Sample records for geophones

  1. Grating geophone signal processing based on wavelet transform (United States)

    Li, Shuqing; Zhang, Huan; Tao, Zhifei


    Grating digital geophone is designed based on grating measurement technique benefiting averaging-error effect and wide dynamic range to improve weak signal detected precision. This paper introduced the principle of grating digital geophone and its post signal processing system. The signal acquisition circuit use Atmega 32 chip as core part and display the waveform on the Labwindows through the RS232 data link. Wavelet transform is adopted this paper to filter the grating digital geophone' output signal since the signal is unstable. This data processing method is compared with the FIR filter that widespread use in current domestic. The result indicates that the wavelet algorithm has more advantages and the SNR of seismic signal improve obviously.

  2. Design of vehicle overload detection system based on geophone (United States)

    Hu, Siquan; Kong, Min; She, Chundong


    A vehicle overload detection system is proposed based on geophone. Under normal circumstances, when overloaded vehicles and ordinary vehicles pass through the road, the amplitude of the ground vibration will be different, and the geophone sensor can detect tiny vibrations of the ground. The system includes information acquisition module, signal conditioning module and wireless transmission module. The collected vibration data is transmitted through the wireless transmission module to the background, and the SVM algorithm is used to classify the information and determine whether the vehicle is overloaded. Experiments show that the system can detect overload accurately.

  3. A novel fiber optic geophone with high sensitivity for geo-acoustic detection (United States)

    Zhang, Zhenhui; Yang, Huayong; Xiong, Shuidong; Luo, Hong; Cao, Chunyan; Ma, Shuqing


    A novel interferometric fiber optic geophone is introduced in this paper. This geophone is mainly used for geo-acoustic signal detection. The geophone use one of the three orthogonal components of mandrel type push-pull structure in mechanically and single-mode fiber optic Michelson interferometer structure with Faraday Rotation Mirror (FRM) elements in optically. The resonance frequency of the geophone is larger than 1000Hz. The acceleration sensitivity is as high as 56.6 dB (0dB re 1rad/g) with a slight sensitivity fluctuation of +/-0. 2dB within the frequency band from 20Hz to 200Hz. The geo-acoustic signals generated by underwater blasting are detected successfully. All the channels show good uniformity in the detected wave shape and the amplitudes exhibit very slight differences. The geo-acoustic signal excitated by the engine of surface vehicles was also detected successfully.

  4. Distributed fiber optic interferometric geophone system based on draw tower gratings (United States)

    Xu, Ruquan; Guo, Huiyong; Liang, Lei


    A distributed fiber optic interferometric geophone array based on draw tower grating (DTG) array is proposed. The DTG geophone array is made by the DTG array fabricated based on a near-contact exposure through a phase mask during the fiber drawing process. A distributed sensing system with 96 identical DTGs in an equal separation of 20 m and an unbalanced Michelson interferometer for vibration measurement has been experimentally validated compared with a moving-coil geophone. The experimental results indicate that the sensing system can linearly demodulate the phase shift. Compared with the moving coil geophone, the fiber optic sensing system based on DTG has higher signal-to-noise ratio at low frequency.

  5. A single geophone to locate seismic events on Mars (United States)

    Roques, Aurélien; Berenguer, Jean-Luc; Bozdag, Ebru


    Knowing the structure of Mars is a key point in understanding the formation of Earth-like planets as plate tectonics and erosion have erased the original suface of the Earth formation. Installing a seismometer on Mars surface makes it possible to identify its structure. An important step in the identification of the structure of a planet is the epicenter's location of a seismic source, typically a meteoric impact or an earthquake. On Earth, the classical way of locating epicenters is triangulation, which requires at least 3 stations. The Mars InSight Project plans to set a single station with 3 components. We propose a software to locate seismic sources on Mars thanks to the 3-components simulated data of an earthquake given by Geoazur (Nice Sophia-Antipolis University, CNRS) researchers. Instrumental response of a sensor is crucial for data interpretation. We study the oscillations of geophone in several situations so as to awaken students to the meaning of damping in second order modeling. In physics, car shock absorbers are often used to illustrate the principle of damping but rarely in practical experiments. We propose the use of a simple seismometer (a string with a mass and a damper) that allows changing several parameters (inductive damping, temperature and pressure) so as to see the effects of these parameters on the impulse response and, in particular, on the damping coefficient. In a second step, we illustrate the effect of damping on a seismogram with the difficulty of identifying and interpreting the different phase arrival times with low damping.

  6. A Low-Cost Energy-Efficient Cableless Geophone Unit for Passive Surface Wave Surveys

    Directory of Open Access Journals (Sweden)

    Kaoshan Dai


    Full Text Available The passive surface wave survey is a practical, non-invasive seismic exploration method that has increasingly been used in geotechnical engineering. However, in situ deployment of traditional wired geophones is labor intensive for a dense sensor array. Alternatively, stand-alone seismometers can be used, but they are bulky, heavy, and expensive because they are usually designed for long-term monitoring. To better facilitate field applications of the passive surface wave survey, a low-cost energy-efficient geophone system was developed in this study. The hardware design is presented in this paper. To validate the system’s functionality, both laboratory and field experiments were conducted. The unique feature of this newly-developed cableless geophone system allows for rapid field applications of the passive surface wave survey with dense array measurements.

  7. A Low-Cost Energy-Efficient Cableless Geophone Unit for Passive Surface Wave Surveys. (United States)

    Dai, Kaoshan; Li, Xiaofeng; Lu, Chuan; You, Qingyu; Huang, Zhenhua; Wu, H Felix


    The passive surface wave survey is a practical, non-invasive seismic exploration method that has increasingly been used in geotechnical engineering. However, in situ deployment of traditional wired geophones is labor intensive for a dense sensor array. Alternatively, stand-alone seismometers can be used, but they are bulky, heavy, and expensive because they are usually designed for long-term monitoring. To better facilitate field applications of the passive surface wave survey, a low-cost energy-efficient geophone system was developed in this study. The hardware design is presented in this paper. To validate the system's functionality, both laboratory and field experiments were conducted. The unique feature of this newly-developed cableless geophone system allows for rapid field applications of the passive surface wave survey with dense array measurements.




    Technique for determining the multicomponent geophone orientation on a seismic line is considered in the report. This technique allowed correcting the components orientation. Methodical and instrumental imperfections of field measurements were also detected in the course of research. Taking these into account may allow avoiding the errors in further data processing.

  9. 陆上高分辨率地震勘探检波器性能及应用效果分析%Analysis of geophone properties effects for land seismic data

    Institute of Scientific and Technical Information of China (English)

    李桂林; 陈高; 钟俊义


    The properties of the seismic geophones are important factors for high-resolution three kinds of geophones currently used in several regions with different geological features:desert, saline-alkali farmland, and carbonate areas in mountainous regions in order to test their property indexes. Based on the geophone vibration equation and from the property index effects of geophone and the connection of the geophones on seismic data, we analyzed seismic data quality acquired in the tested regions and suggest that suitable geophone property indexes, reasonable choice of geophone types, and the suitable geophone connection can enhance the signal/noise ratio of seismic data.

  10. Bedload Dynamics of a Lowland Gravel-Bedded River Monitored Using Geophones (United States)

    Downs, P. W.; Taylor, A.; Soar, P. J.


    Bedload dynamics of the River Avon (Devon, UK) were monitored using geophones during an extremely wet period in 2012-3 which included multiple overtopping discharges and the instantaneous and daily mean flows of record. Seismic impact plate geophones have been suggested to provide a reliable record of transport of grains in excess of ca.20 mm. Our geophones, positioned in a reach with a central flow thalweg, consistently recorded a lower threshold of bedload movement at ~4 m3s-1 which accords to a shear stress theoretically capable of moving sediment just exceeding 20 mm. The relationship of discharge to bedload rate (i.e., impact frequency) during individual events was highly complex: increasing scatter at discharges in excess of bankfull may in part reflect sensitivity of the device to bedload size and saltation dynamics. Considerable intra-event hysteresis including in-bank transport peaks during flow recession may relate to changing sediment supply dynamics due to local mass and cantilever bank failures. Variation in impact frequencies between events may reflect regional changes in sediment supply dynamics although lateral displacement in the dominant track of bedload would provide the same result: later installation of multiple geophones demonstrated a high degree of cross-stream variability in recorded bedload but the persistent dominance of the central plate meant that the discharge-transport relationship was not significantly improved by using multiple plates. Despite this intra- and inter-event variability, the product of instantaneous discharge versus impact frequency indicated an effective discharge for bedload close to the morphological ';bar-full' level - this may be plausible in this exceptionally wet period during which time 20 mm grains were estimated to be mobile during 66% of daily mean flows and the channel underwent appreciable morphological adjustment. The results generally support the value of impact plates as indicators of relative sediment

  11. Comparison of bedload transport measurements at the Suggadinbach stream with geophones and modified pipe hydrophones (United States)

    Chiari, Michael; Berktold, Maximilian; Jäger, Gerald; Hübl, Johannes


    A new bedload transport monitoring station has been designed by the Institute of Mountain Risk engineering at the Suggadinbach in Austria (Vorarlberg). In cooperation with the Austrian Service for Torrent and Avalanche Control the station has been installed in June 2013 in a check dam. Two different types of measuring systems are installed: 13 Swiss type geophone sensors record the vibrations of the transported sediment. Additionally 3 modified Japanese pipe hydrophones are mounted under steel plates in order to record the acoustic signal produced by the sediment transport. Both systems can be compared directly because they are arranged consecutively in flow direction. For calibration of the sensors a series of systematic tests have been carried out during low water conditions. Sediment has been fed by a crane with a concrete container. A flume has been installed in order to obtain controlled flow and transport over the measuring system. Four different grain classes up to 64 mm and a mixture of all classes were tested. A total amount of 4 tons were fed during the experiments. The signal was recorded with 9.6 kHz. Frequency analyses were performed for different grain-classes in order to investigate the influence of the grain-size distribution on the shape of the signal and the influence of neighbouring sensors. The standard evaluation and storage procedure for 1 minute aggregated data show that the modified pipe hydrophone is able to detect finer grain-sizes than the geophone sensor.

  12. Development and programming of Geophonino: A low cost Arduino-based seismic recorder for vertical geophones (United States)

    Soler-Llorens, J. L.; Galiana-Merino, J. J.; Giner-Caturla, J.; Jauregui-Eslava, P.; Rosa-Cintas, S.; Rosa-Herranz, J.


    The commercial data acquisition systems used for seismic exploration are usually expensive equipment. In this work, a low cost data acquisition system (Geophonino) has been developed for recording seismic signals from a vertical geophone. The signal goes first through an instrumentation amplifier, INA155, which is suitable for low amplitude signals like the seismic noise, and an anti-aliasing filter based on the MAX7404 switched-capacitor filter. After that, the amplified and filtered signal is digitized and processed by Arduino Due and registered in an SD memory card. Geophonino is configured for continuous registering, where the sampling frequency, the amplitude gain and the registering time are user-defined. The complete prototype is an open source and open hardware system. It has been tested by comparing the registered signals with the ones obtained through different commercial data recording systems and different kind of geophones. The obtained results show good correlation between the tested measurements, presenting Geophonino as a low-cost alternative system for seismic data recording.

  13. A geophone wireless sensor network for investigating glacier stick-slip motion (United States)

    Martinez, Kirk; Hart, Jane K.; Basford, Philip J.; Bragg, Graeme M.; Ward, Tyler; Young, David S.


    We have developed an innovative passive borehole geophone system, as part of a wireless environmental sensor network to investigate glacier stick-slip motion. The new geophone nodes use an ARM Cortex-M3 processor with a low power design capable of running on battery power while embedded in the ice. Only data from seismic events was stored, held temporarily on a micro-SD card until they were retrieved by systems on the glacier surface which are connected to the internet. The sampling rates, detection and filtering levels were determined from a field trial using a standard commercial passive seismic system. The new system was installed on the Skalafellsjökull glacier in Iceland and provided encouraging results. The results showed that there was a relationship between surface melt water production and seismic event (ice quakes), and these occurred on a pattern related to the glacier surface melt-water controlled velocity changes (stick-slip motion). Three types of seismic events were identified, which were interpreted to reflect a pattern of till deformation (Type A), basal sliding (Type B) and hydraulic transience (Type C) associated with stick-slip motion.

  14. A Fiber-Optic Interferometric Tri-Component Geophone for Ocean Floor Seismic Monitoring

    Directory of Open Access Journals (Sweden)

    Jiandong Chen


    Full Text Available For the implementation of an all fiber observation network for submarine seismic monitoring, a tri-component geophone based on Michelson interferometry is proposed and tested. A compliant cylinder-based sensor head is analyzed with finite element method and tested. The operation frequency ranges from 2 Hz to 150 Hz for acceleration detection, employing a phase generated carrier demodulation scheme, with a responsivity above 50 dB re rad/g for the whole frequency range. The transverse suppression ratio is about 30 dB. The system noise at low frequency originated mainly from the 1/f fluctuation, with an average system noise level −123.55 dB re rad / Hz ranging from 0 Hz to 500 Hz. The minimum detectable acceleration is about 2 ng / Hz , and the dynamic range is above 116 dB.

  15. Basic problems and new potentials in monitoring sediment transport using Japanese pipe type geophone (United States)

    Sakajo, Saiichi


    The authors have conducted a lot of series of monitoring of sediment transport by pipe type geophone in a model hydrological channel with various gradients and water discharge, using the various size of particles from 2 to 21 mm in the diameter. In the case of casting soils particle by particle into the water channel, 1,000 test cases were conducted. In the case of casting all soils at a breath into the water channel, 100 test cases were conducted. The all test results were totally analyzed by the conventional method, with visible judgement by video pictures. Then several important basic problems were found in estimating the volume and particle distributions by the conventional method, which was not found in the past similar studies. It was because the past studies did not consider the types of collisions between sediment particle and pipe. Based on these experiments, the authors have firstly implemented this idea into the old formula to estimate the amount of sediment transport. In the formula, two factors of 1) the rate of sensing in a single collision and 2) the rate of collided particles to a cast all soil particles were concretely considered. The parameters of these factors could be determined from the experimental results and it was found that the obtained formula could estimate grain size distribution. In this paper, they explain the prototype formula to estimate a set of volume and distribution of sediment transport. Another finding in this study is to propose a single collision as a river index to recognize its characteristics of sediment transport. This result could characterize the risk ranking of sediment transport in the rivers and mudflow in the mountainous rivers. Furthermore, in this paper the authors explain how the preciseness of the pipe geophone to sense the smaller sediment particles shall be improved, which has never been able to be sensed.

  16. Phase Velocity and Full-Waveform Analysis of Co-located Distributed Acoustic Sensing (DAS) Channels and Geophone Sensor (United States)

    Parker, L.; Mellors, R. J.; Thurber, C. H.; Wang, H. F.; Zeng, X.


    A 762-meter Distributed Acoustic Sensing (DAS) array with a channel spacing of one meter was deployed at the Garner Valley Downhole Array in Southern California. The array was approximately rectangular with dimensions of 180 meters by 80 meters. The array also included two subdiagonals within the rectangle along which three-component geophones were co-located. Several active sources were deployed, including a 45-kN, swept-frequency, shear-mass shaker, which produced strong Rayleigh waves across the array. Both DAS and geophone traces were filtered in 2-Hz steps between 4 and 20 Hz to obtain phase velocities as a function of frequency from fitting the moveout of travel times over distances of 35 meters or longer. As an alternative to this traditional means of finding phase velocity, it is theoretically possible to find the Rayleigh-wave phase velocity at each point of co-location as the ratio of DAS and geophone responses, because DAS is sensitive to ground strain and geophones are sensitive to ground velocity, after suitable corrections for instrument response (Mikumo & Aki, 1964). The concept was tested in WPP, a seismic wave propagation program, by first validating and then using a 3D synthetic, full-waveform seismic model to simulate the effect of increased levels of noise and uncertainty as data go from ideal to more realistic. The results obtained from this study provide a better understanding of the DAS response and its potential for being combined with traditional seismometers for obtaining phase velocity at a single location. This analysis is part of the PoroTomo project (Poroelastic Tomography by Adjoint Inverse Modeling of Data from Seismology, Geodesy, and Hydrology,

  17. A new geophone device for understanding environmental impacts caused by gravel bedload during artificial floods (United States)

    Tsubaki, Ryota; Kawahara, Yoshihisa; Zhang, Xin-Hua; Tsuboshita, Kentaro


    To assess the contribution of gravel bedload on the removal of attached-algae and aquatic plants from a cobble-bed river during small floods, we propose a geophone type method for measuring the local bedload of non-uniform sized gravel. Due to limited peak discharge for focused events during our study, a large fraction of bed material (here cobbles) was immobile and only a small fraction of bed material (sand and gravel) was expected to be transported during the flushing flows we analyzed. The device we developed has a size equivalent to immobile bed material and a shape similar to bed material (rounded cobbles) at the site. The instrument's design allows avoidance of disturbances in river bed micro-topography during installation and local bedload transport during floods. A flume experiment was conducted in order to establish an empirical algorithm for estimating the diameter of impacted gravel, and uncertainty related to diameter estimation is discussed. The proposed method was utilized to quantify gravel bedload in a cobble-bed river during flushing flows. We also discuss the contribution of measured gravel bedload during flushing flows on the removal of attached-algae (up to a 37% reduction in chlorophyll-a density) and aquatic plants (a reduction of 38% in dry mass per area). Based on time variation for the measured gravel bedload, we also suggest the propagation of a bed-form composed of the fine sediment fraction migrating on immobile larger sediment and implications for the propagation of the fine sediment wave for attached-algae removal.

  18. Orientation of three-component geophones in the San Andreas Fault observatory at depth Pilot Hole, Parkfield, California (United States)

    Oye, V.; Ellsworth, W.L.


    To identify and constrain the target zone for the planned SAFOD Main Hole through the San Andreas Fault (SAF) near Parkfield, California, a 32-level three-component (3C) geophone string was installed in the Pilot Hole (PH) to monitor and improve the locations of nearby earthquakes. The orientation of the 3C geophones is essential for this purpose, because ray directions from sources may be determined directly from the 3D particle motion for both P and S waves. Due to the complex local velocity structure, rays traced from explosions and earthquakes to the PH show strong ray bending. Observed azimuths are obtained from P-wave polarization analysis, and ray tracing provides theoretical estimates of the incoming wave field. The differences between the theoretical and the observed angles define the calibration azimuths. To investigate the process of orientation with respect to the assumed velocity model, we compare calibration azimuths derived from both a homogeneous and 3D velocity model. Uncertainties in the relative orientation between the geophone levels were also estimated for a cluster of 36 earthquakes that was not used in the orientation process. The comparison between the homogeneous and the 3D velocity model shows that there are only minor changes in these relative orientations. In contrast, the absolute orientations, with respect to global North, were significantly improved by application of the 3D model. The average data residual decreased from 13?? to 7??, supporting the importance of an accurate velocity model. We explain the remaining residuals by methodological uncertainties and noise and with errors in the velocity model.

  19. SPE-5 Ground-Motion Prediction at Far-Field Geophone and Accelerometer Array Sites and SPE-5 Moment and Corner-Frequency Prediction

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoning [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Patton, Howard John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chen, Ting [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    This report offers predictions for the SPE-5 ground-motion and accelerometer array sites. These predictions pertain to the waveform and spectral amplitude at certain geophone sites using Denny&Johnson source model and a source model derived from SPE data; waveform, peak velocity and peak acceleration at accelerometer sites using the SPE source model and the finite-difference simulation with LLNL 3D velocity model; and the SPE-5 moment and corner frequency.

  20. Submarine seismic monitoring of El Hierro volcanic eruption with a 3C-geophone string: applying new acquisition and data processing techniques to volcano monitoring (United States)

    Jurado, Maria Jose; Ripepe, Maurizio; Lopez, Carmen; Blanco, Maria Jose; Crespo, Jose


    A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2011 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. Right after the eruption onset, in October 2011 a geophone string was deployed by the CSIC-IGN to monitor seismic activity. Monitoring with the seismic array continued till May 2012. The array was installed less than 2 km away from the new vol¬cano, next to La Restinga village shore in the harbor from 6 to 12m deep into the water. Our purpose was to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. Each geophone consists on a 3-component module based on 3 orthogonal independent sensors that measures ground velocity. Some of the geophones were placed directly on the seabed, some were buried. Due to different factors, as the irregular characteristics of the seafloor. The data was recorded on the surface with a seismometer and stored on a laptop computer. We show how acoustic data collected underwater show a great correlation with the seismic data recorded on land. Finally we compare our data analysis results with the observed sea surface activity (ash and lava emission and degassing). This evidence is disclosing new and innovative tecniques on monitoring submarine volcanic activity. Reference Instituto Geográfico Nacional (IGN), "Serie El Hierro." Internet: /volcanologia/HIERRO.html [May, 17. 2013

  1. SPE-5 Ground-Motion Prediction at Far-Field Geophone and Accelerometer Array Sites and SPE-5 Moment and Corner-Frequency Prediction

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoning [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Patton, Howard John [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Chen, Ting [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    This report offers predictions for the SPE-5 ground-motion and accelerometer array sites. These predictions pertain to the waveform and spectral amplitude at certain geophone sites using Denny&Johnson source model and a source model derived from SPE data; waveform, peak velocity and peak acceleration at accelerometer sites using the SPE source model and the finite-difference simulation with LLNL 3D velocity model; and the SPE-5 moment and corner frequency.

  2. Using a Large N Geophone Array to Identify Hydrothermal Seismic Sources in the Upper Geyser Basin of Yellowstone National Park (United States)

    Farrell, J.; Lin, F. C.; Allam, A. A.; Smith, R. B.; Karplus, M. S.


    The recent availability of large N seismic arrays provides a unique capability for recording environmental seismic signals that can be monitored in detail. In November 2015, the University of Utah, in collaboration with Yellowstone National Park and the University of Texas El Paso, installed a seismic array in the Upper Geyser Basin of Yellowstone National Park centered on Old Faithful geyser. The array consisted of 133 three-component 5 Hz geophones recording continuously at 1000Hz for two weeks, with an average station spacing of 50 m and an aperture of 1 km. The array recorded numerous hydrothermal seismic sources including distinct seismic signals that could be attributed to surficial hydrothermal features as well as those that do not appear to be related to any individual surface feature. Old Faithful geyser eruptions themselves are largely aseismic. However, hydrothermal tremor, likely due to collapsing bubbles within the subsurface plumbing system, starts building about 45 minutes prior to an Old Faithful eruption. Tremor amplitudes slowly increase with time until they reach a peak about 25 minutes prior to the eruption and then slowly decrease until the eruption begins. The seismic signal related to the buildup of the Old Faithful subsurface reservoir is recorded at stations north, south and to the east of Old Faithful but is missing on stations to the northwest. This suggests a shallow subsurface feature that strongly attenuates the seismic signal immediately NW of the cone of Old Faithful. Another of the more interesting signals is observed regularly about every 38 minutes and may come from Doublet Pool on Geyser Hill. This signal has large seismic wave amplitudes and is recorded across much of the seismic array. The Geyser Hill signal may also be affected by the aforementioned subsurface attenuating feature NW of the Old Faithful cone. Interestingly, there is a persistent 20-25 Hz signal at several stations that seems to be affected by variations air

  3. Research of combinatorial methods of geophone for seismic data acquisition in Qiangtang Basin%羌塘盆地地震资料采集检波器组合方法研究

    Institute of Scientific and Technical Information of China (English)

    雷扬; 吴闻静; 刘远志; 余文科; 刘胜


    羌塘盆地前期地震勘探取得的叠加剖面中反射波能量较弱,波组连续性较差,有效波特征不明显,单炮记录上相干噪声、散射噪声较强。对前期勘探单炮记录的特点以及采集参数进行分析后,从提高单炮记录反射波组连续性,压制相干噪声及散射噪声的目的出发,提出了5种改进的检波器组合方式。通过对各方案的理论和实际资料分析,优选有利的检波器组合方式,地震资料采集取得了信噪比相对较高的单炮记录和叠加剖面。%There are weaker reflect wave energy, poor wave group continuity, strong coherent noise and scattering noise in single shot records, and unconspicuous effective wave features in stacked seismic section acquired in early stage of Qian- gtang Basin' s exploration. According to the feature of single shot records and acquisition parameters in early explorations, five improved combinatorial methods of geophone were put forward, to improve wave group continuity of single shot record and suppress the coherent noise and scattering noise. Through the analysis of practical data and theory of the combinatorial methods, a favorable combinatorial method of geophone was selected. Therefore, the single - shot record and stacked profile having higher signal to noise ratio (SNR) can be obtained in seismic data acquisition.

  4. Kinematics of shot-geophone migration

    NARCIS (Netherlands)

    C.C. Stolk; M.V. de Hoop; W.W. Symes


    Recent analysis and synthetic examples have shown that many prestack depth migration methods produce nonflat image gathers containing spurious events, even when provided with a kinematically correct migration velocity field, if this velocity field is highly refractive. This pathology occurs in all m

  5. Improving the Classical Geophone Sensor Element by Digital Correction

    DEFF Research Database (Denmark)

    Brincker, Rune; Lagö, Thomas L.; Andersen, Palle


    of this sensor is that it measures velocity, and that the linear frequency range is limited to frequencies above the natural frequency, typically at 4-12 Hz. It is shown in this paper how the sensor signal can be digitally linearized 2 decades below the natural frequency obtaining a sensor that allows the user...


    Energy Technology Data Exchange (ETDEWEB)

    Erik C. Westman


    Improved ground-imaging capabilities have enormous potential to increase energy, environmental, and economic benefits by improving exploration accuracy and reducing energy consumption during the mining cycle. Seismic tomography has been used successfully to monitor and evaluate geologic conditions ahead of a mining face. A primary limitation to existing seismic tomography, however, is the placement of sensors. The goal of this project is to develop an array of 24 seismic sensors capable of being mounted in either a vertical or horizontal borehole. Development of this technology reduces energy usage in excavation, transportation, ventilation, and processing phases of the mining operation because less waste is mined and the mining cycle suffers fewer interruptions. This new technology benefits all types of mines, including metal/nonmetal, coal, and quarrying. The primary research tasks focused on sensor placement method, sensor housing and clamping design, and cabling and connector selection. An initial design is described in the report. Following assembly, a prototype was tested in the laboratory as well as at a surface stone quarry. Data analysis and tool performance were used for subsequent design modifications. A final design is described, of which several components are available for patent application. Industry partners have shown clear support for this research and demonstrated an interest in commercialization following project completion.

  7. Robust Fusion of Multiple Microphone and Geophone Arrays in a Ground Sensor Network (United States)


    using modern pattern recognition methods that recognize patterns in, for instance, the emitted sound. Admittedly, there still are important obstacles ...d12, d13, and d23. Indeed, by knowing the distance d23 = t23/c, trigonometry gives the sought bearing angle θ. In theory, the t23 could be found as the

  8. Subsurface Imaging at Mount St. Helens with a Large-N Geophone Array (United States)

    Hansen, S. M.; Schmandt, B.; Levander, A.; Kiser, E.; Vidale, J. E.; Moran, S. C.


    The 900-instrument Mount St. Helens nodal array recorded continuous data for approximately two weeks in the summer of 2014 and provides a remarkable opportunity to interrogate the structure beneath an active arc volcano. Two separate imaging techniques are applied to constrain both the distribution of microseismicity and subsurface velocity structure. Reverse-time source imaging is applied to the 10 km3 region beneath the volcanic edifice where most of cataloged seismicity occurred during the experiment. These efforts resulted in an order of magnitude increase in earthquake detections over the normal monitoring operations of the Pacific Northwest Seismic Network. Earthquake locations resolve a narrow, ≤1 km wide, vertical lineament of seismicity that extends from the surface to 4 km depth directly beneath the summit crater, consistent with the historical event distribution of Waite and Moran[2009]. This feature is interpreted as a fracture network that acts as a conduit connecting an underlying magma chamber to the surface. Moho imaging is achieved using the near-offset (PmP phase generated by the iMUSH active source shots that occurred during the deployment. The PmP arrivals are enhanced using short-term-average over long-term-average processing and then migrated using a 3D velocity model. The observed Moho depths range from 35-40 km with a slight eastward deepening across the Mt St Helens fracture zone. Significant variations are observed in the Moho reflectivity. Large amplitude PmP energy is observed in shots originating from the north and east whereas shots from the south-west display little-to-no PmP energy. The region above the reflective Moho is approximately coincident with areas displaying reduced lower-crustal velocities in the initial iMUSH tomography models and may therefore contain fluids and/or partial melt. Additional evidence for lower crustal fluids in this region is provided by deep-long-period (DLP) events which have historically been observed east of the crater and below ~20 km depth [Nichols et al., 2011]. Two DLP events were observed during the nodal deployment [Han and Vidale, this meeting] and are located using the source imaging approach applied to the S-wave coda envelopes. Both events locate at 25-45 km depth, indicating that they occurred at or near the Moho interface.

  9. Suppression of 3D coherent noise by areal geophone array; Menteki jushinki array ni yoru sanjigen coherent noise no yokusei

    Energy Technology Data Exchange (ETDEWEB)

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


    For improving the quality of data collected by reflection seismic exploration, a lattice was deployed at one point of a traverse line, and the data therefrom were used to study the 3D coherent noise suppression effect of the areal array. The test was conducted at a Japan National Oil Corporation test field in Kashiwazaki City, Niigata Prefecture. The deployed lattice had 144 vibration receiving points arrayed at intervals of 8m composing an areal array, and 187 vibration generating points arrayed at intervals of 20m extending over 6.5km. Data was collected at the vibration receiving points in the lattice, each point acting independently from the others, and processed for the composition of a large areal array, with the said data from plural vibration receiving points added up therein. As the result of analysis of the records covering the data collected at the receiving points in the lattice, it is noted that an enlarged areal array leads to a higher S/N ratio and that different reflection waves are emphasized when the array direction is changed. 1 ref., 6 figs.

  10. 光电集成加速度地震检波器中声光波导相位调制器的设计与实验%Design and Experiment of Acousto-Optic Waveguide Phase Modulator in Electro-Optic Integrated Acceleration Seismic Geophone

    Institute of Scientific and Technical Information of China (English)

    张燕君; 陈才和; 钟娟娟; 崔宇明; 吴波



  11. Perimeter Security and Intruder Detection Using Gravity Gradiometry: A Feasibility Study (United States)


    when the background gravity gradient signal at some location is constant. Natural processes like plate tectonics and the water cycle redistribute...10  Seismic ... Seismic Wave Types .................................................................. 13  Figure 4: SM6-U/B Geophone

  12. The forming of lettucc variety examples collection ( Lactuca sativa L. )


    Андрющенко, А. В.; Лещук, Н. В.; Скрипка, А. І.


    Shown the completion of work collection of variety geophone of lettuce (Lactuca saliva L.), morphology description and the methods of taking up the candidates into variety reverence for conducting the examination on distinctness, uniformity and stability.


    Directory of Open Access Journals (Sweden)

    Muhammad Zikrilah


    subsurface layer model, to identify the types of rocks on each layer, and to analyze the depth of bedrock layer located in the subsurface. There are 4 tracks with spaces in between each geophone, and on each track, with the width of 3 m. The total spread on the track is 72 m and the farthest shoot point is 36 m from the farthest geophone point.

  14. Seismic Census Technique for African Elephants (United States)

    Wood, J. D.; O'Connell-Rodwell, C. E.; Klemperer, S. L.


    Large mammal populations are difficult to census and monitor in remote areas. In particular, elephant populations in Central Africa are difficult to census due to dense forest making aerial surveys impractical. Conservation management would be improved by a census technique that was accurate and precise, did not require large efforts in the field, and could record numbers of animals over a period of time. We report a new detection technique that relies on sensing the footfalls of large mammals. Geophones were used to record the footfalls of elephants and other large mammal species at a water hole in Etosha National Park, Namibia. We were able to discriminate between species using the spectral content of their footfalls with an 85% accuracy rate while only using a single geophone. This was done using correlation coefficients comparing the shape of the spectra for various species. An ANOVA found significant differences between these correlation coefficients (F4,1785 = 147.78, P = 0.000). An estimate of the energy created by passing elephants (the area under the amplitude envelope) can be used to estimate the number of elephants passing the geophone. Our best regression line plotting number of elephants versus energy recorded in the geophone explained 55% of the variance in the data. Much of the unexplained variance is due to the variation in distance from the geophone to the passing elephants. By subjecting the recordings to a narrow band-pass filter and using beamforming techniques on array data, we believe that we can control for the variation in distance between animal and geophones, and thus achieve better estimates of the number of animals passing the array. Using 7 pairs of geophones in a linear array, we offset the pairs of time series to correspond with the time delay associated with the signal intersecting the pair of geophones at increments of 2 degrees. The offset time series were then summed and the RMS value calculated. The largest RMS value was then

  15. Double-Difference Tomography for Sequestration MVA [monitoring, verification, and accounting

    Energy Technology Data Exchange (ETDEWEB)

    Westman, Erik


    Analysis of synthetic data was performed to determine the most cost-effective tomographic monitoring system for a geologic carbon sequestration injection site. Double-difference tomographic inversion was performed on 125 synthetic data sets: five stages of CO2 plume growth, five seismic event regions, and five geophone arrays. Each resulting velocity model was compared quantitatively to its respective synthetic velocity model to determine an accuracy value. The results were examined to determine a relationship between cost and accuracy in monitoring, verification, and accounting applications using double-difference tomography. The geophone arrays with widely-varying geophone locations, both laterally and vertically, performed best. Additionally, double difference seismic tomography was performed using travel time data from a carbon sequestration site at the Aneth oil field in southeast Utah as part of a Department of Energy initiative on monitoring, verification, and accounting (MVA) of sequestered CO2. A total of 1,211 seismic events were recorded from a borehole array consisting of 22 geophones. Artificial velocity models were created to determine the ease with which different CO2 plume locations and sizes can be detected. Most likely because of the poor geophone arrangement, a low velocity zone in the Desert Creek reservoir can only be detected when regions of test site containing the highest ray path coverage are considered. MVA accuracy and precision may be improved through the use of a receiver array that provides more comprehensive ray path coverage.

  16. Double-Difference Tomography for Sequestration MVA

    Energy Technology Data Exchange (ETDEWEB)

    Westman, Erik


    Analysis of synthetic data was performed to determine the most cost-effective tomographic monitoring system for a geologic carbon sequestration injection site. Double-difference tomographic inversion was performed on 125 synthetic data sets: five stages of CO2 plume growth, five seismic event regions, and five geophone arrays. Each resulting velocity model was compared quantitatively to its respective synthetic velocity model to determine an accuracy value. The results were examined to determine a relationship between cost and accuracy in monitoring, verification, and accounting applications using double-difference tomography. The geophone arrays with widely-varying geophone locations, both laterally and vertically, performed best. Additionally, double difference seismic tomography was performed using travel time data from a carbon sequestration site at the Aneth oil field in southeast Utah as part of a Department of Energy initiative on monitoring, verification, and accounting (MVA) of sequestered CO2. A total of 1,211 seismic events were recorded from a borehole array consisting of 22 geophones. Artificial velocity models were created to determine the ease with which different CO2 plume locations and sizes can be detected. Most likely because of the poor geophone arrangement, a low velocity zone in the Desert Creek reservoir can only be detected when regions of test site containing the highest ray path coverage are considered. MVA accuracy and precision may be improved through the use of a receiver array that provides more comprehensive ray path coverage.

  17. An adaptive joint focal-mechanism inversion method for microseismic data: Application to Aneth CO2 Enhanced Oil Recovery Field (United States)

    Chen, Y.; Chen, T.; Huang, L.


    A good azimuthal coverage of geophones is essentially important for focal-mechanism inversion of passive seismic data. However, microseismic monitoring for CO2 injection-induced seisimicity using borehole geophones often suffers from a poor azimuthal coverage of geophones, leading to large uncertainties in inversion. The focal mechanisms of microseismic events occurred within a small region are often similar to one another. We develop an adaptive focal-mechanism inversion method to invert microseismic events with similar focal mechanisms. We first classify microseismic events with similar focal mechanisms into clusters, and then invert the events in a cluster with the same focal mechanism simultaneously. Such inversion strategy is capable of improving convergent rate and reducing inversion uncertainty with abundant data from different azimuths. We develop a new double-difference focal-mechanism inversion method to further improve focal-mechanism inversion by minimizing the residual between observed and synthetic waveforms for pairs of microseismic events at adjacent locations. Our new algorithm allows us to constrain the focal mechanisms among events adjacent to one another. We apply our new adaptive joint focal-mechanism inversion method to microseismic data acquired using a borehole geophone string at a CO2 enhanced oil recovery field in Aneth, Utah. We compare our inversion results with those obtained from inverting focal mechanism for each microseismic event independently, demonstrating that our new inversion method greatly reduce the inversion uncertainty caused by the limited azimuthal coverage of borehole geophones.

  18. Analisis Data Seismik Refraksi dengan Metode Generalized-Reciprocal

    Directory of Open Access Journals (Sweden)

    Ashadi Salim


    Full Text Available The analysis of seismic refraction data by the generalized reciprocal method can be used for delineating undulating refractors. The forward and reverse times of arrival at different geophones with XY distance along a refraction profile, are used for calculating time depth. The seismic wave velocity in refractor may be obtained from velocity analysis function, and the depth of refractor under each geophone is obtained from time-depths function. This method has been applied at one line of seismic refraction measurement that was 440 m long with 45 geophone positions. The measurement obtained 20 m as the optimum XY-value and 2250 m/sas the velocity of seismic wave in refractor, and the undulating refractor topography with the depths varies 10.4 – 22.1 m. The optimum XY-value was obtained from approximate calculation derived from the observation, thatwas indicated the absent of undetected layer.

  19. Investigating the seismic signal of elephants: using seismology to mitigate elephant human conflict (United States)

    Webb, S. J.; Manzi, M.; Naidoo, A.; Raveloson, A.


    Human interactions with wild elephants are often a source of conflict, as elephants invade inhabited lands looking for sustenance. In order to mitigate these interactions, a number of elephant defense systems are under development. These include electric fences, bees and the playback of warning calls recorded from elephants. With the discovery that elephants use seismic signals to communicate (O'Connell-Rodwell et al., 2006, Behav. Ecol. Sociobiol.), it is hoped that seismic signals can also be used to help reduce conflict. Our current research project investigates the spectral content of the elephant seismic signal that travels through the ground using a variety of geophones and seismometers. Our experimental setup used a Geometrics Geode 24 channel seismic system with an array of 24 geophones spaced 1 m apart in an area of compact soil overlying weathered granites. Initially we used 14 Hz vertical geophones. The ground and ambient noise conditions were characterized by recording several hammer shots. These were used to identify the air wave, wind noise, and the direct wave, which had a dominant frequency of ~50 Hz. Several trained elephants that 'rumble' on command were then deployed ~5 m perpendicular to a line of 24 (14 Hz) vertical geophones between the 1 and 10 m geophone positions. We recorded a number of different elephants and configurations, and digitally recorded video for comparison. An additional deployment of 20 (14 Hz) horizontal geophones was also used. For all data, the sample interval was 0.25 ms and the recording length was 16 s as the timing of the rumbles could not be precisely controlled. We were able to identify the airwave due to the elephant's rumble with velocities between 305-310 m/s and the ground seismic signal due to the rumble with frequencies between 20-30 Hz. Our next experiment will include broadband seismometers at a further distance, to more fully characterize the frequency content of the elephant signal.

  20. Monitoring the Groningen gas field by seismic noise interferometry (United States)

    Zhou, Wen; Paulssen, Hanneke


    The Groningen gas field in the Netherlands is the world's 7th largest onshore gas field and has been producing from 1963. Since 2013, the year with the highest level of induced seismicity, the reservoir has been monitored by two geophone strings at reservoir level at about 3 km depth. For borehole SDM, 10 geophones with a natural frequency of 15-Hz are positioned from the top to bottom of the reservoir with a geophone spacing of 30 m. We used seismic interferometry to determine, as accurately as possible, the inter-geophone P- and S-wave velocities from ambient noise. We used 1-bit normalization and spectral whitening, together with a bandpass filter from 3 to 400 Hz. After that, for each station pair, the normalized cross-correlation was calculated for 6 seconds segments with 2/3 overlap. These segmented cross-correlations were stacked for every 1 hour, 24(hours)*33(days) segments were obtained for each station pair. The cross-correlations show both day-and-night and weekly variations reflecting fluctuations in cultural noise. The apparent P-wave travel time for each geophone pair is measured from the maximum of the vertical component cross-correlation for each of the hourly stacks. Because the distribution of these (24*33) picked travel times is not Gaussian but skewed, we used Kernel density estimations to obtain probability density functions of the travel times. The maximum likelihood travel times of all the geophone pairs was subsequently used to determine inter-geophone P-wave velocities. A good agreement was found between our estimated P velocity structure and well logging data, with difference less than 5%. The S-velocity structure was obtained from the east-component cross-correlations. They show both the direct P- and S-wave arrivals and, because of the interference, the inferred S-velocity structure is less accurate. From the 9(3x3)-component cross-correlations for all the geophone pairs, not only the direct P and S waves can be identified, but also

  1. Can the flow dynamics of debris flows be identified from seismic data? (United States)

    Kean, J. W.; Coe, J. A.; Smith, J. B.; Coviello, V.; McCoy, S. W.


    There is growing interest in the use of seismic and acoustic data to interpret a variety of geomorphic processes including landslides and debris flows. This measurement technique is attractive because a broad area can be monitored from a safe distance, unlike more direct methods of instrumentation, which are restricted to known flow paths and are vulnerable to damage by the flow. Previous work has shown that measurements of ground vibrations are capable of detecting the timing, speed, and location of landslides and debris flows. A remaining question is whether or not additional flow properties, such as basal stress, impact force, or flow magnitude can be inferred reliably from seismic data. This question has been difficult to answer, because detailed, independent measurements of flow dynamics are lacking. Here, we explore characteristics of debris-flow induced ground vibrations using new data from the Chalk Cliffs monitoring site in central Colorado. Monitoring included a heavily instrumented cross-section consisting of two tri-axial geophones to record ground vibrations (at 333 Hz), a small, 225 cm2 force plate to record basal impact forces (at 333 Hz), a laser distance meter to record flow stage over the plate (at 10 Hz), and a high definition camera to record flow dynamics (at 24 Hz). One geophone (A) was mounted on a boulder partially buried in colluvium; the other (B) was mounted directly to weathered bedrock typical of the site. This combination of instrumentation allowed us to compare the spectral response of different geophone installations to independently measured flow depth and basal impact force. We also compared the response of the geophones to surges that flowed over a sediment-covered bed (40-cm thick) to surges that flowed over a bare bedrock channel. Preliminary results showed that site conditions have a large effect on recorded debris-flow vibrations. The seismic signature of debris flow was very different between the geophones, with geophone B

  2. The planar silicon-based microelectronic technology for electrochemical transducers (United States)

    Novikov, A. V.; Egorchikov, A. E.; Dolgov, A. N.; Gornev, E. S.; Popov, V. G.; Egorov, I. V.; Krishtop, V. G.


    We have developed the new technology for production of sensitive modules for electrochemical sensors of pressure and acceleration. The technology is applicable for mass production and scalable for high-volume production. In this work we demonstrate the new sensing module for electrochemical motion sensors, and its possibility of applying in geophones. We fabricated prototypes of electrochemical planar transducer chips, produced a laboratory prototype of a geophone based on our planar transducer chip, and tested them. This paper presents the preliminary results of the tests.

  3. Rapid Growth of China Petroleum Machinery Manufacturing (continued)

    Institute of Scientific and Technical Information of China (English)

    Huang Zhiqian; Sun Zuchen; Wang Keyu


    @@ Technology for petroleum machinery design and manufacturing upgraded remarkably The basic research on rock bit. drilling pump. pump valve, piston, flooding pumps, derrick, shale shaker.hydraulic blowout preventer, torque converter, pumping unit. sucker rod. submersible pump. fracturing pump centrifugal pump. pneumatic parts, geophone and acquisition station has reached the advanced international level.

  4. Microtremor sequences and tilting in a deep mine

    Energy Technology Data Exchange (ETDEWEB)

    McGarr, A.; Green, R.W.E.


    Reports a study of foreshocks, aftershocks and the corresponding rock deformation associated with two tremors of magnitude 1.5 and 1.2. A small highly sensitive array of geophones was used and the deformation was monitored with a tiltmeter in close proximity to the hypocentres. No indications of instability developing before either of the tremors was found.

  5. Tomographic inversion of near-surface Q factor by combining surface and cross-hole seismic surveys (United States)

    Li, Guo-Fa; Zheng, Hao; Zhu, Wen-Liang; Wang, Ming-Chao; Zhai, Tong-Li


    The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer. We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation. In this study, we drilled number of receiver holes around the source hole, each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys. We also propose a novel tomographic inversion of the Q factor without the effect of the source signature, and examine its stability and reliability using synthetic data. We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield. The results show that seismic absorption in the near-surface layer is much greater than that in the subsurface strata. Thus, it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption. In addition, we derive different Q factors from two frequency bands, which can be treated, to some extent, as evidence of a frequency-dependent Q.

  6. Mobile seismic exploration (United States)

    Dräbenstedt, A.; Cao, X.; Polom, U.; Pätzold, F.; Zeller, T.; Hecker, P.; Seyfried, V.; Rembe, C.


    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

  7. Mobile seismic exploration

    Energy Technology Data Exchange (ETDEWEB)

    Dräbenstedt, A., E-mail:, E-mail:, E-mail:; Seyfried, V. [Research & Development, Polytec GmbH, Waldbronn (Germany); Cao, X.; Rembe, C., E-mail:, E-mail:, E-mail: [Institute of Electrical Information Technology, TU Clausthal, Clausthal-Zellerfeld (Germany); Polom, U., E-mail:, E-mail:, E-mail: [Leibniz Institute of Applied Geophysics, Hannover (Germany); Pätzold, F.; Hecker, P. [Institute of Flight Guidance, TU Braunschweig, Braunschweig (Germany); Zeller, T. [Clausthaler Umwelttechnik Institut CUTEC, Clausthal-Zellerfeld (Germany)


    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDV measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.

  8. Frequency Content of Ambient Seismic Noise in North-Central Illinois (United States)

    Higuera-Diaz, I. C.; Carpenter, P. J.


    High and low-frequency ground motion vibration measurements were made in DeKalb and Kane Counties, Illinois, to characterize different sources of seismic noise and determine directions and magnitude of motion produced by each source. The Seismic Analysis Code 2000 (SAC2000) was used to process seismic noise data recorded with a low-frequency digital system,, earthquake records downloaded from the WILBER Web site, and noise data recorded by an engineering seismograph with high-frequency geophones. Power-spectral density estimates were computed from an autocorrelation series in most cases. Using the power density spectra routine of SAC2000, selecting autocorrelation windows of 20 s for the low-frequency data and 2 s for the high-frequency data, we have found distinctive seismic noise peaks among the different sites, regardless of the background noise level. The earthquake low-frequency data showed a microseism peak at a frequency of 0.2 Hz for stations located in the Midwestern U.S. Microseism peak frequency did not decrease with increasing distance from Lake Michigan, suggesting the lake is not the primary source of the microseisms, which may be generated in ocean basins. Ambient ground motion recorded by the Northern Illinois University seismic station with a 2 Hz natural period seismometer exhibited peaks around 0.8 and 2.2 Hz. Ground motion from trains, traffic, air-conditioning units and water pumping equipment was recorded with an engineering seismograph. Vertical geophones of natural frequency 2, 8, and 50 Hz were used, as well as a 4.5 Hz horizontal geophone. Train noise exhibits strong peaks in the 5-10 Hz range, both for the vertical and horizontal geophones. Noise peaks at 25, 60, 90 and 115 Hz are probably related to traffic, electrical transformers, and air-conditioning units. Measurements made near a sewage treatment plant in DeKalb showed peaks at 10, 30, 93, and 109 Hz, probably related to pumping and mechanical equipment. Seismic noise collected

  9. Active and passive seismic investigations in Alpine Permafrost at Hoher Sonnblick (Austria) (United States)

    Steiner, Matthias; Maierhofer, Theresa; Pfeiler, Stefan; Chwatal, Werner; Behm, Michael; Reisenhofer, Stefan; Schöner, Wolfgang; Straka, Wolfgang; Flores Orozco, Adrian


    Different geophysical measurements have been applied at the Hoher Sonnblick study area to gain information about permafrost distribution as well as heterogeneities controlling heat circulation, in the frame of the ÖAW-AtmoPerm project, which aims at the understanding the impacts of atmospheric extreme events on the thermal state of the active layer. Electrical Resistivity Tomography (ERT) has been widely accepted as a suitable method to characterize permafrost processes; however, limitations are imposed due to the challenges to inject high current densities in the frozen periods and the loss of resolution of electrical images at depth require the application of further geophysical methods. To overcome such problems, we investigate here the application of active and seismic methods. Seismic campaigns were performed using permanent borehole and temporarily installed surface geophones. A total of 15 borehole geophones are installed at depths of 1 m, 2 m, 5 m, 10 m and 20 m in three boreholes which are separated by a horizontal distance of 30 m between each other. Active measurements utilized 41 surface and 15 borehole geophones and a total of 199 excitation points. Surface geophones were laid out along two crossing lines with lengths of 92 m and 64 m, respectively. The longer line was placed directly along the borehole transect and the shorter one was oriented perpendicular to it. Hammer blows were performed with a spacing of 1 m inline the geophones and 4 m in crosslines rotated by 45 degrees, permitting 3D acquisition geometry. In addition to the active sources, data loggers connected to the borehole geophones permitted the collection of continuous 36-hours datasets for two different thermal conditions. Seismic ambient noise interferometry is applied to this data and aims at the identification of velocity changes in the subsurface related to seasonal changes of the active layer. A potential source of ambient seismic energy is the noise excited by hikers and the

  10. Polar Seismic TETwalker: Integrating Engineering Teaching and Research (United States)

    Gifford, C. M.; Ruiz, I.; Carmichael, B. L.; Wade, U. B.; Agah, A.


    Based on the TETwalker robot platform at NASA/Goddard Space Flight Center, the Center for Remote Sensing of Ice Sheets (CReSIS) has begun work on designing and modeling the integration of seismic surveying equipment into the TETwalker robot architecture for use in polar environments. Employing multiple Seismic TETwalker robots will allow gathering of polar seismic data in previously inaccessible or unexplored terrains, as well as help significantly reduce human involvement in such harsh environments. NASA's TETwalker mobile robot uses a unique form of mobility to topple across the surface and over obstacles. This robot therefore does not suffer the fate of other wheeled and tracked robots if tipped over. It is composed of extending struts and nodes, forming a tetrahedral shape which can be strategically adjusted to change the robot's center of gravity for toppling. Of the many platforms the TETwalker architecture can form, the 4-TETwalker robot (consisting of four ground nodes, a center payload node, and interconnecting struts) has been the focus of current research. The center node has been chosen as the geophone deployment medium, designed in such a way to allow geophone insertion using any face of the robot's structure. As the robot comes to rest at the deployment location, one of its faces will rest on the surface. No matter which side it is resting on, a geophone spike will be perpendicular to its face and an extending strut will be vertical for pushing the geophone into the ground. Lengthening and shortening struts allow the deployment node to precisely place the geophone into the ground, as well as vertically orient the geophones for proper data acquisition on non-flat surfaces. Power source integration has been investigated, incorporating possible combinations of solar, wind, and vibration power devices onboard the robot models for long-term survival in a polar environment. Designs have also been modeled for an alternate center node sensor package (e

  11. New means for extending the capacity for graphic presentation and for increasing the calculation power of mine dispatching systems. Part I

    Energy Technology Data Exchange (ETDEWEB)

    Kuciara, I.; Juzwa, J.; Oset, K.; Rozynek, W.; Sicinski, K. (Centrum Mechanizacji i Automstyzacji Gornictwa EMAG (Poland). Zaklad Systemow Dyspozytorskich)


    Characterizes computerized dispatcher systems developed for the needs of coal mines. Five systems developed and produced by the EMAG center and used in Polish coal mines are presented. The ARAMIS system detects, records and analyzes microseismic events according to preset parameters. The ARES systems records seismo-acoustic events sensed by geophones in order to calculate parameters of rock body shocks and fractures. The PASAT seismic apparatus uses geophone signals to determine rock body stress, strength, compactness and geologic nonuniformity. The systems are programmed in the TURBO PASCAL language and use 80x86 assemblers. The MIKROHADES and SKRZ systems for production process control and crew movement monitoring are also described. Hardware and software configuration is described. Application of computer networks and multi-access is discussed. It is concluded that the possibility of using communication controllers with the ASYNC, BCS and SDLC protocols is essential for dispatcher systems.

  12. Analysis of acoustic to seismic coupling technique for buried landmines detection

    Institute of Scientific and Technical Information of China (English)

    WANG Chi; XIE Yulai; LI Xingfei; SUN Fei; ZHANG Guoxiong


    The mechanical interaction between the induced seismic waves and landmines was analyzed according to acoustic-to-seismic coupling theory. And a geophone array based exper-imental system for landmine detection was developed. By modeling a compliant mine and the soil on top of the mine as a mass-spring system, analytic method was adopted to study the resonance mechanism of the system. A loudspeaker was employed as energy source to excite a swept sine tone over the soil. We also used a geophone array to measure the vibration velocity of the ground surface. In order to analysis the landmine effect on the surface vibration, the magnitude spectra curves of the measured velocity values on-and-off mine were plotted. The results showed that the data measured on mine is much bigger than that off target and the proposed system can be applied to further investigation of acoustic landmines detection.

  13. Noise characterization in SWD survey; SWD ni okeru noise ni kansuru kento

    Energy Technology Data Exchange (ETDEWEB)

    Tsuru, T.; Ozawa, T. [Japan National Oil Corp., Tokyo (Japan)


    SWD (Seismic While Drilling) is located as one kind of the reverse VSP (Vertical Seismic Profiling) technology, and a working drill-bit is used as its energy-source. The SWD is carried out for a check-shot survey as well as a prediction ahead of the bit. The largest advantage of the SWD technology may be a prediction, while drilling, of a drilling hazard such as an abnormal pressure zone. On the other hand, a serious disadvantage exists in the data quality due to a contamination by large noises generated from a working rig, because the SWD survey is done `while drilling`. Regarding the characteristics of these noises, especially the noise received by surface geophones has not been clarified quantitatively yet. Through several field experiments, the authors have evaluated the characteristics. In this paper, the dominant frequency range of the surface geophone noise is discussed. Furthermore, the noise from the mud motor is also discussed. 9 refs., 13 figs.

  14. Microseismic Monitoring of CO2 Injection at the Penn West Enhanced Oil Recovery Pilot Project, Canada: Implications for Detection of Wellbore Leakage (United States)

    Martínez-Garzón, Patricia; Bohnhoff, Marco; Kwiatek, Grzegorz; Zambrano-Narváez, Gonzalo; Chalaturnyk, Rick


    A passive seismic monitoring campaign was carried out in the frame of a CO2-Enhanced Oil Recovery (EOR) pilot project in Alberta, Canada. Our analysis focuses on a two-week period during which prominent downhole pressure fluctuations in the reservoir were accompanied by a leakage of CO2 and CH4 along the monitoring well equipped with an array of short-period borehole geophones. We applied state of the art seismological processing schemes to the continuous seismic waveform recordings. During the analyzed time period we did not find evidence of induced micro-seismicity associated with CO2 injection. Instead, we identified signals related to the leakage of CO2 and CH4, in that seven out of the eight geophones show a clearly elevated noise level framing the onset time of leakage along the monitoring well. Our results confirm that micro-seismic monitoring of reservoir treatment can contribute towards improved reservoir monitoring and leakage detection. PMID:24002229

  15. Microseismic Monitoring of CO2 Injection at the Penn West Enhanced Oil Recovery Pilot Project, Canada: Implications for Detection of Wellbore Leakage

    Directory of Open Access Journals (Sweden)

    Gonzalo Zambrano-Narváez


    Full Text Available A passive seismic monitoring campaign was carried out in the frame of a CO2-Enhanced Oil Recovery (EOR pilot project in Alberta, Canada. Our analysis focuses on a two-week period during which prominent downhole pressure fluctuations in the reservoir were accompanied by a leakage of CO2 and CH4 along the monitoring well equipped with an array of short-period borehole geophones. We applied state of the art seismological processing schemes to the continuous seismic waveform recordings. During the analyzed time period we did not find evidence of induced micro-seismicity associated with CO2 injection. Instead, we identified signals related to the leakage of CO2 and CH4, in that seven out of the eight geophones show a clearly elevated noise level framing the onset time of leakage along the monitoring well. Our results confirm that micro-seismic monitoring of reservoir treatment can contribute towards improved reservoir monitoring and leakage detection.

  16. Microseismic monitoring of CO2 injection at the Penn West Enhanced Oil Recovery pilot project, Canada: implications for detection of wellbore leakage. (United States)

    Martínez-Garzón, Patricia; Bohnhoff, Marco; Kwiatek, Grzegorz; Zambrano-Narváez, Gonzalo; Chalaturnyk, Rick


    A passive seismic monitoring campaign was carried out in the frame of a CO2-Enhanced Oil Recovery (EOR) pilot project in Alberta, Canada. Our analysis focuses on a two-week period during which prominent downhole pressure fluctuations in the reservoir were accompanied by a leakage of CO2 and CH4 along the monitoring well equipped with an array of short-period borehole geophones. We applied state of the art seismological processing schemes to the continuous seismic waveform recordings. During the analyzed time period we did not find evidence of induced micro-seismicity associated with CO2 injection. Instead, we identified signals related to the leakage of CO2 and CH4, in that seven out of the eight geophones show a clearly elevated noise level framing the onset time of leakage along the monitoring well. Our results confirm that micro-seismic monitoring of reservoir treatment can contribute towards improved reservoir monitoring and leakage detection.

  17. On the inverse seismic problem for horizontally layered media: Subsidiary study (United States)

    Cuer, Michel; Petit, Jean Louis

    The starting point of this work is the inversion of vertical seismic profiling (VSP) data. The usual processing of VSP data by inverse techniques is restricted to 1D propagation model. In this case, the parameters to identify are the acoustic impedance as function of travel time and the seismic source so that we have as unknowns two functions of one variable and as data a function of two variables, the time and the depth positions of geophones. The problem is thus largely overdetermined and an elementary mathematical analysis can be made. The source is modelled as a boundary condition at the top of the geophones zone. So this boundary condition replaces the true source function and the medium parameters above the geophones zone. The question asked by V. Richard from IFP was the "management" of this unknown source when 3D propagation effects are taken into account in horizontally layered medium where the propagation equations are parametrized by the k parameter of the Hankel transform. Now we think that the answer is that it is impossible to work round the fact that there are at least two unknown functions, the source and the medium parameters above the geophones zone. During this study, we have searched for some non local boundary conditions and this was the opportunity to obtain some results on exact transparent conditions for 3D propagation in 1D media (preliminary communication was made by Petit and Cuer (1994)) and on the discretization of such conditions in the acoustic case (preliminary communication was made by Cuer and Petit (1995)). This is the mathematical substance of this work in which the Poisson summation formula is used to prove the stability of a discrete non local boundary condition.

  18. Strong Motion Studies in the Mines of Kolar Gold Fields (United States)


    Soil Dyn. And Earthq.Eng. 10: (8), 423–428. Uhrhammer, R.A. and Bolt, B.A. (1991). “ the Seismic magnitude of the 1989 Loma Prieta Main Shock...rockburst is its Richter’s local magnitude. It was not possible from the records of geophone due to saturation effect . A strong-motion accelerograph has...magnitude. However, it has not been possible from the records of conventional seismographs due to saturation effect . The rockbursts had been

  19. Multichannel analysis of surface wave method with the autojuggie (United States)

    Tian, G.; Steeples, D.W.; Xia, J.; Miller, R.D.; Spikes, K.T.; Ralston, M.D.


    The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the 'autojuggie') is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys. ?? 2003 Elsevier Science Ltd. All rights reserved.

  20. Bedload transport monitoring with acoustic sensors in the Swiss Albula mountain river (United States)

    Rickenmann, Dieter; Antoniazza, Gilles; Wyss, Carlos R.; Fritschi, Bruno; Boss, Stefan


    Bedload transport measurements with acoustic sensors were obtained during summer 2015 in the Albula River in Switzerland. An impact plate measuring system was used with geophone and accelerometer sensors. This system provides indirect estimations of bedload transport in water courses. In April 2015, 30 impact sensors were installed in a new permanent measuring station to monitor continuously bedload transport in a mountain river with a large annual rate of sediment transport (around 90 000 m3 yr-1). Records of the first year of measurement showed that (i) the signal response in terms of geophone and accelerometer impulses is comparable for both types of sensors; (ii) there is a good correlation between discharge data and impulses recorded by both types of sensors; (iii) the critical discharge at the start of bedload transport is around 5 m3 s-1; (iv) a mean calibration factor for the geophone impulses can be estimated which is in a similar range as values determined from other sites with field calibration measurements.

  1. Monitoring El Hierro submarine volcanic eruption events with a submarine seismic array (United States)

    Jurado, Maria Jose; Molino, Erik; Lopez, Carmen


    A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2012 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. From the beginning of the eruption a geophone string was installed less than 2 km away from the new volcano, next to La Restinga village shore, to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. The analysis of the dataset using spectral techniques allows the characterization of the different phases of the eruption and the study of its dynamics. The correlation of the data analysis results with the observed sea surface activity (ash and lava emission and degassing) and also with the seismic activity recorded by the IGN field seismic monitoring system, allows the identification of different stages suggesting the existence of different signal sources during the volcanic eruption and also the posteruptive record of the degassing activity. The study shows that the high frequency capability of the geophone array allow the study of important features that cannot be registered by the standard seismic stations. The accumulative spectral amplitude show features related to eruptive changes.

  2. Results of vertical seismic profiling at Well 46-28, Rye Patch Geothermal Field, Pershing County, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Feighner, M.A.; Daley, T.M.; Majer, E.L.


    A Vertical Seismic Profile (VSP) was recorded in Rye Patch by LBNL between December 11 and December 13, 1997. Figure 1 shows the location of the Rye Patch Geothermal Field with Well 46-28 located within the marked Rye Patch Anomaly. The VSP in Well 46-28 used a vibroseis source and a single-level, high temperature, hydraulic wall-locking, 3-component seismometer. The vibroseis source was a Mertz P-wave vibrator. The source sweep was 10 Hz to 80 Hz, 10 seconds long, with a 0.2 s cosine taper. The borehole geophone was an SSC model LVHK 6001 using 14 Hz geophones. The recording system was a Geometrics Strataview. Six data channels were recorded: the three geophones, the source pilot, the vibrator reference and the vibrator baseplate accelerometer. The record length was 12,288 samples at a 1 ms sample rate, giving a 2.3 s correlated record length. A 10 Hz low cut filter was used and no high cut filter was used except the anti-alias filter. Results are described.

  3. Transformation of Ground Vibration Signal for Debris-Flow Monitoring and Detection in Alarm Systems

    Directory of Open Access Journals (Sweden)

    José Moya


    Full Text Available Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing debris flows. However, the recording of geophone signals usually requires storing a huge amount of data, which leads to problems in storage capacity and power consumption. This paper presents a method to transform and simplify the signals measured by geophones. The key input parameter is the ground velocity threshold, which removes the seismic noise that is not related to debris flows. A signal conditioner was developed to implement the transformation and the ground velocity threshold was set by electrical resistors. The signal conditioner was installed at various European monitoring sites to test the method. Results show that data amount and power consumption can be greatly reduced without losing much information on the main features of the debris flows. However, the outcome stresses the importance of choosing a ground vibration threshold, which must be accurately calibrated. The transformation is also suitable to detect other rapid mass movements and to distinguish among different processes, which points to a possible implementation in alarm systems.

  4. Analysis of the ground vibration produced by debris flows and other torrential processes at the Rebaixader monitoring site (Central Pyrenees, Spain

    Directory of Open Access Journals (Sweden)

    C. Abancó


    Full Text Available The use of ground vibration sensors for debris-flow monitoring has increased in the last two decades. However, the correct interpretation of the seismic signals produced by debris flows still presents many uncertainties. In the Rebaixader monitoring site (Central Pyrenees, Spain two different ground vibration stations with different characteristics in terms of recording systems and site-specific factors have been compared. The shape of the time series has been recognised as one of the key parameters to identify events and to distinguish between different types of torrential processes. The results show that the site-specific factors strongly influence on the ground vibration registered at each geophone. The attenuation of the signal with the distance has been identified as linear to exponential. In addition, the assembly of the geophones to the terrain also has an important effect on the amplification of the signal. All these results highlight that the definition of ground vibration thresholds for debris-flow detection or warning purposes is a difficult task which is clearly influenced by site-specific conditions of the geophones.

  5. Transformation of ground vibration signal for debris-flow monitoring and detection in alarm systems. (United States)

    Abancó, Clàudia; Hürlimann, Marcel; Fritschi, Bruno; Graf, Christoph; Moya, José


    Debris flows are fast mass movements formed by a mix of water and solid materials, which occur in steep torrents, and are a source of high risks for human settlements. Geophones are widely used to detect the ground vibration induced by passing debris flows. However, the recording of geophone signals usually requires storing a huge amount of data, which leads to problems in storage capacity and power consumption. This paper presents a method to transform and simplify the signals measured by geophones. The key input parameter is the ground velocity threshold, which removes the seismic noise that is not related to debris flows. A signal conditioner was developed to implement the transformation and the ground velocity threshold was set by electrical resistors. The signal conditioner was installed at various European monitoring sites to test the method. Results show that data amount and power consumption can be greatly reduced without losing much information on the main features of the debris flows. However, the outcome stresses the importance of choosing a ground vibration threshold, which must be accurately calibrated. The transformation is also suitable to detect other rapid mass movements and to distinguish among different processes, which points to a possible implementation in alarm systems.

  6. Locating Microseismic Events Using Fat-Ray Double-Difference Tomography for Monitoring CO2 Injection at the Aneth EOR Field (United States)

    Chen, T.; Huang, L.; Rutledge, J. T.


    During CO2 injection, the increase in pore pressure and volume may change stress distribution in the field, and induce microseismic events as brittle failure on small faults or fractures. An accurate location of these induced microseismic events can help understand the migration of CO2 and stress evolution in the reservoir. A geophone string spanning 800-1700 m in depth was cemented into a monitoring well at the Aneth oil field in Utah in 2007 for monitoring CO2 injection for enhanced oil recovery (EOR). The monitoring continued till 2010. A total of 24 geophone levels recorded induced microseismic events, including 18 levels of three-component geophones and six vertical-component levels spaced 106.7 m (350 ft) apart to take full advantage of the entire array aperture. We apply a fat-ray double-difference tomography method to microseismic data acquired at the Aneth EOR field. We obtain high-precision locations of microseismic events and improve the velocity structure simultaneously. We demonstrate the improvements by comparing our results with those obtained using the conventional double-difference tomography.

  7. Passive acoustic monitoring of bed load discharge in a large gravel bed river (United States)

    Geay, T.; Belleudy, P.; Gervaise, C.; Habersack, H.; Aigner, J.; Kreisler, A.; Seitz, H.; Laronne, J. B.


    Surrogate technologies to monitor bed load discharge have been developed to supplement and ultimately take over traditional direct methods. Our research deals with passive acoustic monitoring of bed load flux using a hydrophone continuously deployed near a river bed. This passive acoustic technology senses any acoustic waves propagated in the river environment and particularly the sound due to interparticle collisions emitted during bed load movement. A data set has been acquired in the large Alpine gravel-bedded Drau River. Analysis of the short-term frequency response of acoustic signals allows us to determine the origin of recorded noises and to consider their frequency variations. Results are compared with ancillary field data of water depth and bed load transport inferred from the signals of a geophone array. Hydrophone and geophone signals are well correlated. Thanks to the large network of deployed geophones, analysis of the spatial resolution of hydrophone measurements shows that the sensor is sensitive to bed load motion not only locally but over distances of 5-10 m (10-20% of river width). Our results are promising in terms of the potential use of hydrophones for monitoring bed load transport in large gravel bed rivers: acoustic signals represent a large river bed area, rather than being local; hydrophones can be installed in large floods; they can be deployed at a low cost and provide continuous monitoring at high temporal resolution.

  8. Wind-induced ground motion (United States)

    Naderyan, Vahid; Hickey, Craig J.; Raspet, Richard


    Wind noise is a problem in seismic surveys and can mask the seismic signals at low frequency. This research investigates ground motions caused by wind pressure and shear stress perturbations on the ground surface. A prediction of the ground displacement spectra using the measured ground properties and predicted pressure and shear stress at the ground surface is developed. Field measurements are conducted at a site having a flat terrain and low ambient seismic noise. Triaxial geophones are deployed at different depths to study the wind-induced ground vibrations as a function of depth and wind velocity. Comparison of the predicted to the measured wind-induced ground displacement spectra shows good agreement for the vertical component but significant underprediction for the horizontal components. To validate the theoretical model, a test experiment is designed to exert controlled normal pressure and shear stress on the ground using a vertical and a horizontal mass-spring apparatus. This experiment verifies the linear elastic rheology and the quasi-static displacements assumptions of the model. The results indicate that the existing surface shear stress models significantly underestimate the wind shear stress at the ground surface and the amplitude of the fluctuation shear stress must be of the same order of magnitude as the normal pressure. Measurement results show that mounting the geophones flush with the ground provides a significant reduction in wind noise on all three components of the geophone. Further reduction in wind noise with depth of burial is small for depths up to 40 cm.

  9. Application of wireless sensor system on security network (United States)

    Oh, Sechang; Kwon, Hyeokjun; Yoon, Hargsoon; Varadan, Vijay K.


    In this research we developed wireless sensor system for security application. We have used geophone to detect seismic signals which are generated by footsteps. Geophones are resonant devices. Therefore, vibration on the land can generate seismic waveforms which could be very similar to the signature by footstep. The signals from human footstep have weak signals to noise ratio and the signal strength is subject to the distance between the sensor and human. In order to detect weak signals from footstep, we designed and fabricated 2-stage amplification circuit which consists of active and RC filters and amplifiers. The bandwidth of filter is 0.7Hz-150Hz and the gain of amplifier is set to 1000. The wireless sensor system also developed to monitor the sensing signals at the remote place. The wireless sensor system consists of 3 units; a wireless sensor unit, a wireless receiver unit, and a monitoring unit. The wireless sensor unit transmits amplified signals from geophone with Zigbee, and the wireless receiver unit which has both Zigbee and Wi-Fi module receives signals from the sensor unit and transmits signals to the monitoring system with Zigbee and Wi-Fi, respectively. By using both Zigbee and Wi-Fi, the wireless sensor system can achieve the low power consumption and wide range coverage.

  10. A very low-cost and adaptable DIY seismic station (United States)

    Mendez Chazara, Nahum; Castiñeiras, Pedro


    With the advent of prototyping platforms and low-cost computers, geological do-it-yourself components and sensors can be quickly and inexpensively built. The design of the prototype can also be improved over several iterations, from high-resolution magnetometers to vertical electrical sounding instruments, opening new opportunities to gather data in the field or in the lab. One of the possibilities in the field of DIY geology is seismological research, because the availability and diversity of the parts used can come in handy when developing an instrument. Also, they are really easy to build without a very deep electronics background. Although the range in low-cost seismometers is usually restricted to local seismology, induced seismology or human activities, our approach is able to record data with sampling rates up to 500 Hz. It can record and analyze data with a resolution of 16-bit, but it can be regulated to reach 24-bit if needed. Data transfer can operate all-day with low power consumption, using around 1-Amp per hour, or even less, depending on the final setup chosen. Our first seismograph (vertical geophone with a natural frequency of 10 Hz, an Arduino or similar board, a 16-bit ADC capable of amplify and convert the output signal of the geophone. The latter, connected to a Raspberry Pi, gathers the data from the geophone using a Python script, slices it in 1-hour intervals and draws waveform and frequency spectrum graph for quick analysis with Matplotlib, a common graphing library in Python. The data can be gathered using several methods: If a Wi-Fi network is available, the instrument can be directly connected to the Internet and the data uploaded in real time. If there is no such connection available, a GSM shield can be used to upload the data, and in the worst-case scenario, the data can be accessed directly on the field via Wi-Fi or Ethernet connection if the location of the sensor make unable to connect via WiFi or GSM. Obviously, there can be also

  11. Innovative Bed Load Measurement System for Large Alpine Gravel-Bed Rivers (United States)

    Seitz, H.; Habersack, H. M.


    The aim of the work is to figure out the bed load transport processes using direct and surrogate measurement methods for the free flowing reach of the Drau River and its most important tributary Isel River, both large Alpine gravel-bed rivers, situated in the south western part of Austria. There are some techniques for bed load measurements in natural streams; we used collecting moving particles and indirectly determining transport intensity at the study sites. Former measurements in the study reach were performed also using mobile bed load samplers and fixed bed load samplers. Individually they all are adequate bed load measurement instruments - used in combination they are complementing one another, whereas each applied separately leads to specific deficits. The investigation payed special attention on results out of the geophone installations, whereas steel plate vibrations (the plates are mounted on top of concrete structures even with the river bed surface) caused by bed load particles with a diameter larger than about 20 mm are inducing a signal into the geophones. The signal above a defined threshold voltage than is recorded in a computer system as the sum of impacts during one minute intervals. The spatio-temporal distribution of the transported bed load material, its amount and the transport processes itself could be figured out for the first time out of continuous data collection since 2006 for large alpine gravel-bed rivers. Before building up the gauging stations there were no continuous recordings of bed load transport processes in large alpine rivers over their entire cross section, hence the investigation promises a better process understanding and the possibility to determine bed load transport rates and a rough approximation of the grain size distributions of the transported bed load material under different flow conditions. A relation between detected geophone records, the flow discharge and direct bed load sampling methods (Large Helley Smith

  12. Advanced array techniques for unattended ground sensor applications

    Energy Technology Data Exchange (ETDEWEB)

    Followill, F.E.; Wolford, J.K.; Candy, J.V.


    Sensor arrays offer opportunities to beam form, and time-frequency analyses offer additional insights to the wavefield data. Data collected while monitoring three different sources with unattended ground sensors in a 16-element, small-aperture (approximately 5 meters) geophone array are used as examples of model-based seismic signal processing on actual geophone array data. The three sources monitored were: (Source 01). A frequency-modulated chirp of an electromechanical shaker mounted on the floor of an underground bunker. Three 60-second time-windows corresponding to (a) 50 Hz to 55 Hz sweep, (b) 60 Hz to 70 Hz sweep, and (c) 80 Hz to 90 Hz sweep. (Source 02). A single transient impact of a hammer striking the floor of the bunker. Twenty seconds of data (with the transient event approximately mid-point in the time window.(Source 11)). The transient event of a diesel generator turning on, including a few seconds before the turn-on time and a few seconds after the generator reaches steady-state conditions. The high-frequency seismic array was positioned at the surface of the ground at a distance of 150 meters (North) of the underground bunker. Four Y-shaped subarrays (each with 2-meter apertures) in a Y-shaped pattern (with a 6-meter aperture) using a total of 16 3-component, high-frequency geophones were deployed. These 48 channels of seismic data were recorded at 6000 and 12000 samples per second on 16-bit data loggers. Representative examples of the data and analyses illustrate the results of this experiment.

  13. Seismic source characterisation of a Tunnel Boring Machine (TBM) (United States)

    Kreutzer, Ingrid; Brückl, Ewald; Radinger, Alexander


    The Tunnel Seismic While Drilling (TSWD) method aims at predicting continuously the geological situation ahead of the tunnel without disturbing the construction work. Thereby the Tunnel Boring Machine (TBM) itself is used as seismic source. The cutting process generates seismic waves radiating into the rock mass and vibrations propagating to the main bearing of the cutter head. These vibrations are monitored and used as pilot signal. For the processing and interpretation it was hypothesized so far that the TBM acts like a single force. To prove this assumption the radiation pattern of several TBM's under construction were investigated. Therefore 3-components geophones were installed at the surface, which were situated directly above the tunnel axes and also with lateral offset. Additional, borehole geophones were placed in the wall of one tube of a two-tube tunnel. The geophones collected the forward and backward radiated wave field, as the TBM, operating in the other tube, passed their positions. The obtained seismic data contains continuous records over a range of 600 m of the TBM position. The offsets vary from 25 m to 400 m and the frequency ranges from 20-250 Hertz. The polarisation of the p-wave and the s-wave and their amplitude ratio were determined and compared with modelled seismograms with different source mechanism. The results show that the description of the source mechanism by a single force can be used as a first order approximation. More complex radiation pattern including tensile forces and several source locations like the transmission of reaction forces over the gripper to the tunnel wall are further tested and addressed.

  14. Challenges in Microseismic Monitoring of Hydrualic Fracturing (United States)

    Venkataraman, A.; Li, R.


    To enhance well productivity, hydraulic fractures are stimulated by injecting fluid and/or gas with proppant into the rock matrix. This results in stress perturbations that induce fractures in the formation releasing minor amounts of seismic energy as microseismic events. Microseismicity can be recorded by properly positioned geophones and is one of the indirect methods that allow us to determine the actual volume of rock that was impacted during and after hydraulic fracturing. Specifically, microseismic data is acquired during hydro-fracture treatments to validate and assist completions, assist in placing wells in the formation, identify frac barriers, and to illuminate faults and potential fault re-activation. In the industry, microseismic data is acquired using geophones deployed in borehole and/or surface arrays. Borehole arrays are more traditional and have been used for nearly 20 years. Event location using borehole data is fairly robust, but azimuth and aperture are limited. Moreover, having dedicated boreholes can be expensive. The newer method of acquiring data is the use of geophones deployed on the surface or in shallow boreholes. Since microseismic events are very small (-4 to -0.5), surface records have weak P and S arrivals that are buried in the noise and traditional event location methods which use arrival time picks cannot be used. Migration based approaches which rely on the power of stacking waveforms is the common approach. However, poor signal-to-noise data and polarity in seismic waves generated by micro-earthquakes can result in uncertainty in event location. In this paper, we will discuss the pros and cons of both arrays, the status of the technology, its limitations and challenges. Specifically, we will focus on applications where industry-academic collaborations could lead to step changes in our understanding of the controls on microseismicity.

  15. Underwater Ambient Noise. Proceedings of a Conference Held at SACLANTCEN on 11-14 May 1982. Volume 2. Unclassified Papers. Part 1 (United States)


    20 S^-30 -40 CJ -50 -J-60 -70 -1 1 1 1 1 1 r I 80% HORIZONTAL GEOPHONE (a) 2 4 6 8 10 12 14 16 18 FREQUENCY [ HzJ ... TD 6457, 13 April 1981. 2. A. R, Milne and J. H. Ganton, "Ambient Noise Under Arctic-Sea Ice," J. Acoust. So. Am. Vol. 36, No. 5, May 1964. 3. R...Dwyer, "FRAM II Single Channel Ambient Noise Statistics," NUSC TD 6583, 25 November 1981. 4. R. Dwyer, "A Statistical Frequency Domain Signal

  16. Controlled Noise Seismology

    KAUST Repository

    Hanafy, Sherif M.


    We use controlled noise seismology (CNS) to generate surface waves, where we continuously record seismic data while generating artificial noise along the profile line. To generate the CNS data we drove a vehicle around the geophone line and continuously recorded the generated noise. The recorded data set is then correlated over different time windows and the correlograms are stacked together to generate the surface waves. The virtual shot gathers reveal surface waves with moveout velocities that closely approximate those from active source shot gathers.

  17. Linearized versus non-linear inverse methods for seismic localization of underground sources

    DEFF Research Database (Denmark)

    Oh, Geok Lian; Jacobsen, Finn


    The problem of localization of underground sources from seismic measurements detected by several geophones located on the ground surface is addressed. Two main approaches to the solution of the problem are considered: a beamforming approach that is derived from the linearized inversion problem...... Difference elastic wave-field numerical method. In this paper, the accuracy and performance of the linear beamformer and nonlinear inverse methods to localize a underground seismic source are checked and compared using computer generated synthetic experimental data. © 2013 Acoustical Society of America....

  18. Extracting 220 Hz information from 55 Hz field data by near-field superresolution imaging

    KAUST Repository

    Dutta, Gaurav


    Field experiments are used to unequivocally demonstrate seismic superresolution imaging of subwavelength objects in the near-field region of the source. The field test is for a conventional hammer source striking a metal plate near subwavelength scatterers and the seismic data are recorded by vertical-component geophones in the far-field locations of the sources. Time-reversal mirrors (TRMs) are then used to refocus the scattered energy with subwavelength resolution to the position of the original source. A spatial resolution of lambda/10, where lambda is the dominant wavelength associated with the data, is seen in the field tests that exceeds the Abbe resolution limit of lambda/2.

  19. Seismological studies at Cerro Prieto

    Energy Technology Data Exchange (ETDEWEB)

    Majer, E.L.; McEvilly, T.V.; Albores, A.; Diaz, S.C.


    A radio-telemetered 12-station seismographic network was operated in a dense-array configuration over the Cerro Prieto field as shown in Fig. 1. Horizontal and vertical 4.5-Hz geophones were deployed with interstation distances of order 1 km in a multi-purpose survey for microearthquake occurrence and possible anomalies in P- and S-wave velocities and attenuation associated with the field. Although data obtained thus far are limited, attenuation and velocity studies at Cerro Prieto show anomalies related to the production area. This suggests that these data might be useful for delineating the field boundaries. 16 refs.

  20. A General Purpose Digital System for Field Vibration Testing

    DEFF Research Database (Denmark)

    Brincker, Rune; Larsen, Jesper Abildgaard; Ventura, Carlos


    This paper describes the development and concept implementation of a highly sensitive digital recording system for seismic applications and vibration measurements on large Civil Engineering structures. The system is based on highly sensitive motion transducers that have been used by seismologists...... and geophysicists for decades. The conventional geophone's ratio of cost to performance, including noise, linearity and dynamic range is unmatched by advanced modern accelerometers. The unit comprises six independent sensor elements that can be used in two different configurations for noise reduction and extended...

  1. Applications of Engineering Seismology for Site Characterization

    Institute of Scientific and Technical Information of China (English)

    Oz Yilmaz; Murat Eser; Mehmet Berilgen


    We determined the seismic model of the soil column within a residential project site in Istanbul, Turkey. Specifically, we conducted a refraction seismic survey at 20 locations using a receiver spread with 484.5-Hz vertical geophones at 2-m intervals. We applied nonlinear tomography to first-arrival times to estimate the P-wave velocity-depth profiles and performed Rayleigh-wave inversion to estimate the S-wave velocity-depth profiles down to a depth of 30 m at each of the locations. We then combined the seismic velocities with the geotechnical borehole information regarding the lithology of the soil column and determined the site-specific geotechnical earthquake engineering parameters for the site. Specifically, we computed the maximum soil amplification ratio, maximum surface-bedrock acceleration ratio, depth interval of significant acceleration, maximum soil-rock response ratio, and design spectrum periods TA-TB. We conducted reflection seismic surveys along five line traverses with lengths between 150 and 300 m and delineated landslide failure surfaces within the site. We recorded shot gathers at 2-m intervals along each of the seismic line traverses using a receiver spread with 4 840-Hz vertical geophones at 2-m intervals. We applied nonlinear tomograpby to first-arrival times to estimate a P-wave velocity-depth model and analyzed the reflected waves to obtain a seismic image of the deep near-surface along each of the line traverses.

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

    KAUST Repository

    Fu, Lei


    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.

  3. Relative amplitude preservation processing utilizing surface consistent amplitude correction. Part 3; Surface consistent amplitude correction wo mochiita sotai shinpuku hozon shori. 3

    Energy Technology Data Exchange (ETDEWEB)

    Saeki, T. [Japan National Oil Corporation, Tokyo (Japan). Technology Research Center


    For the seismic reflection method conducted on the ground surface, generator and geophone are set on the surface. The observed waveforms are affected by the ground surface and surface layer. Therefore, it is required for discussing physical properties of the deep underground to remove the influence of surface layer, preliminarily. For the surface consistent amplitude correction, properties of the generator and geophone were removed by assuming that the observed waveforms can be expressed by equations of convolution. This is a correction method to obtain records without affected by the surface conditions. In response to analysis and correction of waveforms, wavelet conversion was examined. Using the amplitude patterns after correction, the significant signal region, noise dominant region, and surface wave dominant region would be separated each other. Since the amplitude values after correction of values in the significant signal region have only small variation, a representative value can be given. This can be used for analyzing the surface consistent amplitude correction. Efficiency of the process can be enhanced by considering the change of frequency. 3 refs., 5 figs.

  4. Automating Shallow Seismic Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Steeples, Don W.


    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

  5. SWD experiment at Southwest Andrews oil field; Nansei Andrews yuden ni okeru SWD jikken

    Energy Technology Data Exchange (ETDEWEB)

    Kozawa, T.; Tsuru, T. [Japan National Oil Corp., Tokyo (Japan)


    Seismic while drilling (SWD) is an accurate drilling method by which time-to-depth (T-D) information for determining the accurate bit location and information of bedding boundaries below the bit can be obtained. However, the signal level is rather low compared with the noise generated from the rig during drilling. It is required for improving the S/N ratio to calculate a correlation using reference signals simultaneously acquired using a pilot sensor which is a geophone attached to the rig. Some experiments were conducted in the Southwest Andrews Oil Field. Deterioration of data quality due to the noise particular to the SWD in this oil field could be reduced by proper data acquisition geometry including the minimum offset distance using a geophone array. In order to correct the time, a velocity of P-wave propagating the drill pipe was estimated using auto-correlation of the pilot traces. The S/N ratio was improved by the VSP deconvolution and the stacking effect during VSP-CDP conversion. Thus, could be obtained the accurate T-D information and reflection wave information below the bit. 12 refs., 19 figs., 1 tab.

  6. Shallow active-source imaging of an andesite dike in southern New Mexico: comparing Reftek Texan and Fairfield Z-Land recordings (United States)

    Karplus, M. S.; Kaip, G.; Harder, S. H.; Johnson, K.


    In October 2015, the Advanced Exploration Seismology class at the University of Texas at El Paso together with additional volunteers acquired a 500-m active-source seismic profile across an andesite dike adjacent to the Rio Grande River near Sunland Park, New Mexico. Receivers included 100 RT-125 Reftek Texans with 4.5-Hz geophones, spaced every 5 m, and 47 Fairfield Z-Land nodes incorporating 5-Hz 3C geophones, spaced approximately every 10 m. A 8-gauge, 400 grain seismic gun source was fired every 5-10 m along most of the profile. Several locations at the ends of the profile experienced multiple gun shots, which have been stacked to increase signal-to-noise. We discuss similarities and differences in field methods and data acquired using the Texans compared to the nodes for a shallow active-source experiment. We extend the discussion to other types of active-source experiments using other recently-acquired nodal datasets. We observe changes in velocity between the andesite dike and surrounding lithologies, and create a seismic reflection image of the andesite dike.

  7. Seismic reflection survey at Ayer Hangat site to investigate shallow subsurface structures (United States)

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


    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.

  8. Variations in geoacoustic emissions in a deep borehole and its correlation with seismicity

    Directory of Open Access Journals (Sweden)

    A. Storcheus


    Full Text Available Continuous geoacoustic emission (GAE measurements were acquired using a three-component geophone placed in a borehole at a depth of near 1000 m at Petropavlovsk-Kamchatsky starting in August 2000. Using geophones consisting of magneto-elastic crystal ferromagnetic sensors, and installed at such a depth allows measurement of natural geoacoustic background with signal amplitude less than 1×10-4 m/s3 in frequency band from 3 to 1500 Hz. According to the data from a 4-year survey period the characteristics of diurnal geoacoustic variations change before every earthquake with MLH? 5.0 that occurs at a distance of less than 300 km from the observation point or before each earthquake with MLH?5.5 occurring at distance R?550 km from the observation point. The changes in GAE regime correlate with the strongest earthquakes that occurred during survey period. Measurements of the natural electromagnetic field of the Earth were carried out simultaneously with the help of an underground electric antenna. The behavior of GAE in aseismic periods appears to be related to the effect of diurnal variations of the natural electromagnetic field.

  9. Space-time clustering of seismic events and hazard assessment in the Zabrze-Bielszowice coal mine, Poland

    Energy Technology Data Exchange (ETDEWEB)

    Lesniak, A.; Isakow, Z. [AGH University of Science & Technology, Krakow (Poland)


    The results of the statistical analysis of seismic activity recorded in the 'Zabrze-Bielszowice' coal mine in Poland are presented in this article. The monitoring was conducted by a small network consisting of four triaxial geophones deployed in vertical holes in the roof. For over 1000 seismic events recorded during the two month's experiment, the location of sources was realized. The seismic sources were mostly located ahead of the active face of the long wall. Since the first day of the monitoring, cluster analysis was sequentially performed for increasing number of sources. At the end of the experiment, 31 clusters were identified. They consisted of different numbers of events and were separated in space. About 40% of the events were not included in the clusters. For each large cluster, hazard analysis was separately performed. The hazard function evaluated for the largest cluster was compared with hypocenters of high energy tremors (E > 1000 J) recorded by the geophones in that area. For some cases, recorded tremors occurred after an abrupt decrease of hazard function, but only one of them was located in the vicinity of the appropriate cluster. We concluded that for the analyzed cluster, a correlation between evaluated hazard function and time occurrences of the high energy tremors existed. Except for one case, there is no space correlation between analyzed clusters and high energy tremors.

  10. High frequency seismic monitoring of debris flows at Chalk Cliffs (CO), USA (United States)

    Coviello, Velio; Kean, Jason; Smith, Joel; Coe, Jeffrey; Arattano, Massimo; McCoy, Scott


    A growing number of studies adopt passive seismic monitoring techniques to investigate slope instabilities and landslide processes. These techniques are attractive and convenient because large areas can be monitored from a safe distance. This is particularly true when the phenomena under investigation are rapid and infrequent mass movements like debris flows. Different types of devices are used to monitor debris flow processes, but among them ground vibration detectors (GVDs) present several, specific advantages that encourage their use. These advantages include: (i) the possibility to be installed outside the channel bed, (ii) the high adaptability to different and harsh field conditions, and (iii) the capability to detect the debris flow front arrival tens of seconds earlier than contact and stage sensors. Ground vibration data can provide relevant information on the dynamics of debris flows such as timing and velocity of the main surges. However, the processing of the raw seismic signal is usually needed, both to obtain a more effective representation of waveforms and to decrease the amount of data that need to be recorded and analyzed. With this objective, the methods of Amplitude and Impulses are commonly adopted to transform the raw signal to a 1-Hz signal that allows for a more useful representation of the phenomenon. In that way, peaks and other features become more visible and comparable with data obtained from other monitoring devices. In this work, we present the first debris flows seismic recordings gathered in the Chalk Cliffs instrumented basin, central Colorado, USA. In May 2014, two 4.5-Hz, three-axial geophones were installed in the upper part of the catchment. Seismic data are sampled at 333 Hz and then recorded by a standalone recording unit. One geophone is directly installed on bedrock, the other one mounted on a 1-m boulder partially buried in colluvium. This latter sensor integrates a heavily instrumented cross-section consisting of a 225 cm2

  11. Acoustic Monitoring of the Arctic Ice Cap (United States)

    Porter, D. L.; Goemmer, S. A.; Chayes, D. N.


    Introduction The monitoring of the Arctic Ice Cap is important economically, tactically, and strategically. In the scenario of ice cap retreat, new paths of commerce open, e.g. waterways from Northern Europe to the Far East. Where ship-going commerce is conducted, the U.S. Navy and U.S. Coast Guard have always stood guard and been prepared to assist from acts of nature and of man. It is imperative that in addition to measuring the ice from satellites, e.g. Icesat, that we have an ability to measure the ice extent, its thickness, and roughness. These parameters play an important part in the modeling of the ice and the processes that control its growth or shrinking and its thickness. The proposed system consists of three subsystems. The first subsystem is an acoustic source, the second is an array of geophones and the third is a system to supply energy and transmit the results back to the analysis laboratory. The subsystems are described below. We conclude with a plan on how to tackle this project and the payoff to the ice cap modeler and hence the users, i.e. commerce and defense. System Two historically tested methods to generate a large amplitude multi-frequency sound source include explosives and air guns. A new method developed and tested by the University of Texas, ARL is a combustive Sound Source [Wilson, et al., 1995]. The combustive sound source is a submerged combustion chamber that is filled with the byproducts of the electrolysis of sea water, i.e. Hydrogen and Oxygen, an explosive mixture which is ignited via a spark. Thus, no additional compressors, gases, or explosives need to be transported to the Arctic to generate an acoustic pulse capable of the sediment and the ice. The second subsystem would be geophones capable of listening in the O(10 Hz) range and transmitting that data back to the laboratory. Thus two single arrays of geophones arranged orthogonal to each other with a range of 1000's of kilometers and a combustive sound source where the two

  12. Near Surface Shear Wave Velocity Model of the Sacramento-San Joaquin Delta (United States)

    Shuler, S.; Craig, M. S.; Hayashi, K.; Galvin, J. L.; Deqiang, C.; Jones, M. G.


    Multichannel analysis of surface wave measurements (MASW) and microtremor array measurements (MAM) were performed at twelve sites across the Sacramento-San Joaquin Delta to obtain high resolution shear wave velocity (VS) models. Deeper surveys were performed at four of the sites using the two station spatial autocorrelation (SPAC) method. For the MASW and MAM surveys, a 48-channel seismic system with 4.5 Hz geophones was used with a 10-lb sledgehammer and a metal plate as a source. Surveys were conducted at various locations on the crest of levees, the toe of the levees, and off of the levees. For MASW surveys, we used a record length of 2.048 s, a sample interval of 1 ms, and 1 m geophone spacing. For MAM, ambient noise was recorded for 65.536 s with a sampling interval of 4 ms and 1 m geophone spacing. VS was determined to depths of ~ 20 m using the MASW method and ~ 40 m using the MAM method. Maximum separation between stations in the two-station SPAC surveys was typically 1600 m to 1800 m, providing coherent signal with wavelengths in excess of 5 km and depth penetration of as much as 2000 m. Measured values of VS30 in the study area ranged from 97 m/s to 257 m/s, corresponding to NEHRP site classifications D and E. Comparison of our measured velocity profiles with available geotechnical logs, including soil type, SPT, and CPT, reveals the existence of a small number of characteristic horizons within the upper 40m in the Delta: levee fill material, peat, transitional silty sand, and eolian sand at depth. Sites with a peat layer at the surface exhibited extremely low values of VS. Based on soil borings, the thickness of peat layers were approximately 0 m to 8 m. The VS for the peat layers ranged from 42 m/s to 150 m/s while the eolian sand layer exhibited VS ranging from of 220 m/s to 370 m/s. Soft near surface soils present in the region pose an increased earthquake hazard risk due to the potential for high ground accelerations.

  13. Can riverside seismic monitoring constrain temporal and spatial variations in bedload transport during a controlled flood of the Trinity River? (United States)

    Glasgow, M. E.; Schmandt, B.; Gaeuman, D.


    To evaluate the utility of riverside seismic monitoring for constraining temporal and spatial variations in coarse bedload transport in gravel-bed rivers we collected seismic data during a dam-controlled flood of the Trinity River in northern California in May 2015. This field area was chosen because the Trinity River Restoration Project conducts extensive monitoring of water and sediment transport, and riverbed morphology to guide management of the river with the goal of improving salmon habitat. Four three component broadband seismometers were collocated with water discharge and bedload physical sampling sites along a ~30 km reach of the Trinity River downstream of the Lewiston Dam. Arrays with 10-80 cable-free vertical component geophones were also deployed at each of the four sites in order to constrain spatial variability and amplitude decay of seismic signals emanating from the river. Nominal inter-station spacing within the geophone arrays was ~30 m. The largest geophone array consisted of 83 nodes along a 700 m reach of the Trinity River with a gravel augmentation site at its upstream end. Initial analyses of the seismic data show that ground velocity power from averaged from ~7 - 90 Hz is correlated with discharge at all sites. The array at the gravel injection site shows greater high frequency (>30 Hz) power at the upstream end where gravel was injected during the release compared to ~300 m downstream, consistent with bedload transport providing a significant source of seismic energy in addition to water discharge. Declining seismic power during a ~3 day plateau at peak discharge when physical sampler data shows decreasing bedload flux provides a further indication that the seismic data are sensitive to bedload transport. We will use the array data to back-project the seismic signals in multiple frequency bands into the channel to create maps of the time-varying spatial intensity of seismic energy production. We hypothesize that the greatest seismic

  14. A High-resolution Seismic Reflection Survey at the Hanford Nuclear Site Using a Land Streamer (United States)

    Hyde, E. R.; Speece, M. A.; Link, C. A.; Repasky, T.; Thompson, M.; Miller, S.; Cummins, G.


    From the 1940s through the mid 1990s, radioactively and chemically contaminated effluent waste was released into the ground at the Hanford Nuclear Site. Currently, Hanford is the site of a large-scale and ongoing environmental cleanup effort which includes the remediation of contaminated ground water. Identifying preferential pathways of groundwater contaminant flow is critical for the groundwater cleanup effort. During the summer of 2009, Montana Tech, in collaboration with the Confederated Tribes of the Umatilla Indian Reservation, collected a high resolution shallow seismic survey on the Hanford Central Plateau near the Gable Gap area of the Hanford Nuclear site. The goal of the survey was to demonstrate the feasibility of using a land streamer/gimbaled geophone acquisition approach to image the basalt bedrock topography. The survey objective is to improve the understanding of the subsurface water flow by identifying the topography of the basement basalt and possible erosional channels created during the Missoula flood events. Data was collected for a total of eight 2D lines with a combined length of about 11 km with a coverage area of approximately 6 The profiles were aligned in north-south and east-west intersecting lines with a total of 5 profile intersections. The survey used a 227 kg accelerated weight drop and a 96-channel land streamer. The land streamer used gimbaled geophones with 2 m spacing. Source spacing was also 2 m for a nominal fold of 48. The rapid deployment land streamer, compared to conventional spiked geophones, significantly increased production in this off-road application. Typically, between 45 and 55 stations could be shot per hour in a pull and shoot approach. Deployment of the land streamer required about 45 minutes and about 30 minutes was required to shut down the survey. The survey successfully imaged the top of the basalt and demonstrated that a land streamer can produce quality seismic data in this area. The basalt bedrock

  15. The use of a Tunnel Boring Machine (TBM) as a seismic source (United States)

    Kreutzer, Ingrid; Chwatal, Werner; Radinger, Alexander; Brückl, Ewald


    The Tunnel Seismic While Drilling (TSWD) method uses the Tunnel Boring Machine (TBM) as the seismic source. The method has been developed to predict the geological situation from reflections ahead of the tunnel face without disturbing the tunneling. The vibrations of the TBM are continuously monitored near the drilling head (pilot signal) as well as the direct and reflected seismic wave field at borehole geophones (geophone signal) situated in the tunnel wall behind the TBM. During the processing these signals are correlated and result in excellent seismic traces comparable to conventional seismic methods. The interpretation of the reflections leads to a nearly daily prognosis about 100 m ahead of the TBM. This system was successfully implemented at three different construction sites in Austria and is currently operating at one further. The cutters on front of the TBM head are pressed against the tunnel face and split the rock during rotating which is called the chipping process. This cutting process generates seismic waves radiated into the rock mass and results also in vibrations of the TBM itself. On the one hand it is important to know the source mechanism of the TBM and the radiation pattern of the seismic waves in all directions. Until now this is not well understood. To investigate this 3C-geophones were installed at the surface above the tunnel axis at different construction sites. The obtained seismograms show the forward and backward radiated seismic wave field of the TBM, for the present without consideration of the influence of the free surface. We compare this data with modelled seismograms in which we use different possible source mechanism, like single force or force due to tensile cracks. First results are shown in the scope of this work. On the other hand it is essential to know how good the recorded pilot signal represents the entire chipping process. Due to technically reasons the pilot signal has been registered so far on the non-rotating part

  16. Test to Extract Soil Properties Using the Seismic HammerTM Active Seismic Source

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Rebekah F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Abbott, Robert E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)


    Geologic material properties are necessary parameters for ground motion modeling and are difficult and expensive to obtain via traditional methods. Alternative methods to estimate soil properties require a measurement of the ground's response to a force. A possible method of obtaining these measurements is active-source seismic surveys, but measurements of the ground response at the source must also be available. The potential of seismic sources to obtain soil properties is limited, however, by the repeatability of the source. Explosives, and hammer surveys are not repeatable because of variable ground coupling or swing strength. On the other hand, the Seismic Hammer TM (SH) is consistent in the amount of energy it inputs into the ground. In addition, it leaves large physical depressions as a result of ground compaction. The volume of ground compaction varies by location. Here, we hypothesize that physical depressions left in the earth by the SH correlate to energy recorded by nearby geophones, and therefore are a measurement of soil physical properties. Using measurements of the volume of shot holes, we compare the spatial distribution of the volume of ground compacted between the different shot locations. We then examine energy recorded by the nearest 50 geophones and compare the change in amplitude across hits at the same location. Finally, we use the percent difference between the energy recorded by the first and later hits at a location to test for a correlation to the volume of the shot depressions. We find that: * Ground compaction at the shot-depression does cluster geographically, but does not correlate to known surface features. * Energy recorded by nearby geophones reflects ground refusal after several hits. * There is no correlation to shot volume and changes in energy at particular shot locations. Deeper material properties (i.e. below the depth of surface compaction) may be contributing to the changes in energy propagation. * Without further

  17. Propagation characteristics of converted refracted wave and its application in static correction of converted wave

    Institute of Scientific and Technical Information of China (English)


    Three-component seismic exploration through P-wave source and three-component geophone is an effective technique used in complicated reservoir exploration. In three-component seismic exploration data processing,one of the difficulties is static correction of converted wave. This paper analyzes propagation characteristics of non-converted and converted refracted waves,and discovers a favor-able condition for the formation of converted refracted wave,i.e. the velocity of overlaying medium S wave is much lower than that of underlying medium S wave. In addition,the paper proposes the static correction method of converted wave based on PPS converted refracted wave,and processes the real three-component seismic data with better results of static correction of converted wave.

  18. Comparison of seismic sources for shallow seismic: sledgehammer and pyrotechnics

    Directory of Open Access Journals (Sweden)

    Brom Aleksander


    Full Text Available The pyrotechnic materials are one of the types of the explosives materials which produce thermal, luminous or sound effects, gas, smoke and their combination as a result of a self-sustaining chemical reaction. Therefore, pyrotechnics can be used as a seismic source that is designed to release accumulated energy in a form of seismic wave recorded by tremor sensors (geophones after its passage through the rock mass. The aim of this paper was to determine the utility of pyrotechnics for shallow seismic engineering. The work presented comparing the conventional method of seismic wave excitation for seismic refraction method like plate and hammer and activating of firecrackers on the surface. The energy released by various sources and frequency spectra was compared for the two types of sources. The obtained results did not determine which sources gave the better results but showed very interesting aspects of using pyrotechnics in seismic measurements for example the use of pyrotechnic materials in MASW.

  19. Obtaining changes in calibration-coil to seismometer output constants using sine waves (United States)

    Ringler, Adam T.; Hutt, Charles R.; Gee, Lind S.; Sandoval, Leo D.; Wilson, David C.


    The midband sensitivity of a broadband seismometer is one of the most commonly used parameters from station metadata. Thus, it is critical for station operators to robustly estimate this quantity with a high degree of accuracy. We develop an in situ method for estimating changes in sensitivity using sine‐wave calibrations, assuming the calibration coil and its drive are stable over time and temperature. This approach has been used in the past for passive instruments (e.g., geophones) but has not been applied, to our knowledge, to derive sensitivities of modern force‐feedback broadband seismometers. We are able to detect changes in sensitivity to well within 1%, and our method is capable of detecting these sensitivity changes using any frequency of sine calibration within the passband of the instrument.

  20. Innovative semielliptical seismic pattern improving line-change efficiency (United States)

    Walus, Artur; Gucma, Lucjan; Bąk, Andrzej


    The paper presents a new method for conducting turns by vessels towing seismic cables. A comparison was made between the traditional way of turning to indicate the advantages of the proposed pattern. In order to improve the overview of the complete geometry of a towed streamer system, a model of marine seismic research quality coefficients was applied. The turning method was tested onboard a seismic vessel towing eight streamers of 6 km in length. A significant reduction of time required for line-change was achieved (up to 45 % depending on ocean current speed and direction, speed of the vessel, skills of navigating team). The introduced quality coefficient of geophysical research works is based on the mathematical model of positions deviation of streamers geophones with relation to their idealized position. The model was created to be used while the vessel is on a steady course to improve the quality of acquired data; however, it was found useful during line changes as well.

  1. Finding Trapped Miners by Using a Prototype Seismic Recording System Made from Music-Recording Hardware (United States)

    Pratt, Thomas L.


    The goal of this project was to use off-the-shelf music recording equipment to build and test a prototype seismic system to listen for people trapped in underground chambers (mines, caves, collapsed buildings). Previous workers found that an array of geophones is effective in locating trapped miners; displaying the data graphically, as well as playing it back into an audio device (headphones) at high speeds, was found to be effective for locating underground tapping. The desired system should record the data digitally to allow for further analysis, be capable of displaying the data graphically, allow for rudimentary analysis (bandpass filter, deconvolution), and allow the user to listen to the data at varying speeds. Although existing seismic reflection systems are adequate to record, display and analyze the data, they are relatively expensive and difficult to use and do not have an audio playback option. This makes it difficult for individual mines to have a system waiting on the shelf for an emergency. In contrast, music recording systems, like the one I used to construct the prototype system, can be purchased for about 20 percent of the cost of a seismic reflection system and are designed to be much easier to use. The prototype system makes use of an ~$3,000, 16-channel music recording system made by Presonus, Inc., of Baton Rouge, Louisiana. Other manufacturers make competitive systems that would serve equally well. Connecting the geophones to the recording system required the only custom part of this system - a connector that takes the output from the geophone cable and breaks it into 16 microphone inputs to be connected to the music recording system. The connector took about 1 day of technician time to build, using about $300 in off-the-shelf parts. Comparisons of the music recording system and a standard seismic reflection system (A 24-channel 'Geode' system manufactured by Geometrics, Inc., of San Jose, California) were carried out at two locations. Initial

  2. Mapping refuse profile in Singapore old dumping ground through electrical resistivity, S-wave velocity and geotechnical monitoring. (United States)

    Yin, Ke; Tong, Huan Huan; Noh, Omar; Wang, Jing-Yuan; Giannis, Apostolos


    The purpose of this study was to track the refuse profile in Lorong Halus Dumping Ground, the largest landfill in Singapore, by electrical resistivity and surface wave velocity after 25 years of closure. Data were analyzed using an orthogonal set of plots by spreading 24 lines in two perpendicular geophone-orientation directions. Both geophysical techniques determined that refuse boundary depth was 13 ± 2 m. The refuse boundary revealed a certain degree of variance, mainly ascribed to the different principle of measurements, as well as the high heterogeneity of the subsurface. Discrepancy was higher in spots with greater heterogeneity. 3D analysis was further conducted detecting refuse pockets, leachate mounding and gas channels. Geotechnical monitoring (borehole) confirmed geophysical outcomes tracing different layers such as soil capping, decomposed refuse materials and inorganic wastes. Combining the geophysical methods with borehole monitoring, a comprehensive layout of the dumping site was presented showing the hot spots of interests.

  3. Artificial and natural electromagnetic signals revealed during two years in the Amare cave (Central Italy

    Directory of Open Access Journals (Sweden)

    W. Plastino


    Full Text Available n 1990, some instrumentation was set up in the Amare cave (southern slope of the Gran Sasso chain, L'Aquila in order to pick up electric signals ranging from 0.3 to 300 kHz, magnetic signals from 0.3 to 30 kHz and seismoacoustic signals by means of three geophones with natural frequencies of 0.3 kHz, 25 kHz and 150 kHz. Data are recorded every ten minutes on a solid state memory. The analysis of the data allows us to establish the existence of electromagnetic fields of distant origin connected with broadcastings and with tropical lightning activity and the discontinuous presence of local electric and magnetic signals, coupled with seismoacoustic ones, connected with weather events. A qualitative explanation of these near fields is given.

  4. Hydraulic impulse generator and frequency sweep mechanism for borehole applications (United States)

    Kolle, Jack J.; Marvin, Mark H.; Theimer, Kenneth J.


    This invention discloses a valve that generates a hydraulic negative pressure pulse and a frequency modulator for the creation of a powerful, broadband swept impulse seismic signal at the drill bit during drilling operations. The signal can be received at monitoring points on the surface or underground locations using geophones. The time required for the seismic signal to travel from the source to the receiver directly and via reflections is used to calculate seismic velocity and other formation properties near the source and between the source and receiver. This information can be used for vertical seismic profiling of formations drilled, to check the location of the bit, or to detect the presence of abnormal pore pressure ahead of the bit. The hydraulic negative pressure pulse can also be used to enhance drilling and production of wells.

  5. Innovative semielliptical seismic pattern improving line-change efficiency (United States)

    Walus, Artur; Gucma, Lucjan; Bąk, Andrzej


    The paper presents a new method for conducting turns by vessels towing seismic cables. A comparison was made between the traditional way of turning to indicate the advantages of the proposed pattern. In order to improve the overview of the complete geometry of a towed streamer system, a model of marine seismic research quality coefficients was applied. The turning method was tested onboard a seismic vessel towing eight streamers of 6 km in length. A significant reduction of time required for line-change was achieved (up to 45 % depending on ocean current speed and direction, speed of the vessel, skills of navigating team). The introduced quality coefficient of geophysical research works is based on the mathematical model of positions deviation of streamers geophones with relation to their idealized position. The model was created to be used while the vessel is on a steady course to improve the quality of acquired data; however, it was found useful during line changes as well.

  6. Imaging near-surface heterogeneities by natural migration of backscattered surface waves

    KAUST Repository

    AlTheyab, Abdullah


    We present a migration method that does not require a velocity model to migrate backscattered surface waves to their projected locations on the surface. This migration method, denoted as natural migration, uses recorded Green\\'s functions along the surface instead of simulated Green\\'s functions. The key assumptions are that the scattering bodies are within the depth interrogated by the surface waves, and the Green\\'s functions are recorded with dense receiver sampling along the free surface. This natural migration takes into account all orders of multiples, mode conversions and non-linear effects of surface waves in the data. The natural imaging formulae are derived for both active source and ambient-noise data, and computer simulations show that natural migration can effectively image near-surface heterogeneities with typical ambient-noise sources and geophone distributions.

  7. Borehole Seismic Monitoring at Otway Using the Naylor-1 Instrument String

    Energy Technology Data Exchange (ETDEWEB)

    Daley, T.M.; Sharma, Sandeep; Dzunic, Aleksander; Urosevic, Milovan; Kepic, Anton; Sherlock, Don


    The Naylor-1 monitoring completion, a unique and innovative instrumentation package, was designed and fabricated in FY 2007 at Berkeley Laboratory. Tom Daley, Barry Freifeld and Duo Wang (all from Berkeley Lab) were on site at the Otway Project between September 26 and October 14, 2007, working with CO2CRC and their subcontractors, AGR Asia Pacific and Eastern Well Services to complete Naylor-1 and initiate baseline data collection. Figure 1 shows a schematic of Naylor-1's sensor layout. There are three U-tube geochemical samplers, with one located near the top of the residual CH{sub 4} gas cap and two located beneath the gas-water contact. The 21 geophones are used for performing three distinct seismic measurements, high resolution travel time (HRTT), walkaway vertical seismic profiling (WVSP), and microseismic monitoring. These activities are separated in to active source seismic and microseismic monitoring, and will be described separately.


    Lee, M.W.


    Particle displacements from incident plane waves at the wall of a fluid-filled borehole are formulated by applying the seismic reciprocity theorem to far-field displacement fields. Such displacement fields are due to point forces acting on a fluid-filled borehole under the assumption of long wavelengths. The displacement fields are analyzed to examine the effect of the borehole on seismic wave propagation, particularly for vertical seismic profiling (VSP) measurements. When the shortest wavelength of interest is approximately 25 times longer than the borehole's diameter, the scattered displacements are proportional to the first power of incident frequency and borehole diameter. When the shortest wavelength of interest is about 40 times longer than the borehole's diameter, borehole effects on VSP measurements using a wall-locking geophone are negligible.

  9. Elastic Time Reversal Mirror Experiment in a Mesoscopic Natural Medium at the Low Noise Underground Laboratory of Rustrel, France

    CERN Document Server

    Gaffet, Stephane; Senechal, Guy; Rousset, Dominique; Zeyen, Hermann; Auguste, Michel; Boyer, Daniel; Cavaillou, Alain


    A seismic time reversal experiment based on Time Reversal Mirror (TRM) technique was conducted in the mesoscopically scaled medium at the LSBB Laboratory, France. Two sets of 50 Hz geophones were distributed at one meter intervals in two horizontal and parallel galleries 100 m apart, buried 250 m below the surface. The shot source used was a 4 kg sledgehammer. Analysis shows that elastic seismic energy is refocused in space and time to the shot locations with good accuracy. The refocusing ability of seismic energy to the shot locations is roughly achieved for the direct field, and with excellent quality, for the early and later coda. Hyper-focussing is achieved at the shot points as a consequence of the fine scale randomly heterogeneous medium between the galleries. TRM experiment is sensitive to the roughness of the mirror used. Roughness induces a slight experimental discrepancy between recording and re-emitting directions degrading the quality of the reversal process.

  10. Application of passive seismic to shallow geological structures in urban areas

    Directory of Open Access Journals (Sweden)

    Mendecki Maciej Jan


    Full Text Available To study the shallow geological structure the Refraction Microtremor (ReMi method was applied. This technique uses seismic noise analysis where a source of this small vibrations is the human activity e.g.: traffic, production, factories. The surveys were carried out in selected urban areas in the region of the Upper Silesian Industrial District : Sosnowiec - Pogoń , Chorzów - Chorzow Stary and Bytom - Karb. Each area is characterized by the presence of nearby roads with a very high traffic. The results of passive seismic (ReMi were confronted with data obtained using Multichannel Analysis of Surface Waves (MASW and resistivity imaging (RI. Seismic surveys were performed by apparatus PASI with 24 channels using geophones of 4.5Hz. The results showed that passive seismic can be satisfactorily used in such urban conditions. The shallow geological structure interpreted by seismic methods have been well-correlated with resistivity studies.

  11. Notch Effect and Frequency Compensation of Dual-Sensor OBC Data in Shallow Water

    Institute of Scientific and Technical Information of China (English)

    Dongkai Wang; Siyou Tong; Huaishan Liu; Weiqiang Zhu


    Reverberation is significant in shallow water and produces obvious notches in OBC spec-tra. It also degrades the quality of sections and increases the difficulty of processing and interpretation. This article presents the relationship between notch, shooting depth, and seabed depth based on the seismic convolution model. Forward modelling based on wave equation theory is used to verify this re-lationship. Dual-sensor summation is applied to suppress receiver-side multiples and remove notches according to the opposite response of geophones and hydrophones to down-going wave fields based on a detailed analysis of the OBC technique. The good results obtained in practical applications reveal the effectiveness of this method.

  12. An example of using oil-production induced microseismicity in characterizing a naturally fractured reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Rutledge, J.T.; Phillips, W.S. [Nambe Geophysical, Inc., Santa Fe, NM (United States); Schuessler, B.K.; Anderson, D.W. [Los Alamos National Lab., NM (United States)


    Microseismic monitoring was conducted using downhole geophone tools deployed in the Seventy-Six oil field, Clinton County, Kentucky. Over a 7-month monitoring period, 3237 microearthquakes were detected during primary oil production; no injection operations were conducted. Gross changes in production rate correlate with microearthquake event rate with event rate lagging production-rate changes by about 2 weeks. Hypocenters and first-motion data have revealed low-angle, thrust fracture zones above and below the currently drained depth interval. Production history, well logs and drill tests indicate the seismically-active fractures are previously drained intervals that have subsequently recovered to hydrostatic pressure via brine invasion. The microseismic data have revealed, for the first time, the importance of the low-angle fractures in the storage and production of oil in the study area. The seismic behavior is consistent with poroelastic models that predict slight increases in compressive stress above and below currently drained volumes.

  13. Near Surface Structure of the Frijoles Strand of the San Gregorio Fault, Point Año Nuevo, San Mateo County, California, from Seismic Imaging (United States)

    Campbell, L.; Catchings, R. D.; Rymer, M. J.; Goldman, M.; Weber, G. E.


    The San Gregorio Fault Zone (SGFZ) is one of the major faults of the San Andreas Fault (SAF) system in the San Francisco Bay region of California. The SGFZ is nearly 200 km long, trends subparallel to the SAF, and is located primarily offshore with two exceptions- between Point Año Nuevo and San Gregorio Beach and between Pillar Point and Moss Beach. It has a total width of 2 to 3 km and is comprised of seven known fault strands with Quaternary activity, five of which also demonstrate late Holocene activity. The fault is clearly a potential source of significant earthquakes and has been assigned a maximum likely magnitude of 7.3. To better understand the structure, geometry, and shallow-depth P-wave velocities associated with the SGFZ, we acquired a 585-m-long, high-resolution, combined seismic reflection and refraction profile across the Frijoles strand of the SGFZ at Point Año Nuevo State Park. Both P- and S-wave data were acquired, but here we present only the P-wave data. We used two 60-channel Geometrics RX60 seismographs and 120 40-Hz single-element geophones connected via cable to record Betsy Seisgun seismic sources (shots). Both shots and geophones were approximately co-located and spaced at 5-m intervals along the profile, with the shots offset laterally from the geophones by 1 m. We measured first-arrival refractions from all shots and geophones to develop a seismic refraction tomography velocity model of the upper 70 m. P-wave velocities range from about 600 m/s near the surface to more than 2400 m/s at 70 m depth. We used the refraction tomography image to infer the depth to the top of the groundwater table on the basis of the 1500 m/s velocity contour. The image suggests that the depth, along the profile, to the top of groundwater varies by about 18 m, with greater depth on the west side of the fault. At about 46 m depth, a 60- to 80-m-wide, low-velocity zone, which is consistent with faulting, is observed southwest of the Frijoles strand of the

  14. 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)


    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.

  15. Mapping the base of sand dunes using a new design of land-streamer for static correction applications

    KAUST Repository

    Almalki, H.


    The complex near-surface structure is a major problem in land seismic data. This is more critical when data acquisition takes place over sand dune surfaces, where the base of the sand acts as a trap for energy and, depending on its shape, can considerably distort conventionally acquired seismic data. Estimating the base of the sand dune surface can help model the sand dune and reduce its harmful influence on conventional seismic data. Among the current methods to do so are drilling upholes and using conventional seismic data to apply static correction. Both methods have costs and limitations. For upholes, the cost factor and their inability to provide a continuous model is well realized. Meanwhile, conventional seismic data lack the resolution necessary to obtain accurate modeling of the sand basement. We developed a method to estimate the sand base from land-streamer seismic acquisition that is developed and geared to sand surfaces. Seismic data acquisition took place over a sand surface in the Al-Thumamah area, where an uphole is located, using the developed land-streamer and conventional spiked geophone systems. Land-streamer acquisition not only provides a more efficient data acquisition system than the conventional spiked geophone approach, but also in our case, the land-streamer provided better quality data with a broader frequency bandwidth. Such data enabled us to do accurate near-surface velocity estimation that resulted in velocities that are very close to those measured using uphole methods. This fact is demonstrated on multiple lines acquired near upholes, and agreement between the seismic velocities and the upholes is high. The stacked depth seismic section shows three layers. The interface between the first and second layers is located at 7 m depth, while the interface between second and third layers is located at 68 m depth, which agrees with the uphole result. 2012 The Author(s).

  16. Monitoring of an active landslide in chaotic clay shales (Emilia Romagna region, Northern Apennines) (United States)

    Squarzoni, Gabriela; Bertello, Lara; Guerriero, Luigi; Berti, Matteo


    Sassi Neri landslide is located in the Farini area (North Apennines), about 40 kilometers southwest of Piacenza city. The geology of the area is quite complex, with strongly tectonically deformed shales (Palombini Shales formation) thrusting over an arenaceous-pelitic flysch (Bettola Flysch formation). Starting from '50s, the landslide has been subjected to many reactivations developed as earthflows, the last one in the period between November 2013 and January 2014. The landslide is about 700 m long with a maximum width of about 200 m and a slip surface lying at a depth varying from 5 m to 15 m (Pizziolo et al 2014). In early fall 2016, Sassi Neri landslide seemed starting to move again; hence, a monitoring system has been installed in order to study the landslide's displacements and displacement rates and their correlation with rainfall events, pore water pressure and shear wave velocity (Vs) variations. The monitoring system consists of: 1) a CR1000 datalogger (Campbell Scientific), 2) a charge controller STECA SOLSUM 88F, 3) two time lapse cameras (Brinno TLC200 pro), 4) a pore water pressure sensor (buried at a depth of almost 1 meter), 5) a rain gauge and 6) four vertical polarized geophones at 4.5 Hz. The geophones are placed at intervals of 2 m and are acquiring the ambient seismic noise (passive mode) with a sampling frequency of 300 Hz for 2min every hours and all the data are collected in a Flash Memory Drive (SC115). The information about the displacements are collected analyzing the time-lapse video and using the free software Tracker. Preliminary collected data are presented here and their possible correlation is analyzed.

  17. RoMi: Refraction Microtremor Using Rotational Seismometers (United States)

    Clark, B.; Abbott, R. E.; Knox, H. A.; Eimer, M. O.; Hart, D. M.; Skaggs, J.; Denning, J. T.


    We present the results of a shallow shear-wave velocity study that utilized both traditional geophones and a newly developed rotational seismometer (Applied Technology Associates ARS-16). We used Refraction Microtremor (ReMi), a method developed by John N. Louie, during processing to determine both Rayleigh and Love wave dispersion curves using both vertical and horizontal sources. ReMi uses a distance-time (x-t) wavefield transformation technique to image the dispersion curve in slowness-frequency (p-f) space. In the course of the ReMi processing, unwanted P waves are transformed into p-f space. As rotational seismometers are insensitive to P waves, they should prove to be superior sensors for Love wave studies, as those P waves would not interfere with interpretation of the p-f wavefield. Our results show that despite having one-fifth the geophone signal-to-noise ratio in the distance-time wavefield, the ARS-16 produced superior results in the p-f wavefield. Specifically, we found increases of up to 50% in ReMi spectral ratio along the dispersion curve. This implies that as more quiet and sensitive rotational sensors are developed, deploying rotational seismometers instead of traditional sensors will yield significantly better results. This will ultimately improve shallow shear-wave velocity resolution, which is vital for calculating seismic hazard. This data was collected at Sandia National Laboratories' Facility for Analysis, Calibration, and Testing (FACT) located in Albuquerque, NM. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  18. Comparison of the bedrock depth from array measurements of Rayleigh waves associated with microtremor and seismic profile obtained the Seismic Reflection Data, Eskisehir Basin, Turkey (United States)

    Tün, Muammer; Karabulut, Savaş; Özel, Oğuz


    Ground motion estimation for future earthquakes is one of the most challenging problems in seismology and earthquake engineering. The bedrock depth has a considerable seismic risk for the urban area of Eskişehir. In this study, multiple station microtremor measurement methods which are more practical, non-distructive, fast and economical compared to seismic reflection method were implemented. These method using microtremor recordings have become a very useful data for microzonation studies because of their simple acquisition and analysis. Extensive ambient noise measurements were performed in the basin of Eskisehir from June 2010 to spring 2012. We use data recorded by a broadband seismometer and digitizer CMG-6TD, Guralp seismometer. Some of the measurement locations, the CMG-6TD sensor was located into 30 cm-deep holes in the ground to avoid strongly wind-generated, long-period noise. Dominant frequency (f), bed-rock depth (h) and shear-wave velocity (Vs) were determined from Spatial Autocorrelation (SPAC) methods. With the SPAC Method, it is possible to constrain the velocity structure underlying the site using microtremor array measurements. The results obtained were compared to the 96-channel seismic reflection data with explosive energy source. Several seismic reflection surveys with P-Gun seismic source have been performed on the same place with array measurements. We used two types of seismic sources: 36 cartridge Gun. Shot interval was 10 meters, group interval (one geophone per group, 48 geophones in total) was 10 meters, near offset was 10 meters, far offset was 480 meters, CDP interval was 5 meters. We adapted the 'Off-End Spread' technique while using the Gun. Reflection images within the sedimentary section correlate well with the velocity structure obtained from SPAC.

  19. Subsurface fracture mapping using microearthquakes detected during primary oil production, Clinton County, Kentucky

    Energy Technology Data Exchange (ETDEWEB)

    Rutledge, J.T.; Phillips, W.S. [Nambe Geophysical, Inc. (United States); Roff, A.; Albright, J.N. [Los Alamos National Lab., NM (United States); Hamilton-Smith, T. [Kentucky Geological Survey (United States); Jones, S.K.; Kimmich, K.C. [Meridian Exploration Corp. (United States)


    Downhole microseismic monitoring tests were conducted in Clinton County, Kentucky to determine if microearthquakes associated with primary production could be detected on a scale of interwell distances ({>=}400 ft) and to determine if such microearthquakes could be used to map reservoir fractures. The oil reservoirs occur in shallow (750 to 2400 ft), low-porosity (< 2%), carbonate rocks of Ordovician age. The reservoir system controlling the occurrence and flow of off and its relationship to the local and regional geology is poorly understood. Discrete reservoir microearthquakes were detected at an average rate of 11 events per week and at distances up to 4000 ft in an initial monitoring test using a single, triaxial downhole geophone receiver. In a second monitoring test 2 downhole, triaxial geophone tools were placed in a monitor well 800 ft from a new, high-volume oil well. Over a 6-month period of continuous monitoring 165 discrete, high-quality, microearthquake waveforms were recorded. Approximately 11,000 barrels of fluid were extracted in the monitor area during the 6-month period. Presently, it is unknown whether or not the microseismicity is induced by production. Hypocenters computed for 121 events delineate 4 extensive (up to 0.15 square-miles), low-angle, planar features striking approximately N65{degrees}E within the Ordovician reservoir depth interval. A composite fault-plane solution indicates a thrust focal mechanism. Such thrust structures are not observed in the surface-exposed Mississippian section, which lies above and is separated from the Ordovician section by a major unconformity of Devonian age. General relationships between the fractures revealed by the microseismicity and oil occurrence have yet to be demonstrated in the study area. The observed microseismicity occurs away from production wells, and to date, no new wells have been drilled into the mapped fracture along which shear displacement was detected.

  20. Seismic data collection from water gun and industrial background sources in the Chicago Sanitary and Ship Canal area, Illinois, 2011 (United States)

    Morrow, William S.; Carpenter, Phillip J.; Adams, Ryan F.


    The water gun is a tool adapted from deep marine geophysical surveys that is being evaluated for use as an acoustic fish deterrent to control the movement of invasive marine species. The water gun creates a seismic signal by using a compressed air discharge to move a piston rapidly within the water, resulting in an implosion. This energy pulse may be able to modify fish behavior or destroy marine life, such as the Asian carp, at some distance. The effects of this energy pulse on structures in the Chicago Sanitary and Ship Canal (CSSC), such as canal walls, shore lines, and lock structures, are not known. The potential effects of the use of a water gun on structures was identified as a concern in the CSSC and was assessed relative to existing background sources during this study. During September 2011, two water guns with piston sizes of 80 and 343 cubic inches, respectively, were tested in the CSSC at varying pressures and distances from a canal wall consisting of dolomite and dolomite setblock. Seismic data were collected during these water gun firings using geophones on land, in boreholes, and at the canal wall interface. Data were collected at varying depths in the canal water using hydrophones. Seismic data were also collected during the occurrences of barge traffic, railroad traffic located near the electric fish barrier in Lemont, and coal-loading operations at a coal power plant near the electric fish barrier. In general, energy produced by barge and railroad sources was less than energy created by the water gun. Energy levels produced by coal-loading operations at least 200 feet from geophones were approximately four times lower than energy levels measured during water gun operations.

  1. High-Resolution Seismic Reflection and Refraction Imaging of the Hayward Fault in Fremont, Alameda County, California (United States)

    Everson, E. D.; Rymer, M. J.; Goldman, M. R.; Catchings, R. D.


    In July 2007, the U.S. Geological Survey acquired a 60-m-long seismic reflection and refraction profile across the main trace of the Hayward fault in Fremont Central Park, Fremont, California. The profile was designed to determine the geometry, seismic velocities, and possible structural complexities of the fault. The study was along a part of the surface rupture of the 1868 M 7.0 Hayward earthquake. We used single-element, 40-Hz vertical geophones placed at 1-m intervals along the profile with 0.5-m lateral offset from the shot points, also with 1-m intervals. Seismic sources were generated by multiple sledgehammer blows at each shot point. Data were recorded unfiltered in the field on a Geometrics Strataview RX-60 seismograph at a sampling rate of 0.5 ms for 2 s. Geophone locations were measured in 3D using differential GPS. We developed a velocity model using the Hole (1992) code to invert P-wave first arrivals of the refraction data. Seismic P-wave velocities range from about 200 m/s near the surface to approximately 800 m/s at a depth of 13 to 16 m. The velocity model was then applied to the reflection data to develop an unmigrated common depth point (CDP) stack. The reflection data indicate the presence of at least three fault strands in an approximately 20-m-wide zone. We believe the three strands define an upwardly flaring 'flower structure', with the central strand being the main strand of the Hayward fault. The three strands project to merge at a depth of about 150 m; the overall dip of the fault zone in the upper 100 m is to the northeast, at about 88 degrees.

  2. Gas expulsions and biological activity recorded offshore Molene Island, Brittany (France): video supervised recording of OBS data and analogue modelling (United States)

    Klingelhoefer, F.; Géli, L.; Dellong, D.; Evangelia, B.; Tary, J. B.; Bayrakci, G.; Lantéri, N.; Lin, J. Y.; Chen, Y. F.; Chang, E. T. Y.


    Ocean bottom seismometers (OBS) commonly record signals from Short Duration Events (SDEs), having characteristics that are very different from those produced by tectonic earthquakes, e.g.: durations trains, with no identified P- nor S-wave arrivals. SDES were first reported by Burkisk et al (1981) who proposed biological activity as a possible cause. Since then, SDEs have been disregarded or discarded as noise by scientists interested in earthquake studies. Interest in SDEs came back recently, when it was realized that SDEs are commonly found and could be due to gas expulsions from the seafloor. To discriminate between the 2 hypotheses (biological activity vs gas emissions), different tests have been made, including seismic recordings combined with video surveillance and analogue experiments. In May 2016, two OBS (4.5 Hz) were deployed offshore Molene Island, Brittany within the field of view of the EMSO-Molene underwater observatory, at a water depth of 12 m. The camera images and the recordings reveal the presence of crabs, octopus and several species of fish. Other acoustic signals can be related to the presence of moving algae or the influence from bad weather. Tides produce characteristic curves in the noise recorded on the geophones. SDEs have been recorded on both instruments, that may well have been caused by gas expulsions from the seabed into the water. In order to verify this hypothesis, an aquarium was filled with water overlying an even grain-sized quartz sand layer. A constant air supply through a narrow tube produced gas bubbles in a regular manner and an immersed ocean bottom geophone recorded the resulting acoustic signals. The bubbles tend to have a uniform size and to produce a waveform very close to those found on the OBSs. By comparing the number of SDEs and the volume of escaped air, estimates can be made regarding the volume of gas escaping the seafloor in different environments.

  3. Shear-wave velocity profiling according to three alternative approaches: A comparative case study (United States)

    Dal Moro, G.; Keller, L.; Al-Arifi, N. S.; Moustafa, S. S. R.


    The paper intends to compare three different methodologies which can be used to analyze surface-wave propagation, thus eventually obtaining the vertical shear-wave velocity (VS) profile. The three presented methods (currently still quite unconventional) are characterized by different field procedures and data processing. The first methodology is a sort of evolution of the classical Multi-channel Analysis of Surface Waves (MASW) here accomplished by jointly considering Rayleigh and Love waves (analyzed according to the Full Velocity Spectrum approach) and the Horizontal-to-Vertical Spectral Ratio (HVSR). The second method is based on the joint analysis of the HVSR curve together with the Rayleigh-wave dispersion determined via Miniature Array Analysis of Microtremors (MAAM), a passive methodology that relies on a small number (4 to 6) of vertical geophones deployed along a small circle (for the common near-surface application the radius usually ranges from 0.6 to 5 m). Finally, the third considered approach is based on the active data acquired by a single 3-component geophone and relies on the joint inversion of the group-velocity spectra of the radial and vertical components of the Rayleigh waves, together with the Radial-to-Vertical Spectral Ratio (RVSR). The results of the analyses performed while considering these approaches (completely different both in terms of field procedures and data analysis) appear extremely consistent thus mutually validating their performances. Pros and cons of each approach are summarized both in terms of computational aspects as well as with respect to practical considerations regarding the specific character of the pertinent field procedures.

  4. Instrumental monitoring of lahars for warning purposes: new developments along the Colima Volcano, Mexico (United States)

    Coviello, Velio; Capra, Lucia; Vázquez, Rosario; Márquez, Víctor H.; Cruz, Sergio


    Early Warning Systems (EWSs) for rapid flow-like landslides can be classified into two main types: advance- and event-systems. Advance EWSs predict the flow occurrence by monitoring the parameters that may lead to initiation conditions, typically rainfall. This kind of EWSs are prone to a high number of false alarms because they are strongly affected by uncertainties in both precipitation measurements and in the estimate of rainfall thresholds. Event EWSs are based on the instrumental detection of the flow when it is already in progress. Those systems can be particularly effective to protect vulnerable infrastructures such as communication routes that do not require an excessively long alert time. However, having a much smaller lead time than advance-systems, their effectiveness strictly depends on the possibility to perform accurate and rapid measurements and to automatically process, store and validate monitoring data, that is to integrate an effective warning algorithm. In mountainous regions, several instrumented catchments exist where debris flow monitoring is performed using stage sensors, video cameras, and ground vibration detectors (GVDs). For early warning purpose, the possibility to detect debris flows from a distance is an important advantage of GVDs. In addition, most monitoring devices need to be installed in the channel bed or very close to it, with consequent great danger to be destructed. Consequently, a growing number of monitoring systems of active basins integrate a linear array of GVDs distributed along the channel, in safe locations. A debris flow warning algorithm based on geophone data was recently developed and implemented in the Gadria testing field for EWSs, Northeastern Italian Alps. This algorithm uses the Signal-to-Noise Ratio (SNR) as warning parameter instead of a classical intensity/duration threshold. The event detection algorithm adopts a non-simultaneous triggering condition requiring that at least two geophones trigger in order

  5. Time-Lapse Seismic Monitoring using a Sparse Seismic Array: Pre-Injection Assessment of Repeatability at the Aquistore CO2 Storage Site (United States)

    Roach, L. A.; White, D.; Roberts, B.


    Aquistore is a deep saline geological storage project. An estimated 2000 tonnes/day of CO2 will be captured and injected at approximately 3200m - 3350m into a sandstone reservoir. CO2 injection is expected to create a measurable change in the seismic properties within the reservoir. Our goal is to utilize a sparse seismic array to improve cost effectiveness and time-lapse SNR by improved repeatability. A permanent surface seismic array has been deployed at the Aquistore CO2 storage site comprising 630 vertical-component geophones deployed at a depth of 20m over a 2.5 x 2.5 km grid. Receiver lines are spaced at intervals of 144m, with an in-line geophone spacing of 72m and with geophones along adjacent lines staggered by 32m in the in-line direction. To assess the repeatability of seismic data acquired using this sparse seismic array, two 3D seismic surveys were conducted prior to the start of CO2 injection. The baseline survey was acquired in March, 2012 with a subsequent monitor survey in April, 2013. Sources consisted of 1kg dynamite shots detonated at 15m depth over a 3 x 3 km grid, with 12 shot lines spaced at 288m and 144m in-line spacing. The permanent receiver array provided for 100% collocated receiver positions, while 90% of the shot points of the repeat survey were placed within 2m of the shots of the baseline survey. These elements of the survey design serve to reduce the non-repeatability that may be related to acquisition effects and seasonal variations. Before processing, the datasets were matched so that the number of common shots and receivers was 256 and 599 respectively which results in a nominal fold of 40. Our preliminary approach of 3D time-lapse processing was to process each vintage separately while applying identical flows with the same parameters (e.g. mutes and time gates) to the repeat dataset. The normalized root-mean-square (nRMS) of the difference of the two data sets was used as the metric for repeatability in assessing the similarity

  6. Seismic characterization of low-magnitude floods and lahars at La Lumbre ravine, Volcán de Colima (Mexico) (United States)

    Coviello, Velio; Capra, Lucia; Márquez, Víctor H.; Procter, Jonathan; Walsh, Braden


    Volcán de Colima currently is the most active volcano in Mexico where a number of rain-induced lahars occur each year. After an explosive phase, lahar frequency increases due to the immediate reworking of pyroclastic material and it progressively decreases in the following years. This behavior was distinctly observed during the two last rainy seasons that followed the intense volcanic activity of July 2015. La Lumbre ravine drains the West-Southwestern slopes of Volcán de Colima and is one of the most active channels of the volcano. Since 2014, monitoring is performed in a heavily instrumented cross-section located at 1580 m a.s.l. on the left bank of the channel. At the present day, the monitoring station is equipped with a raingauge, two stage sensors, a videocamera, and different seismic devices. At La Lumbre, lahars initiate as dilute, sediment-laden stream flows and with the entrainment of additional sediment they evolve into hyper-concentrations and debris flows. The hydro-repellency mechanism of the highly vegetated volcanic soils can explain the high frequency of lahars triggered by low-intensity rainfall events: under these hydrophobic conditions, infiltration is inhibited and runoff is facilitated at less highly peaked discharges that are more likely to initiate lahars that can have an impact on the inhabited areas located downstream. This is the reason why the possibility to detect not only large lahars but also low-magnitude flows is particularly important at La Lumbre. Here we present monitoring data of processes ranging from stream flows to large lahars that occurred during the last rainy seasons along La Lumbre ravine. In particular, we investigate the possibility to estimate the sediment concentration of debris flood and small lahars using a very easy-to-install and low-cost seismic sensor, i.e. a geophone, installed outside the flow path. For instance, we show how a hyper-concentrated flow characterized by a mean velocity of less than 1 meter per

  7. Microseismic monitoring and velocity model building at the Longyearbyen CO2-Lab, Svalbard (United States)

    Oye, V.; Zhao, P.; Lecomte, I.; Braathen, A.; Olaussen, S.


    The Longyearbyen CO2 storage lab project addresses the problem to turn Svalbard into a CO2 neutral community. The project has now confirmed that an injective reservoir (800-1000 m depth) and a sealing cap rock section exist around Longyearbyen, and will proceed towards demonstration and monitoring studies of sub surface CO2 storage over time. The progressive construction of the Longyearbyen CO2 storage lab is currently addressing detailed properties and geometry of the reservoir. Liquids other than CO2 have been used in this initial phase (water, brine, gel). The reservoir below Longyearbyen is considered physically open, and, therefore, will likely experience drift of the injected CO2 towards the Northeast, through gradual mixing and expulsion of saline groundwater. This offers a unique opportunity for studying the behavior of CO2 in subsurface saline aquifers. Four wells have been drilled so far and several new monitoring wells are planned for this purpose. In this study, we try to use induced seismicity to monitor the injection fluid in the test site. A precise estimation of the location and magnitude of the microearthquake will be important to investigate the link between the injection and the sudden stress release as a microearthquake. In August 2010 a fluid injection experiment was carried out at the CO2 lab. In parallel, a microseismic monitoring network was deployed close to the injection well. The network consists of a 5-level string of 3-component geophones in a vertical observation well, with 50m distance between the instruments and a maximum depth of 294 meters. In addition, three shallow boreholes of 12 m depth have been drilled at about 500 m distance to the injection well. These additional surface stations are intended to provide more accurate locations for microearthquakes that are large enough to be recorded at the surface. Approximately 17 hours after the 5-days water injection test (from 20th to 25th August, 2010), a relatively strong

  8. Undersafe: Monitoring safety parameters in touristic mines and caves (United States)

    Parcerisa, David; Sanmiquel, Lluís; Alfonso, Pura; Oliva, Josep


    Tourism is a key sector of the European economy, generating more than 5% of the EU GPD (Gross Domestic Product). Usually, underground touristic sites receive non-expert visitors; nevertheless these activities are poorly regulated or completely deregulated. Nowadays, safety is provided by underground expert professionals whom proceed to regular inspections and by basic safety infrastructures. Even with these measures, some potential personal and environmental dangers are always present and cannot be totally avoided. Therefore, there is a clear need of a new technological product for safety and environmental continuous monitoring of tourist underground attractions. So, the aim of the Undersafe project is to provide underground attractions with a novel and specifically tailored monitoring system, easy to use and maintain. One of the goals of the Undersafe project is to develop a rock falling detection based on a set of cost limited vibration sensors. Based on the technical needs, but with cost constraints, different types of potential sensors are considered: Underground microphone: It is placed in the surface or in the underground. It is based on the consideration that the impact of the stone generates a ground impact vibration which can be understood as a "noise" that is received by a microphone capsule. Airborne sound sensing microphone: It similarly applies to underground use of the microphones, but now the microphone is tested as for its traditional use (I.e. air sound detection). In such case, the microphone detects the environmental noise produced by the impact of the stone falling onto the ground, which will include the impact sound of the stone. Geophone: It is the de facto standard for ground vibrations. Although this technology was initially discarded due to its high cost, recently, low cost geophones have appeared in the market that allows its use inside the underground attractions. Accelerometers: These, can have enough sensibility to act as vibration

  9. Active seismic monitoring of changes of the reflection response of a crystalline shear zone due to fluid injection in the crust at the Continental Deep Drilling Site, Germany (United States)

    Beilecke, T.; Kurt, B.; Stefan, B.


    In theory and in the laboratory variations of the hydraulic pressure can be detected with seismic methods: A lowering of the hydraulic pressure leads to the closure of micro-cracks within the rock (increase of the differential or effective pressure). Subsequently, the seismic velocities increase. An increase of the hydraulic pressure leads to reverse seismic effects. Consequently, seismic impedance contrasts and associated reflection amplitudes vary in the case of a propagating fluid pressure front in a rock matrix with inhomogeneous permeability - as is the case at shear zones. The largest amplitude changes can be expected with vertical ray inclination on the impedance contrast. Generally, the expected effects are small however (Kaselow, 2004). The practical utilization of active seismics for the detection of pressure changes at large scale in hard rock is currently being studied at the Continental Deep Drilling Site (KTB). The injection of water (200 l/min) in a depth of about 4000 m into the so-called SE2 shear zone in the KTB pilot hole was monitored with active seismics between May 2004 and April 2005. The core of the experiment layout is a fixed 5-arm geophone array consisting of 24 3-component geophones, buried at about 70 cm depth. The source signal is a vertical vibrator sweep of 30 s length with the spectrum 30-120 Hz. The signal is sent into the ground 32 times during each cycle, detected with the array and recorded separately for each geophone channel, without prior correlation with the source signal. This allows maximum post-processing with seismic processing and analysis tools and especially permits the use of array properties to increase the signal-to-noise ratio. Critical parameters of the experiment are the repeatability of the source signal as well as the stability of the receiver properties. Another pivot is the hydraulic pressure and its distribution built up within the rock matrix. Estimations based on model calculations show that a change of

  10. Applying the seismic interferometry method to vertical seismic profile data using tunnel excavation noise as source (United States)

    Jurado, Maria Jose; Teixido, Teresa; Martin, Elena; Segarra, Miguel; Segura, Carlos


    In the frame of the research conducted to develop efficient strategies for investigation of rock properties and fluids ahead of tunnel excavations the seismic interferometry method was applied to analyze the data acquired in boreholes instrumented with geophone strings. The results obtained confirmed that seismic interferometry provided an improved resolution of petrophysical properties to identify heterogeneities and geological structures ahead of the excavation. These features are beyond the resolution of other conventional geophysical methods but can be the cause severe problems in the excavation of tunnels. Geophone strings were used to record different types of seismic noise generated at the tunnel head during excavation with a tunnelling machine and also during the placement of the rings covering the tunnel excavation. In this study we show how tunnel construction activities have been characterized as source of seismic signal and used in our research as the seismic source signal for generating a 3D reflection seismic survey. The data was recorded in vertical water filled borehole with a borehole seismic string at a distance of 60 m from the tunnel trace. A reference pilot signal was obtained from seismograms acquired close the tunnel face excavation in order to obtain best signal-to-noise ratio to be used in the interferometry processing (Poletto et al., 2010). The seismic interferometry method (Claerbout 1968) was successfully applied to image the subsurface geological structure using the seismic wave field generated by tunneling (tunnelling machine and construction activities) recorded with geophone strings. This technique was applied simulating virtual shot records related to the number of receivers in the borehole with the seismic transmitted events, and processing the data as a reflection seismic survey. The pseudo reflective wave field was obtained by cross-correlation of the transmitted wave data. We applied the relationship between the transmission

  11. Compact FBG diaphragm accelerometer based on L-shaped rigid cantilever beam

    Institute of Scientific and Technical Information of China (English)

    Yinyan Weng; Xueguang Qiao; Zhongyao Feng; Manli Hu; Jinghua Zhang; YangYang


    A compact fiber Bragg grating (FBG) diaphragm accelerometer based on L-shaped rigid cantilever beam is proposed and experimentally demonstrated. The sensing system is based on the integration of a flat diaphragm and an L-shaped rigid cantilever beam. The FBG is pre-tensioned and the two side points are fixed, efficiently avoiding the unwanted chirp effect of grating. Dynamic vibration measurement shows that the proposed FBG diaphragm accelerometer provides a wide frequency response range (0-110 Hz) and an extremely high sensitivity (106.5 pm/g), indemnifying it as a good candidate for embedding structural health monitoring and seismic wave measurement.%A compact fiber Bragg grating (FBG) diaphragm accelerometer based on L-shaped rigid cantilever beam is proposed and experimentally demonstrated.The sensing system is based on the integration of a flat diaphragm and an L-shaped rigid cantilever beam.The FBG is pre-tensioned and the two side points are fixed,efficiently avoiding the unwanted chirp effect of grating.Dynamic vibration measurement shows that the proposed FBG diaphragm accelerometer provides a wide frequency response range (0-110 Hz) and an extremely high sensitivity (106.5 pm/g),indentifying it as a good candidate for embedding structural health monitoring and seismic wave measurement.In the past few decades,accelerometers based on fiber Bragg grating (FBG) have attracted a great deal of interest from researchers and engineers because they play a vital role in vibration measurements.In recent years,FBG accelerometers have been more and more applied in structural health monitoring[1-3) and seismic wave measurement[4-6].This study concerns about the development of geophones composed of FBG accelerometers in seismic exploration.The main frequency of geophones in seismic wave measurement of oil and gas exploration is usually below 100 Hz.An FBG-based accelerometer consisting of a mass resting on a layer of compliant material supported by a rigid base plate

  12. The sinkhole of Schmalkalden, Germany - Imaging of near-surface subrosion structures and faults (United States)

    Wadas, Sonja H.; Tschache, Saskia; Polom, Ulrich; Krawczyk, Charlotte M.


    In November 2010 a sinkhole of 30 m diameter and 20 m depth opened in a residential area in the village Schmalkalden, Germany, which fortunately led to damage of buildings and property only. The collapse was caused by leaching of soluble rocks in the subsurface, called subrosion. For an improved understanding of the processes leading to subrosion and sinkhole development a detailed characterization of the subsurface structures and elastic parameters is required. We used shear wave reflection seismic, which has proven to be a suitable method for high-resolution imaging of the near-surface. The village Schmalkalden is located in southern Thuringia in Germany. Since the Upper Cretaceous the area is dominated by fault tectonics, fractures and joints, which increase the rock permeability. The circulating groundwater leaches the Permian saline deposits in the subsurface and forms upward migrating cavities, which can develop into sinkholes, if the overburden collapses. In the direct vicinity of the backfilled sinkhole, five 2-D shear wave reflection seismic profiles with total length of ca. 900 m and a zero-offset VSP down to 150 m depth were acquired. For the surface profiles a 120-channel landstreamer attached with horizontal geophones and an electrodynamic micro-vibrator, exciting horizontally polarized shear waves, were used. For the VSP survey an oriented borehole probe equipped with a 3C-geophone and electrodynamic and hydraulic vibrators, exciting compression- and shear waves, were utilized. The seismic sections show high-resolution images from the surface to ca. 100 m depth. They display heterogeneous structures as indicated by strong vertical and lateral variations of the reflectors. In the near-surface, depressions are visible and zones of low seismic velocities < 180 m/s show increased attenuation of the seismic wave field. These are probably the result of the fractured underground, due to fault tectonics and the ongoing subrosion. The unstable zones are

  13. Comparison of high-resolution P- and SH-wave reflection seismic data in alluvial and pyroclastic deposits in Indonesia (United States)

    Wiyono, Wiyono; Polom, Ulrich; Krawczyk, Charlotte M.


    Seismic reflection is one of the stable methods to investigate subsurface conditions. However, there are still many unresolved issues, especially for areas with specific and complex geological environments. Here, each location has an own characteristic due to material compounds and the geological structure. We acquired high-resolution, P-and SH-wave seismic reflection profiles at two different locations in Indonesia. The first location was in Semarang (Central Java) and the second one was in Tiris (East Java). The first region is located on an alluvial plain with thick alluvial deposits of more than 100 m estimated thickness, and the second location was located on pyroclastic deposit material. The seismic measurements for both locations were carried out using a 48-channel recording system (14-Hz P-wave, 10-Hz SH-wave geophones) with geophone intervals of 5 m (P-waves) and 1 m (SH-waves), respectively. The seismic source for the P-wave was a ca. 4 kg sledge hammer which generated a seismic signal by by hitting on an aluminum plate of 30x30 cm, whereas the SH-wave source was a mini-vibrator ELVIS (Electrodynamic Vibrator System), version 3. Thirteen seismic profiles at Semarang and eighth profiles at Tiris were acquired. The results of seismic data in Semarang show fair to good seismic records for both P-and SH-waves. The raw data contain high signal-to-noise-ratio. Many clear reflectors can be detected. The P-wave data shows reflectors down to 250 ms two-way time while the SH-wave records show seismic events up to 600 ms two-way time. This result is in strong contrast to the seismic data result from the Tiris region. The P-wave data show very low signal to noise ratio, there is no reflection signal visible, only the surface waves and the ambient noise from the surrounding area are visible. The SH-waves give a fair to good result which enables reflector detection down to 300 ms two-way time. The results from the two seismic campaigns show that SH-wave reflection

  14. 地震勘探用电容式闭环微加速度计的仿真%Closed-Loop System Simulation of the Capacitive Micro-Accelerometer for the Seismic Exploration

    Institute of Scientific and Technical Information of China (English)

    谌贵辉; 刘建生; 李礼; 杨帆


    The performances of the new geophone are significantly improved by the MEMS acceleration sensors. The mechanical model of the silicon cantilever beam was set up by means of the finite element software ANSYS, and the best design structure size was gained through the stimulation of the mechanical properties. The design result shows that the length L is 150 μm, the width b is-40 μm, the thickness h is 4 μm, and d0 is 1 pm (do is the space between the moving electrode and fixed electrode). Meanwhile, the overall mathematical model of the closed-loop system was established using the sensor circuit simulation software. The simulation results show that the step response and sinusoidal response agree well with the result of the theoretical analysis. The sensor resolution and bandwidth are up to 0. 001 m/s2 and 500 MHz, respectively. The new-type geophone based on the MEMS acceleration sensor will have wide application prospects in the seismic exploration.%MEMS加速度传感器大幅提高了新型地震检波器的各项性能指标.利用有限元软件AN-SYS建立了悬臂硅梁的力学模型,并通过其力学性能仿真,得出优化的设计结构尺寸,即梁长L=150μm,梁宽b=40μm,梁厚h=4μm,活动电极和固定电极的间距d0取为1μm.同时利用电路仿真软件建立了传感器闭环系统的整体仿真数学模型,仿真结果表明其阶跃响应和正弦响应基本和理论分析结果吻合,传感器的分辨率可达0.001m/s2,频带宽度可达500MHz.该基于MEMS加速度传感器的新型地震检波器在地震勘探中将具有广阔的应用前景.

  15. textbf{THE Debris-Flow Monitoring System of Acquabona Torrent (Cortina D'Ampezzo, BL, Italy).} (United States)

    Dallavalle, D.; Scotton, P.; Genevois, R.


    A new debris flow monitoring system has been designed and developed at the Acquabona site (2010), on the left side of the Boite River Valley, near Cortina d'Ampezzo. The monitoring system is composed of two stations. The upstream station is located at the baseof the dolomitic rock cliff where the water feeding area is located, at an altitude of about 1715 m a.s.l., in order to measure the meteorological conditions of the site, at the feet of the dolomite rock massif. The installed weather station allows acquisition of rainfall, wind speed and direction, relative humidity, air temperature, barometric pressure and other secondary parameters. The downstream station, located at 1175 m a.s.l., is closed to the deposition area and is provided by a tipping bucket rain gauge, an ultrasonic and a laser distance meter and a digital video camera. The upstream station is connected via radio modem and directional antenna to the downstream station, allowing the data acquisition by a single board computer that collects and stores locally the data. The processor and the local mass storage are directly managed remotely, via 3G UMTS high speed Internet, from the Department of Geosciences of Padua. Four geophones are distributed along the flow channel, in order to measure travelling times, at a distance of about 100 meters each other: one at the downstream station, two upstream and one downstream. The equipment at the downstream station has been mounted on a reticular structure anchored to a big boulder at the left side of the torrent. The distance from the bottom of the channel is about 3.5 m. The support structure can be rotated around the anchorage vertical axis about 90° . The aim of the monitoring system is to describe the hydrologic conditions for debris-flows occurrence and their dynamic properties, giving continuity to field measurements initiated at the site more than ten years ago. The new monitoring system is active from spring 2011. The 2011 did not record debris

  16. Application of Coalfield 3D Winning District Seismic Prospecting Data Acquisition Technology in Wangjialing Mine Area Loess Tableland%黄土塬区煤田三维采区地震勘探采集技术在王家岭矿区的应用

    Institute of Scientific and Technical Information of China (English)

    武建军; 贺建明; 曾维望


    王家岭矿区属黄土塬地貌,各种干扰波十分发育,地震波吸收、衰减严重,主要煤层埋藏浅、层数多、小构造发育,常规煤田地震采集方法获得的地震资料信噪比和分辨率较低,难以达到采区地震勘探的“三高”要求.针对王家岭矿区实际特点,在精细调查浅表层黄土速度分层结构的基础上,综合采用逐点设计井深、震/检联合组合、低频检波器接收、大偏移距/高覆盖观测系统等关键采集技术,有效提高了地震资料信噪比与分辨率,获得了连续性较好的下组煤层反射波,为精细构造识别与岩性研究奠定了基础.%The Wangjialing mine area has a loess tableland landform, also very developed various seismic disturbing waves, and serious seismic wave absorption and attenuation. Main coal seams have features of shallow buried depth, multiple seams, developed minor structures, thus conventional coalfield seismic acquisition method can only acquire low signal-noise ratio and low resolution, hardly to reach seismic prospecting "3 High" (high signal-noise ratio, resolution and fidelity) requirement. In allusion to Wangjialing area actual characteristics, on the basis of careful survey of near-surface loess velocity layering structure, using integrated key acquisition techniques of well depth roll-along design, source/geophone associated combination, low frequency geophone receiving, large offset/wide coverage field setup, effectively improved seismic data signal-noise ratio and resolution, obtained good continuity reflection of lower coal group, thus laid a foundation for delicate structure identifying and lithologic study.

  17. Deep crustal reflections from a Vibroseis survey in northern Switzerland (United States)

    Finckh, P.; Ansorge, J.; Mueller, St.; Sprecher, Chr.


    In 1982 a Vibroseis survey comprising 180 km of reflection profiles was run in northern Switzerland in order to investigate the suitability of the crystalline basement for the deposition of highly radioactive waste. A configuration was chosen with 144 channels, 25 m of geophone spacing, 20 s sweeps ranging from 11 to 61 Hz and stacking of 4 or 8 sweeps of 3 simultaneous vibrators at twice the geophone spacing. The listening time was generally 4 s and at 4 sites it was extended to 11s for the detection of deeper crustal reflectors. This survey unravelled the complicated fault and thrust system beneath the Swiss folded Jura mountains. The stack from 4 s to 11 s reveals clearly a strong sloping reflector between 3.0 and 3.5 s which is strong evidence for a pronounced differentiation in the upper crust. A series of reflections is observed between 5.8 and 7.2 s the top of which can be correlated with the Conrad discontinuity. A strong "layered" signal between 9.0 and 9.5 s is interpreted as reflections from the M-discontinuity. The main features are compatible with results from nearby refraction surveys in the southern Rhinegraben rift system which show a distinct velocity increase of about 0.5 km/s in the lower crust at a depth ranging from 15 to 20 km, followed by an inversion zone or a laminated structure before reaching the Moho at about 27 km depth. The correlation of the field recordings with the first 10 s of the up-sweep only, shows some loss of resolution in the uppermost 3 s because of the lower frequency content of the signal. However, the lower parts of the sections are nearly identical. The fact that the deeper reflectors in the sections can consistently be traced laterally is a strong argument for using this processing technique. Thus high-coverage Vibroseis surveys utilizing up-sweep can be processed for deep crustal reflections even if the recording time is restricted to the standard 4 s, provided the surface static corrections are carried out with high

  18. Near-surface seismic surveys at Rifle, Colorado for shallow groundwater contamination risk assessment (United States)

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


    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.

  19. Underground structure characterization using motor vehicles as passive seismic sources (United States)

    Kuzma, H. A.; Liu, Y.; Zhao, Y.; Rector, J.; Vaidya, S.


    The ability to detect and characterize underground voids will be critical to the success of On-Site Inspections (OSI) as mandated by the nuclear Comprehensive Test Ban Treaty (CTBT). OSIs may be conducted in order to successfully locate the Ground Zero of underground tests as well as infrastructure related to testing. Recently, our team has shown the potential of a new technique to detect underground objects using the amplitude of seismic surface waves generated by motor vehicles. In an experiment conducted in June, 2009 we were able to detect an abandoned railroad tunnel by recognizing a clear pattern in the surface waves scattered by the tunnel, using a signal generated by driving a car on a dirt road across the tunnel. Synthetic experiments conducted using physically realistic wave-equation models further suggest that the technique can be readily applied to detecting underground features: it may be possible to image structures of importance to OSI simply by laying out an array of geophones (or using an array already in place for passive listening for event aftershocks) and driving vehicles around the site. We present evidence from a set of field experiments and from synthetic modeling and inversion studies to illustrate adaptations of the technique for OSI. Signature of an abandoned underground railroad tunnel at Donner Summit, CA. To produce this image, a line of geophones was placed along a dirt road perpendicular to the tunnel (black box) and a single car was driven along the road. A normalized mean power-spectrum is displayed on a log scale as a function of meters from the center of the tunnel. The top of the tunnel was 18m below ground surface. The tunnel anomaly is made up of a shadow (light) directly above the tunnel and amplitude build-up (dark) on either side of the tunnel. The size of the anomaly (6 orders of magnitude) suggests that the method can be extended to find deep structures at greater distances from the source and receivers.

  20. The Cossack Ranger II Seismograph, Research And Outreach Efforts. (United States)

    Husebye, E. S.; Fedorenko, Y. V.; Pilgaev, S. V.; Matveeva, T. S.


    Earthquake monitoring is a highly desirable endaveour among seismologists but far from easy in practise. The reason for this is 3-fold; costly instrumentation, colleagues who dislike competition in network operations and running costs in terms of data transfer, storage and analysis. However, developments in recent years have off- set technical obstacles of the above kinds thus allowing for personal or small institution seismometry albeit the human factor remains. Anyway, a conventional SP-seismometer costs at least 2000 dollars while a complete 3-component seismograph may well cost 10000 dollars. However, a geophone-based 3-component seismograph may cost less than 2000 dollars but still have a performance matching that of a conventional station. The largest worry is normally not the one-time instrument expenses but operational and maintenance costs over say a 5-years time span. A solution here is socalled Seis Schooloperations implying that stations are deployed close to schools having good 'rocky' sites and permanent Internet access. Such sites are not necessarily optimum regarding ambient noise but on the other hand offer free data transfer to Hub and dedicated teachers taking care of the station operation. We have deployed small seismograph networks based on the above design and operational principles both in Norway and Karelia (NW Russia) as part of national outreach efforts. Noteworthy; recordings from these networks have proved useful in advanced wavefield analysis. A number of countries are economically poor but rich in earthquake activities. In other words, can hardly afford adequate monitoring of local seismicity. An interesting undertaking here is the SENSES project in Bulgaria supported by the "NATO Science for Peace and Security Programme' including 25 seismograph stations deployed nation-wide at sites close to local high schools. The close cooperation with these schools will ensure modest operational costs but also strengthen local outreach efforts in

  1. Penn State geoPebble system: Design,Implementation, and Initial Results (United States)

    Urbina, J. V.; Anandakrishnan, S.; Bilen, S. G.; Fleishman, A.; Burkett, P.


    The Penn State geoPebble system is a new network of wirelessly interconnected seismic and GPS sensor nodes with flexible architecture. This network will be used for studies of ice sheets in Antarctica and Greenland, as well as to investigate mountain glaciers. The network will consist of ˜150 geoPebbles that can be deployed in a user-defined spatial geometry. We present our design methodology, which has enabled us to develop these state-of- the art sensors using commercial-off-the-shelf hardware combined with custom-designed hardware and software. Each geoPebble is a self- contained, wirelessly connected sensor for collecting seismic measurements and position information. Key elements of each node encompasses a three-component seismic recorder, which includes an amplifier, filter, and 24- bit analog-to-digital converter that can sample up to 10 kHz. Each unit also includes a microphone channel to record the ground-coupled airwave. The timing for each node is available from GPS measurements and a local precision oscillator that is conditioned by the GPS timing pulses. In addition, we record the carrier-phase measurement of the L1 GPS signal in order to determine location at sub-decimeter accuracy (relative to other geoPebbles within a few kilometers radius). Each geoPebble includes 16 GB of solid-state storage, wireless communications capability to a central supervisory unit, and auxiliary measurements capability (including tilt from accelerometers, absolute orientation from magnetometers and temperature). A novel aspect of the geoPebble is a wireless charging system for the internal battery (using inductive coupling techniques). The geoPebbles include all the sensors (geophones, GPS, microphone), communications (WiFi), and power (battery and charging) internally, so the geoPebble system can operate without any cabling connections (though we do provide an external connector so that different geophones can be used). We report initial field-deployment results and

  2. Analysis of ground vibrations produced by an 80 in3 water gun in the Chicago Sanitary and Ship Canal, Lemont, Illinois (United States)

    Koebel, Carolyn Michelle

    Since its completion in 1910, the Chicago Sanitary and Ship Canal (CSSC) has become a pathway for invasive species (and potentially Asian carp) to reach the Great Lakes. Currently, an electric barrier is used to prevent Asian carp migration through the canal, but the need for a secondary method is necessary, especially when the electric barrier undergoes maintenance. The underwater Asian carp "cannon" (water gun) provides such a method. Analysis of the ground movement produced by an 80 in3 water gun in the CSSC was performed in order to establish any potential for damage to the either the canal or structures built along the canal. Ground movement was collected using 3-component geophones on both the land surface and in boreholes. The peak particle velocities (PPVs) were analyzed to determine if damage would be caused to structures located along the canal. Vector sum velocity ground movement along the canal wall was as high as 0.28 in/s (7.11 mm/s), which is much lower than the United States Bureau of Mines (USBM) ground vibration damage threshold of 0.75 in/s (19.1 mm/s), causing no potential for damage to structures along the canal wall. The dominant frequency of ground motion produced by the water gun is primarily above 40 Hz, so the wave energy should attenuate fairly quickly away from the canal wall, with little disturbance to structures further from the wall.

  3. OptaSense distributed acoustic and seismic sensing using COTS fiber optic cables for infrastructure protection and counter terrorism (United States)

    Duckworth, Gregory L.; Ku, Emery M.


    The OptaSense® Distributed Acoustic Sensing (DAS) technology can turn any cable with single-mode optical fiber into a very large and densely sampled acoustic/seismic sensor array—covering up to a 50 km aperture per system with "virtual" sensor separations as small as 1 meter on the unmodified cable. The system uses Rayleigh scattering from the imperfections in the fiber to return the optical signals measuring local fiber strain from seismic or air and water acoustic signals. The scalable system architecture can provide border monitoring and high-security perimeter and linear asset protection for a variety of industries—from nuclear facilities to oil and gas pipelines. This paper presents various application architectures and system performance examples for detection, localization, and classification of personnel footsteps, vehicles, digging and tunneling, gunshots, aircraft, and earthquakes. The DAS technology can provide a costeffective alternative to unattended ground sensors and geophone arrays, and a complement or alternative to imaging and radar sensors in many applications. The transduction, signal processing, and operator control and display technology will be described, and performance examples will be given from research and development testing and from operational systems on pipelines, critical infrastructure perimeters, railroads, and roadways. Potential new applications will be discussed that can take advantage of existing fiber-optic telecommunications infrastructure as "the sensor"—leading to low-cost and high-coverage systems.

  4. Seismic techniques in coal mining

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, A.K.; Belleza, G.V.


    This report describes a study of the peripheral fractured zones in coal pillars by the seismic refraction method and a version of the uphole method. The study, conducted at three collieries in New South Wales, investigated the depths of such fractured zones and the degrees of fracturing therein. The equipment consisted of a sledgehammer, 3-component borehole geophone assemblies, and a 12-channel oscillographic recorder with the facility of stacking multiple repetitions of given signals. The application of the refraction method was more complicated than the uphole method. However, the refraction method provided the depths of a fracture zone along the length of the spread, as opposed to the depth at a single location by the uphole method. The depths of the fractured zones obtained from the refraction method were less than the corresponding ones from the uphole method, the latter being closer to the findings of other investigators. The determined depths of the fractured zones in pillars were less than those in continuous ribsides. The depths of fractured zones and the degree of fracturing therein seemed to have some relationship with the depth of the seam from the surface.

  5. Elastic-Waveform Inversion with Compressive Sensing for Sparse Seismic Data

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Youzuo [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Huang, Lianjie [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    Accurate velocity models of compressional- and shear-waves are essential for geothermal reservoir characterization and microseismic imaging. Elastic-waveform inversion of multi-component seismic data can provide high-resolution inversion results of subsurface geophysical properties. However, the method requires seismic data acquired using dense source and receiver arrays. In practice, seismic sources and/or geophones are often sparsely distributed on the surface and/or in a borehole, such as 3D vertical seismic profiling (VSP) surveys. We develop a novel elastic-waveform inversion method with compressive sensing for inversion of sparse seismic data. We employ an alternating-minimization algorithm to solve the optimization problem of our new waveform inversion method. We validate our new method using synthetic VSP data for a geophysical model built using geologic features found at the Raft River enhanced-geothermal-system (EGS) field. We apply our method to synthetic VSP data with a sparse source array and compare the results with those obtained with a dense source array. Our numerical results demonstrate that the velocity mode ls produced with our new method using a sparse source array are almost as accurate as those obtained using a dense source array.

  6. Body-wave retrieval and imaging from ambient seismic fields with very dense arrays (United States)

    Nakata, N.; Boué, P.; Beroza, G. C.


    Correlation-based analyses of ambient seismic wavefields is a powerful tool for retrieving subsurface information such as stiffness, anisotropy, and heterogeneity at a variety of scales. These analyses can be considered to be data-driven wavefield modeling. Studies of ambient-field tomography have been mostly focused on the surface waves, especially fundamental-mode Rayleigh waves. Although the surface-wave tomography is useful to model 3D velocities, the spatial resolution is limited due to the extended depth sensitivity of the surface wave measurements. Moreover, to represent elastic media, we need at least two stiffness parameters (e.g., shear and bulk moduli). We develop a technique to retrieve P diving waves from the ambient field observed by the dense geophone network (~2500 receivers with 100-m spacing) at Long Beach, California. With two-step filtering, we improve the signal-to-noise ratio of body waves to extract P wave observations that we use for tomography to estimate 3D P-wave velocity structure. The small scale-length heterogeneity of the velocity model follows a power law with ellipsoidal anisotropy. We also discuss possibilities to retrieve reflected waves from the ambient field and show other applications of the body-wave extraction at different locations and scales. Note that reflected waves penetrate deeper than diving waves and have the potential to provide much higher spatial resolution.

  7. Seismic wave detection system based on fully distributed acoustic sensing (United States)

    Jiang, Yue; Xu, Tuanwei; Feng, Shengwen; Huang, Jianfen; Yang, Yang; Guo, Gaoran; Li, Fang


    This paper presents a seismic wave detection system based on fully distributed acoustic sensing. Combined with Φ- OTDR and PGC demodulation technology, the system can detect and acquire seismic wave in real time. The system has a frequency response of 3.05 dB from 5 Hz to 1 kHz, whose sampling interval of each channel of 1 meter on total sensing distance up to 10 km. By comparing with the geophone in laboratory, the data show that in the time domain and frequency domain, two waveforms coincide consistently, and the correlation coefficient could be larger than 0.98. Through the analysis of the data of the array experiment and the oil well experiment, DAS system shows a consistent time domain and frequency domain response and a clearer trail of seismic wave signal as well as a higher signal-noise rate which indicate that the system we proposed is expected to become the next generation of seismic exploration equipment.

  8. Design and first tests of a Macroseismic Sensor System (United States)

    Brueckl, Ewald; Polydor, Stefan; Ableitinger, Klaus; Rafeiner-Magor, Walter; Kristufek, Werner; Mertl, Stefan; Lenhardt, Wolfgang


    Seismic observatories are located in remote, low-noise areas for good reason and do not probe areas of dense and sensitive infrastructure. Complementary macroseismic data provide dense, qualitative information on ground motion in populated areas. Motivated by the QCN (Quake Catcher Network), a new low-cost sensor system (Macroseismic Sensor System = MSS) has been developed to support the evaluation of macroseismic data with quantitative information on ground movement in populated and industrial areas. Scholars, alumni and teachers from a technical high school contributed substantially to this development within the Sparkling Science project Schools & Quakes and the Citizen Science project QuakeWatch Austria. The MSS uses horizontal 4.5 Hz geophones and 16Bit AD conversion, and 100 Hz sampling, formatting to MiniSeed, and continuous data transmission via LAN or WLAN to a server are controlled by an integrated microcomputer (Raspberry Pi). Real-time generation of shake and source maps (based on proxies of the PGV in successive time windows) allows for differentiation between local seismic events (e.g., traffic noise, shock close to the sensor) and signals from earthquakes or quarry blasts. The inherent noise of the MSS is about 1% of the PGV corresponding to the lower boundary of intensity I = 2, which is below the ambient noise level at stations in highly populated or industrial areas. The MSS is already being tested at locations around a quarry with regular production blasts. An expansion to a local network in the Vienna Basin will be the next step.

  9. Imaging the Black Hills Fault, Clark County, Nevada Utilizing High-Resolution Seismic Reflection and Vibroseis (United States)

    Zaragoza, S. A.; Snelson, C. M.; Saldana, S. C.; Hirsch, A.; Poche, S.; Taylor, W. J.


    Historically, the location, geometries, and seismic potential of southern Nevada faults are poorly constrained. Collection of such data and seismic hazard characterization of the Black Hills fault (BHF) are important steps in better defining one of these faults. The BHF forms the northwestern structural boundary of the Eldorado Valley, which lies ~20 km southeast of Las Vegas, Nevada, between the growing communities of Henderson and Boulder City. Earthquake magnitude estimates based on surface rupture length (SRL) indicate an earthquake potential of Mw 5.7; however, estimates based on displacement values documented in a paleoseismic trench indicate a higher value of Mw 6.4-6.8. This implies that the subsurface rupture length is significantly greater than the length of the scarp. Although previous attempts to image the fault with a hammer source were inconclusive, gravity studies and local geology imply that the fault continues south of the scarp. Therefore, additional high-resolution seismic reflection and refraction data were acquired in SEG2 format along portions of a 1 km profile at 5 m station spacing utilizing a vibroseis source. At each shot point, a stack of four 30-160 Hz vibroseis sweeps of 15 s duration was recorded on a 60-channel system with 40 Hz geophones. A preliminary examination of these data indicates the existence of an eastward dipping structure, potentially confirming that the BHF continues in the subsurface south of the scarp.

  10. High Spatial Density Ambient Noise Tomography at the El Jefe Geyser, Chile (United States)

    Hakso, A. W.; Seats, K.


    The El Jefe geyser in the Atacama Desert, Chile has been the subject of study to better understand processes of heat transport and eruption mechanisms in geyser systems (Munoz-Saez et al., 2015). Existing seismological literature on geyser and volcanic systems is predominantly focused on seismicity generated in the eruptive process (Benoit and McNutt, 1997; O'Brien et al., 2011). In contrast, this study leverages seismic noise in the repose period to generate an approximation to the Green's function for each receiver pair, known as noise correlation functions (NCFs). A dense seismic array of 51 geophones spaced at 2-10 meter intervals recorded several days of data at a spatial scale and frequency range approximately two orders of magnitude removed from prior seismic interferometry studies. While eruptions of the El Jefe geyser impose a transient signal on a diffuse background noise, a regular eruption interval of 132.52.5 seconds (Munoz-Saez et al., 2015) allows for reliable removal of seismic energy associated with the eruption, improving the azimuthal distribution of noise across the array. The approach to generating noise correlation functions closely follows the methodology of Seats and Lawrence (2014). Moveout of at least two phases of energy is apparent in the calculated NCFs, suggesting that multiple phases of seismic energy may be present in the noise, moving coherently across the array.

  11. Data Release Report for Source Physics Experiment 1 (SPE-1), Nevada National Security Site

    Energy Technology Data Exchange (ETDEWEB)

    Townsend, Margaret [NSTec; Mercadente, Jennifer [NSTec


    The first Source Physics Experiment shot (SPE-1) was conducted in May 2011. The explosive source was a ~100-kilogram TNT-equivalent chemical set at a depth of 60 meters. It was recorded by an extensive set of instrumentation that includes sensors both at near-field (less than 100 meters) and far-field (more than 100 meters) distances. The near-field instruments consisted of three-component accelerometers deployed in boreholes around the shot and a set of singlecomponent vertical accelerometers on the surface. The far-field network comprised a variety of seismic and acoustic sensors, including short-period geophones, broadband seismometers, three-component accelerometers, and rotational seismometers at distances of 100 meters to 25 kilometers. This report coincides with the release of these data for analysts and organizations that are not participants in this program. This report describes the first Source Physics Experiment and the various types of near-field and far-field data that are available.

  12. Imaging near-surface heterogeneities by natural migration of backscattered surface waves: Field data test

    KAUST Repository

    Liu, Zhaolun


    We have developed a methodology for detecting the presence of near-surface heterogeneities by naturally migrating backscattered surface waves in controlled-source data. The near-surface heterogeneities must be located within a depth of approximately one-third the dominant wavelength λ of the strong surface-wave arrivals. This natural migration method does not require knowledge of the near-surface phase-velocity distribution because it uses the recorded data to approximate the Green’s functions for migration. Prior to migration, the backscattered data are separated from the original records, and the band-passed filtered data are migrated to give an estimate of the migration image at a depth of approximately one-third λ. Each band-passed data set gives a migration image at a different depth. Results with synthetic data and field data recorded over known faults validate the effectiveness of this method. Migrating the surface waves in recorded 2D and 3D data sets accurately reveals the locations of known faults. The limitation of this method is that it requires a dense array of receivers with a geophone interval less than approximately one-half λ.

  13. Intelligent seismic sensor with double three component MEMS accelerometers (United States)

    Fu, Jihua; Wang, Jianjun; Li, Zhitao; Liu, Xiaoxi; Wang, Zhongyu


    To better understand the response and damage characteristics of structures under earthquakes, a great number of intelligent seismic sensors with high performance were needed to be installed distributed in the whole country. The intelligent seismic sensor was a cost-sensitive application because of its large number of usages. For this reason, a low cost intelligent seismic sensor was put forward in this paper. This kind of intelligent seismic sensor cut down the cost without sacrificing performance by introducing two three component MEMS accelerometers. It was composed by a microprocessor, two three component MEMS accelerometers, an A/D converter, a flash memory, etc. The MEMS accelerometer has better structure and frequency response characteristics than the conventional geophones'. But one MEMS accelerometer tended to be unreliable and have no enough dynamic range for precision measurement. Therefore two three component MEMS accelerometers were symmetrically mounted on both sides of the circuit board. And their measuring values were composed to describe the ground motion or structure response. The composed value was the in-phase stacking of the two accelerometers' measuring values, which enhanced the signal noise ratio of the sensor and broadened its dynamic range. Through the preliminary theory and experiment analysis, the low cost intelligent seismic sensor could measure the acceleration in accuracy.

  14. Newberry Seismic Deployment Fieldwork Report

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J; Templeton, D C


    This report summarizes the seismic deployment of Lawrence Livermore National Laboratory (LLNL) Geotech GS-13 short-period seismometers at the Newberry Enhanced Geothermal System (EGS) Demonstration site located in Central Oregon. This Department of Energy (DOE) demonstration project is managed by AltaRock Energy Inc. AltaRock Energy had previously deployed Geospace GS-11D geophones at the Newberry EGS Demonstration site, however the quality of the seismic data was somewhat low. The purpose of the LLNL deployment was to install more sensitive sensors which would record higher quality seismic data for use in future seismic studies, such as ambient noise correlation, matched field processing earthquake detection studies, and general EGS microearthquake studies. For the LLNL deployment, seven three-component seismic stations were installed around the proposed AltaRock Energy stimulation well. The LLNL seismic sensors were connected to AltaRock Energy Gueralp CMG-DM24 digitizers, which are powered by AltaRock Energy solar panels and batteries. The deployment took four days in two phases. In phase I, the sites were identified, a cavity approximately 3 feet deep was dug and a flat concrete pad oriented to true North was made for each site. In phase II, we installed three single component GS-13 seismometers at each site, quality controlled the data to ensure that each station was recording data properly, and filled in each cavity with native soil.

  15. Acoustic module of the Acquabona (Italy debris flow monitoring system

    Directory of Open Access Journals (Sweden)

    A. Galgaro


    Full Text Available Monitoring of debris flows aimed to the assessment of their physical parameters is very important both for theoretical and practical purposes. Peak discharge and total volume of debris flows are crucial for designing effective countermeasures in many populated mountain areas where losses of lives and property damage could be avoided. This study quantifies the relationship between flow depth, acoustic amplitude of debris flow induced ground vibrations and front velocity in the experimental catchment of Acquabona, Eastern Dolomites, Italy. The analysis of data brought about the results described in the following. Debris flow depth and amplitude of the flow-induced ground vibrations show a good positive correlation. Estimation of both mean front velocity and peak discharge can be simply obtained monitoring the ground vibrations, through geophones installed close to the flow channel; the total volume of debris flow can be so directly estimated from the integral of the ground vibrations using a regression line. The application of acoustic technique to debris flow monitoring seems to be of the outmost relevance in risk reduction policies and in the correct management of the territory. Moreover this estimation is possible in other catchments producing debris flows of similar characteristics by means of their acoustic characterisation through quick and simple field tests (Standard Penetration Tests and seismic refraction surveys.

  16. Predicting the liquefaction phenomena from shear velocity profiling: Empirical approach to 6.3 Mw, May 2006 Yogyakarta earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Hartantyo, Eddy, E-mail: [PhD student, Physics Department, FMIPA, UGM. Sekip Utara Yogyakarta 55281 Indonesia (Indonesia); Brotopuspito, Kirbani S.; Sismanto; Waluyo [Geophysics Laboratory, FMIPA, Universitas Gadjah Mada, Sekip Utara Yogyakarta 55281 (Indonesia)


    The liquefactions phenomena have been reported after a shocking 6.5Mw earthquake hit Yogyakarta province in the morning at 27 May 2006. Several researchers have reported the damage, casualties, and soil failure due to the quake, including the mapping and analyzing the liquefaction phenomena. Most of them based on SPT test. The study try to draw the liquefaction susceptibility by means the shear velocity profiling using modified Multichannel Analysis of Surface Waves (MASW). This paper is a preliminary report by using only several measured MASW points. The study built 8-channel seismic data logger with 4.5 Hz geophones for this purpose. Several different offsets used to record the high and low frequencies of surface waves. The phase-velocity diagrams were stacked in the frequency domain rather than in time domain, for a clearer and easier dispersion curve picking. All codes are implementing in Matlab. From these procedures, shear velocity profiling was collected beneath each geophone’s spread. By mapping the minimum depth of shallow water table, calculating PGA with soil classification, using empirical formula for saturated soil weight from shear velocity profile, and calculating CRR and CSR at every depth, the liquefaction characteristic can be identify in every layer. From several acquired data, a liquefiable potential at some depth below water table was obtained.

  17. MASW on the standard seismic prospective scale using full spread recording (United States)

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


    The Multichannel Analysis of Surface Waves (MASW) is one of seismic survey methods that use the dispersion curve of surface waves in order to describe the stiffness of the surface. Is is used mainly for geotechnical engineering scale with total length of spread between 5 - 450 m and spread offset between 1 - 100 m, the hummer is the seismic source on this surveys. The standard procedure of MASW survey is: data acquisition, dispersion analysis and inversion of extracting dispersion curve to obtain the closest theoretical curve. The final result includes share-wave velocity (Vs) values at different depth along the surveyed lines. The main goal of this work is to expand this engineering method to the bigger scale with the length of standard prospecting spread of 20 km using 4.5 Hz version of vertical component geophones. The standard vibroseis and explosive method are used as the seismic source. The acquisition were conducted on the full spread all the time during each single shoot. The seismic data acquisition used for this analysis were carried out on the Braniewo 2014 project in north of Poland. The results achieved during standard MASW procedure says that this method can be used on much bigger scale as well. The different methodology of this analysis requires only much stronger seismic source.

  18. Parsimonious Refraction Interferometry and Tomography

    KAUST Repository

    Hanafy, Sherif


    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. Nonlinear acoustic techniques for landmine detection. (United States)

    Korman, Murray S; Sabatier, James M


    Measurements of the top surface vibration of a buried (inert) VS 2.2 anti-tank plastic landmine reveal significant resonances in the frequency range between 80 and 650 Hz. Resonances from measurements of the normal component of the acoustically induced soil surface particle velocity (due to sufficient acoustic-to-seismic coupling) have been used in detection schemes. Since the interface between the top plate and the soil responds nonlinearly to pressure fluctuations, characteristics of landmines, the soil, and the interface are rich in nonlinear physics and allow for a method of buried landmine detection not previously exploited. Tuning curve experiments (revealing "softening" and a back-bone curve linear in particle velocity amplitude versus frequency) help characterize the nonlinear resonant behavior of the soil-landmine oscillator. The results appear to exhibit the characteristics of nonlinear mesoscopic elastic behavior, which is explored. When two primary waves f1 and f2 drive the soil over the mine near resonance, a rich spectrum of nonlinearly generated tones is measured with a geophone on the surface over the buried landmine in agreement with Donskoy [SPIE Proc. 3392, 221-217 (1998); 3710, 239-246 (1999)]. In profiling, particular nonlinear tonals can improve the contrast ratio compared to using either primary tone in the spectrum.

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

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


    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.

  1. Occupant traffic estimation through structural vibration sensing (United States)

    Pan, Shijia; Mirshekari, Mostafa; Zhang, Pei; Noh, Hae Young


    The number of people passing through different indoor areas is useful in various smart structure applications, including occupancy-based building energy/space management, marketing research, security, etc. Existing approaches to estimate occupant traffic include vision-, sound-, and radio-based (mobile) sensing methods, which have placement limitations (e.g., requirement of line-of-sight, quiet environment, carrying a device all the time). Such limitations make these direct sensing approaches difficult to deploy and maintain. An indirect approach using geophones to measure floor vibration induced by footsteps can be utilized. However, the main challenge lies in distinguishing multiple simultaneous walkers by developing features that can effectively represent the number of mixed signals and characterize the selected features under different traffic conditions. This paper presents a method to monitor multiple persons. Once the vibration signals are obtained, features are extracted to describe the overlapping vibration signals induced by multiple footsteps, which are used for occupancy traffic estimation. In particular, we focus on analysis of the efficiency and limitations of the four selected key features when used for estimating various traffic conditions. We characterize these features with signals collected from controlled impulse load tests as well as from multiple people walking through a real-world sensing area. In our experiments, the system achieves the mean estimation error of +/-0.2 people for different occupant traffic conditions (from one to four) using k-nearest neighbor classifier.

  2. Re-evaluation of Apollo 17 Lunar Seismic Profiling Experiment data (United States)

    Heffels, Alexandra; Knapmeyer, Martin; Oberst, Jürgen; Haase, Isabel


    We re-analyzed Apollo 17 Lunar Seismic Profiling Experiment (LSPE) data to improve our knowledge of the subsurface structure of this landing site. We use new geometrically accurate 3-D positions of the seismic equipment deployed by the astronauts, which were previously derived using high-resolution images by Lunar Reconnaissance Orbiter (LRO) in combination with Apollo astronaut photography. These include coordinates of six Explosive Packages (EPs) and four geophone stations. Re-identified P-wave arrival times are used to calculate two- and three-layer seismic velocity models. A strong increase of seismic velocity with depth can be confirmed, in particular, we suggest a more drastic increase than previously thought. For the three-layer model the P-wave velocities were calculated to 285, 580, and 1825 m/s for the uppermost, second, and third layer, respectively, with the boundaries between the layers being at 96 and 773 m depth. When compared with results obtained with previously published coordinates, we find (1) a slightly higher velocity (+4%) for the uppermost layer, and (2) lower P-wave velocities for the second and third layers, representing a decrease of 34% and 12% for second and third layer, respectively. Using P-wave arrival time readings of previous studies, we confirm that velocities increase when changing over from old to new coordinates. In the three-layer case, this means using new coordinates alone leads to thinned layers, velocities rise slightly for the uppermost layer and decrease significantly for the layers below.

  3. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing


    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  4. Mobile platform for acoustic mine detection applications (United States)

    Libbey, Brad; Fenneman, Douglas; Burns, Brian


    Researchers in academia have successfully demonstrated acoustic landmine detection techniques. These typically employ acoustic or seismic sources to induce vibration in the mine/soil system, and use vibration sensors such as laser vibrometers or geophones to measure the resultant surface motion. These techniques exploit the unique mechanical properties of landmines to discriminate the vibration response of a buried mine from an off-target measurement. The Army requires the ability to rapidly and reliably scan an area for landmines and is developing a mobile platform at NVESD to meet this requirement. The platform represents an initial step toward the implementation of acoustic mine detection technology on a representative field vehicle. The effort relies heavily on the acoustic mine detection cart system developed by researchers at the University of Mississippi and Planning Systems, Inc. The NVESD platform consists of a John Deere E-gator configured with a robotic control system to accurately position the vehicle. In its present design, the E-gator has been outfitted with an array of laser vibrometers and a bank of loudspeakers. Care has been taken to ensure that the vehicle"s mounting hardware and data acquisition algorithms are sufficiently robust to accommodate the implementation of other sensor modalities. A thorough discussion of the mobile platform from its inception to its present configuration will be provided. Specific topics to be addressed include the vehicle"s control and data acquisition systems. Preliminary results from acoustic mine detection experiments will also be presented.

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

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


    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.

  6. Experiment of exploration using the active-faults exploration system; Katsudanso tansa system wo mochiita chika tansa jikken

    Energy Technology Data Exchange (ETDEWEB)

    Mikada, H.; Sato, H.; Iwasaki, T.; Hirata, N. [The University of Tokyo, Tokyo (Japan). Earthquake Research Institute; Ikeda, Y. [The University of Tokyo, Tokyo (Japan). Faculty of Science; Ikawa, T.; Kawabe, Y.; Aoki, Y. [JAPEX Geoscience Institute, Tokyo (Japan)


    A system for exploration of active-faults by seismic reflection profiling method was introduced at Earthquake Research Institute, University of Tokyo. A test-run was conducted to check the performance of this system at Ranzan, Saitama Prefecture. This paper describes the confirmed performance of mini-VIB as a wide band frequency seismic source, the quality of data obtained using a digital data acquisition system, and problems for data processing of fault exploration in the future. For the test-run at Ranzan, two-dimensional exploration was conducted by the quasi-three-dimensional data acquisition method using three geophones of 8 Hz, 28 Hz, and 40 Hz, simply arranged in parallel on the measurement line. Using an active seismic vibrator, mini-VIB, data acquisition of faults in the wide band frequency was achieved, which would result in the highly accurate imaging. Operation of data acquisition and processing systems is easy, and the system can be also used as a kind of black box. The existing methods are to be used sufficiently as a tool for imaging of faults. Further research for accumulating experience may become necessary toward the extension of the system expected in the future. 5 refs., 6 figs.

  7. 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)


    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.

  8. Induced liquefaction experiment in relatively dense, clay-rich sand deposits (United States)

    Hatzor, Yossef H.; Gvirtzman, Haim; Wainshtein, Ilia; Orian, Itay


    In this paper we report results from a controlled blast-induced liquefaction experiment at the field scale. The physical and mechanical properties of the materials at the subsurface are characterized by a suite of in situ and laboratory tests, including the Standard Penetration Test (SPT); downhole and cross-hole seismic velocity tests; density, porosity, and gradation tests; and direct shear tests. Since the blast experiment was performed above groundwater table, the subsurface was saturated by a sequence of controlled infiltration tests. A 50-kg TNT charge was detonated at a depth of 10 m, and seismic ground motions were recorded in a vertical geophone array positioned at a horizontal distance of 30 m from the blast borehole. Obtained liquefaction features include a water fountain that erupted from the blast borehole, prolonged bubbling of the water surface inside the infiltration trench (a process equivalent to "sand boils" typically observed at sites which have experienced liquefaction), lateral spreading, and surface settlement. We argue that in contrast to conventional predictions, liquefaction may be induced in relatively dense silty and clayey sands (shear wave velocity >300 m s-1; relative density = 63-89%) relatively rich in clays (fines content >30%) and that the driving mechanism should not necessarily be restricted to cyclic shear stress loading.

  9. Advanced seismic imaging technology. Data acquisition (computer simulation of elastic wave propagation); Koseido imaging gijutsu. Data shutoku gijutsu (danseiha simulation)

    Energy Technology Data Exchange (ETDEWEB)

    Tsuru, T. [Tech. Research Center, Japan National Oil Corp., Tokyo (Japan)


    Development of software was examined for the purpose of making basic data for an advanced seismic imaging technology by obtaining a seismic exploration data from a complicated underground structural model through a numerical simulation. The result in fiscal 1994 was as follows. A dimensional division difference calculus is superior in the stability and accuracy of numerical calculation and capable of calculating by dividing into one dimensional differences. Attenuation items were added which were due to medium absorbing effect by Maxwell viscoelastic model, and simultaneously a function was added which was capable of dealing with the multi focuses and a group installation of geophones. A pseudospectral method is a kind of difference calculus for numerically solving a partial differential equation, and capable of dividing an underground structural model in lattice and calculating the field on the lattice point. The space direction is differentiated by calculating Fourier series without difference approximation; and, therefore, the number of lattice may be reduced to 2 for the maximum wave length; namely, a lattice interval may be coarsened to reduce calculation time. An improvement was made on the parallel calculation part of the program for two-dimensional analysis developed in the preceding fiscal year, enabling reduction in the calculation time. 4 figs.


    Energy Technology Data Exchange (ETDEWEB)



    One of the concerns in using compact superconducting magnets in the final focus region of the ILC is the influence of the cryogen flow on the vibration characteristics. As a first step towards characterizing such motion at nanometer levels, a project was undertaken at BNL to measure the vibrations in a spare RHIC quadrupole under cryogenic conditions. Given the constraints of cryogenic operation, and limited space available, it was decided to use a dual head laser Doppler vibrometer for this work. The performance of the laser vibrometer was tested in a series of room temperature tests and compared with results from Mark L4 geophones. The laser system was then used to measure the vibration of the cold mass of the quadrupole with respect to the outside warm enclosure. These measurements were carried out both with and without the flow of cold helium through the magnet. The results indicate only a minor increase in motion in the horizontal direction (where the cold mass is relatively free to move).

  11. Geophysical Monitoring at the Aquistore CO2 Storage Site, Saskatchewan, Canada (Invited) (United States)

    White, D. J.


    The Aquistore Project, located near Estevan, Saskatchewan, is designed to demonstrate CO2 storage in a deep saline aquifer. CO2 captured from the nearby Boundary Dam coal-fired power plant will be injected into a brine-filled sandstone formation at ~3300 m depth, starting in November, 2013. A key element of the Aquistore research program is the further development of geophysical methods to monitor the security and subsurface distribution of the injected CO2. Toward this end, a spectrum of geophysical techniques are being tested at the Aquistore site. Various time-lapse seismic methods, including 3D surface and vertical seismic profiles (VSP) as well as crosswell seismic tomography, are designed to provide monitoring of the CO2 plume. Novel components of the seismic monitoring include use of a sparse permanent array and borehole recording using a fiber optic distributed acoustic sensor (DAS) system. Gravity and electromagnetic methods are providing complementary monitoring. Pre-injection baseline surveys have been acquired for each of these methods. In addition, continuous pre-injection monitoring has been ongoing since the summer of 2012 to establish background surface deformation patterns and local seismicity prior to the start of CO2 injection. A network of GPS stations, surface tiltmeters and InSAR reflectors has been deployed to monitor injection-related surface deformation. Passive seismic monitoring is being conducted using two orthogonal linear arrays of surface geophones.

  12. Active velocity tomography for assessing rock burst hazards in a kilometer deep mine

    Institute of Scientific and Technical Information of China (English)

    He Hu; Dou Linming; Li Xuwei; Qiao Qiuqiu; Chen Tongjun; Gong Siyuan


    Active velocity tomography was used to determine the stress state and rock burst hazards in a deep coal mine.The deepest longwall face,number 3207 in the Xingcun colliery,was the location of the field trials.The positive correlation between stress and seismic velocity was used to link the velocity data with stratum stresses.A GeoPen SE2404NT data acquisition system was used to collect seismic data from 300g explosive charges fired by instantaneous electric detonator and located in the tail entry.The geophones were installed on the rock bolts in the head entry of LW3207.Velocity inversion shows an inhomogeneous distribution of stress in the longwall face that could not be obtained from theory or numerical simulations.Three abnormally high P-wave velocity regions were identified that were located on the comers of the two roadways and at the face end near the rail entry side.The maximum velocity gradient is located at the open cut off near the rail entry and is the area most dangerous for rock burst.Mining-induced tremors recorded by a micro-seismic monitoring system demonstrated that the position of energy release during mining coincides with the high velocity gradient area.This technology aids technicians in the coal mine as they design measures to weaken or eliminate potential danger during subsequent mining.

  13. Transport of DESY 1.3 GHZ Cryomodule at Fermilab

    Energy Technology Data Exchange (ETDEWEB)

    McGee, M.W.; Arkan, T.; Borissov, E.; Leibfritz, J.; Schappert, W.; /Fermilab; Barbanotti, S.; /LASA, Segrate /INFN, Milan


    In an exchange of technology agreement, Deutsches Elektron-Synchrotron (DESY) Laboratory in Hamburg Germany has provided a 1.3 GHz cryomodule 'kit' to Fermilab. The cryomodule components (qualified dressed cavities, cold mass parts, vacuum vessel, etc.) sent from Germany in pieces were assembled at Fermilab's Cryomodule Assembly Facility (CAF). The cavity string was assembled at CAF-MP9 Class 10 cleanroom and then transported to CAF-ICB cold mass assembly area via a flatbed air ride truck. Finite Element Analysis (FEA) studies were implemented to define location of instrumentation for initial cold mass transport, providing modal frequencies and shapes. Subsequently, the fully assembled cryomodule was transported to the SRF Accelerator Test Facility at New Muon Lab (NML). Internal geophones (velocity sensors) were attached during the coldmass assembly for transport (warm) and operational (cold) measurements. A description of the isolation system that maintained alignment during transport and protected fragile components is provided. Shock and vibration measurement results of each transport and modal analysis are discussed.

  14. Surface and downhole shear wave seismic methods for thick soil site investigations (United States)

    Hunter, J.A.; Benjumea, B.; Harris, J.B.; Miller, R.D.; Pullan, S.E.; Burns, R.A.; Good, R.L.


    Shear wave velocity-depth information is required for predicting the ground motion response to earthquakes in areas where significant soil cover exists over firm bedrock. Rather than estimating this critical parameter, it can be reliably measured using a suite of surface (non-invasive) and downhole (invasive) seismic methods. Shear wave velocities from surface measurements can be obtained using SH refraction techniques. Array lengths as large as 1000 m and depth of penetration to 250 m have been achieved in some areas. High resolution shear wave reflection techniques utilizing the common midpoint method can delineate the overburden-bedrock surface as well as reflecting boundaries within the overburden. Reflection data can also be used to obtain direct estimates of fundamental site periods from shear wave reflections without the requirement of measuring average shear wave velocity and total thickness of unconsolidated overburden above the bedrock surface. Accurate measurements of vertical shear wave velocities can be obtained using a seismic cone penetrometer in soft sediments, or with a well-locked geophone array in a borehole. Examples from thick soil sites in Canada demonstrate the type of shear wave velocity information that can be obtained with these geophysical techniques, and show how these data can be used to provide a first look at predicted ground motion response for thick soil sites. ?? 2002 Published by Elsevier Science Ltd.

  15. Laboratory coupling tests for optimum land streamer design over sand dunes surface

    KAUST Repository

    Almalki, Hashim


    The cost of data acquisition in land is becoming a major issue as we strive to cover larger areas with seismic surveys at high resolution. Over sand dunes the problem is compounded by the week coupling obtain using geophones, which often forces us to bury the phone. A major challenge is designing such a land streamer system that combines durability, mobility and the required coupling. We share a couple of such designs and discuss the merits behind such designs and test their capability. The testing includes, the level of coupling, mobility and drag over sand surfaces. For specific designs loose sand can accumulate inside the steamer reducing its mobility. On the other hand, poor coupling will attenuate the high frequencies and cause an effective delay in the signal. The weight of the streamer is also an important factor in both mobility and coupling as it adds to the coupling it reduces the mobility of the streamer. We study the impact of weight and base plate surface area on the seismic signal quality, as well as the friction factor of different designs.

  16. Application of nodes with multiple orthogonal sensors in moving light vehicles study (United States)

    Ekimov, Alexander


    A sensor node having two types of sensors: sound and seismic units was used for signal collection in a test with different moving light vehicles on a gravel road in a quiet area. An analysis of signals from the node at low frequencies (less than 100 Hz) shows the possibility of tested vehicles detection at long distance. The sound signals for the vehicle motion were detected above the lowest frequencies of 15-20 Hz only while the seismic signals had the maxima in that frequency band. Another test was conducted on the ground to find the common vibrations of a light vehicle and the ground due to vehicle passby in frequencies below 100 Hz. For this signal collection the same sensor node was used. An additional 3-x accelerometer was installed in the vehicle cabin above the transmission. For start time synchronization of recorded signals from the node on the ground and 3-x accelerometer in the vehicle cabin a radio channel was used. Results for this test revealed the vehicle vibrations due to motion were detected on the ground with all three components of the 3-axes geophone for the test track entire distance.

  17. Passive monitoring using traffic noise recordings - case study on the Steinachtal Bridge (United States)

    Salvermoser, Johannes; Stähler, Simon; Hadziioannou, Céline


    Civil structures age continuously. The early recognition of potentially critical damages is an important economical issue, but also one of public safety. Continuous tracking of small changes in the medium by using passive methods would offer an extension to established active non-destructive testing procedures at relatively low cost. Here we present a case study of structural monitoring using continuous recordings of traffic noise on a 200 meter long reinforced concrete highway bridge in Germany. Over two months of continuos geophone records are used in the frequency range of 2-8 Hz. Using passive image interferometry, evaluation of hourly cross-correlations between recordings at pairs of receivers yield velocity variations in the range of -1.5% to +2.1%. We were able to correlate our outcomes with temperature measurements of the same two month period. The measured velocity changes scale with the temperature variations with on average a dv/v of 0.064% per degree Celsius. This value is in accordance with other studies of concrete response to temperature, confirming that we are able to observe subtle changes with physical origin. It is shown that traffic noise is temporally homogenenous enough to fulfill the requirements of passive image interferometry.

  18. Seismic transducer modeling using ABAQUS

    Energy Technology Data Exchange (ETDEWEB)

    Stephen R. Novascone


    A seismic transducer, known as an orbital vibrator, consists of a rotating imbalance driven by an electric motor. When suspended in a liquid-filled wellbore, vibrations of the device are coupled to the surrounding geologic media. In this mode, an orbital vibrator can be used as an efficient rotating dipole source for seismic imaging. Alternately, the motion of an orbital vibrator is affected by the physical properties of the surrounding media. From this point of view, an orbital vibrator can be used as a stand-alone sensor. The reaction to the surroundings can be sensed and recorded by geophones inside the orbital vibrator. These reactions are a function of the media’s physical properties such as modulus, damping, and density, thereby identifying the rock type. This presentation shows how the orbital vibrator and surroundings were modeled with an ABAQUS acoustic FEM. The FEM is found to compare favorably with theoretical predictions. A 2D FEM and analytical model are compared to an experimental data set. Each model compares favorably with the data set.

  19. Comparison of SASW systems for coastal and offshore applications (United States)

    Groenewold, Finn

    Spectral analysis of surface wave (SASW) systems are an increasingly popular tool for the estimation of shear wave velocity profiles of geotechnical sites as a reasonable alternative to expensive and difficult downhole and crosshole tests. However, there are relatively few commercial systems using this new approach. The prime-objective of this study is to understand the application of a commercial SASW system manufactured by Olson Instruments, Inc. and to compare the results obtained with it to a Multi-Channel Analysis of Surface Wave system developed at the University of Rhode Island. For the field testing program, different sized sledgehammers and weights were used to impact the soil while measuring the passing Rayleigh surface waves with pairs of 4.5 Hz and 2 Hz geophones that were connected to a dynamic signal analyzer for different spacings. This data was processed in the programs WinTFS and WinSASW to develop site-specific dispersion curves, which were then inverted to estimate shear wave velocity profiles. After preliminary testing, the system was used to conduct tests at different sites where investigations of shear wave velocity with different systems have already been performed. Additionally, tests were performed at two different beach sites to collect data that might be useful to explore the relationship between soil stiffness and coastal erosion. The results showed some agreement from inversions using a different system and software package. Nevertheless, there is still a need for further investigation to examine the reliability of the measurements and analysis methods.

  20. 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.


    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)

  1. L’utilizzo dei sensori di vibrazione per il monitoraggio delle frane e la salvaguardia del territorio - On the use of ground vibration sensors for landslide monitoring and land conservation

    Directory of Open Access Journals (Sweden)

    Massimo Arattano


    Full Text Available I sensori sismici ed acustici sembrano mostrare promettenti possibilità di utilizzo per la mitigazione del rischio da frana. Recenti ricerche sul M.te Cervino, ad esempio, hanno utilizzato reti microsismiche per individuare le sedi di crolli potenziali e per stabilire la relazione tra variazioni di temperatura ed emissioni acustiche in roccia. È invece attualmente in fase di sperimentazione l’utilizzo di sensori geofonici e sismometri per la realizzazione di innovativi sistemi di allarme per colate detritiche, capaci di rilevarne l’arrivo con un significativo margine di tempo di anticipo. Nell’articolo vengono illustrati e discussi in dettaglio alcuni esempi applicativi. ------ Seismic and acoustic sensors seem to show promising possibilities of employment for the mitigation of landslide hazards. Recent researches carried out on the Matterhorn, as an example, have used microseismic networks to locate potential areas of rockfalls and to establish a relationship between temperature variations and acoustic emissions in rocks. It is currently under investigation, instead, the use of geophone sensors and seismometers for the realization of innovative warning systems for debris flows, capable to detect their arrival with a significant amount of time in advance. In this article some practical examples will be presented and discussed in detail.

  2. Ground vibrations and airborne sounds generated by motion of rock in a river bed

    Directory of Open Access Journals (Sweden)

    C.-J. Huang


    Full Text Available This study investigates how ground vibrations (underground sounds and airborne sounds that are produced by rocks in a river bed differ from each other. Airborne and underground sounds were simultaneously received at three microphones and three geophones, respectively. These sound signals were then analyzed using both the Fast Fourier Transform and the Gabor Transform to represent them in both the frequency and time-frequency domains. Experimental data indicate that the frequency of both airborne and underground sounds produced by the impact of rocks against the river bed is in the range 10–150 Hz. Furthermore, the high-frequency band of underground sounds decays much more rapidly than that of airborne sounds. The spatial decay rate of airborne sounds was also determined and compared with theoretical values. The lower spatial decay rate of airborne sounds than that of underground sounds suggests that monitoring of airborne sounds may be more efficient in the detection of debris flows or other natural hazards that generate both airborne and underground sounds.

  3. Calibration and deployment of a fiber-optic sensing system for monitoring debris flows. (United States)

    Huang, Ching-Jer; Chu, Chung-Ray; Tien, Tsung-Mo; Yin, Hsiao-Yuen; Chen, Ping-Sen


    This work presents a novel fiber-optic sensing system, capable of monitoring debris flows or other natural hazards that produce ground vibrations. The proposed sensing system comprises a demodulator (BraggSCOPE, FS5500), which includes a broadband light source and a data logger, a four-port coupler and four Fiber Bragg Grating (FBG) accelerometers. Based on field tests, the performance of the proposed fiber-optic sensing system is compared with that of a conventional sensing system that includes a geophone or a microphone. Following confirmation of the reliability of the proposed sensing system, the fiber-optic sensing systems are deployed along the Ai-Yu-Zi and Chu-Shui Creeks in Nautou County of central Taiwan for monitoring debris flows. Sensitivity test of the deployed fiber-optic sensing system along the creek banks is also performed. Analysis results of the seismic data recorded by the systems reveal in detail the frequency characteristics of the artificially generated ground vibrations. Results of this study demonstrate that the proposed fiber-optic sensing system is highly promising for use in monitoring natural disasters that generate ground vibrations.

  4. Surface gravity waves and their acoustic signatures, 1-30 Hz, on the mid-Pacific sea floor. (United States)

    Farrell, W E; Munk, Walter


    In 1999, Duennebier et al. deployed a hydrophone and geophone below the conjugate depth in the abyssal Pacific, midway between Hawaii and California. Real time data were transmitted for 3 yr over an abandoned ATT cable. These data have been analyzed in the frequency band 1 to 30 Hz. Between 1 and 6 Hz, the bottom data are interpreted as acoustic radiation from surface gravity waves, an extension to higher frequencies of a non-linear mechanism proposed by Longuet-Higgins in 1950 to explain microseisms. The inferred surface wave spectrum for wave lengths between 6 m and 17 cm is saturated (wind-independent) and roughly consistent with the traditional Phillips κ(-4) wave number spectrum. Shorter ocean waves have a strong wind dependence and a less steep wave number dependence. Similar features are found in the bottom record between 6 and 30 Hz. But this leads to an enigma: The derived surface spectrum inferred from the Longuet-Higgins mechanism with conventional assumptions for the dispersion relation is associated with mean square slopes that greatly exceed those derived from glitter. Regardless of the generation mechanism, the measured bottom intensities between 10 and 30 Hz are well below minimum noise standards reported in the literature.

  5. Site effects in Mexico City: Constraints from surface wave inversion of shallow refraction data (United States)

    Ramos-Martínez, J.; Chávez-García, F. J.; Romero-Jiménez, E.; Rodríguez-Zúñiga, J. L.; Gómez-González, J. M.


    In order to understand and simulate site effects on strong ground motion records of recent earthquakes in Mexico City, it is fundamental to determine the in situ elastic and anelastic properties of the shallow stratigraphy of the basin. The main properties of interest are the shear wave velocities and Q-quality factors and their correlation with similar parameters in zones of the city. Despite population density and paved surfaces, it is feasible to gather shallow refraction data to obtain laterally homogeneous subsoil structures at some locations. We focused our analysis in the Texcoco Lake region of the northeastern Mexico City basin. This area consists of unconsolidated clay sediments, similar to those of the lake bed zone in Mexico City, where ground motion amplification and long duration disturbances are commonly observed. We recorded Rayleigh and Love waves using explosive and sledgehammer sources and 4.5 Hz vertical and horizontal geophones, respectively. Additionally, for the explosive source, we recorded three-component seismograms using 1 Hz seismometers. We obtained phase velocity dispersion curves from ray parameter-frequency domain analyses and inverted them for vertical distribution of S wave velocity. The initial model was obtained from a standard first-break refraction analysis. We also obtained an estimation of the QS shear wave quality factor for the uppermost stratigraphy. Results compare well with tilt and cone penetrometer resistance measurements at the same test site, emphasizing the importance of these studies for engineering purposes.

  6. Opportunities and pitfalls in surface-wave interpretation

    KAUST Repository

    Schuster, Gerard T.


    Many explorationists think of surface waves as the most damaging noise in land seismic data. Thus, much effort is spent in designing geophone arrays and filtering methods that attenuate these noisy events. It is now becoming apparent that surface waves can be a valuable ally in characterizing the near-surface geology. This review aims to find out how the interpreter can exploit some of the many opportunities available in surface waves recorded in land seismic data. For example, the dispersion curves associated with surface waves can be inverted to give the S-wave velocity tomogram, the common-offset gathers can reveal the presence of near-surface faults or velocity anomalies, and back-scattered surface waves can be migrated to detect the location of near-surface faults. However, the main limitation of surface waves is that they are typically sensitive to S-wave velocity variations no deeper than approximately half to one-third the dominant wavelength. For many exploration surveys, this limits the depth of investigation to be no deeper than approximately 0.5-1.0 km.

  7. Microseismic Observations in the Karoo: Leeu-Gamka, South Africa (United States)

    Fynn, Melody; Kahle, Beth; Kahle, Richard; Hartnady, Chris


    We report on a micro-earthquake study in the interior of South Africa, in a tectonically stable intraplate setting centered on the town of Leeu Gamka, Western Cape province. The International Seismological Centre (ISC) catalogue reports localised anomalous seismicity in the region between 2007 and 2012 with local magnitudes up to 4.5. The apparent duration and time history of this anomalous seismicity is likely, in part at least, a reporting artefact. We deployed an array of 23 geophones for three months (March-June) in 2015, covering an area of 60 × 65 km centred on the zone of anomalous seismicity. The array recorded a total of 113 earthquakes over this period, with almost all events clustering in a surprisingly small area (78% of the epicentres fall within a one square kilometre block). Double difference relocation resolves the hypocentres onto a structure with an apparent NW-SE orientation, consistent with large-scale fabric that can be recognised in satellite imagery. Although the hypocentre depths are not very well constrained, their apparent range of 5-7 km puts them at the base of the Karoo basin.

  8. Design and development of digital seismic amplifier recorder

    Energy Technology Data Exchange (ETDEWEB)

    Samsidar, Siti Alaa; Afuar, Waldy; Handayani, Gunawan, E-mail: [Department of Physics, ITB (Indonesia)


    A digital seismic recording is a recording technique of seismic data in digital systems. This method is more convenient because it is more accurate than other methods of seismic recorders. To improve the quality of the results of seismic measurements, the signal needs to be amplified to obtain better subsurface images. The purpose of this study is to improve the accuracy of measurement by amplifying the input signal. We use seismic sensors/geophones with a frequency of 4.5 Hz. The signal is amplified by means of 12 units of non-inverting amplifier. The non-inverting amplifier using IC 741 with the resistor values 1KΩ and 1MΩ. The amplification results were 1,000 times. The results of signal amplification converted into digital by using the Analog Digital Converter (ADC). Quantitative analysis in this study was performed using the software Lab VIEW 8.6. The Lab VIEW 8.6 program was used to control the ADC. The results of qualitative analysis showed that the seismic conditioning can produce a large output, so that the data obtained is better than conventional data. This application can be used for geophysical methods that have low input voltage such as microtremor application.

  9. Design and development of digital seismic amplifier recorder (United States)

    Samsidar, Siti Alaa; Afuar, Waldy; Handayani, Gunawan


    A digital seismic recording is a recording technique of seismic data in digital systems. This method is more convenient because it is more accurate than other methods of seismic recorders. To improve the quality of the results of seismic measurements, the signal needs to be amplified to obtain better subsurface images. The purpose of this study is to improve the accuracy of measurement by amplifying the input signal. We use seismic sensors/geophones with a frequency of 4.5 Hz. The signal is amplified by means of 12 units of non-inverting amplifier. The non-inverting amplifier using IC 741 with the resistor values 1KΩ and 1MΩ. The amplification results were 1,000 times. The results of signal amplification converted into digital by using the Analog Digital Converter (ADC). Quantitative analysis in this study was performed using the software Lab VIEW 8.6. The Lab VIEW 8.6 program was used to control the ADC. The results of qualitative analysis showed that the seismic conditioning can produce a large output, so that the data obtained is better than conventional data. This application can be used for geophysical methods that have low input voltage such as microtremor application.

  10. Accelerometer Sensor Specifications to Predict Hydrocarbon Using Passive Seismic Technique

    Directory of Open Access Journals (Sweden)

    M. H. Md Khir


    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.

  11. 3-D Prestack-migration of Wide-angle Data from a Variscan Transition Zone (United States)

    Bleibinhaus, F.; Bopp, M.; Simon, M.; Gebrande, H.


    In addition to the near normal-incidence observations within the German DEKORP 2 project in 1984, wide-angle observations have been carried out on a parallel profile across the boundary between the Saxothuringian and Moldanubian crust, approximately 50 km NE of the main transect to control three-dimensional variations. Explosion sources have been used for the entire survey, providing excellent conditions for wide-angle registrations. A velocity model has been derived on the basis of in- and off-line refraction measurements using a kinematic raytracer which was extended to three dimensions by interpolation of 2-D velocity fields between parallel sections. Although prestack-migration of the data led to aliasing effects due to large shot and geophone spacing, stable results were obtained by forming envelopes after single-shot migration. The migrated sections reveal a strongly reflective Moho at about 31 km depth and a steeply (50°) dipping intracrustal reflector, which seems to be related to the border between the two Variscan units.

  12. GIPP: Geophysical Instrument Pool Potsdam

    Directory of Open Access Journals (Sweden)

    Christian Haberland


    Full Text Available The Geophysical Instrument Pool Potsdam (GIPP consists of field instruments, sensors and equipment for temporary seismological studies (both controlled source and earthquake seismology as well as for magnetotelluric (electromagnetic experiments. These instruments are mainly mobile digital recorders, broadband seis­mometers and short period sensors, and they are used to reveal the subsurface structure and to investigate earth­quakes. Sensors for magnetotellurics include induction coil and fluxgate magnetometers and non-polarizing silver / silver-chloride electrodes. It is operated by the Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences. The instru­ment facility is open to all academic applicants, both national and international. Instrument applications are evalu­ated and ranked by an external steering board. Currently, for seismological applications >850 geophysical recorders, >170 broadband seis­mo­meters and >1300 short period geophones are available (among others. Available for magnetotelluric experiments are > 50 real-time data-loggers, >150 induction coils, and >500 electrodes. User guidelines and data policy are in force and data archives are provided (standard exchange formats.

  13. Strong ground movement induced by mining activities and its effect on power transmission structures

    Institute of Scientific and Technical Information of China (English)

    DAI Kao-shan; CHEN Shen-en


    Surface mining activities may introduce damages to nearby infrastructure. Concerns are put forward by the power company about structural integrity of electric power transmission structures in areas where coal mining activities cause strong ground vibrations. Common practice in the power industry is to limit ground motion by specifying maximum Peak Particle Velocity. So far, there is a lack of industry-wide recognized guidelines on how ground vibration limits should be set for the transmission structures. In order to develop a defense strategy to protect power transmission lines against strong ground motions in mining areas, a systematic research work was conducted to establish strong ground vibration characteristics and to study impacts of ground excitations on transmission pole structures. Ground movements were recorded using geophones and wireless tri-axial sensing units. The process of generating ground motion response spectra via analyzing actual ground motion measurements is described in the paper. These spectra developed based on peak particle velocities were used as a basis for spectral analysis performed using validated Finite Element models to obtain structural displacements, reactions and stress states of the transmission pole structures in the mining sites. A quantitative ground motion limit was established by comparing structural responses with the corresponding design requirements.

  14. Data Release Report for Source Physics Experiments 2 and 3 (SPE-2 and SPE-3) Nevada National Security Site

    Energy Technology Data Exchange (ETDEWEB)

    Townsend, Margaret [National Security Technologies, LLC, Las Vegas, NV (United States). Nevada Test Site; Obi, Curtis [National Security Technologies, LLC, Las Vegas, NV (United States). Nevada Test Site


    The second Source Physics Experiment shot (SPE-2) was conducted in Nevada on October 25, 2011, at 1900:00.011623 Greenwich Mean Time (GMT). The explosive source was 997 kilograms (kg) trinitrotoluene (TNT) equivalent of sensitized heavy ammonium fuel oil (SHANFO) detonated at a depth of 45.7 meters (m). The third Source Physics Experiment shot (SPE-3) was conducted in Nevada on July 24, 2012, at 1800:00.44835 GMT. The explosive source was 905 kg TNT equivalent of SHANFO detonated at a depth of 45.8 m. Both shots were recorded by an extensive set of instrumentation that includes sensors both at near-field (less than 100 m) and far-field (100 m or greater) distances. The near-field instruments consisted of three-component accelerometers deployed in boreholes at 15, 46, and 55 m depths around the shot and a set of single-component vertical accelerometers on the surface. The far-field network was composed of a variety of seismic and acoustic sensors, including short-period geophones, broadband seismometers, three-component accelerometers, and rotational seismometers at distances of 100 m to 25 kilometers. This report coincides with the release of these data for analysts and organizations that are not participants in this program. This report describes the second and third Source Physics Experiment shots and the various types of near-field and far-field data that are available.

  15. Passive monitoring for near surface void detection using traffic as a seismic source (United States)

    Zhao, Y.; Kuzma, H. A.; Rector, J.; Nazari, S.


    In this poster we present preliminary results based on our several field experiments in which we study seismic detection of voids using a passive array of surface geophones. The source of seismic excitation is vehicle traffic on nearby roads, which we model as a continuous line source of seismic energy. Our passive seismic technique is based on cross-correlation of surface wave fields and studying the resulting power spectra, looking for "shadows" caused by the scattering effect of a void. High frequency noise masks this effect in the time domain, so it is difficult to see on conventional traces. Our technique does not rely on phase distortions caused by small voids because they are generally too tiny to measure. Unlike traditional impulsive seismic sources which generate highly coherent broadband signals, perfect for resolving phase but too weak for resolving amplitude, vehicle traffic affords a high power signal a frequency range which is optimal for finding shallow structures. Our technique results in clear detections of an abandoned railroad tunnel and a septic tank. The ultimate goal of this project is to develop a technology for the simultaneous imaging of shallow underground structures and traffic monitoring near these structures.

  16. Seismic Prediction While Drilling (SPWD: Looking Ahead of the Drill Bit by Application of Phased Array Technology

    Directory of Open Access Journals (Sweden)

    Marco Groh


    Full Text Available Geophysical exploration is indispensable for planning deep drilling. Usually 2D- or 3D-seismics investigations are applied and, depending on the resulting geologic model for the underground, the drill site and drilling path are determined. In recent years the focus of exploration has shifted towards small-scale geological structures such as local layers and faults. Depending on the source frequencies and the target depth, 2D- or 3D-seismics from surface cannot always resolve such structures in particular at larger depths. In general, signal frequencies of about 30–70 Hz are typical for surface seismic methods. The deeper and smaller the sought-after structures are, the worse will be the resolution. Therefore, borehole seismic measurements like Vertical Seismic Profile (VSP or Seismic While Drilling (SWD have been developed (Fig. 1. For the VSP method geophones are normally integrated in the borehole, while the seismicsource generates seismic waves at the surface. The SWD method uses the drill bit as the seismic source. Hence, the quality of the seismic signals is highly dependent on the drilled rock and the type of drill bit, but even well-suited rock conditions and adequate drilling may not provide sufficient data quality.

  17. Observations at a San Jacinto Fault Zone site (Sage Brush Flat) Using a Nodal Seismic High Frequency Array (United States)

    Vernon, F.; Reyes, J. C.; White, M. C. A.; Davis, G. A.; Meyer, J. C.; Sahakian, V. J.; Mancinelli, N. J.; Ben-Zion, Y.; Zigone, D.; Harris, C.; Liu, X.; Qiu, H.; Share, P. E.; Ozakin, Y.; Hollis, D.; Barklage, M.


    Between 7 May 2014 and 13 June 2014 we deployed a tight 1108 element array of 10 Hz vertical geophones in a two-dimensional array with 700 meter aperture centered on the Clark Fault of the San Jacinto Fault Zone. The array was designed to make detailed observations of the shallow damage zone, local failure processes and noise properties of the Clark Fault near the Anza seismic gap. The core of the array consisted of a grid organized with 20 rows perpendicular to and centered on the fault trace, each row with 50 sensors at a nominal 10 meter interstation spacing. The spacing between rows was nominally 30 meters. The remaining 108 sensors were deployed as extensions to multiple rows providing a maximum 700 meter aperture. Each sensor was surveyed using a Real Time Kinematic (RTK) GPS system to an accuracy of approximately 30 cm. The RTK survey was enabled via ad-hoc networking using HPWREN. We will present observations of earthquakes with magnitudes -1 100 kilometers, along with prosperities of local structures and noise characteristics.

  18. Hammering Yucca Flat, Part Two: Shear-Wave Velocity (United States)

    Finlay, T. S.; Abbott, R. E.; Knox, H. A.; Tang, D. G.; James, S. R.; Haney, M. M.; Hampshire, J. B., II


    In preparation for the next phase of the Source Physics Experiment (SPE), we conducted an active-source seismic survey of Yucca Flat, Nevada, on the Nevada National Security Site. Results from this survey will be used to inform the geologic models associated with the SPE project. For this study, we used a novel 13,000 kilogram weight-drop seismic source to interrogate an 18-km North-South transect of Yucca Flat. Source points were spaced every 200 meters and were recorded by 350 to 380 3-component 2-Hz geophones with variable spacings of 10, 20, and 100 meters. We utilized the Refraction-Microtremor (ReMi) technique to create multiple 1D dispersion curves, which were then inverted for shear-wave velocity profiles using the Dix inversion method (Tsai and Haney, 2015). Each of these 1D velocity models was subsequently stitched together to create a 2D profile over the survey area. The dispersion results indicate a general decrease in surface-wave phase velocity to the south. This result is supported by slower shear-wave velocity sediments and increasing basin depth towards the survey's southern extent. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. Application of acoustic noise and self-potential localization techniques to a buried hydrothermal vent (Waimangu Old Geyser site, New Zealand) (United States)

    Vandemeulebrouck, J.; Roux, P.; Gouédard, P.; Legaz, A.; Revil, A.; Hurst, A. W.; Bolève, A.; Jardani, A.


    A seismo-acoustic and self-potential survey has been performed in the hydrothermal area of the old Waimangu Geyser (New Zealand), which was violently erupting a century ago. Nowadays, no surface activity is visible there. We set-up an array of 16 geophones and recorded a high and steady acoustic ambient noise. We applied the matched field processing (MFP) approach to the acoustic data to locate the sources responsible for the ambient noise. The white noise constraint processor reveals the presence of a unique and well-focused acoustic source at a depth of 1.5 m below the seismic array. For this very shallow source, the application of MFP enabled the determination of both the source location and the dispersion curve of seismic velocity. The study was completed by self-potential (SP) measurements on several profiles around the acoustic noise source, which displayed a large positive anomaly above it. The results of the SP inversion gave an electric streaming current density source very close to the acoustic one. Both sources likely belong to a shallow hydrothermal structure interpreted as a small convective cell of boiling water beneath an impermeable layer. The joint application of these methods is a promising technique to recognize hydrothermal structures and to study their dynamics.

  20. Fracture detection, mapping, and analysis of naturally fractured gas reservoirs using seismic technology. Final report, November 1995

    Energy Technology Data Exchange (ETDEWEB)



    Many basins in the Rocky Mountains contain naturally fractured gas reservoirs. Production from these reservoirs is controlled primarily by the shape, orientation and concentration of the natural fractures. The detection of gas filled fractures prior to drilling can, therefore, greatly benefit the field development of the reservoirs. The objective of this project was to test and verify specific seismic methods to detect and characterize fractures in a naturally fractured reservoir. The Upper Green River tight gas reservoir in the Uinta Basin, Northeast Utah was chosen for the project as a suitable reservoir to test the seismic technologies. Knowledge of the structural and stratigraphic geologic setting, the fracture azimuths, and estimates of the local in-situ stress field, were used to guide the acquisition and processing of approximately ten miles of nine-component seismic reflection data and a nine-component Vertical Seismic Profile (VSP). Three sources (compressional P-wave, inline shear S-wave, and cross-line, shear S-wave) were each recorded by 3-component (3C) geophones, to yield a nine-component data set. Evidence of fractures from cores, borehole image logs, outcrop studies, and production data, were integrated with the geophysical data to develop an understanding of how the seismic data relate to the fracture network, individual well production, and ultimately the preferred flow direction in the reservoir. The multi-disciplinary approach employed in this project is viewed as essential to the overall reservoir characterization, due to the interdependency of the above factors.

  1. New style OBS to the abyss (United States)

    Shiobara, H.; Ito, A.; Sugioka, H.; Shinohara, M.


    Generally, we have been trying to widen observation ranges at the seafloor in multi dimensions, such as term of observation, period, area and strength of signal. One of them is a development of the ocean bottom seismometer (OBS) usable even at the bottom of the trench, which has been a target since 1989. Several trials encountered some troubles that would come from the mechanical design and parts used in our standard OBS. To clear this problem, we developed the New design Ultra Deep OBS (NUDOBS) and have started test observations. This OBS is a completely new concept design that can be deployed up to 10000 m depth without using any underwater cables and the traditional anchor releasing system. Its maximum observation term is about one year. The NUDOBS equips 3-component omni-directional geophones (15 Hz) with no gimbal and the 3-axis MEMS accelerometer. The 6-ch data recorder for OBS (LS9100-T6, Hakusan), 21 DD size Li-cells are installed in the titanium pressure case (Ø200×H490) with these sensors. The main point of the NUDOBS lies at the 3-stage mechanical action, the deployment stage, the observation stage and the recovery stage. The newly developed acoustic transponder that enables the two-step action controls transitions between stages twice. To reduce the noise by the bottom current, there is no mechanical coupling of the pressure case with other parts except a thin umbilical rope during the observation stage. The whole system of the NUDOBS is like as a small mooring buoy using 6 glass-sphere floats for the deep water (~12000 m). The deployment was performed to release these floats, the 20-m rope and the main unit of the NUDOBS at last. The descending speed is about 80 m/min. The NUDOBS, although it is still a prototype, has been tested twice. The first one was at the Philippine Sea site (4900 m depth) with other instruments those requires the ROV from Nov. 2012 until Feb. 2013. In this observation, we could watch two transitions of the NUDOBS by video

  2. ONKALO 3D tunnel seismic investigations, Olkiluoto 2013

    Energy Technology Data Exchange (ETDEWEB)

    Enescu, N.; Cosma, C.; Crawford, J. [Vibrometric Oy Cosma, Perttula (Finland)


    POSIVA Oy conducts bedrock investigations at the spent nuclear fuel final disposal site at Olkiluoto, in western Finland. The purpose of these efforts, which include a significant R and D component, is to ensure compliance with the requirements set forth for the long-term safety of final disposal. The excavation of the access tunnel to the repository hosts the ONKALO underground rock characterization facility. The investigations carried out in ONKALO focus on the bedrock and groundwater conditions prevailing on the final disposal site and how construction work affects them. Deformation zones and hydraulically conductive zones can limit the areas which are suitable for a deposition hole to be placed. The main objective of the tunnel seismic investigations presented here is to develop a seismic investigation technique for deposition area characterization. The field work consisted of 3 receiver lines using 3-component geophones and sources locations using the Vibsist-500 for 6 profiles, the Vibsist-20 for 1 profile (sparse), and a mechanical borehole hammer, MH-70, for 5 profiles for a total of 12 profiles. This investigation took place in the ONKALO demonstration area. Design of the seismic field work is based on previous tunnel seismic works in ONKALO (Cosma et al. 2008 and 2011) and pre-survey numerical modeling for field data and processing (Heinonen et al. 2013). The fieldwork was carried out in June 2013. Tomographic inversion of P-wave first arrival times was done on combined data sets, containing data from several shot-receiver configurations along tunnels and boreholes. The velocity distributions derived by tomographic inversion were verified by comparison with the forward modeled profiles. The Image Point (IP) migration method is characterized by is its ability to accumulate reflection events measured in the time distance data sets into points in the IP domain, which permits the enhancement of coherent backscattered events. The result of the 3D IP migration

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

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


    Three high-resolution, 5 m shot and receiver spacing using 141-172 receivers, refraction and reflection seismic profiles for the planning of a major underground energy-storage site near the town of Dalby-Lund within the Scania Tornquist suture zone in southwest of Sweden were acquired during August 2015. The site is situated ca. 1 km north of the RFZ (Romeleåsen fault and flexure zone) with a complex geologic and tectonic history. Near vertical dikes are observed from several quarries in the area crosscutting granitic-gneissic-amphibiotic rocks and form clear magnetic lineaments. These dikes likely have also acted as surfaces on which further faulting have occurred. Although a major high-speed and traffic road runs in the middle of the study area, the seismic data show excellent quality particularly for the data along two profiles (profiles 2 and 3) perpendicular to the road, and slightly noisy, due to high wind, for the data along a profile (profile 4) parallel to the road. A bobcat-mounted drop hammer (500 kg) was used to generate the seismic signal. To provide continuity from one side of the road to another, 51 wireless recorders connected to 10 Hz geophones and operating in an autonomous mode were used. GPS times of the source impacts were used to extract the data from the wireless recorders and then merged with the data from the cabled recorders (also 10 Hz geophones). Three shot records per source position were generated and vertically stacked to improve the signal-to-noise ratio. First arrivals are clear in most shot gathers allowing them to be used for traditional refraction seismic data analysis and also for more advanced traveltime tomography. The velocity models obtained through traveltime tomography clearly depict bedrock surface and its undulations and in many places show good correlation with the boreholes recently drilled in the area. At places where bedrock is intersected at greater depths than usual, for example 25 m at one place, depression

  4. Geoelectrical Resistivity Imaging and Refraction Seismic Investigations at Sg.Udang, Melaka

    Directory of Open Access Journals (Sweden)

    Zeinab Asry


    Full Text Available Problem statement: A Reconnaissance geophysical survey of an area near Sg.Udang, Melaka was conducted using geoelectrical resistivity and seismic refraction methods. The main objective of this study is to determine the depth of bedrock in the study area. The resistivity imaging measurement employing Wenner electrode configuration was carried out using an ABEM SAS 1000 terrameter and electrode selector system ES464. Electrodes were arranged in a straight line with constant spacing and connected to a multicore cable. The refraction seismic was conducted using 24 channel ABEM Mark6 signal enhancement seismograph with 5 m geophone spacing. The resistivity layer is associated with the residual soil with thickness of about 0.5-3 m. The high velocity layer is an average depth of about 9.4 m. The intermediate velocity zone is associated with weathered schist with thickness of about 2.5 m. The low velocity zone is with thickness of about 6 m. The thickness of residual soil obtained by seismic refraction survey appears to agree very well with the borehole data. Resistivity and the seismic refraction data have been successfully used to determine the thickness of residual soil layer and depth of bedrock. Approach: In this survey, electrodes were arranged in a straight line with constant spacing and connected to a multicore cable. The refraction seismic was conducted using 24 channel ABEM Mark6 signal enhancement seismograph with 5 m geophone spacing. The seismic data have been interpreted using SeisOpt@2D which automatically produced 2-D seismic velocity sections of the subsurface. Results: The resistivity results showed that the subsurface layers are associated with variable resistivity (296-2600Ω. m. The resistivity layer is associated with the residual soil with thickness of about 0.5-3 m. The interpreted 2-D seismic sections showed three different velocity layers. The high velocity layer (1600-2000 m sec-1 is interpreted to be associated with bedrock

  5. Acoustic-Seismic Coupling in Porous Ground - Measurements and Analysis for On-Site-Inspection Support (United States)

    Liebsch, Mattes; Gorschlüter, Felix; Altmann, Jürgen


    acoustic signals and geophones were buried in different depths to measure the soil velocity. Additionally, a wooden box coated with acoustic damping foam was placed over some acoustic and seismic sensors to reduce the power of incident acoustic signals and thus the locally created seismic vibrations (under the box). The reduced soil velocity measured by geophones under the box corresponds mainly to vibrations created by acoustic-seismic coupling outside the box which travel through the soil and reach the sensor. Under certain conditions of frequency and incident angle of acoustic signals an increased seismic response was observed. This might indicate the excitation of seismic surface waves and is of special interest for the evaluation. The project aims to deliver a better understanding of the interaction of acoustic waves with the ground when hitting the surface. Recommendations for sensitive seismic measurements during CTBTO on-site inspections will be developed to reduce disturbing vibrations caused by airborne sources.

  6. Experimental Study of the Convergence of Two-Point Cross-Correlation Toward the Green's Function (United States)

    Gouedard, P.; Roux, P.; Campillo, M.; Verdel, A.; Campman, X.


    It has been shown theoretically by several authors that cross-correlation of the seismic motion recorded at two points could yield the Green's Function (GF) between these points. Convergence of cross-correlations toward the GF depends on sources positions and/or the nature of the wavefield. Direct waves from an even distribution of sources can be used to retrieve the GF. On the other hand, in an inhomogeneous medium, recording the diffuse field (coda) is theoretically sufficient to retrieve the GF whatever the sources distribution is. Since none of these two conditions (even distribution of sources or a perfectly diffuse field) is satisfied in practice, the question of convergence toward the GF has to be investigated with real data. A 3D exploration survey with sources and receivers on a dense grid offers such an opportunity. We used a high- resolution survey recorded by Petroleum Development Oman in North Oman. The data have been obtained in a 1x1~km area covered with 1600 geophones located on a 25x25~m-cell grid. Records are 4-seconds long. A unique feature of this survey is that vibrators (working in the [8-120~Hz] frequency band), were located on a similar grid shifted with respect to the receiver grid by half a cell (12.5~m) in both directions. This allows us to compare estimated GF's with measured direct waves (GF's) between the geophones. The shallow subsurface is highly heterogeneous and records include seismic coda. From this dataset, we selected two receiver locations (Ra and Rb) distant from d=158~m. We used both different sets of source locations and time windows to compute the cross-correlation between these two receivers. Then we compared the derivatives of correlation functions with the actual GF measured in Rb (resp.~Ra) for a source close to Ra (resp.~Rb). By doing so, we show the actual influence of source locations and scattering (governed by the records' selected time window) on the Signal-to-Noise Ratio (SNR) of the reconstructed GF. When using

  7. A Cascaded Magnetostrictive Vibration Source System for Underground Construction Applications (United States)

    Hock, S.; Polom, U.; Mikulla, S.; Krüger, K.; Giese, R.; Lüth, S.


    . The survey comprised 103 shot points in general with 1 m spacing and at least 10 excitations per shot point. For S-wave generation the Shover principle (Edelmann, 1981) was applied. Therefore 5 excitations were made with the vibrators in phase and 5 excitations with a phase shift of 180 deg between the two vibrators. 16 three-component geophones, developed by the GFZ, were deployed in small boreholes along a gallery part with geophone intervals of 10 m. For comparison purposes and further optimizing of the source system two different recording systems were partly operated during the survey. First results of the seismic test survey will be presented. This work is supported by the BMBF/DFG programme Geotechnologies through grants No. 03G0637A and 03G0637D. References Edelmann, H.A.K., 1981: Shover Shear-Wave Generation by Vibration Orthogonal to the Polarization. Geophysical Prospecting, 29, 541-549. Hock, S., Polom, U., Mikulla, S., Krüger, K., Giese, R., Lüth, S., 2008: Evaluation of a High-frequency Seismic Source System in Mining Application. Near Surface 2008, 14th European Meeting of Environmental and Engineering Geophysics of the Near Surface Geoscience Division of EAGE, 15.-17.9.2008, Krakow, Poland.

  8. Seismic monitoring experiment of raise boring in 2014

    Energy Technology Data Exchange (ETDEWEB)

    Saari, J.; Malm, M. [AaF-Consult Oy, Espoo (Finland)


    In Olkiluoto, Posiva Oy has operated a local seismic network since February 2002. The purpose of the microearthquake measurements at Olkiluoto is to improve understanding of the structure, behaviour and long term stability of the bedrock. The studies include both tectonic and excavation-induced microearthquakes. An additional task of monitoring is related to safeguarding of ONKALO. The possibility to excavate an illegal access to ONKALO has been concerned when the safeguards are discussed. Therefore all recorded explosions in the Olkiluoto area and in ONKALO are located. If a concentration of explosions is observed, the origin of that is found out. Also a concept of hidden illegal explosions, detonated at the same time as the real excavation blasts, has been examined. According to the experience gained in Olkiluoto, it can be concluded that, as long the seismic network is in operation and the results are analysed by a skilled person, it is practically impossible to do illegal undetected excavation by blasting within the Olkiluoto seismic network area. In this report a possibility of seismic monitoring of undeclared excavation done by tunnel boring machine (TBM) has been investigated. In the earlier investigations the instruments were at the ground surface and the sensors were triaxial short period (1 Hz) geophones or broadband geophones. The characteristics (frequency content, polarity and amplitude) of the continuous seismic vibration generated by TMB were studied. The onset time of the seismic signal were not distinguished. Altogether 16 new 10 kHz accelerometers were installed in boreholes inside ONKALO March 2012. The sensors comprised a new subnetwork that monitored the raise boring of two shafts done 2014, from the level -455 m to the level -290 m. The aim was to record the seismic signal generated when the drill bit hits the rock at the moment the tunnel boring begins. Altogether 113 seismic signals generated by the drill bit were located during the

  9. Self-Locking Avoidance and Stiffness Compensation of a Three-Axis Micromachined Electrostatically Suspended Accelerometer

    Directory of Open Access Journals (Sweden)

    Yonggang Yin


    Full Text Available A micromachined electrostatically-suspended accelerometer (MESA is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM. It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land seismic acquisition. Previous experiments showed that it is hard to lift up the PM successfully during initial levitation as the mass needs to be levitated simultaneously in all six degrees of freedom (DoFs. By analyzing the coupling electrostatic forces and torques between three lateral axes, it is found there exists a self-locking zone due to the cross-axis coupling effect. To minimize the cross-axis coupling and solve the initial levitation problem, this paper proposes an effective control scheme by delaying the operation of one lateral actuator. The experimental result demonstrates that the PM can be levitated up with six-DoF suspension operation at any initial position. We also propose a feed-forward compensation approach to minimize the negative stiffness effect inherent in electrostatic suspension. The experiment results demonstrate that a more broadband linear amplitude-frequency response and higher suspension stiffness can be achieved, which is crucial to maintain high vector fidelity for potential use as a three-component MEMS geophone. The preliminary performance tests of the three-axis linear accelerometer were conducted under normal atmospheric pressure and room temperature. The main results and noise analysis are presented. It is shown that vacuum packaging of the MEMS sensor is essential to extend the bandwidth and lower the noise floor, especially for low-noise seismic data acquisition.

  10. Self-Locking Avoidance and Stiffness Compensation of a Three-Axis Micromachined Electrostatically Suspended Accelerometer (United States)

    Yin, Yonggang; Sun, Boqian; Han, Fengtian


    A micromachined electrostatically-suspended accelerometer (MESA) is a kind of three-axis inertial sensor based on fully-contactless electrostatic suspension of the proof mass (PM). It has the potential to offer broad bandwidth, high sensitivity, wide dynamic range and, thus, would be perfectly suited for land seismic acquisition. Previous experiments showed that it is hard to lift up the PM successfully during initial levitation as the mass needs to be levitated simultaneously in all six degrees of freedom (DoFs). By analyzing the coupling electrostatic forces and torques between three lateral axes, it is found there exists a self-locking zone due to the cross-axis coupling effect. To minimize the cross-axis coupling and solve the initial levitation problem, this paper proposes an effective control scheme by delaying the operation of one lateral actuator. The experimental result demonstrates that the PM can be levitated up with six-DoF suspension operation at any initial position. We also propose a feed-forward compensation approach to minimize the negative stiffness effect inherent in electrostatic suspension. The experiment results demonstrate that a more broadband linear amplitude-frequency response and higher suspension stiffness can be achieved, which is crucial to maintain high vector fidelity for potential use as a three-component MEMS geophone. The preliminary performance tests of the three-axis linear accelerometer were conducted under normal atmospheric pressure and room temperature. The main results and noise analysis are presented. It is shown that vacuum packaging of the MEMS sensor is essential to extend the bandwidth and lower the noise floor, especially for low-noise seismic data acquisition. PMID:27213376

  11. Depth-Dependent Earthquake Properties Beneath Long-Beach, CA: Implications for the Rheology at the Brittle-Ductile Transition Zone (United States)

    Inbal, A.; Clayton, R. W.; Ampuero, J. P.


    Except for a few localities, seismicity along faults in southern California is generally confined to depths shallower than 15 km. Among faults hosting deep seismicity, the Newport-Inglewood Fault (NIF), which traverses the Los-Angeles basin, has an exceptionally mild surface expression and low deformation rates. Moreover, the NIF structure is not as well resolved as other, less well instrumented faults because of poor signal-to-noise ratio. Here we use data from three temporary dense seismic arrays, which were deployed for exploration purposes and contain up to several thousands of vertical geophones, to investigate the properties of deep seismicity beneath Long-Beach (LB), Compton and Santa-Fe Springs (SFS). The latter is located 15 km northeast of the NIF, presumably above a major detachment fault underthrusting the basin.Event detection is carried out using a new approach for microseismic multi-channel picking, in which downward-continued data are back-projected onto the volume beneath the arrays, and locations are derived from statistical analysis of back-projection images. Our technique reveals numerous, previously undetected events along the NIF, and confirms the presence of an active shallow structure gently dipping to the north beneath SFS. Seismicity characteristics vary along the NIF strike and dip. While LB seismicity is uncorrelated with the mapped trace of the NIF, Compton seismicity illuminates a sub-vertical fault that extends down to about 20 km. This result, along with the reported high flux of mantle Helium along the NIF (Boles et al., 2015), suggests that the NIF is deeply rooted and acts as a major conduit for mantle fluids. We find that the LB size distribution obeys the typical power-law at shallow depths, but falls off exponentially for events occurring below 20 km. Because deep seismicity occurs uniformly beneath LB, this transition is attributed to a reduction in seismic asperity density with increasing depth, consistent with a transition

  12. Remote detection of artificially triggered avalanches below a fixed avalanche control installation (United States)

    van Herwijnen, Alec; Simioni, Stephan; Schweizer, Juerg


    Avalanche control by explosives is widely used as a temporary preventive measure to reduce avalanche hazard. The goal is to artificially trigger smaller less destructive avalanches, by detonating charges either above or on the snow surface. Hand charges are most often used, whereby the explosives are deployed by manually hand tossing or lowering onto the snow slope. Given the inherent dangers and limitations of this type of avalanche control, fixed avalanche control installations are increasingly used. These consist of strategically placed remote controlled installations that generate an explosion above the snow pack in an avalanche starting zone. While fixed installations can be used at any time and minimize the risk to avalanche control personnel, visual confirmation is still required to verify if an avalanche released. In order to remotely detect artificially triggered avalanches, we therefore developed a low-cost seismic monitoring system. We deployed the monitoring system in a ski area above the town of Davos , in the eastern Swiss Alps, below a Gazex installation, a remote controlled installation that generates an air blast by detonating a fuel-air explosive above the snow pack. The monitoring system consists of three vertical component geophones inserted in the ground at approximately 14, 27 and 46 meters from the Gazex installation. Our results show that, despite the relatively low precision of the monitoring equipment, both the detonation and the resulting avalanches can clearly be identified in the seismic data. Specifically, detonations are characterized by short, high amplitude broadband signals, while avalanches generate much longer, low frequency signals. Furthermore, information on the size of the artificially triggered avalanches is also obtained as it directly relates to the duration of the generated seismic signal. The overall goal is to assess the effectiveness of the fixed avalanche control installation with regards to yield (i.e. number of

  13. High-Resolution Seismic Reflection Profiling Across the Black Hills Fault, Clark County, Nevada: Preliminary Results (United States)

    Zaragoza, S. A.; Snelson, C. M.; Jernsletten, J. A.; Saldana, S. C.; Hirsch, A.; McEwan, D.


    The Black Hills fault (BHF) is located in the central Basin and Range Province of western North America, a region that has undergone significant Cenozoic extension. The BHF is an east-dipping normal fault that forms the northwestern structural boundary of the Eldorado basin and lies ~20 km southeast of Las Vegas, Nevada. A recent trench study indicated that the fault offsets Holocene strata, and is capable of producing Mw 6.4-6.8 earthquakes. These estimates indicate a subsurface rupture length at least 10 km greater than the length of the scarp. This poses a significant hazard to structures such as the nearby Hoover Dam Bypass Bridge, which is being built to withstand a Mw 6.2-7.0 earthquake on local faults. If the BHF does continue in the subsurface, this structure, as well as nearby communities (Las Vegas, Boulder City, and Henderson), may not be as safe as previously expected. Previous attempts to image the fault with shallow seismics (hammer source) were inconclusive. However, gravity studies imply that the fault continues south of the scarp. Therefore, a new experiment utilizing high-resolution seismic reflection was performed to image subsurface geologic structures south of the scarp. At each shot point, a stack of four 30-160 Hz vibroseis sweeps of 15 s duration was recorded on a 60-channel system with 40 Hz geophones. This produced two 300 m reflection profiles, with a maximum depth of 500-600 m. A preliminary look at these data indicates the existence of two faults, potentially confirming that the BHF continues in the subsurface south of the scarp.

  14. Characterization of the Vajont landslide (North-Eastern Italy) by means of reflection and surface wave seismics (United States)

    Petronio, Lorenzo; Boaga, Jacopo; Cassiani, Giorgio


    The mechanisms of the disastrous Vajont rockslide (North-Eastern Italy, October 9, 1963) have been studied in great detail over the past five decades. Nevertheless, the reconstruction of the rockslide dynamics still presents several uncertainties, including those related to the accurate estimation of the actual landslide mass. This work presents the results of a geophysical characterization of the Vajont landslide body in terms of material properties and buried geometry. Both aspects add new information to the existing dataset and will help a better understanding of the rockslide failure mechanisms and dynamics. In addition, some general considerations concerning the intricacies of landslide characterization can be drawn, with due attention to potential pitfalls. The employed techniques are: (i) high resolution P-wave reflection, (ii) high resolution SH-wave reflection, (iii) controlled source surface wave analysis. We adopted as a seismic source a vibrator both for P waves and SH waves, using vertical and horizontal geophones respectively. For the surface wave seismic survey we used a heavy drop-weight source and low frequency receivers. Despite the high noise level caused by the fractured conditions of the large rock body, a common situation in landslide studies, we managed to achieve a satisfying imaging quality of the landslide structure thanks to the large number of active channels, the short receiver interval and the test of appropriate seismic sources. The joint use of different seismic techniques help focus the investigation on the rock mass mechanical properties. Results are in good agreement with the available borehole data, the geological sections and the mechanical properties of the rockmass estimated by other studies. In general the proposed approach is likely to be applicable successfully to similar situations where scattering and other noise sources are a typical bottleneck to geophysical data acquisition on landslide bodies.

  15. Caracterización geosísmica de un sector de traza de la Ruta Nº 40: Provincia de Santa Cruz - Argentina

    Directory of Open Access Journals (Sweden)

    Armando Luis Imhof


    determination permitted to assess blasting or ripper. The study area presents a typical steppe patagonian landscape with basaltic formations indicating old volcanism. At surface, fine to medium-coarse alluvial soil was observed detecting on occasions organic material and besides great basaltic rocks spreading somewhere. Fifty seismic arrays were performed, deployed linearly one after the other along the trace. At each one, five records were taken, symmetrically upon the array center. Geophones and shooting points were determined upon prior proofs tests and space availability. Generally array extension ranged among 25m and 100m, being 5m the geophone gap, allowing thus a great survey detail. The amount and distribution of shootings had for objective to calculate with utmost precision apparent velocities and their true ones derived; refractor inclinations and rock basement; assuring at least a 15m depth investigation. At the processing stage, first picking were determined, which were displayed versus geophones distances, i.e. time-distance or 'dromocrone' graphs. After calculating critical distances, apparent velocities, were estimated. Then, two interpretation methods were carried through: Intercept Time Method (ITM; and Generalized Reciprocal Method (GRM. With the latter, true velocities and depths beneath each geophone were calculated, and with the former, beneath each shot-point, extending so the determinations. The correlation with geologic data was performed using visual inspection and very scarce geologic information available. At last, seismic profiles were developed in separate form according to trace outreaching showing lateral and in-depth variations of compression wave velocity. In both survey areas, two well different layers were detected, being the first a thin sand-muddy alluvial fill-up and the inferior, altered rock (basalt (Zone 1; or compact alluvial terrain, wet to saturated. Information supported by geoseismic refraction method using GRM with 5 emission

  16. Comparison of Amplitudes and Frequencies of Explosive vs. Hammer Seismic Sources for a 1-km Seismic Line in West Texas (United States)

    Kaip, G.; Harder, S. H.; Karplus, M. S.; Vennemann, A.


    In May 2016, the National Seismic Source Facility (NSSF) located at the University of Texas at El Paso (UTEP) Department of Geological Sciences collected seismic data at the Indio Ranch located 30 km southwest of Van Horn, Texas. Both hammer on an aluminum plate and explosive sources were used. The project objective was to image subsurface structures at the ranch, owned by UTEP. Selecting the appropriate seismic source is important to reach project objectives. We compare seismic sources between explosions and hammer on plate, focusing on amplitude and frequency. The seismic line was 1 km long, trending WSW to ENE, with 200 4.5 Hz geophones at 5m spacing and shot locations at 10m spacing. Clay slurry was used in shot holes to increase shot coupling around booster. Trojan Spartan cast boosters (150g) were used in explosive sources in each shot hole (1 hole per station). The end of line shots had 5 shot holes instead of 1 (750g total). The hammer source utilized a 5.5 kg hammer and an aluminum plate. Five hammer blows were stacked at each location to improve signal-to-noise ratio. Explosive sources yield higher amplitude, but lower frequency content. The explosions exhibit a higher signal-to-noise ratio, allowing us to recognize seismic energy deeper and farther from the source. Hammer sources yield higher frequencies, allowing better resolution at shallower depths but have a lower signal-to-noise ratio and lower amplitudes, even with source stacking. We analyze the details of the shot spectra from the different types of sources. A combination of source types can improve data resolution and amplitude, thereby improving imaging potential. However, cost, logistics, and complexities also have a large influence on source selection.

  17. Bed load transport in a very steep mountain stream (Riedbach, Switzerland): Measurement and prediction (United States)

    Schneider, Johannes M.; Rickenmann, Dieter; Turowski, Jens M.; Schmid, Bastian; Kirchner, James W.


    Compared to lower-gradient channels, steep mountain streams typically have rougher beds and shallower flow depths, making macro-scale flow resistance (due to, e.g., immobile boulders and irregular bedforms) more important as controls on sediment transport. The marked differences in hydraulics, flow resistance, and grain mobility between steep and lower-gradient streams raise the question of whether the same equations can predict bed load transport rates across wide ranges of channel gradients. We studied a steep, glacier-fed mountain stream (Riedbach, Ct. Valais, Switzerland) that provides a natural experiment for exploring how stream gradients affect bed load transport rates. The streambed gradient increases over a 1 km stream reach by roughly one order of magnitude (from 3% to 38%), while flow discharge and width remain approximately constant. Sediment transport rates were determined in the 3% reach using Bunte bed load traps and in the 38% reach using the Swiss plate geophone system. Despite a ten-fold increase in bed gradient, bed load transport rates did not increase substantially. Observed transport rates for these two very different bed gradients could be predicted reasonably well by using a flow resistance partitioning approach to account for increasing bed roughness (D84 changes from 0.17 m to 0.91 m) within a fractional bed load transport equation. This suggests that sediment transport behavior across this large range of steep slopes agrees with patterns established in previous studies for both lower-gradient and steep reaches, and confirms the applicability of the flow resistance and bed load transport equations at very steep slopes.

  18. Application of Microtremor Survey Methods to Determine the Shallow Crustal S-wave Velocity Structure beneath the Wudalianchi Weishan Volcano Area (United States)

    Zhang, B.; LI, Z.; Chu, R.


    Ambient noise has been proven particularly effective in imaging Earth's crust and uppermost mantle on local, regional and global scales, as well as in monitoring temporal variations of the Earth interior and determining earthquake ground truth location. Previous studies also have shown that the Microtremor Survey Method is effective to map the shallow crustal structure. In order to obtain the shallow crustal velocity structure beneath the Wudalianchi Weishan volcano area, an array of 29 new no-cable digital geophones were deployed for three days at the test site (3km×3km) for recording continuously seismic noise. Weishan volcano is located in the far north of Wudalianchi Volcanoes, the volcanic cone is composed of basaltic lava and the volcano area covered by a quaternary sediments layer (gray and black loam, brown and yellow loam, sandy loam). Accurate shallow crustal structure, particularly sedimentary structure model can improve the accuracy of location of volcanic earthquakes and structural imaging. We use ESPAC method, which is one of Microtremor Survey Methods, to calculate surface wave phase velocity dispersion curves between station pairs. A generalized 2-D linear inversion code that is named Surface Wave Tomography (SWT) is adopted to invert phase velocity tomographic maps in 2-5 Hz periods band. On the basis of a series of numerical tests, the study region is parameterized with a grid spacing of 0.1km×0.1km, all damping parameters and regularization are set properly to ensure relatively smooth results and small data misfits as well. We constructed a 3D Shallow Crustal S-wave Velocity model in the area by inverting the phase velocity dispersion curves at each node adopting an iterative linearized least-square inversion scheme of surf96. The tomography model is useful in interpreting volcanic features.

  19. Deep ReMi Imaging - Mapping Shear-Wave Velocities to 1 km Depth and Greater Using Refraction Microtremor (United States)

    Louie, J. N.; Pancha, A.; Munger, D.; Law, C.; Adams, D.; Mick, T. M.; Pullammanappallil, S. K.


    The Refraction Microtremor (ReMi) surface-wave technique, in use since 2002, has become a standard tool for assessing urban shear-wave velocities for engineering applications. ReMi is effective for site-class studies as well as assessing ground conditions, including 1D and 2D velocity-depth profiling to shallow depths of approximately 100 m. Over the last few years, we have successfully extended the application of the method to depths greater than 1 km. The use of deep ReMi, which relies primarily on ambient noise, for estimation of shear-wave velocities to kilometer depths, allows for mapping the thickness and velocity of deep urban basins. Accurate 3D modeling and calibration of recorded earthquake ground motions in urban areas is one use of deep ReMi results. Such models have the potential to be an essential part of seismic hazard evaluation. We present results from several deep ReMi studies conducted in the Reno-area and Tahoe basins of Nevada and California. Wireless instruments coupled with low-frequency geophones deployed in 3-km-long arrays across the densely populated urban environment acquired data in 2012, 2014, and 2015. In addition to mapping basement as deep as 900 m, the lateral velocity variations reveal deep-seated fault structure in the initial studies. A study of the Reno-area basin in 2016 employed arrays of 90 IRIS-PASSCAL Texans, 15 and 22 km long. This data set appears to constrain a sub-basin interface between Tertiary volcanics and Mesozoic basement at 1-2 km depth. Characterization of shear velocity at greater than 100 m depth, to basement, along with previously unknown faults, is vital towards quantifying earthquake ground motion and seismic hazard potential in geologically complex urban basins. Our measurements will allow Nevada communities to become more resilient against natural hazards.

  20. Testing & Validating: 3D Seismic Travel Time Tomography (Detailed Shallow Subsurface Imaging) (United States)

    Marti, David; Marzan, Ignacio; Alvarez-Marron, Joaquina; Carbonell, Ramon


    A detailed full 3 dimensional P wave seismic velocity model was constrained by a high-resolution seismic tomography experiment. A regular and dense grid of shots and receivers was use to image a 500x500x200 m volume of the shallow subsurface. 10 GEODE's resulting in a 240 channels recording system and a 250 kg weight drop were used for the acquisition. The recording geometry consisted in 10x20m geophone grid spacing, and a 20x20 m stagered source spacing. A total of 1200 receivers and 676 source points. The study area is located within the Iberian Meseta, in Villar de Cañas (Cuenca, Spain). The lithological/geological target consisted in a Neogen sedimentary sequence formed from bottom to top by a transition from gyspum to silstones. The main objectives consisted in resolving the underground structure: contacts/discontinuities; constrain the 3D geometry of the lithology (possible cavities, faults/fractures). These targets were achieved by mapping the 3D distribution of the physical properties (P-wave velocity). The regularly space dense acquisition grid forced to acquire the survey in different stages and with a variety of weather conditions. Therefore, a careful quality control was required. More than a half million first arrivals were inverted to provide a 3D Vp velocity model that reached depths of 120 m in the areas with the highest ray coverage. An extended borehole campaign, that included borehole geophysical measurements in some wells provided unique tight constraints on the lithology an a validation scheme for the tomographic results. The final image reveals a laterally variable structure consisting of four different lithological units. In this methodological validation test travel-time tomography features a high capacity of imaging in detail the lithological contrasts for complex structures located at very shallow depths.

  1. 3D Seismic Imaging over a Potential Collapse Structure (United States)

    Gritto, Roland; O'Connell, Daniel; Elobaid Elnaiem, Ali; Mohamed, Fathelrahman; Sadooni, Fadhil


    The Middle-East has seen a recent boom in construction including the planning and development of complete new sub-sections of metropolitan areas. Before planning and construction can commence, however, the development areas need to be investigated to determine their suitability for the planned project. Subsurface parameters such as the type of material (soil/rock), thickness of top soil or rock layers, depth and elastic parameters of basement, for example, comprise important information needed before a decision concerning the suitability of the site for construction can be made. A similar problem arises in environmental impact studies, when subsurface parameters are needed to assess the geological heterogeneity of the subsurface. Environmental impact studies are typically required for each construction project, particularly for the scale of the aforementioned building boom in the Middle East. The current study was conducted in Qatar at the location of a future highway interchange to evaluate a suite of 3D seismic techniques in their effectiveness to interrogate the subsurface for the presence of karst-like collapse structures. The survey comprised an area of approximately 10,000 m2 and consisted of 550 source- and 192 receiver locations. The seismic source was an accelerated weight drop while the geophones consisted of 3-component 10 Hz velocity sensors. At present, we analyzed over 100,000 P-wave phase arrivals and performed high-resolution 3-D tomographic imaging of the shallow subsurface. Furthermore, dispersion analysis of recorded surface waves will be performed to obtain S-wave velocity profiles of the subsurface. Both results, in conjunction with density estimates, will be utilized to determine the elastic moduli of the subsurface rock layers.

  2. Shallow seismic imaging of flank collapse structures in oceanic island volcanoes: Application to the Western Canary Islands (United States)

    Sanchez, L.; González, P.; Tiampo, K. F.


    Volcanic flank collapse counts among the many hazards associated with volcanic activity. This type of event involves the mobilization of large volumes, producing debris avalanches. It affects mostly oceanic island volcanoes, involving the potential for tsunami occurrence. Geophysical imaging can illuminate subvolcanic features such as volcano-tectonic structures, magmatic plumbing systems or differences in rock type. The most commonly used geophysical methods are gravity, electromagnetics and seismics. In particular, seismic measurements quantify anomalies in seismic waves propagation velocities and can be used to obtain information on the subsurface arrangement of different materials. In the Western Canary Islands, the Cumbre Vieja volcano in La Palma (Canary Islands) has been proposed to be near the collapse stage. Previous geophysical studies that have been carried out on the flank of the volcano comprise gravity and electromagnetic methods. These types of surveys gather information on the deep structures of the volcano (1-2 km). In this project, we complement previous studies by using seismic methods to investigate the near-surface seismic structure of the Cumbre Vieja fault system (La Palma Island) and the structure of the well-developed San Andres fault system (El Hierro Island). We aim to compare the Cumbre Vieja and San Andres fault systems to infer the degree of maturity of collapse structures. We carried out reflection and refraction seismic surveys in order to image approximately the first 10 meters of the subsurface. We used 24 low frequency (4,5 Hz) geophones as receivers and a sledge hammer as the seismic source. The survey lines were located across visible parts of the fault systems at the Cumbre Vieja volcano and the San Andres fault in El Hierro. Here, we present the survey setup and results from the preliminary analysis of the data.

  3. Characterization of large mass movements occurred in the Italian Alps using seismic monitoring networks (United States)

    Coviello, Velio; De Santis, Francesca; Chiarle, Marta; Arattano, Massimo; Godio, Alberto


    Passive seismic monitoring techniques have been profusely adopted to detect seismic sources induced by slope deformation and landslide propagation. Seismic signal processing can provide relevant information on the dynamics of unstable slopes, and may allow the identification of collapse precursors. Otherwise, seismic sensors have been used to characterize the volume and propagation velocity of rock-slides and debris-flows. For these purposes, geophone arrays are usually installed in specific monitoring sites. However, also a broadband seismic network can be used to identify signals originated by the detachment and movements of large masses. One advantage of using these networks would be the ability to detect remote events that might otherwise go unnoticed for weeks or months. Furthermore, even if often recorded at a distance, the spectral analysis of the low frequency content of the recorded signal may allow a preliminary characterization of the phenomenon. We selected five well known large mass movements occurred in the Italian Alps with volumes between 300.000 cubic meter (Monte Rosa rock avalanche, 2007) and 34.000.000 cubic meter (Val Pola rock avalanche, 1987). On average, seismic stations located up to 40 km far from these events were able to detect them, except for the Val Pola rock avalanche which was recorded at a distance greater than 100 km. As already observed by other authors, for these phenomena common signal characteristics include emergent onsets on all channels, slowly decaying tails and a triangular spectrogram shape. For this study we used different ground velocity sensors and considering the event magnitude, the distance source-receiver and to ensure a flat frequency response we focused on the 1-40 Hz frequency band. In this work these five large slope instabilities are described and the associated seismograms are presented and analyzed together with a first discussion of their spectral characteristics.

  4. Delineating Bukit Bunuh impact crater boundary by geophysical and geotechnical investigation (United States)

    Azwin, I. N.; Rosli, S.; Mokhtar, S.; Nordiana, M. M.; Ragu, R. R.; Mark, J.


    Evidences of crater morphology and shock metamorphism in Bukit Bunuh, Lenggong, Malaysia were found during the archaeological research conducted by the Centre for Global Archaeological Research Malaysia, Universiti Sains Malaysia. In order to register Bukit Bunuh as one of the world meteorite impact site, detailed studies are needed to verify the boundary of the crater accordingly. Geophysical study was conducted utilising the seismic refraction and 2-D electrical resistivity method. Seismic refraction survey was done using ABEM MK8 24 channel seismograph with 14Hz geophones and 40kg weight drop while 2-D electrical resistivity survey was performed using ABEM SAS4000 Terrameter and ES10-64C electrode selector with pole-dipole array. Bedrock depths were digitized from the sections obtained. The produced bedrock topography map shows that there is low bedrock level circulated by high elevated bedrock and interpreted as crater and rim respectively with diameter approximately 8km. There are also few spots of high elevated bedrock appear at the centre of the crater which interpreted as rebounds zone. Generally, the research area is divided into two layers where the first layer with velocity 400-1100 m/s and resistivity value of 10-800 Om predominantly consists of alluvium mix with gravel and boulders. Second layer represents granitic bedrock with depth of 5-50m having velocity >2100 m/s and resistivity value of >1500 Om. This research is strengthen by good correlation between geophysical data and geotechnical borehole records executed inside and outside of the crater, on the rim, as well as at the rebound area.

  5. High Voltage Seismic Generator (United States)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin


    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  6. Bedload pulses in a hydropower affected alpine gravel bed river (United States)

    Aigner, Johann; Kreisler, Andrea; Rindler, Rolf; Hauer, Christoph; Habersack, Helmut


    This study investigated the sediment resupply and transport dynamics at the Upper Drau River upstream of Lienz (Eastern Tyrol, Austria). Due to a hydropower plant, a 24 km long river reach of this alpine gravel bed river is under residual flow conditions, although sediment is still resupplied into the reach through many active torrents and tributaries. As a result, sediment deposition in the residual flow reach intensified, hence increasing maintenance efforts to stabilize this river section and ensure flood protection. In combination with a new sediment management program, a continuous bedload monitoring system was installed 2 km downstream of the residual reach in 2001 to support the development of adapted sediment management strategies. The surrogate bedload monitoring system consists of 16 impact plate geophones, installed over a 17 m wide cross section. The unprecedented 15-year dataset of high-resolution bedload intensity revealed a complex process of gravel storage and intermittent resupply from the residual reach, allowing the authors a detailed analysis of frequently occurring bedload pulses. These transport features are triggered by increased discharges during floods in the residual reach and created pronounced anticlockwise bedload hysteresis or, with a temporal shift to the event peak, caused distinct shifts in the bedload activity downstream. Bedload pulses produce very high bedload fluxes while in transit, tend to increase bedload flux in the post-event phase, and can alter and reduce the upstream sediment storage leading to a lowering of bedload availability for future pulses. The observed time lags between main discharge events and the arrival of the macro-pulses are correlated with mean water discharge during pulse propagation, thus enabling a prediction of the pulse arrival at the monitoring station solely based on the hydrograph. In combination with the hydrological setup of the reach, the observed bedload pulse time lags allowed an estimation of

  7. Data Release Report for Source Physics Experiments 2 and 3 (SPE-2 and SPE-3) Nevada National Security Site

    Energy Technology Data Exchange (ETDEWEB)

    Townsend, Margaret [National Security Technologies, LLC. (NSTec), Las Vegas, NV (United States); Obi, Curtis [National Security Technologies, LLC. (NSTec), Las Vegas, NV (United States)


    The second Source Physics Experiment shot (SPE-2) was conducted in Nevada on October 25, 2011, at 1900:00.011623 Greenwich Mean Time (GMT). The explosive source was 997 kilograms (kg) trinitrotoluene (TNT) equivalent of sensitized heavy ammonium fuel oil (SHANFO) detonated at a depth of 45.7 meters (m). The third Source Physics Experiment shot (SPE-3) was conducted in Nevada on July 24, 2012, at 1800:00.44835 GMT. The explosive source was 905 kg TNT equivalent of SHANFO detonated at a depth of 45.8 m. Both shots were recorded by an extensive set of instrumentation that includes sensors both at near-field (less than 100 m) and far-field (100 m or greater) distances. The near-field instruments consisted of three-component accelerometers deployed in boreholes at 15, 46, and 55 m depths around the shot and a set of single-component vertical accelerometers on the surface. The far-field network was composed of a variety of seismic and acoustic sensors, including short-period geophones, broadband seismometers, three-component accelerometers, and rotational seismometers at distances of 100 m to 25 kilometers. This report coincides with the release of these data for analysts and organizations that are not participants in this program. This report describes the second and third Source Physics Experiment shots and the various types of near-field and farfield data that are available.This revised document includes reports on baseline shift corrections for the SPE-2 and SPE-3 shots that were missing from the original January 2015 version.

  8. Non-invasive shallow seismic source comparison for hazardous waste site investigations

    Energy Technology Data Exchange (ETDEWEB)

    Doll, W.E. [Oak Ridge National Lab., TN (United States). Environmental Sciences Div.; Miller, R.D.; Xia, J. [Kansas Geological survey, Lawrence, KS (United States)


    Many commonly used shallow seismic sources are unacceptable for hazardous waste site investigations because they risk exhumation of contaminants in the soil, they add contaminants (e.g. lead) which are not allowed by regulations, or they add new migration paths for contaminants. Furthermore, recently developed high frequency vibrators for shallow investigations could be more effective at some sites than non-invasive impulsive sources because of their ability to tailor the source spectrum and reduce interference. The authors show preliminary results of a comparison test of eight non-invasive impulsive and swept sources in preparation for seismic reflection profiling on the Oak Ridge Reservation, Tennessee. Well log data are used to determine geologic contacts and to generate synthetic seismograms for the site. Common midpoint (CMP) seismic data for each source were collected at 95 geophone groups from 125 shot points along a 400m test line. Hydrophone data were obtained at 1.5m spacing between 61m and 133m depth in a hole near the center of the CMP line. As of March, 1994, brute stacks have been completed for three of the eight sources. Depth penetration is demonstrated in brute stacks and shot gathers, which show a 200ms reflector for all of the sources tested along portions of the line. Source effectiveness will also be evaluated by comparing images of several shallower reflectors (40--150ms) which are apparent in many of the records. Imaging of these reflectors appears to depend upon the ability of the source to generate sufficient high frequency energy (>100 Hz).

  9. Microseismic activity analysis for the study of the rupture mechanisms in unstable rock masses (Matterhorn, North-western Alps) (United States)

    Amitrano, D.; Arattano, M.; Chiarle, M.; Mortara, G.; Occhiena, C.; Pirulli, M.; Scavia, C.


    Rockfalls are very frequent events in alpine areas and can endanger human lifes and activities. Since high mountains have been affected by an increasing number of these phenomena in the last years, a possible correlation with the effects of climate changes can be hypothesized. The permafrost degradation, causing the thaw of the ice that fills the rock discontinuities, is then investigated among possible causes of rockfalls. Therefore the monitoring of potential rock instabilities in high mountain in relation with permafrost degradation has been carried out in the frame of the Interreg IIIA ALCOTRA "PERMAdataROC" project. Within the project, a monitoring network has been installed in 2007 on the Italian side of the Matterhorn peak, close to the J. A. Carrel refuge (3829 m a.s.l.). This site is an important destination for climbers going to the Matterhorn peak and is frequently affected by rockfall events. The monitoring network consists of a set of 5 triaxial geophones, to record the existing microseismic activity, and one thermometer, to analyze the temperature trend. A preliminary data processing has concerned the classification of the recorded signals, the identification of the most important microseismic events and the analysis of their distribution in time. As far as this last aspect is concerned, first interpretations have evidenced a possible correlation between the temperature trend and the event concentrations, during particular thermal sequences. The research is still in progress and it is expected that a longer recording period of seismic events and temperatures will help to understand if the microseismic activity is mainly concentrated in some periods of the year, in some parts of the slope and if it is produced by superficial or deep events. A concentration of superficial events in some parts of the slope, together with a structural analysis of those portions, could help to focus on the areas that can be more unstable. While, their correlation with

  10. High-resolution shear-wave seismic reflection as a tool to image near-surface subrosion structures - a case study in Bad Frankenhausen, Germany (United States)

    Wadas, Sonja H.; Polom, Ulrich; Krawczyk, Charlotte M.


    Subrosion is the subsurface leaching of soluble rocks that results in the formation of depression and collapse structures. This global phenomenon is a geohazard in urban areas. To study near-surface subrosion structures, four shear-wave seismic reflection profiles, with a total length of ca. 332 m, were carried out around the famous leaning church tower of Bad Frankenhausen in northern Thuringia, Germany, which shows an inclination of 4.93° from the vertical. Most of the geological underground of Thuringia is characterized by soluble Permian deposits, and the Kyffhäuser Southern Margin Fault is assumed to be a main pathway for water to leach the evaporite. The seismic profiles were acquired with the horizontal micro-vibrator ELVIS, developed at Leibniz Institute for Applied Geophysics (LIAG), and a 72 m long landstreamer equipped with 72 horizontal geophones. The high-resolution seismic sections show subrosion-induced structures to a depth of ca. 100 m and reveal five features associated with the leaching of Permian deposits: (1) lateral and vertical varying reflection patterns caused by strongly heterogeneous strata, (2) discontinuous reflectors, small offsets, and faults, which show the underground is heavily fractured, (3) formation of depression structures in the near-surface, (4) diffractions in the unmigrated seismic sections that indicate increased scattering of the seismic waves, and (5) varying seismic velocities and low-velocity zones that are presumably caused by fractures and upward-migrating cavities. A previously undiscovered southward-dipping listric normal fault was also found, to the north of the church. It probably serves as a pathway for water to leach the Permian formations below the church and causes the tilting of the church tower. This case study shows the potential of horizontal shear-wave seismic reflection to image near-surface subrosion structures in an urban environment with a horizontal resolution of less than 1 m in the uppermost 10

  11. Relating to fossil energy resource characterization, research, technology development, and technology transfer

    Energy Technology Data Exchange (ETDEWEB)

    Poston, S.W.; Berg, R.R.; Friedman, M.M.; Gangi, A.F.; Wu, C.H.


    Geological, geophysical and petroleum engineering aspects of oil recovery from low-permeability reservoirs have been studied over the past three years. Significant advances were made in using Formation Microscanner Surveys (FMS) data to extrapolate fracture orientation, abundance, and spacing from the outcrop to the subsurface. Highly fractured zones within the reservoir can be detected, thus the fracture stratigraphy defined. Multi-component,vertical-seismic profile (VSP), shear wave data were used to improve the detection of fractures. A balancing scheme was developed to improve the geophysical detection of fractures based on balanced source magnitudes and geophone couplings. Resistivity logs can be used to identify the zone of immature organic material, the zone of storage where oil is generated but held in the matrix and the zone of migration whee oil is expelled from the rock to fractures. Natural fractures can be detected in many wells by the response of density logs in combination with gamma-ray, resistivity, and sonic logs. Theoretical studies and analysis of daily production data, from field case histories, have shown the utility of the Chef Type Curves to derive reservoir character from production test data. This information is ordinarily determined from transient pressure data. Laboratory displacement as well as MI and CT studies show that the carbonated water imbibition oil displacement process significantly accelerates and increases recovery from saturated, low-permeability core material. The created gas drive, combined with oil shrinkage significantly increased oil recovery. A cyclic-carbonated-water-imbibition process improves oil recovery. A semi-analytical model (MOD) and a 3-dimensional, 3-phase, dual-porosity, compositional simulator (COMAS) were developed to describe the imbibition carbonated waterflood performance. MOD model is capable of computing the oil recovery and saturation profiles for oil/water viscosity ratios other than one.

  12. Downhole Microseismic Monitoring at a Carbon Capture, Utilization, and Storage Site, Farnsworth Unit, Ochiltree County, Texas (United States)

    Ziegler, A.; Balch, R. S.; van Wijk, J.


    Farnsworth Oil Field in North Texas hosts an ongoing carbon capture, utilization, and storage project. This study is focused on passive seismic monitoring at the carbon injection site to measure, locate, and catalog any induced seismic events. A Geometrics Geode system is being utilized for continuous recording of the passive seismic downhole bore array in a monitoring well. The array consists of 3-component dual Geospace OMNI-2400 15Hz geophones with a vertical spacing of 30.5m. Downhole temperature and pressure are also monitored. Seismic data is recorded continuously and is produced at a rate of over 900GB per month, which must be archived and reviewed. A Short Term Average/Long Term Average (STA/LTA) algorithm was evaluated for its ability to search for events, including identification and quantification of any false positive events. It was determined that the algorithm was not appropriate for event detection with the background level of noise at the field site and for the recording equipment as configured. Alternatives are being investigated. The final intended outcome of the passive seismic monitoring is to mine the continuous database and develop a catalog of microseismic events/locations and to determine if there is any relationship to CO2 injection in the field. Identifying the location of any microseismic events will allow for correlation with carbon injection locations and previously characterized geological and structural features such as faults and paleoslopes. Additionally, the borehole array has recorded over 1200 active sources with three sweeps at each source location that were acquired during a nearby 3D VSP. These data were evaluated for their usability and location within an effective radius of the array and were stacked to improve signal-noise ratio and are used to calibrate a full field velocity model to enhance event location accuracy. Funding for this project is provided by the U.S. Department of Energy under Award No. DE-FC26-05NT42591.

  13. On the Acoustic Filtering of the Pipe and Sensor in a Buried Plastic Water Pipe and its Effect on Leak Detection: An Experimental Investigation (United States)

    Almeida, Fabrício; Brennan, Michael; Joseph, Phillip; Whitfield, Stuart; Dray, Simon; Paschoalini, Amarildo


    Acoustic techniques have been used for many years to find and locate leaks in buried water distribution systems. Hydrophones and accelerometers are typically used as sensors. Although geophones could be used as well, they are not generally used for leak detection. A simple acoustic model of the pipe and the sensors has been proposed previously by some of the authors of this paper, and their model was used to explain some of the features observed in measurements. However, simultaneous measurements of a leak using all three sensor-types in controlled conditions for plastic pipes has not been reported to-date and hence they have not yet been compared directly. This paper fills that gap in knowledge. A set of measurements was made on a bespoke buried plastic water distribution pipe test rig to validate the previously reported analytical model. There is qualitative agreement between the experimental results and the model predictions in terms of the differing filtering properties of the pipe-sensor systems. A quality measure for the data is also presented, which is the ratio of the bandwidth over which the analysis is carried out divided by the centre frequency of this bandwidth. Based on this metric, the accelerometer was found to be the best sensor to use for the test rig described in this paper. However, for a system in which the distance between the sensors is large or the attenuation factor of the system is high, then it would be advantageous to use hydrophones, even though they are invasive sensors. PMID:24658622

  14. Time-Dependent Moment Tensors of the First Four Source Physics Experiments (SPE) Explosions (United States)

    Yang, X.


    We use mainly vertical-component geophone data within 2 km from the epicenter to invert for time-dependent moment tensors of the first four SPE explosions: SPE-1, SPE-2, SPE-3 and SPE-4Prime. We employ a one-dimensional (1D) velocity model developed from P- and Rg-wave travel times for Green's function calculations. The attenuation structure of the model is developed from P- and Rg-wave amplitudes. We select data for the inversion based on the criterion that they show consistent travel times and amplitude behavior as those predicted by the 1D model. Due to limited azimuthal coverage of the sources and the mostly vertical-component-only nature of the dataset, only long-period, diagonal components of the moment tensors are well constrained. Nevertheless, the moment tensors, particularly their isotropic components, provide reasonable estimates of the long-period source amplitudes as well as estimates of corner frequencies, albeit with larger uncertainties. The estimated corner frequencies, however, are consistent with estimates from ratios of seismogram spectra from different explosions. These long-period source amplitudes and corner frequencies cannot be fit by classical P-wave explosion source models. The results motivate the development of new P-wave source models suitable for these chemical explosions. To that end, we fit inverted moment-tensor spectra by modifying the classical explosion model using regressions of estimated source parameters. Although the number of data points used in the regression is small, the approach suggests a way for the new-model development when more data are collected.

  15. Detection of the under-soil intruder activity (United States)

    Cechak, Jaroslav


    The presented paper focuses on the possibilities of technical methods designed to detect a trespasser under the ground, and in general on the possibilities of detection a trespasser behind an obstruction. The paper analyses method of detection of a trespasser that were practically verified by the author of the paper. The first part of the paper discusses the characteristics and use of piezoelectric films that could be used as a replacement for the traditional geophone for detection of underground mining operation. It also provides a block connection diagram of the measuring chain and photos of the practical implementation of the sensor. The consequent part of the paper then discusses the possibilities of detecting a trespasser based on electromagnetic waves emission by humans in the ELF - Extremely Low Frequency band. The paper is supplemented with illustrative photos and results of numeric processing of signals in the form of graphs and courses. The history of excavating and using tunnels spans long into the past. Tunnels were used not only as storage for food and war material but mainly as effective means of protection against attackers. A significant motivating factor for constructing tunnels lies in the hidden possibility of movement of people and transfer of material under the ground of a protected perimeter. At present some tunnels are used as roads for smuggling drugs, weapons, ammunition or illegal passages of people. There are even cases, not exceptional, when tunnels were excavated with the aim to rob a bank safe etc. The fact that construction of tunnels, often quite primitive ones, is not sporadic, can be continually documented not only by historical sources but often also by the daily news summary. The concurrent lack of proper technological means results in the renaissance of using tunnels for illegal purposes even at present. The presented paper focuses on the above mentioned area and points to little used physical principles of detection underground

  16. Simple equations guide high-frequency surface-wave investigation techniques (United States)

    Xia, J.; Xu, Y.; Chen, C.; Kaufmann, R.D.; Luo, Y.


    We discuss five useful equations related to high-frequency surface-wave techniques and their implications in practice. These equations are theoretical results from published literature regarding source selection, data-acquisition parameters, resolution of a dispersion curve image in the frequency-velocity domain, and the cut-off frequency of high modes. The first equation suggests Rayleigh waves appear in the shortest offset when a source is located on the ground surface, which supports our observations that surface impact sources are the best source for surface-wave techniques. The second and third equations, based on the layered earth model, reveal a relationship between the optimal nearest offset in Rayleigh-wave data acquisition and seismic setting - the observed maximum and minimum phase velocities, and the maximum wavelength. Comparison among data acquired with different offsets at one test site confirms the better data were acquired with the suggested optimal nearest offset. The fourth equation illustrates that resolution of a dispersion curve image at a given frequency is directly proportional to the product of a length of a geophone array and the frequency. We used real-world data to verify the fourth equation. The last equation shows that the cut-off frequency of high modes of Love waves for a two-layer model is determined by shear-wave velocities and the thickness of the top layer. We applied this equation to Rayleigh waves and multi-layer models with the average velocity and obtained encouraging results. This equation not only endows with a criterion to distinguish high modes from numerical artifacts but also provides a straightforward means to resolve the depth to the half space of a layered earth model. ?? 2005 Elsevier Ltd. All rights reserved.

  17. The Mount Rainier Lahar Detection System (United States)

    Lockhart, A. B.; Murray, T. L.


    To mitigate the risk of unheralded lahars from Mount Rainier, the U.S. Geological Survey, in cooperation with Pierce County, Washington, installed a lahar-detection system on the Puyallup and Carbon rivers that originate on Mount Rainier's western slopes. The system, installed in 1998, is designed to automatically detect the passage of lahars large enough to potentially affect populated areas downstream (approximate volume threshold 40 million cubic meters), while ignoring small lahars, earthquakes, extreme weather and floods. Along each river valley upstream, arrays of independent lahar-monitoring stations equipped with geophones and short tripwires telemeter data to a pair of redundant computer base stations located in and near Tacoma at existing public safety facilities that are staffed around the clock. Monitored data consist of ground-vibration levels, tripwire status, and transmissions at regular intervals. The base stations automatically evaluate these data to determine if a dangerous lahar is passing through the station array. The detection algorithm requires significant ground vibration to occur at those stations in the array that are above the anticipated level of inundation, while lower level `deadman' stations, inundated by the flow, experience tripwire breakage or are destroyed. Once a base station detects a lahar, it alerts staff who execute a call-down of public-safety officials and schools, initiating evacuation of areas potentially at risk. Because the system's risk-mitigation task imposes high standards of reliability on all components, it has been under test for several years. To date, the system has operated reliably and without false alarms, including during the nearby M6.8 Nisqually Earthquake on February 28, 2001. The system is being turned over to Pierce County, and activated as part of their lahar warning system.

  18. A seismic reflection experiment near Runanga, Westland

    Energy Technology Data Exchange (ETDEWEB)

    Broadbent, M.; Jenkins, R.


    An experiment was performed between Runanga and Rapahoe, a few kilometres north of Greymouth, to determine whether seismic waves reflected from Tertiary and Mesozoic sediments associated with coal seams could be recorded and identified. Reflections were observed at both sites occupied during the experiment, which were centred on National Yard Grid coordinates S44/770 964 and S44/776 957. Reflections observed at the western site have been tentatively associated with boundaries in or at the base of the Island Sandstone (about 180 metres below the ground surface), and within or at the bounds of the Rewanui Coal Measures (at about 400 metres depth). At the eastern site, reflections have been attributed to a boundary at about 170 metres depth. Reflections were generated using explosions 10 metres below the ground surface, and also by using groups of shallower, smaller simultaneous explosions at distances of more than 100 metres from the geophones where the reflections were detected. Average velocity estimates derived from the seismic measurements alone were 2.6 and 3.0 km/s for Rapahoe and Mawheranui Group sediments respectively. Sonic log measurements yield an average velocity of 3.3 km/s fro the Mawheranui Group. The areal coverage of the experiment was restricted by the difficulty of gaining access to locations off roads and the vulnerability of local access routes, services, and structures to vibration induced damage. The scope of the experimentation was further restricted by difficulties encountered in drilling shot holes and by recording equipment limitations. (4 refs.)

  19. High-resolution shallow structure revealed with ambient noise tomography on a dense array (United States)

    Zeng, X.; Thurber, C. H.; Luo, Y.; Matzel, E.; Team, P.


    A dense seismic array was deployed by the PoroTomo research team at Brady Hot Springs, Nevada in March 2016. The array consisted of 238 short-period three-component geophones (5-Hz corner frequency) with about 60 m spacing. Over the 15 day deployment, the array recorded over 6,000 active source signals (vibroseis sweeps) and ambient noise that was dominated by traffic noise.We adopted the one-bit method to better reduce the effect of the active source. Spectral whitening was performed between 0.5 and 2 Hz. The continuous record was chopped into 1 minute segments. The 1-minute cross-correlation functions were initially stacked linearly, and then the phase-weighted stacking method was applied to improve signal quality. More than two million noise correlation functions (NCFs) have been obtained.The Rayleigh wave group velocity was measured on the symmetric component of the NCFs with the frequency-time analysis method. The average group velocity is about 400 m/s at 4 Hz, which is consistent with preliminary active source result. To avoid mis-picking possible precursors, the arrival time was picked at the peak in a two-second time window predicted with the average group velocity of the fundamental mode. The quality of the arrival measurements is defined by the signal-to-noise ratio. We were able to pick reliable arrivals at about 35% of the station-pairs. Since the straight-ray assumption may not be valid in a strongly heterogeneous medium, the wave path was traced with a finite difference scheme and the LSQR method was utilized to invert group velocity. The heterogeneous features of the group velocity map are consistent with a local geologic map. The PoroTomo project is funded by a grant from the U.S. Department of Energy.

  20. Modeling and locating underground water pipe leak with microseismic data (United States)

    Wang, Jing; Liu, Jiangping; Liu, Hao; Tian, Zhijian; Cheng, Fei


    Traditional pipeline leak locating methods require that geophones have to be placed on the pipe wall. While if the exact location of the pipeline is unknown, the leaks may not be identified accurately. To solve this problem, considering the characteristics of pipeline leak, a continuous random seismic source model is proposed and geological models are established. Based on the two dimensional (2D) viscoacoustic equations and the staggered grid finite-difference (FD) algorithm, the microseismic wave field generated by a leaking pipe is modeled. Cross-correlation analysis and the simulated annealing (SA) algorithm are employed to obtain the time difference and the leak location. Analysis and discussions of the effects of number of recorded traces, survey layout, and offset and trace interval on the accuracy of the estimated location are also conducted. Simulation and data field experiment results indicate that: (1) A continuous random source can realistically represent the leak microseismic wave field in a simulation using 2D viscoacoustic equations and staggered grid FD algorithm. (2) For the leak microseismic wave field, the cross-correlation method is effective for calculating time difference of the direct wave relative to the reference trace. However, outside the refraction blind zone, accuracy of the time difference is reduced by the effects of refracted wave. (3) The SA algorithm based upon time difference, helps to identify the leak location effectively, even in the presence of noise. Estimation of the horizontal distance is more accurate than that of the depth, and the locating errors increase with increasing number of traces and offset. Moreover, in the refraction blind zone, trace interval has almost no impact on the accuracy of the location estimate. And the symmetrical array provides a higher estimate accuracy than the asymmetrical array. (4) The acquisition method of time difference based on the microseismic theory and SA algorithm has a great potential

  1. Short-time electrical effects during volcanic eruption: Experiments and field measurements (United States)

    Büttner, Ralf; Zimanowski, Bernd; Röder, Helmut


    Laboratory experiments on the fragmentation and expansion of magmatic melt have been performed using remelted volcanic rock at magmatic temperatures as magma simulant. A specially designed dc amplifier in combination with high speed data recording was used to detect short-time electrostatic field effects related to the fragmentation and expansion history of the experimental system, as documented by simultaneous force and pressure recording, as well as by high-speed cinematography. It was found that (1) the voltage-time ratio of electrostatic field gradients (100 to 104 V/s) reflects different physical mechanisms of fragmentation and expansion and (2) the maximum voltage measured in 1 m distance (-0.1 to -180 V) can be correlated with the intensity of the respective processes. Based on these experimental results, a field method was developed and tested at Stromboli volcano in Italy. A 0.8 m rod antenna was used to detect the dc voltage against local ground (i.e., the electrostatic field gradient), at a distance of 60 to 260 m from the respective vent. Upwind position of the detection site was chosen to prevent interference caused by contact of charged ash particles with the antenna. A standard 8 Hz geophone was used to detect the accompanying seismicity. Three types of volcanic activity occurred during the surveillance operation; two of these could be clearly related to specific electrical and seismical signals. A typical delay time was found between the electrical and the seismical signal, corresponding to the seismic velocity within the crater deposits. Using a simple first-order electrostatic model, the field measurements were recalibrated to the laboratory scale. Comparison of field and laboratory data at first approximation revealed striking similarities, thus encouraging the further development of this technique for real-time surveillance operation at active volcanoes.

  2. On the Acoustic Filtering of the Pipe and Sensor in a Buried Plastic Water Pipe and its Effect on Leak Detection: An Experimental Investigation

    Directory of Open Access Journals (Sweden)

    Fabrício Almeida


    Full Text Available Acoustic techniques have been used for many years to find and locate leaks in buried water distribution systems. Hydrophones and accelerometers are typically used as sensors. Although geophones could be used as well, they are not generally used for leak detection. A simple acoustic model of the pipe and the sensors has been proposed previously by some of the authors of this paper, and their model was used to explain some of the features observed in measurements. However, simultaneous measurements of a leak using all three sensor-types in controlled conditions for plastic pipes has not been reported to-date and hence they have not yet been compared directly. This paper fills that gap in knowledge. A set of measurements was made on a bespoke buried plastic water distribution pipe test rig to validate the previously reported analytical model. There is qualitative agreement between the experimental results and the model predictions in terms of the differing filtering properties of the pipe-sensor systems. A quality measure for the data is also presented, which is the ratio of the bandwidth over which the analysis is carried out divided by the centre frequency of this bandwidth. Based on this metric, the accelerometer was found to be the best sensor to use for the test rig described in this paper. However, for a system in which the distance between the sensors is large or the attenuation factor of the system is high, then it would be advantageous to use hydrophones, even though they are invasive sensors.

  3. Automatic and accurate measurements of P-wave and S-wave polarisation properties with a weighted multi-station complex polarisation analysis (United States)

    de Meersman, K.; van der Baan, M.; Kendall, J.-M.; Jones, R. H.


    We present a weighted multi-station complex polarisation analysis to determine P-wave and S-wave polarisation properties of three-component seismic array data. Complex polarisation analysis of particle motion on seismic data was first introduced by Vidale (1986). In its original form, the method is an interpretation of the eigenvalue decomposition of a 3 by 3, complex data-covariance matrix. We have extended the definition of the data-covariance matrix (C) to C=X^HW-1 X, where C now is a 3n by 3n symmetric complex covariance matrix, with n the number of included three-component (3C) stations. X is the data matrix, the columns of which are the analytic signals of the Northern, Eastern and vertical components of the subsequent 3C stations. X^H is the transpose of the complex conjugate of X and W is a diagonal weighting matrix containing the pre-arrival noise levels of all components and all stations. The signals used in the data-matrix are corrected for arrival time differences. The eigenvectors and eigenvalues of C now describe the polarisation properties within the selected analysis window for all included stations. The main advantages of this approach are a better separation of signal and noise in the covariance matrix and the measurement of signal polarisation properties that are not influenced by the presence of polarised white noise. The technique was incorporated in an automated routine to measure the P-wave and S-wave polarisation properties of a microseismic data-set. The data were recorded in the Valhall oilfield in 1998 with a six level 3C vertical linear array with geophones at 20 m intervals between depths of 2100 m and 2200 m. In total 303 microseismic events were analysed and the results compared with manual interpretations. This comparison showed the advantage and high accuracy of the method.

  4. Using the IODP Expedition 312 Vertical Seismic Profile to Investigate Sub-basement Reflections in Multi-Channel Profiles (United States)

    Nag, S.; Swift, S. A.; Stephen, R. A.


    The Ocean Drilling Program (ODP) initiated drilling at Site 1256D in the Guatemala Basin, about 1000km off the East Pacific Rise to penetrate plutonic rocks, anticipated to be relatively shallow in this region formed at an ultra- fast spreading rate. IODP Expedition E312 successfully drilled into gabbros at ~ 1150m in basement. Multi- channel seismic traces, although not processed for the purpose, show weak laterally-coherent sub-basement reflections at borehole depths (Hallenborg et. al., Journal of Geophysical Research, Vol 108 No. B11, 2532, 2003). Synthetic reflectivity seismograms were computed using a Ricker wavelet and impedance profiles from borehole sonic logs. They strongly suggest the presence of significant sub-basement amplitude peaks - although attenuation has not been modeled. Zero-offset vertical seismic profiles were processed to investigate the authenticity of these reflections and interpret the geological features that caused them. A dual scheme of the median filtering and F-K dip filtering was used. Down-going energy is clearly identified but negligible up-going energy is visible over random noise. The absence of geophones above the basement prevents comparison of basement reflections with sub-basement ones, so that a critical energy level above the noise could be established to identify up-going energy. The negative results are consistent with the topography of geological horizons on horizontal scales less than the Fresnel Zone (~ 300m). This expedition is the first penetration through volcanic extrusives and dikes into plutonic basement. In such a setting, sub-basement reflections, if present, would have been accurately measured. Absence of such clear and comprehensible observations in this area strongly suggests that lava flows and igneous contacts in upper ocean crust have significant topography on lateral scales < 300 m due to igneous and tectonic processes.

  5. Monitoring hydraulic fracturing with seismic emission volume (United States)

    Niu, F.; Tang, Y.; Chen, H.; TAO, K.; Levander, A.


    Recent developments in horizontal drilling and hydraulic fracturing have made it possible to access the reservoirs that are not available for massive production in the past. Hydraulic fracturing is designed to enhance rock permeability and reservoir drainage through the creation of fracture networks. Microseismic monitoring has been proven to be an effective and valuable technology to image hydraulic fracture geometry. Based on data acquisition, seismic monitoring techniques have been divided into two categories: downhole and surface monitoring. Surface monitoring is challenging because of the extremely low signal-to-noise ratio of the raw data. We applied the techniques used in earthquake seismology and developed an integrated monitoring system for mapping hydraulic fractures. The system consists of 20 to 30 state-of-the-art broadband seismographs, which are generally about hundreds times more sensible than regular geophones. We have conducted two experiments in two basins with very different geology and formation mechanism in China. In each case, we observed clear microseismic events, which may correspond to the induced seismicity directly associated with fracturing and the triggered ones at pre-existing faults. However, the magnitude of these events is generally larger than magnitude -1, approximately one to two magnitudes larger than those detected by downhole instruments. Spectrum-frequency analysis of the continuous surface recordings indicated high seismic energy associated with injection stages. The seismic energy can be back-projected to a volume that surrounds each injection stage. Imaging seismic emission volume (SEV) appears to be an effective way to map the stimulated reservior volume, as well as natural fractures.

  6. Shallow Seismic Reflection Survey at Garner Valley Digital Array (United States)

    Lawrence, Z. S.; Brackman, T. B.; Bodin, P.; Stephenson, W. J.; Steidl, J. H.; Gomberg, J.


    The Garner Valley Digital Array (GVDA) site is a NEES-sponsored facility in a small, sediment-filled, intermountain valley in Southern California, established for the purpose of investigating ground motion site response and soil-structure interaction, in situ. The site has been well-characterized geotechnically, and is thoroughly instrumented with both surface and downhole instrumentation of various types. Nevertheless, a borehole recently drilled into lake bed sediments and deeply weathered granitic rocks that comprise the valley fill at GVDA encountered hard, unweathered bedrock at an unexpected depth, suggesting an apparent 38 meter offset in the unweathered bedrock between two wells 40 meters apart. The apparent offset can be most easily explained either by faulting, or as a buried erosional surface. The Hot Springs fault, a strand of the San Jacinto fault zone, runs through Garner Valley, although its inferred location is several hundred meters east of GVDA. To better characterize the subsurface strata, particularly the existence and configuration of faulting that may disturb them; we conducted a 120-meter long, 12-fold shallow seismic reflection common midpoint (CMP) survey at GVDA using a 24-channel seismograph, vertical 4.5 Hz geophones at 2-meter intervals and a sledgehammer seismic source. Preliminary processing reveals strong refractors and surface waves that may mask reflections, although reflections are visible in some raw shot records. Semi-continuous reflections seen in the CMP section from a shallow reflector may coincide with the water table. There are also deeper, discontinuous reflectors obscured by bands of coherent noise. We plan to present a fully migrated and interpreted CMP record section.

  7. Automatic detection of avalanches in seismic data using Hidden Markov Models (United States)

    Heck, Matthias; Hammer, Conny; van Herwijnen, Alec; Schweizer, Jürg; Fäh, Donat


    Seismic monitoring systems are well suited for the remote detection of mass movements, such as landslides, rockfalls and debris flows. For snow avalanches, this has been known since the 1970s and seismic monitoring could potentially provide valuable information for avalanche forecasting. We thus explored continuous seismic data from a string of vertical component geophones in an avalanche starting zone above Davos, Switzerland. The overall goal is to automatically detect avalanches with a Hidden Markov Model (HMM), a statistical pattern recognition tool widely used for speech recognition. A HMM uses a classifier to determine the likelihood that input objects belong to a finite number of classes. These classes are obtained by learning a multidimensional Gaussian mixture model representation of the overall observable feature space. This model is then used to derive the HMM parameters for avalanche waveforms using a single training sample to build the final classifier. We classified data from the winter seasons of 2010 and compared the results to several hundred avalanches manually identified in the seismic data. First results of a classification of a single day have shown, that the model is good in terms of probability of detection while having a relatively low false alarm rate. We further implemented a voting based classification approach to neglect events detected only by one sensor to further improve the model performance. For instance, on 22 March 2010, a day with particular high avalanche activity, 17 avalanches were positively identified by at least three sensors with no false alarms. These results show, that the automatic detection of avalanches in seismic data is feasible, bringing us one step closer to implementing seismic monitoring system in operational forecasting.

  8. Analysis of microseismic signals and temperature recordings for rock slope stability investigations in high mountain areas

    Directory of Open Access Journals (Sweden)

    C. Occhiena


    Full Text Available The permafrost degradation is a probable cause for the increase of rock instabilities and rock falls observed in recent years in high mountain areas, particularly in the Alpine region. The phenomenon causes the thaw of the ice filling rock discontinuities; the water deriving from it subsequently freezes again inducing stresses in the rock mass that may lead, in the long term, to rock falls. To investigate these processes, a monitoring system composed by geophones and thermometers was installed in 2007 at the Carrel hut (3829 m a.s.l., Matterhorn, NW Alps. In 2010, in the framework of the Interreg 2007–2013 Alcotra project no. 56 MASSA, the monitoring system has been empowered and renovated in order to meet project needs.

    In this paper, the data recorded by this renewed system between 6 October 2010 and 5 October 2011 are presented and 329 selected microseismic events are analysed. The data processing has concerned the classification of the recorded signals, the analysis of their distribution in time and the identification of the most important trace characteristics in time and frequency domain. The interpretation of the results has evidenced a possible correlation between the temperature trend and the event occurrence.

    The research is still in progress and the data recording and interpretation are planned for a longer period to better investigate the spatial-temporal distribution of microseismic activity in the rock mass, with specific attention to the relation of microseismic activity with temperatures. The overall goal is to verify the possibility to set up an effective monitoring system for investigating the stability of a rock mass under permafrost conditions, in order to supply the researchers with useful data to better understand the relationship between temperature and rock mass stability and, possibly, the technicians with a valid tool for decision-making.

  9. The deep Algerian margin structure revisited by the Algerian-French SPIRAL research program, stage 2 : Wide-ange seismic experiment (United States)

    Klingelhoefer, Frauke; Yellès, Abdelkarim; Bracène, Rabah; Graindorge, David; Ouabadi, Aziouz; Schnürle, Philippe; Scientific Party, Spiral


    During the second leg of the Algerien - French SPIRAL (Sismique Profonde et Investigation Regionale du Nord de l'ALgerie) cruise conducted on the R/V Atalante in October and November 2009 an extensive wide-angle seismic data-set was acquired on 5 regional transects off Algeria, from Arzew bay to the west, to Annaba to the east. The profiles are between 80 and 180 km in length and around 40 ocean-bottom seismometers were deployed on each profile. A 8350 cu. inch tuned airgun array consisting of 10 Bolt airguns was used to generate of deep frequency to allow for a good penetration. All profiles were extended on land up to 150 km by land-stations to better constrain the structure of the margin and the nature of the ocean-continent transition zone. Coincident reflection seismic, gravity and magnetic data were acquired on all profiles during the first leg of the cruise. The resulting data quality is very good with deep penetrating arrivals on most of the instruments. Only on very few instruments a deep salt layer inhibits deeper penetration of the seismic energy. Two instruments were lost and all other yielded useful information on geophone and hydrophone channels. Instruments located close to the coast show arrivals from thick sedimentary layers. Instruments located on oceanic crust indicate a relatively thin crust overlying a mantle layer characterised by seismic velocities of 8 km/s. Forward and inverse modelling of the wide-angle seismic data will help constrain the deep structure of the margin, the nature of the crust and might help to constrain possible existence of a detached slab in the upper mantle. Integration of the wide-angle seismic data with multichannel seismic, gravity and magnetic data will enable us to better understand the tectonic history and the structure of the Algerian margin.

  10. High Resolution Seismic Imaging of the Brawley Seismic Fault Zone (United States)

    Goldman, M.; Catchings, R. D.; Rymer, M. J.; Lohman, R. B.; McGuire, J. J.; Sickler, R. R.; Criley, C.; Rosa, C.


    In March 2010, we acquired a series of high-resolution P-wave seismic reflection and refraction data sets across faults in the Brawley seismic zone (BSZ) within the Salton Sea Geothermal Field (SSGF). Our objectives were to determine the dip, possible structural complexities, and seismic velocities within the BSZ. One dataset was 3.4 km long trending east-west, and consisted of 334 shots recorded by a 2.4 km spread of 40 hz geophones placed every 10 meters. The spread was initially laid out from the first station at the eastern end of the profile to roughly 2/3 into the profile. After about half the shots, the spread was shifted from roughly 1/3 into the profile to the last station at the western end of the profile. P-waves were generated by Betsy-Seisgun 'shots' spaced every 10 meters. Initial analysis of first breaks indicate near-surface velocities of ~500-600 meters/sec, and deeper velocities of around 2000 meters/sec. Preliminary investigation of shot gathers indicate a prominent fault that extends to the ground surface. This fault is on a projection of the Kalin fault from about 40 m to the south, and broke the surface down to the west with an approximately north-south strike during a local swarm of earthquakes in 2005 and also slipped at the surface in association with the 2010 El Mayor-Cucapah earthquake in Baja California. The dataset is part of the combined Obsidian Creep data set, and provides the most detailed, publicly available subsurface images of fault structures in the BSZ and SSGF.

  11. Possible Non-volcanic Tremor Discovered in the Reelfoot Fault Zone, Northern Tennessee (United States)

    Langston, C. A.; Williams, R. A.; Magnani, M.; Rieger, D. M.


    A swarm of ~80 microearthquakes was fortuitously detected in 20, 14 second-duration long-offset vibroseis shotgathers collected for a seismic reflection experiment near Mooring, TN, directly over the Reelfoot fault zone on the afternoon of 16 November 2006. These natural events show up in the shotgathers as near-vertically incident P waves with a dominant frequency of 10-15 Hz. The reflection line was 715m in length consisting of 144 channels with a sensor spacing of 5m, 8Hz vertical geophones, and recording using a Geometrics 24bit Geode seismograph. Small variations in event moveout across the linear array indicate that the seismicity was not confined to the same hypocenter and probably occurred at depths of approximately 10 km. The largest events in the series are estimated to have local magnitudes of ~-1 if at 10 km distance from the array. This is about 2.5 magnitude units lower than the threshold for local events detected and located by the CERI cooperative network in the area. The seismicity rate was ~1000 events per hour based on the total time duration of the shotgathers. The expected number of earthquakes of ML greater than or equal to -1 for the entire central United States is only 1 per hour. This detection of microseismic swarms in the Reelfoot fault zone indicates active physical processes that may be similar to non-volcanic tremor seen in the Cascadia and San Andreas fault zones and merits long-term monitoring to understand its source.

  12. Development and Test of a 1,000 Level 3C Fiber Optic Borehole Seismic Receiver Array Applied to Carbon Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Paulsson, Bjorn N.P. [Paulsson, Inc., Van Nuys, CA (United States)


    To address the critical site characterization and monitoring needs for CCS programs, US Department of Energy (DOE) awarded Paulsson, Inc. in 2010 a contract to design, build and test a fiber optic based ultra-large bandwidth clamped borehole seismic vector array capable of deploying up to one thousand 3C sensor pods suitable for deployment into high temperature and high pressure boreholes. Paulsson, Inc. has completed a design or a unique borehole seismic system consisting of a novel drill pipe based deployment system that includes a hydraulic clamping mechanism for the sensor pods, a new sensor pod design and most important – a unique fiber optic seismic vector sensor with technical specifications and capabilities that far exceed the state of the art seismic sensor technologies. These novel technologies were all applied to the new borehole seismic system. In combination these technologies will allow for the deployment of up to 1,000 3C sensor pods in vertical, deviated or horizontal wells. Laboratory tests of the fiber optic seismic vector sensors developed during this project have shown that the new borehole seismic sensor technology is capable of generating outstanding high vector fidelity data with extremely large bandwidth: 0.01 – 6,000 Hz. Field tests have shown that the system can record events at magnitudes much smaller than M-2.3 at frequencies up to 2,000 Hz. The sensors have also proved to be about 100 times more sensitive than the regular coil geophones that are used in borehole seismic systems today. The fiber optic seismic sensors have furthermore been qualified to operate at temperatures over 300°C (572°F). The fibers used for the seismic sensors in the system are used to record Distributed Temperature Sensor (DTS) data allowing additional value added data to be recorded simultaneously with the seismic vector sensor data.

  13. Structure Modeling and Validation applied to Source Physics Experiments (SPEs) (United States)

    Larmat, C. S.; Rowe, C. A.; Patton, H. J.


    The U. S. Department of Energy's Source Physics Experiments (SPEs) comprise a series of small chemical explosions used to develop a better understanding of seismic energy generation and wave propagation for low-yield explosions. In particular, we anticipate improved understanding of the processes through which shear waves are generated by the explosion source. Three tests, 100, 1000 and 1000 kg yields respectively, were detonated in the same emplacement hole and recorded on the same networks of ground motion sensors in the granites of Climax Stock at the Nevada National Security Site. We present results for the analysis and modeling of seismic waveforms recorded close-in on five linear geophone lines extending radially from ground zero, having offsets from 100 to 2000 m and station spacing of 100 m. These records exhibit azimuthal variations of P-wave arrival times, and phase velocity, spreading and attenuation properties of high-frequency Rg waves. We construct a 1D seismic body-wave model starting from a refraction analysis of P-waves and adjusting to address time-domain and frequency-domain dispersion measurements of Rg waves between 2 and 9 Hz. The shallowest part of the structure we address using the arrival times recorded by near-field accelerometers residing within 200 m of the shot hole. We additionally perform a 2D modeling study with the Spectral Element Method (SEM) to investigate which structural features are most responsible for the observed variations, in particular anomalously weak amplitude decay in some directions of this topographically complicated locality. We find that a near-surface, thin, weathered layer of varying thickness and low wave speeds plays a major role on the observed waveforms. We anticipate performing full 3D modeling of the seismic near-field through analysis and validation of waveforms on the 5 radial receiver arrays.

  14. Automatic identification of alpine mass movements based on seismic and infrasound signals (United States)

    Schimmel, Andreas; Hübl, Johannes


    The automatic detection and identification of alpine mass movements like debris flows, debris floods or landslides gets increasing importance for mitigation measures in the densely populated and intensively used alpine regions. Since this mass movement processes emits characteristically seismic and acoustic waves in the low frequency range this events can be detected and identified based on this signals. So already several approaches for detection and warning systems based on seismic or infrasound signals has been developed. But a combination of both methods, which can increase detection probability and reduce false alarms is currently used very rarely and can serve as a promising method for developing an automatic detection and identification system. So this work presents an approach for a detection and identification system based on a combination of seismic and infrasound sensors, which can detect sediment related mass movements from a remote location unaffected by the process. The system is based on one infrasound sensor and one geophone which are placed co-located and a microcontroller where a specially designed detection algorithm is executed which can detect mass movements in real time directly at the sensor site. Further this work tries to get out more information from the seismic and infrasound spectrum produced by different sediment related mass movements to identify the process type and estimate the magnitude of the event. The system is currently installed and tested on five test sites in Austria, two in Italy and one in Switzerland as well as one in Germany. This high number of test sites is used to get a large database of very different events which will be the basis for a new identification method for alpine mass movements. These tests shows promising results and so this system provides an easy to install and inexpensive approach for a detection and warning system.

  15. Evaluation of local site effect in the western side of the Suez Canal area by applying H/V and MASW techniques (United States)

    Mohamed, Emad K.; Shokry, M. M. F.; Hassoup, Awad; Helal, A. M. A.


    The soft sediments are one of the most important factors responsible for the amplification of the seismic ground motion in an area of study. Three components, single-station microtremor measurements were performed at 61 sites along the Suez Canal to estimate the fundamental frequencies of the soil and corresponding H/V amplitude ratios by using the horizontal-to-vertical spectral ratio (HVSR) method. We have applied the investigations of the shear wave velocity for supplementing the existing seismic microzonation of the Suez Canal. The multichannel analysis of surface wave (MASW) tests were done along the Suez Canal in the three cities, Suez, Ismailia, and Port Said using 24 channels digital engineering seismograph with 4.5 Hz geophones from September 2014 to January 2015 to get the shear wave velocity VS30. The SeisImager/SW software was used for analyzing the data, and 1D-shear wave velocity model have achieved for each site. The HVSR curves show that the fundamental frequency values are ranging from 0.57 to 1.08 Hz, and H/V amplitude ratios are ranging from 4.05 to 6.46. The average values of VS30 are (548, 301), (241, 319), (194, 110, 238) for Suez, Ismailia, and Port Said respectively. The average of shear wave velocity up to 30 m depth is estimated and used for site classification based on the National Earthquake Hazard Reduction Program (NEHRP) classification. The majority of the sites was classified as Class D (stiff soil) except one site at Port Said city is classified as Class E (soft soils), and another site in the Suez city is classified as Class C (hard rock).

  16. Compressional and Shear Wave Structure of the Upper Crust Beneath the Endeavour Segment, Juan De Fuca Ridge (United States)

    Kim, E.; Toomey, D. R.; Hooft, E. E. E.; Wilcock, W. S. D.; Weekly, R. T.; Lee, S. M.; Kim, Y.


    We present tomographic images of the compressional (Vp) and shear (Vs) wave velocity structure of the upper crust beneath the Endeavour segment of the Juan de Fuca Ridge. This ridge segment is bounded by the Endeavour and Cobb overlapping spreading centers (OSCs) to the north and south, respectively. Near the segment center an axial magma chamber (AMC) reflector underlies 5 hydrothermal vent fields. Our analysis uses data from the Endeavour tomography (ETOMO) experiment. A prior study of the Vp structure indicates that the shallow crust of the Endeavour segment is strongly heterogeneous [Weekly et al., 2014]. Beneath the OSCs Vp is anomalously low, indicating tectonic fracturing. Near the segment center, upper crustal Vp is relatively high beneath the hydrothermal vent fields, likely due to infilling of porosity by mineral precipitation. Lower velocities are observed immediately above the AMC, reflecting increased fracturing or higher temperatures. Anisotropic tomography reveals large amplitude ridge-parallel seismic anisotropy on-axis (>10%), but decreases in the off-axis direction over 5-10 km. Here we use crustal S-wave phases (Sg) — generated by P-to-S conversions near the seafloor — to better constrain crustal properties. Over half the OBSs in the ETOMO experiment recorded horizontal data on two channels that are of sufficiently high quality that we can orient the geophones using the polarizations of water waves from shots within 12 km. For these OBSs, crustal Sg phases are commonly visible out to ranges of ~20-25 km. We invert the Sg data separately for Vs structure, and also jointly invert Pg and Sg data to constrain the Vp/Vs ratio. Preliminary inversions indicate that Vs and Vp/Vs varies both laterally and vertically. These results imply strong lateral variations in both the physical (e.g., crack density and aspect ratio) and chemical (e.g., hydration) properties of oceanic crust.

  17. A methodological approach towards high-resolution surface wave imaging of the San Jacinto Fault Zone using ambient-noise recordings at a spatially dense array (United States)

    Roux, Philippe; Moreau, Ludovic; Lecointre, Albanne; Hillers, Gregor; Campillo, Michel; Ben-Zion, Yehuda; Zigone, Dimitri; Vernon, Frank


    We present a new technique for deriving detailed information on seismic velocities of the subsurface material from continuous ambient noise recorded by spatially dense seismic arrays. This method uses iterative double beamforming between various subarrays to extract surface wave contributions from the ambient-noise data in complex environments with unfavourable noise-source distributions. The iterative double beamforming extraction makes it possible to retrieve large amounts of Rayleigh wave traveltime information in a wide frequency band. The method is applied to data recorded by a highly dense Nodal array with 1108 vertical geophones, centred on the damage zone of the Clark branch of the San Jacinto Fault Zone south of Anza, California. The array covers a region of ˜650 × 700 m2, with instrument spacing of 10-30 m, and continuous recording at 500 samples s-1 over 30 d in 2014. Using this iterative double beamforming on subarrays of 25 sensors and cross-correlations between all of the station pairs, we separate surface waves from body waves that are abundant in the raw cross-correlation data. Focusing solely on surface waves, maps of traveltimes are obtained at different frequencies with unprecedented accuracy at each point of a 15-m-spacing grid. Group velocity inversions at 2-4 Hz reveal depth and lateral variations in the structural properties within and around the San Jacinto Fault Zone in the study area. This method can be used over wider frequency ranges and can be combined with other imaging techniques, such as eikonal tomography, to provide unprecedented detailed structural images of the subsurface material.

  18. Delineating Bukit Bunuh impact crater boundary by geophysical and geotechnical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Azwin, I. N., E-mail:; Rosli, S.; Nordiana, M. M.; Ragu, R. R.; Mark, J. [Geophysics Section, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Mokhtar, S. [Centre for Global Archaeological Research Malaysia, 11800 USM, Penang (Malaysia)


    Evidences of crater morphology and shock metamorphism in Bukit Bunuh, Lenggong, Malaysia were found during the archaeological research conducted by the Centre for Global Archaeological Research Malaysia, Universiti Sains Malaysia. In order to register Bukit Bunuh as one of the world meteorite impact site, detailed studies are needed to verify the boundary of the crater accordingly. Geophysical study was conducted utilising the seismic refraction and 2-D electrical resistivity method. Seismic refraction survey was done using ABEM MK8 24 channel seismograph with 14Hz geophones and 40kg weight drop while 2-D electrical resistivity survey was performed using ABEM SAS4000 Terrameter and ES10-64C electrode selector with pole-dipole array. Bedrock depths were digitized from the sections obtained. The produced bedrock topography map shows that there is low bedrock level circulated by high elevated bedrock and interpreted as crater and rim respectively with diameter approximately 8km. There are also few spots of high elevated bedrock appear at the centre of the crater which interpreted as rebounds zone. Generally, the research area is divided into two layers where the first layer with velocity 400-1100 m/s and resistivity value of 10-800 Om predominantly consists of alluvium mix with gravel and boulders. Second layer represents granitic bedrock with depth of 5-50m having velocity >2100 m/s and resistivity value of >1500 Om. This research is strengthen by good correlation between geophysical data and geotechnical borehole records executed inside and outside of the crater, on the rim, as well as at the rebound area.

  19. Imaging of Scattered Wavefields in Passive and Controlled-source Seismology

    KAUST Repository

    AlTheyab, Abdullah


    Seismic waves are used to study the Earth, exploit its hydrocarbon resources, and understand its hazards. Extracting information from seismic waves about the Earth’s subsurface, however, is becoming more challenging as our questions become more complex and our demands for higher resolution increase. This dissertation introduces two new methods that use scattered waves for improving the resolution of subsurface images: natural migration of passive seismic data and convergent full-waveform inversion. In the first part of this dissertation, I describe a method where the recorded seismic data are used to image subsurface heterogeneities like fault planes. This method, denoted as natural migration of backscattered surface waves, provides higher resolution images for near-surface faults that is complementary to surface-wave tomography images. Our proposed method differ from contemporary methods in that it does not (1) require a velocity model of the earth, (2) assumes weak scattering, or (3) have a high computational cost. This method is applied to ambient noise recorded by the US-Array to map regional faults across the American continent. Natural migration can be formulated as a least-squares inversion to furtherer enhance the resolution and the quality of the fault images. This inversion is applied to ambient noise recorded in Long Beach, California to reveal a matrix of shallow subsurface faults. The second part of this dissertation describes a convergent full waveform inversion method for controlled source data. A controlled source excites waves that scatter from subsurface reflectors. The scattered waves are recorded by a large array of geophones. These recorded waves can be inverted for a high-resolution image of the subsurface by FWI, which is typically convergent for transmitted arrivals but often does not converge for deep reflected events. I propose a preconditioning approach that extends the ability of FWI to image deep parts of the velocity model, which

  20. A deep seismic sounding profile across the Tianshan Mountains

    Institute of Scientific and Technical Information of China (English)


    The deep seismic sounding profile across the Tianshan Mountains revealed a two-layer crustal structure in the Tianshregion, namely the lower and upper crusts. Lateral variations of layer velocity and thickness are evidently shown. Low-velocity layers spread discontinuously at the bottom of the upper crust. The Moho depth is 47 km in the Kuytun area and 50 km in the Xayar area. In the Tianshan Mountains, the Moho becomes deeper with the maximum depth of 62 km around the boundary between the southern and northern Tianshan Mountains. The average velocity ranges from 6.1 to 6.3 km/s in the crust and 8.15 km/s at the top of the upper mantle. Two groups of reliable reflective seismic phases of the Moho (Pm1 and Pm2) are recognized on the shot record section of the Kuytun area. A staked and offset region, 20-30 km long, is displayed within a shot-geophone distance of 190-210 km in Pm1 and Pm2. Calculation shows that the Moho is offset by 10 km in the northern Tianshan region, 62 km deep in the south while 52 km deep in the north, and plunges northwards. In comparison with typical collisional orogenic belts, the structure of the Moho beneath the Tianshan Mountains presents a similar pattern. This can be used to explain the subduction of the Tarim plate towards the Tianshan Mountains. This intracontinental subduction is considered the dynamic mechanism of the Cenozoic uplifting of the Tianshan Mountains. The discovery of seismic phases Pm1 and Pm2 serves as the seismological evidence for the northward subduction of the Tarim plate.

  1. Sweetwater, Texas Large N Experiment (United States)

    Sumy, D. F.; Woodward, R.; Barklage, M.; Hollis, D.; Spriggs, N.; Gridley, J. M.; Parker, T.


    From 7 March to 30 April 2014, NodalSeismic, Nanometrics, and IRIS PASSCAL conducted a collaborative, spatially-dense seismic survey with several thousand nodal short-period geophones complemented by a backbone array of broadband sensors near Sweetwater, Texas. This pilot project demonstrates the efficacy of industry and academic partnerships, and leveraged a larger, commercial 3D survey to collect passive source seismic recordings to image the subsurface. This innovative deployment of a large-N mixed-mode array allows industry to explore array geometries and investigate the value of broadband recordings, while affording academics a dense wavefield imaging capability and an operational model for high volume instrument deployment. The broadband array consists of 25 continuously-recording stations from IRIS PASSCAL and Nanometrics, with an array design that maximized recording of horizontal-traveling seismic energy for surface wave analysis over the primary target area with sufficient offset for imaging objectives at depth. In addition, 2639 FairfieldNodal Zland nodes from NodalSeismic were deployed in three sub-arrays: the outlier, backbone, and active source arrays. The backbone array consisted of 292 nodes that covered the entire survey area, while the outlier array consisted of 25 continuously-recording nodes distributed at a ~3 km distance away from the survey perimeter. Both the backbone and outlier array provide valuable constraints for the passive source portion of the analysis. This project serves as a learning platform to develop best practices in the support of large-N arrays with joint industry and academic expertise. Here we investigate lessons learned from a facility perspective, and present examples of data from the various sensors and array geometries. We will explore first-order results from local and teleseismic earthquakes, and show visualizations of the data across the array. Data are archived at the IRIS DMC under stations codes XB and 1B.

  2. Applications of a fast, continuous wavelet transform

    Energy Technology Data Exchange (ETDEWEB)

    Dress, W.B.


    A fast, continuous, wavelet transform, based on Shannon`s sampling theorem in frequency space, has been developed for use with continuous mother wavelets and sampled data sets. The method differs from the usual discrete-wavelet approach and the continuous-wavelet transform in that, here, the wavelet is sampled in the frequency domain. Since Shannon`s sampling theorem lets us view the Fourier transform of the data set as a continuous function in frequency space, the continuous nature of the functions is kept up to the point of sampling the scale-translation lattice, so the scale-translation grid used to represent the wavelet transform is independent of the time- domain sampling of the signal under analysis. Computational cost and nonorthogonality aside, the inherent flexibility and shift invariance of the frequency-space wavelets has advantages. The method has been applied to forensic audio reconstruction speaker recognition/identification, and the detection of micromotions of heavy vehicles associated with ballistocardiac impulses originating from occupants` heart beats. Audio reconstruction is aided by selection of desired regions in the 2-D representation of the magnitude of the transformed signal. The inverse transform is applied to ridges and selected regions to reconstruct areas of interest, unencumbered by noise interference lying outside these regions. To separate micromotions imparted to a mass-spring system (e.g., a vehicle) by an occupants beating heart from gross mechanical motions due to wind and traffic vibrations, a continuous frequency-space wavelet, modeled on the frequency content of a canonical ballistocardiogram, was used to analyze time series taken from geophone measurements of vehicle micromotions. By using a family of mother wavelets, such as a set of Gaussian derivatives of various orders, features such as the glottal closing rate and word and phrase segmentation may be extracted from voice data.

  3. Distributed Acoustic Sensing Technology in a Magmatic Geothermal Field - First Results From a Survey in Iceland (United States)

    Reinsch, Thomas; Jousset, Philippe; Henninges, Jan; Blanck, Hanna


    Seismic methods are particularly suited for investigating the Earth's subsurface. Compared to surface-measurements , wellbore measurements can be used to acquire more detailed information about rock properties and possible fluid pathways within a geothermal reservoir. For high temperature geothermal wells, however, ambient temperatures are often far above the operating temperature range of conventional geophones. One way to overcome this limitation is the application of fiber optic sensor systems, where only the passive optical fiber is subjected to downhole conditions. Their applicability is thus determined by the operating temperature range of the optical fiber. Choosing appropriate fibers, such sensor systems can be operated at temperatures far above 200°C. Along an optical fiber, the distributed acoustic sensing technology (DAS) can be used to acquire acoustic signals with a high spatial and temporal resolution. Previous experiments have shown that the DAS technology is well suited for active seismic measurements. Within the framework of the EC funded project IMAGE, a fiber optic cable was deployed in a newly drilled geothermal well (RN-34) within the Reykjanes geothermal field, Iceland. Additionally, a >15 km fiber optic cable, already available at the surface, was connected to a DAS read-out unit. Acoustic data was acquired continuously for 9 days. Hammer shots were performed at the wellhead as well as along the surface cable in order to locate individual acoustic traces and calibrate the spatial distribution of the acoustic information. During the monitoring period both signals from on- and offshore explosive sources and natural seismic events could be recorded. We compare the fiber optic data to conventional seismic records from a dense seismic network deployed on the Reykjanes in the course of the IMAGE project. Here, first results from the seismic survey will be presented.

  4. Geometric Reconstruction of Bedrock and Overlying Recent Deposits In An Intra-mountain Basin: The Clusone Basin (southern Alps, Italy) (United States)

    Caielli, G.; Berra, F.

    Regione Lombardia (Direzione Generale Territorio e Urbanistica) and the National Research Council (CNR-IDPA Milano) acquired seismic reflection profiles in the Clu- sone basin (Middle Val Seriana, Southern Alps). In the study area, the bedrock is rep- resented by late Triassic carbonate units (Formazione di Castro, Dolomia Principale and coeval basinal facies, bordered northward by an important alpine fault) covered by a large amount of recent deposits that covers an area of more than 10 km2, with a maximum thickness of more than two hundreds meters, as documented by available well data. The aim of the seismic prospecting was to identify the sediments layering and the rock basement depth. The acquisition parameters were as follows: group in- terval 10 m; shot interval 5 m; geophone frequency 14 Hz; sample rate 1 ms; record length 2 s, energy source hydrapulse. The cable, with 120 channels, remained dur- ing all the experiment allowing reflection/refraction events acquisition. The data were processed by a standard procedure using PROMAX and SUNT5 processing codes. The statics were calculated starting from the refracted first arrivals using a two layer inversion based on least square optimisation. Standard seismic reflection processing was applied to obtain reflection images and it was integrated with seismic refraction data inversion. Seismic profiles allow to reconstruct both the main reflectors in the recent deposits and the geometry of the bedrock. The first results document a complex history in the drainage patterns of the Clusone basin, allowing to identify, in an intra- mountain basin, drainage directions that in some cases are different from the ones that can be observed today. The integration of well data and seismic profiles in this study of an intra-mountain basin allows on one side the identification of the bedrock geome- tries and, on the other, gives constrains for the reconstruction of the geomorphologic evolution of a sector of a mountain chain.

  5. Reflection seismic imaging of shallow aquifers in Milano (northern Italy) (United States)

    Francese, R.; Zaja, A.; Giudici, M.; Schmitt, D.


    A high resolution P-wave seismic reflection survey was conducted in the Lambro park within the city of Milano (northern Italy). The objective of the survey was to image structure and stratigraphy of shallow late tertiary and quaternary deposits. This information is necessary to develop a comprehensive 3D hydrological model of the fresh water aquifers where the municipality drilled several production wells. The expected complexity of the acoustic framework and the urban environment with its complications created a challenging test site for the reflection technique. The aquifer system was targeted with a 2-D high resolution seismic reflection survey to outline its vertical and lateral dimensions to a depth of 150-200 m and to estimate some petrophysical properties of the depositional units. A 0.8-km CMP seismic line, with 1-m station spacing, was deployed to collect reflection data. The recording geometry was a 240-channel split spread array, with 6-m shot separation, resulting in a maximum of 20-fold dataset. A single 40-Hz geophone at each station location detected the incoming signals. Field records exhibit clear reflections although the signal to noise ratio is poor because of strong surface waves and severe disturbances from the nearby highway. Optimized FK and KL transforms were used to attenuate these coherent noises and to enhance the primary reflections from the main horizons. The data analysis was also assisted by forward modeling to guide the selection of the processing parameters. The seismic data have a good correlation thourhgout the section and most of the acoustic units show flat bedding. The boundaries of the three major depositional units are clearly resolved by the seismic images. The stacked section clearly indicates that reflection technique provides a powerful method to characterize aquifers, even in a very noisy environment like the urban areas.

  6. An iterative matching and locating technique for borehole microseismic monitoring (United States)

    Chen, H.; Meng, X.; Niu, F.; Tang, Y.


    Microseismic monitoring has been proven to be an effective and valuable technology to image hydraulic fracture geometry. The success of hydraulic fracturing monitoring relies on the detection and characterization (i.e., location and focal mechanism estimation) of a maximum number of induced microseismic events. All the events are important to quantify the stimulated reservior volume (SRV) and characterize the newly created fracture network. Detecting and locating low magnitude events, however, are notoriously difficult, particularly at a high noisy production environment. Here we propose an iterative matching and locating technique (iMLT) to obtain a maximum detection of small events and the best determination of their locations from continuous data recorded by a single azimuth downhole geophone array. As the downhole array is located in one azimuth, the regular M&L using the P-wave cross-correlation only is not able to resolve the location of a matched event relative to the template event. We thus introduce the polarization direction in the matching, which significantly improve the lateral resolution of the M&L method based on numerical simulations with synthetic data. Our synthetic tests further indicate that the inclusion of S-wave cross-correlation data can help better constrain the focal depth of the matched events. We apply this method to a dataset recorded during hydraulic fracturing treatment of a pilot horizontal well within the shale play in southwest China. Our approach yields a more than fourfold increase in the number of located events, compared with the original event catalog from traditional downhole processing.

  7. Seismic Prediction While Drilling (SPWD): Seismic exploration ahead of the drill bit using phased array sources (United States)

    Jaksch, Katrin; Giese, Rüdiger; Kopf, Matthias


    In the case of drilling for deep reservoirs previous exploration is indispensable. In recent years the focus shifted more on geological structures like small layers or hydrothermal fault systems. Beside 2D- or 3D-seismics from the surface and seismic measurements like Vertical Seismic Profile (VSP) or Seismic While Drilling (SWD) within a borehole these methods cannot always resolute this structures. The resolution is worsen the deeper and smaller the sought-after structures are. So, potential horizons like small layers in oil exploration or fault zones usable for geothermal energy production could be failed or not identified while drilling. The application of a device to explore the geology with a high resolution ahead of the drill bit in direction of drilling would be of high importance. Such a device would allow adjusting the drilling path according to the real geology and would minimize the risk of discovery and hence the costs for drilling. Within the project SPWD a device for seismic exploration ahead of the drill bit will be developed. This device should allow the seismic exploration to predict areas about 50 to 100 meters ahead of the drill bit with a resolution of one meter. At the GFZ a first prototype consisting of different units for seismic sources, receivers and data loggers has been designed and manufactured. As seismic sources four standard magnetostrictive actuators and as receivers four 3-component-geophones are used. Every unit, actuator or geophone, can be rotated in steps of 15° around the longitudinal axis of the prototype to test different measurement configurations. The SPWD prototype emits signal frequencies of about 500 up to 5000 Hz which are significant higher than in VSP and SWD. An increased radiation of seismic wave energy in the direction of the borehole axis allows the view in areas to be drilled. Therefore, every actuator must be controlled independently of each other regarding to amplitude and phase of the source signal to

  8. Using Concatenated Profiles from High-Speed Laser Profile Scanners to Estimate Debris-Flow Characteristics: A Novel Approach Based on Particle Image Velocimetry (United States)

    Jacquemart, M. F.; Meier, L.; Graf, C.; Morsdorf, F.


    We use globally unique datasets from paired laser profile scanners to measure debris-flow height, velocity and discharge in two well-known debris-flow channels in Switzerland. Since 2011, these scanners have been scanning passing debris flows at rates of up to 75 Hz, acquiring millions of cross-bed profiles. The profiles can be concatenated through time, generating unique 2.5D representations of passing debris flows. Applying a large-scale Particle Image Velocimetry (PIV) approach to these datasets has proven successful to measure surface flow velocities. Flow height can also be estimated from the laser scanners, and thus a discharge estimate can be given. To account for changes to the channel bed due to erosion and deposition during the debris flow, we compute two flow height estimates using a pre-event as well as a post-event channel geometry in order to visualize discharge variability.Velocity outliers need to be excluded to provide reliable estimates of peak discharge, and changes to the channel bed are assumed to be the largest source of uncertainty. However, the latter problem is inherent to all debris-flow discharge measurements, and we have found the new system to offer distinct advantages over the conventional system relying on geophones and a radar gauge. The wide scan angle of up to 190° renders the scanners insensitive to changes of the flow path, and the point density of roughly 20 points per meter offer unprecedented spatial coverage.In addition, the geometries of the cross-bed profiles have been analyzed, revealing distinct changes of cross-flow convexity between the front and the tail of the flows in several cases. This is assumed to indicate changes of debris-flow mixtures, but further research is needed to better understand this signal.We hope that our preliminary analysis and toolbox will facilitate working with these kinds of datasets so as to further improve debris-flow understanding, monitoring and modeling efforts in the future.

  9. Near Surface Geophysical Exploration at The Archaeological Site of San Miguel Tocuila, Basin of Mexico. (United States)

    Arciniega, A.; Hernandez, E.; Cabral-Cano, E.; Diaz-Molina, O.; Morett, L.; Soler, A.


    The village of Tocuila is located on the western margin of Lake Texcoco in central Mexico. Volcanic activity during the Late Pleistocene and Early Holocene closed the basin's drainage and facilitated the development of a lacustrine environment and subsequent deposition of volcano-sedimentary sequences with abundant archaeological and paleontological record. Tocuila was one of the most prominent suburbs of the main civic ceremonial complex of the Aztecs. The rapid expansion of Mexico City's Metropolitan areas in the last three decades strongly influenced Tocuila's environment and has compromised several of its archaeological and ancient human settlements. A near surface geophysical survey including magnetometry, seismic refraction tomography and Ground Penetrating Radar (GPR) techniques was conducted to investigate pre-Hispanic structures. The magnetometric survey was performed using an Overhauser magnetometer with an omnidirectional, 0.015 nT/Hz sensor and 1Hz sampling rate over a 80x100 m area, yielding 990 measurements of total intensity magnetic field at 1.0m height above the ground surface. Thirty seismic refraction profiles were obtained with a 48-channel 24 bits Geometrics StrataVisor NZ seismograph, 14 Hz natural frequency vertical geophones with a 2m separation array and an impact source of 5 kg. The GPR survey consisted of 15 cross sections at two different resolutions with a GSSI SIR-3000 instrument, using a GSSI 200 MHz and a RadarTeam 70 MHz antennas. All surveys were georeferenced with a dual frequency GPS local station and a GPS rover attached to the surveying geophysical instruments. Seismic refraction tomography and GPR radargrams show a platform structure of approx. 80x60 m which can be subdivided in three distinctive layers with a total height of ~10m. Based on the history of ancient settlements in the area surrounding Lake Texcoco and considering the characteristics of shape and height of the surveyed structure, we interpreted that the resulting

  10. a Borehole Seismic System for Active and Passive Seimsic Studies to 3 KM at Ptrc's Aquistore Project (United States)

    Schmitt, D. R.; Nixon, C.; Kofman, R.; White, D. J.; Worth, K.


    We have constructed a downhole seismic recording system for application to depths of nearly 3 km and temperatures up to 135 °C at Aquistore, an independent research and monitoring project in which liquid CO2 is being stored in a brine and sandstone water formation. The key component to this system is a set of commercially available slim-hole 3-C sondes carrying 15 Hz geophones deployable in open and cased boreholes with diameters as small as 57 mm. The system is currently hosted on a 4-conductor wireline with digital information streamed to the surface recording unit. We have further incorporated these sondes into a mobile passive monitoring unit that includes a number of redundancies such as a multiple Tbyte network accessible RAID hard-drive system (NAS) and a self-designed uninterruptible power supply. The system can be remotely controlled via the internet. The system is currently deployed covering a range of depths from 2850 m to 2910 m. Ambient temperatures at this depth are approximately 110 °C with onboard tool temperatures running at 115 °C. Data is continuously streamed to the NAS for archiving, approximately 11 GBytes of data is recorded per day at the sampling period of 0.5 ms. The lack of noise at this depth allows short data snippets to be flagged with a simple amplitude threshold criteria. The greatly reduced data volume of the snippets allows for ready access via the internet to the system for ongoing quality control. Spurious events, mostly small amplitude tube waves originating at or near the surface, are readily discounted. Active seismic measurements are carried out simultaneously but these require that an appropriately accurate independent GPS based time synchronization be used. Various experiences with event detection, orientation of sondes using both explosives and seismic vibrator, potential overheating of the surface electronics, and issues related to loss of shore power provide for a detailed case study. Aquistore, managed by the

  11. Stress monitoring versus microseismic ruptures in an active deep mine (United States)

    Tonnellier, Alice; Bouffier, Christian; Bigarré, Pascal; Nyström, Anders; Österberg, Anders; Fjellström, Peter


    Nowadays, underground mining industry has developed high-technology mass mining methods to optimise the productivity at deep levels. Such massive extraction induces high-level stress redistribution generating seismic events around the mining works, threatening safety and economics. For this reason mining irregular deep ore bodies calls for steadily enhanced scientific practises and technologies to guarantee the mine environment to be safer and stable for the miners and the infrastructures. INERIS, within the framework of the FP7 European project I2Mine and in partnership with the Swedish mining company Boliden, has developed new methodologies in order to monitor both quasi-static stress changes and ruptures in a seismic prone area. To this purpose, a unique local permanent microseismic and stress monitoring network has been installed into the deep-working Garpenberg mine situated to the north of Uppsala (Sweden). In this mine, ore is extracted using sublevel stoping with paste fill production/distribution system and long-hole drilling method. This monitoring network has been deployed between about 1100 and 1250 meter depth. It consists in six 1-component and five 3-component microseismic probes (14-Hz geophones) deployed in the Lappberget area, in addition to three 3D stress monitoring cells that focus on a very local exploited area. Objective is three-fold: to quantify accurately quasi-static stress changes and freshly-induced stress gradients with drift development in the orebody, to study quantitatively those stress changes versus induced detected and located microseismic ruptures, and possibly to identify quasi-static stress transfer from those seismic ruptures. Geophysical and geotechnical data are acquired continuously and automatically transferred to INERIS datacenter through the web. They are made available on a secured web cloud monitoring infrastructure called e.cenaris and completed with mine data. Such interface enables the visualisation of the

  12. Estimation of seismically detectable portion of a gas plume: CO2CRC Otway project case study (United States)

    Pevzner, Roman; Caspari, Eva; Bona, Andrej; Galvin, Robert; Gurevich, Boris


    CO2CRC Otway project comprises of several experiments involving CO2/CH4 or pure CO2 gas injection into different geological formations at the Otway test site (Victoria, Australia). During the first stage of the project, which was finished in 2010, more than 64,000 t of gas were injected into the depleted gas reservoir at ~2 km depth. At the moment, preparations for the next stage of the project aiming to examine capabilities of seismic monitoring of small scale injection (up to 15,000 t) into saline formation are ongoing. Time-lapse seismic is one of the most typical methods for CO2 geosequestration monitoring. Significant experience was gained during the first stage of the project through acquisition and analysis of the 4D surface seismic and numerous time-lapse VSP surveys. In order to justify the second stage of the project and optimise parameters of the experiment, several modelling studies were conducted. In order to predict seismic signal we populate realistic geological model with elastic properties, model their changes using fluid substitution technique applied to the fluid flow simulation results and compute synthetic seismic baseline and monitor volumes. To assess detectability of the time-lapse signal caused by the injection, we assume that the time-lapse noise level will be equivalent to the level of difference between the last two Otway 3D surveys acquired in 2009 and 2010 using conventional surface technique (15,000 lbs vibroseis sources and single geophones as the receivers). In order to quantify the uncertainties in plume imaging/visualisation due to the time-lapse noise realisation we propose to use multiple noise realisations with the same F-Kx-Ky amplitude spectra as the field noise for each synthetic signal volume. Having signal detection criterion defined in the terms of signal/time- lapse noise level on a single trace we estimate visible portion of the plume as a function of this criterion. This approach also gives an opportunity to attempt to

  13. Detecting Slow Deformation Signals Preceding Dynamic Failure: A New Strategy For The Mitigation Of Natural Hazards (SAFER) (United States)

    Vinciguerra, Sergio; Colombero, Chiara; Comina, Cesare; Ferrero, Anna Maria; Mandrone, Giuseppe; Umili, Gessica; Fiaschi, Andrea; Saccorotti, Gilberto


    Rock slope monitoring is a major aim in territorial risk assessment and mitigation. The high velocity that usually characterizes the failure phase of rock instabilities makes the traditional instruments based on slope deformation measurements not applicable for early warning systems. On the other hand the use of acoustic emission records has been often a good tool in underground mining for slope monitoring. Here we aim to identify the characteristic signs of impending failure, by deploying a "site specific" microseismic monitoring system on an unstable patch of the Madonna del Sasso landslide on the Italian Western Alps designed to monitor subtle changes of the mechanical properties of the medium and installed as close as possible to the source region. The initial characterization based on geomechanical and geophysical tests allowed to understand the instability mechanism and to design the monitoring systems to be placed. Stability analysis showed that the stability of the slope is due to rock bridges. Their failure progress can results in a global slope failure. Consequently the rock bridges potentially generating dynamic ruptures need to be monitored. A first array consisting of instruments provided by University of Turin, has been deployed on October 2013, consisting of 4 triaxial 4.5 Hz seismometers connected to a 12 channel data logger arranged in a 'large aperture' configuration which encompasses the entire unstable rock mass. Preliminary data indicate the occurrence of microseismic swarms with different spectral contents. Two additional geophones and 4 triaxial piezoelectric accelerometers able to operate at frequencies up to 23 KHz will be installed during summer 2014. This will allow us to develop a network capable of recording events with Mw < 0.5 and frequencies between 700 Hz and 20 kHz. Rock physical and mechanical characterization along with rock deformation laboratory experiments during which the evolution of related physical parameters under

  14. Subduction Processes Off Chile (SPOC): Imaging of the seismogenic coupling zone (United States)

    Stiller, M.; Krawczyk, C. M.; Mechie, J.; Lüth, S.; Spoc Research Group


    The multi-disciplinary offshore project SPOC (Subduction Processes Off Chile), located between 36° and 39°S, was complemented by an onshore extension consisting of different active and passive seismic experiments, with the seismogenic coupling zone at 20-40 km depth as the major target (see Krawczyk et al., Lüth et al., this volume). Here, we report the results from a near-vertical seismic reflection land component which, in addition to the larger-scale 2D/3D wide-angle land experiments, was designed as a pilot reflection study to image the subduction zone between the South American and the Nazca Plate with high resolution. Three receiver spread set-ups (180 geophone groups along 18 km length each) recording ten explosive shots within the 54 km long active spread as well as two far-offset shots in the Pacific Ocean and two far-offset shots E of the spread, resulted in an 87 km long E-W trending 2D CDP reflection line. This line is complemented offshore by a wide-angle section constructed from the airgun pulses shot in prolongation of the land profile. The combined CDP-section images the offshore-onshore transition zone along ~38.2°S, extending from 18 km W of the coast to the Longitudinal Valley in the E, down to a depth of more than 60 km and crossing the rupture area of the Chile 1960 earthquake with magnitude 9.5. The depth-migrated seismic image shows several (at least three) strong ~20° E-dipping reflection bands at different crustal levels. The deepest of these bands coincides with the top of the downgoing plate as defined by the Wadati-Benioff seismicity and as confirmed by the velocity structure derived from the simultaneous wide-angle profiling. Two other horizontal reflection bands at ~8 and ~15 km depth can also be correlated with modelled moderate wide-angle velocity steps in the continental plate. These bands are interpreted to describe the internal structure of the Palaeozoic accretionary wedge in the region. In the central part of the profile, a

  15. A Pilot Near-vertical Seismic Reflection Experiment In Central Chile Landward of The Offshore Spoc Survey (United States)

    Krawczyk, C. M.; Onshore Nvr Party, Spoc

    Between 36 and 39 S, the multi-disciplinary offshore project SPOC (Subduction Processes Off Chile) was extended landwards in November 2001 by different active and passive seismic experiments, with the zone of seismic coupling, generally located between 20-40 km depth, as the prime target. Here, we report the first results from the near-vertical incidence reflection (NVR) seismic experiment component that was designed to image that part of the subduction zone between the S-America and over- riding Nazca-Plate that is located in the offshore-onshore transition zone. The NVR profile was located at 37 15`S. Covering the westernmost part of a long E-W refrac- tion seismic line (one amongst three), the profile spread was 54 km long, with three sections of 18 km length each, and extended from the coast in the west to the east. 180 geophone-groups were deployed with 100 m spacing which recorded the offshore pro- file shot by the R/V SONNE with the airgun array. Furthermore, 2 small shots in the Pacific Ocean (50 kg and 25 kg charge), 11 small shots (75 kg charge) at 7 different lo- cations within the onshore reflection seismic line, and 1 shot (150 kg charge) ca. 22.5 km east of the active spread were shot. This active NVR-experiment thereby resulted in a 45 km long 2-fold CDP line, and single-fold coverage along 72 km profile length. The preliminary data processing of single shots gives an image of different reflection bands in the upper and middle crust. On the entire profile, a 1 s TWT thick strong reflection band is observed between 3 and 4 s TWT, which shows almost no dip. On the western half of the profile, prominent reflections dip eastward from ca. 6 s TWT down to ca. 8 s TWT. Finally, in the central part of the seismic reflection profile, some relatively weaker reflections are found between 10 to 14 s TWT. All theses eastward dipping reflection bands between 6 and 14 s TWT could be interpreted as indications for the downgoing plate.

  16. Investigating the surface and subsurface properties of the Didymos binary asteroid with a landed CubeSat (United States)

    Murdoch, Naomi; Cadu, Alexandre; Mimoun, David; Karatekin, Ozgur; Garcia, Raphael; Carrasco, José; Garcia de Quiros, Javier; Vasseur, Hugues; Ritter, Birgit; Eubanks, Marshall; Radley, Charles; Dehant, Veronique


    Despite the successes of recent space missions (e.g., Cheng et al., 1997; Fujiwara et al., 2006), there is still no clear understanding of the asteroid internal structure(s). Depending on their size, evolution and physical properties, many different asteroid internal structure models have been suggested from completely cohesive bodies, through to rubble pile objects. The Asteroid Geophysical Explorer (AGEX), a COPINS payload selected by ESA*, will land geophysical instrument packages on the surface of Didymoon; the secondary object in the (65803) Didymos (1996 GT) binary system (Karatekin et al 2016). The instruments will characterize the asteroid surface mechanical properties and probe, for the first time, the sub-surface structure of an asteroid. AGEX will be deployed from AIM on a ballistic transfer to the asteroid surface, several days before the MASCOT-2 package. We expect that AGEX will bounce multiple times before coming to rest on the surface of the asteroid thus providing a unique opportunity to study the asteroid surface properties, perhaps at several locations, using accelerometers. Once stationary, the seismological surface-monitoring phase, using a three-axis set of geophones, can begin. The high speed DART impact will be a major seismic source on Didymoon. However, the seismic payload may also be able to perform seismological investigations using natural seismic sources such as micrometeoroid impacts (e.g., Garcia et al., 2015), thermal cracks (e.g., Delbo et al., 2014), internal quakes due to tidal forces (e.g., Richardson et al. 1998) and other geophysical processes (see Murdoch et al., 2015). We will present the expected signal characteristics of the landing and also of the natural seismic sources that may occur on Didymoon. An understanding of the amplitude and frequency content of such signals is necessary in order to design the optimal geophysical payload for small body exploration using a CubeSat platform. [1.] Cheng, A. et al., Journal of

  17. Reflection seismic studies at the Laxemar area; Reflektionsseismiska studier inom Laxemaromraadet

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, B.; Juhlin, C.; Palm, H. [Uppsala Univ. (Sweden). Dept. of Earth Sciences


    Two 2 km long crossing lines with high-resolution reflection seismics were acquired at Laxemar, close to The Aespoe Hard Rock Laboratory, in December 1999. The main goal with the investigation was to make a full-scale test of developed methods in reflection seismics with the use of small shotholes and small explosive charges. The secondary goal was to identify fracture zones that might correlate with water bearing fracture zones found in boreholes. Both lines had 10-meter separation between the geophones and charge holes. Shot sizes were 15-gram plastic explosives for shots in rock and 75-gram ones for shots in lose sediments and till. The results from the measurements show that the small shotholes technique and small charges works well to investigate the rock down to a depth of 3-4 kilometers. The signal penetrates at least to 1500-metres (500 ms travel time for the seismic signal) along both lines. Over some parts of the lines the seismic signal penetrates to c. 6000- metres (2 seconds travel time). Five dipping reflectors (c. 30-50 deg) can be identified. Three of these can be projected up to the surface on both lines and their 3D orientation can be determined. These reflectors also coincide with topographical depressions. The two other dipping reflectors are only visible on one line, but can be assumed to correlate with topographical depressions and that way be assigned a three dimensional orientation. Four of the reflectors correlate with previously mapped fracture zones. A zone of sub-horizontal reflectivity (0-15 deg) is visible at 650-900 meters depth where the lines cross the deep borehole KLX02. This zone dips gently towards the east and can be correlated with sections of greenstones found in KLX02. The zone of sub-horizontal reflectivity continues to the deep borehole KLX01, but is not as clear here. This sub-horizontal zone may be the hydraulic connection between the boreholes in their deeper part. Deeper down at 1100 ms (c. 3 km), there are strong

  18. Seismic Reflection - Focusing on Muting Jacquelyn Daves University of Colorado - Boulder SAGE 2014 (United States)

    Daves, J.


    The SAGE 2014 survey was conducted directly west of the Santo Domingo Pueblo, along Borrego Canyon Road. This survey is a continuation of the SAGE 2010 and 2011 investigations. The survey was aimed to locate a previously mapped fault running orthogonal to the road. The SAGE 2014 seismic line ran 5.6 km long with 20 meter geophone spacing. 8-80 Hz sweeps were utilized with 10 s sweeps and 4 s of listening. Once the data was converted into the proper file type, preprocesses was conducted. After the preprocessing was complete, various processing methods were used to obtain the final Common Midpoint (CMP) stack. Two CMP stacks were created-one containing the muting method and one without. The ideal result would be to interpret stratigraphic structures and potential faults. The Rio Grande Rift is a Cenozoic continental rift zone that extends approximately 1000 km from Leadville, Colorado to west Texas and Chihuahua, Mexico. The Northern most extent of the rift separates the Great Plains from the Colorado Plateau. The rift consists of a series of interconnected grabbens that lie in an asymmetric pattern (Baldridge, 1989). Basins involved with this rifting are a distinct features along with faults that bound one or both sides. SAGE has been investigating these for over a decade to interpolate the complex structures. By examining Borrego Canyon, we were able to add to the investigation. Various geophysical methods were utilized to study Borrego Canyon. AMT, MT, TEM, gravity, seismic reflection and seismic refraction were individually used to understand the subsurface and were subsequently integrated together in order to have a full spectrum of subsurface depths. Each method has unique processing steps and are critical in order to analyze the gathered data. As such, this paper will focus on processing seismic reflection with an emphasis on muting. Each technique used in processing the SAGE 2014 seismic reflection data will be explained. Next, this paper will validate muting

  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


    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. Determining Engineering Properties of the Shallow Lunar Subsurface using Seismic Surface Wave Techniques (United States)

    Yeluru, P. M.; Baker, G. S.


    The geology of Earth's moon has previously been examined via telescopic observations, orbiting spacecraft readings, lunar sample analysis, and also from some geophysical data. Previous researchers have examined layering of the moon and models exist explaining the velocity variations in the mantle and core. However, no studies (or datasets) currently exist regarding the engineering properties of the shallow (civil engineering works, as they characterize the mechanical behavior of geotechnical materials under various types of loading. Therefore, understanding the physical and engineering properties within the upper 30 m of the lunar subsurface will be critical for lunar exploration if deployment of large structures, large-scale excavation, and/or landing of large spacecraft on the surface is desired. Advances in near-surface geophysical techniques, such as Multi-channel Analysis of Surface Wave (MASW), has greatly increased our ability to map subsurface variations in physical properties. The MASW method involves deployment of multiple seismometers to acquire 1-D or 2-D shear wave velocity profiles that can be directly related to various engineering properties. The advantage of this technique over drilling boreholes or any other geophysical technique is that it is less intensive, non-invasive, more cost- effective, and more robust because strong surface-wave records are almost guaranteed. In addition, data processing and analysis is fairly straightforward, and the MASW method allows for analysis of a large area of interest as compared to drilling boreholes. A new scheme using randomly distributed geophones (likely deployed from a mortar-type device) instead of a conventional linear array will be presented. A random array is necessary for lunar exploration because of the logistical constraints involved in deploying a linear or circular array robotically or by astronaut. Initial results indicate that robust dispersion curves (and thus subsurface models of engineering

  1. Shear Wave Reflection Seismics Image Internal Structure of Quick-Clay Landslides in Sweden (United States)

    Polom, U.; Krawczyk, C. M.; Malehmir, A.


    Covering many different sizes of scale, landslides are widespread and pose a severe hazard in many areas as soon as humans or infrastructure are affected. In order to provide geophysical tools and techniques to better characterize sites prone to sliding, a geophysical assessment working towards a geotechnical understanding of landslides is necessary. As part of a joint project studying clay-related landslides in Nordic countries by a suite of geophysical methods, we therefore tested the use of shear wave reflection seismics to survey shallow structures that are known to be related to quick-clay landslide processes in southern Sweden. On two crossing profiles, a land streamer consisting of 120 SH-geophones with 1 m spacing was deployed, and an ELVIS micro-vibrator was shaking every 4 m to generate the shear wave signal. SH-wave data of high quality were thereby acquired to resolve the gaps between P-wave data and electrical and surface wave based methods of lower resolution. After quality control, correlation, subtractive stack, and geometry setup, single shot gathers already demonstrate the high data quality gained in the region, especially on a gravel road. The migrated depth sections image the structural inventory down to ca. 50 m depth with vertical resolution of less than 1 m. Horizontally layered sediments are visible in the upper 40 m of soft (marine) sediments, followed by top basement with a rough topography varying between ca. 20-40 m depth. The imaged, bowl-shaped basement morphology centres near the profile crossing, and basement is exposed at three sides of the profiles. Three distinct sediment sequences are separated by high-amplitude unconformities. The quick-clay layer may be located above the marked reflection set that lies on top of the more transparent sequence that levels out the basement. Located between 15-20 m depth, this correlates with the height of the last scarp that occurred in the area. In addition, shear wave velocities are determined

  2. Crustal structure across the Filchner Ronne Shelf, Antarctica (United States)

    Herter, U.; Jokat, W.


    Crustal structure across the Filchner Ronne Shelf, Antarctica U. Herter, W. Jokat One large gap in understanding the tectonic evolution of Antarctica beside the few rock outcrops on the continent is the missing information on crustal thickness along its margins but also in its interior. E.g., the few marine deep seismic lines are located mainly along the Antarctic Peninsula/Pacific margin, but for most of the East Antarctic margins such information is not available. In this contribution we concentrate on one of the most remote areas in Antarctica, the Filchner Ronne Shelf (FRS). The area is underlain by approximately 12 km of sediments, but its crustal fabric is questionable. Thus, some existing deep seismic sounding data were modeled and reinterpreted. Especially, data gathered in 1995 have been analyzed, and a more detailed 2D P-wave velocity model has been calculated. For the profiles in total 12 RefTek stations each with nine geophone chains were placed on the ice shelf and 3175 airgun shots along a 480 km transect were fired by two 32 l BOLT-Airguns each 60 s. Signals were recorded up to distances of 180 km. Due to the ice coverage it was not possible to acquire the data without gaps or along straight lines, which caused some difficulties in the modeling process. Furthermore, in the new model all data from older experiments of the AWI and Soviet Antarctic expeditions acquired with dynamite sources were incorporated. The model shows a sedimentary basin with a thickness up to 12 km and a large velocity inversion in a deeper sediment unit. The crustal thickness varies from 40 km beneath the Antarctic Peninsula, and 14 km of basement in the center part of the profile. Towards Berkner Island the crust thickens again, but the top of the basement is still 11 km deep. The lower crustal velocities range between 6.8 and 7.2 km/s. We interpret the crustal structure as clear evidence for the presence of a failed rift. The initial stretching of the continental crust

  3. Shallow Shear Wave Velocity Structure of Adapazari (Turkey) Region by MASW And MAM Measurements and Some Implications (United States)

    Ozcep, T.; Ozcep, F.; Ozel, O.


    Wave-propagation method to generate the near-surface Vs profile are called spectral analysis of surface waves that uses the spectral analysis of ground roll generated by an impulsive source and recorded by a pair of receivers. This method has been widely and effectively used in many shallow shear wave velocity structure. The 17 August 1999 Izmit earthquake (Mw=7.4) ruptured a 140 km segment of the North Anatolian Fault, extending from the Izmit bay in the west to Akyazi in the east, and caused about 20,000 loss of life and totally 20,000 collapsed buildings. In the study area, the shear wave velocities are obtained by multi channel analysis of surface wave for 100 points in study area. The phase velocity-dispersion curve for each point and shear wave velocity are obtained by inversion distance profile for first 50 meters of soil. The records that are depending on field conditions with different geophone intervals are taken. Passive source when it is compared by active source reaches deeper parts of soils, because the lower frequency of natural noises are recorded different noises that are given more information from the deeply distance. After the data are collected from the field, data-processing are carried out, the phase velocities for the different frequency are obtained by using a computer program and after the process dispersion curve is obtained. During the field studies, the seismic refraction data are also collected. The initial model that obtained from these data is used the initial model data. By using both forward and inverse solutions algorithm, S wave velocities are calculated and drown depending on distance. For 100 sites, soil classifications are mapped according to the Eurocode-8, UBC (NEHRP) and the Turkish Seismic Design Code. The site classification, based on Vs30 in seismic design codes, are compared with fundamental periods and amplification values that obtained by using real earthquake data obtained from region. This study was supported by

  4. Contribution of geophysical studies on detection of the Petrified Frost Qattamiya, Cairo

    Directory of Open Access Journals (Sweden)

    Sultan Awad Sultan Araffa


    Full Text Available Different geophysical tools such as resistivity, seismic refraction, and magnetic survey have been applied to delineate the subsurface stratigraphy and structural elements, which controlled the distribution and origin of the Petrified wood in Qattamiya, Cairo, Egypt. Land magnetic survey was carried out in the study area through two stages, the first stage includes all area by measuring 11,674 stations and the second stage was carried out in the detailed area that was located at the southeastern part of the all area including 9441 stations. All measurements have been corrected for diurnal variation and reduced to the north magnetic pole. The results of magnetic interpretation indicated that the area dissected by different structural elements trend toward NE–SW, NW–SE, N–S and E–W directions. Twenty-eight samples have been collected from the detailed area to analyze for magnetic susceptibility values. Four electrical resistivity tomography (ERT profiles were measured by using dipole–dipole configuration to estimate the vertical and lateral variation of the subsurface sequence. Results of quantitative interpretation of the ERT data indicate that the subsurface sequence consists of different geoelectric units; the first unit is characterized by high resistivity values upto 1000 ohm m corresponding to sand, gravel and Petrified wood at the surface and extends to a depth of a few meters. The second geoelectric unit is corresponding to sandy clay which exhibits moderate resistivity (few hundred ohm m values with thickness ranging from 6 to10 m. The third geoelectric unit is characterized by very low resistivity corresponding to clay of depth ranging from 10 to 30 m overlaying the fourth unit which reached to a depth ranging from 30 to 56 m and characterized by very high resistivity (8000 ohm m corresponding to limestone. Three shallow seismic refraction spreads of geophone spacing 7.5 m were measured to investigate the subsurface

  5. Latest Development of Marine Braodband Seismic Acquisition Technology%海上宽频地震采集技术新进展

    Institute of Scientific and Technical Information of China (English)

    余本善; 孙乃达


    海上宽频地震采集技术不但能改善盐下、玄武岩下等深层构造成像,还能提高薄层、隐蔽圈闭、特殊岩性体等难识别油区成像品质,因而能有效提高地震资料的解释精度,降低勘探风险。近年来市场的迫切需求极大地推动了海上宽频地震采集技术的快速发展,国外相继出现了倾斜电缆采集、上下双缆采集、双检电缆采集、四分量拖缆采集等多种采集方法,国内在这一研究领域尚处于起步阶段。本文通过介绍上述几种技术的基本原理及效果,以期对国内相关研究起到参考和指导作用。%Marine broadband seismic acquisition technology not only improves the pre-salt and pre-basalt geological imaging precision but also raises the imaging quality of dififcult-to-identify reservoirs, such as thin layers, subtle traps and special lithologic bodies, thus effectively improving interpretation precision of seismic data and lowering the risks for exploration. The strong market demand has stimulated development of marine broadband seismic acquisition technology in recent years. A number of acquisition methods appeared abroad, such as slant streamers, over-under streamers, hydrophone-vertical geophone (dual sensor) streamers and multi-component towed streamers. However, the domestic research is still in its preliminary stage in this area. This paper is focused on the fundamental principles of the above-stated technologies, aiming to offer references for the related study at home.

  6. A 3D Seismic Case: Shooting around a CCS Drill Site (United States)

    Wang, C.


    The reduction of carbon dioxide emission to lessen the global warming has become an important international issue in recent years. The CCS technique (Carbon-dioxide Capture and Storage) is among the most recommended methods. The capture of CO2 during its manufacturing process in the electric power plant and storing in the adjacent area is considered to be an economical and feasible choice. This research uses the 2D and 3D high-resolution seismic reflection method to investigate possible CCS sites along the coast in Taiwan. The site is near an electric power plant and is planned to be a CCS experiment laboratory. The main objective is to detect the proper geologic structure and to prepare the baseline data for the future CO2 monitoring. The size of the high-resolution method applied in this study is much smaller than that used in the oil exploration. The obtained high quality and high resolution data can resolve very detailed structures. The survey parameters in 2D are 4m interval, 240 channels. The bin size in 3D seismic is 8m x 4m, 288 channels. Both 2D and 3D used the Minivibe as a source with 40Hz geophones, and having an average of 30 folds. The 3D seismic survey was conducted around the planned drill site. A surrounding type of 3D data acquisition was taken with sources at outside and receivers at the center. Such a deployment design is quite suitable for the drill site investigation. The structural layer as thin as 4m is able to be detected even under a depth of 3000m. Such a high resolution allows us not only to estimate the structure, but also able to monitor the migration of CO 2 after storage. The results of seismic survey after comparing with a nearby borehole data show that : 1) the caprock is Chinshui shale which is at a depth of 880m to 1000m with a thickness about 120m, 2) the Nanchuang formation and Kueichulin formation with high porosity can be proper reservoir layers which are located at the depth between 1000m to 1700m. In conclusion, this site

  7. 地震波逆时偏移中的层位校正与去噪方法%Imaging Horizon Correction and Denoising Method in Seismic Wave Reverse-time Migration

    Institute of Scientific and Technical Information of China (English)

    牟海波; 何兵寿


    波动方程逆时偏移是目前比较精确的基于波动理论的深度域偏移成像方法,但逆时偏移成像条件的运用会产生低频噪音,影响成像质量及层位的准确性。依据低频噪声的产生机理,运用交错网格有限差分法求取各向同性介质中的地震波场,通过对比炮点与检波点波场在不同频率条件下的互相关成像特征,分析其子波频率与周期差异(或时移)条件下逆时偏移成像对层位解释精度与低频噪音产生的影响,提出了改进的时移逆时偏移成像层位校正方法和低频噪声压制策略。数据算例表明,改进后的时移逆时偏移成像有效的压制了低频噪声,成像层位准确。%The wave equation reverse-time migration is a rather accurate depth domain migration imaging method based on wave theo⁃ry. But the application of reverse-time migration imaging conditions will produce low frequency noise, thus impacting imaging quality and horizon interpretation accuracy. Considering low frequency noise forming mechanism, using staggered grid finite difference method to evaluate seismic wave field in isotropic media, through comparison of shotpoint and geophone station wave fields ’mutual correlation imaging features under different frequency conditions analyzed impacts on horizon interpretation accuracy and low frequency noise from reverse-time migration imaging under wavelet frequency and periodic differences (or time shifting), put forward an improved time shifting reverse-time migration imaging horizon correction method and low frequency suppression tactics. The numerical examples have shown that the improved time shifting reverse-time migration imaging can effectively suppress low frequency noise and get correct imaging horizons.

  8. Ground truth : vertical seismic profile data enables geophysicists to image ahead of the drill bit

    Energy Technology Data Exchange (ETDEWEB)

    Eaton, S. [SR ECO Consultants Inc., Calgary, AB (Canada)


    This paper presented a new technology which makes it possible to obtain a vertical seismic profile (VSP) of a wellbore via a wireline tool. Downhole seismic is of extreme importance in cases when there is a discrepancy between the geology in the well and surface seismic data and when drilling has gone deeper than the prognosis for oil or gas. Once VSP data are interpreted, the decision can be made to either abandon the well or sidetrack it to an optimum target position. The VSP data give the geophysicist the opportunity to recalibrate the processing of conventional 2-D or 3-D surface seismic data while drilling. Crucial assumptions for the velocity fields can be tested. This new technology links geology and geophysics, making it possible to quantify subsurface reservoir parameters and to obtain downhole seismic that provides a higher frequency and spatial resolution than conventional surface seismic surveys. The energy source for downhole seismic is situated at ground level. The signal then travels down into the earth where it is recorded in the subsurface by a vertical array of geophones situated in the wellbore. Some of the signal travels past the bottom of the borehole, through the underlying layers that still have to be drilled. Geophysicists with PanCanadian Petroleum Ltd. and Baker Atlas state that a VSP gives ground truth because the acquired data enables the geophysicist to image ahead of the drill bit. VSP is the ultimate tool in interval velocity and time to depth conversion. Downhole seismic has 25 per cent higher frequencies than surface seismic. The technology has been successfully used by Talisman Energy Inc., to drill Foothills wells in the Monkman Pass area of northeastern British Columbia. VSP data can be used to predict formation pressures, porosities, lithologies or rock types, and fluid content. The technology has been useful in the drilling of hostile holes offshore Sable Island in Nova Scotia where wells can cost up to $30 million. VSPs are

  9. Seismic survey across the Japan trench using ultra-deep water OBSs to reveal the structural evolution within the incoming plate prior to subduction (United States)

    Fujie, G.; Takahashi, T.; Kodaira, S.; Obana, K.; Yamada, T.


    Dehydration processes and the expulsion of the water from the subducting oceanic plate affect various subduction-zone processes, including arc volcanism and generation of earthquakes and tremor. Since the amount of chemically bound water in the oceanic plate is highest in serpentinized mantle, it is important to reveal the water amount that penetrates into the oceanic mantle prior to subduction. In 2009, we conducted wide-angle seismic surveys in the outer rise regions of the Japan trench and the Kuril trench. We found that the P-wave velocity (Vp) within the oceanic crust and mantle gradually decreases toward the trench axis. In addition, we found the Vp/Vs ratio within the oceanic crust gradually increases toward the trench, suggesting the water infiltration into the oceanic crust. However, we could not observe any changes in Vp/Vs ratio within the oceanic mantle. This was probably because our seismic survey profile did not cover the area where we would expect the largest structural changes, the trench axis, because the trench axis was too deep to operate our conventional Ocean Bottom Seismometers (OBSs). To examine the Vp/Vs ratio at the area where the largest structural changes are expected and to evaluate the amount of the water penetrating into the oceanic mantle prior to subduction, we need a seismic survey across the trench axis. In August 2013, we plan to conduct an extensive seismic survey across the Japan trench using newly developed 10 ultra-deep water OBSs that are capable of operating at the deepest point of the Japan trench. The seismic profile is a trenchward extension of the existing outer rise profile and we are going to analyze the new data by combining with the existing seismic survey data in order to reveal the structural evolution of the incoming Pacific plate from the outer rise to the trench axis. Since all the ultra-deep water OBSs are equipped with 3-component geophones (or 3-component accelerometers), we have a possibility to determine S

  10. SeisCube Instrument and Environment Considerations for the Didymos System Geophysical Exploration (United States)

    Cadu, Alexandre; Murdoch, Naomi; Mimoun, David; Karatekin, Ozgur; Garica, Raphaël F.; Carrasco, Jose A.; De Quiros, Francisco G.; Vasseur, Hugues; Eubanks, Marshall; Radley, Charles; Ritter, Birgit; Dehant, Veronique


    In the context of the Asteroid Impact & Deviation Assessment (AIDA) mission proposed by ESA and NASA, the Asteroid Geophysical Explorer (AGEX) mission concept has been selected for a preliminary study phase. Two 3-Unit CubeSats are embedded into the AIM probe and released into the asteroid binary system [1]. SeisCube will be deployed close to the secondary to reach its surface at a low relative velocity in order to stay on the ground after several rebounds, in a similar way that is foreseen for Mascot-2. The purpose of SeisCube is to provide information about the surface, the sub-surface and the internal structure of the asteroid, by analyzing rebound acceleration profile and seismic activity [2]. We describe the considered instrumentation necessary to fulfill the science objectives (gravimeters, accelerometers, geophones, etc.) in terms of measurement dynamics, frequency ranges, acquisition methods and other common budgets for space equipment. We also present the environment considerations which have to be taken into account for the platform and payload designs. The thermal aspect will be particularly discussed since it is a major issue in the airless body exploration [3] [4]. It implies some modifications in the CubeSat structure, integration and thermal regulation to ensure survival and operations under extreme conditions at the asteroid surface. We then describe the platform subsystems needed to ensure the operations after the deployment and the associated budgets and accommodation. As a direct consequence of the previous topics, we will finally discuss the possible trades-off to satisfy the main science requirements and the associated concept of operations. [1] O. Karatekin, D. Mimoun, J. A. Carrasco, N. Murdoch, A. Cadu, R. F. Garcia, F. G. De Quiros, H. Vasseur, B. Ritter, M. Eubanks, C. Radley and V. Dehant, "The Asteroid Geophysical Explorer (AGEX): Proposal to explore Didymos system using Cubsats," in European Geophysical Union, 2016. [2] N. Murdoch, A

  11. TremorScope: A Tool to Image the Deep Workings of the San Andreas Fault near Cholame, CA (United States)

    Hellweg, M.; Burgmann, R.; Taira, T.; Nadeau, R. M.; Dreger, D. S.; Allen, R. M.


    Until recently, active fault zones were thought to deform via seismic slip during earthquakes in the upper, brittle portion of the crust, and by steady, aseismic shear below. However, since 2000, this view has been shaken by seismological observations of seismic tremor deep in the roots of active fault zones, including on the section of the San Andreas to the southeast of Parkfield, CA, deep (~20-30 km) beneath the nucleation zone of the great 1857 Fort Tejon earthquake. With funding from the Gordon and Betty Moore Foundation, we have improved the seismic network in the area above the tremor source by installing four new broadband/strong motion surface stations and four borehole sites with uphole accelerometers and downhole geophones, broadband and strong motion sensors. Data from all stations are telemetered in real-time. They are analysed as part of normal earthquake monitoring, and archived and distributed through the Northern California Earthquake Data Center (NCEDC). Data from the TremorScope project is improving earthquake monitoring in the region south of Parkfield, including allowing empirical Greens function finite fault analysis of moderate events in the area. Locations and characterization of tremor episodes are improved by the data recorded by TremorScope stations. For example, the rate of ambient tremor activity in the TremorScope area increased by a factor of ~8 within ~12 hours of the 2014 Napa M6.0 earthquake and remained elevated for ~ 100 days, exceeding the tremor rate increase following the 2004 Parkfield M6.0 quake despite the differences in epicentral distance (~300 km vs. ~15 km). No comparable increases in tremor rates have been observed between the Parkfield and Napa events. This suggests that the sensitivity to external stressing in the in the deep tremor zone of the TremorScope region may have increased since 2004. We also show how this network's strong motion instrumentation will provide unprecedented and exciting insights into the

  12. 1d Numerical Simulation of A Swiss Debris Flow: Comparison of Flow Laws (United States)

    McArdell, B. W.; Graf, Ch.; Naef, D.; Rickenmann, D.

    Efforts to numerically model debris flows have been limited by a lack of appropriate numerical tools. Here we report on our efforts to systematically evaluate different flow laws using a numerical tool under development at our institute. The model, DFEM, is a finite element solution of the shallow water equations in one or two dimensions and is based on the FEMTOOL libraries from Rutschmann (1993). Debris flow constitu- tive relations or flow laws include turbulent (e.g. Manning, Chézy, Voellmy), laminar (Bingham, Newtonian laminar), and inertial formulations (dilatant/grain shearing) as well as combinations of flow laws when appropriate. The model is applied to a recent debris flow event from the Schipfenbach torrent, Switzerland (Hürlimann, submitted), where we maintain an automated debris flow observation station. Observations include flow depth measurements from ultrasonic depth measurement devices, reach-averaged velocities estimated from the travel time between ultrasonic gages and geophones, velocity and flow behavior from video cam- eras situated near the flow retention basin on the fan, and post-event field surveys. Preliminary results suggest that the flow of debris in the steep reaches of the torrent channel can be reasonably described by a simple turbulent flow law (e.g. Manning- Strickler or Chézy) with a large overall flow resistance, and that both the flow in the channel and the deposition on the fan can be satisfactorily simulated using the Voellmy fluid approach. The results using the Voellmy fluid approach are in agree- ment with results calculated from the AVAL-1D snow avalanche simulation code and input parameters for debris instead of snow, corroborating the implementation in the DFEM model. The AVAL-1D code is commercially available, providing another tool that may be used by workers in the natural hazards field for debris flow routing in torrent channels and on alluvial fans. References: Hürlimann, M., Rickenmann, D. and Graf, Ch., Field

  13. TGP隧道地质超前预报技术的优势%Advantages of TGP Advance Geology Prediction Technology in Tunnels

    Institute of Scientific and Technical Information of China (English)

    刘云祯; 梅汝吾


    Geology prediction by seismic waves, which is one of the important technical means to achieve long-distance advance geology prediction, has great significance for the safe and information-aided construction of tunnels. The development of the study on geology prediction by seismic waves, the technical performance and adaptability of the prediction instruments and devices, the requirements for the geophones and the multi-wave multi-component detections; the coupling conditions of the receiving devices and the amplitude frequency characteristics of signals, excitation means and deviations, identification and treatment of the interference waves, the analysis on the reliability of the prediction results,the contents and display means of the 3D geology prediction result maps, repeated usc and comparative analysis of the signals, assessment on the parameter prediction method and the heterogeneity of the rock mass are discussed in the paper. The theoretical analysis of the technology is rational and the engineering practice demonstrates that the technology is reliable and effective. The paper can be serviced as reference for the development of the technology of geology prediction by seismic waves.%地震波预报是实现长距离地质超前预报的重要技术手段,其成果质量对于隧道的安全施工和信息化施工具有重要意义,为此,从地震波预报技术的研究进程、仪器设备的技术性能与适应性、检波器与多波多分量检测工作要求、接收耦合条件与信号的幅频特征、采集的触发方式与误差、干扰波的认识与处理、成果的可靠性分析、3D地质预报成果图的内容与表现方式、信号的重复利用与对比分析、参数法预报的评述与岩体的各向异性等10个方面进行论述.理论分析合理,工程实践证明可靠有效.对于促进地一震波预报技术的科学发展、克服月前工作中的盲目应用具有一定的指导意义.

  14. Tomography 3D models of S wave from cross-correlation of seismic noise to explore irregularities of subsoil under the artificial lake of Chapultepec Park (United States)

    Cárdenas-Soto, M.; Valdes, J. E.; Escobedo-Zenil, D.


    In June 2006, the base of the artificial lake in Chapultepec Park collapsed. 20 thousand liters of water were filtered to the ground through a crack increasing the dimensions of initial gap. Studies indicated that the collapse was due to saturated material associated with a sudden and massive water filtration process. Geological studies indicates that all the area of this section the subsoil is composed of vulcano-sedimentary materials that were economically exploited in the mid-20th century, leaving a series of underground mines that were rehabilitated for the construction of the Park. Currently, the Lake is rehabilitated and running for recreational activities. In this study we have applied two methods of seismic noise correlation; seismic interferometry (SI) in time domain and the Spatial Power Auto Correlation (SPAC) in frequency domain, in order to explore the 3D subsoil velocity structure. The aim is to highlight major variations in velocity that can be associated with irregularities in the subsoil that may pose a risk to the stability of the Lake. For this purpose we use 96 vertical geophones of 4.5 Hz with 5-m spacing that conform a semi-circular array that provide a length of 480 m around the lake zone. For both correlation methods, we extract the phase velocity associated with the dispersion characteristics between each pair of stations in the frequency range from 4 to 12 Hz. In the SPAC method the process was through the dispersion curve, and in SI method we use the time delay of the maximum amplitude in the correlation pulse, which was previously filtered in multiple frequency bands. The results of both processes were captured in 3D velocity volumes (in the case SI a process of traveltime tomography was applied). We observed that in the frequency range from 6 to 8 Hz, appear irregular structures, with high velocity contrast in relation with the shear wave velocity of surface layer (ten thick m of saturated sediments). One of these anomalies is related

  15. Imaging Seismic Source Variations Using Back-Projection Methods at El Tatio Geyser Field, Northern Chile (United States)

    Kelly, C. L.; Lawrence, J. F.


    During October 2012, 51 geophones and 6 broadband seismometers were deployed in an ~50x50m region surrounding a periodically erupting columnar geyser in the El Tatio Geyser Field, Chile. The dense array served as the seismic framework for a collaborative project to study the mechanics of complex hydrothermal systems. Contemporaneously, complementary geophysical measurements (including down-hole temperature and pressure, discharge rates, thermal imaging, water chemistry, and video) were also collected. Located on the western flanks of the Andes Mountains at an elevation of 4200m, El Tatio is the third largest geyser field in the world. Its non-pristine condition makes it an ideal location to perform minutely invasive geophysical studies. The El Jefe Geyser was chosen for its easily accessible conduit and extremely periodic eruption cycle (~120s). During approximately 2 weeks of continuous recording, we recorded ~2500 nighttime eruptions which lack cultural noise from tourism. With ample data, we aim to study how the source varies spatially and temporally during each phase of the geyser's eruption cycle. We are developing a new back-projection processing technique to improve source imaging for diffuse signals. Our method was previously applied to the Sierra Negra Volcano system, which also exhibits repeating harmonic and diffuse seismic sources. We back-project correlated seismic signals from the receivers back to their sources, assuming linear source to receiver paths and a known velocity model (obtained from ambient noise tomography). We apply polarization filters to isolate individual and concurrent geyser energy associated with P and S phases. We generate 4D, time-lapsed images of the geyser source field that illustrate how the source distribution changes through the eruption cycle. We compare images for pre-eruption, co-eruption, post-eruption and quiescent periods. We use our images to assess eruption mechanics in the system (i.e. top-down vs. bottom-up) and

  16. Crustal Structure Across the Okavango Rift Zone, Botswana: Initial Results From the PRIDE-SEISORZ Active-Source Seismic Profile (United States)

    Canales, J. P.; Moffat, L.; Lizarralde, D.; Laletsang, K.; Harder, S. H.; Kaip, G.; Modisi, M.


    The PRIDE project aims to understand the processes of continental rift initiation and evolution by analyzing along-axis trends in the southern portion of the East Africa Rift System, from Botswana through Zambia and Malawi. The SEISORZ active-source seismic component of PRIDE focused on the Okavango Rift Zone (ORZ) in northwestern Botswana, with the main goal of imaging the crustal structure across the ORZ. This will allow us to estimate total crustal extension, determine the pattern and amount of thinning, assess the possible presence of melt within the rift zone, and assess the contrasts in crustal blocks across the rift, which closely follows the trend of a fold belt. In November 2014 we conducted a crustal-scale, 450-km-long seismic refraction/wide-angle reflection profile consisting of 19 sources (shots in 30-m-deep boreholes) spaced ~25 km apart from each other, and 900 receivers (IRIS/PASSCAL "Texan" dataloggers and 4.5Hz geophones) with ~500 m spacing. From NW to SE, the profile crosses several tectonic domains: the Congo craton, the Damara metamorphic belt and the Ghanzi-Chobe fold belt where the axis of the ORZ is located, and continues into the Kalahari craton. The record sections display clear crustal refraction (Pg) and wide-angle Moho reflection (PmP) phases for all 17 of the good-quality shots, and a mantle refraction arrival (Pn), with the Pg-PmP-Pn triplication appearing at 175 km offset. There are distinct changes in the traveltime and amplitude of these phases along the transect, and on either side of the axis, that seem to correlate with sharp transitions across tectonic terrains. Initial modeling suggests: (1) the presence of a sedimentary half-graben structure at the rift axis beneath the Okavango delta, bounded to the SE by the Kunyere-Thamalakane fault system; (2) faster crustal Vp in the domains to the NW of the ORZ; and (3) thicker crust (45-50 km) at both ends of the profile within the Congo and Kalahari craton domains than at the ORZ and

  17. 全数字高密度煤矿采区三维地震技术研究与实践%All Digital High Density Coalmine Winning District 3D Seismic Prospecting Technology Research and Practices

    Institute of Scientific and Technical Information of China (English)



    通过分析常规煤矿采区三维地震勘探存在的问题及技术瓶颈,提出了全数字高密度煤矿采区三维地震勘探的主要技术框架,即:数字检波器、单点接收、更小的接收道距与线距、更小的激发点距与线距、单炮超多道数、小面元、全方位、高覆盖次数观测,真实记录全波场海量数据的采集技术,及其与之相配套的高精度地震成像处理和精细综合地震解释技术。与以往的常规三维地震勘探相比,全数字高密度煤矿采区三维地震勘探技术在断层方位、小断层识别、陷落柱探测、下组煤层探测、高陡构造勘探等多个方面都有明显优势。%After summarization of technical bottlenecks and problems in conventional coalmine winning district 3D seismic prospecting, put forward all digital high density coalmine winning district 3D seismic prospecting main technical framework. That is: digital geo-phone, single-point receiving, smaller receiving group interval and line spacing, smaller shot point interval and line spacing, single-shot super multi trace number, small surface element, all dimensions, high coverage observation, actually recorded full wave field mass data acquisition technology, and matching high precision seismic imaging processing and fine comprehensive seismic interpretation technology. In contrast with bygone conventional 3D seismic prospecting, the all digital high density coalmine winning district 3D seis-mic prospecting has obvious predominance on multiple aspects of fault orientation, minor fault identification, subsided column detec-tion, lower group coal seams exploration, high dip angle structure exploration etc.

  18. Seismic Borehole Monitoring of CO2 Injection in an Oil Reservoir (United States)

    Gritto, R.; Daley, T. M.; Myer, L. R.


    A series of time-lapse seismic cross well and single well experiments were conducted in a diatomite reservoir to monitor the injection of CO2 into a hydrofracture zone, based on P- and S-wave data. A high-frequency piezo-electric P-wave source and an orbital-vibrator S-wave source were used to generate waves that were recorded by hydrophones as well as three-component geophones. The injection well was located about 12 m from the source well. During the pre-injection phase water was injected into the hydrofrac-zone. The set of seismic experiments was repeated after a time interval of 7 months during which CO2 was injected into the hydrofractured zone. The questions to be answered ranged from the detectability of the geologic structure in the diatomic reservoir to the detectability of CO2 within the hydrofracture. Furthermore it was intended to determine which experiment (cross well or single well) is best suited to resolve these features. During the pre-injection experiment, the P-wave velocities exhibited relatively low values between 1700-1900 m/s, which decreased to 1600-1800 m/s during the post-injection phase (-5%). The analysis of the pre-injection S-wave data revealed slow S-wave velocities between 600-800 m/s, while the post-injection data revealed velocities between 500-700 m/s (-6%). These velocity estimates produced high Poisson ratios between 0.36 and 0.46 for this highly porous (~ 50%) material. Differencing post- and pre-injection data revealed an increase in Poisson ratio of up to 5%. Both, velocity and Poisson estimates indicate the dissolution of CO2 in the liquid phase of the reservoir accompanied by a pore-pressure increase. The single well data supported the findings of the cross well experiments. P- and S-wave velocities as well as Poisson ratios were comparable to the estimates of the cross well data.

  19. A Fiber-Optic Borehole Seismic Vector Sensor System for Geothermal Site Characterization and Monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Paulsson, Bjorn N.P. [Paulsson, Inc.; Thornburg, Jon A [Paulsson, Inc.; He, Ruiqing [Paulsson, Inc.


    that the system can record events at magnitudes much smaller than M-2.6 at frequencies up to 2,000 Hz. The sensors have also proved to be about 100 times more sensitive than the regular coil geophones that are used in borehole seismic systems today. The fiber optic seismic sensors have furthermore been qualified to operate at temperatures over 300°C (572°F). Simultaneously with the fiber optic based seismic 3C vector sensors we are using the lead-in fiber to acquire Distributed Acoustic Sensor (DAS) data from the surface to the bottom of the vector array. While the DAS data is of much lower quality than the vector sensor data it provides a 1 m spatial sampling of the downgoing wavefield which will be used to build the high resolution velocity model which is an essential component in high resolution imaging and monitoring.

  20. The EarthScope USArray Observatories: Status and Results (United States)

    Woodward, R.; Busby, R.; Alvarez, M.; Schultz, A.; Simpson, D.


    The EarthScope USArray program includes three seismic and two magnetotelluric components. The USArray seismic components consist of the Transportable Array (TA), the Flexible Array (FA), and the Reference Network. The TA component of USArray has now occupied over 700 sites in the western United States, from the Pacific coast through the Rocky Mountains. The three component broadband TA stations are deployed in a grid-like arrangement, with 70 km separation between stations. At any given time there are approximately 400 station sites, occupying a ~2000 km by 800 km "footprint." Each station is operated for two years. The FA component of USArray provides a pool of instruments, ranging from high frequency geophones to three- component broadband sensors, and these instruments are typically deployed for focused geological targets for time periods ranging from days to years. Finally, the Reference Network provides a fixed, permanent reference frame for the TA and FA, with approximately 100 broadband stations deployed across the contiguous US, at roughly 300 km spacing. The magnetotelluric (MT) component of USArray consists of both a fixed reference network as well as a transportable array of instruments that are deployed campaign style, using a 70 km by 70 km grid. The geographical extent of USArray allows unprecedented observation of geophysical targets. Instruments have been deployed across the west and mid-west of the US, with TA stations presently moving into the states spanning a north-south line from North Dakota to Texas. MT observations in Cascadia have been augmented by corresponding observations in Canada. Similarly, as the seismic TA moves east, plans are being developed to collaborate on TA seismic observations on both sides of the US-Canada border in the region of the Great Lakes. We will present the current status of USArray activities and progress to-date, with a special emphasis on standardized data products that are produced from USArray data, including

  1. Combining microseismic and geomechanical observations to interpret storage integrity at the In Salah CCS site (United States)

    Goertz-Allmann, Bettina P.; Kühn, Daniela; Oye, Volker; Bohloli, Bahman; Aker, Eyvind


    We present results from microseismic monitoring and geomechanical analysis obtained at the industrial-scale CO2 sequestration site at the In Salah gas development project in Algeria. More than 5000 microseismic events have been detected at a pilot monitoring well using a master event cross-correlation method. The microseismic activity occurs in four distinct clusters and thereof three clearly correlate with injection rates and wellhead pressures. These event clusters are consistent with a location within the reservoir interval. However, due to insufficient network geometry there are large uncertainties on event location. We estimate a fracture pressure of 155 bar (at the wellhead) from the comparison of injection pressure and injection rate and conclude that reservoir fracture pressure of the injection horizon has most likely been exceeded occasionally, accompanied by increased microseismic activity. Our analysis of 3-D ray tracing for direct and converted phases suggests that one of the event clusters is located at a shallower depth than the reservoir injection interval. However, this event cluster is most likely unrelated to changes in the injection activity at a single well, as the event times do not correlate with the wellhead pressures. Furthermore, this event cluster shows b-values close to one, indicating re-activated natural or tectonic seismicity on pre-existing weakness zones rather than injection induced seismicity. Analysis of event azimuths and significant shear wave splitting of up to 5 per cent provide further valuable insight into fluid migration and fracture orientation at the reservoir level. Although only one geophone was available during the critical injection period, the microseismic monitoring of CO2 injection at In Salah is capable of addressing some of the most relevant questions about fluid migration and reservoir integrity. An improved monitoring array with larger aperture and higher sensitivity is highly recommended, as it could greatly

  2. Flume-based calibration of different surrogate devices for bedload monitoring (United States)

    Mao, Luca; Escauriaza, Cristian; Gordo, Fernanda; Carrillo, Ricardo


    Bedload assessment is important for geomorphological, engineering, and ecological studies of gravel-bed rivers. Bedload is usually assessed using portable traps, which allows measuring instantaneous transport rates, but at a single point and at high costs and operational risks. Slot traps or other fixed devices allow measuring bedload rate for longer periods, but require expensive maintenance. The need of measuring continuously bedload intensity and dynamics has therefore increased the use and enhancement of surrogate methods, such as geophones, hydrophones, and acoustic sensors. However, converting the signals recorded by these instruments to actual bedload fluxes, direct bedload measurements are needed to obtain a calibration relationship. Even if some noticeable examples are available in literature, only few flume experiments have been undertaken to calibrate rate and grain size of transported sediments, and to explore rigorously the sensitivity and signal dampening effects of various surrogate devices. Here we present some preliminary results obtained from a set of flume experiments on which different devices have been used. We have tested a 1m-long Japanese acoustic pipe sensor, a 150×130×6 mm steel plate linked to an accelerometer and a count input data logger, and a hydrophone. Experiments were made in a 0.8m-wide flume, using 4 homogeneous (4, 8, 32, and 45 mm) sediment mixtures. These fractions were then combined in order to obtain 3 further heterogeneous mixtures. Experiments with different discharges and slopes were performed, allowing to observe a wide range of shear stresses and transport rates. All transported sediments were captured with traps, weighted, and then manually recirculated at the upstream end of the flume. Preliminary results show that devices have different sensitivity to lower grain size that could be detected, being the transport of 4 mm particles detected relatively well only by the impact plates. Intense transport of 8 mm particles

  3. Applications of a fast continuous wavelet transform (United States)

    Dress, William B.


    A fast, continuous, wavelet transform, justified by appealing to Shannon's sampling theorem in frequency space, has been developed for use with continuous mother wavelets and sampled data sets. The method differs from the usual discrete-wavelet approach and from the standard treatment of the continuous-wavelet transform in that, here, the wavelet is sampled in the frequency domain. Since Shannon's sampling theorem lets us view the Fourier transform of the data set as representing the continuous function in frequency space, the continuous nature of the functions is kept up to the point of sampling the scale-translation lattice, so the scale-translation grid used to represent the wavelet transform is independent of the time-domain sampling of the signal under analysis. Although more computationally costly and not represented by an orthogonal basis, the inherent flexibility and shift invariance of the frequency-space wavelets are advantageous for certain applications. The method has been applied to forensic audio reconstruction, speaker recognition/identification, and the detection of micromotions of heavy vehicles associated with ballistocardiac impulses originating from occupants' heart beats. Audio reconstruction is aided by selection of desired regions in the 2D representation of the magnitude of the transformed signals. The inverse transform is applied to ridges and selected regions to reconstruct areas of interest, unencumbered by noise interference lying outside these regions. To separate micromotions imparted to a mass- spring system by an occupant's beating heart from gross mechanical motions due to wind and traffic vibrations, a continuous frequency-space wavelet, modeled on the frequency content of a canonical ballistocardiogram, was used to analyze time series taken from geophone measurements of vehicle micromotions. By using a family of mother wavelets, such as a set of Gaussian derivatives of various orders, different features may be extracted from voice

  4. Dynamic characterization of the Chamousset rock column before its fall (United States)

    Levy, C.; Baillet, L.; Jongmans, D.


    The rockfall of Chamousset (volume of 21000m3 ) occurred on November 10, 2007, affecting the 300 m high Urgonian cliff of the southern Vercors massif, French Alps. This event took place when the Vercors plateau was covered by snow. The unstable column was previously detected by observations on the development of a 30 m long fracture back on the plateau. Two aerial Lidar scans of the cliff were acquired before and after the failure, allowing the geometry of the column and of the broken plane to be determined. A temporary seismic array along with two extensometers was installed from July to November 2007. The seismic array consisted of 7 short period seismometers (1 three-components and 6 vertical-component). One vertical seismometer was installed on the column while the other 6 were deployed on the plateau with an array aperture of about 70 m. During the last two months of record, short period seismometers were replaced by 4.5 Hz geophones. The monitoring system recorded in a continuous mode (1000 Hz of frequency sampling) but it stopped to work two weeks before the fall, after the solar panels were covered by snow. During the running period, the seismic array recorded hundreds of local seismic events, from short (less than 0.5 s) impulsive signals to events with a long duration (a few tens of seconds). Our study was first focused on the dynamic response of the column and on the seismic noise frequency content. Fourier spectra of the seismic noise signals recorded on the column and the corresponding spectral ratios showed the presence of several resonance frequencies of the column. The first resonance frequency was measured at 3.6 Hz in July 2007 and it decreases regularly with time to reach 2.6 Hz two weeks before the fall. In parallel, extensometer measurements show that the fracture aperture increased with time during the same period. The dynamic response of a block which separates from a rock mass was 2D numerically modelled. Finite element computations showed

  5. Video-Seismic coupling for debris flow study at Merapi Volcano, Indonesia (United States)

    Budi Wibowo, Sandy; Lavigne, Franck; Mourot, Philippe; Sukatja, Bambang


    Previous lahar disasters caused at least 44.252 death toll worldwide from 1600 to 2010 of which 52 % was due to a single event in the late 20th century. The need of a better understanding of lahar flow behavior makes general public and stakeholders much more curious than before. However, the dynamics of lahar in motion is still poorly understood because data acquisition of active flows is difficult. This research presents debris-flow-type lahar on February 28, 2014 at Merapi volcano in Indonesia. The lahar dynamics was studied in the frame of the SEDIMER Project (Sediment-related Disasters following the 2010 centennial eruption of Merapi Volcano, Java, Indonesia) based on coupling between video and seismic data analysis. We installed a seismic station at Gendol river (1090 meters asl, 4.6 km south from the summit) consisting of two geophones placed 76 meters apart parallel to the river, a high definition camera on the edge of the river and two raingauges at east and west side of the river. The results showed that the behavior of this lahar changed continuously during the event. The lahar front moved at an average speed of 4.1 m/s at the observation site. Its maximum velocity reached 14.5 m/s with a peak discharge of 473 m3/s. The maximum depth of the flow reached 7 m. Almost 600 blocks of more than 1 m main axis were identified on the surface of the lahar during 36 minutes, which represents an average block discharge of 17 blocks per minute. Seismic frequency ranged from 10 to 150 Hz. However, there was a clear difference between upstream and downstream seismic characteristics. The interpretation related to this difference could be improved by the results of analysis of video recordings, especially to differentiate the debris flow and hyperconcentrated flow phase. The lahar video is accessible online to the broader community ( Keywords: lahar, video, seismic signal, debris flow, hyperconcentrated flow, Merapi, Indonesia.

  6. Hydrocarbon Induced Seismicity in Northern Netherlands (United States)

    Dost, B.; Spetzler, J.; Kraaijpoel, D.; Caccavale, M.


    The northern Netherlands has been regarded aseismic until the first earthquakes started in 1986, after more than 25 years of gas production from the one of the largest on-shore gas-fields in the World, the Groningen field, and accompanying smaller gas fields. Due to the shallow sources, at approximately 3 km depth, even small magnitude events cause considerable damage to buildings in the region. Since the largest recorded event in the Groningen field in 2012 with ML= 3,6, more than 30.000 damage claims were received by the mining company. Since 1995 a seismic monitoring network is operational in the region, consisting of 8 200m deep boreholes with 4 levels of 3C 4,5 Hz geophones. The network was designed for a location threshold of ML=1,5 over a 40x 80 km region. Average station separation was 20 km. At the end of 2014, 245 events have been recorded with ML ≥ 1,5, out of a total of 1100. Since 2003 a new mining law is in place in the Netherlands, which requires for each gas field in production a seismic risk analysis. Initially, due to the small number of events for specific fields, a general hazard (PSHA) was calculated for all gas-fields and a maximum magnitude was estimated at ML = 3,9. Since 2003 an increase in the activity rate is observed for the Groningen field, leading to the development of new models and a re-assessment of parameters like the maximum magnitude. More recently these models are extended to seismic risk, where also the fragility of the regional buildings is taken into account. Understanding the earthquake process is essential in taking mitigation measures. Continued research is focused on reducing the uncertainties in the hazard and risk models and is accompanied by an upgrade of the monitoring network. In 2014 a new dense network was designed to monitor the Groningen gas field in this region (30*40 km) with an average separation of 4 km. This allows an improved location threshold (M>0,5) and location accuracy (50-100m). A detailed P- and S

  7. LHC beam stability and feedback control

    Energy Technology Data Exchange (ETDEWEB)

    Steinhagen, Ralph


    This report presents the stability and the control of the Large Hadron Collider's (LHC) two beam orbits and their particle momenta using beam-based feedback systems. The aim of this report is to contribute to a safe and reliable LHC commissioning and machine operation. The first part of the analysis gives an estimate of the expected sources of orbit and energy perturbations that can be grouped into environmental sources, machine-inherent sources and machine element failures: the slowest perturbation due to ground motion, tides, temperature fluctuations of the tunnel and other environmental influences are described in this report by a propagation model that is both qualitatively and quantitatively supported by geophone and beam motion measurements at LEP and other CERN accelerators. The second part of this analysis deals with the control of the two LHC beams' orbit and energy through automated feedback systems. Based on the reading of the more than 1056 beam position monitors (BPMs) that are distributed over the machine, a central global feedback controller calculates new deflection strengths for the more than 1060 orbit corrector magnets (CODs) that are suitable to correct the orbit and momentum around their references. this report provides an analysis of the BPMs and CODs involved in the orbit and energy feedback. The BPMs are based on a wide-band time normaliser circuit that converts the transverse beam position reading of each individual particle bunch into two laser pulses that are separated by a time delay and transmitted through optical fibres to an acquisition card that converts the delay signals into a digital position. A simple error model has been tested and compared to the measurement accuracy of LHC type BPMs, obtained through beam-based measurements in the SPS. The average beam position is controlled through 1060 superconducting and individually powered corrector dipole magnets. The proposed correction in 'time-domain' consists of a

  8. Spatio-temporal variability of abient seismic noise repeatedly monitored above a geothermal reservoir (United States)

    Woith, H.; Parolai, S.; Picozzi, M.; Boxberger, T.; Milkereit, C.; Zschau, J.


    A simple method had been proposed to use passive seismic noise measurements as "direct hydrocarbon indicators (DHI)". It had been claimed that low frequency (1-10 Hz) seismic signal anomalies correlate with the occurrence of hydrocarbons. Due to lack of convincing case studies and an underlying theory the approach is severely under discussion. Three mechanisms had been proposed to explain the anomalous seismic signals: (1) macroscopic resonance effects of standing waves, (2) selective attenuation of seismic waves, and (3) resonant scattering/amplification at microscopic scales. In the frame of a theoretical work (co-funded by a consulting company and GFZ) the selective attenuation of seismic waves as a DHI mechanism could be ruled out. Assuming that the seismic noise is originated within the reservoir (source effect), it should be possible to locate the noise source with array techniques by deploying arrays around the reservoir. For this reason, a series of tests have been carried out above oil, gas and geothermal reservoirs - none of them indicating a noise source inside the reservoir. In one case, a nearby wind park could be identified as a noise source. Here, we focus on repeated measurements of seismic noise related to the Heybeli geothermal reservoir in Turkey. We compared repeated noise measurements from 2002, 2010, and 2011. In 2002 profile measurements were performed during the aftershock sequence of the Mw=6.5 Sultandagi earthquake of 03.02.2002, where a distinct cluster of aftershocks was co-located with the geothermal field of Heybeli. In October 2010 six arrays (each consisting of 17 geophones; seismic noise recorded for several hours; thereafter the array was moved to the next position) had been located on and off the reservoir. Again, a clear noise source coming from the reservoir could not be clearly identified. Nevertheless, at some sites in the centre of the reservoir a 6-Hz-signal was observed. The origin of this signal is not clear yet. Hence, it

  9. A Long-Term Seismic Array on the Endeavour Segment of the Juan de Fuca Ridge (United States)

    McGill, P. R.; Wilcock, W. S.; Stakes, D. S.; Barclay, A. H.; Ramirez, T. M.; Toomey, D. R.


    The Keck Foundation with additional support from the Monterey Bay Aquarium Research Institute and the University of Washington has funded a five-year, five-million dollar program for archetypic experiments on the northern Juan de Fuca Plate. The goal of this program is to constrain the linkages between deformation (earthquakes), fluid flow and chemistry, and microbial response across the northern Juan de Fuca Plate in the northeastern Pacific Ocean. A key component of these studies is an array of ocean-bottom seismometers to record the temporal and spatial distribution of seismic activity in the region. The current network, deployed in August of 2003, is comprised of eight autonomous instruments: one broadband seismometer and seven short-period seismometers. The instruments are distributed within and around the axial valley at the center of the Endeavour segment and spaced about 4 km apart, composing an array about 7 km wide and 9 km long. The short-period instruments, sensitive over a frequency range of 1 to 32 Hz, utilize an MBARI/GEOSense BH1 three-axis corehole geophone connected to an MBARI/GEOSense LP1 data logger. For five of these instruments the corehole sensor is inserted into a 7 cm diameter hole drilled into the basaltic basement rock, thus providing excellent coupling. For the other two instruments where suitable drilling sites were not available, the sensors are inserted into 55 kg concrete blocks placed on the sediment. The broadband instrument is a Guralp CMG-1T three-axis seismometer, sensitive over a frequency range of 2.8 mHz (360 sec) to 50 Hz. The sensor is completely buried in sediment inside a 60 cm deep by 60 cm diameter caisson, thus reducing the effects of water currents on the recorded data. A 20 m cable connects the sensor to an LP1 data logger and a 30 kW-hr battery sitting on the sediment. A complete data set will be recovered from the array when the instruments are revisited during the summer of 2004. However, data from two events, an

  10. Source properties of microearthquakes revealed by near-source observation at SAFOD (Invited) (United States)

    Imanishi, K.; Ellsworth, W. L.


    Near-source observation of earthquakes in deep boreholes and mines provides significant opportunities to enhance our understanding of the source properties of earthquakes. Short hypocentral distances and a high-Q environment make it possible to observe earthquake processes that cannot be seen in shallow boreholes or at the surface. The SAFOD Main Hole is a 3.2 km-deep inclined borehole that crosses the active traces of the San Andreas Fault. A 3-component 15 Hz GS-20DM geophone was deployed within the fault zone at depths between 2350 and 2750 m. Because of the close proximity to earthquake sources, we routinely observed earthquakes with Mw noise ratio. Events were recorded at three different sampling rates (1000, 2000, and 4000 sps) depending on observation period (2005 - 2010). This study focuses on earthquakes with S-P time differences shorter than 0.5s, corresponding to hypocentral distance less than 3 km. Among more than 400 earthquakes, we selected 117 events classified into 35 clusters on the basis of waveform similarity at low frequencies. Selected events range in size from approximately Mw -3 to Mw 2. The dataset includes many events in three clusters that formed the SAFOD drilling target; San Francisco, Los Angeles and Hawaii named as their relative positions with respect to those cities. We determined source parameters by the Multi-Window Spectral Ratio (MWSR) method (Imanishi and Ellsworth, 2006). The key step in the method is to stack the ratios calculated from moving windows taken along the record starting with the direct waves. We confirmed that stacking better suppresses the random noise due to differences in path than single-window methods, producing a better estimate of the source spectral ratio. For Mw>-1, the calculated stress drops range between 0.1 and 100 MPa. These observations indicate that there is no breakdown in stress drop scaling for Mw>-1. The stacked spectral ratios show that corner frequencies of events for Mwrocks where repeating

  11. Near-surface properties using seismograms from the GONAF-Tuzla vertical array, SE Istanbul (United States)

    Raub, C.; Malin, P. E.; Bohnhoff, M.; Bulut, F.; Dresen, G. H.; Kilic, T.; Kartal, R. F.; Kadirioglu, F. T.; Nurlu, M.


    As part of the ICDP-GONAF project (Geophysical Observatory at the North Anatolian Fault) geophone arrays have been installed in 300 m deep boreholes around the eastern Sea of Marmara. The objectives of GONAF are to (1) monitor the North Anatolian Fault Zone (NAFZ) at the transition from the 1999 Izmit rupture to the Princes Islands segment offshore Istanbul, where a M ~ 7 earthquake can reasonably be expected to occur and (2) to determine ground-motion amplification and near-surface properties at the GONAF sites. Here we use recordings from the first GONAF borehole on the Tuzla peninsula in eastern Istanbul. The array consists of one 1 Hz 3C Mark Products L4 seismometer at the surface, three 1 Hz vertical Mark Products L4 seismometers at 75 m depth-spacing, and 2 Hz and 15 Hz 3C Geospace HS-1 and DM2400 seismometers at 288 m depth. During April - May 2013 this array recorded a microearthquake swarm located ~ 3.5 km epicentral distance south of the Tuzla site. By cross-correlating the continuous Tuzla data with the only swarm event detected by the regional network (20th of April 2013, Md 1.6) we retrieved an additional of 113 events. The swarm and an additional 15 events located throughout the eastern Marmara region were used to analyze the near-surface properties of the Tuzla site. We derive a velocity model from sonic-log measurements which were conducted upon completion of the Tuzla well. This model is confirmed by modeling travel-time curves with forward ray-tracing and by an analysis of spectral interference effects. In the uppermost ~80 m at this site we observe an unexpectedly high velocity lid (VP ~ 4000 m/s) over a much slower (VP ~ 3000 m/s) ~50 m thick zone. These velocity structure leads to interference effects between up and downgoing waves even at the deepest stations. As a result of this the standard spectral ratio technique for deriving the site response becomes poor approximation. However, waveform deconvolution techniques allow determination of the

  12. Induced Seismicity Monitoring System (United States)

    Taylor, S. R.; Jarpe, S.; Harben, P.


    There are many seismological aspects associated with monitoring of permanent storage of carbon dioxide (CO2) in geologic formations. Many of these include monitoring underground gas migration through detailed tomographic studies of rock properties, integrity of the cap rock and micro seismicity with time. These types of studies require expensive deployments of surface and borehole sensors in the vicinity of the CO2 injection wells. Another problem that may exist in CO2 sequestration fields is the potential for damaging induced seismicity associated with fluid injection into the geologic reservoir. Seismic hazard monitoring in CO2 sequestration fields requires a seismic network over a spatially larger region possibly having stations in remote settings. Expensive observatory-grade seismic systems are not necessary for seismic hazard deployments or small-scale tomographic studies. Hazard monitoring requires accurate location of induced seismicity to magnitude levels only slightly less than that which can be felt at the surface (e.g. magnitude 1), and the frequencies of interest for tomographic analysis are ~1 Hz and greater. We have developed a seismo/acoustic smart sensor system that can achieve the goals necessary for induced seismicity monitoring in CO2 sequestration fields. The unit is inexpensive, lightweight, easy to deploy, can operate remotely under harsh conditions and features 9 channels of recording (currently 3C 4.5 Hz geophone, MEMS accelerometer and microphone). An on-board processor allows for satellite transmission of parameter data to a processing center. Continuous or event-detected data is kept on two removable flash SD cards of up to 64+ Gbytes each. If available, data can be transmitted via cell phone modem or picked up via site visits. Low-power consumption allows for autonomous operation using only a 10 watt solar panel and a gel-cell battery. The system has been successfully tested for long-term (> 6 months) remote operations over a wide range

  13. Sources of high frequency seismic noise: insights from a dense network of ~250 stations in northern Alsace (France) (United States)

    Vergne, Jerome; Blachet, Antoine; Lehujeur, Maximilien


    Monitoring local or regional seismic activity requires stations having a low level of background seismic noise at frequencies higher than few tenths of Hertz. Network operators are well aware that the seismic quality of a site depends on several aspects, among them its geological setting and the proximity of roads, railways, industries or trees. Often, the impact of each noise source is only qualitatively known which precludes estimating the quality of potential future sites before they are tested or installed. Here, we want to take advantage of a very dense temporary network deployed in Northern Alsace (France) to assess the effect of various kinds of potential sources on the level of seismic noise observed in the frequency range 0.2-50 Hz. In September 2014, more than 250 seismic stations (FairfieldNodal@ Zland nodes with 10Hz vertical geophone) have been installed every 1.5 km over a ~25km diameter disc centred on the deep geothermal sites of Soultz-sous-Forêts and Rittershoffen. This region exhibits variable degrees of human imprints from quite remote areas to sectors with high traffic roads and big villages. It also encompasses both the deep sedimentary basin of the Rhine graben and the piedmont of the Vosges massif with exposed bedrock. For each site we processed the continuous data to estimate probability density functions of the power spectral densities. At frequencies higher than 1 Hz most sites show a clear temporal modulation of seismic noise related to human activity with the well-known variations between day and night and between weekdays and weekends. Moreover we observe a clear evolution of the spatial distribution of seismic noise levels with frequency. Basically, between 0.5 and 4 Hz the geological setting modulates the level of seismic noise. At higher frequencies, the amplitude of seismic noise appears mostly related to the distance to nearby roads. Based on road maps and traffic estimation, a forward approach is performed to model the induced

  14. Remote Borehole Strainmeter Sites: Power system optimization improves data quality and increases equipment uptime (United States)

    Pyatt, C.; Van Boskirk, E.; Gallaher, W.; Hodgkinson, K. M.; Henderson, D. B.; Gottlieb, M. H.; Johnson, W.; Fox, O.; Mencin, D.; Mattioli, G.


    The Earthscope Plate Boundary Observatory (PBO) Borehole strainmeter network consists of 74 sites, spanning the west coast of North America from Anza, California to Vancouver Island, British Columbia. Several instruments are installed at each site (including Gladwin Tensor Strainmeter, 3-component geophone, barometer, and rain gauge), with associated data storage and communications equipment. Selected sites also are co-located with high-precision GPS, tiltmeter, pore pressure sensor and metpack. The peak load for a site with VSAT communications is approximately 65W. Most sites are AC powered with battery backup systems. 21 sites are located in remote areas where AC power is unavailable; of these, 18 use solar panels and batteries as the primary power source. During O&M phase of PBO, two issues have brought the borehole solar sites into focus. First, most solar sites cannot continuously operate throughout the winter months because of inclement weather and local topography that blocks the solar array, which results in data loss. Second, high frequency noise is introduced into the instrument data stream by the solar charging system. Reducing noise levels at higher frequencies would decrease the detection threshold for short term transients, such as aseismic creep events, thus allowing researchers to leverage the overlap between simultaneous seismometer and strainmeter observations. Several improvements have been made to optimize the power system as well as decrease noise. TriStar TS-MPPT-60 solar controllers have been installed, which optimize solar flux by tracking and responding to the solar array maximum power point. The battery charge algorithm is designed to provide gains of up to 15% efficiency during winter months. In addition, the new solar controllers have been engineered to limit noise, and also feature remote network interfaces and data logging capability. For those sites where topography impacts the function of the solar power system, methanol fuel cells

  15. Booming Sand Dunes (United States)

    Vriend, Nathalie

    "Booming" sand dunes are able to produce low-frequency sound that resembles a pure note from a music instrument. The sound has a dominant audible frequency (70-105 Hz) and several higher harmonics and may be heard from far distances away. A natural or induced avalanche from a slip face of the booming dune triggers the emission that may last for several minutes. There are various references in travel literature to the phenomenon, but to date no scientific explanation covered all field observations. This thesis introduces a new physical model that describes the phenomenon of booming dunes. The waveguide model explains the selection of the booming frequency and the amplification of the sound in terms of constructive interference in a confined geometry. The frequency of the booming is a direct function of the dimensions and velocities in the waveguide. The higher harmonics are related to the higher modes of propagation in the waveguide. The experimental validation includes quantitative field research at the booming dunes of the Mojave Desert and Death Valley National Park. Microphone and geophone recordings of the acoustic and seismic emission show a variation of booming frequency in space and time. The analysis of the sensor data quantifies wave propagation characteristics such as speed, dispersion, and nonlinear effects and allows the distinction between the source mechanism of the booming and the booming itself. The migration of sand dunes results from a complicated interplay between dune building, wind regime, and precipitation. The morphological and morphodynamical characteristics of two field locations are analyzed with various geophysical techniques. Ground-penetrating radar images the subsurface structure of the dunes and reveal a natural, internal layering that is directly related to the history of dune migration. The seismic velocity increases abruptly with depth and gradually increases with downhill position due to compaction. Sand sampling shows local

  16. Surface-Wave Tomography of Yucca Flat, Nevada (United States)

    Toney, L. D.; Abbott, R. E.; Knox, H. A.; Preston, L. A.; Hoots, C. R.


    In 2015, Sandia National Laboratories conducted an active-source seismic survey of Yucca Flat, Nevada, on the Nevada National Security Site. The Yucca Flat basin hosted over 900 nuclear tests between 1951 and 1992. Data from this survey will help characterize seismic propagation effects of the area, informing models for the next phase of the Source Physics Experiments. The survey source was a 13,000-kg weight-drop at 91 locations along a 19-km N-S transect and 56 locations along an 11-km E-W transect. Over 350 three-component 2-Hz geophones were variably spaced at 10, 20, and 100 m along each line. We employed roll-along survey geometry to ensure 10-m receiver spacing within 2 km of the source. Phase velocity surface-wave analysis via the refraction-microtremor (ReMi) method was previously performed on this data in order to obtain an S-wave velocity model of the subsurface. However, the results of this approach were significantly impacted in areas where ray paths were proximate to underground nuclear tests, resulting in a spatially incomplete model. We have processed the same data utilizing group velocities and the multiple filter technique (MFT), with the hope that the propagation of wave groups is less impacted by the disrupted media surrounding former tests. We created a set of 30 Gaussian band-pass filters with scaled relative passbands and central frequencies ranging from 1 to 50 Hz. We picked fundamental Rayleigh wave arrivals from the filtered data; these picks were then inverted for 2D S-wave velocity along the transects. The new S-wave velocity model will be integrated with previous P-wave tomographic results to yield a more complete model of the subsurface structure of Yucca Flat. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  17. The scientific objectives and program of the Japanese offshore methane hydrate production test (United States)

    Yamamoto, K.; Fujii, T.; Noguchi, S.; Nagao, J.


    -hole geophysical logging before and after the production test. A geophone array in an ocean bottom cable (OBC) will be deployed for a multi-component and time-lapse seismic survey on the seafloor. During the flow test, water and gas production rates, downhole temperature and pressure will be monitored. Comparison between actual well response and computed value from the numerical model will correct and improve our knowledge about reservoir characters and forecast of long-term productivity. JOGMEC, AIST and related scientists and engineers analyze the data to make unseen underground processes visible.;

  18. Large-N in Volcano Settings: Volcanosri (United States)

    Lees, J. M.; Song, W.; Xing, G.; Vick, S.; Phillips, D.


    We seek a paradigm shift in the approach we take on volcano monitoring where the compromise from high fidelity to large numbers of sensors is used to increase coverage and resolution. Accessibility, danger and the risk of equipment loss requires that we develop systems that are independent and inexpensive. Furthermore, rather than simply record data on hard disk for later analysis we desire a system that will work autonomously, capitalizing on wireless technology and in field network analysis. To this end we are currently producing a low cost seismic array which will incorporate, at the very basic level, seismological tools for first cut analysis of a volcano in crises mode. At the advanced end we expect to perform tomographic inversions in the network in near real time. Geophone (4 Hz) sensors connected to a low cost recording system will be installed on an active volcano where triggering earthquake location and velocity analysis will take place independent of human interaction. Stations are designed to be inexpensive and possibly disposable. In one of the first implementations the seismic nodes consist of an Arduino Due processor board with an attached Seismic Shield. The Arduino Due processor board contains an Atmel SAM3X8E ARM Cortex-M3 CPU. This 32 bit 84 MHz processor can filter and perform coarse seismic event detection on a 1600 sample signal in fewer than 200 milliseconds. The Seismic Shield contains a GPS module, 900 MHz high power mesh network radio, SD card, seismic amplifier, and 24 bit ADC. External sensors can be attached to either this 24-bit ADC or to the internal multichannel 12 bit ADC contained on the Arduino Due processor board. This allows the node to support attachment of multiple sensors. By utilizing a high-speed 32 bit processor complex signal processing tasks can be performed simultaneously on multiple sensors. Using a 10 W solar panel, second system being developed can run autonomously and collect data on 3 channels at 100Hz for 6 months

  19. Joint Geophysical Assessments of Geothermal Potential from a Deep Borehole in the Canadian Shield Rocks of NE Alberta (United States)

    Chan, J.; Schmitt, D. R.; Kueck, J.; Moeck, I. S.


    Part of the feasibility study for geothermal development in Northern Alberta consists of investigating the presence of subsurface fluid pathways in the crystalline basement rocks. The deepest borehole drilled in Northeastern Alberta has a depth of 2350 m and offers substantial depth coverage to study the basement rocks. Due to the limited cores available for this deep borehole, a comprehensive suite of geophysical logs and borehole seismic methods are used to provide subsurface characterization of the basement in addition to the existing surface seismic reflection data. Interpretation of the geophysical logs indicate potential fracture zones at different depths that could serve as zones with enhanced fluid potential - a necessary component for any geothermal systems to be viable. Fractures within the subsurface tend to be aligned by the deviatoric stress in the subsurface and their orientations can be imaged using the Formation MicroImager (FMI) log. Two sets of vertical seismic profiles (VSP) were acquired in the deep borehole in July 2011. First, a high resolution zero-offset VSP was acquired to measure the seismic responses at the borehole. Upgoing tube waves can be identified and attributed to fracture zones interpreted from the geophysical logs. Since VSP data contains higher frequency content, the final corridor stack from the zero-offset VSP offers greater resolution in correlating seismic reflections with the primary reflectors and multiples interpreted from the surface seismic reflection data. The second set of VSP data is a multi-azimuth, multi-depth walk-away VSP acquired using three-component receivers placed at depths of 800 and 1780 m. The degree of seismic anisotropy in the crystalline basement can be revealed by analyzing the first arrivals at different geophone depths. Using an assumption that the presence of fractures causes P-wave reflection anisotropy, interpretation from the walk-away VSP can be used as a method for gross fracture detection

  20. Joint Cross Well and Single Well Seismic Studies at Lost Hills, California

    Energy Technology Data Exchange (ETDEWEB)

    Gritto, Roland; Daley, Thomas M.; Myer, Larry R.


    A series of time-lapse seismic cross well and single well experiments were conducted in a diatomite reservoir to monitor the injection of CO{sub 2} into a hydrofracture zone, based on P- and S-wave data. A high-frequency piezo-electric P-wave source and an orbital-vibrator S-wave source were used to generate waves that were recorded by hydrophones as well as three-component geophones. The injection well was located about 12 m from the source well. During the pre-injection phase water was injected into the hydrofrac-zone. The set of seismic experiments was repeated after a time interval of 7 months during which CO{sub 2} was injected into the hydrofractured zone. The questions to be answered ranged from the detectability of the geologic structure in the diatomic reservoir to the detectability of CO{sub 2} within the hydrofracture. Furthermore it was intended to determine which experiment (cross well or single well) is best suited to resolve these features. During the pre-injection experiment, the P-wave velocities exhibited relatively low values between 1700-1900 m/s, which decreased to 1600-1800 m/s during the post-injection phase (-5%). The analysis of the pre-injection S-wave data revealed slow S-wave velocities between 600-800 m/s, while the post-injection data revealed velocities between 500-700 m/s (-6%). These velocity estimates produced high Poisson ratios between 0.36 and 0.46 for this highly porous ({approx} 50%) material. Differencing post- and pre-injection data revealed an increase in Poisson ratio of up to 5%. Both, velocity and Poisson estimates indicate the dissolution of CO{sub 2} in the liquid phase of the reservoir accompanied by a pore-pressure increase. The single well data supported the findings of the cross well experiments. P- and S-wave velocities as well as Poisson ratios were comparable to the estimates of the cross well data. The cross well experiment did not detect the presence of the hydrofracture but appeared to be sensitive to overall

  1. A Type of Non-cable Self-Posioning Seismograph Served For SinoProbe Project In China (United States)

    Yang, H.; Lin, J.; Chen, Z.; Zhang, L.; Huaizhu, Z.; Zheng, F.; Seismic Instrument Design Team


    A type of cableless self-positioning telemetry seismograph designed for deep exploration is introduced in this article. The seismograph adopts 24-bit ADC and the analog circuits are designed carefully to attain a low noise level of 300nV RMS. It also uses 24-bit DAC and FPGA circuits to perform self-test including noise level, trace crosstalk, CMRR, harmonic distortion, geophone resitor testing, pulse testing, gain calibration and etc. As the testing result shows, the analog acquisition performances are similar to the most popular seismograph 428XL system from Sercel. However, the seismograph has a different structure with 428XL. It gets rid of cables and stores seismic data in mass non-volatile memory, and meanwhile it employs GPS combined with Compass global navigation satellite system to implement synchronous data aquisiton and self-positioning. In addition, the seismograph has a built-in WiFi module and can communicate with a cental server in Ad-hoc mode or AP mode depending on the distance between the seismograph and the central server. The working status and seismic data quality can be monitored through the WiFi network and some seismic data can be transmitted back on demand. When the distance between adjacent seismographs exceed 500 metres, the Compass global navigation satellite system which supports global communication can be used to send necessary data. At last, dynamic power management is emplyed and the system working voltage and frequency will be changed as the system runs into different status, and also all circuit modules can be switched off when not needed. Because of all the benefits listed above, the seismograph can be used in a variety of ways as needed, such as seismic network, deep seismic reflection exploration, wide-angle seismic reflection and refraction exploration, ore zone seismic exploration and etc. To sum up, the cable-less self-positioning seismograph employs mass non-volatile storage technology, global navigation satellite sytem, Wi

  2. An Early Warning System from debris flows based on ground vibration monitoring data (United States)

    Arattano, Massimo; Coviello, Velio


    -2014. The algorithm is based on the real time processing of ground vibration data detected by three vertical geophones. During the testing period, two debris flow events occurred that were both correctly detected by the algorithm with a relatively limited number of false alarms.

  3. Investigation of the heat source(s) of the Surprise Valley Geothermal System, Northern California (United States)

    Tanner, N.; Holt, C. D.; Hawkes, S.; McClain, J. S.; Safford, L.; Mink, L. L.; Rose, C.; Zierenberg, R. A.


    Concerns about environmental impacts and energy security have led to an increased interest in sustainable and renewable energy resources, including geothermal systems. It is essential to know the permeability structure and possible heat source(s) of a geothermal area in order to assess the capacity and extent of the potential resource. We have undertaken geophysical surveys at the Surprise Valley Hot Springs in Cedarville, California to characterize essential parameters related to a fault-controlled geothermal system. At present, the heat source(s) for the system are unknown. Igneous bodies in the area are likely too old to have retained enough heat to supply the system, so it is probable that fracture networks provide heat from some deeper or more distributed heat sources. However, the fracture system and permeability structure remain enigmatic. The goal of our research is to identify the pathways for fluid transport within the Surprise Valley geothermal system using a combination of geophysical methods including active seismic surveys and short- and long-period magnetotelluric (MT) surveys. We have collected 14 spreads, consisting of 24 geophones each, of active-source seismic data. We used a "Betsy Gun" source at 8 to 12 locations along each spread and have collected and analyzed about 2800 shot-receiver pairs. Seismic velocities reveal shallow lake sediments, as well as velocities consistent with porous basalts. The latter, with velocities of greater than 3.0 km/s, lie along strike with known hot springs and faulted and tilted basalt outcrops outside our field area. This suggests that basalts may provide a permeable pathway through impermeable lake deposits. We conducted short-period (10Hz-60kHz) MT measurements at 33 stations. Our short-period MT models indicate shallow resistive blocks (>100Ωm) with a thin cover of more conductive sediments ( 10Ωm) at the surface. Hot springs are located in gaps between resistive blocks and are connected to deeper low

  4. Location and Shallow Structure of the Frijoles Strand of the San Gregorio Fault Zone, Pescadero, California (United States)

    Fox-Lent, C.; Catchings, R. D.; Rymer, M. J.; Goldman, M. R.; Steedman, C. E.; Prentice, C. S.


    The San Gregorio fault is one of the principal faults of the San Andreas fault system in the San Francisco Bay area. Located west of the active trace of the San Andreas fault and near the coast, the San Gregorio fault zone consists of at least two northwest-southeast-trending strands, the Coastways and Frijoles faults. Little is known about the slip history on the San Gregorio, and information for the Frijoles fault is especially scarce, as it lies mostly offshore. To better understand the contribution of the San Gregorio fault zone to slip along the San Andreas fault system, we conducted a high-resolution, seismic imaging investigation of the Frijoles fault to locate near-surface, onshore, branches of the fault that may be suitable for paleoseismic trenching. Our seismic survey consisted of a 590-meter-long, east-west-trending, combined seismic reflection and refraction profile across Butano Creek Valley, in Pescadero, California. The profile included 107 shot points and 120 geophones spaced at 5-m increments. Seismic sources were generated by a Betsy Seisgun in 0.3-m-deep holes. Data were recorded on two Geometrics Strataview RX-60 seismographs at a sampling rate of 0.5 ms. Seismic p-wave velocities, determined by inverting first-arrival refractions using tomographic methods, ranged from 900 m/s in the shallow subsurface to 5000 m/s at 200 m depth, with higher velocities in the western half of the profile. Migrated seismic reflection images show clear, planar layering in the top 100-200 meters on the eastern and western ends of the seismic profile. However, to within the shallow subsurface, a 200-m-long zone near the center of the profile shows disturbed stratigraphic layers with several apparent fault strands approaching within a few meters of the surface. The near-surface locations of the imaged strands suggest that the Frijoles fault has been active in the recent past, although further paleoseismic study is needed to detail the slip history of the San Gregorio

  5. Monitoring the Methane Hydrate Dissociation by the Offshore Methane Hydrate Production Tests using Multi-component Seismic (United States)

    Asakawa, Eiichi; Hayashi, Tsutomu; Tsukahara, Hitoshi; Takahashi, Hiroo; Saeki, Tatsuo


    We developed a new OBC (Ocean Bottom Cable), named as 'DSS' (Deep-sea Seismic System). The sensor has 3-component accelerometer and a hydrophone applicable for four-component (4C) seismic survey. Using the DSS, the methane hydrate dissociation zone will be tried to be monitored at the water depth of around 1000m during JOGMEC offshore methane hydrate production test in early 2013. Before the DSS, we had developed the RSCS (Real-time Seismic Cable System) with 3-component gimbaled geophones, and carried out a reflection seismic survey in the Nankai Trough in 2006. Referring this successful survey, we improved the RSCS to the DSS. The receiver size is reduced to 2/3 and the receiver case has a protective metallic exterior and the cable is protected with steel-screened armouring, allowing burial usage using ROV for sub-seabed deployment at the water depth up to 2000m. It will realize a unique survey style that leaves the system on the seabed between pre-test baseline survey and post-test repeated surveys, which might be up to 6 months. The fixed location of the receiver is very important for time-lapse monitoring survey. The DSS has totally 36 sensors and the sensor spacing is 26.5m. The total length is about 1km. We carried out the pre-test baseline survey between off Atsumi and Shima-peninsula in August, 2012.We located the DSS close to the production test well. The nearest sensor is 63m apart from the well. A newly developed real-time 3-D laying simulation system consisting of ADCP (Acoustic Doppler Current Profiler), transponders attached to the DSS, and real-time 3-D plotting system for transponder locations have been adopted. After we laid the cable, we buried the DSS using ROV (Remotely Operated Vehicle). The baseline survey included 2D/3D seismic surveys with shooting vessel and cable laying/observation ship. The resultant 2D section and 3D volume shows the good quality to delineate the methane hydrate concentrated zone. After the baseline survey, we have left

  6. Development of Ocean Bottom Multi-component Seismic System for Methane Hydrate Dissociation Monitoring (United States)

    Takahashi, H.; Asakawa, E.; Hayashi, T.; Inamori, T.; Saeki, T.


    A 2D multi-component seismic survey was carried out in the Nankai Trough using the RSCS (Real-time Seismic Cable System) system in 2006. The RSCS is the newly developed ocean bottom cable system which is usable in more than 2000m water depth. The results of the PP and data PS components gave us much information of the methane hydrates bearing zone. Based on RSCS technology, we are developing a new monitoring system using multi-component seismic sensors to delineate the methane hydrate dissociation zone for the offshore methane hydrate production test scheduled in FY2012. Conventional RSCS is composed of three component gimbaled geophones which require a large volume inside the receiver. We will adopt accelerometers to achieve a small receiver that is 2/3 the size of conventional RSCS. The accelerometer data can be corrected into horizontal or vertical directions based on the gravity acceleration. The receiver case has a protective metallic exterior and the cable is protected with steel-screened armoring, allowing for burial usage using ROV for sub-seabed deployment. It will realize a unique survey style that leaves the system on the seabed between pre-test baseline survey and post-test repeated survey, which might be up to 6 months. The fixed location of the receiver is very important for time-lapse monitoring survey. We name the new system as DSS (Deep-sea Seismic System). A feasibility study to detect the methane hydrate dissociation with the DSS was carried out and we found that the methane hydrate dissociation could be detected with the DSS depending on the area of the dissociation. The first experiment of the DSS performance test in a marine area is planned in November 2011. The main features of DSS are described as follows: (1) Deep-sea /Ultra Deep-sea Operation Methane hydrate exists in equilibrium temperature and pressure holds at water depths greater than 500m. The system water depth resistance target up to 2000m. The receiver case has a protective

  7. Ambient noise tomography for characterize the subsoil structure below a collapsed mine. Integration with 3D models of electric resistivity tomography and micro-gravity data inversion (United States)

    Cárdenas-Soto, M.; Tejero, A.; Nava-Flores, M.; Zenil, D. E.; Vidal-Garcia, M.; Garcia-Serrano, A.


    In this work we build 3D Vs models using seismic tomography of ambient noise. The goal is to characterize the subsurface structure in order to explore the causes of a sudden mine collapse in the 2nd section of Chapultepec park, Mexico City, near to a recreation lake whose subsoil is composed of vulcano-sedimentary materials that were economically exploited in the mid-20th century, leaving a series of underground mines that were rehabilitated for the construction of the Park. In this site we record ambient noise continuously at a 250 Hz sampling rate by intervals of 30 min in three arrays of quadrangular shape with 64 - 4.5 Hz vertical geophones separated 2m. In order to confront the seismic interferometry results, we also obtain 3D models derivated from Electrical Resistivity Tomography (ERT), and inverted surface micro-gravity data. The correlograms show a well defined pulse for those pairs of receivers whose backazimut is perpendicular to the beltway, which is the main source that generates ambient noise. We show that pulses had a dispersive character due to that define a dispersion curve (fundamental mode of Rayleigh wave) whose velocity values are close to 700 m/s at a frequency of 5 Hz, and tend to average values of 380 m/s in frequencies close to 16 Hz. Then, we build tomography images from the maximum time of the envelope pulse filtering in 18 center frequencies between 4 to 16 Hz. Through the relationship f=Vs/4z we create a 3D model in function of the seudo-depth (z). This model allows to distinguish the irregularity of the subsoil around the mine colapse (5m depth), which underlies a competent structure (Vs>450 m/s) surrounded by vulcano sedimentary material with low Vs values (200 m/s). ERT model show that the low velocity zones are associated with saturation areas, result that is corroborated by low-density values derived from micro-gravity model. The results indicate that the collapse was produced by the hydrostatic imbalance of the competent materials

  8. Geophysical Exploration of Faults, Fissures, and Fractures at Four Sites in Mexicali, Baja California, Mexico (United States)

    Lázaro-Mancilla, O.; Gonzalez-Fernandez, A.; Contreras-Corvera, A.; Stock, J. M.; Moreno-Ayala, D.; Ramirez-Hernandez, J.; Carreon-Diazconti, C.; Lopez, D. A. L.; Lopez, J. R.


    We conducted field geophysical measurements in areas in the City of Mexicali that are associated with geological faults, fissures, and fractures. The study sites are: 1) Instituto Tecnologico de Mexicali 2) The buried trace of the Michoacan de Ocampo fault in the urban zone 3) Rio Nuevo 4) A site reported by Frez (2013) with ground rupture SW of Cerro Prieto At Site 1, seismic reflection profiling used a cable with 24 geophones at 1 m spacing. The source was a 3.6 kg sledge hammer, with 3 impacts per shot point. 347 shot points at 2 m spacing provided 6 fold coverage along a straight line with minimal elevation changes. Sample rate was 2000/s, and record length 1 s; reflections were seen down to 0.3 s TWTT. Processing included: frequency filter, fk filter, predictive deconvolution, geometry, velocity analysis, NMO and stacking. Lateral changes in the seismic section are due to surface modification and/or the presence of faults.At site 2, we measured 222Radon in 36 locations along 17 profiles across the fault, using inherent alpha spectrometry with a Durridge RAD7 detector. Each site was measured at a depth of 60 cm, with 31 five-minute readings in a 3 hour period, interspersed with 10 minute of background purge and 3 five-minute background measurements. In a profile parallel to the fault, 78% of the readings were > 100 pCi/L, confirming the presence of the fault along the swath surveyed. At Site 3 we compiled observations of post-earthquake cracks, conducted reconnaissance, and measured some profiles using 100 MHz GPR. These observations showed that the cracks are associated with ground failure due to earthquake shaking. At Site 4 our new 222Radon gas measurements complemented a pre-existing profile that had high 222Radon values lacking a structural explanation. Related to this we found that this region has two NW-SE trending features: a magnetic anomaly low of 360 nT (Evans, Summer and Castillo, 1972) and a graben reported by the Mexican Geological Survey in 2003

  9. A Pilot Experiment in Collaborative Science and Engineering (United States)

    Steidl, J. H.; GVDA Working Group


    a profile across the basin, we also collected reflection data generated by TRex recorded on densely spaced geophone strings, and conducted a sledge-hammer survey at even higher resolution to confirm the location of a suspected buried fault. For the fourth study, we assess the potential for shakers like TRex to do broad-scale, deep imaging as we stack TRex signals emitted repeatedly for nearly an hour, recorded on stations of the regional ANZA and statewide California Integrated Seismic Networks.

  10. On the potential of seismic rotational motion measurements for extraterrestrial seismology (United States)

    Schmelzbach, Cedric; Sollberger, David; Khan, Amir; Greenhalgh, Stewart; Van Renterghem, Cederic; Robertsson, Johan


    Classically, seismological recordings consist of measurements of translational ground motion only. However, in addition to three vector components of translation there are three components of rotation to consider, leading to six degrees of freedom. Of particular interest is thereby the fact that measuring rotational motion means isolating shear (S) waves. Recording the rotational motion requires dedicated rotational sensors. Alternatively, since the rotational motion is given by the curl of the vectorial displacements, the rotational motion around the two horizontal axes can be computed from the horizontal spatial gradients of vertical translational recordings if standard translational seismometers are placed in an areal array at the free surface. This follows from the zero stress free surface condition. Combining rotational and translational motion measurements opens up new ways of analyzing seismic data, such as facilitating much improved arrival identification and wavefield separation (e.g., P-/S-wave separation), and local slowness (arrival direction and velocity) determination. Such combined measurements maximize the seismic information content that a single six-component station or a small station array can provide, and are of particular interest for sparse or single-station measurements such as in extraterrestrial seismology. We demonstrate the value of the analysis of combined translational and rotational recordings by re-evaluating data from the Apollo 17 lunar seismic profiling experiment (LSPE). The LSPE setup consisted of four vertical-component geophones arranged in a star-like geometry. This areal receiver layout enables computing the horizontal spatial gradients by spatial finite differencing of the vertical-component data for two perpendicular directions and, hence, the estimation of rotational motion around two horizontal axes. Specifically, the recorded seismic waveform data originated from eight explosive packages as well as from continuously

  11. Theory of supervirtual refraction interferometry

    KAUST Repository

    Bharadwaj, Pawan


    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

  12. Electrode Response in Seismo-Electric Measurements (United States)

    Dietrich, M.; Devi, M. S.; Cougoulat, G.; Garambois, S.


    Seismo-electric measurements consist in recording the transient electric fields generated by seismic waves propagating in fluid-filled porous or fractured media. These electric fields are usually measured by voltage differences between two electrodes. Unfortunately, the electrode spacing and their locations on the ground surface have a direct influence on the signal-to-noise ratio of the measurements, on the recorded waveforms and on their arrival times. Using a filter theory approach and full waveform numerical simulations of the coupled seismic and electromagnetic (EM) wave propagation in porous media, we show that the co-seismic electric arrivals and the small-amplitude EM interface response can be severely distorted and/or attenuated by conventional surface electrode layouts. To this end, we have computed synthetic electrograms providing the electric potential, to allow us to determine voltage differences between two arbitrary locations of electrodes. Unlike the low-pass filter obtained by connecting two geophones in series, the filter associated with a voltage difference is shown to be a band-pass filter. As a result, not only horizontally and obliquely propagating waves but also vertically propagating waves undergo selective frequency attenuation in the 0-150 Hz frequency band used in field measurements. It also turns out that electrode spacing cannot be optimized to enhance the electric signature of typical seismic reflections and EM interface response, neither with horizontal dipoles nor with reasonably sized vertical dipoles. To circumvent this problem, we consider arrangements of 3 and 5 electrodes analogous to multilayer capacitors in electronics. We show that such arrangements are ideally described by low-pass filters preserving the quasi-plane waves corresponding to the EM interface response. However, in reality, these benefits are challenged by the imperfect coupling between the electrodes and the ground, represented by an electrode contact resistance

  13. The Geomechanics of CO2 Storage in Deep Sedimentary Formations

    Energy Technology Data Exchange (ETDEWEB)

    Rutqvist, Jonny [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)


    This study provides a review of the geomechanics and modeling of geomechanics associated with geologic carbon storage (GCS), focusing on storage in deep sedimentary formations, in particular saline aquifers. The paper first introduces the concept of storage in deep sedimentary formations, the geomechanical processes and issues related with such an operation, and the relevant geomechanical modeling tools. This is followed by a more detailed review of geomechanical aspects, including reservoir stress-strain and microseismicity, well integrity, caprock sealing performance, and the potential for fault reactivation and notable (felt) seismic events. Geomechanical observations at current GCS field deployments, mainly at the In Salah CO2 storage project in Algeria, are also integrated into the review. The In Salah project, with its injection into a relatively thin, low-permeability sandstone is an excellent analogue to the saline aquifers that might be used for large scale GCS in parts of Northwest Europe, the U.S. Midwest, and China. Some of the lessons learned at In Salah related to geomechanics are discussed, including how monitoring of geomechanical responses is used for detecting subsurface geomechanical changes and tracking fluid movements, and how such monitoring and geomechanical analyses have led to preventative changes in the injection parameters. Recently, the importance of geomechanics has become more widely recognized among GCS stakeholders, especially with respect to the potential for triggering notable (felt) seismic events and how such events could impact the long-term integrity of a CO2 repository (as well as how it could impact the public perception of GCS). As described in the paper, to date, no notable seismic event has been reported from any of the current CO2 storage projects, although some unfelt microseismic activities have been detected by geophones. However, potential future commercial GCS operations from large

  14. Testing seismic amplitude source location for fast debris-flow detection at Illgraben, Switzerland (United States)

    Walter, Fabian; Burtin, Arnaud; McArdell, Brian W.; Hovius, Niels; Weder, Bianca; Turowski, Jens M.


    Heavy precipitation can mobilize tens to hundreds of thousands of cubic meters of sediment in steep Alpine torrents in a short time. The resulting debris flows (mixtures of water, sediment and boulders) move downstream with velocities of several meters per second and have a high destruction potential. Warning protocols for affected communities rely on raising awareness about the debris-flow threat, precipitation monitoring and rapid detection methods. The latter, in particular, is a challenge because debris-flow-prone torrents have their catchments in steep and inaccessible terrain, where instrumentation is difficult to install and maintain. Here we test amplitude source location (ASL) as a processing scheme for seismic network data for early warning purposes. We use debris-flow and noise seismograms from the Illgraben catchment, Switzerland, a torrent system which produces several debris-flow events per year. Automatic in situ detection is currently based on geophones mounted on concrete check dams and radar stage sensors suspended above the channel. The ASL approach has the advantage that it uses seismometers, which can be installed at more accessible locations where a stable connection to mobile phone networks is available for data communication. Our ASL processing uses time-averaged ground vibration amplitudes to estimate the location of the debris-flow front. Applied to continuous data streams, inversion of the seismic amplitude decay throughout the network is robust and efficient, requires no manual identification of seismic phase arrivals and eliminates the need for a local seismic velocity model. We apply the ASL technique to a small debris-flow event on 19 July 2011, which was captured with a temporary seismic monitoring network. The processing rapidly detects the debris-flow event half an hour before arrival at the outlet of the torrent and several minutes before detection by the in situ alarm system. An analysis of continuous seismic records furthermore

  15. Automated Sensor Tuning for Seismic Event Detection at a Carbon Capture, Utilization, and Storage Site, Farnsworth Unit, Ochiltree County, Texas (United States)

    Ziegler, A.; Balch, R. S.; Knox, H. A.; Van Wijk, J. W.; Draelos, T.; Peterson, M. G.


    We present results (e.g. seismic detections and STA/LTA detection parameters) from a continuous downhole seismic array in the Farnsworth Field, an oil field in Northern Texas that hosts an ongoing carbon capture, utilization, and storage project. Specifically, we evaluate data from a passive vertical monitoring array consisting of 16 levels of 3-component 15Hz geophones installed in the field and continuously recording since January 2014. This detection database is directly compared to ancillary data (i.e. wellbore pressure) to determine if there is any relationship between seismic observables and CO2 injection and pressure maintenance in the field. Of particular interest is detection of relatively low-amplitude signals constituting long-period long-duration (LPLD) events that may be associated with slow shear-slip analogous to low frequency tectonic tremor. While this category of seismic event provides great insight into dynamic behavior of the pressurized subsurface, it is inherently difficult to detect. To automatically detect seismic events using effective data processing parameters, an automated sensor tuning (AST) algorithm developed by Sandia National Laboratories is being utilized. AST exploits ideas from neuro-dynamic programming (reinforcement learning) to automatically self-tune and determine optimal detection parameter settings. AST adapts in near real-time to changing conditions and automatically self-tune a signal detector to identify (detect) only signals from events of interest, leading to a reduction in the number of missed legitimate event detections and the number of false event detections. Funding for this project is provided by the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) through the Southwest Regional Partnership on Carbon Sequestration (SWP) under Award No. DE-FC26-05NT42591. Additional support has been provided by site operator Chaparral Energy, L.L.C. and Schlumberger Carbon Services. Sandia National

  16. Characterizing Micro- and Macro-Scale Seismicity from Bayou Corne, Louisiana (United States)

    Baig, A. M.; Urbancic, T.; Karimi, S.


    The initiation of felt seismicity in Bayou Corne, Louisiana, coupled with other phenomena detected by residents on the nearby housing development, prompted a call to install a broadband seismic network to monitor subsurface deformation. The initial deployment was in place to characterize the deformation contemporaneous with the formation of a sinkhole located in close proximity to a salt dome. Seismic events generated during this period followed a swarm-like behaviour with moment magnitudes culminating around Mw2.5. However, the seismic data recorded during this sequence suffer from poor signal to noise, onsets that are very difficult to pick, and the presence of a significant amount of energy arriving later in the waveforms. Efforts to understand the complexity in these waveforms are ongoing, and involve invoking the complexities inherent in recording in a highly attenuating swamp overlying a complex three-dimensional structure with the strong material property contrast of the salt dome. In order to understand the event character, as well as to locally lower the completeness threshold of the sequence, a downhole array of 15 Hz sensors was deployed in a newly drilled well around the salt dome. Although the deployment lasted a little over a month in duration, over 1000 events were detected down to moment magnitude -Mw3. Waveform quality tended to be excellent, with very distinct P and S wave arrivals observable across the array for most events. The highest magnitude events were seen as well on the surface network and allowed for the opportunity to observe the complexities introduced by the site effects, while overcoming the saturation effects on the higher-frequency downhole geophones. This hybrid downhole and surface array illustrates how a full picture of subsurface deformation is only made possible by combining the high-frequency downhole instrumentation to see the microseismicity complemented with a broadband array to accurately characterize the source

  17. Seismic Barrier Protection of Critical Infrastructure (United States)

    Haupt, R.; Liberman, V.; Rothschild, M.


    Each year, on average a major magnitude-8 earthquake strikes somewhere in the world. In addition, 10,000 earthquake related deaths occur annually, where collapsing buildings claim by far most lives. Moreover, in recent events, industry activity of oil extraction and wastewater reinjection are suspect to cause earthquake swarms that threaten high-value oil pipeline networks, U.S. oil storage reserves, and civilian homes. Earthquake engineering building structural designs and materials have evolved over many years to minimize the destructive effects of seismic surface waves. However, even under the best engineering practices, significant damage and numbers of fatalities can still occur. In this effort, we present a concept and approach to redirect and attenuate the ground motion amplitudes of earthquake surface waves by implementing an engineered subsurface seismic barrier. The barrier is comprised of a borehole array complex that impedes and diverts destructive surface waves (typically 2-10 km wavelengths). Computational 2D and 3D seismic wave propagation models developed at MIT Lincoln Laboratory suggest that the borehole array arrangement is critical to the redirection and self-interference reduction of broadband hazardous seismic waves in the vicinity of the structure to protect. For validity, the computational models are compared with data obtained from large bench-scale physical models that contain scaled borehole arrays and trenches. Small contact shakers generate elastic waves in solid media, while contact tri-axial accelerometer arrays measure the resultant wave fields. Field tests are presently being conducted to examine the seismic power reduction across a subsurface borehole array generated by controlled, far-field seismic sources. The sources include a weight drop and oriented seismic vibrational sources that generate low frequency surface and body waves. The pre-borehole condition at the site is measured first with a tri-axial geophone arrangement. The

  18. Overview of microseismic monitoring of hydraulic fracturing for unconventional oil and gas plays (United States)

    Shemeta, J. E.


    The exponential growth of unconventional resources for oil and gas production has been driven by the use of horizontal drilling and hydraulic fracturing. These drilling and completion methods increase the contact area of the low permeability and porosity hydrocarbon bearing formations and allow for economic production in what was previously considered uncommercial rock. These new resource plays have sparked an enormous interest in microseismic monitoring of hydraulic fracture treatments. As a hydraulic fracture is pumped, microseismic events are emitted in a volume of rock surrounding the stimulated fracture. The goal of the monitoring is to identify and locate the microseismic events to a high degree of precision and to map the position of the induced hydraulic fracture in time and space. The microseismic events are very small, typically having a moment-magnitude range of -4 to 0. The microseismic data are collected using a variety of seismic array designs and instrumentation, including borehole, shallow borehole, near-surface and surface arrays, using either of three-component clamped 15 Hz borehole sondes to simple vertical 10 Hz geophones for surface monitoring. The collection and processing of these data is currently under rapid technical development. Each monitoring method has technical challenges which include accurate velocity modeling, correct seismic phase identification and signal to noise issues. The microseismic locations are used to guide hydrocarbon exploration and production companies in crucial reservoir development decisions such as the direction to drill the horizontal well bores and the appropriate inter-well spacing between horizontal wells to optimally drain the resource. The fracture mapping is also used to guide fracture and reservoir engineers in designing and calibrating the fluid volumes and types, injection rates and pressures for the hydraulic fracture treatments. The microseismic data can be located and mapped in near real-time during

  19. Rheological behaviour of lahar flow (United States)

    Lafarge, N.; Chambon, G.; Thouret, J. C.; Laigle, D.


    Lahars are mixtures of water and debris flowing down the flanks of volcanoes. These flows generally occur after heavy rainfalls and carry sediments deposited by volcanic eruptions. They are among the most destructive volcanic phenomena, and were responsible, in the 20th century, for 40% of the fatalities associated with volcanic eruptions worldwide. However, the mechanical behaviour and the propagation of these particular debris flows still remain poorly understood. In the frame of the research project Laharisk, Mount Semeru in Java (Indonesia) was chosen as a test site to monitor lahar activity and flows properties owing to the frequent occurrence of lahars on its flanks during the monsoon rainy period. Two observation stations, situated 510 m apart, were installed in the Curah Lengkong Valley on the southeast flank of Semeru volcano. The relatively straight and box-shaped channel between the two stations represents a natural flume well suited to study the hydraulics of the flows. Both stations are equipped with video cameras, pore-pressure and load sensors, AFM geophones, and one broad-band seismometer to measure the evolution over time of lahar flow height, speed, and discharge. Bucket samples are also directly taken in the flows at regular time-intervals in order to provide sediment concentration and grain-size distribution. The rheological behaviour of the material is studied through laboratory vane tests at constant imposed shear rate conducted on the fine-sized fraction (independent of the shear rate. In addition, the friction coefficient increases with sediment concentration. At the scale of the flow, the rheology of the material can also be investigated through the relationship between flow height and discharge in control sections. The obtained relationship has the form of a power law, and is also indicative of a frictional mechanical behaviour. Here also, the concentration appears as an important parameter controlling the rheological behavior of flow

  20. Séparation des ondes P et S à l'aide de la matrice spectrale avec informations à priori The Separation of P and S Waves Using the Spectral Matrix with a Priori Information

    Directory of Open Access Journals (Sweden)

    Mari J. L.


    velocity of the reflected waves. The proposed filtering technique was applied to seismic waves of the offset VSP type. The VSP was recorded in a well between the depths of 1050 and 1755 m. The tool used was a well geophone with three components. The well crossed a complex geological structure. Processing revealed seismic reflections of compressional and shear waves, associated with steeply sloping markers (10 to 25 degrees. Once we have estimated the velocity fields and the dips by means of charts, the depth migration of the picked time horizons provided a faulted structural model. Wave Separation Method - Generally speaking, the filtering technique using the spectral matrix proposed by Mermoz only allows an automatic separation of the waves in the sense of seismic time/distance curves in a number of specific cases, namely when the waves to be separated are naturally aligned with the eigenvectors of the spectral matrix. In the other situations, the introduction of an a priori information on the apparent velocity of some waves and a limitation of their time duration enable to estimate their associated wave vectors. The use of these vectors and a least square projection method lead to an optimal extraction of these waves, without degrading the other waves. In the Fourier domain, for seismic data D (f composed of N recordings, the spectral matrix M consists in N x N components Mk,1(f. This term represents the cross-spectrum averaged between the recordings dk(t and d1(t. The average is introduced to decorrelate the waves. Two types of averaging are routinely used, frequency averaging and distance averaging. Frequency averaging implies a local stationarity of the signals and favors the waves with very high apparent velocities. Distance averaging favors the signals that are coherent on several recordings, regardless of their apparent velocity. We propose a matrix calculated from the recordings modified to optimize the extraction of the desired wave Wi(f. Optimization is carried


    Energy Technology Data Exchange (ETDEWEB)

    Robert Westermark; J. Ford Brett


    This Final Report covers the entire project from July 13, 2000 to June 30, 2003. The report summarizes the details of the work done on the project entitled ''Enhanced Oil Recovery with Downhole Vibration Stimulation in Osage County Oklahoma'' under DOE Contract Number DE-FG26-00BC15191. The project was divided into nine separate tasks. This report is written in an effort to document the lessons learned during the completion of each task. Therefore each task will be discussed as the work evolved for that task throughout the duration of the project. Most of the tasks are being worked on simultaneously, but certain tasks were dependent on earlier tasks being completed. During the three years of project activities, twelve quarterly technical reports were submitted for the project. Many individual topic and task specific reports were included as appendices in the quarterly reports. Ten of these reports have been included as appendices to this final report. Two technical papers, which were written and accepted by the Society of Petroleum Engineers, have also been included as appendices. The three primary goals of the project were to build a downhole vibration tool (DHVT) to be installed in seven inch casing, conduct a field test of vibration stimulation in a mature waterflooded field and evaluate the effects of the vibration on both the produced fluid characteristics and injection well performance. The field test results are as follows: In Phase I of the field test the DHVT performed exceeding well, generating strong clean signals on command and as designed. During this phase Lawrence Berkeley National Laboratory had installed downhole geophones and hydrophones to monitor the signal generated by the downhole vibrator. The signals recorded were strong and clear. Phase II was planned to be ninety-day reservoir stimulation field test. This portion of the field tests was abruptly ended after one week of operations, when the DHVT became stuck in the well

  2. Crust structure of the Northern Margin of North China Craton and adjacent region from Sinoprobe-02 North China seismic WAR/R experiment (United States)

    Li, W.; Gao, R.; Keller, G. R.; Li, Q.; Cox, C. M.; Hou, H.; Guan, Y.


    The Central Asian Orogen Belt (CAOB) or Altaids, situated between the Siberian craton(SC) to the north and north China craton (NCC) with tarim to the south, is one of the world's largest accretionary orogens formed by subduction and accretion of juvenile material from the Neoproterozoic through the Paleozoic. The NCC is the oldest craton in China, which suffered Yanshan intercontinental orogenic process and lithosphere thinning in Mesozoic. In the past 20 years, remarkable studies about this region have been carried out and different tectonic models were proposed, however, some crucial geologic problems remain controversial. In order to obtain better knowledge of deep structure and properties of crust on the northern margin of north China craton, a 450 km long WAR/R section was completed jointly by Institute of Geology, CAGS and University of Oklahoma. Our 450 km long NW-SE WAR/R line extends from west end of the Yanshan orogen, across the Bainaimiao arc, Ondor sum subduction accretion complex to the Solonker suture zone. The recording of seismic waves from 8 explorations was conducted in 4 deployments of 300 reftek-125A records and single-channel 4.5Hz geophones with station spacing of 1km. The shooting procedure was employ 500 or 1500kg explosives in 4-5 or 15-23 boreholes at 40-45m depth. The sampling rate was 100 HZ, and recording time window was 1200s. The P wave field on the sections got high quality data for most part of the profile, but have low signal-to-noise for the south end, where closed to Beijing with a lot of ambient noise from traffic, industry and human activity. Arrivals from of refracted and reflected waves from sediments and basement (Pg), intracrust (Pcp, Plp) and Moho (Pmp) were typically observed, but Pn phase through the upper most mantle was only observed for 2 shots. Identification and correlation of seismic phases was done manually on computer screen Zplot software. Each trace has been bandpass filtered (1-20Hz) and normalized with AGC

  3. Seismic Technology Adapted to Analyzing and Developing Geothermal Systems Below Surface-Exposed High-Velocity Rocks Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; DeAngelo, Michael V. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Ermolaeva, Elena [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Remington, Randy [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Sava, Diana [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wagner, Donald [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wei, Shuijion [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology


    The objective of our research was to develop and demonstrate seismic data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component seismic test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. Seismic contractors have not succeeded in creating good-quality seismic data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sediment were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the boundaries of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled seismic data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the boundaries of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave seismic data for geothermal

  4. Investigation of ULF magnetic pulsations, air conductivity changes, and infra red signatures associated with the 30 October Alum Rock M5.4 earthquake

    Directory of Open Access Journals (Sweden)

    T. Bleier


    Full Text Available Several electromagnetic signal types were observed prior to and immediately after 30 October 2007 (Local Time M5.4 earthquake at Alum Rock, Ca with an epicenter ~15 km NE of San Jose Ca. The area where this event occurred had been monitored since November 2005 by a QuakeFinder magnetometer site, unit 609, 2 km from the epicenter. This instrument is one of 53 stations of the QuakeFinder (QF California Magnetometer Network-CalMagNet. This station included an ultra low frequency (ULF 3-axis induction magnetometer, a simple air conductivity sensor to measure relative airborne ion concentrations, and a geophone to identify the arrival of the P-wave from an earthquake. Similar in frequency content to the increased ULF activity reported two weeks prior to the Loma Prieta M7.0 quake in 1989 (Fraser-Smith, 1990, 1991, the QF station detected activity in the 0.01–12 Hz bands, but it consisted of an increasing number of short duration (1 to 30 s duration pulsations. The pulsations peaked around 13 days prior to the event. The amplitudes of the pulses were strong, (3–20 nT, compared to the average ambient noise at the site, (10–250 pT, which included a component arising from the Bay Area Rapid Transit (BART operations. The QF station also detected different pulse shapes, e.g. negative or positive only polarity, with some pulses including a combination of positive and negative. Typical pulse counts over the previous year ranged from 0–15 per day, while the count rose to 176 (east-west channel on 17 October, 13 days prior to the quake. The air conductivity sensor saturated for over 14 h during the night and morning prior to the quake, which occurred at 20:29 LT. Anomalous IR signatures were also observed in the general area, within 50 km of the epicenter, during the 2 weeks prior to the quake. These three simultaneous EM phenomena were compared with data collected over a 1–2-year period at the site. The data was also compared against accounts of air

  5. Managing glacier related risks in the Chucchún Catchment, Cordillera Blanca, Peru (United States)

    Muñoz, Randy; Gonzáles, César; Price, Karen; Frey, Holger; Huggel, Christian; Cochachin, Alejo; García, Javier; Mesa, Luis


    On April 11 2010, the city of Carhuaz and settlements in the Chucchún Catchment (Ancash region, Peru) suffered the impact of a glacier lake outburst flood. An avalanche of rock and ice from the Mount Hualcán hit the glacier lake 513, triggering a glacial lake outburst flood (GLOF) of 1 million m3 which destroyed farmland and several infrastructures. Although there was no loss of human life, the event caused panic in the population. In consequence, the Municipality of Carhuaz prioritized GLOF-related risk management. The Glacier Project, funded by Swiss Agency for Development and Cooperation, and executed by CARE Peru and the University of Zurich, fosters the coordination among public institutions (Glaciological Unit of the National Water Authority, the Ministry of Environment and Municipality) and the population for risk management. In this contribution we present all components of the risk management strategy as well as the lessons learned during the implementation. Risk management involves managing both glacier hazard as well as the vulnerability of the population. In this framework a glaciological and geomorphological characterization of Mount Hualcán and lake 513 was perfomed in order to model past and potential future outburst floods and to assess the slope stability conditions. Based on three potential GLOF scenarios of different magnitudes, a hazard map was produced for the entire catchment, which served as the basis for the vulnerability and risk assessment as well as for the design and the implementation of an Early Warning System (EWS), including evacuation planning. The EWS consists of 4 components: 1) knowledge of risk, through hazard and vulnerability characterization; 2) monitoring and alert, through the installation of monitoring stations on lake 513 for detecting avalanches with geophones and cameras; 3) broadcasting and communications, through the implementation of communication protocols between the Municipality of Carhuaz and emergency

  6. Assessment and management of debris-flow risk in a tropical high-mountain catchment in Santa Teresa, Peru (United States)

    Frey, Holger; Buis, Daniel; Huggel, Christian; Bühler, Yves; Choquevilca, Walter; Fernandez, Felipe; García, Javier; Giráldez, Claudia; Loarte, Edwin; Masias, Paul; Portocarreo, César; Price, Karen; Walser, Marco


    movements and temporal damming of the river with trigger cables, geophones, and water level measurements. Independent energy supply, real-time data transfer to the data center in the municipality of Santa Teresa and remote access to the system via internet allows constant monitoring from within and outside the catchment. On a later stage the system is open to be enhanced by adding further sensors, cameras, meteorological stations, monitoring stations at glacier lakes, and related communication infrastructure. Risk management in such a context is a complex task: on one hand the data and information scarcity as well as the environmental conditions challenge scientific and technical aspects of debris-flow modeling and the design of the EWS. On the other hand, social aspects must be taken into account to make actions coherent with local risk perceptions and to achieve a good preparedness of the population. For a successful realization of the EWS and the entire risk management scheme, the local and regional institutional framework must also be considered. This contribution thus illustrates the implementation of an integrated risk management strategy under the challenging conditions common for remote high-mountain regions.

  7. Constructing a Sediment Budget for the Johnsbach, Styria - Adding up numbers and drawing arrows? (United States)

    Rascher, Eric; Sass, Oliver


    flow processes on the hillslopes was achieved by means of TLS surveys two times a year from 2013-2015. The precedent mapping and the ALS overview surveys (DEMs from 2010 and 2015) ensure that the measured processes are representative for wider areas. The thickness and structure of important sediment storage bodies at the slopes and in the side valleys were investigated using geophysical methods (ERT, GPR, seismics). The fluvial sediment transport was analyzed using impact sensors, geophone installations and mobile basket samplers. The results of all steps of quantification will later be transferred to the entire study area (Johnsbach catchment) using the mapping results and GIS analyses. The output will be a sediment budget model of the Johnsbachtal. The step towards application comprises the analysis of current management problems (amount of "missing" sediment for ecological purposes, and effects on hydropower plants) and the possible consequences of artificial barriers being altered or removed.

  8. Processes and mechanisms governing hard rock cliff erosion in western Brittany, France (United States)

    Laute, Katja; Letortu, Pauline; Le Dantec, Nicolas


    failure in the otherwise rather resistant rock. The density of the fracture network and the principal directions of fracturation play a significant role in controlling the rate of mass wasting. The characterization of cliff micro-fracturing will be accomplished through in-situ monitoring of cliff-top ground motion with a seismometer installed at the cliff top and geophones installed within the cliff face. Wave impact will be monitored by setting up a real-time video system in front of the cliff face in combination with pressure- and wave load sensors that will be installed on the beach in a cross-shore array and directly at the cliff toe. Temperature sensors will be placed in shallow boreholes at the cliff face in order to record surface rock temperature. In addition, a weather station and a piezometer will be deployed in order to monitor local weather and groundwater conditions at the study site. This novel combination of the different field measurements is expected to yield new insights into the processes controlling cliff erosion and retreat along rocky coastlines. In particular, we hope to gain understanding on the possible importance of rock micro-fracturing as a precursor to cliff failure.

  9. 五号桩地区滩浅海高精度三维地震采集技术%3D high-precision seismic acquisition techniques in Wuhaozhuang beach and shallow sea area

    Institute of Scientific and Technical Information of China (English)

    邸志欣; 丁伟; 吕公河; 刘怀山; 段卫星; 刘斌


    Wuhaozhuang area is the key and old oil area of Shengli Oilfield for oil-gas exploration in beach and shallow sea. It has great potential on increase in oil reserve and production, but the energy in middle-deep layer of the existing seismic data is weak, and its signal-to-noise ratio is low, so it is hard to meet the requirements for further detailed structure interpretation and reservoir description. Aimed at the characteristics and difficulties of the complex surface and underground conditions, based on complex structure modeling and prestack imaging result analysis, we designed and proved high-precision geometries for seismic acquisition suitable for the beach and shallow sea in Wuhaozhuang area, which ensured seamless data acquisition in the land-beach-shallow-sea area. By studying 'high-efficient dynamite source and using the shooting techniques based on near-surface lithology layering and modeling, the shooting effect of intertidal zone was improved. By studying and testing air gun array parameters, we optimized airgun array mode and shooting depth with good wavelet characteristics and strong energy. The platelike long-tail cone geophone coupler was adopted to improve the seismic wave receiving effect in intertidal zone as well. Besides, the repositioning technology and counter measurements were utilized to improve the positioning accuracy of underwater hydrophone. By jointly using all the techniques and methods, we achieved high-quality seismic data and obvious geological effect in Wuhaozhuang area.%五号桩地区是胜利油田滩浅海油气勘探的重点老区,增储上产的潜力巨大,但以往地震资料中深层能量弱,信噪比较低,无法满足进一步精细构造解释和油藏描述要求.针对该区复杂的地表和地下特点及难点,基于复杂构造模型正演和叠前成像效果分析,设计论证了适合于该区滩浅海高精度地震采集的观测系统形式,确保了全区陆-滩-海资料的无缝连接采集;通过

  10. The application of Double-difference technique to improve localization of induced microseismic events at Pyhäsalmi copper mine, Pyhäjärvi, Finland. (United States)

    Nevalainen, Jouni; Usoltseva, Olga; Kozlovskaya, Elena; Mäki, Timo


    Pyhäsalmi mine, an underground copper mine at Pyhäjärvi, Finland, have been known to have induced seismicity due ore excavation for over half of a century. In 2002, the excavation depth increased as mining activity focused to Pyhäsalmi deep ore body, a potato shaped ore concentration that lies roughly from 1000 meter to 1425 meters below the surface. The stress level in the rock was detected to be very high with clear main direction and due to this microseismicity started occurring immediately when the construction of "new mine" section began. Thus a microseismic monitoring system was installed to trace this frequently occurring induced seismicity as seismic observations are one of the quickest ways to map mines state-of-health. The system consist over 25 geophones that are mainly around the excavation site. Since the installation, over 250000 events have been observed. Currently the automated (triggered) and afterwards manually verified seismic events localization routine is applied by absolute location method that minimizes the penalty function of calculated location and origin time to match as good as possibly for corresponding events observed arrivaltimes. However with this method the best location accuracy is around 20 meters at center of the excavation, since it uses homogenous velocity model that have been applied to whole mine but in reality the seismic velocity structure is very complex with tunnels, fill material and ore. For mines seismic alarm purposes this suits well, but for more advanced source analysis this accuracy is not enough. We apply Double-difference technique to relocate microseismic scale events at Pyhäsalmi mine. This iterative least-squares procedure method utilizes pairs of events with common receiver. The basic principle of the technique is that it relates the residual between the observed and the predicted phase traveltime difference for pairs of earthquakes observed at common station to adjustments in the vector that connects

  11. P-wave and surface wave survey for permafrost analysis in alpine regions (United States)

    Godio, A.; Socco, L. V.; Garofalo, F.; Arato, A.; Théodule, A.


    In various high mountain environments the estimate of mechanical properties of slope and sediments are relevant for the link of the geo-mechanical properties with the climate change effects. Two different locations were selected to perform seismic and georadar surveying, the Tsanteleina glacier (Gran Paradiso) and the Blue Lake in Val d'Ayas in the massif of Monterosa. The analysis of the seismic and GPR lines allowed to characterize the silty soil (top layer) and underlying bedrock. We applied seismic survey in time lapse mode to check the presence of "active" layer and estimate the mechanical properties of the moraines material and their sensitivity to the permafrost changes. Mechanical properties of sediments and moraines in glacial areas are related to the grain-size, the compaction of the material subjected to the past glacial activity, the presence of frozen materials and the reactivity of the permafrost to the climate changes. The test site of Tsanteleina has been equipped with sensors to monitor the temperature of soil and air and with time domain reflectometry to estimate the soil moisture and the frozen and thawing cycle of the uppermost material. Seismic reflections from the top of the permafrost layer are difficult to identify as they are embedded in the source-generated noise. Therefore we estimate seismic velocities from the analysis of traveltime refraction tomography and the analysis of surface wave. This approach provides information on compressional and shear waves using a single acquisition layout and a hammer acts as source. This reduces the acquisition time in complex logistical condition especially in winter period. The seismic survey was performed using 48 vertical geophones with 2 m spacing. The survey has been repeated in two different periods: summer 2011 and winter 2011. Common offset reflection lines with a 200 MHz GPR system (in summer) permitted to investigate the sediments and obtain information on the subsoil layering. The processing

  12. Geophysical characterization of karst features above an underground mine near Quincy, Il (United States)

    Morozov, Vitaliy Alekseyevich

    Extensive knowledge of subsurface structure is required for safe underground mining. Fractures and unexpected caves may make mining dangerous and/or impossible. The purpose of this study was to assess various geophysical methods that can identify karst cavities and associated features in bedrock to depths of up to 30 m. Two-dimensional electrical resistivity tomography (ERT), azimuthal resistivity (AR), electromagnetic (EM) conductivity, seismic refraction, and ground-penetrating radar (GPR) surveys were made over a known cavity in the Mississippian Haight Creek dolomite near Quincy, IL. The dolomite is covered by approximately 20-30 m of glacial deposits. ERT and EM methods were used along multiple lines to detect spatial changes in subsurface structure, whereas AR was used to investigate electrical anisotropy in the subsurface. GPR surveys were conducted over the GPS location of the cavity. Seismic refraction surveys attempted to determine depth to bedrock in the vicinity of the karst feature. Nearby soil pipes and fractures may be a surface manifestation of this feature. The ERT surveys used a dipole-dipole array with maximum electrode spacing of 6 m and total line length of 114 m to achieve an approximate depth penetration of 24 m. AR measurements consisted of Wenner array soundings along lines of varying azimuth. EM surveys, performed with 40 m coil spacing, achieved a maximum signal response from 20-30 m depth in the vertical dipole mode. GPR surveys were made with 25 and 50 MHz antennas. Seismic experiments used a sledgehammer source and a 24-channel seismograph with 5 m geophone spacing. The EM conductivity method proved to be the most effective at delineating the target feature. Distinct high-conductivity anomalies were detected in the vicinity of the solution cavity, suggesting that it is filled with soil and/or water. Additional high-conductivity anomalies were also observed and may mean that undiscovered karst features are present to the south

  13. New Seismic Reflection Profiling Across the Northern Newark Basin USA: Data Acquisition and Preliminary Results (United States)

    Tymchak, M.; Collins, D.; Brown, C.; Conrad, J.; Papadeas, P.; Coueslan, M. L.; Tamulonis, K.; Goldberg, D.; Olsen, P. E.


    Deep saline formations in basins underlying major population centers represent opportunities for carbon (CO2) sequestration, but intensive surface development in such settings can hinder field operations to acquire geologic and geophysical data critical to effective characterization. Seismic-reflection is a tool that can be used to characterize basins and their potential capacity for carbon storage. The northern part of the Triassic-Jurassic Newark Rift Basin represents a potential storage opportunity for carbon as a result of its proximity to large-scale CO2 emitters; however, a lack of deep geologic and seismic data from this area has precluded evaluation of this basin to date. As part of the Department of Energy's (DOE) National Energy Technology Labs (NETL) Carbon Sequestration programs portion of the American Recovery and Reinvestment Act (ARRA)- and NYSERDA-funded TriCarb Consortium for Carbon Sequestration basin characterization project, two new seismic-reflection profiles were acquired in the northern portion of the Newark Basin in Rockland County, NY and Bergen County NJ. This densely developed region, proximal to New York City, presents a variety of challenges for seismic surveys, including route selection and access, community acceptance, high traffic volumes and associated data noise, in addition to regulatory requirements and private property limitations. In spite of these challenges, two high-resolution, perpendicular lines were successfully surveyed in late March and early April, 2011; one dip line extending 21 km (13 mi) across most of the basin (east-west), and a shorter strike line extending 8 km (5 mi, north-south). The survey lines intersected near the location of a planned 8,000 ft stratigraphic borehole to be drilled by the TriCarb consortium. Three vibroseis trucks comprised the source array. Source points were spaced at 36.5 m (120-ft) intervals and geophone accelerometers collected data at a 3.05 m (10 ft) intervals. Seismic-reflection data

  14. Measurement and characterization of a soundscape of captive southern white rhinoceros (Ceratotherium simum simum) at a wildlife park conservation center (United States)

    Wiseman, Susan M.

    the tools available to those investigating their environment, to invite geographers and others from non-acoustic backgrounds to become aware of the soundscape and to pose new questions; 4. To demonstrate how the processing and analysis of the data collected at FRWC can be formulated to characterize the soundscape that their rhinos experience. This study is undertaken at the white rhinoceros enclosure of Fossil Rim Wildlife Center (FRWC), one of nine U.S. facilities to breed this species in recent years. Fossil Rim's white rhino soundscape was recorded continuously throughout a week of normal park activities by five acoustic, infrasonic and seismic acquisition systems to sense frequencies from 0.1 Hz to 22,020 kHz, and the resultant broadband sound metrics were measured. It is not within the scope of this project to publish all the possible results, but a sample is provided to illustrate the use and effectiveness of the system. Friday 18th October, 2014 was subjectively analyzed via a sound event log before recordings were processed using Raven Interactive Sound Analysis Software, and by SongMeter SM2+ Data Logs. Data from three infrasonic channels were averaged and preliminarily processed in Matlab, as were the three geophone seismic channels. For perspective, Friday was compared to a preliminary sonic analysis of Monday 21st October. It was ascertained that the FRWC white rhinoceros enclosure retains many characteristics of a natural environment, despite being exposed to some form of anthrophonic noise much of the time. Once a wide variety of rhino enclosure soundscapes have been measured, if relationships are discovered between certain acoustic parameters and the health and well-being of their animals, the soundscapes of other captive species could be similarly examined and acoustic environments could be modified to better suit the species concerned.

  15. Ambient seismic noise as an interesting indirect cue for the Cerithidea decollata migrations (United States)

    Pazzi, Veronica; Lotti, Alessia


    geophones. The acquisition run for 11 days (29th June, 2013 - 9th July, 2013). We assumed that the tide transgressions/regressions generate pressure fluctuations on the ground, that are locally transformed into microseismic waves at seafloor propagating inland. Therefore, we evaluated a possible correlation, in terms of decision to climb up or not, between the seismic signals amplitude fluctuations and the snails' movements. To do so we performed: a) the analysis of the trend of the LF (0.1-2 Hz) and HF (2-60 Hz) seismic noise amplitudes, and b) the comparison of the seismic signals with the height of tide, the number of animals that climbed to the safety level, and the height that they reached during each tide cycle. The study showed an interesting similarity between the time evolution (mean value) of the LF amplitude trend and the animals' movements. Even thought additional data should be collected to improve the results, it is the first time that a consistent physical cue other than the obvious but discarded ones (visual and chemical), has been identified that could potentially be detected by the snails as well as by other intertidal organisms.

  16. The Obsidian Creep Project: Seismic Imaging in the Brawley Seismic Zone and Salton Sea Geothermal Field, Imperial County, California (United States)

    Catchings, R. D.; Rymer, M. J.; Goldman, M.; Lohman, R. B.; McGuire, J. J.


    In March 2010, we acquired medium- and high-resolution P- and S-wave seismic reflection and refraction data across faults in the Brawley seismic zone (BSZ) and across part of the Salton Sea Geothermal Field (SSGF), Imperial Valley, California. Our objectives were to determine the dip, possible structural complexities, and seismic velocities associated with the BSZ and SSGF. We acquired multiple seismic data sets along a north-south profile and a high-resolution P-wave profile along an east-west profile. The north-south profile included: 1) a 6.4-km-long P-wave (main) profile that was recorded on 320 Texan seismographs spaced at 20-m intervals, 2) a 1.2-km-long cabled, high-resolution profile along the northern end of the main profile, and 3) an approximately 1.2-km-long S-wave profile along the cabled profile. P-wave sources along the main profile were generated by 0.15- to 0.45-kg buried explosions spaced every 40 m, and P-wave sources along the cabled profile were generated by Betsy-Seisgun ‘shots’ spaced every 10 m. S-waves sources were generated by hammer impacts on the ends of an aluminum block. The east-west profile consisted of a 3.4-km-long high-resolution P-wave seismic profile with shots (Betsy-Seisgun) and geophones spaced every 10 m. Preliminary interpretation of shot gathers from blasts in the north-south profile suggests that the BSZ and SSGF are structurally complex, with abundant faults extending to or near the ground surface. Also, we observe relatively high-velocity material, apparent velocities of about 4.0 km/s in one direction and about 2.8 km/s in another relative to about 1.6 km/s for shallower material, that shallows beneath the SSGF. This may be due to high temperatures and resultant metamorphism of buried materials in the SSGF. From preliminary interpretation of shot gathers along the east-west profile we interpret a prominent fault that extends to the ground surface. This fault is on projection of the Kalin fault, from about 40 m to

  17. Data Exploration using Unsupervised Feature Extraction for Mixed Micro-Seismic Signals (United States)

    Meyer, Matthias; Weber, Samuel; Beutel, Jan


    We present a system for the analysis of data originating in a multi-sensor and multi-year experiment focusing on slope stability and its underlying processes in fractured permafrost rock walls undertaken at 3500m a.s.l. on the Matterhorn Hörnligrat, (Zermatt, Switzerland). This system incorporates facilities for the transmission, management and storage of large-scales of data ( 7 GB/day), preprocessing and aggregation of multiple sensor types, machine-learning based automatic feature extraction for micro-seismic and acoustic emission data and interactive web-based visualization of the data. Specifically, a combination of three types of sensors are used to profile the frequency spectrum from 1 Hz to 80 kHz with the goal to identify the relevant destructive processes (e.g. micro-cracking and fracture propagation) leading to the eventual destabilization of large rock masses. The sensors installed for this profiling experiment (2 geophones, 1 accelerometers and 2 piezo-electric sensors for detecting acoustic emission), are further augmented with sensors originating from a previous activity focusing on long-term monitoring of temperature evolution and rock kinematics with the help of wireless sensor networks (crackmeters, cameras, weather station, rock temperature profiles, differential GPS) [Hasler2012]. In raw format, the data generated by the different types of sensors, specifically the micro-seismic and acoustic emission sensors, is strongly heterogeneous, in part unsynchronized and the storage and processing demand is large. Therefore, a purpose-built signal preprocessing and event-detection system is used. While the analysis of data from each individual sensor follows established methods, the application of all these sensor types in combination within a field experiment is unique. Furthermore, experience and methods from using such sensors in laboratory settings cannot be readily transferred to the mountain field site setting with its scale and full exposure to

  18. Geomechanical Modeling of Fault Responses and the Potential for Notable Seismic Events during Underground CO2 Injection (United States)

    Rutqvist, J.; Cappa, F.; Mazzoldi, A.; Rinaldi, A.


    The importance of geomechanics associated with large-scale geologic carbon storage (GCS) operations is now widely recognized. There are concerns related to the potential for triggering notable (felt) seismic events and how such events could impact the long-term integrity of a CO2 repository (as well as how it could impact the public perception of GCS). In this context, we review a number of modeling studies and field observations related to the potential for injection-induced fault reactivations and seismic events. We present recent model simulations of CO2 injection and fault reactivation, including both aseismic and seismic fault responses. The model simulations were conducted using a slip weakening fault model enabling sudden (seismic) fault rupture, and some of the numerical analyses were extended to fully dynamic modeling of seismic source, wave propagation, and ground motion. The model simulations illustrated what it will take to create a magnitude 3 or 4 earthquake that would not result in any significant damage at the groundsurface, but could raise concerns in the local community and could also affect the deep containment of the stored CO2. The analyses show that the local in situ stress field, fault orientation, fault strength, and injection induced overpressure are critical factors in determining the likelihood and magnitude of such an event. We like to clarify though that in our modeling we had to apply very high injection pressure to be able to intentionally induce any fault reactivation. Consequently, our model simulations represent extreme cases, which in a real GCS operation could be avoided by estimating maximum sustainable injection pressure and carefully controlling the injection pressure. In fact, no notable seismic event has been reported from any of the current CO2 storage projects, although some unfelt microseismic activities have been detected by geophones. On the other hand, potential future commercial GCS operations from large power plants

  19. Drilling, Completion, and Data Collection Plans An Assessment of Geological Carbon Sequestration Options in the Illinois Basin: Phase III

    Energy Technology Data Exchange (ETDEWEB)

    Malkewicz, Nicholas; Kirksey, Jim; Finley, Robert


    Executive Summary The Illinois Basin – Decatur Project (IBDP) is managed by the Midwest Geological Sequestration Consortium (MGSC) and is led by the Illinois State Geological Survey (ISGS) at the University of Illinois. The project site is located on the Archer Daniels Midland Company (ADM) property in Decatur, Illinois, and is a fully integrated carbon capture and storage (CCS) project that uses CO₂ captured from the ethanol-producing fermentation process at the ADM corn-processing plant (Finley et. al., 2013). IBDP has a goal of injecting one million tonnes of CO₂ into the basal sands of the Mt. Simon Sandstone over a three-year period. This is a multifaceted project, and this report details the planning and results of the drilling, completions, well testing, log data acquisition, and the Health, Safety, and Environment (HSE) aspects of the project. Three deep wells were planned for the IBDP: • The injection well: Injection Well #1 (CCS1); • The monitoring well (both in-zone and above seal): Verification Well #1 (VW1); and • The geophone monitoring well: Geophysical Monitoring Well #1 (GM1). The detailed plans for these wells are attached to the appendices of this document. The wells were drilled successfully with little deviation from the original plans. The biggest change from the plan to execution was the need to adjust for larger-than-expected loss of circulation in the Potosi section of the Knox Formation. The completions reports also attached to this document detail the well constructions as they were actually built. Injectivity testing was carried out, and the perforating plans were adjusted based on the results. Additional perforations and acidizing were performed as a result of the injectivity testing. The testing plans are detailed in this report along with the actual testing results. The injectivity testing results were used in the modeling and simulation efforts. Detailed HSE plans were developed and implemented during the planning and

  20. The Highland Terrain Hopper: a new locomotion system for exploration of Mars and other low-gravity planetary bodies (United States)

    Gurgurewicz, Joanna; Grygorczuk, Jerzy; Wisniewski, Lukasz; Mege, Daniel; Rickman, Hans

    ), turning over, and tilting. Many risky displacements are made possible by robot symmetry and leg configuration. In case of failed jump, one leg at least is in contact with the ground and can be used for a new jump and a new attempt. Due to low weight and cost, several galagos may be sent to study the geology and geophysics along profiles tens of km long or grids covering up to hundreds of km2, with either duplicate or complementary payloads. Payload weight is limited to ca. 1 kg per one Galago. In order to save space and weight, the main system and payload will be highly miniaturized and designed simultaneously in order to share as much components as possible; no moving parts will be allowed. On Mars, the full stratigraphy, from the pre-Noachian to some of the most recent deposits, may be obtained using a small swarm of galagos dropped along a traverse going through one of the main Valles Marineris chasmata equipped with a payload including a visible-NIR multispectral camera and an inclinometer. At the same time, data regarding rock fracturing, hydrogeologic and paleohydrologic conditions, paleogeography, paleoenvironments, soils and paleosoils, would be collected. Such measurements would provide helpful information as to early volatile delivery and the very early climate, as well as assessment of past habitability. Galagos carrying a ground resistivity meter could probe the subsurface and look for buried ice; with geophones the present geologic activity and surface dynamics (slope processes such as recurring slope lineae, ice movement in rock- or dust-covered glaciers etc.) could be monitored and identified; a magnetometer would provide the first in situ measurements of Martian rock magnetization induced by the early dynamo. The Galago capabilities will be illustrated by a site study in Valles Marineris.

  1. Bringing New Tools and Techniques to Bear on Earthquake Hazard Analysis and Mitigation (United States)

    Willemann, R. J.; Pulliam, J.; Polanco, E.; Louie, J. N.; Huerta-Lopez, C.; Schmitz, M.; Moschetti, M. P.; Huerfano Moreno, V.; Pasyanos, M.


    During July 2013, IRIS held an Advanced Studies Institute in Santo Domingo, Dominican Republic, that was designed to enable early-career scientists who already have mastered the fundamentals of seismology to begin collaborating in frontier seismological research. The Institute was conceived of at a strategic planning workshop in Heredia, Costa Rica, that was supported and partially funded by USAID, with a goal of building geophysical capacity to mitigate the effects of future earthquakes. To address this broad goal, we drew participants from a dozen different countries of Middle America. Our objectives were to develop understanding of the principles of earthquake hazard analysis, particularly site characterization techniques, and to facilitate future research collaborations. The Institute was divided into three main sections: overviews on the fundamentals of earthquake hazard analysis and lectures on the theory behind methods of site characterization; fieldwork where participants acquired new data of the types typically used in site characterization; and computer-based analysis projects in which participants applied their newly-learned techniques to the data they collected. This was the first IRIS institute to combine an instructional short course with field work for data acquisition. Participants broke into small teams to acquire data, analyze it on their own computers, and then make presentations to the assembled group describing their techniques and results.Using broadband three-component seismometers, the teams acquired data for Spatial Auto-Correlation (SPAC) analysis at seven array locations, and Horizontal to Vertical Spectral Ratio (HVSR) analysis at 60 individual sites along six profiles throughout Santo Domingo. Using a 24-channel geophone string, the teams acquired data for Refraction Microtremor (SeisOptReMi™ from Optim) analysis at 11 sites, with supplementary data for active-source Multi-channel Spectral Analysis of Surface Waves (MASW) analysis at

  2. Saudi Arabian seismic deep-refraction profiles; final project report (United States)

    Healy, J.H.; Mooney, W.D.; Blank, H.R.; Gettings, M.E.; Kohler, W.M.; Lamson, R.J.; Leone, L.E.


    In February 1978 a seismic deep-refraction profile was recorded by the U.S. Geological Survey along a 1000-km line across the Arabian Shield in western Saudi Arabia. The line begins in 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 most charges placed below the water table in drill holes, and one at sea, with charges placed on the sea floor and detonated from a ship. Slightly more than 61 metric tons of explosives were used in 19 discrete firings. Seismic energy was recorded by 100 newly-developed portable seismic stations deployed in approximately 200 km-long arrays for each firing. Each station consisted of a standard 2-Hz vertical component geophone coupled to a self-contained analog recording instrument equipped with a magnetic-tape cassette. In this final report, we fully document the field and data-processing procedures and present the final seismogram data set as both a digital magnetic tape and as record sections for each shot point. Record sections include a normalized set of seismograms, reduced at 6 km/s, and a true-amplitude set, reduced at 8 km/s, which have been adjusted for amplifier gain, individual shot size, and distance from the shot point. Appendices give recorder station and shot information, digital data set descriptions, computer program listings, arrival times used in the interpretation, and a bibliography of reports published as a result of this project. We used two-dimensional ray-tracing techniques in the data analysis, and our interpretation is based primarily on horizontally layered models. The Arabian Shield is composed, to first-order, of two layers, each about 20 km

  3. Geological and geophysical activities at Spallanzani Science Department (Liceo Scientifico Statale "Lazzaro Spallanzani" - Tivoli, Italy) (United States)

    Favale, T.; De Angelis, F.; De Filippis, L.


    :// and Furthermore, until the end of January 2012 a semi-professional seismograph will work with educational aims. These activities allowed the school to receive the first prize in the 2002 contest held by the italian scientific magazine Quark "Giornalisti Scientifici si diventa" (How to become a scientific journalist), with an article co-authored with three students titled "Una TAC per il Vesuvio" (CT scan for Vesuvius). The article was published in the n. 15 issue of Quark magazine, May 2002. The school also runs a Science and Chemistry Laboratory, equipped with: (a) 1 mobile seismograph with six geophones for seismic invesitgation (rifraction, reflection, REMI, MASW, and HVSR), (b) 1 polarized microscope for mineralogy and petrography, (c) various geochemical instruments for water analysis (pH, Eh, T, etc.), (d) 1 Geiger counter to detect β- particles and γ rays, and (e) 2 calcimeters to calculate the percentage of calcium carbonate in calcareous rocks. Two meteorological stations managed by Physics Laboratory, both online with data processing in real time, are hosted inside school building. Finally, we are planning a new scientific project for the next school year, involving students and science teachers, probably named "Gas hazard in volcanic and geothermal areas of the eastern Rome province".

  4. Advancing internal erosion monitoring using seismic methods in field and laboratory studies (United States)

    Parekh, Minal L.

    This dissertation presents research involving laboratory and field investigation of passive and active methods for monitoring and assessing earthen embankment infrastructure such as dams and levees. Internal erosion occurs as soil particles in an earthen structure migrate to an exit point under seepage forces. This process is a primary failure mode for dams and levees. Current dam and levee monitoring practices are not able to identify early stages of internal erosion, and often the result is loss of structure utility and costly repairs. This research contributes to innovations for detection and monitoring by studying internal erosion and monitoring through field experiments, laboratory experiments, and social and political framing. The field research in this dissertation included two studies (2009 and 2012) of a full-scale earthen embankment at the IJkdijk in the Netherlands. In both of these tests, internal erosion occurred as evidenced by seepage followed by sand traces and boils, and in 2009, eventual failure. With the benefit of arrays of closely spaced piezometers, pore pressure trends indicated internal erosion near the initiation time. Temporally and spatially dense pore water pressure measurements detected two pore water pressure transitions characteristic to the development of internal erosion, even in piezometers located away from the backward erosion activity. At the first transition, the backward erosion caused anomalous pressure decrease in piezometers, even under constant or increasing upstream water level. At the second transition, measurements stabilized as backward erosion extended further upstream of the piezometers, as shown in the 2009 test. The transitions provide an indication of the temporal development and the spatial extent of backward erosion. The 2012 IJkdijk test also included passive acoustic emissions (AE) monitoring. This study analyzed AE activity over the course of the 7-day test using a grid of geophones installed on the

  5. Integration of satellite radar interferometry into a GLOF early warning system: a pilot study from the Andes of Peru (United States)

    Strozzi, Tazio; Wiesmann, Andreas; Caduff, Rafael; Frey, Holger; Huggel, Christian; Kääb, Andreas; Cochachin, Alejo


    Glacier lake outburst floods (GLOF) have killed thousands of people in the Andes of Peru and in many other high-mountain regions of the world. The last years have seen progress in the integrative assessment of related hazards, through combined focus on the glacier lake, its dam properties, and processes in the lake surrounding, including the position and fluctuations of the glacier tongue and potential displacements and thermal conditions of adjacent slopes. Only a transient perspective on these factors allows anticipating potential future developments. For a very limited number of cases worldwide, where GLOF hazards and risks have been recognized, early warning systems (EWS) have been developed and implemented. Lake 513 in the Cordillera Blanca of Peru is one of those. Structural GLOF mitigation measures (tunnels to lower the lake level) have been undertaken in the 1990s and could successfully reduce, but not fully prevent, impacts of a GLOF such as that of April 2010 triggered by a rock/ice avalanche from Mount Hualcán. The EWS was implemented during recent years and disposes of automatic cameras, geophones, river run-off measurements, a meteorological station, and real-time communication with the municipality of Carhuaz and the communities in the catchment. An EWS is by definition limited in its concept and Earth Observation (EO) data offer a promising possibility to complement the assessment of the current hazard. In particular, the monitoring and early detection of slope instabilities in ice, rock and sediments that could impact the lake and trigger a GLOF is still a major challenge. Therefore, the potential of optical and SAR satellite data is currently tested for integration into the EWS within the project S:GLA:MO (Slope stability and Glacier LAke MOnitoring) project, funded by the European Space Agency (ESA) in collaboration with the GLACIARES project supported by the Swiss Agency for Development and Cooperation. EO data (optical and SAR) are considered

  6. Borehole seismic in crystalline environment at the COSC-project in Central Sweden (United States)

    Krauß, Felix; Hedin, Peter; Almqvist, Bjarne; Simon, Helge; Giese, Rüdiger; Buske, Stefan; Juhlin, Christopher; Lorenz, Henning


    -component geophones and a receiver spacing of 2 m over the whole borehole length. As first pre-processing steps, the three component VSP data were decoded and vertically stacked. Afterwards, the shots were merged to get a continuous shot gather. A horizontal rotation was performed, based on the S-wave arrivals. The rotated ZVSP-data show a high signal-to-noise ratio and good data quality. Signal frequencies up to 150 Hz were observed. On the vertical component, clear direct P-wave arrivals are visible. Several P-wave reflections occur below 1600 m logging depth. On both horizontal components, clear direct S-wave arrivals are visible after rotation what suggests that the penetrated rock is anisotropic. In addition, several PS-converted waves can be identified. In order to integrate the borehole data into the 3D surface seismic data, further processing concentrated only on the P-waves. First, deconvolution was applied to sharpen the signals and to suppress multiples. Then the wave field was separated into upgoing and downgoing components by median filtering. Finally, a corridor stack was generated using the upgoing wave field in order to allow correlation with the borehole logging data and the surface seismic data.

  7. Seismic Fracture Characterization Methodologies for Enhanced Geothermal Systems

    Energy Technology Data Exchange (ETDEWEB)

    Queen, John H. [Hi-Geophysical, Inc., Ponca, OK (United States)


    Executive Summary The overall objective of this work was the development of surface and borehole seismic methodologies using both compressional and shear waves for characterizing faults and fractures in Enhanced Geothermal Systems. We used both surface seismic and vertical seismic profile (VSP) methods. We adapted these methods to the unique conditions encountered in Enhanced Geothermal Systems (EGS) creation. These conditions include geological environments with volcanic cover, highly altered rocks, severe structure, extreme near surface velocity contrasts and lack of distinct velocity contrasts at depth. One of the objectives was the development of methods for identifying more appropriate seismic acquisition parameters for overcoming problems associated with these geological factors. Because temperatures up to 300º C are often encountered in these systems, another objective was the testing of VSP borehole tools capable of operating at depths in excess of 1,000 m and at temperatures in excess of 200º C. A final objective was the development of new processing and interpretation techniques based on scattering and time-frequency analysis, as well as the application of modern seismic migration imaging algorithms to seismic data acquired over geothermal areas. The use of surface seismic reflection data at Brady's Hot Springs was found useful in building a geological model, but only when combined with other extensive geological and geophysical data. The use of fine source and geophone spacing was critical in producing useful images. The surface seismic reflection data gave no information about the internal structure (extent, thickness and filling) of faults and fractures, and modeling suggests that they are unlikely to do so. Time-frequency analysis was applied to these data, but was not found to be significantly useful in their interpretation. Modeling does indicate that VSP and other seismic methods with sensors located at depth in wells will be the most

  8. Integrated Geophysical Monitoring Program to Study Flood Performance and Incidental CO2 Storage Associated with a CO2 EOR Project in the Bell Creek Oil Field (United States)

    Burnison, S. A.; Ditty, P.; Gorecki, C. D.; Hamling, J. A.; Steadman, E. N.; Harju, J. A.


    The Plains CO2 Reduction (PCOR) Partnership, led by the Energy & Environmental Research Center, is working with Denbury Onshore LLC to determine the effect of a large-scale injection of carbon dioxide (CO2) into a deep clastic reservoir for the purpose of simultaneous CO2 enhanced oil recovery (EOR) and to study incidental CO2 storage at the Bell Creek oil field located in southeastern Montana. This project will reduce CO2 emissions by more than 1 million tons a year while simultaneously recovering an anticipated 30 million barrels of incremental oil. The Bell Creek project provides a unique opportunity to use and evaluate a comprehensive suite of technologies for monitoring, verification, and accounting (MVA) of CO2 on a large-scale. The plan incorporates multiple geophysical technologies in the presence of complementary and sometimes overlapping data to create a comprehensive data set that will facilitate evaluation and comparison. The MVA plan has been divided into shallow and deep subsurface monitoring. The deep subsurface monitoring plan includes 4-D surface seismic, time-lapse 3-D vertical seismic profile (VSP) surveys incorporating a permanent borehole array, and baseline and subsequent carbon-oxygen logging and other well-based measurements. The goal is to track the movement of CO2 in the reservoir, evaluate the recovery/storage efficiency of the CO2 EOR program, identify fluid migration pathways, and determine the ultimate fate of injected CO2. CO2 injection at Bell Creek began in late May 2013. Prior to injection, a monitoring and characterization well near the field center was drilled and outfitted with a distributed temperature-monitoring system and three down-hole pressure gauges to provide continuous real-time data of the reservoir and overlying strata. The monitoring well allows on-demand access for time-lapse well-based measurements and borehole seismic instrumentation. A 50-level permanent borehole array of 3-component geophones was installed in a

  9. Joint inversion of apparent resistivity and seismic surface and body wave data (United States)

    Garofalo, Flora; Sauvin, Guillaume; Valentina Socco, Laura; Lecomte, Isabelle


    this constraint further reducing the maximum error to 30 %. The same test was performed on field data acquired in a landslide-prone area close by the town of Hvittingfoss, Norway. Seismic data were recorded on two 160-m long profiles in roll-along mode using a 5-kg sledgehammer as source and 24 4.5-Hz vertical geophones with 4-m separation. First-arrival travel times were picked at every shot locations and surface wave dispersion curves extracted at 8 locations for each profile. 2D resistivity measurements were carried out on the same profiles using Gradient and Dipole-Dipole arrays with 2-m electrode spacing. The apparent resistivity curves were extracted at the same location as for the dispersion curves. The data were subsequently jointly inverted and the resulting model compared to individual inversions. Although models from both, individual and joint inversions are consistent, the estimation error is smaller for joint inversion, and more especially for first-arrival travel times. The joint inversion exploits different sensitivities of the methods to model parameters and therefore mitigates solution nonuniqueness and the effects of intrinsic limitations of the different techniques. Moreover, it produces an internally consistent multi-parametric final model that can be profitably interpreted to provide a better understanding of subsurface properties.

  10. Application of Genetic Algorithms in Seismic Tomography (United States)

    Soupios, Pantelis; Akca, Irfan; Mpogiatzis, Petros; Basokur, Ahmet; Papazachos, Constantinos


    application of hybrid genetic algorithms in seismic tomography is examined and the efficiency of least squares and genetic methods as representative of the local and global optimization, respectively, is presented and evaluated. The robustness of both optimization methods has been tested and compared for the same source-receiver geometry and characteristics of the model structure (anomalies, etc.). A set of seismic refraction synthetic (noise free) data was used for modeling. Specifically, cross-well, down-hole and typical refraction studies using 24 geophones and 5 shoots were used to confirm the applicability of the genetic algorithms in seismic tomography. To solve the forward modeling and estimate the traveltimes, the revisited ray bending method was used supplemented by an approximate computation of the first Fresnel volume. The root mean square (rms) error as the misfit function was used and calculated for the entire random velocity model for each generation. After the end of each generation and based on the misfit of the individuals (velocity models), the selection, crossover and mutation (typical process steps of genetic algorithms) were selected continuing the evolution theory and coding the new generation. To optimize the computation time, since the whole procedure is quite time consuming, the Matlab Distributed Computing Environment (MDCE) was used in a multicore engine. During the tests, we noticed that the fast convergence that the algorithm initially exhibits (first 5 generations) is followed by progressively slower improvements of the reconstructed velocity models. Thus, to improve the final tomographic models, a hybrid genetic algorithm (GA) approach was adopted by combining the GAs with a local optimization method after several generations, on the basis of the convergence of the resulting models. This approach is shown to be efficient, as it directs the solution search towards a model region close to the global minimum solution.

  11. Homogenization of seismic surface wave profiling in highly heterogeneous improved ground (United States)

    Lin, C.; Chien, C.


    Seismic surface wave profiling is gaining popularity in engineering practice for determining shear-wave velocity profile since the two-station SASW (Spectral Analysis of Surface Wave) was introduced. Recent developments in the multi-station approach (Multi-station Analysis of Surface Wave, MASW) result in several convenient commercial tools. Unlike other geophysical tomography methods, the surface wave method is essentially a 1-D method assuming horizontally-layered medium. Nevertheless, MASW is increasingly used to map lateral variation of S-wave velocity by multiple surveys overlooking the effect of lateral heterogeneity. MASW typically requires long receiver spread in order to have enough depth coverage. The accuracy and lateral resolution of 2-D S-wave velocity imaging by surface wave is not clear. Many geotechnical applications involves lateral variation in a scale smaller than the geophone spread and wave length. For example, soft ground is often improved to increase strength and stiffness by methods such as jet grouting and stone column which result in heterogeneous ground with improved columns. Experimental methods (Standard Penetration Test, sampling and laboratory testing, etc.) used to assess such ground improvement are subjected to several limitations such as small sampling volume, time-consuming, and cost ineffectiveness. It's difficult to assess the average property of the improved ground and the actual replacement ratio of ground improvement. The use of seismic surface wave method for such a purpose seems to be a good alternative. But what MASW measures in such highly heterogeneous improved ground remains to be investigated. This study evaluated the feasibility of MASW in highly heterogeneous ground with improved columns and investigated the homogenization of shear wave velocity measured by MASW. Field experiments show that MASW testing in such a composite ground behaves similar to testing in horizontally layered medium. It seems to measure some sort

  12. Real Time Seismic Prediction while Drilling (United States)

    Schilling, F. R.; Bohlen, T.; Edelmann, T.; Kassel, A.; Heim, A.; Gehring, M.; Lüth, S.; Giese, R.; Jaksch, K.; Rechlin, A.; Kopf, M.; Stahlmann, J.; Gattermann, J.; Bruns, B.


    Efficient and safe drilling is a prerequisite to enhance the mobility of people and goods, to improve the traffic as well as utility infrastructure of growing megacities, and to ensure the growing energy demand while building geothermal and in hydroelectric power plants. Construction within the underground is often building within the unknown. An enhanced risk potential for people and the underground building may arise if drilling enters fracture zones, karsts, brittle rocks, mixed solid and soft rocks, caves, or anthropogenic obstacles. Knowing about the material behavior ahead of the drilling allows reducing the risk during drilling and construction operation. In drilling operations direct observations from boreholes can be complemented with geophysical investigations. In this presentation we focus on “real time” seismic prediction while drilling which is seen as a prerequisite while using geophysical methods in modern drilling operations. In solid rocks P- and S-wave velocity, refraction and reflection as well as seismic wave attenuation can be used for the interpretation of structures ahead of the drilling. An Integrated Seismic Imaging System (ISIS) for exploration ahead of a construction is used, where a pneumatic hammer or a magnetostrictive vibration source generate repetitive signals behind the tunneling machine. Tube waves are generated which travel along the tunnel to the working face. There the tube waves are converted to mainly S- but also P-Waves which interact with the formation ahead of the heading face. The reflected or refracted waves travel back to the working front are converted back to tube waves and recorded using three-component geophones which are fit into the tips of anchor rods. In near real time, the ISIS software allows for an integrated 3D imaging and interpretation of the observed data, geological and geotechnical parameters. Fracture zones, heterogeneities, and variations in the rock properties can be revealed during the drilling

  13. A Thermal Technique of Fault Nucleation, Growth, and Slip (United States)

    Garagash, D.; Germanovich, L. N.; Murdoch, L. C.; Martel, S. J.; Reches, Z.; Elsworth, D.; Onstott, T. C.


    -Coulomb strength criterion with standard Byerlee parameters, a fault will initiate before the net tension occurs. After a new fault is created, hot fluid can be injected into the boreholes to increase the temperature and reverse the direction of fault slip. This process can be repeated to study the formation of gouge, and how the properties of gouge control fault slip and associated seismicity. Instrumenting the site with arrays of geophones, tiltmeters, strain gauges, and displacement transducers as well as back mining - an opportunity provided by the DUSEL project - can reveal details of the fault geometry and gouge. We also expect to find small faults (with cm-scale displacement) during construction of DUSEL drifts. The same thermal technique can be used to induce slip on one of them and compare the “man-made” and natural gouges. The thermal technique appears to be a relatively simple way to rapidly change the stress field and either create slip on existing fractures or create new faults at scales up to 10 m or more.

  14. EDITORIAL: The 20th International Conference on Optical Fibre Sensors, OFS-20 The 20th International Conference on Optical Fibre Sensors, OFS-20 (United States)

    Culshaw, Brian; Ecke, Wolfgang; Jones, Julian; Tatam, Ralph; Willsch, Reinhardt


    Welcome to our special issue on fibre optic sensors. Fibre optic sensors were first suggested in the patent literature in the mid 1960s as an innovative means for making measurements. This proposed a surface finish measurement tool with high precision and resulted in an instrument that remains available today. Much has happened since, with significant innovation in the techniques through which light propagating whilst guided in a fibre can be unambiguously, repeatedly and predictably modulated in response to an external phenomenon. The technique offers not only the precision mentioned earlier but also inherent electromagnetic immunity, the capability to sense at long distances, light weight, small size and a multiplicity of network architectures, all of which can be interrogated from a single point. Even so, fibre sensors is a niche technology, attractive only when its very special features offer substantial user benefit. There are, however, many such niches exemplified in the electrical power supply industry, in gyroscopes for navigational instruments, in hydrophones and geophones. Then there are the distributed sensing architectures that enable useful measurements of pressure, strain and temperature fields affecting the optical properties of the fibre itself to map these parameter fields as a function of position along lengths of fibre to many tens of kilometres. The fibre sensing concept spawned its own research community, and the international conference on Optical Fibre Sensors first appeared in 1983 in London then emerged into a series travelling from Europe to the Americas and into the Asia-Pacific region. The 20th in the series took place in Edinburgh at the end of 2009 and this special issue of Measurement Science and Technology presents extended versions of some of the papers that first appeared at the conference. The science and technology of fibre sensing have evolved significantly over the history of the conference, drawing on developments in optical

  15. Drilling, Completion, and Data Collection Plans An Assessment of Geological Carbon Sequestration Options in the Illinois Basin: Phase III

    Energy Technology Data Exchange (ETDEWEB)

    Malkewicz, Nicholas; Kirksey, Jim; Finley, Robert


    Executive Summary The Illinois Basin – Decatur Project (IBDP) is managed by the Midwest Geological Sequestration Consortium (MGSC) and is led by the Illinois State Geological Survey (ISGS) at the University of Illinois. The project site is located on the Archer Daniels Midland Company (ADM) property in Decatur, Illinois, and is a fully integrated carbon capture and storage (CCS) project that uses CO₂ captured from the ethanol-producing fermentation process at the ADM corn-processing plant (Finley et. al., 2013). IBDP has a goal of injecting one million tonnes of CO₂ into the basal sands of the Mt. Simon Sandstone over a three-year period. This is a multifaceted project, and this report details the planning and results of the drilling, completions, well testing, log data acquisition, and the Health, Safety, and Environment (HSE) aspects of the project. Three deep wells were planned for the IBDP: • The injection well: Injection Well #1 (CCS1); • The monitoring well (both in-zone and above seal): Verification Well #1 (VW1); and • The geophone monitoring well: Geophysical Monitoring Well #1 (GM1). The detailed plans for these wells are attached to the appendices of this document. The wells were drilled successfully with little deviation from the original plans. The biggest change from the plan to execution was the need to adjust for larger-than-expected loss of circulation in the Potosi section of the Knox Formation. The completions reports also attached to this document detail the well constructions as they were actually built. Injectivity testing was carried out, and the perforating plans were adjusted based on the results. Additional perforations and acidizing were performed as a result of the injectivity testing. The testing plans are detailed in this report along with the actual testing results. The injectivity testing results were used in the modeling and simulation efforts. Detailed HSE plans were developed and implemented during the planning and

  16. Seismic refraction profile, Kingdom of Saudi Arabia: field operations, instrumentation, and initial results (United States)

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


    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

  17. Efficient and automatic wireless geohazard monitoring (United States)

    Rubin, Marc J.

    In this dissertation, we present our research contributions geared towards creating an automated and efficient wireless sensor network (WSN) for geohazard monitoring. Specifically, this dissertation addresses three overall technical research problems inherent in implementing and deploying such a WSN, i.e., 1) automated event detection from geophysical data, 2) efficient wireless transmission, and 3) low-cost wireless hardware. In addition, after presenting algorithms, experimentation, and results from these three overall problems, we take a step back and discuss how, when, and why such scientific work matters in a geohazardous risk scenario. First, in Chapter 2, we discuss automated geohazard event detection within geophysical data. In particular, we present our pattern recognition workflow that can automatically detect snow avalanche events in seismic (geophone sensor) data. This workflow includes customized signal preprocessing for feature extraction, cluster-based stratified sub-sampling for majority class reduction, and experimentation with 12 different machine learning algorithms; results show that a decision stump classifier achieved 99.8% accuracy, 88.8% recall, and 13.2% precision in detecting avalanches within seismic data collected in the mountains above Davos, Switzerland, an improvement on previous work in the field. To address the second overall research problem (i.e., efficient wireless transmission), we present and evaluate our on-mote compressive sampling algorithm called Randomized Timing Vector (RTV) in Chapter 3 and compare our approach to four other on-mote, lossy compression algorithms in Chapter 4. Results from our work show that our RTV algorithm outperforms current on-mote compressive sampling algorithms and performs comparably to (and in many cases better than) the four state-of-the-art, on-mote lossy compression techniques. The main benefit of RTV is that it can guarantee a desired level of compression performance (and thus, radio usage

  18. Correlation of pre-earthquake electromagnetic signals with laboratory and field rock experiments

    Directory of Open Access Journals (Sweden)

    T. Bleier


    Full Text Available Analysis of the 2007 M5.4 Alum Rock earthquake near San José California showed that magnetic pulsations were present in large numbers and with significant amplitudes during the 2 week period leading up the event. These pulsations were 1–30 s in duration, had unusual polarities (many with only positive or only negative polarities versus both polarities, and were different than other pulsations observed over 2 years of data in that the pulse sequence was sustained over a 2 week period prior to the quake, and then disappeared shortly after the quake. A search for the underlying physics process that might explain these pulses was was undertaken, and one theory (Freund, 2002 demonstrated that charge carriers were released when various types of rocks were stressed in a laboratory environment. It was also significant that the observed charge carrier generation was transient, and resulted in pulsating current patterns. In an attempt to determine if this phenomenon occurred outside of the laboratory environment, the authors scaled up the physics experiment from a relatively small rock sample in a dry laboratory setting, to a large 7 metric tonne boulder comprised of Yosemite granite. This boulder was located in a natural, humid (above ground setting at Bass Lake, Ca. The boulder was instrumented with two Zonge Engineering, Model ANT4 induction type magnetometers, two Trifield Air Ion Counters, a surface charge detector, a geophone, a Bruker Model EM27 Fourier Transform Infra Red (FTIR spectrometer with Sterling cycle cooler, and various temperature sensors. The boulder was stressed over about 8 h using expanding concrete (Bustartm, until it fractured into three major pieces. The recorded data showed surface charge build up, magnetic pulsations, impulsive air conductivity changes, and acoustical cues starting about 5 h before the boulder actually broke. These magnetic and air conductivity pulse signatures resembled both the laboratory