRACTION INVESTIGATION OF GROUNDWATER ...

    African Journals Online (AJOL)

    There was a good correlation between seismic interpretation and borehole lithologic section within the study area. With a considerable saturated thickness, areas of good potential aquifers for groundwater development abound in the study area. KeyWords: Seismic refraction, groundwater development, basement, Oban ...

  4. Integral Analysis of Seismic Refraction and Ambient Vibration Survey for Subsurface Profile Evaluation

    Science.gov (United States)

    Hazreek, Z. A. M.; Kamarudin, A. F.; Rosli, S.; Fauziah, A.; Akmal, M. A. K.; Aziman, M.; Azhar, A. T. S.; Ashraf, M. I. M.; Shaylinda, M. Z. N.; Rais, Y.; Ishak, M. F.; Alel, M. N. A.

    2018-04-01

    Geotechnical site investigation as known as subsurface profile evaluation is the process of subsurface layer characteristics determination which finally used for design and construction phase. Traditionally, site investigation was performed using drilling technique thus suffers from several limitation due to cost, time, data coverage and sustainability. In order to overcome those problems, this study adopted surface techniques using seismic refraction and ambient vibration method for subsurface profile depth evaluation. Seismic refraction data acquisition and processing was performed using ABEM Terraloc and OPTIM software respectively. Meanwhile ambient vibration data acquisition and processing was performed using CityShark II, Lennartz and GEOPSY software respectively. It was found that studied area consist of two layers representing overburden and bedrock geomaterials based on p-wave velocity value (vp = 300 – 2500 m/s and vp > 2500 m/s) and natural frequency value (Fo = 3.37 – 3.90 Hz) analyzed. Further analysis found that both methods show some good similarity in term of depth and thickness with percentage accuracy at 60 – 97%. Consequently, this study has demonstrated that the application of seismic refractin and ambient vibration method was applicable in subsurface profile depth and thickness estimation. Moreover, surface technique which consider as non-destructive method adopted in this study was able to compliment conventional drilling method in term of cost, time, data coverage and environmental sustainaibility.

  5. High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash area, Joshua Tree National Park, California

    Science.gov (United States)

    Langenheim, Victoria E.; Rymer, Michael J.; Catchings, Rufus D.; Goldman, Mark R.; Watt, Janet T.; Powell, Robert E.; Matti, Jonathan C.

    2016-03-02

    We describe high-resolution gravity and seismic refraction surveys acquired to determine the thickness of valley-fill deposits and to delineate geologic structures that might influence groundwater flow beneath the Smoke Tree Wash area in Joshua Tree National Park. These surveys identified a sedimentary basin that is fault-controlled. A profile across the Smoke Tree Wash fault zone reveals low gravity values and seismic velocities that coincide with a mapped strand of the Smoke Tree Wash fault. Modeling of the gravity data reveals a basin about 2–2.5 km long and 1 km wide that is roughly centered on this mapped strand, and bounded by inferred faults. According to the gravity model the deepest part of the basin is about 270 m, but this area coincides with low velocities that are not characteristic of typical basement complex rocks. Most likely, the density contrast assumed in the inversion is too high or the uncharacteristically low velocities represent highly fractured or weathered basement rocks, or both. A longer seismic profile extending onto basement outcrops would help differentiate which scenario is more accurate. The seismic velocities also determine the depth to water table along the profile to be about 40–60 m, consistent with water levels measured in water wells near the northern end of the profile.

  6. United States Geological Survey (USGS) FM cassette seismic-refraction recording system

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, J.M.

    1988-12-31

    In this two chapter report, instrumentation used to collect seismic data is described. This data acquisition system has two parts: (1) portable anolog seismic recorders and related ``hand-held-testers`` (HHT) and (2) portable digitizing units. During the anolog recording process, ground motion is sensed by a 2-Hz vertical-component seismometer. The voltage output from the seismometer is split without amplification and sent to three parallel amplifier circuit boards. Each circuit board amplifiers the seismic signal in three stages and then frequency modulates the signal. Amplification at the last two stages can be set by the user. An internal precision clock signal is also frequency modulated. The three data carrier frequencies, the clock carrier frequency, and a tape-speed compensation carrier frequency are summed and recorded on a recorded on a cassette tape. During the digitizing process, the cassette tapes are played back and the signals are demultiplexed and demodulated. An anolog-to-digital converter converts the signals to digital data which are stored on 8-inch floppy disks. 7 refs., 19 figs., 6 tabs.

  7. Bayesian inversion of refraction seismic traveltime data

    Science.gov (United States)

    Ryberg, T.; Haberland, Ch

    2018-03-01

    We apply a Bayesian Markov chain Monte Carlo (McMC) formalism to the inversion of refraction seismic, traveltime data sets to derive 2-D velocity models below linear arrays (i.e. profiles) of sources and seismic receivers. Typical refraction data sets, especially when using the far-offset observations, are known as having experimental geometries which are very poor, highly ill-posed and far from being ideal. As a consequence, the structural resolution quickly degrades with depth. Conventional inversion techniques, based on regularization, potentially suffer from the choice of appropriate inversion parameters (i.e. number and distribution of cells, starting velocity models, damping and smoothing constraints, data noise level, etc.) and only local model space exploration. McMC techniques are used for exhaustive sampling of the model space without the need of prior knowledge (or assumptions) of inversion parameters, resulting in a large number of models fitting the observations. Statistical analysis of these models allows to derive an average (reference) solution and its standard deviation, thus providing uncertainty estimates of the inversion result. The highly non-linear character of the inversion problem, mainly caused by the experiment geometry, does not allow to derive a reference solution and error map by a simply averaging procedure. We present a modified averaging technique, which excludes parts of the prior distribution in the posterior values due to poor ray coverage, thus providing reliable estimates of inversion model properties even in those parts of the models. The model is discretized by a set of Voronoi polygons (with constant slowness cells) or a triangulated mesh (with interpolation within the triangles). Forward traveltime calculations are performed by a fast, finite-difference-based eikonal solver. The method is applied to a data set from a refraction seismic survey from Northern Namibia and compared to conventional tomography. An inversion test

  8. Seismic reflection and refraction methods

    Digital Repository Service at National Institute of Oceanography (India)

    Chaubey, A.K.

    of noise that we attempt to suppress. In all of the remaining discussion about seismic waves, we will consider only body waves. 216 Factors affecting the amplitude of seismic waves Many factors affect the amplitude of seismic waves and some.... Factors which affect amplitude of seismic wave. Absorption is another factor, which affects amplitude. The loss of energy in the Earth due to absorption is described in various ways viz., i) by a quantity called ‘Q’ (the amount of energy in a seismic...

  9. Application of seismic refraction tomography for subsurface imaging ...

    African Journals Online (AJOL)

    Seismic refraction tomography involves the measurement of the travel times of seismic refracted raypaths in order to define an image of seismic velocity in the intervening ground. This technique was used to estimate the depth to the fresh basement, estimate thickness of the weathered basement and to determine the ...

  10. Cokriging surface elevation and seismic refraction data for bedrock topography

    International Nuclear Information System (INIS)

    Nyquist, J.E.; Doll, W.E.; Davis, R.K.; Hopkins, R.A.

    1992-01-01

    Analysis of seismic refraction data collected at a proposed site of the Advanced Neutron Source (ANS) Facility showed a strong correlation between surface and bedrock topography. By combining seismically determined bedrock elevation data with surface elevation data using cokriging, we were able to significantly improve our map of bedrock topography without collecting additional seismic data

  11. Joint analysis of refraction seismic survey with multilevel hydrophone measurement (application for detecting the high velocity thin lid); Kussekiho jishin tansa data to kochu hydrophone data no fukugo kaiseki no rei

    Energy Technology Data Exchange (ETDEWEB)

    Mori, S.; Harada, T.; Hayashi, K. [OYO Corp., Tokyo (Japan)

    1996-05-01

    During a refraction seismic survey conducted at a spot where a high-speed lava layer is supposedly concealed, the distribution of lava layer was estimated, and a composite analysis involving the vibration data received via hydrophones arranged in a bore hole was accomplished using a high-speed model based on an assumed geological section. The refraction survey centered on the bore hole and was accomplished using 250m-long traverse lines extending therefrom, one to the upstream and the other to the downstream of a river, producing a total length of 500m. The hydrophones were installed in the bore hole, and the measurement was carried out in an offset VSP-like observation pattern. In the analysis, the velocities obtained by the refraction survey and velocity logging were assigned to each layer on the basis of the assumed geological section for the construction of a velocity distribution model, which served as the early model for the repetition of calculation. Calculation was repeated with help of the said model, and a geological structure, capable of explaining the travel time data collected during the refraction survey and velocity logging, was successfully estimated. 1 ref., 5 figs.

  12. Compilation of seismic-refraction crustal data in the Soviet Union

    Science.gov (United States)

    Rodriguez, Robert; Durbin, William P.; Healy, J.H.; Warren, David H.

    1964-01-01

    The U.S. Geological Survey is preparing a series of terrain atlases of the Sino-Soviet bloc of nations for use in a possible nuclear-test detection program. Part of this project is concerned with the compilation and evaluation of crustal-structure data. To date, a compilation has been made of data from Russian publications that discuss seismic refraction and gravity studies of crustal structure. Although this compilation deals mainly with explosion seismic-refraction measurements, some results from earthquake studies are also included. None of the data have been evaluated.

  13. Geophysical investigation program Northern Switzerland: Refraction-seismic measurements 84

    International Nuclear Information System (INIS)

    Fromm, G.; Driessen, L.; Lehnen, I.

    1985-01-01

    Acting on instructions from the SGPK/Nagra working group (Baden, Switzerland), PRAKLA-SEISMOS GmbH, Hanover, planned, processed and interpreted seismic refraction measurements in northern Switzerland; CGG, Massy (France) was responsible for carrying out the field work. The aim of the survey was to investigate the shape and depth of a regional, WSW-ENE striking Permocarboniferous trough which underlays the mesozoic sediments of the Tabular Jura. The crystalline basement surface and possibly other geological boundaries were to be identified on the basis of refractor velocities. The recording arrangement included a 36 km spread in the assumed trough axis and four 12 km long spreads perpendicular to the axis (broad side 'T') which covered the trough edges. The resulting good quality data indicated two refractors: horizon H5 which is attributable to the lower Permocarboniferous could only be detected in the western half of the spread with any certainty. Horizon H6 probably represents the crystalline basement surface. If anisotropy is taken into account, the refractor velocity closely corresponds to the Gneiss of the WEIACH- and the Granite 3 of the BOETTSTEIN-borehole. This horizon was clearly discernible on all recordings and allowed the approximate mapping of the trough's shape. The assumed strike direction and depth was largely confirmed. In the WSW section the trough is more than 3300 m deep, it rises to - 3000 m in the ESE section and shows only in the east of the survey area a tendency towards a narrower width and shallower depth (depth data relate to the seismic reference datum at 500 m above MSL). (author)

  14. seismic refraction investigation of the subsurface structure

    African Journals Online (AJOL)

    DR. AMINU

    hidden from direct view by measuring their physical properties with appropriate instruments, usually on ... academic institution with large students population which depend only on pipe water. The water supply is .... thickness of the weathered layer across the survey area. This is an indication of the heterogeneous nature of ...

  15. The application of refraction seismics in alpine permafrost studies

    Science.gov (United States)

    Draebing, Daniel

    2017-04-01

    Permafrost studies in alpine environments focus on landslides from permafrost-affected rockwalls, landslide deposits or periglacial sediment dynamics. Mechanical properties of soils or rocks are influenced by permafrost and changed strength properties affect these periglacial processes. To assess the effects of permafrost thaw and degradation, monitoring techniques for permafrost distribution and active-layer thaw are required. Seismic wave velocities are sensitive to freezing and, therefore, refraction seismics presents a valuable tool to investigate permafrost in alpine environments. In this study, (1) laboratory and field applications of refraction seismics in alpine environments are reviewed and (2) data are used to quantify effects of rock properties (e.g. lithology, porosity, anisotropy, saturation) on p-wave velocities. In the next step, (3) influence of environmental factors are evaluated and conclusions drawn on permafrost differentiation within alpine periglacial landforms. This study shows that p-wave velocity increase is susceptible to porosity which is pronounced in high-porosity rocks. In low-porosity rocks, p-wave velocity increase is controlled by anisotropy decrease due to ice pressure (Draebing and Krautblatter, 2012) which enables active-layer and permafrost differentiation at rockwall scale (Krautblatter and Draebing, 2014; Draebing et al., 2016). However, discontinuity distribution can result in high anisotropy effects on seismic velocities which can impede permafrost differentiation (Phillips et al., 2016). Due to production or deposition history, porosity can show large spatial differences in deposited landforms. Landforms with large boulders such as rock glaciers and moraines show highest p-wave velocity differences between active-layer and permafrost which facilitates differentiation (Draebing, 2016). Saturation with water is essential for the successful application of refraction seismics for permafrost detection and can be controlled at

  16. Microclimate controls on weathering: Insights into deep critical zone evolution from seismic refraction surveys in the Susquehanna Shale Hills Critical Zone Observatory

    Science.gov (United States)

    West, N.; Kirby, E.; Nyblade, A.; Brantley, S. L.; Clarke, B. A.

    2015-12-01

    The formation of regolith is fundamental to the functioning and structure of the critical zone - the physically and chemically altered material formed from in situ parent bedrock that is available for transport. Understanding how regolith production and transport respond to perturbations in climate and/or tectonic forcing remains a first-order question. At the Susquehanna Shale Hills Critical Zone Observatory (SSHO), high resolution LiDAR-derived topographic data and depths to hand auger refusal reveal a systematic asymmetry in hillslope gradient and mobile regolith thickness; both are greater on north-facing hillslopes. Hydrologic and geochemical studies at the SSHO also suggest asymmetric sediment transport, fluid flow, and mineral weathering with respect to hillslope aspect. Here, we combine shallow seismic surveys completed along 4 hillslope transects (2 north-facing and 2-south facing), 2 ridgetops transects, and subsurface observations in boreholes to investigate the role of climate in inducing fracturing and priming the development of the observed asymmetry. Comparisons of shallow p-wave velocities with borehole and pit observations lead us to hypothesize the presence of three distinct layers at SSHO: 1) a deep, high velocity layer that is consistent with unweathered shale bedrock; 2) an intermediate velocity layer that is consistent with fractured and chemically altered bedrock which overlies unaltered bedrock, and 3) a shallow, slow velocity layer that is consistent with mobile material or shallow soil. Shallow p-wave velocity profiles suggest differences in thickness for both the mobile and immobile regolith material with respect to aspect. Patterns of p-wave velocities with depth are consistent with patterns of fracture densities observed in boreholes and with predictive cracking intensity models related to frost action. The models and data are consistent with climate as a primary driver for the development of asymmetry in the subsurface architecture at

  17. Crustal structure of Shatsky Rise from joint refraction and reflection seismic tomography

    Science.gov (United States)

    Korenaga, J.; Sager, W. W.

    2011-12-01

    Shatsky Rise in the western Pacific is one of a few gigantic oceanic plateaus in the world, with a surface area of ˜ 4.8 ± 105~km2 (about the same size as California). In contrast to other large oceanic plateaus formed during the Cretaceous Quite Period, Shatsky Rise formed during the frequent reversals of magnetic polarity, allowing its tectonic environment to be resolved in detail. It was formed at a rapidly spreading ridge-ridge-ridge triple junction, so the effect of lithospheric lid on magma migration is expected to be minimal, thereby facilitating the petrological interpretation of its seismic structure in terms of parental mantle processes. In the summer of 2010, a seismic refraction survey combined with multichannel seismic profiling was conducted across Shatsky Rise. Twenty eight ocean-bottom seismometers were deployed along two crossing perpendicular lines, and all of the instruments were recovered successfully, yielding a large volume of high-quality wide-angle refraction and reflection data, with the source-receiver distance often exceeding 200~km. In this contribution, we present the P-wave velocity structure of the Shatsky Rise crust, which is constructed by joint refraction and reflection travel time tomography, and also discuss its implications for the origin of Shatsky Rise.

  18. Shallow seismic refraction and magnetic studies at Lake Ngami, The Okavango Delta, Northwest Botswana

    Science.gov (United States)

    Laletsang, K.; Modisi, M. P.; Shemang, E. M.; Moffat, L.; Moagi, O. R.

    2007-06-01

    A seismic refraction analysis was carried out on data acquired on an 8.5 km profile at Lake Ngami, NW Botswana, to determine the structure and stratigraphy underlying the lake. The seismic spread comprised a 48-channel seismograph with a 9.5 m receiver and source spacing. The seismic source comprised 10 hammer blows on an aluminum plate, from which a vertical stack was recorded. The data were processed with WinSism™ version 10 program using the intercept time method. A total field magnetic survey was also carried out along the same line. The seismic refraction profile shows a low velocity layer (400-1600 m/s) extending from the surface at the southern end of the line to a maximum depth of 30 m in the middle of the profile, returning to a depth of 20 m from 4.5 km to the northern end of the line. The low velocity layer consists of the unconsolidated sediments and is underlain by more compact and saturated material with seismic velocities of 1600-3600 m/s. This material is interpreted to comprise semi- to fully consolidated sandstone. The base of these sandstones, however, could only be mapped near the southern end of the line out to 2 km. High seismic velocity rocks (3600-5000 m/s), interpreted to be weathered to fresh basement, were mapped below the sandstones at the southern end of the line. The magnetic profile shows a high at the beginning of the line which progressively declines to a low at 3 km. The field strength increases rapidly over the next 1.5 km to reach a plateau level at 4.5 km. The magnetic high at the beginning of the line corresponds to shallow basement which is mapped in the refraction profile. The magnetic low at 3 km is indicative of a thickened sediment section at this location. The southern end of the line with high seismic velocities comprises basement rocks located in the footwall block of the Kunyere Border Fault of the Okavango Rift. The step-wise downthrown hanging wall block consists of the low to intermediate velocity basin deposits

  19. Seismic characteristics of central Brazil crust and upper mantle: A deep seismic refraction study

    Science.gov (United States)

    Soares, J.E.; Berrocal, J.; Fuck, R.A.; Mooney, W.D.; Ventura, D.B.R.

    2006-01-01

    A two-dimensional model of the Brazilian central crust and upper mantle was obtained from the traveltime interpretation of deep seismic refraction data from the Porangatu and Cavalcante lines, each approximately 300 km long. When the lines were deployed, they overlapped by 50 km, forming an E-W transect approximately 530 km long across the Tocantins Province and western Sa??o Francisco Craton. The Tocantins Province formed during the Neoproterozoic when the Sa??o Francisco, the Paranapanema, and the Amazon cratons collided, following the subduction of the former Goia??s ocean basin. Average crustal VP and VP/VS ratios, Moho topography, and lateral discontinuities within crustal layers suggest that the crust beneath central Brazil can be associated with major geological domains recognized at the surface. The Moho is an irregular interface, between 36 and 44 km deep, that shows evidences of first-order tectonic structures. The 8.05 and 8.23 km s-1 P wave velocities identify the upper mantle beneath the Porangatu and Cavalcante lines, respectively. The observed seismic features allow for the identification of (1) the crust has largely felsic composition in the studied region, (2) the absence of the mafic-ultramafic root beneath the Goia??s magmatic arc, and (3) block tectonics in the foreland fold-and-thrust belt of the northern Brasi??lia Belt during the Neoproterozoic. Seismic data also suggested that the Bouguer gravimetric discontinuities are mainly compensated by differences in mass distribution within the lithospheric mantle. Finally, the Goia??s-Tocantins seismic belt can be interpreted as a natural seismic alignment related to the Neoproterozoic mantle domain. Copyright 2006 by the American Geophysical Union.

  20. Seismic Methods

    Science.gov (United States)

    Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

  1. Three-dimensional tomographic inversion of combined reflection and refraction seismic traveltime data

    Science.gov (United States)

    Hobro, James W. D.; Singh, Satish C.; Minshull, Timothy A.

    2003-01-01

    A tomographic inversion method is presented for the determination of 3-D velocity and interface structure from a wide range of body-wave seismic traveltime data types. It is applicable to refraction, wide-angle reflection, normal-incidence and multichannel seismic data, and is best suited to a combination of these that provides good independent constraints on seismic velocities and interface depths. The inversion process seeks a layer-interface minimum-structure model that is able to explain the given data satisfactorily by inverting to minimize data misfit and model roughness norms simultaneously. This regularized inversion, and the use of smooth functions to describe velocities and depths, allows the highly non-linear tomographic problem to be approximated as a series of linear steps. The inversion process begins by optimizing the fit to the data of a highly-smoothed initial model. In each subsequent step, structure is allowed to develop in the model with successively greater detail evolving until a satisfactory fit to the data is obtained. Parameter uncertainties for the final model are then estimated using an a posteriori covariance matrix analysis. Smooth layer-interface models are parametrized using regular grids of velocity and depth nodes from which spline-interpolated interface surfaces and velocity fields are defined. Forward modelling is achieved using ray perturbation theory and a two-point ray tracing method that is optimized for a large number of closely-spaced shot or receiver points. The method may be used to generate 1- and 2-D models (from, for example vertical seismic profile data or 2-D surveys) in which the 3-D geometry of a survey is correctly accounted for. The ability of the method to resolve typical target structures is tested in a synthetic salt dome inversion. From a set of noisy traveltime data, the model converges quickly to a well-resolved final model from different starting models. The application of this method to real data is

  2. Analyzing the subsurface structure using seismic refraction method: Case study STMKG campus

    International Nuclear Information System (INIS)

    Wibowo, Bagus Adi; Ngadmanto, Drajat; Daryono

    2015-01-01

    A geophysic survey is performed to detect subsurface structure under STMKG Campus in Pondok Betung, South Tangerang, Indonesia, using seismic refraction method. The survey used PASI 16S24-U24. The waveform data is acquired from 3 different tracks on the research location with a close range from each track. On each track we expanded 24 geofons with spacing between receiver 2 meters and the total length of each track about 48 meters. The waveform data analysed using 2 different ways. First, used a seismic refractionapplication WINSISIM 12 and second, used a Hagiwara Method. From both analysis, we known the velocity of P-wave in the first and second layer and the thickness of the first layer. From the velocity and the thickness informations we made 2-D vertical subsurface profiles. In this research, we only detect 2 layers in each tracks. The P-wave velocity of first layer is about 200-500 m/s with the thickness of this layer about 3-6 m/s. The P-wave velocity of second layer is about 400-900 m/s. From the P-wave velocity data we interpreted that both layer consisted by similar materials such as top soil, soil, sand, unsaturated gravel, alluvium and clay. But, the P-wave velocity difference between those 2 layers assumed happening because the first layer is soil embankment layer, having younger age than the layer below

  3. Analyzing the subsurface structure using seismic refraction method: Case study STMKG campus

    Energy Technology Data Exchange (ETDEWEB)

    Wibowo, Bagus Adi, E-mail: bagusadiwibowo1993@gmail.com [The State College of Meteorology, Climatology and Geophysics (STMKG), The Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG), Perhubungan 1 Street, South Tangerang, 15221 (Indonesia); Ngadmanto, Drajat [The Center of Research and Development (PUSLITBANG), The Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG), Angkasa I, Jakarta, 10620 (Indonesia); Daryono [The Mitigation of Earthquake and Tsunami, The Indonesian Meteorology, Climatology, and Geophysics Agency (BMKG), Angkasa I, Jakarta, 10620 (Indonesia)

    2015-04-24

    A geophysic survey is performed to detect subsurface structure under STMKG Campus in Pondok Betung, South Tangerang, Indonesia, using seismic refraction method. The survey used PASI 16S24-U24. The waveform data is acquired from 3 different tracks on the research location with a close range from each track. On each track we expanded 24 geofons with spacing between receiver 2 meters and the total length of each track about 48 meters. The waveform data analysed using 2 different ways. First, used a seismic refractionapplication WINSISIM 12 and second, used a Hagiwara Method. From both analysis, we known the velocity of P-wave in the first and second layer and the thickness of the first layer. From the velocity and the thickness informations we made 2-D vertical subsurface profiles. In this research, we only detect 2 layers in each tracks. The P-wave velocity of first layer is about 200-500 m/s with the thickness of this layer about 3-6 m/s. The P-wave velocity of second layer is about 400-900 m/s. From the P-wave velocity data we interpreted that both layer consisted by similar materials such as top soil, soil, sand, unsaturated gravel, alluvium and clay. But, the P-wave velocity difference between those 2 layers assumed happening because the first layer is soil embankment layer, having younger age than the layer below.

  4. Hydrodynamic properties of the basal aquifer of Santa Cruz Island using seismic refraction, Galapagos - Ecuador

    Science.gov (United States)

    Loaiza, S.; Fortin, J.; Adelinet, M.; Guéguen, Y.; Violette, S.

    2012-04-01

    Santa Cruz Island is the most inhabited of the Galapagos archipelago, Ecuador. It faces important water resource problems which might lead to a major impact on their unique and pristine ecosystem, Endangered World Heritage list (2007). The scarcity of geological and hydrological data combined with the difficulty of access for field measurements lead to a poor understanding of the island hydrogeology. The Island is formed by series of thick fractured basaltic lava flows dissected by faults. The low-lying, extensive "basal" aquifer is the unique groundwater body identified on the island. This basal aquifer is subjected to sea-water intrusion, which has been mapped from electrical resistivity imaging with an airborne electromagnetic SkyTEM survey (D'Ozouville et al. 2008). In order to better understand the hydrodynamic properties of the basal aquifer, we acquired, in summer 2011, geophysical data based on seismic refraction. The experiment was conducted on three study sites located at different altitudes above the see level (Beagle site altitude +7m , Mirador +20m, and Villacis +393m). The P-wave refraction data were obtained using 24 geophones (1 component) and an acquisition system Daklink III. A hammer was used as an energy source. This source was the most environmentally friendly source that could be obtained and used in the Galapagos Island. Geophone spacing for the spreads was 1.2 or 5 m depending on the site. From our geophysical data, we could identify the different geological layers that constitute this basal aquifer and to estimate the thickness of these layers. We could as well clearly see the water level in the aquifer. More interesting, we found a P-wave velocity of ~1600 m/s in the dry fractured basalt lava flow, and a P-wave velocity of ~2700 m/s in the water saturated fractured basalt lava flow. The same velocity values were obtained in the different sites. This tends to show that the elastic properties of the aquifer are homogeneous and isotropic (at

  5. Survey of Radar Refraction Error Corrections

    Science.gov (United States)

    2016-11-01

    RANGE YUMA PROVING GROUND NAVAL AIR WARFARE CENTER AIRCRAFT DIVISION NAVAL AIR WARFARE CENTER WEAPONS DIVISION NAVAL UNDERSEA WARFARE CENTER...estimation for an electromagnetic wave propagating at radio frequencies through the earth’s atmosphere. Appendices contain descriptive material on the...of Radar Refraction Error Corrections, RCC 266-16 vii Acronyms BAE BAE Systems CRPL Central Radio Propagation Laboratory EM electromagnetic

  6. US trends in refractive surgery: 2002 ISRS survey.

    Science.gov (United States)

    Duffey, Richard J; Leaming, David

    2003-01-01

    To determine the latest trends in refractive surgery in the United States. The full U.S. membership of the International Society of Refractive Surgery (ISRS) (approximately 900 members) was mailed the 2002 refractive surgery survey dealing with volumes, types, preferences of refractive surgery performed, and use of emerging technology. Questions regarding RK, AK, PRK, LASIK, LASEK, intracorneal ring segments (ICRS), laser thermal keratoplasty (LTK), conductive keratoplasty (CK), phakic intraocular lenses (PIOL), and clear lens extractions (CLE) were examined in the survey. Procedure preference for low, moderate, and high myopia, and hyperopia, were compared with the results from the surveys of the previous 5 years. Preference for unilateral versus bilateral same-day surgery, laser type, and microkeratome choice were also compared with the survey data from previous years. Incidence and frequency of co-management of refractive surgery patients were compared with 1999-2001 data. New questions regarding pupil measurement/documentation, wavefront aberrometry, and custom ablations were incorporated into the 2002 survey. As refractive surgery grows in the mainstream of ophthalmology, trends and changes in the United States continue to be elucidated by this professional organization survey. LASIK continues to dominate for refractive errors between -10.00 to +3.00 D. LASIK, LASEK, CLE, PIOL, and CK appear to have bright futures, whereas, RK, ICR, and LTK are on the decline. VISX continues to be utilized 2:1 over all other lasers combined, and instrumentation pupillometry is preferred 2:1 over pupil gauge cards. Currently, wavefront aberrometry and custom ablations are minimally employed but appear poised to be the wave of the future.

  7. US trends in refractive surgery: 2003 ISRS/AAO survey.

    Science.gov (United States)

    Duffey, Richard J; Leaming, David

    2005-01-01

    To determine the latest trends in refractive surgery in the United States. All U.S. members of the International Society of Refractive Surgery of the American Academy of Ophthalmology were mailed the 2003 refractive surgery survey dealing with volumes, types, preferences of refractive surgery performed, and use of new emerging technology. Questions regarding radial keratotomy (RK), astigmatic keratotomy (AK), limbal relaxing incisions (LRI), photorefractive keratectomy (PRK), laser in situ keratomileusis (LASIK), laser subepithelial keratomileusis (LASEK), intracorneal ring segments (ICRS), laser thermokeratoplasty (LTK), conductive keratoplasty (CK), phakic intraocular lenses (PIOL), clear lens extractions (CLE), and scleral expansion (SE) procedures were examined in the survey. Use of lasers, microkeratomes, pupillometry instruments, postoperative medications, wavefront analyzers, topographers, etc were examined. In 2003, LASIK continued to dominate for refractive errors between -8.00 to +3 diopters. Surgeons are waiting on the PIOL for high myopes and are performing CLE for high hyperopes. Photorefractive keratectomy, LASIK, LASEK, CLE, PIOL, and CK appeared to have bright futures; whereas, RK, ICR, LTK and SE were on the decline. Bilateral LASIK at the same surgical session is offered by 98% of surgeons. VISX lasers are used 2:1 over all other lasers in the United States. Zeiss-Humphrey still dominates topographers at 37%. The Bausch & Lomb Hansatome (48%) leads microkeratomes. Surgeons are charging, on average, 300-500 dollars more per eye for custom ablations and these ablations have already been accepted and integrated into refractive practices. Comanaging of refractive surgery patients is significantly down from previous years. Fourth-generation fluoroquinolones overtook the postoperative antibiotic prescriptions, with prednisolone and fluoromethalone dominating as anti-inflammatories. Trends and changes as refractive surgery grows in the mainstream of

  8. Seismic refraction investigation of the Salton Sea geothermal area, Imperial Valley, California

    Energy Technology Data Exchange (ETDEWEB)

    Frith, R.B.

    1978-12-01

    Seven seismic refraction profiles and four long-distance refraction shots have been used to investigate the Salton Sea geothermal area. From these data, two models of the geothermal and adjacent area are proposed. Model 1 proposes a basement high within the geothermal area trending parallel to the axis of the Imperial Valley. Model 2 assumes a horizontal basement in the E-W direction, and proposes a seismic velocity gradient that increases the apparent basement velocity from east to west approximately 15% within the geothermal area. Both models propose basement dip of 3 degrees to the south, yielding a thickness of sediments of 6.6 km near Brawley, California, in the center of the Imperial Valley. Based on offsets inferred in the sedimentary seismic layers of the geothermal area, two NW-SE trending fault zones are proposed.

  9. Crustal structure of the North Iberian continental margin from seismic refraction/wide-angle reflection profiles

    Science.gov (United States)

    Ruiz, M.; Díaz, J.; Pedreira, D.; Gallart, J.; Pulgar, J. A.

    2017-10-01

    The structure and geodynamics of the southern margin of the Bay of Biscay have been investigated from a set of 11 multichannel seismic reflection profiles, recorded also at wide angle offsets in an onshore-offshore network of 24 OBS/OBH and 46 land sites. This contribution focuses on the analysis of the wide-angle reflection/refraction data along representative profiles. The results document strong lateral variations of the crustal structure along the margin and provide an extensive test of the crustal models previously proposed for the northern part of the Iberian Peninsula. Offshore, the crust has a typical continental structure in the eastern tip of the bay, which disappears smoothly towards the NW to reach crustal thickness close to 10 km at the edge of the studied area ( 45°N, 6°W). The analysis of the velocity-depth profiles, altogether with additional information provided by the multichannel seismic data and magnetic surveys, led to the conclusion that the crust in this part of the bay should be interpreted as transitional from continental to oceanic. Typical oceanic crust has not been imaged in the investigated area. Onshore, the new results are in good agreement with previous results and document the indentation of the Bay of Biscay crust into the Iberian crust, forcing its subduction to the North. The interpreted profiles show that the extent of the southward indentation is not uniform, with an Alpine root less developed in the central and western sector of the Basque-Cantabrian Basin. N-S to NE-SW transfer structures seem to control those variations in the indentation degree.

  10. Using Seismic Refraction and Ground Penetrating Radar (GPR) to Characterize the Valley Fill in Beaver Meadows, Rocky Mountain National Park

    Science.gov (United States)

    Kramer, N.; Harry, D. L.; Wohl, E. E.

    2010-12-01

    This study is one of the first to use near surface geophysical techniques to characterize the subsurface stratigraphy in a high alpine, low gradient valley with a past glacial history and to obtain a preliminary grasp on the impact of Holocene beaver activity. Approximately 1 km of seismic refraction data and 5 km of GPR data were collected in Beaver Meadows, Rocky Mountain National Park. An asymmetric wedge of sediment ranging in depth from 0-20 m transverse to the valley profile was identified using seismic refraction. Complementary analysis of the GPR data suggests that the valley fill can be subdivided into till deposited during the Pleistocene glaciations and alluvium deposited during the Holocene. Two main facies were identified in the GPR profiles through pattern recognition. Facie Fd, which consists of chaotic discontinuous reflectors with an abundance of diffractions, is interpreted to be glacial till. Facie Fc, which is a combination of packages of complex slightly continuous reflectors interfingered with continuous horizontal to subhorizontal reflectors, is interpreted to be post-glacial alluvium and includes overbank, pond and in-channel deposits. Fc consistently overlies Fd throughout the study area and is no more than 7 m thick in the middle of the valley. The thickness of Holocene sedimentation (fill identified in the seismic refraction survey (0-20 m). A subfacie of Fc, Fch, which has reflectors with long periods was identified within Fc and is interpreted to be ponded sediments. The spatial distribution of facie Fch, along with: slight topographical features resembling buried beaver dams, a high abundance of fine sediment including silts and clays, historical records of beavers, and the name "Beaver Meadows" all suggest that Holocene beaver activity played a large role in sediment accumulation at this site, despite the lack of surficial relict beaver dams containing wood.

  11. Seismic reflection data imaging and interpretation from Braniewo2014 experiment using additional wide-angle refraction and reflection and well-logs data

    Science.gov (United States)

    Trzeciak, Maciej; Majdański, Mariusz; Białas, Sebastian; Gaczyński, Edward; Maksym, Andrzej

    2015-04-01

    Braniewo2014 reflection and refraction experiment was realized in cooperation between Polish Oil and Gas Company (PGNiG) and the Institute of Geophysics (IGF), Polish Academy of Sciences, near the locality of Braniewo in northern Poland. PGNiG realized a 20-km-long reflection profile, using vibroseis and dynamite shooting; the aim of the reflection survey was to characterise Silurian shale gas reservoir. IGF deployed 59 seismic stations along this profile and registered additional full-spread wide-angle refraction and reflection data, with offsets up to 12 km; maximum offsets from the seismic reflection survey was 3 km. To improve the velocity information two velocity logs from near deep boreholes were used. The main goal of the joint reflection-refraction interpretation was to find relations between velocity field from reflection velocity analysis and refraction tomography, and to build a velocity model which would be consistent for both, reflection and refraction, datasets. In this paper we present imaging results and velocity models from Braniewo2014 experiment and the methodology we used.

  12. Seismic Reflection Methods

    Science.gov (United States)

    Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

  13. 3-D cross-gradient joint inversion of seismic refraction and DC resistivity data

    Science.gov (United States)

    Shi, Zhanjie; Hobbs, Richard W.; Moorkamp, Max; Tian, Gang; Jiang, Lu

    2017-06-01

    We present a 3-D cross-gradient joint inversion algorithm for seismic refraction and DC resistivity data. The structural similarity between seismic slowness and resistivity models is enforced by a cross-gradient term in the objective function that also includes misfit and regularization terms. A limited memory quasi-Newton approach is used to perform the optimization of the objective function. To validate the proposed methodology and its implementation, tests were performed on a typical archaeological geophysical synthetic model. The results show that the inversion model and physical parameters estimated by our joint inversion method are more consistent with the true model than those from single inversion algorithm. Moreover, our approach appears to be more robust in conditions of noise. Finally, the 3-D cross-gradient joint inversion algorithm was applied to the field data from Lin_an ancient city site in Hangzhou of China. The 3-D cross-gradient joint inversion models are consistent with the archaeological excavation results of the ancient city wall remains. However, by single inversion, seismic slowness model does not show the anomaly of city wall remains and resistivity model does not fit well with the archaeological excavation results. Through these comparisons, we conclude that the proposed algorithm can be used to jointly invert 3-D seismic refraction and DC resistivity data to reduce the uncertainty brought by single inversion scheme.

  14. High resolution seismic refraction method with multichannel digital data acquisition system; Digital ta channel sokutei system wo mochiita koseido kussetsuho jishin tansa

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, K. [Oyo Corp., Tokyo (Japan)

    1997-05-27

    This paper introduces a multichannel digital data acquisition system and examples of measurements with the system in seismic exploration using the high resolution seismic refraction method. The high resolution seismic refraction system performs analyses nearly automatically by using a computer after initial travel time has been read. Therefore, the system requires high-accuracy travel time data, for which a multichannel digital measuring instrument developed recently for seismic exploration using the refraction method has been used for the measurement. The specification specifies the number of channels at 144 as a maximum, a sampling time of 62.5 {mu}sec to 4 m sec, the maximum number of sampling of 80,000 samples, and gain accuracy of {plus_minus} 1%. The system was used for surveying a tunnel having a maximum soil cover of about 800 m. The traverse line length is about 6 km, the distance between vibration receiving points is 50 m, and the number of vibration receiving points is 194. Executing measurements of single point system using GPS can derive accurate velocity in the vicinity of the basic face of the tunnel construction. Results were obtained from the investigation, which can serve more for actual construction work. 10 refs., 6 figs., 1 tab.

  15. Application of super-virtual seismic refraction interferometry to enhance first arrivals: A case study from Saudi Arabia

    KAUST Repository

    Alshuhail, Abdulrahman Abdullatif Abdulrahman

    2012-01-01

    Complex near-surface anomalies are one of the main onshore challenges facing seismic data processors. Refraction tomography is becoming a common technology to estimate an accurate near-surface velocity model. This process involves picking the first arrivals of refracted waves. One of the main challenges with refraction tomography is the low signal-to-noise ratio characterizing the first-break waveform arrivals, especially for the far-offset receivers. This is especially evident in data recorded using reflection acquisition geometry. This low signal-to-noise ratio is caused by signal attenuation due to geometrical spreading of the seismic wavefield, near-surface-generated noise, and amplitude absorption. Super-virtual refraction interferometry improves the quality of the first-break picks by enhancing the amplitude of the refracted waves and attenuating the amplitude of the random noise.

  16. Constraints on crustal structure in the Southeastern United States from the SUGAR 2 refraction seismic refraction experiment

    Science.gov (United States)

    Marzen, R. E.; Shillington, D. J.; Lizarralde, D.; Harder, S. H.

    2016-12-01

    The Southeastern United States is an ideal location to study the interactions between continental collision, extensive but short-lived magmatism, and continental rifting. Continental collision during the Alleghenian Orogeny ( 290 Ma) formed the supercontinent Pangea. Extension leading to the breakup of Pangea began 230 Ma, forming the South Georgia Basin and other rift basins. The extensive Central Atlantic Magmatic Province (CAMP) magmatism was emplaced at 200 Ma, and continental separation occurred afterwards. During these processes, part of the African continent was added to North America. Prior work has raised questions including (1) the location and geometry of the suture zone and implications for the style of collision (thin-skinned versus thick-skinned), (2) the role of pre-existing structures on later rifting, and (3) the distribution of magmatism, and possible relationships between magmatism and rifting. To address these questions, we present preliminary velocity models for the 400-km-long refraction seismic line from the SUwanee Suture and GA Rift basin experiment (SUGAR) Line 2. This line is central to CAMP magmatism, and crosses the South Georgia rift basin and two hypothesized locations for the ancient suture zone. The data were collected in August 2015 by a team of over 40 students and scientists. Fifteen shots spaced at 20-40 km were recorded by 1981 Texans spaced at 250 m. We observe refractions from the basin, crust, and upper mantle, and wide-angle reflections from the base of the sediments, within the crust, and from the Moho. Prominent mid crustal reflections may arise from the top of elevated lower crustal velocities and possible lower crustal layering. The starting velocity model and constraints on the upper sedimentary basin velocity structure are obtained through forward modeling, which show basin sediment thickness increasing to the South. We then invert for smooth 2D velocity structure using first arrivals (FAST) and a layered velocity

  17. Seismic imaging for an ocean drilling site survey and its verification in the Izu rear arc

    Science.gov (United States)

    Yamashita, Mikiya; Takahashi, Narumi; Tamura, Yoshihiko; Miura, Seiichi; Kodaira, Shuichi

    2018-01-01

    To evaluate the crustal structure of a site proposed for International Ocean Discovery Program drilling, the Japan Agency for Marine-Earth Science and Technology carried out seismic surveys in the Izu rear arc between 2006 and 2008, using research vessels Kaiyo and Kairei. High-resolution dense grid surveys, consisting of three kinds of reflection surveys, generated clear seismic profiles, together with a seismic velocity image obtained from a seismic refraction survey. In this paper, we compare the seismic profiles with the geological column obtained from the drilling. Five volcaniclastic sedimentary units were identified in seismic reflection profiles above the 5 km/s and 6 km/s contours of P-wave velocity obtained from the velocity image from the seismic refraction survey. However, some of the unit boundaries interpreted from the seismic images were not recognised in the drilling core, highlighting the difficulties of geological target identification in volcanic regions from seismic images alone. The geological core derived from drilling consisted of seven lithological units (labelled I to VII). Units I to V were aged at 0-9 Ma, and units VI and VII, from 1320-1806.5 m below seafloor (mbsf) had ages from 9 to ~15 Ma. The strong heterogeneity of volcanic sediments beneath the drilling site U1437 was also identified from coherence, calculated using cross-spectral analysis between grid survey lines. Our results suggest that use of a dense grid configuration is important in site surveys for ocean drilling in volcanic rear-arc situations, in order to recognise heterogeneous crustal structure, such as sediments from different origins.

  18. Seismic refraction data constrain along-axis structure of the Mid-Cayman spreading center

    Science.gov (United States)

    Van Avendonk, H. J.; Hayman, N. W.; Harding, J.; Grevemeyer, I.; Peirce, C.; Dannowski, A.; Papenberg, C. A.

    2015-12-01

    The Mid-Cayman Spreading Center (MCSC) is an ultraslow (15 mm/yr) spreading ridge between the Caribbean and North American plates. From north to south the MCSC is just ~140 km long, as it is bounded to the north by the Oriente transform fault, and to the south by the Swan Islands and Walton fault systems. The neovolcanic zone is characterized by an axial valley with depths to 6000 m, and a few off-axis bathymetric highs that can be as shallow as 2000 m. The role of tectonic and magmatic processes in the creation of this bathymetric relief is not yet understood. In the 2015 CaySEIS experiment, a collaboration between German, US and UK scientists, we gathered ocean-bottom seismic refraction data along five lines across and parallel to the MCSC to determine its crustal structure. We here present the tomographic analysis of marine seismic refractions recorded along the spreading axis. The presence of thin crust here shows that the bathymetric relief of the MCSC is at least in part isostatically compensated. Much of the older ultraslow spread crust on the flanks of the MCSC may not have accreted along the deep axial valley, but it may instead have formed by exhumation of gabbros along extensional faults in the adjacent seafloor.

  19. Seismic refraction profile, Kingdom of Saudi Arabia: field operations, instrumentation, and initial results

    Science.gov (United States)

    Blank, H. Richard; Healy, J.H.; Roller, John; Lamson, Ralph; Fisher, Fred; McClearn, Robert; Allen, Steve

    1979-01-01

    In February 1978 a seismic deep-refraction profile was recorded by the USGS along a 1000-km line across the Arabian Shield in western Saudi Arabia. The line begins in Paleozoic and Mesozoic cover rocks near Riyadh on the Arabian Platform, leads southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan (Tihamat Asir), and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, including 19 in the Farasan Islands. Six shot points were used--five on land, with charges placed mostly below water table in drill holes, and one at sea, with charges placed on the sea floor and fired from a ship. The total charge consumed was slightly in excess of 61 metric tons in 21 discrete firings. Seismic energy was recorded by means of a set of 100 newly developed portable seismic stations. Each station consists of a standard 2-Hz vertical geophone coupled to a self-contained analog recording instrument equipped with a magnetic-tape cassette. The stations were deployed in groups of 20 by five observer teams, each generally consisting of two scientist-technicians and a surveyor-guide. On the day prior to deployment, the instruments were calibrated and programmed for automatic operation by means of a specially designed device called a hand-held tester. At each of ten pre-selected recording time windows on a designated firing day, the instruments were programmed to turn on, stabilize, record internal calibration signals, record the seismic signals at three levels of amplification, and then deactivate. After the final window in the firing sequence, all instruments were retrieved and their data tapes removed for processing. A specially designed, field tape- dubbing system was utilized at shot point camps to organize and edit data recorded on the cassette tapes. The main functions of this system are to concatenate all data from each shot on any given day

  20. Avoidance of seismic survey activities by penguins.

    Science.gov (United States)

    Pichegru, Lorien; Nyengera, Reason; McInnes, Alistair M; Pistorius, Pierre

    2017-11-24

    Seismic surveys in search for oil or gas under the seabed, produce the most intense man-made ocean noise with known impacts on invertebrates, fish and marine mammals. No evidence to date exists, however, about potential impacts on seabirds. Penguins may be expected to be particularly affected by loud underwater sounds, due to their largely aquatic existence. This study investigated the behavioural response of breeding endangered African Penguins Spheniscus demersus to seismic surveys within 100 km of their colony in South Africa, using a multi-year GPS tracking dataset. Penguins showed a strong avoidance of their preferred foraging areas during seismic activities, foraging significantly further from the survey vessel when in operation, while increasing their overall foraging effort. The birds reverted to normal behaviour when the operation ceased, although longer-term repercussions on hearing capacities cannot be precluded. The rapid industrialization of the oceans has increased levels of underwater anthropogenic noises globally, a growing concern for a wide range of taxa, now also including seabirds. African penguin numbers have decreased by 70% in the last 10 years, a strong motivation for precautionary management decisions, including the exclusion of seismic exploratory activities within at least 100 km of their breeding colonies.

  1. Refraction and reflection seismic investigations for geological energy-storage site characterization: Dalby (Tornquist Zone), southwest Sweden

    Science.gov (United States)

    Malehmir, Alireza; Bergman, Bo; Andersson, Benjamin; Sturk, Robert; Johansson, Mattis

    2017-04-01

    -looking bedrock is clearly observed in the tomograms suggesting the possibility of weakness zones (likely highly fractured and/or weathered) in the bedrock. Signs of reflections in the raw shot gathers were encouraging and motivated to process the reflection component of the data for the purpose of subsurface imaging. Several northeast dipping, about 60-65 degree, reflections were imaged down to 400 m depth thanks to the close shot and receiver spacing strategy of the data acquisition. These reflections often show coherent character but at occasions are discontinuous and have different appearances. Reflections along profile 4 have for example different characters, shorter and more gently dipping, compared to those observed in profiles 2 and 3 suggesting that the main dip favors the orientation of profiles 2 and 3. The origins of the reflections are unclear ranging from amphibolite sheets to diabase dykes within the gneissic rocks, and each of this implies a different geological scenario (when compared with the geological data from a nearby quarry north of the study area) at where the site will be developed. Future studies should aim at understanding the cause of the reflections, constraining their locations at depth, and if they play any major role for the planning of the underground facilities. This study however illustrates the potential of the combined refraction and reflection imaging for these types of projects. For future developments of the site however a full 3D seismic survey can highly be useful. Acknowledgments: This work was supported by Skanska, and benefited collaborations among experts from Sweco, Lund University and Skanska. Trust project (http://www.trust-geoinfra.se) was fundamental to initiate this project.

  2. The crustal structure of the Southern Nain and Makkovik Provinces of Labrador deriverd from seismic refraction data

    DEFF Research Database (Denmark)

    Funck, T.; Hansen, A.K.; Reid, Ian Derry

    2008-01-01

    A refraction seismic profile was used to determine the crustal structure across the Nain/ Makkovik boundary, and to look for an offshore continuation of the  Nain Plutonic Suite (NPS). Velocity models were developed from forward and inverse modeling of travel times. There are. In the Saglek block...

  3. Vertical Cable Seismic Survey for Hydrothermal Deposit

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2012-04-01

    The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques

  4. Preliminary Results of Seismic Refraction/Reflection Experiment in Northwestern Nevada and Northeastern California

    Science.gov (United States)

    Colgan, J. P.; Lerch, D. L.; Gashawbeza, E. M.; Wilson, C. K.; Klemperer, S. L.; Miller, E. L.

    2004-12-01

    In September 2004, Stanford University is conducting a 260-km seismic refraction/reflection experiment across the northwestern margin of the Basin and Range Province between Winnemucca, Nevada and Alturas, California. This area was the locus of intense mid-Miocene (c. 17-15 Ma) volcanism and subsequent high-angle extensional faulting, and is often thought to be the breakout region of the Yellowstone hotspot. Today the region is characterized by high heat flow and is presumed to have relatively thin crust (c. 25 km), but little is known about the overall structure of the crust and how it relates to magmatism and extensional faulting. Our seismic experiment is designed to collect information on the crustal thickness, velocity structure, and crustal-scale reflectivity of this area, and consists of four parts: 1) A 260-km crustal refraction profile, with five in-line shots (1.25 to 2 tons each) and one 1.25 ton fan shot to the south, with over 1000 receivers spaced 100 to 300 m apart, acquired with ACS/PRF and NSF/EarthScope funding. The goals of the refraction profile are to determine crustal thickness and overall velocity and reflectivity structure. 2) While geophones are deployed along the refraction profile, we will collect reflection data in P, SV and SH modes using the tri-axial "T-Rex" vibrator truck operated by the Network for Earthquake Engineering Seismology (NEES) and the University of Texas at Austin. This experiment will asses the capability of this instrument to collect useful crustal-scale reflection data in conjunction with PASSCAL and EarthScope recorders, and if successful will help constrain the types of rocks and structures present beneath the flat-lying Miocene volcanic rocks that cover much of northwestern Nevada and largely obscure older structures. 3) 48 short-period 3-component receivers will be embedded in the main refraction line, supplemented by two 16-receiver offline deployments perpendicular to the main line. This experiment is designed

  5. A refraction seismic transect from the Faroe Islands to the Hatton-Rockall Basin

    Science.gov (United States)

    Funck, Thomas; Andersen, Morten S.; Keser Neish, Judith; Dahl-Jensen, Trine

    2008-12-01

    The crustal structure of the Faroe-Rockall Plateau was studied by a 790-km-long refraction seismic transect consisting of two intersecting lines. The air gun shot spacing was 200 m, and the signals were recorded by 77 ocean bottom seismometers. A P wave velocity model was developed from forward and inverse modeling of the wide-angle seismic data and incorporation of coincident multichannel reflection seismic data. Continental crust with velocities ranging from 5.6 to 6.8 km/s can be traced from the Faroe Islands, across the banks to the SW of the Faroes and into the Hatton-Rockall Basin. The thickness of the subvolcanic crust is up to 25 km on the banks but is as little as 8 km in the channels between the banks. The thinning in the channels may be related to NW-trending shear zones extending from major lineaments in NE Rockall Trough. Basalt layers are found along the entire transect with a total thickness of up to 4 km. Two layers with velocities of 4.9-5.2 and 5.3-5.6 km/s are thought to represent Paleogene flood basalts that can be correlated from the Faroe Islands to George Bligh Bank. Close to George Bligh Bank, an 80-km-wide and up to 9-km-thick body with velocities of 6.5 km/s is interpreted as intrusion. A 5-km-thick, high-velocity lower crustal layer (7.3 km/s) extends from the area of the intrusion into the northern Hatton-Rockall Basin. At the northern flank of Lousy Bank the transition zone to oceanic crust was encountered.

  6. Interlobate esker architecture and related hydrogeological features derived from a combination of high-resolution reflection seismics and refraction tomography, Virttaankangas, southwest Finland

    Science.gov (United States)

    Maries, Georgiana; Ahokangas, Elina; Mäkinen, Joni; Pasanen, Antti; Malehmir, Alireza

    2017-05-01

    A novel high-resolution (2-4 m source and receiver spacing) reflection and refraction seismic survey was carried out for aquifer characterization and to confirm the existing depositional model of the interlobate esker of Virttaankangas, which is part of the Säkylänharju-Virttaankangas glaciofluvial esker-chain complex in southwest Finland. The interlobate esker complex hosting the managed aquifer recharge (MAR) plant is the source of the entire water supply for the city of Turku and its surrounding municipalities. An accurate delineation of the aquifer is therefore critical for long-term MAR planning and sustainable use of the esker resources. Moreover, an additional target was to resolve the poorly known stratigraphy of the 70-100-m-thick glacial deposits overlying a zone of fractured bedrock. Bedrock surface as well as fracture zones were confirmed through combined reflection seismic and refraction tomography results and further validated against existing borehole information. The high-resolution seismic data proved successful in accurately delineating the esker cores and revealing complex stratigraphy from fan lobes to kettle holes, providing valuable information for potential new pumping wells. This study illustrates the potential of geophysical methods for fast and cost-effective esker studies, in particular the digital-based landstreamer and its combination with geophone-based wireless recorders, where the cover sediments are reasonably thick.

  7. The British Geological Survey seismic monitoring system

    Science.gov (United States)

    Ottemoller, L.; Baptie, B.; Luckett, R.

    2009-04-01

    The British Geological Survey (BGS) monitors the seismicity in and around the British Isles. The seismic network was started in the seventies and built up over the years to 146 short-period stations. An upgrade of this network started a few years ago and will result in a modern network with broadband seismometers, high dynamic range digitizers and real-time communication (Internet, ADSL, satellite). In total the network will comprise about 50 stations, with only few short-period stations remaining. Equipment is used from both Guralp and Nanometrics, and their respective software for data acquisition is used to bring the data to the centre in near real-time. The automated data processing is done through Earthworm. Event data are analysed using SEISAN. Continuous data are kept for all broadband stations and checked for quality and completeness. Real-time data is also exchanged with neighbouring networks. The data is used for routine monitoring, but also research. The main research objectives are to understand distribution of seismicity and relating earthquakes to tectonics, develop velocity and attenuation models and study the seismic hazard and earthquake effects.

  8. Preliminary seismic hazard assessment, shallow seismic refraction and resistivity sounding studies for future urban planning at the Gebel Umm Baraqa area, Egypt

    Science.gov (United States)

    Khalil, Mohamed H.; Hanafy, Sherif M.; Gamal, Mohamed A.

    2008-12-01

    Gebel Umm Baraqa Fan, west Gulf of Aqaba, Sinai, is one of the most important tourism areas in Egypt. However, it is located on the active Dead Sea-Gulf of Aqaba Levant transform fault system. Geophysical studies, including fresh water aquifer delineation, shallow seismic refraction, soil characterization and preliminary seismic hazard assessment, were conducted to help in future city planning. A total of 11 vertical electrical soundings (1000-3000 m maximum AB/2) and three bore-holes were drilled in the site for the analysis of ground water, total dissolved solids (TDS) and fresh water aquifer properties. The interpretation of the one-dimensional (1D) inversion of the resistivity data delineated the fresh water aquifer and determined its hydro-geologic parameters. Eleven shallow seismic refraction profiles (125 m in length) have been collected and interpreted using the generalized reciprocal method, and the resulting depth-velocity models were verified using an advanced finite difference (FD) technique. Shallow seismic refraction effectively delineates two subsurface layers (VP ~ 450 m s-1 and VP ~ 1000 m s-1). A preliminary seismic hazard assessment in Umm Baraqa has produced an estimate of the probabilistic peak ground acceleration hazard in the study area. A recent and historical earthquake catalog for the time period 2200 BC to 2006 has been compiled for the area. New accurate seismic source zoning is considered because such details affect the degree of hazard in the city. The estimated amount of PGA reveals values ranging from 250 to 260 cm s-2 in the bedrock of the Umm Baraqa area during a 100 year interval (a suitable time window for buildings). Recommendations as to suitable types of buildings, considering the amount of shaking and the aquifer properties given in this study, are expected to be helpful for the Umm Baraqa area.

  9. Time-lapse Seismic Refraction Monitoring of an Active Landslide in Lias Group Mudrocks, North Yorkshire, UK

    Science.gov (United States)

    Uhlemann, S.; Whiteley, J.; Chambers, J. E.; Inauen, C.; Swift, R. T.

    2017-12-01

    Geophysical monitoring of the internal moisture content and processes of landslides is an increasingly common approach to the characterisation and assessment of the hydrogeological condition of rainfall-triggered landslides. Geoelectrical monitoring methods are sensitive to changes in the subsurface moisture conditions that cause the failure of unstable slopes, typically through the increase of pore water pressures and softening of materials within the landslide system. The application of seismic methods to the monitoring of landslides has not been as extensively applied as geoelectrical approaches, but the seismic method can determine elastic properties of landslide materials that can characterise and identify changes in the geomechanical condition of landslide systems that also lead to slope failure. We present the results of a seismic refraction monitoring campaign undertaken at the Hollin Hill Landslide Observatory in North Yorkshire, UK. This campaign has involved the repeat acquisition of surface acquired high resolution P- and S-wave seismic refraction data. The monitoring profile traverses a 142m long section from the crest to the toe of an active landslide comprising of mudstone and sandstone. Data were acquired at six to nine week intervals between October 2016 and October 2017. This repeat acquisition approach allowed for the imaging of seismically determined property changes of the landslide throughout the annual climatic cycle. Initial results showed that changes in the moisture dynamics of the landslide are reflected by changes in the seismic character of the inverted tomograms. Changes in the seismic properties are linked to the changes in the annual climatic cycle, particularly in relation to effective rainfall. The results indicate that the incorporation of seismic monitoring data into ongoing geoelectrical monitoring programmes can provide complementary geomechanical data to enhance our understanding of the internal condition of landslide systems

  10. Vertical Cable Seismic Survey for SMS exploration

    Science.gov (United States)

    Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hotoshi; Mizohata, Shigeharu

    2014-05-01

    The Vertical Cable Seismic (VCS) survey is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by sea-surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because the VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed it for the SMS survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We have been developing the VCS survey system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of these surveys are from 100m up to 2100 m. Through these experiments, our VCS data acquisition system has been also completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system is available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed a new approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In 2013, we have carried out the second VCS survey using the surface-towed high-voltage sparker and ocean bottom source in the Izena Cauldron, which is one of the most promising SMS areas around Japan. The positions of ocean bottom source estimated by this method are consistent with the VCS field records. The VCS data with the sparker have been processed with 3D PSTM. It gives the very high resolution 3D volume deeper than two

  11. Seismic-refraction field experiments on Galapagos Islands: A quantitative tool for hydrogeology

    Science.gov (United States)

    Adelinet, M.; Domínguez, C.; Fortin, J.; Violette, S.

    2018-01-01

    Due to their complex structure and the difficulty of collecting data, the hydrogeology of basaltic islands remains misunderstood, and the Galapagos islands are not an exception. Geophysics allows the possibility to describe the subsurface of these islands and to quantify the hydrodynamical properties of its ground layers, which can be useful to build robust hydrogeological models. In this paper, we present seismic refraction data acquired on Santa Cruz and San Cristobal, the two main inhabited islands of Galapagos. We investigated sites with several hydrogeological contexts, located at different altitudes and at different distances to the coast. At each site, a 2D P-wave velocity profile is built, highlighting unsaturated and saturated volcanic layers. At the coastal sites, seawater intrusion is identified and basal aquifer is characterized in terms of variations in compressional sound wave velocities, according to saturation state. At highlands sites, the limits between soils and lava flows are identified. On San Cristobal Island, the 2D velocity profile obtained on a mid-slope site (altitude 150 m), indicates the presence of a near surface freshwater aquifer, which is in agreement with previous geophysical studies and the hydrogeological conceptual model developed for this island. The originality of our paper is the use of velocity data to compute field porosity based on poroelasticity theory and the Biot-Gassmann equations. Given that porosity is a key parameter in quantitative hydrogeological models, it is a step forward to a better understanding of shallow fluid flows within a complex structure, such as Galapagos volcanoes.

  12. Along-axis crustal structure of the Porcupine Basin from seismic refraction data modelling

    Science.gov (United States)

    Prada, Manel; Watremez, Louise; Chen, Chen; O'Reilly, Brian; Minshull, Tim; Reston, Tim; Wagner, Gerlind; Gaws, Viola; Klaschen, Dirk; Shannon, Patrick

    2016-04-01

    The Porcupine Basin is a tongue-shaped offshore basin SW of Ireland that formed during the opening of the North Atlantic Ocean. Its history of development involved several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on subsidence analysis, showed that stretching factors (β) in the northern part of the basin are 6. However, recent studies based on seismic reflection and refraction profiles concluded that β in places along the basin axis were significantly higher, and suggested the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Constraining β and the processes related to the formation of the basin will provide insights into aspects such as the tectonic response to lithospheric extension and the thermal evolution of the basin. Here we present the tomography results of five wide-angle seismic (WAS) profiles acquired across and along the basin axis. We used a travel time inversion method to model the WAS data and obtain P-wave velocity (Vp) models of the crust and uppermost mantle, together with the geometry of the main geological interfaces along each of these lines. Coincident seismic reflection profiles to each WAS line were also used to integrate the tectonic structure with the Vp model. These results improved constrains on the location of the base of the crust and allow to estimate maximum β (βmax) along each profile. The analysis shows that βmax values in the northern part of the basin are 5-6 times larger than estimates based on subsidence analysis. Towards the south, βmax increases up to 10, but then rapidly decreases to 3.3 southwards. These values are well within the range of crustal extension at which the crust becomes entirely brittle at magma-poor margins allowing the formation of major crustal faulting and serpentinization of the mantle. In agreement with this observation, Vp

  13. Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography

    Science.gov (United States)

    Korenaga, J.; Holbrook, W. S.; Kent, G. M.; Kelemen, P. B.; Detrick, R. S.; Larsen, H.-C.; Hopper, J. R.; Dahl-Jensen, T.

    2000-09-01

    We present results from a combined multichannel seismic reflection (MCS) and wideangle onshore/offshore seismic experiment conducted in 1996 across the southeast Greenland continental margin. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a two-dimensional velocity structure. We employ a hybrid ray-tracing scheme based on the graph method and the local ray-bending refinement to efficiently obtain an accurate forward solution, and we employ smoothing and optional damping constraints to regularize an iterative inversion. We invert 2318 Pg and 2078 PmP travel times to construct a compressional velocity model for the 350-km-long transect, and a long-wavelength structure with strong lateral heterogeneity is recovered, including (1) ˜30-km-thick, undeformed continental crust with a velocity of 6.0 to 7.0 km/s near the landward end, (2) 30- to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone, and (3) 15- to 9-km-thick oceanic crust toward the seaward end. The thickness of the igneous upper crust characterized by a high-velocity gradient also varies from 6 km within the transition zone to ˜3 km seaward. The bottom half of the lower crust generally has a velocity higher than 7.0 km/s, reaching a maximum of 7.2 to 7.5 km/s at the Moho. A nonlinear Monte Carlo uncertainty analysis is performed to estimate the a posteriori model variance, showing that most velocity and depth nodes are well determined with one standard deviation of 0.05-0.10 km/s and 0.25-1.5 km, respectively. Despite significant variation in crustal thickness, the mean velocity of the igneous crust, which serves as a proxy for the bulk crustal composition, is surprisingly constant (˜7.0 km/s) along the transect. On the basis of a mantle melting model incorporating the effect of active mantle upwelling, this velocity-thickness relationship is used to constrain the mantle melting process during the breakup of Greenland

  14. Seismic site survey investigations in urban environments: The case of the underground metro project in Copenhagen, Denmark.

    Science.gov (United States)

    Martínez, K.; Mendoza, J. A.; Colberg-Larsen, J.; Ploug, C.

    2009-05-01

    Near surface geophysics applications are gaining more widespread use in geotechnical and engineering projects. The development of data acquisition, processing tools and interpretation methods have optimized survey time, reduced logistics costs and increase results reliability of seismic surveys during the last decades. However, the use of wide-scale geophysical methods under urban environments continues to face great challenges due to multiple noise sources and obstacles inherent to cities. A seismic pre-investigation was conducted to investigate the feasibility of using seismic methods to obtain information about the subsurface layer locations and media properties in Copenhagen. Such information is needed for hydrological, geotechnical and groundwater modeling related to the Cityringen underground metro project. The pre-investigation objectives were to validate methods in an urban environment and optimize field survey procedures, processing and interpretation methods in urban settings in the event of further seismic investigations. The geological setting at the survey site is characterized by several interlaced layers of clay, till and sand. These layers are found unevenly distributed throughout the city and present varying thickness, overlaying several different unit types of limestone at shallow depths. Specific results objectives were to map the bedrock surface, ascertain a structural geological framework and investigate bedrock media properties relevant to the construction design. The seismic test consisted of a combined seismic reflection and refraction analyses of a profile line conducted along an approximately 1400 m section in the northern part of Copenhagen, along the projected metro city line. The data acquisition was carried out using a 192 channels array, receiver groups with 5 m spacing and a Vibroseis as a source at 10 m spacing. Complementarily, six vertical seismic profiles (VSP) were performed at boreholes located along the line. The reflection

  15. Crustal structure and tectonic history of the Kermadec arc inferred from MANGO seismic refraction profiles

    Science.gov (United States)

    Bassett, D.; Kopp, H.; Sutherland, R.; Henrys, S.; Watts, A. B.; Timm, C.; Scherwath, M.; Grevemeyer, I.; de Ronde, C. E. J.

    2016-12-01

    We have analyzed three wide-angle seismic reflection and refraction profiles and applied spectral averaging techniques to regional grids of bathymetry and free-air gravity anomaly to place the first regional constraints on the crustal structure of the Kermadec arc. These observations are used to test contrasting tectonic models for an along-strike transition in margin structure, across which, 1) the remnant Lau-Colville and active Kermadec arc ridges narrow by >50%; 2) the backarc and forearc deepen by 1 km, and 3) the active volcanic arc is deflected west into the deepest known backarc basin. We use residual bathymetric anomalies to constrain the geometry of this boundary and propose the name Central Kermadec Discontinuity (CKD). North of the CKD, the buried Tonga Ridge occupies the forearc with VP 6.5-7.3 km s-1 and residual free-air gravity anomalies constrain its latitudinal extent (north of 30.5°S), width (110±20 km) and strike ( 005° south of 25°S). South of the CKD the forearc is structurally homogeneous down-dip with VP 5.7-7.3 km s-1. Lower crustal velocities are similar to the northern Kermadec forearc, but there is no seismic or gravimetric evidence for an extinct arc ridge within the forearc. In the Havre Trough backarc, crustal thickness south of the CKD is 8-9 km, which is up-to 4 km thinner than the northern Havre Trough and at least 1 km thinner than the southern Havre Trough. The northern Kermadec/Tonga arc preserves a substrate of the Eocene arc, the southern Kermadec forearc preserves Mesozoic forearc rocks accreted at the Gondwana margin, and the central Kermadec arc may have fomed in the Kupe Abyssal Plain. The oldest arc related rocks recovered north and south of the CKD are 52 Ma and 16.7 Ma respectively, and plate tectonic reconstruction suggest the Eocene arc was originally conjoined with the Three Kings Ridge. The separation of these ridges during the early Oligocene likely formed the CKD. In contrast to previous interpretations, we

  16. Deep structure of Porcupine Basin and nature of the Porcupine Median Ridge from seismic refraction tomography

    Science.gov (United States)

    Watremez, L.; Chen, C.; Prada, M.; Minshull, T. A.; O'Reilly, B.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

    2015-12-01

    The Porcupine Basin is a narrow V-shaped failed rifted basin located offshore SW Ireland. It is of Permo-Triassic to Cenozoic age, with the main rifting phase in the Late Jurassic to Early Cretaceous. Porcupine Basin is a key study area to learn about the processes of continental extension and to understand the thermal history of this rifted basin. Previous studies show increasing stretching factors, from less than 1.5 to the North to more than 6 to the South. A ridge feature, the Porcupine Median Ridge, has been identified in the middle of the southernmost part of the basin. During the last three decades, this ridge has been successively interpreted as a volcanic structure, a diapir of partially serpentinized mantle, or a block of continental crust. Its nature still remains debated today. In this study, we use arrival times from refractions and wide-angle reflections in the sedimentary, crustal and mantle layers to image the crustal structure of the thinnest part of the basin, the geometry of the continental thinning from margin to margin, and the Porcupine Median Ridge. The final velocity model is then compared with coincident seismic reflection data. We show that (1) the basin is asymmetric, (2) P-wave velocities in the uppermost mantle are lower than expected for unaltered peridotites, implying upper-mantle serpentinisation, (3) the nature of Porcupine Median Ridge is probably volcanic, and (4) the amount of thinning is greater than shown in previous studies. We discuss the thermal implications of these results for the evolution of this rift system and the processes leading to the formation of failed rifts. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

  17. Analysis of the Seismic Reflection Survey in the KURT Site

    International Nuclear Information System (INIS)

    Kim, Kyung Su; Koh, Yong Kwon; Bae, Dae Seok; Kim, Geon Young; Park, Kyung Woo; Ji, Sung Hoon; Ryu, Ji Hun

    2009-08-01

    The connectivity and features of fracture zones around KURT site were analyzed using the data from the reflection seismic survey. The reflection seismic survey was performed in KURT site. The information for geologic lineament structures was acquired and it would be thought that the additional data processing was required in order to check the more detailed expected lineament

  18. Inhomogeneous Crustal Structure of the Rifting in the Okinawa Trough, a Backarc Basin West of Kyushu, Japan, Deduced from Seismic Reflection and Refraction Data

    Science.gov (United States)

    Nishizawa, A.; Kaneda, K.; Oikawa, M.; Horiuchi, D.; Fujioka, Y.; Okada, C.

    2017-12-01

    Several depressions found under the thick sediments in the East China Sea shelf have been considered as failed rift basins. Their formation age becomes progressively younger from NW to SE and the youngest rift basin is the Okinawa Trough, an active backarc basin of the Ryukyu (Nansei-Shoto) arc-trench system, to the southwest of Kyusyu, Japan. Its rifting is in progress and related hydrothermal activity is present in the trough. The knowledge of the crustal structure of the trough is fundamental to understand the current active tectonics and predict the future of the trough. We, Japan Coast Guard, have conducted extensive seismic reflection and refraction surveys in the Ryukyu region since 2008 and compiled the seismic structures of the Okinawa Trough. We will show the crustal structures along seven along-trough and ten across-trough seismic survey lines. The P-wave velocity models beneath the Okinawa Trough generally show a thinned continental/island arc crust consisting of upper, middle, and lower crusts. Moho depths below the trough were estimated mainly from Moho reflection (PmP) travel times. The crustal thickness of the trough is thinner than those of the East China Sea shelf and of the Ryukyu Islands. The depth of the Moho below the trough decreases from over 30 km in the north to about 13 km in the south, indicating a difference in degree of the rifting process. The position of the shallowest Moho along the across-trough lines in the northern trough does not necessarily correspond to the center of the trough defined as the deepest water depth, but it corresponds to the transition area between the East China Sea shelf and the Okinawa Trough. An M7.1 earthquake occurred at the transition area on Nov. 14, 2015 (JST) and many aftershocks were observed along the transition. This seismic activity demonstrated that the area is under rifting tectonics in the present.

  19. Interpretation of shallow seismic refraction data using raytracing inversion: A simple example from a groundwater resource study in Pocatello, Idaho

    International Nuclear Information System (INIS)

    Pelton, J.R.; Dougherty, M.E.; Welhan, J.A.

    1994-01-01

    Raytracing inversion of seismic refraction data acquired on the northeast side of the Portneuf River valley at the base of Red HIll in Pocatello shows that the thickness of Quaternary and Tertiary sediments above much older quartzite bedrock is 46-53 m. This estimate, which was derived independently of any borehole data, is consistent with the lithologic log of a recently drilled monitoring well (PMW-3) drilled about 1 km northwest of the seismic line. The water table is horizontal at a depth of 22-29 m beneath a gently rising topography (20m/km to the southeast) in the vicinity of the seismic line. The top surface of the quartzite bedrock is either horizontal or dips slightly (1.2 degrees) to the southeast. Unsaturated sediments are characterized by a strong vertical velocity gradient (13-16 s -1 ) probably caused by compaction of the near-surface materials. Seismic P-velocities are estimated as follows: unsaturated sediments (320-780 m/s), saturated sediments (1,670 m/s), and quartzite bedrock (2,950-3,050 m/s). 52 refs

  20. Combined analysis of 2-D electrical resistivity, seismic refraction and geotechnical investigations for Bukit Bunuh complex crater

    International Nuclear Information System (INIS)

    Azwin, I N; Saad, Rosli; Nordiana, M M; Bery, Andy Anderson; Hidayah, I N E; Saidin, Mokhtar

    2015-01-01

    Interest in studying impact crater on earth has increased tremendously due to its importance in geologic events, earth inhabitant history as well as economic value. The existences of few shock metamorphism and crater morphology evidences are discovered in Bukit Bunuh, Malaysia thus detailed studies are performed using geophysical and geotechnical methods to verify the type of the crater and characteristics accordingly. This paper presents the combined analysis of 2-D electrical resistivity, seismic refraction, geotechnical SPT N value, moisture content and RQD within the study area. Three stages of data acquisition are made starting with regional study followed by detailed study on West side and East side. Bulk resistivity and p-wave seismic velocity were digitized from 2-D resistivity and seismic sections at specific distance and depth for corresponding boreholes and samples taken. Generally, Bukit Bunuh shows the complex crater characteristics. Standard table of bulk resistivity and p-wave seismic velocity against SPT N value, moisture content and RQD are produce according to geological classifications of impact crater; inside crater, rim/slumped terrace and outside crater

  1. Combined analysis of 2-D electrical resistivity, seismic refraction and geotechnical investigations for Bukit Bunuh complex crater

    Science.gov (United States)

    Azwin, I. N.; Saad, Rosli; Saidin, Mokhtar; Nordiana, M. M.; Anderson Bery, Andy; Hidayah, I. N. E.

    2015-01-01

    Interest in studying impact crater on earth has increased tremendously due to its importance in geologic events, earth inhabitant history as well as economic value. The existences of few shock metamorphism and crater morphology evidences are discovered in Bukit Bunuh, Malaysia thus detailed studies are performed using geophysical and geotechnical methods to verify the type of the crater and characteristics accordingly. This paper presents the combined analysis of 2-D electrical resistivity, seismic refraction, geotechnical SPT N value, moisture content and RQD within the study area. Three stages of data acquisition are made starting with regional study followed by detailed study on West side and East side. Bulk resistivity and p-wave seismic velocity were digitized from 2-D resistivity and seismic sections at specific distance and depth for corresponding boreholes and samples taken. Generally, Bukit Bunuh shows the complex crater characteristics. Standard table of bulk resistivity and p-wave seismic velocity against SPT N value, moisture content and RQD are produce according to geological classifications of impact crater; inside crater, rim/slumped terrace and outside crater.

  2. Cost-efficiency analyses of offshore 3D seismic survey

    OpenAIRE

    Liu, Youjun

    2015-01-01

    Master's thesis in Industrial economics The main objective of this project is to analyses the factors that affect the cost and efficiency during the offshore 3D seismic survey. Four parts will be discussed to support the main objective--the equipment, environment, decision making on the investment and human factors. These parts will analyze how those elements affect the cost and efficiency in 3D seismic surveys and how to optimize these effects during production. The study focus on e...

  3. New seismic source `BLASTER` for seismic survey; Hasaiyaku wo shingen to shite mochiita danseiha tansa

    Energy Technology Data Exchange (ETDEWEB)

    Koike, G.; Yoshikuni, Y. [OYO Corp., Tokyo (Japan)

    1996-10-01

    Built-up weight and vacuole have been conceived as seismic sources without using explosive. There have been problems that they have smaller energy to generate elastic wave than explosive, and that they have inferior working performance. Concrete crushing explosive is tried to use as a new seismic source. It is considered to possess rather large seismic generating energy, and it is easy to handle from the viewpoint of safety. Performance as seismic source and applicability to exploration works of this crushing explosive were compared with four kinds of seismic sources using dynamite, dropping weight, shot-pipe utilizing shot vacuole, and impact by wooden maul. When considered by the velocity amplitude, the seismic generating energy of the crushing explosive of 120 g is about one-fifth of dynamite of 100 g. Elastic wave generated includes less high frequency component than that by dynamite, and similar to that using seismic source without explosive, such as the weight dropping. The maximum seismic receiving distance obtained by the seismic generation was about 100 m. This was effective for the slope survey with the exploration depth between 20 m and 30 m. 1 ref., 9 figs., 2 tabs.

  4. Survey on Visual Impairment and Refractive Errors on Ta′u Island, American Samoa

    Directory of Open Access Journals (Sweden)

    Shawn S Barnes

    2011-01-01

    Full Text Available Purpose: To assess the prevalence of presenting visual impairment and refractive errors on the isolated island of Ta′u, American Samoa. Methods: Presenting visual acuity and refractive errors of 124 adults over 40 years of age (55 male and 69 female were measured using the Snellen chart and an autorefractometer. This sample represented over 50% of the island′s eligible population. Results: In this survey, all presenting visual acuity (VA was uncorrected. Of the included sample, 10.5% presented with visual impairment (visual acuity lower than 6/18, but equal to or better than 3/60 in the better eye and 4.8% presented with VA worse than 6/60 in the better eye. Overall, 4.0% of subjects presented with hyperopia (+3 D or more, 3.2% were myopic (‑1 D or less, and 0.8% presented with high myopia (‑5 D or less. There was no significant difference between genders in terms of visual impairment or refractive errors. Conclusion: This study represents the first population-based survey on presenting visual acuity and refractive errors in American Samoa. In addition to providing baseline data on vision and refractive errors, we found that the prevalence of myopia and hyperopia was much lower than expected.

  5. Mapping the fresh-water aquifer structure of the Okavango Delta, Botswana, using seismic-reflection and seismic-refraction imaging

    Science.gov (United States)

    Reiser, Fabienne; Schmelzbach, Cedric; Podgorski, Joel E.; Horstmeyer, Heinrich; Green, Alan G.; Kalscheuer, Thomas; Maurer, Hansruedi; Kinzelbach, Wolfgang

    2013-04-01

    The Okavango Delta in Botswana is one of the world's great inland deltas. Situated within the semi-arid Kalahari Desert, it is one of the largest wetlands in Africa with an enormous biodiversity. Inversions of extensive airborne time-domain electromagnetic (TEM) data recorded across the Okavango Delta yield a general three-layer electrical resistivity model consisting of: (1) an upper resistive layer of dry and fresh-water saturated sands, (2) an intermediate conductive layer of clay or saline-water saturated sands and (3) a lower resistive layer of fresh-water saturated sands or crystalline basement. If the third layer comprises fresh water saturated sands, it would provide a new deep source of fresh water for the local population. In an attempt to constrain the interpretations of the second and third layers, two high-resolution seismic-reflection and seismic-refraction data sets were acquired at each of two locations: (i) Jedibe Island (Jao) situated near the estuary of the Okavango River and (ii) an area located near the western border of the delta (HR2). High-quality seismic-reflection images and first-arrival traveltime tomography models suggest a basement depth at Jao of around 115 m. Except for a transition from dry to saturated sands in the uppermost part, the sedimentary section at shallow to intermediate depths is practically featureless in the seismic data. The featureless seismic response is not consistent with the presence of horizontal boundaries between sand and clay layers, but is compatible with depth variations in salt content, the second of the two possible interpretations for the conductive layer at intermediate depths in the TEM model. The quality of the HR2 tomography models is somewhat inferior to the Jao models, with only poor constraints on the basement depth and velocities in the middle and lower parts of the sedimentary section. In contrast, the two HR2 seismic-reflection images appear to be of relatively high quality, revealing a number

  6. Seismic image of the Cantabrian Mountains in the western extension of the Pyrenees from integrated ESCIN reflection and refraction data

    Science.gov (United States)

    Pulgar, J. A.; Gallart, J.; Fernández-Viejo, G.; Pérez-Estaún, A.; Álvarez-Marrón, J.; Escin Group

    1996-10-01

    Integrated analysis of normal-incidence and large-aperture seismic reflection data collected in 1992 and 1993 within the Spanish ESCIN and complementary projects provide a first complete NS crustal transect across the Northern Iberian Peninsula and continental margin. Images of the crustal structure of the Cantabrian Mountains and their transition to the Duero basin and to the Cantabrian margin are obtained from: (a) a 65-km-long vertical reflection profile ESCIN-2 on land; (b) a 200-km-long reversed refraction profile; and (c) wide-angle recordings of the marine ESCIN-4 profile. Consistent results between reflectivity pattern and velocity-depth distribution reveal important lateral variations in the deep structure. The reflective crust imaged in the ESCIN-2 profile changes its attitude from sub-horizontal beneath the Duero basin to north-dipping beyond the Mountain front. Basement thrusts are observed in the upper crust merging into a detachment at 6 s (TWT) and may have triggered the Alpine uplift of the range. The Moho is identified at the bottom of the reflective lower crust and deepens from 12 to 15 s at the northern end of the profile, about 35 km inland. Modelling of the refraction data laterally extends the seismic image and provides evidence for Variscan crustal features beneath the Duero basin. Northwards, the velocity in the lower crust decreases and the Moho, constrained by the wide-angle data from profile ESCIN-2, deepens to about 60 km ending abruptly at the shoreline. The velocity-depth model is constrained along the Asturian platform up to the continental slope, where the crust-mantle boundary is located at 24 km depth. This 'margin Moho' shows a progressive deepening southwards, and extends to the coast where it is found at 30 km depth. The present seismic data support an important Alpine reworking and thickening of the crust under the Cantabrian Mountains. The onshore/offshore transition is marked by an imbrication of two crusts of very

  7. Crustal structure of southwestern Montana and east-central Idaho: Results of a reversed seismic refraction line

    Science.gov (United States)

    Sheriff, Steven D.; Stickney, Michael C.

    1984-04-01

    On October 20, 1982, we collected seismic refraction data on a 250 km line segment between Butte, Montana and Challis, Idaho. These data are from two open pit mine blasts; one at Anaconda Minerals Companys' southeast Berkely pit and the other at Cyprus Mines Corporations' Thompson creek mine. Eight of our ten recorders wrote clear records of both blasts with measured travel times accurate to +/-0.2 seconds. We supplemented these data with data from permanent stations in the Butte area. The Pg (crustal) velocity is 5.8 km/s to the southwest and 6.0 km/s to the northeast. The Pn (mantle) velocity is 7.9 km/s to the northeast and 8.1 km/s to the southwest; total travel-times are equal. The S-wave velocity in the crust is about 3.5 km/s. The symmetry of the travel-time results, with their intersection within one kilometer of the midpoint between the pit blasts, strongly suggests the refraction line overlies a horizontal Moho or parallels the strike line of a dipping Moho surface. These data indicate the crust in southwestern Montana and east-central Idaho is approximately 33 km thick. Contrasting tectonic processes, compression and thickening during the Laramide orogeny with extension and thinning since the Paleocene, resulted in a crust with slightly less than normal thickness.

  8. Deep crustal structure of the conjugate margins of the SW South China Sea from wide-angle refraction seismic data

    Science.gov (United States)

    Pichot, T.; Delescluse, M.; Chamot-Rooke, N. R.; Pubellier, M. F.; Qiu, Y.; Meresse, F.; Savva, D.; Watremez, L.; Auxietre, J.

    2013-12-01

    The South China Sea (SCS) is the largest marginal basin of SE Asia. Yet its mechanism of formation is still debated. While the NE part of the SCS northern margin exhibits ~400 km of extended continental crust, its SW part shows nearly 800 km of extended continental crust, which makes it one of the widest rifted margin in the world. In June 2011, Chinese and French scientists conducted a joint geophysical experiment on board the R/V Tan Bao across the SW sub-basin of the SCS. A 1000-km-long wide-angle refraction seismic profile was acquired along the conjugate margins using a total of 50 Ocean Bottom Seismometers (OBS). 41,100 first refraction and 6,622 PmP reflection arrival traveltimes have been picked. A joint reflection and refraction traveltime tomography inversion is performed to obtain a 2-D velocity model of the crustal and upper mantle structures. Based on this new tomographic model, northern and southern margins are found genetically linked since they share common structural characteristics: an average 12-km-thick crust and crustal scale lateral velocity variations. These lateral variations correlate well with seismic reflection observations of the crustal structures. Small-scale normal faults (grabens and horsts, with a spacing of ~15-30 km) are often associated with an apparent tilt of the iso-velocity contours affecting the upper crust. The upper-middle crust shows clear high lateral velocity variations defining low velocity bodies (LVB) bounded by large-scale normal faults (also referred as 'Throughgoing crustal faulting'). Major sedimentary basins are located above the LVBs, interpreted as hanging-wall blocks. The Moho interface remains rather flat (less than 4°) over the extended domain, suggesting that large normal faults root in a ductile lower crust, allowing isostatic compensation of the large normal fault blocks. Along the northern margin, the wavelength of the LVBs decreases from 90 to 45 km as the total crust thins toward the Continent

  9. Ground penetrating radar and seismic refraction investigation of fracture patterns in the basalt of Lucky Peak near Boise, Idaho

    International Nuclear Information System (INIS)

    Dougherty, M.E.; Hudson, W.K.; Kay, S.E.; Vincent, R.J.

    1994-01-01

    In hard rock environments, fluid flow and basement integrity are often controlled by the degree and connectivity of fracturing on an outcrop scale, rather than strictly by laboratory values of the permeability and competence of the matrix rock. Therefore, in many cases it is important to have a subsurface image of fracture characteristics of rock units in addition to an image of gross rock type. Fortunately, within a single rock type, many physical properties on outcrop scale are greatly influenced by fracturing, and changes in these physical properties should be detectable through the innovative use of geophysical methods. Work presented here is an attempt to use surface geophysical methods to delineate areas within a basalt flow which display different fracture characteristics and which have different electrical and seismic properties. The Basalt of Luck Peak is an intracanyon basalt flow exposed in cliffs around Lucky Peak Reservoir and in a terrace downstream from Lucky Peak Dam near Boise, Idaho. Visible in the face of the terrace below Lucky Peak Dam are the colonnade and entablature structures characteristic of differential cooling rates within basalt flows. Exposure of structural units within the cliff face is used to ground truth results from ground penetrating radar (GPR) and seismic refraction data collected along a line running perpendicular and away from the top edge of the cliff. 19 refs., 6 figs

  10. A method to eliminate refraction artifacts in EM1002 multibeam echosounder system (Swath bathymetry and seabed surveys of EEZ)

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, W.A.

    - NIO/TR-01/2011 A METHOD TO ELIMINATE REFRACTION ARTIFACTS IN EM1002 MULTIBEAM ECHOSOUNDER SYSTEM (Swath Bathymetry & Seabed Surveys of Exclusive Economic Zone) By WILLIAM A. FERNANDES... are extracted. This information is written in a defined packet type format (binary) to an output file. A Method Employed to Eliminate Refraction Artifacts in EM1002 Multibeam Echosounder 2011...

  11. Seismotectonics and Seismic Structure of the Alboran Sea, Western Mediterranean - Constraints from Local Earthquake Monitoring and Seismic Refraction and Wide-Angle Profiling

    Science.gov (United States)

    Leuchters, W.; Grevemeyer, I.; Ranero, C. R.; Villasenor, A.; Booth-Rea, G.; Gallart, J.

    2011-12-01

    The Alboran Basin is located in the western-most Mediterranean Sea and is surrounded by the Gibraltar-Betic and Rif orogenic arc. Geological evidence suggests that the most important phase of formation started in the early-to-mid-Miocene. Currently two conflicting models are discussed for its formation: One model proposes contractive tectonics producing strike-slip faults and folds with sedimentation occurring in synclinal basins and in regions of subsidiary extension in transtensional fault segments. A second model proposes slab roll back that caused contraction at the front of the arc and coeval overriding plate bending and extension and associated arc magmatism. However, this phase has been partially masked by late Miocene to present contractive structures, caused by the convergence of Africa and Iberia. Two German/Spanish collaborative research projects provided excellent new seismological and seismic data. Onshore/offshore earthquake monitoring received a wealth of local earthquake data to study seismotectonics and yielded the average 1D velocity structure of the Alboran/Betics/Rif domain. In the Alboran Basin most earthquakes occur below 20 km along a diffuse fault zone, crossing the Alboran Sea from the Moroccan to the Spanish coast. Further, earthquakes along the northern portion of the Alboran Ridge show thrust mechanisms and compression roughly normal to the vector of plate convergence between Africa and Iberia. A 250 km long seismic refraction and wide-angle profile was acquired coincident with the existing multi-channel seismic (MCS) ESCI-Alb2 line using the German research vessel Meteor. Shots fired with a 64-litre airgun array were recorded on 24 ocean-bottom seismometer (OBS) and ocean-bottom hydrophone (OBH) stations. The profile run roughly along the axis of the basin, circa 65 km off the coast of Morocco, north of the Alboran Ridge. It continues in an ENE direction to end north of the Algeria coast. Using seismic tomography we mapped the crustal

  12. Seismic reflection surveys at Horonobe coastal land area

    International Nuclear Information System (INIS)

    Yokota, Toshiyuki; Uchida, Toshihiro; Ueda, Takumi; Inazaki, Tomio; Mizohata, Shigeharu

    2012-01-01

    We carried out a series of seismic surveys at the coastal land area of Horonobe district. Hokkaido to clarify subsurface structure of the shallow zone around Horonobe town located at the west coast of northern part of the Teshio plain. The series of surveys included a P-wave reflection survey targeting relatively shallow zone and an S-wave reflection survey targeting extremely shallow zone. We interpreted subsurface geological structure by comparing the seismic survey results with the borehole data acquired in a borehole drilled at the research area. P-wave reflection survey clarified that each Quaternary to Neogene layer thickly deposited at west end of survey line makes deposition depth shallower while making its layer thickness rapidly thinner toward the Sarobetsu fold located at the eastern part of a survey line. S-wave reflection survey clearly images two major reflection events. The former one is the reflection from the boundaries between nearshore sediments and lower sediments at the depth range of about 30-40 m. The lower sediments are composed with clayey to silty deposits at the most part of the survey line, and with lagoon deposits at the central part of the survey line. The latter one is the reflection from the basement of the alluvial deposit at a depth of about 80 m. From those results, we can conclude that we revealed the sedimental environment of approximately the last 10,000 years in detail. (author)

  13. Superficial structures cartography of the Essaouira basin under ground (Morocco, by small refraction seismic: contribution of the static corrections in the reinterpretation of the speeds variations.

    Directory of Open Access Journals (Sweden)

    Dahaoui M.

    2018-01-01

    Full Text Available The static corrections are a necessary step in the sequence of the seismic processing. This paper presents a study of these corrections in the Essaouira basin. The main objective of this study is to calculate the static corrections by exploiting the seismic data acquired in the field to improve the deep structures imaging. It is to determine the roof and the basis of the superficial layers which constitute the weathered zone while calculating the delays of seismic wave’s arrivals in these layers. The purpose is to cancel the effect of the topography and the weathered zone, in order to avoid any confusion when the seismic and geological interpretation. The results obtained show the average values of the static corrections varying between - 127 and 282 ms (double time, with existence of high values by location, particularly in the Eastern and North-Eastern of the basin, which meant the presence of altered zone with irregular topography and whose thickness and speeds vary laterally. In effect the variations of velocities in the fifty meters from the surface may introduce significant anomalies in seismic refraction, with heavy consequences when the interpretation or the drilling establishment. These variations are mainly due to lateral changes in facies and variations in the formations thickness. The calculation of the static corrections, revealed high values at certain areas (East and North-East, which will enable us to better orient the future campaigns in these zones. It is therefore necessary to concentrate the seismic cores drillings and the small refraction seismic profiles by tightening the seismic lines meshes in order to have the maximum values of static corrections and thereafter a better imaging of the reflectors.

  14. Seismic reflection survey conducted in Benton County, Washinton

    International Nuclear Information System (INIS)

    Beggs, H.G.; Heineck, R.L.

    1980-01-01

    The massive Columbia River Basalt group that underlies the Hanford Site is being considered as a potential geologic repository for spent nuclear fuel. As part of the effort to ascertain and better understand the physical and geological properties of these basalt flows, a multiphased seismic reflection program has been undertaken. This phase was designed to more thoroughly define geologic features and structural attitudes in an areas in the central part of the Hanford Site. The specific feature of interest is known as the Cold Creek Syncline. This seismic survey, utilized the ''VIBROSEIS'' energy source and multifold common depth point recording. 2 figs

  15. A seismic refraction study of the boundary between Bida basin and ...

    African Journals Online (AJOL)

    The average velocity of the second layer is 6100 ms-1, which indicates that the basement in the survey area consists of rocks mostly of granite schists, with other ... part, the thickness reduced to 2.3m indicating that the survey area lies over the boundary between the Zaria basement complex and the Bida sedimentary basin.

  16. Seismicity surveying in central and north mexico region

    Science.gov (United States)

    Gómez, J. M.; Guzmán, M.; Nieto, A.; Zúñiga, R.; Alaniz, S.; Barboza, R.

    2003-04-01

    The seismic nature of Central Mexico is poorly understood due to insufficient sampling. This region is characterized by a very low deformation rate. The seismic activity is variable and ranges from microseismicity to large earthquakes. Some large earthquakes have occurred with an unknown returning period; structural studies show this recurrence could range from hundreds to thousands of years. Some authors argue that there is not connection between ancient and recent activity. We carried out several seismic surveys in part of the TransMexican Volcanic Belt (TMVB) and the Altiplano Central. We installed a temporal network, in order to record spatial seismic distribution. This network consists of 3-5 short period instruments, consisting of triaxial digital velocity recorders (0.01-4.5 Hz). We registered several swarms; one took place in Guanajuato and lasted for 2 weeks. Another crisis occurred at the northern limit of the TMVB at Sierra Gorda. Over five weeks several micro-earthquakes M < 2 were felt with anomaously high intensity. Relocated seismicity shows very shallow (< 10km) activity. The regional crust conditions appear to be roughly uniform even though the seismicity varies significantly. In some cases like seismic swarms, several microearthquakes are aligned, and seem to be quasi-parallel to the direction of the fault strike, some other times they are perpendicular. However, surface ruptures associated to earthquakes are not observed to confirm this. Then, a challenge is to locate the seismogenic structures, basically because of the surface structures are too old to be still active. Increased seismotectonic knowledge of this region may give further insight into the details of the interaction between surface structures driven by the regional stress field.

  17. Seismicity Surveying in Central and North Mexico Regions

    Science.gov (United States)

    Nieto-Samaniego, A.; Gomez-Gonzalez, J. M.; Guzman-Speziale, M.; Zuniga, R.; Alaniz-Alvarez, S.; Barboza, R.; Davalos, O.

    2003-12-01

    The seismic nature of Central Mexico is poorly understood due to insufficient sampling. We carried out a seismic survey in part of the TransMexican Volcanic Belt (TMVB) and the Central Altiplano. These regions are characterized by a very low deformation rates. Seismic activity is variable and ranges from microseismicity to large earthquakes, but no large historic earthquake has been instrumentally recorded. Only few direct observations such as intensity reconstructions and recent paleoseismic studies (e.g. the Acambay-Tixmadej earthquake of 1912) are available. Large earthquakes have occurred but their recurrence period is unknown; structural studies show this recurrence could range from hundreds to thousands of years. In order to understand the regional seismic behavior, we installed a temporal network. This network consists of 3-5 short period instruments, consisting of 16-bits triaxial digital velocity recorders (0.01-4.5 Hz). We registered several seismic sequences over a period of several months. One of them took place in Guanajuato within a graben structure in the TMVB and lasted for 2 weeks. Another sequence occurred at the northern limit of the TMVB in the Sierra Gorda. Over five weeks, several micro-earthquakes M Sierra Gorda, the event distribution is aligned along a small valley, but perpendicular to the main structural grain imposed by the Sierra Madre Oriental range. In no instances have surface ruptures been observed; those seismogenic structures could be blind ones. A challenge is to locate this structures which are may be too old to be still active. Increased seismotectonic knowledge of this region will yield further insight into the details of the interaction between surface structures driven by the regional stress field. Our results provide evidence that the region requires more intensive seismic surveying, and in some cases that some structures have been reactivated recently.

  18. Two dimensional joint inversion of direct current resistivity, radio-magnetotelluric and seismic refraction data: An application from Bafra Plain, Turkey

    Science.gov (United States)

    Demirci, İsmail; Candansayar, Mehmet Emin; Vafidis, Antonis; Soupios, Pantelis

    2017-04-01

    Direct current resistivity, radio-magnetotelluric and seismic refraction methods are widely used in the identification of near surface structures with collected data generally being interpreted separately. In recent decades, the use of joint inversion algorithms in geosciences has become widespread to identify near surface structures. However, there is no developed joint inversion algorithm using direct current resistivity, radio-magnetotelluric and seismic refraction methods. In this study, we developed a new two-dimensional joint inversion algorithm for direct current resistivity, radio-magnetotelluric and seismic refraction data based on a cross gradient approach. In addition, we proposed a new data weighting matrix to stabilize the convergence behavior of the joint inversion algorithms. We used synthetic data to show the advantage of the algorithm. The developed joint inversion algorithm found resistivity and velocity models that are better than the individual inversion of each data set. We also tested an algorithm with the field data collected in the Bafra Plain (Samsun, Turkey) to investigate saltwater intrusion. In comparing the field data inversion results with the sounding log, it can be seen that the developed joint inversion algorithm with the proposed data weighting matrix recovered the resistivity and velocity model better than the individual inversion and classical joint inversion of each data set. Our results showed that a more unique hydrogeological scenario might be obtained, especially in highly conductive media, with the joint usage of these methods.

  19. Preliminary results of layered modelling of seismic refraction data at the East Limpopo Margin, Mozambique (PAMELA project, MOZ3/5 cruise)

    Science.gov (United States)

    Watremez, Louise; Evain, Mikael; Leprêtre, Angélique; Verrier, Fanny; Aslanian, Daniel; Leroy, Sylvie; Dias, Nuno; Afilhado, Alexandra; Schnurle, Philippe; d'Acremont, Elia; de Clarens, Philippe; Castilla, Raymi; Moulin, Maryline

    2017-04-01

    The East Limpopo Margin is a continental margin located offshore southern Mozambique, in the Mozambique Channel. The southern Mozambique margin has not been studied much until now, but its formation is assumed to be the result of the separation of the African plate from the Antarctica plate. A new geophysical survey MOZ3/5 (February-April 2016; PAMELA project*) allowed the acquisition of seven wide-angle reflection and refraction seismic profiles across the southernmost Mozambique margin. In this work, we show the first results obtained from the layered modelling of an approximately 400 km long transect crossing the East Limpopo Margin and including information from 22 ocean-bottom seismometers and 18 land seismometers. The velocity model, compared to coincident seismic reflection data, allows to observe (1) the variations of seismic velocities together with the variations of reflectivity characteristics in the sediments, including the occurrence of some magmatism, (2) some deep features located below the acoustic basement and that can be related to the pre-to-syn-rift history of the margin, (3) the velocities and Moho depths in the different areas of the crust, from the thick continental crust to the clear oceanic crust (magnetic anomalies), helping to define the nature of the crust and the presence of magmatic features along the whole profile, and (4) some velocity information in the uppermost mantle. These results will allow us to (1) understand the deep structures of the East Limpopo Margin and to have better constraints on the formation of the margin, helping kinematic reconstructions, improving the quantification of the magmatism along this margin, and (2) improve the knowledge of both the thermal evolution of the sediments and the potential magmatic sources in the study area. *The PAMELA project (PAssive Margin Exploration Laboratories) is a scientific project led by Ifremer and TOTAL in collaboration with Université de Bretagne Occidentale, Universit

  20. Visual Survey of Infantry Troops. Part 1. Visual Acuity, Refractive Status, Interpupillary Distance and Visual Skills

    Science.gov (United States)

    1989-06-01

    prevalence of refractive error types among infantrymen .............................. 35 15. 2ercentages of refractive errors by sphere and cylinder...not prescribing for a minimum amount. Table 14. Classification and prevalence of refractive error types among infantrymen Prevalence Refractive...with a 10 mm IPD difference was probably an accommodative esotrope. This five-plus diopter hyperope demonstrated left-eye amblyopia , 4 prism diopters

  1. A seismic refraction and wide-angle reflection exploration in 2002 on the Mizuho Plateau, East Antarctica-Outline of observations (JARE-43-

    Directory of Open Access Journals (Sweden)

    Hiroki Miyamachi

    2003-03-01

    Full Text Available A seismic refraction and wide-angle reflection exploration was successfully conducted along a profile crossing the JARE-41 seismic profile on the Mizuho Plateau, in East Antarctica, in the austral summer season of 2001-2002 (JARE-43. One hundred sixty-one seismic stations were temporarily installed along a profile about 151 km long and seven large shots with about 700 kg of dynamite were fired. In addition, one shot with charge size of 20 kg was also arranged along the profile. The obtained seismic records show the clear onsets of the first arrivals at distances of less than 100 km from each large shot. In particular, seismic waves traveling through the ice sheet and dispersed surface waves were clearly observed. Some later reflection phases were also detected. The obtained first travel time data show that the ice sheet is a two-layered structure consisting of an upper layer with a P wave velocity of 2.7-2.9 km/s and a lower layer of 3.7-3.9 km/s. The thickness of the upper layer is estimated to be about 36-45 m. The apparent velocity in the basement rock just beneath the ice sheet is 6.1-6.2 km/s in the central and southern parts of the profile and almost 5.9 km/s in the northern part. This report describes basic outlines of the exploration and the obtained seismic data.

  2. Marine biota sightings during 3D marine seismic surveys

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Joao Luiz Martinez de; Uller, George A. [CGG do Brasil, Rio de Janeiro, RJ (Brazil); Derntl, Jose Renato; Ribeiro, Camila Castroviejo da Silva; Pereira, Edisio [GEOCOOP Cooperativa de Trabalho, Rio de Janeiro, RJ (Brazil); Miranda, Cristina Maschio de [Nautilus Cooperativa de Trabalho (Brazil); Ferraz, Alexandre Almeida; Costa, Leandro Damiao Soares da [Okeanos Consultoria e Meio Ambiente Ltda. (Brazil)

    2004-07-01

    This work intends to make a correlation between the presence of the marine biota and the seismic source activity (air guns) during seismic surveys, in Campos (BM-C-25 and BM-C-16) and Santos (BM-S-3) Basin, since July 2003 until March 2004. Environmental data were acquired onboard of the Seismic Vessel CGG Harmattan by a team of four oceanographers (environmental technicians), working on the highest place of the Vessel to record and identify the animals whenever was possible. The data were recorded in forms where fields about the biotic and environmental aspects were filled. In 212 days of observations, 2580,1 hours of sighting's effort were recorded; the air guns worked during 37,6% of the time of the effort. These efforts were made during the daylight reaching an average value of 11,35 hours/day. Sightings were divided into the suborders Odontocetes and Mysticetes, and others (fishes, turtles and non identified mammals). 175 sightings were recorded, being 54% when the air gun was off (24% Mysticetes, 56% Odontocetes, 20% others). Similarly, when the air gun was working, 46% of the records were made (24% Mysticetes, 61% Odontocetes, 6% others); the major concentration (58%) of individuals was inside the 1000 m radius around the ship, followed by 14% of the individuals occurring between 3001-4000 m radius away from the ship. The analysis of the data suggests a non-evasive behavior related to the working of the seismic source, corroborating the results reached by other publications using the data collected onboard CGG Vessels. (author)

  3. Active and passive seismic methods for characterization and monitoring of unstable rock masses: field surveys, laboratory tests and modeling.

    Science.gov (United States)

    Colombero, Chiara; Baillet, Laurent; Comina, Cesare; Jongmans, Denis; Vinciguerra, Sergio

    2016-04-01

    Appropriate characterization and monitoring of potentially unstable rock masses may provide a better knowledge of the active processes and help to forecast the evolution to failure. Among the available geophysical methods, active seismic surveys are often suitable to infer the internal structure and the fracturing conditions of the unstable body. For monitoring purposes, although remote-sensing techniques and in-situ geotechnical measurements are successfully tested on landslides, they may not be suitable to early forecast sudden rapid rockslides. Passive seismic monitoring can help for this purpose. Detection, classification and localization of microseismic events within the prone-to-fall rock mass can provide information about the incipient failure of internal rock bridges. Acceleration to failure can be detected from an increasing microseismic event rate. The latter can be compared with meteorological data to understand the external factors controlling stability. On the other hand, seismic noise recorded on prone-to-fall rock slopes shows that the temporal variations in spectral content and correlation of ambient vibrations can be related to both reversible and irreversible changes within the rock mass. We present the results of the active and passive seismic data acquired at the potentially unstable granitic cliff of Madonna del Sasso (NW Italy). Down-hole tests, surface refraction and cross-hole tomography were carried out for the characterization of the fracturing state of the site. Field surveys were implemented with laboratory determination of physico-mechanical properties on rock samples and measurements of the ultrasonic pulse velocity. This multi-scale approach led to a lithological interpretation of the seismic velocity field obtained at the site and to a systematic correlation of the measured velocities with physical properties (density and porosity) and macroscopic features of the granitic cliff (fracturing, weathering and anisotropy). Continuous

  4. High resolution 3D seismic survey off-shore the Netherlands

    NARCIS (Netherlands)

    Steeghs, P.; Vandeweijer, V.P.; Meekes, J.A.C.; Paap, B.F.; Kleine, M.P.E. de

    2014-01-01

    TNO has carried out a high resolution 3D seismic survey off-shore Rotterdam. The new deployment concept that was tested with this survey results in high-quality 3D images of the shallow subsurface at relatively low cost, particularly in comparison with conventional 3D seismic data acquisition.

  5. A survey of the prevalence of refractive errors among children in ...

    African Journals Online (AJOL)

    Background : Refractive errors are a known cause of visual impairment and may cause blindness worldwide. In children, refractive errors may prevent those afflicted from progressing with their studies. In Uganda, like in many developing countries, there is no established vision-screening programme for children on ...

  6. Sound source localization technique using a seismic streamer and its extension for whale localization during seismic surveys.

    Science.gov (United States)

    Abadi, Shima H; Wilcock, William S D; Tolstoy, Maya; Crone, Timothy J; Carbotte, Suzanne M

    2015-12-01

    Marine seismic surveys are under increasing scrutiny because of concern that they may disturb or otherwise harm marine mammals and impede their communications. Most of the energy from seismic surveys is low frequency, so concerns are particularly focused on baleen whales. Extensive mitigation efforts accompany seismic surveys, including visual and acoustic monitoring, but the possibility remains that not all animals in an area can be observed and located. One potential way to improve mitigation efforts is to utilize the seismic hydrophone streamer to detect and locate calling baleen whales. This study describes a method to localize low frequency sound sources with data recoded by a streamer. Beamforming is used to estimate the angle of arriving energy relative to sub-arrays of the streamer which constrains the horizontal propagation velocity to each sub-array for a given trial location. A grid search method is then used to minimize the time residual for relative arrival times along the streamer estimated by cross correlation. Results from both simulation and experiment are shown and data from the marine mammal observers and the passive acoustic monitoring conducted simultaneously with the seismic survey are used to verify the analysis.

  7. A Survey study on design procedure of Seismic Base Isolation ...

    African Journals Online (AJOL)

    Michael Horsfall

    . Mehdi ShekariSoleimanloo ... Keywords: Seismic Isolation, Base Isolation, Earthquake Resistant Design, Seismic Protective Systems. ABSTRACT: Adding shear .... Where Eloop is the energy dissipation per cycle of loading. Bilinear model ...

  8. Age-related association of refractive error with intraocular pressure in the Korea National Health and Nutrition Examination Survey.

    Science.gov (United States)

    Choi, Jin A; Han, Kyungdo; Park, Yong-Moon; Park, Chan Kee

    2014-01-01

    To investigate the distribution of intraocular pressure (IOP) and refractive errors according to age group in a representative sample of non-glaucomatous Korean adults. A total of 7,277 adults (≥ 19 years) who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) from 2008 to 2011 underwent ophthalmic examination were divided into three groups according to age: the young- (19-39 years), middle- (40-59 years), and old- (≥ 60 years) age groups. Simple and multiple regression analyses between IOP and various parameters (including the refractive error) were conducted. The mean IOP of the total population was 14.0 ± 0.1 mmHg [young: 13.9 ± 0.1 mmHg; middle: 14.1 ± 0.1 mmHg; old: 13.8 ± 0.2 mmHg (P for trend = 0.085)]. Myopia and high myopia were more prevalent in the young- (70.8% and 16.1%, respectively), compared to the middle- (44.6% and 10.9%) and old- (8.9% and 2.2%) age groups. Univariate analysis in the total population showed that higher IOP was associated with myopic refractive error, the female gender, higher body mass index (BMI), diabetes, hypertension, and hypercholesterolemia (all Prefractive error, the female gender, higher BMI, hypercholesterolemia and diabetes (all Prefractive error was not significant (P = 0.828). In multiple linear regression analysis, similar significant relationships between the refractive error and IOP were found in the young- and middle-age groups (beta =  -0.08 and -0.12; P = 0.002 and refractive error was an independent predictor of higher IOP in non- glaucomatous eyes, and the association between refractive error and IOP differed according to age.

  9. Land 3D-seismic data: Preprocessing quality control utilizing survey design specifications, noise properties, normal moveout, first breaks, and offset

    Science.gov (United States)

    Raef, A.

    2009-01-01

    The recent proliferation of the 3D reflection seismic method into the near-surface area of geophysical applications, especially in response to the emergence of the need to comprehensively characterize and monitor near-surface carbon dioxide sequestration in shallow saline aquifers around the world, justifies the emphasis on cost-effective and robust quality control and assurance (QC/QA) workflow of 3D seismic data preprocessing that is suitable for near-surface applications. The main purpose of our seismic data preprocessing QC is to enable the use of appropriate header information, data that are free of noise-dominated traces, and/or flawed vertical stacking in subsequent processing steps. In this article, I provide an account of utilizing survey design specifications, noise properties, first breaks, and normal moveout for rapid and thorough graphical QC/QA diagnostics, which are easy to apply and efficient in the diagnosis of inconsistencies. A correlated vibroseis time-lapse 3D-seismic data set from a CO2-flood monitoring survey is used for demonstrating QC diagnostics. An important by-product of the QC workflow is establishing the number of layers for a refraction statics model in a data-driven graphical manner that capitalizes on the spatial coverage of the 3D seismic data. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  10. Seismic reflection surveys in central Palo Duro basin

    International Nuclear Information System (INIS)

    Acharya, H.; Buller, M.L.; Lewkowicz, J.; Murphy, P.

    1983-01-01

    Seismic reflection surveys have been conducted in the central Palo Duro basin to provide a basis for identifying localities suitable for the emplacement of an underground high level nuclear waste repository. The objectives of this effort were to determine the structure and stratigraphy in the central Palo Duro basin and evaluate the potential for hydrocarbon resources. Of primary interest is the Upper Permian salt section to a depth of about 3000 ft (914 m). Various tests were carried out along a 3 mi (5 km) segment to determine the most appropriate combination of vibrating source and recording parameters. Approximately 130 mi (209 km) of 24-fold CDP stacked data were acquired. The survey lines were tied to test wells in which velocity surveys were conducted. These data were supplemented by about 400 mi (644 km) of available proprietary CDP stacked data. Analysis of these data strongly suggests that central Palo Duro basin has been tectonically stable since Early Permian time. The maximum offset of the basement is about 600 ft (183 m). These basement faults do not appear to affect any strata above. The San Andres Formation and underlying formations can be traced continuously throughout the area surveyed. Available velocity data from various wells in the central Palo Duro basin show few anomalies, confirming the continuity of the reflecting horizons and the tectonic stability of the area. Hydrocarbon potential of the area is presently being evaluated. The preliminary results of this study are in agreement with the stratigraphic correlations among well logs in the Palo Duro basin

  11. High-resolution seismic reflection and refraction imaging across the epicentral area of the 2009, Mw 6.1 Aquila (Italy) earthquake.

    Science.gov (United States)

    Bruno, Pier Paolo G.; Villani, Fabio; Improta, Luigi; Castiello, Antonio; Pucci, Stefano; Civico, Riccardo; Pantosti, Stefania

    2017-04-01

    We present for the first time the results of high-resolution seismic reflection profiling aimed at imaging the shallow structure of Paganica and Bazzano Quaternary sub-basins across the shallow segments of the Paganica-S. Demetrio Fault, which has been indicated as the causative fault of the 6th April 2009 (Mw 6.1) L'Aquila earthquake (central Italy). The seismic data were collected along five dense and partly overlapping wide-aperture profiles, which run SW-NE for a total length of 6 km, mostly in the hanging wall of the Paganica-S. Demetrio Fault. To evaluate the optimal seismic reflection imaging strategy, we applied three different processing techniques to the dense, wide-aperture acquired data: a conventional CMP reflection processing; pre-stack depth migration (PSDM); and finally the Common-Reflection-Surface (CRS) stack technique. PSDM has proven capable of overcoming many of the typical drawbacks of CMP processing in the presence of complex subsurface velocity distributions. However, PSDM is highly sensitive to the accuracy of the background velocity model. Despite the use of an acquisition geometry effective for refraction tomography (e.g. dense wide-aperture), we were able to estimate a high-resolution background tomographic model suitable for migration purpose for Bazzano profile, whereas this was not the case for Paganica profile, due to greater structural complexity and a higher level of ambient noise. In these settings, the data-driven and velocity-independent CRS method provided a feasible alternative for seismic imaging in Paganica sub-basin. Integration of reflection seismology with refraction tomography and with new surface, paleoseismological and borehole data during interpretation provides new insights on the shallow architecture of the 2009 Mw 6.1 L'Aquila earthquake fault-system and related basins. Bazzano sub-basin is about 50-100 m deeper than Paganica sub-basin. The latter is offset by a large number of NE and SW-dipping faults affecting

  12. Multiple field-based methods to assess the potential impacts of seismic surveys on scallops.

    Science.gov (United States)

    Przeslawski, Rachel; Huang, Zhi; Anderson, Jade; Carroll, Andrew G; Edmunds, Matthew; Hurt, Lynton; Williams, Stefan

    2017-10-30

    Marine seismic surveys are an important tool to map geology beneath the seafloor and manage petroleum resources, but they are also a source of underwater noise pollution. A mass mortality of scallops in the Bass Strait, Australia occurred a few months after a marine seismic survey in 2010, and fishing groups were concerned about the potential relationship between the two events. The current study used three field-based methods to investigate the potential impact of marine seismic surveys on scallops in the region: 1) dredging and 2) deployment of Autonomous Underwater Vehicles (AUVs) were undertaken to examine the potential response of two species of scallops (Pecten fumatus, Mimachlamys asperrima) before, two months after, and ten months after a 2015 marine seismic survey; and 3) MODIS satellite data revealed patterns of sea surface temperatures from 2006-2016. Results from the dredging and AUV components show no evidence of scallop mortality attributable to the seismic survey, although sub-lethal effects cannot be excluded. The remote sensing revealed a pronounced thermal spike in the eastern Bass Strait between February and May 2010, overlapping the scallop beds that suffered extensive mortality and coinciding almost exactly with dates of operation for the 2010 seismic survey. The acquisition of in situ data coupled with consideration of commercial seismic arrays meant that results were ecologically realistic, while the paired field-based components (dredging, AUV imagery) provided a failsafe against challenges associated with working wholly in the field. This study expands our knowledge of the potential environmental impacts of marine seismic survey and will inform future applications for marine seismic surveys, as well as the assessment of such applications by regulatory authorities. Copyright © 2017. Published by Elsevier Ltd.

  13. Seismically induced landslides: current research by the US Geological Survey.

    Science.gov (United States)

    Harp, E.L.; Wilson, R.C.; Keefer, D.K.; Wieczorek, G.F.

    1986-01-01

    We have produced a regional seismic slope-stability map and a probabilistic prediction of landslide distribution from a postulated earthquake. For liquefaction-induced landslides, in situ measurements of seismically induced pore-water pressures have been used to establish an elastic model of pore pressure generation. -from Authors

  14. A Survey study on design procedure of Seismic Base Isolation ...

    African Journals Online (AJOL)

    Adding shear walls or braced frames can decrease the potential damage caused by earthquakes.We can isolate the structures from the ground using the Seismic Base Isolation Systems that is flexible approach to decrease the potential damage. In this research we present information on the design procedure of seismic ...

  15. SURVEY OF SELECTED PROCEDURES FOR THE INDIRECT DETERMINATION OF THE GROUP REFRACTIVE INDEX OF AIR

    Directory of Open Access Journals (Sweden)

    Filip Dvořáček

    2018-02-01

    Full Text Available The main aim of the research was to evaluate numeric procedures of the indirect determination of the group refractive index of air and to choose the suitable ones for requirements of ordinary and high accuracy distance measurement in geodesy and length metrology. For this purpose, 10 existing computation methods were derived from various authors’ original publications and all were analysed for wide intervals of wavelengths and atmospheric parameters. The determination of the phase and the group refractive indices are essential parts in the evaluation of the first velocity corrections of laser interferometers and electronic distance meters. The validity of modern procedures was tested with respect to updated CIPM-2007 equations of the density of air. The refraction model of Leica AT401 laser tracker was analysed.

  16. Inversion of travel times obtained during active seismic refraction experiments CELEBRATION 2000, ALP 2002 and SUDETES 2003

    Czech Academy of Sciences Publication Activity Database

    Růžek, Bohuslav; Hrubcová, Pavla; Novotný, Miroslav; Špičák, Aleš; Karousová, Olga

    2007-01-01

    Roč. 51, č. 1 (2007), s. 141-164 ISSN 0039-3169 R&D Projects: GA MŽP SB/630/3/02; GA ČR GA205/03/0999 Institutional research plan: CEZ:AV0Z30120515 Keywords : seismic tomography * kinematic velocity inversion * Bohemian Massif Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.733, year: 2007

  17. Nature of the uppermost mantle below the Porcupine Basin, offshore Ireland: new insights from seismic refraction and gravity data modeling

    Science.gov (United States)

    Prada, M.; Watremez, L.; Chen, C.; O'Reilly, B.; Minshull, T. A.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

    2015-12-01

    The Porcupine Basin is a tongue-shaped basin SW of Ireland formed during the opening of the North Atlantic Ocean. Its history of sedimentation reveals several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on seismic and gravity data, suggest the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Serpentinization is a key factor in lithospheric extension since it reduces the strength of mantle rocks, and hence, influences the tectonics of the lithosphere. Besides reducing the seismic velocity of the rock, serpentinization decreases mantle rock density favoring isostatic rebound and basin uplift, thus affecting the tectonic and thermal evolution of the basin. Here we characterize the deep structure of the Porcupine Basin from wide-angle seismic (WAS) and gravity data, with especial emphasis on the nature of the underlying mantle. The WAS data used were acquired along a 300 km long transect across the northern region of the basin. We used a travel time inversion method to model the data and obtain a P-wave velocity (Vp) model of the crust and uppermost mantle, together with the geometry of the main geological interfaces. The crustal structure along the model reveals a maximum stretching factor of ~5-6. These values are well within the range of crustal extension at which the crust becomes entirely brittle allowing the formation of major crustal faulting and serpentinization of the mantle. To further constrain the seismic structure and hence the nature of the mantle we assess the Vp uncertainty of the model by means of a Monte Carlo analysis and perform gravity modeling to test different interpretations regarding mantle rock nature. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

  18. Refractive Errors in Koreans: The Korea National Health and Nutrition Examination Survey 2008-2012.

    Science.gov (United States)

    Rim, Tyler Hyungtaek; Kim, Seung-Hyun; Lim, Key Hwan; Choi, Moonjung; Kim, Hye Young; Baek, Seung-Hee

    2016-06-01

    Our study provides epidemiologic data on the prevalence of refractive errors in all age group ≥5 years in Korea. In 2008 to 2012, a total of 33,355 participants aged ≥5 years underwent ophthalmologic examinations. Using the right eye, myopia was defined as a spherical equivalent (SE) less than -0.5 or -1.0 diopters (D) in subjects aged 19 years and older or as an SE less than -0.75 or -1.25 D in subjects aged 5 to 18 years according to non-cycloplegic refraction. Other refractive errors were defined as follows: high myopia as an SE less than -6.0 D; hyperopia as an SE larger than +0.5 D; and astigmatism as a cylindrical error less than -1.0 D. The prevalence and risk factors of myopia were evaluated. Prevalence rates with a 95% confidence interval were determined for myopia (SE prevalence of myopia demonstrated a nonlinear distribution with the highest peak between the ages of 19 and 29 years. The prevalence of hyperopia decreased with age in subjects aged 39 years or younger and then increased with age in subjects aged 40 years or older. The prevalence of astigmatism gradually increased with age. Education was associated with all refractive errors; myopia was more prevalent and hyperopia and astigmatism were less prevalent in the highly educated groups. In young generations, the prevalence of myopia in Korea was much higher compared to the white or black populations in Western countries and is consistent with the high prevalence found in most other Asian countries. The overall prevalence of hyperopia was much lower compared to that of the white Western population. Age and education level were significant predictive factors associated with all kinds of refractive errors.

  19. Subsurface investigation on Quarter 27 of May 15th city, Cairo, Egypt using electrical resistivity tomography and shallow seismic refraction techniques

    Directory of Open Access Journals (Sweden)

    Sultan Awad Sultan Araffa

    2014-12-01

    Full Text Available Geophysical tools such as electrical resistivity tomography (ERT and shallow seismic (both P-wave seismic refraction and Multi-channel Analysis of Surface Waves (MASW are interesting techniques for delineating the subsurface configurations as stratigraphy, structural elements, caves and water saturated zones. The ERT technique is used to delineate the contamination, to detect the buried objects, and to quantify some aquifer properties. Eight 2-D (two dimensional electrical resistivity sections were measured using two different configurations (dipole–dipole and Wenner. The spread length is of 96 m and the electrodes spacing are 2, 4 and 6 m, respectively to reach a depth ranging from 13 to 17 m. The results indicate that, the subsurface section is divided into main three geo-electrical units, the first is fractured marl and limestone which exhibits high resistivity values ranging from 40 to 300 ohm m. The second unit is corresponding to marl of moderate resistivity values and the third unit, which is the deeper unit, exhibits very low resistivity values corresponding to clayey marl. The fourth layer is marly clay with water. The presence of clay causes the most geotechnical problems. Fourteen shallow seismic sections (both for P-wave and MASW were carried out using spread of 94 m and geophone spacing of 2 m for each P-wave section. The results demonstrate that the deduced subsurface section consists of four layers, the first layer exhibits very low P-wave velocity ranging from 280 to 420 m/s, the second layer reveals P-wave velocity ranging from 400 to 1200 m/s, the third layer has P-wave velocity ranging from 970 to 2000 m/s and the fourth layer exhibits high velocity ranging from 1900 to 3600 m/s. The ERT and shallow seismic results, reflect the presence of two parallel faults passing through Quarter 27 and trending NW-SE.

  20. High Resolution Seismic Reflection Survey for Coal Mine: fault detection

    Science.gov (United States)

    Khukhuudei, M.; Khukhuudei, U.

    2014-12-01

    High Resolution Seismic Reflection (HRSR) methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration. Modern coal mining requires certainly about geological faults and structural features. This paper focuses on 2D Seismic section mapping results from an "Zeegt" lignite coal mine in the "Mongol Altai" coal basin, which required the establishment of major structure for faults and basement. HRSR method was able to detect subsurface faults associated with the major fault system. We have used numerical modeling in an ideal, noise free environment with homogenous layering to detect of faults. In a coal mining setting where the seismic velocity of the high ranges from 3000m/s to 3600m/s and the dominant seismic frequency is 100Hz, available to locate faults with a throw of 4-5m. Faults with displacements as seam thickness detected down to several hundred meter beneath the surface.

  1. Seismic data processing for the survey over the Korean continental shelf using the Geobit

    Energy Technology Data Exchange (ETDEWEB)

    Suh, Sang Yong; Chung, Bu Heung; Jang, Seong Hyung [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1997-12-01

    The Geobit, a seismic data processing software developed by the Korea Institute of Geology, Mining and Materials recently, is the token of the achievement for the development of technology in the oil exploration over the Korean continental shelf. In comparison with the commercial seismic data processing systems previously used in Korea, the Geobit system has some advanced facilities, it provides an interactive mode which makes the seismic processing easier and has the user-friendly programs which allow the construction of a job control file simpler. Most of all, the Geobit can be run with many computer hardware systems, from PC to supercomputer. The current version of the Geobit can take care of the two-dimensional multi-channel seismic data and is open to the public for an education tool and a research purpose. The seismic field data used in this research had been acquired in Block 3 in the Korean continental shelf over the Yellow Sea in 1970. Among them we had processed 10 lines with 34,000 shot points and about 1,700 km line. These seismic data were originally recorded on 21 track reel tape. These were transformed to SEG Y format on CD-ROM. The seismic field data of the Block 3 had severe noise like mechanical, recording noise and refraction and it had so many dead traces and shots. In this report, the used computer system is the Pentium-200 Hz with 128 MB main memory, 72 GB HDD and operating system is Linux 2.0.30 kernel. (author). 7 refs., 2 tabs., 21 figs.

  2. The ancient harbour system of Terracina (Latium, Italy) obtained by gravity and seismic surveys.

    Science.gov (United States)

    di Nezza, Maria; di Filippo, Michele

    2010-05-01

    Historical research has shown that Terracina (Latina, Latium) played a fundamental role in the maritime and land traffic since before the foundation of the colony. The settlement was established where the organized system of maritime, land, coastal, and fluvial transport had the most ideal conditions to constitute an important commercial crossroads, apparently since the beginning of recorded history. In order to reconstruction the buried archaeological structures attributed to the ancient Roman port, traditionally attributed to Traiano, in the current area of the harbour of Terracina, it was carried out a gravity survey, more than 380 gravity stations. The gravity method enables to recognize the cavity and the structures of the buildings underground through the results of variations density in the subsoil. Seismic tomography treats the problem of identifying a buried structure as a wave propagation process by inverting the linearized wave equation to compute the spatial distribution of the slowness of the velocity. The purpose of our tomographic study is to further test the method and to guide archaeologists in their future excavations by locating and identifying buried structures. In the residual gravity anomaly map a series of positive anomalies are visible which confirm the round structures and the pier of the buried foundations of the Imperial harbour. Unfortunately, little remains of the functioning facilities of the harbour's activities. The modern construction of the harbour, in fact, has to be developed around the new inhabitable commercial area, know today as Terracina Bassa or Borgo alla Marina. It had to be developed with a modern infrastructure of a harbor area, as in the construction of the rooms for storage of goods, warehouses, as well as for the thermal baths, hotels and amphitheatre. Furthermore, there are always the positive anomalies that characterize the area to the north-east of "Montone" hill where archaeological remains are easily visible

  3. Near-surface 3D reflections seismic survey; Sanjigen senso hanshaho jishin tansa

    Energy Technology Data Exchange (ETDEWEB)

    Nakahigashi, H.; Mitsui, H.; Nakano, O.; Kobayashi, T. [DIA Consultants Co. Ltd., Tokyo (Japan)

    1997-05-27

    Faults are being actively investigated across Japan since the Great Hanshin-Awaji Earthquake. Discussed in this report is the application of the 3D near-surface reflection seismic survey in big cities. Data from trenching and drilling is used for the geological interpretation of the surroundings of a fault, and the reflection seismic survey is used to identify the position, etc., of the fault. In this article, when the results obtained from the experimental field are examined, it is found that the conventional 2D imaging reflection survey betrays the limit of its capability when the geological structure is complicated, that the 3D reflection seismic survey, on the contrary, is capable of high-precision imaging and, when augmented by drilling, etc., becomes capable of a more detailed interpretation, and that it also contributes effectively to the improvement of local disaster prevention in big cities. Using as the model the Tachikawa fault that runs near JR Tachikawa Station, embodiment of the 3D reflection seismic survey is reviewed. For the acquisition of data excellent in quality in a 3D reflection seismic survey conducted utilizing the roads in the sector chosen for experiment in the urban area, the shock generating points and receiving points should be positioned by taking into account the parameters in the bin arranging process so that the mid-points will be regularly distributed on the surface. 3 refs., 11 figs., 1 tab.

  4. Balancing Mitigation Against Impact: A Case Study From the 2005 Chicxulub Seismic Survey

    Science.gov (United States)

    Barton, P.; Diebold, J.; Gulick, S.

    2006-05-01

    In early 2005 the R/V Maurice Ewing conducted a large-scale deep seismic reflection-refraction survey offshore Yucatan, Mexico, to investigate the internal structure of the Chicxulub impact crater, centred on the coastline. Shots from a tuned 20 airgun, 6970 cu in array were recorded on a 6 km streamer and 25 ocean bottom seismometers (OBS). The water is exceptionally shallow to large distances offshore, reaching 30 m about 60 km from the land, making it unattractive to the larger marine mammals, although there are small populations of Atlantic and spotted dolphins living in the area, as well as several turtle breeding and feeding grounds on the Yucatan peninsula. In the light of calibrated tests of the Ewing's array (Tolstoy et al., 2004, Geophysical Research Letters 31, L14310), a 180 dB safety radius of 3.5 km around the gun array was adopted. An energetic campaign was organised by environmentalists opposing the work. In addition to the usual precautions of visual and listening watches by independent observers, gradual ramp-ups of the gun arrays, and power-downs or shut-downs for sightings, constraints were also placed to limit the survey to daylight hours and weather conditions not exceeding Beaufort 4. The operations were subject to several on-board inspections by the Mexican environmental authorities, causing logistical difficulties. Although less than 1% of the total working time was lost to shutdowns due to actual observation of dolphins or turtles, approximately 60% of the cruise time was taken up in precautionary inactivity. A diver in the water 3.5 km from the profiling ship reported that the sound in the water was barely noticeable, leading us to examine the actual sound levels recorded by both the 6 km streamer and the OBS hydrophones. The datasets are highly self-consistent, and give the same pattern of decay with distance past about 2 km offset, but with different overall levels: this may be due to geometry or calibration differences under

  5. Seismic survey in southeastern Socorro Island: Background noise measurements, seismic events, and T phases

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, Raul W [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D.F. (Mexico); Galindo, Marta [Comprehensive Nuclear-Test-Ban Treaty Organization, IMS, Vienna (Austria); Pacheco, Javier F; Iglesias, Arturo; Teran, Luis F [Instituto de Geofisica, Universidad Nacional Autonoma de Mexico, D.F. (Mexico); Barreda, Jose L; Coba, Carlos [Facultad de Ingenieria, Benemerita Universidad Autonoma de Puebla, Puebla (Mexico)

    2005-01-15

    We carried out a seismic survey and installed five portable, broadband seismometers in the southeastern corner of Socorro Island during June 1999. Power spectral densities for all five sites were relatively noisy when compared to reference curves around the world. Power spectral densities remain constant regardless of the time of day, or the day of the week. Cultural noise at the island is very small. Quiet and noisy sites were identified to determine the best location of the T phase station to be installed jointly by the Universidad Nacional Autonoma de Mexico and the Comprehensive Nuclear-Test-Ban Treaty Organization. During the survey six earthquakes were recorded at epicentral distances between 42 km and 2202 km, with magnitudes between 2.8 and 7.0. Two small earthquakes (M{sub c} = 2.8 and 3.3) occurred on the Clarion Fracture Zone. The four largest and more distant earthquakes produced T waves. One T wave from an epicenter near the coast of Guatemala had a duration of about 100 s and a frequency content between 2 and 8 Hz, with maximum amplitude at about 4.75 Hz. The Tehuacan earthquake of June 15, 1999 (M{sub w} = 7.0) produced arrivals of P {yields} T and S {yields} T waves, with energy between 2 Hz and 3.75 Hz. The earthquake occurred inland within the subducted Cocos plate at a depth of 60 km; a significant portion of the path was continental. Seismic P and S waves probably propagated upward in the subducted slab, and were converted to acoustic energy at the continental slope. Total duration of the T phase is close to 500 s and reaches its maximum amplitude about 200 s after the P {yields} T arrival. The T wave contains energy at frequencies between 2 and 10 Hz and reaches its maximum amplitude at about 2.5 Hz. T phases were also recorded from two earthquakes in Guerrero, Mexico and in the Rivera Fracture Zone. [Spanish] En junio de 1999 instalamos cinco sismometros portatiles de banda ancha en el sureste de la Isla Socorro. Se encontro que las densidades

  6. A seismic survey of Pine Lake environmental center

    Energy Technology Data Exchange (ETDEWEB)

    Knezevic, J.J. (Hartwick Coll., Oneonta, NY (United States). Dept. of Geology); Meltzer, A.S. (Lehigh Univ., Bethlehem, PA (United States). Dept. of Earth and Environmental Sciences)

    1993-03-01

    Pine Lake sits within a 900+ acre property owned by Hartwick College in West Davenport, NY. The property is an environmental center where biological and geochemical research is ongoing. Pine Lake itself is a 12 acre kettle hole lake created during the Woodfordian stage of the Wisconsonian glaciation. Bedrock is not exposed locally, but is buried beneath till. Preliminary geochemical analyses of the lake water suggest that the lake has a significant capacity to buffer the detrimental effects of acid precipitation (Adams, 1992). Water percolating through the glacial till on which the lake is situated is thought to play a major part in the introduction of buffering agents. The authors collected four refraction profiles adjacent to the lake to determine depth to bedrock and extent of glacial till. This will provide constraints for hydrologic models. Data was collected from two pairs of refraction lines. Two lines were placed on the north side of the lake and two on the east side. On each side of the lake, lines were oriented perpendicular to each other to constrain the dip of underlying bedrock. Data represent high resolution reversed refraction profiles and will allow the authors to constrain thickness of till and underlying bedrock geometry. Data was downloaded to a workstation, bandpass filtered from 5--280 Hz., scaled using a single window gain, and statically corrected. They see refracted arrivals from two interfaces. The upper interface is located at approximately 13 feet with a velocity of roughly 5,000 ft/sec and the lower interface at approximately 88 feet with a velocity of 12,000 ft/sec. These interfaces are essentially flat-lying and are most likely part of the Upper Devonian Unadilla Formation. The glacial till that blankets the area ranges in thickness from 13 feet to 71 feet.

  7. Integration of Electrical Resistivity and Seismic Refraction using Combine Inversion for Detecting Material Deposits of Impact Crater at Bukit Bunuh, Lenggong, Perak

    Science.gov (United States)

    Yusoh, R.; Saad, R.; Saidin, M.; Muhammad, S. B.; Anda, S. T.

    2018-04-01

    Both electrical resistivity and seismic refraction profiling has become a common method in pre-investigations for visualizing subsurface structure. The encouragement to use these methods is that combined of both methods can decrease the obscure inherent to the distinctive use of these methods. Both method have their individual software packages for data inversion, but potential to combine certain geophysical methods are restricted; however, the research algorithms that have this functionality was exists and are evaluated personally. The interpretation of subsurface were improve by combining inversion data from both method by influence each other models using closure coupling; thus, by implementing both methods to support each other which could improve the subsurface interpretation. These methods were applied on a field dataset from a pre-investigation for archeology in finding the material deposits of impact crater. There were no major changes in the inverted model by combining data inversion for this archetype which probably due to complex geology. The combine data analysis shows the deposit material start from ground surface to 20 meter depth which the class separation clearly separate the deposit material.

  8. USE of seismic refraction method for the determination of the depth of water table at ozalla, owan west l.g.a edo state. Nigeria USE of seismic refraction method for the determination of the depth of water table at ozalla, owan west l.g.a edo state. Nigeria USE of seismic refraction method for the determination of the depth of water table at ozalla, owan west l.g.a edo state. Nigeria USE of seismic refraction method for the determination of the depth of water table at ozalla, Nigeria

    Science.gov (United States)

    Aikpitanyi, C. U.

    2012-12-01

    This Project research was carried out using seismic refraction method at st Patrick catholic church( site) ozalla owan west l.g.a Edo state. Nigeria A MCSEIS- 160M Seismograph was used as the recording instrument with 12 geophones as wave detectors in series with one another, each of 1.5m Perpendicular to a firing line of of36m long. but the geophones are spread at a predetermined distance. the impact of heavy metal(about 5kg) on a flat metal plate served as the source of artificial wave generation. The wave front method of interpretation was used in interpreting the field results at fine distance . Plot reveals that the subsurface under Investigation is three layers of velocities, 208ms-1 750ms-1 and 1250ms-1 for the first, second and third layers respectively. And the depth of the first and second layer is 12 .7m and 14.0m respectively. This investigation has further revealed that at approximately 27m from the surface a possible aquifer could be encountered, this result agreed with electrical resistivity Studies carried out in the past within the studied area.

  9. Seismic refraction technique aplications in the geotechnical characterization of the Cachoeira deposit massif, Caetite, State of Bahia, Brazil

    International Nuclear Information System (INIS)

    Malagutti Filho, W.; Oliveira Braga, T. de.

    1984-01-01

    Geophysical surveys throught the Cachoeira Uranium deposit massif were carried out with the purpose of assisting in the geotechnical characterization for the implantation of the Mining-Industrial Complex projects on the Lagoa Real uranium deposits, Caetite municipality, state of Bahia, Brazil. This study discusses the methodology utilized in the geophysical surveys and their results as well as their applications to the geotechnical characterization as a whole. (D.J.M.) [pt

  10. Parsimonious refraction interferometry

    KAUST Repository

    Hanafy, Sherif

    2016-09-06

    We present parsimonious refraction interferometry where a densely populated refraction data set can be obtained from just two shot gathers. The assumptions are that the first arrivals are comprised of head waves and direct waves, and a pair of reciprocal shot gathers is recorded over the line of interest. The refraction traveltimes from these reciprocal shot gathers can be picked and decomposed into O(N2) refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. This enormous increase in the number of virtual traveltime picks and associated rays, compared to the 2N traveltimes from the two reciprocal shot gathers, allows for increased model resolution and better condition numbers in the normal equations. Also, a reciprocal survey is far less time consuming than a standard refraction survey with a dense distribution of sources.

  11. Seismic surveys negatively affect humpback whale singing activity off northern Angola.

    Directory of Open Access Journals (Sweden)

    Salvatore Cerchio

    Full Text Available Passive acoustic monitoring was used to document the presence of singing humpback whales off the coast of Northern Angola, and opportunistically test for the effect of seismic survey activity in the vicinity on the number of singing whales. Two Marine Autonomous Recording Units (MARUs were deployed between March and December 2008 in the offshore environment. Song was first heard in mid June and continued through the remaining duration of the study. Seismic survey activity was heard regularly during two separate periods, consistently throughout July and intermittently in mid-October/November. Numbers of singers were counted during the first ten minutes of every hour for the period from 24 May to 1 December, and Generalized Additive Mixed Models (GAMMs were used to assess the effect of survey day (seasonality, hour (diel variation, moon phase and received levels of seismic survey pulses (measured from a single pulse during each ten-minute sampled period on singer number. Application of GAMMs indicated significant seasonal variation, which was the most pronounced effect when assessing the full dataset across the entire season (p<0.001; however seasonality almost entirely dropped out of top-ranked models when applied to a reduced dataset during the July period of seismic survey activity. Diel variation was significant in both the full and reduced datasets (from p<0.01 to p<0.05 and often included in the top-ranked models. The number of singers significantly decreased with increasing received level of seismic survey pulses (from p<0.01 to p<0.05; this explanatory variable was included among the top ranked models for one MARU in the full dataset and both MARUs in the reduced dataset. This suggests that the breeding display of humpback whales is disrupted by seismic survey activity, and thus merits further attention and study, and potentially conservation action in the case of sensitive breeding populations.

  12. Visual impairment attributable to uncorrected refractive error and other causes in the Ghanaian youth: The University of Cape Coast Survey.

    Science.gov (United States)

    Abokyi, Samuel; Ilechie, Alex; Nsiah, Peter; Darko-Takyi, Charles; Abu, Emmanuel Kwasi; Osei-Akoto, Yaw Jnr; Youfegan-Baanam, Mathurin

    2016-01-01

    To determine the prevalence of visual impairment attributable to refractive error and other causes in a youthful Ghanaian population. A prospective survey of all consecutive visits by first-year tertiary students to the Optometry clinic between August, 2013 and April, 2014. Of the 4378 first-year students aged 16-39 years enumerated, 3437 (78.5%) underwent the eye examination. The examination protocol included presenting visual acuity (PVA), ocular motility, and slit-lamp examination of the external eye, anterior segment and media, and non-dilated fundus examination. Pinhole acuity and fundus examination were performed when the PVA≤6/12 in one or both eyes to determine the principal cause of the vision loss. The mean age of participants was 21.86 years (95% CI: 21.72-21.99). The prevalence of bilateral visual impairment (BVI; PVA in the better eye ≤6/12) and unilateral visual impairment UVI; PVA in the worse eye ≤6/12) were 3.08% (95% CI: 2.56-3.72) and 0.79% (95% CI: 0.54-1.14), respectively. Among 106 participants with BVI, refractive error (96.2%) and corneal opacity (3.8%) were the causes. Of the 27 participants with UVI, refractive error (44.4%), maculopathy (18.5%) and retinal disease (14.8%) were the major causes. There was unequal distribution of BVI in the different age groups, with those above 20 years having a lesser burden. Eye screening and provision of affordable spectacle correction to the youth could be timely to eliminate visual impairment. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  13. Development of Vertical Cable Seismic System for Hydrothermal Deposit Survey (2) - Feasibility Study

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Mikada, H.; Takekawa, J.; Shimura, T.

    2010-12-01

    In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. . (1) VCS is an effective high-resolution 3D seismic survey within limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Various types of marine source are applicable with VCS such as sea-surface source (air gun, water gun etc.) , deep-towed or ocean bottom sources. (5) Autonomous recording system. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN. in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. The result gives clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Uncertainty of the source/receiver poisons in water causes the serious problem of the imaging. We used several transducer/transponder to estimate these positions. The VCS seismic records themselves can also provide sensor position using the first break of each trace and we calibrate the positions. We are currently developing the autonomous recording VCS system and planning the trial experiment in actual ocean to establish the way of deployment/recovery and the examine the position through the current flow in November, 2010. The second VCS survey will planned over the actual hydrothermal deposit with deep-towed source in February, 2011.

  14. Prevalence and risk factors for refractive errors: Korean National Health and Nutrition Examination Survey 2008-2011.

    Directory of Open Access Journals (Sweden)

    Eun Chul Kim

    Full Text Available PURPOSE: To examine the prevalence and risk factors of refractive errors in a representative Korean population aged 20 years old or older. METHODS: A total of 23,392 people aged 20+ years were selected for the Korean National Health and Nutrition Survey 2008-2011, using stratified, multistage, clustered sampling. Refractive error was measured by autorefraction without cycloplegia, and interviews were performed regarding associated risk factors including gender, age, height, education level, parent's education level, economic status, light exposure time, and current smoking history. RESULTS: Of 23,392 participants, refractive errors were examined in 22,562 persons, including 21,356 subjects with phakic eyes. The overall prevalences of myopia ( 0.5 D were 48.1% (95% confidence interval [CI], 47.4-48.8, 4.0% (CI, 3.7-4.3, and 24.2% (CI, 23.6-24.8, respectively. The prevalence of myopia sharply decreased from 78.9% (CI, 77.4-80.4 in 20-29 year olds to 16.1% (CI, 14.9-17.3 in 60-69 year olds. In multivariable logistic regression analyses restricted to subjects aged 40+ years, myopia was associated with younger age (odds ratio [OR], 0.94; 95% Confidence Interval [CI], 0.93-0.94, p < 0.001, education level of university or higher (OR, 2.31; CI, 1.97-2.71, p < 0.001, and shorter sunlight exposure time (OR, 0.84; CI, 0.76-0.93, p = 0.002. CONCLUSIONS: This study provides the first representative population-based data on refractive error for Korean adults. The prevalence of myopia in Korean adults in 40+ years (34.7% was comparable to that in other Asian countries. These results show that the younger generations in Korea are much more myopic than previous generations, and that important factors associated with this increase are increased education levels and reduced sunlight exposures.

  15. High-resolution reflection seismic survey at a CCS site, Taiwan

    Science.gov (United States)

    Wang, Chien-Ying; Chung, Chen-Tung; Kuo, Hsuan-Yu; Wu, Ming-shyan; Kuo-Chen, Hao

    2017-04-01

    To control the effect of greenhouse gas on global warming, the reduction of carbon dioxide emission has become a significant international issue in recent years. The capture of carbon dioxide during its manufacturing and storing in adjacent areas are the most economical way. This research uses high-resolution seismic reflection survey to investigate the region around the world's largest coal-fired power plant at Taichung Port, Taiwan. We aim to detect proper geological structures and to evaluate the possible way to store carbon dioxide. This research uses reflection seismic survey with two mini-vibrators and 240 channels to investigate detailed underground structures. The total length of seismic lines is more than 20 kilometers. By aligning sequential seismic lines, we are able to correlate stratigraphic layers over a wide area. Two adjacent wells along the seismic line are used to identified possible formations. The TaiChung Power Plant (TCPP) at Taichung Port is our target which has more cross-tied seismic lines and a seismic line even extending into the sea water. We analyze these seismic profiles to establish the geological model for carbon dioxide storage and evaluate the possibility of storage systems. Furthermore, this research may prepare some baseline data for the future carbon dioxide injection monitoring. The result shows that the geological structures striking 8 degrees east of north and dipping 2.8 degrees to the east. This means that carbon dioxide will migrate toward the sea direction after injection. The structural layers are relatively flat without any sign of faults. Three carbon dioxide storage systems : Mushan Wuchihshan—Paling(bottom), Peiliao—Talu(middle) and Kueichulin—Chinshui(upper) system are identified. All has the proper reservoir with high porosity and capable caprocks more than 100 meters thick. The geological storage of carbon dioxide injected into TCPP site is a feasible, commercial and safe way to reduce the emission of carbon

  16. A critical review of the potential impacts of marine seismic surveys on fish & invertebrates.

    Science.gov (United States)

    Carroll, A G; Przeslawski, R; Duncan, A; Gunning, M; Bruce, B

    2017-01-15

    Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

  17. 3D Traveltime Tomography and 1D Wavefield Inversion of Dense 3D Seismic Refraction Data From a Shallow Groundwater Contamination Site

    Science.gov (United States)

    Zelt, C. A.; Chen, J.; Levander, A.

    2016-12-01

    In 2012 Rice University carried out a shallow seismic survey in Rifle, Colorado where the groundwater was contaminated by vanadium and uranium ore-processing operations ending in 1958. The purpose of the seismic survey is to provide constraints to improve hydrogeologic modeling. The 3-D P-wave survey over 96 m x 60 m included 2158 shots recorded by 384 channels yielding 828,672 traces. An accelerated weight drop provided data with good signal-to-noise ratio (SNR) and a dominant frequency of 60 Hz. The overall good SNR allows for precise picking and an average uncertainty of 0.65 ms was assigned based on an analysis of all reciprocal time differences. Unreliable source triggering necessitated solving for shot time corrections during travelitme tomography, creating a mixed-parameter inverse problem. Several steps in addition to conventional 3-D traveltime tomography were applied to exploit the dense data and precise picking to overcome the data's low frequency content: (1) stacking the arrival-time-corrected traces in offset bins for 1-D reflectivity modeling to constrain discontinuities; (2) reduced smoothing regularization based on the local angular distribution of raypaths; and (3) a frequency-dependent form of traveltime tomography to account for the data's frequency content. Model assessment techniques include: (1) removal of the best and poorest fit data to assess the effect of outliers, (2) a jackknife procedure to estimate the uncertainty of each velocity node, and (3) checkerboard tests to estimate lateral model resolution using random shot and picking errors consistent with the real data. The results show that most of the velocity model has a relative error of less than 2% and lateral resolution of better than 5, 10 and 20 m to depths of 5, 10 and 20 m, respectively. Results include an isovelocity surface that represents the top of the Wasatch formation.

  18. Near-vertical seismic reflection image using a novel acquisition technique across the Vrancea Zone and Foscani Basin, south-eastern Carpathians (Romania).

    NARCIS (Netherlands)

    Panea, I; Stephenson, R.A.; Knapp, C.; Mocanu, V.I.; Drijkoningen, G.; Matenco, L.C.; Knapp, J.; Prodehl, K.

    2005-01-01

    The DACIA PLAN (Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics) deep seismic sounding survey was performed in August-September 2001 in south-eastern Romania, at the same time as the regional deep refraction seismic survey VRANCEA 2001. The main goal of the

  19. Seismic surveys negatively affect humpback whale singing activity off northern Angola.

    Science.gov (United States)

    Cerchio, Salvatore; Strindberg, Samantha; Collins, Tim; Bennett, Chanda; Rosenbaum, Howard

    2014-01-01

    Passive acoustic monitoring was used to document the presence of singing humpback whales off the coast of Northern Angola, and opportunistically test for the effect of seismic survey activity in the vicinity on the number of singing whales. Two Marine Autonomous Recording Units (MARUs) were deployed between March and December 2008 in the offshore environment. Song was first heard in mid June and continued through the remaining duration of the study. Seismic survey activity was heard regularly during two separate periods, consistently throughout July and intermittently in mid-October/November. Numbers of singers were counted during the first ten minutes of every hour for the period from 24 May to 1 December, and Generalized Additive Mixed Models (GAMMs) were used to assess the effect of survey day (seasonality), hour (diel variation), moon phase and received levels of seismic survey pulses (measured from a single pulse during each ten-minute sampled period) on singer number. Application of GAMMs indicated significant seasonal variation, which was the most pronounced effect when assessing the full dataset across the entire season (pseismic survey activity. Diel variation was significant in both the full and reduced datasets (from pseismic survey pulses (from pseismic survey activity, and thus merits further attention and study, and potentially conservation action in the case of sensitive breeding populations.

  20. Imaging of Subsurface Faults using Refraction Migration with Fault Flooding

    KAUST Repository

    Metwally, Ahmed Mohsen Hassan

    2017-05-31

    We propose a novel method for imaging shallow faults by migration of transmitted refraction arrivals. The assumption is that there is a significant velocity contrast across the fault boundary that is underlain by a refracting interface. This procedure, denoted as refraction migration with fault flooding, largely overcomes the difficulty in imaging shallow faults with seismic surveys. Numerical results successfully validate this method on three synthetic examples and two field-data sets. The first field-data set is next to the Gulf of Aqaba and the second example is from a seismic profile recorded in Arizona. The faults detected by refraction migration in the Gulf of Aqaba data were in agreement with those indicated in a P-velocity tomogram. However, a new fault is detected at the end of the migration image that is not clearly seen in the traveltime tomogram. This result is similar to that for the Arizona data where the refraction image showed faults consistent with those seen in the P-velocity tomogram, except it also detected an antithetic fault at the end of the line. This fault cannot be clearly seen in the traveltime tomogram due to the limited ray coverage.

  1. Time-lapse high-resolution seismic surveys in the Mississippi Delta mudflow area, offshore Louisiana

    Energy Technology Data Exchange (ETDEWEB)

    Son-Hindmarsh, R.; Hughson, R.A.; Ploessel, M.R.

    1984-05-01

    Time-lapse high-resolution surveys are useful for studying rapidly changing geologic features such as the mudflows of the Mississippi Delta, and for assessing how these potentially hazardous features might affect offshore structures. For time-lapse surveys, an initial high-resolution seismic survey is repeated at specified time intervals, following the same grid of tracklines, using the same seismic systems and a precise navigation system. Time-lapse surveys have been used successfully to monitor the active mudflow about 6 miles upslope from Shell Offshore Inc.'s Cognac Platform. The surveys show that mudflow activity has had no effect on the Platform. Time-lapse surveys obtain the most accurate determination of seafloor changes available at the present time. If one compares two or more random surveys in an area, instead of carefully performed time-lapse surveys, the accuracy of the results may be less than the actural amount of change; so results may be meaningless or misleading. Time-lapse surveys can produce results with vertical accuracy of about + or 5 feet along survey tracklines.

  2. Seismic monitoring at Deception Island volcano (Antarctica): the 2010-2011 survey

    Science.gov (United States)

    Martín, R.; Carmona, E.; Almendros, J.; Serrano, I.; Villaseñor, A.; Galeano, J.

    2012-04-01

    As an example of the recent advances introduced in seismic monitoring of Deception Island volcano (Antarctica) during recent years, we describe the instrumental network deployed during the 2010-2011 survey by the Instituto Andaluz de Geofísica of University of Granada, Spain (IAG-UGR). The period of operation extended from December 19, 2010 to March 5, 2011. We deployed a wireless seismic network composed by four three-component seismic stations. These stations are based on 24-bit SL04 SARA dataloggers sampling at 100 sps. They use a PC with embedded linux and SEISLOG data acquisition software. We use two types of three-component seismometers: short-period Mark L4C with natural frequency of 1 Hz and medium-period Lennartz3D/5s with natural frequency of 0.2 Hz. The network was designed for an optimum spatial coverage of the northern half of Deception, where a magma chamber has been reported. Station locations include the vicinity of the Spanish base "Gabriel de Castilla" (GdC), Obsidianas Beach, a zone near the craters from the 1970 eruptions, and the Chilean Shelter located south of Pendulum Cove. Continuous data from the local seismic network are received in real-time in the base by wifi transmission. We used Ubiquiti Networks Nanostation2 antennas with 2.4 GHz, dual-polarity, 10 dBi gain, and 54 Mbps transmission rate. They have shown a great robustness and speed for real-time applications. To prioritize data acquisition when the battery level is low, we have designed a circuit that allows independent power management for the seismic station and wireless transmission system. The reception antenna located at GdC is connected to a computer running SEISCOMP. This software supports several transmission protocols and manages the visualization and recording of seismic data, including the generation of summary plots to show the seismic activity. These twelve data channels are stored in miniseed format and displayed in real time, which allows for a rapid evaluation of

  3. Shallow seismic surveys at Dabhol minor port in Maharashtra

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    Detailed surveys comprising of echosounding and subbottom profiling followed by sea bed sampling were carried out in the creek off Dabhol to know the surficial and subsurface geology of the area for suggesting alignment of the approach channel route...

  4. High-resolution seismic reflection/refraction imaging from Interstate 10 to Cherry Valley Boulevard, Cherry Valley, Riverside County, California: implications for water resources and earthquake hazards

    Science.gov (United States)

    Gandhok, G.; Catchings, R.D.; Goldman, M.R.; Horta, E.; Rymer, M.J.; Martin, P.; Christensen, A.

    1999-01-01

    This report is the second of two reports on seismic imaging investigations conducted by the U.S. Geological Survey (USGS) during the summers of 1997 and 1998 in the Cherry Valley area in California (Figure 1a). In the first report (Catchings et al., 1999), data and interpretations were presented for four seismic imaging profiles (CV-1, CV-2, CV-3, and CV-4) acquired during the summer of 1997 . In this report, we present data and interpretations for three additional profiles (CV-5, CV-6, and CV-7) acquired during the summer of 1998 and the combined seismic images for all seven profiles. This report addresses both groundwater resources and earthquake hazards in the San Gorgonio Pass area because the shallow (upper few hundred meters) subsurface stratigraphy and structure affect both issues. The cities of Cherry Valley and Beaumont are located approximately 130 km (~80 miles) east of Los Angeles, California along the southern alluvial fan of the San Bernardino Mountains (see Figure 1b). These cities are two of several small cities that are located within San Gorgonio Pass, a lower-lying area between the San Bernardino and the San Jacinto Mountains. Cherry Valley and Beaumont are desert cities with summer daytime temperatures often well above 100 o F. High water usage in the arid climate taxes the available groundwater supply in the region, increasing the need for efficient management of the groundwater resources. The USGS and the San Gorgonio Water District (SGWD) work cooperatively to evaluate the quantity and quality of groundwater supply in the San Gorgonio Pass region. To better manage the water supplies within the District during wet and dry periods, the SGWD sought to develop a groundwater recharge program, whereby, excess water would be stored in underground aquifers during wet periods (principally winter months) and retrieved during dry periods (principally summer months). The SGWD preferred a surface recharge approach because it could be less expensive than a

  5. Results of a 3D seismic survey at the Travale (Italy) test site

    Energy Technology Data Exchange (ETDEWEB)

    Casini, Michele; Ciuffi, Simonetta; Fiordelisi, Adolfo [ENEL Produzione S.p.A., Geothermal Production, Via Andrea Pisano 120, 56122 Pisa (Italy); Mazzotti, Alfredo [University of Pisa, Earth Sciences Department, Via S. Maria 53, 56126 Pisa (Italy); Stucchi, Eusebio [Universita di Milano, Earth Sciences Department, Via Cicognara 7, 20129 Milano (Italy)

    2010-03-15

    In the last 15 years geothermal exploration in Tuscany, Italy, has addressed deep reservoirs (depth {>=} 3000 m), hosted within complex geological systems, such as metamorphic formations and/or intrusive bodies. Reservoir productivity is linked to fractured and permeable zones that are rather confined and not uniformly distributed. In this context, the seismic methods represent one of the most reliable geophysical techniques for locating potential drilling targets. A 3D seismic survey has been acquired at the Travale test site, and its results have been used to develop a geological and structural model of the site, and to identify and characterize fractured zones inside the deep geothermal reservoir. A correlation between a high-amplitude reflector (H marker) and fractured contact-metamorphic rocks has been highlighted. More than 70% of the total geothermal fluid production at the Travale area comes from this seismic marker. (author)

  6. Survey Methods for Seismic Vulnerability Assessment of Historical Masonry Buildings

    Science.gov (United States)

    Ballarin, M.; Balletti, C.; Faccio, P.; Guerra, F.; Saetta, A.; Vernier, P.

    2017-05-01

    On 20th and 29th of May 2012, two powerful earthquakes struck northern Italy. The epicentres were recorded respectively in Finale Emilia (magnitude 5.9 Ml) and Medolla (magnitude 5.8 Ml) in the province of Modena, though the earthquake was formed by a series of seismic shakes located in the district of the Emilian Po Valley, mainly in the provinces of Modena, Ferrara, Mantova, Reggio Emilia, Bologna and Rovigo. Many monuments in the city of Mantova were hit by the earthquake and, among these, Palazzo Ducale with the well-known Castello di San Giorgio which host the noteworthy "Camera degli Sposi". This building, the most famous of the city, was so damaged that it was closed for more than one year after the earthquake. The emblem of the Palace and Mantova itself, the previously cited "Camera degli Sposi" realized by Andrea Mantegna, was damaged and all the economic and social life of the city was deeply affected. Immediately after the earthquake, the Soprintendenza per i Beni Architettonici e Paesaggistici of Brescia, Cremona and Mantova establish an agreement with the University Iuav of Venice, requiring an analysis and assessment of the damage in order to proceed with the development of an intervention project. This activity turned out to be very important not only from the point of view of the recovery of the architectural and artistic heritage but also because the city's economy is based primarily on tourism. The closure of one of the most important monuments of Mantova has led to a significant and alarming decline in the government income.

  7. SURVEY METHODS FOR SEISMIC VULNERABILITY ASSESSMENT OF HISTORICAL MASONRY BUILDINGS

    Directory of Open Access Journals (Sweden)

    M. Ballarin

    2017-05-01

    Full Text Available On 20th and 29th of May 2012, two powerful earthquakes struck northern Italy. The epicentres were recorded respectively in Finale Emilia (magnitude 5.9 Ml and Medolla (magnitude 5.8 Ml in the province of Modena, though the earthquake was formed by a series of seismic shakes located in the district of the Emilian Po Valley, mainly in the provinces of Modena, Ferrara, Mantova, Reggio Emilia, Bologna and Rovigo. Many monuments in the city of Mantova were hit by the earthquake and, among these, Palazzo Ducale with the well-known Castello di San Giorgio which host the noteworthy “Camera degli Sposi”. This building, the most famous of the city, was so damaged that it was closed for more than one year after the earthquake. The emblem of the Palace and Mantova itself, the previously cited “Camera degli Sposi” realized by Andrea Mantegna, was damaged and all the economic and social life of the city was deeply affected. Immediately after the earthquake, the Soprintendenza per i Beni Architettonici e Paesaggistici of Brescia, Cremona and Mantova establish an agreement with the University Iuav of Venice, requiring an analysis and assessment of the damage in order to proceed with the development of an intervention project. This activity turned out to be very important not only from the point of view of the recovery of the architectural and artistic heritage but also because the city's economy is based primarily on tourism. The closure of one of the most important monuments of Mantova has led to a significant and alarming decline in the government income.

  8. Super-virtual refraction interferometry: an engineering field data example

    KAUST Repository

    Hanafy, Sherif M.

    2012-10-01

    The theory of super-virtual refraction interferometry (SVI) was recently developed to enhance the signal-to-noise ratio (SNR) of far-offset traces in refraction surveys. This enhancement of the SNR is proportional to √N and can be as high as N if an iterative procedure is used. Here N is the number of post-critical shot positions that coincides with the receiver locations. We now demonstrate the SNR enhancement of super-virtual refraction traces for one engineering-scale synthetic data and two field seismic data sets. The field data are collected over a normal fault in Saudi Arabia. Results show that both the SNR of the super-virtual data set and the number of reliable first-arrival traveltime picks are significantly increased. © 2012 European Association of Geoscientists & Engineers.

  9. Data quality of a low fold seismic survey employing a buried multi-component array at Ketzin

    NARCIS (Netherlands)

    Meekes, J.A.C.; Vandeweijer, V.P.; Arts, R.J.

    2011-01-01

    To monitor the migration of the injected CO2 in the Ketzin project (Germany) a permanently buried multi-component seismic array has been installed in August 2009. Besides passive seismic recordings, this monitoring system was used to record data for an active survey carried out in 2009, resulting in

  10. Uncorrected refractive errors

    Directory of Open Access Journals (Sweden)

    Kovin S Naidoo

    2012-01-01

    Full Text Available Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC, were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR Development, Service Development and Social Entrepreneurship.

  11. Uncorrected refractive errors.

    Science.gov (United States)

    Naidoo, Kovin S; Jaggernath, Jyoti

    2012-01-01

    Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

  12. Deformation Study of Papandayan Volcano using GPS Survey Method and Its Correlation with Seismic Data Observation

    Directory of Open Access Journals (Sweden)

    Dina A. Sarsito

    2006-11-01

    Full Text Available Papandayan volcano located in the southern part of Garut regency, around 70 km away from Bandung city, West Java. Many methods carried out to monitoring the activities of volcano, both continuously or periodically, one of the monitoring method is periodically GPS survey. Basically those surveys are carried out to understand the pattern and velocity of displacement which occurred in the volcano body, both horizontally and vertically, and also others deformation elements such as; translation, rotation and dilatation. The Mogi modeling was also used to determine the location and volume of the pressure source which caused deformation of volcano body. By comparing seismic activity and the deformation reveal from GPS measurement, before, during and after eruption, it could be understood there is a correlation between the seismicity and its deformation. These studies is hoping that GPS measurement in Papandayan volcano could be one of supported method to determine the volcano activities, at least in Papandayan volcano.

  13. Structure and Velocities of the Northeastern Santa Cruz Mountains and the Western Santa Clara Valley, California, from the SCSI-LR Seismic Survey

    Science.gov (United States)

    Catchings, R.D.; Goldman, M.R.; Gandhok, G.

    2006-01-01

    earthquakes sources. As one component of these joint studies, the U. S. Geological Survey acquired more than 28 km of combined seismic reflection/refraction data from the Santa Cruz Mountains to the central Santa Clara Valley in December 2000. The seismic investigation included both high-resolution (~5-m shot and sensor spacing) and relatively lower-resolution (~50-m sensor) seismic surveys from the central Santa Cruz Mountains to the central part of the valley. Collectively, we refer to these seismic investigations as the 2000 western Santa Clara Seismic Investigations (SCSI).

  14. Population-based survey of refractive error among school-aged children in rural northern China: the Heilongjiang eye study.

    Science.gov (United States)

    Li, Zhijian; Xu, Keke; Wu, Shubin; Lv, Jia; Jin, Di; Song, Zhen; Wang, Zhongliang; Liu, Ping

    2014-01-01

    The prevalence of refractive error in the north of China is unknown. The study aimed to estimate the prevalence and associated factors of refractive error in school-aged children in a rural area of northern China. Cross-sectional study. The cluster random sampling method was used to select the sample. A total of 1700 subjects of 5 to 18 years of age were examined. All participants underwent ophthalmic evaluation. Refraction was performed under cycloplegia. Association of refractive errors with age, sex, and education was analysed. The main outcome measure was prevalence rates of refractive error among school-aged children. Of the 1700 responders, 1675 were eligible. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 6.3%, 3.0% and 1.2%, respectively. The prevalence of myopia was 5.0% (84/1675, 95% CI, 4.8%-5.4%) and of hyperopia was 1.6% (27/1675, 95% CI, 1.0%-2.2%). Astigmatism was evident in 2.0% of the subjects. Myopia increased with increasing age, whereas hyperopia and astigmatism were associated with younger age. Myopia, hyperopia and astigmatism were more common in females. We also found that prevalence of refractive error were associated with education. Myopia and astigmatism were more common in those with higher degrees of education. This report has provided details of the refractive status in a rural school-aged population. Although the prevalence of refractive errors is lower in the population, the unmet need for spectacle correction remains a significant challenge for refractive eye-care services. © 2013 Royal Australian and New Zealand College of Ophthalmologists.

  15. Near-surface seismic surveys at Rifle, Colorado for shallow groundwater contamination risk assessment

    Science.gov (United States)

    Chen, J.; Zelt, C. A.; Levander, A.

    2013-12-01

    In August 2012, we carried out a series of seismic surveys at a site located approximately 0.3 mile east of the city of Rifle in Garfield County, Colorado. The ground water beneath this site was contaminated by former vanadium and uranium ore-processing operations from 1924 through 1958. The site is on an alluvial terrace created by a flood-plain meander of the Colorado River. On the south side, the terrace is bounded by a steep descending slope to the Colorado River; on the other sides, it is bounded by ascending slopes of the more resistant sedimentary rocks of the Wasatch Formation. Although remedial actions have been taken to remove the contaminated surface materials, there are still potential risks from residual materials and redistribution of the contaminated water harming human health. This seismic project, funded by The U.S. Department of Energy, was designed to provide hydrogeologic information through sub-surface velocity model building and imaging of the water aquifer. A 3D compressional wave seismic survey covers an area that is 96 m in the N-S direction by 60 m in the E-W direction. An orthogonal, symmetric receiver and source template was used with 24 receiver lines, 96 channels per receiver line, and 2.5 m between lines. The inline shot and receiver spacing is 2 m and 1 m, respectively. The source was an accelerated weight drop striking a metal plate. The source has a dominant frequency at ~60 Hz, and is down by 20 db at 20 Hz and 150 Hz, providing data suitable for seismic tomography and seismic migration methods. Besides this 3D survey, three other seismic experiments were performed: (1) a 2D multi-component source and receiver survey, (2) a 3D surface wave experiment using 4.5 Hz geophones, and (3) an ambient noise experiment using 4.5 Hz geophones to record passing vehicles and trains. Preliminary results of the data analysis will be presented.

  16. Faults survey by 3D reflection seismics; Sanjigen hanshaho jishin tansa ni yoru danso chosa

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, T.; Ejiri, T.; Yamada, N.; Narita, N.; Aso, H.; Takano, H.; Matsumura, M. [Dia Consultants Company, Tokyo (Japan)

    1996-10-01

    This paper describes fault survey by 3D seismic reflection exploration. Survey has been conducted mainly at flat land area without pavement not in urban area in Japan. Subsurface structure is complicated with intersecting multiple faults. In this area, a lot of geological investigations have been done prior to the seismic reflection exploration. Fairly certain images of faults have been obtained. However, there were still unknown structures. Survey was conducted at an area of 170m{times}280m in the CDP range. Measurements were carried out by using 100 g of dynamite per seismic generation point combined with 40 Hz velocity geophones. Fixed distribution consisting of lattice points of 12{times}12 was adopted as an observation method. In and around the lattice, a great number of explosions were carried out. The CDP stacking method and the method of migration after stacking were used for the data processing. The 3D structures of six horizons and five faults could be interpreted. Interpreted horizons were well agreed with the logging results. 3 figs.

  17. A review of shallow seismic methods

    Directory of Open Access Journals (Sweden)

    D. W. Steeples

    2000-06-01

    Full Text Available Shallow seismic methods have historical roots dating to the 1930s, when limited shallow refraction work was performed using the Intercept-Time (IT method. Because of high costs and the general lack of appropriate equipment - particularly data-processing equipment and software - the shallow-reflection and surface-wave techniques did not catch on as quickly as the refraction techniques. However, since 1980 substantial progress has been made in the development of all of the shallow seismic approaches. The seismic-reflection method has been used increasingly in applications at depths of less than 30 m, incorporating both the standard Common-Midpoint (CMP method of the petroleum industry and the Common-Offset (CO method, which was developed specifically as a low-cost technique for use in shallow surveying. In refraction studies, the Generalized Reciprocal Method (GRM largely has replaced the classical intercept-time method, and tomographic approaches are rapidly gaining popularity. The Spectral Analysis of Surface Waves (SASW has been developed by civil engineers, and surface-wave analysis involving many seismograph channels (MASW recently has shown promise. With any of the shallow seismic methods, however, selecting the appropriate seismic recording equipment, energy sources, and data-acquisition parameters, along with processing and interpretation strategies, often is critical to the success of a project.

  18. Widely used marine seismic survey air gun operations negatively impact zooplankton.

    Science.gov (United States)

    McCauley, Robert D; Day, Ryan D; Swadling, Kerrie M; Fitzgibbon, Quinn P; Watson, Reg A; Semmens, Jayson M

    2017-06-22

    Zooplankton underpin the health and productivity of global marine ecosystems. Here we present evidence that suggests seismic surveys cause significant mortality to zooplankton populations. Seismic surveys are used extensively to explore for petroleum resources using intense, low-frequency, acoustic impulse signals. Experimental air gun signal exposure decreased zooplankton abundance when compared with controls, as measured by sonar (~3-4 dB drop within 15-30 min) and net tows (median 64% decrease within 1 h), and caused a two- to threefold increase in dead adult and larval zooplankton. Impacts were observed out to the maximum 1.2 km range sampled, which was more than two orders of magnitude greater than the previously assumed impact range of 10 m. Although no adult krill were present, all larval krill were killed after air gun passage. There is a significant and unacknowledged potential for ocean ecosystem function and productivity to be negatively impacted by present seismic technology.

  19. Application of uphole data from petroleum seismic surveys to groundwater investigations, Abu Dhabi (United Arab Emirates)

    Science.gov (United States)

    Woodward, D.; Menges, C.M.

    1991-01-01

    Velocity data from uphole surveys were used to map the water table and the contact at the base dune sand/top alluvium as part of a joint National Drilling Company-United States Geological Survey Ground Water Research Project in the Emirate of Abu Dhabi. During 1981-1983, a reconnaissance seismic survey was conducted for petroleum exploration in the eastern region of Abu Dhabi. Approximately 2800 kilometers of seismic data, consisting of 92 lines, were acquired in the 2500 km2 concession area near Al Ain. Uphole surveys were conducted about 2 km apart along each seismic line, and were used to calculate weathering corrections required to further process in the seismic data. Approximately 1300 uphole surveys were completed in the concession area between March 1981 and June 1983. Reinterpretation of the velocity profiles derived from the uphole surveys provided data for determining the following subsurface layers, listed in descending order: (1) a surficial, unconsolidated weathering layer with a velocity from 300 to 450 m/s; (2) surficial dune sand, from 750 to 900 m/s; (3) unsaturated, unconsolidated alluvium, from 1000 to 1300 m/s; and (4) saturated, unconsolidated alluvium, from 1900 to 2200 m/s. Two interfaces-the water table and the base dune sand/top alluvium - were identified and mapped from boundaries between these velocity layers. Although the regional water table can fluctuate naturally as much as 3 m per year in this area and the water-table determinations from the uphole data span a 27-month period, an extremely consistent and interpretable water-table map was derived from the uphole data throughout the entire concession area. In the northern part of the area, unconfined groundwater moves northward and northwestward toward the Arabian Gulf; and in the central and southern parts of the area, groundwater moves westward away from the Oman Mountains. In the extreme southern area east of Jabal Hafit, groundwater moves southward into Oman. The map of the base

  20. Vertical Cable Seismic (VCS) Survey for SMS exploration in Izena Cauldron, Okinawa-Trough

    Science.gov (United States)

    Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hitoshi; Mizohata, Shigeharu; Tara, Kenji

    2015-04-01

    In 2014, the Japanese government started the Cross-ministerial Strategic Innovation Promotion Program (SIP), which includes 'New-generation Offshore Exploration Techniques' as an area of interest. We proposed the Vertical Cable Seismic (VCS) survey technique for this program, especially for the exploration of Seafloor Massive Sulfides (SMS). VCS is a reflection seismic method that uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by various acoustic sources. This method is useful to delineate detailed structures in a spatially-limited area below the seabed in the deep sea where conventional surface seismic is not effective. We have been developing an autonomous VCS system with the financial support of the Japanese government since 2009. We have carried out several VCS surveys and completed our VCS system. Izena Cauldron, Okinawa Trough is one of the most promising SMS areas around Japan. There are two high potential areas, the north and south mound. We carried out the first VCS survey around the north mound in 2011 and the second survey around the south mound in 2013 respectively. The first VCS survey in Izena Cauldron was carried out using a GI gun in September, 2011, with the objective of surveying the large-scale and deeper structure of the hydrothermal system. The water depth was 1,500-1,600m. Four VCS systems were deployed. The shooting lines covered an area of 9 km x 9 km with a shooting interval of about 25m and line spacing of 200m to 400m. In the second survey, we used a high-voltage sparker. The objective is to explore very shallow parts to delineate very thin SMS deposits. The survey area was about 4 km x 4km with a 12.5 m shooting interval and 100m to 200m line spacing. Three VCS systems were deployed in this survey. The result of the first GI gun VCS survey was a 3D PSDM volume of the subsurface structure. It extends 2,000m horizontally and down to 1,500m in depth. Further, by re-processing the data with a

  1. Locating Desired Source Rocks by Using Shallow Ground Penetrating Radar and Seismic Survey Methods in western Washington, Pacific Northwest of the U.S

    Science.gov (United States)

    Cakir, R.; Meng, X.; Butler, Q.; Jenkins, J.; Keck, J.; Walsh, T. J.

    2015-12-01

    The Washington State Department of Natural Resources (WADNR) manages 2.1 million acres of forested state trust lands in Washington. WADNR sells timber and other agricultural products to help fund local services and the construction of institutions such as public schools and universities. Quality of rocks used as a surface on the roads built to access the timber is the essential and selecting appropriate rock quarry locations is challenging. Traditional borehole drilling methods only provide information from discrete locations. The study was conducted in the Capitol Forest area of western Washington. In our previous study, we suggested that a combination of P-wave seismic and ground penetrating radar (GPR) can be a rapid, comprehensive and cost effective alternative for identifying desired rock sources. In this study, we further improved upon that method and accomplished the following: 1) rock quality at a relatively fine resolution was distinguished and 2) the spatial variability of the rock was identified. Both 450 MHz and 80 MHz GPR antennas were used to obtain high resolution radargrams in the near-surface zone with 5m maximum penetration depth and lower resolution radargrams in the deeper subsurface zone with about 20m maximum penetration depth. We then correlated the GPR radargrams with P-wave velocities using the refraction survey data as well as S-wave velocities, estimated using Multi-Channel Analysis of Surface Waves (MASW) survey data. Additionally, nearby test pits and boreholes (maximum depth = 15 meters) were used to confirm the geophysical measurements. Our study results demonstrate that the combination of GPR, using the two antennas, and seismic surveys provides very useful subsurface information regarding quality and spatial distribution of the rocks beneath the overburden. Subsurface images gathered from these combined geophysical methods do assist quarry operators to rapidly locate the desired rock sources.

  2. Baseline seismic survey for the 2nd offshore methane hydrate production test in the Eastern Nankai Trough

    Science.gov (United States)

    Teranishi, Y.; Inamori, T.; Kobayashi, T.; Fujii, T.; Saeki, T.; Takahashi, H.; Kobayashi, F.

    2017-12-01

    JOGMEC carries out seismic monitoring surveys before and after the 2nd offshore methane hydrate (MH) production test in the Eastern Nankai Trough and evaluates MH dissociation behavior from the time-lapse seismic response. In 2016, JOGMEC deployed Ocean Bottom Cable (OBC) system provided by OCC in the Daini Atsumi Knoll with water depths of 900-1100 m. The main challenge of the seismic survey was to optimize the cable layout for ensuring an effective time-lapse seismic detectability while overcoming the following two issues: 1. OBC receiver lines were limited to only two lines. It was predicted that the imaging of shallow reflectors would suffer from lack of continuity and resolution due to this limitation of receiver lines. 2. The seafloor and shallow sedimentary layers including monitoring target are dipping to the Northwest direction. It was predicted that the refection points would laterally shift to up-dip direction (Southeast direction). In order to understand the impact of the issues above, the seismic survey was designed with elastic wave field simulation. The reflection seismic survey for baseline data was conducted in August 2016. A total of 70 receiver stations distributed along one cable were deployed successfully and a total of 9952 shots were fired. After the baseline seismic survey, the hydrophone and geophone vertical component datasets were processed as outlined below: designaturing, denoising, surface consistent deconvolution and surface consistent amplitude correction. High-frequency imaging with Reverse Time Migration (RTM) was introduced to these data sets. Improvements in imaging from the RTM are remarkable compared to the Kirchhoff migration and the existing Pre-stack time migration with 3D marine surface seismic data obtained and processed in 2002, especially in the following parts. The MH concentrated zone which has complex structures. Below the Bottom Simulating Reflector (BSR) which is present as a impedance-contrast boundary

  3. Comment on the seismic method Depth-Recursive Tomography on Grid (DRTG) developed by Miroslav Novotný and recently published in three papers in Surveys in Geophysics

    Czech Academy of Sciences Publication Activity Database

    Hrubcová, Pavla; Środa, P.; Vavryčuk, Václav; Babuška, Vladislav; Grad, M.

    2013-01-01

    Roč. 34, č. 4 (2013), s. 521-529 ISSN 0169-3298 Institutional support: RVO:67985530 Keywords : seismic refraction method * Bohemian Massif * DRTG tomography approach Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 5.112, year: 2013

  4. GPR surveys for the characterization of foundation plinths within a seismic vulnerability analysis

    International Nuclear Information System (INIS)

    De Domenico, Domenica; Teramo, Antonio; Campo, Davide

    2013-01-01

    We present the results of GPR surveys performed to identify the foundation plinths of 12 buildings of a school, whose presence is uncertain since the structural drawings were not available. Their effective characterization is an essential element within a study aimed at assessing the seismic vulnerability of the buildings, which are non-seismically designed structures, located in an area classified as a seismic zone after their construction. Through GPR profiles acquired by two 250 MHz antennas, both in reflection mode and in a WARR configuration, the actual geometry and depth of the building plinths were successfully identified, limiting the number of invasive tests necessary to validate the GPR data interpretation, thus enabling the choice of the most suitable sites that would not alter the serviceability of the structure. The collected data were also critically analysed with reference to local environmental noise that, if causing reflections superimposed on those of the subsoil, could undermine the success of the investigation. Due to the homogeneity of the ground, the processing and results relative to each pair of profiles carried out for all of these buildings is very similar, so the results concerning only two of them are reported. (paper)

  5. Seismic Survey Report for Central Nevada Test Area, Subsurface, Correction Action Unit 443, Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Liberty, Lee M. [Boise State Univ., ID (United States). Dept. of Geosciences. Center for Geophysical Investigation of the Shallow Subsurface (CGISS)

    2008-12-19

    The seismic survey was successful in imaging the water table and underlying structures at the site. The configuration of the water table reflector confirms the general southeast horizontal flow direction in the alluvial aquifer. Offsets in the water table reflector, both at known faults that reach the surface and at subsurface faults not previously recognized, indicate that both extension and blast-related faults are barriers to lateral groundwater flow. The results from this study have been used to optimally locate two new wells designed to monitor head levels and possible contaminant migration in the alluvial aquifer at CTNA.

  6. Geophysical surveys and velocimetric measures in the Cerreto di Spoleto (Perugia) area, aiming at a seismic microzoning; Indagini geofisiche e misure velocimetriche finalizzate alla microzonazione sismica dell'area di Cerreto di Spoleto (Perugia)

    Energy Technology Data Exchange (ETDEWEB)

    Bongiovanni, G.; Martino, S.; Paciello, A.; Verrubbi, V. [ENEA, Div. Caratterizzazione dell' Ambiente e del Territorio, Centro Ricerche Csaccia, S. Maria di Galeria, Rome (Italy)

    2001-07-01

    Geophysical prospectings and velocimetric measures, aiming at the seismic microzoning of Cerreto di Spoleto area, are presented. Starting from the data obtained by previous geological-geomechanical surveys, seismic-refraction prospectings were carried on in order to obtain a dynamic characterisation and a geometrical description both of soil and rock materials. The velocimetric measures were performed by temporary free-field arrays, recording both environmental noise and small-magnitude seismic events. The analysis of the obtained records is still in progress, in order to evaluate the local seismic wave amplification. [Italian] Vengono illustrate le indagini geofisiche e le misure velocimetriche condotte nell'area di Cerreto di Spoleto (PG) per la microzonazione sismica. In particolare, sulla base dei dati geologici e geomeccanici precedentemente acquisiti, sono state effettuate indagini di sismica a rifrazione che hanno portato alla caratterizzazione dinamica dei litotipi ed alla definizione delle loro geometrie. Le misure velometriche sono state condotte installando array temporanei in free-field per la registrazione di rumore ambientale ed eventi sismici di piccola magnitudo. E' in corso l'elaborazione delle registrazioni ottenute, finalizzata all'analisi degli effetti di amplificazione sismica locale.

  7. The effect of deformation after backarc spreading between the rear arc and current volcanic front in Shikoku Basin obtained by seismic reflection survey

    Science.gov (United States)

    Yamashita, M.; Takahashi, N.; Nakanishi, A.; Kodaira, S.; Tamura, Y.

    2012-12-01

    Detailed crustal structure information of a back-arc basin must be obtained to elucidate the mechanism of its opening. Especially, the Shikoku Basin, which occupies the northern part of the Philippine Sea Plate between the Kyushu-Palau Ridge and the Izu-Bonin (Ogasawara) Arc, is an important area to understand the evolution of the back-arc basins as a part of the growth process of the Philippine Sea. Especially, the crustal structure oft the east side of Shikoku Basin is complicated by colliding to the Izu Peninsula Japan Agency for Marine-Earth Science and Technology has been carried out many multi-channel seismic reflection surveys since 2004 in Izu-Bonin region. Kodaira et al. (2008) reported the results of a refraction seismic survey along a north-south profile within paleoarc in the rear arc (i.e., the Nishi-shichito ridge) about 150 km west of current volcanic front. According to their results, the variation relationship of crustal thickness between the rear arc and volcanic front is suggested the evidence of rifting from current volcanic arc. There is the en-echelon arrangement is located in the eastern side of Shikoku Basin from current arc to rear arc, and it is known to activate after ceased spreading at 15 Ma (Okino et al., 1994) of Shikoku Basin by geologic sampling of Ishizuka et al. (2003). Our MCS results are also recognized the recent lateral fault zone is located in east side of Shikoku Basin. We carried out high density grid multi-channel seismic reflection (MCS) survey using tuned airgun in order to obtain the relationship between the lateral faults and en-echelon arrangement in KR08-04 cruise. We identified the deformation of sediments in Shikoku Basin after activity of Kanbun seamount at 8 Ma in MCS profile. It is estimated to activate a part of the eastern side of Shikoku Basin after construction of en-echelon arrangement and termination of Shikoku Basin spreading. Based on analyses of magnetic and gravity anomalies, Yamazaki and Yuasa (1998

  8. Experimental investigation on multidisciplinary geophysical characterization of deep underground structure using multi-scale, multi-mode seismic profiling for the evaluation of ground motion and seismic model building

    International Nuclear Information System (INIS)

    Abe, Susumu

    2014-01-01

    Recent advancements in data acquisition and velocity estimation for multi-mode, multiscale seismic exploration were explained along with the basic concept of strategic geophysical surveys for NPP siting assessment. Then, as a case study using this concept, multidisciplinary geophysical characterization results pertaining to the deep underground structure beneath the JNES Kashiwazaki Center were explained in detail. At the site, reflection/refraction surveys and magnetotelluric/gravity surveys were also conducted. It was shown that these surveys can be used complementary because at the upsurge part, where clear images cannot be obtained by reflection/refraction surveys, magnetotelluric /gravity surveys can be used to obtain clear images. (author)

  9. Refractive Errors

    Science.gov (United States)

    ... Conditions Frequently Asked Questions Español Condiciones Chinese Conditions Refractive Errors in Children En Español Read in Chinese How does the ... birth and can occur at any age. The prevalence of myopia is low in US children under the age of eight, but much higher ...

  10. A comparative clinical survey of the prevalence of refractive errors and eye diseases in urban and rural school children.

    Science.gov (United States)

    Uzma, Nazia; Kumar, B Santhosh; Khaja Mohinuddin Salar, B M; Zafar, Mohammed Atheshm; Reddy, V Devender

    2009-06-01

    To assess the prevalence of refractive error and common ocular diseases in school-aged children in urban and rural populations in and around Hyderabad, India. Population-based, cross-sectional study. A total of 3314 school children, 1789 from urban areas and 1525 from rural areas. The examination included visual acuity measurements, retinoscopy and autorefraction under cycloplegia, examination of the anterior segment and external eye, and ocular motility evaluation. In the urban group the prevalence of uncorrected presenting and best-corrected visual impairment (prevalence of refractive error was greater (25.2%) in the urban than the rural group (8%). Myopia measured with autorefraction was observed in 51.4% of urban children and 16.7% in rural children. Increased literacy rate, duration of study hours, and older age of the child were found to have contributed more to the prevalence of myopia in the urban group. Hyperopia with autorefraction was found to be 3.3% in the urban and 3.1% in the rural group. Hyperopia was associated with younger age in the study group. Trachoma was the leading cause of ocular morbidity in the rural group (3.5%) compared with the urban group (0.16%). Night blindness was reported in 3.2% of children in the rural group and 0.33% in the urban group. Vitamin A deficiency, low socio-economic status, and poor personal and environmental hygienic practice were found to have a positive correlation with ocular morbidity among rural group children. Provision of health education, periodic visual screening programs, and primary eye care by trained health care personnel in the elementary schools will prevent the prevalence of refractive errors and common ocular diseases in school children.

  11. Environmental implications of offshore oil and gas development in Australia. Part 2; Seismic surveys

    International Nuclear Information System (INIS)

    McCauley, R.D.

    1994-01-01

    The primary environmental concern from marine seismic surveys is the effect of the low frequency noise source on marine animals. A full spectrum of possible direct effects includes: lethal effects; pathological damage to hearing systems or other organs; behavioural changes, including repulsion from the source, startle and alarm responses and attraction to the source; and interference with the use of acoustic communication signals, or naturally produced cues used by marine animals. Indirect effects may also arise for some animals, such as changes in the abundance or behaviour of prey animals. This review defines the extent of these types of effect and elaborates on any influence with regard to the Australian marine fauna. Fauna groups discussed include plankton, invertebrates, turtles, fish, the little penguin and marine mammals such as: whales, sea lions, seals and dugong. 378 refs., 9 tabs., 16 figs

  12. Information system evolution at the French National Network of Seismic Survey (BCSF-RENASS)

    Science.gov (United States)

    Engels, F.; Grunberg, M.

    2013-12-01

    The aging information system of the French National Network of Seismic Survey (BCSF-RENASS), located in Strasbourg (EOST), needed to be updated to satisfy new practices from Computer science world. The latter means to evolve our system at different levels : development method, datamining solutions, system administration. The new system had to provide more agility for incoming projects. The main difficulty was to maintain old system and the new one in parallel the time to validate new solutions with a restricted team. Solutions adopted here are coming from standards used by the seismological community and inspired by the state of the art of devops community. The new system is easier to maintain and take advantage of large community to find support. This poster introduces the new system and choosen solutions like Puppet, Fabric, MongoDB and FDSN Webservices.

  13. Historical centers rehabilitation: documentation, survey and communication achieving sustainable development and seismic protection

    Directory of Open Access Journals (Sweden)

    Giuseppe Amoruso

    2009-12-01

    Full Text Available Italian conservation areas are recognized as the result of a generative process that shaped their form and created a complex system of layers and local languages trough centuries. Enhance the role of traditions allows to develop a sustainable built environment, to densify towns, to make strategies for social services and to make an efficient use of conservation areas for commercial purposes. The design coding address integrated actions and the interventions in conservation areas; for this purpose it is necessary to implement a correct workflow: field survey, measured drawings, pattern books, design codes and graphic building regulations. In the contemporary practice the market of sustainability and seismic protection is addressing just technology based solutions forgetting to solve the actual issues of urban design, the social and cultural growth of communities.

  14. 4-Component seismic survey in the first offshore production test of methane hydrate

    Science.gov (United States)

    Kobayashi, T.; Saeki, T.; Fujii, T.; Aoki, N.; Inamori, T.; Asakawa, E.; Takahashi, H.; Fujii, Y.

    2016-12-01

    JOGMEC conducted a gas production test in the offshore field where methane hydrates exist in the first offshore production test in March 2013. 4-component seismic survey was carried out as geophysical monitoring to assess the dissociation behaviour of methane hydrates by comparing the characteristics of seismic data before and after the gas production test. The data acquisition was performed three times using an ocean bottom cable (OBC), which installed on the sea bottom of 1000m water depth around the gas production well, consists of 36 receiver devices at an interval of 26.5 meters. The first data acquisition was performed in August 2012 before the gas production test. The second and final data acquisitions were performed in April and August 2013 after the gas production test respectively. The shooting operations using air gun source were executed in 2D lines along OBC and in pseudo 3D layout. The OBC was not collected, a connection with a recording boat was disconnected, the terminal of the OBC was waterproofed, and it had been left in the survey area after the first and the second data acquisitions. The terminal of the OBC installing on the sea bottom was fished and the OBC was reconnected into the recording boat before the second and the final data acquisitions. The OBC had been left on the sea bottom for 8 months and 4 months respectively, but the OBC could work normally and provided high quality data. In the result of the analysis of the acquired data, the change in physical properties and the decrease in impedance were seen by the data comparison before and after the gas production test, and the result which suggests dissociation of methane hydrates was obtained. In addition, the increase phenomenon of impedance from the second to the final data acquisition was seen, which suggests a possibility of the regeneration of methane hydrates.

  15. Three dimensional marine seismic survey has no measurable effect on species richness or abundance of a coral reef associated fish community

    International Nuclear Information System (INIS)

    Miller, Ian; Cripps, Edward

    2013-01-01

    Highlights: • A marine seismic survey was conducted at Scott Reef, North Western Australia. • Effects of the survey on demersal fish were gauged using underwater visual census. • There was no detectable impact of the seismic survey on species abundance. • There was no detectable impact of the seismic survey on species richness. -- Abstract: Underwater visual census was used to determine the effect of a three dimensional seismic survey on the shallow water coral reef slope associated fish community at Scott Reef. A census of the fish community was conducted on six locations at Scott Reef both before and after the survey. The census included small site attached demersal species belonging to the family Pomacentridae and larger roving demersal species belonging to the non-Pomacentridae families. These data were combined with a decade of historical data to assess the impact of the seismic survey. Taking into account spatial, temporal, spatio-temporal and observer variability, modelling showed no significant effect of the seismic survey on the overall abundance or species richness of Pomacentridae or non-Pomacentridae. The six most abundant species were also analysed individually. In all cases no detectable effect of the seismic survey was found on the abundance of these fish species at Scott Reef

  16. Characteristics of seismic survey pulses and the ambient soundscape in Baffin Bay and Melville Bay, West Greenland.

    Science.gov (United States)

    Martin, S Bruce; Matthews, Marie-Noël R; MacDonnell, Jeff T; Bröker, Koen

    2017-12-01

    In 2012 a seismic survey campaign involving four vessels was conducted in Baffin Bay, West Greenland. Long-distance (150 km) pre-survey acoustic modeling was performed in accordance with regulatory requirements. Four acoustic recorders, three with hydrophones at 100, 200, and 400 m depths, measured ambient and anthropogenic sound during the survey. Additional recordings without the surveys were made from September 2013 to September 2014. The results show that (1) the soundscape of Baffin Bay is typical for open ocean environments and Melville Bay's soundscape is dominated by glacial ice noise; (2) there are distinct multipath arrivals of seismic pulses 40 km from the array; (3) seismic sound levels vary little as a function of depth; (4) high fidelity pre-survey acoustic propagation modeling produced reliable results; (5) the daily SEL did not exceed regulatory thresholds and were different using Southall, Bowles, Ellison, Finneran, Gentry, Greene, Kastak, Ketten, Miller, Nachtigall, Richardson, Thomas, and Tyack [(2007) Aquat. Mamm. 33, 411-521] or NOAA weightings [National Marine Fisheries Service (2016). NOAA Technical Memorandum NMFS-OPR-55, p. 178]; (6) fluctuations of SPL with range were better described by additive models than linear regression; and (7) the survey increased the 1-min SPL by 28 dB, with most of the energy below 100 Hz; energy in the 16 000 Hz octave band was 20 dB above the ambient background 6 km from the source.

  17. A tomographic image of upper crustal structure using P and S wave seismic refraction data in the southern granulite terrain (SGT), India

    Science.gov (United States)

    Rajendra Prasad, B.; Behera, Laxmidhar; Rao, P. Koteswara

    2006-07-01

    We present a 2-D tomographic P and S wave velocity (Vp and Vs) image with Vp/Vs ratios along N-S trending 220 km long deep seismic profile acquired in 2005, which traverses across major shear and tectonically disturbed zones in southern granulite terrain (SGT), India. The 2-D velocity model constrained down to maximum 8 km depth shows velocity anomalies (>0.2 km/s) beneath major shear zones with good spatial resolution (>0.05 km/s). The presence of high Vp (6.3-6.5 km/s), Vs (3.5-3.8 km/s), Vp/Vs (>1.75) and Poisson's ratio (0.25-0.29) indicate significant compositional changes of rocks at shallow depths (0.5 to 8 km) reveal rapid crustal exhumation of mid to lower crustal rocks. This crustal exhumation could be responsible due to Pan-African tectonothermal activity during Neoproterozoic period.

  18. Parsimonious Refraction Interferometry and Tomography

    KAUST Repository

    Hanafy, Sherif

    2017-02-04

    We present parsimonious refraction interferometry and tomography where a densely populated refraction data set can be obtained from two reciprocal and several infill shot gathers. The assumptions are that the refraction arrivals are head waves, and a pair of reciprocal shot gathers and several infill shot gathers are recorded over the line of interest. Refraction traveltimes from these shot gathers are picked and spawned into O(N2) virtual refraction traveltimes generated by N virtual sources, where N is the number of geophones in the 2D survey. The virtual traveltimes can be inverted to give the velocity tomogram. This enormous increase in the number of traveltime picks and associated rays, compared to the many fewer traveltimes from the reciprocal and infill shot gathers, allows for increased model resolution and a better condition number with the system of normal equations. A significant benefit is that the parsimonious survey and the associated traveltime picking is far less time consuming than that for a standard refraction survey with a dense distribution of sources.

  19. Super-virtual refraction interferometry: Field data example over a colluvial wedge

    KAUST Repository

    Hanafy, Sherif M.

    2011-01-01

    The theory of super-virtual refraction interferometry was recently developed to enhance the signal-to-noise ratio (SNR) of far-offset traces in refraction surveys. This enhancement of SNR is proportional to N, and can be as high as N if an iterative procedure is used. Here N is the number of post-critical shot positions that coincides with the receiver locations. We now demonstrate the enhancement of SNR of the super-virtual refraction traces for seismic data collected over a normal fault in Saudi Arabia. Results show that both the SNR of the super-virtual data set and the number of reliable first-arrival-traveltime picks are significantly increased. © 2011 Society of Exploration Geophysicists.

  20. Assessing risk of baleen whale hearing loss from seismic surveys: The effect of uncertainty and individual variation.

    Science.gov (United States)

    Gedamke, Jason; Gales, Nick; Frydman, Sascha

    2011-01-01

    The potential for seismic airgun "shots" to cause acoustic trauma in marine mammals is poorly understood. There are just two empirical measurements of temporary threshold shift (TTS) onset levels from airgun-like sounds in odontocetes. Considering these limited data, a model was developed examining the impact of individual variability and uncertainty on risk assessment of baleen whale TTS from seismic surveys. In each of 100 simulations: 10000 "whales" are assigned TTS onset levels accounting for: inter-individual variation; uncertainty over the population's mean; and uncertainty over weighting of odontocete data to obtain baleen whale onset levels. Randomly distributed whales are exposed to one seismic survey passage with cumulative exposure level calculated. In the base scenario, 29% of whales (5th/95th percentiles of 10%/62%) approached to 1-1.2 km range were exposed to levels sufficient for TTS onset. By comparison, no whales are at risk outside 0.6 km when uncertainty and variability are not considered. Potentially "exposure altering" parameters (movement, avoidance, surfacing, and effective quiet) were also simulated. Until more research refines model inputs, the results suggest a reasonable likelihood that whales at a kilometer or more from seismic surveys could potentially be susceptible to TTS and demonstrate that the large impact uncertainty and variability can have on risk assessment.

  1. Seismic investigations in downtown Copenhagen, Denmark

    Science.gov (United States)

    Martinez, K.; Mendoza, J. A.; Olsen, H.

    2009-12-01

    Near surface geophysics are gaining widespread use in major infrastructure projects with respect to geotechnical and engineering applications. The development of data acquisition, processing tools and interpretation methods have optimized survey production, reduced logistics costs and increase results reliability of seismic surveys during the last decades. However, the use of geophysical methods under urban environments continues to face challenges due to multiple noise sources and obstacles inherent to cities. A seismic investigation was conducted in Copenhagen aiming to produce information needed for hydrological, geotechnical and groundwater modeling assessments related to the planned Cityringen underground metro project. The particular objectives were a) map variations in subsurface Quaternary and limestone properties b) to map for near surface structural features. The geological setting in the Copenhagen region is characterized by several interlaced layers of glacial till and meltwater sand deposits. These layers, which are found unevenly distributed throughout the city and present in varying thicknesses, overlie limestone of different generations. There are common occurrences of incised valley structures containing localized instances of weathered or fractured limestone. The surveys consisted of combined seismic reflection and refraction profiles accounting for approximately 13 km along sections of the projected metro line. The data acquisition was carried out using standard 192 channels arrays, receiver groups with 5 m spacing and a Vibroseis as a source at 5 m spacing. In order to improve the resolution of the data, 29 Walkaway-Vertical Seismic Profiles were performed at selected wells along the surface seismic lines. The refraction data was processed with travel-time tomography and the reflection data underwent standard interpretation. The refraction data inversion was performed twofold; a surface refraction alone and combined with the VSP data. Three

  2. Seismic stability of the survey areas of potential sites for the deep geological repository of the spent nuclear fuel

    Directory of Open Access Journals (Sweden)

    Kaláb Zdeněk

    2017-07-01

    Full Text Available This paper deals with the seismic stability of the survey areas of potential sites for the deep geological repository of the spent nuclear fuel in the Czech Republic. The basic source of data for historical earthquakes up to 1990 was the seismic website [10]. The most intense earthquake described occurred on September 15, 1590 in the Niederroesterreich region (Austria in the historical period; its reported intensity is Io = 8-9. The source of the contemporary seismic data for the period since 1991 to the end of 2014 was the website [11]. It may be stated based on the databases and literature review that in the period from 1900, no earthquake exceeding magnitude 5.1 originated in the territory of the Czech Republic.

  3. Geological Constraints on the Evolution of the Angolan Margin Based on Reflection and Refraction Seismic Data (ZaïAngo project)

    Science.gov (United States)

    Moulin, M.; Aslanian, D.; Olivet, J.; Contrucci, I.; Matias, L.; Geli, L.; Klingelhoefer, F.; Nouze, H.; Rabineau, M.; Labails, C.; Rehault, J.; Unternehr, P.

    2005-05-01

    Deep penetration multi-channel reflection and OBS wide-angle seismic data from the Congo-Angola margin were collected in 2000 during the ZaiAngo cruise (Ifremer and Total). These data help constrain the deep structure of the non-volcanic continental margin, the geometry of the pre-salt sediment layers and the geometry of the Aptian salt layer. Dating the deposition of the salt relative to the chronology of the margin formation is an issue of fundamental importance for reconstructing the evolution of the margin and for the understanding of the crustal thinning processes. The data show that the crust thins abruptly, from a 30 - 40km thickness to less than 10km, over a lateral distance of less than 50km. The transitional domain is a 180km wide basin with a thickness lower than 7 km. The pre-salt sediment layering within this basin is parallel to the base of the salt and hardly affected by tectonic deformation. In addition, the presence of a continuous salt cover, from the continental platform down to the presumed oceanic boundary, provides indications on the conditions of salt deposition that constrain the geometry of the margin at that time. These crucial observations imply shallow deposition environments during the rifting and suggest that vertical motions prevailed - compared to horizontal motions - during the formation of the basin.

  4. Geological constraints on the evolution of the Angolan margin based on reflection and refraction seismic data (ZaïAngo project)

    Science.gov (United States)

    Moulin, Maryline; Aslanian, Daniel; Olivet, Jean-Louis; Contrucci, Isabelle; Matias, Luis; Géli, Louis; Klingelhoefer, Frauke; Nouzé, Hervé; Réhault, Jean-Pierre; Unternehr, Patrick

    2005-09-01

    Deep penetration multichannel reflection and Ocean Bottom Seismometer wide-angle seismic data from the Congo-Angola margin were collected in 2000 during the ZaïAngo cruise. These data help constrain the deep structure of the continental margin, the geometry of the pre-salt sediment layers and the geometry of the Aptian salt layer. Dating the deposition of the salt relative to the chronology of the margin formation is an issue of fundamental importance for reconstructing the evolution of the margin and for the understanding of the crustal thinning processes. The data show that the crust thins abruptly, from a 30-40 km thickness to less than 10 km, over a lateral distance of less than 50 km. The transitional domain is a 180-km-wide basin. The pre-salt sediment layering within this basin is parallel to the base of the salt and hardly affected by tectonic deformation. In addition, the presence of a continuous salt cover, from the continental platform down to the presumed oceanic boundary, provides indications on the conditions of salt deposition that constrain the geometry of the margin at that time. These crucial observations imply shallow deposition environments during the rifting and suggest that vertical motions prevailed-compared to horizontal motions-during the formation of the basin.

  5. Seismic VSP and HSP surveys on preliminary investigation areas in Finland for final disposal of spent nuclear fuel

    International Nuclear Information System (INIS)

    Keskinen, J.; Cosma, C.; Heikkinen, P.

    1992-10-01

    Seismic reflection surveys in boreholes were carried out for Teollisuuden Voima Oy at five sites in Finland (Eurajoki Olkiluoto, Hyrynsalmi Veitsivaara, Konginkangas Kivetty, Kuhmo Romuvaara and Sievi Syyry). The vertical Seismic Profiling (VSP) surveys were a part of the investigation programme for the final disposal of spent nuclear fuel. The purpose was to detect fractured zones, lithological contacts and other anomalies in the structure of the rockmass and to determine their position and orientation. Horizontal Seismic Profiling (HSP) was used at the Olkiluoto site, additionally to VSP. The data has been organized in profiles containing seismograms recorded from the same shotpoint (shot gathers). One of the most powerful processing methods used with this project has been the Image Space Filtering, a new technique, which has been developed (in the project) for seismic reflection studies in crystalline rock. The method can be applied with other rock types where steeply inclined or vertical anomalies are of interest. It acts like a multichannel filter, enhancing the reflected events and also as an interpretation tool, to estimate the strength and position of the reflectors. This approach has been of great help in emphasizing the weak reflections from uneven and sometimes vanishing interfaces encountered in crystalline

  6. NNWSI [Nevada Nuclear Waste Storage Investigations] 51 seismic hole histories

    International Nuclear Information System (INIS)

    1987-09-01

    This report is a compilation of data from fifty-one shallow boreholes drilled within the Nevada Test Site (NTS) and the adjacent Bureau of Land Management (BLM) lands. The boreholes were drilled to determine the alluvial thickness and subsurface structure. Once drilled the boreholes were used to emplace explosive charges of three seismic refraction surveys conducted in 1981, 1983 and 1984. The information presented in this report includes location maps, daily activities and reviews of hole condition

  7. Generalized reciprocal method applied in processing seismic ...

    African Journals Online (AJOL)

    A geophysical investigation was carried out at Shika, near Zaria, using seismic refraction method; with the aim of analyzing the data obtained using the generalized reciprocal method (GRM). The technique is for delineating undulating refractors at any depth from in-line seismic refraction data consisting of forward and ...

  8. Comparing methods suitable for monitoring marine mammals in low visibility conditions during seismic surveys.

    Science.gov (United States)

    Verfuss, Ursula K; Gillespie, Douglas; Gordon, Jonathan; Marques, Tiago A; Miller, Brianne; Plunkett, Rachael; Theriault, James A; Tollit, Dominic J; Zitterbart, Daniel P; Hubert, Philippe; Thomas, Len

    2018-01-01

    Loud sound emitted during offshore industrial activities can impact marine mammals. Regulations typically prescribe marine mammal monitoring before and/or during these activities to implement mitigation measures that minimise potential acoustic impacts. Using seismic surveys under low visibility conditions as a case study, we review which monitoring methods are suitable and compare their relative strengths and weaknesses. Passive acoustic monitoring has been implemented as either a complementary or alternative method to visual monitoring in low visibility conditions. Other methods such as RADAR, active sonar and thermal infrared have also been tested, but are rarely recommended by regulatory bodies. The efficiency of the monitoring method(s) will depend on the animal behaviour and environmental conditions, however, using a combination of complementary systems generally improves the overall detection performance. We recommend that the performance of monitoring systems, over a range of conditions, is explored in a modelling framework for a variety of species. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  9. Seismic motions from project Rulison

    International Nuclear Information System (INIS)

    Loux, P.C.

    1970-01-01

    In the range from a few to a few hundred km, seismic measurements from the Rulison event are shown and compared with experimentally and analytically derived pre-event estimates. Seismograms, peak accelerations, and response spectra are given along with a description of the associated geologic environment. Techniques used for the pre-event estimates are identified with emphasis on supportive data and on Rulison results. Of particular interest is the close-in seismic frequency content which is expected to contain stronger high frequency components. This higher frequency content translates into stronger accelerations within the first tens of km, which in turn affect safety preparations. Additionally, the local geologic structure at nearby population centers must be considered. Pre-event reverse profile refraction surveys are used to delineate the geology at Rifle, Rulison, Grand Valley, and other sites. The geologic parameters are then used as input to seismic amplification models which deliver estimates of local resonant frequencies. Prediction of such resonances allows improved safety assurance against seismic effects hazards. (author)

  10. The availability of hydrogeologic data associated with areas identified by the US Geological Survey as experiencing potentially induced seismicity resulting from subsurface injection

    Science.gov (United States)

    Barnes, Caitlin; Halihan, Todd

    2018-05-01

    A critical need exists for site-specific hydrogeologic data in order to determine potential hazards of induced seismicity and to manage risk. By 2015, the United States Geological Survey (USGS) had identified 17 locations in the USA that are experiencing an increase in seismicity, which may be potentially induced through industrial subsurface injection. These locations span across seven states, which vary in geological setting, industrial exposure and seismic history. Comparing the research across the 17 locations revealed patterns for addressing induced seismicity concerns, despite the differences between geographical locations. Most induced seismicity studies evaluate geologic structure and seismic data from areas experiencing changes in seismic activity levels, but the inherent triggering mechanism is the transmission of hydraulic pressure pulses. This research conducted a systematic review of whether data are available in these locations to generate accurate hydrogeologic predictions, which could aid in managing seismicity. After analyzing peer-reviewed research within the 17 locations, this research confirms a lack of site-specific hydrogeologic data availability for at-risk areas. Commonly, formation geology data are available for these sites, but hydraulic parameters for the seismically active injection and basement zones are not available to researchers conducting peer-reviewed research. Obtaining hydrogeologic data would lead to better risk management for injection areas and provide additional scientific evidential support for determining a potentially induced seismic area.

  11. The availability of hydrogeologic data associated with areas identified by the US Geological Survey as experiencing potentially induced seismicity resulting from subsurface injection

    Science.gov (United States)

    Barnes, Caitlin; Halihan, Todd

    2017-12-01

    A critical need exists for site-specific hydrogeologic data in order to determine potential hazards of induced seismicity and to manage risk. By 2015, the United States Geological Survey (USGS) had identified 17 locations in the USA that are experiencing an increase in seismicity, which may be potentially induced through industrial subsurface injection. These locations span across seven states, which vary in geological setting, industrial exposure and seismic history. Comparing the research across the 17 locations revealed patterns for addressing induced seismicity concerns, despite the differences between geographical locations. Most induced seismicity studies evaluate geologic structure and seismic data from areas experiencing changes in seismic activity levels, but the inherent triggering mechanism is the transmission of hydraulic pressure pulses. This research conducted a systematic review of whether data are available in these locations to generate accurate hydrogeologic predictions, which could aid in managing seismicity. After analyzing peer-reviewed research within the 17 locations, this research confirms a lack of site-specific hydrogeologic data availability for at-risk areas. Commonly, formation geology data are available for these sites, but hydraulic parameters for the seismically active injection and basement zones are not available to researchers conducting peer-reviewed research. Obtaining hydrogeologic data would lead to better risk management for injection areas and provide additional scientific evidential support for determining a potentially induced seismic area.

  12. Borehole-explosion and air-gun data acquired in the 2011 Salton Seismic Imaging Project (SSIP), southern California: description of the survey

    Science.gov (United States)

    Rose, Elizabeth J.; Fuis, Gary S.; Stock, Joann M.; Hole, John A.; Kell, Annie M.; Kent, Graham; Driscoll, Neal W.; Goldman, Mark; Reusch, Angela M.; Han, Liang; Sickler, Robert R.; Catchings, Rufus D.; Rymer, Michael J.; Criley, Coyn J.; Scheirer, Daniel S.; Skinner, Steven M.; Slayday-Criley, Coye J.; Murphy, Janice M.; Jensen, Edward G.; McClearn, Robert; Ferguson, Alex J.; Butcher, Lesley A.; Gardner, Max A.; Emmons, Iain; Loughran, Caleb L.; Svitek, Joseph R.; Bastien, Patrick C.; Cotton, Joseph A.; Croker, David S.; Harding, Alistair J.; Babcock, Jeffrey M.; Harder, Steven H.; Rosa, Carla M.

    2013-01-01

    The Imperial and Coachella Valleys are being formed by active plate-tectonic processes. From the Imperial Valley southward into the Gulf of California, plate motions are rifting the continent apart. In the Coachella Valley, the plates are sliding past one another along the San Andreas and related faults (fig. 1). These processes build the stunning landscapes of the region, but also produce damaging earthquakes. Rupture of the southern section of the San Andreas Fault (SAF), from the Coachella Valley to the Mojave Desert, is believed to be the greatest natural hazard that California will face in the near future. With an estimated magnitude between 7.2 and 8.1, such an event would result in violent shaking, loss of life, and disruption of infrastructure (freeways, aqueducts, power, petroleum, and communication lines) that might bring much of southern California to a standstill. As part of the nation’s efforts to avert a catastrophe of this magnitude, a number of projects have been undertaken to more fully understand and mitigate the effects of such an event. The Salton Seismic Imaging Project (SSIP), funded jointly by the National Science Foundation (NSF) and the U.S. Geological Survey (USGS), seeks to understand, through seismic imaging, the structure of the Earth surrounding the SAF, including the sedimentary basins on which cities are built. The principal investigators (PIs) of this collaborative project represent the USGS, Virginia Polytechnic Institute and State University (Virginia Tech), California Institute of Technology (Caltech), Scripps Institution of Oceanography (Scripps), University of Nevada, Reno (UNR), and Stanford University. SSIP will create images of underground structure and sediments in the Imperial and Coachella Valleys and adjacent mountain ranges to investigate the earthquake hazards posed to cities in this area. Importantly, the images will help determine the underground geometry of the SAF, how deep the sediments are, and how fast

  13. Deep Seismic Reflection Profiling in Africa

    Science.gov (United States)

    Attoh, K.; Brown, L. D.

    2006-05-01

    Africa represents one of the true frontiers for systematic deep seismic reflection profiling of the type pioneered by COCORP, LITHOPROBE, BIRPS, DEKORP, and ECORS in the northern hemisphere. However, there have been a number of notable individual surveys that have sampled key components of the African lithosphere, and several systematic regional geophysical initiatives which suggest African is fertile ground for future efforts. Among the latter are the KRISP refraction/wide-angle program to probe the East African Rift system in the 1990's, the Kaapvaal Experiment to image the deep lithosphere with passive techniques and most recently the EAGLE active/passive experiments in the Afar. Examples of true multichannel deep reflection surveys to delineate crustal structure include the transects of the Limpopo Belt, a Neoarchean mobile zone that sutures the Kaapval and Zimbabwe cratons, deep oil prospecting surveys in the Nosop basin of southern Botswana that reveal dramatic basement reflectors off the NW margin of the Kaapvaal craton, and most recently deep vibroseis surveys within the Kaapvaal craton that indicate a crustal stack of tectonic slivers as well as tectonic shingling of the upper mantle. The passive margin of western Africa, with its strategic oil resources, has been a target of several deep studies using marine seismic surveys, including the PROBE initiative of the late 1980's and more recent deep surveys offshore Angola. Reprocessing of lines from oil exploration grids reveal Proterozoic mid-lower crustal features offshore of Ghana. Among the potentially rich targets for future surveys in Africa are the West African and Congo cratons and their suturing Pan-African (Neoproterozoic) mobile belts. This suite of cratonic lithosphere elements is largely largely untouched by modern high resolution seismic methodologies. New initiatives such as LEGENDS ( targeting the East African Orogen) and exploitation of existing oil industry seismic data for deep information

  14. REFRACTIVE NEUTRON LENS

    OpenAIRE

    Petrov, P. V.; Kolchevsky, N. N.

    2013-01-01

    Compound concave refractive lenses are used for focusing neutron beam. Investigations of spectral and focusing properties of a refractive neutron lens are presented. Resolution of the imaging system on the base of refractive neutron lenses depends on material properties and parameters of neutron source. Model of refractive neutron lens are proposed. Results of calculation diffraction resolution and focal depth of refractive neutron lens are discussed.

  15. Assessing the deep drilling potential of Lago de Tota, Colombia, with a seismic survey

    Science.gov (United States)

    Bird, B. W.; Wattrus, N. J.; Fonseca, H.; Velasco, F.; Escobar, J.

    2015-12-01

    Reconciling orbital-scale patterns of inter-hemispheric South American climate during the Quaternary requires continuous, high-resolution paleoclimate records that span multiple glacial cycles from both hemispheres. Southern Andean Quaternary climates are represented by multi-proxy results from Lake Titicaca (Peru-Bolivia) spanning the last 400 ka and by pending results from the Lago Junin Drilling Project (Peru). Although Northern Andean sediment records spanning the last few million years have been retrieved from the Bogota and Fúquene Basins in the Eastern Cordillera of the Colombian Andes, climatic reconstructions based on these cores have thus far been limited to pollen-based investigations. When viewed together with the Southern Hemisphere results, these records suggest an anti-phased hemispheric climatic response during glacial cycles. In order to better assess orbital-scale climate responses, however, independent temperature and hydroclimate proxies from the Northern Hemisphere are needed in addition to vegetation histories. As part of this objective, an effort is underway to develop a paleoclimate record from Lago de Tota (3030 m asl), the largest lake in Colombia and the third largest lake in the Andes. One of 17 highland tectonic basins in Eastern Cordillera, Lago de Tota formed during Tertiary uplift that deformed pre-foreland megasequences, synrift and back-arc megasequences. The precise age and thickness of sediments in the Lago de Tota basin has not previously been established. Here, we present results from a recent single-channel seismic reflection survey collected with a small (5 cubic inch) air gun and high-resolution CHIRP sub-bottom data. With these data, we examine the depositional history and sequence stratigraphy of Lago de Tota and assess its potential as a deep drilling target.

  16. Seismic texture and amplitude analysis of large scale fluid escape pipes using time lapses seismic surveys: examples from the Loyal Field (Scotland, UK)

    Science.gov (United States)

    Maestrelli, Daniele; Jihad, Ali; Iacopini, David; Bond, Clare

    2016-04-01

    Fluid escape pipes are key features of primary interest for the analysis of vertical fluid flow and secondary hydrocarbon migration in sedimentary basin. Identified worldwide (Løset et al., 2009), they acquired more and more importance as they represent critical pathways for supply of methane and potential structure for leakage into the storage reservoir (Cartwright & Santamarina, 2015). Therefore, understanding their genesis, internal characteristics and seismic expression, is of great significance for the exploration industry. Here we propose a detailed characterization of the internal seismic texture of some seal bypass system (e.g fluid escape pipes) from a 4D seismic survey (released by the BP) recently acquired in the Loyal Field. The seal by pass structure are characterized by big-scale fluid escape pipes affecting the Upper Paleogene/Neogene stratigraphic succession in the Loyal Field, Scotland (UK). The Loyal field, is located on the edge of the Faroe-Shetland Channel slope, about 130 km west of Shetland (Quadrants 204/205 of the UKCS) and has been recently re-appraised and re developed by a consortium led by BP. The 3D detailed mapping analysis of the full and partial stack survey (processed using amplitude preservation workflows) shows a complex system of fluid pipe structure rooted in the pre Lista formation and developed across the paleogene and Neogene Units. Geometrical analysis show that pipes got diameter varying between 100-300 m and a length of 500 m to 2 km. Most pipes seem to terminate abruptly at discrete subsurface horizons or in diffuse termination suggesting multiple overpressured events and lateral fluid migration (through Darcy flows) across the overburden units. The internal texture analysis of the large pipes, (across both the root and main conduit zones), using near, medium and far offset stack dataset (processed through an amplitude preserved PSTM workflow) shows a tendency of up-bending of reflection (rather than pulls up artefacts

  17. Subsurface Deformation in the Gangetic Plain - First results from the BrahmaSeis multichannel seismic survey on Bangladesh Rivers

    Science.gov (United States)

    Spiess, V.; Schwenk, T.; Palamenghi, L.; Goodbred, S. L.; Steckler, M. S.; Seeber, L.; Petter, A. L.; Akhter, S. H.; Mondal, D.; Khan, S. R.

    2012-12-01

    In Bangladesh, the northeastern boundary of the Indian-Asian collision zone is buried under thick delta sediments, delivered in huge volumes by the Ganges-Brahmaputra-Meghna river system. Monsoon-induced erosion provided several tens of meters of Holocene sediments to a subsiding delta plain, and it therefore remains a challenge to reconstruct the plate boundary, fault planes and main deformational styles and phases. While structural investigations with seismic methods on land are particularly difficult in the country, the distinctly elevated water level after the peak monsoon season provided the opportunity of a water seismic survey, utilizing marine seismic equipment and approaches. As part of the BanglaPIRE project, a first multichannel seismic survey had been carried out in September 2011 particularly on the rivers Meghna and Jamuna to find and map indications for subsurface deformation and the associated response of the sediment dispersal system during the late Quaternary development of the Gangetic delta plain. Using a high-resolution 48-channel streamer and a micro GI-Gun with 0.1 L volume, supported by two small diving compressors, continuous airgun profiles were acquired in several daily stretches along both rivers northward to the Indian border. Major challenges were, among others, a lack of navigational fixpoints in a rapidly changing delta and river landscape, the lack of clearly defined strata in a predominantly sandy environment, and the widespread occurrence of large amounts of shallow gas. In the northernmost stretch of the survey, the Dauki Fault, bounding the Shillong Plateau uplift on the southern side, is supposed to be covered by sediment in the slowly subsiding Sylhet Basin. On the Meghna river in central Bangladesh, the westernmost extent of the Indo-Burman Fold Belt was assumed. And on Jamuna, the western extension of the Dauki Fault and its interaction with the main river system is as unclear. The acquired multichannel seismic data, using

  18. Refractive errors survey in primary school children (6-12 year old) in 2 provinces: Bangkok and Nakhonpathom (one year result).

    Science.gov (United States)

    Yingyong, Penpimol

    2010-10-01

    Refractive error is an important cause of preventable visual impairment and blindness worldwide. Population-based studies will continue to be a key part in identification ofthe magnitude and the importance of this common eye disease. To assess the prevalence of the refractive error in primary school-aged children in Bangkok and Nakhonpathom together with the provision of the appropriately free of charge spectacles. A Population-based cross-sectional analytic study was conducted between October 2008 and September 2009. Random selection of geographically defined clusters was used to identify the study sample. The examination included visual acuity (VA) by Snellen chart and pinhole correction, autorefraction under cycloplegic refraction, ocular motility evaluation, examination of the external eye, anterior segment, media, and fundus. Ophthalmologists screened for ocular abnormalities. Among 2340 children, 1100 in Bangkok and 1240 in Nakhonpathom were examined The prevalence of refractive error in Bangkok and Nakhornpathom were 12.7% and 5.7% respectively. Refractive error was the cause in 97.6% of eyes with reduced vision, amblyopia in 0.5%, other causes in 0.8%, and unexplained causes in 1.1%. The present study showed a relative high prevalence of uncorrected refractive error in the central part of Thailand especially in Bangkok. Eye health education and screening is recommended to evaluate the need for refractive correction with appropriate prescription of spectacles.

  19. Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

    KAUST Repository

    Aldawood, Ali

    2012-02-26

    onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data. To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets. We use Interferometric Green\\'s functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this "virtual" trace. We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a "super-virtual" trace at B in the far-offset from a source at W. Stacking N traces gives a vN-improvement. We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage

  20. RADIO REFRACTIVITY RADIO REFRACTIVITY STUDY IN AKURE ...

    African Journals Online (AJOL)

    eobe

    P. O. Otasowie. O. Otasowie1,* and F. O. Edeko2. 1, 2 DEPT. OF ELECTRICAL AND ELECTRONIC ENGINEERING, UNIVERSITY OF BENIN, BENIN CITY, EDO ... refractivity gradient is thus defined as: ∆. ∆. (4). Refractivity gradients change with time leading to anomalous propagation conditions. There is a convenient ...

  1. National Archive of Marine Seismic Surveys (NAMSS): A USGS-Boem Partnership to Provide Free and Easy Access to Previously Proprietary Seismic Reflection Data on the U.S. Outer Continental Shelf

    Science.gov (United States)

    Triezenberg, P. J.; Hart, P. E.; Childs, J. R.

    2014-12-01

    The National Archive of Marine Seismic Surveys (NAMSS) was established by the USGS in 2004 in an effort to rescue marine seismic reflection profile data acquired largely by the oil exploration industry throughout the US outer continental shelf (OCS). It features a Web interface for easy on-line geographic search and download. The commercial value of these data had decreased significantly because of drilling moratoria and newer acquisition technology, and large quantities were at risk of disposal. But, the data still had tremendous value for scientific research and education purposes, and an effort was undertaken to ensure that the data were preserved and publicly available. More recently, the USGS and Bureau of Ocean Energy Management (BOEM) have developed a partnership to make similarly available a much larger quantity of 2D and 3D seismic data acquired by the U.S. government for assessment of resources in the OCS. Under Federal regulation, BOEM is required to publicly release all processed geophysical data, including seismic profiles, acquired under an exploration permit, purchased and retained by BOEM, no sooner than 25 years after issuance of the permit. Data acquired prior to 1989 are now eligible for release. Currently these data are distributed on CD or DVD, but data discovery can be tedious. Inclusion of these data within NAMSS vastly increases the amount of seismic data available for research purposes. A new NAMSS geographical interface provides easy and intuitive access to the data library. The interface utilizes OpenLayers, Mapnik, and the Django web framework. In addition, metadata capabilities have been greatly increased using a PostgresSQL/PostGIS database incorporating a community-developed ISO-compliant XML template. The NAMSS database currently contains 452 2D seismic surveys comprising 1,645,956 line km and nine 3D seismic surveys covering 9,385 square km. The 2D data holdings consist of stack, migrated and depth sections, most in SEG-Y format.

  2. Pattern Of Refractive Errors Among Computer Users In A Nigerian ...

    African Journals Online (AJOL)

    Background: Refractive error is a common cause of ocular morbidity. Computer use is associated with eye strain which may be due to refractive errors. Objective: To ascertain the prevalence and pattern of refractive errors among computer users. Method: A cross-sectional survey of 560 computer users in Enugu urban, ...

  3. Existing reflection seismic data re-processing

    International Nuclear Information System (INIS)

    Higashinaka, Motonori; Sano, Yukiko; Kozawa, Takeshi

    2005-08-01

    This document is to report the results of existing seismic data re-processing around Horonobe town, Hokkaido, Japan, which is a part of the Horonobe Underground Research Project. The main purpose of this re-processing is to recognize the subsurface structure of Omagari Fault and fold system around Omagari Fault. The seismic lines for re-processing are TYHR-A3 line and SHRB-2 line, which JAPEX surveyed in 1975. Applying weathering static correction using refraction analysis and noise suppression procedure, we have much enhanced seismic profile. Following information was obtained from seismic re-processing results. TYHR-A3 line: There are strong reflections, dipping to the west. These reflections are corresponding western limb of anticline to the west side of Omagari Fault. SHRB-2 line: There are strong reflections, dipping to the west, at CDP 60-140, while there are reflections, dipping to the east, to the east side of CDP 140. These reflections correspond to the western limb and the eastern limb of the anticline, which is parallel to Omagari FAULT. This seismic re-processing provides some useful information to know the geological structure around Omagari Fault. (author)

  4. Contributions to a shallow aquifer study by reprocessed seismic sections from petroleum exploration surveys, eastern Abu Dhabi, United Arab Emirates

    Science.gov (United States)

    Woodward, D.

    1994-01-01

    The US Geological Survey, in cooperation with the National Drilling Company of Abu Dhabi, is conducting a 4-year study of the fresh and slightly saline groundwater resources of the eastern Abu Dhabi Emirate. Most of this water occurs in a shallow aquifer, generally less than 150 m deep, in the Al Ain area. A critical part of the Al Ain area coincides with a former petroleum concession area where about 2780 km of vibroseis data were collected along 94 seismic lines during 1981-1983. Field methods, acquistion parameters, and section processing were originally designed to enhance reflections expected at depths ranging from 5000 to 6000 m, and subsurface features directly associated with the shallow aquifer system were deleted from the original seismic sections. The original field tapes from the vibroseis survey were reprocessed in an attempt to extract shallow subsurface information (depths less than 550 m) for investigating the shallow aquifer. A unique sequence of reproccessing parameters was established after reviewing the results from many experimental tests. Many enhancements to the resolution of shallow seismic reflections resulted from: (1) application of a 20-Hz, low-cut filter; (2) recomputation of static corrections to a datum nearer the land surface; (3) intensive velocity analyses; and (4) near-trace muting analyses. The number, resolution, and lateral continuity of shallow reflections were greatly enhanced on the reprocessed sections, as was the delineation of shallow, major faults. Reflections on a synthetic seismogram, created from a borehole drilled to a depth of 786 m on seismic line IQS-11, matcheddprecisely with shallow reflections on the reprocessed section. The 33 reprocessed sections were instrumental in preparing a map showing the major structural features that affect the shallow aquifer system. Analysis of the map provides a better understanding of the effect of these shallow features on the regional occurrence, movement, and quality of

  5. Surface-wave separation and its impact on seismic survey design

    NARCIS (Netherlands)

    Ishiyama, T.

    2015-01-01

    Surface waves in seismic data are often dominant and mask primaries in land or shallow-water environments. Separating them from the primaries is of great importance either for removing them as noise for reservoir imaging and characterization, or for considering them as signal for near-surface

  6. Three-dimensional seismic survey planning based on the newest data acquisition design technique; Saishin no data shutoku design ni motozuku sanjigen jishin tansa keikaku

    Energy Technology Data Exchange (ETDEWEB)

    Minehara, M.; Nakagami, K.; Tanaka, H. [Japan National Oil Corp., Tokyo (Japan). Technology Research Center

    1996-10-01

    Theory of parameter setting for data acquisition is arranged, mainly as to the seismic generating and receiving geometry. This paper also introduces an example of survey planning for three-dimensional land seismic exploration in progress. For the design of data acquisition, fundamental parameters are firstly determined on the basis of the characteristics of reflection records at a given district, and then, the layout of survey is determined. In this study, information through modeling based on the existing interpretation of geologic structures is also utilized, to reflect them for survey specifications. Land three-dimensional seismic survey was designed. Ground surface of the surveyed area consists of rice fields and hilly regions. The target was a nose-shaped structure in the depth about 2,500 m underground. A survey area of 4km{times}5km was set. Records in the shallow layers could not obtained when near offset was not ensured. Quality control of this distribution was important for grasping the shallow structure required. In this survey, the seismic generating point could be ensured more certainly than initially expected, which resulted in the sufficient security of near offset. 2 refs., 2 figs.

  7. A critique of the UK's JNCC seismic survey guidelines for minimising acoustic disturbance to marine mammals: Best practise?

    International Nuclear Information System (INIS)

    Parsons, E.C.M.; Dolman, Sarah J.; Jasny, Michael; Rose, Naomi A.; Simmonds, Mark P.; Wright, Andrew J.

    2009-01-01

    The United Kingdom's statutory conservation agency, the Joint Nature Conservation Committee (JNCC), developed guidelines in 1995 to minimise acoustic disturbance of marine mammals by oil and gas industry seismic surveys. These were the first national guidelines to be developed and have subsequently become the standard, or basis, of international mitigation measures for noise pollution during seismic surveys. However, relatively few aspects of these measures have a firm scientific basis or proven efficacy. Existing guidelines do not offer adequate protection to marine mammals, given the complex propagation of airgun pulses; the difficulty of monitoring in particular the smaller, cryptic, and/or deep-diving species, such as beaked whales and porpoises; limitations in monitoring requirements; lack of baseline data; and other biological and acoustical complications or unknowns. Current guidelines offer a 'common sense' approach to noise mitigation, but in light of recent research and ongoing concerns, they should be updated, with broader measures needed to ensure adequate species protection and to address data gaps.

  8. Seismic reflection survey in Omama fan area, Gunma prefecture; Gunma Omama senjochi ni okeru hanshaho jishin tansa

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, K.; Kano, N.; Yokokura, T.; Kiguchi, T.; Yokota, T.; Matsushima, J. [Geological Survey of Japan, Tsukuba (Japan)

    1996-10-01

    Seismic reflection survey was performed for the Medial Tectonic Line, an important geological tectonic line in the Kanto plains, at Kushibiki district, Saitama prefecture in the north-western part of the Kanto plains. It was estimated that movements of the basement were different in the individual sides of the active fault. In this study, the seismic reflection survey was performed at the Omama fan area, Gunma prefecture, which is located at the north-eastern extension of the Kushibiki plateau, to grasp the structure of basement to the depth of about 1.0 s of return travel time, and the upper sediments. Two traverse lines passing Ota city, Kiryu city, and Nitta town were used. Southern part of the traverse line-1 was in the bottom land in the middle of Tone river, and northern part was in the Omama fan area. The ground surface along the traverse line was flat. Hachioji heights are the heights elongating in the NW-SE direction and having relative height of 100 to 200 m against the surrounding plain. Another traverse line-2 was set on the steep slope having relative height more than 100 m. The Brute stack time section of each traverse line was characterized by the gradient reflection surface AA of the traverse line-1. It was suggested that the AA or intermittent parts of reflection surfaces deeper than AA may relate to the tectonic lines in the more ancient geological ages. 2 figs., 1 tab.

  9. A critique of the UK's JNCC seismic survey guidelines for minimising acoustic disturbance to marine mammals: best practise?

    Science.gov (United States)

    Parsons, E C M; Dolman, Sarah J; Jasny, Michael; Rose, Naomi A; Simmonds, Mark P; Wright, Andrew J

    2009-05-01

    The United Kingdom's statutory conservation agency, the Joint Nature Conservation Committee (JNCC), developed guidelines in 1995 to minimise acoustic disturbance of marine mammals by oil and gas industry seismic surveys. These were the first national guidelines to be developed and have subsequently become the standard, or basis, of international mitigation measures for noise pollution during seismic surveys. However, relatively few aspects of these measures have a firm scientific basis or proven efficacy. Existing guidelines do not offer adequate protection to marine mammals, given the complex propagation of airgun pulses; the difficulty of monitoring in particular the smaller, cryptic, and/or deep-diving species, such as beaked whales and porpoises; limitations in monitoring requirements; lack of baseline data; and other biological and acoustical complications or unknowns. Current guidelines offer a 'common sense' approach to noise mitigation, but in light of recent research and ongoing concerns, they should be updated, with broader measures needed to ensure adequate species protection and to address data gaps.

  10. Toward long-term all-sky time domain surveys-SINDICS: a prospective concept for a Seismic INDICes Survey of half a million red giants

    Directory of Open Access Journals (Sweden)

    Michel Eric

    2015-01-01

    Full Text Available CoRoT and Kepler have brought a new and deep experience in long-term photometric surveys and how to use them. This is true for exoplanets characterizing, stellar seismology and beyond for studying several other phenomena, like granulation or activity. Based on this experience, it has been possible to propose new generation projects, like TESS and PLATO, with more specific scientific objectives and more ambitious observational programs in terms of sky coverage and/or duration of the observations. In this context and as a prospective exercise, we explore here the possibility to set up an all-sky survey optimized for seismic indices measurement, providing masses, radii and evolution stages for half a million solar-type pulsators (subgiants and red giants, in our galactic neighborhood and allowing unprecedented stellar population studies.

  11. Predictive habitat modelling of humpback (Megaptera novaeangliae) and Antarctic minke (Balaenoptera bonaerensis) whales in the Southern Ocean as a planning tool for seismic surveys

    Science.gov (United States)

    Bombosch, Annette; Zitterbart, Daniel P.; Van Opzeeland, Ilse; Frickenhaus, Stephan; Burkhardt, Elke; Wisz, Mary S.; Boebel, Olaf

    2014-09-01

    Seismic surveys are frequently a matter of concern regarding their potentially negative impacts on marine mammals. In the Southern Ocean, which provides a critical habitat for several endangered cetacean species, seismic research activities are undertaken at a circumpolar scale. In order to minimize impacts of these surveys, pre-cruise planning requires detailed, spatio-temporally resolved knowledge on the likelihood of encountering these species in the survey area. In this publication we present predictive habitat modelling as a potential tool to support decisions for survey planning. We associated opportunistic sightings (2005-2011) of humpback (Megaptera novaeangliae, N=93) and Antarctic minke whales (Balaenoptera bonaerensis, N=139) with a range of static and dynamic environmental variables. A maximum entropy algorithm (Maxent) was used to develop habitat models and to calculate daily basinwide/circumpolar prediction maps to evaluate how species-specific habitat conditions evolved throughout the spring and summer months. For both species, prediction maps revealed considerable changes in habitat suitability throughout the season. Suitable humpback whale habitat occurred predominantly in ice-free areas, expanding southwards with the retreating sea ice edge, whereas suitable Antarctic minke whale habitat was consistently predicted within sea ice covered areas. Daily, large-scale prediction maps provide a valuable tool to design layout and timing of seismic surveys as they allow the identification and consideration of potential spatio-temporal hotspots to minimize potential impacts of seismic surveys on Antarctic cetacean species.

  12. Optimization of dynamic source depth for seismic surveys. Part 7; Dynamite shingen no hasshin shindo no saitekika ni tsuite (hyoso kozo no suitei (kusssetsuho jishin tansa oyobi denki denjiho tansa)). 7

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, H.; Murayama, R.; Mitsuhata, Y.; Ishikawa, H. [Japan National Oil Corp., Tokyo (Japan). Technology Research Center

    1996-05-01

    For the improvement of quality of data collected by reflection aided seismic exploration using dynamite as the seismic source, information has to be collected about the surface layer structure before the charge depth is determined. For this purpose, refraction, electric, and electromagnetic exploration methods were tried. In the refraction method, an impactor was used as the seismic source. In the records, the surface wave prevails because vibration was generated on the surface. Analysis was made by the use of the initial travel time tomography. In the electric exploration, a double pole array was used to measure resistivity. The measured data was subjected to a fully automatic inversion for analysis. As the result, it was disclosed that it was useful to know the deep-level structure directly by use of tomographic methods in refraction seismic exploration so as to find the optimum charge level. Furthermore, about the electric and electromagnetic exploration techniques, it was found that these methods can be applied making use of resistivity to the evaluation of groundwater saturation. 7 refs., 5 figs., 3 tabs.

  13. Three dimensional marine seismic survey has no measurable effect on species richness or abundance of a coral reef associated fish community.

    Science.gov (United States)

    Miller, Ian; Cripps, Edward

    2013-12-15

    Underwater visual census was used to determine the effect of a three dimensional seismic survey on the shallow water coral reef slope associated fish community at Scott Reef. A census of the fish community was conducted on six locations at Scott Reef both before and after the survey. The census included small site attached demersal species belonging to the family Pomacentridae and larger roving demersal species belonging to the non-Pomacentridae families. These data were combined with a decade of historical data to assess the impact of the seismic survey. Taking into account spatial, temporal, spatio-temporal and observer variability, modelling showed no significant effect of the seismic survey on the overall abundance or species richness of Pomacentridae or non-Pomacentridae. The six most abundant species were also analysed individually. In all cases no detectable effect of the seismic survey was found on the abundance of these fish species at Scott Reef. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  14. A 3D Numerical Survey of Seismic Waves Inside and Around an Underground Cavity

    Science.gov (United States)

    Esterhazy, S.; Schneider, F. M.; Perugia, I.; Bokelmann, G.

    2016-12-01

    Motivated by the need to detect an underground cavity within the procedure of an On-Site-Inspection (OSI) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), which might be caused by a nuclear explo- sion/weapon testing, we present our findings of a numerical study on the elastic wave propagation inside and around such an underground cavity.The aim of the CTBTO is to ban all nuclear explosions of any size anywhere, by anyone. Therefore, it is essential to build a powerful strategy to efficiently investigate and detect critical signatures such as gas filled cavities, rubble zones and fracture networks below the surface. One method to investigate the geophysical properties of an under- ground cavity allowed by the Comprehensive Nuclear-test Ban Treaty is referred to as "resonance seismometry" - a resonance method that uses passive or active seismic techniques, relying on seismic cavity vibrations. This method is in fact not yet entirely determined by the Treaty and there are also only few experimental examples that have been suitably documented to build a proper scientific groundwork. This motivates to investigate this problem on a purely numerical level and to simulate these events based on recent advances in the mathematical understanding of the underlying physical phenomena.Our numerical study includes the full elastic wave field in three dimensions. We consider the effects from an in- coming plane wave as well as point source located in the surrounding of the cavity at the surface. While the former can be considered as passive source like a tele-seismic earthquake, the latter represents a man-made explosion or a viborseis as used for/in active seismic techniques. For our simulations in 3D we use the discontinuous Galerkin Spectral Element Code SPEED developed by MOX (The Laboratory for Modeling and Scientific Computing, Department of Mathematics) and DICA (Department of Civil and Environmental Engineering) at the Politecnico di Milano. The

  15. On the quantitative determination of coal seam thickness by means of in-seam seismic surveys

    Czech Academy of Sciences Publication Activity Database

    Schott, W.; Waclawik, Petr

    2015-01-01

    Roč. 52, č. 10 (2015), s. 1496-1504 ISSN 0008-3674. [International Colloquium on Geomechanics and Geophysics /5./. Karolinka, 25.06.2014-27.06.2014] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : in-seam seismic (ISS) * ISS wave * Love wave * coal seam thickness * dispersion Subject RIV: DH - Mining , incl. Coal Mining Impact factor: 1.877, year: 2015 http://www.nrcresearchpress.com/doi/full/10.1139/cgj-2014-0466#.VgqE1Zc70mt

  16. On the quantitative determination of coal seam thickness by means of in-seam seismic surveys

    Czech Academy of Sciences Publication Activity Database

    Schott, W.; Waclawik, Petr

    2015-01-01

    Roč. 52, č. 10 (2015), s. 1496-1504 ISSN 0008-3674. [International Colloquium on Geomechanics and Geophysics /5./. Karolinka, 25.06.2014-27.06.2014] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : in-seam seismic (ISS) * ISS wave * Love wave * coal seam thickness * dispersion Subject RIV: DH - Mining, incl. Coal Mining Impact factor: 1.877, year: 2015 http://www.nrcresearchpress.com/doi/full/10.1139/cgj-2014-0466#.VgqE1Zc70mt

  17. Multisensor surveys of historical buildings before, during and after a seismic sequence: the leaning bell tower of Ficarolo (Rovigo)

    Science.gov (United States)

    Teza, Giordano; Pesci, Arianna; Trevisani, Sebastiano

    2014-05-01

    Three regions of Northern Italy (Emilia Romagna, Veneto and Lombardy) were struck in May-June 2012 by a seismic sequence that included a moment magnitude 5.9 earthquake. Such a sequence caused significant damage to several historical buildings; in some cases complete structural collapse occurred. The 69-m high bell tower of Ficarolo (Rovigo province, Northern Italy) leans at a significant angle (~3° in the shaft). Because the combination of height and leaning angle is visually impressive, Ficarolo is also known as the 'Pisa of Polesine' (Polesine is the Venetian bank of the Po River), referring to the well-known 55-m high, 4° leaning tower of Pisa. A project aimed at studying the geometry of the tower, by means of terrestrial laser scanning (TLS), possible local seismic amplification and soil-structure interaction (SSI), by means of low-cost operational modal analysis (OMA) and geophysical measurements, began in early 2012, before the earthquake. In particular, the first series of data were taken in February 2012 (OMA) and April 2012 (TLS). The distance from Ficarolo of the epicenters of the six events with moment magnitude higher than 5.0 ranged from 9 km to 37 km. Several cracks appeared in the bell tower belfry and cusp. An inclinometer installed in 2003 showed that the base was unchanged, but the upper part of the shaft had moved by 2.5 cm after the main shock. No further displacements were detected as a result of the aftershocks. The repetition of the TLS and OMA surveys during and after the seismic sequence, together with infrared thermal imaging (IRT) measurements, allowed an evaluation of the changes caused by the earthquake. Two main results were obtained: (1) an estimate of earthquake induced damage to the Ficarolo's bell tower, which were relatively limited thanks to absence of SSI, and (2) it was demonstrated that fast measurements can be repeated during earthquake emergencies and that preventive measures can be carried out under reasonable time and

  18. Seismic reflection survey at Ayer Hangat site to investigate shallow subsurface structures

    Science.gov (United States)

    Khalil, Amin E.; Nawawi, Mohd; Kamel, Rami

    2016-01-01

    Ayer Hangat site is located in the island of Langkawi, northwest Malaysia. The site is characterized by the presence of hot spring. This hot spring is believed to be related to granitic intrusion nearby. Hence the present work is focusing on defining the shallow subsurface structures that control the migration of hot water to the surface. Seismic reflection method is used to achieve the goal of the present study. Forty three shot points were used with an offset of 5m of the nearest geophone. The shot-points interval is set to 1m. Seismograms were recorded on 24 channel TERRALOC instrument. The Geophone interval used was 1m. Conventional seismic data processing scheme was adopted. However, due to the fact that TERRALOC produce SEG2 data files, a script based on Obspy was written and used to convert to SEG-Y format. Afterwards, analyses were carried out using SU Package. The processed data is used to develop a model for the subsurface controlling structures. Such model will help in the understanding of the geothermal hot spring system in the area.

  19. Global positioning system survey data for active seismic and volcanic areas of eastern Sicily, 1994 to 2013.

    Science.gov (United States)

    Bonforte, Alessandro; Fagone, Sonia; Giardina, Carmelo; Genovese, Simone; Aiesi, Gianpiero; Calvagna, Francesco; Cantarero, Massimo; Consoli, Orazio; Consoli, Salvatore; Guglielmino, Francesco; Puglisi, Biagio; Puglisi, Giuseppe; Saraceno, Benedetto

    2016-08-01

    This work presents and describes a 20-year long database of GPS data collected by geodetic surveys over the seismically and volcanically active eastern Sicily, for a total of more than 6300 measurements. Raw data were initially collected from the various archives at the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania-Osservatorio Etneo and organized in a single repository. Here, quality and completeness checks were performed, while all necessary supplementary information were searched, collected, validated and organized together with the relevant data. Once all data and information collections were completed, raw binary data were converted into the universal ASCII RINEX format; all data are provided in this format with the necessary information for precise processing. In order to make the data archive readily consultable, we developed software allowing the user to easily search and obtain the needed data by simple alphanumeric and geographic queries.

  20. Global positioning system survey data for active seismic and volcanic areas of eastern Sicily, 1994 to 2013

    Science.gov (United States)

    Bonforte, Alessandro; Fagone, Sonia; Giardina, Carmelo; Genovese, Simone; Aiesi, Gianpiero; Calvagna, Francesco; Cantarero, Massimo; Consoli, Orazio; Consoli, Salvatore; Guglielmino, Francesco; Puglisi, Biagio; Puglisi, Giuseppe; Saraceno, Benedetto

    2016-08-01

    This work presents and describes a 20-year long database of GPS data collected by geodetic surveys over the seismically and volcanically active eastern Sicily, for a total of more than 6300 measurements. Raw data were initially collected from the various archives at the Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania—Osservatorio Etneo and organized in a single repository. Here, quality and completeness checks were performed, while all necessary supplementary information were searched, collected, validated and organized together with the relevant data. Once all data and information collections were completed, raw binary data were converted into the universal ASCII RINEX format; all data are provided in this format with the necessary information for precise processing. In order to make the data archive readily consultable, we developed software allowing the user to easily search and obtain the needed data by simple alphanumeric and geographic queries.

  1. Atmospheric refraction : a history

    NARCIS (Netherlands)

    Lehn, WH; van der Werf, S

    2005-01-01

    We trace the history of atmospheric refraction from the ancient Greeks up to the time of Kepler. The concept that the atmosphere could refract light entered Western science in the second century B.C. Ptolemy, 300 years later, produced the first clearly defined atmospheric model, containing air of

  2. Iterative supervirtual refraction interferometry

    KAUST Repository

    Al-Hagan, Ola

    2014-05-02

    In refraction tomography, the low signal-to-noise ratio (S/N) can be a major obstacle in picking the first-break arrivals at the far-offset receivers. To increase the S/N, we evaluated iterative supervirtual refraction interferometry (ISVI), which is an extension of the supervirtual refraction interferometry method. In this method, supervirtual traces are computed and then iteratively reused to generate supervirtual traces with a higher S/N. Our empirical results with both synthetic and field data revealed that ISVI can significantly boost up the S/N of far-offset traces. The drawback is that using refraction events from more than one refractor can introduce unacceptable artifacts into the final traveltime versus offset curve. This problem can be avoided by careful windowing of refraction events.

  3. Improvement of high resolution borehole seismics. Part 1: Development of processing methods for VSP surveys. Part 2: Piezoelectric signal transmitter for seismic measurements

    International Nuclear Information System (INIS)

    Cosma, C.; Heikkinen, P.; Pekonen, S.

    1991-05-01

    The purpose of the high resolution borehole seismics project has been to improve the reliability and resolution of seismic methods in the particular environment of nuclear waste repository sites. The results obtained, especially the data processing and interpretation methods developed, are applicable also to other geophysical methods (e.g. Georadar). The goals of the seismic development project have been: the development of processing and interpretation techniques for mapping fractured zones, and the design and construction of a seismic source complying with the requirements of repository site characterization programs. Because these two aspects of the work are very different in nature, we have structured the report as two self contained parts. Part 1 describes the development of interpretive techniques. We have used for demonstrating the effect of different methods a VSP data set collected at the SCV site during Stage 1 of the project. Five techniques have been studied: FK-filtering, three versions of Tau-p filtering and a new technique that we have developed lately, Image Space filtering. Part 2 refers to the construction of the piezoelectric source. Earlier results obtained over short distances with low energy piezoelectric transmitters let us believe that the same principle could be applied for seismic signal transmitters, if solutions for higher energy and lower frequency output were found. The instrument which we have constructed is a cylindrical unit which can be placed in a borehole and is able to produce a radial strain when excited axially. The minimum borehole diameter is 56 mm. (au)

  4. Laboratory seismic anisotropy in mylonites

    Science.gov (United States)

    Almqvist, B. S. G.; Herwegh, M.; Hirt, A. M.; Ebert, A.; Linckens, J.; Precigout, J.; Leiss, B.; Walter, J. M.; Burg, J.-P.

    2012-04-01

    Tectonic strain is often accommodated along narrow zones in the Earth's crust and upper mantle, and these high-strain zones represent an important mechanical and rheological component in geodynamics. In outcrop we observe the intense deformation along and across these structures. But at depth, in the mid and lower crust, and in the mantle, we are dependent on geophysical methods for analysis of structures, such as seismic reflection and refraction surveys. A natural progression has therefore been to understand the remote geophysical signal in terms of laboratory ultrasonic pulse transmission measurements on rock cores, collected in the field or from borehole drill core. Here we first present a brief review that consider key studies in the area of laboratory seismic measurements in strongly anisotropic rocks, ranging from calcite mylonites to metapelites. In the second part we focus attention on ongoing research projects targetting laboratory seismic anisotropy in mylonitized rocks, and associated challenges. Measurements of compressional (P) and shear (S) waves were made at high confining pressure (up to 5 kbar). Mineral texture analysis was performed with electron backscatter diffraction (EBSD) and neutron texture diffraction to determine crystallographic preferred orientation (CPO). So-called "rock-recipe" models are used to calculate seismic anisotropy, which consider the elastic properties of minerals that constitutes the rock, and their respective CPO. However, the outcome of such models do not always simply correspond to the measured seismic anisotropy. Differences are attributed to several factors, such as grain boundaries, mineral microstructures including shape-preferred orientation (SPO), micro-cracks and pores, and grain-scale stress-strain conditions. We highlight the combination of these factors in case studies on calcite and peridotite mylonites. In calcite mylonites, sampled in the Morcles nappe shear zone, the measured seismic anisotropy generally

  5. Forearc oceanic crust in the Izu-Bonin arc - new insights from active-source seismic survey -

    Science.gov (United States)

    Kodaira, S.; Noguchi, N.; Takahashi, N.; Ishizuka, O.; Kaneda, Y.

    2009-12-01

    Petrological studies have suggested that oceanic crust is formed in forearc areas during the initial stage of subduction. However, there is little geophysical evidence for the formation of oceanic crust in those regions. In order to examine crustal formation process associated with a subduction initiation process, we conducted an active-source seismic survey at a forearc region in the Izu-Bonin intra-oceanic arc. The resultant seismic image shows a remarkably thin crust (less than 10 km) at the northern half of the Bonin ridge (at the north of the Chichi-jima) and abrupt thickening the crust (~ 20 km thick) toward the south (at the Haha-jima). Comparison of velocity-depth profiles of the thin forearc crust of the Bonin ridge with those of typical oceanic crusts showed them to be seismologically identical. The observed structural variation also well corresponds to magmatic activities along the forearc. Boninitic magmatism is evident in the area of thin crust and tholeiitic-calcalkaline andesitic volcanism in the area of thick crust. Based on high precision dating studies of those volcanic rocks, we interpreted that the oceanic-type thin crust associated with boninitic volcanism has been created soon after the initiation of subduction (45-48 Ma) and and that the nonoceanic thick crust was created by tholeiitic-calcalkaline andesitic magmatism after the boninitic magmatism was ceased. The above seismological evidences strongly support the idea of forearc oceanic crust (or phiolite) created by forearc spreading in the initial stage of subduction along the intra-oceanic arc.

  6. Earthquake Scenarios Based Upon the Data and Methodologies of the U.S. Geological Survey's National Seismic Hazard Mapping Project

    Science.gov (United States)

    Rukstales, K. S.; Petersen, M. D.; Frankel, A. D.; Harmsen, S. C.; Wald, D. J.; Quitoriano, V. R.; Haller, K. M.

    2011-12-01

    The U.S. Geological Survey's (USGS) National Seismic Hazard Mapping Project (NSHMP) utilizes a database of over 500 faults across the conterminous United States to constrain earthquake source models for probabilistic seismic hazard maps. Additionally, the fault database is now being used to produce a suite of deterministic ground motions for earthquake scenarios that are based on the same fault source parameters and empirical ground motion prediction equations used for the probabilistic hazard maps. Unlike the calculated hazard map ground motions, local soil amplification is applied to the scenario calculations based on the best available Vs30 (average shear-wave velocity down to 30 meters) mapping, or in some cases using topographic slope as a proxy. Systematic outputs include all standard USGS ShakeMap products, including GIS, KML, XML, and HAZUS input files. These data are available from the ShakeMap web pages with a searchable archive. The scenarios are being produced within the framework of a geographic information system (GIS) so that alternative scenarios can readily be produced by altering fault source parameters, Vs30 soil amplification, as well as the weighting of ground motion prediction equations used in the calculations. The alternative scenarios can then be used for sensitivity analysis studies to better characterize uncertainty in the source model and convey this information to decision makers. By providing a comprehensive collection of earthquake scenarios based upon the established data and methods of the USGS NSHMP, we hope to provide a well-documented source of data which can be used for visualization, planning, mitigation, loss estimation, and research purposes.

  7. Crustal characteristic variation in the central Yamato Basin, Japan Sea back-arc basin, deduced from seismic survey results

    Science.gov (United States)

    Sato, Takeshi; No, Tetsuo; Miura, Seiichi; Kodaira, Shuichi

    2018-02-01

    The crustal structure of the Yamato Bank, the central Yamato Basin, and the continental shelf in the southern Japan Sea back-arc basin is obtained based on a seismic survey using ocean bottom seismographs and seismic shot to elucidate the back-arc basin formation processes. The central Yamato Basin can be divided into three domains based on the crustal structure: the deep basin, the seamount, and the transition domains. In the deep basin domain, the crust without the sedimentary layer is about 12-13 km thick. Very few units have P-wave velocity of 5.4-6.0 km/s, which corresponds to the continental upper crust. In the seamount and transition domains, the crust without the sedimentary layer is about 12-16 km thick. The P-wave velocities of the upper and lower crusts differs among the deep basin, the seamount, and the transition domains. These results indicate that the central Yamato Basin displays crustal variability in different domains. The crust of the deep basin domain is oceanic in nature and suggests advanced back-arc basin development. The seamount domain might have been affected by volcanic activity after basin opening. In the transition domain, the crust comprises mixed characters of continental and oceanic crust. This crustal variation might represent the influence of different processes in the central Yamato Basin, suggesting that crustal development was influenced not only by back-arc opening processes but also by later volcanic activity. In the Yamato Bank and continental shelf, the upper crust has thickness of about 17-18 km and P-wave velocities of 3.3-4.1 to 6.6 km/s. The Yamato Bank and the continental shelf suggest a continental crustal character.

  8. Use of shallow seismic surveys in the exploration of nearshore placers off Maharashtra coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Rajamanickam, G.V.; Ramana, M.V.; Gujar, A.R.

    depth. These surveys water used for the first time in this country by the authors to determine (1) the lateral continuity of the placers below the clay, (2) the vertical thickness of placer sand and to use the same for the calculation of the inferred...

  9. Seismic Vulnerability Evaluations Within The Structural And Functional Survey Activities Of The COM Bases In Italy

    International Nuclear Information System (INIS)

    Zuccaro, G.; Cacace, F.; Albanese, V.; Mercuri, C.; Papa, F.; Pizza, A. G.; Sergio, S.; Severino, M.

    2008-01-01

    The paper describes technical and functional surveys on COM buildings (Mixed Operative Centre). This activity started since 2005, with the contribution of both Italian Civil Protection Department and the Regions involved. The project aims to evaluate the efficiency of COM buildings, checking not only structural, architectonic and functional characteristics but also paying attention to surrounding real estate vulnerability, road network, railways, harbours, airports, area morphological and hydro-geological characteristics, hazardous activities, etc. The first survey was performed in eastern Sicily, before the European Civil Protection Exercise ''EUROSOT 2005''. Then, since 2006, a new survey campaign started in Abruzzo, Molise, Calabria and Puglia Regions. The more important issue of the activity was the vulnerability assessment. So this paper deals with a more refined vulnerability evaluation technique by means of the SAVE methodology, developed in the 1st task of SAVE project within the GNDT-DPC programme 2000-2002 (Zuccaro, 2005); the SAVE methodology has been already successfully employed in previous studies (i.e. school buildings intervention programme at national scale; list of strategic public buildings in Campania, Sicilia and Basilicata). In this paper, data elaborated by SAVE methodology are compared with expert evaluations derived from the direct inspections on COM buildings. This represents a useful exercise for the improvement either of the survey forms or of the methodology for the quick assessment of the vulnerability

  10. Seismic Vulnerability Evaluations Within The Structural And Functional Survey Activities Of The COM Bases In Italy

    Science.gov (United States)

    Zuccaro, G.; Albanese, V.; Cacace, F.; Mercuri, C.; Papa, F.; Pizza, A. G.; Sergio, S.; Severino, M.

    2008-07-01

    The paper describes technical and functional surveys on COM buildings (Mixed Operative Centre). This activity started since 2005, with the contribution of both Italian Civil Protection Department and the Regions involved. The project aims to evaluate the efficiency of COM buildings, checking not only structural, architectonic and functional characteristics but also paying attention to surrounding real estate vulnerability, road network, railways, harbours, airports, area morphological and hydro-geological characteristics, hazardous activities, etc. The first survey was performed in eastern Sicily, before the European Civil Protection Exercise "EUROSOT 2005". Then, since 2006, a new survey campaign started in Abruzzo, Molise, Calabria and Puglia Regions. The more important issue of the activity was the vulnerability assessment. So this paper deals with a more refined vulnerability evaluation technique by means of the SAVE methodology, developed in the 1st task of SAVE project within the GNDT-DPC programme 2000-2002 (Zuccaro, 2005); the SAVE methodology has been already successfully employed in previous studies (i.e. school buildings intervention programme at national scale; list of strategic public buildings in Campania, Sicilia and Basilicata). In this paper, data elaborated by SAVE methodology are compared with expert evaluations derived from the direct inspections on COM buildings. This represents a useful exercise for the improvement either of the survey forms or of the methodology for the quick assessment of the vulnerability.

  11. 75 FR 39335 - Incidental Takes of Marine Mammals During Specified Activities; Marine Seismic Survey in the...

    Science.gov (United States)

    2010-07-08

    ... enforcement of laws and treaties. The Healy is a USCG icebreaker, capable of traveling at 5.6 km/hour (three... (Haley and Ireland, 2006; Haley, 2006; Jackson and DesRoches, 2008; Mosher et al., 2009). The estimated... Breaking Ice Outside of U.S. Waters for the Proposed Arctic Ocean Survey (Haley and Ireland, 2006; Haley...

  12. Structural characteristics around the frontal thrust along the Nankai Trough revealed by bathymetric and seismic reflection survey

    Science.gov (United States)

    Yamashita, M.; Nakanishi, A.; Moore, G. F.; Kodaira, S.; Nakamura, Y.; Miura, S.; Kaneda, Y.

    2016-12-01

    Great earthquakes with tsunamis with recurrence intervals of 100-200 years have occurred along the Nankai Trough near central Japan where the Shikoku Basin is subducting with thick sediments on the Philippine Sea plate. To predict the exact height of the tsunami on the coast region generated by these large ruptures, it is important to estimate the vertical deformation that occurs on the seaward end of the rupture area. Recent drilling results have also yielded evidence not only of splay faults that generate tsunamigenic rupture, but also new evidence of tsunamigenic rupture along the frontal thrust at the trench axis in the Nankai Trough. In order to understand the deformation around the frontal thrust at the trench axis, we conducted a dense high-resolution seismic reflection survey with 10-20 km spacing over 1500 km of line length during 2013 and 2014. Clear seismic reflection images of frontal thrusts in the accretionary prism and subducting Shikoku Basin, image deformation along the trench axis between off Muroto Cape and off Ashizuri Cape. The cumulative displacement along the frontal thrust and second thrust are measured from picked distinct reflectors in depth-converted profiles. The average value of cumulative displacement of the frontal thrust is more than 100 m within 2 km depth beneath the seafloor. The location of highest displacement of 300 m displacement agree with the seaward end of slip distribution of the 1946 Nankai event calculated by numerical simulations. We also evaluate the seaward structure for understanding the future rupture distribution. The protothrust zone (PTZ) consisting of many incipient thrusts is identifiable in the portion of trough-fill sediments seaward of the frontal thrust. In order to emphasize the characteristics of frontal thrust and PTZ, we construct the detailed relief image for focusing on the lineated slope of the PTZ at the trough axis. Although our surveys covered a part of Nankai seismogenic zone, it is important to

  13. Alternative Refractive Surgery Procedures

    Science.gov (United States)

    ... the epithelial cells. Once the epithelial flap is created and moved aside, the procedure is the same ... Sites EyeWiki International Society of Refractive Surgery * Required * First Name: * Last Name: Member ID: * Phone Number: * Email: * ...

  14. A comparison of the seismic structure of oceanic island arc crust and continental accreted arc terranes

    Science.gov (United States)

    Calvert, A. J.

    2015-12-01

    Amalgamation of island arcs and their accretion to pre-existing continents is considered to have been one of the primary mechanisms of continental growth over the last 3 Ga, with arc terranes identified within Late Archean, Proterozoic, and Phanerozoic continental crust. Crustal-scale seismic refraction surveys can provide P wave velocity models that can be used as a proxy for crustal composition, and although they indicate some velocity variation in accreted arcs, these terranes have significantly lower velocities, and are hence significantly more felsic, than modern island arcs. Modern oceanic arcs exhibit significant variations in crustal thickness, from as little as 10 km in the Bonin arc to 35 km in the Aleutian and northern Izu arcs. Although globally island arcs appear to have a mafic composition, intermediate composition crust is inferred in central America and parts of the Izu arc. The absence of a sharp velocity contrast at the Moho appears to be a first order characteristic of island arc crust, and indicates the existence of a broad crust-mantle transition zone. Multichannel seismic reflection surveys complement refraction surveys by revealing structures associated with variations in density and seismic velocity at the scale of a few hundred meters or less to depths of 60 km or more. Surveys from the Mariana and Aleutian arcs show that modern middle and lower arc crust is mostly non-reflective, but reflections are observed from depths 5-25 km below the refraction Moho suggesting the localized presence of arc roots that may comprise gabbro, garnet gabbro, and pyroxenite within a broad transition from mafic lower crust to ultramafic mantle. Such reflective, high velocity roots are likely separated from the overlying arc crust prior to, or during arc-continent collision, and seismic reflections within accreted arc crust document the collisional process and final crustal architecture.

  15. Increasing the number and signal-to-noise ratio of OBS traces with supervirtual refraction interferometry and free-surface multiples

    KAUST Repository

    Bharadwaj, P.

    2013-01-10

    The theory of supervirtual interferometry is modified so that free-surface related multiple refractions can be used to enhance the signal-to-noise ratio (SNR) of primary refraction events by a factor proportional to√Ns, where Ns is the number of post-critical sources for a specified refraction multiple. We also show that refraction multiples can be transformed into primary refraction events recorded at virtual hydrophones located between the actual hydrophones. Thus, data recorded by a coarse sampling of ocean bottom seismic (OBS) stations can be transformed, in principle, into a virtual survey with P times more OBS stations, where P is the order of the visible free-surface related multiple refractions. The key assumption is that the refraction arrivals are those of head waves, not pure diving waves. The effectiveness of this method is validated with both synthetic OBS data and an OBS data set recorded offshore from Taiwan. Results show the successful reconstruction of far-offset traces out to a source-receiver offset of 120 km. The primary supervirtual traces increase the number of pickable first arrivals from approximately 1600 to more than 3100 for a subset of the OBS data set where the source is only on one side of the recording stations. In addition, the head waves associated with the first-order free-surface refraction multiples allow for the creation of six new common receiver gathers recorded at virtual OBS station located about half way between the actual OBS stations. This doubles the number of OBS stations compared to the original survey and increases the total number of pickable traces from approximately 1600 to more than 6200. In summary, our results with the OBS data demonstrate that refraction interferometry can sometimes more than quadruple the number of usable traces, increase the source-receiver offsets, fill in the receiver line with a denser distribution of OBS stations, and provide more reliable picking of first arrivals. Apotential liability

  16. TOMO-ETNA MED-SUV.ISES an active seismic and passive seismic experiment at Mt. Etna volcano. An integrated marine and onland geophysical survey.

    Science.gov (United States)

    Ibáñez, Jesus. M.; Patane, Domenico; Puglisi, Guisseppe; Zuccarello, Lucciano; Bianco, Francesca; Luehr, Birger; Diaz-Moreno, Alejandro; Prudencio, Janire; Koulakov, Ivan; Del Pezzo, Edoardo; Cocina, Ornella; Coltelli, Mauro; Scarfi, Lucciano; De Gori, Pascuale; Carrion, Francisco

    2014-05-01

    An active seismic experiment to study the internal structure of Etna Volcano is going to carried out on Sicily and Aeolian islands. The main objective of the TOMO-ETNA MED-SUV.ISES experiment, beginning in summer 2014, is to perform a high resolution seismic tomography, in velocity and attenuation, in Southern Italy, by using active and passive seismic data, in an area encompassing outstanding volcanoes as Mt. Etna, and Aeolian volcanoes. The achievement of this objective is based on the integration and sharing of the in-situ marine and land experiments and observations and on the implementation of new instruments and monitoring systems. For the purpose, onshore and offshore seismic stations and passive and active seismic data generated both in marine and terrestrial environment will be used. Additionally, other geophysical data, mainly magnetic and gravimetric data will be considered to obtain a joint Upper Mantle-Crust structure that could permit to make progress in the understanding of the dynamic of the region. This multinational experiment which involves institutions from Spain, Italy, Germany, United Kingdom, Ireland, France, Malta, Portugal, Russia, USA and Mexico. During the experiment more than 6.600 air gun shots performed by the Spanish Oceanographic vessel "Sarmiento de Gamboa" will be recorder on a dense local seismic network consisting of 100 on land non-permanent stations, 70 on land permanent stations and 20-25 OBSs. Contemporaneously other marine geophysical measures will be performed using a marine Gravimeter LaCoste&Romberg Air-Sea Gravity System II and a Marine Magnetometer SeaSPY. The experiments will provide a unique data set in terms of data quantity and quality, and it will provide a detailed velocity and attenuation structural image of volcano edifice. The results will be essential in the development and interpretation of future volcanic models. It is noteworthy that this project is fully transversal, multidisciplinary and crosses several

  17. Controlled-Source Seismic Imaging of Rift Processes and Earthquake Hazards in the Salton Trough

    Science.gov (United States)

    Hole, J. A.; Stock, J. M.; Fuis, G. S.

    2008-12-01

    The NSF MARGINS program, the NSF EarthScope program, and the U.S. Geological Survey have funded a large seismic refraction and reflection survey of the Salton Trough in southern California and northern Mexico, including the Coachella, Imperial, and Mexicali Valleys. The purpose of this presentation is to communicate plans for the seismic project and encourage synergy with piggyback and complementary studies. Fieldwork is tentatively scheduled for January 2010. The goals of the project include both rifting processes at the northern end of the Gulf of California extensional province and earthquake hazards at the southern end of the San Andreas Fault system. In the central Salton Trough, North American lithosphere appears to have been rifted completely apart. The 20-22 km thick crust is apparently composed entirely of new crust added by magmatism from below and sedimentation from above. The seismic survey will investigate the style of continental breakup, the role and mode of magmatism, the effects of rapid Colorado River sedimentation upon extension and magmatism, and the partitioning of oblique extension. The southernmost San Andreas Fault is considered at high risk of producing a large damaging earthquake, yet structure of the fault and adjacent basins are not currently well constrained. To improve hazard models, the seismic survey will image the structure of the San Andreas and Imperial Faults, structure of sedimentary basins in the Salton Trough, and three-dimensional seismic velocity of the crust and uppermost mantle.

  18. JNCC guidelines for minimising the risk of injury and disturbance to marine mammals from seismic surveys: We can do better.

    Science.gov (United States)

    Wright, Andrew J; Cosentino, A Mel

    2015-11-15

    The U.K.'s Joint Nature Conservation Committee 1998 guidelines for minimising acoustic impacts from seismic surveys on marine mammals were the first of their kind. Covering both planning and operations, they included various measures for reducing the potential for damaging hearing - an appropriate focus at the time. Since introduction, the guidelines have been criticised for, among other things: the arbitrarily-sized safety zones; the lack of shut-down provisions; the use of mitigation measures that introduce more noise into the environment (e.g., soft-starts); inadequate observer training; and the lack of standardised data collection protocols. Despite the concerns, the guidelines have remained largely unchanged. Moreover, increasing scientific recognition of the scope and magnitude of non-injurious impacts of sound on marine life has become much more widespread since the last revisions in 2010. Accordingly, here we present feasible and realistic recommendations for such improvements, in light of the current state of knowledge. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Controlled-source seismic reflection interferometry : Virtual-source retrieval, survey infill and identification of surface multiples

    NARCIS (Netherlands)

    Boullenger, B.

    2017-01-01

    The theory of seismic interferometry predicts that the cross-correlation (and possibly summation) between seismic recordings at two separate receivers allows the retrieval of an estimate of the inter-receiver response, or Green's function, from a virtual source at one of the receiver positions.

  20. Prevalence of refractive errors among junior high school students in ...

    African Journals Online (AJOL)

    Among school children, uncorrected refractive errors have a considerable impact on their participation and learning in class. The aim of this study was to assess the prevalence of refractive error among students in the Ejisu-Juabeng Municipality of Ghana. A survey with multi-stage sampling was undertaken. We interviewed ...

  1. Cetaceans and chelonians stranding coastal monitoring: fundamental tool to mitigate impacts of seismic survey activities; Projeto de monitoramento costeiro de encalhes de cetacoes e quelonios: ferramenta fundamental para mitigacao de impactos em atividades de pesquisa sismica

    Energy Technology Data Exchange (ETDEWEB)

    Amaro, Thays P.C.; Carloni, Giuliano G.; Erber, Claudia; Sabino, Carla M. [Ecologus Engenharia Consultiva, Rio de Janeiro, RJ (Brazil); Uller, George A. [CGGVeritas, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The objective of this research is to highlight PMVE implementation as a basic tool to conservation of marine cetaceans and turtles. These organisms are threaten to extinction and are pointed out as the organisms potentially affected by the seismic survey. The monitoring of the seismic survey activity realized in blocks BM-C-26 e BM-C-27 lasted six months embracing 200 km of beaches, from Rio de Janeiro North up to the Espirito Santo South coasts. It was realized by thirty four monitors, who covered a beach section daily registering the founded animal. 159 chelonians occurrence registers were realized and fifteen registers of cetaceans. The results gotten in PMVE give additional information for the evaluation of possible impacts of seismic survey's activities in registered species. Besides, these information contribute to increase technical scientific knowledge related to effect of seismic survey activity in marine biot at Campos Basin. (author)

  2. Estimation of subsurface structures in a Minami Noshiro 3D seismic survey region by seismic-array observations of microtremors; Minami Noshiro sanjigen jishin tansa kuikinai no hyoso kozo ni tsuite. Bido no array kansoku ni yoru suitei

    Energy Technology Data Exchange (ETDEWEB)

    Okada, H.; Ling, S.; Ishikawa, K. [Hokkaido University, Sapporo (Japan); Tsuburaya, Y.; Minegishi, M. [Japan National Oil Corp., Tokyo (Japan). Technology Research Center

    1997-05-27

    Japan National Oil Corporation Technology Research Center has carried out experiments on the three-dimensional seismic survey method which is regarded as an effective means for petroleum exploration. The experiments were conducted at the Minami Noshiro area in Akita Prefecture. Seismometer arrays were developed in radii of 30 to 300 m at seven points in the three-dimensional seismic exploration region to observe microtremors. The purpose is to estimate S-wave velocities from the ground surface to the foundation by using surface waves included in microtremors. Estimation of the surface bed structure is also included in the purpose since this is indispensable in seismic exploration using the reflection method. This paper reports results of the microtremor observations and the estimation on S-wave velocities (microtremor exploration). One or two kinds of arrays with different sizes composed of seven observation points per area were developed to observe microtremors independently. The important point in the result obtained in the present experiments is that a low velocity bed suggesting existence of faults was estimated. It will be necessary to repeat experiments and observations in the future to verify whether this microtremor exploration method has that much of exploration capability. For the time being, however, interest is addressed to considerations on comparison with the result of 3D experiments using the reflection method. 4 refs., 7 figs.

  3. Areal seismic reflection

    International Nuclear Information System (INIS)

    Bading, R.

    1977-01-01

    Areal seismic-reflection-survey techniques lead to areally equally spaced density of seismic subsurface information, whereby the miniumum spacing may be as narrow as 10 m, compared to the relatively wide gridding based on conventional line-seismic surveys. The seismic data bank reulting from an areal survey - as a consequence of the narrowly and equally spaced density of the subsurface points - allows the extraction of: 1) arbitrarily selectable plane seismic sections presenting the true image of the subsurface structure after 3 D-migration processing; 2) large series in arbitrary direction of subsequent seismic cross-section, socalled echelon profiles. The immense informational density enables for interpretation without need of interpolations, leading to up-to-now unusual reliability. - The variety in types of building-block systems of the field survey methods grants optimum adaption to the respective exploration target. Application of multichannel recording instruments is the prerequisite of economy. The areas covered up-to-now with this kind of seismic field survey extended to about 10 - 20 km 2 each time. (orig.) [de

  4. Angola Seismicity MAP

    Science.gov (United States)

    Neto, F. A. P.; Franca, G.

    2014-12-01

    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  5. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature by observing an apparent angular shift in an interference fringe pattern produced by back or forward scattering interferometry, ambiguities in the measurement caused...

  6. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    In a method for performing a refractive index based measurement of a property of a fluid such as chemical composition or temperature, a chirp in the local spatial frequency of interference fringes of an interference pattern is reduced by mathematical manipulation of the recorded light intensity...

  7. Refractive index based measurements

    DEFF Research Database (Denmark)

    2014-01-01

    A refractive index based measurement of a property of a fluid is measured in an apparatus comprising a variable wavelength coherent light source (16), a sample chamber (12), a wavelength controller (24), a light sensor (20), a data recorder (26) and a computation apparatus (28), by - directing...

  8. Seismic Readings from the Deepest Borehole in the New Madrid Seismic Zone

    Energy Technology Data Exchange (ETDEWEB)

    Woolery, Edward W [KY Geological Survey, Univ of KY; Wang, Zhenming [KY Geological Survey, Univ of KY; Sturchio, Neil C [Dept of earth and Env. Sciences, Univ of Ill at Chicago

    2006-03-01

    Since the 1980s, the research associated with the UK network has been primarily strong-motion seismology of engineering interest. Currently the University of Kentucky operates a strong-motion network of nine stations in the New Madrid Seismic Zone. A unique feature of the network is the inclusions of vertical strong-motion arrays, each with one or two downhole accelerometers. The deepest borehole array is 260 m below the surfaces at station VASA in Fulton County, Kentucky. A preliminary surface seismic refraction survey was conducted at the site before drilling the hole at VSAS (Woolery and Wang, 2002). The depth to the Paleozoic bedrock at the site was estimated to be approximately 595 m, and the depth to the first very stiff layer (i.e. Porters Creek Clay) was found to be about 260 m. These depths and stratigraphic interpretation correlated well with a proprietary seismic reflection line and the Ken-Ten Oil Exploration No. 1 Sanger hole (Schwalb, 1969), as well as our experience in the area (Street et al., 1995; Woolery et al., 1999).

  9. Neutron microscope with refractive wedge

    International Nuclear Information System (INIS)

    Masalovich, S.V.

    1990-01-01

    A possibility of applying a refractive element in a mirror-neutron microscope using ultracold neutrons to reduce neutron aberrations is considered. Application of a refractive element in a neutron microscope with horizontal optical axis is studied. A scheme of neutron microscope with a refractive wedge is presented, evaluation of quartz wedge parameters is made. It is stressed that application of refractive elements in neutron microscopes facilitates aberration reduction in neutron-optical systems

  10. Ambient seismic noise levels: A survey of the permanent and temporary seismographic networks in Morocco, North Africa

    Science.gov (United States)

    El Fellah, Y.; Khairy Abd Ed-Aal, A.; El Moudnib, L.; Mimoun, H.; Villasenor, A.; Gallart, J.; Thomas, C.; Elouai, D.; Mimoun, C.; Himmi, M.

    2013-12-01

    Abstract The results, of a conducted study carried out to analyze variations in ambient seismic noise levels at sites of the installed broadband stations in Morocco, North Africa, are obtained. The permanent and the temporary seismic stations installed in Morocco of the Scientific Institute ( IS, Rabat, Morocco), institute de Ciencias de la Tierra Jaume almera (ICTJA, Barcelona, Spain) and Institut für Geophysik (Munster, Germany) were used in this study. In this work, we used 23 broadband seismic stations installed in different structural domains covering all Morocco from south to north. The main purposes of the current study are: 1) to present a catalog of seismic background noise spectra for Morocco obtained from recently installed broadband stations, 2) to assess the effects of experimental temporary seismic vault construction, 3) to determine the time needed for noise at sites to stabilize, 4) to establish characteristics and origin of seismic noise at those sites. We calculated power spectral densities of background noise for each component of each broadband seismometer deployed in the different investigated sites and then compared them with the high-noise model and low-noise Model of Peterson (1993). All segments from day and night local time windows were included in the calculation without parsing out earthquakes. The obtained results of the current study could be used forthcoming to evaluate permanent station quality. Moreover, this study could be considered as a first step to develop new seismic noise models in North Africa not included in Peterson (1993). Keywords Background noise; Power spectral density; Model of Peterson; Scientific Institute; Institute de Ciencias de la Tierra Jaume almera; Institut für Geophysik

  11. Subbottom seismic profiling survey of Lake Azuei, Haiti: Seismic signature of paleo-shorelines in a transpressional environment and possible tectonic implications

    Science.gov (United States)

    Sloan, H.; Cormier, M. H.; Boisson, D.; Brown, B.; Guerrier, K.; Hearn, C. K.; Heil, C. W., Jr.; Hines, L.; Kelly, R. P.; King, J. W.; Knotts, P.; Lucier, O. F.; Momplaisir, R.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.; Wattrus, N. J.

    2017-12-01

    The left-lateral Enriquillo-Plantain Garden Fault (EPGF) is one of two major transform faults that form the North American-Caribbean plate boundary. GPS measurements indicate that relative motion evolves from nearly pure strike-slip in western Haiti to highly transpressional near Lake Azuei in eastern Haiti, where the EPGF may terminate against a south-dipping oblique reverse fault. Lake Azuei, one of the largest lakes in the Caribbean region (10 km x 23 km), is surrounded by two high-elevation sierras (> 2,000 m). Because the lake has no outlet to the sea, its level is sensitive to variations in precipitation and is thought to have fluctuated by 10's of meters during the Holocene. A rise of 5 m over the past 10 years has had a devastating impact, submerging villages, farmland, and roads. A grid of high-resolution ( 10 cm) subbottom seismic (CHIRP) profiles acquired in January 2017 captures the subtle signature of the 5 m-deep shoreline and also images a prominent paleo-shoreline at 10 m water depth. This 10 m paleo-shoreline is well expressed in the CHIRP data suggesting it was occupied for a long period of time. It is buried beneath a thin (< 20 cm-thick) veneer of sediments, indicating that it was submerged centuries to millennia ago. This paleo-shoreline represents a key horizontal marker that may have been warped by local transpressional tectonics. We therefore catalogued its varying seismic signature with the goal of detecting any subtle but systematic depth variations of the associated shoreline angle around the periphery of the lake. Two sediment cores, collected in water depths of 14 m and 17 m, each bottomed 80-90 cm below the lakebed into a distinctively coarser bed. On-going radiometric dating is expected to constrain the age of this distinctive layer. Should this layer be tied to the perduring 10-m lowstand of the lake, determining its age could help quantify vertical deformation rates around Lake Azuei.

  12. Seismic reflection constraints on the glacial dynamics of Johnsons Glacier, Antarctica

    Science.gov (United States)

    Benjumea, Beatriz; Teixidó, Teresa

    2001-01-01

    During two Antarctic summers (1996-1997 and 1997-1998), five seismic refraction and two reflection profiles were acquired on the Johnsons Glacier (Livingston Island, Antarctica) in order to obtain information about the structure of the ice, characteristics of the ice-bed contact and basement topography. An innovative technique has been used for the acquisition of reflection data to optimise the field survey schedule. Different shallow seismic sources were used during each field season: Seismic Impulse Source System (SISSY) for the first field survey and low-energy explosives (pyrotechnic noisemakers) during the second one. A comparison between these two shallow seismic sources has been performed, showing that the use of the explosives is a better seismic source in this ice environment. This is one of the first studies where this type of source has been used. The analysis of seismic data corresponding to one of the reflection profiles (L3) allows us to delineate sectors with different glacier structure (accumulation and ablation zones) without using glaciological data. Moreover, vertical discontinuities were detected by the presence of back-scattered energy and the abrupt change in frequency content of first arrivals shown in shot records. After the raw data analysis, standard processing led us to a clear seismic image of the underlying bed topography, which can be correlated with the ice flow velocity anomalies. The information obtained from seismic data on the internal structure of the glacier, location of fracture zones and the topography of the ice-bed interface constrains the glacial dynamics of Johnsons Glacier.

  13. The accuracy of multimeridional refraction.

    Science.gov (United States)

    Long, W F

    1981-12-01

    The accuracy of meridional refraction using equally spaced preselected meridians was investigated by using populations of computer-simulated patients. The number of meridians refracted, patient refractive error, and the coarseness of phoroptor steps were varied. Results indicate that the accuracy of meridional refraction is independent of the relative orientation of the axis of the patient's astigmatism and the preselected meridians, that little is to be gained by use of a phoropter with steps finer than the usual 0.25 D, and that with a sufficient number of meridians, meridional refraction can be as accurate as more conventional techniques.

  14. Quantitative elastic migration. Applications to 3D borehole seismic surveys; Migration elastique quantitative. Applications a la sismique de puits 3D

    Energy Technology Data Exchange (ETDEWEB)

    Clochard, V.

    1998-12-02

    3D VSP imaging is nowadays a strategic requirement by petroleum companies. It is used to precise in details the geology close to the well. Because of the lack of redundancy and limited coverage in the data. this kind of technology is more restrictive than surface seismic which allows an investigation at a higher scale. Our contribution was to develop an elastic quantitative imagine (GRT migration) which can be applied to 3 components borehole dataset. The method is similar to the Kirchhoff migration using sophistical weighting of the seismic amplitudes. In reality. GRT migration uses pre-calculated Green functions (travel time. amplitude. polarization). The maps are obtained by 3D ray tracing (wavefront construction) in the velocity model. The migration algorithm works with elementary and independent tasks. which is useful to process different kind of dataset (fixed or moving geophone antenna). The study has been followed with validations using asymptotic analytical solution. The ability of reconstruction in 3D borehole survey has been tested in the Overthrust synthetic model. The application to a real circular 3D VSP shows various problems like velocity model building, anisotropy factor and the preprocessing (deconvolution. wave mode separation) which can destroy seismic amplitudes. An isotropic 3 components preprocessing of the whole dataset allows a better lateral reconstruction. The choice of a big migration aperture can help the reconstruction of strong geological dip in spite of migration smiles. Finally, the methodology can be applied to PS converted waves. (author)

  15. Seismic stability of the survey areas of potential sites for the deep geological repository of the spent nuclear fuel

    Czech Academy of Sciences Publication Activity Database

    Kaláb, Zdeněk; Šílený, Jan; Lednická, Markéta

    2017-01-01

    Roč. 15, č. 1 (2017), s. 486-493 E-ISSN 2391-5471 R&D Projects: GA MŠk LM2010008; GA MŠk(CZ) LM2015079 Institutional support: RVO:68145535 ; RVO:67985530 Keywords : deep geological repository * earthquake * seismicity * neo-deterministic analysis * probabilistic seismic hazard assessment Subject RIV: DC - Siesmology, Volcanology, Earth Structure; DC - Siesmology, Volcanology, Earth Structure (GFU-E) OBOR OECD: Environmental and geological engineering, geotechnics; Environmental and geological engineering, geotechnics (GFU-E) Impact factor: 0.745, year: 2016 https://www.degruyter.com/downloadpdf/j/phys.2017.15.issue-1/phys-2017-0055/phys-2017-0055.pdf

  16. Determination of the position and capacity of stratal traps in the Southern Siberian platform according to reflected wave seismic survey data

    Energy Technology Data Exchange (ETDEWEB)

    Pompik, V.I.

    1977-01-01

    The association between the recording form of reference reflections A and B from plutonic horizons of a sedimentary layer and the trap sill embedded in the summits of the Motskaya and lower levels of the Usol'skaya strata of the Lower Cambrian in the southern Siberian platform was found by designing synthetic seismograms according to reflected wave seismic surveys. This method also made it possible to compile a capacity map of this trap sill and the level of its deposition, and to compile a seismogeological regionalization in accordance with the recording form of the reference reflections A and B.

  17. Signal Apparition - A seismic shift for imaging the Earth's interior

    Science.gov (United States)

    Robertsson, Johan; Amundsen, Lasse; van Manen, Dirk-Jan; Andersson, Fredrik; Eggenberger, Kurt; Pedersen, Åsmund; Thompson, Mark; Schmelzbach, Cedric

    2017-04-01

    The concept of signal apparition, introduced by Robertsson et al. (2016), offers a new perspective on the sampling of seismic wavefields. Signal apparition has range of applications in seismic data processing and imaging. In particular, for simultaneous source data acquisition, and through the use of periodic source modulation functions to encode sources during simultaneous shooting, energy can be partially injected or "apparated" along the wavenumber axis in the frequency-wavenumber (f-k) domain that would otherwise not be occupied by any signal. In the non-overlapping regions of the f-k domain, the individual sources can be exactly recovered by using linear combinations of weighted versions of the apparated data. In this fashion, the cost of acquiring a seismic survey can be reduced proportionally to the number of sources that can be activated simultaneously - thus enabling very significant cost reductions and/or increased image quality. We present results from an exploration scale simultaneous source field test carried out over a producing hydrocarbon reservoir in the North Sea in 2016. The test demonstrates excellent results with unprecedented low-noise separated results fit for time-lapse reservoir analysis. We expect that signal apparition will also transform the way that imaging of the Earth's deeper structure in the crust and mantle is carried out during refraction and reflection seismic experiments. In particular our acquisition approach will allow for 3D imaging using 2D-like acquisition geometries and will also allow for a significant increase in data quality in the low-frequency band below 5Hz. We will discuss specific seismic data acquisition configurations that will allow for a step-change in imaging of crustal-scale Earth structures without significantly increasing acquisition cost compared to current practice for academic seismic data experimentation. Robertsson, J. O. A., Amundsen, L. and Pedersen, Å. S. [2016]. Express Letter: Signal apparition

  18. Comparing Models GRM, Refraction Tomography and Neural Network to Analyze Shallow Landslide

    Directory of Open Access Journals (Sweden)

    Armstrong F. Sompotan

    2011-11-01

    Full Text Available Detailed investigations of landslides are essential to understand fundamental landslide mechanisms. Seismic refraction method has been proven as a useful geophysical tool for investigating shallow landslides. The objective of this study is to introduce a new workflow using neural network in analyzing seismic refraction data and to compare the result with some methods; that are general reciprocal method (GRM and refraction tomography. The GRM is effective when the velocity structure is relatively simple and refractors are gently dipping. Refraction tomography is capable of modeling the complex velocity structures of landslides. Neural network is found to be more potential in application especially in time consuming and complicated numerical methods. Neural network seem to have the ability to establish a relationship between an input and output space for mapping seismic velocity. Therefore, we made a preliminary attempt to evaluate the applicability of neural network to determine velocity and elevation of subsurface synthetic models corresponding to arrival times. The training and testing process of the neural network is successfully accomplished using the synthetic data. Furthermore, we evaluated the neural network using observed data. The result of the evaluation indicates that the neural network can compute velocity and elevation corresponding to arrival times. The similarity of those models shows the success of neural network as a new alternative in seismic refraction data interpretation.

  19. Using seismic reflection to locate a tracer testing complex south of Yucca Mountain, Nye County, Nevada

    Science.gov (United States)

    Kryder, Levi

    subset of the current seismic reflection data in the area chosen for a tracer complex; processing the existing reflection data set with refraction processing software; and conducting additional seismic reflection testing with different survey geometry.

  20. The reflection seismic survey of project TIPTEQ - the inventory of the Chilean subduction zone at 38.2° S

    OpenAIRE

    K. Groß; U. Micksch; Seismics Team and TIPTEQ Research Group; M. Araneda; K. Bataille; Jens Bribach; S. Buske; C. M. Krawczyk; Stefan Lüth; James Mechie; Albrecht Schulze; S. A. Shapiro; Manfred Stiller; P. Wigger; Thomas Ziegenhagen

    2008-01-01

    We describe results of an active-source seismology experiment across the Chilean subduction zone at 38.2◦S. The seismic sections clearly show the subducted Nazca plate with varying reflectivity. Below the coast the plate interface occurs at 25 km depth as the sharp lower boundary of a 2–5 km thick, highly reflective region, which we interpret as the subduction channel, that is, a zone of subducted material with a velocity gradient with respect to the upper and lower plate. Further downdip alo...

  1. Understanding the seismic wave propagation inside and around an underground cavity from a 3D numerical survey

    Science.gov (United States)

    Esterhazy, Sofi; Schneider, Felix; Perugia, Ilaria; Bokelmann, Götz

    2017-04-01

    Motivated by the need to detect an underground cavity within the procedure of an On-Site-Inspection (OSI) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), which might be caused by a nuclear explosion/weapon testing, we aim to provide a basic numerical study of the wave propagation around and inside such an underground cavity. One method to investigate the geophysical properties of an underground cavity allowed by the Comprehensive Nuclear-test Ban Treaty is referred to as "resonance seismometry" - a resonance method that uses passive or active seismic techniques, relying on seismic cavity vibrations. This method is in fact not yet entirely determined by the Treaty and so far, there are only very few experimental examples that have been suitably documented to build a proper scientific groundwork. This motivates to investigate this problem on a purely numerical level and to simulate these events based on recent advances in numerical modeling of wave propagation problems. Our numerical study includes the full elastic wave field in three dimensions. We consider the effects from an incoming plane wave as well as point source located in the surrounding of the cavity at the surface. While the former can be considered as passive source like a tele-seismic earthquake, the latter represents a man-made explosion or a viborseis as used for/in active seismic techniques. Further we want to demonstrate the specific characteristics of the scattered wave field from a P-waves and S-wave separately. For our simulations in 3D we use the discontinuous Galerkin Spectral Element Code SPEED developed by MOX (The Laboratory for Modeling and Scientific Computing, Department of Mathematics) and DICA (Department of Civil and Environmental Engineering) at the Politecnico di Milano. The computations are carried out on the Vienna Scientific Cluster (VSC). The accurate numerical modeling can facilitate the development of proper analysis techniques to detect the remnants of an

  2. New evidence of an early Pridoli barrier reef in the southern part of the Baltic Silurian basin based on three-dimensional seismic survey, Lithuania

    Directory of Open Access Journals (Sweden)

    Donatas Kaminskas

    2015-02-01

    Full Text Available Reefs and a barrier reef have been newly identified and mapped by three-dimensional (3D seismic survey in Lithuania. Seismic data analysis has allowed the size and geometry of these reefs to be determined. The largest reefs occur at Pavasaris and South Bliudziai. They have a similar shape and are about 1.5 km long and 1 km wide. A circle-shaped smaller patch reef at North Bliudziai is 1 km in diameter. The overall heights of the studied structures do not exceed 30–40 m. The reefs consist of coarse-grained bioclastic stromatoporoid limestone. A barrier reef rising structurally from SW to NE was established in the west of the mapped area. The stratigraphic position (early Minija Regional Stage and lateral distribution of the barrier reef suggest it started to form earlier than the group of patch reefs. The development of patch reefs was related to the transgression of the Silurian Baltic basin.

  3. High-resolution, three-dimensional, seismic survey over the geopressured-geothermal reservoir at Parcperdue, Louisiana. Final report, January 1, 1981-July 31, 1985

    Energy Technology Data Exchange (ETDEWEB)

    Kinsland, G.L.

    1985-07-01

    A high resolution three-dimensional seismic survey was performed over the reservoir of the geopressured-geothermal production experiment at Parcperdue, Louisiana and high quality results have been obtained. The reservoir is now mapped with more control and assurance than was possible with the previously existing data. Three differences between the map of this project and those available before are significant in the interpretation of the depletion experiment: (1) the western bounding fault is further west leading to a larger reservoir volume; (2) a down to the north (relief) fault through the reservoir has been found; and (3) there are structural highs in which small petroleum accumulations may exist within the reservoir. An original goal of testing the before and after seismic experiment idea as a production monitor has not been realized. However, the quality of the data at the stages of processing presently available is high enough that, had the well not failed, it would have been prudent to have proceeded with the project toward the second experiment. 3 refs., 16 figs., 3 tabs.

  4. Excimer lasers for refractive surgery

    Science.gov (United States)

    Vartapetov, Serge K.

    2003-10-01

    Over the last decade excimer lasers have been broadly used for technological and medical processes. One of the most widespread applications of excimer laser is the clinical use for refractive surgery. Refractive surgery with excimer lasers is the prevalent method for the eye acuity correction. Operation at 193 nanometers, the excimer laser is able to precisely sculpt the corneal surface to correct refractive errors. Both the increase in the accuracy of sculpturing and the predictability of procedures are the key elements of the excimer laser designed for refractive surgery. The novel excimer laser for refractive surgery is offered for small aberration treatment. The excimer laser with both a full aperture Gaussian beam and fly spot system is described. The comparison of different systems of laser correction is reviewed.

  5. Transpressional Tectonics across the N. American-Caribbean Plate Boundary: Preliminary Results of a Multichannel Seismic Survey of Lake Azuei, Haiti.

    Science.gov (United States)

    Hearn, C. K.; Cormier, M. H.; Sloan, H.; Wattrus, N. J.; Boisson, D.; Brown, B.; Guerrier, K.; King, J. W.; Knotts, P.; Momplaisir, R.; Sorlien, C. C.; Stempel, R.; Symithe, S. J.; Ulysse, S. M. J.

    2017-12-01

    On January 12, 2010, a Mw 7.0 earthquake struck Haiti, killing over 200,000 people and devastating the Capital city of Port-au-Prince and the surrounding regions. It ruptured a previously unknown blind-thrust fault that abuts the Enriquillo Plantain Garden Fault (EPGF), one of two transform faults that define the North American-Caribbean plate boundary. That earthquake highlighted how transpression across this complex boundary is accommodated by slip partitioning into strike-slip and compressional structures. Because the seismic hazard is higher for a rupture on a reverse or oblique-slip fault than on a vertical strike-slip fault, the need to characterize the geometry of that fault system is clear. Lake Azuei overlies this plate boundary 60 km east of the 2010 epicenter. The lake's 23 km long axis trends NW-SE, parallel to the Haitian fold-and-thrust belt and oblique to the EPGF. This tectonic context makes it an ideal target for investigating the partitioning of plate motion between strike-slip and compressional structures. In January 2017, we acquired 222 km of multichannel seismic (MCS) profiles in the lake, largely concurrent with subbottom seismic (CHIRP) profiles. The MCS data were acquired using a high-frequency BubbleGun source and a 75 m-long, 24-channel streamer, achieving a 24 seismic fold with a penetration of 200 m below lakebed. With the goal of resolving tectonic structures in 3-D, survey lines were laid out in a grid with profiles spaced 1.2 km apart. Additional profiles were acquired at the SE end of the lake where most of the tectonic activity is presumably occurring. The co-located CHIRP and MCS profiles document the continuity of tectonic deformation between the surficial sediments and the deeper strata. Preliminary processing suggests that a SW-dipping blind thrust fault, expressed updip as a large monocline fold, may control the western edge of the lake. Gentle, young folds that protrude from the flat lakebed are also imaged with the CHIRP

  6. Seismic processing in the inverse data space

    NARCIS (Netherlands)

    Berkhout, A.J.

    2006-01-01

    Until now, seismic processing has been carried out by applying inverse filters in the forward data space. Because the acquired data of a seismic survey is always discrete, seismic measurements in the forward data space can be arranged conveniently in a data matrix (P). Each column in the data matrix

  7. Redatuming of sparse 3D seismic data

    NARCIS (Netherlands)

    Tegtmeier, S.

    2007-01-01

    The purpose of a seismic survey is to produce an image of the subsurface providing an overview of the earth's discontinuities. The aim of seismic processing is to recreate this image. The seismic method is especially well suited for the exploration and the monitoring of hydrocarbon reservoirs. A

  8. Crustal investigations of the earthquake-prone Vrancea region in Romania - Part 2: Novel deep seismic reflection experiment in the southeastern Carpathian belt and its foreland basin - survey target, design, and first results

    Science.gov (United States)

    Mocanu, V. I.; Stephenson, R. A.; Diaconescu, C. C.; Knapp, J. H.; Matenco, L.; Dinu, C.; Harder, S.; Prodehl, C.; Hauser, F.; Raileanu, V.; Cloetingh, S. A.; Leever, K.

    2001-12-01

    Seismic studies of the outer Carpathian Orogen and its foreland (Focsani Basin) in the vicinity of the Vrancea Zone and Danube Delta (Romania) forms one component of a new multidisciplinary initiative of ISES (Netherlands Centre for Integrated Solid Earth Sciences) called DACIA PLAN ("Danube and Carpathian Integrated Action on Processes in the Lithosphere and Neotectonics"). The study area, at the margin of the European craton, constitutes one of the most active seismic zones in Europe, yet has remained a geological and geodynamic enigma within the Alpine-Himalayan orogenic system. Intermediate depth (50-220 km) mantle earthquakes of significant magnitude occur in a geographically restricted area in the south-east Carpathians bend. The adjacent, foreland Focsani Basin appears to exhibit recent extensional deformation in what is otherwise understood to be a zone of convergence. The deep seismic reflection component of DACIA PLAN comprises a ~140-km near-vertical profile across the Vrancea Zone and Focsani Basin. Data acquisition took place in August-September 2001, as part of the integrated refraction/reflection seismic field programme "Vrancea-2001" co-ordinated at Karlsruhe University (cf. Abstract, Part 1), utilising 640 independently deployed recorders provided by UTEP and IRIS/PASSCAL ("Texans"). Station spacing was every 100-m with shots every 1-km. These data are to be integrated with industry seismic as well as planned new medium-high resolution seismic reflection profiling across key neotectonically active structures in the Focsani Basin. Particular goals of DACIA PLAN include: (1) the architecture of the Tertiary/Quaternary basins developed within and adjacent to this zone, including the foreland Focsani Basin; (2) the presence and geometry of structural detachment(s) in relation with foreland basin development, including constraints for balanced cross-sections and geodynamic modelling of basin origin and evolution; (3) the relationship between crustal

  9. High-resolution seismic survey for the characterization of planned PIER-ICDP fluid-monitoring sites in the Eger Rift zone

    Science.gov (United States)

    Simon, H.; Buske, S.

    2017-12-01

    The Eger Rift zone (Czech Republic) is a intra-continental non-volcanic region and is characterized by outstanding geodynamic activities, which result in earthquake swarms and significant CO2 emanations. Because fluid-induced stress can trigger earthquake swarms, both natural phenomena are probably related to each other. The epicentres of the earthquake swarms cluster at the northern edge of the Cheb Basin. Although the location of the cluster coincides with the major Mariánské-Lázně Fault Zone (MLFZ) the strike of the focal plane indicates another fault zone, the N-S trending Počátky-Plesná Zone (PPZ). Isotopic analysis of the CO2-rich fluids revealed a significant portion of upper mantle derived components, hence a magmatic fluid source in the upper mantle was postulated. Because of these phenomena, the Eger Rift area is a unique site for interdisciplinary drilling programs to study the fluid-earthquake interaction. The ICDP project PIER (Probing of Intra-continental magmatic activity: drilling the Eger Rift) will set up an observatory, consisting of five monitoring boreholes. In preparation for the drilling, the goal of the seismic survey is the characterization of the projected fluid-monitoring drill site at the CO2 degassing mofette field near Hartoušov. This will be achieved by a 6 km long profile with dense source and receiver spacing. The W-E trending profile will cross the proposed drill site and the surface traces of MLFZ and PPZ. The outcome of the seismic survey will be a high-resolution structural image of potential reflectors related to these fault zones. This will be achieved by the application of advanced pre-stack depth migration methods and a detailed P-wave velocity distribution of the area obtained from first arrival tomography. During interpretation of the seismic data, a geoelectrical resistivity model, acquired along the same profile line, will provide important constraints, especially with respect to fluid pathways.

  10. Megaptera Novaeangliae sightings recorder (Borowski, 1781) in the capixaba coast during marine seismic survey; Registro de avistagens de Megaptera Novaeangliae (Borowski, 1781) no litoral capixaba durante levantamento sismico maritimo

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Leandro Damiao S. da; Almeida, Alexandre N. Ferraz de [Okeanos Consultoria e Meio Ambiente Ltda. (Brazil); Uller, George A.; Oliveira, Joao Luiz Martinez de [CGG do Brasil, Rio de Janeiro, RJ (Brazil); Derntl, Jose Renato; Pereira, Edisio; Silva, Camila C. da [GEOCOOP Cooperativa de Trabalho, Rio de Janeiro, RJ (Brazil); Miranda, Cristina M. de [Nautilus Cooperativa de Trabalho (Brazil)

    2004-07-01

    This work presents Megaptera novaeangliae (Humpback Whale) sightings recorded during CGG seismic survey along south of Espirito Santo coast. The seismic vessel executed transects perpendicular to the coastline between 50 and 3.200 m depth. Two environmental technicians recorded all sightings during seismic survey; They worked on the highest point of the vessel (bridge) observing the presence and behavior of the marine biota around vessel. There were recorded 38 sightings of Humpback Whales and a total of 81 organisms. 61% of the sightings were concentrated between 40 and 80 m depth. About 60,5% of the sightings were recorded females with puppies, mainly in the afternoon. There were observed no difference between sightings with the source working on and off. The results obtained suggest similarity between the number of sightings and the distance of the animals related to seismic source activity, suggesting non evasive behavior, as well as any indicative change on the behavior regarding to the presence of the Seismic Vessel. Nevertheless, we know that it's necessary to make more studies to obtain definitive conclusions about the subject. (author)

  11. Hydrothermal activity and the evolution of the seismic properties of upper oceanic crust

    Science.gov (United States)

    Grevemeyer, Ingo; Kaul, Norbert; Villinger, Heinrich; Weigel, Wilfried

    1999-03-01

    In order to investigate the impact of off-axis hydrothermal circulation on changes of the seismic properties of upper oceanic crust (layer 2A), we performed an extensive geophysical survey on the eastern flank of the East Pacific Rise at 14°S. Seismic refraction and heat flow data were obtained along a 720-km-long and 25 to 40-km wide corridor, covering thinly sedimented seafloor created since 8.5 Ma. The seismic data yield a seismic velocity of ˜2.9 km/s at the top of 0.5-m.y.-old basement rocks. Within about 8 m.y. the velocity increases gradually to a value of mature oceanic crust (˜4.3 km/s). Heat flow data, derived from 43 in situ thermal conductivity and 86 geothermal gradient measurements, suggest that an open hydrothermal circulation system persists for at least 6-7 m.y. In crust older than 7 Ma, regional heat flow is close to values predicted by plate cooling models, suggesting that hydrothermal circulation is going to cease. Considering published dating of alteration minerals, it appears that the permeability of uppermost oceanic crust has decreased to values insufficient to promote a vigorous hydrothermal circulation within 10-15 m.y. This idea may explain why seismic velocities in the Pacific ocean have not changed significantly in igneous crust older than 8-10 Ma. In regions where juvenile and consistently hot crust is buried rapidly by sediments the evolution of the seismic properties is quite different; velocities increase rapidly and reach values of mature oceanic crust within 1-2 m.y. We therefore favor a model where basement temperature is governing the evolution of the seismic properties of upper oceanic crust [Stephen and Harding, 1983; Rohr, 1994].

  12. 3D super-virtual refraction interferometry

    KAUST Repository

    Lu, Kai

    2014-08-05

    Super-virtual refraction interferometry enhances the signal-to-noise ratio of far-offset refractions. However, when applied to 3D cases, traditional 2D SVI suffers because the stationary positions of the source-receiver pairs might be any place along the recording plane, not just along a receiver line. Moreover, the effect of enhancing the SNR can be limited because of the limitations in the number of survey lines, irregular line geometries, and azimuthal range of arrivals. We have developed a 3D SVI method to overcome these problems. By integrating along the source or receiver lines, the cross-correlation or the convolution result of a trace pair with the source or receiver at the stationary position can be calculated without the requirement of knowing the stationary locations. In addition, the amplitudes of the cross-correlation and convolution results are largely strengthened by integration, which is helpful to further enhance the SNR. In this paper, both synthetic and field data examples are presented, demonstrating that the super-virtual refractions generated by our method have accurate traveltimes and much improved SNR.

  13. Integrated seismic interpretation of the Carlsberg Fault zone, Copenhagen, Denmark

    DEFF Research Database (Denmark)

    Nielsen, Lars; Thybo, Hans; Jørgensen, Mette Iwanouw

    2005-01-01

    the fault zone. The fault zone is a shadow zone to shots detonated outside the fault zone. Finite-difference wavefield modelling supports the interpretations of the fan recordings. Our fan recording approach facilitates cost-efficient mapping of fault zones in densely urbanized areas where seismic normal......We locate the concealed Carlsberg Fault zone along a 12-km-long trace in the Copenhagen city centre by seismic refraction, reflection and fan profiling. The Carlsberg Fault is located in a NNW-SSE striking fault system in the border zone between the Danish Basin and the Baltic Shield. Recent...... earthquakes indicate that this area is tectonically active. A seismic refraction study across the Carlsberg Fault shows that the fault zone is a low-velocity zone and marks a change in seismic velocity structure. A normal incidence reflection seismic section shows a coincident flower-like structure. We have...

  14. The uncorrected refractive error challenge

    Directory of Open Access Journals (Sweden)

    Kovin Naidoo

    2016-11-01

    Full Text Available Refractive error affects people of all ages, socio-economic status and ethnic groups. The most recent statistics estimate that, worldwide, 32.4 million people are blind and 191 million people have vision impairment. Vision impairment has been defined based on distance visual acuity only, and uncorrected distance refractive error (mainly myopia is the single biggest cause of worldwide vision impairment. However, when we also consider near visual impairment, it is clear that even more people are affected. From research it was estimated that the number of people with vision impairment due to uncorrected distance refractive error was 107.8 million,1 and the number of people affected by uncorrected near refractive error was 517 million, giving a total of 624.8 million people.

  15. Crustal structure of the Central-Eastern Greenland: results from the Topo Greenland refraction profile

    DEFF Research Database (Denmark)

    Shulgin, Alexey; Thybo, Hans

    2014-01-01

    refraction/wide-angle reflection profile. The seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the ice cap in the interior of central-eastern Greenland. The presence of an up to 3.4 km thick ice sheet, permanently covering most of the land mass, made...

  16. Earth modeling and estimation of the local seismic ground motion due to site geology in complex volcanoclastic areas

    Directory of Open Access Journals (Sweden)

    V. Di Fiore

    2002-06-01

    Full Text Available Volcanic areas often show complex behaviour as far as seismic waves propagation and seismic motion at surface are concerned. In fact, the finite lateral extent of surface layers such as lava flows, blocks, differential welding and/or zeolitization within pyroclastic deposits, introduces in the propagation of seismic waves effects such as the generation of surface waves at the edge, resonance in lateral direction, diffractions and scattering of energy, which tend to modify the amplitude as well as the duration of the ground motion. The irregular topographic surface, typical of volcanic areas, also strongly influences the seismic site response. Despite this heterogeneity, it is unfortunately a common geophysical and engineering practice to evaluate even in volcanic environments the subsurface velocity field with monodimensional investigation method (i.e. geognostic soundings, refraction survey, down-hole, etc. prior to the seismic site response computation which in a such cases is obviously also made with 1D algorithms. This approach often leads to highly inaccurate results. In this paper we use a different approach, i.e. a fully 2D P-wave Çturning rayÈ tomographic survey followed by 2D seismic site response modeling. We report here the results of this approach in three sites located at short distance from Mt. Vesuvius and Campi Flegrei and characterized by overburdens constituted by volcanoclastic deposits with large lateral and vertical variations of their elastic properties. Comparison between 1D and 2D Dynamic Amplification Factor shows in all reported cases entirely different results, both in terms of peak period and spectral contents, as expected from the clear bidimensionality of the geological section. Therefore, these studies suggest evaluating carefully the subsoil geological structures in areas characterized by possible large lateral and vertical variations of the elastic properties in order to reach correct seismic site response

  17. Program and plans of the U.S. Geological Survey for producing information needed in National Seismic hazards and risk assessment, fiscal years 1980-84

    Science.gov (United States)

    Hays, Walter W.

    1979-01-01

    In accordance with the provisions of the Earthquake Hazards Reduction Act of 1977 (Public Law 95-124), the U.S. Geological Survey has developed comprehensive plans for producing information needed to assess seismic hazards and risk on a national scale in fiscal years 1980-84. These plans are based on a review of the needs of Federal Government agencies, State and local government agencies, engineers and scientists engaged in consulting and research, professional organizations and societies, model code groups, and others. The Earthquake Hazards Reduction Act provided an unprecedented opportunity for participation in a national program by representatives of State and local governments, business and industry, the design professions, and the research community. The USGS and the NSF (National Science Foundation) have major roles in the national program. The ultimate goal of the program is to reduce losses from earthquakes. Implementation of USGS research in the Earthquake Hazards Reduction Program requires the close coordination of responsibility between Federal, State and local governments. The projected research plan in national seismic hazards and risk for fiscal years 1980-84 will be accomplished by USGS and non-USGS scientists and engineers. The latter group will participate through grants and contracts. The research plan calls for (1) national maps based on existing methods, (2) improved definition of earthquake source zones nationwide, (3) development of improved methodology, (4) regional maps based on the improved methodology, and (5) post-earthquake investigations. Maps and reports designed to meet the needs, priorities, concerns, and recommendations of various user groups will be the products of this research and provide the technical basis for improved implementation.

  18. Application of the seismic survey ahead of tunnel face; Danseiha wo mochiita kiriha zenpo tansa no tekiyo

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, S.; Nakajima, N. [JDC Corporation, Tokyo (Japan)

    1997-10-22

    Measurements have been made in a water channel tunnel having a small diameter and shallow earth covering, by using a tunnel seismic prediction (TSP) system to predict the nature of soil up to about 150 meters ahead of a face, which uses reflection method elastic waves. The water channel tunnel has a diameter of 2.8 m, and extends over a total distance of 706 m. The nature of soil at the face is composed of rocks, in which dark gray and hard striped phthanites are distributed and joint interval is about 20 cm. The measurements were performed on 24 vibration holes with hole interval of about 1.5 m using an explosive of 50 grams per hole. Diffraction stack processing method was used to execute the analysis. As a result of the discussions, a point changing from hard to soft soil was predicted at a point 18 m ahead of the face, and a point changing from soft to hard soil at a point 70 m ahead of the face. The changing point for the soil nature as observed by drilling showed a discrepancy of 10 m at the point changing from hard to soft soil as compared with the prediction derived by using the TSP exploration. No discrepancy was recognized in the point changing from soft to hard soil. The discrepancy is thought to have been caused from the geological change in the explored area being moderate and the lithofacies being free from change. 8 figs., 2 tabs.

  19. Optimization of Broadband Seismic Network in the Kingdom of Saudi Arabia

    KAUST Repository

    Alshuhail, Abdulrahman

    2011-05-01

    Saudi Arabia covers a large portion of the Arabian plate, a region characterized by seismic activity, along complex divergent and convergent plate boundaries. In order to understand these plate boundaries it is essential to optimize the design of the broadband seismic station network to accurately locate earthquakes. In my study, I apply an optimization method to design the broadband station distribution in Saudi Arabia. This method is based on so called D-optimal planning criterion that optimizes the station distribution for locating the hypocenters of earthquakes. Two additional adjustments were implemented: to preferentially acquire direct and refracted wave, and to account for geometric spreading of seismic waves (and thus increases the signal to noise ratio). The method developed in this study for optimizing the geographical location of broadband stations uses the probability of earthquake occurrence and a 1-D velocity model of the region, and minimizes the ellipsoid volume of the earthquake location errors. The algorithm was applied to the current seismic network, operated by the Saudi Geologic Survey (SGS). Based on the results, I am able to make recommendations on, how to expand the existing network. Furthermore, I quantify the efficiency of our method by computing the standard error of epicenter and depth before and after adding the proposed stations.

  20. Seismic reflection imaging with conventional and unconventional sources

    Science.gov (United States)

    Quiros Ugalde, Diego Alonso

    This manuscript reports the results of research using both conventional and unconventional energy sources as well as conventional and unconventional analysis to image crustal structure using reflected seismic waves. The work presented here includes the use of explosions to investigate the Taiwanese lithosphere, the use of 'noise' from railroads to investigate the shallow subsurface of the Rio Grande rift, and the use of microearthquakes to image subsurface structure near an active fault zone within the Appalachian mountains. Chapter 1 uses recordings from the land refraction and wide-angle reflection component of the Taiwan Integrated Geodynamic Research (TAIGER) project. The most prominent reflection feature imaged by these surveys is an anomalously strong reflector found in northeastern Taiwan. The goal of this chapter is to analyze the TAIGER recordings and to place the reflector into a geologic framework that fits with the modern tectonic kinematics of the region. Chapter 2 uses railroad traffic as a source for reflection profiling within the Rio Grande rift. Here the railroad recordings are treated in an analogous way to Vibroseis recordings. These results suggest that railroad noise in general can be a valuable new tool in imaging and characterizing the shallow subsurface in environmental and geotechnical studies. In chapters 3 and 4, earthquakes serve as the seismic imaging source. In these studies the methodology of Vertical Seismic Profiling (VSP) is borrowed from the oil and gas industry to develop reflection images. In chapter 3, a single earthquake is used to probe a small area beneath Waterboro, Maine. In chapter 4, the same method is applied to multiple earthquakes to take advantage of the increased redundancy that results from multiple events illuminating the same structure. The latter study demonstrates how dense arrays can be a powerful new tool for delineating, and monitoring temporal changes of deep structure in areas characterized by significant

  1. Geophysical Surveys Over a Terminal Moraine

    Science.gov (United States)

    Bentley, L. R.; Langston, G.; Hayashi, M.

    2007-12-01

    Alpine watersheds represent the headwaters of many major rivers in western Canada. Consequently, understanding the hydrological cycle within these watersheds is critical for modeling the effects of climate change on water resources in western Canada and for developing informed water management strategies. Terminal moraines represent a significant hydrological response unit within many alpine watersheds in western Canada. Recent studies suggest that these features may provide sites for water storage. The preliminary results of a geophysical survey of a terminal moraine exhibiting geomorphological characteristics suggesting an ice-core will be presented. It is hypothesized that bedrock topography and the presence of ice creates barriers and channels groudwater flow. The focus of the survey was to delineate the hydrologically significant features within the moraine using electrical resistivity imaging (ERI), seismic refraction, and ground penetrating radar (GPR). Buried ice was easily detected using ERI due to high resistivity of over 1 MOhm-m. However, it was not as extensive as expected. Seismic refraction proved to be most useful in detecting the underlying bedrock. GPR images showed many reflection fragments but were noisy and difficult to interpret. Regions of relatively high electrical conductivity suggest some degree of channelization of groundwater in the vicinity of a tarn.

  2. Annual Hanford seismic report - fiscal year 1996

    International Nuclear Information System (INIS)

    Hartshorn, D.C.; Reidel, S.P.

    1996-12-01

    Seismic monitoring (SM) at the Hanford Site was established in 1969 by the US Geological Survey (USGS) under a contract with the US Atomic Energy Commission. Since 1980, the program has been managed by several contractors under the US Department of Energy (USDOE). Effective October 1, 1996, the Seismic Monitoring workscope, personnel, and associated contracts were transferred to the USDOE Pacific Northwest National Laboratory (PNNL). SM is tasked to provide an uninterrupted collection and archives of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) located on and encircling the Hanford Site. SM is also tasked to locate and identify sources of seismic activity and monitor changes in the historical pattern of seismic activity at the Hanford Site. The data compiled are used by SM, Waste Management, and engineering activities at the Hanford Site to evaluate seismic hazards and seismic design for the Site

  3. refractive error status of patients in bayelsa state, nigeria

    African Journals Online (AJOL)

    Adebayo Adio

    hyperopia (>+0.50D) to be 20.6% in Bangladesh. A recent national survey in Pakistan reported that refractive error is the commonest cause of moderate visual impairment (VA <6/18 to. $6/60) accounting for 43%, followed by cataract. A hospital-based. 8. Correspondence: A Koroye-Egbe, Niger Delta University Teaching ...

  4. Seismic velocity model of the crust and upper mantle along profile PANCAKE across the Carpathians between the Pannonian Basin and the East European Craton

    DEFF Research Database (Denmark)

    Starostenko, V.; Janik, T.; Kolomiyets, K.

    2013-01-01

    Results are presented of a seismic wide-angle reflection/refraction survey along a profile between the Pannonian Basin (PB) and the East European Craton (EEC) called PANCAKE. The P- and S-wave velocity model derived can be divided into three sectors: the PB; the Carpathians, including the Transca......Results are presented of a seismic wide-angle reflection/refraction survey along a profile between the Pannonian Basin (PB) and the East European Craton (EEC) called PANCAKE. The P- and S-wave velocity model derived can be divided into three sectors: the PB; the Carpathians, including...... the Transcarpathian Depression and the Carpathian Foredeep; and the south-western part of the EEC, including the Trans European Suture Zone (TESZ). Seismic data support a robust model of the Vp velocity structure of the crust. In the PB, the 22-23km thick crust consists of a 2-5km thick sedimentary layer (Vp=2...... of the lower crust towards the Ukrainian Shield, where a high velocity lower crust (Vp>7.2km/s) is observed. Two low-velocity lenses in the upper crust of the EEC are interpreted beneath major sedimentary troughs (Lviv and Volyn-Podolsk). Mantle reflectors are observed at depths of ~45km and ~75km below the PB...

  5. Landslide seismic magnitude

    Science.gov (United States)

    Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

    2015-11-01

    Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

  6. Advances in Rotational Seismic Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Pierson, Robert [Applied Technology Associates, Albuquerque, NM (United States); Laughlin, Darren [Applied Technology Associates, Albuquerque, NM (United States); Brune, Robert [Applied Technology Associates, Albuquerque, NM (United States)

    2016-10-19

    Rotational motion is increasingly understood to be a significant part of seismic wave motion. Rotations can be important in earthquake strong motion and in Induced Seismicity Monitoring. Rotational seismic data can also enable shear selectivity and improve wavefield sampling for vertical geophones in 3D surveys, among other applications. However, sensor technology has been a limiting factor to date. The US Department of Energy (DOE) and Applied Technology Associates (ATA) are funding a multi-year project that is now entering Phase 2 to develop and deploy a new generation of rotational sensors for validation of rotational seismic applications. Initial focus is on induced seismicity monitoring, particularly for Enhanced Geothermal Systems (EGS) with fracturing. The sensors employ Magnetohydrodynamic (MHD) principles with broadband response, improved noise floors, robustness, and repeatability. This paper presents a summary of Phase 1 results and Phase 2 status.

  7. Seismic explosion sources on an ice cap

    DEFF Research Database (Denmark)

    Shulgin, Alexey; Thybo, Hans

    2015-01-01

    Controlled source seismic investigation of crustal structure below ice covers is an emerging technique. We have recently conducted an explosive refraction/wide-angle reflection seismic experiment on the ice cap in east-central Greenland. The data-quality is high for all shot points and a full...... as a strong ice wave. The ice cap leads to low transmission of energy into the crust such that charges need be larger than in conventional onshore experiments to obtain reliable seismic signals. The strong reflection coefficient at the base of the ice generates strong multiples which may mask for secondary...... phases. This effect may be crucial for acquisition of reflection seismic profiles on ice caps. Our experience shows that it is essential to use optimum depth for the charges and to seal the boreholes carefully....

  8. Refractive surgery trends and practice style changes in Germany over a 3-year period.

    Science.gov (United States)

    Schmack, Ingo; Auffarth, Gerd U; Epstein, Daniel; Holzer, Mike P

    2010-03-01

    To study the current practice styles and preferences of refractive surgeons in Germany. In February 2008, a seven-item questionnaire regarding the practice of refractive surgery was mailed to 282 members of the German Society of Intra-ocular Lens Implantation, Interventional, and Refractive Surgery (DGII) and the Commission of Refractive Surgery (KRC). Most questions were identical to our 2005 German refractive surgery survey. All data were analyzed in a masked fashion. The response rate was 42.2%. The majority (68%) of respondents reported that they perform refractive surgery in laser centers (exclusively or partially) followed by general hospitals (19.4%) and universities (12.6%). Although LASIK was the predominant type of refractive surgery performed (80.6%), other refractive procedures included refractive lens exchange (60.2%), photorefractive keratectomy (47.6%), phakic intraocular lens implants (45.6%), laser-assisted subepithelial keratectomy (36.9%), epithelial laser in situ keratomileusis (15.5%), intracorneal rings (5.8%), and limbal relaxing incisions (2.9%). The volume of refractive surgery procedures and the preferred type of excimer laser systems, microkeratomes, and diagnostic devices varied at different institutions. Most respondents performed either wavefront-guided custom ablation or wavefront-optimized ablation (63.1%) compared with conventional excimer laser correction (36.9%). Refractive surgery practice styles and preferences in Germany are comparable to trends in other European countries. Although LASIK is the most commonly performed refractive procedure, the numbers of various surface ablation techniques and refractive intraocular lens procedures are increasing. Copyright 2010, SLACK Incorporated.

  9. Finding Large Aperture Fractures in Geothermal Resource Areas Using a Three-Component Long-Offset Surface Seismic Survey, PSInSAR and Kinematic Structural Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Teplow, William J. [US Geothermal, Inc., Boise, ID (United States); Warren, Ian [US Geothermal, Inc., Boise, ID (United States)

    2015-08-12

    The DOE cost-share program applied innovative and cutting edge seismic surveying and processing, permanent scatter interferometry-synthetic aperture radar (PSInSAR) and structural kinematics to the exploration problem of locating and mapping largeaperture fractures (LAFs) for the purpose of targeting geothermal production wells. The San Emidio geothermal resource area, which is under lease to USG, contains production wells that have encountered and currently produce from LAFs in the southern half of the resource area (Figure 2). The USG lease block, incorporating the northern extension of the San Emidio geothermal resource, extends 3 miles north of the operating wellfield. The northern lease block was known to contain shallow thermal waters but was previously unexplored by deep drilling. Results of the Phase 1 exploration program are described in detail in the Phase 1 Final Report (Teplow et al., 2011). The DOE cost shared program was completed as planned on September 30, 2014. This report summarizes results from all of Phase 1 and 2 activities.

  10. Seismic waves and seismic barriers

    Science.gov (United States)

    Kuznetsov, S. V.

    2011-05-01

    The basic idea of seismic barrier is to protect an area occupied by a building or a group of buildings from seismic waves. Depending on nature of seismic waves that are most probable in a specific region, different kinds of seismic barriers are suggested. For example, vertical barriers resembling a wall in a soil can protect from Rayleigh and bulk waves. The FEM simulation reveals that to be effective, such a barrier should be (i) composed of layers with contrast physical properties allowing "trapping" of the wave energy inside some of the layers, and (ii) depth of the barrier should be comparable or greater than the considered seismic wave length. Another type of seismic barrier represents a relatively thin surface layer that prevents some types of surface seismic waves from propagating. The ideas for these barriers are based on one Chadwick's result concerning non-propagation condition for Rayleigh waves in a clamped half-space, and Love's theorem that describes condition of non-existence for Love waves. The numerical simulations reveal that to be effective the length of the horizontal barriers should be comparable to the typical wavelength.

  11. Seismic reflection survey of the Uemachi fault in Osaka Prefecture; Osaka Uemachi danso no hanshaho danseiha tansa

    Energy Technology Data Exchange (ETDEWEB)

    Sugiyama, Y. [Geological Survey of Japan, Tsukuba (Japan); Yoshizawa, M.; Hirooka, S. [Nikko Exploration and Development Co. Ltd., Tokyo (Japan); Yokota, H.; Ito, S. [Hanshin Consultant Co., Osaka (Japan); Hayashi, K.; Aizawa, H.

    1997-05-27

    Reflection survey is conducted using three traverse lines in Sakai City for confirming the presence of a southward stretch of the Uemachi fault underground along the western periphery of the Uemachi terrace, Osaka, and for elucidating its connection to the Sakamoto fault distributed near Izumi. Another reflection survey is conducted in the bed of Kanzaki river, Osaka, for the confirmation of its connection to the Nembutsuji-zan fault in Senri hillock. It is estimated on the basis of boring data that there exists another flexural structure approximately 3km south of the flexural structure whose presence is confirmed by the Sakai second traverse line. Accordingly, possibilities are high that the southward stretch of the Uemachi fault connects to the Sakamoto fault. The confirmation by the Kanzaki river traverse line of the flexural structure again confirms the continuity between the Uemachi fault and Nembutsuji-zan fault. The above-said findings enable an inference that the three faults of Nembutsuji-zan, Uemachi, and Sakamoto constitute a chain of active faults. Furthermore, there exists an active fault to the south of the Sakamoto fault, which zigzags to the south on the right-hand side as far as the south of the Kumeda pond. Accordingly, the Uemachi fault system as a whole spans approximately 43km from the northern end of the Nembutsuji-zan fault as far as the south of the Kumeda pond. 5 refs., 6 figs.

  12. Near-vertical seismic reflection image using a novel acquisition technique across the Vrancea Zone and Foscani Basin, south-eastern Carpathians (Romania)

    Science.gov (United States)

    Panea, I.; Stephenson, R.; Knapp, C.; Mocanu, V.; Drijkoningen, G.; Matenco, L.; Knapp, J.; Prodehl, K.

    2005-12-01

    The DACIA PLAN (Danube and Carpathian Integrated Action on Process in the Lithosphere and Neotectonics) deep seismic sounding survey was performed in August-September 2001 in south-eastern Romania, at the same time as the regional deep refraction seismic survey VRANCEA 2001. The main goal of the experiment was to obtain new information on the deep structure of the external Carpathians nappes and the architecture of Tertiary/Quaternary basins developed within and adjacent to the seismically-active Vrancea zone, including the Focsani Basin. The seismic reflection line had a WNW-ESE orientation, running from internal East Carpathians units, across the mountainous south-eastern Carpathians, and the foreland Focsani Basin towards the Danube Delta. There were 131 shot points along the profile, with about 1 km spacing, and data were recorded with stand-alone RefTek-125s (also known as "Texans"), supplied by the University Texas at El Paso and the PASSCAL Institute. The entire line was recorded in three deployments, using about 340 receivers in the first deployment and 640 receivers in each of the other two deployments. The resulting deep seismic reflection stacks, processed to 20 s along the entire profile and to 10 s in the eastern Focsani Basin, are presented here. The regional architecture of the latter, interpreted in the context of abundant independent constraint from exploration seismic and subsurface data, is well imaged. Image quality within and beneath the thrust belt is of much poorer quality. Nevertheless, there is good evidence to suggest that a thick (˜10 km) sedimentary basin having the structure of a graben and of indeterminate age underlies the westernmost part of the Focsani Basin, in the depth range 10-25 km. Most of the crustal depth seismicity observed in the Vrancea zone (as opposed to the more intense upper mantle seismicity) appears to be associated with this sedimentary basin. The sedimentary successions within this basin and other horizons

  13. Digitized analog boomer seismic-reflection data collected during U.S. Geological Survey cruises Erda 90-1_HC, Erda 90-1_PBP, and Erda 91-3 in Mississippi Sound, June 1990 and September 1991

    Science.gov (United States)

    Bosse, Stephen T.; Flocks, James G.; Forde, Arnell S.

    2017-04-21

    The U.S. Geological Survey (USGS) Coastal and Marine Geology Program has actively collected geophysical and sedimentological data in the northern Gulf of Mexico for several decades, including shallow subsurface data in the form of high-resolution seismic-reflection profiles (HRSP). Prior to the mid-1990s most HRSP data were collected in analog format as paper rolls of continuous profiles up to 25 meters long. A large portion of this data resides in a single repository with minimal metadata. As part of the National Geological and Geophysical Data Preservation Program, scientists at the USGS St. Petersburg Coastal and Marine Science Center are converting the analog paper records to digital format using a large-format continuous scanner.This report, along with the accompanying USGS data release (Bosse and others, 2017), serves as an archive of seismic profiles with headers, converted Society of Exploration Geophysicists Y format (SEG-Y) files, navigation data, and geographic information system data files for digitized boomer seismic-reflection data collected from the Research Vessel (R/V) Erda during two cruises in 1990 and 1991. The Erda 90-1 geophysical cruise was conducted in two legs. The first leg included seismic data collected from the Hancock County region of the Mississippi Sound (Erda 90-1_HC) from June 4 to June 6, 1990. The second leg included seismic data collected from the Petit Bois Pass area of Mississippi Sound (Erda 90-1_PBP) from June 8 to June 9, 1990. The Erda 91-3 cruise occurred between September 12 and September 23, 1991, and surveyed the Mississippi Sound region just west of Horn Island, Mississippi.

  14. Refractive status and prevalence of refractive errors in suburban school-age children.

    Science.gov (United States)

    Pi, Lian-Hong; Chen, Lin; Liu, Qin; Ke, Ning; Fang, Jing; Zhang, Shu; Xiao, Jun; Ye, Wei-Jiang; Xiong, Yan; Shi, Hui; Yin, Zheng-Qin

    2010-10-18

    This study investigated the distribution pattern of refractive status and prevalence of refractive errors in school-age children in Western China to determine the possible environmental factors. A random sampling strategy in geographically defined clusters was used to identify children aged 6-15 years in Yongchuan, a socio-economically representative area in Western China. We carried out a door-to-door survey and actual eye examinations, including visual acuity measurements, stereopsis examination, anterior segment and eyeball movements, fundus examinations, and cycloplegic retinoscopy with 1% cyclopentolate. A total of 3469 children living in 2552 households were selected, and 3070 were examined. The distributions of refractive status were positively-skewed for 6-8-year-olds, and negatively-skewed for 9-12 and 13-15-year-olds. The prevalence of hyperopia (≥+2.00 D spherical equivalent [SE]), myopia (≤-0.50 D SE), and astigmatism (≥1.00 diopter of cylinder [DC]) were 3.26%, 13.75%, and 3.75%, respectively. As children's ages increased, the prevalence rate of hyperopia decreased (PChildren in academically challenging schools had a higher risk of myopia (Prefractive status changes gradually from positively-skewed to negatively-skewed distributions as age increases, with 9-year-old being the critical age for the changes. Environmental factors and study intensity influence the occurrence and development of myopia.

  15. [Diurnal fluctuations in human refraction].

    Science.gov (United States)

    Krause, K; Taege, A

    1988-01-01

    The spectacle values of young healthy students were determined morning and afternoon by means of phoropter and autorefractometer. In addition, keratometry was performed. When the morning and afternoon refraction values were compared the latter were found to be about 0.25 diopters lower. This effect cannot be attributed exclusively to changes in the radius of the cornea.

  16. Seismic structure at the Kairei Hydrothermal vent field near the Rodriguez Triple Junction in the Indian Ocean

    Science.gov (United States)

    Takata, H.; Sato, T.; Imai, Y.; Mori, T.; Noguchi, Y.; Kono, A.; Yamada, T.; Shinohara, M.

    2014-12-01

    Central Indian Ridge is located at the north of the Rodriguez Triple Junction and shows slow-intermediate spreading rate. The Kairei hydrothermal Field (KHF) was discovered in the first segment of Central Indian Ridge near the Rodriguez Triple Junction. The vent fluid which is extruding at the KHF has higher H2 content compared with other hydrothermal vent fluid in the world. Although The KHF itself exists above a basaltic rock massif, gabbro and mafic rocks were discovered on the seafloor around the KHF. These deep-seated rocks may contribute to the high H2concentration of the Kairei vent fluid .To understand how gabbro and mafic rocks are uplifted and exhumed on the seafloor, we conducted a seismic refraction/reflection survey using ocean bottom seismograms (OBSs). We conducted the seismic refraction/reflection survey from January 27 to March 19 in 2013 using S/V Yokosuka of Jamstec. In the experiment, we used 21 OBSs, an air gun (G.I.gun) and a single channel steamer cable. We obtained 5 survey lines NNW-SSE direction parallel to the ridge axis, 5 lines E-W direction and 5 lines NNE-SSW direction. In addition to these lines, we acquired other 5 lines passing through the point above the KHF or Yokoniwa Rise, which is the north of the KHF. In analysis of refraction data, firstly, we estimated 2D velocity model under survey lines, which are parallel to the ridge axis, using the progressive model development method developed by Sato and Kennett (2000). Then, we constructed a 3D initial model and run the 3D tomographic method developed by Zelt and Barton (1998). The 1D velocity profile of the KHF seems to be similar to that of mid ocean ridges such as Mid Atlantic Ridge, East Pacific Rise. Seismic velocities under the KHF and Yokoniwa Rise reach about 6km/s at depth of 1~2 km below seafloor, probably indicating uplift of deep-seated rocks. In this presentation we will show 3D seismic structure of this area.

  17. application of the uphole seismic data in the determination of the ...

    African Journals Online (AJOL)

    server

    A total of 10 uphole data was acquired and analyzed from a seismic prospecting area of the East-Central Niger Delta,. Nigeria. The thickness ... KEYWORDS: Low velocity layer, uphole, statics correction, normal move out correction, seismic refraction. INTRODUCTION ... It is composed of marine shales with local sandy and ...

  18. Elastic-Wavefield Seismic Stratigraphy: A New Seismic Imaging Technology

    Energy Technology Data Exchange (ETDEWEB)

    Bob A. Hardage; Milo M. Backus; Michael V. DeAngelo; Sergey Fomel; Khaled Fouad; Robert J. Graebner; Paul E. Murray; Randy Remington; Diana Sava

    2006-07-31

    The purpose of our research has been to develop and demonstrate a seismic technology that will provide the oil and gas industry a better methodology for understanding reservoir and seal architectures and for improving interpretations of hydrocarbon systems. Our research goal was to expand the valuable science of seismic stratigraphy beyond the constraints of compressional (P-P) seismic data by using all modes (P-P, P-SV, SH-SH, SV-SV, SV-P) of a seismic elastic wavefield to define depositional sequences and facies. Our objective was to demonstrate that one or more modes of an elastic wavefield may image stratal surfaces across some stratigraphic intervals that are not seen by companion wave modes and thus provide different, but equally valid, information regarding depositional sequences and sedimentary facies within that interval. We use the term elastic wavefield stratigraphy to describe the methodology we use to integrate seismic sequences and seismic facies from all modes of an elastic wavefield into a seismic interpretation. We interpreted both onshore and marine multicomponent seismic surveys to select the data examples that we use to document the principles of elastic wavefield stratigraphy. We have also used examples from published papers that illustrate some concepts better than did the multicomponent seismic data that were available for our analysis. In each interpretation study, we used rock physics modeling to explain how and why certain geological conditions caused differences in P and S reflectivities that resulted in P-wave seismic sequences and facies being different from depth-equivalent S-wave sequences and facies across the targets we studied.

  19. Issues related to seismic surveys in the Estuary and Gulf of St. Lawrence : public inquiry report; Les enjeux lies aux leves sismiques dans l'estuaire et le golfe du Saint-Laurent : rapport d'enquete et d'audience publique

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2004-08-01

    Quebec's Office of Public Inquiry on the Environment (Bureau d'audiences publiques sur l'environnement) conducted public hearings on the environmental issues associated with seismic surveys carried out in the Gulf of St. Lawrence and its estuaries for the purpose of petroleum and natural gas exploration. The inquiry focused on the effect of sound waves on aquatic ecosystems and marine organisms and the associated environmental, social and economic consequences of seismic surveys. Environmental groups, scientists, fishermen and the maritime tourist industry have been concerned with the impact of seismic surveys in the Estuary and the Gulf of St. Lawrence since the autumn of 2002, when Hydro-Quebec publicized its 2002-2010 plan for oil and gas exploration and when Geophysical Service Inc. received a mandate from Hydro-Quebec to carry out seismic surveys in the area. This report presents 10 recommendations and 16 opinions resulting from 18 public hearings held in communities along the Gulf of St. Lawrence. Although the thousands of kilometres of seismic survey lines acquired in the Estuary and the Gulf of St. Lawrence since 1960 do not seem to have had any visible impact on the marine environment, the Commission has taken a precautionary approach and recommends that some practices should be limited until a review of literature demonstrates that seismic surveys do not affect the ecological integrity of the St. Lawrence for fisheries or ecotourism. 16 refs., 9 tabs., 5 figs., 2 appendices.

  20. Seismic instrumentation

    International Nuclear Information System (INIS)

    Maubach, K.

    1982-01-01

    For better understanding of the specification for seismic instrumentation of a nuclear power plant, the lecture gives some fundamental remarks to the seismic risk in the Federal Republic of Germany and to the data characterizing an earthquake event. Coming from the geophysical properties of an earthquake, the quantities are explained which are used in the design process of nuclear power plants. This process is shortly described in order to find the requirements for the specification of the seismic instrumentation. In addition the demands of licensing authorities are given. As an example the seismic instrumentation of KKP-1, BWR, is shown. The paper deals with kind and number of instruments, their location in the plant and their sensitivity and calibration. Final considerations deal with the evaluation of measured data and with plant operation after an earthquake. Some experience concerning the earthquake behaviour of equipment not designed to withstand earthquake loads is mentioned. This experience has initiated studies directed to quantification of the degree of conservatism of the assumptions in the seismic design of nuclear power plants. A final garget of these studies are more realistic design rules. (RW)

  1. Refraction in the lower troposphere: Higher order image distortion effects due to refractive profile curvature

    Science.gov (United States)

    Short, Daniel J.

    There are many applications that rely on the propagation of light through the atmosphere - all of which are subject to atmospheric conditions. While there are obvious processes such as scattering due to particulates like clouds and dust that affect the received intensity of the radiation, the clear atmosphere can also cause significant effects. Refraction is a clear air effect that can cause a variety of phenomena such as apparent relocation, stretching and compression of objects when viewed through the atmosphere. Recently, there has been significant interest in studying the refractive effects for low angle paths within the troposphere, and in particular, near-horizontal paths in the Earth's boundary layer, which is adjacent to the ground. Refractive effects in this case become problematic for many terrestrial optical applications. For example, the pointing of a free space optical communication or a remote sensing system can suffer wandering effects, high-resolution imagery can present distorted and/or dislocated targets, optical tracking of targets can be inaccurate, and optical geodetic surveying accuracy is also very sensitive to the effects of refraction. The work in this dissertation was inspired by data from a time-lapse camera system that collects images of distant targets over a near-horizontal path along the ground. This system was used previously to study apparent diurnal image displacement and this dissertation extends that work by exploring the higher order effects that result from curvature in the vertical refractive index profile of the atmosphere. There are surprisingly few experiments involving atmospheric refractive effects that carefully correlate field data to analytical expressions and other factors such as meteorological data. In working with the time-lapse data, which is comprised of sequences of hundreds or thousands of images collected over durations of weeks or months, it is important to develop straightforward analysis techniques that can

  2. Refracting surface plasmon polaritons with nanoparticle arrays

    DEFF Research Database (Denmark)

    Radko, I.P.; Evlyukhin, A.B.; Boltasseva, Alexandra

    2008-01-01

    Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive...... to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation....

  3. Seismic protection

    International Nuclear Information System (INIS)

    Herbert, R.

    1988-01-01

    To ensure that a nuclear reactor or other damage-susceptible installation is, so far as possible, tripped and already shut down before the arrival of an earthquake shock at its location, a ring of monitoring seismic sensors is provided around it, each sensor being spaced from it by a distance (possibly several kilometres) such that (taking into account the seismic-shock propagation velocity through the intervening ground) a shock monitored by the sensor and then advancing to the installation site will arrive there later than a warning signal emitted by the sensor and received at the installation, by an interval sufficient to allow the installation to trip and shut down, or otherwise assume an optimum anti-seismic mode, in response to the warning signal. Extra sensors located in boreholes may define effectively a three-dimensional (hemispherical) sensing boundary rather than a mere two-dimensional ring. (author)

  4. Seismic Studies

    Energy Technology Data Exchange (ETDEWEB)

    R. Quittmeyer

    2006-09-25

    This technical work plan (TWP) describes the efforts to develop and confirm seismic ground motion inputs used for preclosure design and probabilistic safety 'analyses and to assess the postclosure performance of a repository at Yucca Mountain, Nevada. As part of the effort to develop seismic inputs, the TWP covers testing and analyses that provide the technical basis for inputs to the seismic ground-motion site-response model. The TWP also addresses preparation of a seismic methodology report for submission to the U.S. Nuclear Regulatory Commission (NRC). The activities discussed in this TWP are planned for fiscal years (FY) 2006 through 2008. Some of the work enhances the technical basis for previously developed seismic inputs and reduces uncertainties and conservatism used in previous analyses and modeling. These activities support the defense of a license application. Other activities provide new results that will support development of the preclosure, safety case; these results directly support and will be included in the license application. Table 1 indicates which activities support the license application and which support licensing defense. The activities are listed in Section 1.2; the methods and approaches used to implement them are discussed in more detail in Section 2.2. Technical and performance objectives of this work scope are: (1) For annual ground motion exceedance probabilities appropriate for preclosure design analyses, provide site-specific seismic design acceleration response spectra for a range of damping values; strain-compatible soil properties; peak motions, strains, and curvatures as a function of depth; and time histories (acceleration, velocity, and displacement). Provide seismic design inputs for the waste emplacement level and for surface sites. Results should be consistent with the probabilistic seismic hazard analysis (PSHA) for Yucca Mountain and reflect, as appropriate, available knowledge on the limits to extreme ground

  5. Modification of Low Refractive Index Polycarbonate for High Refractive Index Applications

    Directory of Open Access Journals (Sweden)

    Gunjan Suri

    2009-01-01

    Full Text Available Polycarbonates and polythiourethanes are the most popular materials in use today, for optical applications. Polycarbonates are of two types which fall in the category of low refractive index and medium refractive index. The present paper describes the conversion of low refractive index polycarbonates into high refractive index material by the use of a high refractive index monomer, polythiol, as an additive. Novel polycarbonates, where the properties of refractive index and Abbe number can be tailor made, have been obtained. Thermal studies and refractive index determination indicate the formation of a new polymer with improved properties and suitable for optical applications.

  6. Mapping a buried Quaternary valley and pre-Quaternary faults through seismic methods in Copenhagen, Denmark.

    Science.gov (United States)

    Martinez, Kerim; Alfredo Mendoza, Jose; Henrik, Olsen

    2010-05-01

    Limited knowledge of the subsurface geology motivates the use of geophysical techniques before large engineering projects are conducted. These applications are normally restricted to satisfy the project aims, like mapping the near surface sediments, unconsolidated rocks and/or geological structures that may affect the construction locally. However, the applications can also contribute to the general knowledge of the regional geology around the location of interest. This report highlights the mapping of a buried Quaternary valley and identification of regional faults by a reflection and refraction seismic survey performed in Copenhagen. A 13.9 Km seismic survey was carried out at Copenhagen city along six crooked lines in order to determine the velocity fields in the near subsurface segment of a planned metro line and reflection patterns in deeper levels. The aim of the survey was to collect information needed for designing the underground metro. In particular it was sought to map the interface between Quaternary sedimentary layers of clay, till and sand, and the underlying layers of Palaeogene limestone found between 7 and 40 m below the ground surface. The data acquisition was carried out using a 192 channels array, receiver groups with 5 m spacing and a Vibroseis as a source at 5 m spacing following a roll along technique to complete the survey spreads. The urban environment demanded extensive survey planning including traffic control, notifications to residents and a fluent coordination with municipal authorities in order to minimize disturbances and ensure data acquisition. The reflection data was processed under a conventional scheme and the refraction data was interpreted using a non-linear traveltime tomography algorithm. The reflection results indicate the presence of faults oriented NW-SE to NNW-SSE affecting the limestone sequences. The faults may be associated to the Sorgenfrei-Tornquist Zone at the transition between the Danish Basin and the Baltic

  7. Cetaceans occurrence visual monitoring during seismic survey in the North of Campos Basin; Monitoramento visual de ocorrencia de cetaceos durante o levantamento de dados sismicos no norte da Bacia de Campos

    Energy Technology Data Exchange (ETDEWEB)

    Flor, Karina C.A.; Amaro, Thays P.C.; Carloni, Giuliano G. [Ecologus Engenharia Consultiva, Rio de Janeiro, RJ (Brazil); Uller, George A. [CGGVeritas, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The objective of this research is to present the results of the marine biota visual monitoring developed during the seismic survey in the north area of Campos Basin. The monitoring lasted five months, between 14 February and 14 July 2007, reaching, on average, eleven hours and fifty one minutes of sign effort per day. It was conducted by fourteen marine biota catch sign, three for each period of boarding, that took over during all period of the activity. Sixty two cetaceans were registered, eight belonging to suborder Odontoceti and four belonging to suborder Mysticeti. Tursiops truncatus was the predominant species in number of registers, followed by Megaptera novaeangliae. It's important to report that during all seismic activity period there wasn't any cetacean register presenting any behavior disturbance. (author)

  8. What is refractive optical bistability

    International Nuclear Information System (INIS)

    Dzhehov, Tomislav

    1993-01-01

    The basic elements of the theory of refractive optical bistability, assuming mediums with linear absorption are given. Special attention is paid to bistable etalons of semiconductor materials an oxide glasses, since some of them are considered as promising components for optical bistability applications. The design optimization of such devices for minimum switching intensity is analyzed. Computer simulation of the transfer characteristic recording for two InSb etalons is presented. (author)

  9. Parsimonious wave-equation travel-time inversion for refraction waves

    KAUST Repository

    Fu, Lei

    2017-02-14

    We present a parsimonious wave-equation travel-time inversion technique for refraction waves. A dense virtual refraction dataset can be generated from just two reciprocal shot gathers for the sources at the endpoints of the survey line, with N geophones evenly deployed along the line. These two reciprocal shots contain approximately 2N refraction travel times, which can be spawned into O(N2) refraction travel times by an interferometric transformation. Then, these virtual refraction travel times are used with a source wavelet to create N virtual refraction shot gathers, which are the input data for wave-equation travel-time inversion. Numerical results show that the parsimonious wave-equation travel-time tomogram has about the same accuracy as the tomogram computed by standard wave-equation travel-time inversion. The most significant benefit is that a reciprocal survey is far less time consuming than the standard refraction survey where a source is excited at each geophone location.

  10. Seismic scatterer distribution beneath the Wellington region, southernmost part of New Zealand's North Island

    Science.gov (United States)

    Kurashimo, E.; Sato, H.; Iidaka, T.; Ishiyama, T.; Iwasaki, T.; Henrys, S. A.; Sutherland, R.; Stern, T. A.; Savage, M. K.; Okaya, D. A.

    2012-12-01

    A detailed crustal and upper mantle structure of the subducting oceanic lithosphere and the overlying continental crust is inevitably important to constrain the physical process of earthquake occurrence. Structural images of many subduction zones have been obtained: for example, the Kanto region, central Japan (e.g., Sato et al., 2005). In the Kanto region, the Philippine Sea Plate subducts beneath the Tokyo Metropolitan area. Similar tectonic situation is found in the southernmost North Island, New Zealand, where the Pacific plate subducts beneath the Australian plate. It is also noted that capital cities are situated in both the regions. In May of 2011, the second phase of the Seismic Array Hikurangi Experiment (SAHKE) was conducted to obtain the detailed subduction structure beneath the southern North Island. The transect line ran from the Wairarapa coast to Kapiti coast over an 80 km profile. Twelve explosives were fired as controlled seismic source on the survey line between 6-10 km apart. The energy was recorded on 878 seismic stations (294 three-component and 584 vertical sensors) deployed at 100 m spacing and 50 m between Kaitoke and Featherston. Data collected on the survey line have high signal-to-noise ratio, from which we can easily recognize, not only the first arrival phases, but also latter phases. The seismic coda waves are generally interpreted as scattered waves from inhomogeneities in the Earth [e.g., Aki, 1969]. Array recordings of seismic events are useful to locate scatterers. In this study, semblance analysis [Neidell and Tarner, 1971] is applied to our waveform data for imaging seismic scatterer distribution, assuming an isotropic scattering model. To locate scatterers, we established 3-D imaginary grid points beneath the survey area. The velocity structure beneath the survey area was derived by refraction tomography method [Zelt and Barton, 1998], which was used to calculate travel times between a source/receiver to a grid point. If a

  11. High-resolution seismic imaging of the Sohagpur Gondwana basin ...

    Indian Academy of Sciences (India)

    ing) were applied to the seismic records. High amplitude noise, polarity reversals and the signals related to the direct and refracted waves in the data were eliminated. Elevation statics were applied to correct the effect of topography and near-surface heterogeneity such as weathering. Power function was used for spherical ...

  12. Seismic Symphonies

    Science.gov (United States)

    Strinna, Elisa; Ferrari, Graziano

    2015-04-01

    The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

  13. Time-lapse seismic within reservoir engineering

    NARCIS (Netherlands)

    Oldenziel, T.

    2003-01-01

    Time-lapse 3D seismic is a fairly new technology allowing dynamic reservoir characterisation in a true volumetric sense. By investigating the differences between multiple seismic surveys, valuable information about changes in the oil/gas reservoir state can be captured. Its interpretation involves

  14. Refractions

    DEFF Research Database (Denmark)

    Hougaard, Anna Katrine; Søberg, Martin; Lorentsen, Elise

    2016-01-01

    The book focuses on new directions in architectural research, how architects develop new knowledge through their artistic design practice, working in a field between Art and Science. What new digital potentials are there in architectural media like models and drawings and how to put words on arti...... on artistic research? The book offers theoretical articles, picture galleries of artistic projects, and interviews with senior-researchers at the Danish Academy of Architecture in Copenhagen and their built architectural projects.......The book focuses on new directions in architectural research, how architects develop new knowledge through their artistic design practice, working in a field between Art and Science. What new digital potentials are there in architectural media like models and drawings and how to put words...

  15. Possibilities of seismic exploration for crystalline basement study

    Directory of Open Access Journals (Sweden)

    А. Н. Телегин

    2017-03-01

    Full Text Available Possibilities of seismic methods of reflected and refracted waves have been examined for the purposes of detailed study on crystalline basement structure. Investigation of depth and structure of the basement plays an important role in the exploration of various deposits. Sedimentary cover is usually associated with oil and gas reserves. Ore deposits are formed in the basement rocks, basement splits and structure of its surface have a genetic relation not only to ore minerals, but also to oil resources. Reflection seismology is one of the main seismic methods of investigating structural geometry of the sedimentation mass, forecasting its material composition and possible hydrocarbon reserves. However, its possibilities for investigating crystalline basement are limited. Basing on many years’ experience of reflection seismology and physical modeling it has been identified that actual roughness of basement surface limits the obtainable amount of waves reflected from it. Possibilities of reflection seismology for basement structure study are mostly related to investigation of discontinuous faults as diffraction objects using diffracted waves. Method of refracted waves combined with modern procedures and material processing aimed at getting dynamic seismic sections holds much significance for the basement study, especially in the process of surface mapping and, to a lesser extent, in investigating discontinuous faults. Combining seismic methods of reflected and refracted waves in basement study increases reliability of forecasting its geological structure: in particular, its surface can be well defined by means of refraction seismology, and zones of discontinuous faults are identified from diffraction objects using both reflection and refraction methods. As a result of applying both reflection and refraction seismology, an opportunity arises to carry out detailed analysis of basement structure and to predict its oil and gas content.

  16. Oklahoma seismic network

    International Nuclear Information System (INIS)

    Luza, K.V.; Lawson, J.E. Jr.; Univ. of Oklahoma, Norman, OK

    1993-07-01

    The US Nuclear Regulatory Commission has established rigorous guidelines that must be adhered to before a permit to construct a nuclear-power plant is granted to an applicant. Local as well as regional seismicity and structural relationships play an integral role in the final design criteria for nuclear power plants. The existing historical record of seismicity is inadequate in a number of areas of the Midcontinent region because of the lack of instrumentation and (or) the sensitivity of the instruments deployed to monitor earthquake events. The Nemaha Uplift/Midcontinent Geophysical Anomaly is one of five principal areas east of the Rocky Mountain front that has a moderately high seismic-risk classification. The Nemaha uplift, which is common to the states of Oklahoma, Kansas, and Nebraska, is approximately 415 miles long and 12-14 miles wide. The Midcontinent Geophysical Anomaly extends southward from Minnesota across Iowa and the southeastern corner of Nebraska and probably terminates in central Kansas. A number of moderate-sized earthquakes--magnitude 5 or greater--have occurred along or west of the Nemaha uplift. The Oklahoma Geological Survey, in cooperation with the geological surveys of Kansas, Nebraska, and Iowa, conducted a 5-year investigation of the seismicity and tectonic relationships of the Nemaha uplift and associated geologic features in the Midcontinent. This investigation was intended to provide data to be used to design nuclear-power plants. However, the information is also being used to design better large-scale structures, such as dams and high-use buildings, and to provide the necessary data to evaluate earthquake-insurance rates in the Midcontinent

  17. The Crustal Structure and Seismicity of Eastern Venezuela

    Science.gov (United States)

    Schmitz, M.; Martins, A.; Sobiesiak, M.; Alvarado, L.; Vasquez, R.

    2001-12-01

    Eastern Venezuela is characterized by a moderate to high seismicity, evidenced recently by the 1997 Cariaco earthquake located on the El Pilar Fault, a right lateral strike slip fault which marks the plate boundary between the Caribbean and South-American plates in this region. Recently, the seismic activity seems to migrate towards the zone of subduction of the Lesser Antilles in the northeast, where a mb 6.0 earthquake occurred in October 2000 at 120 km of depth. Periodical changes in the seismic activity are related to the interaction of the stress fields of the strike-slip and the subduction regimes. The seismic activity decreases rapidly towards to the south with some disperse events on the northern edge of the Guayana Shield, related to the Guri fault system. The crustal models used in the region are derived from the information generated by the national seismological network since 1982 and by microseismicity studies in northeastern Venezuela, coinciding in a crustal thickness of about 35 km in depth. Results of seismic refraction measurements for the region were obtained during field campains in 1998 (ECOGUAY) for the Guayana Shield and the Cariaco sedimentary basin and in 2001 (ECCO) for the Oriental Basin. The total crustal thickness decreases from about 45 km on the northern edge of the Guayana Shield to some 36 km close to El Tigre in the center of the Oriental Basin. The average crustal velocity decreases in the same sense from 6.5 to 5.8 km/s. In the Cariaco sedimentary basin a young sedimentary cover of 1 km thickness with a seismic velocity of 2 km/s was derived. Towards the northern limit of the South-American plate, no deep seismic refraction data are available up to now. The improvement of the crustal models used in that region would constitute a step forward in the analysis of the seismic hazard. Seismic refraction studies funded by CONICIT S1-97002996 and S1-2000000685 projects and PDVSA (additional drilling and blasting), recording equipment

  18. Refractive Surgery: Malpractice Litigation Outcomes.

    Science.gov (United States)

    Custer, Benjamin L; Ballard, Steven R; Carroll, Robert B; Barnes, Scott D; Justin, Grant A

    2017-10-01

    To review data on malpractice claims related to refractive surgery to identify common allegations and injuries and financial outcomes. The WestlawNext database was reviewed for all malpractice lawsuits/settlements related to refractive eye surgery. Data evaluated included patient demographics, type of operation performed, plaintiff allegation, nature of injury, and litigation outcomes. A total of 167 cases met the inclusion criteria, of which 108 cases (64.7%) were found to be favorable and 59 cases (35.3%) unfavorable to the defendant. A total of 141 cases were tried by a jury with 108 cases (76.4%) favorable and 33 cases (23.6%) unfavorable to the defendant. Laser in situ keratomileusis was performed in 127 cases (76%). The most common allegations were negligence in treatment or surgery in 127 cases (76%) and lack of informed consent in 83 cases (49.7%). For all cases, the need for future surgery (P = 0.0001) and surgery resulting in keratoconus (P = 0.05) were more likely to favor the plaintiff. In jury verdict decisions, cases in which failure to diagnose a preoperative condition was alleged favored the defendant (P = 0.03), whereas machine malfunction (P = 0.05) favored the plaintiff. After adjustment for inflation, the overall mean award was $1,287,872. Jury verdicts and settlements led to mean awards of $1,604,801 and $826,883, respectively. Malpractice litigation in refractive surgery tends to favor the defendant. However, large awards and settlements were given in cases that were favorable to the plaintiff. The need for future surgery and surgery leading to keratoconus increased the chance of an unfavorable outcome.

  19. Theory of supervirtual refraction interferometry

    KAUST Repository

    Bharadwaj, Pawan

    2012-01-01

    Inverting for the subsurface velocity distribution by refraction traveltime tomography is a well-accepted imaging method by both the exploration and earthquake seismology communities. A significant drawback, however, is that the recorded traces become noisier with increasing offset from the source position, and so accurate picking of traveltimes in far-offset traces is often prevented. To enhance the signal-to-noise ratio (SNR) of the far-offset traces, we present the theory of supervirtual refraction interferometry where the SNR of far-offset head-wave arrivals can be theoretically increased by a factor proportional to; here, N is the number of receiver or source positions associated with the recording and generation of the head-wave arrival. There are two steps to this methodology: correlation and summation of the data to generate traces with virtual head-wave arrivals, followed by the convolution of the data with the virtual traces to create traces with supervirtual head-wave arrivals. This method is valid for any medium that generates head-wave arrivals recorded by the geophones. Results with both synthetic traces and field data demonstrate the feasibility of this method. There are at least four significant benefits of supervirtual interferometry: (1) an enhanced SNR of far-offset traces so the first-arrival traveltimes of the noisy far-offset traces can be more reliably picked to extend the useful aperture of the data, (2) the SNR of head waves in a trace that arrive later than the first arrival can be enhanced for accurate traveltime picking and subsequent inversion by later-arrival traveltime tomography, (3) common receiver-pair gathers can be analysed to detect the presence of diving waves in the first arrivals, which can be used to assess the nature of the refracting boundary, and (4) the source statics term is eliminated in the correlation operations so that the timing of the virtual traces is independent of the source excitation time. This suggests the

  20. Updated Colombian Seismic Hazard Map

    Science.gov (United States)

    Eraso, J.; Arcila, M.; Romero, J.; Dimate, C.; Bermúdez, M. L.; Alvarado, C.

    2013-05-01

    possible to determinate environments and scenarios where the seismic hazard is a function of distance and magnitude and also the principal seismic sources that contribute to the seismic hazard at each site (dissagregation). This project was conducted by the Servicio Geológico Colombiano (Colombian Geological Survey) and the Universidad Nacional de Colombia (National University of Colombia), with the collaboration of national and foreign experts and the National System of Prevention and Attention of Disaster (SNPAD). It is important to stand out that this new seismic hazard map was used in the updated national building code (NSR-10). A new process is ongoing in order to improve and present the Seismic Hazard Map in terms of intensity. This require new knowledge in site effects, in both local and regional scales, checking the existing and develop new acceleration to intensity relationships, in order to obtain results more understandable and useful for a wider range of users, not only in the engineering field, but also all the risk assessment and management institutions, research and general community.

  1. Seismic and tsunami safety margin assessment

    International Nuclear Information System (INIS)

    2013-01-01

    Nuclear Regulation Authority is going to establish new seismic and tsunami safety guidelines to increase the safety of NPPs. The main purpose of this research is testing structures/components important to safety and tsunami resistant structures/components, and evaluating the capacity of them against earthquake and tsunami. Those capacity data will be utilized for the seismic and tsunami back-fit review based on the new seismic and tsunami safety guidelines. The summary of the program in 2012 is as follows. 1. Component seismic capacity test and quantitative seismic capacity evaluation. PWR emergency diesel generator partial-model seismic capacity tests have been conducted and quantitative seismic capacities have been evaluated. 2. Seismic capacity evaluation of switching-station electric equipment. Existing seismic test data investigation, specification survey and seismic response analyses have been conducted. 3. Tsunami capacity evaluation of anti-inundation measure facilities. Tsunami pressure test have been conducted utilizing a small breakwater model and evaluated basic characteristics of tsunami pressure against seawall structure. (author)

  2. Seismic Discrimination

    Science.gov (United States)

    1979-09-30

    Plate Tectonics ,’ in The Earth: Its Origin. Structure and Evolution (Academic Press. London. f9-79). pp. 491-542. 185. M. A. Chinnery. "A Comparison of...stations in Eurasia-SHIO (Shillong, india), ANTO ( Ankara , Turkey), GRFO (Graefenberg, Germany), and KONO (Kongsberg, Norway) started producing data, and we...34 Tectonics of the Caribbean and Middle America Regions from Focal Mechanisms and Seismicity." Geol. Soc. Am. Bull. 80. 1639-1684 (1969). 10. T. J

  3. Martian seismicity

    International Nuclear Information System (INIS)

    Goins, N.R.; Lazarewicz, A.R.

    1979-01-01

    During the Viking mission to Mars, the seismometer on Lander II collected approximately 0.24 Earth years of observations data, excluding periods of time dominated by wind-induced Lander vibration. The ''quiet-time'' data set contains no confirmed seismic events. A proper assessment of the significance of this fact requires quantitative estimates of the expected detection rate of the Viking seismometer. The first step is to calculate the minimum magnitude event detectable at a given distance, including the effects of geometric spreading, anelastic attenuation, seismic signal duration, seismometer frequency response, and possible poor ground coupling. Assuming various numerical quantities and a Martian seismic activity comparable to that of intraplate earthquakes, the appropriate integral gives an expected annual detection rate of 10 events, nearly all of which are local. Thus only two to three events would be expected in the observational period presently on hand and the lack of observed events is not in gross contradiction to reasonable expectations. Given the same assumptions, a seismometer 20 times more sensitive than the present instrument would be expected to detect about 120 events annually

  4. Considerations in comparing the U.S. Geological Survey one‐year induced‐seismicity hazard models with “Did You Feel It?” and instrumental data

    Science.gov (United States)

    White, Isabel; Liu, Taojun; Luco, Nicolas; Liel, Abbie

    2017-01-01

    The recent steep increase in seismicity rates in Oklahoma, southern Kansas, and other parts of the central United States led the U.S. Geological Survey (USGS) to develop, for the first time, a probabilistic seismic hazard forecast for one year (2016) that incorporates induced seismicity. In this study, we explore a process to ground‐truth the hazard model by comparing it with two databases of observations: modified Mercalli intensity (MMI) data from the “Did You Feel It?” (DYFI) system and peak ground acceleration (PGA) values from instrumental data. Because the 2016 hazard model was heavily based on earthquake catalogs from 2014 to 2015, this initial comparison utilized observations from these years. Annualized exceedance rates were calculated with the DYFI and instrumental data for direct comparison with the model. These comparisons required assessment of the options for converting hazard model results and instrumental data from PGA to MMI for comparison with the DYFI data. In addition, to account for known differences that affect the comparisons, the instrumental PGA and DYFI data were declustered, and the hazard model was adjusted for local site conditions. With these adjustments, examples at sites with the most data show reasonable agreement in the exceedance rates. However, the comparisons were complicated by the spatial and temporal completeness of the instrumental and DYFI observations. Furthermore, most of the DYFI responses are in the MMI II–IV range, whereas the hazard model is oriented toward forecasts at higher ground‐motion intensities, usually above about MMI IV. Nevertheless, the study demonstrates some of the issues that arise in making these comparisons, thereby informing future efforts to ground‐truth and improve hazard modeling for induced‐seismicity applications.

  5. Application of GPR and seismic methods in landslides investigation and determination of hydrogeological conditions

    Science.gov (United States)

    Czaja, Klaudia; Matuła, Rafał

    2013-04-01

    Ground Penetrating Radar (GPR) belongs to non-invasive geophysical methods which use an artificially induced electromagnetic field as the way for inspection. GPR is applied not only to recognition of shallow geological structure but also to archeological studies. The basic assumption of the applicability of GPR is the existance of a distinct boundary between two lithological horizons defined by a change in permittivity values, which results in a change in electromagnetic wave velocity. For that reason this method is used to locate empty spaces and saturated zones. The purpose of this measurements was to determine the details of the sliding body, including the thickness and lateral extension of the landslide material, the depth of the sliding surface and water content of the subsurface. What is more correlation between GPR and seismic methods was searched. Studied area was located in the Southern part of Poland. Geological structure is characteristic for Carpathian flysch - overlaying claystones, shales and sandstones. Measurements were carried out using GPR equipment from the Swedish company Mala Geoscience. Due to the required depth range and resolution unshielded antennas with frequencies from 25 MHz to 200 MHz were used. Profiles were traced parallel to the landslide axis. Following forms of GPR survey were applied: CO (common offset), CMP (common mid point), WARR (wide-angle reflection-refraction). Modeling attempt electromagnetic field distribution in the medium was undertaken to select the most appropriate measurement parameters and to improve the interpretation. Programme GPRMax2D v. 2.0 was used to create models. The GPR numerical analysis uses the finite - difference time - domain method (FDTD). The FDTD approach to the numerical solution of Maxwell's equations consist of discretization both the space and the time continua. Due to geological structure (presence of low resistivity clays and shales) attenuation of electromagnetic wave was high. In order to

  6. [Complications after refractive surgery abroad].

    Science.gov (United States)

    Terzi, E; Kern, T; Kohnen, T

    2008-05-01

    In this article a retrospective analysis of patients presenting at a German university following refractive surgery abroad is presented. A total of 20 cases of patients who had undergone treatment between 1998 and 2006 in China (1 case), Greece (1 case), Iran (1 case), Russia (2 cases), Switzerland (1 case), Slovakia (1 case), Spain (2 cases), South Africa (3 cases), Turkey (6 cases) and the USA (2 cases) were analyzed retrospectively. The following complications were observed: epithelial ingrowth into the interface with or without melting of the flap (6 cases), corneal ectasia (2 cases), dislocation of a phakic posterior chamber intraocular lens and prolapse into the anterior chamber with endothelial cell loss (1 case), secondary increase of intraocular pressure following implantation of a phakic intraocular lens (1 case), flap-related complications following laser-in-situ keratomileusis (LASIK) (2 cases), keratitis (1 case), dislocation of the complete flap (1 case), diffuse lamellar keratitis (DLK) grade IV (1 case), hyperopia as a consequence of radial keratotomy (1 case), and under correction/over correction and poor optical quality following laser epithelial keratomileusis (LASEK) and LASIK for high myopia (5 cases) with possible early corneal ectasia. There are four important problems arising from refractive surgery abroad, often referred to as "LASIK tourism": wrong indications, insufficient management of complications, lack of postoperative care and the health economic aspect.

  7. 3D seismic travel time surveying - a comparison of the time-term method and tomography (an example from an archaeological site)

    Czech Academy of Sciences Publication Activity Database

    Valenta, Jan; Dohnal, J.

    2007-01-01

    Roč. 63, č. 1 (2007), s. 46-58 ISSN 0926-9851 Institutional research plan: CEZ:AV0Z30460519 Keywords : shallow seismic * tomography * archaeology Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.938, year: 2007

  8. Refractive index of plant cell walls

    Science.gov (United States)

    Gausman, H. W.; Allen, W. A.; Escobar, D. E.

    1974-01-01

    Air was replaced with media of higher refractive indices by vacuum infiltration in leaves of cucumber, blackeye pea, tomato, and string bean plants, and reflectance of noninfiltrated and infiltrated leaves was spectrophotometrically measured. Infiltrated leaves reflected less light than noninfiltrated leaves over the 500-2500-nm wavelength interval because cell wall-air interfaces were partly eliminated. Minimal reflectance should occur when the average refractive index of plant cell walls was matched by the infiltrating fluid. Although refractive indices that resulted in minimal reflectance differed among the four plant genera, an average value of 1.425 approximates the refractive index of plant cell walls for the four plant genera.

  9. Seismic Model and Geological Interpretation of the Basement Beneath the Doupovske Hory Volcanic Complex (NW Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Valenta, Jan; Brož, Milan; Málek, Jiří; Mlčoch, B.; Rapprich, V.; Skácelová, Z.

    2011-01-01

    Roč. 59, č. 3 (2011), s. 597-617 ISSN 1895-6572 R&D Projects: GA AV ČR IAA300460602 Institutional research plan: CEZ:AV0Z30460519 Keywords : seismic refraction * seismic tomography * Doupovske Hory Volcanic Complex Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.617, year: 2011

  10. Influence of refraction index strength on the light propagation in dielectrics material with periodic refraction index

    Energy Technology Data Exchange (ETDEWEB)

    Hidayat, Arif, E-mail: arif.hidayat.fmipa@um.ac.id; Latifah, Eny; Kurniati, Diana; Wisodo, Hari [Nonlinear Optics Group Department of Physics, Faculty of Mathematics and Natural Sciences State University of Malang (Indonesia)

    2016-04-19

    This study investigated the influence of refraction index strength on the light propagation in refraction index-varied dielectric material. This dielectric material served as photonic lattice. The behavior of light propagation influenced by variation of refraction index in photonic lattice was investigated. Modes of the guiding light were determined numerically using squared-operator iteration method. It was found that the greater the strength of refraction index, the smaller the guiding modes.

  11. Analysis of nonvolcanic tremor on the San Andreas Fault near Parkfield, CA using U.S. Geological Survey Parkfield Seismic Array

    Science.gov (United States)

    Fletcher, Jon B.; Baker, Lawrence M.

    2010-01-01

    Reports by Nadeau and Dolenc (2005) that tremor had been detected near Cholame Valley spawned an effort to use UPSAR (U. S. Geological Survey Parkfield Seismic Array) to study characteristics of tremor. UPSAR was modified to record three channels of velocity at 40–50 sps continuously in January 2005 and ran for about 1 month, during which time we recorded numerous episodes of tremor. One tremor, on 21 January at 0728, was recorded with particularly high signal levels as well as another episode 3 days later. Both events were very emergent, had a frequency content between 2 and 8 Hz, and had numerous high-amplitude, short-duration arrivals within the tremor signal. Here using the first episode as an example, we discuss an analysis procedure, which yields azimuth and apparent velocity of the tremor at UPSAR. We then provide locations for both tremor episodes. The emphasis here is how the tremor episode evolves. Twelve stations were operating at the time of recording. Slowness of arrivals was determined using cross correlation of pairs of stations; the same method used in analyzing the main shock data from 28 September 2004. A feature of this analysis is that 20 s of the time series were used at a time to calculate correlation; the longer windows resulted in more consistent estimates of slowness, but lower peak correlations. These values of correlation (peaks of about 0.25), however, are similar to that obtained for the S wave of a microearthquake. Observed peaks in slowness were traced back to source locations assumed to lie on the San Andreas fault. Our inferred locations for the two tremor events cluster near the locations of previously observed tremor, south of the Cholame Valley. Tremor source depths are in the 14–24 km range, which is below the seismogenic brittle zone, but above the Moho. Estimates of error do not preclude locations below the Moho, however. The tremor signal is very emergent but contains packets that are several times larger than the

  12. Prevalence of refractive error, presbyopia and spectacle coverage in Kahama District, Tanzania: a rapid assessment of refractive error.

    Science.gov (United States)

    Mashayo, Eden R; Chan, Ving Fai; Ramson, Prasidh; Chinanayi, Farai; Naidoo, Kovin S

    2015-01-01

    In Tanzania, the prevalence of refractive error and presbyopia have not been comprehensively assessed, limiting appropriate planning and implementation of delivery of vision care. This study sought to determine the prevalence of refractive error and presbyopia, spectacle coverage and the barriers to uptake of refractive services in people aged 15 years and older in the Kahama district of Tanzania. A cross-sectional community-based survey was conducted using 54 randomly selected clusters. Respondents 15 years and older were interviewed and underwent standardised clinical eye examinations. Uncorrected refractive error (URE) was defined as presenting vision worse than 6/12 that could be corrected to better than 6/12 using a pinhole. Spectacle coverage was defined as the proportion of need that was met (those that improved from unaided vision with their own spectacle correction). A total of 3,230 subjects (99.75 per cent of 3,240 eligible) participated in the study with 57.2 per cent males and the median age of participants was 35 years (inter-quartile range, 24 to 49). The prevalence of visual impairment was 10.4 per cent (95% CI 9.4 to 11.4) and was lower in those who had completed their primary school education (odds ratio (OR) 0.54, 95% CI: 0.40 to 0.72) and highest in subjects 40 years and older (OR 3.17, 95% CI: 2.14 to 4.70) and farmers (OR 8.57 95% CI: 2.27 to 32.43). Refractive error prevalence was 7.5 per cent (95% CI: 6.65 to 8.54) and this was highest in participants over 40 years (OR 1.60, 95% CI: 1.14 to 2.25) and in students (OR 3.64, 95% CI: 1.35 to 9.86). Prevalence of presbyopia was 46.5 per cent (773/1,663, 95% CI: 44.34 to 48.75). Spectacle coverage for refractive error and presbyopia was 1.69% (95% CI: 0 to 3.29) and 0.42% (95% CI: 0 to 1.26), respectively. Uncorrected refractive error is a public health challenge in the Kahama district and sustainable service delivery and health promotion efforts are needed. © 2014 The Authors. Clinical and

  13. Measurements of photoinduced refractive index changes in ...

    Indian Academy of Sciences (India)

    Abstract. We report the pump–probe measurements of nonlinear refractive index changes in photochromic bacteriorhodopsin films. The photoinduced absorption is caused by pump beam at 532 nm and the accompanying refractive index changes are studied using a probe beam at 633 nm. The proposed technique is ...

  14. Refractive index measurement based on confocal method

    Science.gov (United States)

    An, Zhe; Xu, XiPing; Yang, JinHua; Qiao, Yang; Liu, Yang

    2017-10-01

    The development of transparent materials is closed to optoelectronic technology. It plays an increasingly important role in various fields. It is not only widely used in optical lens, optical element, optical fiber grating, optoelectronics, but also widely used in the building material, pharmaceutical industry with vessel, aircraft windshield and daily wear glasses.Regard of solving the problem of refractive index measurement in optical transparent materials. We proposed that using the polychromatic confocal method to measuring the refractive index of transparent materials. In this article, we describes the principle of polychromatic confocal method for measuring the refractive index of glass,and sketched the optical system and its optimization. Then we establish the measurement model of the refractive index, and set up the experimental system. In this way, the refractive index of the glass has been calibrated for refractive index experiment. Due to the error in the experimental process, we manipulated the experiment data to compensate the refractive index measurement formula. The experiment taking the quartz glass for instance. The measurement accuracy of the refractive index of the glass is +/-1.8×10-5. This method is more practical and accurate, especially suitable for non-contact measurement occasions, which environmental requirements is not high. Environmental requirements are not high, the ordinary glass production line up to the ambient temperature can be fully adapted. There is no need for the color of the measured object that you can measure the white and a variety of colored glass.

  15. Microstructured optical fiber refractive index sensor

    DEFF Research Database (Denmark)

    Town, Graham E.; McCosker, Ravi; Yuan, Scott Wu

    2010-01-01

    We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show...

  16. REFRACTIVE ERROR STATUS IN BAYELSA STATE, NIGERIA

    African Journals Online (AJOL)

    LIVINGSTON

    vision) thus making refractive error the leading cause of low vision and the second leading cause of blindness following cataract which remained the leading cause of blindness globally. Various studies have documented the prevalence of refractive errors in different population groups. Among adult Chinese population in ...

  17. Seismic instrumentation

    International Nuclear Information System (INIS)

    1984-06-01

    RFS or Regles Fondamentales de Surete (Basic Safety Rules) applicable to certain types of nuclear facilities lay down requirements with which compliance, for the type of facilities and within the scope of application covered by the RFS, is considered to be equivalent to compliance with technical French regulatory practice. The object of the RFS is to take advantage of standardization in the field of safety, while allowing for technical progress in that field. They are designed to enable the operating utility and contractors to know the rules pertaining to various subjects which are considered to be acceptable by the Service Central de Surete des Installations Nucleaires, or the SCSIN (Central Department for the Safety of Nuclear Facilities). These RFS should make safety analysis easier and lead to better understanding between experts and individuals concerned with the problems of nuclear safety. The SCSIN reserves the right to modify, when considered necessary, any RFS and specify, if need be, the terms under which a modification is deemed retroactive. The aim of this RFS is to define the type, location and operating conditions for seismic instrumentation needed to determine promptly the seismic response of nuclear power plants features important to safety to permit comparison of such response with that used as the design basis

  18. Crustal seismicity in central Chile

    Science.gov (United States)

    Barrientos, S.; Vera, E.; Alvarado, P.; Monfret, T.

    2004-06-01

    Both the genesis and rates of activity of shallow intraplate seismic activity in central Chile are poorly understood, mainly because of the lack of association of seismicity with recognizable fault features at the surface and a poor record of seismic activity. The goal of this work is to detail the characteristics of seismicity that takes place in the western flank of the Andes in central Chile. This region, located less than 100 km from Santiago, has been the site of earthquakes with magnitudes up to 6.9, including several 5+ magnitude shocks in recent years. Because most of the events lie outside the Central Chile Seismic Network, at distances up to 60 km to the east, it is essential to have adequate knowledge of the velocity structure in the Andean region to produce the highest possible quality of epicentral locations. For this, a N-S refraction line, using mining blasts of the Disputada de Las Condes open pit mine, has been acquired. These blasts were detected and recorded as far as 180 km south of the mine. Interpretation of the travel times indicates an upper crustal model consisting of three layers: 2.2-, 6.7-, and 6.1-km thick, overlying a half space; their associated P wave velocities are 4.75-5.0 (gradient), 5.8-6.0 (gradient), 6.2, and 6.6 km/s, respectively. Hypocentral relocation of earthquakes in 1986-2001, using the newly developed velocity model, reveals several regions of concentrated seismicity. One clearly delineates the fault zone and extensions of the strike-slip earthquake that took place in September 1987 at the source of the Cachapoal River. Other regions of activity are near the San José volcano, the source of the Maipo River, and two previously recognized lineaments that correspond to the southern extension of the Pocuro fault and Olivares River. A temporary array of seismographs, installed in the high Maipo River (1996) and San José volcano (1997) regions, established the hypocentral location of events with errors of less than 1 km

  19. Buried volcanic structures in the Gulf of Naples (Southern Tyrrhenian Sea, Italy resulting from high resolution magnetic survey and seismic profiling

    Directory of Open Access Journals (Sweden)

    S. Ruggieri

    2005-06-01

    Full Text Available In this paper we present a correlation between volcanic structures and magnetic anomalies in the Gulf of Naples (Southern Tyrrhenian Sea based on high resolution magnetic profiling. A densely spaced grid of magnetic profiles coupled with multichannel seismics (seismic source Watergun 15 cubic inch was recorded in the Gulf of Naples, representing an active volcanic area during the Late Quaternary (volcanic centers of Somma-Vesuvius, Phlegraean Fields and Ischia and Procida islands. The dataset was collected during the oceanographic cruise GMS00-05 which took place during October-November 2000 in the South Tyrrhenian Sea onboard of the R/V Urania (National Research Council, Italy. Shallow volcanic structures in the subsurface of the gulf were recognized by seismo-stratigraphic analysis of high resolution profiles; the volcanic nature of some of these structures was inferred identifying the magnetic anomalies on a high resolution magnetic anomaly map of the gulf. Even if qualitative, the correlations between seismic and magnetic profiles allow us to better assess the geological structure of the Gulf of Naples.

  20. Fully 3D refraction correction dosimetry system

    International Nuclear Information System (INIS)

    Manjappa, Rakesh; Makki, S Sharath; Kanhirodan, Rajan; Kumar, Rajesh; Vasu, Ram Mohan

    2016-01-01

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  1. Prevalence of uncorrected refractive errors in adults aged 30 years and above in a rural population in Pakistan

    International Nuclear Information System (INIS)

    Abdullah, A.S.; Azam, M.; Nigar, M.

    2015-01-01

    Uncorrected refractive errors are a leading cause of visual disability globally. This population-based study was done to estimate the prevalence of uncorrected refractive errors in adults aged 30 years and above of village Pawakah, Khyber Pakhtunkhwa (KPK), Pakistan. Methods: It was a cross-sectional survey in which 1000 individuals were included randomly. All the individuals were screened for uncorrected refractive errors and those whose visual acuity (VA) was found to be less than 6/6 were refracted. In whom refraction was found to be unsatisfactory (i.e., a best corrected visual acuity of <6/6) further examination was done to establish the cause for the subnormal vision. Results: A total of 917 subjects participated in the survey (response rate 92%). The prevalence of uncorrected refractive errors was found to be 23.97% among males and 20% among females. The prevalence of visually disabling refractive errors was 6.89% in males and 5.71% in females. The prevalence was seen to increase with age, with maximum prevalence in 51-60 years age group. Hypermetropia (10.14%) was found to be the commonest refractive error followed by Myopia (6.00%) and Astigmatism (5.6%). The prevalence of Presbyopia was 57.5% (60.45% in males and 55.23% in females). Poor affordability was the commonest barrier to the use of spectacles, followed by unawareness. Cataract was the commonest reason for impaired vision after refractive correction. The prevalence of blindness was 1.96% (1.53% in males and 2.28% in females) in this community with cataract as the commonest cause. Conclusions: Despite being the most easily avoidable cause of subnormal vision uncorrected refractive errors still account for a major proportion of the burden of decreased vision in this area. Effective measures for the screening and affordable correction of uncorrected refractive errors need to be incorporated into the health care delivery system. (author)

  2. Repeatability of subjective and objective refraction.

    Science.gov (United States)

    Rosenfield, M; Chiu, N N

    1995-08-01

    Although several studies have examined the repeatability of objective refraction, data concerning the repeatability of subjective refraction under masked conditions, i.e., where the examiner is unaware of the refractive results, are limited. Accordingly, the present study compared the variability of both subjective and objective refractive techniques. Refractive error was measured in 12 subjects on 5 separate occasions. Conventional subjective procedures were used, with the exception that the sphere power scale on the phoropter was covered so that the examiner was unaware of the final result. Objective measurements were obtained using a Canon Autoref R-1 infrared autorefractor. The standard deviation (SD) of the five examinations was calculated for each individual and the mean values for the population sample determined. The mean SD's for the subjective and objective techniques were +/- 0.14 and +/- 0.18 D, indicating 95% confidence limits of +/- 0.27 and +/- 0.35 D, respectively. It is concluded that with either assessment technique, a change in refractive error of at least +/- 0.50 D should be adopted as the minimum significant shift in refractive status.

  3. Dark refraction shift with allowance for astigmatism

    Directory of Open Access Journals (Sweden)

    W.D.H. Gillan

    2005-12-01

    Full Text Available Purpose: To show that the dark refraction shift (dark focus is a more complicated phenomenon than implied when presented as spherical. Methods: Fifty autorefractor measurements of refractive state of the right eye were obtained in light  and  dark  conditions.  Multivariate  methods were used to analyze the data and stereo-pair scat-ter plots, polar meridional profiles and other means of presenting results are used to show important characteristics of the dark refraction shift. Results: The complexity of the dark refrac-tion shift is indicated by stereo-pair scatter plots showing the amount of stigmatic and antistigmatic variation that occurs in light and dark conditions. The mean dark refraction shift is presented in a complete manner including all three components of refractive state. The greater variance and covari-ance under dark conditions is clearly shown by the term-by-term dark-light variance-covariance ratio and polar profiles  of variance and covariance.Conclusions: The  dark  refraction  shift  is  a more complicated phenomenon than implied by representations as purely spherical in nature.

  4. Seismic risk perception test

    Science.gov (United States)

    Crescimbene, Massimo; La Longa, Federica; Camassi, Romano; Pino, Nicola Alessandro

    2013-04-01

    population and territory); seismic risk in general; risk information and their sources; comparison between seismic risk and other natural hazards. Informative data include: Region, Province, Municipality of residence, Data compilation, Age, Sex, Place of Birth, Nationality, Marital status, Children, Level of education, Employment. The test allows to obtain the perception score for each factor: Hazard, Exposed value, Vulnerability. These scores can be put in relation with the scientific data relating to hazard, vulnerability and the exposed value. On January 2013 started a Survey in the Po Valley and Southern Apennines. The survey will be conducted via web using institutional sites of regions, provinces, municipalities, online newspapers to local spreading, etc. Preliminary data will be discussed. Improve our understanding of the perception of seismic risk would allow us to inform more effectively and to built better educational projects to mitigate risk.

  5. How to incorporate generic refraction models into multistatic tracking algorithms

    Science.gov (United States)

    Crouse, D. F.

    The vast majority of literature published on target tracking ignores the effects of atmospheric refraction. When refraction is considered, the solutions are generally tailored to a simple exponential atmospheric refraction model. This paper discusses how arbitrary refraction models can be incorporated into tracking algorithms. Attention is paid to multistatic tracking problems, where uncorrected refractive effects can worsen track accuracy and consistency in centralized tracking algorithms, and can lead to difficulties in track-to-track association in distributed tracking filters. Monostatic and bistatic track initialization using refraction-corrupted measurements is discussed. The results are demonstrated using an exponential refractive model, though an arbitrary refraction profile can be substituted.

  6. The 7.8 Mw Earthquake and Tsunami of the 16th April 2016 in Ecuador - Seismic evaluation, Geological field survey and Economic implications

    OpenAIRE

    Mato Méndez, Fernando José

    2017-01-01

    We evaluated the recent earthquake and tsunami responsible for considerable damage and 663 deaths due to a 7.8Mw movement on the 16th of April 2016. The seismic event filled tens of thousands in refugee camps and affected some two million persons directly. The potential of high losses and damage with a total of 29,672 properties, including family houses, is also given by the fact that the infrastructure of the fishing, tourism and other industries and the movement to live along the beaches, h...

  7. Understanding refraction contrast using a comparison of absorption and refraction computed tomographic techniques

    Science.gov (United States)

    Wiebe, S.; Rhoades, G.; Wei, Z.; Rosenberg, A.; Belev, G.; Chapman, D.

    2013-05-01

    Refraction x-ray contrast is an imaging modality used primarily in a research setting at synchrotron facilities, which have a biomedical imaging research program. The most common method for exploiting refraction contrast is by using a technique called Diffraction Enhanced Imaging (DEI). The DEI apparatus allows the detection of refraction between two materials and produces a unique ''edge enhanced'' contrast appearance, very different from the traditional absorption x-ray imaging used in clinical radiology. In this paper we aim to explain the features of x-ray refraction contrast as a typical clinical radiologist would understand. Then a discussion regarding what needs to be considered in the interpretation of the refraction image takes place. Finally we present a discussion about the limitations of planar refraction imaging and the potential of DEI Computed Tomography. This is an original work that has not been submitted to any other source for publication. The authors have no commercial interests or conflicts of interest to disclose.

  8. Cetaceans trading monitoring during seismic survey in North Fluminense (Rio de Janeiro) and South Capixaba (Espirito Santo) coasts; Monitoramento de encalhe de cetaceos durante levantamento de dados sismicos na costa norte fluminense (Rio de Janeiro) e sul capixaba (Espirito Santo)

    Energy Technology Data Exchange (ETDEWEB)

    Amaro, Thays P.C.; Carloni, Giuliano G.; Erber, Claudia; Sabino, Carla M. [Ecologus Engenharia Consultiva, Rio de Janeiro, RJ (Brazil); Uller, George A. [CGGVeritas, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The objective of this research is to present the results of the cetaceans stranding monitoring developed during and after the seismic survey in the north area of Rio de Janeiro and south of Espirito Santo. The monitoring lasted six months, reaching 200 km of beaches, from the Rio de Janeiro North up to the Espirito Santo South coasts. It was conducted by 34 monitors, who covered predefined beach sections daily, registering the stranded animals. At the end of the project, 15 cetaceans stranded were registered. The species Sotalia guianensis was prevailing in number and distribution. Megaptera novaeangliae was the second specie in geographic distribution and number of registers. The other species identified were Tursiops truncatus and Peponocephala electra. (author)

  9. Chelonians trading monitoring during seismic survey in North Fluminense (Rio de Janeiro) and South Capixaba (Espirito Santo); Monitoramento de encalhe de quelonios marinhos durante levantamento de dados sismicos na costa norte fluminense (Rio de Janeiro) e sul capixaba (Espirito Santo)

    Energy Technology Data Exchange (ETDEWEB)

    Amaro, Thays P.C.; Carloni, Giuliano G.; Erber, Claudia; Sabino, Carla M. [Ecologus Engenharia Consultiva, Rio de Janeiro, RJ (Brazil); Uller, George A. [CGGVeritas, Rio de Janeiro, RJ (Brazil)

    2008-07-01

    The objective of this research is to present the results of the marine chelonians stranding monitoring developed during and after the seismic survey in the north area of Rio de Janeiro and south of Espirito Santo. The monitoring lasted six months, reaching 200 km of beaches, from the Rio de Janeiro North up to the Espirito Santo South coasts. It was conducted by 34 monitors, who covered predefined beach sections daily, registering the stranded animals. At the end of the project, 159 chelonians stranded were registered. The species Chelonia mydas was prevailing in number and distribution. This species make use of this beach area to food. Lepidochelys olivacea was the second species in geographic distribution and number of registers. The other species identified were Caretta caretta and Eretmochelys imbricata. There was only one reproductive register, of Caretta caretta species. (author)

  10. The Refractive Index is a complex quantity…

    Indian Academy of Sciences (India)

    In the ionosphere, the index of refraction is given by Appleton-Hartee formula. The formula is based on some important assumptions … It considers electron motions only; Medium is considered as cold plasma; The problem is linearized.

  11. Wave Refraction Over Complex Nearshore Bathymetry

    National Research Council Canada - National Science Library

    Peak, Scott D

    2004-01-01

    .... Although linear spectral-refraction theory is used by the main operational forecasting centers in the world for these predictions, owing to a lack of field studies its accuracy in regions of complex...

  12. Intelligent Planning for Laser Refractive Surgeries

    Science.gov (United States)

    Wang, Wei; Yue, Yong; Elsheikh, Ahmed; Bao, Fangjun

    2018-02-01

    Refractive error is one of leading ophthalmic diseases for both genders all over the world. Laser refractive correction surgery, e.g., laser in-situ keratomileusis (LASIK), has been commonly used worldwide. The prediction of surgical parameters, e.g., corneal ablation depth, depends on the doctor’s experience, theoretical formula and surgery reference manual in the preoperative diagnosis. The error of prediction may present a potential surgical risk and complication. Being aware of the surgery parameters is important because these can be used to estimate a patient’s post-operative visual quality and help the surgeon plan a suitable treatment. Therefore, in this paper we discuss data mining techniques that can be utilized for the prediction of laser refractive correction surgery parameters. It can provide the surgeon with a reference for possible surgical parameters and outcomes of the patient before the laser refractive correction surgery.

  13. Isaac Newton and the astronomical refraction.

    Science.gov (United States)

    Lehn, Waldemar H

    2008-12-01

    In a short interval toward the end of 1694, Isaac Newton developed two mathematical models for the theory of the astronomical refraction and calculated two refraction tables, but did not publish his theory. Much effort has been expended, starting with Biot in 1836, in the attempt to identify the methods and equations that Newton used. In contrast to previous work, a closed form solution is identified for the refraction integral that reproduces the table for his first model (in which density decays linearly with elevation). The parameters of his second model, which includes the exponential variation of pressure in an isothermal atmosphere, have also been identified by reproducing his results. The implication is clear that in each case Newton had derived exactly the correct equations for the astronomical refraction; furthermore, he was the first to do so.

  14. Relationship between conjunctivochalasis and refractive error.

    Science.gov (United States)

    Mimura, Tatsuya; Usui, Tomohiko; Yamagami, Satoru; Funatsu, Hideharu; Noma, Hidetaka; Toyono, Tetsuya; Mori, Mikiro; Amano, Shiro

    2011-03-01

    To assess the relation between the prevalence and grade of conjunctivochalasis and refractive error and to compare the grade of conjunctivochalasis between myopic and hyperopic patients. Consecutive patients aged from 3 to 94 years were chosen for this study. Exclusion criteria included a history of using contact lenses, ocular surgeries, infectious conjunctivitis, or corneal diseases. The age, gender, medical history, ocular history, the grade and other parameters of inferior conjunctivochalasis classified into three locations (nasal, middle, and temporal), and refractive error were determined in all subjects. Patients were divided into three groups as follows: a hyperopic group (≥0.0 D), an emmetropic group (refractive error, especially in patients over 40 years old (Prefractive error and the grade of conjunctivochalasis in a large consecutive series of patients. Our results suggest that the prevalence and grade of conjunctivochalasis are dependent on refractive error, with hyperopia being an important risk factor for conjunctivochalasis.

  15. The refractive index of relic gravitons

    CERN Document Server

    Giovannini, Massimo

    2016-01-01

    The dynamical evolution of the refractive index of the tensor modes of the geometry produces a specific class of power spectra characterized by a blue (i.e. slightly increasing) slope which is directly determined by the competition of the slow-roll parameter and of the rate of variation of the refractive index. Throughout the conventional stages of the inflationary and post-inflationary evolution, the microwave background anisotropies measurements, the pulsar timing limits and the big-bang nucleosythesis constraints set stringent bounds on the refractive index and on its rate of variation. Within the physically allowed region of the parameter space the cosmic background of relic gravitons leads to a potentially large signal for the ground based detectors (in their advanced version) and for the proposed space-borne interferometers. Conversely, the lack of direct detection of the signal will set a qualitatively new bound on the dynamical variation of the refractive index.

  16. Advanced Refractive Effects Prediction System (AREPS)

    National Research Council Canada - National Science Library

    Patterson, Wayne L

    2001-01-01

    ...), the world's first electromagnetic prediction system for shipboard use. Advances in research and technology have led to the replacement of IREPS with the Advanced Refractive Effects Prediction System (AREPS...

  17. Deviations of Lambert-Beer???s law affect corneal refractive parameters after refractive surgery

    OpenAIRE

    Jim??nez Cuesta, Jos?? Ram??n; Rodr??guez-Mar??n, Francisco; Gonz??lez Anera, Rosario; Jim??nez del Barco Jaldo, Luis Miguel

    2006-01-01

    We calculate whether deviations of Lambert-Beer???s law, which regulates depth ablation during corneal ablation, significantly influence corneal refractive parameters after refractive surgery and whether they influence visual performance. For this, we compute a point-to-point correction on the cornea while assuming a non-linear (including a quadratic term) fit for depth ablation. Post-surgical equations for refractive parameters using a non-linear fit show significant differences with respect...

  18. Acoustic metasurface for refracted wave manipulation

    Science.gov (United States)

    Han, Li-Xiang; Yao, Yuan-Wei; Zhang, Xin; Wu, Fu-Gen; Dong, Hua-Feng; Mu, Zhong-Fei; Li, Jing-bo

    2018-02-01

    Here we present a design of a transmitted acoustic metasurface based on a single row of Helmholtz resonators with varying geometric parameters. The proposed metasurface can not only steer an acoustic beam as expected from the generalized Snell's law of refraction, but also exhibits various interesting properties and potential applications such as insulation of two quasi-intersecting transmitted sound waves, ultrasonic Bessel beam generator, frequency broadening effect of anomalous refraction and focusing.

  19. The repeatability of automated and clinician refraction.

    Science.gov (United States)

    Bullimore, M A; Fusaro, R E; Adams, C W

    1998-08-01

    Auto-refractors are used as a starting point for clinicians' refractions and in studies of refractive error. We investigated the repeatability of the Hoya AR-570 and clinician refraction. Eighty-six subjects, aged 11 to 60 years, were recruited by mailing inquiries to 500 randomly selected patients who had received recent examinations at the University of California Optometric Eye Center. Contact lens wearers, patients with best corrected visual acuity worse than 20/30 in either eye, and patients with a history of diabetes were excluded. Each subject was examined by two clinicians during one visit. The first clinician obtained five auto-refractor readings for each eye (which were later averaged), performed a balanced subjective refraction (with spherical masking lenses in the phoropter), and repeated the automated refractor measurements. This protocol was then repeated by the second clinician. Clinicians were randomized with regard to testing order and masked to automated refractor results, each other's refractions, and previous spectacle prescriptions. To quantify repeatability, we used mixed model analyses of variance to estimate the appropriate variance components while accounting for the correlation among, for example, repeated measurements of the same eye. Astigmatic data were analyzed by converting into Fourier form: two cross-cylinders at axis 0 degrees (J0) and axis 45 degrees (J45). For mean spherical equivalent, the average difference between five averaged automated refractor readings, taken by two different optometrists, was +0.02 D (95% limits of agreement = -0.36 to +0.40 D). The average difference between the two optometrists' subjective refractions was -0.12 D (95% limits of agreement = -0.90 to +0.65 D). The 95% limits of agreement for the automated refractor were about half those of the clinician for both astigmatic terms (J0 and J45) and for all comparisons. Automated refraction is more repeatable than subjective refraction and therefore more

  20. Myopia onset and role of peripheral refraction

    Directory of Open Access Journals (Sweden)

    Rotolo M

    2017-06-01

    Full Text Available Maurilia Rotolo,1,2 Giancarlo Montani,2 Raul Martin1,3 1Optometry Research Group, IOBA Eye Institute, School of Optometry, Universidad de Valladolid, Valladolid, Spain; 2Optics and Optometry, Corso di Ottica e Optometria, Universita del Salento, Lecce, Italy; 3Faculty of Health and Human Sciences, School of Health Professions, Plymouth University, Peninsula Allied Health Centre, Plymouth, UK Background: To determine the peripheral refraction characteristics related to 18-month changes in refraction in Caucasian (Mediterranean children.Methods: Non-cycloplegic peripheral refraction at 10° intervals over the central ±30° of horizontal visual field over 18 months (baseline, 12 months, and 18 months of follow-up was conducted in 50 healthy children who were 8 years old. Axial length (AL was also recorded. Relative peripheral refraction (RPR was calculated and eyes were divided into three study groups: non-myopic eyes, myopic eyes, and eyes that develop myopia.Results: Myopic eyes showed hyperopic RPR and emetropic and hyperopic eyes showed myopic RPR. Univariate analysis of variance did not find any statistically significant effect of peripheral refraction (F36=0.13; P=1.00 and RPR (F36=0.79; P=0.80 on myopia onset (eyes that developed myopia along the study. All the studied groups showed an increase of AL, without statistically significant differences between the studied groups (F6=0.09; P=0.99.Conclusion: Hyperopic relative peripheral shift change in eyes that develop myopia has been found with differences in RPR between myopic (hyperopic RPR and hyperopic or emmetropic eyes (with myopic RPR. The results suggest that RPR cannot predict development or progression of myopia in Caucasian (Mediterranean children and the efficacy in slowing myopia progression obtained with treatments that manipulate the peripheral refraction is not just driven with RPR. Keywords: myopia, refractive errors, myopia onset, peripheral refraction, relative peripheral

  1. Seismic sources

    Science.gov (United States)

    Green, Michael A.; Cook, Neville G. W.; McEvilly, Thomas V.; Majer, Ernest L.; Witherspoon, Paul A.

    1992-01-01

    Apparatus is described for placement in a borehole in the earth, which enables the generation of closely controlled seismic waves from the borehole. Pure torsional shear waves are generated by an apparatus which includes a stator element fixed to the borehole walls and a rotor element which is electrically driven to rapidly oscillate on the stator element to cause reaction forces transmitted through the borehole walls to the surrounding earth. Logitudinal shear waves are generated by an armature that is driven to rapidly oscillate along the axis of the borehole relative to a stator that is clamped to the borehole, to cause reaction forces transmitted to the surrounding earth. Pressure waves are generated by electrically driving pistons that press against opposite ends of a hydraulic reservoir that fills the borehole. High power is generated by energizing the elements at a power level that causes heating to over 150.degree. C. within one minute of operation, but energizing the elements for no more than about one minute.

  2. ON THE SOURCE OF ASTROMETRIC ANOMALOUS REFRACTION

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, M. Suzanne [Department of Natural and Environmental Sciences, Western State Colorado University, 128 Hurst Hall, Gunnison, CO 81230 (United States); McGraw, John T.; Zimmer, Peter C. [Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131 (United States); Pier, Jeffrey R., E-mail: mstaylor@western.edu [Division of Astronomical Sciences, NSF 4201 Wilson Blvd, Arlington, VA 22230 (United States)

    2013-03-15

    More than a century ago, astronomers using transit telescopes to determine precise stellar positions were hampered by an unexplained periodic shifting of the stars they were observing. With the advent of CCD transit telescopes in the past three decades, this unexplained motion, termed 'anomalous refraction' by these early astronomers, is again being observed. Anomalous refraction is described as a low-frequency, large angular scale ({approx}2 Degree-Sign ) motion of the entire image plane with respect to the celestial coordinate system as observed and defined by astrometric catalogs. These motions, of typically several tenths of an arcsecond amplitude with timescales on the order of 10 minutes, are ubiquitous to ground-based drift-scan astrometric measurements regardless of location or telescopes used and have been attributed to the effect of tilting of equal-density layers of the atmosphere. The cause of this tilting has often been attributed to atmospheric gravity waves, but this cause has never been confirmed. Although theoretical models of atmospheric refraction show that atmospheric gravity waves are a plausible cause of anomalous refraction, an observational campaign specifically directed at defining this relationship provides clear evidence that anomalous refraction is not consistent with the passage of atmospheric gravity waves. The source of anomalous refraction is found to be meter-scale, slowly evolving quasi-coherent dynamical structures in the boundary layer below 60 m above ground level.

  3. Refractive index contrast in porous silicon multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nava, R.; Mora, M.B. de la; Tagueena-Martinez, J. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Rio, J.A. del [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Temixco, Morelos (Mexico); Centro Morelense de Innovacion y Transferencia Tecnologica, Consejo de Ciencia y Tecnologia del Estado de Morelos (Mexico)

    2009-07-15

    Two of the most important properties of a porous silicon multilayer for photonic applications are flat interfaces and a relative large refractive index contrast between layers in the optical wavelength range. In this work, we studied the effect of the current density and HF electrolyte concentration on the refractive index of porous silicon. With the purpose of increasing the refractive index contrast in a multilayer, the refractive index of porous silicon produced at low current was studied in detail. The current density applied to produce the low porosity layers was limited in order to keep the electrolyte flow through the multilayer structure and to avoid deformation of layer interfaces. We found that an electrolyte composed of hydrofluoric acid, ethanol and glycerin in a ratio of 3:7:1 gives a refractive index contrast around 1.3/2.8 at 600 nm. Several multilayer structures with this refractive index contrast were fabricated, such as dielectric Bragg mirrors and microcavities. Reflectance spectra of the structures show the photonic quality of porous silicon multilayers produced under these electrochemical conditions. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. PREVALENCE OF UNCORRECTED REFRACTIVE ERRORS IN ADULTS AGED 30 YEARS AND ABOVE IN A RURAL POPULATION IN PAKISTAN.

    Science.gov (United States)

    Abdullah, Ayesha S; Jadoon, Milhammad Zahid; Akram, Mohammad; Awan, Zahid Hussain; Azam, Mohammad; Safdar, Mohammad; Nigar, Mohammad

    2015-01-01

    Uncorrected refractive errors are a leading cause of visual disability globally. This population-based study was done to estimate the prevalence of uncorrected refractive errors in adults aged 30 years and above of village Pawakah, Khyber Pakhtunkhwa (KPK), Pakistan. It was a cross-sectional survey in which 1000 individuals were included randomly. All the individuals were screened for uncorrected refractive errors and those whose visual acuity (VA) was found to be less than 6/6 were refracted. In whom refraction was found to be unsatisfactory (i.e., a best corrected visual acuity of prevalence of uncorrected refractive errors was found to be 23.97% among males and 20% among females. The prevalence of visually disabling refractive errors was 6.89% in males and 5.71% in females. The prevalence was seen to increase with age, with maximum prevalence in 51-60 years age group. Hypermetropia (10.14%) was found to be the commonest refractive error followed by Myopia (6.00%) and Astigmatism (5.6%). The prevalence of Presbyopia was 57.5% (60.45% in males and 55.23% in females). Poor affordability was the commonest barrier to the use of spectacles, followed by unawareness. Cataract was the commonest reason for impaired vision after refractive correction. The prevalence of blindness was 1.96% (1.53% in males and 2.28% in females) in this community with cataract as the commonest cause. Despite being the most easily avoidable cause of subnormal vision uncorrected refractive errors still account for a major proportion of the burden of decreased vision in this area. Effective measures for the screening and affordable correction of uncorrected refractive errors need to be incorpora'ted into the health care delivery system.

  5. Database of seismic wave travel times in the Bohemian Massif

    Czech Academy of Sciences Publication Activity Database

    Růžek, Bohuslav; Zedník, Jan; Hrubcová, Pavla

    2005-01-01

    Roč. 5, č. 2 (2005), s. 145-152 ISSN 1213-1962. [Nové poznatky a měření v seizmologii, inženýrské geofyzice a geotechnice. Ostrava, 12.04.2005-13.04.2005] Institutional research plan: CEZ:AV0Z30120515 Keywords : refraction seismic experiments * Bohemian Massif * database Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  6. SURVEY

    DEFF Research Database (Denmark)

    SURVEY er en udbredt metode og benyttes inden for bl.a. samfundsvidenskab, humaniora, psykologi og sundhedsforskning. Også uden for forskningsverdenen er der mange organisationer som f.eks. konsulentfirmaer og offentlige institutioner samt marketingsafdelinger i private virksomheder, der arbejder...... med surveys. Denne bog gennemgår alle surveyarbejdets faser og giver en praktisk indføring i: • design af undersøgelsen og udvælgelse af stikprøver, • formulering af spørgeskemaer samt indsamling og kodning af data, • metoder til at analysere resultaterne...

  7. Pseudo-random data acquisition geometry in 3D seismic survey; Sanjigen jishin tansa ni okeru giji random data shutoku reiauto ni tsuite

    Energy Technology Data Exchange (ETDEWEB)

    Minegishi, M.; Tsuburaya, Y. [Japan National Oil Corp., Tokyo (Japan). Technology Research Center

    1996-10-01

    Influence of pseudo-random geometry on the imaging for 3D seismic exploration data acquisition has been investigate using a simple model by comparing with the regular geometry. When constituting wave front by the interference of elemental waves, pseudo-random geometry data did not always provide good results. In the case of a point diffractor, the imaging operation, where the constituted wave front was returned to the point diffractor by the interference of elemental waves for the spatial alias records, did not always give clear images. In the case of multi point diffractor, good images were obtained with less noise generation in spite of alias records. There are a lot of diffractors in the actual geological structures, which corresponds to the case of multi point diffractors. Finally, better images could be obtained by inputting records acquired using the pseudo-random geometry rather than by inputting spatial alias records acquired using the regular geometry. 7 refs., 6 figs.

  8. China's first intermediate resolution multi-channel seismic survey in the northern Victoria Land Basin and Terror Rift, Ross Sea, Antarctica

    Science.gov (United States)

    Shen, Zhongyan; Gao, Jinyao; Zhang, Tao; Wang, Wei; Ding, Weifeng; Zhang, Sheng

    2017-04-01

    The West Antarctic Rift System (WARS) represents one of the largest active continental rift systems on Earth and is less well known than other rift systems because it is largely covered by thick ice. The Terror Rift (TR), superimposing on the Victoria Land Basin (VLB) in the western Ross Sea, is identified as the most recent deformational zone of the WARS, thus will provide knowledge of the active deformation process of the WARS. The structure and kinematics of the TR is under debate. Originally, the TR was thought to consist of two parts: the Discovery Graben and the magmatically-intruded Lee Arch. New denser seismic grid in the middle and southern segments of the TR revealed a different structure of the Lee Arch while the northern segment of the TR is not well studied. The glacial history of the VLB/TR region is another attractive issue to the geologists since this area records the behavior information of EAIS and WAIS. In the southern part of the VLB, especially in the McMurdo Sound, the framework of the glacial history is well established after several deep cores which recovery the whole stratigraphic sequences since the onset of the glaciation. However, the glacial history of the northern part of the VLB/TR is less well studied and here we emphasize its importance because the northern part of the VLB/TR is a link between the well-studied southern VLB and the sediment-well-preserved Northern Basin. During the 32nd Chinese National Antarctic Research Expedition, on the board of the RV XueLong, we collected intermediate resolution multi-channel seismic reflection data in the northern VLB/TR. These data will establish new constraints on the timing of deformation, structure and kinematics of the TR, and the history of the EAIS and WAIS.

  9. Post-collapse evolution of a coastal caldera system: Insights from a 3D multichannel seismic survey from the Campi Flegrei caldera (Italy)

    Science.gov (United States)

    Steinmann, Lena; Spiess, Volkhard; Sacchi, Marco

    2018-01-01

    In this study we present the first 3D high-resolution multichannel seismic dataset from a (partly) submerged caldera setting, the Campi Flegrei caldera (CFc). Our work aims at examining the spatial and temporal evolution of the CFc since the last caldera-forming event, the Neapolitan Yellow Tuff (NYT, 15 ka) eruption. The main objectives are to investigate the caldera's shallow ( 200 m) outer caldera ring-fault zone. The seismic data revealed that the NYT collapse occurred exclusively along the inner caldera ring-fault and that the related NYT caldera depression is filled with on average 61 m of sediment deposited between 15 and 8.6 ka. The geometry of the inner ring-fault, consisting of four fault segments, seems to be strongly influenced by regional NW-SE and NE SW-trending faults. Furthermore, we found that the ring-faults have acted as pathway for the recent (Bank (10.3-9.5 ka), Nisida Island ( 3.98 ka), and Capo Miseno (3.7 ka) eruptions, yielding DRE values of 0.15 km3, 0.1 km3, and 0.08 km3, respectively, and an explosive magnitude of at least moderate-large scale (VEI 3). Our findings highlight that eruption volumes may be underestimated by 3 to 4 times if the submerged portion of a (partly) submerged caldera is not considered, implying severe consequences for the hazard and risk evaluation. The spatial response of the post-collapse (< 15 ka) depositional environment to volcanic activity, deformational processes and sea-level variations is presented in a comprehensive 3D evolutionary model.

  10. Seismic intrusion detector system

    Science.gov (United States)

    Hawk, Hervey L.; Hawley, James G.; Portlock, John M.; Scheibner, James E.

    1976-01-01

    A system for monitoring man-associated seismic movements within a control area including a geophone for generating an electrical signal in response to seismic movement, a bandpass amplifier and threshold detector for eliminating unwanted signals, pulse counting system for counting and storing the number of seismic movements within the area, and a monitoring system operable on command having a variable frequency oscillator generating an audio frequency signal proportional to the number of said seismic movements.

  11. National Seismic Station

    International Nuclear Information System (INIS)

    Stokes, P.A.

    1982-06-01

    The National Seismic Station was developed to meet the needs of regional or worldwide seismic monitoring of underground nuclear explosions to verify compliance with a nuclear test ban treaty. The Station acquires broadband seismic data and transmits it via satellite to a data center. It is capable of unattended operation for periods of at least a year, and will detect any tampering that could result in the transmission of unauthentic seismic data

  12. Quantitative Seismic Amplitude Analysis

    NARCIS (Netherlands)

    Dey, A.K.

    2011-01-01

    The Seismic Value Chain quantifies the cyclic interaction between seismic acquisition, imaging and reservoir characterization. Modern seismic innovation to address the global imbalance in hydrocarbon supply and demand requires such cyclic interaction of both feed-forward and feed-back processes.

  13. Refractive Secondary Concentrators for Solar Thermal Applications

    Science.gov (United States)

    Wong, Wayne A.; Macosko, Robert P.

    1999-01-01

    The NASA Glenn Research Center is developing technologies that utilize solar energy for various space applications including electrical power conversion, thermal propulsion, and furnaces. Common to all of these applications is the need for highly efficient, solar concentration systems. An effort is underway to develop the innovative single crystal refractive secondary concentrator, which uses refraction and total internal reflection to efficiently concentrate and direct solar energy. The refractive secondary offers very high throughput efficiencies (greater than 90%), and when used in combination with advanced primary concentrators, enables very high concentration ratios (10,0(X) to 1) and very high temperatures (greater than 2000 K). Presented is an overview of the refractive secondary concentrator development effort at the NASA Glenn Research Center, including optical design and analysis techniques, thermal modeling capabilities, crystal materials characterization testing, optical coatings evaluation, and component testing. Also presented is a discussion of potential future activity and technical issues yet to be resolved. Much of the work performed to date has been in support of the NASA Marshall Space Flight Center's Solar Thermal Propulsion Program. The many benefits of a refractive secondary concentrator that enable efficient, high temperature thermal propulsion system designs, apply equally well to other solar applications including furnaces and power generation systems such as solar dynamics, concentrated thermal photovoltaics, and thermionics.

  14. Cryogenic refractive index of Heraeus homosil glass

    Science.gov (United States)

    Miller, Kevin H.; Quijada, Manuel A.; Leviton, Douglas B.

    2017-08-01

    This paper reports measurements of the refractive index of Homosil (Heraeus) over the wavelength range of 0.34—3.16 μm and temperature range of 120—335 K. These measurements were performed by using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at the NASA's Goddard Space Flight Center. These measurements were in support of an integrated Structural-Thermal-Optical-Performance (STOP) model that was developed for a fieldwidened Michelson interferometer that is being built and tested for the High Spectral Resolution Lidar (HSRL) project at the NASA Langley Research Center (LaRC). The cryogenic refractive index measurements were required in order to account for the highly sensitive performance of the HSRL instrument to changes in refractive index with temperature, temperature gradients, thermal expansion, and deformation due to mounting stresses. A dense coverage of the absolute refractive index over the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dn/dT) and dispersion relation (dn/dλ) as a function of wavelength and temperature. Our measurements of Homosil will be compared with measurements of other glasses from the fused silica family studied in CHARMS as well as measurements reported elsewhere in the literature.

  15. Application of the uphole seismic data in the determination of the ...

    African Journals Online (AJOL)

    Refraction statics was computed automatically from first break picks using CGG's SDITR interactive programme. The seismic data section with and without static correction were discussed. Normal move out correction was applied to the data collected using CGG's automated VELCOM programme. An interpretation of the ...

  16. FAST TRACK PAPER: The reflection seismic survey of project TIPTEQ-the inventory of the Chilean subduction zone at 38.2° S

    Science.gov (United States)

    Groß, K.; Micksch, U.

    2008-02-01

    We describe results of an active-source seismology experiment across the Chilean subduction zone at 38.2°S. The seismic sections clearly show the subducted Nazca plate with varying reflectivity. Below the coast the plate interface occurs at 25 km depth as the sharp lower boundary of a 2-5 km thick, highly reflective region, which we interpret as the subduction channel, that is, a zone of subducted material with a velocity gradient with respect to the upper and lower plate. Further downdip along the seismogenic coupling zone the reflectivity decreases in the area of the presumed 1960 Valdivia hypocentre. The plate interface itself can be traced further down to depths of 50-60 km below the Central Valley. We observe strong reflectivity at the plate interface as well as in the continental mantle wedge. The sections also show a segmented forearc crust in the overriding South American plate. Major features in the accretionary wedge, such as the Lanalhue fault zone, can be identified. At the eastern end of the profile a bright west-dipping reflector lies perpendicular to the plate interface and may be linked to the volcanic arc.

  17. Refraction interface radiography; Refraktions-Interface-Radiographie

    Energy Technology Data Exchange (ETDEWEB)

    Hentschel, Manfred P.; Kupsch, Andreas; Lange, Axel; Mueller, Bernd R. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany). Fachbereich 8.5. ' Mikro-ZfP'

    2013-07-01

    Nano-scale structures and interfaces are more and more coming to determine the function of modern materials and components. This calls for methods for their nondestructive characterisation with adapted spatial resolution, a task for which x-ray refraction techniques are well suited on account of their wavelength range. The resulting small-angle scattering causes high local intensity levels which can exceed that of the primary radiation as a result of shift and focussing effects. The predominance of refraction intensity over that of total reflection can be demonstrated using monochromatic synchrotron radiation on homogeneous samples of simple geometry (plates or cylinders). The refraction effect can be used with incidence angles up to a few degrees. Scattering angles are typically in the range of arc seconds to arc minutes.

  18. Neutron refraction by cylindrical metal wires

    International Nuclear Information System (INIS)

    Plomp, J.; Barker, J.G.; Haan, V.O. de; Bouwman, W.G.; Well, A.A. van

    2007-01-01

    Undesired Small-Angle Neutron Scattering (SANS) from interior features of an object can be minimised by reducing the sample thickness. However, refraction effects produced by the exterior shape of the object depend upon the scattering cross-section and not on the thickness of the object. In the field of polarised neutrons a wire coil is often used to manipulate the polarisation vector of the neutron. In this paper, we show that the cylindrical shape of the wire together with the refractive index introduces an angular distribution in the neutron beam. This can be observed in instrumentation sensitive to SANS. We show results measured on three different SANS instruments: Ultra Small-Angle Neutrons Scattering (USANS), Spin-Echo Small-Angle Neutron Scattering (SESANS) and a Time-of-Flight (TOF) SESANS. These results are all in good agreement with the theory of refraction

  19. Neutron refraction by cylindrical metal wires

    Energy Technology Data Exchange (ETDEWEB)

    Plomp, J. [Faculty of Applied Sciences, Delft University of Technology, Delft (Netherlands)]. E-mail: j.plomp@tudelft.nl; Barker, J.G. [NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899 (United States); Haan, V.O. de [Faculty of Applied Sciences, Delft University of Technology, Delft (Netherlands); Bouwman, W.G. [Faculty of Applied Sciences, Delft University of Technology, Delft (Netherlands); Well, A.A. van [Faculty of Applied Sciences, Delft University of Technology, Delft (Netherlands)

    2007-05-01

    Undesired Small-Angle Neutron Scattering (SANS) from interior features of an object can be minimised by reducing the sample thickness. However, refraction effects produced by the exterior shape of the object depend upon the scattering cross-section and not on the thickness of the object. In the field of polarised neutrons a wire coil is often used to manipulate the polarisation vector of the neutron. In this paper, we show that the cylindrical shape of the wire together with the refractive index introduces an angular distribution in the neutron beam. This can be observed in instrumentation sensitive to SANS. We show results measured on three different SANS instruments: Ultra Small-Angle Neutrons Scattering (USANS), Spin-Echo Small-Angle Neutron Scattering (SESANS) and a Time-of-Flight (TOF) SESANS. These results are all in good agreement with the theory of refraction.

  20. France's seismic zoning

    International Nuclear Information System (INIS)

    Mohammadioun, B.

    1997-01-01

    In order to assess the seismic hazard in France in relation to nuclear plant siting, the CEA, EDF and the BRGM (Mine and Geology Bureau) have carried out a collaboration which resulted in a seismic-tectonic map of France and a data base on seismic history (SIRENE). These studies were completed with a seismic-tectonic zoning, taking into account a very long period of time, that enabled a probabilistic evaluation of the seismic hazard in France, and that may be related to adjacent country hazard maps

  1. Multi-method Near-surface Geophysical Surveys for Site Response and Earthquake Damage Assessments at School Sites in Washington, USA

    Science.gov (United States)

    Cakir, R.; Walsh, T. J.; Norman, D. K.

    2017-12-01

    We, Washington Geological Survey (WGS), have been performing multi-method near surface geophysical surveys to help assess potential earthquake damage at public schools in Washington. We have been conducting active and passive seismic surveys, and estimating Shear-wave velocity (Vs) profiles, then determining the NEHRP soil classifications based on Vs30m values at school sites in Washington. The survey methods we have used: 1D and 2D MASW and MAM, P- and S-wave refraction, horizontal-to-vertical spectral ratio (H/V), and 2ST-SPAC to measure Vs and Vp at shallow (0-70m) and greater depths at the sites. We have also run Ground Penetrating Radar (GPR) surveys at the sites to check possible horizontal subsurface variations along and between the seismic survey lines and the actual locations of the school buildings. The seismic survey results were then used to calculate Vs30m for determining the NEHRP soil classifications at school sites, thus soil amplification effects on the ground motions. Resulting shear-wave velocity profiles generated from these studies can also be used for site response and liquefaction potential studies, as well as for improvement efforts of the national Vs30m database, essential information for ShakeMap and ground motion modeling efforts in Washington and Pacific Northwest. To estimate casualties, nonstructural, and structural losses caused by the potential earthquakes in the region, we used these seismic site characterization results associated with structural engineering evaluations based on ASCE41 or FEMA 154 (Rapid Visual Screening) as inputs in FEMA Hazus-Advanced Engineering Building Module (AEBM) analysis. Compelling example surveys will be presented for the school sites in western and eastern Washington.

  2. Automating Shallow Seismic Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Steeples, Don W.

    2004-12-09

    This seven-year, shallow-seismic reflection research project had the aim of improving geophysical imaging of possible contaminant flow paths. Thousands of chemically contaminated sites exist in the United States, including at least 3,700 at Department of Energy (DOE) facilities. Imaging technologies such as shallow seismic reflection (SSR) and ground-penetrating radar (GPR) sometimes are capable of identifying geologic conditions that might indicate preferential contaminant-flow paths. Historically, SSR has been used very little at depths shallower than 30 m, and even more rarely at depths of 10 m or less. Conversely, GPR is rarely useful at depths greater than 10 m, especially in areas where clay or other electrically conductive materials are present near the surface. Efforts to image the cone of depression around a pumping well using seismic methods were only partially successful (for complete references of all research results, see the full Final Technical Report, DOE/ER/14826-F), but peripheral results included development of SSR methods for depths shallower than one meter, a depth range that had not been achieved before. Imaging at such shallow depths, however, requires geophone intervals of the order of 10 cm or less, which makes such surveys very expensive in terms of human time and effort. We also showed that SSR and GPR could be used in a complementary fashion to image the same volume of earth at very shallow depths. The primary research focus of the second three-year period of funding was to develop and demonstrate an automated method of conducting two-dimensional (2D) shallow-seismic surveys with the goal of saving time, effort, and money. Tests involving the second generation of the hydraulic geophone-planting device dubbed the ''Autojuggie'' showed that large numbers of geophones can be placed quickly and automatically and can acquire high-quality data, although not under rough topographic conditions. In some easy

  3. Reservoir Characterization using Seismic and Well Logs Data (A ...

    African Journals Online (AJOL)

    During analysis, hydrocarbon saturation in relatively unconsolidated sandstone reservoirs is a pore fluid property that has been successfully mapped using seismic surveys. The presence of hydrocarbon typically lowers the seismic velocity and density of unconsolidated to moderately consolidated sandstone and this in turn ...

  4. Effects of Seismic Exploration on Mangrove Habitat in Tanzania

    African Journals Online (AJOL)

    a compressed air hose down the line and drilled holes for seismic charges; loading crews (4) laid charges; recording crews (10) laid geophones; shooting crews (4-5) laid ..... at preventing vehicle access. Fig. 4. The 2005 seismic survey line at plot 2 showing the path cleared between the mangroves. EFFECTS OF SEISMIC ...

  5. Negative refraction angular characterization in one-dimensional photonic crystals.

    Directory of Open Access Journals (Sweden)

    Jesus Eduardo Lugo

    2011-04-01

    Full Text Available Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here we experimentally characterize negative refraction in a one dimensional photonic crystal structure; near the low frequency edge of the fourth photonic bandgap. We compare the experimental results with current theory and a theory based on the group velocity developed here. We also analytically derived the negative refraction correctness condition that gives the angular region where negative refraction occurs.By using standard photonic techniques we experimentally determined the relationship between incidence and negative refraction angles and found the negative refraction range by applying the correctness condition. In order to compare both theories with experimental results an output refraction correction was utilized. The correction uses Snell's law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theories in the negative refraction zone.Since both theories and the experimental observations agreed well in the negative refraction region, we can use both negative refraction theories plus the output correction to predict negative refraction angles. This can be very useful from a practical point of view for space filtering applications such as a photonic demultiplexer or for sensing applications.

  6. Advanced Seismic While Drilling System

    Energy Technology Data Exchange (ETDEWEB)

    Robert Radtke; John Fontenot; David Glowka; Robert Stokes; Jeffery Sutherland; Ron Evans; Jim Musser

    2008-06-30

    . An APS Turbine Alternator powered the SeismicPULSER{trademark} to produce two Hz frequency peak signals repeated every 20 seconds. Since the ION Geophysical, Inc. (ION) seismic survey surface recording system was designed to detect a minimum downhole signal of three Hz, successful performance was confirmed with a 5.3 Hz recording with the pumps running. The two Hz signal generated by the sparker was modulated with the 3.3 Hz signal produced by the mud pumps to create an intense 5.3 Hz peak frequency signal. The low frequency sparker source is ultimately capable of generating selectable peak frequencies of 1 to 40 Hz with high-frequency spectra content to 10 kHz. The lower frequencies and, perhaps, low-frequency sweeps, are needed to achieve sufficient range and resolution for realtime imaging in deep (15,000 ft+), high-temperature (150 C) wells for (a) geosteering, (b) accurate seismic hole depth, (c) accurate pore pressure determinations ahead of the bit, (d) near wellbore diagnostics with a downhole receiver and wired drill pipe, and (e) reservoir model verification. Furthermore, the pressure of the sparker bubble will disintegrate rock resulting in an increased overall rates of penetration. Other applications for the SeismicPULSER{trademark} technology are to deploy a low-frequency source for greater range on a wireline for Reverse Vertical Seismic Profiling (RVSP) and Cross-Well Tomography. Commercialization of the technology is being undertaken by first contacting stakeholders to define the value proposition for rig site services utilizing SeismicPULSER{trademark} technologies. Stakeholders include national oil companies, independent oil companies, independents, service companies, and commercial investors. Service companies will introduce a new Drill Bit SWD service for deep HTHP wells. Collaboration will be encouraged between stakeholders in the form of joint industry projects to develop prototype tools and initial field trials. No barriers have been identified

  7. Photorefractive keratectomy in refractive accommodative esotropia.

    Science.gov (United States)

    Bilgihan, K; Akata, F; Or, M; Hasanreisoğlu, B

    1997-01-01

    Photorefractive keratectomy (PRK) was performed on a 19-year-old man with hyperopic astigmatism and refractive accommodative esotropia. The patient was orthophoric while wearing spectacles, but had an esotropia of 30 prism dioptres at near and distance vision without spectacles. The best corrected visual acuity of the right eye was 20/50 and of the left eye was 20/20. The excessive accommodative convergence of the patient was eliminated by correcting the hyperopic refractive error by performing PRK, and the patient became orthophoric after the treatment.

  8. Field test investigation of high sensitivity fiber optic seismic geophone

    Science.gov (United States)

    Wang, Meng; Min, Li; Zhang, Xiaolei; Zhang, Faxiang; Sun, Zhihui; Li, Shujuan; Wang, Chang; Zhao, Zhong; Hao, Guanghu

    2017-10-01

    Seismic reflection, whose measured signal is the artificial seismic waves ,is the most effective method and widely used in the geophysical prospecting. And this method can be used for exploration of oil, gas and coal. When a seismic wave travelling through the Earth encounters an interface between two materials with different acoustic impedances, some of the wave energy will reflect off the interface and some will refract through the interface. At its most basic, the seismic reflection technique consists of generating seismic waves and measuring the time taken for the waves to travel from the source, reflect off an interface and be detected by an array of geophones at the surface. Compared to traditional geophones such as electric, magnetic, mechanical and gas geophone, optical fiber geophones have many advantages. Optical fiber geophones can achieve sensing and signal transmission simultaneously. With the development of fiber grating sensor technology, fiber bragg grating (FBG) is being applied in seismic exploration and draws more and more attention to its advantage of anti-electromagnetic interference, high sensitivity and insensitivity to meteorological conditions. In this paper, we designed a high sensitivity geophone and tested its sensitivity, based on the theory of FBG sensing. The frequency response range is from 10 Hz to 100 Hz and the acceleration of the fiber optic seismic geophone is over 1000pm/g. sixteen-element fiber optic seismic geophone array system is presented and the field test is performed in Shengli oilfield of China. The field test shows that: (1) the fiber optic seismic geophone has a higher sensitivity than the traditional geophone between 1-100 Hz;(2) The low frequency reflection wave continuity of fiber Bragg grating geophone is better.

  9. DISPLACEMENT BASED SEISMIC DESIGN CRITERIA

    Energy Technology Data Exchange (ETDEWEB)

    HOFMAYER,C.H.

    1999-03-29

    The USNRC has initiated a project to determine if any of the likely revisions to traditional earthquake engineering practice are relevant to seismic design of the specialized structures, systems and components of nuclear power plants and of such significance to suggest that a change in design practice might be warranted. As part of the initial phase of this study, a literature survey was conducted on the recent changes in seismic design codes/standards, on-going activities of code-writing organizations/communities, and published documents on displacement-based design methods. This paper provides a summary of recent changes in building codes and on-going activities for future codes. It also discusses some technical issues for further consideration.

  10. Displacement Based Seismic Design Criteria

    International Nuclear Information System (INIS)

    Costello, J.F.; Hofmayer, C.; Park, Y.J.

    1999-01-01

    The USNRC has initiated a project to determine if any of the likely revisions to traditional earthquake engineering practice are relevant to seismic design of the specialized structures, systems and components of nuclear power plants and of such significance to suggest that a change in design practice might be warranted. As part of the initial phase of this study, a literature survey was conducted on the recent changes in seismic design codes/standards, on-going activities of code-writing organizations/communities, and published documents on displacement-based design methods. This paper provides a summary of recent changes in building codes and on-going activities for future codes. It also discusses some technical issues for further consideration

  11. Hybrid Streamers for Polar Seismic

    Science.gov (United States)

    Gifford, C. M.; Agah, A.; Tsoflias, G. P.

    2006-12-01

    We propose a new hybrid streamer seismic approach for polar regions that incorporates insertion of spiked geophones, the land streamer method of transportation, and mobile robotics. Current land streamers do not plant the geophone spike at each node location on the streamer(s) nor use robotic control. This approach combines the two methods, and is therefore termed "Hybrid Streamers". Land seismic 3D surveying is costly and time consuming due to manual handling of geophones and cables. Multiple streamers make this process simpler by allowing efficient deployment of large numbers of geophones. Hybrid streamers go further to robotically insert the geophone spike at each node location to achieve higher frequency and better resolution seismic images. For deployment and retrieval, the geophone spikes are drilled into the ground, or inserted using heat. This can be accomplished by modifying the geophone spike to be similar to a threaded screw or similar to a soldering iron for polar environments. Heat could help melt the ice during deployment, which would refreeze around the geophone for firm coupling. Heat could also be used to make polar geophone retrieval easier. By ensuring that the towing robots are robust and effective, the problem of single point of failure can be less of an issue. Polar rovers have proven useful in harsh environments, and could be utilized in polar seismic applications. Towing geophone nodes in a tethered fashion not only provides all nodes with power to operate the onboard equipment, but also gives them a medium to transfer data to the towing rover. Hybrid streamers could be used in several ways. One or more hybrid streamers could be tethered and towed by a single robot. Several robots could be used to form a single grid, working in conjunction to image larger areas in three dimensions. Such an approach could speed up entire missions and make efficient use of seismic source ignitions. The reduction of human involvement by use of mobile robots

  12. Seismic effects on bedrock and underground constructions. A literature survey of damage on constructions; Changes in groundwater levels and flow; Changes in chemistry in groundwater and gases

    International Nuclear Information System (INIS)

    Roeshoff, Kennert.

    1989-06-01

    This report is a literature review of direct and indirect effects of earthquakes on underground constructions as tunnels, caverns and mines. The direct damage will cause vibrations, shaking and displacement, which may lead to partial or total destruction of the underground facility. Damage caused by shaking has been reported in several studies, and several hundreds of events have been reported both from mines and tunnels. These reports are mainly from active earthquake areas. There are very few reports of damage caused by displacements on an existing fault. The damage, which may be severe, is generally concentrated to the vicinity of the fault zone. The report also includes a review of the effects caused by earthquakes on groundwater level, flow, pressure, chemistry and constituents in the ground. Such changes are mainly reported from studies in wells near active faults. The interesting coupling of changes in groundwater characteristics around an underground construction is, unfortunately, very seldom reported. The groundwater level and pressure changes are discussed in Chapter 4. The bases for this part of the review is taken from the Alaska earthquake 1964. Other observations are reported from wells and reservoirs located near existing faults. Changes of the geochemistry in groundwater and soil gases are reviewed in Chapter 4. The mechanisms of seismochemical anomalies are discussed and examples of short and long term monitoring are given from USA, Soviet Union and China. Gases in ground water and soil is reported in Chapter 5. Radon is so far one of the most studied species and its variation in short, medium and long term with seismic activity is rather well understood. Other gases or isotopes that have been studied include helium, carbon dioxide, hydrogen, argon and methane, radium and uranium. The paper also includes same statements for repository design based on the result of the review. (81 refs.)

  13. Results of a monitoring pilot with a permanent buried multicomponent seismic array at Ketzin

    NARCIS (Netherlands)

    Arts, R.J.; Meekes, J.A.C.; Brouwer, J.H.; Werf, M. van der; Noorlandt, R.P.; Paap, B.; Visser, W.; Vandeweijer, V.; Lüth, S.; Giese, R.; Maas, J.

    2011-01-01

    To monitor the migration of the injected CO2 in the Ketzin project (Germany) a permanently buried multi-component seismic array has been installed in August 2009. Since then the array has been continuously recording passive seismic data. Additionally an active seismic survey resulting in a 230 m

  14. Environmental Challenges Related to the Acquisition of the Trans Carpathian Wide Angle Reflection and Refraction Line

    Science.gov (United States)

    Dragut, Dorina-Alina; Schultz, Gehrig; Mocanu, Victor; Stephenson, Randell; Janik, Tomasz; Starostenko, Vitaly

    2015-04-01

    Complex structures like the Carpathian Orogen and its neighbouring platforms and related inter-orogenic basin system can be understood only by complex integration of complementary investigative tools. Most of regional geoscientific investigations in Romania have targeted the very intricate, high intermediate-depth seismicity, clustered Carpathian Bend Zone: Vrancea. Despite huge geological and geophysical efforts, the area remains a matter of robust debate, at least from the point of view of geodynamic driving mechanisms. However, other areas outside Vrancea remained somehow "orphaned". However, a large wide angle refraction and reflection (WARR) survey was carried out in the summer of 2014 by a large international partnership in order to study the transition from the East European Platform to the northern part of the Romanian Eastern Carpathians, Transylvanian Basin and the Apuseni Mountains. The main scientific objectives of the WARR project relate to three main investigation domains: crustal architecture; affinity of crystalline basement and sedimentary basins architecture. The profile is about 700 km in total, in Ukraine and Romania. Recorders were placed at 1.75 - 2.0 km intervals along an alignment forming the Romanian segment. Recorders used were stand-alone DSS Cubes from the Helmholz Center of GFZ Potsdam and from the Institute of Geophysics of the Polish Academy of Sciences. The seismic sources were explosives ("Riogel" and "Riodet" by Maxam), with shotpoints spaced at 20 - 65 km with a total of 800 - 1200 kg explosives/site in clusters of drill-holes loaded with 50 kg explosive/hole, average depth of 25 m. Very complicated and legally-challenging environmental permitting requirements represented a real issue for successful implementation of the project. The main concern of local and central authorities related to potential pollution of sensitive components. Here, we present the strategy, actions and results concluded in order to reach the scientific and

  15. Second harmonic conical refraction in GUHP

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Jan

    2010-01-01

    Roč. 12, č. 4 (2010), 045706/1-045706/3 ISSN 2040-8978 R&D Projects: GA ČR GA203/09/0878 Institutional research plan: CEZ:AV0Z10100520 Keywords : nonlinear optics * refraction * polarization * birefringence * crystal optics Subject RIV: BM - Solid Matter Physics ; Magnetism

  16. Compound refractive X-ray lens

    International Nuclear Information System (INIS)

    Nygren, D.R.; Cahn, R.; Cederstrom, B.; Danielsson, M.; Vestlund, J.

    2000-01-01

    An apparatus and method are disclosed for focusing X-rays. In one embodiment, his invention is a commercial-grade compound refractive X-ray lens. The commercial-grade compound refractive X-ray lens includes a volume of low-Z material. The volume of low-Z material has a first surface which is adapted to receive X-rays of commercially-applicable power emitted from a commercial-grade X-ray source. The volume of low-Z material also has a second surface from which emerge the X-rays of commercially-applicable power which were received at the first surface. Additionally, the commercial-grade compound refractive X-ray lens includes a plurality of openings which are disposed between the first surface and the second surface. The plurality of openings are oriented such that the X-rays of commercially-applicable power which are received at the first surface, pass through the volume of low-Z material and through the plurality openings. In so doing, the X-rays which emerge from the second surface are refracted to a focal point

  17. Wave refraction studies off Agonda beach (Goa)

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnakumar, V.; Pathak, M.C.; Kotnala, K.L.

    Analysis of wave refraction and longshore current has been carried out for a narrow strip off the shores of Agonda (Goa, India). Zones with high wave energy and rip currents have been demarcated. It is found from the analysis that the southern part...

  18. Characterising refractive index dispersion in chalcogenide glasses

    DEFF Research Database (Denmark)

    Fang, Y.; Sojka, L.; Jayasuriya, D.

    2016-01-01

    Much effort has been devoted to the study of glasses that contain the chalcogen elements (sulfur, selenium and tellurium) for photonics' applications out to MIR wavelengths. In this paper we describe some techniques for determining the refractive index dispersion characteristics of these glasses...

  19. Real time refractive index measurement by ESPI

    International Nuclear Information System (INIS)

    Torroba, R.; Joenathan, C.

    1991-01-01

    In this paper a method to measure refractive index variations in real time is reported. A technique to introduce reference fringes in real time is discussed. Both the theoretical and experimental results are presented and an example with phase shifting is given. (author). 8 refs, 5 figs

  20. 37 REFRACTIVE ERROR BLINDNESS IN YENAGOA, BAYELSA ...

    African Journals Online (AJOL)

    Vol. 12 No. 1 December, 2010. Refractive Error Blindness in Yenagoa, Bayelsa State, Nigeria. 39. (PVA) was measured using a snellen visual acuity chart and a full ocular examination was carried out including anterior segment examination using a. Haag-Streit slit lamp biomicroscope and a posterior segment examination.

  1. Prevalence of refractive error in the United States, 1999-2004.

    Science.gov (United States)

    Vitale, Susan; Ellwein, Leon; Cotch, Mary Frances; Ferris, Frederick L; Sperduto, Robert

    2008-08-01

    To describe the prevalence of refractive error in the United States. The 1999-2004 National Health and Nutrition Examination Survey (NHANES) used an autorefractor to obtain refractive error data on a nationally representative sample of the US noninstitutionalized, civilian population 12 years and older. Using data from the eye with a greater absolute spherical equivalent (SphEq) value, we defined clinically important refractive error as follows: hyperopia, SphEq value of 3.0 diopters (D) or greater; myopia, SphEq value of -1.0 D or less; and astigmatism, cylinder of 1.0 D or greater in either eye. Of 14,213 participants 20 years or older who completed the NHANES, refractive error data were obtained for 12,010 (84.5%). The age-standardized prevalences of hyperopia, myopia, and astigmatism were 3.6% (95% confidence interval [CI], 3.2%-4.0%), 33.1% (95% CI, 31.5%-34.7%), and 36.2% (95% CI, 34.9%-37.5%), respectively. Myopia was more prevalent in women (39.9%) than in men (32.6%) (P refractive error affects half of the US population 20 years or older.

  2. Prevalence and associated risk factors of undercorrected refractive errors among people with diabetes in Shanghai.

    Science.gov (United States)

    Zhu, Mengjun; Tong, Xiaowei; Zhao, Rong; He, Xiangui; Zhao, Huijuan; Zhu, Jianfeng

    2017-11-28

    To investigate the prevalence and risk factors of undercorrected refractive error (URE) among people with diabetes in the Baoshan District of Shanghai, where data for undercorrected refractive error are limited. The study was a population-based survey of 649 persons (aged 60 years or older) with diabetes in Baoshan, Shanghai in 2009. One copy of the questionnaire was completed for each subject. Examinations included a standardized refraction and measurement of presenting and best-corrected visual acuity (BCVA), tonometry, slit lamp biomicroscopy, and fundus photography. The calculated age-standardized prevalence rate of URE was 16.63% (95% confidence interval [CI] 13.76-19.49). For visual impairment subjects (presenting vision worse than 20/40 in the better eye), the prevalence of URE was up to 61.11%, and 75.93% of subjects could achieve visual acuity improvement by at least one line using appropriate spectacles. Under multiple logistic regression analysis, older age, female gender, non-farmer, increasing degree of myopia, lens opacities status, diabetic retinopathy (DR), body mass index (BMI) index lower than normal, and poor glycaemic control were associated with higher URE levels. Wearing distance eyeglasses was a protective factor for URE. The undercorrected refractive error in diabetic adults was high in Shanghai. Health education and regular refractive assessment are needed for diabetic adults. Persons with diabetes should be more aware that poor vision is often correctable, especially for those with risk factors.

  3. Seismic load experiments under mean seismic excitation

    International Nuclear Information System (INIS)

    Steinhilber, H.; Jehlicka, P.; Malcher, L.

    1979-01-01

    The seismic load experiments carried out within the framework of the HDR safety programme are aimed at enlarging and verifying the know-how with regard to the design of nuclear power plants so as to protect them against the impact of earth-quakes. One of the main objectives is to find out computing methods yielding sufficiently reliable results defining the actual vibrational behaviour of real structures under high seismic excitation. (orig./GL) [de

  4. Seismic qualification of civil engineering structures - Temelin NPP

    International Nuclear Information System (INIS)

    Schererova, K.; Holub, I.; Stepan, J.; Maly, J.

    2004-01-01

    Basic information is presented about the input data and methodology used for evaluation of Temelin NPP civil structures. The existing conditions as listed in POSAR report for the two reactor units are considered. The original design of the power plant assumed a lower level of locality seismic hazard, as followed from seismological surveys that where then available. Later the seismic assessment was updated while fully respecting IAEA recommendations and using a minimum value of acceleration in the horizontal direction PGAHOR = 0.1 g at free field level for SL-2. In relation to the new seismic project, new qualification of the structures, components and systems classed as seismic resistance category 1 was carried out. Since the Czech Republic has no specific technical standards for seismic resistance evaluation of nuclear power plants, a detailed methodology was elaborated, comprising principles of seismic resistance evaluation based on IAEA guides and on common practice in countries with advanced nuclear power engineering. (P.A.)

  5. Temporally resolved refractive index structure parameter measurement

    Science.gov (United States)

    Henriksson, Markus; Forsling, Robin

    2017-09-01

    The refractive index structure parameter is the most common measure of optical turbulence. It is defined as a statistical quantity for the Kolmogorov spectrum energy cascade of turbulent eddies of different sizes. As such it is formally assumed to be constant in time and space. However, the large scale variation with the diurnal cycle, with altitude or with terrain characteristics is well known. The ensemble average in the definition of the refractive index structure parameter is thus assumed to be applied over a restricted region in space and time. The question of how large volume is needed to determine the refractive index structure parameter and on how short temporal scales it can vary has not received significant attention. To study the temporal variation we have used two independent measurement systems to measure the path-averaged refractive index structure parameter over a 171 m path at 1 m above ground with higher than 1 Hz temporal resolution. One measurement system uses the differential angle-of-arrival of an array of LEDs. The other system measures the scintillation of a single path laser beam using a photon counting system, with time correlation of picosecond pulses for simultaneous measurement of signal and background and with temporal autocorrelation-based variance determination to separate turbulence related scintillations from shot noise. The data shows excellent agreement between the two measurement systems on second level temporal variation, giving confidence in that the measured values show true variation of the refractive index structure parameter. Large scale variation of up to two orders of magnitude can be coupled to solar insolation on this partly cloudy day. High frequency variations that are consistent between the systems used show factor two changes at time scales below one second.

  6. [ISO 9001-2000 certification for refractive laser treatment].

    Science.gov (United States)

    Lebuisson, D A; Arson, B; Abenhaïm, A; Albou-Ganem, C; Assouline, M; Chong Sit, D; Danan, A; Montefiore, G; Montin, J-F; Nguyen-Khoa, J-L; Pietrini, D; Saragoussi, J-J; Trong, Th; Amar, R

    2005-05-01

    To obtain ISO 9001-2000 certification for laser corneal refractive treatment, never before sought in Europe. The consulting firm Veritas led the certification process with the clinic's staff manager. This ISO norm is dedicated to the implementation of a quality management system. We assessed and optimized all necessary resources, evaluating customer satisfaction using patient and referring-physician surveys. We started quality rounds including surgeons, nurses, and technicians. Based on this preparation, we redefined and explained all processes including staff responsibilities and necessary resources in the quality manual. The procedure lasted 14 months with substantial involvement on the part of the management. Unconditional ISO 9001-2000 certification was granted by the independent audit firm, BVQI, in december 2003 for refractive laser treatment. The 2000 version of the new ISO 9001-2000 seeks to meet the demand for improving health care delivery in this field, most particularly by establishing a clear procedural orientation. Such certification enhances team work, stabilizes methodologies, and reinforces cohesion and self-audit. Patients notice that the center follows a consistent quality policy and are assured that the clinic respects rules and regulations. Certification is an advantageous alternative when accreditation cannot be considered. Our article discusses the steps taken in upper management, quality management, procedural guidance, as well as customer and staff counselling. It also discusses the project's cost/benefit ratio for the organization.

  7. Seismic Investigations of an Accommodation zone in the Northern Rio Grande Rift, New Mexico, USA

    Science.gov (United States)

    Baldridge, W. S.; Valdes, J.; Nedorub, O.; Phrampus, B.; Braile, L. W.; Ferguson, J. F.; Benage, M. C.; Litherland, M.

    2010-12-01

    Seismic reflection and refraction data acquired in the Rio Grande rift near Santa Fe, New Mexico, in 2009 and 2010 by the SAGE (Summer of Applied Geophysical Experience) program imaged the La Bajada fault (LBF) and strata offset across the associated, perpendicular Budagher fault (BF). The LBF is a major basin-bounding normal fault, offset down to the west; the smaller BF is an extensional fault that breaks the hanging wall ramp of the LBF. We chose this area because it is in a structurally complex region of the rift, comprising a small sub-basin and plunging relay ramps, where north-trending, en echelon basin-bounding faults (including the LBF) transfer crustal extension laterally between the larger Española (to north) and Albuquerque rift basins. Our data help determine the precise location and geometry of the poorly exposed LBF, which, near the survey location, offsets the rift margin vertically about 3,000 m. When integrated with industry reflection data and other SAGE seismic, gravity, and magnetotelluric surveys, we are able to map differences in offset and extension laterally (especially southward) along the fault. We interpret only about 200 m of normal offset across the BF. Our continuing work helps define multiple structural elements, partly buried by syn-rift basin-filling sedimentary rocks, of a complex intra-rift accommodation zone. We are also able to discriminate pre-Eocene (Laramide) from post-Miocene (rift) structures. Our data help determine the amount of vertical offset of pre-rift strata across structural elements of the accommodation zone, and depth and geometry of basin fill. A goal is to infer the kinematic development of this margin of the rift, linkages among faults, growth history, and possible pre-rift structural controls. This information will be potentially useful for evaluation of resources, including oil and/or gas in pre-rift strata and ground water in Late Miocene to Holocene rift-filling units.

  8. Seismic Risk Perception compared with seismic Risk Factors

    Science.gov (United States)

    Crescimbene, Massimo; La Longa, Federica; Pessina, Vera; Pino, Nicola Alessandro; Peruzza, Laura

    2016-04-01

    The communication of natural hazards and their consequences is one of the more relevant ethical issues faced by scientists. In the last years, social studies have provided evidence that risk communication is strongly influenced by the risk perception of people. In order to develop effective information and risk communication strategies, the perception of risks and the influencing factors should be known. A theory that offers an integrative approach to understanding and explaining risk perception is still missing. To explain risk perception, it is necessary to consider several perspectives: social, psychological and cultural perspectives and their interactions. This paper presents the results of the CATI survey on seismic risk perception in Italy, conducted by INGV researchers on funding by the DPC. We built a questionnaire to assess seismic risk perception, with a particular attention to compare hazard, vulnerability and exposure perception with the real data of the same factors. The Seismic Risk Perception Questionnaire (SRP-Q) is designed by semantic differential method, using opposite terms on a Likert scale to seven points. The questionnaire allows to obtain the scores of five risk indicators: Hazard, Exposure, Vulnerability, People and Community, Earthquake Phenomenon. The questionnaire was administered by telephone interview (C.A.T.I.) on a statistical sample at national level of over 4,000 people, in the period January -February 2015. Results show that risk perception seems be underestimated for all indicators considered. In particular scores of seismic Vulnerability factor are extremely low compared with house information data of the respondents. Other data collected by the questionnaire regard Earthquake information level, Sources of information, Earthquake occurrence with respect to other natural hazards, participation at risk reduction activities and level of involvement. Research on risk perception aims to aid risk analysis and policy-making by

  9. Seismic detectability of meteorite impacts on Europa

    Science.gov (United States)

    Tsuji, Daisuke; Teanby, Nicholas

    2016-04-01

    Europa, the second of Jupiter's Galilean satellites, has an icy outer shell, beneath which there is probably liquid water in contact with a rocky core. Europa, may thus provide an example of a sub-surface habitable environment so is an attractive object for future lander missions. In fact, the Jupiter Icy Moon Explorer (JUICE) mission has been selected for the L1 launch slot of ESA's Cosmic Vision science programme with the aim of launching in 2022 to explore Jupiter and its potentially habitable icy moons. One of the best ways to probe icy moon interiors in any future mission will be with a seismic investigation. Previously, the Apollo seismic experiment, installed by astronauts, enhanced our knowledge of the lunar interior. For a recent mission, NASA's 2016 InSight Mars lander aims to obtain seismic data and will deploy a seismometer directly onto Mars' surface. Motivated by these works, in this study we show how many meteorite impacts will be detected using a single seismic station on Europa, which will be useful for planning the next generation of outer solar system missions. To this end, we derive: (1) the current small impact flux on Europa from Jupiter impact rate models; (2) a crater diameter versus impactor energy scaling relation for ice by merging previous experiments and simulations; (3) scaling relations for seismic signals as a function of distance from an impact site for a given crater size based on analogue explosive data obtained on Earth's icy surfaces. Finally, resultant amplitudes are compared to the noise level of a likely seismic instrument (based on the NASA InSight mission seismometers) and the number of detectable impacts are estimated. As a result, 0.5-3.0 local/regional small impacts (i.e., direct P-waves through the ice crust) are expected to be detected per year, while global-scale impact events (i.e., PKP-waves refracted through the mantle) are rare and unlikely to be detected by a short duration mission. We note that our results are

  10. A Hammer-Impact, Aluminum, Shear-Wave Seismic Source

    Science.gov (United States)

    Haines, Seth S.

    2007-01-01

    Near-surface seismic surveys often employ hammer impacts to create seismic energy. Shear-wave surveys using horizontally polarized waves require horizontal hammer impacts against a rigid object (the source) that is coupled to the ground surface. I have designed, built, and tested a source made out of aluminum and equipped with spikes to improve coupling. The source is effective in a variety of settings, and it is relatively simple and inexpensive to build.

  11. Relative seismic shaking vulnerability microzonation using an ...

    Indian Academy of Sciences (India)

    An alternative seismic shaking vulnerability survey method to computational intensive theoretical ... test/reference site spectral ratio method and the single site horizontal/vertical spectral ration method. Keywords. Microzonation; earthquake hazard; Nakamura; ground ... direct measure of the horizontal ground movement.

  12. Delivering refractive error services: primary eye care centres and outreach

    OpenAIRE

    Naidoo, Kovin; Ravilla, Dhivya

    2007-01-01

    Addressing refractive errors, the second major cause of preventable blindness, is now a priority for eye care programmes.Although a simple pair of spectacles will correct refractive error, there exists a high prevalence of uncorrected refractive error. This is due in large part to the cost and inaccessibility of refraction and spectacle dispensing services, which are usually offered only at secondary and tertiary eye care centres.

  13. [Results of refractive surgery in hyperopic and combined astigmatism].

    Science.gov (United States)

    Vlaicu, Valeria

    2013-01-01

    The refractive surgery includes a lot of procedures for changing the refraction of the eye to obtain a better visual acuity with no glasses or contact lenses. LASIK is the most commonly performed laser refractive surgery today. The goal is to present the postoperative evolution of the refraction and visual acuity after LASIK for Mixed and Hyperopic Astigmatism. The results show that LASIK is safe and predictible if we have well performed interventions and well-selected patients.

  14. Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China

    Directory of Open Access Journals (Sweden)

    Wen-Jun Zhou

    2016-07-01

    Full Text Available Background: To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China. Methods: A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia. Results: Longitudinal data were available for 1858 children (60.5%. The cumulative mean change in refractive error was −2.21 (standard deviation [SD], 1.87 diopters (D for the entire study population, with an annual progression of refraction in a myopic direction of −0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of −0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%–63.5%, with an annual incidence of 10.6% (95% CI, 8.7%–13.1%. Myopia was found more likely to happen in female and older children. Conclusions: In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China.

  15. Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China

    Science.gov (United States)

    Zhou, Wen-Jun; Zhang, Yong-Ye; Li, Hua; Wu, Yu-Fei; Xu, Ji; Lv, Sha; Li, Ge; Liu, Shi-Chun; Song, Sheng-Fang

    2016-01-01

    Background To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China. Methods A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia. Results Longitudinal data were available for 1858 children (60.5%). The cumulative mean change in refractive error was −2.21 (standard deviation [SD], 1.87) diopters (D) for the entire study population, with an annual progression of refraction in a myopic direction of −0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of −0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%–63.5%), with an annual incidence of 10.6% (95% CI, 8.7%–13.1%). Myopia was found more likely to happen in female and older children. Conclusions In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China. PMID:26875599

  16. Five-Year Progression of Refractive Errors and Incidence of Myopia in School-Aged Children in Western China.

    Science.gov (United States)

    Zhou, Wen-Jun; Zhang, Yong-Ye; Li, Hua; Wu, Yu-Fei; Xu, Ji; Lv, Sha; Li, Ge; Liu, Shi-Chun; Song, Sheng-Fang

    2016-07-05

    To determine the change in refractive error and the incidence of myopia among school-aged children in the Yongchuan District of Chongqing City, Western China. A population-based cross-sectional survey was initially conducted in 2006 among 3070 children aged 6 to 15 years. A longitudinal follow-up study was then conducted 5 years later between November 2011 and March 2012. Refractive error was measured under cycloplegia with autorefraction. Age, sex, and baseline refractive error were evaluated as risk factors for progression of refractive error and incidence of myopia. Longitudinal data were available for 1858 children (60.5%). The cumulative mean change in refractive error was -2.21 (standard deviation [SD], 1.87) diopters (D) for the entire study population, with an annual progression of refraction in a myopic direction of -0.43 D. Myopic progression of refractive error was associated with younger age, female sex, and higher myopic or hyperopic refractive error at baseline. The cumulative incidence of myopia, defined as a spherical equivalent refractive error of -0.50 D or more, among initial emmetropes and hyperopes was 54.9% (95% confidence interval [CI], 45.2%-63.5%), with an annual incidence of 10.6% (95% CI, 8.7%-13.1%). Myopia was found more likely to happen in female and older children. In Western China, both myopic progression and incidence of myopia were higher than those of children from most other locations in China and from the European Caucasian population. Compared with a previous study in China, there was a relative increase in annual myopia progression and annual myopia incidence, a finding which is consistent with the increasing trend on prevalence of myopia in China.

  17. Refractive errors in presbyopic patients in Kano, Nigeria | Lawan ...

    African Journals Online (AJOL)

    Background: The study is a retrospective review of the pattern of refractive errors in presbyopic patients seen in the eye clinic from January to December, 2009. Patients and Methods: The clinic refraction register was used to retrieve the case folders of all patients refracted during the review period. Information extracted ...

  18. Refractive Error Status In Bayelsa State, Nigeria | Koroye-Egbe ...

    African Journals Online (AJOL)

    Refractive errors affect the whole spectrum of the population without regard to age, gender, race and ethnic group. Uncorrected refractive errors have severe consequences for the individual, family and society.Records showthat no study documenting the distribution of refractive errors in Bayelsa State had been carried out.

  19. Refractive errors in presbyopic patients in Kano, Nigeria

    African Journals Online (AJOL)

    Background:The study is a retrospective review of the pattern of refractive errors in presbyopic patients seen in the eye clinic from January to December, 2009. Patients and Methods: The clinic refraction register was used to retrieve the case folders of all patients refracted during the review period. Information extracted ...

  20. Patterns of Seismicity Associated with USGS Identified Areas of Potentially Induced Seismicity.

    Science.gov (United States)

    Barnes, Caitlin; Halihan, Todd

    2018-03-13

    A systematic review across U.S. Geological Survey (USGS) identified potentially induced seismic locations was conducted to discover seismic distance patterns and trends over time away from injection disposal wells. Previous research indicates a 10 km (6 miles) average where the majority of induced seismicity is expected to occur within individual locations, with some areas reporting a larger radius of 35 km (22 miles) to over 70 km (43 miles). This research analyzed earthquake occurrences within nine USGS locations where specified wells were identified as contributors to induced seismicity to determine distance patterns from disposal wells or outward seismic migration over time using established principles of hydrogeology. Results indicate a radius of 31.6 km (20 miles) where 90% of felt earthquakes occur among locations, with the closest proximal felt seismic events, on average, occurring 3 km (1.9 miles) away from injection disposal wells. The results of this research found distance trends across multiple locations of potentially induced seismicity. © 2018, National Ground Water Association.

  1. Seismic measurements of explosions in the Tatum Salt Dome, Mississippi

    Science.gov (United States)

    Borcherdt, Roger D.; Healy, J.H.; Jackson, W.H.; Warren, D.R.

    1967-01-01

    Project Sterling provided for the detonation of a nuclear device in the cavity resulting from the Salmon nuclear explosion in the Tatum salt dome in southern Mississippi. It also provided for a high explosive (HE) comparison shot in a nearby drill hole. The purpose of the experiment was to gather information on the seismic decoupling of a nuclear explosion in a cavity by comparing seismic signals from a nuclear shot in the Salmon cavity with seismic signals recorded from Salmon and with seismic signals recorded from a muall (about 2 tons) HE shot in the salt dome. Surface seismic measurements were made by the U.S. Geological Survey, the U.S. Coast and Geodetic Survey, and the Air Force Technical Applications Center with coordination and overall direction by the Lawrence Radiation Laboratory. This report covers only the seismic measurements made by the U. S. Geological Survey. The first objective of this report is to describe the field recording procedures and the data obtained by the U. S. Geological Survey from these events. The second objective is to describe the spectral analyses which have been made on the data and the relative seismic amplitudes which have been determined from these analyses.

  2. Seismic Catalogue and Seismic Network in Haiti

    Science.gov (United States)

    Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

    2013-05-01

    The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

  3. Development of Vertical Cable Seismic System

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2011-12-01

    In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by

  4. Diffraction limit of refractive compound lens

    International Nuclear Information System (INIS)

    Kolchevsky, N.N.; Petrov, P.V.

    2015-01-01

    A compound X-ray and neutron lenses is an array of lenses with a common axis. The resolution limited by aberration and by diffraction. Diffraction limit comes from theory based on absorption aperture of the compound refractive lenses. Beam passing through transparent lenses form Airy pattern. Results of calculation of diffraction resolution limit for non-transparent X-ray and neutron lenses are discussed. (authors)

  5. The Index of Refraction of Seawater

    Science.gov (United States)

    1976-01-01

    the three temper- atures. By integrating these linear gradients, we recovered the index of refrection dependence on pressure, at each of the three...U.S. DEPARTMENT OF COMMERCE National Technical Information Service AD-A024 800 The Index of Refraction of Seawater Scripps Institution of...or Government Reports NTIS reports are distributed in the SAIM Announcements and Index categories, or to program. You will receive a notice in your the

  6. Effective spectral dispersion of refractive index modulation

    Czech Academy of Sciences Publication Activity Database

    Vojtíšek, Petr; Květoň, M.; Richter, I.

    2017-01-01

    Roč. 19, č. 4 (2017), č. článku 045603. ISSN 2040-8978 R&D Projects: GA MŠk(CZ) LO1206 Institutional support: RVO:61389021 Keywords : volume gratings * holography * dispersion * refractive index modulation Subject RIV: BH - Optics, Masers, Lasers OBOR OECD: Optics (including laser optics and quantum optics) Impact factor: 1.741, year: 2016 http://iopscience.iop.org/article/10.1088/2040-8986/aa6092/meta

  7. Hillslope characterization in terms of geophysical units based on the joint interpretation of electrical resistivity and seismic velocity data

    Science.gov (United States)

    Feskova, Tatiana; Dietrich, Peter

    2015-04-01

    Hydrological conditions in a catchment depend on many factors such as climatic, geological, geomorphological, biological and human, which interact with each other and influence water balance in a catchment. This interaction leads to the subordination in the landscape structure, namely the weak elements subordinate to the powerful elements. Thereby, geological and geomorphological factors play an essential role in catchment development and organization. A hillslope consequently can be allocated to one class of the representative units because the important flow processes run at the hillslope. Moreover, a hillslope can be subdivided into stratigraphic subsurface units and significant hillslope areas based on the lithological change of contrasting interfaces. The knowledge of subsurface structures is necessary to understand and predicate complex hydrological processes in a catchment. Geophysical techniques provide a good opportunity to explore the subsurface. A complete geophysical investigation of subsurface in a catchment with difficult environmental conditions never will be achieved because of large time effort in the field, equipment logistic, and ambiguity in the data interpretation. The case study demonstrates how a catchment can be investigated using geophysical methods in an effective manner in terms of characterization of representative units with respect to a functional role in the catchment. This case study aims to develop combined resistivity and seismic velocity hillslope subsurface models for the distinction of representative functional units. In order to identify the contrasting interfaces of the hillslope, to localize significant hillslope areas, and to address the ambiguity in the geophysical data interpretation, the case study combined resistivity surveys (vertical electrical soundings and electrical resistivity tomography) with refraction seismic method, and conducted these measurements at one single profile along the hillslope transect and

  8. Electron refraction at lateral atomic interfaces

    Science.gov (United States)

    Abd El-Fattah, Z. M.; Kher-Elden, M. A.; Yassin, O.; El-Okr, M. M.; Ortega, J. E.; García de Abajo, F. J.

    2017-11-01

    We present theoretical simulations of electron refraction at the lateral atomic interface between a "homogeneous" Cu(111) surface and the "nanostructured" one-monolayer (ML) Ag/Cu(111) dislocation lattice. Calculations are performed for electron binding energies barely below the 1 ML Ag/Cu(111) M ¯ -point gap (binding energy EB = 53 meV, below the Fermi level) and slightly above its Γ ¯ -point energy (EB = 160 meV), both characterized by isotropic/circular constant energy surfaces. Using plane-wave-expansion and boundary-element methods, we show that electron refraction occurs at the interface, the Snell law is obeyed, and a total internal reflection occurs beyond the critical angle. Additionally, a weak negative refraction is observed for EB = 53 meV electron energy at beam incidence higher than the critical angle. Such an interesting observation stems from the interface phase-matching and momentum conservation with the umklapp bands at the second Brillouin zone of the dislocation lattice. The present analysis is not restricted to our Cu-Ag/Cu model system but can be readily extended to technologically relevant interfaces with spin-polarized, highly featured, and anisotropic constant energy contours, such as those characteristic for Rashba systems and topological insulators.

  9. Topography-guided laser refractive surgery.

    Science.gov (United States)

    Pasquali, Theodore; Krueger, Ronald

    2012-07-01

    Topography-guided laser refractive surgery seeks to correct vision by altering the major refractive surface of the eye. Whereas results are not significantly different from current treatment options for primary surgery, topography-guided treatment is uniquely effective in eyes with corneal irregularity. This review highlights topography-guided ablations, emphasizing recent advances in treating highly aberrated eyes, including treatment for corneal ectasia in conjunction with collagen cross-linking (CXL). Studies continue to document similar outcomes between topography-guided and wavefront-guided customized corneal ablations while exploring the indications for each modality. Topography-guided ablations demonstrate good outcomes for the correction of astigmatism after penetrating keratoplasty, laser-assisted in-situ keratomileusis (LASIK) flap or interface complications, post-radial keratotomy eyes, and other highly aberrated corneas, many of which are poor candidates for wavefront-guided therapy. The use of topography-guided ablations with CXL seeks to address both the refractive and structural abnormalities of corneal ectasias. This combination therapy has shown promising results for keratoconus, post-LASIK ectasia, and pellucid marginal degeneration. Topography-guided customized corneal ablation is well tolerated and effective. Recent attention has been focused on the unique therapeutic benefits of this treatment for highly irregular and ectatic corneas with encouraging results.

  10. Compound Refractive Lenses for Thermal Neutron Applications

    Energy Technology Data Exchange (ETDEWEB)

    Gary, Charles K.

    2013-11-12

    This project designed and built compound refractive lenses (CRLs) that are able to focus, collimate and image using thermal neutrons. Neutrons are difficult to manipulate compared to visible light or even x rays; however, CRLs can provide a powerful tool for focusing, collimating and imaging neutrons. Previous neutron CRLs were limited to long focal lengths, small fields of view and poor resolution due to the materials available and manufacturing techniques. By demonstrating a fabrication method that can produce accurate, small features, we have already dramatically improved the focal length of thermal neutron CRLs, and the manufacture of Fresnel lens CRLs that greatly increases the collection area, and thus efficiency, of neutron CRLs. Unlike a single lens, a compound lens is a row of N lenslets that combine to produce an N-fold increase in the refraction of neutrons. While CRLs can be made from a variety of materials, we have chosen to mold Teflon lenses. Teflon has excellent neutron refraction, yet can be molded into nearly arbitrary shapes. We designed, fabricated and tested Teflon CRLs for neutrons. We demonstrated imaging at wavelengths as short as 1.26 ? with large fields of view and achieved resolution finer than 250 μm which is better than has been previously shown. We have also determined designs for Fresnel CRLs that will greatly improve performance.

  11. Deblending of seismic data

    NARCIS (Netherlands)

    Mahdad, A.

    2012-01-01

    Seismic imaging is one of the most common geophysical techniques for hydrocarbon exploration. Seismic acquisition is a trade-off between economy and quality. In conventional acquisition, the time intervals between successively firing sources are large enough to avoid interference in time. To obtain

  12. Refractive error in Chinese with type 2 diabetes and its association with glycaemic control.

    Science.gov (United States)

    Song, E; Qian, Deng-Juan; Wang, Shan; Xu, Cailian; Pan, Chen-Wei

    2018-03-01

    The aim of this study was to determine the prevalence of refractive errors and their association with glycaemic control among adults with type 2 diabetes mellitus (T2DM) in eastern China. A community-based survey, including 913 adults with T2DM aged 30 to 89 years, was conducted. Refractive error was assessed by autorefraction, after which subjective refraction was performed. Ocular biometric parameters were measured by non-contact partial coherence laser interferometry. Myopia was defined as spherical equivalent (SE) less than -0.50 dioptres (D), high myopia as SE less than -5.00 D, hyperopia as SE greater than 0.50 D and astigmatism as cylinder less than -0.50 D. After excluding participants who had undergone cataract surgery, 839 were included in the data analyses and 96.1 per cent were found to have refractive errors. The overall prevalences of myopia, high myopia, hyperopia and astigmatism were 28.2 per cent (95 per cent confidence interval [CI] 25.2-31.3), 6.3 per cent (95 per cent CI 4.7-8.0), 46.4 per cent (95 per cent CI 43.0-49.7) and 81.0 per cent (95 per cent CI 78.4-83.7) with no gender differences observed (all p > 0.10). In multivariate analysis, myopia was associated with decreasing age (odds ratio [OR] = 0.86, p = 0.01; per year increase), higher blood levels of haemoglobin A 1c (HbA 1c ) (OR = 1.12, p = 0.05; per unit increase), higher education levels (OR = 5.10, p Refractive errors may be associated with glycaemic control among T2DM patients. Longitudinal analyses are warranted to examine the relationship between changes in HbA 1c and the development of refractive errors. © 2017 Optometry Australia.

  13. Refractive error in school children in an urban and rural setting in Cambodia.

    Science.gov (United States)

    Gao, Zoe; Meng, Ngy; Muecke, James; Chan, Weng Onn; Piseth, Horm; Kong, Aimee; Jnguyenphamhh, Theresa; Dehghan, Yalda; Selva, Dinesh; Casson, Robert; Ang, Kim

    2012-02-01

    To assess the prevalence of refractive error in schoolchildren aged 12-14 years in urban and rural settings in Cambodia's Phnom Penh and Kandal provinces. Ten schools from Phnom Penh Province and 26 schools from Kandal Province were randomly selected and surveyed in October 2010. Children were examined by teams of Australian and Cambodian optometrists, ophthalmic nurses and ophthalmologists who performed visual acuity (VA) testing and cycloplegic refraction. A total of 5527 children were included in the study. The prevalence of uncorrected, presenting and best-corrected VA ≤ 6/12 in the better eye were 2.48% (95% confidence interval [CI] 2.02-2.83%), 1.90% (95% CI 1.52-2.24%) and 0.36% (95% CI 0.20-0.52%), respectively; 43 children presented with glasses whilst a total of 315 glasses were dispensed. The total prevalence of refractive error was 6.57% (95% CI 5.91-7.22%), but there was a significant difference between urban (13.7%, 95% CI 12.2-15.2%) and rural (2.5%, 95% CI 2.03-3.07%) schools (P Refractive error accounted for 91.2% of visually impaired eyes, cataract for 1.7%, and other causes for 7.1%. Myopia (spherical equivalent ≤ -0.50 diopters [D] in either eye) was associated with increased age, female gender and urban schooling. The prevalence of refractive error was significantly higher in urban Phnom Penh schools than rural schools in Kandal Province. The prevalence of refractive error, particularly myopia was relatively low compared to previous reports in Asia. The majority of children did not have appropriate correction with spectacles, highlighting the need for more effective screening and optical intervention.

  14. Study on seismic hazard assessment of large active fault systems. Evolution of fault systems and associated geomorphic structures: fault model test and field survey

    International Nuclear Information System (INIS)

    Ueta, Keichi; Inoue, Daiei; Miyakoshi, Katsuyoshi; Miyagawa, Kimio; Miura, Daisuke

    2003-01-01

    Sandbox experiments and field surveys were performed to investigate fault system evolution and fault-related deformation of ground surface, the Quaternary deposits and rocks. The summary of the results is shown below. 1) In the case of strike-slip faulting, the basic fault sequence runs from early en echelon faults and pressure ridges through linear trough. The fault systems associated with the 2000 western Tottori earthquake are shown as en echelon pattern that characterize the early stage of wrench tectonics, therefore no thoroughgoing surface faulting was found above the rupture as defined by the main shock and aftershocks. 2) Low-angle and high-angle reverse faults commonly migrate basinward with time, respectively. With increasing normal fault displacement in bedrock, normal fault develops within range after reverse fault has formed along range front. 3) Horizontal distance of surface rupture from the bedrock fault normalized by the height of the Quaternary deposits agrees well with those of model tests. 4) Upward-widening damage zone, where secondary fractures develop, forms in the handing wall side of high-angle reverse fault at the Kamioka mine. (author)

  15. Micro-seismicity in the Gulf of Cadiz: Is there a link between micro-seismicity, high magnitude earthquakes and active faults?

    Science.gov (United States)

    Silva, Sónia; Terrinha, Pedro; Matias, Luis; Duarte, João C.; Roque, Cristina; Ranero, César R.; Geissler, Wolfram H.; Zitellini, Nevio

    2017-10-01

    The Gulf of Cadiz seismicity is characterized by persistent low to intermediate magnitude earthquakes, occasionally punctuated by high magnitude events such as the M 8.7 1755 Great Lisbon earthquake and the M = 7.9 event of February 28th, 1969. Micro-seismicity was recorded during 11 months by a temporary network of 25 ocean bottom seismometers (OBSs) in an area of high seismic activity, encompassing the potential source areas of the mentioned large magnitude earthquakes. We combined micro-seismicity analysis with processing and interpretation of deep crustal seismic reflection profiles and available refraction data to investigate the possible tectonic control of the seismicity in the Gulf of Cadiz area. Three controlling mechanisms are explored: i) active tectonic structures, ii) transitions between different lithospheric domains and inherited Mesozoic structures, and iii) fault weakening mechanisms. Our results show that micro-seismicity is mostly located in the upper mantle and is associated with tectonic inversion of extensional rift structures and to the transition between different lithospheric/rheological domains. Even though the crustal structure is well imaged in the seismic profiles and in the bathymetry, crustal faults show low to negligible seismic activity. A possible explanation for this is that the crustal thrusts are thin-skinned structures rooting in relatively shallow sub-horizontal décollements associated with (aseismic) serpentinization levels at the top of the lithospheric mantle. Therefore, co-seismic slip along crustal thrusts may only occur during large magnitude events, while for most of the inter-seismic cycle these thrusts remain locked, or slip aseismically. We further speculate that high magnitude earthquake's ruptures may only nucleate in the lithospheric mantle and then propagate into the crust across the serpentinized layers.

  16. Bergermeer Seismicity Study

    Energy Technology Data Exchange (ETDEWEB)

    Muntendam-Bos, A.G.; Wassing, B.B.T.; Geel, C.R.; Louh, M.; Van Thienen-Visser, K.

    2008-11-15

    The Bergermeer seismicity study has been carried out with the objective to provide the required insight in the seismic risks of re-pressurization of the Bergermeer field. This requires a thorough analysis of the geomechanical behaviour of the field, in particular the processes related to pressure variations leading to seismic activity. At a later stage (23.04.2008), the scope was extended with scrutinizing the geomechanical consequences of thermal variations in the reservoir due to cold gas injection on the processes leading to seismic activity. This report describes the general background of the Bergermeer field and the processes inducing seismicity. This is followed by a description of the geological model of the Bergermeer field, the subsidence modelling, reservoir engineering and geomechanical analysis.

  17. LASIK for spherical refractive myopia: effect of topographic astigmatism (ocular residual astigmatism, ORA) on refractive outcome.

    Science.gov (United States)

    Frings, Andreas; Richard, Gisbert; Steinberg, Johannes; Skevas, Christos; Druchkiv, Vasyl; Katz, Toam; Linke, Stephan J

    2015-01-01

    In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK). This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristic analysis was used to find the cut-off values of preoperative ocular residual astigmatism (= topographic astigmatism) that can best discriminate between groups of efficacy and safety indices in preoperative plano refractive cylinder eyes. Preoperative ocular residual astigmatism (ORA) (or topographic astigmatism) of ≤0.9 diopters (D) resulted in an efficacy index of at least 0.8 statistically significantly more frequently than eyes with a preoperative ORA of >0.9 D. Eyes with a high ORA preoperatively also had a high ORA postoperatively. Regression analysis showed that each diopter of preoperative ORA reduced efficacy by 0.07. A preoperative corneal astigmatism of ≥0.9 D could (partially) be taken into account in the LASIK design, even if the subjective refractive astigmatism is neutral.

  18. LASIK for spherical refractive myopia: effect of topographic astigmatism (ocular residual astigmatism, ORA on refractive outcome.

    Directory of Open Access Journals (Sweden)

    Andreas Frings

    Full Text Available In eyes with a preoperative plano refractive cylinder, it would appear that there is no rationale for astigmatic treatment. The aim of this retrospective, cross-sectional data analysis was to determine the amount of topographic astigmatism in refractive plano eyes that results in reduced efficacy after myopic laser in situ keratomileusis (LASIK.This study included 267 eyes from 267 consecutive myopic patients with a refractive plano cylinder. Receiver operating characteristic analysis was used to find the cut-off values of preoperative ocular residual astigmatism (= topographic astigmatism that can best discriminate between groups of efficacy and safety indices in preoperative plano refractive cylinder eyes.Preoperative ocular residual astigmatism (ORA (or topographic astigmatism of ≤0.9 diopters (D resulted in an efficacy index of at least 0.8 statistically significantly more frequently than eyes with a preoperative ORA of >0.9 D. Eyes with a high ORA preoperatively also had a high ORA postoperatively. Regression analysis showed that each diopter of preoperative ORA reduced efficacy by 0.07.A preoperative corneal astigmatism of ≥0.9 D could (partially be taken into account in the LASIK design, even if the subjective refractive astigmatism is neutral.

  19. Nanofocusing refractive X-ray lenses

    International Nuclear Information System (INIS)

    Boye, Pit

    2010-01-01

    This thesis is concerned with the optimization and development of the production of nanofocusing refractive X-ray lenses. These optics made of either silicon or diamond are well-suited for high resolution X-ray microscopy. The goal of this work is the design of a reproducible manufacturing process which allows the production of silicon lenses with high precision, high quality and high piece number. Furthermore a process for the production of diamond lenses is to be developed and established. In this work, the theoretical basics of X-rays and their interaction with matter are described. Especially, aspects of synchrotron radiation are emphasized. Important in X-ray microscopy are the different optics. The details, advantages and disadvantages, in particular those of refractive lenses are given. To achieve small X-ray beams well beyond the 100 nm range a small focal length is required. This is achieved in refractive lenses by moving to a compact lens design where several single lenses are stacked behind each other. The, so-called nanofocusing refractive lenses (NFLs) have a parabolic cylindrical shape with lateral structure sizes in the micrometer range. NFLs are produced by using micro-machining techniques. These micro-fabrication processes and technologies are introduced. The results of the optimization and the final fabrication process for silicon lenses are presented. Subsequently, two experiments that are exemplary for the use of NFLs, are introduced. The rst one employs a high-resolution scanning fluorescence mapping of a geological sample, and the second one is a coherent x-ray diffraction imaging (CXDI) experiment. CXDI is able to reconstruct the illuminated object from recorded coherent diffraction patterns. In a scanning mode, referred to as ptychography, this method is even able to reconstruct the illumination and the object simultaneously. Especially the reconstructed illumination and the possibility of computed propagation of the wave field along the

  20. Nanofocusing refractive X-ray lenses

    Energy Technology Data Exchange (ETDEWEB)

    Boye, Pit

    2010-02-05

    This thesis is concerned with the optimization and development of the production of nanofocusing refractive X-ray lenses. These optics made of either silicon or diamond are well-suited for high resolution X-ray microscopy. The goal of this work is the design of a reproducible manufacturing process which allows the production of silicon lenses with high precision, high quality and high piece number. Furthermore a process for the production of diamond lenses is to be developed and established. In this work, the theoretical basics of X-rays and their interaction with matter are described. Especially, aspects of synchrotron radiation are emphasized. Important in X-ray microscopy are the different optics. The details, advantages and disadvantages, in particular those of refractive lenses are given. To achieve small X-ray beams well beyond the 100 nm range a small focal length is required. This is achieved in refractive lenses by moving to a compact lens design where several single lenses are stacked behind each other. The, so-called nanofocusing refractive lenses (NFLs) have a parabolic cylindrical shape with lateral structure sizes in the micrometer range. NFLs are produced by using micro-machining techniques. These micro-fabrication processes and technologies are introduced. The results of the optimization and the final fabrication process for silicon lenses are presented. Subsequently, two experiments that are exemplary for the use of NFLs, are introduced. The rst one employs a high-resolution scanning fluorescence mapping of a geological sample, and the second one is a coherent x-ray diffraction imaging (CXDI) experiment. CXDI is able to reconstruct the illuminated object from recorded coherent diffraction patterns. In a scanning mode, referred to as ptychography, this method is even able to reconstruct the illumination and the object simultaneously. Especially the reconstructed illumination and the possibility of computed propagation of the wave field along the

  1. Seismic texture classification. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Vinther, R.

    1997-12-31

    The seismic texture classification method, is a seismic attribute that can both recognize the general reflectivity styles and locate variations from these. The seismic texture classification performs a statistic analysis for the seismic section (or volume) aiming at describing the reflectivity. Based on a set of reference reflectivities the seismic textures are classified. The result of the seismic texture classification is a display of seismic texture categories showing both the styles of reflectivity from the reference set and interpolations and extrapolations from these. The display is interpreted as statistical variations in the seismic data. The seismic texture classification is applied to seismic sections and volumes from the Danish North Sea representing both horizontal stratifications and salt diapers. The attribute succeeded in recognizing both general structure of successions and variations from these. Also, the seismic texture classification is not only able to display variations in prospective areas (1-7 sec. TWT) but can also be applied to deep seismic sections. The seismic texture classification is tested on a deep reflection seismic section (13-18 sec. TWT) from the Baltic Sea. Applied to this section the seismic texture classification succeeded in locating the Moho, which could not be located using conventional interpretation tools. The seismic texture classification is a seismic attribute which can display general reflectivity styles and deviations from these and enhance variations not found by conventional interpretation tools. (LN)

  2. New comprehensive standard seismic noise models and 3D seismic noise variation for Morocco territory, North Africa, obtained using seismic broadband stations

    Science.gov (United States)

    El Fellah, Younes; El-Aal, Abd El-Aziz Khairy Abd; Harnafi, Mimoun; Villaseñor, Antonio

    2017-05-01

    In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in north-west Africa to be used for seismological and engineering purposes. Indeed, the original global standard seismic noise models published by Peterson (1993) and their following updates by Astiz and Creager (1995), Ekström (2001) and Berger et al. (2003) had no contributing seismic stations deployed in North Africa. Consequently, this preliminary study was conducted to shed light on seismic noise levels specific to north-west Africa. For this purpose, 23 broadband seismic stations recently installed in different structural domains throughout Morocco are used to study the nature and characteristics of seismic noise and to create seismic noise models for Morocco. Continuous data recorded during 2009, 2010 and 2011 were processed and analysed to construct these new noise models and 3D noise levels from all stations. We compared the Peterson new high-noise model (NHNM) and low-noise model (NLNM) with the Moroccan high-noise model (MHNM) and low-noise model (MLNM). These new noise models are comparable to the United States Geological Survey (USGS) models in the short period band; however, in the period range 1.2 s to 1000 s for MLNM and 10 s to 1000 s for MHNM display significant variations. This variation is attributed to differences in the nature of seismic noise sources that dominate Morocco in these period bands. The results of this study have a new perception about permanent seismic noise models for this spectacular region and can be considered a significant contribution because it supplements the Peterson models and can also be used to site future permanent seismic stations in Morocco.

  3. Reducing Uncertainty in the Seismic Design Basis for the Waste Treatment Plant, Hanford, Washington

    International Nuclear Information System (INIS)

    Brouns, Thomas M.; Rohay, Alan C.; Reidel, Steve; Gardner, Martin G.

    2007-01-01

    The seismic design basis for the Waste Treatment Plant (WTP) at the Department of Energy's (DOE) Hanford Site near Richland was re-evaluated in 2005, resulting in an increase by up to 40% in the seismic design basis. The original seismic design basis for the WTP was established in 1999 based on a probabilistic seismic hazard analysis completed in 1996. The 2005 analysis was performed to address questions raised by the Defense Nuclear Facilities Safety Board (DNFSB) about the assumptions used in developing the original seismic criteria and adequacy of the site geotechnical surveys. The updated seismic response analysis used existing and newly acquired seismic velocity data, statistical analysis, expert elicitation, and ground motion simulation to develop interim design ground motion response spectra which enveloped the remaining uncertainties. The uncertainties in these response spectra were enveloped at approximately the 84th percentile to produce conservative design spectra, which contributed significantly to the increase in the seismic design basis.

  4. Prevalence and association of refractive anisometropia with near work habits among young schoolchildren: The evidence from a population-based study.

    Science.gov (United States)

    Lee, Chia-Wei; Fang, Shao-You; Tsai, Der-Chong; Huang, Nicole; Hsu, Chih-Chien; Chen, Shing-Yi; Chiu, Allen Wen-Hsiang; Liu, Catherine Jui-Ling

    2017-01-01

    Lifestyle behaviour may play a role in refractive error among children, but the association between near work habits and refractive anisometropia remains unclear. We estimated the prevalence of refractive anisometropia and examined its association with near work activities among 23,114 children in the Myopia Investigation Study in Taipei who were grade 2 elementary school students at baseline in 2013 and 2014. Baseline data on demographics, medical history, parental history and near work habits were collected by parent-administered questionnaire survey. Refractive status was determined by cycloplegic autorefraction. Refractive anisometropia was defined as the spherical equivalent difference ≥ 1.0 diopter between eyes. The prevalence of refractive anisometropia was 5.3% (95% confidence interval [CI], 5.0% to 5.6%). The prevalence and severity of refractive anisometropia increased with both myopic and hyperopic refractive error. Multivariate logistic regression analysis revealed that refractive anisometropia was significantly associated with myopia (odds ratio [OR], 2.98; 95% CI, 2.53-3.51), hyperopia (OR, 2.37; 95% CI, 1.98-2.83), degree of astigmatism (OR, 1.005; 95% CI, 1.005-1.006), amblyopia (OR, 2.54; 95% CI, 2.06-3.12), male gender (OR, 0.88; 95% CI, 0.78-0.99) and senior high school level of maternal education (OR, 0.69; 95% CI, 0.52-0.92). Though anisometropic children were more likely to spend more time on near work (crude OR, 1.15; 95% CI, 1.02-1.29) and to have less eye-to-object distance in doing near work (crude OR, 1.15; 95% CI, 1.01-1.30), these associations became insignificant after additional adjustment for ocular, demographic and parental factors. The present study provides large-scale, population-based evidence showing no independent association between refractive anisometropia and near work habits, though myopia is associated with refractive anisometropia.

  5. The Seismic Analyzer: Interpreting and Illustrating 2D Seismic Data

    OpenAIRE

    Patel, Daniel; Giertsen, Christopher; Thurmond, John; Gjelberg, John; Gröller, Eduard

    2008-01-01

    We present a toolbox for quickly interpreting and illustrating 2D slices of seismic volumetric reflection data. Searching for oil and gas involves creating a structural overview of seismic reflection data to identify hydrocarbon reservoirs. We improve the search of seismic structures by precalculating the horizon structures of the seismic data prior to interpretation. We improve the annotation of seismic structures by applying novel illustrative rendering algorithms tailored to seism...

  6. Using Seismic Interferometry to Investigate Seismic Swarms

    Science.gov (United States)

    Matzel, E.; Morency, C.; Templeton, D. C.

    2017-12-01

    Seismicity provides a direct means of measuring the physical characteristics of active tectonic features such as fault zones. Hundreds of small earthquakes often occur along a fault during a seismic swarm. This seismicity helps define the tectonically active region. When processed using novel geophysical techniques, we can isolate the energy sensitive to the fault, itself. Here we focus on two methods of seismic interferometry, ambient noise correlation (ANC) and the virtual seismometer method (VSM). ANC is based on the observation that the Earth's background noise includes coherent energy, which can be recovered by observing over long time periods and allowing the incoherent energy to cancel out. The cross correlation of ambient noise between a pair of stations results in a waveform that is identical to the seismogram that would result if an impulsive source located at one of the stations was recorded at the other, the Green function (GF). The calculation of the GF is often stable after a few weeks of continuous data correlation, any perturbations to the GF after that point are directly related to changes in the subsurface and can be used for 4D monitoring.VSM is a style of seismic interferometry that provides fast, precise, high frequency estimates of the Green's function (GF) between earthquakes. VSM illuminates the subsurface precisely where the pressures are changing and has the potential to image the evolution of seismicity over time, including changes in the style of faulting. With hundreds of earthquakes, we can calculate thousands of waveforms. At the same time, VSM collapses the computational domain, often by 2-3 orders of magnitude. This allows us to do high frequency 3D modeling in the fault region. Using data from a swarm of earthquakes near the Salton Sea, we demonstrate the power of these techniques, illustrating our ability to scale from the far field, where sources are well separated, to the near field where their locations fall within each other

  7. EDITORIAL: Sensitive structures: refractive indices in nanotechnology Sensitive structures: refractive indices in nanotechnology

    Science.gov (United States)

    Demming, Anna

    2012-12-01

    Refractive index effects using nanoscale systems are frequently applied in new imaging, sensing and even visibility cloaking technology. In this issue, researchers in Japan use simulations and experiments to describe the confinement of optical vortices in nanoscale fin structures and the sensitivity of these systems to the refractive index of the surrounding media [1]. The effects of refraction as light rays pass between different media were recorded as long ago as the first century AD, by Ptolemy [2]. Over the following centuries the phenomena inspired Ibn Sahl in 984 [3], Thomas Harriot in 1602 [4], Willebrord Snellius in 1621 [5] and Rene Descartes in 1637 [6] to independently derive the more accurate and elegant equation for refraction so familiar to us today. Recent studies of the interactions between light and matter continue to reveal a wealth of phenomena that originate in the effects of the refractive indices of materials. Nanostructures can be used to manipulate conditions that affect the refractive indices of materials, such as temperature. A E Aliev et al at the University of Texas reported a striking demonstration of temperature-dependent refractive index effects using a free-standing, highly aligned carbon nanotube aerogel sheet [7]. They used the extremely low thermal capacitance and high heat transfer ability of transparent carbon nanotube sheets to enable high-frequency modulation of the sheet temperature over an enormous temperature range. The resulting sharp, rapidly changing gradient of the refractive index in the surrounding liquid or gas makes objects seem to disappear and can be used for visibility cloaking. Light-matter interaction resonances, where light is confined at the nanoscale, can be extremely sensitive to changes in the refractive index of the surrounding media [8], even allowing single-molecule detection [9]. Plasmons, the collective oscillations of electrons in response to incident light, are a typical example. Researchers at Rice

  8. The refractive index of human hemoglobin in the visible range

    International Nuclear Information System (INIS)

    Zhernovaya, O; Tuchin, V; Sydoruk, O; Douplik, A

    2011-01-01

    Because the refractive index of hemoglobin in the visible range is sensitive to the hemoglobin concentration, optical investigations of hemoglobin are important for medical diagnostics and treatment. Direct measurements of the refractive index are, however, challenging; few such measurements have previously been reported, especially in a wide wavelength range. We directly measured the refractive index of human deoxygenated and oxygenated hemoglobin for nine wavelengths between 400 and 700 nm for the hemoglobin concentrations up to 140 g l -1 . This paper analyzes the results and suggests a set of model functions to calculate the refractive index depending on the concentration. At all wavelengths, the measured values of the refractive index depended on the concentration linearly. Analyzing the slope of the lines, we determined the specific refraction increments, derived a set of model functions for the refractive index depending on the concentration, and compared our results with those available in the literature. Based on the model functions, we further calculated the refractive index at the physiological concentration within the erythrocytes of 320 g l -1 . The results can be used to calculate the refractive index in the visible range for arbitrary concentrations provided that the refractive indices depend on the concentration linearly.

  9. Seismic effects on technological equipment and systems of nuclear power plants

    International Nuclear Information System (INIS)

    Masopust, R.; Pecinka, L.; Podrouzek, J.

    1983-01-01

    A survey is given of problems related to the construction of nuclear power plants with regard to seismic resistance. Sei--smic resistance of technological equipment is evaluated by experimental trials, calculation or the combination of both. Existing and future standards are given for the given field. The Czechoslovak situation is discussed as related to the construction of the Mochovce nuclear power plant. Procedures for testing seismic resistance, types of tests and methods of simulating seismic excitation are described. Antiseismic measures together with structural elements for limiting the seismic effects on technological equipment and nuclear power plant systems are summed up on the basis of foreign experience. (E.F.)

  10. Refractive Index of Black and Green Liquors

    Directory of Open Access Journals (Sweden)

    E. A. Avramenko

    2015-01-01

    Full Text Available Lack of reliable data on the optical properties of black and green liquors complicates control of their composition in technological process of sulphate cellulose production. In this regard the paper presents measurement results of refraction index of black liquors n (k,t at concentration in solutions of bone-dry solids up to k = 70% and at temperatures t = 10-90 °C, as well as in green liquors n(C,t at the total alkalinity of C = 0-250 g/l and in the same temperature range. All samples of solutions of black and green liquors were provided by Segezha Pulp and Paper Mill and certified in factory laboratory. Measurements were taken by means of the laboratory Abbe refractometer (URL-1, digital refractometer "Expert pro", goniometer spectrometer GS-5, and ultra-violet spectrophotometer as well. The work also presents optical D density spectra in the ultra-violet region of the wavelengths for the samples of a green liquor and main mineral component to form it, i.e. Na2S (sodium sulphide. To calculate dispersion of n (λ in the visible spectral range, here a Lorentz single-oscillator model was used. The paper discusses study results of dispersive dependence of refraction index in green liquors with various concentration and chemical components of n (λ, C forming them at t = 20°C. Computing and experimental dependences of n (λ had not only good qualitative, but also quite satisfactory quantitative compliance. The work also describes main mineral components defining optical properties in these liquors. Given here data on concentration and temperature dependences of a refraction index in black n(k,t and green n(C,t liquors have been never published before. These data are of essential interest to control soda recovery technologies in manufacturing sulphate cellulose. The received results can be also used to tune and calibrate modern domestic and foreign industrial refractometers.

  11. Super-virtual refraction interferometry: Theory

    KAUST Repository

    Bharadwaj, Pawan

    2011-01-01

    Inverting for the subsurface velocity distribution by refraction traveltime tomography is a well-accepted imaging method by both the exploration and earthquake seismology communities. A significant drawback, however, is that the recorded traces become noisier with increasing offset from the source position, and so prevents accurate picking of traveltimes in far-offset traces. To enhance the signal-to-noise ratio of the far-offset traces, we present the theory of super-virtual refraction interferometry where the signal-to-noise ratio (SNR) of far-offset head-wave arrivals can be theoretically increased by a factor proportional to N; here, N is the number of receiver and source positions associated with the recording and generation of the head-wave arrival. There are two steps to this methodology: correlation and summation of the data to generate traces with virtual head-wave arrivals, followed by the convolution of the data with the virtual traces to create traces with super-virtual head-wave arrivals. This method is valid for any medium that generates head-wave arrivals. There are at least three significant benefits to this methodology: 1). enhanced SNR of far-offset traces so the first-arrival traveltimes of the noisy far-offset traces can be more reliably picked to extend the useful aperture of data, 2). the SNR of head waves in a trace that arrive after the first arrival can be enhanced for accurate traveltime picking and subsequent inversion by traveltime tomography, and 3). common receiver-pair gathers can be analyzed to detect the presence of diving waves in the first arrivals, which can be used to assess the nature of the refracting boundary. © 2011 Society of Exploration Geophysicists.

  12. Pliocene paleoenvironment evolution as interpreted from 3D-seismic data in the southern North Sea, Dutch offshore sector

    NARCIS (Netherlands)

    Kuhlmann, G.; Wong, T.E.

    2008-01-01

    A high-resolution 3D-seismic survey from the Dutch offshore sector has been interpreted and subsequently correlated with existing regional seismo-stratigraphic concepts derived from conventional 2D-seismic data sets. The interpreted 13 seismic units have been related to a newly established

  13. Diffraction tomography for plasma refractive index measurements

    International Nuclear Information System (INIS)

    Howard, J.; Nazikian, R.; Sharp, L.E.

    1989-01-01

    Measurement of the properties of probing beams of coherent electromagnetic radiation yields essential information about the line of sight integrated plasma refractive index. Presented is a scalar diffraction treatment of forward angle scattering plasma diagnostics based on the diffraction projection theorem first presented by E. Wolf in 1969. New results are obtained for near field scattering from probing Gaussian beams and it is demonstrated that the effects of diffraction need to be addressed for tomographic inversion of near field scattering and interferometry data. 33 refs., 10 figs

  14. Refraction and absorption of microwaves in wood

    International Nuclear Information System (INIS)

    Ziherl, Saša; Bajc, Jurij; Čepič, Mojca

    2013-01-01

    A demonstration experiment for physics students showing the dependence of the refractive index and absorption coefficient of wood on the direction of microwaves is presented. Wood and microwaves enable study of anisotropic properties, which are typically found in crystals. Wood is used as the persuasive representative of uniaxial anisotropic materials due to its visible structure and its consequent anisotropic properties. Wood can be cut in a general direction and wooden plates a few centimetres thick with well-defined fibre orientation are easily prepared. Microwaves are used because wood is transparent for microwaves and their centimetre-scale wavelength is comparable to the wood structure. (paper)

  15. Structuring agreements for seismic group shoots

    International Nuclear Information System (INIS)

    Keeping, C.E.

    1999-01-01

    Sigma Explorations Inc. sells licenses to use Sigma owned seismic data. The company participates with exploration and production companies in the joint acquisition of semi-private participation surveys. This paper discusses three major types of seismic group shoots and the essential elements of the agreements that govern or should govern them. They are: (1) exploration and production company joint ventures, (2) publicly offered spec shoots, and (3) semi-private participation surveys. The key issue with the exploration and production company joint ventures is that the companies are owners of the seismic data in proportion to their contribution towards the cost of the program. Their use of the data should be restricted to those situations permitted by the other owners. These are not often well documented, and there is much concern in the industry as a result. The key issue with publicly offered spec shoots is that the seismic company ultimately owns the data and the client exploration and production company is a licensee and must behave as such. In most such cases the rights and responsibilities are well documented in formal agreements that are signed in advance of the program's beginning date

  16. Association of refractive error with optic nerve hypoplasia.

    Science.gov (United States)

    Pang, Yi; Frantz, Kelly A; Roberts, Daniel K

    2015-09-01

    To evaluate the association of refractive error with optic nerve hypoplasia (ONH). A total of 30 ONH subjects were recruited and underwent comprehensive eye exams. Refractive error data from this group was compared to data from a group of 3232 non-ONH subjects from the same facility. Spherical equivalent was calculated to assess refractive error. Multiple logistic regression was used to evaluate the relationship between ONH and refractive error while controlling for age, race, and gender. The prevalence of hyperopia (≥+1.00 D), myopia (refractive errors, particularly hyperopia. Anisometropia tended to be more likely to occur in subjects with unilateral ONH than in bilateral ONH. Based on our findings, we recommend that clinicians perform a comprehensive eye examination on all patients with ONH and prescribe for existing refractive error when visual acuity or general visual function can realistically be improved. © 2015 The Authors Ophthalmic & Physiological Optics © 2015 The College of Optometrists.

  17. BUILDING 341 Seismic Evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Halle, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-06-15

    The Seismic Evaluation of Building 341 located at Lawrence Livermore National Laboratory in Livermore, California has been completed. The subject building consists of a main building, Increment 1, and two smaller additions; Increments 2 and 3.

  18. Seismic anisotropy - Introduction

    Czech Academy of Sciences Publication Activity Database

    Grechka, V.; Pšenčík, Ivan; Ravve, I.; Tsvankin, I.

    2017-01-01

    Roč. 82, č. 4 (2017), WAI-WAII ISSN 0016-8033 Institutional support: RVO:67985530 Keywords : seismic anisotropy Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 2.391, year: 2016

  19. Reproducibility in Seismic Imaging

    Directory of Open Access Journals (Sweden)

    González-Verdejo O.

    2012-04-01

    Full Text Available Within the field of exploration seismology, there is interest at national level of integrating reproducibility in applied, educational and research activities related to seismic processing and imaging. This reproducibility implies the description and organization of the elements involved in numerical experiments. Thus, a researcher, teacher or student can study, verify, repeat, and modify them independently. In this work, we document and adapt reproducibility in seismic processing and imaging to spread this concept and its benefits, and to encourage the use of open source software in this area within our academic and professional environment. We present an enhanced seismic imaging example, of interest in both academic and professional environments, using Mexican seismic data. As a result of this research, we prove that it is possible to assimilate, adapt and transfer technology at low cost, using open source software and following a reproducible research scheme.

  20. Seismic Creep, USA Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden rupture associated with an earthquake. It is a usually slow deformation...

  1. PSMG switchgear seismic analysis

    International Nuclear Information System (INIS)

    Kuehster, C.J.

    1977-01-01

    LOFT primary coolant system motor generator (PSMG) switchgear boxes were analyzed for sliding and overturning during a seismic event. Boxes are located in TAN-650, Room B-239, with the PSMG generators. Both boxes are sufficiently anchored to the floor

  2. Case Finding for Refractive Errors: Assessment of Refractive Error and Visual Impairment in Children

    OpenAIRE

    Ellwein, Leon B

    2002-01-01

    The World Health Organization informal planning meeting, in July 2000, clearly indicated that detailed comparisons of refractive error prevalence across study reports are generally not possible because of different measurement methods and definitions.1 Further, because most studies are carried out using samples of unknown representativeness, interpretation of the findings in a population-based context has problems.

  3. Case Finding for Refractive Errors: Assessment of Refractive Error and Visual Impairment in Children

    Directory of Open Access Journals (Sweden)

    Leon B Ellwein

    2002-01-01

    Full Text Available The World Health Organization informal planning meeting, in July 2000, clearly indicated that detailed comparisons of refractive error prevalence across study reports are generally not possible because of different measurement methods and definitions.1 Further, because most studies are carried out using samples of unknown representativeness, interpretation of the findings in a population-based context has problems.

  4. Seismic facies; Facies sismicas

    Energy Technology Data Exchange (ETDEWEB)

    Johann, Paulo Roberto Schroeder [PETROBRAS, Rio de Janeiro, RJ (Brazil). Exploracao e Producao Corporativo. Gerencia de Reservas e Reservatorios]. E-mail: johann@petrobras.com.br

    2004-11-01

    The method presented herein describes the seismic facies as representations of curves and vertical matrixes of the lithotypes proportions. The seismic facies are greatly interested in capturing the spatial distributions (3D) of regionalized variables, as for example, lithotypes, sedimentary facies groups and/ or porosity and/or other properties of the reservoirs and integrate them into the 3D geological modeling (Johann, 1997). Thus when interpreted as curves or vertical matrixes of proportions, seismic facies allow us to build a very important tool for structural analysis of regionalized variables. The matrixes have an important application in geostatistical modeling. In addition, this approach provides results about the depth and scale of the wells profiles, that is, seismic data is integrated to the characterization of reservoirs in depth maps and in high resolution maps. The link between the different necessary technical phases involved in the classification of the segments of seismic traces is described herein in groups of predefined traces of two approaches: a) not supervised and b) supervised by the geological knowledge available on the studied reservoir. The multivariate statistical methods used to obtain the maps of the seismic facies units are interesting tools to be used to provide a lithostratigraphic and petrophysical understanding of a petroleum reservoir. In the case studied these seismic facies units are interpreted as representative of the depositional system as a part of the Namorado Turbiditic System, Namorado Field, Campos Basin.Within the scope of PRAVAP 19 (Programa Estrategico de Recuperacao Avancada de Petroleo - Strategic Program of Advanced Petroleum Recovery) some research work on algorithms is underway to select new optimized attributes to apply seismic facies. One example is the extraction of attributes based on the wavelet transformation and on the time-frequency analysis methodology. PRAVAP is also carrying out research work on an

  5. Refraction traveltime tomography based on damped wave equation for irregular topographic model

    Science.gov (United States)

    Park, Yunhui; Pyun, Sukjoon

    2018-03-01

    Land seismic data generally have time-static issues due to irregular topography and weathered layers at shallow depths. Unless the time static is handled appropriately, interpretation of the subsurface structures can be easily distorted. Therefore, static corrections are commonly applied to land seismic data. The near-surface velocity, which is required for static corrections, can be inferred from first-arrival traveltime tomography, which must consider the irregular topography, as the land seismic data are generally obtained in irregular topography. This paper proposes a refraction traveltime tomography technique that is applicable to an irregular topographic model. This technique uses unstructured meshes to express an irregular topography, and traveltimes calculated from the frequency-domain damped wavefields using the finite element method. The diagonal elements of the approximate Hessian matrix were adopted for preconditioning, and the principle of reciprocity was introduced to efficiently calculate the Fréchet derivative. We also included regularization to resolve the ill-posed inverse problem, and used the nonlinear conjugate gradient method to solve the inverse problem. As the damped wavefields were used, there were no issues associated with artificial reflections caused by unstructured meshes. In addition, the shadow zone problem could be circumvented because this method is based on the exact wave equation, which does not require a high-frequency assumption. Furthermore, the proposed method was both robust to an initial velocity model and efficient compared to full wavefield inversions. Through synthetic and field data examples, our method was shown to successfully reconstruct shallow velocity structures. To verify our method, static corrections were roughly applied to the field data using the estimated near-surface velocity. By comparing common shot gathers and stack sections with and without static corrections, we confirmed that the proposed tomography

  6. Ethnic differences in undercorrected refractive error in Asians.

    Science.gov (United States)

    Pan, Chen-Wei; Chiang, Peggy Pei-Chia; Wong, Tien Y; Zheng, Ying-Feng; Chew, Merwyn; Saw, Seang-Mei; Lamoureux, Ecosse L; Cheng, Ching-Yu

    2014-02-01

    To describe the ethnic variations in the prevalence and risk factors for undercorrected refractive error and its impact on vision-specific functioning (VF) in a multiethnic Asian population. A total of 3353 Chinese, 3400 Indians, and 3280 Malays in Singapore participated in this population-based cross-sectional study. Distance presenting visual acuity (VA) was measured using a logarithm of the minimum angle of resolution number chart. Best-corrected VA was assessed using the same test protocol as presenting VA. Undercorrected refractive error was defined as an improvement of at least 0.2 logarithm of the minimum angle of resolution (two lines equivalent) in the best-corrected VA compared with the presenting VA in the better eye when presenting VA was less than 20/40 in the better eye. The VF-11 questionnaire measured participants' VF. Multivariate linear regression was performed to assess the impact of undercorrected refractive error on the overall VF score. Regardless of ethnicity, participants with undercorrected refractive error had a reduction in VF score compared to those with normal vision in both eyes. The overall prevalence of undercorrected refractive error was highest in Indians (25.1%), followed by Malays (22.2%) and Chinese (19.7%). Undercorrected refractive error was less common in spectacles or contact lenses wearers than in non-spectacle wearers or non-contact lenses wearers. Adults with mild to moderate refractive errors were most likely to have undercorrected refractive error (p refractive errors (p refractive error. In Singapore, undercorrected refractive error is most prevalent in Indians and least prevalent in Chinese. The impact of undercorrected refractive error on VF was consistent across all three ethnicities. There may be higher barriers to visual correction among Malays or Indians compared with Chinese in Singapore.

  7. Refractive error among urban preschool children in Xuzhou, China

    OpenAIRE

    Wang, Xiaojuan; Liu, Dan; Feng, Ruifang; Zhao, Huashuo; Wang, Qinmei

    2014-01-01

    The prevalence of refractive errors in urban preschool children in Xuzhou, China remains unknown. Children attending twelve randomly selected kindergartens participated in this study. Visual acuity, ocular alignment, cover-uncover test, cycloplegic refraction, slit-lamp and funduscopy were performed under a standardized testing environment. Cycloplegic streak retinoscopy was performed for all subjects. The mean spherical equivalent (SE) refractive error was the main outcome measure. Emmetropi...

  8. Training to meet the need for refractive error services

    Directory of Open Access Journals (Sweden)

    Hannah Faal

    2007-09-01

    Full Text Available In many low- and middle-income countries, there are inadequate refractive error services for the many people who are currently either blind or visually impaired because they lack a pair of spectacles.The prioritisation of refractive error and low vision services within VISION 2020: The Right to Sight has provided an impetus and framework for the development of refractive error programmes to meet this need for services.

  9. The prevalence and risk indicators of uncorrected refractive error and unmet refractive need in Latinos: the Los AngelesLatino Eye Study.

    Science.gov (United States)

    Varma, Rohit; Wang, Michelle Y; Ying-Lai, Mei; Donofrio, Jill; Azen, Stanley P

    2008-12-01

    To determine the age- and sex-specific prevalence and risk indicators of uncorrected refractive error and unmet refractive need among a population-based sample of Latino adults. Self-identified Latinos 40 years of age and older (n = 6129) from six census tracts in La Puente, California, underwent a complete ophthalmic examination, and a home-administered questionnaire provided self-reported data on potential risk indicators. Uncorrected refractive error was defined as a >or=2-line improvement with refraction in the better seeing eye. Unmet refractive need was defined as having or=20/40 after refraction (definition 1) or having or=2-line improvement with refraction (definition 2). Sex- and age-specific prevalence and significant risk indicators for uncorrected refractive error and unmet refractive need were calculated. The overall prevalence of uncorrected refractive error was 15.1% (n = 926). The overall prevalence of unmet refractive need was 8.9% (n = 213, definition 1) and 9.6% (n = 218, definition 2). The prevalence of uncorrected refractive error and either definition of unmet refractive need increased with age (P refractive error and unmet refractive need. The data suggest that the prevalence of uncorrected refractive error and unmet refractive need is high in Latinos of primarily Mexican ancestry. Better education and access to care in older Latinos are likely to decrease the burden of uncorrected refractive error in Latinos.

  10. Seismic Consequence Abstraction

    International Nuclear Information System (INIS)

    Gross, M.

    2004-01-01

    The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274])

  11. Seismic Consequence Abstraction

    Energy Technology Data Exchange (ETDEWEB)

    M. Gross

    2004-10-25

    The primary purpose of this model report is to develop abstractions for the response of engineered barrier system (EBS) components to seismic hazards at a geologic repository at Yucca Mountain, Nevada, and to define the methodology for using these abstractions in a seismic scenario class for the Total System Performance Assessment - License Application (TSPA-LA). A secondary purpose of this model report is to provide information for criticality studies related to seismic hazards. The seismic hazards addressed herein are vibratory ground motion, fault displacement, and rockfall due to ground motion. The EBS components are the drip shield, the waste package, and the fuel cladding. The requirements for development of the abstractions and the associated algorithms for the seismic scenario class are defined in ''Technical Work Plan For: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The development of these abstractions will provide a more complete representation of flow into and transport from the EBS under disruptive events. The results from this development will also address portions of integrated subissue ENG2, Mechanical Disruption of Engineered Barriers, including the acceptance criteria for this subissue defined in Section 2.2.1.3.2.3 of the ''Yucca Mountain Review Plan, Final Report'' (NRC 2003 [DIRS 163274]).

  12. Accelerometer Sensor Specifications to Predict Hydrocarbon Using Passive Seismic Technique

    Directory of Open Access Journals (Sweden)

    M. H. Md Khir

    2016-01-01

    Full Text Available The ambient seismic ground noise has been investigated in several surveys worldwide in the last 10 years to verify the correlation between observed seismic energy anomalies at the surface and the presence of hydrocarbon reserves beneath. This is due to the premise that anomalies provide information about the geology and potential presence of hydrocarbon. However a technology gap manifested in nonoptimal detection of seismic signals of interest is observed. This is due to the fact that available sensors are not designed on the basis of passive seismic signal attributes and mainly in terms of amplitude and bandwidth. This is because of that fact that passive seismic acquisition requires greater instrumentation sensitivity, noise immunity, and bandwidth, with active seismic acquisition, where vibratory or impulsive sources were utilized to receive reflections through geophones. Therefore, in the case of passive seismic acquisition, it is necessary to select the best monitoring equipment for its success or failure. Hence, concerning sensors performance, this paper highlights the technological gap and motivates developing dedicated sensors for optimal solution at lower frequencies. Thus, the improved passive seismic recording helps in oil and gas industry to perform better fracture mapping and identify more appropriate stratigraphy at low frequencies.

  13. Personalized pseudophakic model for refractive assessment.

    Directory of Open Access Journals (Sweden)

    Filomena J Ribeiro

    Full Text Available PURPOSE: To test a pseudophakic eye model that allows for intraocular lens power (IOL calculation, both in normal eyes and in extreme conditions, such as post-LASIK. METHODS: PARTICIPANTS: The model's efficacy was tested in 54 participants (104 eyes who underwent LASIK and were assessed before and after surgery, thus allowing to test the same method in the same eye after only changing corneal topography. MODELLING: The Liou-Brennan eye model was used as a starting point, and biometric values were replaced by individual measurements. Detailed corneal surface data were obtained from topography (Orbscan® and a grid of elevation values was used to define corneal surfaces in an optical ray-tracing software (Zemax®. To determine IOL power, optimization criteria based on values of the modulation transfer function (MTF weighted according to contrast sensitivity function (CSF, were applied. RESULTS: Pre-operative refractive assessment calculated by our eye model correlated very strongly with SRK/T (r = 0.959, p0.05. Comparison of post-operative refractive assessment obtained using our eye model with the average of currently used formulas showed a strong correlation (r = 0.778, p0.05. CONCLUSIONS: Results suggest that personalized pseudophakic eye models and ray-tracing allow for the use of the same methodology, regardless of previous LASIK, independent of population averages and commonly used regression correction factors, which represents a clinical advantage.

  14. Personalized pseudophakic model for refractive assessment.

    Science.gov (United States)

    Ribeiro, Filomena J; Castanheira-Dinis, António; Dias, João M

    2012-01-01

    To test a pseudophakic eye model that allows for intraocular lens power (IOL) calculation, both in normal eyes and in extreme conditions, such as post-LASIK. The model's efficacy was tested in 54 participants (104 eyes) who underwent LASIK and were assessed before and after surgery, thus allowing to test the same method in the same eye after only changing corneal topography. MODELLING: The Liou-Brennan eye model was used as a starting point, and biometric values were replaced by individual measurements. Detailed corneal surface data were obtained from topography (Orbscan®) and a grid of elevation values was used to define corneal surfaces in an optical ray-tracing software (Zemax®). To determine IOL power, optimization criteria based on values of the modulation transfer function (MTF) weighted according to contrast sensitivity function (CSF), were applied. Pre-operative refractive assessment calculated by our eye model correlated very strongly with SRK/T (r = 0.959, p0.05). Comparison of post-operative refractive assessment obtained using our eye model with the average of currently used formulas showed a strong correlation (r = 0.778, p0.05). Results suggest that personalized pseudophakic eye models and ray-tracing allow for the use of the same methodology, regardless of previous LASIK, independent of population averages and commonly used regression correction factors, which represents a clinical advantage.

  15. Influence of uncorrected refractive error and unmet refractive error on visual impairment in a Brazilian population.

    Science.gov (United States)

    Ferraz, Fabio H; Corrente, José E; Opromolla, Paula; Schellini, Silvana A

    2014-06-25

    The World Health Organization (WHO) definitions of blindness and visual impairment are widely based on best-corrected visual acuity excluding uncorrected refractive errors (URE) as a visual impairment cause. Recently, URE was included as a cause of visual impairment, thus emphasizing the burden of visual impairment due to refractive error (RE) worldwide is substantially higher. The purpose of the present study is to determine the reversal of visual impairment and blindness in the population correcting RE and possible associations between RE and individual characteristics. A cross-sectional study was conducted in nine counties of the western region of state of São Paulo, using systematic and random sampling of households between March 2004 and July 2005. Individuals aged more than 1 year old were included and were evaluated for demographic data, eye complaints, history, and eye exam, including no corrected visual acuity (NCVA), best corrected vision acuity (BCVA), automatic and manual refractive examination. The definition adopted for URE was applied to individuals with NCVA > 0.15 logMAR and BCVA ≤ 0.15 logMAR after refractive correction and unmet refractive error (UREN), individuals who had visual impairment or blindness (NCVA > 0.5 logMAR) and BCVA ≤ 0.5 logMAR after optical correction. A total of 70.2% of subjects had normal NCVA. URE was detected in 13.8%. Prevalence of 4.6% of optically reversible low vision and 1.8% of blindness reversible by optical correction were found. UREN was detected in 6.5% of individuals, more frequently observed in women over the age of 50 and in higher RE carriers. Visual impairment related to eye diseases is not reversible with spectacles. Using multivariate analysis, associations between URE and UREN with regard to sex, age and RE was observed. RE is an important cause of reversible blindness and low vision in the Brazilian population.

  16. Human eye ocular component analysis for refractive state and refractive surgery

    Directory of Open Access Journals (Sweden)

    Chao-Kai Chang

    2017-07-01

    Full Text Available AIM: To analyze the clinical factors influencing the human vision corrections via the changing of ocular components of human eye in various applications; and to analyze refractive state via a new effective axial length. METHODS: An effective eye model was introduced by the ocular components of human eye including refractive indexes, surface radius (r1, r2, R1, R2 and thickness (t, T of the cornea and lens, the anterior chamber depth (S1 and the vitreous length (S2. Gaussian optics was used to calculate the change rate of refractive error per unit amount of ocular components of a human eye (the rate function M. A new criterion of myopia was presented via an effective axial length. RESULTS: For typical corneal and lens power of 42 and 21.9 diopters, the rate function Mj (j=1 to 6 were calculated for a 1% change of r1, r2, R1, R2, t, T (in diopters M1=+0.485, M2=-0.063, M3=+0.053, M4=+0.091, M5=+0.012, and M6=-0.021 diopters. For 1.0 mm increase of S1 and S2, the rate functions were M7=+1.35, and M8=-2.67 diopter/mm, respectively. These rate functions were used to analyze the clinical outcomes in various applications including laser in situ keratomileusis surgery, corneal cross linking procedure, femtosecond laser surgery and scleral ablation for accommodation. CONCLUSION: Using Gaussian optics, analytic formulas are presented for the change of refractive power due to various ocular parameter changes. These formulas provide useful clinical guidance in refractive surgery and other related procedures.

  17. Development of near surface seismic methods for urban and mining applications

    Science.gov (United States)

    Malehmir, Alireza; Brodic, Bojan; Place, Joachim; Juhlin, Christopher; Bastani, Mehrdad

    2014-05-01

    traditional landstreamers, which are either constructed for refraction and MASW methods or for reflection seismic imaging purposes. The landstreamer system, assembled in 2013, has so far been tested against planted 10- and 28-Hz coil-based sensors. Two preliminary surveys were performed in 2013, one for imaging the shallow (access tunnel in the city of Stockholm. The comparison test showed that the digital sensors on the streamer provided superior results (in terms of resolution and sensitivity to noise) than the planted geophones, suggesting that digital sensors are more suitable for urban and mining applications. In the Stockholm survey, the system was coupled to twelve 3C-digital wireless sensors to cover areas where the access was restricted due to road traffic and existing city infrastructures. The wireless sensors were used to collect data in a passive mode during the survey; these data were later harvested and merged with the active data using GPS time stamps (nanoseconds accuracy). The system thus also allows a combination of active and passive seismic data acquisition if required. Preliminary results for the mining application show successful imaging of the shallow crystalline basement as a high-velocity (> 4000 m/s) media. Clear refracted and reflected arrivals are present in raw shot gathers. Future efforts will be geared to (i) exploiting information recorded on the horizontal components in order to extract rock mechanic parameters and anisotropy information, (ii) the development and application of a multi-component source to complement the landstreamer system, and (iii) a number of tests at underground sites. Acknowledgments: Formas, SGU, BeFo, SBUF, Skanska, Boliden, FQM and NGI

  18. Seismicity at Baru Volcano, Western Panama, Panama

    Science.gov (United States)

    Camacho, E.; Novelo-Casanova, D. A.; Tapia, A.; Rodriguez, A.

    2008-12-01

    The Baru volcano in Western Panama (8.808°N, 82.543°W) is a 3,475 m high strato volcano that lies at about 50 km from the Costa Rican border. The last major eruptive event at this volcano occurred c.1550 AD and no further eruptive activity from that time is known. Since the 1930´s, approximately every 30 years a series of seismic swarms take place in the surroundings of the volcanic edifice. Theses swarms last several weeks alarming the population who lives near the volcano. The last of these episodes occurred on May 2006 and lasted one and a half months. More than 20,000 people live adjacent to the volcano and any future eruption has the potential to be very dangerous. In June 2007, a digital seismic monitoring network of ten stations, linked via internet, was installed around the volcano in a collaborative project between the University of Panama and the Panamanian Government. The seismic data acquisition at the sites is performed using LINUX-SEISLOG and the events are recorded by four servers at different locations using the Earth Worm system. In this work we analyze the characteristics of the volcano seismicity recorded from May 4th, 2006 to July 31st, 2008 by at least 4 stations and located at about 15 km from the summit. To determine the seismic parameters, we tested several crustal velocity models and used the seismic analysis software package SEISAN. Our final velocity model was determined using seismic data for the first four km obtained from a temporal seismic network deployed in 1981 by the British Geological Survey (BGS) as part of geothermal studies conducted at Cerro Pando, Western Panama Highlands. Our results indicate that all the events recorded in the quadrant 8.6-9.0°N and 82.2-82.7°W are located in the depth range of 0.1 to 8 km. Cross sections show vertical alignments of hypocenters below the summit although most of the seismicity is concentrated in its eastern flank reaching the town of Boquete. All the calculated focal mechanisms are of

  19. Earthquake experience suggests new approach to seismic criteria

    International Nuclear Information System (INIS)

    Knox, R.

    1983-01-01

    Progress in seismic qualification of nuclear power plants as reviewed at the 4th Pacific Basin Nuclear Conference in Vancouver, September 1983, is discussed. The lack of experience of earthquakes in existing nuclear plants can be compensated by the growing experience of actual earthquake effects in conventional power plants and similar installations. A survey of the effects on four power stations, with a total of twenty generating units, in the area strongly shaken by the San Fernando earthquake in California in 1971 is reported. The Canadian approach to seismic qualification, international criteria, Canadian/Korean experience, safety related equipment, the Tadotsu test facility and seismic tests are discussed. (U.K.)

  20. Seismic analysis of liquid metal fast breeder reactors

    International Nuclear Information System (INIS)

    Gilbert, R.J.; Martelli, A.

    1989-06-01

    This report is a general survey of the recent methods to predict the seismic structural behaviour of LMFBRs. It shall put into evidence the impact of seismic analysis on the design of the different structures of the reactor. This report is addressed to specialists and institutions of governmental organizations in industrialized and developing countries responsible for the design and operation of LMFBRs. The information presented should enable specialists in the R and D institutions and industries likely to be involved, to establish the correct course of the design and operation of LMFBRs. Also, the safety aspect of seismic risk are emphasized in the report. Refs and figs

  1. Refractivity variations and propagation at Ultra High Frequency

    Directory of Open Access Journals (Sweden)

    I. Alam

    Full Text Available Present framework is established to deal with the refractivity variations normally affected the radio waves propagation at different frequencies, ranges and different environments. To deal such kind of effects, many researchers proposed several methodologies. One method is to use the parameters from meteorology to investigate these effects of variations in refractivity on propagation. These variations are region specific and we have selected a region of one kilometer height over the English Channel. We have constructed different modified refractivity profiles based on the local meteorological data. We have recorded more than 48 million received signal strength from a communication links of 50 km operating at 2015 MHz in the Ultra High Frequency band giving path loss between transmitting and receiving stations of the experimental setup. We have used parabolic wave equation method to simulate an hourly value of signal strength and compared the obtained simulated loss to the experimental loss. The analysis is made to compute refractivity distribution of standard (STD and ITU (International Telecommunication Union refractivity profiles for various evaporation ducts. It is found that a standard refractivity profile is better than the ITU refractivity profiles for the region at 2015 MHz. Further, it is inferred from the analysis of results that 10 m evaporation duct height is the dominant among all evaporation duct heights considered in the research. Keywords: Refractive index, Refractivity, Parabolic wave equation, Propagation, UHF, Antennas

  2. Ultrasensitive twin-core photonic bandgap fiber refractive index sensor

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Town, Graham; Bang, Ole

    2009-01-01

    We propose a microfluidic refractive index sensor based on new polymer twin-core photonic bandgap fiber (PBGF). The sensor can achieve ultrahigh detection limit, i.e. >1.4times10-7RIU refractive index unit (RIU), by measuring the coupling wavelength shift.......We propose a microfluidic refractive index sensor based on new polymer twin-core photonic bandgap fiber (PBGF). The sensor can achieve ultrahigh detection limit, i.e. >1.4times10-7RIU refractive index unit (RIU), by measuring the coupling wavelength shift....

  3. Newton's theory of the atmospheric refraction of light

    Science.gov (United States)

    Nauenberg, Michael

    2017-12-01

    Newton's unpublished theory for the trajectory of a light beam in a medium with varying index of refraction and spherical symmetry is reconstructed. He assumed that light consisted of particles (corpuscles), and derived Snell's refraction law from the assumption that the velocity of these corpuscles is proportional to the index of refraction of the medium, and the acceleration is proportional to its gradient. Surprisingly, Newton's theory leads to a relation for the refraction of light in such a medium that is identically the same as the modern theory based on the wave theory of light.

  4. PREVALENCE OF REFRACTIVE ERRORS IN MADRASSA STUDENTS OF HARIPUR DISTRICT.

    Science.gov (United States)

    Atta, Zoia; Arif, Abdus Salam; Ahmed, Iftikhar; Farooq, Umer

    2015-01-01

    Visual impairment due to refractive errors is one of the most common problems among school-age children and is the second leading cause of treatable blindness. The Right to Sight, a global initiative launched by a coalition of non-government organizations and the World Health Organization (WHO), aims to eliminate avoidable visual impairment and blindness at a global level. In order to achieve this goal it is important to know the prevalence of different refractive errors in a community. Children and teenagers are the most susceptible groups to be affected by refractive errors. So, this population needs to be screened for different types of refractive errors. The study was done with the objective to find the frequency of different types of refractive errors in students of madrassas between the ages of 5-20 years in Haripur. This cross sectional study was done with 300 students between ages of 5-20 years in Madrassas of Haripur. The students were screened for refractive errors and the types of the errors were noted. After screening for refractive errors-the glasses were prescribed to the students. Myopia being 52.6% was the most frequent refractive error in students, followed by hyperopia 28.4% and astigmatism 19%. This study showed that myopia is an important problem in madrassa population. Females and males are almost equally affected. Spectacle correction of refractive errors is the cheapest and easy solution of this problem.

  5. Seismic Wave Propagation in Layered Viscoelastic Media

    Science.gov (United States)

    Borcherdt, R. D.

    2008-12-01

    Advances in the general theory of wave propagation in layered viscoelastic media reveal new insights regarding seismic waves in the Earth. For example, the theory predicts: 1) P and S waves are predominantly inhomogeneous in a layered anelastic Earth with seismic travel times, particle-motion orbits, energy speeds, Q, and amplitude characteristics that vary with angle of incidence and hence, travel path through the layers, 2) two types of shear waves exist, one with linear and the other with elliptical particle motions each with different absorption coefficients, and 3) surface waves with amplitude and particle motion characteristics not predicted by elasticity, such as Rayleigh-Type waves with tilted elliptical particle motion orbits and Love-Type waves with superimposed sinusoidal amplitude dependencies that decay exponentially with depth. The general theory provides closed-form analytic solutions for body waves, reflection-refraction problems, response of multiple layers, and surface wave problems valid for any material with a viscoelastic response, including the infinite number of models, derivable from various configurations of springs and dashpots, such as elastic, Voight, Maxwell, and Standard Linear. The theory provides solutions independent of the amount of intrinsic absorption and explicit analytic expressions for physical characteristics of body waves in low-loss media such as the deep Earth. The results explain laboratory and seismic observations, such as travel-time and wide-angle reflection amplitude anomalies, not explained by elasticity or one dimensional Q models. They have important implications for some forward modeling and inverse problems. Theoretical advances and corresponding numerical results as recently compiled (Borcherdt, 2008, Viscoelastic Waves in Layered Media, Cambridge University Press) will be reviewed.

  6. Comparison of field and laboratory seismic velocity anisotropy measurement (scaling factor)

    Czech Academy of Sciences Publication Activity Database

    Vilhelm, J.; Rudajev, Vladimír; Živor, Roman; Lokajíček, Tomáš; Pros, Zdeněk

    2008-01-01

    Roč. 5, č. 2 (2008), s. 161-169 ISSN 1214-9705. [Czech-Polish-Slovak Symposium on Mining and Environmental Geophysics. Janov nad Nisou, 24.09.2007-27.09.2007] R&D Projects: GA ČR GA205/06/0906 Institutional research plan: CEZ:AV0Z30130516 Keywords : ultrasound sounding * seismic velocity * anisotropy * shallow seismic refraction Subject RIV: DC - Siesmology, Volcanology, Earth Structure http://www.irsm.cas.cz/?Lang=ENG&Menu=25,29,0,0;&File=Obsah/AGG/Contents/AGGC5_2(150)08.htm

  7. Hawaiian Volcano Observatory seismic data, January to March 2009

    Science.gov (United States)

    Nakata, Jennifer S.; Okubo, Paul G.

    2010-01-01

    This U.S. Geological Survey (USGS), Hawaiian Volcano Observatory (HVO) summary presents seismic data gathered during January–March 2009. The seismic summary offers earthquake hypocenters without interpretation as a source of preliminary data and is complete in that most data for events of M≥1.5 are included. All latitude and longitude references in this report are stated in Old Hawaiian Datum.

  8. Planning for shallow high resolution seismic surveys

    CSIR Research Space (South Africa)

    Fourie, CJS

    2008-11-01

    Full Text Available amplitude of the electromagnetic wave attenuated by 1/e or 67%. This measure is influenced by the physical properties of the subsurface and uses the resistivity, the angular frequency (w) of the electromagnetic field and the magnetic permeability (m...

  9. Crustal structure due to collisional and escape tectonics in the Eastern Alps region based on profiles Alp01 and Alp02 from the ALP 2002 seismic experiment

    Czech Academy of Sciences Publication Activity Database

    Brückl, E.; Bleibinhaus, F.; Gosar, A.; Grad, M.; Guterch, A.; Hrubcová, Pavla; Keller, G. R.; Majdański, M.; Šumanovac, F.; Tiira, T.; Yliniemi, J.; Hegedüs, E.; Thybo, H.

    2007-01-01

    Roč. 112, č. B6 (2007), B06308/1-B06308/25 ISSN 0148-0227 R&D Projects: GA MŽP SB/630/3/02 Institutional research plan: CEZ:AV0Z30120515 Keywords : crustal structure * ALP 2002 seismic experiment * seismic refraction Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.953, year: 2007

  10. The Summerville Formation: Evidence for a sub-horizontal stratigraphic sequence below the post-rift unconformity in the Middleton Place Summerville Seismic Zone

    Science.gov (United States)

    Getz, Joseph Edward

    The Middleton Place Summerville Seismic Zone (MPSSZ) near Summerville, South Carolina was the site of renewed extensive investigation, beginning in the 1970's, for the source of the 1886 Charleston earthquake. Reactivation of faults associated with a putative fault-bounded Triassic rift basin through analysis of seismic reflection, seismic refraction, and well data has since become the favored interpretation for the source of MPSSZ seismicity. Critical to this interpretation is the association of continental redbed sedimentary rocks with Triassic basins identified throughout the North American Atlantic margin. Reanalysis of 18 seismic reflection profiles and 25 seismic refraction profiles within the MPSSZ suggests that the red beds found here are a thin, sub-horizontal, regionally extensive, generally unbroken subsurface stratigraphic sequence distinct from the sedimentary architecture observed in analog Triassic rift systems. In addition, this sequence appears to unconformably overly a structural depression (the Jedberg basin) previously interpreted as a Triassic rift basin in the vicinity of the MPSSZ. In addition to the geometries observed on seismic reflection profiles, seismic refraction velocities ranging from 4.2 to 6.1 km/s can be correlated with (1) Jurassic basalt flows, (2) the newly proposed Summerville Formation, and (3) the Basement (B) sequences respectively. The current study maps the Summerville red bed section and its bounding reflectors. In addition to mapping the regional extent of the newly proposed Summerville Formation, refraction velocities and changes in reflection character, the lateral extent of the basalt flows can be changed to a more localized flow rather than a regionally extensive flow of which was previously thought. Reanalysis of data in the MPSSZ suggests that the area may not be part of the Triassic South Georgia Rift system due to the sub-horizontal geometry of the red bed reflections, the apparent lack of faulting, and their

  11. NATIONAL SEISMIC, RADAR AND SEISMOLOGICAL STUDIES OF SUBGLACIAL LAKE VOSTOK

    Directory of Open Access Journals (Sweden)

    S. V. Popov

    2012-01-01

    Full Text Available The results of the remote sensing which carried out in the LakeVostokarea are discussed in the paper. A.P. Kapitsa and O.G. Sorokhtin started the geophysical researches in this area in 1950s. Satellite altimetry data, which analyzed in 1990s yielded to the discovering of the LakeVostok. After that, PMGE and RAE started the systematic studying of this natural phenomenon by seismic and radio-echo sounding. Total, 318 seismic soundings and 5190 kmof the radio-echo profiles has been collected by 2008. Special precise measurements which carried out in the 5G-1 borehole vicinity are resulted in the ice thickness over Vostok Station is 3760±30 mby seismic and 3775±15 mby radio-echo sounding. Thus, the error of geophysical measurements is less than 0.3%. The Russian investigations are resulted in definition the border of the lake, the discovering of 56 subglacial water caves around the lake and compilation the maps including ice thickness, ice base and bedrock topography and the depth of the lake. Average depth of the LakeVostokis about 400 m; water volume is 6100 km3. After 2008, the remote sensing works have been concentrated to the studying of the bottom sediments by refraction seismic technique. The firsts result shown that the bottom sediments thickness varies from 400 to1200 m.

  12. Seismic explosion sources on an ice cap - Technical considerations

    Science.gov (United States)

    Shulgin, Alexey; Thybo, Hans

    2015-03-01

    Controlled source seismic investigation of crustal structure below ice covers is an emerging technique. We have recently conducted an explosive refraction/wide-angle reflection seismic experiment on the ice cap in east-central Greenland. The data-quality is high for all shot points and a full crustal model can be modelled. A crucial challenge for applying the technique is to control the sources. Here, we present data that describe the efficiency of explosive sources in the ice cover. Analysis of the data shows, that the ice cap traps a significant amount of energy, which is observed as a strong ice wave. The ice cap leads to low transmission of energy into the crust such that charges need be larger than in conventional onshore experiments to obtain reliable seismic signals. The strong reflection coefficient at the base of the ice generates strong multiples which may mask for secondary phases. This effect may be crucial for acquisition of reflection seismic profiles on ice caps. Our experience shows that it is essential to use optimum depth for the charges and to seal the boreholes carefully.

  13. Recent GPS Surveys Reveal Coupling Complexities in the TalTal Area, Chile (24°S-26°S) : Consequences on Seismic Hazard in the Atacama-Antofagasta Regions.

    Science.gov (United States)

    Vigny, C.; Klein, E.; Metois, M.; Meneses, G.; Delorme, A.

    2017-12-01

    GPS surveys have been extensively used over the past 20 years to quantify crustal deformation associated to the Andean subduction zone in Chile. Such measurements revealed the coupling variations associated to the seismic segmentation of the subduction. However, because of data gaps mostly due to access difficulties, the Atacama-Antofagasta regions of North Chile remain poorly known. We present here an upgraded interseismic velocity field aggregating new data acquired in the region of Taltal (24°S - 26°S) over a small scale network of 20 benchmarks between 2012 and 2016. This denser data set reveals a new complexity. First, a large scale rigid Andean sliver, running from central to North Chile, does not match well the velocities measured in the region of Taltal. This region shows an additional coherent block motion of almost 5 mm/yr with respect to the inland motion generated by the rotation of the sliver proposed by [e.g. Brooks et al., 2003; Métois et al., 2013]. Second, once this local coherent additional motion is taken into account, the coupling in the Taltal area is refined and shows as a relatively low coupling zone (LCZ). Although coupling values there are still high, it potentially cuts a long section of the subduction into two independent segments: The Paranal segment, north of Taltal - between 23°S and 25°S; and the Chañaral segment, south of Taltal - between 26°S and 28°S. These segments may rupture individually with magnitude 8 earthquakes or simultaneously which would produce a larger earthquake, especially if a third segment (Atacama - between 26°S and 28°S) is involved. The Mw 8.5 earthquake of 1922 ruptured the two southern segments of Atacama and Chañaral, with a complex scenario possibly involving at least two main shocks, which was also the case of the earlier megathrust earthquake in this area of 1819 [Willis 1929]. A repeat of these earthquakes is plausible to occur soon, since both segments are fully coupled and accumulated enough

  14. Upper Mantle Dynamics of Bangladesh by Splitting Analyzes of Core Refracted SKS and SKKS Waves

    Science.gov (United States)

    Tiwari, A. K.; Bhushan, K.; Eken, T.; Singh, A.

    2017-12-01

    New shear wave splitting measurements are obtained from hitherto less studied Bengal Basin using core refracted SKS and SKKS phases. Splitting parameters, time delays (δt) and fast polarization directions (Φ) were estimated through analysis of 64 high-quality waveforms (≥ 2.5 signal to noise ratio) from 29 earthquakes with magnitude ≥5.5 recorded at eight seismic stations deployed over Bangladesh. We found no evidence of splitting which indicates azimuthal isotropy beneath the region. Null measurements can be explained by near vertical axis of anisotropy or by the presence of multiple anisotropic layers with different fast polarization directions, where combined effect results in null. We consider that the presence of partial melts within the upper mantle due to Kerguelen mantle plume activities may be the potential geodynamic cause for observed null measurements. It locally perturbed mantle convection flow beneath the region and reoriented the lattice preferred orientation of the upper mantle mineral mainly olivine as this disabled the core refracted SKS and SKKS phases to scan the anisotropic characteristics of the region, and hence null measurements are obtained.

  15. Seismic isolation - efficient procedure for seismic response assessement

    International Nuclear Information System (INIS)

    Zamfir, M. A.; Androne, M.

    2016-01-01

    The aim of this analysis is to reduce the dynamic response of a structure. The seismic isolation solution must take into consideration the specific site ground motion. In this paper will be presented results obtained by applying the seismic isolation method. Based on the obtained results, important conclusions can be outlined: the seismic isolation device has the ability to reduce seismic acceleration of the seismic isolated structure to values that no longer present a danger to people and environment; the seismic isolation solution is limiting devices deformations to safety values for ensuring structural integrity and stability of the entire system; the effective seismic energy dissipation and with no side effects both for the seismic isolated building and for the devices used, and the return to the initial position before earthquake occurence are obtained with acceptable permanent displacement. (authors)

  16. Excavatability Assessment of Weathered Sedimentary Rock Mass Using Seismic Velocity Method

    International Nuclear Information System (INIS)

    Bin Mohamad, Edy Tonnizam; Noor, Muhazian Md; Isa, Mohamed Fauzi Bin Md.; Mazlan, Ain Naadia; Saad, Rosli

    2010-01-01

    Seismic refraction method is one of the most popular methods in assessing surface excavation. The main objective of the seismic data acquisition is to delineate the subsurface into velocity profiles as different velocity can be correlated to identify different materials. The physical principal used for the determination of excavatability is that seismic waves travel faster through denser material as compared to less consolidated material. In general, a lower velocity indicates material that is soft and a higher velocity indicates more difficult to be excavated. However, a few researchers have noted that seismic velocity method alone does not correlate well with the excavatability of the material. In this study, a seismic velocity method was used in Nusajaya, Johor to assess the accuracy of this seismic velocity method with excavatability of the weathered sedimentary rock mass. A direct ripping run by monitoring the actual production of ripping has been employed at later stage and compared to the ripper manufacturer's recommendation. This paper presents the findings of the seismic velocity tests in weathered sedimentary area. The reliability of using this method with the actual rippability trials is also presented.

  17. Seismic fragility analyses

    International Nuclear Information System (INIS)

    Kostov, Marin

    2000-01-01

    In the last two decades there is increasing number of probabilistic seismic risk assessments performed. The basic ideas of the procedure for performing a Probabilistic Safety Analysis (PSA) of critical structures (NUREG/CR-2300, 1983) could be used also for normal industrial and residential buildings, dams or other structures. The general formulation of the risk assessment procedure applied in this investigation is presented in Franzini, et al., 1984. The probability of failure of a structure for an expected lifetime (for example 50 years) can be obtained from the annual frequency of failure, β E determined by the relation: β E ∫[d[β(x)]/dx]P(flx)dx. β(x) is the annual frequency of exceedance of load level x (for example, the variable x may be peak ground acceleration), P(fI x) is the conditional probability of structure failure at a given seismic load level x. The problem leads to the assessment of the seismic hazard β(x) and the fragility P(fl x). The seismic hazard curves are obtained by the probabilistic seismic hazard analysis. The fragility curves are obtained after the response of the structure is defined as probabilistic and its capacity and the associated uncertainties are assessed. Finally the fragility curves are combined with the seismic loading to estimate the frequency of failure for each critical scenario. The frequency of failure due to seismic event is presented by the scenario with the highest frequency. The tools usually applied for probabilistic safety analyses of critical structures could relatively easily be adopted to ordinary structures. The key problems are the seismic hazard definitions and the fragility analyses. The fragility could be derived either based on scaling procedures or on the base of generation. Both approaches have been presented in the paper. After the seismic risk (in terms of failure probability) is assessed there are several approaches for risk reduction. Generally the methods could be classified in two groups. The

  18. Corneal sensation after cataract and refractive surgery.

    Science.gov (United States)

    Kohlhaas, M

    1998-10-01

    Most surgical procedures involving the anterior segment of the eye disrupt the normal organization of corneal innervation. Since denervation of the cornea results in impaired epithelial wound healing, increased epithelial permeability, decreased epithelial metabolic activity, and loss of cytoskeletal structures associated with cellular adhesion, it is important to identify the factors that determine the extent of neural regeneration. Mechanisms of corneal nerve damage and studies of corneal nerve fiber loss and reinnervation after cataract and refractive surgery--epikeratophakia, cryokeratomileusis, keratomileusis in situ, photorefractive keratectomy, laser in situ keratomileusis, and phacoemulsification--are reviewed and the decrease in corneal sensitivity, as a measure of corneal destruction and corneal metabolism, after these surgical procedures is compared.

  19. Pickering seismic safety margin

    International Nuclear Information System (INIS)

    Ghobarah, A.; Heidebrecht, A.C.; Tso, W.K.

    1992-06-01

    A study was conducted to recommend a methodology for the seismic safety margin review of existing Canadian CANDU nuclear generating stations such as Pickering A. The purpose of the seismic safety margin review is to determine whether the nuclear plant has sufficient seismic safety margin over its design basis to assure plant safety. In this review process, it is possible to identify the weak links which might limit the seismic performance of critical structures, systems and components. The proposed methodology is a modification the EPRI (Electric Power Research Institute) approach. The methodology includes: the characterization of the site margin earthquake, the definition of the performance criteria for the elements of a success path, and the determination of the seismic withstand capacity. It is proposed that the margin earthquake be established on the basis of using historical records and the regional seismo-tectonic and site specific evaluations. The ability of the components and systems to withstand the margin earthquake is determined by database comparisons, inspection, analysis or testing. An implementation plan for the application of the methodology to the Pickering A NGS is prepared

  20. Performance of a Be Refractive Lens

    International Nuclear Information System (INIS)

    Smither, R.K.; Khounsary, A.M.; Mancini, D.C.; Saleem, K. Abu

    2004-01-01

    The performance of a beryllium compound refractive lens (CRL) was tested in the energy range of 11.5 to 8.0 keV. The beryllium refractive lens consists of 50 aligned, 1-mm-diameter, hollow spheres in a solid block of beryllium, 30 mm x 20 mm x 55 mm. The minimum web between each hollow sphere was 0.10 mm. The measured focal length of the lens for x-rays close to the axis of the beam was 147.7 cm +/- 2.0 cm at 10 keV and 120.2 +/- 2.0 cm at 9.1 keV. These values agree well with the theoretical values of 146.6 cm and 121.4 cm, respectively. The diameter of the best focus obtained at 10 keV was 35 μm horizontal and 45 μm vertical. For the modified version of the lens used in the 9.1 keV experiment these values were 25 μm horizontal and 35 μm vertical. The x-ray beam cross section for the 10 keV and the 9.1 keV experiments were 0.50 mm x 0.50 mm and 0.30 mm x 0.30 mm, respectively. The enhancement of the flux (photons per sq. mm) was 50:1 at 10 keV and 80:1 in the 9.1 keV experiment

  1. A seismic hazard overview of the Mitidja Basin (Northern Algeria)

    Science.gov (United States)

    Fontiela, J. F.; Borges, J.; Ouyed, M.; Bezzeghoud, M.; Idres, M.; Caldeira, B.; Boughacha, M. S.; Carvalho, J.; Samai, S.; Aissa, S.; Benfadda, A.; Chimouni, R.; Yalaoui, R.; Dias, R.

    2017-12-01

    The Mitidja Basin (MB) is located in N Algeria and it is filled by quaternary sediments with a length of 100 km on the EW direction and around 20 km width. The S and N limites comprise the Boumerdes-Larbaa-Blida, and the Thenia-Sahel active fault system, respectively. Both fault systems are of the reverse type with opposed dips and accommodate a general slip rate of ˜4 mm/year. In the basin occurred earthquakes that caused severe damage and losses such as the ones of Algiers (1365, Io=X; 1716, Io=X) and the Bourmedes earthquake (Mw 6.9; May 2003) that affected the area of Zemmouri and caused 2.271 deaths. The event was caused by the reactivation of the MB boundary faults. The earthquake generated a max uplift of 0.8m along the coast and a horizontal max. slip of 0.24m.Recent studies show that the Boumerdes earthquake overloaded the adjacent faults system with a stress increase between 0.4 and 1.5 bar. The stress change recommends a detailed study of mentioned faults system due to the increase of the seismic hazard. The high seismogenic potential of the fault system bordering the MB, increases the vulnerability of densely populated areas of Algiers and the amplification effect caused by the basin are the motivation of this project that will focus on the evaluation of the seismic hazard of the region. To achieve seismic hazard assessment on the MB, through realistic predictions of strong ground motion, caused by moderate and large earthquakes, it is important 1) develop a detailed 3D velocity/structure model of the MB that includes geological constraints, seismic reflection data acquired on wells, refraction velocities and seismic noise data, and determination of the attenuation laws based on instrumental records; 2) evaluate the seismic potential and parameters of the main active faults of the MB; 3) develop numerical methods (deterministic and stochastic) to simulate strong ground motions produced by extended seismic sources. To acquire seismic noise were used

  2. Screening for Uncorrected Refractive Error Among Primary School ...

    African Journals Online (AJOL)

    A study on screening for uncorrected refractive error in primary school children has not been done in Bayelsa State, South-South Nigeria. This study aims to screen for uncorrected refractive error among primary school children in Bayelsa State and use the data to plan for an effective school Eye Health Program. A cross ...

  3. 1D Photonic Crystals with a Sawtooth Refractive Index

    OpenAIRE

    Morozov, G. V.; Sprung, D. W. L.; Martorell, J.

    2013-01-01

    Exact analytical results (in terms of Bessel functions) for the bandgaps, reflectance, and transmittance of one-dimensional photonic crystals with a sawtooth refractive index profile on the period are derived for the first time. This extends a group of exactly solvable models of periodic refractive indices. The asymptotic approximations of the above exact results have been also obtained.

  4. Atmospheric stability index using radio occultation refractivity profiles

    Indian Academy of Sciences (India)

    A new stability index based on atmospheric refractivity at ∼500 hPa level and surface measurements of temperature, pressure and humidity is formulated. The new index named here as refractivity based lifted index (RLI) is designed to give similar results as traditionally used lifted index derived from radiosonde profiles of ...

  5. Determining the Thickness and Refractive Index of a Mirror

    Science.gov (United States)

    Uysal, Ahmet

    2010-01-01

    When a laser beam reflects from a back surface glass mirror and falls on a screen, a pattern of discrete bright spots is created by partial reflection and refraction of the light at the air-glass interface and reflection at the mirror surface (Fig. 1). This paper explains how this phenomenon can be used to determine the refractive index and the…

  6. transient refractive changes in a newly diagnosed diabetic

    African Journals Online (AJOL)

    LIVINGSTON

    Diabetes mellitus is one of the systemic diseases that has ocular manifestation. Hyperglycemia is the most frequently observed sign of diabetes and is considered the etiological source of diabetes complication both in the body and in the eye. Changes in refraction are very common in diabetes . Transient refractive changes ...

  7. Screening for refractive error among primary school children in ...

    African Journals Online (AJOL)

    Introduction: Background: Vision screening study in primary school children has not been done in Bayelsa State. This study aims to screen for refractive error among primary school children in Bayelsa State and use the data to plan for school Eye Health Program. Methods: A cross sectional study on screening for refractive ...

  8. Paediatric Refractive Errors in an Eye Clinic in Osogbo, Nigeria ...

    African Journals Online (AJOL)

    Background: Paediatric ophthalmology is an emerging subspecialty in Nigeria and as such there is paucity of data on refractive errors in the country. This study set out to determine the pattern of refractive errors in children attending an eye clinic in South West Nigeria. Methods: A descriptive study of 180 consecutive ...

  9. Pattern of refractive anomalies in Warri Metropolis, Delta State of ...

    African Journals Online (AJOL)

    A cross-sectional prevalent study of refractive errors conducted in Warri, a metropolitan town in delta state of Nigeria revealed peculiar prevalent rates. One thousand and eighteen eyes of 6 to 64 year olds were screened for refractive anomalies and 752 (73.9%) eyes (369 male and 383 female eyes) were found with ...

  10. Comparison of atmospheric refraction at radar and optical wavelengths

    NARCIS (Netherlands)

    Kunz, G.J.; Heemskerk, E.; Eijk, A.M.J. van

    2005-01-01

    A study is carried out to classify possible combinations of refractivity conditions