Joint Inversion of Earthquake Source Parameters with local and teleseismic body waves

Science.gov (United States)

Chen, W.; Ni, S.; Wang, Z.

2011-12-01

In the classical source parameter inversion algorithm of CAP (Cut and Paste method, by Zhao and Helmberger), waveform data at near distances (typically less than 500km) are partitioned into Pnl and surface waves to account for uncertainties in the crustal models and different amplitude weight of body and surface waves. The classical CAP algorithms have proven effective for resolving source parameters (focal mechanisms, depth and moment) for earthquakes well recorded on relatively dense seismic network. However for regions covered with sparse stations, it is challenging to achieve precise source parameters . In this case, a moderate earthquake of ~M6 is usually recorded on only one or two local stations with epicentral distances less than 500 km. Fortunately, an earthquake of ~M6 can be well recorded on global seismic networks. Since the ray paths for teleseismic and local body waves sample different portions of the focal sphere, combination of teleseismic and local body wave data helps constrain source parameters better. Here we present a new CAP mothod (CAPjoint), which emploits both teleseismic body waveforms (P and SH waves) and local waveforms (Pnl, Rayleigh and Love waves) to determine source parameters. For an earthquake in Nevada that is well recorded with dense local network (USArray stations), we compare the results from CAPjoint with those from the traditional CAP method involving only of local waveforms , and explore the efficiency with bootstraping statistics to prove the results derived by CAPjoint are stable and reliable. Even with one local station included in joint inversion, accuracy of source parameters such as moment and strike can be much better improved.

The Shock Wave in the ionosphere during an Earthquake

Directory of Open Access Journals (Sweden)

Kuznetsov Vladimir

2016-01-01

Full Text Available Fundamentally new model of the shock wave (SW generation in atmosphere and ionosphere during earthquake is proposed. The model proceeds from the idea of cooperative shock water crystallization in a cloud.

Statistical distributions of earthquakes and related non-linear features in seismic waves

International Nuclear Information System (INIS)

Apostol, B.-F.

2006-01-01

A few basic facts in the science of the earthquakes are briefly reviewed. An accumulation, or growth, model is put forward for the focal mechanisms and the critical focal zone of the earthquakes, which relates the earthquake average recurrence time to the released seismic energy. The temporal statistical distribution for average recurrence time is introduced for earthquakes, and, on this basis, the Omori-type distribution in energy is derived, as well as the distribution in magnitude, by making use of the semi-empirical Gutenberg-Richter law relating seismic energy to earthquake magnitude. On geometric grounds, the accumulation model suggests the value r = 1/3 for the Omori parameter in the power-law of energy distribution, which leads to β = 1,17 for the coefficient in the Gutenberg-Richter recurrence law, in fair agreement with the statistical analysis of the empirical data. Making use of this value, the empirical Bath's law is discussed for the average magnitude of the aftershocks (which is 1.2 less than the magnitude of the main seismic shock), by assuming that the aftershocks are relaxation events of the seismic zone. The time distribution of the earthquakes with a fixed average recurrence time is also derived, the earthquake occurrence prediction is discussed by means of the average recurrence time and the seismicity rate, and application of this discussion to the seismic region Vrancea, Romania, is outlined. Finally, a special effect of non-linear behaviour of the seismic waves is discussed, by describing an exact solution derived recently for the elastic waves equation with cubic anharmonicities, its relevance, and its connection to the approximate quasi-plane waves picture. The properties of the seismic activity accompanying a main seismic shock, both like foreshocks and aftershocks, are relegated to forthcoming publications. (author)

The finite-difference and finite-element modeling of seismic wave propagation and earthquake motion

International Nuclear Information System (INIS)

Moszo, P.; Kristek, J.; Galis, M.; Pazak, P.; Balazovijech, M.

2006-01-01

Numerical modeling of seismic wave propagation and earthquake motion is an irreplaceable tool in investigation of the Earth's structure, processes in the Earth, and particularly earthquake phenomena. Among various numerical methods, the finite-difference method is the dominant method in the modeling of earthquake motion. Moreover, it is becoming more important in the seismic exploration and structural modeling. At the same time we are convinced that the best time of the finite-difference method in seismology is in the future. This monograph provides tutorial and detailed introduction to the application of the finite-difference, finite-element, and hybrid finite-difference-finite-element methods to the modeling of seismic wave propagation and earthquake motion. The text does not cover all topics and aspects of the methods. We focus on those to which we have contributed. (Author)

Control strategy to limit duty cycle impact of earthquakes on the LIGO gravitational-wave detectors

Science.gov (United States)

Biscans, S.; Warner, J.; Mittleman, R.; Buchanan, C.; Coughlin, M.; Evans, M.; Gabbard, H.; Harms, J.; Lantz, B.; Mukund, N.; Pele, A.; Pezerat, C.; Picart, P.; Radkins, H.; Shaffer, T.

2018-03-01

Advanced gravitational-wave detectors such as the laser interferometer gravitational-wave observatories (LIGO) require an unprecedented level of isolation from the ground. When in operation, they measure motion of less than 10‑19 m. Strong teleseismic events like earthquakes disrupt the proper functioning of the detectors, and result in a loss of data. An earthquake early-warning system, as well as a prediction model, have been developed to understand the impact of earthquakes on LIGO. This paper describes a control strategy to use this early-warning system to reduce the LIGO downtime by  ∼30%. It also presents a plan to implement this new earthquake configuration in the LIGO automation system.

Long-period ground motions at near-regional distances caused by the PL wave from, inland earthquakes: Observation and numerical simulation of the 2004 Mid-Niigata, Japan, Mw6.6 earthquake

Science.gov (United States)

Furumura, T.; Kennett, B. L. N.

2017-12-01

We examine the development of large, long-period ground motions at near-regional distances (D=50-200 km) generated by the PL wave from large, shallow inland earthquakes, based on the analysis of strong motion records and finite-difference method (FDM) simulations of seismic wave propagation. PL wave can be represented as leaking modes of the crustal waveguide and are commonly observed at regional distances between 300 to 1000 km as a dispersed, long-period signal with a dominant period of about 20 s. However, observations of recent earthquakes at the dense K-NET and KiK-net strong motion networks in Japan demonstrate the dominance of the PL wave at near-regional (D=50-200 km) distances as, e.g., for the 2004 Mid Niigata, Japan, earthquake (Mw6.6; h=13 km). The observed PL wave signal between P and S wave shows a large, dispersed wave packet with dominant period of about T=4-10 s with amplitude almost comparable to or larger than the later arrival of the S and surface waves. Thus, the early arrivals of the long-period PL wave immediately after P wave can enhance resonance with large-scale constructions such as high-rise buildings and large oil-storage tanks etc. with potential for disaster. Such strong effects often occurred during the 2004 Mid Niigata earthquakes and other large earthquakes which occurred nearby the Kanto (Tokyo) basin. FDM simulation of seismic wave propagation employing realistic 3-D sedimentary structure models demonstrates the process by which the PL wave develops at near-regional distances from shallow, crustal earthquakes by constructive interference of the P wave in the long-period band. The amplitude of the PL wave is very sensitive to low-velocity structure in the near-surface. Lowered velocities help to develop large SV-to-P conversion and weaken the P-to-SV conversion at the free surface. Both effects enhance the multiple P reflections in the crustal waveguide and prevent the leakage of seismic energy into the mantle. However, a very

Sensitivity of tsunami wave profiles and inundation simulations to earthquake slip and fault geometry for the 2011 Tohoku earthquake

KAUST Repository

Goda, Katsuichiro; Mai, Paul Martin; Yasuda, Tomohiro; Mori, Nobuhito

2014-01-01

In this study, we develop stochastic random-field slip models for the 2011 Tohoku earthquake and conduct a rigorous sensitivity analysis of tsunami hazards with respect to the uncertainty of earthquake slip and fault geometry. Synthetic earthquake slip distributions generated from the modified Mai-Beroza method captured key features of inversion-based source representations of the mega-thrust event, which were calibrated against rich geophysical observations of this event. Using original and synthesised earthquake source models (varied for strike, dip, and slip distributions), tsunami simulations were carried out and the resulting variability in tsunami hazard estimates was investigated. The results highlight significant sensitivity of the tsunami wave profiles and inundation heights to the coastal location and the slip characteristics, and indicate that earthquake slip characteristics are a major source of uncertainty in predicting tsunami risks due to future mega-thrust events.

Sensitivity of tsunami wave profiles and inundation simulations to earthquake slip and fault geometry for the 2011 Tohoku earthquake

KAUST Repository

Goda, Katsuichiro

2014-09-01

In this study, we develop stochastic random-field slip models for the 2011 Tohoku earthquake and conduct a rigorous sensitivity analysis of tsunami hazards with respect to the uncertainty of earthquake slip and fault geometry. Synthetic earthquake slip distributions generated from the modified Mai-Beroza method captured key features of inversion-based source representations of the mega-thrust event, which were calibrated against rich geophysical observations of this event. Using original and synthesised earthquake source models (varied for strike, dip, and slip distributions), tsunami simulations were carried out and the resulting variability in tsunami hazard estimates was investigated. The results highlight significant sensitivity of the tsunami wave profiles and inundation heights to the coastal location and the slip characteristics, and indicate that earthquake slip characteristics are a major source of uncertainty in predicting tsunami risks due to future mega-thrust events.

SeismoDome: Sonic and visual representation of earthquakes and seismic waves in the planetarium

Science.gov (United States)

Holtzman, B. K.; Candler, J.; Repetto, D.; Pratt, M. J.; Paté, A.; Turk, M.; Gualtieri, L.; Peter, D. B.; Trakinski, V.; Ebel, D. S. S.; Gossmann, J.; Lem, N.

2017-12-01

Since 2014, we have produced four "Seismodome" public programs in the Hayden Planetarium at the American Museum of Natural History in New York City. To teach the general public about the dynamics of the Earth, we use a range of seismic data (seismicity catalogs, surface and body wave fields, ambient noise, free oscillations) to generate movies and sounds conveying aspects of the physics of earthquakes and seismic waves. The narrative aims to stretch people's sense of time and scale, starting with 2 billion years of convection, then zooming in seismicity over days to twenty years at different length scales, to hours of global seismic wave propagation, all compressed to minute long movies. To optimize the experience in the planetarium, the 180-degree fisheye screen corresponds directly to the surface of the Earth, such that the audience is inside the planet. The program consists of three main elements (1) Using sonified and animated seismicity catalogs, comparison of several years of earthquakes on different plate boundaries conveys the dramatic differences in their dynamics and the nature of great and "normal" earthquakes. (2) Animations of USArray data (based on "Ground Motion Visualizations" methods from IRIS but in 3D, with added sound) convey the basic observations of seismic wave fields, with which we raise questions about what they tell us about earthquake physics and the Earth's interior structure. (3) Movies of spectral element simulations of global seismic wave fields synchronized with sonified natural data push these questions further, especially when viewed from the interior of the planet. Other elements include (4) sounds of the global ambient noise field coupled to movies of mean ocean wave height (related to the noise source) and (5) three months of free oscillations / normal modes ringing after the Tohoku earthquake. We use and develop a wide range of sonification and animation methods, written mostly in python. Flat-screen versions of these movies

Drought and Heat Waves: The Role of SST and Land Surface Feedbacks

Science.gov (United States)

Schubert, Siegfried

2011-01-01

Drought occurs on a wide range of time scales, and within a variety of different types of regional climates. At the shortest time scales it is often associated with heat waves that last only several weeks to a few months but nevertheless can have profound detrimental impacts on society (e.g., heat-related impacts on human health, desiccation of croplands, increased fire hazard), while at the longest time scales it can extend over decades and can lead to long term structural changes in many aspects of society (e.g., agriculture, water resources, wetlands, tourism, population shifts). There is now considerable evidence that sea surface temperatures (SSTs) play a leading role in the development of drought world-wide, especially at seasonal and longer time scales, though land-atmosphere feedbacks can also play an important role. At shorter (subseasonal) time scales, SSTs are less important, but land feedbacks can play a critical role in maintaining and amplifying the atmospheric conditions associated with heat waves and short-term droughts. This talk reviews our current understanding of the physical mechanisms that drive precipitation and temperature variations on subseasonal to centennial time scales. This includes an assessment of predictability, prediction skill, and user needs at all time scales.

Seismic wave triggering of nonvolcanic tremor, episodic tremor and slip, and earthquakes on Vancouver Island

Science.gov (United States)

Rubinstein, Justin L.; Gomberg, Joan; Vidale, John E.; Wech, Aaron G.; Kao, Honn; Creager, Kenneth C.; Rogers, Garry

2009-02-01

We explore the physical conditions that enable triggering of nonvolcanic tremor and earthquakes by considering local seismic activity on Vancouver Island, British Columbia during and immediately after the arrival of large-amplitude seismic waves from 30 teleseismic and 17 regional or local earthquakes. We identify tremor triggered by four of the teleseismic earthquakes. The close temporal and spatial proximity of triggered tremor to ambient tremor and aseismic slip indicates that when a fault is close to or undergoing failure, it is particularly susceptible to triggering of further events. The amplitude of the triggering waves also influences the likelihood of triggering both tremor and earthquakes such that large amplitude waves triggered tremor in the absence of detectable aseismic slip or ambient tremor. Tremor and energy radiated from regional/local earthquakes share the same frequency passband so that tremor cannot be identified during these smaller, more frequent events. We confidently identify triggered local earthquakes following only one teleseism, that with the largest amplitude, and four regional or local events that generated vigorous aftershock sequences in their immediate vicinity. Earthquakes tend to be triggered in regions different from tremor and with high ambient seismicity rates. We also note an interesting possible correlation between large teleseismic events and episodic tremor and slip (ETS) episodes, whereby ETS events that are "late" and have built up more stress than normal are susceptible to triggering by the slight nudge of the shaking from a large, distant event, while ETS events that are "early" or "on time" are not.

Auto Correlation Analysis of Coda Waves from Local Earthquakes for Detecting Temporal Changes in Shallow Subsurface Structures: the 2011 Tohoku-Oki, Japan Earthquake

Science.gov (United States)

Nakahara, Hisashi

2015-02-01

For monitoring temporal changes in subsurface structures I propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers, which probably contain more body waves than surface waves. Use of coda waves requires earthquakes resulting in decreased time resolution for monitoring. Nonetheless, it may be possible to monitor subsurface structures in sufficient time resolutions in regions with high seismicity. In studying the 2011 Tohoku-Oki, Japan earthquake (Mw 9.0), for which velocity changes have been previously reported, I try to validate the method. KiK-net stations in northern Honshu are used in this analysis. For each moderate earthquake normalized auto correlation functions of surface records are stacked with respect to time windows in the S-wave coda. Aligning the stacked, normalized auto correlation functions with time, I search for changes in phases arrival times. The phases at lag times of <1 s are studied because changes at shallow depths are focused. Temporal variations in the arrival times are measured at the stations based on the stretching method. Clear phase delays are found to be associated with the mainshock and to gradually recover with time. The amounts of the phase delays are 10 % on average with the maximum of about 50 % at some stations. The deconvolution analysis using surface and subsurface records at the same stations is conducted for validation. The results show the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis, which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths. The auto correlation analysis seems to have an accuracy of about several percent, which is much larger than methods using earthquake doublets and borehole array data. So this analysis might be applicable in detecting larger changes. In spite of these disadvantages, this analysis is still attractive because it can

North American Drought and Links to Northern Eurasia: The Role of Stationary Rossby Waves

Science.gov (United States)

Wang, Hailan; Schubert, Siegfried D.; Koster, Randal D.

2017-01-01

This chapter provides an overview of the role of stationary Rossby waves in the sub-seasonal development of warm season drought over North America and subsequent downstream development of climate anomalies over northern Eurasia. The results are based on a case study of a stationary Rossby wave event that developed during 20 May 15 June 1988. Simulations with the NASA Goddard Earth Observing System (GEOS-5) atmospheric general circulation model highlight the importance of the mean jet streams in guiding and constraining the path and speed of wave energy propagation. In particular, convective anomalies that developed over the western Pacific in late May (in the presence of the strong North Pacific jet) produce a predilection for persistent upper-level high anomalies over central North America about ten days later, leading to the rapid development of severe dry conditions there. There are indications of continued downstream wave energy propagation that reaches northern Eurasia about two weeks later, leading to the development of dry conditions over eastern Europe and western Russia, and cool and wet conditions over western Europe and central northern Eurasia. The results suggest that stationary Rossby waves can serve as a source of predictability for sub-seasonal development of droughts over North America and northern Eurasia.

Conversion of Local and Surface-Wave Magnitudes to Moment Magnitude for Earthquakes in the Chinese Mainland

Science.gov (United States)

Li, X.; Gao, M.

2017-12-01

The magnitude of an earthquake is one of its basic parameters and is a measure of its scale. It plays a significant role in seismology and earthquake engineering research, particularly in the calculations of the seismic rate and b value in earthquake prediction and seismic hazard analysis. However, several current types of magnitudes used in seismology research, such as local magnitude (ML), surface wave magnitude (MS), and body-wave magnitude (MB), have a common limitation, which is the magnitude saturation phenomenon. Fortunately, the problem of magnitude saturation was solved by a formula for calculating the seismic moment magnitude (MW) based on the seismic moment, which describes the seismic source strength. Now the moment magnitude is very commonly used in seismology research. However, in China, the earthquake scale is primarily based on local and surface-wave magnitudes. In the present work, we studied the empirical relationships between moment magnitude (MW) and local magnitude (ML) as well as surface wave magnitude (MS) in the Chinese Mainland. The China Earthquake Networks Center (CENC) ML catalog, China Seismograph Network (CSN) MS catalog, ANSS Comprehensive Earthquake Catalog (ComCat), and Global Centroid Moment Tensor (GCMT) are adopted to regress the relationships using the orthogonal regression method. The obtained relationships are as follows: MW=0.64+0.87MS; MW=1.16+0.75ML. Therefore, in China, if the moment magnitude of an earthquake is not reported by any agency in the world, we can use the equations mentioned above for converting ML to MW and MS to MW. These relationships are very important, because they will allow the China earthquake catalogs to be used more effectively for seismic hazard analysis, earthquake prediction, and other seismology research. We also computed the relationships of and (where Mo is the seismic moment) by linear regression using the Global Centroid Moment Tensor. The obtained relationships are as follows: logMo=18

P-wave attenuation in the Pacific slab beneath northeastern Japan revealed by the spectral ratio of intraslab earthquakes

Science.gov (United States)

Shiina, Takahiro; Nakajima, Junichi; Matsuzawa, Toru

2018-05-01

We investigate P-wave attenuation, Qp-1, in the Pacific slab beneath northeastern (NE) Japan, adopting for the first time the spectral ratio technique for intraslab earthquakes. When seismograms of two earthquakes are recorded at a station and their ray paths to the station are largely overlapped, station-dependent amplification and structural effects on the overlapped rays can be canceled out from the ratio of the spectral amplitudes of the seismograms. Therefore, adopting the spectral ratio technique for intraslab earthquakes has a great advantage for the precise evaluation of Qp-1 in the slab because the structural effects above the slab, including the high-attenuation mantle wedge, are removed. For estimating the intraslab Qp-1, we determined corner frequency of the intraslab earthquakes using the S-coda wave spectral ratio as the first step. Then, we evaluated the inter-event path attenuation, Δt*, from the ratio of the spectral amplitudes of P waves. The obtained result shows that P-wave attenuation in the Pacific slab marks Qp-1 of 0.0015 (Qp of ∼670) at depths of 50-250 km. This indicates that the P-wave attenuation in the Pacific slab is weaker than that in the mantle wedge. The relatively high-Qp-1 is correlated with the distributions of intraslab earthquakes, suggesting that the P-wave amplitude is more attenuated around active seismicity zones in the slab. Therefore, our observations likely indicate the presence of fractures, hydrous minerals, and dehydrated fluid around seismogenic zones in the slab at intermediate depths.

Scaling relation between earthquake magnitude and the departure time from P wave similar growth

Science.gov (United States)

Noda, Shunta; Ellsworth, William L.

2016-01-01

We introduce a new scaling relation between earthquake magnitude (M) and a characteristic of initial P wave displacement. By examining Japanese K-NET data averaged in bins partitioned by Mw and hypocentral distance, we demonstrate that the P wave displacement briefly displays similar growth at the onset of rupture and that the departure time (Tdp), which is defined as the time of departure from similarity of the absolute displacement after applying a band-pass filter, correlates with the final M in a range of 4.5 ≤ Mw ≤ 7. The scaling relation between Mw and Tdp implies that useful information on the final M can be derived while the event is still in progress because Tdp occurs before the completion of rupture. We conclude that the scaling relation is important not only for earthquake early warning but also for the source physics of earthquakes.

Determination of Love- and Rayleigh-Wave Magnitudes for Earthquakes and Explosions and Other Studies

Science.gov (United States)

2012-12-30

09-C-0012 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62601F 6. AUTHOR(S) Jessie L. Bonner, Anastasia Stroujkova, Dale Anderson, Jonathan...AND RAYLEIGH-WAVE MAGNITUDES FOR EARTHQUAKES AND EXPLOSIONS Jessie L. Bonner, Anastasia Stroujkova, and Dale Anderson INTRODUCTION Since...MAXIMUM LIKELIHOOD ESTIMATION: APPLICATION TO MIDDLE EAST EARTHQUAKE DATA Anastasia Stroujkova and Jessie Bonner Weston Geophysical Corporation

Mantle Attenuation Estimated from Regional and Teleseismic P-waves of Deep Earthquakes and Surface Explosions

Science.gov (United States)

Ichinose, G.; Woods, M.; Dwyer, J.

2014-03-01

We estimated the network-averaged mantle attenuation t*(total) of 0.5 s beneath the North Korea test site (NKTS) by use of P-wave spectra and normalized spectral stacks from the 25 May 2009 declared nuclear test (mb 4.5; IDC). This value was checked using P-waves from seven deep (580-600 km) earthquakes (4.8 test, which confirms the equality with the sum of t*(u) and t*(d). We included constraints on seismic moment, depth, and radiation pattern by using results from a moment tensor analysis and corner frequencies from modeling of P-wave spectra recorded at local distances. We also avoided finite-faulting effects by excluding earthquakes with complex source time functions. We assumed ω2 source models for earthquakes and explosions. The mantle attenuation beneath the NKTS is clearly different when compared with the network-averaged t* of 0.75 s for the western US and is similar to values of approximately 0.5 s for the Semipalatinsk test site within the 0.5-2 Hz range.

Body-wave seismic interferometry applied to earthquake- and storm-induced wavefield

NARCIS (Netherlands)

Ruigrok, E.N.

2012-01-01

Seismology is the study of the vibration of the Earth. Seismologists pay much attention to the main source of Earth vibration: earthquakes. But also other seismic sources, like mining blasts, ocean storms and windmills, are studied. All these sources induce seismic waves, which can eventually be

Future heat-waves, droughts and floods in 571 European cities

Science.gov (United States)

Guerreiro, Selma B.; Dawson, Richard J.; Kilsby, Chris; Lewis, Elizabeth; Ford, Alistair

2018-03-01

Cities are particularly vulnerable to climate risks due to their agglomeration of people, buildings and infrastructure. Differences in methodology, hazards considered, and climate models used limit the utility and comparability of climate studies on individual cities. Here we assess, for the first time, future changes in flood, heat-waves (HW), and drought impacts for all 571 European cities in the Urban Audit database using a consistent approach. To capture the full range of uncertainties in natural variability and climate models, we use all climate model runs from the Coupled Model Inter-comparison Project Phase 5 (CMIP5) for the RCP8.5 emissions scenario to calculate Low, Medium and High Impact scenarios, which correspond to the 10th, 50th and 90th percentiles of each hazard for each city. We find that HW days increase across all cities, but especially in southern Europe, whilst the greatest HW temperature increases are expected in central European cities. For the low impact scenario, drought conditions intensify in southern European cities while river flooding worsens in northern European cities. However, the high impact scenario projects that most European cities will see increases in both drought and river flood risks. Over 100 cities are particularly vulnerable to two or more climate impacts. Moreover, the magnitude of impacts exceeds those previously reported highlighting the substantial challenge cities face to manage future climate risks.

Auto correlation analysis of coda waves from local earthquakes for detecting temporal changes in shallow subsurface structures - The 2011 Tohoku-Oki, Japan, earthquake -

Science.gov (United States)

Nakahara, H.

2013-12-01

For monitoring temporal changes in subsurface structures, I propose to use auto correlation functions of coda waves from local earthquakes recorded at surface receivers, which probably contain more body waves than surface waves. Because the use of coda waves requires earthquakes, time resolution for monitoring decreases. But at regions with high seismicity, it may be possible to monitor subsurface structures in sufficient time resolutions. Studying the 2011 Tohoku-Oki (Mw 9.0), Japan, earthquake for which velocity changes have been already reported by previous studies, I try to validate the method. KiK-net stations in northern Honshu are used in the analysis. For each moderate earthquake, normalized auto correlation functions of surface records are stacked with respect to time windows in S-wave coda. Aligning the stacked normalized auto correlation functions with time, I search for changes in arrival times of phases. The phases at lag times of less than 1s are studied because changes at shallow depths are focused. Based on the stretching method, temporal variations in the arrival times are measured at the stations. Clear phase delays are found to be associated with the mainshock and to gradually recover with time. Amounts of the phase delays are in the order of 10% on average with the maximum of about 50% at some stations. For validation, the deconvolution analysis using surface and subsurface records at the same stations are conducted. The results show that the phase delays from the deconvolution analysis are slightly smaller than those from the auto correlation analysis, which implies that the phases on the auto correlations are caused by larger velocity changes at shallower depths. The auto correlation analysis seems to have an accuracy of about several percents, which is much larger than methods using earthquake doublets and borehole array data. So this analysis might be applicable to detect larger changes. In spite of these disadvantages, this analysis is

Imaging the 2017 MW 8.2 Tehuantepec intermediate-depth earthquake using Teleseismic P Waves

Science.gov (United States)

Brudzinski, M.; Zhang, H.; Koper, K. D.; Pankow, K. L.

2017-12-01

The September 8, 2017 MW 8.1 Tehuantepec, Mexico earthquakes in the middle American subduction zone is one of the largest intermediate-depth earthquake ever recorded and could provide an unprecedented opportunity for understanding the mechanism of intermediate-depth earthquakes. While the hypocenter and centroid depths for this earthquake are shallower than typically considered for intermediate depth earthquakes, the normal faulting mechanism consistent with down-dip extension and location within the subducting plate align with properties of intermediate depth earthquakes. Back-projection of high-frequency teleseismic P-waves from two regional arrays for this earthquake shows unilateral rupture on a southeast-northwest striking fault that extends north of the Tehuantepec fracture zone (TFZ), with an average horizontal rupture speed of 3.0 km/s and total duration of 60 s. Guided by these back-projection results, 47 globally distributed low-frequency P-waves were inverted for a finite-fault model (FFM) of slip for both nodal planes. The FFM shows a slip deficit in proximity to the extension of the TFZ, as well as the minor rupture beyond the TFZ (confirmed by the synthetic tests), which indicates that the TFZ acted as a barrier for this earthquake. Analysis of waveform misfit leads to the preference of a subvertical plane as the causative fault. The FFM shows that the majority of the rupture is above the focal depth and consists of two large slip patches: the first one is near the hypocenter ( 55 km depth) and the second larger one near 30 km depth. The distribution of the two patches spatially agrees with seismicity that defines the upper and lower zones of a double Benioff zone (DBZ). It appears there was single fault rupture across the two depth zones of the DBZ. This is uncommon because a stark aseismic zone is typically observed between the upper and lower zones of the DBZ. This finding indicates that the mechanism for intraslab earthquakes must allow for

Modeling subduction earthquake sources in the central-western region of Colombia using waveform inversion of body waves

Science.gov (United States)

Monsalve-Jaramillo, Hugo; Valencia-Mina, William; Cano-Saldaña, Leonardo; Vargas, Carlos A.

2018-05-01

Source parameters of four earthquakes located within the Wadati-Benioff zone of the Nazca plate subducting beneath the South American plate in Colombia were determined. The seismic moments for these events were recalculated and their approximate equivalent rupture area, slip distribution and stress drop were estimated. The source parameters for these earthquakes were obtained by deconvolving multiple events through teleseismic analysis of body waves recorded in long period stations and with simultaneous inversion of P and SH waves. The calculated source time functions for these events showed different stages that suggest that these earthquakes can reasonably be thought of being composed of two subevents. Even though two of the overall focal mechanisms obtained yielded similar results to those reported by the CMT catalogue, the two other mechanisms showed a clear difference compared to those officially reported. Despite this, it appropriate to mention that the mechanisms inverted in this work agree well with the expected orientation of faulting at that depth as well as with the wave forms they are expected to produce. In some of the solutions achieved, one of the two subevents exhibited a focal mechanism considerably different from the total earthquake mechanism; this could be interpreted as the result of a slight deviation from the overall motion due the complex stress field as well as the possibility of a combination of different sources of energy release analogous to the ones that may occur in deeper earthquakes. In those cases, the subevents with very different focal mechanism compared to the total earthquake mechanism had little contribution to the final solution and thus little contribution to the total amount of energy released.

Drought assessment by evapotranspiration mapping in Twente

Science.gov (United States)

Eden, U.; Timmermans, J.; van der Velde, R.; Su, Z.

2012-04-01

Drought is a reoccurring worldwide problem with impacts ranging from food production to infrastructure. Droughts are different from other natural hazards (floods, hurricanes, and earthquakes) because the effects can only be witnessed slowly and with a time delay. Effects of droughts are diverse, like famine and migration of people. Droughts are caused by natural causes but also by interaction between the natural events and water demand. Not only typical dry regions, like the Horn of Africa, are affected, but even semi-humid environments, like Europe. Temperature rise and precipitation deficit in the summers of 2003 and 2006 caused substantial crop losses in the agricultural sector in the Netherlands. In addition increased river water temperatures and low water levels caused cooling problems for power plants. Heat waves and prolonged absence of precipitation is expected to increase due to climate change. Therefore assessing and monitoring drought in the Netherlands is thus very important. Various drought indices are available to assess the severity, duration and spatial extend of the drought. Some of the commonly indices used are Standardized precipitation index (SPI) and the Palmer Drought Severity Index (PDSI). However each of these indices do not take into account the actual state of the land surface in respect to the dryness. By analysing drought through actual evapotranspiration (ET) estimations from remote sensing this can be circumvented. The severity of the droughts was quantified by ET-mapping from 2003-2010. The assessment was based on the spatial and temporal distribution of ET using the Evapotranspiration Deficit Index (ETDI) drought index. Surface energy fluxes, like ET, were estimated using WACMOS methodology. The input data consisted of remote sensing products like land surface temperature, LAI, and albedo from MODIS; and meteorological data like air-temperature, humidity and wind speed from the European Centre for Medium weather forecast (ECMWF

Atmospheric gravity wave detection following the 2011 Tohoku earthquakes combining COSMIC occultation and GPS observations

Science.gov (United States)

Yan, X.; Tao, Y.; Xia, C.; Qi, Y.; Zuo, X.

2017-12-01

Several studies have reported the earthquake-induced atmospheric gravity waves detected by some new technologies such as airglow (Makela et al., 2011), GOCE (Garcia et al., 2013), GRACE (Yang et al., 2014), F3/C radio occultation sounding (Coïsson et al., 2015). In this work, we collected all occultation events on 11 March, and selected four events to analyze at last. The original and filtered podTEC is represented as function of the altitude of the impact parameter and UT of the four events. Then, the travel time diagrams of filtered podTEC derived from the events were analyzed. The occultation signal from one event (marked as No.73) is consistent with the previous results reported by Coïsson. 2015, which is corresponds to the ionospheric signal induced from tsunami gravity wave. What is noticeable, in this work, is that three occultation events of No.403, 77 and 118 revealed a disturbance of atmospheric gravity wave with velocity 300m/s, preceding the tsunami. It would probably be correspond to the gravity waves caused by seismic rupture but not tsunami. In addition, it can be seen that the perturbation height of occultation observation TEC is concentrated at 200-400km, corresponding ionosphere F region. The signals detected above are compared with GPS measurements of TEC from GEONET and IGS. From GPS data, traveling ionospheric disturbances were observed spreading out from the epicenter as a quasi-circular propagation pattern with the time. Exactly, we observed an acoustic wave coupled with Rayleigh wave starting from the epicenter with a speed of 3.0km/s and a superimposed acoustic-gravity wave moving with a speed of 800m/s. The acoustic-gravity wave generated at the epicenter and gradually attenuated 800km away, then it is replaced by a gravity wave coupled with the tsunami that moves with a speed of between 100 and 300m/s. It is necessary to confirm the propagation process of the waves if we attempt to evaluate the use of ionospheric seismology as a

Wave-Wave Coupling and Disasters: The 1985 Mexico Earthquake and the 2001 WTC Collapse

Science.gov (United States)

Lomnitz, C.

2002-12-01

Wave-wave coupling occurs in the presence of weak nonlinearity. It can generate quite dramatic, unexpected effects. In the 1985 earthquake disaster in Mexico City more than 400 high-rise buildings collapsed on soft ground with a loss of life of around 10,000. The emergence of a large, monochromatic, coherent ground wave was an unforeseen factor. Linear modeling failed to reproduce the main features of this signal including the prominent spectral peak close to the resonant frequency of the high-rise buildings, and an extremely long time duration (more than five minutes). The signal was apparently due to coupling of a fundamental Rayleigh mode to the quarter-wavelength shear resonance in the surface mud layer through their common frequency at 0.4 Hz. An additional unexpected feature was the low attenuation of these modes in the mud layer, and the presence of prograde particle motion. Prograde rotation, though not necessarily caused by nonlinear effects, will couple with structural modes of vibration that tend to destabilize a tall building, much like a tall ship in ocean waves. Such unanticipated features may play a critical role in earthquake disasters on soft ground. A related case is the World Trade Center disaster of 11 September 2001, which was presumed to be due to gradual heat softening of steel girders. If so, the Twin Towers should have leaned over sideways but actually the collapse occurred vertically and quite suddenly. A likely alternative is coupling between a fireball caused by a phase transition between low- and high-oxygen consumption modes in burning jet fuel: (low-oxygen) 2CnH2n+2 + (n+1)O2 = nC2 + (2n+2)H2O, (1) (high-oxygen) 2CnH2n+2 + (3n+1)O2 = 2nCO2 + (2n+2)H2O, (2) and a pressure pulse propagating vertically inside the tubular structure. The pulse would have taken out the concrete floors, thus initiating collapse by implosion of the structural shell. Linear thinking may fail to anticipate coupling, and thus appropriate preventive measures may

Regional seismic-wave propagation from the M5.8 23 August 2011, Mineral, Virginia, earthquake

Science.gov (United States)

Pollitz, Fred; Mooney, Walter D.

2015-01-01

The M5.8 23 August 2011 Mineral, Virginia, earthquake was felt over nearly the entire eastern United States and was recorded by a wide array of seismic broadband instruments. The earthquake occurred ~200 km southeast of the boundary between two distinct geologic belts, the Piedmont and Blue Ridge terranes to the southeast and the Valley and Ridge Province to the northwest. At a dominant period of 3 s, coherent postcritical P-wave (i.e., direct longitudinal waves trapped in the crustal waveguide) arrivals persist to a much greater distance for propagation paths toward the northwest quadrant than toward other directions; this is probably related to the relatively high crustal thickness beneath and west of the Appalachian Mountains. The seismic surface-wave arrivals comprise two distinct classes: those with weakly dispersed Rayleigh waves and those with strongly dispersed Rayleigh waves. We attribute the character of Rayleigh wave arrivals in the first class to wave propagation through a predominantly crystalline crust (Blue Ridge Mountains and Piedmont terranes) with a relatively thin veneer of sedimentary rock, whereas the temporal extent of the Rayleigh wave arrivals in the second class are well explained as the effect of the thick sedimentary cover of the Valley and Ridge Province and adjacent Appalachian Plateau province to its northwest. Broadband surface-wave ground velocity is amplified along both north-northwest and northeast azimuths from the Mineral, Virginia, source. The former may arise from lateral focusing effects arising from locally thick sedimentary cover in the Appalachian Basin, and the latter may result from directivity effects due to a northeast rupture propagation along the finite fault plane.

The music of earthquakes and Earthquake Quartet #1

Science.gov (United States)

Michael, Andrew J.

2013-01-01

Earthquake Quartet #1, my composition for voice, trombone, cello, and seismograms, is the intersection of listening to earthquakes as a seismologist and performing music as a trombonist. Along the way, I realized there is a close relationship between what I do as a scientist and what I do as a musician. A musician controls the source of the sound and the path it travels through their instrument in order to make sound waves that we hear as music. An earthquake is the source of waves that travel along a path through the earth until reaching us as shaking. It is almost as if the earth is a musician and people, including seismologists, are metaphorically listening and trying to understand what the music means.

3D Crust and Uppermost Mantle Structure beneath Tian Shan Region from ambient noise and earthquake surface waves

Science.gov (United States)

Xiao, X.; Wen, L.

2017-12-01

As a typical active intracontinental mountain range in Central Asia, Tian Shan Mt serves as the prototype in studying geodynamic processes and mechanism of intracontinental mountain building. We study 3D crust and the uppermost mantle structure beneath Tian Shan region using ambient noise and earthquake surface waves. Our dataset includes vertical component records of 62 permanent broadband seismic stations operated by the Earthquake Administration of China. Firstly, we calculate two-year stacked Cross-Correlation Functions (CCFs) of ambient noise records between the stations. The CCFs are treated as the Empirical Green's Functions (EGFs) of each station pair, from which we measured phase velocities of fundamental-mode Rayleigh wave in the period of 3-40 s using a frequency-time analysis method. Secondly, we collect surface wave data from tele-seismic events with Mw > 5.5 and depth shallower than 200 km and measure phase velocities of the fundamental-mode of Rayleigh wave in the period of 30-150 s using a two-station method. Finally, we combine the phase velocity measurements from ambient noise and earthquake surface waves, obtain lateral isotropic phase velocity maps at different periods based on tomography and invert a 3D Vsv model of crust and uppermost mantle down to about 150 km using a Monte Carlo Inversion method. We will discuss our inversion results in detail, as well as their implications to the tectonics in the region.

Wheat yield loss attributable to heat waves, drought and water excess at the global, national and subnational scales

Science.gov (United States)

Zampieri, M.; Ceglar, A.; Dentener, F.; Toreti, A.

2017-06-01

Heat waves and drought are often considered the most damaging climatic stressors for wheat. In this study, we characterize and attribute the effects of these climate extremes on wheat yield anomalies (at global and national scales) from 1980 to 2010. Using a combination of up-to-date heat wave and drought indexes (the latter capturing both excessively dry and wet conditions), we have developed a composite indicator that is able to capture the spatio-temporal characteristics of the underlying physical processes in the different agro-climatic regions of the world. At the global level, our diagnostic explains a significant portion (more than 40%) of the inter-annual production variability. By quantifying the contribution of national yield anomalies to global fluctuations, we have found that just two concurrent yield anomalies affecting the larger producers of the world could be responsible for more than half of the global annual fluctuations. The relative importance of heat stress and drought in determining the yield anomalies depends on the region. Moreover, in contrast to common perception, water excess affects wheat production more than drought in several countries. We have also performed the same analysis at the subnational level for France, which is the largest wheat producer of the European Union, and home to a range of climatic zones. Large subnational variability of inter-annual wheat yield is mostly captured by the heat and water stress indicators, consistently with the country-level result.

Investigation on relationship between epicentral distance and growth curve of initial P-wave propagating in local heterogeneous media for earthquake early warning system

Science.gov (United States)

Okamoto, Kyosuke; Tsuno, Seiji

2015-10-01

In the earthquake early warning (EEW) system, the epicenter location and magnitude of earthquakes are estimated using the amplitude growth rate of initial P-waves. It has been empirically pointed out that the growth rate becomes smaller as epicentral distance becomes far regardless of the magnitude of earthquakes. So, the epicentral distance can be estimated from the growth rate using this empirical relationship. However, the growth rates calculated from different earthquakes at the same epicentral distance mark considerably different values from each other. Sometimes the growth rates of earthquakes having the same epicentral distance vary by 104 times. Qualitatively, it has been considered that the gap in the growth rates is due to differences in the local heterogeneities that the P-waves propagate through. In this study, we demonstrate theoretically how local heterogeneities in the subsurface disturb the relationship between the growth rate and the epicentral distance. Firstly, we calculate seismic scattered waves in a heterogeneous medium. First-ordered PP, PS, SP, and SS scatterings are considered. The correlation distance of the heterogeneities and fractional fluctuation of elastic parameters control the heterogeneous conditions for the calculation. From the synthesized waves, the growth rate of the initial P-wave is obtained. As a result, we find that a parameter (in this study, correlation distance) controlling heterogeneities plays a key role in the magnitude of the fluctuation of the growth rate. Then, we calculate the regional correlation distances in Japan that can account for the fluctuation of the growth rate of real earthquakes from 1997 to 2011 observed by K-NET and KiK-net. As a result, the spatial distribution of the correlation distance shows locality. So, it is revealed that the growth rates fluctuate according to the locality. When this local fluctuation is taken into account, the accuracy of the estimation of epicentral distances from initial P-waves

The finite-difference and finite-element modeling of seismic wave propagation and earthquake motion

International Nuclear Information System (INIS)

Moczo, P.; Kristek, J.; Pazak, P.; Balazovjech, M.; Moczo, P.; Kristek, J.; Galis, M.

2007-01-01

Numerical modeling of seismic wave propagation and earthquake motion is an irreplaceable tool in investigation of the Earth's structure, processes in the Earth, and particularly earthquake phenomena. Among various numerical methods, the finite-difference method is the dominant method in the modeling of earthquake motion. Moreover, it is becoming more important in the seismic exploration and structural modeling. At the same time we are convinced that the best time of the finite-difference method in seismology is in the future. This monograph provides tutorial and detailed introduction to the application of the finite difference (FD), finite-element (FE), and hybrid FD-FE methods to the modeling of seismic wave propagation and earthquake motion. The text does not cover all topics and aspects of the methods. We focus on those to which we have contributed. We present alternative formulations of equation of motion for a smooth elastic continuum. We then develop alternative formulations for a canonical problem with a welded material interface and free surface. We continue with a model of an earthquake source. We complete the general theoretical introduction by a chapter on the constitutive laws for elastic and viscoelastic media, and brief review of strong formulations of the equation of motion. What follows is a block of chapters on the finite-difference and finite-element methods. We develop FD targets for the free surface and welded material interface. We then present various FD schemes for a smooth continuum, free surface, and welded interface. We focus on the staggered-grid and mainly optimally-accurate FD schemes. We also present alternative formulations of the FE method. We include the FD and FE implementations of the traction-at-split-nodes method for simulation of dynamic rupture propagation. The FD modeling is applied to the model of the deep sedimentary Grenoble basin, France. The FD and FE methods are combined in the hybrid FD-FE method. The hybrid

Rupture imaging of the Mw 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves

Science.gov (United States)

Xu, Yan; Koper, Keith D.; Sufri, Oner; Zhu, Lupei; Hutko, Alexander R.

2009-04-01

The Mw 7.9 Wenchuan earthquake of 12 May 2008 was the most destructive Chinese earthquake since the 1976 Tangshan event. Tens of thousands of people were killed, hundreds of thousands were injured, and millions were left homeless. Here we infer the detailed rupture process of the Wenchuan earthquake by back-projecting teleseismic P energy from several arrays of seismometers. This technique has only recently become feasible and is potentially faster than traditional finite-fault inversion of teleseismic body waves; therefore, it may reduce the notification time to emergency response agencies. Using the IRIS DMC, we collected 255 vertical component broadband P waves at 30-95° from the epicenter. We found that at periods of 5 s and greater, nearly all of these P waves were coherent enough to be used in a global array. We applied a simple down-sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function (ARF). We also considered three regional subarrays of seismometers in Alaska, Australia, and Europe that had apertures less than 30° and P waves that were coherent to periods as short as 1 s. Individual ARFs for these subarrays were skewed toward the subarrays; however, the linear sum of the regional subarray beams at 1 s produced a symmetric ARF, similar to that of the groomed global subarray at 5 s. For both configurations we obtained the same rupture direction, rupture length, and rupture time. We found that the Wenchuan earthquake had three distinct pulses of high beam power at 0, 23, and 57 s after the origin time, with the pulse at 23 s being highest, and that it ruptured unilaterally to the northeast for about 300 km and 110 s, with an average speed of 2.8 km/s. It is possible that similar results can be determined for future large dip-slip earthquakes within 20-30 min of the origin time using relatively sparse global networks of seismometers such as those the USGS uses to locate

Rupture imaging of the Mw 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves

Science.gov (United States)

Xu, Y.; Koper, K.D.; Sufri, O.; Zhu, L.; Hutko, Alexander R.

2009-01-01

[1] The Mw 7.9 Wenchuan earthquake of 12 May 2008 was the most destructive Chinese earthquake since the 1976 Tangshan event. Tens of thousands of people were killed, hundreds of thousands were injured, and millions were left homeless. Here we infer the detailed rupture process of the Wenchuan earthquake by back-projecting teleseismic P energy from several arrays of seismometers. This technique has only recently become feasible and is potentially faster than traditional finite-fault inversion of teleseismic body waves; therefore, it may reduce the notification time to emergency response agencies. Using the IRIS DMC, we collected 255 vertical component broadband P waves at 30-95?? from the epicenter. We found that at periods of 5 s and greater, nearly all of these P waves were coherent enough to be used in a global array. We applied a simple down-sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function (ARF). We also considered three regional subarrays of seismometers in Alaska, Australia, and Europe that had apertures less than 30?? and P waves that were coherent to periods as short as 1 s. Individual ARFs for these subarrays were skewed toward the subarrays; however, the linear sum of the regional subarray beams at 1 s produced a symmetric ARF, similar to that of the groomed global subarray at 5 s. For both configurations we obtained the same rupture direction, rupture length, and rupture time. We found that the Wenchuan earthquake had three distinct pulses of high beam power at 0, 23, and 57 s after the origin time, with the pulse at 23 s being highest, and that it ruptured unilaterally to the northeast for about 300 km and 110 s, with an average speed of 2.8 km/s. It is possible that similar results can be determined for future large dip-slip earthquakes within 20-30 min of the origin time using relatively sparse global networks of seismometers such as those the USGS uses to locate

SCARDEC: a new technique for the rapid determination of seismic moment magnitude, focal mechanism and source time functions for large earthquakes using body-wave deconvolution

Science.gov (United States)

Vallée, M.; Charléty, J.; Ferreira, A. M. G.; Delouis, B.; Vergoz, J.

2011-01-01

Accurate and fast magnitude determination for large, shallow earthquakes is of key importance for post-seismic response and tsumami alert purposes. When no local real-time data are available, which is today the case for most subduction earthquakes, the first information comes from teleseismic body waves. Standard body-wave methods give accurate magnitudes for earthquakes up to Mw= 7-7.5. For larger earthquakes, the analysis is more complex, because of the non-validity of the point-source approximation and of the interaction between direct and surface-reflected phases. The latter effect acts as a strong high-pass filter, which complicates the magnitude determination. We here propose an automated deconvolutive approach, which does not impose any simplifying assumptions about the rupture process, thus being well adapted to large earthquakes. We first determine the source duration based on the length of the high frequency (1-3 Hz) signal content. The deconvolution of synthetic double-couple point source signals—depending on the four earthquake parameters strike, dip, rake and depth—from the windowed real data body-wave signals (including P, PcP, PP, SH and ScS waves) gives the apparent source time function (STF). We search the optimal combination of these four parameters that respects the physical features of any STF: causality, positivity and stability of the seismic moment at all stations. Once this combination is retrieved, the integration of the STFs gives directly the moment magnitude. We apply this new approach, referred as the SCARDEC method, to most of the major subduction earthquakes in the period 1990-2010. Magnitude differences between the Global Centroid Moment Tensor (CMT) and the SCARDEC method may reach 0.2, but values are found consistent if we take into account that the Global CMT solutions for large, shallow earthquakes suffer from a known trade-off between dip and seismic moment. We show by modelling long-period surface waves of these events that

Heat waves, intense droughts and desertification. summer 1994 in Southeast of Spain; Olas de calor, sequias intensas y desertificacion, durante el verano 1994 en el Sureste espanol (Murcia)

Energy Technology Data Exchange (ETDEWEB)

Avila, F.

2009-07-01

The South-East of spain, which has semiarid climate, is one of the hottest and dries areas in Europe. This region is specialized in irrigated agricultures and citrus fruits (lemons). the drought can last a long period, sometimes two or three years. The lack of water is becoming the biggest problem, especially since the development of irrigated cultures. Drought and heat waves are the major climatic risks and they cause most of the economic losses in agricultural activity. 1994 summer was exceptional in this region of Spain: heat waves and drought. A major disaster that revealed a crisis that began many years ago. The need of water is growing while the volume of available water tends to go down. 1994 summer and its disasters (fire, burnt crops by heat) generated social and politic tensions. Desertification is threatening the region. This situation is not new the drought is a normal phenomenon in a semiarid area, but the accumulation of drought, aridity and human actions worsening desertification. After 1994, new droughts and heat waves increased the lack of water because agriculture needs more and more water. Nonetheless this cultural method is compacting soil by the reduction of organic matter and by the heavy falls of rain. No solution has been found yet, they have to find new resources of water or change agricultural irrigation methods to save water and build up a sustainable development of this semiarid area. (Author) 12 refs.

Future Developments for the Earthquake Early Warning System following the 2011 off the Pacific Coast of Tohoku Earthquake

Science.gov (United States)

Yamada, M.; Mori, J. J.

2011-12-01

The 2011 off the Pacific Coast of Tohoku Earthquake (Mw9.0) caused significant damage over a large area of northeastern Honshu. An earthquake early warning was issued to the public in the Tohoku region about 8 seconds after the first P-arrival, which is 31 seconds after the origin time. There was no 'blind zone', and warnings were received at all locations before S-wave arrivals, since the earthquake was fairly far offshore. Although the early warning message was properly reported in Tohoku region which was the most severely affected area, a message was not sent to the more distant Tokyo region because the intensity was underestimated. . This underestimation was because the magnitude determination in the first few seconds was relatively small (Mj8.1)., and there was no consideration of a finite fault with a long length. Another significant issue is that warnings were sometimes not properly provided for aftershocks. Immediately following the earthquake, the waveforms of some large aftershocks were contaminated by long-period surface waves from the mainshock, which made it difficult to pick P-wave arrivals. Also, correctly distinguishing and locating later aftershocks was sometimes difficult, when multiple events occurred within a short period of time. This masinhock begins with relatively small moment release for the first 10 s . Since the amplitude of the initial waveforms is small, most methods that use amplitudes and periods of the P-wave (e.g. Wu and Kanamori, 2005) cannot correctly determine the size of the4 earthquake in the first several seconds. The current JMA system uses the peak displacement amplitude for the magnitude estimation, and the magnitude saturated at about M8 1 minute after the first P-wave arrival. . Magnitudes of smaller earthquakes can be correctly identified from the first few seconds of P- or S-wave arrivals, but this M9 event cannot be characterized in such a short time. The only way to correctly characterize the size of the Tohoku

Ground water and earthquakes

Energy Technology Data Exchange (ETDEWEB)

Ts' ai, T H

1977-11-01

Chinese folk wisdom has long seen a relationship between ground water and earthquakes. Before an earthquake there is often an unusual change in the ground water level and volume of flow. Changes in the amount of particulate matter in ground water as well as changes in color, bubbling, gas emission, and noises and geysers are also often observed before earthquakes. Analysis of these features can help predict earthquakes. Other factors unrelated to earthquakes can cause some of these changes, too. As a first step it is necessary to find sites which are sensitive to changes in ground stress to be used as sensor points for predicting earthquakes. The necessary features are described. Recording of seismic waves of earthquake aftershocks is also an important part of earthquake predictions.

Duration of Tsunami Generation Longer than Duration of Seismic Wave Generation in the 2011 Mw 9.0 Tohoku-Oki Earthquake

Science.gov (United States)

Fujihara, S.; Korenaga, M.; Kawaji, K.; Akiyama, S.

2013-12-01

We try to compare and evaluate the nature of tsunami generation and seismic wave generation in occurrence of the 2011 Tohoku-Oki earthquake (hereafter, called as TOH11), in terms of two type of moment rate functions, inferred from finite source imaging of tsunami waveforms and seismic waveforms. Since 1970's, the nature of "tsunami earthquakes" has been discussed in many researches (e.g. Kanamori, 1972; Kanamori and Kikuchi, 1993; Kikuchi and Kanamori, 1995; Ide et al., 1993; Satake, 1994) mostly based on analysis of seismic waveform data , in terms of the "slow" nature of tsunami earthquakes (e.g., the 1992 Nicaragura earthquake). Although TOH11 is not necessarily understood as a tsunami earthquake, TOH11 is one of historical earthquakes that simultaneously generated large seismic waves and tsunami. Also, TOH11 is one of earthquakes which was observed both by seismic observation network and tsunami observation network around the Japanese islands. Therefore, for the purpose of analyzing the nature of tsunami generation, we try to utilize tsunami waveform data as much as possible. In our previous studies of TOH11 (Fujihara et al., 2012a; Fujihara et al., 2012b), we inverted tsunami waveforms at GPS wave gauges of NOWPHAS to image the spatio-temporal slip distribution. The "temporal" nature of our tsunami source model is generally consistent with the other tsunami source models (e.g., Satake et al, 2013). For seismic waveform inversion based on 1-D structure, here we inverted broadband seismograms at GSN stations based on the teleseismic body-wave inversion scheme (Kikuchi and Kanamori, 2003). Also, for seismic waveform inversion considering the inhomogeneous internal structure, we inverted strong motion seismograms at K-NET and KiK-net stations, based on 3-D Green's functions (Fujihara et al., 2013a; Fujihara et al., 2013b). The gross "temporal" nature of our seismic source models are generally consistent with the other seismic source models (e.g., Yoshida et al

Earthquake behavior at deep underground observed by three-dimensional array

International Nuclear Information System (INIS)

Komada, Hiroya; Sawada, Yoshihiro; Aoyama, Shigeo.

1989-01-01

The earthquake observation has been carried out using an eight point three-dimensional array between on-ground and the depth of about 400 m at Hosokura Mine in Miyagi prefecture, for the purpose of obtaining the basic datum on the characteristics of the seismic waves for the earthquake resistance design of the deep underground disposal facility of high level waste. The following results ware obtained. (1) The maximum accelerations at the underground are damped to about 60 % of those at on-ground horizontal and to about 70 % vertical. (2) Although the frequency characteristics of the seismic waves varies for each earthquake, the transfer characteristics of seismic waves from deep underground to on-ground is the same for each earthquake. (3) The horizontal dirrections of seismic wave incidence are similar to the directions from epicenters of each earthquake. The vertical directions of seismic wave incidence are in the range of about 3deg to 35deg from vertical line. (author)

Nucleation speed limit on remote fluid induced earthquakes

Science.gov (United States)

Parsons, Thomas E.; Akinci, Aybige; Malignini, Luca

2017-01-01

Earthquakes triggered by other remote seismic events are explained as a response to long-traveling seismic waves that temporarily stress the crust. However, delays of hours or days after seismic waves pass through are reported by several studies, which are difficult to reconcile with the transient stresses imparted by seismic waves. We show that these delays are proportional to magnitude and that nucleation times are best fit to a fluid diffusion process if the governing rupture process involves unlocking a magnitude-dependent critical nucleation zone. It is well established that distant earthquakes can strongly affect the pressure and distribution of crustal pore fluids. Earth’s crust contains hydraulically isolated, pressurized compartments in which fluids are contained within low-permeability walls. We know that strong shaking induced by seismic waves from large earthquakes can change the permeability of rocks. Thus, the boundary of a pressurized compartment may see its permeability rise. Previously confined, overpressurized pore fluids may then diffuse away, infiltrate faults, decrease their strength, and induce earthquakes. Magnitude-dependent delays and critical nucleation zone conclusions can also be applied to human-induced earthquakes.

Exceptional Drought and Unconventional Energy Production

Directory of Open Access Journals (Sweden)

Reid B. Stevens

2018-04-01

Full Text Available The hydraulic fracturing boom in Texas required massive water flows. Beginning in the summer of 2011, water became scarce as a prolonged heat wave and subsequent severe drought spread across the state. Oil and gas producers working in drought areas needed to purchase expensive local water or transport water from a non-drought county far from the drill site. In response to decreased water availability in drought areas, these producers completed fewer wells and completed wells that used less water. This decrease in well-level water use had a measurable effect on the amount of oil and gas produced by wells completed during exceptional conditions.

Observation of earthquake in the neighborhood of a large underground cavity. The Izu-Hanto-Toho-Oki earthquake, June 29, 1980

Energy Technology Data Exchange (ETDEWEB)

Komada, H; Hayashi, M [Central Research Inst. of Electric Power Industry, Abiko, Chiba (Japan). Civil Engineering Lab.

1980-12-01

Studies on the earthquake resistance design of underground site for such large important structures as nuclear power plants, high-level radioactive waste repositories, LNG tanks, petroleum tanks, big power transmission installations and compressed air energy storage installations have been examined at our research institute. The observations of earthquake have been examined at Shiroyama underground hydroelectric power station since July 1976 as one of the demonstration of the earthquake resistance, and the first report was already published. After the time accelerometers and dynamic strain meters were additionally installed. Good acceleration waves and dynamic strain waves of the Izu-Hanto-Toho-Oki Earthquake, June 29, 1980 were observed at Shiroyama site, at which the hypocentral distance is 77 km and the intensity scale is about 4. In this report, the characteristic of the oscillation wave in the neighborhood of underground cavity and the relationships among accelerations, velocities, deformations and dynamic strains are studied in detail on the above earthquake data.

Time-lapse changes of P- and S-wave velocities and shear wave splitting in the first year after the 2011 Tohoku earthquake, Japan: shallow subsurface

Science.gov (United States)

Sawazaki, Kaoru; Snieder, Roel

2013-04-01

We detect time-lapse changes in P- and S-wave velocities (hereafter, VP and VS, respectively) and shear wave splitting parameters associated with the 2011 Tohoku earthquake, Japan, at depths between 0 and 504 m. We estimate not only medium parameters but also the 95 per cent confidence interval of the estimated velocity change by applying a new least squares inversion scheme to the deconvolution analysis of KiK-net vertical array records. Up to 6 per cent VS reduction is observed at more than half of the analysed KiK-net stations in northeastern Japan with over 95 per cent confidence in the first month after the main shock. There is a considerable correlation between the S-wave traveltime delay and the maximum horizontal dynamic strain (MDS) by the main shock motion when the strain exceeds 5 × 10- 4 on the ground surface. This correlation is not clearly observed for MDS at the borehole bottom. On the contrary, VP and shear wave splitting parameters do not show systematic changes after the Tohoku earthquake. These results indicate that the time-lapse change is concentrated near the ground surface, especially in loosely packed soil layers. We conclude that the behaviour of VP, VS and shear wave splitting parameters are explained by the generation of omnidirectional cracks near the ground surface and by the diffusion of water in the porous subsurface. Recovery of VS should be related to healing of the crack which is proportional to the logarithm of the lapse time after the main shock and/or to decompaction after shaking.

Seismogeodesy for rapid earthquake and tsunami characterization

Science.gov (United States)

Bock, Y.

2016-12-01

Rapid estimation of earthquake magnitude and fault mechanism is critical for earthquake and tsunami warning systems. Traditionally, the monitoring of earthquakes and tsunamis has been based on seismic networks for estimating earthquake magnitude and slip, and tide gauges and deep-ocean buoys for direct measurement of tsunami waves. These methods are well developed for ocean basin-wide warnings but are not timely enough to protect vulnerable populations and infrastructure from the effects of local tsunamis, where waves may arrive within 15-30 minutes of earthquake onset time. Direct measurements of displacements by GPS networks at subduction zones allow for rapid magnitude and slip estimation in the near-source region, that are not affected by instrumental limitations and magnitude saturation experienced by local seismic networks. However, GPS displacements by themselves are too noisy for strict earthquake early warning (P-wave detection). Optimally combining high-rate GPS and seismic data (in particular, accelerometers that do not clip), referred to as seismogeodesy, provides a broadband instrument that does not clip in the near field, is impervious to magnitude saturation, and provides accurate real-time static and dynamic displacements and velocities in real time. Here we describe a NASA-funded effort to integrate GPS and seismogeodetic observations as part of NOAA's Tsunami Warning Centers in Alaska and Hawaii. It consists of a series of plug-in modules that allow for a hierarchy of rapid seismogeodetic products, including automatic P-wave picking, hypocenter estimation, S-wave prediction, magnitude scaling relationships based on P-wave amplitude (Pd) and peak ground displacement (PGD), finite-source CMT solutions and fault slip models as input for tsunami warnings and models. For the NOAA/NASA project, the modules are being integrated into an existing USGS Earthworm environment, currently limited to traditional seismic data. We are focused on a network of

Antarctic icequakes triggered by the 2010 Maule earthquake in Chile

Science.gov (United States)

Peng, Zhigang; Walter, Jacob I.; Aster, Richard C.; Nyblade, Andrew; Wiens, Douglas A.; Anandakrishnan, Sridhar

2014-09-01

Seismic waves from distant, large earthquakes can almost instantaneously trigger shallow micro-earthquakes and deep tectonic tremor as they pass through Earth's crust. Such remotely triggered seismic activity mostly occurs in tectonically active regions. Triggered seismicity is generally considered to reflect shear failure on critically stressed fault planes and is thought to be driven by dynamic stress perturbations from both Love and Rayleigh types of surface seismic wave. Here we analyse seismic data from Antarctica in the six hours leading up to and following the 2010 Mw 8.8 Maule earthquake in Chile. We identify many high-frequency seismic signals during the passage of the Rayleigh waves generated by the Maule earthquake, and interpret them as small icequakes triggered by the Rayleigh waves. The source locations of these triggered icequakes are difficult to determine owing to sparse seismic network coverage, but the triggered events generate surface waves, so are probably formed by near-surface sources. Our observations are consistent with tensile fracturing of near-surface ice or other brittle fracture events caused by changes in volumetric strain as the high-amplitude Rayleigh waves passed through. We conclude that cryospheric systems can be sensitive to large distant earthquakes.

Charles Darwin's earthquake reports

Science.gov (United States)

Galiev, Shamil

2010-05-01

As it is the 200th anniversary of Darwin's birth, 2009 has also been marked as 170 years since the publication of his book Journal of Researches. During the voyage Darwin landed at Valdivia and Concepcion, Chile, just before, during, and after a great earthquake, which demolished hundreds of buildings, killing and injuring many people. Land was waved, lifted, and cracked, volcanoes awoke and giant ocean waves attacked the coast. Darwin was the first geologist to observe and describe the effects of the great earthquake during and immediately after. These effects sometimes repeated during severe earthquakes; but great earthquakes, like Chile 1835, and giant earthquakes, like Chile 1960, are rare and remain completely unpredictable. This is one of the few areas of science, where experts remain largely in the dark. Darwin suggested that the effects were a result of ‘ …the rending of strata, at a point not very deep below the surface of the earth…' and ‘…when the crust yields to the tension, caused by its gradual elevation, there is a jar at the moment of rupture, and a greater movement...'. Darwin formulated big ideas about the earth evolution and its dynamics. These ideas set the tone for the tectonic plate theory to come. However, the plate tectonics does not completely explain why earthquakes occur within plates. Darwin emphasised that there are different kinds of earthquakes ‘...I confine the foregoing observations to the earthquakes on the coast of South America, or to similar ones, which seem generally to have been accompanied by elevation of the land. But, as we know that subsidence has gone on in other quarters of the world, fissures must there have been formed, and therefore earthquakes...' (we cite the Darwin's sentences following researchspace. auckland. ac. nz/handle/2292/4474). These thoughts agree with results of the last publications (see Nature 461, 870-872; 636-639 and 462, 42-43; 87-89). About 200 years ago Darwin gave oneself airs by the

Surface wave tomography across the Sorgenfrei-Tornquist Zone, SW Scandinavia, using ambient noise and earthquake data

Science.gov (United States)

Köhler, Andreas; Maupin, Valérie; Balling, Niels

2015-10-01

We produce a S-wave velocity model of the crust and upper mantle around the Sorgenfrei-Tornquist Zone, southern Scandinavia, by analysing ambient seismic noise and earthquake recordings on temporary and permanent regional network stations. In a first step, we perform tomographical inversion of surface wave dispersion data from seismic noise to obtain Rayleigh and Love wave phase-velocity maps from 3 to about 30 s period. Local dispersion curves are then combined with regionally averaged surface wave velocities from earthquake data measured between 15 and about 100 s period. Dispersion curves are jointly inverted for a 3-D model of the S-wave velocity and radial velocity anisotropy by using a combined Monte Carlo and linearized inversion approach. Results reveal significant crustal as well as uppermost mantle velocity variations at all depth levels. Upper crustal structural variations are mainly controlled by the thick sedimentary Danish Basin with both low S-wave velocities and high anisotropy. Despite of the known limited capability of surface wave inversion to constrain interface depths and model parameter trade-offs, obtained Moho depths are in good agreement with previous studies in the region. Marked crustal thinning is clearly revealed beneath the Danish Basin with a narrow transition to the thicker crust in Swedish shield areas. Despite very different crustal and morphological structures, Denmark and southern Norway both have similar well-defined upper-mantle low-velocity zones, interpreted as asthenosphere, starting a depth of about 100 km. Compared with southern Sweden, showing high upper-mantle velocities, characteristic for shields, velocities are reduced by 0.30-0.40 km s-1 (6-8 per cent) at the depth levels of 140-200 km and radial anisotropy of 2-4 per cent is observed. Our study confirms the importance of the Sorgenfrei-Tornquist Zone, as a very deep structural boundary, separating old, thick, cratonic Baltica lithosphere in southern Sweden from

Drought priming effects on alleviating later damages of heat and drought stress in different wheat cultivars

DEFF Research Database (Denmark)

Mendanha, Thayna; Hyldgaard, Benita; Ottosen, Carl-Otto

The ongoing change is climate; in particular the increase of drought and heat waves episodes are a major challenge in the prospect of food safety. Under many field conditions, plants are usually exposed to mild intermittent stress episodes rather than a terminal stress event. Previous, but limited...... studies suggest that plants subjected to early stress (primed) can be more resistant to future stress exposure than those not stressed during seedling stage. In our experiment we aimed to test if repeated mild drought stresses could improve heat and drought tolerance during anthesis heat and drought...... stresses in wheat cultivars. Two wheat cultivars, Gladius and Paragon, were grown in a fully controlled gravimetric platform and subjected to either no stress (control) or two (P) drought cycles during seedling stage, at three and five complete developed leaves. Each cycle consisted of withholding water...

Nucleation speed limit on remote fluid-induced earthquakes

Science.gov (United States)

Parsons, Tom; Malagnini, Luca; Akinci, Aybige

2017-01-01

Earthquakes triggered by other remote seismic events are explained as a response to long-traveling seismic waves that temporarily stress the crust. However, delays of hours or days after seismic waves pass through are reported by several studies, which are difficult to reconcile with the transient stresses imparted by seismic waves. We show that these delays are proportional to magnitude and that nucleation times are best fit to a fluid diffusion process if the governing rupture process involves unlocking a magnitude-dependent critical nucleation zone. It is well established that distant earthquakes can strongly affect the pressure and distribution of crustal pore fluids. Earth’s crust contains hydraulically isolated, pressurized compartments in which fluids are contained within low-permeability walls. We know that strong shaking induced by seismic waves from large earthquakes can change the permeability of rocks. Thus, the boundary of a pressurized compartment may see its permeability rise. Previously confined, overpressurized pore fluids may then diffuse away, infiltrate faults, decrease their strength, and induce earthquakes. Magnitude-dependent delays and critical nucleation zone conclusions can also be applied to human-induced earthquakes. PMID:28845448

The 2012 Mw5.6 earthquake in Sofia seismogenic zone - is it a slow earthquake

Science.gov (United States)

Raykova, Plamena; Solakov, Dimcho; Slavcheva, Krasimira; Simeonova, Stela; Aleksandrova, Irena

2017-04-01

very low rupture velocity. The low rupture velocity can mean slow-faulting, which brings to slow release of accumulated seismic energy. The slow release energy does principally little to moderate damages. Additionally wave form of the earthquake shows low frequency content of P-waves (the maximum P-wave is at 1.19 Hz) and the specific P- wave displacement spectral is characterise with not expressed spectrum plateau and corner frequency. These and other signs suggest us to the conclusion, that the 2012 Mw5.6 earthquake can be considered as types of slow earthquake, like a low frequency quake. The study is based on data from Bulgarian seismological network (NOTSSI), the local network (LSN) deployed around Kozloduy NPP and System of Accelerographs for Seismic Monitoring of Equipment and Structures (SASMES) installed in the Kozloduy NPP. NOTSSI jointly with LSN and SASMES provide reliable information for multiple studies on seismicity in regional scale.

Earthquake related dynamic groundwater pressure changes observed at the Kamaishi Mine

International Nuclear Information System (INIS)

Sasaki, Shunji; Yasuike, Shinji; Komada, Hiroya; Kobayashi, Yoshimasa; Kawamura, Makoto; Aoki, Kazuhiro

1999-01-01

From 342 seismic records observed at the Kamaishi Mine form 1990 to 1998, a total of 92 data whose acceleration is greater than 1 gal or ground water pressure is greater than 1 kPa were selected and dynamic ground water pressure changes associated with earthquakes were studied. The results obtained are as follows: (1) A total of 27 earthquakes accompanied by static ground water pressure changes were observed. Earthquake-related static ground water pressure changes are smaller than 1/10 of the annual range of ground water pressure changes. There is also a tendency that the ground water pressure changes recovers to its original trend in several weeks after earthquakes. (2) Dynamic ground water pressure changes associated with earthquakes occur when P-waves arrive. However, the largest dynamic ground water pressure changes occur on S-wave part arrivals where the amplitude of seismic wave is the largest. A positive correlation is recognized between the maximum value of velocity wave form and that of dynamic ground water pressure changes. (3) The characteristic of dynamic change in ground water pressure due to earthquakes can be explained qualitatively by mechanism in which the P-wave converted from an incident SV wave propagates along the borehole. (author)

Compounded effects of heat waves and droughts over the Western Electricity Grid: spatio-temporal scales of impacts and predictability toward mitigation and adaptation.

Science.gov (United States)

Voisin, N.; Kintner-Meyer, M.; Skaggs, R.; Xie, Y.; Wu, D.; Nguyen, T. B.; Fu, T.; Zhou, T.

2016-12-01

Heat waves and droughts are projected to be more frequent and intense. We have seen in the past the effects of each of those extreme climate events on electricity demand and constrained electricity generation, challenging power system operations. Our aim here is to understand the compounding effects under historical conditions. We present a benchmark of Western US grid performance under 55 years of historical climate, and including droughts, using 2010-level of water demand and water management infrastructure, and 2010-level of electricity grid infrastructure and operations. We leverage CMIP5 historical hydrology simulations and force a large scale river routing- reservoir model with 2010-level sectoral water demands. The regulated flow at each water-dependent generating plants is processed to adjust water-dependent electricity generation parameterization in a production cost model, that represents 2010-level power system operations with hourly energy demand of 2010. The resulting benchmark includes a risk distribution of several grid performance metrics (unserved energy, production cost, carbon emission) as a function of inter-annual variability in regional water availability and predictability using large scale climate oscillations. In the second part of the presentation, we describe an approach to map historical heat waves onto this benchmark grid performance using a building energy demand model. The impact of the heat waves, combined with the impact of droughts, is explored at multiple scales to understand the compounding effects. Vulnerabilities of the power generation and transmission systems are highlighted to guide future adaptation.

Napa Earthquake impact on water systems

Science.gov (United States)

Wang, J.

2014-12-01

South Napa earthquake occurred in Napa, California on August 24 at 3am, local time, and the magnitude is 6.0. The earthquake was the largest in SF Bay Area since the 1989 Loma Prieta earthquake. Economic loss topped $ 1 billion. Wine makers cleaning up and estimated the damage on tourism. Around 15,000 cases of lovely cabernet were pouring into the garden at the Hess Collection. Earthquake potentially raise water pollution risks, could cause water crisis. CA suffered water shortage recent years, and it could be helpful on how to prevent underground/surface water pollution from earthquake. This research gives a clear view on drinking water system in CA, pollution on river systems, as well as estimation on earthquake impact on water supply. The Sacramento-San Joaquin River delta (close to Napa), is the center of the state's water distribution system, delivering fresh water to more than 25 million residents and 3 million acres of farmland. Delta water conveyed through a network of levees is crucial to Southern California. The drought has significantly curtailed water export, and salt water intrusion reduced fresh water outflows. Strong shaking from a nearby earthquake can cause saturated, loose, sandy soils liquefaction, and could potentially damage major delta levee systems near Napa. Napa earthquake is a wake-up call for Southern California. It could potentially damage freshwater supply system.

Determination of Design Basis Earthquake ground motion

Energy Technology Data Exchange (ETDEWEB)

Kato, Muneaki [Japan Atomic Power Co., Tokyo (Japan)

1997-03-01

This paper describes principle of determining of Design Basis Earthquake following the Examination Guide, some examples on actual sites including earthquake sources to be considered, earthquake response spectrum and simulated seismic waves. In sppendix of this paper, furthermore, seismic safety review for N.P.P designed before publication of the Examination Guide was summarized with Check Basis Earthquake. (J.P.N.)

Determination of Design Basis Earthquake ground motion

International Nuclear Information System (INIS)

Kato, Muneaki

1997-01-01

This paper describes principle of determining of Design Basis Earthquake following the Examination Guide, some examples on actual sites including earthquake sources to be considered, earthquake response spectrum and simulated seismic waves. In sppendix of this paper, furthermore, seismic safety review for N.P.P designed before publication of the Examination Guide was summarized with Check Basis Earthquake. (J.P.N.)

e-Science on Earthquake Disaster Mitigation by EUAsiaGrid

Science.gov (United States)

Yen, Eric; Lin, Simon; Chen, Hsin-Yen; Chao, Li; Huang, Bor-Shoh; Liang, Wen-Tzong

2010-05-01

Although earthquake is not predictable at this moment, with the aid of accurate seismic wave propagation analysis, we could simulate the potential hazards at all distances from possible fault sources by understanding the source rupture process during large earthquakes. With the integration of strong ground-motion sensor network, earthquake data center and seismic wave propagation analysis over gLite e-Science Infrastructure, we could explore much better knowledge on the impact and vulnerability of potential earthquake hazards. On the other hand, this application also demonstrated the e-Science way to investigate unknown earth structure. Regional integration of earthquake sensor networks could aid in fast event reporting and accurate event data collection. Federation of earthquake data center entails consolidation and sharing of seismology and geology knowledge. Capability building of seismic wave propagation analysis implies the predictability of potential hazard impacts. With gLite infrastructure and EUAsiaGrid collaboration framework, earth scientists from Taiwan, Vietnam, Philippine, Thailand are working together to alleviate potential seismic threats by making use of Grid technologies and also to support seismology researches by e-Science. A cross continental e-infrastructure, based on EGEE and EUAsiaGrid, is established for seismic wave forward simulation and risk estimation. Both the computing challenge on seismic wave analysis among 5 European and Asian partners, and the data challenge for data center federation had been exercised and verified. Seismogram-on-Demand service is also developed for the automatic generation of seismogram on any sensor point to a specific epicenter. To ease the access to all the services based on users workflow and retain the maximal flexibility, a Seismology Science Gateway integating data, computation, workflow, services and user communities would be implemented based on typical use cases. In the future, extension of the

Earthquake simulation, actual earthquake monitoring and analytical methods for soil-structure interaction investigation

Energy Technology Data Exchange (ETDEWEB)

Tang, H T [Seismic Center, Electric Power Research Institute, Palo Alto, CA (United States)

1988-07-01

Approaches for conducting in-situ soil-structure interaction experiments are discussed. High explosives detonated under the ground can generate strong ground motion to induce soil-structure interaction (SSI). The explosive induced data are useful in studying the dynamic characteristics of the soil-structure system associated with the inertial aspect of the SSI problem. The plane waves generated by the explosives cannot adequately address the kinematic interaction associated with actual earthquakes because of he difference in wave fields and their effects. Earthquake monitoring is ideal for obtaining SSI data that can address all aspects of the SSI problem. The only limitation is the level of excitation that can be obtained. Neither the simulated earthquake experiments nor the earthquake monitoring experiments can have exact similitude if reduced scale test structures are used. If gravity effects are small, reasonable correlations between the scaled model and the prototype can be obtained provided that input motion can be scaled appropriately. The key product of the in-situ experiments is the data base that can be used to qualify analytical methods for prototypical applications. (author)

Strong ground motion prediction using virtual earthquakes.

Science.gov (United States)

Denolle, M A; Dunham, E M; Prieto, G A; Beroza, G C

2014-01-24

Sedimentary basins increase the damaging effects of earthquakes by trapping and amplifying seismic waves. Simulations of seismic wave propagation in sedimentary basins capture this effect; however, there exists no method to validate these results for earthquakes that have not yet occurred. We present a new approach for ground motion prediction that uses the ambient seismic field. We apply our method to a suite of magnitude 7 scenario earthquakes on the southern San Andreas fault and compare our ground motion predictions with simulations. Both methods find strong amplification and coupling of source and structure effects, but they predict substantially different shaking patterns across the Los Angeles Basin. The virtual earthquake approach provides a new approach for predicting long-period strong ground motion.

The severity of an earthquake

Science.gov (United States)

,

1997-01-01

The severity of an earthquake can be expressed in terms of both intensity and magnitude. However, the two terms are quite different, and they are often confused. Intensity is based on the observed effects of ground shaking on people, buildings, and natural features. It varies from place to place within the disturbed region depending on the location of the observer with respect to the earthquake epicenter. Magnitude is related to the amount of seismic energy released at the hypocenter of the earthquake. It is based on the amplitude of the earthquake waves recorded on instruments

Limitation of the Predominant-Period Estimator for Earthquake Early Warning and the Initial Rupture of Earthquakes

Science.gov (United States)

Yamada, T.; Ide, S.

2007-12-01

Earthquake early warning is an important and challenging issue for the reduction of the seismic damage, especially for the mitigation of human suffering. One of the most important problems in earthquake early warning systems is how immediately we can estimate the final size of an earthquake after we observe the ground motion. It is relevant to the problem whether the initial rupture of an earthquake has some information associated with its final size. Nakamura (1988) developed the Urgent Earthquake Detection and Alarm System (UrEDAS). It calculates the predominant period of the P wave (τp) and estimates the magnitude of an earthquake immediately after the P wave arrival from the value of τpmax, or the maximum value of τp. The similar approach has been adapted by other earthquake alarm systems (e.g., Allen and Kanamori (2003)). To investigate the characteristic of the parameter τp and the effect of the length of the time window (TW) in the τpmax calculation, we analyze the high-frequency recordings of earthquakes at very close distances in the Mponeng mine in South Africa. We find that values of τpmax have upper and lower limits. For larger earthquakes whose source durations are longer than TW, the values of τpmax have an upper limit which depends on TW. On the other hand, the values for smaller earthquakes have a lower limit which is proportional to the sampling interval. For intermediate earthquakes, the values of τpmax are close to their typical source durations. These two limits and the slope for intermediate earthquakes yield an artificial final size dependence of τpmax in a wide size range. The parameter τpmax is useful for detecting large earthquakes and broadcasting earthquake early warnings. However, its dependence on the final size of earthquakes does not suggest that the earthquake rupture is deterministic. This is because τpmax does not always have a direct relation to the physical quantities of an earthquake.

Do diurnal patterns of branch carbon uptake and transpiration recover after heat waves? Results from a Mediterranean-type ecosystem experiencing seasonal and exceptional drought

Science.gov (United States)

Pivovaroff, A. L.; Pesqueira, A.; Sun, W.; Seibt, U.

2016-12-01

Mediterranean-type ecosystems are biodiversity hotspots, but increasing temperature and changes in precipitation will have significant impacts on vegetation, as evidenced by the current die-back of many woody species in southern California, USA, due to exceptional drought conditions. We installed flow-through chambers on four native woody plant species at Stunt Ranch, a University of California Natural Reserve System site, in order to continuously monitor fluxes of carbon and water at the branch-scale from the growing season through the annual seasonal drought period. Study species included Heteromeles arbutifolia, Malosma laurina, Salvia leucophylla, and Quercus agrifolia. Here we present the results of diurnal flux patterns before, during, and after two extreme heat waves events, when daily maximum temperatures doubled. Under typical summer conditions, which include hot, sunny days, study species exhibited two peaks in carbon assimilation during a diurnal cycle: a peak in the morning and a smaller, secondary peak in the afternoon, separated by a midday depression. During heat wave events, which generally lasted 3 days, species exhibited a small morning peak and no afternoon peak at all. All study species returned to their pre-heat wave diurnal flux patterns, which included the second afternoon peak, when weather conditions returned to normal. Since soil moisture was not affected by the short-term heat wave events, we conclude that the pronounced changes in diurnal patterns, including disappearance of the secondary afternoon peak, are the result of stomatal regulation in response to atmospheric water demand rather than root responses to soil moisture deficits. Our results demonstrate that carbon uptake of native species may be impacted under ongoing climate change when increased temperatures and drought conditions may be sustained.

New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

Energy Technology Data Exchange (ETDEWEB)

Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P. [ITB, Faculty of Earth Sciences and Tecnology (Indonesia); BMKG (Indonesia)

2012-06-20

The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance ({Delta}) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log {Delta}+ 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

Science.gov (United States)

Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P.

2012-06-01

The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance (Δ) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log Δ + 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

New approach of determinations of earthquake moment magnitude using near earthquake source duration and maximum displacement amplitude of high frequency energy radiation

International Nuclear Information System (INIS)

Gunawan, H.; Puspito, N. T.; Ibrahim, G.; Harjadi, P. J. P.

2012-01-01

The new approach method to determine the magnitude by using amplitude displacement relationship (A), epicenter distance (Δ) and duration of high frequency radiation (t) has been investigated for Tasikmalaya earthquake, on September 2, 2009, and their aftershock. Moment magnitude scale commonly used seismic surface waves with the teleseismic range of the period is greater than 200 seconds or a moment magnitude of the P wave using teleseismic seismogram data and the range of 10-60 seconds. In this research techniques have been developed a new approach to determine the displacement amplitude and duration of high frequency radiation using near earthquake. Determination of the duration of high frequency using half of period of P waves on the seismograms displacement. This is due tothe very complex rupture process in the near earthquake. Seismic data of the P wave mixing with other wave (S wave) before the duration runs out, so it is difficult to separate or determined the final of P-wave. Application of the 68 earthquakes recorded by station of CISI, Garut West Java, the following relationship is obtained: Mw = 0.78 log (A) + 0.83 log Δ+ 0.69 log (t) + 6.46 with: A (m), d (km) and t (second). Moment magnitude of this new approach is quite reliable, time processing faster so useful for early warning.

The effects of core-reflected waves on finite fault inversions with teleseismic body wave data

Science.gov (United States)

Qian, Yunyi; Ni, Sidao; Wei, Shengji; Almeida, Rafael; Zhang, Han

2017-11-01

Teleseismic body waves are essential for imaging rupture processes of large earthquakes. Earthquake source parameters are usually characterized by waveform analyses such as finite fault inversions using only turning (direct) P and SH waves without considering the reflected phases from the core-mantle boundary (CMB). However, core-reflected waves such as ScS usually have amplitudes comparable to direct S waves due to the total reflection from the CMB and might interfere with the S waves used for inversion, especially at large epicentral distances for long duration earthquakes. In order to understand how core-reflected waves affect teleseismic body wave inversion results, we develop a procedure named Multitel3 to compute Green's functions that contain turning waves (direct P, pP, sP, direct S, sS and reverberations in the crust) and core-reflected waves (PcP, pPcP, sPcP, ScS, sScS and associated reflected phases from the CMB). This ray-based method can efficiently generate synthetic seismograms for turning and core-reflected waves independently, with the flexibility to take into account the 3-D Earth structure effect on the timing between these phases. The performance of this approach is assessed through a series of numerical inversion tests on synthetic waveforms of the 2008 Mw7.9 Wenchuan earthquake and the 2015 Mw7.8 Nepal earthquake. We also compare this improved method with the turning-wave only inversions and explore the stability of the new procedure when there are uncertainties in a priori information (such as fault geometry and epicentre location) or arrival time of core-reflected phases. Finally, a finite fault inversion of the 2005 Mw8.7 Nias-Simeulue earthquake is carried out using the improved Green's functions. Using enhanced Green's functions yields better inversion results as expected. While the finite source inversion with conventional P and SH waves is able to recover large-scale characteristics of the earthquake source, by adding PcP and ScS phases

One dimensional P wave velocity structure of the crust beneath west Java and accurate hypocentre locations from local earthquake inversion

International Nuclear Information System (INIS)

Supardiyono; Santosa, Bagus Jaya

2012-01-01

A one-dimensional (1-D) velocity model and station corrections for the West Java zone were computed by inverting P-wave arrival times recorded on a local seismic network of 14 stations. A total of 61 local events with a minimum of 6 P-phases, rms 0.56 s and a maximum gap of 299° were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn out from our reasearch. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of West Java.

One dimensional P wave velocity structure of the crust beneath west Java and accurate hypocentre locations from local earthquake inversion

Energy Technology Data Exchange (ETDEWEB)

Supardiyono; Santosa, Bagus Jaya [Physics Department, Faculty of Mathematics and Natural Sciences, State University of Surabaya, Surabaya (Indonesia) and Physics Department, Faculty of Mathematics and Natural Sciences, Sepuluh Nopember Institute of Technology, Surabaya (Indonesia); Physics Department, Faculty of Mathematics and Natural Sciences, Sepuluh Nopember Institute of Technology, Surabaya (Indonesia)

2012-06-20

A one-dimensional (1-D) velocity model and station corrections for the West Java zone were computed by inverting P-wave arrival times recorded on a local seismic network of 14 stations. A total of 61 local events with a minimum of 6 P-phases, rms 0.56 s and a maximum gap of 299 Degree-Sign were selected. Comparison with previous earthquake locations shows an improvement for the relocated earthquakes. Tests were carried out to verify the robustness of inversion results in order to corroborate the conclusions drawn out from our reasearch. The obtained minimum 1-D velocity model can be used to improve routine earthquake locations and represents a further step toward more detailed seismotectonic studies in this area of West Java.

Fan-structure wave as a source of earthquake instability

Science.gov (United States)

Tarasov, Boris

2015-04-01

Today frictional shear resistance along pre-existing faults is considered to be the lower limit on rock shear strength at confined compression corresponding to the seismogenic layer. This determines the lithospheric strength and the primary earthquake mechanism associated with frictional stick-slip instability on pre-existing faults. This paper introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. In the new mechanism the rock failure, associated with consecutive creation of small slabs (known as 'domino-blocks') from the intact rock in the rupture tip, is driven by a fan-shaped domino structure representing the rupture head. The fan-head combines such unique features as: extremely low shear resistance (below the frictional strength), self-sustaining stress intensification in the rupture tip (providing easy formation of new domino-blocks), and self-unbalancing conditions in the fan-head (making the failure process inevitably spontaneous and violent). An important feature of the fan-mechanism is the fact that for the initial formation of the fan-structure an enhanced local shear stress is required, however, after completion of the fan-structure it can propagate as a dynamic wave through intact rock mass at shear stresses below the frictional strength. Paradoxically low shear strength of pristine rocks provided by the fan-mechanism determines the lower limit of the lithospheric strength and favours the generation of new faults in pristine rocks in preference to frictional stick-slip instability along pre-existing faults. The new approach reveals an alternative role of pre-existing faults in earthquake activity: they represent local stress concentrates in pristine rock adjoining the fault where special conditions for the fan-mechanism nucleation are created

The Effect of Heat Waves and Drought on Surface Wind Circulations in the Northeast of the Iberian Peninsula during the Summer of 2003

NARCIS (Netherlands)

Jiménez, P.A.; Vilà-Guerau de Arellano, J.; González-Rouco, J.F.; Navarro, J.; Montávez, J.P.; García-Bustamante, E.; Dudhia, J.

2011-01-01

Variations in the diurnal wind pattern associated with heat waves and drought conditions are investigated climatologically at a regional level (northeast of the Iberian Peninsula). The study, based on high-density observational evidence and fine spatial-scale mesoscale modeling for the 1992–2004

Historic Eastern Canadian earthquakes

International Nuclear Information System (INIS)

Asmis, G.J.K.; Atchinson, R.J.

1981-01-01

Nuclear power plants licensed in Canada have been designed to resist earthquakes: not all plants, however, have been explicitly designed to the same level of earthquake induced forces. Understanding the nature of strong ground motion near the source of the earthquake is still very tentative. This paper reviews historical and scientific accounts of the three strongest earthquakes - St. Lawrence (1925), Temiskaming (1935), Cornwall (1944) - that have occurred in Canada in 'modern' times, field studies of near-field strong ground motion records and their resultant damage or non-damage to industrial facilities, and numerical modelling of earthquake sources and resultant wave propagation to produce accelerograms consistent with the above historical record and field studies. It is concluded that for future construction of NPP's near-field strong motion must be explicitly considered in design

Regional relationships among earthquake magnitude scales. Seismic safety margins research program

International Nuclear Information System (INIS)

Chung, D.H.; Bernreuter, D.L.

1980-09-01

The seismic body-wave magnitude m b of an earthquake is strongly affected by regional variations in the Q structure, composition, and physical state within the earth. Therefore, because of differences in attenuation of P-waves between the western and eastern United States, a problem arises when comparing m b 's for the two regions. A regional m b magnitude bias exists which, depending on where the earthquake occurs and where the P-waves are recorded, can lead to magnitude errors as large as one-third unit. There is also a significant difference between m b and M L values for earthquakes in the western United States. An empirical link between the m b of an eastern U.S. earthquake and the M L of an equivalent western earthquake is given y M L = 0.57 + 0.92(m b ) East . This result is important when comparing ground motion between the two regions and for choosing a set of real western U.S. earthquake records to represent eastern earthquakes. (author)

The potential of imaging subsurface heterogeneities by local, natural earthquakes

NARCIS (Netherlands)

Nishitsuji, Y.; Doi, I.; Draganov, D.S.

2014-01-01

We have developed a new imaging technique of subsurface heterogeneities that uses Sp-waves from natural earthquakes. This technique can be used as a first screening tool in frontier exploration areas before conventional active exploration. Analyzing Sp-waves from 28 earthquakes (Mj 2.0 to 4.2)

Remote Triggering of the Mw 6.9 Hokkaido Earthquake as a Result of the Mw 6.6 Indonesian Earthquake on September 11, 2008

Directory of Open Access Journals (Sweden)

Cheng-Horng Lin

2012-01-01

Full Text Available Only just recently, the phenomenon of earthquakes being triggered by a distant earthquake has been well established. Yet, most of the triggered earthquakes have been limited to small earthquakes (M < 3. Also, the exact triggering mechanism for earthquakes is still not clear. Here I show how one strong earthquake (Mw = 6.6 is capable of triggering another (Mw = 6.9 at a remote distance (~4750 km. On September 11, 2008, two strong earthquakes with magnitudes (Mw of 6.6 and 6.9 hit respectively in Indonesia and Japan within a short interval of ~21 minutes time. Careful examination of broadband seismograms recorded in Japan shows that the Hokkaido earthquake occurred just as the surface waves generated by the Indonesia earthquake arrived. Although the peak dynamic stress estimated at the focus of the Hokkaido earthquake was just reaching the lower bound for the capability of triggering earthquakes in general, a more plausible mechanism for triggering an earthquake might be attributed to the change of a fault property by fluid infiltration. These observations suggest that the Hokkaido earthquake was likely triggered from a remote distance by the surface waves generated from the Indonesia earthquake. If some more cases can be observed, a temporal warning of possible interaction between strong earthquakes might be concerned in the future.

Mechanism of High Frequency Shallow Earthquake Source in Mount Soputan, North Sulawesi

Directory of Open Access Journals (Sweden)

Yasa Suparman

2014-06-01

Full Text Available DOI: 10.17014/ijog.v6i3.122Moment tensor analysis had been conducted to understand the source mechanism of earthquakes in Soputan Volcano during October - November 2010 period. The record shows shallow earthquakes with frequency about 5 - 9 Hz. Polarity distribution of P-wave first onset indicates that the recorded earthquakes are predominated by earthquakes where almost at all stations have the same direction of P-wave first motions, and earthquakes with upward first motions.In this article, the source mechanism is described as the second derivative of moment tensor, approached with first motion amplitude inversion of P-wave at some seismic stations. The result of moment tensor decomposition are predominated by earthquakes with big percentage in ISO and CLVD component. Focal mechanism shows that the recorded earthquakes have the same strike in northeast-southwest direction with dip about 400 - 600. The sources of the high frequency shallow earthquakes are in the form of tensile-shear cracks or a combination between crack and tensile faulting.

The 1985 central chile earthquake: a repeat of previous great earthquakes in the region?

Science.gov (United States)

Comte, D; Eisenberg, A; Lorca, E; Pardo, M; Ponce, L; Saragoni, R; Singh, S K; Suárez, G

1986-07-25

A great earthquake (surface-wave magnitude, 7.8) occurred along the coast of central Chile on 3 March 1985, causing heavy damage to coastal towns. Intense foreshock activity near the epicenter of the main shock occurred for 11 days before the earthquake. The aftershocks of the 1985 earthquake define a rupture area of 170 by 110 square kilometers. The earthquake was forecast on the basis of the nearly constant repeat time (83 +/- 9 years) of great earthquakes in this region. An analysis of previous earthquakes suggests that the rupture lengths of great shocks in the region vary by a factor of about 3. The nearly constant repeat time and variable rupture lengths cannot be reconciled with time- or slip-predictable models of earthquake recurrence. The great earthquakes in the region seem to involve a variable rupture mode and yet, for unknown reasons, remain periodic. Historical data suggest that the region south of the 1985 rupture zone should now be considered a gap of high seismic potential that may rupture in a great earthquake in the next few tens of years.

High-Resolution Near Real-Time Drought Monitoring in South Asia

Science.gov (United States)

Aadhar, S.; Mishra, V.

2017-12-01

Drought in South Asia affect food and water security and pose challenges for millions of people. For policy-making, planning and management of water resources at the sub-basin or administrative levels, high-resolution datasets of precipitation and air temperature are required in near-real time. Here we develop a high resolution (0.05 degree) bias-corrected precipitation and temperature data that can be used to monitor near real-time drought conditions over South Asia. Moreover, the dataset can be used to monitor climatic extremes (heat waves, cold waves, dry and wet anomalies) in South Asia. A distribution mapping method was applied to correct bias in precipitation and air temperature (maximum and minimum), which performed well compared to the other bias correction method based on linear scaling. Bias-corrected precipitation and temperature data were used to estimate Standardized precipitation index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) to assess the historical and current drought conditions in South Asia. We evaluated drought severity and extent against the satellite-based Normalized Difference Vegetation Index (NDVI) anomalies and satellite-driven Drought Severity Index (DSI) at 0.05˚. We find that the bias-corrected high-resolution data can effectively capture observed drought conditions as shown by the satellite-based drought estimates. High resolution near real-time dataset can provide valuable information for decision-making at district and sub- basin levels.

Reliability of Soil Sublayers Under Earthquake Excitation

DEFF Research Database (Denmark)

Nielsen, Søren R. K.; Mørk, Kim Jørgensen

A hysteretic model is formulated for a multi-layer subsoil subjected to horizontal earthquake shear waves (SH-waves). For each layer a modified Bouc-Wen model is used, relating the increments of the hysteretic shear stress to increments of the shear strain of the layer. Liquefaction is considered...... for each layer. The horizontal earthquake acceleration process at bedrock level is modelled as a non-stationary white noise, filtered through a time-invariant linear second order filter....

Fast 3D seismic wave simulations of 24 August 2016 Mw 6.0 central Italy earthquake for visual communication

Directory of Open Access Journals (Sweden)

Emanuele Casarotti

2016-12-01

Full Text Available We present here the first application of the fast reacting framework for 3D simulations of seismic wave propagation generated by earthquakes in the Italian region with magnitude Mw 5. The driven motivation is to offer a visualization of the natural phenomenon to the general public but also to provide preliminary modeling to expert and civil protection operators. We report here a description of this framework during the emergency of 24 August 2016 Mw 6.0 central Italy Earthquake, a discussion on the accuracy of the simulation for this seismic event and a preliminary critical analysis of the visualization structure and of the reaction of the public.

Epicenter Location of Regional Seismic Events Using Love Wave and Rayleigh Wave Ambient Seismic Noise Green's Functions

Science.gov (United States)

Levshin, A. L.; Barmin, M. P.; Moschetti, M. P.; Mendoza, C.; Ritzwoller, M. H.

2011-12-01

We describe a novel method to locate regional seismic events based on exploiting Empirical Green's Functions (EGF) that are produced from ambient seismic noise. Elastic EGFs between pairs of seismic stations are determined by cross-correlating long time-series of ambient noise recorded at the two stations. The EGFs principally contain Rayleigh waves on the vertical-vertical cross-correlations and Love waves on the transverse-transverse cross-correlations. Earlier work (Barmin et al., "Epicentral location based on Rayleigh wave empirical Green's functions from ambient seismic noise", Geophys. J. Int., 2011) showed that group time delays observed on Rayleigh wave EGFs can be exploited to locate to within about 1 km moderate sized earthquakes using USArray Transportable Array (TA) stations. The principal advantage of the method is that the ambient noise EGFs are affected by lateral variations in structure similarly to the earthquake signals, so the location is largely unbiased by 3-D structure. However, locations based on Rayleigh waves alone may be biased by more than 1 km if the earthquake depth is unknown but lies between 2 km and 7 km. This presentation is motivated by the fact that group time delays for Love waves are much less affected by earthquake depth than Rayleigh waves; thus exploitation of Love wave EGFs may reduce location bias caused by uncertainty in event depth. The advantage of Love waves to locate seismic events, however, is mitigated by the fact that Love wave EGFs have a smaller SNR than Rayleigh waves. Here, we test the use of Love and Rayleigh wave EGFs between 5- and 15-sec period to locate seismic events based on the USArray TA in the western US. We focus on locating aftershocks of the 2008 M 6.0 Wells earthquake, mining blasts in Wyoming and Montana, and small earthquakes near Norman, OK and Dallas, TX, some of which may be triggered by hydrofracking or injection wells.

Shallow microearthquakes near Chongqing, China triggered by the Rayleigh waves of the 2015 M7.8 Gorkha, Nepal earthquake

Science.gov (United States)

Han, Libo; Peng, Zhigang; Johnson, Christopher W.; Pollitz, Fred F.; Li, Lu; Wang, Baoshan; Wu, Jing; Li, Qiang; Wei, Hongmei

2017-12-01

We present a case of remotely triggered seismicity in Southwest China by the 2015/04/25 M7.8 Gorkha, Nepal earthquake. A local magnitude ML3.8 event occurred near the Qijiang district south of Chongqing city approximately 12 min after the Gorkha mainshock. Within 30 km of this ML3.8 event there are 62 earthquakes since 2009 and only 7 ML > 3 events, which corresponds to a likelihood of 0.3% for a ML > 3 on any given day by a random chance. This observation motivates us to investigate the relationship between the ML3.8 event and the Gorkha mainshock. The ML3.8 event was listed in the China Earthquake National Center (CENC) catalog and occurred at shallow depth (∼3 km). By examining high-frequency waveforms, we identify a smaller local event (∼ML 2.5) ∼ 15 s before the ML3.8 event. Both events occurred during the first two cycles of the Rayleigh waves from the Gorkha mainshock. We perform seismic event detection based on envelope function and waveform matching by using the two events as templates. Both analyses found a statistically significant rate change during the mainshock, suggesting that they were indeed dynamically triggered by the Rayleigh waves. Both events occurred during the peak normal and dilatational stress changes (∼10-30 kPa), consistent with observations of dynamic triggering in other geothermal/volcanic regions. Although other recent events (i.e., the 2011 M9.1 Tohoku-Oki earthquake) produced similar peak ground velocities, the 2015 Gorkha mainshock was the only event that produced clear dynamic triggering in this region. The triggering site is close to hydraulic fracturing wells that began production in 2013-2014. Hence we suspect that fluid injections may increase the region's susceptibility to remote dynamic triggering.

A Study on distinguishing seismic waves caused by natural earthquakes and underground nuclear explosion within North Korean Context

Science.gov (United States)

Premlet, B.; Sabu, S.; Kamarudheen, R.; Subair, S.

2017-12-01

Since the first nuclear test on 15 July 1945 , there have been over 2,051 other weapon tests around the world . The waveforms of a natural earthquake which generates strong S waves and an underground explosion which is dominated by P waves were distinguished from the analysis of data corresponding to a 2005 M5.0 Earthquake and a 2016 North Korean nuclear test , both at similar distances from seismometer . Further differences between the seismograms were evaluated and successfully distinguished between the origins of the elastic waves through the data using Moment Tensor Solution using stations BJT , HIA and INCN . North Korea has developed a nuclear fuel cycle capability and has both plutonium and enriched uranium programs at Pyongyang . Seismic recordings of vertical ground motion at Global Seismographic Network station IC.MDJ of the 4 seismic events at Punggye-ri , North Korea , which occurred on the 9th of October 2006 , 25th of May 2009, 12th of February 2013 and on the 6th of January and 9th of September , 2016 were examined and the P waves of these seismic waves , which show very similar wave form , were inspected and compared to the seismic data of the latest underground nuclear test on the 3rd of September 2017 at 03:30 UTC at the same site which is many times more powerful than the previous tests . The country , which is the only nation to have tested nuclear weapons in this millennium , has successfully prevented the release of radioactive isotopes and hampered data collection but further studies were done using acoustic data which was analysed from sonograms of the 4 North Korean tests at station MDJ. The latest explosion data from 3rd September was also compared to 42 presumed underground explosions which occurred in China , India , the U.S.S.R , Iran , Turkey and recorded at Arkansas Seismic Network.

Superconducting Gravimeters Detect Gravity Fluctuations Induced by Mw 5.7 Earthquake Along South Pacific Rise Few Hours Before the 2011 Mw 9.0 Tohoku-Oki Earthquake

Directory of Open Access Journals (Sweden)

Keliang Zhang Jin Ma

2014-01-01

Full Text Available Gravity changes sometimes appear before a big earthquake. To determine the possible sources is important for recognizing the mechanism and further geodynamic studies. During the first two hours on March 11 before the Mw 9.0 Tohoku-Oki earthquake, the non-tidal gravity time series of superconducting gravimeters worldwide showed low-frequency (< 0.10 Hz fluctuations with amplitude of ~1 to 4 × 10-8 ms-2 lasting ~10 - 20 minutes. Through comparing global seismicity with the arrival times of seismic waves, we find that the fluctuations were induced by the Mw 5.7 earthquake that occurred at 0:14:54.68 at (53.27°S, 118.18°W along the eastern South Pacific Rise. Several body waves such as P, S are clearly recorded in the station with ~400 km distance to the hypocenter. The fluctuations are in response to the waves that propagate with a velocity of about 4 km s-1. Their amplitudes are proportional to the inverse of the epicentral distances even though the fluctuations of European sites were overlapped with waves associated with a smaller, i.e., Mw 2.6, event in Europe during this period. That is, the Mw 5.7 earthquake induced remarkable gravity fluctuations over long distances at stations all over the world. As such, the foreshocks with larger magnitudes occurred before the Mw 9.0 earthquake would have more significant influence on the gravity recordings and the seismic-wave induced component should be removed during the analysis of anomalies prior to a great earthquake in future studies.

Exploring Earthquakes in Real-Time

Science.gov (United States)

Bravo, T. K.; Kafka, A. L.; Coleman, B.; Taber, J. J.

2013-12-01

Earthquakes capture the attention of students and inspire them to explore the Earth. Adding the ability to view and explore recordings of significant and newsworthy earthquakes in real-time makes the subject even more compelling. To address this opportunity, the Incorporated Research Institutions for Seismology (IRIS), in collaboration with Moravian College, developed ';jAmaSeis', a cross-platform application that enables students to access real-time earthquake waveform data. Students can watch as the seismic waves are recorded on their computer, and can be among the first to analyze the data from an earthquake. jAmaSeis facilitates student centered investigations of seismological concepts using either a low-cost educational seismograph or streamed data from other educational seismographs or from any seismic station that sends data to the IRIS Data Management System. After an earthquake, students can analyze the seismograms to determine characteristics of earthquakes such as time of occurrence, distance from the epicenter to the station, magnitude, and location. The software has been designed to provide graphical clues to guide students in the analysis and assist in their interpretations. Since jAmaSeis can simultaneously record up to three stations from anywhere on the planet, there are numerous opportunities for student driven investigations. For example, students can explore differences in the seismograms from different distances from an earthquake and compare waveforms from different azimuthal directions. Students can simultaneously monitor seismicity at a tectonic plate boundary and in the middle of the plate regardless of their school location. This can help students discover for themselves the ideas underlying seismic wave propagation, regional earthquake hazards, magnitude-frequency relationships, and the details of plate tectonics. The real-time nature of the data keeps the investigations dynamic, and offers students countless opportunities to explore.

Modeling of Wave Propagation in the Osaka Sedimentary Basin during the 2013 Awaji Island Earthquake (Mw5.8)

Science.gov (United States)

Asano, K.; Sekiguchi, H.; Iwata, T.; Yoshimi, M.; Hayashida, T.; Saomoto, H.; Horikawa, H.

2013-12-01

The three-dimensional velocity structure model for the Osaka sedimentary basin, southwest Japan is developed and improved based on many kinds of geophysical explorations for decades (e.g., Kagawa et al., 1993; Horikawa et al., 2003; Iwata et al., 2008). Recently, our project (Sekiguchi et al., 2013) developed a new three-dimensional velocity model for strong motion prediction of the Uemachi fault earthquake in the Osaka basin considering both geophysical and geological information by adding newly obtained exploration data such as reflection surveys, microtremor surveys, and receiver function analysis (hereafter we call UMC2013 model) . On April 13, 2013, an inland earthquake of Mw5.8 occurred in Awaji Island, which is close to the southwestern boundary of the aftershock area of the 1995 Kobe earthquake. The strong ground motions are densely observed at more than 100 stations in the basin. The ground motion lasted longer than four minutes in the Osaka urban area where its bedrock depth is about 1-2 km. This long-duration ground motions are mainly due to the surface waves excited in this sedimentary basin whereas the magnitude of this earthquake is moderate and the rupture duration is expected to be less than 5 s. In this study, we modeled long-period (more than 2s) ground motions during this earthquake to check the performance of the present UMC2013 model and to obtain a better constraint on the attenuation factor of sedimentary part of the basin. The seismic wave propagation in the region including the source and the Osaka basin is modeled by the finite difference method using the staggered grid solving the elasto-dynamic equations. The domain of 90km×85km×25.5km is modeled and discretized with a grid spacing of 50 m. Since the minimum S-wave velocity of the UMC2013 model is about 250 m/s, this calculation is valid up to the period of about 1 s. The effect of attenuation is included in the form of Q(f)=Q0(T0/T) proposed by Graves (1996). A PML is implemented in

Earthquake Warning Performance in Vallejo for the South Napa Earthquake

Science.gov (United States)

Wurman, G.; Price, M.

2014-12-01

In 2002 and 2003, Seismic Warning Systems, Inc. installed first-generation QuakeGuardTM earthquake warning devices at all eight fire stations in Vallejo, CA. These devices are designed to detect the P-wave of an earthquake and initiate predetermined protective actions if the impending shaking is estimated at approximately Modifed Mercalli Intensity V or greater. At the Vallejo fire stations the devices were set up to sound an audio alert over the public address system and to command the equipment bay doors to open. In August 2014, after more than 11 years of operating in the fire stations with no false alarms, the five units that were still in use triggered correctly on the MW 6.0 South Napa earthquake, less than 16 km away. The audio alert sounded in all five stations, providing fire fighters with 1.5 to 2.5 seconds of warning before the arrival of the S-wave, and the equipment bay doors opened in three of the stations. In one station the doors were disconnected from the QuakeGuard device, and another station lost power before the doors opened completely. These problems highlight just a small portion of the complexity associated with realizing actionable earthquake warnings. The issues experienced in this earthquake have already been addressed in subsequent QuakeGuard product generations, with downstream connection monitoring and backup power for critical systems. The fact that the fire fighters in Vallejo were afforded even two seconds of warning at these epicentral distances results from the design of the QuakeGuard devices, which focuses on rapid false positive rejection and ground motion estimates. We discuss the performance of the ground motion estimation algorithms, with an emphasis on the accuracy and timeliness of the estimates at close epicentral distances.

Real-time capture of seismic waves using high-rate multi-GNSS observations: Application to the 2015 Mw 7.8 Nepal earthquake

Science.gov (United States)

Geng, Tao; Xie, Xin; Fang, Rongxin; Su, Xing; Zhao, Qile; Liu, Gang; Li, Heng; Shi, Chuang; Liu, Jingnan

2016-01-01

The variometric approach is investigated to measure real-time seismic waves induced by the 2015 Mw 7.8 Nepal earthquake with high-rate multi-GNSS observations, especially with the contribution of newly available BDS. The velocity estimation using GPS + BDS shows an additional improvement of around 20% with respect to GPS-only solutions. We also reconstruct displacements by integrating GNSS-derived velocities after a linear trend removal (IGV). The displacement waveforms with accuracy of better than 5 cm are derived when postprocessed GPS precise point positioning results are used as ground truth, even if those stations have strong ground motions and static offsets of up to 1-2 m. GNSS-derived velocity and displacement waveforms with the variometric approach are in good agreement with results from strong motion data. We therefore conclude that it is feasible to capture real-time seismic waves with multi-GNSS observations using the IGV-enhanced variometric approach, which has critical implications for earthquake early warning, tsunami forecasting, and rapid hazard assessment.

Full wave field recording of the vertical strain at SAFOD from local, regional and teleseismic earthquakes

Science.gov (United States)

Ellsworth, W. L.; Karrenbach, M. H.; Zumberge, M. A.

2017-12-01

The main borehole at the San Andreas Fault Observatory at Depth (SAFOD) contains optical fibers cemented in place in between casing strings from the surface to just below the top of the basement. The fibers are under tension of approximately 1 N and are housed in a 0.9 mm diameter stainless steel tube. Earth strain is transmitted to the fiber by frictional contact with the tube wall. One fiber has been in use as a vertical strainmeter since 2005, measuring the total strain between 9 and 740 m by laser interferometry. In June 2017 we attached an OptaSense Distributed Acoustic Sensing (DAS) system, model ODH3.1, to a second fiber that terminates at 864 m depth. The DAS laser interrogator measures the strain over a gauge length with a set spacing between gauge intervals. For this experiment we set the gauge length to 10 m with 1 m spacing between gauges. Including the surface run of the fiber, this gives us 936 channels measuring the vertical strain at a sample interval of 0.4 msec (2500 samples/s). Continuous recording of the string produces approximately 1 TB/day. During one month of data collection, we recorded local, regional and teleseismic earthquakes. With this recording geometry, the DAS system captures the full vertical wavefield between the basement interface and free surface, revealing direct, converted and refracted waves. Both P- and S- strain waves are clearly visible in the data, even for 10 km deep earthquakes located almost directly below the well (see figure). The incident and surface reflected wavefields can be separated by frequency-wavenumber filtering due to the large-aperture and fine spatial and temporal sampling. Up- and downgoing strain waves illuminate the subsurface within the sensor array's depth range. Accurate arrival time determinations of the initial arrival phase are possible due to consistent wave forms recorded at 1 m spatial intervals that can be used for fine-scale shallow velocity model estimation.

Scaling relationship between corner frequencies and seismic moments of ultra micro earthquakes estimated with coda-wave spectral ratio -the Mponeng mine in South Africa

Science.gov (United States)

Wada, N.; Kawakata, H.; Murakami, O.; Doi, I.; Yoshimitsu, N.; Nakatani, M.; Yabe, Y.; Naoi, M. M.; Miyakawa, K.; Miyake, H.; Ide, S.; Igarashi, T.; Morema, G.; Pinder, E.; Ogasawara, H.

2011-12-01

Scaling relationship between corner frequencies, fc, and seismic moments, Mo is an important clue to understand the seismic source characteristics. Aki (1967) showed that Mo is proportional to fc-3 for large earthquakes (cubic law). Iio (1986) claimed breakdown of the cubic law between fc and Mo for smaller earthquakes (Mw law holds even for micro earthquakes (-1 4) by using high quality data observed at a deep borehole (Abercrombie, 1995; Ogasawara et al., 2001; Hiramatsu et al., 2002; Yamada et al., 2007). In order to clarify the scaling relationship for smaller earthquakes (Mw Africa. We used 4 tri-axial accelerometers of three-component that have a flat response up to 25 kHz. They were installed to be 10 to 30 meters apart from each other at 3,300 meters deep. During the period from 2008/10/14 to 2008/10/30 (17 days), 8,927 events were recorded. We estimated fc and Mo for 60 events (-3 Common practice is using direct waves from adjacent events. However, there were only 5 event pairs with the distance between them less than 20 meters and Mw difference over one. In addition, the observation array is very small (radius less than 30 m), which means that effects of directivity and radiation pattern on direct waves are similar at all stations. Hence, we used spectral ratio of coda waves, since these effects are averaged and will be effectively reduced (Mayeda et al., 2007; Somei et al., 2010). Coda analysis was attempted only for relatively large 20 events (we call "coda events" hereafter) that have coda energy large enough for analysis. The results agree with those of the direct S-wave analysis for the same events, though the latter showed more scattering in fc-Mo trend. So, we combine the results from the both analyses to examine the fc-Mo trend down to very small events. Therefore, we adopted fc and (relative) Mo estimated from coda spectral ratios for coda events, while we adopted them from direct spectra for other events despite of their lower reliability. We

FEATURES AND PROBLEMS WITH HISTORICAL GREAT EARTHQUAKES AND TSUNAMIS IN THE MEDITERRANEAN SEA

Directory of Open Access Journals (Sweden)

Lobkovsky L.

2016-11-01

Full Text Available The present study examines the historical earthquakes and tsunamis of 21 July 365 and of 9 February 1948 in the Eastern Mediterranean Sea. Numerical simulations were performed for the tsunamis generated by underwater seismic sources in frames of the keyboard model, as well as for their propagation in the Mediterranean Sea basin. Similarly examined were three different types of seismic sources at the same localization near the Island of Crete for the earthquake of 21 July 365, and of two different types of seismic sources for the earthquake of 9 February 1948 near the Island of Karpathos. For each scenario, the tsunami wave field characteristics from the earthquake source to coastal zones in Mediterranean Sea’s basin were obtained and histograms were constructed showing the distribution of maximum tsunami wave heights, along a 5-m isobath. Comparison of tsunami wave characteristics for all the above mentioned scenarios, demonstrates that underwater earthquakes with magnitude M > 7 in the Eastern Mediterranean Sea basin, can generate waves with coastal runup up to 9 m.

Refresher Course on Physics of Earthquakes -98 ...

Indian Academy of Sciences (India)

The objective of this course is to help teachers gain an understanding of the earhquake phenomenon and the physical processes involved in its genesis as well as offhe earthquake waves which propagate the energy released by the earthquake rupture outward from the source. The Course will begin with mathematical ...

Protecting your family from earthquakes: The seven steps to earthquake safety

Science.gov (United States)

Developed by American Red Cross, Asian Pacific Fund

2007-01-01

This book is provided here because of the importance of preparing for earthquakes before they happen. Experts say it is very likely there will be a damaging San Francisco Bay Area earthquake in the next 30 years and that it will strike without warning. It may be hard to find the supplies and services we need after this earthquake. For example, hospitals may have more patients than they can treat, and grocery stores may be closed for weeks. You will need to provide for your family until help arrives. To keep our loved ones and our community safe, we must prepare now. Some of us come from places where earthquakes are also common. However, the dangers of earthquakes in our homelands may be very different than in the Bay Area. For example, many people in Asian countries die in major earthquakes when buildings collapse or from big sea waves called tsunami. In the Bay Area, the main danger is from objects inside buildings falling on people. Take action now to make sure your family will be safe in an earthquake. The first step is to read this book carefully and follow its advice. By making your home safer, you help make our community safer. Preparing for earthquakes is important, and together we can make sure our families and community are ready. English version p. 3-13 Chinese version p. 14-24 Vietnamese version p. 25-36 Korean version p. 37-48

2003 hydrological drought - natural disaster

International Nuclear Information System (INIS)

Trninic, Dusan; Bosnjak, Tomislava

2004-01-01

An exceptionally dry and warm period from February to early October 2003 resulted in hydrological drought with attributes of a natural disaster in most of the Croatian regions. The paper presents hydrological analysis of the Sava River near Zupanja for the period 1945-2003 (N=59 years). In defining maximum annual volumes of isolated waves below the reference discharges, the following reference discharges were used:Q 30,95% = 202m 3 s -1 - minimum mean 30-day discharge, 95 % probability, Q 30,80% = 254m 3 s -1 - minimum mean 30-day discharge, 80 % probability, Q 95% = 297m 3 s -1 - (H = -17cm minimum navigation level = 95 % of water level duration from average duration curve). The analysis results have shown that the hydrological drought recorded during the current year belongs to the most thoroughly studied droughts in 59 years. For example, hydrological analysis of the reference discharge of 297m 3 s -1 has shown that this year drought comes second, immediately after the driest year 1946. However, this year hydrological drought hit the record duration of 103 days, unlike the one from 1946, which lasted 98 days. It is interesting that the hydrological droughts affect the Sava River usually in autumn and summer, rarely in winter, and it has never been recorded in spring (referring to the analysed 1945-2003 period). In conclusion, some recommendations are given for increase in low streamflows and on possible impacts of climate changes on these flows.(Author)

Earthquake free design of pipe lines

International Nuclear Information System (INIS)

Kurihara, Chizuko; Sakurai, Akio

1974-01-01

Long structures such as cooling sea water pipe lines of nuclear power plants have a wide range of extent along the ground surface, and are incurred by not only the inertia forces but also forces due to ground deformations or the seismic wave propagation during earthquakes. Since previous reports indicated the earthquake free design of underground pipe lines, it is discussed in this report on behaviors of pipe lines on the ground during earthquakes and is proposed the aseismic design of pipe lines considering the effects of both inertia forces and ground deformations. (author)

Assessment of precast beam-column using capacity demand response spectrum subject to design basis earthquake and maximum considered earthquake

Science.gov (United States)

Ghani, Kay Dora Abd.; Tukiar, Mohd Azuan; Hamid, Nor Hayati Abdul

2017-08-01

Malaysia is surrounded by the tectonic feature of the Sumatera area which consists of two seismically active inter-plate boundaries, namely the Indo-Australian and the Eurasian Plates on the west and the Philippine Plates on the east. Hence, Malaysia experiences tremors from far distant earthquake occurring in Banda Aceh, Nias Island, Padang and other parts of Sumatera Indonesia. In order to predict the safety of precast buildings in Malaysia under near field ground motion the response spectrum analysis could be used for dealing with future earthquake whose specific nature is unknown. This paper aimed to develop of capacity demand response spectrum subject to Design Basis Earthquake (DBE) and Maximum Considered Earthquake (MCE) in order to assess the performance of precast beam column joint. From the capacity-demand response spectrum analysis, it can be concluded that the precast beam-column joints would not survive when subjected to earthquake excitation with surface-wave magnitude, Mw, of more than 5.5 Scale Richter (Type 1 spectra). This means that the beam-column joint which was designed using the current code of practice (BS8110) would be severely damaged when subjected to high earthquake excitation. The capacity-demand response spectrum analysis also shows that the precast beam-column joints in the prototype studied would be severely damaged when subjected to Maximum Considered Earthquake (MCE) with PGA=0.22g having a surface-wave magnitude of more than 5.5 Scale Richter, or Type 1 spectra.

Drought and Heat Wave Impacts on Electricity Grid Reliability in Illinois

Science.gov (United States)

Stillwell, A. S.; Lubega, W. N.

2016-12-01

A large proportion of thermal power plants in the United States use cooling systems that discharge large volumes of heated water into rivers and cooling ponds. To minimize thermal pollution from these discharges, restrictions are placed on temperatures at the edge of defined mixing zones in the receiving waters. However, during extended hydrological droughts and heat waves, power plants are often granted thermal variances permitting them to exceed these temperature restrictions. These thermal variances are often deemed necessary for maintaining electricity reliability, particularly as heat waves cause increased electricity demand. Current practice, however, lacks tools for the development of grid-scale operational policies specifying generator output levels that ensure reliable electricity supply while minimizing thermal variances. Such policies must take into consideration characteristics of individual power plants, topology and characteristics of the electricity grid, and locations of power plants within the river basin. In this work, we develop a methodology for the development of these operational policies that captures necessary factors. We develop optimal rules for different hydrological and meteorological conditions, serving as rule curves for thermal power plants. The rules are conditioned on leading modes of the ambient hydrological and meteorological conditions at the different power plant locations, as the locations are geographically close and hydrologically connected. Heat dissipation in the rivers and cooling ponds is modeled using the equilibrium temperature concept. Optimal rules are determined through a Monte Carlo sampling optimization framework. The methodology is applied to a case study of eight power plants in Illinois that were granted thermal variances in the summer of 2012, with a representative electricity grid model used in place of the actual electricity grid.

P-Wave Velocity Tomography from Local Earthquakes in Western Mexico

Science.gov (United States)

Ochoa-Chávez, Juan A.; Escudero, Christian R.; Núñez-Cornú, Francisco J.; Bandy, William L.

2016-10-01

In western Mexico, the subduction of the Rivera and Cocos plates beneath the North America plate has deformed and fragmented the overriding plate, forming several structural rifts and crustal blocks. To obtain a reliable subsurface image of the continental crust and uppermost mantle in this complex area, we used P-wave arrivals of local earthquakes along with the Fast Marching Method tomography technique. We followed an inversion scheme consisting of (1) the use of a high-quality earthquake catalog and corrected phase picks, (2) the selection of earthquakes using a maximum location error threshold, (3) the estimation of an improved 1-D reference velocity model, and (4) the use of checkerboard testing to determine the optimum configuration of the velocity nodes and inversion parameters. Surprisingly, the tomography results show a very simple δVp distribution that can be described as being controlled by geologic structures formed during two stages of the separation of the Rivera and Cocos plates. The earlier period represents the initial stages of the separation of the Rivera and Cocos plates beneath western Mexico; the later period represents the more advanced stage of rifting where the Rivera and Cocos plates had separated sufficiently to allow melt to accumulate below the Colima Volcanic complex. During the earlier period (14 or 10-1.6 Ma), NE-SW-oriented structures/lineaments (such as the Southern Colima Rift) were formed as the two plates separated. During the second period (1.6 Ma to the present), the deformation is attributed to magma, generated within and above the tear zone between the Rivera and Cocos plates, rising beneath the region of the Colima Volcanic Complex. The rising magma fractured the overlying crust, forming a classic triple-rift junction geometry. This triple-rift system is confined to the mid- to lower crust perhaps indicating that this rifting process is still in an early stage. This fracturing, along with fluid circulation and associated

Investigation of Backprojection Uncertainties With M6 Earthquakes

Science.gov (United States)

Fan, Wenyuan; Shearer, Peter M.

2017-10-01

We investigate possible biasing effects of inaccurate timing corrections on teleseismic P wave backprojection imaging of large earthquake ruptures. These errors occur because empirically estimated time shifts based on aligning P wave first arrivals are exact only at the hypocenter and provide approximate corrections for other parts of the rupture. Using the Japan subduction zone as a test region, we analyze 46 M6-M7 earthquakes over a 10 year period, including many aftershocks of the 2011 M9 Tohoku earthquake, performing waveform cross correlation of their initial P wave arrivals to obtain hypocenter timing corrections to global seismic stations. We then compare backprojection images for each earthquake using its own timing corrections with those obtained using the time corrections from other earthquakes. This provides a measure of how well subevents can be resolved with backprojection of a large rupture as a function of distance from the hypocenter. Our results show that backprojection is generally very robust and that the median subevent location error is about 25 km across the entire study region (˜700 km). The backprojection coherence loss and location errors do not noticeably converge to zero even when the event pairs are very close (<20 km). This indicates that most of the timing differences are due to 3-D structure close to each of the hypocenter regions, which limits the effectiveness of attempts to refine backprojection images using aftershock calibration, at least in this region.

Triggered Seismicity in Utah from the November 3, 2002, Denali Fault Earthquake

Science.gov (United States)

Pankow, K. L.; Nava, S. J.; Pechmann, J. C.; Arabasz, W. J.

2002-12-01

Coincident with the arrival of the surface waves from the November 3, 2002, Mw 7.9 Denali Fault, Alaska earthquake (DFE), the University of Utah Seismograph Stations (UUSS) regional seismic network detected a marked increase in seismicity along the Intermountain Seismic Belt (ISB) in central and north-central Utah. The number of earthquakes per day in Utah located automatically by the UUSS's Earthworm system in the week following the DFE was approximately double the long-term average during the preceding nine months. From these preliminary data, the increased seismicity appears to be characterized by small magnitude events (M = 3.2) and concentrated in five distinct spatial clusters within the ISB between 38.75°and 42.0° N. The first of these earthquakes was an M 2.2 event located ~20 km east of Salt Lake City, Utah, which occurred during the arrival of the Love waves from the DFE. The increase in Utah earthquake activity at the time of the arrival of the surface waves from the DFE suggests that these surface waves triggered earthquakes in Utah at distances of more than 3,000 km from the source. We estimated the peak dynamic shear stress caused by these surface waves from measurements of their peak vector velocities at 43 recording sites: 37 strong-motion stations of the Advanced National Seismic System and six broadband stations. (The records from six other broadband instruments in the region of interest were clipped.) The estimated peak stresses ranged from 1.2 bars to 3.5 bars with a mean of 2.3 bars, and generally occurred during the arrival of Love waves of ~15 sec period. These peak dynamic shear stress estimates are comparable to those obtained from recordings of the 1992 Mw 7.3 Landers, California, earthquake in regions where the Landers earthquake triggered increased seismicity. We plan to present more complete analyses of UUSS seismic network data, further testing our hypothesis that the DFE remotely triggered seismicity in Utah. This hypothesis is

What Caused the Winter Drought in Western Nepal during Recent Years?

Energy Technology Data Exchange (ETDEWEB)

Wang, S-Y (Simon); Yoon, Jin-Ho; Gillies, R.; Cho, Changrae

2013-11-01

Western Nepal has experienced consecutive and worsened winter drought conditions since 2000 culminating in a severe drought episode during 2008-2009. In this study, the meteorological conditons and a historical pespective of the winter droughts in western Nepal were analyzed using respectively instumental records and a paleoclimatic drought index. Althought decadal-scale drought conditions were found to be recurrent in the paleoclimate record, the severity of the recent decadal drought (since 2000) clearly stands out in the 700 years of record and, this is suggestive of potential anthropogenic influences in the recent decades. Meteorological diagnosis using atmospheric reanalysis in the recent decades revealed that (1) winter drought in western Nepal is linked to the Arctic Oscillation and its decadal variability, which initiates a tropospheric short-wave train across the Europe, Eurasia and South Asia, and that (2) the persistent warming of the Indian Ocean likely contributes to the suppression of rainfall through enhanced local Hadley circultion. It is therefore conceivable that the recent spells of decadal drought in Nepal drought are symptomatic of both natural variability and anthropogenic influences.

Rupture processes of the 2013-2014 Minab earthquake sequence, Iran

Science.gov (United States)

Kintner, Jonas A.; Ammon, Charles J.; Cleveland, K. Michael; Herman, Matthew

2018-06-01

We constrain epicentroid locations, magnitudes and depths of moderate-magnitude earthquakes in the 2013-2014 Minab sequence using surface-wave cross-correlations, surface-wave spectra and teleseismic body-wave modelling. We estimate precise relative locations of 54 Mw ≥ 3.8 earthquakes using 48 409 teleseismic, intermediate-period Rayleigh and Love-wave cross-correlation measurements. To reduce significant regional biases in our relative locations, we shift the relative locations to align the Mw 6.2 main-shock centroid to a location derived from an independent InSAR fault model. Our relocations suggest that the events lie along a roughly east-west trend that is consistent with the faulting geometry in the GCMT catalogue. The results support previous studies that suggest the sequence consists of left-lateral strain release, but better defines the main-shock fault length and shows that most of the Mw ≥ 5.0 aftershocks occurred on one or two similarly oriented structures. We also show that aftershock activity migrated westwards along strike, away from the main shock, suggesting that Coulomb stress transfer played a role in the fault failure. We estimate the magnitudes of the relocated events using surface-wave cross-correlation amplitudes and find good agreement with the GCMT moment magnitudes for the larger events and underestimation of small-event size by catalogue MS. In addition to clarifying details of the Minab sequence, the results demonstrate that even in tectonically complex regions, relative relocation using teleseismic surface waves greatly improves the precision of relative earthquake epicentroid locations and can facilitate detailed tectonic analyses of remote earthquake sequences.

Temporal change in shallow subsurface P- and S-wave velocities and S-wave anisotropy inferred from coda wave interferometry

Science.gov (United States)

Yamamoto, M.; Nishida, K.; Takeda, T.

2012-12-01

Recent progresses in theoretical and observational researches on seismic interferometry reveal the possibility to detect subtle change in subsurface seismic structure. This high sensitivity of seismic interferometry to the medium properties may thus one of the most important ways to directly observe the time-lapse behavior of shallow crustal structure. Here, using the coda wave interferometry, we show the co-seismic and post-seismic changes in P- and S-wave velocities and S-wave anisotropy associated with the 2011 off the Pacific coast of Tohoku earthquake (M9.0). In this study, we use the acceleration data recorded at KiK-net stations operated by NIED, Japan. Each KiK-net station has a borehole whose typical depth is about 100m, and two three-component accelerometers are installed at the top and bottom of the borehole. To estimate the shallow subsurface P- and S-wave velocities and S-wave anisotropy between two sensors and their temporal change, we select about 1000 earthquakes that occurred between 2004 and 2012, and extract body waves propagating between borehole sensors by computing the cross-correlation functions (CCFs) of 3 x 3 component pairs. We use frequency bands of 2-4, 4-8, 8-16 Hz in our analysis. Each averaged CCF shows clear wave packets traveling between borehole sensors, and their travel times are almost consistent with those of P- and S-waves calculated from the borehole log data. Until the occurrence of the 2011 Tohoku earthquake, the estimated travel time at each station is rather stable with time except for weak seasonal/annual variation. On the other hand, the 2011 Tohoku earthquake and its aftershocks cause sudden decrease in the S-wave velocity at most of the KiK-net stations in eastern Japan. The typical value of S-wave velocity changes, which are measured by the time-stretching method, is about 5-15%. After this co-seismic change, the S-wave velocity gradually recovers with time, and the recovery continues for over one year following the

Floods and droughts on the lower Vistula

Directory of Open Access Journals (Sweden)

Marzenna Sztobryn

2013-06-01

Full Text Available The study analyses floods and droughts on the lower Vistula based on the data (water levels and flow rates recorded in stations of the Institute of Meteorology and Water Management – National Research Institute (IMGW-PIB in Warsaw, Kępa Polska, Toruń and Tczew. It also includes the causes of flooding and drought in the lower Vistula with the hydrological characteristics from the years 1951–2010. The variability in maximum and minimum annual and monthly flow rates has been analysed for the aforementioned period as well. In addition, the authors have analysed changes in the shape of the flood wave after passing through the reservoir and cascade in Włocławek based on the hydrograph of May and June 2010. It has been found that the flood wave is flattened and extended. This phenomenon is favourable from the point of view of flood actions.

Real Time Earthquake Information System in Japan

Science.gov (United States)

Doi, K.; Kato, T.

2003-12-01

An early earthquake notification system in Japan had been developed by the Japan Meteorological Agency (JMA) as a governmental organization responsible for issuing earthquake information and tsunami forecasts. The system was primarily developed for prompt provision of a tsunami forecast to the public with locating an earthquake and estimating its magnitude as quickly as possible. Years after, a system for a prompt provision of seismic intensity information as indices of degrees of disasters caused by strong ground motion was also developed so that concerned governmental organizations can decide whether it was necessary for them to launch emergency response or not. At present, JMA issues the following kinds of information successively when a large earthquake occurs. 1) Prompt report of occurrence of a large earthquake and major seismic intensities caused by the earthquake in about two minutes after the earthquake occurrence. 2) Tsunami forecast in around three minutes. 3) Information on expected arrival times and maximum heights of tsunami waves in around five minutes. 4) Information on a hypocenter and a magnitude of the earthquake, the seismic intensity at each observation station, the times of high tides in addition to the expected tsunami arrival times in 5-7 minutes. To issue information above, JMA has established; - An advanced nationwide seismic network with about 180 stations for seismic wave observation and about 3,400 stations for instrumental seismic intensity observation including about 2,800 seismic intensity stations maintained by local governments, - Data telemetry networks via landlines and partly via a satellite communication link, - Real-time data processing techniques, for example, the automatic calculation of earthquake location and magnitude, the database driven method for quantitative tsunami estimation, and - Dissemination networks, via computer-to-computer communications and facsimile through dedicated telephone lines. JMA operationally

The study of earthquakes in the hundred years following the Lisbon earthquake of 1755

Czech Academy of Sciences Publication Activity Database

Oldroyd, D. R.; Amador, F.; Kozák, Jan; Carneiro, A.; Pinto, M.

2007-01-01

Roč. 26, č. 2 (2007), s. 321-370 ISSN 0736-623X Institutional research plan: CEZ:AV0Z30120515 Keywords : 1755 Lisbon earthquake * post-Lisbon seismology * seismic waves Subject RIV: DC - Siesmology, Volcanology, Earth Structure

Rayleigh wave ellipticity across the Iberian Peninsula and Morocco

Science.gov (United States)

Gómez García, Clara; Villaseñor, Antonio

2015-04-01

Spectral amplitude ratios between horizontal and vertical components (H/V ratios) from seismic records are useful to evaluate site effects, predict ground motion and invert for S velocity in the top several hundred meters. These spectral ratios can be obtained from both ambient noise and earthquakes. H/V ratios from ambient noise depend on the content and predominant wave types: body waves, Rayleigh waves, a mixture of different waves, etc. The H/V ratio computed in this way is assumed to measure Rayleigh wave ellipticity since ambient vibrations are dominated by Rayleigh waves. H/V ratios from earthquakes are able to determine the local crustal structure at the vicinity of the recording station. These ratios obtained from earthquakes are based on surface wave ellipticity measurements. Although long period (>20 seconds) Rayleigh H/V ratio is not currently used because of large scatter has been reported and uncertainly about whether these measurements are compatible with traditional phase and group velocity measurements, we will investigate whether it is possible to obtain stable estimates after collecting statistics for many earthquakes. We will use teleseismic events from shallow earthquakes (depth ≤ 40 km) between 2007 January 1 and 2012 December 31 with M ≥ 6 and we will compute H/V ratios for more than 400 stations from several seismic networks across the Iberian Peninsula and Morocco for periods between 20 and 100 seconds. Also H/V ratios from cross-correlations of ambient noise in different components for each station pair will be computed. Shorter period H/V ratio measurements based on ambient noise cross-correlations are strongly sensitive to near-surface structure, rather than longer period earthquake Rayleigh waves. The combination of ellipticity measurements based on earthquakes and ambient noise will allow us to perform a joint inversion with Rayleigh wave phase velocity. Upper crustal structure is better constrained by the joint inversion compared

Identified EM Earthquake Precursors

Science.gov (United States)

Jones, Kenneth, II; Saxton, Patrick

2014-05-01

Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for

Earthquake Drill using the Earthquake Early Warning System at an Elementary School

Science.gov (United States)

Oki, Satoko; Yazaki, Yoshiaki; Koketsu, Kazuki

2010-05-01

economic repercussion. We provide the school kids with the "World Seismicity Map" to let them realize that earthquake disasters take place unequally. Then we let the kids jump in front of the seismometer with projecting the real-time data to the wall. Grouped kids contest the largest amplitude by carefully considering how to jump high but nail the landing with their teammates. Their jumps are printed out via portable printer and compared with the real earthquake which occurred even 600km away but still huge when printed out in the same scale. Actually, a magnitude 7 earthquake recorded 600km away needs an A0 paper when scaled with a jump of 10 kids printed in an A4 paper. They've got to understand what to do not to be killed with the great big energy. We also offer earthquake drills using the Earthquake Early Warning System (EEW System). An EEW System is officially introduced in 2007 by JMA (Japan Meteorological Agency) to issue prompt alerts to provide several to several ten seconds before S-wave arrives. When hearing the alarm, school kids think fast to find a place to protect themselves. It is not always when they are in their classrooms but in the chemical lab, music room which does not have any desks to protect them, or in the PE class. Then in the science class, we demonstrate how the EEW System works. A 8m long wave propagation device made with spindles connected with springs is used to visualize the P- and S-waves. In the presentation, we would like to show the paper materials and sufficient movies.

Simultaneous estimation of earthquake source parameters and ...

Indian Academy of Sciences (India)

moderate-size aftershocks (Mw 2.1–5.1) of the Mw 7.7 2001 Bhuj earthquake. The horizontal- ... claimed a death toll of 20,000 people. This earth- .... quake occurred west of Kachchh, with an epicenter at 24. ◦. N, 68 ..... for dominance of body waves for R ≤ 100 km ...... Bhuj earthquake sequence; J. Asian Earth Sci. 40.

Search for Anisotropy Changes Associated with Two Large Earthquakes in Japan and New Zealand

Science.gov (United States)

Savage, M. K.; Graham, K.; Aoki, Y.; Arnold, R.

2017-12-01

Seismic anisotropy is often considered to be an indicator of stress in the crust, because the closure of cracks due to differential stress leads to waves polarized parallel to the cracks travelling faster than the orthogonal direction. Changes in shear wave splitting have been suggested to result from stress changes at volcanoes and earthquakes. However, the effects of mineral or structural alignment, and the difficulty of distinguishing between changes in anisotropy along an earthquake-station path from distinguishing changes in the path itself, have made such findings controversial. Two large earthquakes in 2016 provide unique datasets to test the use of shear wave splitting for measuring variations in stress because clusters of closely-spaced earthquakes occurred both before and after a mainshock. We use the automatic, objective splitting analysis code MFAST to speed process and minimize unwitting observer bias when determining time variations. The sequence of earthquakes related to the M=7.2 Japanese Kumamoto earthquake of 14 April 2016 includes both foreshocks, mainshocks and aftershocks. The sequence was recorded by the NIED permanent network, which already contributed background seismic anisotropy measurements in a previous study of anisotropy and stress in Kyushu. Preliminary measurements of shear wave splitting from earthquakes that occurred in 2016 show results at some stations that clearly differ from those of the earlier study. They also change between earthquakes recorded before and after the mainshock. Further work is under way to determine whether the changes are more likely due to changes in stress during the observation time, or due to spatial changes in anisotropy combined with changes in earthquake locations. Likewise, background seismicity and also foreshocks and aftershocks in the 2013 Cook Strait earthquake sequence including two M=6.5 earthquakes in 2013 in New Zealand were in the same general region as aftershocks of the M=7.8 Kaikoura

Long-period effects of the Denali earthquake on water bodies in the Puget Lowland: Observations and modeling

Science.gov (United States)

Barberopoulou, A.; Qamar, A.; Pratt, T.L.; Steele, W.P.

2006-01-01

Analysis of strong-motion instrument recordings in Seattle, Washington, resulting from the 2002 Mw 7.9 Denali, Alaska, earthquake reveals that amplification in the 0.2-to 1.0-Hz frequency band is largely governed by the shallow sediments both inside and outside the sedimentary basins beneath the Puget Lowland. Sites above the deep sedimentary strata show additional seismic-wave amplification in the 0.04- to 0.2-Hz frequency range. Surface waves generated by the Mw 7.9 Denali, Alaska, earthquake of 3 November 2002 produced pronounced water waves across Washington state. The largest water waves coincided with the area of largest seismic-wave amplification underlain by the Seattle basin. In the current work, we present reports that show Lakes Union and Washington, both located on the Seattle basin, are susceptible to large water waves generated by large local earthquakes and teleseisms. A simple model of a water body is adopted to explain the generation of waves in water basins. This model provides reasonable estimates for the water-wave amplitudes in swimming pools during the Denali earthquake but appears to underestimate the waves observed in Lake Union.

Evaluation of groundwater droughts in Austria

Science.gov (United States)

Haas, Johannes Christoph; Birk, Steffen

2015-04-01

Droughts are abnormally dry periods that affect various aspects of human life on earth, ranging from negative impacts on agriculture or industry, to being the cause for conflict and loss of human life. The changing climate reinforces the importance of investigations into this phenomenon. Various methods to analyze and classify droughts have been developed. These include drought indices such as the Standard Precipitation Index SPI, the Palmer Drought Severity Index PDSI or the Crop Moisture Index CMI. These and other indices consider meteorological parameters and/or their effects on soil moisture. A depletion of soil moisture triggered by low precipitation and high evapotranspiration may also cause reduced groundwater recharge and thus decreasing groundwater levels and reduced groundwater flow to springs, streams, and wetlands. However, the existing indices were generally not designed to address such drought effects on groundwater. Thus, a Standardized Groundwater level Index has recently been proposed by Bloomfied and Marchant (2013). Yet, to our knowledge, this approach has only been applied to consolidated aquifers in the UK. This work analyzes time series of groundwater levels from various, mostly unconsolidated aquifers in Austria in order to characterize the effects of droughts on aquifers in different hydrogeologic and climatic settings as well as under different usage scenarios. In particular, comparisons are made between the water rich Alpine parts of Austria, and the dryer parts situated in the East. The time series of groundwater levels are compared to other data, such as meteorological time series and written weather records about generally accepted phenomena, such as the 2003 European drought and heat wave. Thus, valuable insight is gained into the propagation of meteorological droughts through the soil and the aquifer in different types of hydrogeologic and climatic settings, which provides a prerequisite for the assessment of the aquifers' drought

Application of τc*Pd for identifying damaging earthquakes for earthquake early warning

Science.gov (United States)

Huang, P. L.; Lin, T. L.; Wu, Y. M.

2014-12-01

Earthquake Early Warning System (EEWS) is an effective approach to mitigate earthquake damage. In this study, we used the seismic record by the Kiban Kyoshin network (KiK-net), because it has dense station coverage and co-located borehole strong-motion seismometers along with the free-surface strong-motion seismometers. We used inland earthquakes with moment magnitude (Mw) from 5.0 to 7.3 between 1998 and 2012. We choose 135 events and 10950 strong ground accelerograms recorded by the 696 strong ground accelerographs. Both the free-surface and the borehole data are used to calculate τc and Pd, respectively. The results show that τc*Pd has a good correlation with PGV and is a robust parameter for assessing the potential of damaging earthquake. We propose the value of τc*Pd determined from seconds after the arrival of P wave could be a threshold for the on-site type of EEW.

Instruction system upon occurrence of earthquakes

International Nuclear Information System (INIS)

Inagaki, Masakatsu; Morikawa, Matsuo; Suzuki, Satoshi; Fukushi, Naomi.

1987-01-01

Purpose: To enable rapid re-starting of a nuclear reactor after earthquakes by informing various properties of encountered earthquake to operators and properly displaying the state of damages in comparison with designed standard values of facilities. Constitution: Even in a case where the maximum accelerations due to the movements of earthquakes encountered exceed designed standard values, it may be considered such a case that equipments still remain intact depending on the wave components of the seismic movements and the vibration properties inherent to the equipments. Taking notice of the fact, the instruction device comprises a system that indicates the relationship between the seismic waveforms of earthquakes being encountered and the scram setting values, a system for indicating the comparison between the floor response spectrum of the seismic waveforms of the encountered earthquakes and the designed floor response spectrum used for the design of the equipments and a system for indicating those equipments requiring inspection after the earthquakes. Accordingly, it is possible to improve the operationability upon scram of a nuclear power plant undergoing earthquakes and improve the power saving and safety by clearly defining the inspection portion after the earthquakes. (Kawakami, Y.)

ASSESSMENT OF EARTHQUAKE HAZARDS ON WASTE LANDFILLS

DEFF Research Database (Denmark)

Zania, Varvara; Tsompanakis, Yiannis; Psarropoulos, Prodromos

Earthquake hazards may arise as a result of: (a) transient ground deformation, which is induced due to seismic wave propagation, and (b) permanent ground deformation, which is caused by abrupt fault dislocation. Since the adequate performance of waste landfills after an earthquake is of outmost...... importance, the current study examines the impact of both types of earthquake hazards by performing efficient finite-element analyses. These took also into account the potential slip displacement development along the geosynthetic interfaces of the composite base liner. At first, the development of permanent...

Ground-motion modeling of the 1906 San Francisco earthquake, part I: Validation using the 1989 Loma Prieta earthquake

Science.gov (United States)

Aagaard, Brad T.; Brocher, T.M.; Dolenc, D.; Dreger, D.; Graves, R.W.; Harmsen, S.; Hartzell, S.; Larsen, S.; Zoback, M.L.

2008-01-01

We compute ground motions for the Beroza (1991) and Wald et al. (1991) source models of the 1989 magnitude 6.9 Loma Prieta earthquake using four different wave-propagation codes and recently developed 3D geologic and seismic velocity models. In preparation for modeling the 1906 San Francisco earthquake, we use this well-recorded earthquake to characterize how well our ground-motion simulations reproduce the observed shaking intensities and amplitude and durations of recorded motions throughout the San Francisco Bay Area. All of the simulations generate ground motions consistent with the large-scale spatial variations in shaking associated with rupture directivity and the geologic structure. We attribute the small variations among the synthetics to the minimum shear-wave speed permitted in the simulations and how they accommodate topography. Our long-period simulations, on average, under predict shaking intensities by about one-half modified Mercalli intensity (MMI) units (25%-35% in peak velocity), while our broadband simulations, on average, under predict the shaking intensities by one-fourth MMI units (16% in peak velocity). Discrepancies with observations arise due to errors in the source models and geologic structure. The consistency in the synthetic waveforms across the wave-propagation codes for a given source model suggests the uncertainty in the source parameters tends to exceed the uncertainty in the seismic velocity structure. In agreement with earlier studies, we find that a source model with slip more evenly distributed northwest and southeast of the hypocenter would be preferable to both the Beroza and Wald source models. Although the new 3D seismic velocity model improves upon previous velocity models, we identify two areas needing improvement. Nevertheless, we find that the seismic velocity model and the wave-propagation codes are suitable for modeling the 1906 earthquake and scenario events in the San Francisco Bay Area.

Constraining the source location of the 30 May 2015 (Mw 7.9) Bonin deep-focus earthquake using seismogram envelopes of high-frequency P waveforms: Occurrence of deep-focus earthquake at the bottom of a subducting slab

Science.gov (United States)

Takemura, Shunsuke; Maeda, Takuto; Furumura, Takashi; Obara, Kazushige

2016-05-01

In this study, the source location of the 30 May 2015 (Mw 7.9) deep-focus Bonin earthquake was constrained using P wave seismograms recorded across Japan. We focus on propagation characteristics of high-frequency P wave. Deep-focus intraslab earthquakes typically show spindle-shaped seismogram envelopes with peak delays of several seconds and subsequent long-duration coda waves; however, both the main shock and aftershock of the 2015 Bonin event exhibited pulse-like P wave propagations with high apparent velocities (~12.2 km/s). Such P wave propagation features were reproduced by finite-difference method simulations of seismic wave propagation in the case of slab-bottom source. The pulse-like P wave seismogram envelopes observed from the 2015 Bonin earthquake show that its source was located at the bottom of the Pacific slab at a depth of ~680 km, rather than within its middle or upper regions.

Investigation of Back-Projection Uncertainties with M6 Earthquakes

Science.gov (United States)

Fan, W.; Shearer, P. M.

2017-12-01

We investigate possible biasing effects of inaccurate timing corrections on teleseismic P-wave back-projection imaging of large earthquake ruptures. These errors occur because empirically-estimated time shifts based on aligning P-wave first arrivals are exact only at the hypocenter and provide approximate corrections for other parts of the rupture. Using the Japan subduction zone as a test region, we analyze 46 M6-7 earthquakes over a ten-year period, including many aftershocks of the 2011 M9 Tohoku earthquake, performing waveform cross-correlation of their initial P-wave arrivals to obtain hypocenter timing corrections to global seismic stations. We then compare back-projection images for each earthquake using its own timing corrections with those obtained using the time corrections for other earthquakes. This provides a measure of how well sub-events can be resolved with back-projection of a large rupture as a function of distance from the hypocenter. Our results show that back-projection is generally very robust and that sub-event location errors average about 20 km across the entire study region ( 700 km). The back-projection coherence loss and location errors do not noticeably converge to zero even when the event pairs are very close (<20 km). This indicates that most of the timing differences are due to 3D structure close to each of the hypocenter regions, which limits the effectiveness of attempts to refine back-projection images using aftershock calibration, at least in this region.

Triggered creep as a possible mechanism for delayed dynamic triggering of tremor and earthquakes

Science.gov (United States)

Shelly, David R.; Peng, Zhigang; Hill, David P.; Aiken, Chastity

2011-01-01

The passage of radiating seismic waves generates transient stresses in the Earth's crust that can trigger slip on faults far away from the original earthquake source. The triggered fault slip is detectable in the form of earthquakes and seismic tremor. However, the significance of these triggered events remains controversial, in part because they often occur with some delay, long after the triggering stress has passed. Here we scrutinize the location and timing of tremor on the San Andreas fault between 2001 and 2010 in relation to distant earthquakes. We observe tremor on the San Andreas fault that is initiated by passing seismic waves, yet migrates along the fault at a much slower velocity than the radiating seismic waves. We suggest that the migrating tremor records triggered slow slip of the San Andreas fault as a propagating creep event. We find that the triggered tremor and fault creep can be initiated by distant earthquakes as small as magnitude 5.4 and can persist for several days after the seismic waves have passed. Our observations of prolonged tremor activity provide a clear example of the delayed dynamic triggering of seismic events. Fault creep has been shown to trigger earthquakes, and we therefore suggest that the dynamic triggering of prolonged fault creep could provide a mechanism for the delayed triggering of earthquakes. ?? 2011 Macmillan Publishers Limited. All rights reserved.

Hovsgol earthquake 5 December 2014, M W = 4.9: seismic and acoustic effects

Science.gov (United States)

Dobrynina, Anna A.; Sankov, Vladimir A.; Tcydypova, Larisa R.; German, Victor I.; Chechelnitsky, Vladimir V.; Ulzibat, Munkhuu

2018-03-01

A moderate shallow earthquake occurred on 5 December 2014 ( M W = 4.9) in the north of Lake Hovsgol (northern Mongolia). The infrasonic signal with duration 140 s was recorded for this earthquake by the "Tory" infrasound array (Institute of Solar-Terrestrial Physics of the Siberian Branch of the Russian Academy of Science, Russia). Source parameters of the earthquake (seismic moment, geometrical sizes, displacement amplitudes in the focus) were determined using spectral analysis of direct body P and S waves. The spectral analysis of seismograms and amplitude variations of the surface waves allows to determine the effect of the propagation of the rupture in the earthquake focus, the azimuth of the rupture propagation direction and the velocity of displacement in the earthquake focus. The results of modelling of the surface displacements caused by the Hovsgol earthquake and high effective velocity of propagation of infrasound signal ( 625 m/s) indicate that its occurrence is not caused by the downward movement of the Earth's surface in the epicentral region but by the effect of the secondary source. The position of the secondary source of infrasound signal is defined on the northern slopes of the Khamar-Daban ridge according to the data on the azimuth and time of arrival of acoustic wave at the Tory station. The interaction of surface waves with the regional topography is proposed as the most probable mechanism of formation of the infrasound signal.

Shear wave velocity model beneath CBJI station West Java, Indonesia from joint inversion of teleseismic receiver functions and surface wave dispersion

Science.gov (United States)

Simanungkalit, R. H.; Anggono, T.; Syuhada; Amran, A.; Supriyanto

2018-03-01

Earthquake signal observations around the world allow seismologists to obtain the information of internal structure of the Earth especially the Earth’s crust. In this study, we used joint inversion of receiver functions and surface wave group velocities to investigate crustal structure beneath CBJI station in West Java, Indonesia. Receiver function were calculated from earthquakes with magnitude more than 5 and at distance 30°-90°. Surface wave group velocities were calculated using frequency time analysis from earthquakes at distance of 30°- 40°. We inverted shear wave velocity model beneath the station by conducting joint inversion from receiver functions and surface wave dispersions. We suggest that the crustal thickness beneath CBJI station, West Java, Indonesia is about 35 km.

Earthquake hazard assessment and small earthquakes

International Nuclear Information System (INIS)

Reiter, L.

1987-01-01

The significance of small earthquakes and their treatment in nuclear power plant seismic hazard assessment is an issue which has received increased attention over the past few years. In probabilistic studies, sensitivity studies showed that the choice of the lower bound magnitude used in hazard calculations can have a larger than expected effect on the calculated hazard. Of particular interest is the fact that some of the difference in seismic hazard calculations between the Lawrence Livermore National Laboratory (LLNL) and Electric Power Research Institute (EPRI) studies can be attributed to this choice. The LLNL study assumed a lower bound magnitude of 3.75 while the EPRI study assumed a lower bound magnitude of 5.0. The magnitudes used were assumed to be body wave magnitudes or their equivalents. In deterministic studies recent ground motion recordings of small to moderate earthquakes at or near nuclear power plants have shown that the high frequencies of design response spectra may be exceeded. These exceedances became important issues in the licensing of the Summer and Perry nuclear power plants. At various times in the past particular concerns have been raised with respect to the hazard and damage potential of small to moderate earthquakes occurring at very shallow depths. In this paper a closer look is taken at these issues. Emphasis is given to the impact of lower bound magnitude on probabilistic hazard calculations and the historical record of damage from small to moderate earthquakes. Limited recommendations are made as to how these issues should be viewed

Amplification of drawdown and runup over Hawaii's insular shelves by tsunami N-waves from mega Aleutian earthquakes

Science.gov (United States)

Bai, Yefei; Yamazaki, Yoshiki; Cheung, Kwok Fai

2018-04-01

The latest tsunami evacuation maps of Hawaii include an extreme scenario triggered by an Mw 9.3 Aleutian earthquake with large near-trench rupture. The tectonic plate motion produces concentrated seafloor uplift toward the deepest part of the trench generating a tsunami with strong non-hydrostatic characters. A parametric study shows the skewed seafloor uplift produces a dispersive leading crest followed by a prominent trough in the form of an N-wave. The trough maintains its depth across the ocean in the absence of side lobes and dispersion. Shifting of the uplift toward the trench tends to deepen the trough, but has diminishing effects on the wave crest away from the source. While the attenuated leading crest produces relatively moderate runup on north-facing shores of the Hawaiian Islands, with matching of the N-wave and shelf resonance periods, the trough produces an impulsive drawdown followed by an energetic upswing with unprecedented runup for a far-field tsunami. A set of control computations without dispersion reaffirms that a non-hydrostatic model is essential to account for these complex wave processes from the source to the shore. This case study highlights the unique tsunami hazards posed by the Aleutians to Hawaii and the role of wave troughs in delineating the impacts for hazard assessment and engineering design.

Spatial Distribution of earthquakes off the coast of Fukushima Two Years after the M9 Earthquake: the Southern Area of the 2011 Tohoku Earthquake Rupture Zone

Science.gov (United States)

Yamada, T.; Nakahigashi, K.; Shinohara, M.; Mochizuki, K.; Shiobara, H.

2014-12-01

Huge earthquakes cause vastly stress field change around the rupture zones, and many aftershocks and other related geophysical phenomenon such as geodetic movements have been observed. It is important to figure out the time-spacious distribution during the relaxation process for understanding the giant earthquake cycle. In this study, we pick up the southern rupture area of the 2011 Tohoku earthquake (M9.0). The seismicity rate keeps still high compared with that before the 2011 earthquake. Many studies using ocean bottom seismometers (OBSs) have been doing since soon after the 2011 Tohoku earthquake in order to obtain aftershock activity precisely. Here we show one of the studies at off the coast of Fukushima which is located on the southern part of the rupture area caused by the 2011 Tohoku earthquake. We deployed 4 broadband type OBSs (BBOBSs) and 12 short-period type OBSs (SOBS) in August 2012. Other 4 BBOBSs attached with absolute pressure gauges and 20 SOBSs were added in November 2012. We recovered 36 OBSs including 8 BBOBSs in November 2013. We selected 1,000 events in the vicinity of the OBS network based on a hypocenter catalog published by the Japan Meteorological Agency, and extracted the data after time corrections caused by each internal clock. Each P and S wave arrival times, P wave polarity and maximum amplitude were picked manually on a computer display. We assumed one dimensional velocity structure based on the result from an active source experiment across our network, and applied time corrections every station for removing ambiguity of the assumed structure. Then we adopted a maximum-likelihood estimation technique and calculated the hypocenters. The results show that intensive activity near the Japan Trench can be seen, while there was a quiet seismic zone between the trench zone and landward high activity zone.

Automated Determination of Magnitude and Source Length of Large Earthquakes

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Wang, D.; Kawakatsu, H.; Zhuang, J.; Mori, J. J.; Maeda, T.; Tsuruoka, H.; Zhao, X.

2017-12-01

Rapid determination of earthquake magnitude is of importance for estimating shaking damages, and tsunami hazards. However, due to the complexity of source process, accurately estimating magnitude for great earthquakes in minutes after origin time is still a challenge. Mw is an accurate estimate for large earthquakes. However, calculating Mw requires the whole wave trains including P, S, and surface phases, which takes tens of minutes to reach stations at tele-seismic distances. To speed up the calculation, methods using W phase and body wave are developed for fast estimating earthquake sizes. Besides these methods that involve Green's Functions and inversions, there are other approaches that use empirically simulated relations to estimate earthquake magnitudes, usually for large earthquakes. The nature of simple implementation and straightforward calculation made these approaches widely applied at many institutions such as the Pacific Tsunami Warning Center, the Japan Meteorological Agency, and the USGS. Here we developed an approach that was originated from Hara [2007], estimating magnitude by considering P-wave displacement and source duration. We introduced a back-projection technique [Wang et al., 2016] instead to estimate source duration using array data from a high-sensitive seismograph network (Hi-net). The introduction of back-projection improves the method in two ways. Firstly, the source duration could be accurately determined by seismic array. Secondly, the results can be more rapidly calculated, and data derived from farther stations are not required. We purpose to develop an automated system for determining fast and reliable source information of large shallow seismic events based on real time data of a dense regional array and global data, for earthquakes that occur at distance of roughly 30°- 85° from the array center. This system can offer fast and robust estimates of magnitudes and rupture extensions of large earthquakes in 6 to 13 min (plus

Parallel Earthquake Simulations on Large-Scale Multicore Supercomputers

KAUST Repository

Wu, Xingfu

2011-01-01

Earthquakes are one of the most destructive natural hazards on our planet Earth. Hugh earthquakes striking offshore may cause devastating tsunamis, as evidenced by the 11 March 2011 Japan (moment magnitude Mw9.0) and the 26 December 2004 Sumatra (Mw9.1) earthquakes. Earthquake prediction (in terms of the precise time, place, and magnitude of a coming earthquake) is arguably unfeasible in the foreseeable future. To mitigate seismic hazards from future earthquakes in earthquake-prone areas, such as California and Japan, scientists have been using numerical simulations to study earthquake rupture propagation along faults and seismic wave propagation in the surrounding media on ever-advancing modern computers over past several decades. In particular, ground motion simulations for past and future (possible) significant earthquakes have been performed to understand factors that affect ground shaking in populated areas, and to provide ground shaking characteristics and synthetic seismograms for emergency preparation and design of earthquake-resistant structures. These simulation results can guide the development of more rational seismic provisions for leading to safer, more efficient, and economical50pt]Please provide V. Taylor author e-mail ID. structures in earthquake-prone regions.

Rapid estimation of the moment magnitude of large earthquake from static strain changes

Science.gov (United States)

Itaba, S.

2014-12-01

The 2011 off the Pacific coast of Tohoku earthquake, of moment magnitude (Mw) 9.0, occurred on March 11, 2011. Based on the seismic wave, the prompt report of the magnitude which the Japan Meteorological Agency announced just after earthquake occurrence was 7.9, and it was considerably smaller than an actual value. On the other hand, using nine borehole strainmeters of Geological Survey of Japan, AIST, we estimated a fault model with Mw 8.7 for the earthquake on the boundary between the Pacific and North American plates. This model can be estimated about seven minutes after the origin time, and five minute after wave arrival. In order to grasp the magnitude of a great earthquake earlier, several methods are now being suggested to reduce the earthquake disasters including tsunami (e.g., Ohta et al., 2012). Our simple method of using strain steps is one of the strong methods for rapid estimation of the magnitude of great earthquakes.

Refinements on the inferred causative faults of the great 2012 Indian Ocean earthquakes

Science.gov (United States)

Revathy, P. M.; Rajendran, K.

2014-12-01

As the largest known intra-plate strike-slip events, the pair of 2012 earthquakes in the Wharton Basin is a rarity. Separated in time by 2 hours these events rouse interest also because of their short inter-event duration, complex rupture mechanism, and spatial-temporal proximity to the great 2004 Sumatra plate boundary earthquake. Reactivation of fossil ridge-transform pairs is a favoured mechanism for large oceanic plate earthquakes and their inherent geometry triggers earthquakes on conjugate fault systems, as observed previously in the Wharton Basin. The current debate is whether the ruptures occurred on the WNW-ESE paleo ridges or the NNE-SSW paleo transforms. Back-projection models give a complex rupture pattern that favours the WNW-ESE fault [1]. However, the static stress changes due to the 2004 Sumatra earthquake and 2005 Nias earthquake favour the N15°E fault [2]. We use the Teleseismic Body-Wave Inversion Program [3] and waveform data from Global Seismic Network, to obtain the best fit solutions using P and S-wave synthetic modelling. The preliminary P-wave analysis of both earthquakes gives source parameters that are consistent with the Harvard CMT solutions. The obtained slip distribution complies with the NNE-SSW transforms. Both these earthquakes triggered small tsunamis which appear as two distinctive pulses on 13 Indian Ocean tide gauges and buoys. Frequency spectra of the tsunami recordings from various azimuths provide additional constraint for the choice of the causative faults. References: [1] Yue, H., T. Lay, and K. D. Koper (2012), En echelon and orthogonal fault ruptures of the 11 April 2012 great intraplate earthquakes, Nature, 490, 245-249, doi:10.1038/nature11492 [2] Delescluse, M., N. Chamot-Rooke, R. Cattin, L. Fleitout, O. Trubienko and C. Vigny April 2012 intra-oceanic seismicity off Sumatra boosted by the Banda-Aceh megathrust, Nature, 490(2012), pp. 240-244, doi:10.1038/nature11520 [3] M. Kikuchi and H. Kanamori, Note on

Tsunami waves generated by dynamically triggered aftershocks of the 2010 Haiti earthquake

Science.gov (United States)

Ten Brink, U. S.; Wei, Y.; Fan, W.; Miller, N. C.; Granja, J. L.

2017-12-01

Dynamically-triggered aftershocks, thought to be set off by the passage of surface waves, are currently not considered in tsunami warnings, yet may produce enough seafloor deformation to generate tsunamis on their own, as judged from new findings about the January 12, 2010 Haiti earthquake tsunami in the Caribbean Sea. This tsunami followed the Mw7.0 Haiti mainshock, which resulted from a complex rupture along the north shore of Tiburon Peninsula, not beneath the Caribbean Sea. The mainshock, moreover, had a mixed strike-slip and thrust focal mechanism. There were no recorded aftershocks in the Caribbean Sea, only small coastal landslides and rock falls on the south shore of Tiburon Peninsula. Nevertheless, a tsunami was recorded on deep-sea DART buoy 42407 south of the Dominican Republic and on the Santo Domingo tide gauge, and run-ups of ≤3 m were observed along a 90-km-long stretch of the SE Haiti coast. Three dynamically-triggered aftershocks south of Haiti have been recently identified within the coda of the mainshock (stacks, and back-projecting the arrivals to the vicinity of the main shock (50-300 km). Two of the aftershocks, coming 20-40 s and 40-60 s after the mainshock, plot along NW-SE-trending submarine ridges in the Caribbean Sea south of Haiti. The third event, 120-140 s was located along the steep eastern slope of Bahoruco Peninsula, which is delineated by a normal fault. Forward tsunami models show that the arrival times of the DART buoy and tide gauge times are best fit by the earliest of the three aftershocks, with a Caribbean source 60 km SW of the mainshock rupture zone. Preliminary inversion of the DART buoy time series for fault locations and orientations confirms the location of the first source, but requires an additional unidentified source closer to shore 40 km SW of the mainshock rupture zone. This overall agreement between earthquake and tsunami analyses suggests that land-based earthquake ruptures and/or non-thrust main shocks can

The "Tsunami Earthquake" of 13 April 1923 in Northern Kamchatka: Seismological and Hydrodynamic Investigations

Science.gov (United States)

Salaree, Amir; Okal, Emile A.

2018-04-01

We present a seismological and hydrodynamic investigation of the earthquake of 13 April 1923 at Ust'-Kamchatsk, Northern Kamchatka, which generated a more powerful and damaging tsunami than the larger event of 03 February 1923, thus qualifying as a so-called "tsunami earthquake". On the basis of modern relocations, we suggest that it took place outside the fault area of the mainshock, across the oblique Pacific-North America plate boundary, a model confirmed by a limited dataset of mantle waves, which also confirms the slow nature of the source, characteristic of tsunami earthquakes. However, numerical simulations for a number of legitimate seismic models fail to reproduce the sharply peaked distribution of tsunami wave amplitudes reported in the literature. By contrast, we can reproduce the distribution of reported wave amplitudes using an underwater landslide as a source of the tsunami, itself triggered by the earthquake inside the Kamchatskiy Bight.

Incorporating fault zone head wave and direct wave secondary arrival times into seismic tomography: Application at Parkfield, California

Science.gov (United States)

Bennington, Ninfa L.; Thurber, Clifford; Peng, Zhigang; Zhang, Haijiang; Zhao, Peng

2013-03-01

We present a three-dimensional (3D) P wave velocity (Vp) model of the Parkfield region that utilizes existing P wave arrival time data, including fault zone head waves (FZHWs), and data from direct wave secondary arrivals (DWSAs). The first-arrival and DWSA travel times are obtained as the global- and local-minimum travel time paths, respectively. The inclusion of FZHWs and DWSAs results in as much as a 5% and a 10% increase in the across-fault velocity contrast, respectively, for the Vp model at Parkfield relative to that of Thurber et al. [2006]. Viewed along strike, three pronounced velocity contrast regions are observed: a pair of strong positive velocity contrasts (SW fast), one NW of the 1966 Parkfield earthquake hypocenter and the other SE of the 2004 Parkfield earthquake hypocenter, and a strong negative velocity contrast (NE fast) between the two hypocenters. The negative velocity contrast partially to entirely encompasses peak coseismic slip estimated in several slip models for the 2004 earthquake, suggesting that the negative velocity contrast played a part in defining the rupture patch of the 2004 Parkfield earthquake. Following Ampuero and Ben-Zion (2008), the pattern of velocity contrasts is consistent with the observed bilateral rupture propagation for the 2004 Parkfield earthquake. Although the velocity contrasts also suggest bilateral rupture propagation for the 1966 Parkfield earthquake, the fault is creeping to the NW here, i.e., exhibiting velocity-strengthening behavior. Thus, it is not surprising that rupture propagated only SE during this event.

Earthquakes, detecting and understanding them

International Nuclear Information System (INIS)

2008-05-01

The signatures at the surface of the Earth is continually changing on a geological timescale. The tectonic plates, which make up this surface, are moving in relation to each other. On human timescale, these movements are the result of earthquakes, which suddenly, release energy accumulated over a period of time. The vibrations they produce propagate through the interior of the Earth: these are seismic waves. However, other phenomena can generate seismic waves, such as volcanoes, quarry blasts, etc. The surf of the ocean waves on the coasts, the wind in the trees and human activity (industry and road traffic) all contribute to the 'seismic background noise'. Sensors are able to detect signals from events which are then discriminated, analyzed and located. Earthquakes and active volcanoes are not distributed randomly over the surface of the globe: they mainly coincide with mountain chains and ocean trenches and ridges. 'An earthquake results from the abrupt release of the energy accumulated by movements and rubbing of different plates'. The study of the propagation of seismic waves has allowed to determine the outline of the plates inside the Earth and has highlighted their movements. There are seven major plates which are colliding, diverging or sliding past each other. Each year the continents move several centimeters with respect to one another. This process, known as 'continental drift', was finally explained by plate tectonics. The initial hypothesis for this science dates from the beginning of the 20. century, but it was not confirmed until the 1960's. It explains that convection inside the Earth is the source of the forces required for these movements. This science, as well as explaining these great movements, has provided a coherent, unifying and quantitative framework, which unites the explanations for all the geophysical phenomena under one mechanism. (authors)

Marmara Island earthquakes, of 1265 and 1935; Turkey

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Y. Altınok

2006-01-01

Full Text Available The long-term seismicity of the Marmara Sea region in northwestern Turkey is relatively well-recorded. Some large and some of the smaller events are clearly associated with fault zones known to be seismically active, which have distinct morphological expressions and have generated damaging earthquakes before and later. Some less common and moderate size earthquakes have occurred in the vicinity of the Marmara Islands in the west Marmara Sea. This paper presents an extended summary of the most important earthquakes that have occurred in 1265 and 1935 and have since been known as the Marmara Island earthquakes. The informative data and the approaches used have therefore the potential of documenting earthquake ruptures of fault segments and may extend the records kept on earthquakes far before known history, rock falls and abnormal sea waves observed during these events, thus improving hazard evaluations and the fundamental understanding of the process of an earthquake.

Physics of Earthquake Disaster: From Crustal Rupture to Building Collapse

Science.gov (United States)

Uenishi, Koji

2018-05-01

Earthquakes of relatively greater magnitude may cause serious, sometimes unexpected failures of natural and human-made structures, either on the surface, underground, or even at sea. In this review, by treating several examples of extraordinary earthquake-related failures that range from the collapse of every second building in a commune to the initiation of spontaneous crustal rupture at depth, we consider the physical background behind the apparently abnormal earthquake disaster. Simple but rigorous dynamic analyses reveal that such seemingly unusual failures actually occurred for obvious reasons, which may remain unrecognized in part because in conventional seismic analyses only kinematic aspects of the effects of lower-frequency seismic waves below 1 Hz are normally considered. Instead of kinematics, some dynamic approach that takes into account the influence of higher-frequency components of waves over 1 Hz will be needed to anticipate and explain such extraordinary phenomena and mitigate the impact of earthquake disaster in the future.

Sensing the earthquake

Science.gov (United States)

Bichisao, Marta; Stallone, Angela

2017-04-01

Making science visual plays a crucial role in the process of building knowledge. In this view, art can considerably facilitate the representation of the scientific content, by offering a different perspective on how a specific problem could be approached. Here we explore the possibility of presenting the earthquake process through visual dance. From a choreographer's point of view, the focus is always on the dynamic relationships between moving objects. The observed spatial patterns (coincidences, repetitions, double and rhythmic configurations) suggest how objects organize themselves in the environment and what are the principles underlying that organization. The identified set of rules is then implemented as a basis for the creation of a complex rhythmic and visual dance system. Recently, scientists have turned seismic waves into sound and animations, introducing the possibility of "feeling" the earthquakes. We try to implement these results into a choreographic model with the aim to convert earthquake sound to a visual dance system, which could return a transmedia representation of the earthquake process. In particular, we focus on a possible method to translate and transfer the metric language of seismic sound and animations into body language. The objective is to involve the audience into a multisensory exploration of the earthquake phenomenon, through the stimulation of the hearing, eyesight and perception of the movements (neuromotor system). In essence, the main goal of this work is to develop a method for a simultaneous visual and auditory representation of a seismic event by means of a structured choreographic model. This artistic representation could provide an original entryway into the physics of earthquakes.

Site response, shallow shear-wave velocity, and damage in Los Gatos, California, from the 1989 Loma Prieta earthquake

Science.gov (United States)

Hartzell, S.; Carver, D.; Williams, R.A.

2001-01-01

Aftershock records of the 1989 Loma Prieta earthquake are used to calculate site response in the frequency band of 0.5-10 Hz at 24 locations in Los Gatos, California, on the edge of the Santa Clara Valley. Two different methods are used: spectral ratios relative to a reference site on rock and a source/site spectral inversion method. These two methods complement each other and give consistent results. Site amplification factors are compared with surficial geology, thickness of alluvium, shallow shear-wave velocity measurements, and ground deformation and structural damage resulting from the Loma Prieta earthquake. Higher values of site amplification are seen on Quaternary alluvium compared with older Miocene and Cretaceous units of Monterey and Franciscan Formation. However, other more detailed correlations with surficial geology are not evident. A complex pattern of alluvial sediment thickness, caused by crosscutting thrust faults, is interpreted as contributing to the variability in site response and the presence of spectral resonance peaks between 2 and 7 Hz at some sites. Within the range of our field measurements, there is a correlation between lower average shear-wave velocity of the top 30 m and 50% higher values of site amplification. An area of residential homes thrown from their foundations correlates with high site response. This damage may also have been aggravated by local ground deformation. Severe damage to commercial buildings in the business district, however, is attributed to poor masonry construction.

The effect of regional variation of seismic wave attenuation on the strong ground motion from earthquakes

Energy Technology Data Exchange (ETDEWEB)

Chung, D H; Bernreuter, D L

1981-10-01

Attenuation is caused by geometric spreading and absorption. Geometric spreading is almost independent of crustal geology and physiographic region, but absorption depends strongly on crustal geology and the state of the earth's upper mantle. Except for very high frequency waves, absorption does not affect ground motion at distances less than about 25 to 50 km. Thus, in the near-field zone, the attenuation in the eastern United States is similar to that in the western United States. Beyond the near field, differences in ground motion can best be accounted for by differences in attenuation caused by differences in absorption. The stress drop of eastern earthquakes may be higher than for western earthquakes of the same seismic moment, which would affect the high-frequency spectral content. But we believe this factor is of much less significance than differences in absorption in explaining the differences in ground motion between the East and the West. The characteristics of strong ground motion in the conterminous United States are discussed in light of these considerations, and estimates are made of the epicentral ground motions in the central and eastern United States. (author)

Swedish earthquakes and acceleration probabilities

International Nuclear Information System (INIS)

Slunga, R.

1979-03-01

A method to assign probabilities to ground accelerations for Swedish sites is described. As hardly any nearfield instrumental data is available we are left with the problem of interpreting macroseismic data in terms of acceleration. By theoretical wave propagation computations the relation between seismic strength of the earthquake, focal depth, distance and ground accelerations are calculated. We found that most Swedish earthquake of the area, the 1904 earthquake 100 km south of Oslo, is an exception and probably had a focal depth exceeding 25 km. For the nuclear power plant sites an annual probability of 10 -5 has been proposed as interesting. This probability gives ground accelerations in the range 5-20 % for the sites. This acceleration is for a free bedrock site. For consistency all acceleration results in this study are given for bedrock sites. When applicating our model to the 1904 earthquake and assuming the focal zone to be in the lower crust we get the epicentral acceleration of this earthquake to be 5-15 % g. The results above are based on an analyses of macrosismic data as relevant instrumental data is lacking. However, the macroseismic acceleration model deduced in this study gives epicentral ground acceleration of small Swedish earthquakes in agreement with existent distant instrumental data. (author)

The TeraShake Computational Platform for Large-Scale Earthquake Simulations

Science.gov (United States)

Cui, Yifeng; Olsen, Kim; Chourasia, Amit; Moore, Reagan; Maechling, Philip; Jordan, Thomas

Geoscientific and computer science researchers with the Southern California Earthquake Center (SCEC) are conducting a large-scale, physics-based, computationally demanding earthquake system science research program with the goal of developing predictive models of earthquake processes. The computational demands of this program continue to increase rapidly as these researchers seek to perform physics-based numerical simulations of earthquake processes for larger meet the needs of this research program, a multiple-institution team coordinated by SCEC has integrated several scientific codes into a numerical modeling-based research tool we call the TeraShake computational platform (TSCP). A central component in the TSCP is a highly scalable earthquake wave propagation simulation program called the TeraShake anelastic wave propagation (TS-AWP) code. In this chapter, we describe how we extended an existing, stand-alone, wellvalidated, finite-difference, anelastic wave propagation modeling code into the highly scalable and widely used TS-AWP and then integrated this code into the TeraShake computational platform that provides end-to-end (initialization to analysis) research capabilities. We also describe the techniques used to enhance the TS-AWP parallel performance on TeraGrid supercomputers, as well as the TeraShake simulations phases including input preparation, run time, data archive management, and visualization. As a result of our efforts to improve its parallel efficiency, the TS-AWP has now shown highly efficient strong scaling on over 40K processors on IBM’s BlueGene/L Watson computer. In addition, the TSCP has developed into a computational system that is useful to many members of the SCEC community for performing large-scale earthquake simulations.

Ground water level, Water storage, Soil moisture, Precipitation Variability Using Multi Satellite Data during 2003-2016 Associated with California Drought

Science.gov (United States)

Li, J. W.; Singh, R. P.

2017-12-01

The agricultural market of California is a multi-billion-dollar industry, however in the recent years, the state is facing severe drought. It is important to have a deeper understanding of how the agriculture is affected by the amount of rainfall as well as the ground conditions in California. We have considered 5 regions (each 2 degree by 2 degree) covering whole of California. Multi satellite (MODIS Terra, GRACE, GLDAS) data through NASA Giovanni portal were used to study long period variability 2003 - 2016 of ground water level and storage, soil moisture, root zone moisture level, precipitation and normalized vegetation index (NDVI) in these 5 regions. Our detailed analysis of these parameters show a strong correlation between the NDVI and some of these parameters. NDVI represents greenness showing strong drought conditions during the period 2011-2016 due to poor rainfall and recharge of ground water in the mid and southern parts of California. Effect of ground water level and underground storage will be also discussed on the frequency of earthquakes in five regions of California. The mid and southern parts of California show increasing frequency of small earthquakes during drought periods.

The Differences in Source Dynamics Between Intermediate-Depth and Deep EARTHQUAKES:A Comparative Study Between the 2014 Rat Islands Intermediate-Depth Earthquake and the 2015 Bonin Islands Deep Earthquake

Science.gov (United States)

Twardzik, C.; Ji, C.

2015-12-01

It has been proposed that the mechanisms for intermediate-depth and deep earthquakes might be different. While previous extensive seismological studies suggested that such potential differences do not significantly affect the scaling relationships of earthquake parameters, there has been only a few investigations regarding their dynamic characteristics, especially for fracture energy. In this work, the 2014 Mw7.9 Rat Islands intermediate-depth (105 km) earthquake and the 2015 Mw7.8 Bonin Islands deep (680 km) earthquake are studied from two different perspectives. First, their kinematic rupture models are constrained using teleseismic body waves. Our analysis reveals that the Rat Islands earthquake breaks the entire cold core of the subducting slab defined as the depth of the 650oC isotherm. The inverted stress drop is 4 MPa, compatible to that of intra-plate earthquakes at shallow depths. On the other hand, the kinematic rupture model of the Bonin Islands earthquake, which occurred in a region lacking of seismicity for the past forty years, according to the GCMT catalog, exhibits an energetic rupture within a 35 km by 30 km slip patch and a high stress drop of 24 MPa. It is of interest to note that although complex rupture patterns are allowed to match the observations, the inverted slip distributions of these two earthquakes are simple enough to be approximated as the summation of a few circular/elliptical slip patches. Thus, we investigate subsequently their dynamic rupture models. We use a simple modelling approach in which we assume that the dynamic rupture propagation obeys a slip-weakening friction law, and we describe the distribution of stress and friction on the fault as a set of elliptical patches. We will constrain the three dynamic parameters that are yield stress, background stress prior to the rupture and slip weakening distance, as well as the shape of the elliptical patches directly from teleseismic body waves observations. The study would help us

The economic costs of natural disasters globally from 1900-2015: historical and normalised floods, storms, earthquakes, volcanoes, bushfires, drought and other disasters

Science.gov (United States)

Daniell, James; Wenzel, Friedemann; Schaefer, Andreas

2016-04-01

For the first time, a breakdown of natural disaster losses from 1900-2015 based on over 30,000 event economic losses globally is given based on increased analysis within the CATDAT Damaging Natural Disaster databases. Using country-CPI and GDP deflator adjustments, over 7 trillion (2015-adjusted) in losses have occurred; over 40% due to flood/rainfall, 26% due to earthquake, 19% due to storm effects, 12% due to drought, 2% due to wildfire and under 1% due to volcano. Using construction cost indices, higher percentages of flood losses are seen. Depending on how the adjustment of dollars are made to 2015 terms (CPI vs. construction cost indices), between 6.5 and 14.0 trillion USD (2015-adjusted) of natural disaster losses have been seen from 1900-2015 globally. Significant reductions in economic losses have been seen in China and Japan from 1950 onwards. An AAL of around 200 billion in the last 16 years has been seen equating to around 0.25% of Global GDP or around 0.1% of Net Capital Stock per year. Normalised losses have also been calculated to examine the trends in vulnerability through time for economic losses. The normalisation methodology globally using the exposure databases within CATDAT that were undertaken previously in papers for the earthquake and volcano databases, are used for this study. The original event year losses are adjusted directly by capital stock change, very high losses are observed with respect to floods over time (however with improved flood control structures). This shows clear trends in the improvement of building stock towards natural disasters and a decreasing trend in most perils for most countries.

Towards the Future "Earthquake" School in the Cloud: Near-real Time Earthquake Games Competition in Taiwan

Science.gov (United States)

Chen, K. H.; Liang, W. T.; Wu, Y. F.; Yen, E.

2014-12-01

To prevent the future threats of natural disaster, it is important to understand how the disaster happened, why lives were lost, and what lessons have been learned. By that, the attitude of society toward natural disaster can be transformed from training to learning. The citizen-seismologists-in-Taiwan project is designed to elevate the quality of earthquake science education by means of incorporating earthquake/tsunami stories and near-real time earthquake games competition into the traditional curricula in schools. Through pilot of courses and professional development workshops, we have worked closely with teachers from elementary, junior high, and senior high schools, to design workable teaching plans through a practical operation of seismic monitoring at home or school. We will introduce how the 9-years-old do P- and S-wave picking and measure seismic intensity through interactive learning platform, how do scientists and school teachers work together, and how do we create an environment to facilitate continuous learning (i.e., near-real time earthquake games competition), to make earthquake science fun.

Monitoring 2015 drought in West Java using Normalized Difference Water Index (NDWI)

Science.gov (United States)

Febrina Amalo, Luisa; Ma’rufah, Ummu; Ayu Permatasari, Prita

2018-05-01

Drought is a slow developing phenomenon that accumulates over period and affecting various sectors. It is one of natural hazards that occurs each year, particularly in Indonesia over Australian Monsoon period. During drought event, vegetation’s cover can be affected by water stress. Normalized Difference Water Index (NDWI) is a method for water resource assessment and known to be strongly related to the plant water content. NDWI is produced from MODIS bands Near-infrared (NIR) and Short Wave Infrared (SWIR). This research aims to monitor drought using NDWI in West Java during El Niño 2015 and its impact on rainfall variability. The result showed rainfall was decreased significantly starting from May-June, then increased in November. According to NDWI, it also showed that mostly West Java Region affected by drought during May-November. Very strong drought occurred on September-November. On December, areal extent of drought was decreasing significantly because rainfall had increased during November. Generally, areal extent of drought in West Java was dominated by strong and moderate drought. It implied that El Niño 2015, give great impact on increasing drought and decreasing rainfall in West Java. NDWI can be detected drought occurrence as it have good correlation with rainfall spatially.

Coherent Seismic Arrivals in the P Wave Coda of the 2012 Mw 7.2 Sumatra Earthquake: Water Reverberations or an Early Aftershock?

Science.gov (United States)

Fan, Wenyuan; Shearer, Peter M.

2018-04-01

Teleseismic records of the 2012 Mw 7.2 Sumatra earthquake contain prominent phases in the P wave train, arriving about 50 to 100 s after the direct P arrival. Azimuthal variations in these arrivals, together with back-projection analysis, led Fan and Shearer (https://doi.org/10.1002/2016GL067785) to conclude that they originated from early aftershock(s), located ˜150 km northeast of the mainshock and landward of the trench. However, recently, Yue et al. (https://doi.org/10.1002/2017GL073254) argued that the anomalous arrivals are more likely water reverberations from the mainshock, based mostly on empirical Green's function analysis of a M6 earthquake near the mainshock and a water phase synthetic test. Here we present detailed back-projection and waveform analyses of three M6 earthquakes within 100 km of the Mw 7.2 earthquake, including the empirical Green's function event analyzed in Yue et al. (https://doi.org/10.1002/2017GL073254). In addition, we examine the waveforms of three M5.5 reverse-faulting earthquakes close to the inferred early aftershock location in Fan and Shearer (https://doi.org/10.1002/2016GL067785). These results suggest that the reverberatory character of the anomalous arrivals in the mainshock coda is consistent with water reverberations, but the origin of this energy is more likely an early aftershock rather than delayed and displaced water reverberations from the mainshock.

Far-field coseismic ionospheric disturbances of Tohoku earthquake

Czech Academy of Sciences Publication Activity Database

Krasnov, V. M.; Drobzheva, Ya. V.; Chum, Jaroslav

2015-01-01

Roč. 135, December (2015), s. 12-21 ISSN 1364-6826 R&D Projects: GA ČR(CZ) GC15-07281J Institutional support: RVO:68378289 Keywords : earthquake * infrasonic waves * ionospheric disturbances * infrasound triggered by the earthquake * co-seismic ionospheric perturbations * modeling * remote sensing Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.463, year: 2015 http://www.sciencedirect.com/science/article/pii/S1364682615300584

Permeability, storage and hydraulic diffusivity controlled by earthquakes

Science.gov (United States)

Brodsky, E. E.; Fulton, P. M.; Xue, L.

2016-12-01

Earthquakes can increase permeability in fractured rocks. In the farfield, such permeability increases are attributed to seismic waves and can last for months after the initial earthquake. Laboratory studies suggest that unclogging of fractures by the transient flow driven by seismic waves is a viable mechanism. These dynamic permeability increases may contribute to permeability enhancement in the seismic clouds accompanying hydraulic fracking. Permeability enhancement by seismic waves could potentially be engineered and the experiments suggest the process will be most effective at a preferred frequency. We have recently observed similar processes inside active fault zones after major earthquakes. A borehole observatory in the fault that generated the M9.0 2011 Tohoku earthquake reveals a sequence of temperature pulses during the secondary aftershock sequence of an M7.3 aftershock. The pulses are attributed to fluid advection by a flow through a zone of transiently increased permeability. Directly after the M7.3 earthquake, the newly damaged fault zone is highly susceptible to further permeability enhancement, but ultimately heals within a month and becomes no longer as sensitive. The observation suggests that the newly damaged fault zone is more prone to fluid pulsing than would be expected based on the long-term permeability structure. Even longer term healing is seen inside the fault zone of the 2008 M7.9 Wenchuan earthquake. The competition between damage and healing (or clogging and unclogging) results in dynamically controlled permeability, storage and hydraulic diffusivity. Recent measurements of in situ fault zone architecture at the 1-10 meter scale suggest that active fault zones often have hydraulic diffusivities near 10-2 m2/s. This uniformity is true even within the damage zone of the San Andreas fault where permeability and storage increases balance each other to achieve this value of diffusivity over a 400 m wide region. We speculate that fault zones

An improvement of the Earthworm Based Earthquake Alarm Reporting system in Taiwan

Science.gov (United States)

Chen, D. Y.; Hsiao, N. C.; Yih-Min, W.

2017-12-01

The Central Weather Bureau of Taiwan (CWB) has operated the Earthworm Based Earthquake Alarm Reporting (eBEAR) system for the purpose of earthquake early warning (EEW). The system has been used to report EEW messages to the general public since 2016 through text message from the mobile phones and the television programs. The system for inland earthquakes is able to provide accurate and fast warnings. The average epicenter error is about 5 km and the processing time is about 15 seconds. The epicenter error is defined as the distance between the epicenter estimated by the EEW system and the epicenter estimated by man. The processing time is defined as the time difference between the time earthquakes occurred and the time the system issued warning. The CWB seismic network consist about 200 seismic stations. In some area of Taiwan the distance between each seismic station is about 10 km. It means that when an earthquake occurred the seismic P wave is able to propagate through 6 stations, which is the minimum number of required stations in the EEW system, within 20 km. If the latency of data transmitting is about 1 sec, the P-wave velocity is about 6 km per sec and we take 3-sec length time window to estimate earthquake magnitude, then the processing should be around 8 sec. In fact, however, the average processing time is larger than this figure. Because some outliers of P-wave onset picks may exist in the beginning of the earthquake occurrence, the Geiger's method we used in the EEW system for earthquake location is not stable. It usually takes more time to wait for enough number of good picks. In this study we used grid search method to improve the estimations of earthquake location. The MAXEL algorithm (Sheen et al., 2015, 2016) was tested in the EEW system by simulating historical earthquakes occurred in Taiwan. The results show the processing time can be reduced and the location accuracy is acceptable for EEW purpose.

Research and development of earthquake-resistant structure model for nuclear fuel facility

Energy Technology Data Exchange (ETDEWEB)

Uryu, Mitsuru; Terada, S.; Shioya, I. [and others

1999-05-01

It is important for a nuclear fuel facility to reduce an input intensity of earthquake on the upper part of the building. To study of a response of the building caused by earthquake, an earthquake-resistant structure model is constructed. The weight of the structure model is 90 ton, and is supported by multiple layers of natural ruber and steel. And a weight support device which is called 'softlanding' is also installed to prevent the structure model from loosing the function at excess deformation. The softlanding device consists of Teflon. Dynamic response characteristics of the structure model caused by sine wave and simulated seismic waves are measured and analyzed. Soil tests of the fourth geologic stratum on which the structure model is sited are made to confirm the safety of soil-structure interactions caused by earthquake. (M. Suetake)

Anticipating U.S. severe droughts - A NASA NEWS initiative on extremes

Science.gov (United States)

Wang, S.; Oglesby, R. J.; Hilburn, K. A.; Barandiaran, D.; Pan, M.; Pinker, R. T.; Wang, H.; Santanello, J. A.

2013-12-01

The 2012-2013 drought may not have been predictable as based on current schemes employed for such purposes, but it may have been anticipatable due to knowledge of key precursors such as favorable (remote) SST patterns, and reduced regional soil moisture and winter snow packs. A working group was assembled under the NASA Energy and Water cycle Study (NEWS) to examine the extent to which the 2012 drought could be anticipated and to put recent severe droughts in perspective. A recent NOAA report analyzing the drought of 2012 in the central US has concluded that the drought was not inherently predictable, representing a very anomalous atmospheric circulation pattern. This ';predictability' is based on what happened in the atmosphere, and further, depends on the capabilities of the predictive schemes currently employed. The current prediction schemes emphasize the role of the large-scale atmospheric circulation, but the extent to which the long wave patterns and subsequent short wave effects can be predicted in advance remains unclear. These schemes generally lack full consideration of the local surface state, especially the effect of precursor anomalies in key elements such as soil moisture and snow pack. It is also not clear how well they account for the effects of either interannual or lower-frequency oceanic anomaly patterns. The role of the aforesaid precursors, combined with knowledge of their state, allow some assessment of the ';likelihood' of drought that is not currently being considered. For example, by late winter of 2012 much of the central US was already experiencing dry conditions, including reduced soil moisture, and the snowpack in the Rockies was well below normal. SST patterns appear to have been largely neutral. While the manifestation of the resultant drought also critically dependent on the large-scale atmospheric circulation that subsequently developed, it is clear that the region was preconditioned towards being dry. The other factor about

Crustal seismic anisotropy beneath Shillong plateau - Assam valley in North East India: Shear-wave splitting analysis using local earthquakes

Science.gov (United States)

Sharma, Antara; Baruah, Santanu; Piccinini, Davide; Saikia, Sowrav; Phukan, Manoj K.; Chetia, Monisha; Kayal, J. R.

2017-10-01

We present crustal anisotropy estimates constrained by shear wave splitting (SWS) analysis using local earthquakes in the Shillong plateau and Assam valley area, North East India (NE India) region. Splitting parameters are determined using an automated cross-correlation (CC) method. We located 330 earthquakes recorded by 17 broadband seismic stations during 2001-2014 in the study area. Out of these 330 events, seismograms of 163 events are selected for the SWS analysis. Relatively small average delay times (0.039-0.084 s) indicate existence of moderate crack density in the crust below the study area. It is found that fast polarization directions vary from station to station depending on the regional stress system as well as geological conditions. The spatial pattern of crustal anisotropy in the area is controlled mostly by tectonic movement of the Indian plate towards NE. Presence of several E-W and N-S trending active faults in the area also play an important role on the observed pattern of crustal anisotropy.

New streams and springs after the 2014 Mw6.0 South Napa earthquake.

Science.gov (United States)

Wang, Chi-Yuen; Manga, Michael

2015-07-09

Many streams and springs, which were dry or nearly dry before the 2014 Mw6.0 South Napa earthquake, started to flow after the earthquake. A United States Geological Survey stream gauge also registered a coseismic increase in discharge. Public interest was heightened by a state of extreme drought in California. Since the new flows were not contaminated by pre-existing surface water, their composition allowed unambiguous identification of their origin. Following the earthquake we repeatedly surveyed the new flows, collecting data to test hypotheses about their origin. We show that the new flows originated from groundwater in nearby mountains released by the earthquake. The estimated total amount of new water is ∼ 10(6) m(3), about 1/40 of the annual water use in the Napa-Sonoma area. Our model also makes a testable prediction of a post-seismic decrease of seismic velocity in the shallow crust of the affected region.

Estimating drought risk across Europe from reported drought impacts, drought indices, and vulnerability factors

Science.gov (United States)

Blauhut, Veit; Stahl, Kerstin; Stagge, James Howard; Tallaksen, Lena M.; De Stefano, Lucia; Vogt, Jürgen

2016-07-01

Drought is one of the most costly natural hazards in Europe. Due to its complexity, drought risk, meant as the combination of the natural hazard and societal vulnerability, is difficult to define and challenging to detect and predict, as the impacts of drought are very diverse, covering the breadth of socioeconomic and environmental systems. Pan-European maps of drought risk could inform the elaboration of guidelines and policies to address its documented severity and impact across borders. This work tests the capability of commonly applied drought indices and vulnerability factors to predict annual drought impact occurrence for different sectors and macro regions in Europe and combines information on past drought impacts, drought indices, and vulnerability factors into estimates of drought risk at the pan-European scale. This hybrid approach bridges the gap between traditional vulnerability assessment and probabilistic impact prediction in a statistical modelling framework. Multivariable logistic regression was applied to predict the likelihood of impact occurrence on an annual basis for particular impact categories and European macro regions. The results indicate sector- and macro-region-specific sensitivities of drought indices, with the Standardized Precipitation Evapotranspiration Index (SPEI) for a 12-month accumulation period as the overall best hazard predictor. Vulnerability factors have only limited ability to predict drought impacts as single predictors, with information about land use and water resources being the best vulnerability-based predictors. The application of the hybrid approach revealed strong regional and sector-specific differences in drought risk across Europe. The majority of the best predictor combinations rely on a combination of SPEI for shorter and longer accumulation periods, and a combination of information on land use and water resources. The added value of integrating regional vulnerability information with drought risk prediction

S-wave attenuation in northeastern Sonora, Mexico, near the faults that ruptured during the earthquake of 3 May 1887 Mw 7.5.

Science.gov (United States)

Villalobos-Escobar, Gina P; Castro, Raúl R

2014-01-01

We used a new data set of relocated earthquakes recorded by the Seismic Network of Northeastern Sonora, Mexico (RESNES) to characterize the attenuation of S-waves in the fault zone of the 1887 Sonora earthquake (M w 7.5). We determined spectral attenuation functions for hypocentral distances (r) between 10 and 140 km using a nonparametric approach and found that in this fault zone the spectral amplitudes decay slower with distance at low frequencies (f < 4 Hz) compared to those reported in previous studies in the region using more distant recordings. The attenuation functions obtained for 23 frequencies (0.4 ≤ f ≤ 63.1 Hz) permit us estimating the average quality factor Q S  = (141 ± 1.1 )f ((0.74 ± 0.04)) and a geometrical spreading term G(r) = 1/r (0.21). The values of Q estimated for S-wave paths traveling along the fault system that rupture during the 1887 event, in the north-south direction, are considerably lower than the average Q estimated using source-station paths from multiple stations and directions. These results indicate that near the fault zone S waves attenuate considerably more than at regional scale, particularly at low frequencies. This may be the result of strong scattering near the faults due to the fractured upper crust and higher intrinsic attenuation due to stress concentration near the faults.

Studies of the subsurface effects of earthquakes

International Nuclear Information System (INIS)

Marine, I.W.

1980-01-01

As part of the National Terminal Waste Storage Program, the Savannah River Laboratory is conducting a series of studies on the subsurface effects of earthquakes. This report summarizes three subcontracted studies. (1) Earthquake damage to underground facilities: the purpose of this study was to document damage and nondamage caused by earthquakes to tunnels and shallow underground openings; to mines and other deep openings; and to wells, shafts, and other vertical facilities. (2) Earthquake related displacement fields near underground facilities: the study included an analysis of block motion, an analysis of the dependence of displacement on the orientation and distance of joints from the earthquake source, and displacement related to distance and depth near a causative fault as a result of various shapes, depths, and senses of movement on the causative fault. (3) Numerical simulation of earthquake effects on tunnels for generic nuclear waste repositories: the objective of this study was to use numerical modeling to determine under what conditions seismic waves might cause instability of an underground opening or create fracturing that would increase the permeability of the rock mass

Tsunami generation and associated waves in the water column and seabed due to an asymmetric earthquake motion within an anisotropic substratum

Science.gov (United States)

Bagheri, Amirhossein; Greenhalgh, Stewart; Khojasteh, Ali; Rahimian, Mohammad; Attarnejad, Reza

2016-10-01

In this paper, closed-form integral expressions are derived to describe how surface gravity waves (tsunamis) are generated when general asymmetric ground displacement (due to earthquake rupturing), involving both horizontal and vertical components of motion, occurs at arbitrary depth within the interior of an anisotropic subsea solid beneath the ocean. In addition, we compute the resultant hydrodynamic pressure within the seawater and the elastic wavefield within the seabed at any position. The method of potential functions and an integral transform approach, accompanied by a special contour integration scheme, are adopted to handle the equations of motion and produce the numerical results. The formulation accounts for any number of possible acoustic-gravity modes and is valid for both shallow and deep water situations as well as for any focal depth of the earthquake source. Phase and group velocity dispersion curves are developed for surface gravity (tsunami mode), acoustic-gravity, Rayleigh, and Scholte waves. Several asymptotic cases which arise from the general analysis are discussed and compared to existing solutions. The role of effective parameters such as hypocenter location and frequency of excitation is examined and illustrated through several figures which show the propagation pattern in the vertical and horizontal directions. Attention is directed to the unexpected contribution from the horizontal ground motion. The results have important application in several fields such as tsunami hazard prediction, marine seismology, and offshore and coastal engineering. In a companion paper, we examine the effect of ocean stratification on the appearance and character of internal and surface gravity waves.

Changes in groundwater chemistry before two consecutive earthquakes in Iceland

KAUST Repository

Skelton, Alasdair

2014-09-21

Groundwater chemistry has been observed to change before earthquakes and is proposed as a precursor signal. Such changes include variations in radon count rates1, 2, concentrations of dissolved elements3, 4, 5 and stable isotope ratios4, 5. Changes in seismic wave velocities6, water levels in boreholes7, micro-seismicity8 and shear wave splitting9 are also thought to precede earthquakes. Precursor activity has been attributed to expansion of rock volume7, 10, 11. However, most studies of precursory phenomena lack sufficient data to rule out other explanations unrelated to earthquakes12. For example, reproducibility of a precursor signal has seldom been shown and few precursors have been evaluated statistically. Here we analyse the stable isotope ratios and dissolved element concentrations of groundwater taken from a borehole in northern Iceland between 2008 and 2013. We find that the chemistry of the groundwater changed four to six months before two greater than magnitude 5 earthquakes that occurred in October 2012 and April 2013. Statistical analyses indicate that the changes in groundwater chemistry were associated with the earthquakes. We suggest that the changes were caused by crustal dilation associated with stress build-up before each earthquake, which caused different groundwater components to mix. Although the changes we detect are specific for the site in Iceland, we infer that similar processes may be active elsewhere, and that groundwater chemistry is a promising target for future studies on the predictability of earthquakes.

Changes in groundwater chemistry before two consecutive earthquakes in Iceland

KAUST Repository

Skelton, Alasdair; André n, Margareta; Kristmannsdó ttir, Hrefna; Stockmann, Gabrielle; Mö rth, Carl-Magnus; Sveinbjö rnsdó ttir, Á rny; Jonsson, Sigurjon; Sturkell, Erik; Guð rú nardó ttir, Helga Rakel; Hjartarson, Hreinn; Siegmund, Heike; Kockum, Ingrid

2014-01-01

Groundwater chemistry has been observed to change before earthquakes and is proposed as a precursor signal. Such changes include variations in radon count rates1, 2, concentrations of dissolved elements3, 4, 5 and stable isotope ratios4, 5. Changes in seismic wave velocities6, water levels in boreholes7, micro-seismicity8 and shear wave splitting9 are also thought to precede earthquakes. Precursor activity has been attributed to expansion of rock volume7, 10, 11. However, most studies of precursory phenomena lack sufficient data to rule out other explanations unrelated to earthquakes12. For example, reproducibility of a precursor signal has seldom been shown and few precursors have been evaluated statistically. Here we analyse the stable isotope ratios and dissolved element concentrations of groundwater taken from a borehole in northern Iceland between 2008 and 2013. We find that the chemistry of the groundwater changed four to six months before two greater than magnitude 5 earthquakes that occurred in October 2012 and April 2013. Statistical analyses indicate that the changes in groundwater chemistry were associated with the earthquakes. We suggest that the changes were caused by crustal dilation associated with stress build-up before each earthquake, which caused different groundwater components to mix. Although the changes we detect are specific for the site in Iceland, we infer that similar processes may be active elsewhere, and that groundwater chemistry is a promising target for future studies on the predictability of earthquakes.

Identification of T-Waves in the Alboran Sea

Science.gov (United States)

Carmona, Enrique; Almendros, Javier; Alguacil, Gerardo; Soto, Juan Ignacio; Luzón, Francisco; Ibáñez, Jesús M.

2015-11-01

Analyses of seismograms from ~1,100 north-Moroccan earthquakes recorded at stations of the Red Sísmica de Andalucía (Southern Spain) reveal the systematic presence of late phases embedded in the earthquake codas. These phases have distinctive frequency contents, similar to the P and S spectra and quite different to the frequency contents of the earthquake codas. They are best detected at near-shore stations. Their amplitudes decay significantly with distance to the shoreline. The delays with respect to the P-wave onsets of the preceding earthquakes are consistently around 85 s. Late phases are only detected for earthquakes located in a small region of about 100 × 60 km centered at 35.4°N, 4.0°W near the northern coast of Morocco. Several hypotheses could, in principle, explain the presence of these late phases in the seismograms, for example, the occurrence of low-energy aftershocks, efficient wave reflections, or Rayleigh waves generated along the source-station paths. However, we conclude that the most-likely origin of these phases corresponds to the incidence of T-waves (generated by conversion from elastic to acoustic energy in the north-Moroccan coast) in the southern coast of the Iberian Peninsula. T-waves are thought to be generated by energy trapping in low-velocity channels along long oceanic paths; in this case, we demonstrate that they can be produced in much shorter paths as well. Although T-waves have been already documented in other areas of the Mediterranean Sea, this is the first time that they have been identified in the Alboran Sea.

QuakeUp: An advanced tool for a network-based Earthquake Early Warning system

Science.gov (United States)

Zollo, Aldo; Colombelli, Simona; Caruso, Alessandro; Elia, Luca; Brondi, Piero; Emolo, Antonio; Festa, Gaetano; Martino, Claudio; Picozzi, Matteo

2017-04-01

The currently developed and operational Earthquake Early warning, regional systems ground on the assumption of a point-like earthquake source model and 1-D ground motion prediction equations to estimate the earthquake impact. Here we propose a new network-based method which allows for issuing an alert based upon the real-time mapping of the Potential Damage Zone (PDZ), e.g. the epicentral area where the peak ground velocity is expected to exceed the damaging or strong shaking levels with no assumption about the earthquake rupture extent and spatial variability of ground motion. The platform includes the most advanced techniques for a refined estimation of the main source parameters (earthquake location and magnitude) and for an accurate prediction of the expected ground shaking level. The new software platform (QuakeUp) is under development at the Seismological Laboratory (RISSC-Lab) of the Department of Physics at the University of Naples Federico II, in collaboration with the academic spin-off company RISS s.r.l., recently gemmated by the research group. The system processes the 3-component, real-time ground acceleration and velocity data streams at each station. The signal quality is preliminary assessed by checking the signal-to-noise ratio both in acceleration, velocity and displacement and through dedicated filtering algorithms. For stations providing high quality data, the characteristic P-wave period (τ_c) and the P-wave displacement, velocity and acceleration amplitudes (P_d, Pv and P_a) are jointly measured on a progressively expanded P-wave time window. The evolutionary measurements of the early P-wave amplitude and characteristic period at stations around the source allow to predict the geometry and extent of PDZ, but also of the lower shaking intensity regions at larger epicentral distances. This is done by correlating the measured P-wave amplitude with the Peak Ground Velocity (PGV) and Instrumental Intensity (I_MM) and by mapping the measured and

Precursory changes in seismic velocity for the spectrum of earthquake failure modes

Science.gov (United States)

Scuderi, M.M.; Marone, C.; Tinti, E.; Di Stefano, G.; Collettini, C.

2016-01-01

Temporal changes in seismic velocity during the earthquake cycle have the potential to illuminate physical processes associated with fault weakening and connections between the range of fault slip behaviors including slow earthquakes, tremor and low frequency earthquakes1. Laboratory and theoretical studies predict changes in seismic velocity prior to earthquake failure2, however tectonic faults fail in a spectrum of modes and little is known about precursors for those modes3. Here we show that precursory changes of wave speed occur in laboratory faults for the complete spectrum of failure modes observed for tectonic faults. We systematically altered the stiffness of the loading system to reproduce the transition from slow to fast stick-slip and monitored ultrasonic wave speed during frictional sliding. We find systematic variations of elastic properties during the seismic cycle for both slow and fast earthquakes indicating similar physical mechanisms during rupture nucleation. Our data show that accelerated fault creep causes reduction of seismic velocity and elastic moduli during the preparatory phase preceding failure, which suggests that real time monitoring of active faults may be a means to detect earthquake precursors. PMID:27597879

Modern earthquake engineering offshore and land-based structures

CERN Document Server

Jia, Junbo

2017-01-01

This book addresses applications of earthquake engineering for both offshore and land-based structures. It is self-contained as a reference work and covers a wide range of topics, including topics related to engineering seismology, geotechnical earthquake engineering, structural engineering, as well as special contents dedicated to design philosophy, determination of ground motions, shock waves, tsunamis, earthquake damage, seismic response of offshore and arctic structures, spatial varied ground motions, simplified and advanced seismic analysis methods, sudden subsidence of offshore platforms, tank liquid impacts during earthquakes, seismic resistance of non-structural elements, and various types of mitigation measures, etc. The target readership includes professionals in offshore and civil engineering, officials and regulators, as well as researchers and students in this field.

Teleseismic analysis of the 1990 and 1991 earthquakes near Potenza

Directory of Open Access Journals (Sweden)

G. Ekstrom

1994-06-01

Full Text Available Analysis of the available teleseismic data for two moderate earthquakes near the town of Potenza in the Southern Apennines shows that both involve strike-slip faulting on a plane oriented approximately east-west. Only the larger, 5 May 1990, earthquake is sufficiently large for analysis by conventional teleseismic waveform inversion methods, and is seen to consist of a foreshock followed 11 seconds later by the main release of moment. The focal mechanism and seismic moment of the 26 May 1991 earthquake is determined by quantitative comparison of its 15-60 s period surface waves with those generated by the 5 May 1990 event. The focal mechanisms for the two events are found to be very similar. The 1991 earthquake has a scalar moment that is approximately 18% that of the 1990 mainshock. Comparison of higher frequency P waves for the two events, recorded at regional distance, shows that the ratio of trace amplitudes is smaller than the ratio of scalar moments, suggesting that the stress drop for the 1991 event is distinctly smaller than for the 1990 mainshock.

Love waves trains observed after the MW 8.1 Tehuantepec earthquake by an underground ring laser gyroscope

Science.gov (United States)

Simonelli, A.; Belfi, J.; Beverini, N.; Di Virgilio, A.; Giacomelli, U.; De Luca, G.; Igel, H.

2017-12-01

We report the observation and analysis of the MW 8.1 Tehuantepec earthquake-induced rotational ground motion as observed by the Gingerino ring laser gyroscope (RLG).This instrument is located inside the National laboratory of the "Istituto Nazionale di Fisica Nucleare" in Gran Sasso (Italy) in a deep underground environment.We compare the vertical rotation rate with the horizontal acceleration measured by a co-located broadband seismometer. This analysis, performed by means of a wavelet-based correlation method, permits to identify the G1,G2,G3,G4 onsets of the surface Love waves in the 120 to 280 seconds period range.

Extreme wildfire events are linked to global-change-type droughts in the northern Mediterranean

Science.gov (United States)

Ruffault, Julien; Curt, Thomas; Martin-StPaul, Nicolas K.; Moron, Vincent; Trigo, Ricardo M.

2018-03-01

Increasing drought conditions under global warming are expected to alter the frequency and distribution of large and high-intensity wildfires. However, our understanding of the impact of increasing drought on extreme wildfires events remains incomplete. Here, we analyzed the weather conditions associated with the extreme wildfires events that occurred in Mediterranean France during the exceptionally dry summers of 2003 and 2016. We identified that these fires were related to two distinct shifts in the fire weather space towards fire weather conditions that had not been explored before and resulting from specific interactions between different types of drought and different fire weather types. In 2016, a long-lasting press drought intensified wind-driven fires. In 2003, a hot drought combining a heat wave with a press drought intensified heat-induced fires. Our findings highlight that increasing drought conditions projected by climate change scenarios might affect the dryness of fuel compartments and lead to a higher frequency of extremes wildfires events.

Seismic Observations Indicating That the 2015 Ogasawara (Bonin) Earthquake Ruptured Beneath the 660 km Discontinuity

Science.gov (United States)

Kuge, Keiko

2017-11-01

The termination of deep earthquakes at a depth of 700 km is a key feature for understanding the physical mechanism of deep earthquakes. The 680 km deep 30 May 2015, Ogasawara (Bonin) earthquake (Mw 7.9) and its aftershocks were recorded by seismic stations at distances from 7° to 19°. Synthetic seismograms indicate that the P waveforms depend on whether the earthquake is located above or below the 660 km discontinuity. In this study, I show that broadband recordings indicate that the 2015 earthquake may have occurred below the 660 km velocity discontinuity. Recordings of the P wave from the strongest aftershock lack evidence for wave triplication expected when a subhorizontal discontinuity underlies the hypocenter. Theoretical waveforms computed with a 660 km discontinuity above the aftershock and mainshock match the observed waveforms more accurately. These observations may indicate earthquake ruptures due to mantle minerals other than olivine or strong deformation of the 660 km phase transition.

Permanently enhanced dynamic triggering probabilities as evidenced by two M ≥ 7.5 earthquakes

Science.gov (United States)

Gomberg, Joan S.

2013-01-01

The 2012 M7.7 Haida Gwaii earthquake radiated waves that likely dynamically triggered the 2013M7.5 Craig earthquake, setting two precedents. First, the triggered earthquake is the largest dynamically triggered shear failure event documented to date. Second, the events highlight a connection between geologic structure, sedimentary troughs that act as waveguides, and triggering probability. The Haida Gwaii earthquake excited extraordinarily large waves within and beyond the Queen Charlotte Trough, which propagated well into mainland Alaska and likely triggering the Craig earthquake along the way. Previously, focusing and associated dynamic triggering have been attributed to unpredictable source effects. This case suggests that elevated dynamic triggering probabilities may exist along the many structures where sedimentary troughs overlie major faults, such as subduction zones’ accretionary prisms and transform faults’ axial valleys. Although data are sparse, I find no evidence of accelerating seismic activity in the vicinity of the Craig rupture between it and the Haida Gwaii earthquake.

Real-time earthquake source imaging: An offline test for the 2011 Tohoku earthquake

Science.gov (United States)

Zhang, Yong; Wang, Rongjiang; Zschau, Jochen; Parolai, Stefano; Dahm, Torsten

2014-05-01

In recent decades, great efforts have been expended in real-time seismology aiming at earthquake and tsunami early warning. One of the most important issues is the real-time assessment of earthquake rupture processes using near-field seismogeodetic networks. Currently, earthquake early warning systems are mostly based on the rapid estimate of P-wave magnitude, which contains generally large uncertainties and the known saturation problem. In the case of the 2011 Mw9.0 Tohoku earthquake, JMA (Japan Meteorological Agency) released the first warning of the event with M7.2 after 25 s. The following updates of the magnitude even decreased to M6.3-6.6. Finally, the magnitude estimate stabilized at M8.1 after about two minutes. This led consequently to the underestimated tsunami heights. By using the newly developed Iterative Deconvolution and Stacking (IDS) method for automatic source imaging, we demonstrate an offline test for the real-time analysis of the strong-motion and GPS seismograms of the 2011 Tohoku earthquake. The results show that we had been theoretically able to image the complex rupture process of the 2011 Tohoku earthquake automatically soon after or even during the rupture process. In general, what had happened on the fault could be robustly imaged with a time delay of about 30 s by using either the strong-motion (KiK-net) or the GPS (GEONET) real-time data. This implies that the new real-time source imaging technique is helpful to reduce false and missing warnings, and therefore should play an important role in future tsunami early warning and earthquake rapid response systems.

Real-time earthquake monitoring using a search engine method.

Science.gov (United States)

Zhang, Jie; Zhang, Haijiang; Chen, Enhong; Zheng, Yi; Kuang, Wenhuan; Zhang, Xiong

2014-12-04

When an earthquake occurs, seismologists want to use recorded seismograms to infer its location, magnitude and source-focal mechanism as quickly as possible. If such information could be determined immediately, timely evacuations and emergency actions could be undertaken to mitigate earthquake damage. Current advanced methods can report the initial location and magnitude of an earthquake within a few seconds, but estimating the source-focal mechanism may require minutes to hours. Here we present an earthquake search engine, similar to a web search engine, that we developed by applying a computer fast search method to a large seismogram database to find waveforms that best fit the input data. Our method is several thousand times faster than an exact search. For an Mw 5.9 earthquake on 8 March 2012 in Xinjiang, China, the search engine can infer the earthquake's parameters in <1 s after receiving the long-period surface wave data.

The Pacific Tsunami Warning Center's Response to the Tohoku Earthquake and Tsunami

Science.gov (United States)

Weinstein, S. A.; Becker, N. C.; Shiro, B.; Koyanagi, K. K.; Sardina, V.; Walsh, D.; Wang, D.; McCreery, C. S.; Fryer, G. J.; Cessaro, R. K.; Hirshorn, B. F.; Hsu, V.

2011-12-01

The largest Pacific basin earthquake in 47 years, and also the largest magnitude earthquake since the Sumatra 2004 earthquake, struck off of the east coast of the Tohoku region of Honshu, Japan at 5:46 UTC on 11 March 2011. The Tohoku earthquake (Mw 9.0) generated a massive tsunami with runups of up to 40m along the Tohoku coast. The tsunami waves crossed the Pacific Ocean causing significant damage as far away as Hawaii, California, and Chile, thereby becoming the largest, most destructive tsunami in the Pacific Basin since 1960. Triggers on the seismic stations at Erimo, Hokkaido (ERM) and Matsushiro, Honshu (MAJO), alerted Pacific Tsunami Warning Center (PTWC) scientists 90 seconds after the earthquake began. Four minutes after its origin, and about one minute after the earthquake's rupture ended, PTWC issued an observatory message reporting a preliminary magnitude of 7.5. Eight minutes after origin time, the Japan Meteorological Agency (JMA) issued its first international tsunami message in its capacity as the Northwest Pacific Tsunami Advisory Center. In accordance with international tsunami warning system protocols, PTWC then followed with its first international tsunami warning message using JMA's earthquake parameters, including an Mw of 7.8. Additional Mwp, mantle wave, and W-phase magnitude estimations based on the analysis of later-arriving seismic data at PTWC revealed that the earthquake magnitude reached at least 8.8, and that a destructive tsunami would likely be crossing the Pacific Ocean. The earthquake damaged the nearest coastal sea-level station located 90 km from the epicenter in Ofunato, Japan. The NOAA DART sensor situated 600 km off the coast of Sendai, Japan, at a depth of 5.6 km recorded a tsunami wave amplitude of nearly two meters, making it by far the largest tsunami wave ever recorded by a DART sensor. Thirty minutes later, a coastal sea-level station at Hanasaki, Japan, 600 km from the epicenter, recorded a tsunami wave amplitude of

Localizing Submarine Earthquakes by Listening to the Water Reverberations

Science.gov (United States)

Castillo, J.; Zhan, Z.; Wu, W.

2017-12-01

Mid-Ocean Ridge (MOR) earthquakes generally occur far from any land based station and are of moderate magnitude, making it complicated to detect and in most cases, locate accurately. This limits our understanding of how MOR normal and transform faults move and the manner in which they slip. Different from continental events, seismic records from earthquakes occurring beneath the ocean floor show complex reverberations caused by P-wave energy trapped in the water column that are highly dependent of the source location and the efficiency to which energy propagated to the near-source surface. These later arrivals are commonly considered to be only a nuisance as they might sometimes interfere with the primary arrivals. However, in this study, we take advantage of the wavefield's high sensitivity to small changes in the seafloor topography and the present-day availability of worldwide multi-beam bathymetry to relocate submarine earthquakes by modeling these water column reverberations in teleseismic signals. Using a three-dimensional hybrid method for modeling body wave arrivals, we demonstrate that an accurate hypocentral location of a submarine earthquake (<5 km) can be achieved if the structural complexities near the source region are appropriately accounted for. This presents a novel way of studying earthquake source properties and will serve as a means to explore the influence of physical fault structure on the seismic behavior of transform faults.

Electrocardiographic features of patients with earthquake related posttraumatic stress disorder

Science.gov (United States)

İlhan, Erkan; Kaplan, Abdullah; Güvenç, Tolga Sinan; Biteker, Murat; Karabulut, Evindar; Işıklı, Serhan

2013-01-01

AIM: To analyze electrocardiographic features of patients diagnosed with posttraumatic stress disorder (PTSD) after the Van-Erciş earthquake, with a shock measuring 7.2 on the Richter scale that took place in Turkey in October 2011. METHODS: Surface electrocardiograms of 12 patients with PTSD admitted to Van Erciş State Hospital (Van, Turkey) from February 2012 to May 2012 were examined. Psychiatric interviews of the sex and age matched control subjects, who had experienced the earthquake, confirmed the absence of any known diagnosable psychiatric conditions in the control group. RESULTS: A wide range of electrocardiogram (ECG) parameters, such as P-wave dispersion, QT dispersion, QT interval, Tpeak to Tend interval, intrinsicoid deflection durations and other traditional parameters were similar in both groups. There was no one with an abnormal P wave axis, short or long PR interval, long or short QT interval, negative T wave in lateral leads, abnormal T wave axis, abnormal left or right intrinsicoid deflection duration, low voltage, left bundle branch block, right bundle branch block, left posterior hemiblock, left or right axis deviation, left ventricular hypertrophy, right or left atrial enlargement and pathological q(Q) wave in either group. CONCLUSION: The study showed no direct effect of earthquake related PTSD on surface ECG in young patients. So, we propose that PTSD has no direct effect on surface ECG but may cause electrocardiographic changes indirectly by triggering atherosclerosis and/or contributing to the ongoing atherosclerotic process. PMID:23538549

Temporal Changes in Stress Drop, Frictional Strength, and Earthquake Size Distribution in the 2011 Yamagata-Fukushima, NE Japan, Earthquake Swarm, Caused by Fluid Migration

Science.gov (United States)

Yoshida, Keisuke; Saito, Tatsuhiko; Urata, Yumi; Asano, Youichi; Hasegawa, Akira

2017-12-01

In this study, we investigated temporal variations in stress drop and b-value in the earthquake swarm that occurred at the Yamagata-Fukushima border, NE Japan, after the 2011 Tohoku-Oki earthquake. In this swarm, frictional strengths were estimated to have changed with time due to fluid diffusion. We first estimated the source spectra for 1,800 earthquakes with 2.0 ≤ MJMA < 3.0, by correcting the site-amplification and attenuation effects determined using both S waves and coda waves. We then determined corner frequency assuming the omega-square model and estimated stress drop for 1,693 earthquakes. We found that the estimated stress drops tended to have values of 1-4 MPa and that stress drops significantly changed with time. In particular, the estimated stress drops were very small at the beginning, and increased with time for 50 days. Similar temporal changes were obtained for b-value; the b-value was very high (b 2) at the beginning, and decreased with time, becoming approximately constant (b 1) after 50 days. Patterns of temporal changes in stress drop and b-value were similar to the patterns for frictional strength and earthquake occurrence rate, suggesting that the change in frictional strength due to migrating fluid not only triggered the swarm activity but also affected earthquake and seismicity characteristics. The estimated high Q-1 value, as well as the hypocenter migration, supports the presence of fluid, and its role in the generation and physical characteristics of the swarm.

Geological structure analysis in Central Java using travel time tomography technique of S waves

International Nuclear Information System (INIS)

Palupi, I. R.; Raharjo, W.; Nurdian, S. W.; Giamboro, W. S.; Santoso, A.

2016-01-01

Java is one of the islands in Indonesia that is prone to the earthquakes, in south of Java, there is the Australian Plate move to the Java island and press with perpendicular direction. This plate movement formed subduction zone and cause earthquakes. The earthquake is the release of energy due to the sudden movement of the plates. When an earthquake occurs, the energy is released and record by seismometers in the waveform. The first wave recorded is called the P waves (primary) and the next wave is called S waves (secondary). Both of these waves have different characteristics in terms of propagation and direction of movement. S wave is composed of waves of Rayleigh and Love waves, with each direction of movement of the vertical and horizontal, subsurface imaging by using S wave tomography technique can describe the type of the S wave through the medium. The variation of wave velocity under Central Java (esearch area) is ranging from -10% to 10% at the depth of 20, 30 and 40 km, the velocity decrease with the depth increase. Moho discontinuity is lies in the depth of 32 km under the crust, it is indicates there is strong heterogenity in Moho. (paper)

One-dimensional velocity model of the Middle Kura Depresion from local earthquakes data of Azerbaijan

Science.gov (United States)

Yetirmishli, G. C.; Kazimova, S. E.; Kazimov, I. E.

2011-09-01

We present the method for determining the velocity model of the Earth's crust and the parameters of earthquakes in the Middle Kura Depression from the data of network telemetry in Azerbaijan. Application of this method allowed us to recalculate the main parameters of the hypocenters of the earthquake, to compute the corrections to the arrival times of P and S waves at the observation station, and to significantly improve the accuracy in determining the coordinates of the earthquakes. The model was constructed using the VELEST program, which calculates one-dimensional minimal velocity models from the travel times of seismic waves.

Earthquake location in island arcs

Science.gov (United States)

Engdahl, E.R.; Dewey, J.W.; Fujita, K.

1982-01-01

A comprehensive data set of selected teleseismic P-wave arrivals and local-network P- and S-wave arrivals from large earthquakes occurring at all depths within a small section of the central Aleutians is used to examine the general problem of earthquake location in island arcs. Reference hypocenters for this special data set are determined for shallow earthquakes from local-network data and for deep earthquakes from combined local and teleseismic data by joint inversion for structure and location. The high-velocity lithospheric slab beneath the central Aleutians may displace hypocenters that are located using spherically symmetric Earth models; the amount of displacement depends on the position of the earthquakes with respect to the slab and on whether local or teleseismic data are used to locate the earthquakes. Hypocenters for trench and intermediate-depth events appear to be minimally biased by the effects of slab structure on rays to teleseismic stations. However, locations of intermediate-depth events based on only local data are systematically displaced southwards, the magnitude of the displacement being proportional to depth. Shallow-focus events along the main thrust zone, although well located using only local-network data, are severely shifted northwards and deeper, with displacements as large as 50 km, by slab effects on teleseismic travel times. Hypocenters determined by a method that utilizes seismic ray tracing through a three-dimensional velocity model of the subduction zone, derived by thermal modeling, are compared to results obtained by the method of joint hypocenter determination (JHD) that formally assumes a laterally homogeneous velocity model over the source region and treats all raypath anomalies as constant station corrections to the travel-time curve. The ray-tracing method has the theoretical advantage that it accounts for variations in travel-time anomalies within a group of events distributed over a sizable region of a dipping, high

Locating the Tohoku-Oki 2011 tsunami source using acoustic-gravity waves

OpenAIRE

Andriamiranto Raveloson; Rainer Kind; Xiaohui Yuan; L. Cerana

2012-01-01

The giant Tohoku-Oki earthquake of 11 March 2011 in offshore Japan did not only generate tsunami waves in the ocean but also infrasound (or acoustic-gravity) waves in the atmosphere. We indentified ultra-long-period signals (>500s) in the recordings of infrasound stations in northeast Asia, the northwest Pacific, and Alaska. Their source was fond close to the earthquake epicenter. Therefore, we conclude that in general, infrasound observations after a large offshore earthquake are evidence th...

The vertical propagation of disturbances triggered by seismic waves of the 11 March 2011 M9.0 Tohoku earthquake over Taiwan

Czech Academy of Sciences Publication Activity Database

Liu, J. Y.; Chen, C. H.; Sun, Y. Y.; Chen, C.; Tsai, H. F.; Yen, H. Y.; Chum, Jaroslav; Laštovička, Jan; Yang, Q. S.; Chen, W. S.; Wen, S.

2016-01-01

Roč. 43, č. 4 (2016), s. 1759-1765 ISSN 0094-8276 R&D Projects: GA ČR(CZ) GC15-07281J Grant - others:Akademie věd České republiky(CZ) M100421201 Institutional support: RVO:68378289 Keywords : ionospheric disturbances * Pacific Coast * surface-waves * Tohoku-oki earthquake * ionograms Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 4.253, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2015GL067487/full

Cascading elastic perturbation in Japan due to the 2012 M w 8.6 Indian Ocean earthquake.

Science.gov (United States)

Delorey, Andrew A; Chao, Kevin; Obara, Kazushige; Johnson, Paul A

2015-10-01

Since the discovery of extensive earthquake triggering occurring in response to the 1992 M w (moment magnitude) 7.3 Landers earthquake, it is now well established that seismic waves from earthquakes can trigger other earthquakes, tremor, slow slip, and pore pressure changes. Our contention is that earthquake triggering is one manifestation of a more widespread elastic disturbance that reveals information about Earth's stress state. Earth's stress state is central to our understanding of both natural and anthropogenic-induced crustal processes. We show that seismic waves from distant earthquakes may perturb stresses and frictional properties on faults and elastic moduli of the crust in cascading fashion. Transient dynamic stresses place crustal material into a metastable state during which the material recovers through a process termed slow dynamics. This observation of widespread, dynamically induced elastic perturbation, including systematic migration of offshore seismicity, strain transients, and velocity transients, presents a new characterization of Earth's elastic system that will advance our understanding of plate tectonics, seismicity, and seismic hazards.

Earthquake source studies and seismic imaging in Alaska

Science.gov (United States)

Tape, C.; Silwal, V.

2015-12-01

Alaska is one of the world's most seismically and tectonically active regions. Its enhanced seismicity, including slab seismicity down to 180 km, provides opportunities (1) to characterize pervasive crustal faulting and slab deformation through the estimation of moment tensors and (2) to image subsurface structures to help understand the tectonic evolution of Alaska. Most previous studies of earthquakes and seismic imaging in Alaska have emphasized earthquake locations and body-wave travel-time tomography. In the past decade, catalogs of seismic moment tensors have been established, while seismic surface waves, active-source data, and potential field data have been used to improve models of seismic structure. We have developed moment tensor catalogs in the regions of two of the largest sedimentary basins in Alaska: Cook Inlet forearc basin, west of Anchorage, and Nenana basin, west of Fairbanks. Our moment tensor solutions near Nenana basin suggest a transtensional tectonic setting, with the basin developing in a stepover of a left-lateral strike-slip fault system. We explore the effects of seismic wave propagation from point-source and finite-source earthquake models by performing three-dimensional wavefield simulations using seismic velocity models that include major sedimentary basins. We will use our catalog of moment tensors within an adjoint-based, iterative inversion to improve the three-dimensional tomographic model of Alaska.

On the Resonant Behavior of a Weakly Compressible Water Layer During Tsunamigenic Earthquakes

Science.gov (United States)

Cecioni, Claudia; Bellotti, Giorgio

2018-01-01

Tsunamigenic earthquakes trigger pressure waves in the ocean, given the weak compressibility of the sea water. For particular conditions, a resonant behavior of the water layer can occur, which influences the energy transfer from the sea-bed motion to the ocean. In this paper, the resonance conditions are explained and analyzed, focusing on the hydro-acoustic waves in the proximity of the earthquake area. A preliminary estimation of the generation parameters (sea-bed rising time, velocity) is given, by means of parametric numerical simulations for simplified conditions. The results confirm the importance of measuring, modeling, and interpreting such waves for tsunami early detection and warning.

Performance of Real-time Earthquake Information System in Japan

Science.gov (United States)

Nakamura, H.; Horiuchi, S.; Wu, C.; Yamamoto, S.

2008-12-01

Horiuchi et al. (2005) developed a real-time earthquake information system (REIS) using Hi-net, a densely deployed nationwide seismic network, which consists of about 800 stations operated by NIED, Japan. REIS determines hypocenter locations and earthquake magnitudes automatically within a few seconds after P waves arrive at the closest station and calculates focal mechanisms within about 15 seconds. Obtained hypocenter parameters are transferred immediately by using XML format to a computer in Japan Meteorological Agency (JMA), who started the service of EEW to special users in June 2005. JMA also developed EEW using 200 stations. The results by the two systems are merged. Among all the first issued EEW reports by both systems, REIS information accounts for about 80 percent. This study examines the rapidity and credibility of REIS by analyzing the 4050 earthquakes which occurred around the Japan Islands since 2005 with magnitude larger than 3.0. REIS re-determines hypocenter parameters every one second according to the revision of waveform data. Here, we discuss only about the results by the first reports. On rapidness, our results show that about 44 percent of the first reports are issued within 5 seconds after the P waves arrives at the closest stations. Note that this 5-second time window includes time delay due to data package and transmission delay of about 2 seconds. REIS waits till two stations detect P waves for events in the network but four stations outside the network so as to get reliable solutions. For earthquakes with hypocentral distance less than 100km, 55 percent of earthquakes are warned in 5 seconds and 87 percent are warned in 10 seconds. Most of events having long time delay are small and triggered by S wave arrivals. About 80 percent of events have difference in epicenter distances less than 20km relative to JMA manually determined locations. Because of the existence of large lateral heterogeneity in seismic velocity, the difference depends

Shear wave velocity investigation of soil liquefaction sites from the Tangshan, China M7.8 earthquake of 1976 using active and passive surface wave methods

Science.gov (United States)

Kayen, Robert E; Tao, Xiaxin; Shi, Lijing; Shi, Hailiang

2008-01-01

An initial investigation of soil liquefaction sites from the July, 28 1976 Tangshan M7.8 earthquake was conducted between 1976 and 1978 by the National Ministry of Railways, China. These data are the basis of the ‘Chinese Method’ for assessment of liquefaction potential of silty-sand deposits, and are an important component of the worldwide data set for modern probabilistic methods for assessment of soil liquefaction using Bayesian updating and system reliability tools. We revisited 26 sites identified in the maps and published 198 report of the Ministry of Railways in order to investigate these locations with a suite of active- and passive-array surface wave methods. These sites are clustered along the north coast of the Bo Hai Sea in three areas: Lutai, Tianjin; Tangshan City and outlying village, Hebei; and Luannan county, Hebei. First, we gathered and evaluated the Rayleigh wave dispersion characteristics of the ground by comparing dispersion curves from the active source harmonic wave-spectral analysis of surface waves (SASW) method and the passive array Spatial Auto-Correlation method (SPAC). The dispersive properties of the liquefied ground as measured by these two methods were found to be almost identical. These tests were hybridized and the data sets merged in order to invert of shear wave velocities for analysis of liquefaction potential using a probabilistic framework. The data from high-values of seismic intensity near Tangshan city to low-intensities distant of the event in Luannan County segregate out into clusters of liquefied and non liquefied points clearly separated by liquefaction boundary curves developed from a large global data set of 310 sites

Bacterial mediated amelioration of drought stress in drought tolerant ...

African Journals Online (AJOL)

Bacterial mediated amelioration of drought stress in drought tolerant and susceptible cultivars of rice ( Oryza sativa L.) ... and IR-64 (drought sensitive) cultivars of rice (Oryza sativa L.) under different level of drought stress. ... from 32 Countries:.

Real-time 3-D space numerical shake prediction for earthquake early warning

Science.gov (United States)

Wang, Tianyun; Jin, Xing; Huang, Yandan; Wei, Yongxiang

2017-12-01

In earthquake early warning systems, real-time shake prediction through wave propagation simulation is a promising approach. Compared with traditional methods, it does not suffer from the inaccurate estimation of source parameters. For computation efficiency, wave direction is assumed to propagate on the 2-D surface of the earth in these methods. In fact, since the seismic wave propagates in the 3-D sphere of the earth, the 2-D space modeling of wave direction results in inaccurate wave estimation. In this paper, we propose a 3-D space numerical shake prediction method, which simulates the wave propagation in 3-D space using radiative transfer theory, and incorporate data assimilation technique to estimate the distribution of wave energy. 2011 Tohoku earthquake is studied as an example to show the validity of the proposed model. 2-D space model and 3-D space model are compared in this article, and the prediction results show that numerical shake prediction based on 3-D space model can estimate the real-time ground motion precisely, and overprediction is alleviated when using 3-D space model.

Effect of earthquake and tsunami. Ground motion and tsunami observed at nuclear power station

International Nuclear Information System (INIS)

Hijikata, Katsuichirou

2012-01-01

Fukushima Daiichi and Daini Nuclear Power Stations (NPSs) were struck by the earthquake off the pacific coast in the Tohoku District, which occurred at 14:46 on March 11, 2011. Afterwards, tsunamis struck the Tohoku District. In terms of the earthquake observed at the Fukushima NPSs, the acceleration response spectra of the earthquake movement observed on the basic board of reactor buildings exceeded the acceleration response spectra of the response acceleration to the standard seismic ground motion Ss for partial periodic bands at the Fukushima Daiichi NPS. As for the Fukushima Daini NPS, the acceleration response spectra of the earthquake movement observed on the basic board of the reactor buildings was below the acceleration response spectra of the response acceleration to the standard seismic ground motion Ss. Areas inundated by Tsunami at each NPS were investigated and tsunami inversion analysis was made to build tsunami source model to reproduce tide record, tsunami height, crustal movement and inundated area, based on tsunami observation records in the wide areas from Hokkaido to Chiba prefectures. Tsunami heights of Fukushima Daiichi and Daini NPSs were recalculated as O.P. +13m and +9m respectively and tsunami peak height difference was attributed to the extent of superposition of tsunami waves of tsunami earthquake type of wave source in the area along interplane trench off the coast in the Fukushima prefecture and interplane earthquake type of wave source in rather deep interplate area off the coast in the Miyagi prefecture. (T. Tanaka)

Earthquakes: Risk, Monitoring, Notification, and Research

Science.gov (United States)

2008-06-19

States are as much as 30% lower for certain types of ground motion, called long-period seismic waves, which affect taller , multistory buildings. Ground...jump between connected faults. Earthquakes that occur along the Sierra Madre Fault in southern California, for example, could trigger a series of

Developing drought impact functions for drought risk management

Directory of Open Access Journals (Sweden)

S. Bachmair

2017-11-01

Full Text Available Drought management frameworks are dependent on methods for monitoring and prediction, but quantifying the hazard alone is arguably not sufficient; the negative consequences that may arise from a lack of precipitation must also be predicted if droughts are to be better managed. However, the link between drought intensity, expressed by some hydrometeorological indicator, and the occurrence of drought impacts has only recently begun to be addressed. One challenge is the paucity of information on ecological and socioeconomic consequences of drought. This study tests the potential for developing empirical drought impact functions based on drought indicators (Standardized Precipitation and Standardized Precipitation Evaporation Index as predictors and text-based reports on drought impacts as a surrogate variable for drought damage. While there have been studies exploiting textual evidence of drought impacts, a systematic assessment of the effect of impact quantification method and different functional relationships for modeling drought impacts is missing. Using Southeast England as a case study we tested the potential of three different data-driven models for predicting drought impacts quantified from text-based reports: logistic regression, zero-altered negative binomial regression (hurdle model, and an ensemble regression tree approach (random forest. The logistic regression model can only be applied to a binary impact/no impact time series, whereas the other two models can additionally predict the full counts of impact occurrence at each time point. While modeling binary data results in the lowest prediction uncertainty, modeling the full counts has the advantage of also providing a measure of impact severity, and the counts were found to be reasonably predictable. However, there were noticeable differences in skill between modeling methodologies. For binary data the logistic regression and the random forest model performed similarly well based on

Drought, Agriculture, and Labor: Understanding Drought Impacts and Vulnerability in California

Science.gov (United States)

Greene, C.

2015-12-01

Hazardous drought impacts are a product of not only the physical intensity of drought, but also the economic, social, and environmental characteristics of the region exposed to drought. Drought risk management requires understanding the complex links between the physical and human dimensions of drought. Yet, there is a research gap in identifying and explaining the socio-economic complexities of drought in the context of the first world, especially for economic and socially marginal groups who rely on seasonal and temporary jobs. This research uses the current drought in California as a case study to identify the socioeconomic impacts of drought on farmworker communities in California's San Joaquin Valley, with a specific focus on the relationship between drought and agricultural labor. Through both a narrative analysis of drought coverage in newspaper media, drought policy documents, and interviews with farmworkers, farmers, community based organizations, and government officials in the San Joaquin Valley, this research aims to highlight the different understandings and experiences of the human impacts of drought and drought vulnerability in order to better inform drought risk planning and policy.

1881 and 1949 earthquakes at the Chios-Cesme Strait (Aegean Sea and their relation to tsunamis

Directory of Open Access Journals (Sweden)

Y. Altinok

2005-01-01

Full Text Available The most earthquake-prone areas in the eastern central Aegean Sea are the Izmir Bay, the Karaburun peninsula and the island of Chios. The level of seismic activity and tsunami potential are influenced by the presence of normal faults around the region. There have been about 20 moderate-size earthquakes from 496 BC to 1949 AD. Among these earthquakes, the ones on the dates 20 March 1389, 13 November 1856, 19/22 January 1866, 3 April 1881 and 23 July 1949 produced tsunamis. The Chios-Cesme earthquake (1881, Mw 6.5 took place in the South of the Cesme strait while the Chios-Karaburun earthquake (1949, Mw 6.7 occurred in the North. The tsunamis caused by the earthquakes affected the coasts of Chios Island and Cesme. These waves are thought to be associated with the earthquakes and co-seismic underwater failures possibly occurred along the coasts of the Chios Island and Karaburun Peninsula or on the complex subaqueous morphology between these lands. Some sea waves or oscillations observed following the aftershocks are believed to be related to other natural phenomena; e.g. the seiches occurred mainly in open-narrow bays as triggered by the earthquakes.

Studies of earthquakes stress drops, seismic scattering, and dynamic triggering in North America

Science.gov (United States)

Escudero Ayala, Christian Rene

I use the Relative Source Time Function (RSTF) method to determine the source properties of earthquakes within southeastern Alaska-northwestern Canada in a first part of the project, and earthquakes within the Denali fault in a second part. I deconvolve a small event P-arrival signal from a larger event by the following method: select arrivals with a tapered cosine window, fast fourier transform to obtain the spectrum, apply water level deconvolution technique, and bandpass filter before inverse transforming the result to obtain the RSTF. I compare the source processes of earthquakes within the area to determine stress drop differences to determine their relation with the tectonic setting of the earthquakes location. Results show an consistency with previous results, stress drop independent of moment implying self-similarity, correlation of stress drop with tectonic regime, stress drop independent of depth, stress drop depends of focal mechanism where strike-slip present larger stress drops, and decreasing stress drop as function of time. I determine seismic wave attenuation in the central western United States using coda waves. I select approximately 40 moderate earthquakes (magnitude between 5.5 and 6.5) located alocated along the California-Baja California, California-Nevada, Eastern Idaho, Gulf of California, Hebgen Lake, Montana, Nevada, New Mexico, off coast of Northern California, off coast of Oregon, southern California, southern Illinois, Vancouver Island, Washington, and Wyoming regions. These events were recorded by the EarthScope transportable array (TA) network from 2005 to 2009. We obtain the data from the Incorporated Research Institutions for Seismology (IRIS). In this study we implement a method based on the assumption that coda waves are single backscattered waves from randomly distributed heterogeneities to calculate the coda Q. The frequencies studied lie between 1 and 15 Hz. The scattering attenuation is calculated for frequency bands centered

Drivers of Complexity in Humanitarian Operations

Science.gov (United States)

2013-12-04

shaking) Volcano Volcanic eruption General Flood Flash flood Mass movement wet Landslide Mudslide Extratropical cyclone (winter storm ) Local storm Blizzard...Type Rank Count Drought 1 4 Epidemic 2 0 Viral Infectious Diseases 3 2 Cold Wave 4 2 Heat Wave 5 7 Extratropical  Cyclone (Winter  Storm ) 6 1 Tropical...catastrophe (including any hurricane, tornado, storm , high water, wind-driven water, tidal wave, tsunami, earthquake, volcanic eruption, landslide, mudslide

Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle.

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Prieto, Germán A; Froment, Bérénice; Yu, Chunquan; Poli, Piero; Abercrombie, Rachel

2017-03-01

Earthquakes deep in the continental lithosphere are rare and hard to interpret in our current understanding of temperature control on brittle failure. The recent lithospheric mantle earthquake with a moment magnitude of 4.8 at a depth of ~75 km in the Wyoming Craton was exceptionally well recorded and thus enabled us to probe the cause of these unusual earthquakes. On the basis of complete earthquake energy balance estimates using broadband waveforms and temperature estimates using surface heat flow and shear wave velocities, we argue that this earthquake occurred in response to ductile deformation at temperatures above 750°C. The high stress drop, low rupture velocity, and low radiation efficiency are all consistent with a dissipative mechanism. Our results imply that earthquake nucleation in the lithospheric mantle is not exclusively limited to the brittle regime; weakening mechanisms in the ductile regime can allow earthquakes to initiate and propagate. This finding has significant implications for understanding deep earthquake rupture mechanics and rheology of the continental lithosphere.

Cascading elastic perturbation in Japan due to the 2012 Mw 8.6 Indian Ocean earthquake

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Delorey, Andrew A.; Chao, Kevin; Obara, Kazushige; Johnson, Paul A.

2015-01-01

Since the discovery of extensive earthquake triggering occurring in response to the 1992 Mw (moment magnitude) 7.3 Landers earthquake, it is now well established that seismic waves from earthquakes can trigger other earthquakes, tremor, slow slip, and pore pressure changes. Our contention is that earthquake triggering is one manifestation of a more widespread elastic disturbance that reveals information about Earth’s stress state. Earth’s stress state is central to our understanding of both natural and anthropogenic-induced crustal processes. We show that seismic waves from distant earthquakes may perturb stresses and frictional properties on faults and elastic moduli of the crust in cascading fashion. Transient dynamic stresses place crustal material into a metastable state during which the material recovers through a process termed slow dynamics. This observation of widespread, dynamically induced elastic perturbation, including systematic migration of offshore seismicity, strain transients, and velocity transients, presents a new characterization of Earth’s elastic system that will advance our understanding of plate tectonics, seismicity, and seismic hazards. PMID:26601289

Remotely triggered seismicity in north China following the 2008 M w 7.9 Wenchuan earthquake

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Peng, Zhigang; Wang, Weijun; Chen, Qi-Fu; Jiang, Tao

2010-11-01

We conduct a systematic survey of remote triggering of earthquakes in north China following the 2008 M w 7.9 Wenchuan earthquake. We identify triggered earthquakes as impulsive seismic energies with clear P and S arrivals on 5 Hz high-pass-filtered three-component velocity seismograms during and immediately after the passage of teleseismic waves. We find clearly triggered seismic activity near the Babaoshan and Huangzhuang-Gaoliying faults southwest of Beijing, and near the aftershock zone of the 1976 M W 7.6 Tangshan earthquake. While several earthquakes occur during and immediately after the teleseismic waves in the aftershock zone of the 1975 M w 7.0 Haicheng earthquake, the change of seismicity is not significant enough to establish the direct triggering relationship. Our results suggest that intraplate regions with active faults associated with major earthquakes during historic or recent times are susceptible to remote triggering. We note that this does not always guarantee the triggering to occur, indicating that other conditions are needed. Since none of these regions is associated with any active geothermal or volcanic activity, we infer that dynamic triggering could be ubiquitous and occur in a wide range of tectonic environments.

Adapting Controlled-source Coherence Analysis to Dense Array Data in Earthquake Seismology

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Schwarz, B.; Sigloch, K.; Nissen-Meyer, T.

2017-12-01

Exploration seismology deals with highly coherent wave fields generated by repeatable controlled sources and recorded by dense receiver arrays, whose geometry is tailored to back-scattered energy normally neglected in earthquake seismology. Owing to these favorable conditions, stacking and coherence analysis are routinely employed to suppress incoherent noise and regularize the data, thereby strongly contributing to the success of subsequent processing steps, including migration for the imaging of back-scattering interfaces or waveform tomography for the inversion of velocity structure. Attempts have been made to utilize wave field coherence on the length scales of passive-source seismology, e.g. for the imaging of transition-zone discontinuities or the core-mantle-boundary using reflected precursors. Results are however often deteriorated due to the sparse station coverage and interference of faint back-scattered with transmitted phases. USArray sampled wave fields generated by earthquake sources at an unprecedented density and similar array deployments are ongoing or planned in Alaska, the Alps and Canada. This makes the local coherence of earthquake data an increasingly valuable resource to exploit.Building on the experience in controlled-source surveys, we aim to extend the well-established concept of beam-forming to the richer toolbox that is nowadays used in seismic exploration. We suggest adapted strategies for local data coherence analysis, where summation is performed with operators that extract the local slope and curvature of wave fronts emerging at the receiver array. Besides estimating wave front properties, we demonstrate that the inherent data summation can also be used to generate virtual station responses at intermediate locations where no actual deployment was performed. Owing to the fact that stacking acts as a directional filter, interfering coherent wave fields can be efficiently separated from each other by means of coherent subtraction. We

TSUNAMIS AND TSUNAMI-LIKE WAVES OF THE EASTERN UNITED STATES

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James F. Lander

2002-01-01

Full Text Available The threat of tsunamis and tsunami-like waves hitting the eastern United States is very real despite a general impression to the contrary. We have cataloged 40 tsunamis and tsunami-like waves that have occurred in the eastern United States since 1600. Tsunamis were generated from such events as the 1755 Queen Anne’s earthquake, the Grand Banks event of 1929, the Charleston earthquake of 1886, and the New Madrid earthquakes of 1811-1812. The Queen Anne tsunami was observed as far away as St. Martin in the West Indies and is the only known teletsunami generated in this source region.Since subduction zones are absent around most of the Atlantic basin, tsunamis and tsunami-like waves along the United States East Coast are not generated from this traditional source, but appear, in most cases to be the result of slumping or landsliding associated with local earthquakes or with wave action associated with strong storms. Other sources of tsunamis and tsunami-like waves along the eastern seaboard have recently come to light including volcanic debris falls or catastrophic failure of volcanic slopes; explosive decompression of underwater methane deposits or oceanic meteor splashdowns. These sources are considered as well.

Relations between source parameters for large Persian earthquakes

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Majid Nemati

2015-11-01

Full Text Available Empirical relationships for magnitude scales and fault parameters were produced using 436 Iranian intraplate earthquakes of recently regional databases since the continental events represent a large portion of total seismicity of Iran. The relations between different source parameters of the earthquakes were derived using input information which has usefully been provided from the databases after 1900. Suggested equations for magnitude scales relate the body-wave, surface-wave as well as local magnitude scales to scalar moment of the earthquakes. Also, dependence of source parameters as surface and subsurface rupture length and maximum surface displacement on the moment magnitude for some well documented earthquakes was investigated. For meeting this aim, ordinary linear regression procedures were employed for all relations. Our evaluations reveal a fair agreement between obtained relations and equations described in other worldwide and regional works in literature. The M0-mb and M0-MS equations are correlated well to the worldwide relations. Also, both M0-MS and M0-ML relations have a good agreement with regional studies in Taiwan. The equations derived from this study mainly confirm the results of the global investigations about rupture length of historical and instrumental events. However, some relations like MW-MN and MN-ML which are remarkably unlike to available regional works (e.g., American and Canadian were also found.

Spatiotemporal Drought Analysis and Drought Indices Comparison in India

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Janardhanan, A.

2017-12-01

Droughts and floods are an ever-occurring phenomenon that has been wreaking havoc on humans since the start of time. As droughts are on a very large scale, studying them within a regional context can minimize confounding factors such as climate change. Droughts and floods are extremely erratic and very difficult to predict and therefore necessitate modeling through advanced statistics. The SPI (Standard Precipitation Index) and the SPEI (Standard Precipitation Evapotranspiration Index) are two ways to temporally model drought and flood patterns across each metrological sub basin in India over a variety of different time scales. SPI only accounts for precipitation values, while the SPEI accounts for both precipitation and temperature and is commonly regarded as a more reliable drought index. Using monthly rainfall and temperature data from 1871-2016, these two indices were calculated. The results depict the drought and flood severity index, length of drought, and average SPI or SPEI value for each meteorological sub region in India. A Wilcox Ranksum test was then conducted to determine whether these two indices differed over the long term for drought analysis. The drought return periods were analyzed to determine if the population mean differed between the SPI and SPEI values. Our analysis found no statistical difference between SPI and SPEI with regards to long-term drought analysis. This indicates that temperature is not needed when modeling drought on a long-term time scale and that SPI is just as effective as SPEI, which has the potential to save a lot of time and resources on calculating drought indices.

Tangshan 1976 earthquake: Modelling of the SH-wave motion in the area of Xiji-Langfu

International Nuclear Information System (INIS)

Sun, R.

1995-06-01

The reasons for the anomalous high macroseismic intensity caused in the Xiji-Langfu area by the Tangshan, 1976 earthquake can be found in its special geological conditions. This area is formed of deep deposits beside the Xiadian fault, that consist mainly of alluvium sands and clays, which are poorly consolidated with high water content. Resonances, excitation of local surface waves and their propagation cause strong amplifications and long durations of signals. Based on simulated strong ground motion, we have computed quantities commonly used for engineering purposes: the maximum amplitude (AMAX) and the total energy of ground motion (W), which is related to the Arias Intensity. AMAX and W do not decrease gradually as the epicentral distance increases, since the low velocities and the thickness of the deposits are responsible for the large increment of the values of AMAX and W inside the basin. On the two sides of the Xiadian fault AMAX and W can vary by 200% and 700% respectively. This computational result can be used to explain the large macroseismic intensity observed in the Xiji-Langfu area, in connection with the Tangshan earthquake. The spectral ratios show that over the whole area significant amplifications occur in the range of frequencies from 0.3 Hz to 1.5 Hz, while the largest amplification is above 6 and takes place around 3 Hz at a distance of about 112 km. from the epicentre. (author). 18 refs, 15 figs, 2 tabs

Nonlinear waves in earth crust faults: application to regular and slow earthquakes

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Gershenzon, Naum; Bambakidis, Gust

2015-04-01

The genesis, development and cessation of regular earthquakes continue to be major problems of modern geophysics. How are earthquakes initiated? What factors determine the rapture velocity, slip velocity, rise time and geometry of rupture? How do accumulated stresses relax after the main shock? These and other questions still need to be answered. In addition, slow slip events have attracted much attention as an additional source for monitoring fault dynamics. Recently discovered phenomena such as deep non-volcanic tremor (NVT), low frequency earthquakes (LFE), very low frequency earthquakes (VLF), and episodic tremor and slip (ETS) have enhanced and complemented our knowledge of fault dynamic. At the same time, these phenomena give rise to new questions about their genesis, properties and relation to regular earthquakes. We have developed a model of macroscopic dry friction which efficiently describes laboratory frictional experiments [1], basic properties of regular earthquakes including post-seismic stress relaxation [3], the occurrence of ambient and triggered NVT [4], and ETS events [5, 6]. Here we will discuss the basics of the model and its geophysical applications. References [1] Gershenzon N.I. & G. Bambakidis (2013) Tribology International, 61, 11-18, http://dx.doi.org/10.1016/j.triboint.2012.11.025 [2] Gershenzon, N.I., G. Bambakidis and T. Skinner (2014) Lubricants 2014, 2, 1-x manuscripts; doi:10.3390/lubricants20x000x; arXiv:1411.1030v2 [3] Gershenzon N.I., Bykov V. G. and Bambakidis G., (2009) Physical Review E 79, 056601 [4] Gershenzon, N. I, G. Bambakidis, (2014a), Bull. Seismol. Soc. Am., 104, 4, doi: 10.1785/0120130234 [5] Gershenzon, N. I.,G. Bambakidis, E. Hauser, A. Ghosh, and K. C. Creager (2011), Geophys. Res. Lett., 38, L01309, doi:10.1029/2010GL045225. [6] Gershenzon, N.I. and G. Bambakidis (2014) Bull. Seismol. Soc. Am., (in press); arXiv:1411.1020

Topography Estimation of the Core Mantle Boundary with ScS Reverberations and Diffraction Waves

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Hein, B. E.; Nakata, N.

2017-12-01

In this study, we use the propagation of global seismic waves to study the Core Mantle Boundary (CMB). We focus on the use of S-wave reflections at the CMB (ScS reverberations) and outer-core diffracted waves. It is difficult imaging the CMB with the ScS wave because the complexity of the structure in the near surface ( 50 km); the complex structure degrades the signal-to-noise ratio of of the ScS. To avoid estimating the structure in the crust, we rely on the concept of seismic interferometry to extract wave propagation through mantle, but not through the crust. Our approach is compute the deconvolution between the ScS (and its reverberation) and direct S waves generated by intermediate to deep earthquakes (>50 km depth). Through this deconvolution, we have the ability to filter out the direct S wave and retrieve the wave field propagating from only the hypocenter to the outer core, but not between the hypocenter to the receiver. After the deconvolution, we can isolate the CMB reflected waves from the complicated wave phenomena because of the near-surface structure. Utilizing intermediate and deep earthquakes is key since we can suppress the near-surface effect from the surface to the hypocenter of the earthquakes. The variation of such waves (e.g., travel-time perturbation and/or wavefield decorrelation) at different receivers and earthquakes provides the information of the topography of the CMB. In order to get a more detailed image of the topography of the CMB we use diffracted seismic waves such as Pdiff , Sdiff, and P'P'. By using two intermediate to deep earthquakes on a great circle path with a station we can extract the wave propagation between the two earthquakes to simplify the waveform, similar to how it is preformed using the ScS wave. We generate more illumination of the CMB by using diffracted waves rather than only using ScS reverberations. The accurate topography of CMB obtained by these deconvolution analyses may provide new insight of the

Earthquake responses of a beam supported by a mechanical snubber

International Nuclear Information System (INIS)

Ohmata, Kenichiro; Ishizu, Seiji.

1989-01-01

The mechanical snubber is an earthquakeproof device for piping systems under particular circumstances such as high temperature and radioactivity. It has nonlinearities in both load and frequency response. In this report, the resisting force characteristics of the snubber and earthquake responses of piping (a simply supported beam) which is supported by the snubber are simulated using Continuous System Simulation Language (CSSL). Digital simulations are carried out for various kinds of physical properties of the snubber. The restraint effect and the maximum resisting force of the snubber during earthquakes are discussed and compared with the case of an oil damper. The earthquake waves used here are E1 Centro N-S and Akita Harbour N-S (Nihonkai-Chubu earthquake). (author)

Relationship between large slip area and static stress drop of aftershocks of inland earthquake :Example of the 2007 Noto Hanto earthquake

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Urano, S.; Hiramatsu, Y.; Yamada, T.

2013-12-01

The 2007 Noto Hanto earthquake (MJMA 6.9; hereafter referred to the main shock) occurred at 0:41(UTC) on March 25, 2007 at a depth of 11km beneath the west coast of Noto Peninsula, central Japan. The dominant slip of the main shock was on a reverse fault with a right-lateral slip and the large slip area was distributed from hypocenter to the shallow part on the fault plane (Horikawa, 2008). The aftershocks are distributed not only in the small slip area but also in the large slip area (Hiramatsu et al., 2011). In this study, we estimate static stress drops of aftershocks on the fault plane of the main shock. We discuss the relationship between the static stress drops of the aftershocks and the large slip area of the main shock by investigating spatial pattern of the values of the static stress drops. We use the waveform data obtained by the group for the joint aftershock observations of the 2007 Noto Hanto Earthquake (Sakai et al., 2007). The sampling frequency of the waveform data is 100 Hz or 200 Hz. Focusing on similar aftershocks reported by Hiramatsu et al. (2011), we analyze static stress drops by using the method of empirical Green's function (EGF) (Hough, 1997) as follows. The smallest earthquake (MJMA≥2.0) of each group of similar earthquakes is set to the EGF earthquake, and the largest earthquake (MJMA≥2.5) is set to the target earthquake. We then deconvolve the waveform of an interested earthquake with that of the EGF earthquake at each station and obtain the spectral ratio of the sources that cancels the propagation effects (path and site effects). Following the procedure of Yamada et al. (2010), we finally estimate static stress drops for P- and S-waves from corner frequencies of the spectral ratio by using a model of Madariaga (1976). The estimated average value of static stress drop is 8.2×1.3 MPa (8.6×2.2 MPa for P-wave and 7.8×1.3 MPa for S-wave). These values are coincident approximately with the static stress drop of aftershocks of other

Identification of earthquakes that generate tsunamis in Java and Nusa Tenggara using rupture duration analysis

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Pribadi, S., E-mail: sugengpribadimsc@gmail.com [Tsunami Warning Information Division, Indonesian Meteorological Climatological and Geophysical Agency (BMKG), Jalan Angkasa I No. 2, Jakarta13920 and Graduate Student of Earth Sciences, Faculty of Earth Sciences and Technology, Bandung Institute of T (Indonesia); Puspito, N. T.; Yudistira, T.; Afnimar,; Ibrahim, G. [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Bandung Institute of Technology (ITB), Jalan Ganesha 10, Bandung 40132 (Indonesia); Laksono, B. I. [Database Maintenance Division, Indonesian Meteorological Climatological and Geophysical Agency (BMKG), Jalan Angkasa I No.2, Jakarta 13920 (Indonesia); Adnan, Z. [Database Maintenance Division, Indonesian Meteorological Climatological and Geophysical Agency (BMKG), Jalan Angkasa I No. 2, Jakarta 13920 and Graduate Student of Earth Sciences, Faculty of Earth Sciences and Technology, Bandung Institute of Technol (Indonesia)

2014-09-25

Java and Nusa Tenggara are the tectonically active of Sunda arc. This study discuss the rupture duration as a manifestation of the power of earthquake-generated tsunami. We use the teleseismic (30° - 90°) body waves with high-frequency energy Seismometer is from IRIS network as amount 206 broadband units. We applied the Butterworth high bandpass (1 - 2 Hz) filtered. The arrival and travel times started from wave phase of P - PP which based on Jeffrey Bullens table with TauP program. The results are that the June 2, 1994 Banyuwangi and the July 17, 2006 Pangandaran earthquakes identified as tsunami earthquakes with long rupture duration (To > 100 second), medium magnitude (7.6 < Mw < 7.9) and located near the trench. The others are 4 tsunamigenic earthquakes and 3 inland earthquakes with short rupture duration start from To > 50 second which depend on its magnitude. Those events are located far from the trench.

Rapid estimation of the moment magnitude of the 2011 off the Pacific coast of Tohoku earthquake from coseismic strain steps

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Itaba, S.; Matsumoto, N.; Kitagawa, Y.; Koizumi, N.

2012-12-01

The 2011 off the Pacific coast of Tohoku earthquake, of moment magnitude (Mw) 9.0, occurred at 14:46 Japan Standard Time (JST) on March 11, 2011. The coseismic strain steps caused by the fault slip of this earthquake were observed in the Tokai, Kii Peninsula and Shikoku by the borehole strainmeters which were carefully set by Geological Survey of Japan, AIST. Using these strain steps, we estimated a fault model for the earthquake on the boundary between the Pacific and North American plates. Our model, which is estimated only from several minutes' strain data, is largely consistent with the final fault models estimated from GPS and seismic wave data. The moment magnitude can be estimated about 6 minutes after the origin time, and 4 minutes after wave arrival. According to the fault model, the moment magnitude of the earthquake is 8.7. On the other hand, based on the seismic wave, the prompt report of the magnitude which the Japan Meteorological Agency announced just after earthquake occurrence was 7.9. Generally coseismic strain steps are considered to be less reliable than seismic waves and GPS data. However our results show that the coseismic strain steps observed by the borehole strainmeters, which were carefully set and monitored, can be relied enough to decide the earthquake magnitude precisely and rapidly. In order to grasp the magnitude of a great earthquake earlier, several methods are now being suggested to reduce the earthquake disasters including tsunami. Our simple method of using strain steps is one of the strong methods for rapid estimation of the magnitude of great earthquakes.

Demonstration of improved seismic source inversion method of tele-seismic body wave

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Yagi, Y.; Okuwaki, R.

2017-12-01

Seismic rupture inversion of tele-seismic body wave has been widely applied to studies of large earthquakes. In general, tele-seismic body wave contains information of overall rupture process of large earthquake, while the tele-seismic body wave is inappropriate for analyzing a detailed rupture process of M6 7 class earthquake. Recently, the quality and quantity of tele-seismic data and the inversion method has been greatly improved. Improved data and method enable us to study a detailed rupture process of M6 7 class earthquake even if we use only tele-seismic body wave. In this study, we demonstrate the ability of the improved data and method through analyses of the 2016 Rieti, Italy earthquake (Mw 6.2) and the 2016 Kumamoto, Japan earthquake (Mw 7.0) that have been well investigated by using the InSAR data set and the field observations. We assumed the rupture occurring on a single fault plane model inferred from the moment tensor solutions and the aftershock distribution. We constructed spatiotemporal discretized slip-rate functions with patches arranged as closely as possible. We performed inversions using several fault models and found that the spatiotemporal location of large slip-rate area was robust. In the 2016 Kumamoto, Japan earthquake, the slip-rate distribution shows that the rupture propagated to southwest during the first 5 s. At 5 s after the origin time, the main rupture started to propagate toward northeast. First episode and second episode correspond to rupture propagation along the Hinagu fault and the Futagawa fault, respectively. In the 2016 Rieti, Italy earthquake, the slip-rate distribution shows that the rupture propagated to up-dip direction during the first 2 s, and then rupture propagated toward northwest. From both analyses, we propose that the spatiotemporal slip-rate distribution estimated by improved inversion method of tele-seismic body wave has enough information to study a detailed rupture process of M6 7 class earthquake.

Drought occurence

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John W. Coulston

2007-01-01

Why Is Drought Important? Drought is an important forest disturbance that occurs regularly in the Western United States and irregularly in the Eastern United States (Dale and others 2001). Moderate drought stress tends to slow plant growth while severedrought stress can also reduce photosynthesis (Kareiva and others 1993). Drought can also interact with...

THE RESPONSE OF MONTEREY BAY TO THE 2010 CHILEAN EARTHQUAKE

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Laurence C. Breaker

2011-01-01

Full Text Available The primary frequencies contained in the arrival sequence produced by the tsunami from the Chilean earthquake of 2010 in Monterey Bay were extracted to determine the seiche modes that were produced. Singular Spectrum Analysis (SSA and Ensemble Empirical Mode Decomposition (EEMD were employed to extract the primary frequencies of interest. The wave train from the Chilean tsunami lasted for at least four days due to multipath arrivals that may not have included reflections from outside the bay but most likely did include secondary undulations, and energy trapping in the form of edge waves, inside the bay. The SSA decomposition resolved oscillations with periods of 52-57, 34-35, 26-27, and 21-22 minutes, all frequencies that have been predicted and/or observed in previous studies. The EEMD decomposition detected oscillations with periods of 50-55 and 21-22 minutes. Periods in the range of 50-57 minutes varied due to measurement uncertainties but almost certainly correspond to the first longitudinal mode of oscillation for Monterey Bay, periods of 34-35 minutes correspond to the first transverse mode of oscillation that assumes a nodal line across the entrance of the bay, a period of 26- 27 minutes, although previously observed, may not represent a fundamental oscillation, and a period of 21-22 minutes has been predicted and observed previously. A period of ~37 minutes, close to the period of 34-35 minutes, was generated by the Great Alaskan Earthquake of 1964 in Monterey Bay and most likely represents the same mode of oscillation. The tsunamis associated with the Great Alaskan Earthquake and the Chilean Earthquake both entered Monterey Bay but initially arrived outside the bay from opposite directions. Unlike the Great Alaskan Earthquake, however, which excited only one resonant mode inside the bay, the Chilean Earthquake excited several modes suggesting that the asymmetric shape of the entrance to Monterey Bay was an important factor and that the

Comprehensive drought characteristics analysis based on a nonlinear multivariate drought index

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Yang, Jie; Chang, Jianxia; Wang, Yimin; Li, Yunyun; Hu, Hui; Chen, Yutong; Huang, Qiang; Yao, Jun

2018-02-01

It is vital to identify drought events and to evaluate multivariate drought characteristics based on a composite drought index for better drought risk assessment and sustainable development of water resources. However, most composite drought indices are constructed by the linear combination, principal component analysis and entropy weight method assuming a linear relationship among different drought indices. In this study, the multidimensional copulas function was applied to construct a nonlinear multivariate drought index (NMDI) to solve the complicated and nonlinear relationship due to its dependence structure and flexibility. The NMDI was constructed by combining meteorological, hydrological, and agricultural variables (precipitation, runoff, and soil moisture) to better reflect the multivariate variables simultaneously. Based on the constructed NMDI and runs theory, drought events for a particular area regarding three drought characteristics: duration, peak, and severity were identified. Finally, multivariate drought risk was analyzed as a tool for providing reliable support in drought decision-making. The results indicate that: (1) multidimensional copulas can effectively solve the complicated and nonlinear relationship among multivariate variables; (2) compared with single and other composite drought indices, the NMDI is slightly more sensitive in capturing recorded drought events; and (3) drought risk shows a spatial variation; out of the five partitions studied, the Jing River Basin as well as the upstream and midstream of the Wei River Basin are characterized by a higher multivariate drought risk. In general, multidimensional copulas provides a reliable way to solve the nonlinear relationship when constructing a comprehensive drought index and evaluating multivariate drought characteristics.

Laboratory generated M -6 earthquakes

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McLaskey, Gregory C.; Kilgore, Brian D.; Lockner, David A.; Beeler, Nicholas M.

2014-01-01

We consider whether mm-scale earthquake-like seismic events generated in laboratory experiments are consistent with our understanding of the physics of larger earthquakes. This work focuses on a population of 48 very small shocks that are foreshocks and aftershocks of stick–slip events occurring on a 2.0 m by 0.4 m simulated strike-slip fault cut through a large granite sample. Unlike the larger stick–slip events that rupture the entirety of the simulated fault, the small foreshocks and aftershocks are contained events whose properties are controlled by the rigidity of the surrounding granite blocks rather than characteristics of the experimental apparatus. The large size of the experimental apparatus, high fidelity sensors, rigorous treatment of wave propagation effects, and in situ system calibration separates this study from traditional acoustic emission analyses and allows these sources to be studied with as much rigor as larger natural earthquakes. The tiny events have short (3–6 μs) rise times and are well modeled by simple double couple focal mechanisms that are consistent with left-lateral slip occurring on a mm-scale patch of the precut fault surface. The repeatability of the experiments indicates that they are the result of frictional processes on the simulated fault surface rather than grain crushing or fracture of fresh rock. Our waveform analysis shows no significant differences (other than size) between the M -7 to M -5.5 earthquakes reported here and larger natural earthquakes. Their source characteristics such as stress drop (1–10 MPa) appear to be entirely consistent with earthquake scaling laws derived for larger earthquakes.

HYDROACOUSTIC OBSERVATIONS OF WEAK EARTHQUAKES IN SHALLOW WATERS OF THE SOUTHERN KURIL ISLANDS

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Alexander S. Borisov

2012-01-01

Full Text Available Results of hydroacoustic observations of signals from weak earthquakes in natural conditions in the region of the Southern Kuril Islands are presented. Some earthquakes were registered by the the Yuzhno-Kurilsk Seismic Station, other were only recorded by hydrophone stations. The observations were specific as seismic signals were recorded in shallow waters, i.e. in high noise level conditions. Hydrophones were installed in Lake Lagunnoe (Kunashir and Khromovaya Bay (Shikotan. Our analysis of hydroacoustic records received from the hydrophone stations revealed no evident precursory response of the geological medium to weak distant events. This means that neither before the period of earthquake preparation nor during the earthquake preparation period, any geoacoustic emission was not detected. It is shown that despite the unfavourable noise level conditions, even distant weak earthquakes can be confidently registered by hydrophone stations, and pending application of proper signal processing techniques, it can be possible to determine arrival times of seismic waves and to measure parameters of seismic waves. It is also established that the frequency spectrum of acoustic signals from the weak earthquakes recordable by the hydrophone stations is continuous and of noise type in the frequency range up to 90–100 Hz. It is revealed that in some cases, weak earthquakes and microearthquakes may be forerun by low frequency signals.

Study on seismic stability of seawall in man-made island. Pt. 5. Deformation of actual seawall during earthquake and estimation of seismic performance

International Nuclear Information System (INIS)

Kanatani, Mamoru; Tochigi, Hitoshi; Kawai, Tadashi; Sakakiyama, Tsutomu; Kudo, Koji

1999-01-01

In the development of the man-made island siting technology of nuclear power plants, assessing the stability of the seawall against large ocean waves and earthquakes is indispensable. Concerning the seismic stability of the seawall, prediction of the deformation of the seawall during earthquake is important to evaluate the seismic performance of the seawall after the earthquake. In the this report, the deformation of the actual seawall was predicted from the results of the centrifuge model tests and the case studies by the numerical analyses. Furthermore, wave flume model tests of the seawall with the deformed armour embankment by the earthquake shaking were conducted to investigate the effects of the deformation of the armoured embankment to the overtopping discharge by the waves. Obtained results were as follows: (1) It was experimentally confirmed that the slope gentleness and the decrease of the top elevation of the armoured embankment induced by the earthquake did not lead to the increase of the overtopping discharge by the waves after the earthquake. (2) Subsidence and lateral displacement at the top of the parapet of the seawall caused by the S2 scale earthquake were approximately 0.12 m-0.2 m and 0.18 m-0.6 m respectively under the condition that the thickness of the sand seabed was 10 m and relative density was 60%. (3) Even though such displacements were induced at the top of the parapet of the seawall, seismic performance of the seawall against the large waves was kept after the earthquake. (author)

Proteomic responses of drought-tolerant and drought-sensitive cotton varieties to drought stress.

Science.gov (United States)

Zhang, Haiyan; Ni, Zhiyong; Chen, Quanjia; Guo, Zhongjun; Gao, Wenwei; Su, Xiujuan; Qu, Yanying

2016-06-01

Drought, one of the most widespread factors reducing agricultural crop productivity, affects biological processes such as development, architecture, flowering and senescence. Although protein analysis techniques and genome sequencing have made facilitated the proteomic study of cotton, information on genetic differences associated with proteomic changes in response to drought between different cotton genotypes is lacking. To determine the effects of drought stress on cotton seedlings, we used two-dimensional polyacrylamide gel electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry to comparatively analyze proteome of drought-responsive proteins during the seedling stage in two cotton (Gossypium hirsutum L.) cultivars, drought-tolerant KK1543 and drought-sensitive Xinluzao26. A total of 110 protein spots were detected on 2-DE maps, of which 56 were identified by MALDI-TOF and MALDI-TOF/TOF mass spectrometry. The identified proteins were mainly associated with metabolism (46.4 %), antioxidants (14.2 %), and transport and cellular structure (23.2 %). Some key proteins had significantly different expression patterns between the two genotypes. In particular, 5-methyltetrahydropteroyltriglutamate-homocysteine methyltransferase, UDP-D-glucose pyrophosphorylase and ascorbate peroxidase were up-regulated in KK1543 compared with Xinluzao26. Under drought stress conditions, the vacuolar H(+)-ATPase catalytic subunit, a 14-3-3g protein, translation initiation factor 5A and pathogenesis-related protein 10 were up-regulated in KK1543, whereas ribosomal protein S12, actin, cytosolic copper/zinc superoxide dismutase, protein disulfide isomerase, S-adenosylmethionine synthase and cysteine synthase were down-regulated in Xinluzao26. This work represents the first characterization of proteomic changes that occur in response to drought in roots of cotton plants. These differentially expressed proteins may be related to

Strong motion duration and earthquake magnitude relationships

International Nuclear Information System (INIS)

Salmon, M.W.; Short, S.A.; Kennedy, R.P.

1992-06-01

Earthquake duration is the total time of ground shaking from the arrival of seismic waves until the return to ambient conditions. Much of this time is at relatively low shaking levels which have little effect on seismic structural response and on earthquake damage potential. As a result, a parameter termed ''strong motion duration'' has been defined by a number of investigators to be used for the purpose of evaluating seismic response and assessing the potential for structural damage due to earthquakes. This report presents methods for determining strong motion duration and a time history envelope function appropriate for various evaluation purposes, for earthquake magnitude and distance, and for site soil properties. There are numerous definitions of strong motion duration. For most of these definitions, empirical studies have been completed which relate duration to earthquake magnitude and distance and to site soil properties. Each of these definitions recognizes that only the portion of an earthquake record which has sufficiently high acceleration amplitude, energy content, or some other parameters significantly affects seismic response. Studies have been performed which indicate that the portion of an earthquake record in which the power (average rate of energy input) is maximum correlates most closely with potential damage to stiff nuclear power plant structures. Hence, this report will concentrate on energy based strong motion duration definitions

Real-time numerical shake prediction and updating for earthquake early warning

Science.gov (United States)

Wang, Tianyun; Jin, Xing; Wei, Yongxiang; Huang, Yandan

2017-12-01

Ground motion prediction is important for earthquake early warning systems, because the region's peak ground motion indicates the potential disaster. In order to predict the peak ground motion quickly and precisely with limited station wave records, we propose a real-time numerical shake prediction and updating method. Our method first predicts the ground motion based on the ground motion prediction equation after P waves detection of several stations, denoted as the initial prediction. In order to correct the prediction error of the initial prediction, an updating scheme based on real-time simulation of wave propagation is designed. Data assimilation technique is incorporated to predict the distribution of seismic wave energy precisely. Radiative transfer theory and Monte Carlo simulation are used for modeling wave propagation in 2-D space, and the peak ground motion is calculated as quickly as possible. Our method has potential to predict shakemap, making the potential disaster be predicted before the real disaster happens. 2008 M S8.0 Wenchuan earthquake is studied as an example to show the validity of the proposed method.

Signals of ENPEMF Used in Earthquake Prediction

Science.gov (United States)

Hao, G.; Dong, H.; Zeng, Z.; Wu, G.; Zabrodin, S. M.

2012-12-01

The signals of Earth's natural pulse electromagnetic field (ENPEMF) is a combination of the abnormal crustal magnetic field pulse affected by the earthquake, the induced field of earth's endogenous magnetic field, the induced magnetic field of the exogenous variation magnetic field, geomagnetic pulsation disturbance and other energy coupling process between sun and earth. As an instantaneous disturbance of the variation field of natural geomagnetism, ENPEMF can be used to predict earthquakes. This theory was introduced by A.A Vorobyov, who expressed a hypothesis that pulses can arise not only in the atmosphere but within the Earth's crust due to processes of tectonic-to-electric energy conversion (Vorobyov, 1970; Vorobyov, 1979). The global field time scale of ENPEMF signals has specific stability. Although the wave curves may not overlap completely at different regions, the smoothed diurnal ENPEMF patterns always exhibit the same trend per month. The feature is a good reference for observing the abnormalities of the Earth's natural magnetic field in a specific region. The frequencies of the ENPEMF signals generally locate in kilo Hz range, where frequencies within 5-25 kilo Hz range can be applied to monitor earthquakes. In Wuhan, the best observation frequency is 14.5 kilo Hz. Two special devices are placed in accordance with the S-N and W-E direction. Dramatic variation from the comparison between the pulses waveform obtained from the instruments and the normal reference envelope diagram should indicate high possibility of earthquake. The proposed detection method of earthquake based on ENPEMF can improve the geodynamic monitoring effect and can enrich earthquake prediction methods. We suggest the prospective further researches are about on the exact sources composition of ENPEMF signals, the distinction between noise and useful signals, and the effect of the Earth's gravity tide and solid tidal wave. This method may also provide a promising application in

Parallel Earthquake Simulations on Large-Scale Multicore Supercomputers

KAUST Repository

Wu, Xingfu; Duan, Benchun; Taylor, Valerie

2011-01-01

, such as California and Japan, scientists have been using numerical simulations to study earthquake rupture propagation along faults and seismic wave propagation in the surrounding media on ever-advancing modern computers over past several decades. In particular

South American Monsoon: Recent Droughts in the Context of Changing Global Circulation.

Science.gov (United States)

Seth, A.; Fernandes, K.; Camargo, S. J.

2016-12-01

The 2013-2015 drought in Southeast Brazil led to water shortages in São Paulo, the country's most populous city. The observed drought during austral summers of 2013/2014 and 2014/2015 and related large-scale dynamics are examined. The 2013-2014 precipitation deficits were more concentrated in the state of São Paulo, while in 2014-2015 moderate deficits were seen throughout the region. We find that a persistent warm sea surface temperature (SST) anomaly in the western tropical Pacific Ocean was an important driver of drought via atmospheric teleconnection in the two December-February seasons. The warm SST and associated convective heating initiated a wave train across the South Pacific. The resulting anticyclonic geopotential height anomaly over the southwest Atlantic expanded the westward margin of the South Atlantic high and prevented low-pressure systems from entering southeast Brazil from midlatitudes. This mechanism suggests a hemispheric symmetry to that proposed for the recent California drought. A first look at CMIP5 model projections to examine the role of large scale circulation changes to drought in the Sao Paulo region will be presented.

POST Earthquake Debris Management - AN Overview

Science.gov (United States)

Sarkar, Raju

Every year natural disasters, such as fires, floods, earthquakes, hurricanes, landslides, tsunami, and tornadoes, challenge various communities of the world. Earthquakes strike with varying degrees of severity and pose both short- and long-term challenges to public service providers. Earthquakes generate shock waves and displace the ground along fault lines. These seismic forces can bring down buildings and bridges in a localized area and damage buildings and other structures in a far wider area. Secondary damage from fires, explosions, and localized flooding from broken water pipes can increase the amount of debris. Earthquake debris includes building materials, personal property, and sediment from landslides. The management of this debris, as well as the waste generated during the reconstruction works, can place significant challenges on the national and local capacities. Debris removal is a major component of every post earthquake recovery operation. Much of the debris generated from earthquake is not hazardous. Soil, building material, and green waste, such as trees and shrubs, make up most of the volume of earthquake debris. These wastes not only create significant health problems and a very unpleasant living environment if not disposed of safely and appropriately, but also can subsequently impose economical burdens on the reconstruction phase. In practice, most of the debris may be either disposed of at landfill sites, reused as materials for construction or recycled into useful commodities Therefore, the debris clearance operation should focus on the geotechnical engineering approach as an important post earthquake issue to control the quality of the incoming flow of potential soil materials. In this paper, the importance of an emergency management perspective in this geotechnical approach that takes into account the different criteria related to the operation execution is proposed by highlighting the key issues concerning the handling of the construction

Tsunami Source Modeling of the 2015 Volcanic Tsunami Earthquake near Torishima, South of Japan

Science.gov (United States)

Sandanbata, O.; Watada, S.; Satake, K.; Fukao, Y.; Sugioka, H.; Ito, A.; Shiobara, H.

2017-12-01

An abnormal earthquake occurred at a submarine volcano named Smith Caldera, near Torishima Island on the Izu-Bonin arc, on May 2, 2015. The earthquake, which hereafter we call "the 2015 Torishima earthquake," has a CLVD-type focal mechanism with a moderate seismic magnitude (M5.7) but generated larger tsunami waves with an observed maximum height of 50 cm at Hachijo Island [JMA, 2015], so that the earthquake can be regarded as a "tsunami earthquake." In the region, similar tsunami earthquakes were observed in 1984, 1996 and 2006, but their physical mechanisms are still not well understood. Tsunami waves generated by the 2015 earthquake were recorded by an array of ocean bottom pressure (OBP) gauges, 100 km northeastern away from the epicenter. The waves initiated with a small downward signal of 0.1 cm and reached peak amplitude (1.5-2.0 cm) of leading upward signals followed by continuous oscillations [Fukao et al., 2016]. For modeling its tsunami source, or sea-surface displacement, we perform tsunami waveform simulations, and compare synthetic and observed waveforms at the OBP gauges. The linear Boussinesq equations are adapted with the tsunami simulation code, JAGURS [Baba et al., 2015]. We first assume a Gaussian-shaped sea-surface uplift of 1.0 m with a source size comparable to Smith Caldera, 6-7 km in diameter. By shifting source location around the caldera, we found the uplift is probably located within the caldera rim, as suggested by Sandanbata et al. [2016]. However, synthetic waves show no initial downward signal that was observed at the OBP gauges. Hence, we add a ring of subsidence surrounding the main uplift, and examine sizes and amplitudes of the main uplift and the subsidence ring. As a result, the model of a main uplift of around 1.0 m with a radius of 4 km surrounded by a ring of small subsidence shows good agreement of synthetic and observed waveforms. The results yield two implications for the deformation process that help us to understanding

Characterization of the Virginia earthquake effects and source parameters from website traffic analysis

Science.gov (United States)

Bossu, R.; Lefebvre, S.; Mazet-Roux, G.; Roussel, F.

2012-12-01

This paper presents an after the fact study of the Virginia earthquake of 2011 August 23 using only the traffic observed on the EMSC website within minutes of its occurrence. Although the EMSC real time information services remain poorly identified in the US, a traffic surge was observed immediately after the earthquake's occurrence. Such surges, known as flashcrowd and commonly observed on our website after felt events within the Euro-Med region are caused by eyewitnesses looking for information about the shaking they have just felt. EMSC developed an approach named flashsourcing to map the felt area, and in some circumstances, the regions affected by severe damage or network disruption. The felt area is mapped simply by locating the Internet Protocol (IP) addresses of the visitors to the website during these surges while the existence of network disruption is detected by the instantaneous loss at the time of earthquake's occurrence of existing Internet sessions originating from the impacted area. For the Virginia earthquake, which was felt at large distances, the effects of the waves propagation are clearly observed. We show that the visits to our website are triggered by the P waves arrival: the first visitors from a given locality reach our website 90s after their location was shaken by the P waves. From a processing point of view, eyewitnesses can then be considered as ground motion detectors. By doing so, the epicentral location is determined through a simple dedicated location algorithm within 2 min of the earthquake's occurrence and 30 km accuracy. The magnitude can be estimated in similar time frame by using existing empirical relationships between the surface of the felt area and the magnitude. Concerning the effects of the earthquake, we check whether one can discriminate localities affected by strong shaking from web traffic analysis. This is actually the case. Localities affected by strong level of shaking exhibit higher ratio of visitors to the number

Updated earthquake catalogue for seismic hazard analysis in Pakistan

Science.gov (United States)

Khan, Sarfraz; Waseem, Muhammad; Khan, Muhammad Asif; Ahmed, Waqas

2018-03-01

A reliable and homogenized earthquake catalogue is essential for seismic hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40-83° N and 20-40° E) includes 36,563 earthquake events, which are reported as 4.0-8.3 moment magnitude (M W) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude M W. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical boundaries in seismic hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, seismicity parameters of the seismic sources are reported, and recommendations are made for seismic hazard assessment studies in Pakistan.

Drought Risk Identification: Early Warning System of Seasonal Agrometeorological Drought

Science.gov (United States)

Dalecios, Nicolas; Spyropoulos, Nicos V.; Tarquis, Ana M.

2014-05-01

By considering drought as a hazard, drought types are classified into three categories, namely meteorological or climatological, agrometeorological or agricultural and hydrological drought and as a fourth class the socioeconomic impacts can be considered. This paper addresses agrometeorological drought affecting agriculture within the risk management framework. Risk management consists of risk assessment, as well as a feedback on the adopted risk reduction measures. And risk assessment comprises three distinct steps, namely risk identification, risk estimation and risk evaluation. This paper deals with the quantification and monitoring of agrometeorological drought, which constitute part of risk identification. For the quantitative assessment of agrometeorological or agricultural drought, as well as the computation of spatiotemporal features, one of the most reliable and widely used indices is applied, namely the Vegetation Health Index (VHI). The computation of VHI is based on satellite data of temperature and the Normalized Difference Vegetation Index (NDVI). The spatiotemporal features of drought, which are extracted from VHI are: areal extent, onset and end time, duration and severity. In this paper, a 20-year (1981-2001) time series of NOAA/AVHRR satellite data is used, where monthly images of VHI are extracted. Application is implemented in Thessaly, which is the major agricultural region of Greece characterized by vulnerable and drought-prone agriculture. The results show that every year there is a seasonal agrometeorological drought with a gradual increase in the areal extent and severity with peaks appearing usually during the summer. Drought monitoring is conducted by monthly remotely sensed VHI images. Drought early warning is developed using empirical relationships of severity and areal extent. In particular, two second-order polynomials are fitted, one for low and the other for high severity drought, respectively. The two fitted curves offer a seasonal

INFLUENCE OF THE SPATIAL ARRANGEMENT OF SEISMIC DETECTORS ON THE ACCURACY OF EARTHQUAKE HYPOCENTRE DETERMINATION

Directory of Open Access Journals (Sweden)

T. G. Aslanov

2016-01-01

Full Text Available Objectives. To determine the coordinates of the seismic focus of an earthquake with a minimum margin of error with the use of an optimal selection of seismic sensors. Method. Seismic wave velocity data, relying on the time discrepancies between the registering of seismic waves on the seismic sensor and the defined error in determining the time difference, were used to identify errors in the location of an earthquake's hypocenter depending on the respective positions of three seismic sensors. Discrepancies between data containing an error and those without it used to determine two hypocenters provide information about the hypocenter locating error. An analysis of the influence of the respective arrangements of the seismic sensors and the earthquake epicentre on the accuracy of determination of epicentre coordinates was carried out. Results. It is established that, in order to improve the accuracy of epicenter and hypocenter earthquake coordinate determination, it is preferable to use different combinations of seismic sensors. The present recommendations are based on the desire to reduce errors in determining the earthquake source coordinates. Due to earthquake epicenter distance determination errors found in different seismic sensors both with increasing and decreasing distance, the hypocenter coordinate determining error has been found to depend on the respective arrangement of seismic sensors and on the earthquake source's geographical location. In order to determine the dependence of the source coordinate determining error on the relative position of three seismic sensors, the third seismic sensor was displaced on a horizontal plane at the location centered at the coordinate of the origin. Conclusion. When selecting seismic sensors it is essential that one of them be located perpendicular to the center of the segment formed by the other two seismic sensors. The probability of a multidirectional error of measurement at the moment of arrival of

Stress Drops of Earthquakes on the Subducting Pacific Plate in the South-East off Hokkaido, Japan

Science.gov (United States)

Saito, Y.; Yamada, T.

2013-12-01

Large earthquakes have been occurring repeatedly in the South-East of Hokkaido, Japan, where the Pacific Plate subducts beneath the Okhotsk Plate in the north-west direction. For example, the 2003 Tokachi-oki earthquake (Mw8.3 determined by USGS) took place in the region on September 26, 2003. Yamanaka and Kikuchi (2003) analyzed the slip distribution of the earthquake and concluded that the 2003 earthquake had ruptured the deeper half of the fault plane of the 1952 Tokachi-oki earthquake. Miyazaki et al. (2004) reported that a notable afterslip was observed at adjacent areas to the coseismic rupture zone of the 2003 earthquake, which suggests that there would be significant heterogeneities of strength, stress and frictional properties on the surface of the Pacific Plate in the region. In addition, some previous studies suggest that the region with a large slip in large earthquakes permanently have large difference of strength and the dynamic frictional stress level and that it would be able to predict the spatial pattern of slip in the next large earthquake by analyzing the stress drop of small earthquakes (e.g. Allmann and Shearer, 2007 and Yamada et al., 2010). We estimated stress drops of 150 earthquakes (4.2 ≤ M ≤ 5.0), using S-coda waves, or the waveforms from 4.00 to 9.11 seconds after the S wave arrivals, of Hi-net data. The 150 earthquakes were the ones that occurred from June, 2002 to December, 2010 in south-east of Hokkaido, Japan, from 40.5N to 43.5N and from 141.0E to 146.5E. First we selected waveforms of the closest earthquakes with magnitudes between 3.0 and 3.2 to individual 150 earthquakes as empirical Green's functions. We then calculated source spectral ratios of the 150 pairs of interested earthquakes and EGFs by deconvolving the individual S-coda waves. We finally estimated corner frequencies of earthquakes from the spectral ratios by assuming the omega-squared model of Boatwright (1978) and calculated stress drops of the earthquakes by

Complex Non-volcanic Tremor in Guerrero Mexico Triggered by the 2010 Mw 8.8 Chilean Earthquake

Science.gov (United States)

Zigone, D.; Campillo, M.; Husker, A. L.; Kostoglodov, V.; Payero, J. S.; Frank, W.; Shapiro, N. M.; Voisin, C.; Cougoulat, G.; Cotte, N.

2010-12-01

In this study we analyze the tremors triggered in Guerrero region (Mexico) by the 2010 magnitude 8.8 Chilean Earthquake using mini-seismic array data from the French-Mexican G-GAP project and broadband data from the Servicio Sismologico Nacional of Mexico. The strong dynamic shaking by the earthquake produced the first observed triggered non-volcanic tremors (NVT) in Mexico so far with at least 3 different types of tremors at different time scales. There was a slow slip event (SSE) occurring at the time of the earthquake, which may have increased the probability of tremor triggering in the region. The first type of observed triggered tremors occurred during the S waves, Love waves and Rayleigh waves as already reported in other subductions zones and continental faults (Miyazawa and Mori, 2005, 2006; Rubinstein et al., 2007; Gomberg et al., 2008; Peng et al, 2009…). The greatest amount of energy and duration accompanies the long-period Rayleigh waves, with smaller bursts during the S and Love waves. For this particular tremor we observed the dispersion of Rayleigh waves in the envelopes of triggered tremors, which indicates a very strong modulation of the source by the passing surface wave. An unexpected short-term tremor occurred approximately one hour later of the arrival of the surface waves on the coastal stations. The NVT has only been previously observed at distances > 100 km inland. It also has a shorter frequency range (3-6 Hz) than other NVT (1-10 Hz) observed in the region. Finally, we observed a significant increase of so-called ambient tremor activity with higher intensity than all triggered NVT during the days after the earthquake. This study adds new types of tremors to the lexicon of triggered NVT observed in the world.

The results of the Seismic Alert System of Mexico SASMEX, during the earthquakes of 7 and 19 of September 2017

Science.gov (United States)

Espinosa Aranda, J. M., Sr.; Cuellar Martinez, A.

2017-12-01

The Seismic Alert System of Mexico, SASMEX began in 1991, is integrated by the seismic alert system of Mexico City and the seismic alert system of Oaxaca. SASMEX has 97 seismic sensors which are distributed in the seismic regions of the Pacific coast and the South of the Trans-Mexican Volcanic Belt of states of Jalisco, Colima, Michoacán, Guerrero, Oaxaca and Puebla. The alert dissemination covers the cities of: Acapulco, Chilpancingo, Morelia, Puebla, Oaxaca, Toluca and Mexico City, reaching the earthquake warnings to more than 25 millions of people. SASMEX has detected correctly more than 5600 earthquakes and warned 156. Mexico City has different alert dissemination systems like several Radio and Tv commercial broadcasters, dedicated radio receivers, EAS-SAME-SARMEX radio receivers and more tha 6700 public loud speakers. The other cities have only some of those systems. The Mw 8.2 Chiapas earthquake on September 7, despite the epicentral distance far of the first seismic detections (more than 180 km) and the low amplitudes of the P waves, the earthquake warning time gave more than 90 seconds to Mexico City before the arrivals of S waves with minor damages to the city in contrast with high damages in towns in the coast. This earthquake offered an opportunity to show the developments and lacks to reduce the risk, such as the need to increase the seismic detection coverage and the earthquake warning dissemination in towns with high seismic vulnerability. The Mw 7.1 Morelos earthquake on September 19 caused thousands of damages and hundreds of deaths and injuries in Mexico City, this earthquake is the second with the most damages after the Mw 8.1 Michoacán earthquake of September 19 on 1985. The earthquake early warning gave 11 seconds after the arrivals of S waves, however the activation occurred few seconds after the P waves arrives to Mexico City, and due to the seismic focus was near to the city, the P waves were felt for the people. The Accelerographic Network

Assessment of earthquake-induced tsunami hazard at a power plant site

International Nuclear Information System (INIS)

Ghosh, A.K.

2008-01-01

This paper presents a study of the tsunami hazard due to submarine earthquakes at a power plant site on the east coast of India. The paper considers various sources of earthquakes from the tectonic information, and records of past earthquakes and tsunamis. Magnitude-frequency relationship for earthquake occurrence rate and a simplified model for tsunami run-up height as a function of earthquake magnitude and the distance between the source and site have been developed. Finally, considering equal likelihood of generation of earthquakes anywhere on each of the faults, the tsunami hazard has been evaluated and presented as a relationship between tsunami height and its mean recurrence interval (MRI). Probability of exceedence of a certain wave height in a given period of time is also presented. These studies will be helpful in making an estimate of the tsunami-induced flooding potential at the site

Evaluation of steam generator tube integrity during earthquakes

Energy Technology Data Exchange (ETDEWEB)

Kusakabe, Takaya; Kodama, Toshio [Mitsubishi Heavy Industries Ltd., Kobe (Japan). Kobe Shipyard and Machinery Works; Takamatsu, Hiroshi; Matsunaga, Tomoya

1999-07-01

This report shows an experimental study on the strength of PWR steam generator (SG) tubes with various defects under cyclic loads which simulate earthquakes. The tests were done using same SG tubing as actual plants with axial and circumferential defects with various length and depth. In the tests, straight tubes were loaded with cyclic bending moments to simulate earthquake waves and number of load cycles at which tube leak started or tube burst was counted. The test results showed that even tubes with very long crack made by EDM more than 80% depth could stand the maximum earthquake, and tubes with corrosion crack were far stronger than those. Thus the integrity of SG tubes with minute potential defects was demonstrated. (author)

The 2009 Samoa-Tonga great earthquake triggered doublet

Science.gov (United States)

Lay, T.; Ammon, C.J.; Kanamori, H.; Rivera, L.; Koper, K.D.; Hutko, Alexander R.

2010-01-01

Great earthquakes (having seismic magnitudes of at least 8) usually involve abrupt sliding of rock masses at a boundary between tectonic plates. Such interplate ruptures produce dynamic and static stress changes that can activate nearby intraplate aftershocks, as is commonly observed in the trench-slope region seaward of a great subduction zone thrust event1-4. The earthquake sequence addressed here involves a rare instance in which a great trench-slope intraplate earthquake triggered extensive interplate faulting, reversing the typical pattern and broadly expanding the seismic and tsunami hazard. On 29 September 2009, within two minutes of the initiation of a normal faulting event with moment magnitude 8.1 in the outer trench-slope at the northern end of the Tonga subduction zone, two major interplate underthrusting subevents (both with moment magnitude 7.8), with total moment equal to a second great earthquake of moment magnitude 8.0, ruptured the nearby subduction zone megathrust. The collective faulting produced tsunami waves with localized regions of about 12metres run-up that claimed 192 lives in Samoa, American Samoa and Tonga. Overlap of the seismic signals obscured the fact that distinct faults separated by more than 50km had ruptured with different geometries, with the triggered thrust faulting only being revealed by detailed seismic wave analyses. Extensive interplate and intraplate aftershock activity was activated over a large region of the northern Tonga subduction zone. ?? 2010 Macmillan Publishers Limited. All rights reserved.

Ground-motion site effects from multimethod shear-wave velocity characterization at 16 seismograph stations deployed for aftershocks of the August 2011 Mineral, Virginia earthquake

Science.gov (United States)

Stephenson, William J.; Odum, Jackson K.; McNamara, Daniel E.; Williams, Robert A.; Angster, Stephen J

2014-01-01

We characterize shear-wave velocity versus depth (Vs profile) at 16 portable seismograph sites through the epicentral region of the 2011 Mw 5.8 Mineral (Virginia, USA) earthquake to investigate ground-motion site effects in the area. We used a multimethod acquisition and analysis approach, where active-source horizontal shear (SH) wave reflection and refraction as well as active-source multichannel analysis of surface waves (MASW) and passive-source refraction microtremor (ReMi) Rayleigh wave dispersion were interpreted separately. The time-averaged shear-wave velocity to a depth of 30 m (Vs30), interpreted bedrock depth, and site resonant frequency were estimated from the best-fit Vs profile of each method at each location for analysis. Using the median Vs30 value (270–715 m/s) as representative of a given site, we estimate that all 16 sites are National Earthquake Hazards Reduction Program (NEHRP) site class C or D. Based on a comparison of simplified mapped surface geology to median Vs30 at our sites, we do not see clear evidence for using surface geologic units as a proxy for Vs30 in the epicentral region, although this may primarily be because the units are similar in age (Paleozoic) and may have similar bulk seismic properties. We compare resonant frequencies calculated from ambient noise horizontal:vertical spectral ratios (HVSR) at available sites to predicted site frequencies (generally between 1.9 and 7.6 Hz) derived from the median bedrock depth and average Vs to bedrock. Robust linear regression of HVSR to both site frequency and Vs30 demonstrate moderate correlation to each, and thus both appear to be generally representative of site response in this region. Based on Kendall tau rank correlation testing, we find that Vs30 and the site frequency calculated from average Vs to median interpreted bedrock depth can both be considered reliable predictors of weak-motion site effects in the epicentral region.

Rapid earthquake magnitude determination for Vrancea early warning system

International Nuclear Information System (INIS)

Marmureanu, Alexandru

2009-01-01

Due to the huge amount of recorded data, an automatic procedure was developed and used to test different methods to rapidly evaluate earthquake magnitude from the first seconds of the P wave. In order to test all the algorithms involved in detection and rapid earthquake magnitude estimation, several tests were performed, in order to avoid false alarms. A special detection algorithm was developed, that is based on the classical STA/LTA algorithm and tuned for early warning purpose. A method to rapidly estimate magnitude in 4 seconds from detection of P wave in the epicenter is proposed. The method was tested on al recorded data, and the magnitude error determination is acceptable taking into account that it is computed from only 3 stations in a very short time interval. (author)

From Multi-Sensors Observations Towards Cross-Disciplinary Study of Pre-Earthquake Signals. What have We Learned from the Tohoku Earthquake?

Science.gov (United States)

Ouzounov, D.; Pulinets, S.; Papadopoulos, G.; Kunitsyn, V.; Nesterov, I.; Hayakawa, M.; Mogi, K.; Hattori, K.; Kafatos, M.; Taylor, P.

2012-01-01

The lessons we have learned from the Great Tohoku EQ (Japan, 2011) how this knowledge will affect our future observation and analysis is the main focus of this presentation.We present multi-sensors observations and multidisciplinary research in our investigation of phenomena preceding major earthquakes. These observations revealed the existence of atmospheric and ionospheric phenomena occurring prior to theM9.0 Tohoku earthquake of March 11, 2011, which indicates s new evidence of a distinct coupling between the lithosphere and atmosphere/ionosphere, as related to underlying tectonic activity. Similar results have been reported before the catastrophic events in Chile (M8.8, 2010), Italy (M6.3, 2009) and Sumatra (M9.3, 2004). For the Tohoku earthquake, our analysis shows a synergy between several independent observations characterizing the state of the lithosphere /atmosphere coupling several days before the onset of the earthquakes, namely: (i) Foreshock sequence change (rate, space and time); (ii) Outgoing Long wave Radiation (OLR) measured at the top of the atmosphere; and (iii) Anomalous variations of ionospheric parameters revealed by multi-sensors observations. We are presenting a cross-disciplinary analysis of the observed pre-earthquake anomalies and will discuss current research in the detection of these signals in Japan. We expect that our analysis will shed light on the underlying physics of pre-earthquake signals associated with some of the largest earthquake events

Propagation of SLF/ELF electromagnetic waves

CERN Document Server

Pan, Weiyan

2014-01-01

This book deals with the SLF/ELF wave propagation, an important branch of electromagnetic theory. The SLF/ELF wave propagation theory is well applied in earthquake electromagnetic radiation, submarine communication, thunderstorm detection, and geophysical prospecting and diagnostics. The propagation of SLF/ELF electromagnetic waves is introduced in various media like the earth-ionospheric waveguide, ionospheric plasma, sea water, earth, and the boundary between two different media or the stratified media. Applications in the earthquake electromagnetic radiation and the submarine communications are also addressed. This book is intended for scientists and engineers in the fields of radio propagation and EM theory and applications. Prof. Pan is a professor at China Research Institute of Radiowave Propagation in Qingdao (China). Dr. Li is a professor at Zhejiang University in Hangzhou (China).

Modelling guided waves in the Alaskan-Aleutian subduction zone

Science.gov (United States)

Coulson, Sophie; Garth, Thomas; Reitbrock, Andreas

2016-04-01

Subduction zone guided wave arrivals from intermediate depth earthquakes (70-300 km depth) have a huge potential to tell us about the velocity structure of the subducting oceanic crust as it dehydrates at these depths. We see guided waves as the oceanic crust has a slower seismic velocity than the surrounding material, and so high frequency energy is retained and delayed in the crustal material. Lower frequency energy is not retained in this crustal waveguide and so travels at faster velocities of the surrounding material. This gives a unique observation at the surface with low frequency energy arriving before the higher frequencies. We constrain this guided wave dispersion by comparing the waveforms recorded in real subduction zones with simulated waveforms, produced using finite difference full waveform modelling techniques. This method has been used to show that hydrated minerals in the oceanic crust persist to much greater depths than accepted thermal petrological subduction zone models would suggest in Northern Japan (Garth & Rietbrock, 2014a), and South America (Garth & Rietbrock, in prep). These observations also suggest that the subducting oceanic mantle may be highly hydrated at intermediate depth by dipping normal faults (Garth & Rietbrock 2014b). We use this guided wave analysis technique to constrain the velocity structure of the down going ~45 Ma Pacific plate beneath Alaska. Dispersion analysis is primarily carried out on guided wave arrivals recorded on the Alaskan regional seismic network. Earthquake locations from global earthquake catalogues (ISC and PDE) and regional earthquake locations from the AEIC (Alaskan Earthquake Information Centre) catalogue are used to constrain the slab geometry and to identify potentially dispersive events. Dispersed arrivals are seen at stations close to the trench, with high frequency (>2 Hz) arrivals delayed by 2 - 4 seconds. This dispersion is analysed to constrain the velocity and width of the proposed waveguide

The Effect of Sonic Booms on Earthquake Warning Systems

Science.gov (United States)

Wurman, Gilead; Haering, Edward A, Jr.; Price, Michael J.

2011-01-01

Several aerospace companies are designing quiet supersonic business jets for service over the United States. These aircraft have the potential to increase the occurrence of mild sonic booms across the country. This leads to interest among earthquake warning (EQW) developers and the general seismological community in characterizing the effect of sonic booms on seismic sensors in the field, their potential impact on EQW systems, and means of discriminating their signatures from those of earthquakes. The SonicBREWS project (Sonic Boom Resistant Earthquake Warning Systems) is a collaborative effort between Seismic Warning Systems, Inc. (SWS) and NASA Dryden Flight Research Center. This project aims to evaluate the effects of sonic booms on EQW sensors. The study consists of exposing high-sample-rate (1000 sps) triaxial accelerometers to sonic booms with overpressures ranging from 10 to 600 Pa in the free field and the built environment. The accelerometers record the coupling of the sonic boom to the ground and surrounding structures, while microphones record the acoustic wave above ground near the sensor. Sonic booms are broadband signals with more high-frequency content than earthquakes. Even a 1000 sps accelerometer will produce a significantly aliased record. Thus the observed peak ground velocity is strongly dependent on the sampling rate, and increases as the sampling rate is reduced. At 1000 sps we observe ground velocities that exceed those of P-waves from ML 3 earthquakes at local distances, suggesting that sonic booms are not negligible for EQW applications. We present the results of several experiments conducted under SonicBREWS showing the effects of typical-case low amplitude sonic booms and worst-case high amplitude booms. We show the effects of various sensor placements and sensor array geometries. Finally, we suggest possible avenues for discriminating sonic booms from earthquakes for the purposes of EQW.

Inertial Forces from Earthquakes on a Hyperloop Pod

OpenAIRE

Heaton, Thomas H.

2017-01-01

High‐speed transit (1300  km/hr) using pods traveling in evacuated tubes has been proposed. This Short Note addresses how earthquake ground shaking is changed when it is experienced by a high‐speed pod that is confined to a track. In particular, earthquake motions can cause lateral deformations of the tube that cause centripetal forces in the pod. I discuss the nature of these forces for the cases of (1) a tube that crosses a fault offset, (2) a tube that is deformed by traveling waves in the...

Extraction of two tsunamis signals generated by earthquakes around the Pacific rim

Directory of Open Access Journals (Sweden)

Chu Yonghai

2014-05-01

Full Text Available As one of the ocean sudden natural disasters, the tsunami is not easily to differentiate from the ocean variation in the open ocean due to the tsunami wave amplitude is lees than one meter with hundreds of kilometers wavelength. But the wave height will increases up to tens of meters with enormous energy when the tsunami aarives at the coast. It would not only devastate entire cities near coast, but also kill miilions of people. It is necessary to forecast and make warning before the tsunami aariving for many countries and regions around the Pacific rim. Two kinds of data were used in this study to extract the signals of 2011 Tohoku tsunami and 2014 Iquique tsunami. Wave undulations from DART (Deep-ocean Assessment and Reporting of Tsunamis buoys and SLA from altimetry could extract the tsunami signals generated by this two earthquake. The signals of Tohoku tsunami were stronger than that of Iquique tsunami probably due to the 2011 Tohoku tsunami was generated by a magnitude 9. 0 earthquake and the 2014 Iquique tsunami was triggered by a magnitude 8. 2 earthquake.

Understanding dynamic friction through spontaneously evolving laboratory earthquakes.

Science.gov (United States)

Rubino, V; Rosakis, A J; Lapusta, N

2017-06-29

Friction plays a key role in how ruptures unzip faults in the Earth's crust and release waves that cause destructive shaking. Yet dynamic friction evolution is one of the biggest uncertainties in earthquake science. Here we report on novel measurements of evolving local friction during spontaneously developing mini-earthquakes in the laboratory, enabled by our ultrahigh speed full-field imaging technique. The technique captures the evolution of displacements, velocities and stresses of dynamic ruptures, whose rupture speed range from sub-Rayleigh to supershear. The observed friction has complex evolution, featuring initial velocity strengthening followed by substantial velocity weakening. Our measurements are consistent with rate-and-state friction formulations supplemented with flash heating but not with widely used slip-weakening friction laws. This study develops a new approach for measuring local evolution of dynamic friction and has important implications for understanding earthquake hazard since laws governing frictional resistance of faults are vital ingredients in physically-based predictive models of the earthquake source.

The Asian earthquakes detected in the ATLAS cavern

CERN Multimedia

2005-01-01

At the end of December, mysterious vibrations were picked up by the deformation sensors under the feet that are to support the ATLAS detector. It transpired that they had detected waves produced by the earthquakes responsible for the terrible tsunami in Asia.

The 2011 Tohoku-oki Earthquake related to a large velocity gradient within the Pacific plate

Science.gov (United States)

Matsubara, Makoto; Obara, Kazushige

2015-04-01

We conduct seismic tomography using arrival time data picked by the high sensitivity seismograph network (Hi-net) operated by National Research Institute for Earth Science and Disaster Prevention (NIED). We used earthquakes off the coast outside the seismic network around the source region of the 2011 Tohoku-oki Earthquake with the centroid depth estimated from moment tensor inversion by NIED F-net (broadband seismograph network) as well as earthquakes within the seismic network determined by Hi-net. The target region, 20-48N and 120-148E, covers the Japanese Islands from Hokkaido to Okinawa. A total of manually picked 4,622,346 P-wave and 3,062,846 S-wave arrival times for 100,733 earthquakes recorded at 1,212 stations from October 2000 to August 2009 is available for use in the tomographic method. In the final iteration, we estimate the P-wave slowness at 458,234 nodes and the S-wave slowness at 347,037 nodes. The inversion reduces the root mean square of the P-wave traveltime residual from 0.455 s to 0.187 s and that of the S-wave data from 0.692 s to 0.228 s after eight iterations (Matsubara and Obara, 2011). Centroid depths are determined using a Green's function approach (Okada et al., 2004) such as in NIED F-net. For the events distant from the seismic network, the centroid depth is more reliable than that determined by NIED Hi-net, since there are no stations above the hypocenter. We determine the upper boundary of the Pacific plate based on the velocity structure and earthquake hypocentral distribution. The upper boundary of the low-velocity (low-V) oceanic crust corresponds to the plate boundary where thrust earthquakes are expected to occur. Where we do not observe low-V oceanic crust, we determine the upper boundary of the upper layer of the double seismic zone within high-V Pacific plate. We assume the depth at the Japan Trench as 7 km. We can investigate the velocity structure within the Pacific plate such as 10 km beneath the plate boundary since the

Napa earthquake: An earthquake in a highly connected world

Science.gov (United States)

Bossu, R.; Steed, R.; Mazet-Roux, G.; Roussel, F.

2014-12-01

The Napa earthquake recently occurred close to Silicon Valley. This makes it a good candidate to study what social networks, wearable objects and website traffic analysis (flashsourcing) can tell us about the way eyewitnesses react to ground shaking. In the first part, we compare the ratio of people publishing tweets and with the ratio of people visiting EMSC (European Mediterranean Seismological Centre) real time information website in the first minutes following the earthquake occurrence to the results published by Jawbone, which show that the proportion of people waking up depends (naturally) on the epicentral distance. The key question to evaluate is whether the proportions of inhabitants tweeting or visiting the EMSC website are similar to the proportion of people waking up as shown by the Jawbone data. If so, this supports the premise that all methods provide a reliable image of the relative ratio of people waking up. The second part of the study focuses on the reaction time for both Twitter and EMSC website access. We show, similarly to what was demonstrated for the Mineral, Virginia, earthquake (Bossu et al., 2014), that hit times on the EMSC website follow the propagation of the P waves and that 2 minutes of website traffic is sufficient to determine the epicentral location of an earthquake on the other side of the Atlantic. We also compare with the publication time of messages on Twitter. Finally, we check whether the number of tweets and the number of visitors relative to the number of inhabitants is correlated to the local level of shaking. Together these results will tell us whether the reaction of eyewitnesses to ground shaking as observed through Twitter and the EMSC website analysis is tool specific (i.e. specific to Twitter or EMSC website) or whether they do reflect people's actual reactions.

Numerical simulations (2D) on the influence of pre-existing local structures and seismic source characteristics in earthquake-volcano interactions

Science.gov (United States)

Farías, Cristian; Galván, Boris; Miller, Stephen A.

2017-09-01

Earthquake triggering of hydrothermal and volcanic systems is ubiquitous, but the underlying processes driving these systems are not well-understood. We numerically investigate the influence of seismic wave interaction with volcanic systems simulated as a trapped, high-pressure fluid reservoir connected to a fluid-filled fault system in a 2-D poroelastic medium. Different orientations and earthquake magnitudes are studied to quantify dynamic and static stress, and pore pressure changes induced by a seismic event. Results show that although the response of the system is mainly dominated by characteristics of the radiated seismic waves, local structures can also play an important role on the system dynamics. The fluid reservoir affects the seismic wave front, distorts the static overpressure pattern induced by the earthquake, and concentrates the kinetic energy of the incoming wave on its boundaries. The static volumetric stress pattern inside the fault system is also affected by the local structures. Our results show that local faults play an important role in earthquake-volcanic systems dynamics by concentrating kinetic energy inside and acting as wave-guides that have a breakwater-like behavior. This generates sudden changes in pore pressure, volumetric expansion, and stress gradients. Local structures also influence the regional Coulomb yield function. Our results show that local structures affect the dynamics of volcanic and hydrothermal systems, and should be taken into account when investigating triggering of these systems from nearby or distant earthquakes.

Could the 2012 Drought in Central U.S. Have Been Anticipated? A Review of NASA Working Group Research

Science.gov (United States)

Wang, S.-Y. Simon; Barandiaran, Danny; Hilburn, Kyle; Houser, Paul; Oglesby, Bob; Pan, Ming; Pinker, Rachel; Santanello, Joe; Schubert, Siegfried; Wang, Hailan;

Connecting slow earthquakes to huge earthquakes.

Science.gov (United States)

Obara, Kazushige; Kato, Aitaro

2016-07-15

Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of their high sensitivity to stress changes in the seismogenic zone. Episodic stress transfer to megathrust source faults leads to an increased probability of triggering huge earthquakes if the adjacent locked region is critically loaded. Careful and precise monitoring of slow earthquakes may provide new information on the likelihood of impending huge earthquakes. Copyright © 2016, American Association for the Advancement of Science.

Drought in a human-modified world: reframing drought definitions, understanding, and analysis approaches

Science.gov (United States)

Van Loon, Anne F.; Stahl, Kerstin; Di Baldassarre, Giuliano; Clark, Julian; Rangecroft, Sally; Wanders, Niko; Gleeson, Tom; Van Dijk, Albert I. J. M.; Tallaksen, Lena M.; Hannaford, Jamie; Uijlenhoet, Remko; Teuling, Adriaan J.; Hannah, David M.; Sheffield, Justin; Svoboda, Mark; Verbeiren, Boud; Wagener, Thorsten; Van Lanen, Henny A. J.

2016-09-01

In the current human-modified world, or Anthropocene, the state of water stores and fluxes has become dependent on human as well as natural processes. Water deficits (or droughts) are the result of a complex interaction between meteorological anomalies, land surface processes, and human inflows, outflows, and storage changes. Our current inability to adequately analyse and manage drought in many places points to gaps in our understanding and to inadequate data and tools. The Anthropocene requires a new framework for drought definitions and research. Drought definitions need to be revisited to explicitly include human processes driving and modifying soil moisture drought and hydrological drought development. We give recommendations for robust drought definitions to clarify timescales of drought and prevent confusion with related terms such as water scarcity and overexploitation. Additionally, our understanding and analysis of drought need to move from single driver to multiple drivers and from uni-directional to multi-directional. We identify research gaps and propose analysis approaches on (1) drivers, (2) modifiers, (3) impacts, (4) feedbacks, and (5) changing the baseline of drought in the Anthropocene. The most pressing research questions are related to the attribution of drought to its causes, to linking drought impacts to drought characteristics, and to societal adaptation and responses to drought. Example questions include (i) What are the dominant drivers of drought in different parts of the world? (ii) How do human modifications of drought enhance or alleviate drought severity? (iii) How do impacts of drought depend on the physical characteristics of drought vs. the vulnerability of people or the environment? (iv) To what extent are physical and human drought processes coupled, and can feedback loops be identified and altered to lessen or mitigate drought? (v) How should we adapt our drought analysis to accommodate changes in the normal situation (i.e. what

Rapid Large Earthquake and Run-up Characterization in Quasi Real Time

Science.gov (United States)

Bravo, F. J.; Riquelme, S.; Koch, P.; Cararo, S.

2017-12-01

Several test in quasi real time have been conducted by the rapid response group at CSN (National Seismological Center) to characterize earthquakes in Real Time. These methods are known for its robustness and realibility to create Finite Fault Models. The W-phase FFM Inversion, The Wavelet Domain FFM and The Body Wave and FFM have been implemented in real time at CSN, all these algorithms are running automatically and triggered by the W-phase Point Source Inversion. Dimensions (Large and Width ) are predefined by adopting scaling laws for earthquakes in subduction zones. We tested the last four major earthquakes occurred in Chile using this scheme: The 2010 Mw 8.8 Maule Earthquake, The 2014 Mw 8.2 Iquique Earthquake, The 2015 Mw 8.3 Illapel Earthquake and The 7.6 Melinka Earthquake. We obtain many solutions as time elapses, for each one of those we calculate the run-up using an analytical formula. Our results are in agreements with some FFM already accepted by the sicentific comunnity aswell as run-up observations in the field.

Spatial Relationships between Deep-focus Earthquakes and Structural Heterogeneities within the Subducting Slabs of the Western Pacific Subduction Zones

Science.gov (United States)

Chen, M.; Kiser, E.; Niu, F.

2016-12-01

The nature of deep-focus earthquakes with depths greater than 300 km has long been controversial. Mechanisms that may promote brittle deformation at such depths include dehydration embrittlement, phase transformational faulting, and thermal runaway instabilities. Of these, the most commonly referenced mechanism—phase transformational faulting—involves the breakdown of metastable olivine within the core of a cold subducting slab. Seismic observations of the metastable olivine wedge, as well as its spatial relationship to deep-focus seismicity, are limited. Classical 1-D ray-theory based tomography images indicate that deep-focus hypocenters coincide with the highest wave speed anomalies within the slab, traditionally viewed as the slab's cold core. However, our latest full waveform tomography images of the Kuril, Japan, and Izu-Bonin slabs show systematically deep-focus earthquakes located near the top of high wave speed regions, with hypocentral or centroid locations determined by EHB, global CMT, or JMA. In order to reduce location bias in global CMT solutions due to unmodeled 3-D structure, we relocate tens of deep-focus earthquakes within the new 3-D structural model based on a full wavefield modeling code SPECFEM3D_GLOBE, with seismic waves simulated to the shortest period of 9 seconds. We also determine the centroid locations of high-frequency energy (0.8 Hz-2 Hz) from back-projection results of several large earthquakes to understand how rupture propagates within the slab. The spatial correlations between the 3-D wave speed model and high-precision centroid locations from both long period and high frequency seismic waves further indicate that the deep-focus earthquakes occur and propagate near the top of the subducting slab. We will discuss the constraints that these relationships place on the mechanism of deep-focus earthquakes.

Engineering Seismic Base Layer for Defining Design Earthquake Motion

International Nuclear Information System (INIS)

Yoshida, Nozomu

2008-01-01

Engineer's common sense that incident wave is common in a widespread area at the engineering seismic base layer is shown not to be correct. An exhibiting example is first shown, which indicates that earthquake motion at the ground surface evaluated by the analysis considering the ground from a seismic bedrock to a ground surface simultaneously (continuous analysis) is different from the one by the analysis in which the ground is separated at the engineering seismic base layer and analyzed separately (separate analysis). The reason is investigated by several approaches. Investigation based on eigen value problem indicates that the first predominant period in the continuous analysis cannot be found in the separate analysis, and predominant period at higher order does not match in the upper and lower ground in the separate analysis. The earthquake response analysis indicates that reflected wave at the engineering seismic base layer is not zero, which indicates that conventional engineering seismic base layer does not work as expected by the term ''base''. All these results indicate that wave that goes down to the deep depths after reflecting in the surface layer and again reflects at the seismic bedrock cannot be neglected in evaluating the response at the ground surface. In other words, interaction between the surface layer and/or layers between seismic bedrock and engineering seismic base layer cannot be neglected in evaluating the earthquake motion at the ground surface

Quasi real-time estimation of the moment magnitude of large earthquake from static strain changes

Science.gov (United States)

Itaba, S.

2016-12-01

The 2011 Tohoku-Oki (off the Pacific coast of Tohoku) earthquake, of moment magnitude 9.0, was accompanied by large static strain changes (10-7), as measured by borehole strainmeters operated by the Geological Survey of Japan in the Tokai, Kii Peninsula, and Shikoku regions. A fault model for the earthquake on the boundary between the Pacific and North American plates, based on these borehole strainmeter data, yielded a moment magnitude of 8.7. On the other hand, based on the seismic wave, the prompt report of the magnitude which the Japan Meteorological Agency (JMA) announced just after earthquake occurrence was 7.9. Such geodetic moment magnitudes, derived from static strain changes, can be estimated almost as rapidly as determinations using seismic waves. I have to verify the validity of this method in some cases. In the case of this earthquake's largest aftershock, which occurred 29 minutes after the mainshock. The prompt report issued by JMA assigned this aftershock a magnitude of 7.3, whereas the moment magnitude derived from borehole strain data is 7.6, which is much closer to the actual moment magnitude of 7.7. In order to grasp the magnitude of a great earthquake earlier, several methods are now being suggested to reduce the earthquake disasters including tsunami. Our simple method of using static strain changes is one of the strong methods for rapid estimation of the magnitude of large earthquakes, and useful to improve the accuracy of Earthquake Early Warning.

MIGRATION OF SEISMIC AND VOLCANIC ACTIVITY AS DISPLAY OF WAVE GEODYNAMIC PROCESS

Directory of Open Access Journals (Sweden)

Alexander V. Vikulin

2012-01-01

Full Text Available Publications about the earthquake foci migration have been reviewed. An important result of such studies is establishment of wave nature of seismic activity migration that is manifested by two types of rotational waves; such waves are responsible for interaction between earthquakes foci and propagate with different velocities. Waves determining long-range interaction of earthquake foci are classified as Type 1; their limiting velocities range from 1 to 10 cm/s. Waves determining short-range interaction of foreshocks and aftershocks of individual earthquakes are classified as Type 2; their velocities range from 1 to 10 km/s. According to the classification described in [Bykov, 2005], these two types of migration waves correspond to slow and fast tectonic waves. The most complete data on earthquakes (for a period over 4.1 million of years and volcanic eruptions (for 12 thousand years of the planet are consolidated in a unified systematic format and analyzed by methods developed by the authors. For the Pacific margin, Alpine-Himalayan belt and the Mid-Atlantic Ridge, which are the three most active zones of the Earth, new patterns of spatial and temporal distribution of seismic and volcanic activity are revealed; they correspond to Type 1 of rotational waves. The wave nature of the migration of seismic and volcanic activity is confirmed. A new approach to solving problems of geodynamics is proposed with application of the data on migration of seismic and volcanic activity, which are consolidated in this study, in combination with data on velocities of movement of tectonic plate boundaries. This approach is based on the concept of integration of seismic, volcanic and tectonic processes that develop in the block geomedium and interact with each other through rotating waves with a symmetric stress tensor. The data obtained in this study give grounds to suggest that a geodynamic value, that is mechanically analogous to an impulse

Connecting slow earthquakes to huge earthquakes

OpenAIRE

Obara, Kazushige; Kato, Aitaro

2016-01-01

Slow earthquakes are characterized by a wide spectrum of fault slip behaviors and seismic radiation patterns that differ from those of traditional earthquakes. However, slow earthquakes and huge megathrust earthquakes can have common slip mechanisms and are located in neighboring regions of the seismogenic zone. The frequent occurrence of slow earthquakes may help to reveal the physics underlying megathrust events as useful analogs. Slow earthquakes may function as stress meters because of th...

Comprehensive analysis of earthquake source spectra in southern California

OpenAIRE

Shearer, Peter M.; Prieto, Germán A.; Hauksson, Egill

2006-01-01

We compute and analyze P wave spectra from earthquakes in southern California between 1989 and 2001 using a method that isolates source-, receiver-, and path-dependent terms. We correct observed source spectra for attenuation using both fixed and spatially varying empirical Green's function methods. Estimated Brune-type stress drops for over 60,000 M_L = 1.5 to 3.1 earthquakes range from 0.2 to 20 MPa with no dependence on moment or local b value. Median computed stress drop increases with de...

POST Earthquake Debris Management — AN Overview

Science.gov (United States)

Sarkar, Raju

Every year natural disasters, such as fires, floods, earthquakes, hurricanes, landslides, tsunami, and tornadoes, challenge various communities of the world. Earthquakes strike with varying degrees of severity and pose both short- and long-term challenges to public service providers. Earthquakes generate shock waves and displace the ground along fault lines. These seismic forces can bring down buildings and bridges in a localized area and damage buildings and other structures in a far wider area. Secondary damage from fires, explosions, and localized flooding from broken water pipes can increase the amount of debris. Earthquake debris includes building materials, personal property, and sediment from landslides. The management of this debris, as well as the waste generated during the reconstruction works, can place significant challenges on the national and local capacities. Debris removal is a major component of every post earthquake recovery operation. Much of the debris generated from earthquake is not hazardous. Soil, building material, and green waste, such as trees and shrubs, make up most of the volume of earthquake debris. These wastes not only create significant health problems and a very unpleasant living environment if not disposed of safely and appropriately, but also can subsequently impose economical burdens on the reconstruction phase. In practice, most of the debris may be either disposed of at landfill sites, reused as materials for construction or recycled into useful commodities Therefore, the debris clearance operation should focus on the geotechnical engineering approach as an important post earthquake issue to control the quality of the incoming flow of potential soil materials. In this paper, the importance of an emergency management perspective in this geotechnical approach that takes into account the different criteria related to the operation execution is proposed by highlighting the key issues concerning the handling of the construction

Constraints on the source parameters of low-frequency earthquakes on the San Andreas Fault

Science.gov (United States)

Thomas, Amanda M.; Beroza, Gregory C.; Shelly, David R.

2016-01-01

Low-frequency earthquakes (LFEs) are small repeating earthquakes that occur in conjunction with deep slow slip. Like typical earthquakes, LFEs are thought to represent shear slip on crustal faults, but when compared to earthquakes of the same magnitude, LFEs are depleted in high-frequency content and have lower corner frequencies, implying longer duration. Here we exploit this difference to estimate the duration of LFEs on the deep San Andreas Fault (SAF). We find that the M ~ 1 LFEs have typical durations of ~0.2 s. Using the annual slip rate of the deep SAF and the average number of LFEs per year, we estimate average LFE slip rates of ~0.24 mm/s. When combined with the LFE magnitude, this number implies a stress drop of ~104 Pa, 2 to 3 orders of magnitude lower than ordinary earthquakes, and a rupture velocity of 0.7 km/s, 20% of the shear wave speed. Typical earthquakes are thought to have rupture velocities of ~80–90% of the shear wave speed. Together, the slow rupture velocity, low stress drops, and slow slip velocity explain why LFEs are depleted in high-frequency content relative to ordinary earthquakes and suggest that LFE sources represent areas capable of relatively higher slip speed in deep fault zones. Additionally, changes in rheology may not be required to explain both LFEs and slow slip; the same process that governs the slip speed during slow earthquakes may also limit the rupture velocity of LFEs.

Rocking motion of structures under earthquakes. Overturning of 2-DOF system

International Nuclear Information System (INIS)

Kobayashi, Koichi; Watanabe, Tetsuya; Tanaka, Kihachiro; Tomoda, Akinori

2011-01-01

In recent years, huge earthquakes happen, for example, The South Hyogo prefecture Earthquake in 1995, The Mid Niigata Prefecture Earthquake in 2004, The Iwate-Miyagi Nairiku Earthquake in 2008. In The Niigataken Chuetsu-oki Earthquake in 2007, hundreds of drums fell down and water spilled out. A lot of studies about rocking behavior of rigid body had been performed from 1960's. However, these studies were only for a specific condition of the structure size or input vibration characteristics. Therefore, generalizes fall condition for earthquake is required. This paper deals with the analytical and the experimental study of the rocking vibration of 1-DOF rocking system, 2-DOF vibration-rocking system and 2-DOF rocking system under earthquakes. In this study, the equation of motion for each rocking systems are developed. The numerical model of 2-DOF rocking system is evaluated by free rocking experiment. In this paper, 'Overturning Map' which can distinguish whether structures falls or not is proposed. The overturning map of each rocking systems excited by the artificial earthquake wave calculated from the design spectrum is shown. As the result, overturning condition of structures is clarified. (author)

Seismoacoustic Coupled Signals From Earthquakes in Central Italy : Epicentral and Secondary Sources of Infrasound

NARCIS (Netherlands)

Shani Kadmiel, S.; Assink, Jelle D.; Smets, P.S.M.; Evers, L.G.

2018-01-01

In this study we analyze infrasound signals from three earthquakes in central Italy. The M_w 6.0 Amatrice, M_w 5.9 Visso, and M_w 6.5 Norcia earthquakes generated significant epicentral ground motions that couple to the atmosphere and produce infrasonic waves.

Decadal summer drought frequency in China: the increasing influence of the Atlantic Multi-decadal Oscillation

International Nuclear Information System (INIS)

Qian, Chengcheng; Yu, Jin-Yi; Chen, Ge

2014-01-01

Decadal variations in summer drought events during 1956–2005 are examined over Eastern China to identify their leading variability modes and their linkages to the Pacific Decadal Oscillation (PDO), Atlantic Multi-decadal Oscillation (AMO), and global warming. The PDO influence is found to dominate China drought frequency from the 1960s to early 1990s via modulating the Western Pacific Subtropical High and the Mongolian High. The four-pole drought pattern produced by the PDO diminished after the early 1990s, being replaced by a dipolar drought pattern that is produced by the AMO via a Eurasian wave train emanating from North Atlantic to China. The increasing influence of the AMO on China drought since the early 1990s is further shown to be a consequence of global warming. This study indicates that the early 1990s is a time when the Atlantic began to exert a stronger influence on climate over China and even larger part of Asia. (letter)

Blended Drought Index: Integrated Drought Hazard Assessment in the Cuvelai-Basin

Directory of Open Access Journals (Sweden)

Robert Luetkemeier

2017-07-01

Full Text Available Drought is one of the major threats to societies in Sub-Saharan Africa, as the majority of the population highly depends on rain-fed subsistence agriculture and traditional water supply systems. Hot-spot areas of potential drought impact need to be identified to reduce risk and adapt a growing population to a changing environment. This paper presents the Blended Drought Index (BDI, an integrated tool for estimating the impact of drought as a climate-induced hazard in the semi-arid Cuvelai-Basin of Angola and Namibia. It incorporates meteorological and agricultural drought characteristics that impair the population’s ability to ensure food and water security. The BDI uses a copula function to combine common standardized drought indicators that describe precipitation, evapotranspiration, soil moisture and vegetation conditions. Satellite remote sensing products were processed to analyze drought frequency, severity and duration. As the primary result, an integrated drought hazard map was built to spatially depict drought hot-spots. Temporally, the BDI correlates well with millet/sorghum yield (r = 0.51 and local water consumption (r = −0.45 and outperforms conventional indicators. In the light of a drought’s multifaceted impact on society, the BDI is a simple and transferable tool to identify areas highly threatened by drought in an integrated manner.

Exploration of deep S-wave velocity structure using microtremor array technique to estimate long-period ground motion

International Nuclear Information System (INIS)

Sato, Hiroaki; Higashi, Sadanori; Sato, Kiyotaka

2007-01-01

In this study, microtremor array measurements were conducted at 9 sites in the Niigata plain to explore deep S-wave velocity structures for estimation of long-period earthquake ground motion. The 1D S-wave velocity profiles in the Niigata plain are characterized by 5 layers with S-wave velocities of 0.4, 0.8, 1.5, 2.1 and 3.0 km/s, respectively. The depth to the basement layer is deeper in the Niigata port area located at the Japan sea side of the Niigata plain. In this area, the basement depth is about 4.8 km around the Seirou town and about 4.1 km around the Niigata city, respectively. These features about the basement depth in the Niigata plain are consistent with the previous surveys. In order to verify the profiles derived from microtremor array exploration, we estimate the group velocities of Love wave for four propagation paths of long-period earthquake ground motion during Niigata-ken tyuetsu earthquake by multiple filter technique, which were compared with the theoretical ones calculated from the derived profiles. As a result, it was confirmed that the group velocities from the derived profiles were in good agreement with the ones from long-period earthquake ground motion records during Niigata-ken tyuetsu earthquake. Furthermore, we applied the estimation method of design basis earthquake input for seismically isolated nuclear power facilities by using normal mode solution to estimate long-period earthquake ground motion during Niigata-ken tyuetsu earthquake. As a result, it was demonstrated that the applicability of the above method for the estimation of long-period earthquake ground motion were improved by using the derived 1D S-wave velocity profile. (author)

An Overview of Soil Models for Earthquake Response Analysis

Directory of Open Access Journals (Sweden)

Halida Yunita

2015-01-01

Full Text Available Earthquakes can damage thousands of buildings and infrastructure as well as cause the loss of thousands of lives. During an earthquake, the damage to buildings is mostly caused by the effect of local soil conditions. Depending on the soil type, the earthquake waves propagating from the epicenter to the ground surface will result in various behaviors of the soil. Several studies have been conducted to accurately obtain the soil response during an earthquake. The soil model used must be able to characterize the stress-strain behavior of the soil during the earthquake. This paper compares equivalent linear and nonlinear soil model responses. Analysis was performed on two soil types, Site Class D and Site Class E. An equivalent linear soil model leads to a constant value of shear modulus, while in a nonlinear soil model, the shear modulus changes constantly,depending on the stress level, and shows inelastic behavior. The results from a comparison of both soil models are displayed in the form of maximum acceleration profiles and stress-strain curves.

Chapter 8: Droughts, Floods, and Wildfires

Science.gov (United States)

Wehner, M. F.; Arnold, J. R.; Knutson, T.; Kunkel, K. E.; LeGrande, A. N.

2017-01-01

Recent droughts and associated heat waves have reached record intensity in some regions of the United States; however, by geographical scale and duration, the Dust Bowl era of the 1930s remains the benchmark drought and extreme heat event in the historical record (very high confidence). While by some measures drought has decreased over much of the continental United States in association with long-term increases in precipitation, neither the precipitation increases nor inferred drought decreases have been confidently attributed to anthropogenic forcing. The human effect on recent major U.S. droughts is complicated. Little evidence is found for a human influence on observed precipitation deficits, but much evidence is found for a human influence on surface soil moisture deficits due to increased evapotranspiration caused by higher temperatures. Future decreases in surface (top 10 cm) soil moisture from anthropogenic forcing over most of the United States are likely as the climate warms under higher scenarios. Substantial reductions in western U.S. winter and spring snowpack are projected as the climate warms. Earlier spring melt and reduced snow water equivalent have been formally attributed to human-induced warming (high confidence) and will very likely be exacerbated as the climate continues to warm (very high confidence). Under higher scenarios, and assuming no change to current water resources management, chronic, long-duration hydrological drought is increasingly possible by the end of this century. Detectable changes in some classes of flood frequency have occurred in parts of the United States and are a mix of increases and decreases. Extreme precipitation, one of the controlling factors in flood statistics, is observed to have generally increased and is projected to continue to do so across the United States in a warming atmosphere. However, formal attribution approaches have not established a significant connection of increased riverine flooding to human

The effect of severe drought and management after drought on the ...

African Journals Online (AJOL)

The False Thornveld of the Eastern Cape experienced a particularly intense drought during the 1982/1983 growing season. Extensive grass mortality took place during the drought. After the drought, recovery was particularly sensitive to the post-drought management treatment applied. Veld that was grazed immediately ...

Adaptation to high temperature mitigates the impact of water deficit during combined heat and drought stress in C3 sunflower and C4 maize varieties with contrasting drought tolerance.

Science.gov (United States)

Killi, Dilek; Bussotti, Filippo; Raschi, Antonio; Haworth, Matthew

2017-02-01

Heat and drought stress frequently occur together, however, their impact on plant growth and photosynthesis (P N ) is unclear. The frequency, duration and severity of heat and drought stress events are predicted to increase in the future, having severe implications for agricultural productivity and food security. To assess the impact on plant gas exchange, physiology and morphology we grew drought tolerant and sensitive varieties of C3 sunflower (Helianthus annuus) and C4 maize (Zea mays) under conditions of elevated temperature for 4 weeks prior to the imposition of water deficit. The negative impact of temperature on P N was most apparent in sunflower. The drought tolerant sunflower retained ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) activity under heat stress to a greater extent than its drought sensitive counterpart. Maize exhibited no varietal difference in response to increased temperature. In contrast to previous studies, where a sudden rise in temperature induced an increase in stomatal conductance (G s ), we observed no change or a reduction in G s with elevated temperature, which alongside lower leaf area mitigated the impact of drought at the higher temperature. The drought tolerant sunflower and maize varieties exhibited greater investment in root-systems, allowing greater uptake of the available soil water. Elevated temperatures associated with heat-waves will have profound negative impacts on crop growth in both sunflower and maize, but the deleterious effect on P N was less apparent in the drought tolerant sunflower and both maize varieties. As C4 plants generally exhibit water use efficiency (WUE) and resistance to heat stress, selection on the basis of tolerance to heat and drought stress would be more beneficial to the yields of C3 crops cultivated in drought prone semi-arid regions. © 2016 Scandinavian Plant Physiology Society.

Using Tectonic Tremor to Constrain Seismic-wave Attenuation in Cascadia

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Littel, G.; Thomas, A.; Baltay, A.

2017-12-01

In addition to fast, seismic slip, many subduction zones also host slow, largely aseismic slip, accompanied by a weak seismic signal known as tectonic tremor. Tremor is a small amplitude, low-frequency seismic signal that originates at the plate interface, down-dip of where large earthquakes typically occur. The Cascadia subduction zone has not seen a large megathrust earthquake since 1700, yet its recurrence interval of 350-500 years motivates heightened interest in understanding the seismic hazard of the region. Of great importance is to understand the degree to which waves are attenuated as they leave the plate interface and travel towards populated regions of interest. Ground motion prediction equations (GMPEs) relate ground motion to a number of parameters, including earthquake magnitude, depth, style of faulting, and anelastic attenuation, and are typically determined empirically from earthquake ground motion recordings. In Cascadia, however, earthquakes of the moderate size typically used to constrain GMPEs occur relatively infrequently compared to tectonic tremor events, which, in contrast, occur periodically approximately every 10-19 months. Studies have shown that the abundant tectonic tremor in Cascadia, despite its small amplitudes, can be used to constrain seismic wave attenuation in GMPEs. Here we quantify seismic wave attenuation and determine its spatial variations in Cascadia by performing an inversion using tremor ground motion amplitudes, taken as peak ground acceleration (PGA) and peak ground velocity (PGV) from 1 min window waveforms of each individual tremor event. We estimate the anelastic attenuation parameter for varying regional sections along the Cascadia margin. Changes in seismic-wave attenuation along the Cascadia Subduction Zone could result in significantly different ground motions in the event of a very large earthquake, hence quantifying attenuation may help to better estimate the severity of shaking in densely populated

Regional earthquakes followed by delayed ground uplifts at Campi Flegrei Caldera, Italy: Arguments for a causal link

Science.gov (United States)

Lupi, Matteo; Frehner, Marcel; Weis, Philipp; Skelton, Alasdair; Saenger, Erik H.; Tisato, Nicola; Geiger, Sebastian; Chiodini, Giovanni; Driesner, Thomas

2017-09-01

Earthquake-triggered volcanic activity promoted by dynamic and static stresses are considered rare and difficult-to-capture geological processes. Calderas are ideal natural laboratories to investigate earthquake-volcano interactions due to their sensitivity to incoming seismic energy. The Campi Flegrei caldera, Italy, is one of the most monitored volcanic systems worldwide. We compare ground elevation time series at Campi Flegrei with earthquake catalogues showing that uplift events at Campi Flegrei are associated with large regional earthquakes. Such association is supported by (yet non-definitive) binomial tests. Over a 70-year time window we identify 14 uplift events, 12 of them were preceded by an earthquake, and for 8 of them the earthquake-to-uplift timespan ranges from immediate responses to 1.2 yr. Such variability in the response delay may be due to the preparedness of the system with faster responses probably occurring in periods during which the Campi Flegrei system was already in a critical state. To investigate the process that may be responsible for the proposed association we simulate the propagation of elastic waves and show that passing body waves impose high dynamic strains at the roof of the magmatic reservoir of the Campi Flegrei at about 7 km depth. This may promote a short-lived embrittlement of the magma reservoir's carapace otherwise marked by a ductile behaviour. Such failure allows magma and exsolved volatiles to be released from the magmatic reservoir. The fluids, namely exsolved volatiles and/or melts, ascend through a nominally plastic zone above the magmatic reservoir. This mechanism and the associated inherent uncertainties require further investigations but the new concept already implies that geological processes triggered by passing seismic waves may become apparent several months after passage of the seismic waves.

Development of rupture process analysis method for great earthquakes using Direct Solution Method

Science.gov (United States)

Yoshimoto, M.; Yamanaka, Y.; Takeuchi, N.

2010-12-01

Conventional rupture process analysis methods using teleseismic body waves were based on ray theory. Therefore, these methods have the following problems in applying to great earthquakes such as 2004 Sumatra earthquake: (1) difficulty in computing all later phases such as the PP reflection phase, (2) impossibility of computing called “W phase”, the long period phase arriving before S wave, (3) implausibility of hypothesis that the distance is far enough from the observation points to the hypocenter compared to the fault length. To solve above mentioned problems, we have developed a new method which uses the synthetic seismograms computed by the Direct Solution Method (DSM, e.g. Kawai et al. 2006) as Green’s functions. We used the DSM software (http://www.eri.u-tokyo.ac.jp/takeuchi/software/) for computing the Green’s functions up to 1 Hz for the IASP91 (Kennett and Engdahl, 1991) model, and determined the final slip distributions using the waveform inversion method (Kikuchi et al. 2003). First we confirmed whether the Green’s functions computed by DSM were accurate in higher frequencies up to 1 Hz. Next we performed the rupture process analysis of this new method for Mw8.0 (GCMT) large Solomon Islands earthquake on April 1, 2007. We found that this earthquake consisted of two asperities and the rupture propagated across the subducting Sinbo ridge. The obtained slip distribution better correlates to the aftershock distributions than existing method. Furthermore, this new method keep same accuracy of existing method (which has the advantage of calculating) with respect to direct P-wave and reflection phases near the source, and also accurately calculate the later phases such a PP-wave.

A new strategy for earthquake focal mechanisms using waveform-correlation-derived relative polarities and cluster analysis: Application to the 2014 Long Valley Caldera earthquake swarm

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Shelly, David R.; Hardebeck, Jeanne L.; Ellsworth, William L.; Hill, David P.

2016-01-01

In microseismicity analyses, reliable focal mechanisms can typically be obtained for only a small subset of located events. We address this limitation here, presenting a framework for determining robust focal mechanisms for entire populations of very small events. To achieve this, we resolve relative P and S wave polarities between pairs of waveforms by using their signed correlation coefficients—a by-product of previously performed precise earthquake relocation. We then use cluster analysis to group events with similar patterns of polarities across the network. Finally, we apply a standard mechanism inversion to the grouped data, using either catalog or correlation-derived P wave polarity data sets. This approach has great potential for enhancing analyses of spatially concentrated microseismicity such as earthquake swarms, mainshock-aftershock sequences, and industrial reservoir stimulation or injection-induced seismic sequences. To demonstrate its utility, we apply this technique to the 2014 Long Valley Caldera earthquake swarm. In our analysis, 85% of the events (7212 out of 8494 located by Shelly et al. [2016]) fall within five well-constrained mechanism clusters, more than 12 times the number with network-determined mechanisms. Of the earthquakes we characterize, 3023 (42%) have magnitudes smaller than 0.0. We find that mechanism variations are strongly associated with corresponding hypocentral structure, yet mechanism heterogeneity also occurs where it cannot be resolved by hypocentral patterns, often confined to small-magnitude events. Small (5–20°) rotations between mechanism orientations and earthquake location trends persist when we apply 3-D velocity models and might reflect a geometry of en echelon, interlinked shear, and dilational faulting.

Seismological investigation of earthquakes in the New Madrid Seismic Zone

International Nuclear Information System (INIS)

Herrmann, R.B.; Nguyen, B.

1993-08-01

Earthquake activity in the New Madrid Seismic Zone had been monitored by regional seismic networks since 1975. During this time period, over 3,700 earthquakes have been located within the region bounded by latitudes 35 degrees--39 degrees N and longitudes 87 degrees--92 degrees W. Most of these earthquakes occur within a 1.5 degrees x 2 degrees zone centered on the Missouri Bootheel. Source parameters of larger earthquakes in the zone and in eastern North America are determined using surface-wave spectral amplitudes and broadband waveforms for the purpose of determining the focal mechanism, source depth and seismic moment. Waveform modeling of broadband data is shown to be a powerful tool in defining these source parameters when used complementary with regional seismic network data, and in addition, in verifying the correctness of previously published focal mechanism solutions

Retrospective stress-forecasting of earthquakes

Science.gov (United States)

Gao, Yuan; Crampin, Stuart

2015-04-01

Observations of changes in azimuthally varying shear-wave splitting (SWS) above swarms of small earthquakes monitor stress-induced changes to the stress-aligned vertical microcracks pervading the upper crust, lower crust, and uppermost ~400km of the mantle. (The microcracks are intergranular films of hydrolysed melt in the mantle.) Earthquakes release stress, and an appropriate amount of stress for the relevant magnitude must accumulate before each event. Iceland is on an extension of the Mid-Atlantic Ridge, where two transform zones, uniquely run onshore. These onshore transform zones provide semi-continuous swarms of small earthquakes, which are the only place worldwide where SWS can be routinely monitored. Elsewhere SWS must be monitored above temporally-active occasional swarms of small earthquakes, or in infrequent SKS and other teleseismic reflections from the mantle. Observations of changes in SWS time-delays are attributed to stress-induced changes in crack aspect-ratios allowing stress-accumulation and stress-relaxation to be identified. Monitoring SWS in SW Iceland in 1988, stress-accumulation before an impending earthquake was recognised and emails were exchanged between the University of Edinburgh (EU) and the Iceland Meteorological Office (IMO). On 10th November 1988, EU emailed IMO that a M5 earthquake could occur soon on a seismically-active fault plane where seismicity was still continuing following a M5.1 earthquake six-months earlier. Three-days later, IMO emailed EU that a M5 earthquake had just occurred on the specified fault-plane. We suggest this is a successful earthquake stress-forecast, where we refer to the procedure as stress-forecasting earthquakes as opposed to predicting or forecasting to emphasise the different formalism. Lack of funds has prevented us monitoring SWS on Iceland seismograms, however, we have identified similar characteristic behaviour of SWS time-delays above swarms of small earthquakes which have enabled us to

Identification of earthquakes that generate tsunamis in Java and Nusa Tenggara using rupture duration analysis

International Nuclear Information System (INIS)

Pribadi, S.; Puspito, N. T.; Yudistira, T.; Afnimar,; Ibrahim, G.; Laksono, B. I.; Adnan, Z.

2014-01-01

Java and Nusa Tenggara are the tectonically active of Sunda arc. This study discuss the rupture duration as a manifestation of the power of earthquake-generated tsunami. We use the teleseismic (30° - 90°) body waves with high-frequency energy Seismometer is from IRIS network as amount 206 broadband units. We applied the Butterworth high bandpass (1 - 2 Hz) filtered. The arrival and travel times started from wave phase of P - PP which based on Jeffrey Bullens table with TauP program. The results are that the June 2, 1994 Banyuwangi and the July 17, 2006 Pangandaran earthquakes identified as tsunami earthquakes with long rupture duration (To > 100 second), medium magnitude (7.6 50 second which depend on its magnitude. Those events are located far from the trench

Earthquake ground motion research in Sapporo city; Sapporoshi ni okeru jishindo no kenkyu

Energy Technology Data Exchange (ETDEWEB)

Sasatani, T [Hokkaido University, Sapporo (Japan)

1997-10-22

The Research Group on Earthquake Ground Motion in Sapporo City established in May 1996 has inaugurated collection of information on ground structures and observations of strong earthquakes in Sapporo City. The Research Group on Earthquake Ground Motion in Sapporo City has carried out geological investigations, electric logging and PS logging to date in three boring holes each with a depth of about 100 m, 200 m and 600 m. According to the result of the logging in the new Ishikari Bay port (600-m deep hole), the S-wave velocity has increased slowly as it starts from the ground surface to greater depths, but showed no noticeable velocity boundaries in this range of the depth. The Sapporo municipal office has drilled three observation wells (500-m deep) for the purpose of determining focal points of microtremors directly under the city area. Hole-bottom observation has been inaugurated since the beginning of this year. According to comparison of the results of loggings at great depths, a depth at which the S-wave velocity reaches about 700 m/s becomes greater toward the sea area. The result of calculations on amplification characteristics of the SH wave on rock beds revealed that a seismic wave of about 0.5 Hz is amplified by a little more than two times. 1 ref., 5 figs., 1 tab.

Comparative proteome analysis of drought-sensitive and drought-tolerant rapeseed roots and their hybrid F1 line under drought stress.

Science.gov (United States)

Mohammadi, Payam Pour; Moieni, Ahmad; Komatsu, Setsuko

2012-11-01

Rapeseed (Brassica napus L.), which is the third leading source of vegetable oil, is sensitive to drought stress during the early vegetative growth stage. To investigate the initial response of rapeseed to drought stress, changes in the protein expression profiles of drought-sensitive (RGS-003) and drought-tolerant lines (SLM-003), and their F1 hybrid, were analyzed using a proteomics approach. Seven-day-old rapeseed seedlings were treated with drought stress by restricting water for 7 days, and proteins were extracted from roots and separated by two-dimensional polyacrylamide gel electrophoresis. In the sensitive rapeseed line, 35 protein spots were differentially expressed under drought stress, and proteins related to metabolism, energy, disease/defense, and transport were decreased. In the tolerant line, 32 protein spots were differentially expressed under drought stress, and proteins involved in metabolism, disease/defense, and transport were increased, while energy-related proteins were decreased. Six protein spots in F1 hybrid were common among expressed proteins in the drought-sensitive and -tolerant lines. Notably, tubulin beta-2 and heat shock protein 70 were decreased in the drought-sensitive line and hybrid F1 plants, while jasmonate-inducible protein and 20S proteasome subunit PAF1 were increased in the F1 hybrids and drought-tolerant line. These results indicate that (1) V-type H(+) ATPase, plasma-membrane associated cation-binding protein, HSP 90, and elongation factor EF-2 have a role in the drought tolerance of rapeseed; (2) The decreased levels of heat shock protein 70 and tubulin beta-2 in the drought-sensitive and hybrid F1 lines might explain the reduced growth of these lines in drought conditions.

The Mw=8.8 Maule earthquake aftershock sequence, event catalog and locations

Science.gov (United States)

Meltzer, A.; Benz, H.; Brown, L.; Russo, R. M.; Beck, S. L.; Roecker, S. W.

2011-12-01

The aftershock sequence of the Mw=8.8 Maule earthquake off the coast of Chile in February 2010 is one of the most well-recorded aftershock sequences from a great megathrust earthquake. Immediately following the Maule earthquake, teams of geophysicists from Chile, France, Germany, Great Britain and the United States coordinated resources to capture aftershocks and other seismic signals associated with this significant earthquake. In total, 91 broadband, 48 short period, and 25 accelerometers stations were deployed above the rupture zone of the main shock from 33-38.5°S and from the coast to the Andean range front. In order to integrate these data into a unified catalog, the USGS National Earthquake Information Center develop procedures to use their real-time seismic monitoring system (Bulletin Hydra) to detect, associate, location and compute earthquake source parameters from these stations. As a first step in the process, the USGS has built a seismic catalog of all M3.5 or larger earthquakes for the time period of the main aftershock deployment from March 2010-October 2010. The catalog includes earthquake locations, magnitudes (Ml, Mb, Mb_BB, Ms, Ms_BB, Ms_VX, Mc), associated phase readings and regional moment tensor solutions for most of the M4 or larger events. Also included in the catalog are teleseismic phases and amplitude measures and body-wave MT and CMT solutions for the larger events, typically M5.5 and larger. Tuning of automated detection and association parameters should allow a complete catalog of events to approximately M2.5 or larger for that dataset of more than 164 stations. We characterize the aftershock sequence in terms of magnitude, frequency, and location over time. Using the catalog locations and travel times as a starting point we use double difference techniques to investigate relative locations and earthquake clustering. In addition, phase data from candidate ground truth events and modeling of surface waves can be used to calibrate the

P-wave pulse analysis to retrieve source and propagation effects in the case of Vrancea earthquakes

International Nuclear Information System (INIS)

Popescu, E.; Popa, M.; Placinta, A.; Grecu, B.; Radulian, M.

2004-01-01

Seismic source parameters and attenuation structure properties are obtained from the first P-wave pulse analysis and empirical Green's function deconvolution. The P pulse characteristics are combined effects of source and path properties. To reproduce the real source and structure parameters it is crucial to apply a method able to distinguish between the different factors affecting the observed seismograms. For example the empirical Green's function deconvolution method (Hartzell, 1978) allows the retrieval of the apparent source time function or source spectrum corrected for path, site and instrumental effects. The apparent source duration is given by the width of the deconvoluted source pulse and is directly related to the source dimension. Once the source time function established, next we can extract the parameters related to path effects. The difference between the pulse recorded at a given station and the source pulse obtained by deconvolution is a measure of the attenuation along the path from focus to the station. On the other hand, the pulse width variations with azimuth depend critically on the fault plane orientation and source directivity. In favourable circumstances (high signal/noise ratio, high resolution and station coverage), the method of analysis proposed in this paper allows the constraint of the rupture plane among the two nodal planes characterizing the fault plane solution, even for small events. P-wave pulse analysis was applied for 25 Vrancea earthquakes recorded between 1999 and 2003 by the Romanian local network to determine source parameters and attenuation properties. Our results outline high-stress drop seismic energy release with relatively simple rupture process for the considered events and strong lateral variation of attenuation of seismic waves across Carpathians Arc. (authors)

Prospective testing of Coulomb short-term earthquake forecasts

Science.gov (United States)

Jackson, D. D.; Kagan, Y. Y.; Schorlemmer, D.; Zechar, J. D.; Wang, Q.; Wong, K.

2009-12-01

Earthquake induced Coulomb stresses, whether static or dynamic, suddenly change the probability of future earthquakes. Models to estimate stress and the resulting seismicity changes could help to illuminate earthquake physics and guide appropriate precautionary response. But do these models have improved forecasting power compared to empirical statistical models? The best answer lies in prospective testing in which a fully specified model, with no subsequent parameter adjustments, is evaluated against future earthquakes. The Center of Study of Earthquake Predictability (CSEP) facilitates such prospective testing of earthquake forecasts, including several short term forecasts. Formulating Coulomb stress models for formal testing involves several practical problems, mostly shared with other short-term models. First, earthquake probabilities must be calculated after each “perpetrator” earthquake but before the triggered earthquakes, or “victims”. The time interval between a perpetrator and its victims may be very short, as characterized by the Omori law for aftershocks. CSEP evaluates short term models daily, and allows daily updates of the models. However, lots can happen in a day. An alternative is to test and update models on the occurrence of each earthquake over a certain magnitude. To make such updates rapidly enough and to qualify as prospective, earthquake focal mechanisms, slip distributions, stress patterns, and earthquake probabilities would have to be made by computer without human intervention. This scheme would be more appropriate for evaluating scientific ideas, but it may be less useful for practical applications than daily updates. Second, triggered earthquakes are imperfectly recorded following larger events because their seismic waves are buried in the coda of the earlier event. To solve this problem, testing methods need to allow for “censoring” of early aftershock data, and a quantitative model for detection threshold as a function of

DEFORMATION WAVES AS A TRIGGER MECHANISM OF SEISMIC ACTIVITY IN SEISMIC ZONES OF THE CONTINENTAL LITHOSPHERE

Directory of Open Access Journals (Sweden)

S. I. Sherman

2013-01-01

Full Text Available Deformation waves as a trigger mechanism of seismic activity and migration of earthquake foci have been under discussion by researchers in seismology and geodynamics for over 50 years. Four sections of this article present available principal data on impacts of wave processes on seismicity and new data. The first section reviews analytical and experimental studies aimed at identification of relationships between wave processes in the lithosphere and seismic activity manifested as space-and-time migration of individual earthquake foci or clusters of earthquakes. It is concluded that with a systematic approach, instead of using a variety of terms to denote waves that trigger seismic process in the lithosphere, it is reasonable to apply the concise definition of ‘deformation waves’, which is most often used in fact.The second section contains a description of deformation waves considered as the trigger mechanism of seismic activity. It is concluded that a variety of methods are applied to identify deformation waves, and such methods are based on various research methods and concepts that naturally differ in sensitivity concerning detection of waves and/or impact of the waves on seismic process. Epicenters of strong earthquakes are grouped into specific linear or arc-shaped systems, which common criterion is the same time interval of the occurrence of events under analysis. On site the systems compose zones with similar time sequences, which correspond to the physical notion of moving waves (Fig. 9. Periods of manifestation of such waves are estimated as millions of years, and a direct consideration of the presence of waves and wave parameters is highly challenging. In the current state-of-the-art, geodynamics and seismology cannot provide any other solution yet.The third section presents a solution considering record of deformation waves in the lithosphere. With account of the fact that all the earthquakes with М≥3.0 are associated with

Earthquake Strong Ground Motion Scenario at the 2008 Olympic Games Sites, Beijing, China

Science.gov (United States)

Liu, L.; Rohrbach, E. A.; Chen, Q.; Chen, Y.

2006-12-01

Historic earthquake record indicates mediate to strong earthquakes have been frequently hit greater Beijing metropolitan area where is going to host the 2008 summer Olympic Games. For the readiness preparation of emergency response to the earthquake shaking for a mega event in a mega city like Beijing in summer 2008, this paper tries to construct the strong ground motion scenario at a number of gymnasium sites for the 2008 Olympic Games. During the last 500 years (the Ming and Qing Dynasties) in which the historic earthquake record are thorough and complete, there are at least 12 earthquake events with the maximum intensity of VI or greater occurred within 100 km radius centered at the Tiananmen Square, the center of Beijing City. Numerical simulation of the seismic wave propagation and surface strong ground motion is carried out by the pseudospectral time domain methods with viscoelastic material properties. To improve the modeling efficiency and accuracy, a multi-scale approach is adapted: the seismic wave propagation originated from an earthquake rupture source is first simulated by a model with larger physical domain with coarser grids. Then the wavefield at a given plane is taken as the source input for the small-scale, fine grid model for the strong ground motion study at the sites. The earthquake source rupture scenario is based on two particular historic earthquake events: One is the Great 1679 Sanhe-Pinggu Earthquake (M~8, Maximum Intensity XI at the epicenter and Intensity VIII in city center)) whose epicenter is about 60 km ENE of the city center. The other one is the 1730 Haidian Earthquake (M~6, Maximum Intensity IX at the epicenter and Intensity VIII in city center) with the epicentral distance less than 20 km away from the city center in the NW Haidian District. The exist of the thick Tertiary-Quaternary sediments (maximum thickness ~ 2 km) in Beijing area plays a critical role on estimating the surface ground motion at the Olympic Games sites, which

The HayWired Earthquake Scenario—Earthquake Hazards

Science.gov (United States)

Detweiler, Shane T.; Wein, Anne M.

2017-04-24

The HayWired scenario is a hypothetical earthquake sequence that is being used to better understand hazards for the San Francisco Bay region during and after an earthquake of magnitude 7 on the Hayward Fault. The 2014 Working Group on California Earthquake Probabilities calculated that there is a 33-percent likelihood of a large (magnitude 6.7 or greater) earthquake occurring on the Hayward Fault within three decades. A large Hayward Fault earthquake will produce strong ground shaking, permanent displacement of the Earth’s surface, landslides, liquefaction (soils becoming liquid-like during shaking), and subsequent fault slip, known as afterslip, and earthquakes, known as aftershocks. The most recent large earthquake on the Hayward Fault occurred on October 21, 1868, and it ruptured the southern part of the fault. The 1868 magnitude-6.8 earthquake occurred when the San Francisco Bay region had far fewer people, buildings, and infrastructure (roads, communication lines, and utilities) than it does today, yet the strong ground shaking from the earthquake still caused significant building damage and loss of life. The next large Hayward Fault earthquake is anticipated to affect thousands of structures and disrupt the lives of millions of people. Earthquake risk in the San Francisco Bay region has been greatly reduced as a result of previous concerted efforts; for example, tens of billions of dollars of investment in strengthening infrastructure was motivated in large part by the 1989 magnitude 6.9 Loma Prieta earthquake. To build on efforts to reduce earthquake risk in the San Francisco Bay region, the HayWired earthquake scenario comprehensively examines the earthquake hazards to help provide the crucial scientific information that the San Francisco Bay region can use to prepare for the next large earthquake, The HayWired Earthquake Scenario—Earthquake Hazards volume describes the strong ground shaking modeled in the scenario and the hazardous movements of

Time-lapse changes in velocity and anisotropy in Japan's near surface after the 2011 Tohoku earthquake

Science.gov (United States)

Snieder, R.; Nakata, N.

2012-12-01

A strong-motion recording network, KiK-net, helps us to monitor temporal changes in the near surface in Japan. Each KiK-net station has two seismometers at the free surface and in a borehole a few hundred meters deep, and we can retrieve a traveling wave from the borehole receiver to the surface receiver by applying deconvolution based seismic interferometry. KiK-net recorded the 2011 Tohoku earthquake, which is one of the largest earthquakes in recent history, and seismicity around the time of the main shock. Using records of these seismicity and computing mean values of near-surface shear-wave velocities in the periods of January 1--March 10 and March 12--May 26 in 2011, we detect about a 5% reduction in the velocity after the Tohoku earthquake. The area of the velocity reduction is about 1,200 km wide, which is much wider than earlier studies reporting velocity reductions after larger earthquakes. The reduction partly recovers with time. We can also estimate the azimuthal anisotropy by detecting shear-wave splitting after applying seismic interferometry. Estimating mean values over the same periods as the velocity, we find the strength of anisotropy increased in most parts of northeastern Japan, but fast shear-wave polarization directions in the near surface did not significantly change. The changes in anisotropy and velocity are generally correlated, especially in the northeastern Honshu (the main island in Japan).

Delayed inflation triggerd by regional earthquakes at Campi Flegrei Caldera, Italy.

Science.gov (United States)

Lupi, M.; Frehner, M.; Weis, P.; Skelton, A.; Saenger, E.; Tisato, N.; Geiger, S.; Chiodini, G.; Driesner, T.

2017-12-01

What if earthquakes were affecting volcanoes more than we currently think because their effects are not immediately visible? Earthquake-volcano interactions promoted by dynamic and static stresses are considered seldom and difficult-to-capture geological processes. The Campi Flegrei caldera, Italy, is one of the best-monitored volcanic systems worldwide. We use a 70-years long time series to suggest a provocative and intriguing hypothesis to explain bradyseismic activity at Campi Flegrei. By comparing ground elevation time series at Campi Flegrei with seismic catalogues we show that uplift events at Campi Flegrei follow within 1.2 years large regional earthquakes. The accelerated uplifts are over-imposed on long-term inflation or deflation trends. Such association is supported by (yet-non definitive) binomial tests. Due to the non-definitive nature of the statistical tests we carried on additional numerical tests. We simulate the propagation of elastic waves showing that passing body waves impose high dynamic strains at the roof of the magmatic reservoir of the Campi Flegrei at about 7 km depth. Such elevated dynamic strains promote a brittle behaviour in an otherwise ductile material (i.e. the crystal mush) at near-lithostatic conditions. Such failure allows magma and exsolved volatiles to be released from the magmatic reservoir. The fluids would ascend through a plastic zone above the magmatic reservoir and inject into the shallow hydrothermal system where they phase-separate and expand causing a delayed effect, i.e. inflation. This mechanism and the associated inherent uncertainties require further investigations. However, the new concept already implies that geological processes triggered by passing seismic waves may become apparent several months after the triggering earthquake.

Spatial distribution of earthquake hypocenters in the Crimea—Black Sea region

Science.gov (United States)

Burmin, V. Yu; Shumlianska, L. O.

2018-03-01

Some aspects of the seismicity the Crime—Black Sea region are considered on the basis of the catalogued data on earthquakes that have occurred between 1970 and 2012. The complete list of the Crimean earthquakes for this period contains about 2140 events with magnitude ranging from -1.5 to 5.5. Bulletins contain information about compressional and shear waves arrival times regarding nearly 2000 earthquakes. A new approach to the definition of the coordinates of all of the events was applied to re-establish the hypocenters of the catalogued earthquakes. The obtained results indicate that the bulk of the earthquakes' foci in the region are located in the crust. However, some 2.5% of the foci are located at the depths ranging from 50 to 250 km. The new distribution of foci of earthquakes shows the concentration of foci in the form of two inclined branches, the center of which is located under the Yalto-Alushta seismic focal zone. The whole distribution of foci in depth corresponds to the relief of the lithosphere.

PRELIMINARY ANALYSIS OF THE EARTHQUAKE (MW 8.1 AND TSUNAMI OF APRIL 1, 2007, IN THE SOLOMON ISLANDS, SOUTHWESTERN PACIFIC OCEAN

Directory of Open Access Journals (Sweden)

Michael A. Fisher

2007-01-01

Full Text Available On April 1, 2007, a destructive earthquake (Mw 8.1 and tsunami struck the central Solomon Islands arc in the southwestern Pacific Ocean. The earthquake had a thrust-fault focal mechanism and occurred at shallow depth (between 15 km and 25 km beneath the island arc. The combined effects of the earthquake and tsunami caused dozens of fatalities and thousands remain without shelter. We present a preliminary analysis of the Mw-8.1 earthquake and resulting tsunami. Multichannel seismic- reflection data collected during 1984 show the geologic structure of the arc’s frontal prism within the earthquake’s rupture zone. Modeling tsunami-wave propagation indicates that some of the islands are so close to the earthquake epicenter that they were hard hit by tsunami waves as soon as 5 min. after shaking began, allowing people scant time to react.

Linking meteorological drivers of spring-summer drought regimes to agricultural drought risk in China

Science.gov (United States)

Dai, L.; Wright, J. S.; Yu, C.; Huang, W. Y.

2017-12-01

As a drought prone country, China has experienced frequent severe droughts in recent decades. Drought frequency and severity are projected to increase in China under climate change. An understanding of the physical processes that contribute to extreme droughts is essential for seasonal forecasting, but the dominant physical mechanisms responsible for droughts in most parts of China are still unclear. Moreover, despite numerous studies on droughts in China, there are few clear connections between the meteorological and climatological drivers of extreme droughts and the associated agricultural consequences. This knowledge gap limits the capacity for decision-making support in drought management. The objectives of this study are (1) to identify robust spring-summer drought regimes over China, (2) to investigate the physical mechanisms associated with each regime, and (3) to better clarify connections between meteorological drought regimes and agricultural drought risk. First, we identify six drought regimes over China by applying an area-weighted k-means clustering technique to spatial patterns of spring-summer Standardized Precipitation Index (SPI) obtained from the ten-member ERA-20CM ensemble for 1900-2010. Second, we project these drought regimes onto agricultural drought risk maps for the three major cereal crops (rice, maize, and wheat) in China. Taking into account historical harvest areas for these crops, we then evaluate the potential impact of each drought regime on agricultural production. Third, the physical mechanisms and meteorological context behind each drought regimes are investigated based on monthly outputs from ERA20CM. We analyze the preceding and concurrent atmospheric circulation anomalies associated with each regime, and propose mechanistic explanations for drought development. This work provides a new perspective on diagnosing the physical mechanisms behind seasonal droughts, and lays a foundation for improving seasonal drought prediction and

A Kinesthetic Demonstration for Locating Earthquake Epicenters

Science.gov (United States)

Keyantash, J.; Sperber, S.

2005-12-01

During Spring 2005, an inquiry-based curriculum for plate tectonics was developed for implementation in sixth-grade classrooms within the Los Angeles Unified School District (LAUSD). Two cohorts of LAUSD teachers received training and orientation to the plate tectonics unit during one week workshops in July 2005. However, during the training workshops, it was observed that there was considerable confusion among the teachers as to how the traditional "textbook" explanation of the time lag between P and S waves on a seismogram could possibly be used to determine the epicenter of an earthquake. One of the State of California science content standards for sixth grade students is that they understand how the epicenters of earthquakes are determined, so it was critical that the teachers themselves grasped the concept. In response to the adult learner difficulties, the classroom explanation of earthquake epicenter location was supplemented with an outdoor kinesthetic activity. Based upon the experience of the kinesthetic model, it was found that the hands-on model greatly cemented the teachers' understanding of the underlying theory. This paper details the steps of the kinesthetic demonstration for earthquake epicenter identification, as well as offering extended options for its classroom implementation.

GRACE-Assimilated Drought Indicators for the U.S. Drought Monitor

Science.gov (United States)

Rui, Hualan; Vollmer, Bruce; Teng, Bill; Loeser, Carlee; Beaudoing, Hiroko; Rodell, Matt

2018-01-01

The Gravity Recovery and Climate Experiment (GRACE) mission detects changes in Earth's gravity field by precisely monitoring the changes in distance between two satellites orbiting the Earth in tandem. Scientists at NASA's Goddard Space Flight Center generate GRACE-assimilated groundwater and soil moisture drought indicators each week, for drought monitor-related studies and applications. The GRACE-assimilated Drought Indicator Version 2.0 data product (GRACE-DA-DM V2.0) is archived at, and distributed by, the NASA GES DISC (Goddard Earth Sciences Data and Information Services Center). More information about the data and data access is available on the data product landing page at https://disc.gsfc.nasa.gov/datasets /GRACEDADM_CLSM0125US_7D_2.0/summary. The GRACE-DA-DM V2.0 data product contains three drought indicators: Groundwater Percentile, Root Zone Soil Moisture Percentile, and Surface Soil Moisture Percentile. The drought indicators are of wet or dry conditions, expressed as a percentile, indicating the probability of occurrence within the period of record from 1948 to 2012. These GRACE-assimilated drought indicators, with improved spatial and temporal resolutions, should provide a more comprehensive and objective identification of drought conditions. This presentation describes the basic characteristics of the data and data services at NASA GES DISC and collaborative organizations, and uses a few examples to demonstrate the simple ways to explore the GRACE-assimilated drought indicator data.

Joint inversion of high resolution S-wave velocity structure underneath North China Basin

Science.gov (United States)

Yang, C.; Li, G.; Niu, F.

2017-12-01

North China basin is one of earthquake prone areas in China. Many devastating earthquakes occurred in the last century and before, such as the 1937 M7.0 Heze Earthquake in Shandong province, the 1966 M7.2 Xingtai Earthquake and 1976 Tangshan Earthquake in Hebei province. Knowing the structure of the sediment cover is of great importance to predict strong ground motion caused by earthquakes. Unconsolidated sediments are loose materials, ranging from clay to sand to gravel. Earthquakes can liquefy unconsolidated sediments, thus knowing the distribution and thickness of the unconsolidated sediments has significant implication in seismic hazard analysis of the area. Quantitative estimates of the amount of extension of the North China basin is important to understand the thinning and evolution of the eastern North China craton and the underlying mechanism. In principle, the amount of lithospheric stretching can be estimated from sediment and crustal thickness. Therefore an accurate estimate of the sediment and crustal thickness of the area is also important in understanding regional tectonics. In this study, we jointly invert the Rayleigh wave phase-velocity dispersion and Z/H ratio data to construct a 3-D S-wave velocity model beneath North China area. We use 4-year ambient noise data recorded from 249 temporary stations, and 139 earthquake events to extract Rayleigh wave Z/H ratios. The Z/H ratios obtained from ambient noise data and earthquake data show a good agreement within the overlapped periods. The phase velocity dispersion curve was estimated from the same ambient noise data. The preliminary result shows a relatively low Z/H ratio and low velocity anomaly at the shallow part of sediment basins.

Improved tolerance to post-anthesis drought stress by pre-drought priming at vegetative stages in drought-tolerant and -sensitive wheat cultivars.

Science.gov (United States)

Abid, Muhammad; Tian, Zhongwei; Ata-Ul-Karim, Syed Tahir; Liu, Yang; Cui, Yakun; Zahoor, Rizwan; Jiang, Dong; Dai, Tingbo

2016-09-01

Wheat crop endures a considerable penalty of yield reduction to escape the drought events during post-anthesis period. Drought priming under a pre-drought stress can enhance the crop potential to tolerate the subsequent drought stress by triggering a faster and stronger defense mechanism. Towards these understandings, a set of controlled moderate drought stress at 55-60% field capacity (FC) was developed to prime the plants of two wheat cultivars namely Luhan-7 (drought tolerant) and Yangmai-16 (drought sensitive) during tillering (Feekes 2 stage) and jointing (Feekes 6 stage), respectively. The comparative response of primed and non-primed plants, cultivars and priming stages was evaluated by applying a subsequent severe drought stress at 7 days after anthesis. The results showed that primed plants of both cultivars showed higher potential to tolerate the post-anthesis drought stress through improved leaf water potential, more chlorophyll, and ribulose-1, 5-bisphosphate carboxylase/oxygenase contents, enhanced photosynthesis, better photoprotection and efficient enzymatic antioxidant system leading to less yield reductions. The primed plants of Luhan-7 showed higher capability to adapt the drought stress events than Yangmai-16. The positive effects of drought priming to sustain higher grain yield were pronounced in plants primed at tillering than those primed at jointing. In consequence, upregulated functioning of photosynthetic apparatus and efficient enzymatic antioxidant activities in primed plants indicated their superior potential to alleviate a subsequently occurring drought stress, which contributed to lower yield reductions than non-primed plants. However, genotypic and priming stages differences in response to drought stress also contributed to affect the capability of primed plants to tolerate the post-anthesis drought stress conditions in wheat. Copyright © 2016. Published by Elsevier Masson SAS.

The origin of high frequency radiation in earthquakes and the geometry of faulting

Science.gov (United States)

Madariaga, R.

2004-12-01

In a seminal paper of 1967 Kei Aki discovered the scaling law of earthquake spectra and showed that, among other things, the high frequency decay was of type omega-squared. This implies that high frequency displacement amplitudes are proportional to a characteristic length of the fault, and radiated energy scales with the cube of the fault dimension, just like seismic moment. Later in the seventies, it was found out that a simple explanation for this frequency dependence of spectra was that high frequencies were generated by stopping phases, waves emitted by changes in speed of the rupture front as it propagates along the fault, but this did not explain the scaling of high frequency waves with fault length. Earthquake energy balance is such that, ignoring attenuation, radiated energy is the change in strain energy minus energy released for overcoming friction. Until recently the latter was considered to be a material property that did not scale with fault size. Yet, in another classical paper Aki and Das estimated in the late 70s that energy release rate also scaled with earthquake size, because earthquakes were often stopped by barriers or changed rupture speed at them. This observation was independently confirmed in the late 90s by Ide and Takeo and Olsen et al who found that energy release rates for Kobe and Landers were in the order of a MJ/m2, implying that Gc necessarily scales with earthquake size, because if this was a material property, small earthquakes would never occur. Using both simple analytical and numerical models developed by Addia-Bedia and Aochi and Madariaga, we examine the consequence of these observations for the scaling of high frequency waves with fault size. We demonstrate using some classical results by Kostrov, Husseiny and Freund that high frequency energy flow measures energy release rate and is generated when ruptures change velocity (both direction and speed) at fault kinks or jogs. Our results explain why super shear ruptures are

Large scale earthquake simulator of 3-D (simultaneous X-Y-Z direction)

International Nuclear Information System (INIS)

Shiraki, Kazuhiro; Inoue, Masao

1983-01-01

Japan is the country where earthquakes are frequent, accordingly it is necessary to examine sufficiently the safety against earthquakes of important machinery and equipment such as nuclear and thermal power plants and chemical plants. For this purpose, aseismatic safety is evaluated by mounting an actual thing or a model on a vibration table and vibrating it by the magnitude several times as large as actual earthquakes. The vibration tables used so far can vibrate only in one direction or in two directions simultaneously, but this time, a three-dimensional vibration table was completed, which can vibrate in three directions simultaneously with arbitrary wave forms, respectively. By the advent of this vibration table, aseismatic test can be carried out, using the earthquake waves close to actual ones. It is expected that this vibration table achieves large role for the improvement of aseismatic reliability of nuclear power machinery and equipment. When a large test body is vibrated on the vibration table, the center of gravity of the test body and the point of action of vibrating force are different, therefore the rotating motion around three axes is added to the motion in three axial directions, and these motions must be controlled so as to realize three-dimensional earthquake motion. The main particulars and the construction of the vibration table, the mechanism of three-direction vibration, the control of the table and the results of test of the table are reported. (Kako, I.)

Near-fault earthquake ground motion prediction by a high-performance spectral element numerical code

International Nuclear Information System (INIS)

Paolucci, Roberto; Stupazzini, Marco

2008-01-01

Near-fault effects have been widely recognised to produce specific features of earthquake ground motion, that cannot be reliably predicted by 1D seismic wave propagation modelling, used as a standard in engineering applications. These features may have a relevant impact on the structural response, especially in the nonlinear range, that is hard to predict and to be put in a design format, due to the scarcity of significant earthquake records and of reliable numerical simulations. In this contribution a pilot study is presented for the evaluation of seismic ground-motions in the near-fault region, based on a high-performance numerical code for 3D seismic wave propagation analyses, including the seismic fault, the wave propagation path and the near-surface geological or topographical irregularity. For this purpose, the software package GeoELSE is adopted, based on the spectral element method. The set-up of the numerical benchmark of 3D ground motion simulation in the valley of Grenoble (French Alps) is chosen to study the effect of the complex interaction between basin geometry and radiation mechanism on the variability of earthquake ground motion

CreativeDrought: An interdisciplinary approach to building resilience to drought

Science.gov (United States)

Rangecroft, Sally; Van Loon, Anne; Rohse, Melanie; Day, Rosie; Birkinshaw, Stephen; Makaya, Eugine

2017-04-01

Drought events cause severe water and food insecurities in many developing countries where resilience to natural hazards and change is low due to a number of reasons (including poverty, social and political inequality, and limited access to information). Furthermore, with climate change and increasing pressures from population and societal change, populations are expected to experience future droughts outside of their historic range. Integrated water resources management is an established tool combining natural science, engineering and management to help address drought and associated impacts. However, it often lacks a strong social and cultural aspect, leading to poor implementation on the ground. For a more holistic approach to building resilience to future drought, a stronger interdisciplinary approach is required which can incorporate the local cultural context and perspectives into drought and water management, and communicate information effectively to communities. In this pilot project 'CreativeDrought', we use a novel interdisciplinary approach aimed at building resilience to future drought in rural Africa by combining hydrological modelling with rich local information and engaging communicative approaches from social sciences. The work is conducted through a series of steps in which we i) engage with local rural communities to collect narratives on drought experiences; ii) generate hydrological modelling scenarios based on IPCC projections, existing data and the collected narratives; iii) feed these back to the local community to gather their responses to these scenarios; iv) iteratively adapt them to obtain hypothetical future drought scenarios; v) engage the community with the scenarios to formulate new future drought narratives; and vi) use this new data to enhance local water resource management. Here we present some of the indigenous knowledge gathered through narratives and the hydrological modelling scenarios for a rural community in Southern Africa

Difference of horizontal-to-vertical spectral ratios of observed earthquakes and microtremors and its application to S-wave velocity inversion based on the diffuse field concept

Science.gov (United States)

Kawase, Hiroshi; Mori, Yuta; Nagashima, Fumiaki

2018-01-01

We have been discussing the validity of using the horizontal-to-vertical spectral ratios (HVRs) as a substitute for S-wave amplifications after Nakamura first proposed the idea in 1989. So far a formula for HVRs had not been derived that fully utilized their physical characteristics until a recent proposal based on the diffuse field concept. There is another source of confusion that comes from the mixed use of HVRs from earthquake and microtremors, although their wave fields are hardly the same. In this study, we compared HVRs from observed microtremors (MHVR) and those from observed earthquake motions (EHVR) at one hundred K-NET and KiK-net stations. We found that MHVR and EHVR share similarities, especially until their first peak frequency, but have significant differences in the higher frequency range. This is because microtremors mainly consist of surface waves so that peaks associated with higher modes would not be prominent, while seismic motions mainly consist of upwardly propagating plain body waves so that higher mode resonances can be seen in high frequency. We defined here the spectral amplitude ratio between them as EMR and calculated their average. We categorize all the sites into five bins by their fundamental peak frequencies in MHVR. Once we obtained EMRs for five categories, we back-calculated EHVRs from MHVRs, which we call pseudo-EHVRs (pEHVR). We found that pEHVR is much closer to EHVR than MHVR. Then we use our inversion code to invert the one-dimensional S-wave velocity structures from EHVRs based on the diffuse field concept. We also applied the same code to pEHVRs and MHVRs for comparison. We found that pEHVRs yield velocity structures much closer to those by EHVRs than those by MHVRs. This is natural since what we have done up to here is circular except for the average operation in EMRs. Finally, we showed independent examples of data not used in the EMR calculation, where better ground structures were successfully identified from p

S-Wave Velocity Structure beneath Southwest North America from Seismogram Comparisons of the Mexico Earthquake on 22 June 1997

Directory of Open Access Journals (Sweden)

Bagus Jaya Santosa

2008-09-01

Full Text Available This research investigates earth structure beneath the Southwest North America landmass, especially between Mexico and California. Models based on S wave velocities for this area were obtained by carrying out seismogram fitting in time domain and three Cartesian components simultaneously. The data used is from an event, coded as C052297B that occurred in the state of Guerrero, Mexico and it was fitted to synthetic data computed with the GEMINI program at TS network stations. Earth model IASPEI91 and SPREM were used as input to create the synthetic data. Real and synthetic seismograms were subjected to a low-pass filter with a frequency corner of 20 mHz.Waveform analysis results show very unsystematic and strong deviations in the waveform, arrival times, amount of oscillation and the height of the wave amplitude. Discrepancies are met on S, Love, Rayleigh and ScS waves, where the stations epicentral distances are below 300. Deviation in analysis waveform because of the usage of model 1-D of SPREM and IASPEI91, because the 1-D was a kind of average value an elastic property at one particular depth of global earth. With the method of waveform analysis we can see how sensitive waveform is to structures within the layers of the Earth.To explain the discrepancies, a correction to the earth structure is essential. The corrections account for the thickness of the crust, speed gradient of bh, the coefficient for the bh and bv in the upper mantle for surface wave fitting, a small variation of the S speed structure at a layer under the upper mantle above 771 km for S wave fitting, and a small variation at the base the mantle layers for ScS wave fitting. At some stations, a correction for S speed structure have yielded P wave fitting. Results of this research indicate that the 1-D earth model obtained through seismogram fitting at every hypocenter-observation station pair is unique. The S-wave velocity on the upper mantle has strong negative anomalies. This

Examination of earthquake Ground Motion in the deep underground environment of Japan

International Nuclear Information System (INIS)

Goto, J.; Tsuchi, H.; Mashimo, M.

2009-01-01

Among the possible impacts of earthquakes on the geological disposal system, ground motion is not included in the criteria for selecting a candidate repository site because, in general, ground motion deep underground is considered to be smaller than at the surface. Also, after backfilling/closure, the repository moves together with the surrounding rock. We have carried out a detailed examination of earthquake ground motion deep underground using extensive data from recent observation networks to support the above assumption. As a result, it has been reconfirmed that earthquake ground motion deep underground is relatively smaller than at the surface. Through detailed analysis of data, we have identified the following important parameters for evaluating earthquake ground motion deep underground: depth and velocity distribution of the rock formations of interest, the intensity of the short period component of earthquakes and incident angle of seismic waves to the rock formations. (authors)

Artificial earthquake record generation using cascade neural network

Directory of Open Access Journals (Sweden)

Bani-Hani Khaldoon A.

2017-01-01

Full Text Available This paper presents the results of using artificial neural networks (ANN in an inverse mapping problem for earthquake accelerograms generation. This study comprises of two parts: 1-D site response analysis; performed for Dubai Emirate at UAE, where eight earthquakes records are selected and spectral matching are performed to match Dubai response spectrum using SeismoMatch software. Site classification of Dubai soil is being considered for two classes C and D based on shear wave velocity of soil profiles. Amplifications factors are estimated to quantify Dubai soil effect. Dubai’s design response spectra are developed for site classes C & D according to International Buildings Code (IBC -2012. In the second part, ANN is employed to solve inverse mapping problem to generate time history earthquake record. Thirty earthquakes records and their design response spectrum with 5% damping are used to train two cascade forward backward neural networks (ANN1, ANN2. ANN1 is trained to map the design response spectrum to time history and ANN2 is trained to map time history records to the design response spectrum. Generalized time history earthquake records are generated using ANN1 for Dubai’s site classes C and D, and ANN2 is used to evaluate the performance of ANN1.

Enhanced ULF radiation observed by DEMETER two months around the strong 2010 Haiti earthquake

Directory of Open Access Journals (Sweden)

M. A. Athanasiou

2011-04-01

Full Text Available In this paper we study the energy of ULF electromagnetic waves that were recorded by the satellite DEMETER, during its passing over Haiti before and after a destructive earthquake. This earthquake occurred on 12 January 2010, at geographic Latitude 18.46° and Longitude 287.47°, with Magnitude 7.0 R. Specifically, we are focusing on the variations of energy of Ez-electric field component concerning a time period of 100 days before and 50 days after the strong earthquake. In order to study these variations, we have developed a novel method that can be divided in two stages: first we filter the signal, keeping only the ultra low frequencies and afterwards we eliminate its trend using techniques of Singular Spectrum Analysis (SSA, combined with a third-degree polynomial filter. As it is shown, a significant increase in energy is observed for the time interval of 30 days before the earthquake. This result clearly indicates that the change in the energy of ULF electromagnetic waves could be related to strong precursory earthquake phenomena. Moreover, changes in energy associated with strong aftershock activity were also observed 25 days after the earthquake. Finally, we present results concerning the comparison between changes in energy during night and day passes of the satellite over Haiti, which showed differences in the mean energy values, but similar results as far as the rate of the energy change is concerned.

Feasibility study of EEW application in Korea ; Testing different frequency bands for small earthquakes.

Science.gov (United States)

Chi, H. C.; Park, J. H.; Sheen, D. H.

2009-04-01

At present, it seems almost impossible to predict where and how much strong a earthquake will happen within very limited time such as two or three days before it occurs. However, the advantage of modern electronic techniques can support us very fast communication tools around nation-wide area so that we can receive P- waves arrival information from seismic stations through communication lines before S-waves strike our living site. This is the key of EEW(Earthquake Early Warning) concept that is under development around world especially including Japan, United State of America, and Taiwan. In this pilot study we proposed the direction for developing Korean Earthquake Early Warning System. Considering the state of the art techniques used in Japan, USA and Taiwan, ElarmS would be more adaptable to Korea since ElarmS can work from the low limit of moderate earthquakes around magnitude 3.5, which would annually happen in Korea. Using 27 events ranging in magnitude from 2.2 to 4.9 occurring in South Korea for 2007, we investigate empirical magnitude scaling relationships in South Korea due to the variation of the duration of the P waveform. We measure the maximum predominant period and the peak displacement or velocity amplitude from the first few seconds of P wave arrivals to derive period-magnitude and amplitude-magnitude scaling relationship, respectively. We find that it is possible to determine the magnitude of earthquakes only using the first 2 seconds of the P wave and, for the period-magnitude relationship, 10 Hz low-pass filter yields better estimate than 3 Hz. This is because the magnitudes of most events used in this study are too small (<3.0). It is also shown that peak displacement for velocity instruments and peak velocity for accelerometers have their own magnitude scaling relationships, respectively. Thus, for the amplitude-magnitude relationship, like the relationships in northern California, two individual amplitude scaling relationships would be

Multiple Spectral Ratio Analyses Reveal Earthquake Source Spectra of Small Earthquakes and Moment Magnitudes of Microearthquakes

Science.gov (United States)

Uchide, T.; Imanishi, K.

2016-12-01

Spectral studies for macroscopic earthquake source parameters are helpful for characterizing earthquake rupture process and hence understanding earthquake source physics and fault properties. Those studies require us mute wave propagation path and site effects in spectra of seismograms to accentuate source effect. We have recently developed the multiple spectral ratio method [Uchide and Imanishi, BSSA, 2016] employing many empirical Green's function (EGF) events to reduce errors from the choice of EGF events. This method helps us estimate source spectra more accurately as well as moment ratios among reference and EGF events, which are useful to constrain the seismic moment of microearthquakes. First, we focus on earthquake source spectra. The source spectra have generally been thought to obey the omega-square model with single corner-frequency. However recent studies imply the existence of another corner frequency for some earthquakes. We analyzed small shallow inland earthquakes (3.5 multiple spectral ratio analyses. For 20000 microearthquakes in Fukushima Hamadori and northern Ibaraki prefecture area, we found that the JMA magnitudes (Mj) based on displacement or velocity amplitude are systematically below Mw. The slope of the Mj-Mw relation is 0.5 for Mj 5. We propose a fitting curve for the obtained relationship as Mw = (1/2)Mj + (1/2)(Mjγ + Mcorγ)1/γ+ c, where Mcor is a corner magnitude, γ determines the sharpness of the corner, and c denotes an offset. We obtained Mcor = 4.1, γ = 5.6, and c = -0.47 to fit the observation. The parameters are useful for characterizing the Mj-Mw relationship. This non-linear relationship affects the b-value of the Gutenberg-Richter law. Quantitative discussions on b-values are affected by the definition of magnitude to use.

Earthquake-proof test of the bookshelf; Shoka no taishinsei shiken

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-10-01

The seismic fragility testing was carried out on the bookshelf of 2 types 4 bodies submitted from the Co.,Ltd. primary steel industry place. (1) The vibration testing by seismic wave. The excitation by the Hyogo-ken Nanbu Earthquake wave is carried out. The following are examined: Behavior of test specimen for seismic wave, degree of the damage, response speed. (2) The sweep test. The sweep excitation of the sine wave in which the frequency automatically decreases is carried out, while the acceleration is fixedly kept. The following are examined: Behavior of test specimen, degree of the damage, response speed, and resonance point. (NEDO)

The current California drought through EDDI's eyes: early warning and monitoring of agricultural and hydrologic drought with the new Evaporative Demand Drought Index.

Science.gov (United States)

Hobbins, M.; McEvoy, D.; Huntington, J. L.; Wood, A. W.; Morton, C.; Verdin, J. P.

2015-12-01

We have developed a physically based, multi-scalar drought index—the Evaporative Demand Drought Index (EDDI)—to improve treatment of evaporative dynamics in drought monitoring. Existing popular drought indices—such as the Palmer Drought Severity Index that informs much of the US Drought Monitor (USDM)—have primarily relyied on precipitation and temperature (T) to represent hydroclimatic anomalies, leaving evaporative demand (E0) most often derived from poorly performing T-based parameterizations then used to derive actual evapotranspiration (ET) from LSMs. Instead, EDDI leverages the inter-relations of E0 and ET, measuring E0's physical response to surface drying anomalies due to two distinct land surface/atmosphere interactions: (i) in sustained drought, limited moisture availability forces E0 and ET into a complementary relation, whereby ET declines as E0 increases; and (ii) in "flash" droughts, E0 increases due to increasing advection or radiation. E0's rise in response to both drought types suggests EDDI's robustness as a monitor and leading indicator of drought. To drive EDDI, we use for E0 daily reference ET from the ASCE Standardized Reference ET equation forced by North American Land Data Assimilation System drivers. EDDI is derived by aggregating E0 anomalies from its long-term mean across a period of interest and normalizing them to a Z-score. Positive EDDI indicates drier than normal conditions (and so drought). We use the current historic California drought as a test-case in which to examine EDDI's performance in monitoring agricultural and hydrologic drought. We observe drought development and decompose the behavior of drought's evaporative drivers during in-drought intensification periods and wetting events. EDDI's performance as a drought leading indicator with respect to the USDM is tested in important agricultural regions. Comparing streamflow from several USGS gauges in the Sierra Nevada to EDDI, we find that EDDI tracks most major

The 1911 M ~6.6 Calaveras earthquake: Source parameters and the role of static, viscoelastic, and dynamic coulomb stress changes imparted by the 1906 San Francisco earthquake

Science.gov (United States)

Doser, D.I.; Olsen, K.B.; Pollitz, F.F.; Stein, R.S.; Toda, S.

2009-01-01

The occurrence of a right-lateral strike-slip earthquake in 1911 is inconsistent with the calculated 0.2-2.5 bar static stress decrease imparted by the 1906 rupture at that location on the Calaveras fault, and 5 yr of calculated post-1906 viscoelastic rebound does little to reload the fault. We have used all available first-motion, body-wave, and surface-wave data to explore possible focal mechanisms for the 1911 earthquake. We find that the event was most likely a right-lateral strikeslip event on the Calaveras fault, larger than, but otherwise resembling, the 1984 Mw 6.1 Morgan Hill earthquake in roughly the same location. Unfortunately, we could recover no unambiguous surface fault offset or geodetic strain data to corroborate the seismic analysis despite an exhaustive archival search. We calculated the static and dynamic Coulomb stress changes for three 1906 source models to understand stress transfer to the 1911 site. In contrast to the static stress shadow, the peak dynamic Coulomb stress imparted by the 1906 rupture promoted failure at the site of the 1911 earthquake by 1.4-5.8 bar. Perhaps because the sample is small and the aftershocks are poorly located, we find no correlation of 1906 aftershock frequency or magnitude with the peak dynamic stress, although all aftershocks sustained a calculated dynamic stress of ???3 bar. Just 20 km to the south of the 1911 epicenter, we find that surface creep of the Calaveras fault at Hollister paused for ~17 yr after 1906, about the expected delay for the calculated static stress drop imparted by the 1906 earthquake when San Andreas fault postseismic creep and viscoelastic relaxation are included. Thus, the 1911 earthquake may have been promoted by the transient dynamic stresses, while Calaveras fault creep 20 km to the south appears to have been inhibited by the static stress changes.

Modeling drought impact occurrence based on climatological drought indices for four European countries

Science.gov (United States)

Stagge, James H.; Kohn, Irene; Tallaksen, Lena M.; Stahl, Kerstin

2014-05-01

The relationship between atmospheric conditions and the likelihood of a significant drought impact has, in the past, been difficult to quantify, particularly in Europe where political boundaries and language have made acquiring comprehensive drought impact information difficult. As such, the majority of studies linking meteorological drought with the occurrence or severity of drought impacts have previously focused on specific regions, very detailed impact types, or both. This study describes a new methodology to link the likelihood of drought impact occurrence with climatological drought indices across different European climatic regions and impact sectors using the newly developed European Drought Impact report Inventory (EDII), a collaborative database of drought impact information (www.geo.uio.no/edc/droughtdb/). The Standardized Precipitation Index (SPI) and Standardized Precipitation-Evapotranspiration Index (SPEI) are used as predictor variables to quantify meteorological drought severity over prior time periods (here 1, 2, 3, 6, 9, 12, and 24 months are used). The indices are derived using the gridded WATCH Forcing Datasets, covering the period 1958-2012. Analysis was performed using logistic regression to identify the climatological drought index and accumulation period, or linear combination of drought indices, that best predicts the likelihood of a documented drought impact, defined by monthly presence/absence. The analysis was carried out for a subset of four European countries (Germany, UK, Norway, Slovenia) and four of the best documented impact sectors: Public Water Supply, Agriculture and Livestock Farming, Energy and Industry, and Environmental Quality. Preliminary results show that drought impacts in these countries occur most frequently due to a combination of short-term (2-6 month) precipitation deficits and long-term (12-24 month) potential evapotranspiration anomaly, likely associated with increased temperatures. Agricultural drought impacts

Analysis of seismic waves crossing the Santa Clara Valley using the three-component MUSIQUE array algorithm

Science.gov (United States)

Hobiger, Manuel; Cornou, Cécile; Bard, Pierre-Yves; Le Bihan, Nicolas; Imperatori, Walter

2016-10-01

We introduce the MUSIQUE algorithm and apply it to seismic wavefield recordings in California. The algorithm is designed to analyse seismic signals recorded by arrays of three-component seismic sensors. It is based on the MUSIC and the quaternion-MUSIC algorithms. In a first step, the MUSIC algorithm is applied in order to estimate the backazimuth and velocity of incident seismic waves and to discriminate between Love and possible Rayleigh waves. In a second step, the polarization parameters of possible Rayleigh waves are analysed using quaternion-MUSIC, distinguishing retrograde and prograde Rayleigh waves and determining their ellipticity. In this study, we apply the MUSIQUE algorithm to seismic wavefield recordings of the San Jose Dense Seismic Array. This array has been installed in 1999 in the Evergreen Basin, a sedimentary basin in the Eastern Santa Clara Valley. The analysis includes 22 regional earthquakes with epicentres between 40 and 600 km distant from the array and covering different backazimuths with respect to the array. The azimuthal distribution and the energy partition of the different surface wave types are analysed. Love waves dominate the wavefield for the vast majority of the events. For close events in the north, the wavefield is dominated by the first harmonic mode of Love waves, for farther events, the fundamental mode dominates. The energy distribution is different for earthquakes occurring northwest and southeast of the array. In both cases, the waves crossing the array are mostly arriving from the respective hemicycle. However, scattered Love waves arriving from the south can be seen for all earthquakes. Combining the information of all events, it is possible to retrieve the Love wave dispersion curves of the fundamental and the first harmonic mode. The particle motion of the fundamental mode of Rayleigh waves is retrograde and for the first harmonic mode, it is prograde. For both modes, we can also retrieve dispersion and ellipticity

The Alaska earthquake, March 27, 1964: lessons and conclusions

Science.gov (United States)

Eckel, Edwin B.

1970-01-01

One of the greatest earthquakes of all time struck south-central Alaska on March 27, 1964. Strong motion lasted longer than for most recorded earthquakes, and more land surface was dislocated, vertically and horizontally, than by any known previous temblor. Never before were so many effects on earth processes and on the works of man available for study by scientists and engineers over so great an area. The seismic vibrations, which directly or indirectly caused most of the damage, were but surface manifestations of a great geologic event-the dislocation of a huge segment of the crust along a deeply buried fault whose nature and even exact location are still subjects for speculation. Not only was the land surface tilted by the great tectonic event beneath it, with resultant seismic sea waves that traversed the entire Pacific, but an enormous mass of land and sea floor moved several tens of feet horizontally toward the Gulf of Alaska. Downslope mass movements of rock, earth, and snow were initiated. Subaqueous slides along lake shores and seacoasts, near-horizontal movements of mobilized soil (“landspreading”), and giant translatory slides in sensitive clay did the most damage and provided the most new knowledge as to the origin, mechanics, and possible means of control or avoidance of such movements. The slopes of most of the deltas that slid in 1964, and that produced destructive local waves, are still as steep or steeper than they were before the earthquake and hence would be unstable or metastable in the event of another great earthquake. Rockslide avalanches provided new evidence that such masses may travel on cushions of compressed air, but a widely held theory that glaciers surge after an earthquake has not been substantiated. Innumerable ground fissures, many of them marked by copious emissions of water, caused much damage in towns and along transportation routes. Vibration also consolidated loose granular materials. In some coastal areas, local

Scientific, Engineering, and Financial Factors of the 1989 Human-Triggered Newcastle Earthquake in Australia

Science.gov (United States)

Klose, C. D.

2006-12-01

This presentation emphasizes the dualism of natural resources exploitation and economic growth versus geomechanical pollution and risks of human-triggered earthquakes. Large-scale geoengineering activities, e.g., mining, reservoir impoundment, oil/gas production, water exploitation or fluid injection, alter pre-existing lithostatic stress states in the earth's crust and are anticipated to trigger earthquakes. Such processes of in- situ stress alteration are termed geomechanical pollution. Moreover, since the 19th century more than 200 earthquakes have been documented worldwide with a seismic moment magnitude of 4.5losses of triggered earthquakes. An hazard assessment, based on a geomechanical crust model, shows that only four deep coal mines were responsible for triggering this severe earthquake. A small-scale economic risk assessment identifies that the financial loss due to earthquake damage has reduced mining profits that have been re-invested in the Newcastle region for over two centuries beginning in 1801. Furthermore, large-scale economic risk assessment reveals that the financial loss is equivalent to 26% of the Australian Gross Domestic Product (GDP) growth in 1988/89. These costs account for 13% of the total costs of all natural disasters (e.g., flooding, drought, wild fires) and 94% of the costs of all earthquakes recorded in Australia between 1967 and 1999. In conclusion, the increasing number and size of geoengineering activities, such as coal mining near Newcastle or planned carbon dioxide Geosequestration initiatives, represent a growing hazard potential, which can negatively affect socio-economic growth and sustainable development. Finally, hazard and risk degrees, based on geomechanical-mathematical models, can be forecasted in space and over time for urban planning in order to prevent economic losses of human-triggered earthquakes in the future.

ShakeAlert—An earthquake early warning system for the United States west coast

Science.gov (United States)

Burkett, Erin R.; Given, Douglas D.; Jones, Lucile M.

2014-08-29

Earthquake early warning systems use earthquake science and the technology of monitoring systems to alert devices and people when shaking waves generated by an earthquake are expected to arrive at their location. The seconds to minutes of advance warning can allow people and systems to take actions to protect life and property from destructive shaking. The U.S. Geological Survey (USGS), in collaboration with several partners, has been working to develop an early warning system for the United States. ShakeAlert, a system currently under development, is designed to cover the West Coast States of California, Oregon, and Washington.

Earthquake precursory events around epicenters and local active faults; the cases of two inland earthquakes in Iran

Science.gov (United States)

Valizadeh Alvan, H.; Mansor, S.; Haydari Azad, F.

2012-12-01

source and propagation of seismic waves. In many cases, active faults are capable of buildup and sudden release of tectonic stress. Hence, monitoring the active fault systems near epicentral regions of past earthquakes would be a necessity. In this paper, we try to detect possible anomalies in SLHF and AT during two moderate earthquakes of 6 - 6.5 M in Iran and explain the relationships between the seismic activities prior to these earthquake and active faulting in the area. Our analysis shows abnormal SLHF 5~10 days before these earthquakes. Meaningful anomalous concentrations usually occurred in the epicentral area. On the other hand, spatial distributions of these variations were in accordance with the local active faults. It is concluded that the anomalous increase in SLHF shows great potential in providing early warning of a disastrous earthquake, provided that there is a better understanding of the background noise due to the seasonal effects and climatic factors involved. Changes in near surface air temperature along nearby active faults, one or two weeks before the earthquakes, although not as significant as SLHF changes, can be considered as another earthquake indicator.

Feasibility study of short-term earthquake prediction using ionospheric anomalies immediately before large earthquakes

Science.gov (United States)

Heki, K.; He, L.

2017-12-01

We showed that positive and negative electron density anomalies emerge above the fault immediately before they rupture, 40/20/10 minutes before Mw9/8/7 earthquakes (Heki, 2011 GRL; Heki and Enomoto, 2013 JGR; He and Heki 2017 JGR). These signals are stronger for earthquake with larger Mw and under higher background vertical TEC (total electron conetent) (Heki and Enomoto, 2015 JGR). The epicenter, the positive and the negative anomalies align along the local geomagnetic field (He and Heki, 2016 GRL), suggesting electric fields within ionosphere are responsible for making the anomalies (Kuo et al., 2014 JGR; Kelley et al., 2017 JGR). Here we suppose the next Nankai Trough earthquake that may occur within a few tens of years in Southwest Japan, and will discuss if we can recognize its preseismic signatures in TEC by real-time observations with GNSS.During high geomagnetic activities, large-scale traveling ionospheric disturbances (LSTID) often propagate from auroral ovals toward mid-latitude regions, and leave similar signatures to preseismic anomalies. This is a main obstacle to use preseismic TEC changes for practical short-term earthquake prediction. In this presentation, we show that the same anomalies appeared 40 minutes before the mainshock above northern Australia, the geomagnetically conjugate point of the 2011 Tohoku-oki earthquake epicenter. This not only demonstrates that electric fields play a role in making the preseismic TEC anomalies, but also offers a possibility to discriminate preseismic anomalies from those caused by LSTID. By monitoring TEC in the conjugate areas in the two hemisphere, we can recognize anomalies with simultaneous onset as those caused by within-ionosphere electric fields (e.g. preseismic anomalies, night-time MSTID) and anomalies without simultaneous onset as gravity-wave origin disturbances (e.g. LSTID, daytime MSTID).

Earthquake wave propagation in immiscibly compressible porous soil

International Nuclear Information System (INIS)

Xue, S.; Kurita, S.; Izumi, M.

1993-01-01

This paper utilizes the formalism of the theory of immiscible compressible mixtures to formulate the wave propagation equation for the soil where the soil has been assumed as a binary mixture consisting of one solid phase and one fluid phase. The method is developed to solve the one dimensional wave equation by the above theory. The relations between the wave attenuating characteristic value Q and the volume fraction, the relative motion of two phases have been shown. It is concluded that based on such theory we can solve more precisely the soil behaviors while considering the interaction of structure and soil of immiscible mixture. (author)

A strong-motion hot spot of the 2016 Meinong, Taiwan, earthquake (Mw = 6.4

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Hiroo Kanamori

2017-01-01

Full Text Available Despite a moderate magnitude, Mw = 6.4, the 5 February 2016 Meinong, Taiwan, earthquake caused significant damage in Tainan City and the surrounding areas. Several seismograms display an impulsive S-wave velocity pulse with an amplitude of about 1 m s-1, which is similar to large S-wave pulses recorded for the past several larger damaging earthquakes, such as the 1995 Kobe, Japan, earthquake (Mw = 6.9 and the 1994 Northridge, California, earthquake (Mw = 6.7. The observed PGV in the Tainan area is about 10 times larger than the median PGV of Mw = 6.4 crustal earthquakes in Taiwan. We investigate the cause of the localized strong ground motions. The peak-to-peak ground-motion displacement at the basin sites near Tainan is about 35 times larger than that at a mountain site with a similar epicentral distance. At some frequency bands (0.9 - 1.1 Hz, the amplitude ratio is as large as 200. Using the focal mechanism of this earthquake, typical “soft” and “hard” crustal structures, and directivity inferred from the observed waveforms and the slip distribution, we show that the combined effect yields an amplitude ratio of 17 to 34. The larger amplitude ratios at higher frequency bands can be probably due to the effects of complex 3-D basin structures. The result indicates that even from a moderate event, if these effects simultaneously work together toward amplifying ground motions, the extremely large ground motions as observed in Tainan can occur. Such occurrences should be taken into consideration in hazard mitigation measures in the place with frequent moderate earthquakes.

Remotely Triggered Earthquakes Recorded by EarthScope's Transportable Array and Regional Seismic Networks: A Case Study Of Four Large Earthquakes

Science.gov (United States)

Velasco, A. A.; Cerda, I.; Linville, L.; Kilb, D. L.; Pankow, K. L.

2013-05-01

Changes in field stress required to trigger earthquakes have been classified in two basic ways: static and dynamic triggering. Static triggering occurs when an earthquake that releases accumulated strain along a fault stress loads a nearby fault. Dynamic triggering occurs when an earthquake is induced by the passing of seismic waves from a large mainshock located at least two or more fault lengths from the epicenter of the main shock. We investigate details of dynamic triggering using data collected from EarthScope's USArray and regional seismic networks located in the United States. Triggered events are identified using an optimized automated detector based on the ratio of short term to long term average (Antelope software). Following the automated processing, the flagged waveforms are individually analyzed, in both the time and frequency domains, to determine if the increased detection rates correspond to local earthquakes (i.e., potentially remotely triggered aftershocks). Here, we show results using this automated schema applied to data from four large, but characteristically different, earthquakes -- Chile (Mw 8.8 2010), Tokoku-Oki (Mw 9.0 2011), Baja California (Mw 7.2 2010) and Wells Nevada (Mw 6.0 2008). For each of our four mainshocks, the number of detections within the 10 hour time windows span a large range (1 to over 200) and statistically >20% of the waveforms show evidence of anomalous signals following the mainshock. The results will help provide for a better understanding of the physical mechanisms involved in dynamic earthquake triggering and will help identify zones in the continental U.S. that may be more susceptible to dynamic earthquake triggering.

Estimation of earthquake source parameters in the Kachchh seismic ...

Indian Academy of Sciences (India)

SEISAN software has been used to locate the identified local earthquakes, which were recorded at least three or more stations of the Kachchh seismological network. Three component spectra of S-wave are being inverted by using the Levenberg–Marquardt non-linear inversion technique, wherein the inversion scheme is ...

Building the Southern California Earthquake Center

Science.gov (United States)

Jordan, T. H.; Henyey, T.; McRaney, J. K.

2004-12-01

Kei Aki was the founding director of the Southern California Earthquake Center (SCEC), a multi-institutional collaboration formed in 1991 as a Science and Technology Center (STC) under the National Science Foundation (NSF) and the U. S. Geological Survey (USGS). Aki and his colleagues articulated a system-level vision for the Center: investigations by disciplinary working groups would be woven together into a "Master Model" for Southern California. In this presentation, we will outline how the Master-Model concept has evolved and how SCEC's structure has adapted to meet scientific challenges of system-level earthquake science. In its first decade, SCEC conducted two regional imaging experiments (LARSE I & II); published the "Phase-N" reports on (1) the Landers earthquake, (2) a new earthquake rupture forecast for Southern California, and (3) new models for seismic attenuation and site effects; it developed two prototype "Community Models" (the Crustal Motion Map and Community Velocity Model) and, perhaps most important, sustained a long-term, multi-institutional, interdisciplinary collaboration. The latter fostered pioneering numerical simulations of earthquake ruptures, fault interactions, and wave propagation. These accomplishments provided the impetus for a successful proposal in 2000 to reestablish SCEC as a "stand alone" center under NSF/USGS auspices. SCEC remains consistent with the founders' vision: it continues to advance seismic hazard analysis through a system-level synthesis that is based on community models and an ever expanding array of information technology. SCEC now represents a fully articulated "collaboratory" for earthquake science, and many of its features are extensible to other active-fault systems and other system-level collaborations. We will discuss the implications of the SCEC experience for EarthScope, the USGS's program in seismic hazard analysis, NSF's nascent Cyberinfrastructure Initiative, and other large collaboratory programs.

Global patterns of drought recovery

Energy Technology Data Exchange (ETDEWEB)

Schwalm, Christopher R.; Anderegg, William R. L.; Michalak, Anna M.; Fisher, Joshua B.; Biondi, Franco; Koch, George; Litvak, Marcy; Ogle, Kiona; Shaw, John D.; Wolf, Adam; Huntzinger, Deborah N.; Schaefer, Kevin; Cook, Robert; Wei, Yaxing; Fang, Yuanyuan; Hayes, Daniel; Huang, Maoyi; Jain, Atul; Tian, Hanqin

2017-08-09

Drought is a recurring multi-factor phenomenon with major impacts on natural and human systems1-3. Drought is especially important for land carbon sink variability, influencing climate regulation of the terrestrial biosphere4. While 20th Century trends in drought regime are ambiguous, “more extreme extremes” as well as more frequent and severe droughts3,7 are expected in the 21st Century. Recovery time, the length of time an ecosystem requires to revert to its pre-drought functional state, is a critical metric of drought impact. Yet the spatiotemporal patterning and controls of drought recovery are largely unknown. Here we use three distinct global datasets of gross primary productivity to show that across diverse terrestrial ecosystems drought recovery times are driven by biological productivity and biodiversity, with drought length and severity of secondary importance. Recovery time, especially for extreme droughts, and the areal extent of ecosystems in recovery from drought generally increase over the 20th Century, supporting an increase globally in drought impact8. Our results indicate that if future Anthropocene droughts become more widespread as expected, that droughts will become more frequent relative to recovery time. This increases the risk of entering a new regime where vegetation never recovers to its original state and widespread degradation of the land carbon sink ensues.

Comparative Analysis of Drought Indices for Drought Zone Scheme of Northern Khorasan Province of Iran

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Ehsan EYSHI REZAEI

2011-08-01

Full Text Available Drought is one of the natural disasters which deeply influenced agricultural production. Drought monitoring programs could help to forecast and mitigate the impacts of drought. In this study occurrence, severity, and duration of drought were evaluated by monthly rainfall data (1986-2005 that were recorded at all meteorological stations in north Khorasan province of Iran. Drought indices include Standard Rainfall Index (SPI, Decades Index (DI and Percent of Normal (PNI calculated and compared to determine drought severity, duration and drought occurrence for all stations. In addition, drought maps were prepared by Inverse Distance Weighted (IDW method, for each study zone. Based on these indices, the most extensive drought occurred in 1989, 1990, 1995, 1996, 2000, and 2001 years. The longest duration of drought based on SPI happened in 1994 and 1997 years. Furthermore, the extreme drought occurred in 1990 and 2001 in all stations. In conclusion, Central part of this province was more exposed to extreme drought during study period than other parts of this region.

Dynamic Earthquake Triggering on Seismogenic Faults in Oklahoma

Science.gov (United States)

Qin, Y.; Chen, X.; Peng, Z.; Aiken, C.

2016-12-01

Regions with high pore pressure are generally more susceptible to dynamic triggering from transient stress change caused by surface wave of distant earthquakes. The stress threshold from triggering studies can help understand the stress state of seismogenic faults. The recent dramatic seismicity increase in central US provides a rich database for assessing dynamic triggering phenomena. We begin our study by conducting a systematic analysis of dynamic triggering for the continental U.S using ANSS catalog (with magnitude of completeness Mc=3) from 49 global mainshocks (Ms>6.5, depth1kPa). We calculate β value for each 1° by 1° bins in 30 days before and 10 days after the mainshock. To identify regions that experience triggering from a distant mainshock, we generate a stacked map using β≥2 - which represents significant seismicity rate increase. As expected, the geothermal and volcanic fields in California show clear response to distant earthquakes. We also note areas in Oklahoma and north Texas show enhanced triggering, where wastewater-injection induced seismicity are occurring. Next we focus on Oklahoma and use a local catalog from Oklahoma Geological Survey with lower completeness threshold Mc to calculate the beta map in 0.2° by 0.2° bins for each selected mainshock to obtain finer spatial resolutions of the triggering behavior. For those grids with β larger than 2.0, we use waveforms from nearby stations to search for triggered events. The April 2015 M7.8 Nepal earthquake causes a statistically significant increase of local seismicity (β=3.5) in the Woodward area (west Oklahoma) during an on-going earthquake sequence. By visually examining the surface wave from the nearest station, we identify 3 larger local events, and 10 additional smaller events with weaker but discernable amplitude. Preliminary analysis shows that the triggering is related to Rayleigh wave, which would cause dilatational or shear stress changes along the strike direction of

FDM simulation of earthquakes off western Kyushu, Japan, using a land-ocean unified 3D structure model

Science.gov (United States)

Okamoto, Taro; Takenaka, Hiroshi; Nakamura, Takeshi; Hara, Tatsuhiko

2017-07-01

Seismic activity occurred off western Kyushu, Japan, at the northern end of the Okinawa Trough on May 6, 2016 (14:11 JST), 22 days after the onset of the 2016 Kumamoto earthquake sequence. The area is adjacent to the Beppu-Shimabara graben where the 2016 Kumamoto earthquake sequence occurred. In the area off western Kyushu, a M7.1 earthquake also occurred on November 14, 2015 (5:51 JST), and a tsunami with a height of 0.3 m was observed. In order to better understand these seismic activity and tsunamis, it is necessary to study the sources of, and strong motions due to, earthquakes in the area off western Kyushu. For such studies, validation of synthetic waveforms is important because of the presence of the oceanic water layer and thick sediments in the source area. We show the validation results for synthetic waveforms through nonlinear inversion analyses of small earthquakes ( M5). We use a land-ocean unified 3D structure model, 3D HOT finite-difference method ("HOT" stands for Heterogeneity, Ocean layer and Topography) and a multi-graphic processing unit (GPU) acceleration to simulate the wave propagations. We estimate the first-motion augmented moment tensor (FAMT) solution based on both the long-period surface waves and short-period body waves. The FAMT solutions systematically shift landward by about 13 km, on average, from the epicenters determined by the Japan Meteorological Agency. The synthetics provide good reproductions of the observed full waveforms with periods of 10 s or longer. On the other hand, for waveforms with shorter periods (down to 4 s), the later surface waves are not reproduced well, while the first parts of the waveforms (comprising P- and S-waves) are reproduced to some extent. These results indicate that the current 3D structure model around Kyushu is effective for generating full waveforms, including surface waves with periods of about 10 s or longer. Based on these findings, we analyze the 2015 M7.1 event using the cross

A Full-Wave Seismic Tomography for the Crustal Structure in the Metropolitan Beijing Region

Science.gov (United States)

Sun, A.; Zhao, L.; Chen, Q.

2008-12-01

The greater Beijing metropolitan region is located in an old cratonic block in northeast China with complex geology and several large historic earthquakes, such as the Sanhe-Pinggu earthquake (~M8.0) in 1679, the Xingtai earthquake (M7.2) in 1966, and the Tangshan earthquake (M7.8) in 1976. To enhance our understanding of the crustal structure and the seismotectonics under this region, we conduct a full-wave three-dimensional (3D) tomographic study of this region using the waveforms recorded by the newly established Beijing metropolitan digital seismic network. Since the Beijing network was put into operation in October 2001, there have been 89 local earthquakes of magnitude 3.0 and above. From these, we selected 23 events of magnitude 3.2 and above and obtained their waveform records at 50 stations within our area of interest. The types of instruments at these stations include broadband, short-period and very broadband. First-motion focal mechanisms were determined for these events. We used a regional 3D model obtained by seismic reflection surveys as the reference model and calculated the synthetic seismograms by the finite-difference method. In this first attempt at finite- frequency tomography for the Beijing region, we focus on the variation of the P-wave speed using the first- arriving P waves. We measure the frequency-dependent traveltime anomalies of the P waves by the cross- correlation between observed and synthetic P waveforms within several discrete frequency bands between 20-sec and 5-sec periods. The sensitivity or Frechet kernels of these measurements for the perturbations in P-wave speed were computed by the same finite-difference method. We will present the preliminary result in our full-wave seismic tomography for the Beijing region.

Systematic Analysis of Dynamic Earthquake Triggering Using the EarthScope's USArray Data

Science.gov (United States)

Cerda, I.; Gonzalez-Huizar, H.; Velasco, A. A.; Kilb, D. L.; Pankow, K. L.

2011-12-01

Advances are continually made in our understanding of the physics governing earthquake triggering, yet many questions remain. Here, we investigate if there exists a minimum dynamic stress threshold (i.e., in amplitude, frequency or both) required to trigger remote earthquakes using data collected by >400 stations in EarthScope's USArray Transportable Array (USArray TA) network, supplemented by data from ~100 local seismic network stations when available. We also assess if remote triggering is enhanced if the orientation of the passing seismic waves aligns favorably with the local stress field and/or orientation of faults in the local triggered region. The uniform spacing of the USArray TA stations across the contiguous USA allows us to examine these types of characteristics of remote triggering within a variety of tectonic provinces, background seismicity rates, and within regions of both documented cases of triggered earthquakes and areas of no known triggered earthquakes. Our work focuses on assessing remote triggering capabilities of two teleseismic megatrust events (Japan M=9.0 2011 and Chile M=8.8 2010) and two large regional events (Baja California M=7.2 2010 and Wells Nevada M=6.0 2008). These events provide a range of seismic wave amplitudes and orientations across the footprint of the USArray TA stations. We use the Antelope software to develop an automated detection algorithm that computes the short-term (1 s) average (STA) to long-term (10 s) average (LTA) ratio, which we apply to 5 Hz high pass filtered data. Using a threshold ratio of 3.5 we apply this algorithm to data spanning ±5 hours from the mainshock's P-wave arrival time. We find that for each of our four mainshocks our algorithm nets, on average, hundreds of detections within the 10 hour time windows. Results suggest the orientation of the passing seismic waves can play a role in the high (or low) number of detections in select regions (e.g., western part of Texas), but in other regions there

Future Drought Projections over the Iberian Peninsula using Drought Indices

Science.gov (United States)

Garcia-Valdecasas Ojeda, M.; Yeste Donaire, P.; Góngora García, T. M.; Gámiz-Fortis, S. R.; Castro-Diez, Y.; Esteban-Parra, M. J.

2017-12-01

Currently, drought events are the cause of numerous annual economic losses. In a context of climate change, it is expected an increase in the severity and the frequency of drought occurrences, especially in areas such as the Mediterranean region. This study makes use of two drought indices in order to analyze the potential changes on future drought events and their effects at different time scales over a vulnerable region, the Iberian Peninsula. The indices selected were the Standardized Precipitation Evapotranspiration Index (SPEI), which takes into account the global warming through the temperature, and the Standardized Precipitation Index (SPI), based solely on precipitation data, at a spatial resolution of 0.088º ( 10 km). For their computation, current (1980-2014) and future (2021-2050 and 2071-2100) high resolution simulations were carried out using the Weather Research and Forecasting (WRF) model over a domain centered in the Iberian Peninsula, and nested in the 0.44 EUROCORDEX region. WRF simulations were driven by two different global bias-corrected climate models: the version 1 of NCAR's Community Earth System Model (CESM1) and the Max Planck Institute's Earth System Model (MPI-ESM-LR), and under two different Representative Concentration Pathway (RCP) scenarios: RCP 4.5 and RCP 8.5. Future projections were analyzed regarding to changes in mean, median and variance of drought indices with respect to the historical distribution, as well as changes in the frequency and duration of moderate and severe drought events. In general, results suggest an increase in frequency and severity of drought, especially for 2071-2100 period in the RCP 8.5 scenario. Results also shown an increase of drought phenomena more evident using the SPEI. Conclusions from this study could provide a valuable contribution to the understanding of how the increase of the temperature would affect the drought variability in the Mediterranean regions which is necessary for a suitable

Shear-wave polarization analysis of the seismic swarm following the July 9th 1998 Faial (Azores) earthquake

Science.gov (United States)

Dias, N. A.; Matias, L.; Tellez, J.; Senos, L.; Gaspar, J. L.

2003-04-01

The Azores Islands, located at a tectonic triple Junction, geodynamically are a highly active place. The seismicity in this region occurs mainly in the form of two types of seismic swarms with tectonic and/or volcanic origins, lasting from hours to years. In some cases the swarm follows a main stronger shock, while in others the more energetic event occurs sometime after the beginning of the swarm. In order to understand the complex phenomena of this region, a multidisciplinary approach is needed, involving geophysical, geological and geochemical studies such as the one being carried under the MASHA project (POCTI/CTA/39158/2001), On July 9th 1998 an Mw=6.2 earthquake stroked the island of Faial, in the central group of the Azores archipelago, followed by a seismic swarm still active today. We will present some preliminary results of the shear-wave polarization analysis of a selected dataset of events of this swarm. These correspond to the 112 best- constrained events, record during the first 2 weeks by the seismic network deployed on the 3 islands surrounding the area of the main shock. The objective was to analyse the behaviour of the S wave polarization and the eventual relationship with the presence of seismic anisotropy under the seismic stations, and to correlate this with the regional structure and origin of the Azores plateau. Two main tectonic features are observable on the islands, one primarily orientated SE-NW and the other crossing it roughly with the WNW-ESE direction. The polarization direction observed in the majority of the seismic stations is not stable, varying from SE-NW to WSW-ENE, and showing also the presence in same cases of shear-wave splitting, indicating the presence of anisotropy. Part of the polarization seems to be coherent with the direction of the local tectonic features, but its instability suggest a more complex seismic anisotropy than that proposed by the model EDA of Crampin. Furthermore, the dataset revealed some limitations to

SIMULATION OF ANALYTICAL TRANSIENT WAVE DUE TO DOWNWARD BOTTOM THRUST

Directory of Open Access Journals (Sweden)

Sugih Sudharma Tjandra

2015-11-01

Full Text Available Generation process is an important part of understanding waves, especially tsunami. Large earthquake under the sea is one major cause of tsunamis. The sea surface deforms as a response from the sea bottom motion caused by the earthquake. Analytical description of surface wave generated by bottom motion can be obtained from the linearized dispersive model. For a bottom motion in the form of a downward motion, the result is expressed in terms of improper integral. Here, we focus on analyzing the convergence of this integral, and then the improper integral is approximated into a finite integral so that the integral can be evaluated numerically. Further, we simulate free surface elevation for three different type of bottom motions, classified as impulsive, intermediate, and slow  movements. We demonstrate that the wave propagating to the right, with a depression as the leading wave, followed with subsequent wave crests. This phenomena is often observed in most tsunami events.

Site Effect Assessment of Earthquake Ground Motion Based on Advanced Data Processing of Microtremor Array Measurements

Science.gov (United States)

Liu, L.; He, K.; Mehl, R.; Wang, W.; Chen, Q.

2008-12-01

High-resolution near-surface geologic information is essential for earthquake ground motion prediction. The near-surface geology forms the critical constituent to influence seismic wave propagation, which is known as the local site effects. We have collected microtremor data over 1000 sites in Beijing area for extracting the much needed earthquake engineering parameters (primarily sediment thickness, with the shear wave velocity profiling at a few important control points) in this heavily populated urban area. Advanced data processing algorithms are employed in various stages in assessing the local site effect on earthquake ground motion. First, we used the empirical mode decomposition (EMD), also known as the Hilbert-Huang transform (HHT), to enhance the microtremor data analysis by excluding the local transients and continuous monochromic industrial noises. With this enhancement we have significantly increased the number of data points to be useful in delineating sediment thickness in this area. Second, we have used the cross-correlation of microtremor data acquired for the pairs of two adjacent sites to generate a 'pseudo-reflection' record, which can be treated as the Green function of the 1D layered earth model at the site. The sediment thickness information obtained this way is also consistent with the results obtained by the horizontal to vertical spectral ratio method (HVSR). For most sites in this area, we can achieve 'self consistent' results among different processing skechems regarding to the sediment thickness - the fundamental information to be used in assessing the local site effect. Finally, the pseudo-spectral time domain method was used to simulate the seismic wave propagation caused by a scenario earthquake in this area - the 1679 M8 Sanhe-pinggu earthquake. The characteristics of the simulated earthquake ground motion have found a general correlation with the thickness of the sediments in this area. And more importantly, it is also in agreement

Phase characteristics of earthquake accelerogram and its application

International Nuclear Information System (INIS)

Ohsaki, Y.; Iwasaki, R.; Ohkawa, I.; Masao, T.

1979-01-01

As the input earthquake motion for seismic design of nuclear power plant structures and equipments, an artificial time history compatible with smoothed design response spectrum is frequently used. This paper deals with a wave generation technique based on phase characteristics in earthquake accelerograms as an alternate of envelope time function. The concept of 'phase differences' distribution' is defined to represent phase characteristics of earthquake motion. The procedure proposed in this paper consists of following steps; (1) Specify a design response spectrum and derive a corresponding initial modal amplitude. (2) Determine a phase differences' distribution corresponding to an envelope function, the shape of which is dependent on magnitude and epicentral distance of an earthquake. (3) Derive the phase angles at all modal frequencies from the phase differences' distribution. (4) Generate a time history by inverse Fourier transeform on the basis of the amplitudes and the phase angles thus determined. (5) Calculate the response spectrum. (6) Compare the specified and calculated response spectra, and correct the amplitude at each frequency so that the response spectrum will be consistent with the specified. (7) Repeat the steps 4 through 6, until the specified and calculated response spectra become consistent with sufficient accuracy. (orig.)

Imaging the Fine-Scale Structure of the San Andreas Fault in the Northern Gabilan Range with Explosion and Earthquake Sources

Science.gov (United States)

Xin, H.; Thurber, C. H.; Zhang, H.; Wang, F.

2014-12-01

A number of geophysical studies have been carried out along the San Andreas Fault (SAF) in the Northern Gabilan Range (NGR) with the purpose of characterizing in detail the fault zone structure. Previous seismic research has revealed the complex structure of the crustal volume in the NGR region in two-dimensions (Thurber et al., 1996, 1997), and there has been some work on the three-dimensional (3D) structure at a coarser scale (Lin and Roecker, 1997). In our study we use earthquake body-wave arrival times and differential times (P and S) and explosion arrival times (only P) to image the 3D P- and S-wave velocity structure of the upper crust along the SAF in the NGR using double-difference (DD) tomography. The earthquake and explosion data types have complementary strengths - the earthquake data have good resolution at depth and resolve both Vp and Vs structure, although only where there are sufficient seismic rays between hypocenter and stations, whereas the explosions contribute very good near-surface resolution but for P waves only. The original dataset analyzed by Thurber et al. (1996, 1997) included data from 77 local earthquakes and 8 explosions. We enlarge the dataset with 114 more earthquakes that occurred in the study area, obtain improved S-wave picks using an automated picker, and include absolute and cross-correlation differential times. The inversion code we use is the algorithm tomoDD (Zhang and Thurber, 2003). We assess how the P and S velocity models and earthquake locations vary as we alter the inversion parameters and the inversion grid. The new inversion results show clearly the fine-scale structure of the SAF at depth in 3D, sharpening the image of the velocity contrast from the southwest side to the northeast side.

Analyses of surface motions caused by the magnitude 9.0 2004 Sumatra earthquake

DEFF Research Database (Denmark)

Khan, Shfaqat Abbas; Gudmundsson, Ó.

The Sumatra, Indonesia, earthquake on December 26th was one of the most devastating earthquakes in history. With a magnitude of Mw = 9.0 it is the forth largest earthquake recorded since 1900. It occurred about one hundred kilometers off the west coast of northern Sumatra, where the relatively thin...... of years. The result was a devastating tsunami hitting coastlines across the Indian Ocean killing more than 225,000 people in Sri Lanka, India, Indonesia, Thailand and Malaysia. An earthquake of this magnitude is expected to involve a displacement on the fault on the order of 10 meters. But, what...... was the actual amplitude of the surface motions that triggered the tsunami? This can be constrained using the amplitudes of elastic waves radiated from the earthquake, or by direct measurements of deformation. Here we present estimates of the deformation based on continuous Global Positioning System (GPS...

Seismic moment tensor for anisotropic media: implication for Non-double-couple earthquakes

Science.gov (United States)

Cai, X.; Chen, X.; Chen, Y.; Cai, M.

2008-12-01

It is often found that the inversion results of seismic moment tensor from real seismic recorded data show the trace of seismic moment tensor M is not zero, a phenomenon called non-double-couple earthquake sources mechanism. Recently we have derived the analytical expressions of M in transversely isotropic media with the titled axis of symmetry and the results shows even only pure shear-motion of fault can lead to the implosive components determined by several combined anisotropic elastic constants. Many non-double-couple earthquakes from observations often appear in volcanic and geothermal areas (Julian, 1998), where there exist a mount of stress-aligned fluid-saturated parallel vertical micro-cracks identical to transversely isotropic media (Crampin, 2008), this stress-aligned crack will modify the seismic moment tensor. In another word, non-double-couple earthquakes don't mean to have a seismic failure movement perpendicular to the fault plane, while traditional research of seismic moment tensor focus on the case of isotropy, which cannot provide correct interpretation of seismic source mechanism. Reference: Julian, B.R., Miller, A.D. and Foulger, G.R., 1998. Non-double-couple earthquakes,1. Theory, Rev. Geophys., 36, 525¨C549. Crampin,S., Peacock,S., 2008, A review of the current understanding of seismic shear-wave splitting in the Earth's crust and common fallacies in interpretation, wave motion, 45,675-722

The U.S./Canadian GEO Bilateral Drought Indices and Definitions Study: Implications for the Canadian Drought Monitor and a Global Drought Early Warning System

Science.gov (United States)

Hadwen, T.; Heim, R. R.; Howard, A.

2011-12-01

Drought is a difficult phenomenon to define; the way in which it is monitored, measured, assessed and even the very definition of drought vary from location to location based on the regional climate and the potential impacts. Drought is not an absolute condition but an evolving state brought on by relatively dry weather, growing more severe over time. There are many factors that define a drought and many more that define its impacts. Many definitions and indices are based solely on meteorological characteristics. Although this approach has merit, it is often necessary to go further to define those meteorological conditions in a way that is relevant to the land and water use in a region. A Drought Indices and Definitions Study was initiated in 2010 as part of a GEO Bilateral effort to examine drought across the U.S. and Canada. The Study's deliverables will include a survey of the drought indices used to monitor drought, and a bibliography of research addressing the nature of drought, across the diverse climates of the continent. With an increasing pressure to utilize drought monitoring as a primary indicator of need for disaster assistance, the reliability of drought indices must be validated and utilized in appropriate in various regions. In 2009, following over five years of participation in the North American Drought Monitor (NA-DM), the National Agroclimate Information Service of Agriculture and Agri-Food Canada initiated a project to develop a Canadian Drought Monitor (Can-DM), based on primary principles used in the NA-DM and the US Drought Monitor (US-DM). The process of developing an operational monitoring tool and using drought indices in a vast and environmentally diverse country has been challenging. in Canada, many of the commonly used indices are not appropriate in certain regions or data densities do not allow for proper use. This paper will discuss the experiences that the Can-DM team has had dealing with these challenges, how these experiences

Elusive drought: uncertainty in observed trends and short- and long-term CMIP5 projections

Directory of Open Access Journals (Sweden)

B. Orlowsky

2013-05-01

Full Text Available Recent years have seen a number of severe droughts in different regions around the world, causing agricultural and economic losses, famines and migration. Despite their devastating consequences, the Standardised Precipitation Index (SPI of these events lies within the general range of observation-based SPI time series and simulations from the 5th phase of the Coupled Model Intercomparison Project (CMIP5. In terms of magnitude, regional trends of SPI over the last decades remain mostly inconclusive in observation-based datasets and CMIP5 simulations, but Soil Moisture Anomalies (SMAs in CMIP5 simulations hint at increased drought in a few regions (e.g., the Mediterranean, Central America/Mexico, the Amazon, North-East Brazil and South Africa. Also for the future, projections of changes in the magnitude of meteorological (SPI and soil moisture (SMA drought in CMIP5 display large spreads over all time frames, generally impeding trend detection. However, projections of changes in the frequencies of future drought events display more robust signal-to-noise ratios, with detectable trends towards more frequent drought before the end of the 21st century in the Mediterranean, South Africa and Central America/Mexico. Other present-day hot spots are projected to become less drought-prone, or display non-significant changes in drought occurrence. A separation of different sources of uncertainty in projections of meteorological and soil moisture drought reveals that for the near term, internal climate variability is the dominant source, while the formulation of Global Climate Models (GCMs generally becomes the dominant source of spread by the end of the 21st century, especially for soil moisture drought. In comparison, the uncertainty from Green-House Gas (GHG concentrations scenarios is negligible for most regions. These findings stand in contrast to respective analyses for a heat wave index, for which GHG concentrations scenarios constitute the main source

Characteristics and drivers of drought in Europe-a summary of the DROUGHT-R&SPI project

NARCIS (Netherlands)

Tallaksen, Lena M.; Stagge, James H.; Stahl, Kerstin; Gudmundsson, Lukas; Orth, Rene; Seneviratne, Sonia I.; Loon, van Anne F.; Lanen, van Henny A.J.

2015-01-01

A prerequisite to mitigate the wide range of drought impacts is to establish a good understanding of the drought generating mechanisms from their initiation as a meteorological drought through to their development as soil moisture and hydrological drought. The DROUGHT-R&SPI project has

Inversion of GPS-measured coseismic displacements for source parameters of Taiwan earthquake

Science.gov (United States)

Lin, J. T.; Chang, W. L.; Hung, H. K.; Yu, W. C.

2016-12-01

We performed a method of determining earthquake location, focal mechanism, and centroid moment tensor by coseismic surface displacements from daily and high-rate GPS measurements. Unlike commonly used dislocation model where fault geometry is calculated nonlinearly, our method makes a point source approach to evaluate these parameters in a solid and efficient way without a priori fault information and can thus provide constrains to subsequent finite source modeling of fault slip. In this study, we focus on the resolving ability of GPS data for moderate (Mw=6.0 7.0) earthquakes in Taiwan, and four earthquakes were investigated in detail: the March 27 2013 Nantou (Mw=6.0), the June 2 2013 Nantou (Mw=6.3) , the October 31 2013 Ruisui (Mw=6.3), and the March 31 2002 Hualien (ML=6.8) earthquakes. All these events were recorded by the Taiwan continuous GPS network with data sampling rates of 30-second and 1 Hz, where the Mw6.3 Ruisui earthquake was additionally recorded by another local GPS network with a sampling rate of 20 Hz. Our inverted focal mechanisms of all these earthquakes are consistent with the results of GCMT and USGS that evaluates source parameters by dynamic information from seismic waves. We also successfully resolved source parameters of the Mw6.3 Ruisui earthquake within only 10 seconds following the earthquake occurrence, demonstrating the potential of high-rate GPS data on earthquake early warning and real-time determination of earthquake source parameters.

Effects in Morocco of the Lisboa earthquake 1 November 1755

International Nuclear Information System (INIS)

Levret, A.

1988-05-01

Within the framework of a cooperative agreement Sofratome/Office National d'Electricite of Morocco and Sofratome/Electricidade de Portugal, a study has been conducted as to the effects of the November 1, 1755 Lisbon earthquake in Morocco. This event, the effects of which have been described at length in Portugal, was likewise strongly felt in Morocco, especially on the Atlantic coast, which was laid waste not only through the direct agency of seismic waves, but also through that of a formidable tsunami. In old texts, the descriptions of these conjugate effects has been rendered with varying degrees of overstatement. The procedure adopted in order to arrive at a precise identification of the effects and their origin and an evaluation of intensity involves three stages: a) an assessment of the reliability of the documents used; b) a thoroughgoing analysis of the descriptions with the object of discriminating between the direct effects of the earthquake and those ascribable to the action of the tidal wave: c) a readjustment of the intensities by analysis of the global effects of the earthquake not only in Morocco but also in Portugal and Spain. Then a comparison of these with the well- documented effects of the recent, February 28, 1969 earthquake, originating at the same source. Extrapolated isoseismals for the effects in Morocco of the 1755 event derived from this study are then assigned. In the light of current knowledge concerning the historical seismicity of the Iberian African collision zone, an outline of the maximum observed intensities is proposed [fr

Observations of an ionospheric perturbation arising from the Coalinga earthquake of May 2, 1983

International Nuclear Information System (INIS)

Wolcott, J.H.; Simons, D.J.; Lee, D.D.; Nelson, R.A.

1984-01-01

An ionospheric perturbation that was produced by the Coalinga earthquake of May 2, 1983, was detected by a network of high-frequency radio links in northern California. The ionospheric refraction regions of all five HF propagation paths, at distances between 160 and 285 km (horizontal range) from the epicenter, were affected by a ground-motion-induced acoustic pulse that propagated to ionospheric heights. The acoustic pulse was produced by the earthquake-induced seismic waves rather than the vertical ground motion above the epicenter. These observations appear to be the first ionospheric disturbances to be reported this close to an earthquake epicenter

Stress Regime in the Nepalese Himalaya from Recent Earthquakes.

Science.gov (United States)

Pant, M.; Karplus, M. S.; Velasco, A. A.; Nabelek, J.; Kuna, V. M.; Ghosh, A.; Mendoza, M.; Adhikari, L. B.; Sapkota, S. N.; Klemperer, S. L.; Patlan, E.

2017-12-01

The two recent earthquakes, April 25, 2015 Mw 7.8 (Gorkha earthquake) and May 12, 2015 Mw 7.2, at the Indo-Eurasian plate margin killed thousands of people and caused billion dollars of property loss. In response to these events, we deployed a dense array of seismometers to record the aftershocks along Gorkha earthquake rupture area. Our network NAMASTE (Nepal Array Measuring Aftershock Seismicity Trailing Earthquake) included 45 different seismic stations (16 short period, 25 broadband, and 4 strong motion sensors) covering a large area from north-central Nepal to south of the Main Frontal Thrust at a spacing of 20 km. The instruments recorded aftershocks from June 2015 to May 2016. We used time domain short term average (STA) and long term average (LTA) algorithms (1/10s and 4/40s) respectively to detect the arrivals and then developed an earthquake catalog containing 9300 aftershocks. We are manually picking the P-wave first motion arrival polarity to develop a catalog of focal mechanisms for the larger magnitude (>M3.0) events with adequate (>10) arrivals. We hope to characterize the seismicity and stress mechanisms of the complex fault geometries in the Nepalese Himalaya and to address the geophysical processes controlling seismic cycles in the Indo-Eurasian plate margin.

Earthquake Hazard for Aswan High Dam Area

Science.gov (United States)

Ismail, Awad

2016-04-01

Earthquake activity and seismic hazard analysis are important components of the seismic aspects for very essential structures such as major dams. The Aswan High Dam (AHD) created the second man-made reservoir in the world (Lake Nasser) and is constructed near urban areas pose a high-risk potential for downstream life and property. The Dam area is one of the seismically active regions in Egypt and is occupied with several cross faults, which are dominant in the east-west and north-south. Epicenters were found to cluster around active faults in the northern part of Lake and AHD location. The space-time distribution and the relation of the seismicity with the lake water level fluctuations were studied. The Aswan seismicity separates into shallow and deep seismic zones, between 0 and 14 and 14 and 30 km, respectively. These two seismic zones behave differently over time, as indicated by the seismicity rate, lateral extent, b-value, and spatial clustering. It is characterized by earthquake swarm sequences showing activation of the clustering-events over time and space. The effect of the North African drought (1982 to present) is clearly seen in the reservoir water level. As it decreased and left the most active fault segments uncovered, the shallow activity was found to be more sensitive to rapid discharging than to the filling. This study indicates that geology, topography, lineations in seismicity, offsets in the faults, changes in fault trends and focal mechanisms are closely related. No relation was found between earthquake activity and both-ground water table fluctuations and water temperatures measured in wells located around the Kalabsha area. The peak ground acceleration is estimated in the dam site based on strong ground motion simulation. This seismic hazard analyses have indicated that AHD is stable with the present seismicity. The earthquake epicenters have recently took place approximately 5 km west of the AHD structure. This suggests that AHD dam must be

Evaluation of seismic source, ground motion, tsunami based on the Tohoku earthquake

Energy Technology Data Exchange (ETDEWEB)

NONE

2012-08-15

Our source models for the Mw9.0 Tohoku earthquake either inferred using tsunami data or from seismic data are featured with large slip along the Japan Trench. Our results indicated that the tsunami water levels at the Fukushima Daiichi and Daini NPPs were dominated by the large slip along the Japan Trench. Our analysis suggested that the difference in water levels at these two sites were caused by the waveform overlap effects due to delays of rupture starting times and wave propagation time. It also follows that the short period ground motions recorded during such an Mw9.0 mega thrust earthquake were comparable with those of an Mw8.0 earthquake. (author)

Tsunami simulation of 2011 Tohoku-Oki Earthquake. Evaluation of difference in tsunami wave pressure acting around Fukushima Daiichi Nuclear Power Station and Fukushima Daini Nuclear Power Station among different tsunami source models

International Nuclear Information System (INIS)

Fujihara, Satoru; Hashimoto, Norihiko; Korenaga, Mariko; Tamiya, Takahiro

2016-01-01

Since the 2011 Tohoku-Oki Earthquake, evaluations based on a tsunami simulation approach have had a very important role in promoting tsunami disaster prevention measures in the case of mega-thrust earthquakes. When considering tsunami disaster prevention measures based on the knowledge obtained from tsunami simulations, it is important to carefully examine the type of tsunami source model. In current tsunami simulations, there are various ways to set the tsunami source model, and a considerable difference in tsunami behavior can be expected among the tsunami source models. In this study, we carry out a tsunami simulation of the 2011 Tohoku-Oki Earthquake around Fukushima Daiichi (I) Nuclear Power Plant and Fukushima Daini (II) Nuclear Power Plant in Fukushima Prefecture, Japan, using several tsunami source models, and evaluate the difference in the tsunami behavior in the tsunami inundation process. The results show that for an incoming tsunami inundating an inland region, there are considerable relative differences in the maximum tsunami height and wave pressure. This suggests that there could be false information used in promoting tsunami disaster prevention measures in the case of mega-thrust earthquakes, depending on the tsunami source model. (author)

Central Asia earthquake catalogue from ancient time to 2009

Directory of Open Access Journals (Sweden)

Natalya N. Mikhailova

2015-04-01

Full Text Available In this work, we present the seismic catalogue compiled for Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan and Turkmenistan in the framework of the Earthquake Model Central Asia (EMCA project. The catalogue from 2000 B.C. to 2009 A.D. is composed by 33,034 earthquakes in the MLH magnitude (magnitude by surface waves on horizontal components widely used in practice of the former USSR countries range from 1.5 to 8.3. The catalogue includes both macroseimic and instrumental constrained data, with about 32,793 earthquake after 1900 A.D. The main sources and procedure used to compile the catalogues are discussed, and the comparison with the ISC-GEM catalogue presented. Magnitude of completeness analysis shows that the catalogue is complete down to magnitude 4 from 1959 and to magnitude 7 from 1873, whereas the obtained regional b value is 0.805.

The association between preceding drought occurrence and heat waves in the Mediterranean

Science.gov (United States)

Russo, Ana; Gouveia, Célia M.; Ramos, Alexandre M.; Páscoa, Patricia; Trigo, Ricardo M.

2017-04-01

A large number of weather driven extreme events has occurred worldwide in the last decade, namely in Europe that has been struck by record breaking extreme events with unprecedented socio-economic impacts, including the mega-heatwaves of 2003 in Europe and 2010 in Russia, and the large droughts in southwestern Europe in 2005 and 2012. The last IPCC report on extreme events points that a changing climate can lead to changes in the frequency, intensity, spatial extent, duration, and timing of weather and climate extremes. These, combined with larger exposure, can result in unprecedented risk to humans and ecosystems. In this context it is becoming increasingly relevant to improve the early identification and predictability of such events, as they negatively affect several socio-economic activities. Moreover, recent diagnostic and modelling experiments have confirmed that hot extremes are often preceded by surface moisture deficits in some regions throughout the world. In this study we analyze if the occurrence of hot extreme months is enhanced by the occurrence of preceding drought events throughout the Mediterranean area. In order to achieve this purpose, the number of hot days in the regions' hottest month will be associated with a drought indicator. The evolution and characterization of drought was analyzed using both the Standardized Precipitation Evaporation Index (SPEI) and the Standardized Precipitation Index (SPI), as obtained from CRU TS3.23 database for the period 1950-2014. We have used both SPI and SPEI for different time scales between 3 and 9 months with a spatial resolution of 0.5°. The number of hot days and nights per month (NHD and NHN) was determined using the ECAD-EOBS daily dataset for the same period and spatial resolution (dataset v14). The NHD and NHN were computed, respectively, as the number of days with a maximum or minimum temperature exceeding the 90th percentile. Results show that the most frequent hottest months for the Mediterranean

Possible Mechanisms for Generation of Anomalously High PGA During the 2011 Tohoku Earthquake

Science.gov (United States)

Pavlenko, O. V.

2017-08-01

Mechanisms are suggested that could explain anomalously high PGAs (peak ground accelerations) exceeding 1 g recorded during the 2011 Tohoku earthquake ( M w = 9.0). In my previous research, I studied soil behavior during the Tohoku earthquake based on KiK-net vertical array records and revealed its `atypical' pattern: instead of being reduced in the near-source zones as usually observed during strong earthquakes, shear moduli in soil layers increased, indicating soil hardening, and reached their maxima at the moments of the highest intensity of strong motion, then reduced. We could explain this assuming that the soils experienced some additional compression. The observed changes in the shapes of acceleration time histories with distance from the source, such as a decrease of the duration and an increase of the intensity of strong motion, indicate phenomena similar to overlapping of seismic waves and a shock wave generation, which led to the compression of soils. The phenomena reach their maximum in the vicinity of stations FKSH10, TCGH16, and IBRH11, where the highest PGAs were recorded; at larger epicentral distances, PGAs sharply fall. Thus, the occurrence of anomalously high PGAs on the surface can result from the combination of the overlapping of seismic waves at the bottoms of soil layers and their increased amplification by the pre-compressed soils.

Drought in the Emerald City

International Nuclear Information System (INIS)

Babcock, S.D.

1993-01-01

This paper discusses a drought preparedness study being conducted for the Cedar River and Green River basins in western Washington state. The study is one of four regional case studies being managed by the U.S. Army Corps of Engineers as part of the National Study of Water Management During Drought. The overriding objective of the drought preparedness study is to leave the region better prepared for drought, through demonstration and test of drought preparedness tools and strategies. The study has served as a vehicle to promote a greater regional focus on drought related water supply problem solving. The 1992 drought in the Seattle/Tacoma metropolitan area provided a unique opportunity for the study team to demonstrate approaches to drought management being researched and tested as part of the study

Estimating drought risk across Europe from reported drought impacts, hazard indicators and vulnerability factors

Science.gov (United States)

Blauhut, V.; Stahl, K.; Stagge, J. H.; Tallaksen, L. M.; De Stefano, L.; Vogt, J.

2015-12-01

Drought is one of the most costly natural hazards in Europe. Due to its complexity, drought risk, the combination of the natural hazard and societal vulnerability, is difficult to define and challenging to detect and predict, as the impacts of drought are very diverse, covering the breadth of socioeconomic and environmental systems. Pan-European maps of drought risk could inform the elaboration of guidelines and policies to address its documented severity and impact across borders. This work (1) tests the capability of commonly applied hazard indicators and vulnerability factors to predict annual drought impact occurrence for different sectors and macro regions in Europe and (2) combines information on past drought impacts, drought hazard indicators, and vulnerability factors into estimates of drought risk at the pan-European scale. This "hybrid approach" bridges the gap between traditional vulnerability assessment and probabilistic impact forecast in a statistical modelling framework. Multivariable logistic regression was applied to predict the likelihood of impact occurrence on an annual basis for particular impact categories and European macro regions. The results indicate sector- and macro region specific sensitivities of hazard indicators, with the Standardised Precipitation Evapotranspiration Index for a twelve month aggregation period (SPEI-12) as the overall best hazard predictor. Vulnerability factors have only limited ability to predict drought impacts as single predictor, with information about landuse and water resources as best vulnerability-based predictors. (3) The application of the "hybrid approach" revealed strong regional (NUTS combo level) and sector specific differences in drought risk across Europe. The majority of best predictor combinations rely on a combination of SPEI for shorter and longer aggregation periods, and a combination of information on landuse and water resources. The added value of integrating regional vulnerability information

Traveling waves in a spring-block chain sliding down a slope

Science.gov (United States)

Morales, J. E.; James, G.; Tonnelier, A.

2017-07-01

Traveling waves are studied in a spring slider-block model. We explicitly construct front waves (kinks) for a piecewise-linear spinodal friction force. Pulse waves are obtained as the matching of two traveling fronts with identical speeds. Explicit formulas are obtained for the wavespeed and the wave form in the anticontinuum limit. The link with localized waves in a Burridge-Knopoff model of an earthquake fault is briefly discussed.

Good practice at Onagawa power plant during the 3.11 Great East Japan Earthquake

International Nuclear Information System (INIS)

Wakabayashi, Toshiaki

2016-01-01

This paper describes the situation of Onagawa Nuclear Power Station after The off the Pacific Coast of Tohoku Earthquake on March 11, 2011: (1) outline of situation of nuclear power plant Unit 1, 2 and 3, (2) assumption of push wave from the recognition of the tsunami due to large earthquakes that occurred in the past and tsunami countermeasures, and securement of cooling function at the time of push/pull wave based on emergency seawater pumps, (3) installation of handrail sticks on the central control room monitoring and control panel as a countermeasure from the lessons from the past earthquakes, (4) improvement of the seismic tolerance of facilities, and (5) earthquake resistant reinforcement of main office building and new construction of a seismic isolation office building. As response to emergency situation, the following are described: (1) unification of external response service at the head office, and the helicopter transportation of goods due to power plant needs as the power station support from the head office, and (2) as the countermeasures of on-site power plant, the duplication of information transmission route and the survey/examination and countermeasures by individual teams for each problem (especially, fire at Unit 1 and seawater infiltration at Unit 2). In additive, through the emergency response at the time of The off the Pacific Coast of Tohoku Earthquake, this paper examined the required qualities of an on-site commander based on the experience stories of persons concerned. (A.O.)

Explosion Generated Seismic Waves and P/S Methods of Discrimination from Earthquakes with Insights from the Nevada Source Physics Experiments

Science.gov (United States)

Walter, W. R.; Ford, S. R.; Pitarka, A.; Pyle, M. L.; Pasyanos, M.; Mellors, R. J.; Dodge, D. A.

2017-12-01

The relative amplitudes of seismic P-waves to S-waves are effective at identifying underground explosions among a background of natural earthquakes. These P/S methods appear to work best at frequencies above 2 Hz and at regional distances ( >200 km). We illustrate this with a variety of historic nuclear explosion data as well as with the recent DPRK nuclear tests. However, the physical basis for the generation of explosion S-waves, and therefore the predictability of this P/S technique as a function of path, frequency and event properties such as size, depth, and geology, remains incompletely understood. A goal of current research, such as the Source Physics Experiments (SPE), is to improve our physical understanding of the mechanisms of explosion S-wave generation and advance our ability to numerically model and predict them. The SPE conducted six chemical explosions between 2011 and 2016 in the same borehole in granite in southern Nevada. The explosions were at a variety of depths and sizes, ranging from 0.1 to 5 tons TNT equivalent yield. The largest were observed at near regional distances, with P/S ratios comparable to much larger historic nuclear tests. If we control for material property effects, the explosions have very similar P/S ratios independent of yield or magnitude. These results are consistent with explosion S-waves coming mainly from conversion of P- and surface waves, and are inconsistent with source-size based models. A dense sensor deployment for the largest SPE explosion allowed this conversion to be mapped in detail. This is good news for P/S explosion identification, which can work well for very small explosions and may be ultimately limited by S-wave detection thresholds. The SPE also showed explosion P-wave source models need to be updated for small and/or deeply buried cases. We are developing new P- and S-wave explosion models that better match all the empirical data. Historic nuclear explosion seismic data shows that the media in which

Earthquakes

Science.gov (United States)

An earthquake happens when two blocks of the earth suddenly slip past one another. Earthquakes strike suddenly, violently, and without warning at any time of the day or night. If an earthquake occurs in a populated area, it may cause ...

Tsunami hazard assessments with consideration of uncertain earthquakes characteristics

Science.gov (United States)

Sepulveda, I.; Liu, P. L. F.; Grigoriu, M. D.; Pritchard, M. E.

2017-12-01

the 2014 Chilean earthquake. Results show that leading wave measurements fall within the tsunami sample space. At later times, however, there are mismatches between measured data and the simulated results, suggesting that other sources of uncertainty are as relevant as the uncertainty of the studied earthquake characteristics.

First measurements by the DEMETER satellite of ionospheric perturbations associated with earthquakes

International Nuclear Information System (INIS)

Blecki, J.; Slominski, J.; Wronowski, R.; Parrot, M.; Lagoutte, D.; Brochot, J.-Y.

2005-01-01

DEMETER is a French project of a low altitude microsatellite. Its main scientific goals are to study the ionospheric perturbations related to the seismic and volcanic activity and the Earth's electromagnetic environment. The payload of the DEMETER microsatellite allows to measure waves and also some important plasma parameters (ion composition, electron density and temperature, energetic particles). The launch of the satellite was done by the Ukrainian rocket Dnepr from Baikonour on June 29, 2004. The regular measurements started in the middle of July. Since the beginning of the data gathering some earthquakes with magnitude M>6 were registered. The analysis of the data has been done for selected passes of DEMETER over the epicenters. The results of the measurements for two Earthquakes- one during the pass 5 days before Japanese Earthquake (23.10.2004) and the second one just 3 minutes after Mexico Earthquake (9.09.04) will be shown. (author)

Earthquake Loss Scenarios: Warnings about the Extent of Disasters

Science.gov (United States)

Wyss, M.; Tolis, S.; Rosset, P.

2016-12-01

It is imperative that losses expected due to future earthquakes be estimated. Officials and the public need to be aware of what disaster is likely in store for them in order to reduce the fatalities and efficiently help the injured. Scenarios for earthquake parameters can be constructed to a reasonable accuracy in highly active earthquake belts, based on knowledge of seismotectonics and history. Because of the inherent uncertainties of loss estimates however, it would be desirable that more than one group calculate an estimate for the same area. By discussing these estimates, one may find a consensus of the range of the potential disasters and persuade officials and residents of the reality of the earthquake threat. To model a scenario and estimate earthquake losses requires data sets that are sufficiently accurate of the number of people present, the built environment, and if possible the transmission of seismic waves. As examples we use loss estimates for possible repeats of historic earthquakes in Greece that occurred between -464 and 700. We model future large Greek earthquakes as having M6.8 and rupture lengths of 60 km. In four locations where historic earthquakes with serious losses have occurred, we estimate that 1,000 to 1,500 people might perish, with an additional factor of four people injured. Defining the area of influence of these earthquakes as that with shaking intensities larger and equal to V, we estimate that 1.0 to 2.2 million people in about 2,000 settlements may be affected. We calibrate the QLARM tool for calculating intensities and losses in Greece, using the M6, 1999 Athens earthquake and matching the isoseismal information for six earthquakes, which occurred in Greece during the last 140 years. Comparing fatality numbers that would occur theoretically today with the numbers reported, and correcting for the increase in population, we estimate that the improvement of the building stock has reduced the mortality and injury rate in Greek

Assessing Agricultural Drought in the Anthropocene: A Modified Palmer Drought Severity Index

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Mingzhi Yang

2017-09-01

Full Text Available In the current human-influenced era, drought is initiated by natural and human drivers, and human activities are as integral to drought as meteorological factors. In large irrigated agricultural regions with high levels of human intervention, where the natural farmland soil moisture has usually been changed significantly by high-frequency irrigation, the actual severity of agricultural drought is distorted in traditional drought indices. In this work, an agricultural drought index that considering irrigation processes based on the Palmer drought severity index (IrrPDSI was developed to interpret the real agricultural drought conditions in irrigated regions, with a case study in the Haihe River Basin in northeast China. The water balance model in the original PDSI was revised by an auto-irrigation threshold method combined with a local irrigation schedule. The auto-irrigation setting of the index was used by taking irrigation quotas during specific growth stages of specific crops (wheat–corn into consideration. A series of weekly comparative analyses are as follows: (1 The soil moisture analyses showed that soil moisture values calculated by the modified water balance model were close to the real values; (2 The statistical analyses indicated that most of the stations in the study area based on IrrPDSI had nearly normal distributed values; (3 The time series and spatial analyses showed that the results of the IrrPDSI-reported dry-wet evaluation were more consistent with documented real conditions. All the results revealed that IrrPDSI performed well when used to assess agricultural drought. This work has direct significance for agricultural drought management in large irrigated areas heavily disturbed by human activity.

Analysis of Droughts of Northwest of Iran Using the Reconnaissance Drought Index

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behrouz hosseini

2016-02-01

Full Text Available Introduction: Drought is a creeping natural phenomenon, which can occur in any region. Such phenomenon not only affects the region subjected to drought, but its adverse effects can also be extended to other adjacent regions. This phenomenon mainly starts with water deficiency (say less than long- term mean of variable under study such as rainfall, streamflow, groundwater level or soil moisture and progress in time. This period can be ended by increasing the rainfall and reaching the mean level. Even after the ending of a drought period, its adverse effects can be continued for several months. Although, it is not possible (at least at this time to prevent the occurrence of drought in a given region, it is not impossible to alleviate the drought consequences by scientific water management. Such a management should be employed before drought initiation as well as during it and continue on even after the end of the drought period. The frequency of the main drought characteristics is a major concern of this study. The Northwest of Iran recently encountered severe and prolonged droughts, such that a major portion of the Urmia Lake surface disappeared during the last drought in recent years. In order to study drought characteristics, we used the Reconnaissance Drought Index (RDI. This index is based on annual rainfall and potential reference crop evapotranspiration (abbreviated by PET here. This study employed the Monte Carlo simulation technique for synthetic data generation for analysis. Materials and Methods: The information from the 17 synoptic weather stations located in the North-west of Iran was used for drought analysis. Data was gathered from the Islamic Republic of Iran’s Meteorological Organization (IRIMO. In the first stage of research, the ratio of long term mean annual precipitation to evapotranspiration was calculated for each of the stations. For this purpose, the Penman-Montheis (FAO 56 method was selected for PET estimation. In the

Seismoacoustic Coupled Signals From Earthquakes in Central Italy: Epicentral and Secondary Sources of Infrasound

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Shani-Kadmiel, Shahar; Assink, Jelle D.; Smets, Pieter S. M.; Evers, Läslo G.

2018-01-01

In this study we analyze infrasound signals from three earthquakes in central Italy. The Mw 6.0 Amatrice, Mw 5.9 Visso, and Mw 6.5 Norcia earthquakes generated significant epicentral ground motions that couple to the atmosphere and produce infrasonic waves. Epicentral seismic and infrasonic signals are detected at I26DE; however, a third type of signal, which arrives after the seismic wave train and before the epicentral infrasound signal, is also detected. This peculiar signal propagates across the array at acoustic wave speeds, but the celerity associated with it is 3 times the speed of sound. Atmosphere-independent backprojections and full 3-D ray tracing using atmospheric conditions of the European Centre for Medium-Range Weather Forecasts are used to demonstrate that this apparently fast-arriving infrasound signal originates from ground motions more than 400 km away from the epicenter. The location of the secondary infrasound patch coincides with the closest bounce point to I26DE as depicted by ray tracing backprojections.

Analysis of Earthquake Source Spectra in Salton Trough

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Chen, X.; Shearer, P. M.

2009-12-01

Previous studies of the source spectra of small earthquakes in southern California show that average Brune-type stress drops vary among different regions, with particularly low stress drops observed in the Salton Trough (Shearer et al., 2006). The Salton Trough marks the southern end of the San Andreas Fault and is prone to earthquake swarms, some of which are driven by aseismic creep events (Lohman and McGuire, 2007). In order to learn the stress state and understand the physical mechanisms of swarms and slow slip events, we analyze the source spectra of earthquakes in this region. We obtain Southern California Seismic Network (SCSN) waveforms for earthquakes from 1977 to 2009 archived at the Southern California Earthquake Center (SCEC) data center, which includes over 17,000 events. After resampling the data to a uniform 100 Hz sample rate, we compute spectra for both signal and noise windows for each seismogram, and select traces with a P-wave signal-to-noise ratio greater than 5 between 5 Hz and 15 Hz. Using selected displacement spectra, we isolate the source spectra from station terms and path effects using an empirical Green’s function approach. From the corrected source spectra, we compute corner frequencies and estimate moments and stress drops. Finally we analyze spatial and temporal variations in stress drop in the Salton Trough and compare them with studies of swarms and creep events to assess the evolution of faulting and stress in the region. References: Lohman, R. B., and J. J. McGuire (2007), Earthquake swarms driven by aseismic creep in the Salton Trough, California, J. Geophys. Res., 112, B04405, doi:10.1029/2006JB004596 Shearer, P. M., G. A. Prieto, and E. Hauksson (2006), Comprehensive analysis of earthquake source spectra in southern California, J. Geophys. Res., 111, B06303, doi:10.1029/2005JB003979.

A New Empirical Relation between Surface Wave Magnitude and Rupture Length for Turkey Earthquakes

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Serkan Ozturk

2014-01-01

Full Text Available Many practical problems encountered in quantitative oriented disciplines entail finding the best approximate solution to an over determined system of linear equations. In this study, it is investigated the usage of different regression methods as a theoretical, practical and correct estimation tool in order to obtain the best empirical relationship between surface wave magnitude and rupture length for Turkey earthquakes. For this purpose, a detailed comparison is made among four different regression norms: (1 Least Squares, (2 Least Sum of Absolute Deviations, (3 Total Least Squares or Orthogonal and, (4 Robust Regressions. In order to assess the quality of the fit in a linear regression and to select the best empirical relationship for data sets, the correlation coefficient as a quite simple and very practicable tool is used. A list of all earthquakes where the surface wave magnitude (Ms and surface rupture length (L are available is compiled. In order to estimate the empirical relationships between these parameters for Turkey earthquakes, log-linear fit is used and following equations are derived from different norms: for L2 Norm regression (R2=0.71, for L1 Norm regression (R2=0.92, for Robust regression (R2=0.75, for Orthogonal regression (R2=0.68,                            Consequently, the empirical equation given by the Least Sum of Absolute Deviations regression as  with a strong correlation coefficient (R2=0.92 can be thought as more suitable and more reliable for Turkey earthquakes. Also, local differences in rupture length for a given magnitude can be interpreted in terms of local variation in geologic and seismic efficiencies.  Furthermore, this result suggests that seismic efficiency in a region is dependent on rupture length or magnitude.    Resumen Muchos problemas prácticos encontrados en las disciplinas de orientación cuantitativa implican encontrar la mejor solución aproximada para un sistema

Plasma turbulence in the ionosphere prior to earthquakes, some remarks on the DEMETER registrations

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Błęcki, Jan; Parrot, Michel; Wronowski, Roman

2011-06-01

The question about presence of some precursors of the earthquakes has a long history. The answer is still not resolved, but researchers are looking for the effects which can be registered prior to earthquakes. One of the factors which has been found is the variation of the electromagnetic field observed on ground as well as onboard satellites. The disturbances of the electromagnetic field around areas of the earthquakes as pre-seismic events can occur few hours or even few days before the main shock. The payload of the DEMETER French microsatellite allows to measure waves and also some important plasma parameters (ion composition, electron density and temperature, energetic particles) with high temporal resolution in the ionosphere over the seismic regions. In the present work, analysis of the low frequency fluctuations of the electric fields for selected strong earthquakes in Japan (2004), China (2008), Taiwan (2006) and New Zealand (2009) are given. Special attention will be given to the study of the spectral characteristics of these variations and the search for nonlinear effects. This analysis is possible in the time interval where the waveform has been transmitted. The mechanism of the energy transmission from earthquakes to the ionosphere is not clear, but we can discuss the behavior of the ionospheric plasma and the search for instabilities which could be a source of electromagnetic field variations. A brief discussion of the characteristics of the spectra and multi-spectra is given in this paper. Attention is particularly given to the effect prior to the earthquake in New Zealand, when a nonlinear interaction leading to a lower hybrid wave generation was directly seen.

The Challenge of Centennial Earthquakes to Improve Modern Earthquake Engineering

International Nuclear Information System (INIS)

Saragoni, G. Rodolfo

2008-01-01

The recent commemoration of the centennial of the San Francisco and Valparaiso 1906 earthquakes has given the opportunity to reanalyze their damages from modern earthquake engineering perspective. These two earthquakes plus Messina Reggio Calabria 1908 had a strong impact in the birth and developing of earthquake engineering. The study of the seismic performance of some up today existing buildings, that survive centennial earthquakes, represent a challenge to better understand the limitations of our in use earthquake design methods. Only Valparaiso 1906 earthquake, of the three considered centennial earthquakes, has been repeated again as the Central Chile, 1985, Ms = 7.8 earthquake. In this paper a comparative study of the damage produced by 1906 and 1985 Valparaiso earthquakes is done in the neighborhood of Valparaiso harbor. In this study the only three centennial buildings of 3 stories that survived both earthquakes almost undamaged were identified. Since for 1985 earthquake accelerogram at El Almendral soil conditions as well as in rock were recoded, the vulnerability analysis of these building is done considering instrumental measurements of the demand. The study concludes that good performance of these buildings in the epicentral zone of large earthquakes can not be well explained by modern earthquake engineering methods. Therefore, it is recommended to use in the future of more suitable instrumental parameters, such as the destructiveness potential factor, to describe earthquake demand

Apparent splitting of S waves propagating through an isotropic lowermost mantle

KAUST Repository

Parisi, Laura

2018-03-24

Observations of shear‐wave anisotropy are key for understanding the mineralogical structure and flow in the mantle. Several researchers have reported the presence of seismic anisotropy in the lowermost 150–250 km of the mantle (i.e., D” layer), based on differences in the arrival times of vertically (SV) and horizontally (SH) polarized shear waves. By computing waveforms at period > 6 s for a wide range of 1‐D and 3‐D Earth structures we illustrate that a time shift (i.e., apparent splitting) between SV and SH may appear in purely isotropic simulations. This may be misinterpreted as shear wave anisotropy. For near‐surface earthquakes, apparent shear wave splitting can result from the interference of S with the surface reflection sS. For deep earthquakes, apparent splitting can be due to the S‐wave triplication in D”, reflections off discontinuities in the upper mantle and 3‐D heterogeneity. The wave effects due to anomalous isotropic structure may not be easily distinguished from purely anisotropic effects if the analysis does not involve full waveform simulations.

Apparent splitting of S waves propagating through an isotropic lowermost mantle

KAUST Repository

Parisi, Laura; Ferreira, Ana M. G.; Ritsema, Jeroen

2018-01-01

Observations of shear‐wave anisotropy are key for understanding the mineralogical structure and flow in the mantle. Several researchers have reported the presence of seismic anisotropy in the lowermost 150–250 km of the mantle (i.e., D” layer), based on differences in the arrival times of vertically (SV) and horizontally (SH) polarized shear waves. By computing waveforms at period > 6 s for a wide range of 1‐D and 3‐D Earth structures we illustrate that a time shift (i.e., apparent splitting) between SV and SH may appear in purely isotropic simulations. This may be misinterpreted as shear wave anisotropy. For near‐surface earthquakes, apparent shear wave splitting can result from the interference of S with the surface reflection sS. For deep earthquakes, apparent splitting can be due to the S‐wave triplication in D”, reflections off discontinuities in the upper mantle and 3‐D heterogeneity. The wave effects due to anomalous isotropic structure may not be easily distinguished from purely anisotropic effects if the analysis does not involve full waveform simulations.

Experimental droughts: Are precipitation variability and methodological trends hindering our understanding of ecological sensitivities to drought?

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Hoover, D. L.; Wilcox, K.; Young, K. E.

2017-12-01

Droughts are projected to increase in frequency and intensity with climate change, which may have dramatic and prolonged effects on ecosystem structure and function. There are currently hundreds of published, ongoing, and new drought experiments worldwide aimed to assess ecosystem sensitivities to drought and identify the mechanisms governing ecological resistance and resilience. However, to date, the results from these experiments have varied widely, and thus patterns of drought sensitivities have been difficult to discern. This lack of consensus at the field scale, limits the abilities of experiments to help improve land surface models, which often fail to realistically simulate ecological responses to extreme events. This is unfortunate because models offer an alternative, yet complementary approach to increase the spatial and temporal assessment of ecological sensitivities to drought that are not possible in the field due to logistical and financial constraints. Here we examined 89 published drought experiments, along with their associated historical precipitation records to (1) identify where and how drought experiments have been imposed, (2) determine the extremity of drought treatments in the context of historical climate, and (3) assess the influence of precipitation variability on drought experiments. We found an overall bias in drought experiments towards short-term, extreme experiments in water-limited ecosystems. When placed in the context of local historical precipitation, most experimental droughts were extreme, with 61% below the 5th, and 43% below the 1st percentile. Furthermore, we found that interannual precipitation variability had a large and potentially underappreciated effect on drought experiments due to the co-varying nature of control and drought treatments. Thus detecting ecological effects in experimental droughts is strongly influenced by the interaction between drought treatment magnitude, precipitation variability, and key

ON THE RELATION BETWEEN EARTHQUAKE AND ATMOSPHERIC ELECTRICITY

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Kuznetsov V.V.

2017-07-01

Full Text Available The change in the magnitude of the atmospheric electric field (AEF before the earthquake and immediately after it, according to our model, is due to the fact that the protons of water atmospheric complexes turn out to be quantum-entangled to protons of hydrogen bonds (HB in lithosphere material. After the establishment of the quantum entanglement regime in the system, a decoherence follows. It manifests itself in AEF change, and then there is a recoherence, during which the quantum entanglement of the largest possible number of elements in the system with HB which ends with a new decoherence, is again tuned in the system. It is during this process that a shock wave or an earthquake entailing the change of AEF magnitude is generated.

A new reference global instrumental earthquake catalogue (1900-2009)

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Di Giacomo, D.; Engdahl, B.; Bondar, I.; Storchak, D. A.; Villasenor, A.; Bormann, P.; Lee, W.; Dando, B.; Harris, J.

2011-12-01

For seismic hazard studies on a global and/or regional scale, accurate knowledge of the spatial distribution of seismicity, the magnitude-frequency relation and the maximum magnitudes is of fundamental importance. However, such information is normally not homogeneous (or not available) for the various seismically active regions of the Earth. To achieve the GEM objectives (www.globalquakemodel.org) of calculating and communicating earthquake risk worldwide, an improved reference global instrumental catalogue for large earthquakes spanning the entire 100+ years period of instrumental seismology is an absolute necessity. To accomplish this task, we apply the most up-to-date techniques and standard observatory practices for computing the earthquake location and magnitude. In particular, the re-location procedure benefits both from the depth determination according to Engdahl and Villaseñor (2002), and the advanced technique recently implemented at the ISC (Bondár and Storchak, 2011) to account for correlated error structure. With regard to magnitude, starting from the re-located hypocenters, the classical surface and body-wave magnitudes are determined following the new IASPEI standards and by using amplitude-period data of phases collected from historical station bulletins (up to 1970), which were not available in digital format before the beginning of this work. Finally, the catalogue will provide moment magnitude values (including uncertainty) for each seismic event via seismic moment, via surface wave magnitude or via other magnitude types using empirical relationships. References Engdahl, E.R., and A. Villaseñor (2002). Global seismicity: 1900-1999. In: International Handbook of Earthquake and Engineering Seismology, eds. W.H.K. Lee, H. Kanamori, J.C. Jennings, and C. Kisslinger, Part A, 665-690, Academic Press, San Diego. Bondár, I., and D. Storchak (2011). Improved location procedures at the International Seismological Centre, Geophys. J. Int., doi:10.1111/j

Deep geological strucure of a volcano verified by seismic wave. Jishinha de mita kazan no shinbu kozo

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Hasegawa, A. (Tohoku University, Sendai (Japan). Faculty of Science)

1991-09-01

Three dimensional structure of seismic wave velocity for the crest and upper mantle under the North East Japan is determined by the seismic tomography which is prepared by the natural earthquakes confirmed by the observation network for micro earthquakes, indicating that the low velocity region exists just under the corresponding volcano to the upper mantle. Further, the following contents can be verified: Any micro earthquakes which are verified by the above observation network and occur at the depth of 25-40km show the lower generation rate less than 1% and the low dominant frequency compared with the conventional inland earthquake(lower limit of depth is 15km) in the same region and occur around volcanos. The existence of the remarkable reflection surface for S wave which is found at the depth of 10-20km seems to be caused by the melting mass. The above mentioned low velocity region is estimated to correspond to the lifting region of high temperature magma, micro earthquakes of low frequency to the magma activity around that magma and the reflection surface for S wave to the part of the magma. 8 refs., 4 figs.