WorldWideScience

Sample records for seismicity earthquake forecasts

  1. Adaptively smoothed seismicity earthquake forecasts for Italy

    Directory of Open Access Journals (Sweden)

    Yan Y. Kagan

    2010-11-01

    Full Text Available We present a model for estimation of the probabilities of future earthquakes of magnitudes m ≥ 4.95 in Italy. This model is a modified version of that proposed for California, USA, by Helmstetter et al. [2007] and Werner et al. [2010a], and it approximates seismicity using a spatially heterogeneous, temporally homogeneous Poisson point process. The temporal, spatial and magnitude dimensions are entirely decoupled. Magnitudes are independently and identically distributed according to a tapered Gutenberg-Richter magnitude distribution. We have estimated the spatial distribution of future seismicity by smoothing the locations of past earthquakes listed in two Italian catalogs: a short instrumental catalog, and a longer instrumental and historic catalog. The bandwidth of the adaptive spatial kernel is estimated by optimizing the predictive power of the kernel estimate of the spatial earthquake density in retrospective forecasts. When available and reliable, we used small earthquakes of m ≥ 2.95 to reveal active fault structures and 29 probable future epicenters. By calibrating the model with these two catalogs of different durations to create two forecasts, we intend to quantify the loss (or gain of predictability incurred when only a short, but recent, data record is available. Both forecasts were scaled to five and ten years, and have been submitted to the Italian prospective forecasting experiment of the global Collaboratory for the Study of Earthquake Predictability (CSEP. An earlier forecast from the model was submitted by Helmstetter et al. [2007] to the Regional Earthquake Likelihood Model (RELM experiment in California, and with more than half of the five-year experimental period over, the forecast has performed better than the others.

  2. A way to synchronize models with seismic faults for earthquake forecasting

    DEFF Research Database (Denmark)

    González, Á.; Gómez, J.B.; Vázquez-Prada, M.

    2006-01-01

    Numerical models are starting to be used for determining the future behaviour of seismic faults and fault networks. Their final goal would be to forecast future large earthquakes. In order to use them for this task, it is necessary to synchronize each model with the current status of the actual....... Earthquakes, though, provide indirect but measurable clues of the stress and strain status in the lithosphere, which should be helpful for the synchronization of the models. The rupture area is one of the measurable parameters of earthquakes. Here we explore how it can be used to at least synchronize fault...... models between themselves and forecast synthetic earthquakes. Our purpose here is to forecast synthetic earthquakes in a simple but stochastic (random) fault model. By imposing the rupture area of the synthetic earthquakes of this model on other models, the latter become partially synchronized...

  3. Forecasting Induced Seismicity Using Saltwater Disposal Data and a Hydromechanical Earthquake Nucleation Model

    Science.gov (United States)

    Norbeck, J. H.; Rubinstein, J. L.

    2017-12-01

    The earthquake activity in Oklahoma and Kansas that began in 2008 reflects the most widespread instance of induced seismicity observed to date. In this work, we demonstrate that the basement fault stressing conditions that drive seismicity rate evolution are related directly to the operational history of 958 saltwater disposal wells completed in the Arbuckle aquifer. We developed a fluid pressurization model based on the assumption that pressure changes are dominated by reservoir compressibility effects. Using injection well data, we established a detailed description of the temporal and spatial variability in stressing conditions over the 21.5-year period from January 1995 through June 2017. With this stressing history, we applied a numerical model based on rate-and-state friction theory to generate seismicity rate forecasts across a broad range of spatial scales. The model replicated the onset of seismicity, the timing of the peak seismicity rate, and the reduction in seismicity following decreased disposal activity. The behavior of the induced earthquake sequence was consistent with the prediction from rate-and-state theory that the system evolves toward a steady seismicity rate depending on the ratio between the current and background stressing rates. Seismicity rate transients occurred over characteristic timescales inversely proportional to stressing rate. We found that our hydromechanical earthquake rate model outperformed observational and empirical forecast models for one-year forecast durations over the period 2008 through 2016.

  4. Seismic forecast using geostatistics

    International Nuclear Information System (INIS)

    Grecu, Valeriu; Mateiciuc, Doru

    2007-01-01

    The main idea of this research direction consists in the special way of constructing a new type of mathematical function as being a correlation between a computed statistical quantity and another physical quantity. This type of function called 'position function' was taken over by the authors of this study in the field of seismology with the hope of solving - at least partially - the difficult problem of seismic forecast. The geostatistic method of analysis focuses on the process of energy accumulation in a given seismic area, completing this analysis by a so-called loading function. This function - in fact a temporal function - describes the process of energy accumulation during a seismic cycle from a given seismic area. It was possible to discover a law of evolution of the seismic cycles that was materialized in a so-called characteristic function. This special function will help us to forecast the magnitude and the occurrence moment of the largest earthquake in the analysed area. Since 2000, the authors have been evolving to a new stage of testing: real - time analysis, in order to verify the quality of the method. There were five large earthquakes forecasts. (authors)

  5. Earthquake number forecasts testing

    Science.gov (United States)

    Kagan, Yan Y.

    2017-10-01

    We study the distributions of earthquake numbers in two global earthquake catalogues: Global Centroid-Moment Tensor and Preliminary Determinations of Epicenters. The properties of these distributions are especially required to develop the number test for our forecasts of future seismic activity rate, tested by the Collaboratory for Study of Earthquake Predictability (CSEP). A common assumption, as used in the CSEP tests, is that the numbers are described by the Poisson distribution. It is clear, however, that the Poisson assumption for the earthquake number distribution is incorrect, especially for the catalogues with a lower magnitude threshold. In contrast to the one-parameter Poisson distribution so widely used to describe earthquake occurrences, the negative-binomial distribution (NBD) has two parameters. The second parameter can be used to characterize the clustering or overdispersion of a process. We also introduce and study a more complex three-parameter beta negative-binomial distribution. We investigate the dependence of parameters for both Poisson and NBD distributions on the catalogue magnitude threshold and on temporal subdivision of catalogue duration. First, we study whether the Poisson law can be statistically rejected for various catalogue subdivisions. We find that for most cases of interest, the Poisson distribution can be shown to be rejected statistically at a high significance level in favour of the NBD. Thereafter, we investigate whether these distributions fit the observed distributions of seismicity. For this purpose, we study upper statistical moments of earthquake numbers (skewness and kurtosis) and compare them to the theoretical values for both distributions. Empirical values for the skewness and the kurtosis increase for the smaller magnitude threshold and increase with even greater intensity for small temporal subdivision of catalogues. The Poisson distribution for large rate values approaches the Gaussian law, therefore its skewness

  6. Modeling, Forecasting and Mitigating Extreme Earthquakes

    Science.gov (United States)

    Ismail-Zadeh, A.; Le Mouel, J.; Soloviev, A.

    2012-12-01

    Recent earthquake disasters highlighted the importance of multi- and trans-disciplinary studies of earthquake risk. A major component of earthquake disaster risk analysis is hazards research, which should cover not only a traditional assessment of ground shaking, but also studies of geodetic, paleoseismic, geomagnetic, hydrological, deep drilling and other geophysical and geological observations together with comprehensive modeling of earthquakes and forecasting extreme events. Extreme earthquakes (large magnitude and rare events) are manifestations of complex behavior of the lithosphere structured as a hierarchical system of blocks of different sizes. Understanding of physics and dynamics of the extreme events comes from observations, measurements and modeling. A quantitative approach to simulate earthquakes in models of fault dynamics will be presented. The models reproduce basic features of the observed seismicity (e.g., the frequency-magnitude relationship, clustering of earthquakes, occurrence of extreme seismic events). They provide a link between geodynamic processes and seismicity, allow studying extreme events, influence of fault network properties on seismic patterns and seismic cycles, and assist, in a broader sense, in earthquake forecast modeling. Some aspects of predictability of large earthquakes (how well can large earthquakes be predicted today?) will be also discussed along with possibilities in mitigation of earthquake disasters (e.g., on 'inverse' forensic investigations of earthquake disasters).

  7. Multicomponent ensemble models to forecast induced seismicity

    Science.gov (United States)

    Király-Proag, E.; Gischig, V.; Zechar, J. D.; Wiemer, S.

    2018-01-01

    In recent years, human-induced seismicity has become a more and more relevant topic due to its economic and social implications. Several models and approaches have been developed to explain underlying physical processes or forecast induced seismicity. They range from simple statistical models to coupled numerical models incorporating complex physics. We advocate the need for forecast testing as currently the best method for ascertaining if models are capable to reasonably accounting for key physical governing processes—or not. Moreover, operational forecast models are of great interest to help on-site decision-making in projects entailing induced earthquakes. We previously introduced a standardized framework following the guidelines of the Collaboratory for the Study of Earthquake Predictability, the Induced Seismicity Test Bench, to test, validate, and rank induced seismicity models. In this study, we describe how to construct multicomponent ensemble models based on Bayesian weightings that deliver more accurate forecasts than individual models in the case of Basel 2006 and Soultz-sous-Forêts 2004 enhanced geothermal stimulation projects. For this, we examine five calibrated variants of two significantly different model groups: (1) Shapiro and Smoothed Seismicity based on the seismogenic index, simple modified Omori-law-type seismicity decay, and temporally weighted smoothed seismicity; (2) Hydraulics and Seismicity based on numerically modelled pore pressure evolution that triggers seismicity using the Mohr-Coulomb failure criterion. We also demonstrate how the individual and ensemble models would perform as part of an operational Adaptive Traffic Light System. Investigating seismicity forecasts based on a range of potential injection scenarios, we use forecast periods of different durations to compute the occurrence probabilities of seismic events M ≥ 3. We show that in the case of the Basel 2006 geothermal stimulation the models forecast hazardous levels

  8. Method for forecasting an earthquake from precursor signals

    International Nuclear Information System (INIS)

    Farnworth, D.F.

    1996-01-01

    A method for forecasting an earthquake from precursor signals by employing characteristic first electromagnetic signals, second, seismically induced electromagnetic signals, seismically induced mechanical signals, and infrasonic acoustic signals which have been observed to precede an earthquake. From a first electromagnetic signal, a magnitude, depth beneath the surface of the earth, distance, latitude, longitude, and first and second forecasts of the time of occurrence of the impending earthquake may be derived. From a second, seismically induced electromagnetic signal and the mechanical signal, third and fourth forecasts of the time of occurrence of an impending earthquake determined from the analysis above, a magnitude, depth beneath the surface of the earth and fourth and fifth forecasts of the time of occurrence of the impending earthquake may be derived. The forecasts of time available from the above analyses range from up to five weeks to substantially within one hour in advance of the earthquake. (author)

  9. Next-generation probabilistic seismicity forecasting

    Energy Technology Data Exchange (ETDEWEB)

    Hiemer, S.

    2014-07-01

    The development of probabilistic seismicity forecasts is one of the most important tasks of seismologists at present time. Such forecasts form the basis of probabilistic seismic hazard assessment, a widely used approach to generate ground motion exceedance maps. These hazard maps guide the development of building codes, and in the absence of the ability to deterministically predict earthquakes, good building and infrastructure planning is key to prevent catastrophes. Probabilistic seismicity forecasts are models that specify the occurrence rate of earthquakes as a function of space, time and magnitude. The models presented in this thesis are time-invariant mainshock occurrence models. Accordingly, the reliable estimation of the spatial and size distribution of seismicity are of crucial importance when constructing such probabilistic forecasts. Thereby we focus on data-driven approaches to infer these distributions, circumventing the need for arbitrarily chosen external parameters and subjective expert decisions. Kernel estimation has been shown to appropriately transform discrete earthquake locations into spatially continuous probability distributions. However, we show that neglecting the information from fault networks constitutes a considerable shortcoming and thus limits the skill of these current seismicity models. We present a novel earthquake rate forecast that applies the kernel-smoothing method to both past earthquake locations and slip rates on mapped crustal faults applied to Californian and European data. Our model is independent from biases caused by commonly used non-objective seismic zonations, which impose artificial borders of activity that are not expected in nature. Studying the spatial variability of the seismicity size distribution is of great importance. The b-value of the well-established empirical Gutenberg-Richter model forecasts the rates of hazard-relevant large earthquakes based on the observed rates of abundant small events. We propose a

  10. Next-generation probabilistic seismicity forecasting

    International Nuclear Information System (INIS)

    Hiemer, S.

    2014-01-01

    The development of probabilistic seismicity forecasts is one of the most important tasks of seismologists at present time. Such forecasts form the basis of probabilistic seismic hazard assessment, a widely used approach to generate ground motion exceedance maps. These hazard maps guide the development of building codes, and in the absence of the ability to deterministically predict earthquakes, good building and infrastructure planning is key to prevent catastrophes. Probabilistic seismicity forecasts are models that specify the occurrence rate of earthquakes as a function of space, time and magnitude. The models presented in this thesis are time-invariant mainshock occurrence models. Accordingly, the reliable estimation of the spatial and size distribution of seismicity are of crucial importance when constructing such probabilistic forecasts. Thereby we focus on data-driven approaches to infer these distributions, circumventing the need for arbitrarily chosen external parameters and subjective expert decisions. Kernel estimation has been shown to appropriately transform discrete earthquake locations into spatially continuous probability distributions. However, we show that neglecting the information from fault networks constitutes a considerable shortcoming and thus limits the skill of these current seismicity models. We present a novel earthquake rate forecast that applies the kernel-smoothing method to both past earthquake locations and slip rates on mapped crustal faults applied to Californian and European data. Our model is independent from biases caused by commonly used non-objective seismic zonations, which impose artificial borders of activity that are not expected in nature. Studying the spatial variability of the seismicity size distribution is of great importance. The b-value of the well-established empirical Gutenberg-Richter model forecasts the rates of hazard-relevant large earthquakes based on the observed rates of abundant small events. We propose a

  11. Stress-based aftershock forecasts made within 24h post mainshock: Expected north San Francisco Bay area seismicity changes after the 2014M=6.0 West Napa earthquake

    Science.gov (United States)

    Parsons, Thomas E.; Segou, Margaret; Sevilgen, Volkan; Milner, Kevin; Field, Edward; Toda, Shinji; Stein, Ross S.

    2014-01-01

    We calculate stress changes resulting from the M= 6.0 West Napa earthquake on north San Francisco Bay area faults. The earthquake ruptured within a series of long faults that pose significant hazard to the Bay area, and we are thus concerned with potential increases in the probability of a large earthquake through stress transfer. We conduct this exercise as a prospective test because the skill of stress-based aftershock forecasting methodology is inconclusive. We apply three methods: (1) generalized mapping of regional Coulomb stress change, (2) stress changes resolved on Uniform California Earthquake Rupture Forecast faults, and (3) a mapped rate/state aftershock forecast. All calculations were completed within 24 h after the main shock and were made without benefit of known aftershocks, which will be used to evaluative the prospective forecast. All methods suggest that we should expect heightened seismicity on parts of the southern Rodgers Creek, northern Hayward, and Green Valley faults.

  12. 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

  13. A prospective earthquake forecast experiment in the western Pacific

    Science.gov (United States)

    Eberhard, David A. J.; Zechar, J. Douglas; Wiemer, Stefan

    2012-09-01

    Since the beginning of 2009, the Collaboratory for the Study of Earthquake Predictability (CSEP) has been conducting an earthquake forecast experiment in the western Pacific. This experiment is an extension of the Kagan-Jackson experiments begun 15 years earlier and is a prototype for future global earthquake predictability experiments. At the beginning of each year, seismicity models make a spatially gridded forecast of the number of Mw≥ 5.8 earthquakes expected in the next year. For the three participating statistical models, we analyse the first two years of this experiment. We use likelihood-based metrics to evaluate the consistency of the forecasts with the observed target earthquakes and we apply measures based on Student's t-test and the Wilcoxon signed-rank test to compare the forecasts. Overall, a simple smoothed seismicity model (TripleS) performs the best, but there are some exceptions that indicate continued experiments are vital to fully understand the stability of these models, the robustness of model selection and, more generally, earthquake predictability in this region. We also estimate uncertainties in our results that are caused by uncertainties in earthquake location and seismic moment. Our uncertainty estimates are relatively small and suggest that the evaluation metrics are relatively robust. Finally, we consider the implications of our results for a global earthquake forecast experiment.

  14. Earthquake forecasting and warning

    Energy Technology Data Exchange (ETDEWEB)

    Rikitake, T.

    1983-01-01

    This review briefly describes two other books on the same subject either written or partially written by Rikitake. In this book, the status of earthquake prediction efforts in Japan, China, the Soviet Union, and the United States are updated. An overview of some of the organizational, legal, and societal aspects of earthquake prediction in these countries is presented, and scientific findings of precursory phenomena are included. A summary of circumstances surrounding the 1975 Haicheng earthquake, the 1978 Tangshan earthquake, and the 1976 Songpan-Pingwu earthquake (all magnitudes = 7.0) in China and the 1978 Izu-Oshima earthquake in Japan is presented. This book fails to comprehensively summarize recent advances in earthquake prediction research.

  15. A parimutuel gambling perspective to compare probabilistic seismicity forecasts

    Science.gov (United States)

    Zechar, J. Douglas; Zhuang, Jiancang

    2014-10-01

    Using analogies to gaming, we consider the problem of comparing multiple probabilistic seismicity forecasts. To measure relative model performance, we suggest a parimutuel gambling perspective which addresses shortcomings of other methods such as likelihood ratio, information gain and Molchan diagrams. We describe two variants of the parimutuel approach for a set of forecasts: head-to-head, in which forecasts are compared in pairs, and round table, in which all forecasts are compared simultaneously. For illustration, we compare the 5-yr forecasts of the Regional Earthquake Likelihood Models experiment for M4.95+ seismicity in California.

  16. Results of the Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California.

    Science.gov (United States)

    Lee, Ya-Ting; Turcotte, Donald L; Holliday, James R; Sachs, Michael K; Rundle, John B; Chen, Chien-Chih; Tiampo, Kristy F

    2011-10-04

    The Regional Earthquake Likelihood Models (RELM) test of earthquake forecasts in California was the first competitive evaluation of forecasts of future earthquake occurrence. Participants submitted expected probabilities of occurrence of M ≥ 4.95 earthquakes in 0.1° × 0.1° cells for the period 1 January 1, 2006, to December 31, 2010. Probabilities were submitted for 7,682 cells in California and adjacent regions. During this period, 31 M ≥ 4.95 earthquakes occurred in the test region. These earthquakes occurred in 22 test cells. This seismic activity was dominated by earthquakes associated with the M = 7.2, April 4, 2010, El Mayor-Cucapah earthquake in northern Mexico. This earthquake occurred in the test region, and 16 of the other 30 earthquakes in the test region could be associated with it. Nine complete forecasts were submitted by six participants. In this paper, we present the forecasts in a way that allows the reader to evaluate which forecast is the most "successful" in terms of the locations of future earthquakes. We conclude that the RELM test was a success and suggest ways in which the results can be used to improve future forecasts.

  17. From Tornadoes to Earthquakes: Forecast Verification for Binary Events Applied to the 1999 Chi-Chi, Taiwan,Earthquake

    Directory of Open Access Journals (Sweden)

    Chien-Chih Chen

    2006-01-01

    Full Text Available Forecast verification procedures for statistical events with binary outcomes typically rely on the use of contingency tables and Relative Operating Characteristic (ROC diagrams. Originally developed for the statistical evaluation of tornado forecasts on a county-by-county basis, these methods can be adapted to the evaluation of competing earthquake forecasts. Here we apply these methods retrospectively to two forecasts for the M 7.3 1999 Chi-Chi, Taiwan, earthquake. We show that a previously proposed forecast method that is based on evaluating changes in seismic intensity on a regional basis is superior to a forecast based only on the magnitude of seismic intensity in the same region. Our results confirm earlier suggestions that the earthquake preparation process for events such as the Chi-Chi earthquake involves anomalous activation or quiescence, and that signatures of these processes can be detected in seismicity data using appropriate methods.

  18. An interdisciplinary approach for earthquake modelling and forecasting

    Science.gov (United States)

    Han, P.; Zhuang, J.; Hattori, K.; Ogata, Y.

    2016-12-01

    Earthquake is one of the most serious disasters, which may cause heavy casualties and economic losses. Especially in the past two decades, huge/mega earthquakes have hit many countries. Effective earthquake forecasting (including time, location, and magnitude) becomes extremely important and urgent. To date, various heuristically derived algorithms have been developed for forecasting earthquakes. Generally, they can be classified into two types: catalog-based approaches and non-catalog-based approaches. Thanks to the rapid development of statistical seismology in the past 30 years, now we are able to evaluate the performances of these earthquake forecast approaches quantitatively. Although a certain amount of precursory information is available in both earthquake catalogs and non-catalog observations, the earthquake forecast is still far from satisfactory. In most case, the precursory phenomena were studied individually. An earthquake model that combines self-exciting and mutually exciting elements was developed by Ogata and Utsu from the Hawkes process. The core idea of this combined model is that the status of the event at present is controlled by the event itself (self-exciting) and all the external factors (mutually exciting) in the past. In essence, the conditional intensity function is a time-varying Poisson process with rate λ(t), which is composed of the background rate, the self-exciting term (the information from past seismic events), and the external excitation term (the information from past non-seismic observations). This model shows us a way to integrate the catalog-based forecast and non-catalog-based forecast. Against this background, we are trying to develop a new earthquake forecast model which combines catalog-based and non-catalog-based approaches.

  19. The Value, Protocols, and Scientific Ethics of Earthquake Forecasting

    Science.gov (United States)

    Jordan, Thomas H.

    2013-04-01

    Earthquakes are different from other common natural hazards because precursory signals diagnostic of the magnitude, location, and time of impending seismic events have not yet been found. Consequently, the short-term, localized prediction of large earthquakes at high probabilities with low error rates (false alarms and failures-to-predict) is not yet feasible. An alternative is short-term probabilistic forecasting based on empirical statistical models of seismic clustering. During periods of high seismic activity, short-term earthquake forecasts can attain prospective probability gains up to 1000 relative to long-term forecasts. The value of such information is by no means clear, however, because even with hundredfold increases, the probabilities of large earthquakes typically remain small, rarely exceeding a few percent over forecasting intervals of days or weeks. Civil protection agencies have been understandably cautious in implementing operational forecasting protocols in this sort of "low-probability environment." This paper will explore the complex interrelations among the valuation of low-probability earthquake forecasting, which must account for social intangibles; the protocols of operational forecasting, which must factor in large uncertainties; and the ethics that guide scientists as participants in the forecasting process, who must honor scientific principles without doing harm. Earthquake forecasts possess no intrinsic societal value; rather, they acquire value through their ability to influence decisions made by users seeking to mitigate seismic risk and improve community resilience to earthquake disasters. According to the recommendations of the International Commission on Earthquake Forecasting (www.annalsofgeophysics.eu/index.php/annals/article/view/5350), operational forecasting systems should appropriately separate the hazard-estimation role of scientists from the decision-making role of civil protection authorities and individuals. They should

  20. Operational Earthquake Forecasting: Proposed Guidelines for Implementation (Invited)

    Science.gov (United States)

    Jordan, T. H.

    2010-12-01

    The goal of operational earthquake forecasting (OEF) is to provide the public with authoritative information about how seismic hazards are changing with time. During periods of high seismic activity, short-term earthquake forecasts based on empirical statistical models can attain nominal probability gains in excess of 100 relative to the long-term forecasts used in probabilistic seismic hazard analysis (PSHA). Prospective experiments are underway by the Collaboratory for the Study of Earthquake Predictability (CSEP) to evaluate the reliability and skill of these seismicity-based forecasts in a variety of tectonic environments. How such information should be used for civil protection is by no means clear, because even with hundredfold increases, the probabilities of large earthquakes typically remain small, rarely exceeding a few percent over forecasting intervals of days or weeks. Civil protection agencies have been understandably cautious in implementing formal procedures for OEF in this sort of “low-probability environment.” Nevertheless, the need to move more quickly towards OEF has been underscored by recent experiences, such as the 2009 L’Aquila earthquake sequence and other seismic crises in which an anxious public has been confused by informal, inconsistent earthquake forecasts. Whether scientists like it or not, rising public expectations for real-time information, accelerated by the use of social media, will require civil protection agencies to develop sources of authoritative information about the short-term earthquake probabilities. In this presentation, I will discuss guidelines for the implementation of OEF informed by my experience on the California Earthquake Prediction Evaluation Council, convened by CalEMA, and the International Commission on Earthquake Forecasting, convened by the Italian government following the L’Aquila disaster. (a) Public sources of information on short-term probabilities should be authoritative, scientific, open, and

  1. Statistical physics approach to earthquake occurrence and forecasting

    Energy Technology Data Exchange (ETDEWEB)

    Arcangelis, Lucilla de [Department of Industrial and Information Engineering, Second University of Naples, Aversa (CE) (Italy); Godano, Cataldo [Department of Mathematics and Physics, Second University of Naples, Caserta (Italy); Grasso, Jean Robert [ISTerre, IRD-CNRS-OSUG, University of Grenoble, Saint Martin d’Héres (France); Lippiello, Eugenio, E-mail: eugenio.lippiello@unina2.it [Department of Mathematics and Physics, Second University of Naples, Caserta (Italy)

    2016-04-25

    There is striking evidence that the dynamics of the Earth crust is controlled by a wide variety of mutually dependent mechanisms acting at different spatial and temporal scales. The interplay of these mechanisms produces instabilities in the stress field, leading to abrupt energy releases, i.e., earthquakes. As a consequence, the evolution towards instability before a single event is very difficult to monitor. On the other hand, collective behavior in stress transfer and relaxation within the Earth crust leads to emergent properties described by stable phenomenological laws for a population of many earthquakes in size, time and space domains. This observation has stimulated a statistical mechanics approach to earthquake occurrence, applying ideas and methods as scaling laws, universality, fractal dimension, renormalization group, to characterize the physics of earthquakes. In this review we first present a description of the phenomenological laws of earthquake occurrence which represent the frame of reference for a variety of statistical mechanical models, ranging from the spring-block to more complex fault models. Next, we discuss the problem of seismic forecasting in the general framework of stochastic processes, where seismic occurrence can be described as a branching process implementing space–time-energy correlations between earthquakes. In this context we show how correlations originate from dynamical scaling relations between time and energy, able to account for universality and provide a unifying description for the phenomenological power laws. Then we discuss how branching models can be implemented to forecast the temporal evolution of the earthquake occurrence probability and allow to discriminate among different physical mechanisms responsible for earthquake triggering. In particular, the forecasting problem will be presented in a rigorous mathematical framework, discussing the relevance of the processes acting at different temporal scales for

  2. Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

    Science.gov (United States)

    Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

    2016-04-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced Seismicity Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

  3. 1/f and the Earthquake Problem: Scaling constraints that facilitate operational earthquake forecasting

    Science.gov (United States)

    yoder, M. R.; Rundle, J. B.; Turcotte, D. L.

    2012-12-01

    The difficulty of forecasting earthquakes can fundamentally be attributed to the self-similar, or "1/f", nature of seismic sequences. Specifically, the rate of occurrence of earthquakes is inversely proportional to their magnitude m, or more accurately to their scalar moment M. With respect to this "1/f problem," it can be argued that catalog selection (or equivalently, determining catalog constraints) constitutes the most significant challenge to seismicity based earthquake forecasting. Here, we address and introduce a potential solution to this most daunting problem. Specifically, we introduce a framework to constrain, or partition, an earthquake catalog (a study region) in order to resolve local seismicity. In particular, we combine Gutenberg-Richter (GR), rupture length, and Omori scaling with various empirical measurements to relate the size (spatial and temporal extents) of a study area (or bins within a study area) to the local earthquake magnitude potential - the magnitude of earthquake the region is expected to experience. From this, we introduce a new type of time dependent hazard map for which the tuning parameter space is nearly fully constrained. In a similar fashion, by combining various scaling relations and also by incorporating finite extents (rupture length, area, and duration) as constraints, we develop a method to estimate the Omori (temporal) and spatial aftershock decay parameters as a function of the parent earthquake's magnitude m. From this formulation, we develop an ETAS type model that overcomes many point-source limitations of contemporary ETAS. These models demonstrate promise with respect to earthquake forecasting applications. Moreover, the methods employed suggest a general framework whereby earthquake and other complex-system, 1/f type, problems can be constrained from scaling relations and finite extents.; Record-breaking hazard map of southern California, 2012-08-06. "Warm" colors indicate local acceleration (elevated hazard

  4. Non-seismic tsunamis: filling the forecast gap

    Science.gov (United States)

    Moore, C. W.; Titov, V. V.; Spillane, M. C.

    2015-12-01

    Earthquakes are the generation mechanism in over 85% of tsunamis. However, non-seismic tsunamis, including those generated by meteorological events, landslides, volcanoes, and asteroid impacts, can inundate significant area and have a large far-field effect. The current National Oceanographic and Atmospheric Administration (NOAA) tsunami forecast system falls short in detecting these phenomena. This study attempts to classify the range of effects possible from these non-seismic threats, and to investigate detection methods appropriate for use in a forecast system. Typical observation platforms are assessed, including DART bottom pressure recorders and tide gauges. Other detection paths include atmospheric pressure anomaly algorithms for detecting meteotsunamis and the early identification of asteroids large enough to produce a regional hazard. Real-time assessment of observations for forecast use can provide guidance to mitigate the effects of a non-seismic tsunami.

  5. 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

  6. Earthquake focal mechanism forecasting in Italy for PSHA purposes

    Science.gov (United States)

    Roselli, Pamela; Marzocchi, Warner; Mariucci, Maria Teresa; Montone, Paola

    2018-01-01

    In this paper, we put forward a procedure that aims to forecast focal mechanism of future earthquakes. One of the primary uses of such forecasts is in probabilistic seismic hazard analysis (PSHA); in fact, aiming at reducing the epistemic uncertainty, most of the newer ground motion prediction equations consider, besides the seismicity rates, the forecast of the focal mechanism of the next large earthquakes as input data. The data set used to this purpose is relative to focal mechanisms taken from the latest stress map release for Italy containing 392 well-constrained solutions of events, from 1908 to 2015, with Mw ≥ 4 and depths from 0 down to 40 km. The data set considers polarity focal mechanism solutions until to 1975 (23 events), whereas for 1976-2015, it takes into account only the Centroid Moment Tensor (CMT)-like earthquake focal solutions for data homogeneity. The forecasting model is rooted in the Total Weighted Moment Tensor concept that weighs information of past focal mechanisms evenly distributed in space, according to their distance from the spatial cells and magnitude. Specifically, for each cell of a regular 0.1° × 0.1° spatial grid, the model estimates the probability to observe a normal, reverse, or strike-slip fault plane solution for the next large earthquakes, the expected moment tensor and the related maximum horizontal stress orientation. These results will be available for the new PSHA model for Italy under development. Finally, to evaluate the reliability of the forecasts, we test them with an independent data set that consists of some of the strongest earthquakes with Mw ≥ 3.9 occurred during 2016 in different Italian tectonic provinces.

  7. Varenna workshop report. Operational earthquake forecasting and decision making

    Directory of Open Access Journals (Sweden)

    Warner Marzocchi

    2015-09-01

    Full Text Available A workshop on Operational earthquake forecasting and decision making was convened in Varenna, Italy, on June 8-11, 2014, under the sponsorship of the EU FP 7 REAKT (Strategies and tools for Real-time EArthquake risK reducTion project, the Seismic Hazard Center at the Istituto Nazionale di Geofisica e Vulcanologia (INGV, and the Southern California Earthquake Center (SCEC. The main goal was to survey the interdisciplinary issues of operational earthquake forecasting (OEF, including the problems that OEF raises for decision making and risk communication. The workshop was attended by 64 researchers from universities, research centers, and governmental institutions in 11 countries. Participants and the workshop agenda are listed in the appendix.The workshop comprised six topical sessions structured around three main themes: the science of operational earthquake forecasting, decision making in a low-probability environment, and communicating hazard and risk. Each topic was introduced by a moderator and surveyed by a few invited speakers, who were then empaneled for an open discussion. The presentations were followed by poster sessions. During a wrap-up session on the last day, the reporters for each topical session summarized the main points that they had gleaned from the talks and open discussions. This report attempts to distill this workshop record into a brief overview of the workshop themes and to describe the range of opinions expressed during the discussions.

  8. Earthquake forecasting test for Kanto district to reduce vulnerability of urban mega earthquake disasters

    Science.gov (United States)

    Yokoi, S.; Tsuruoka, H.; Nanjo, K.; Hirata, N.

    2012-12-01

    Collaboratory for the Study of Earthquake Predictability (CSEP) is a global project on earthquake predictability research. The final goal of this project is to search for the intrinsic predictability of the earthquake rupture process through forecast testing experiments. The Earthquake Research Institute, the University of Tokyo joined CSEP and started the Japanese testing center called as CSEP-Japan. This testing center provides an open access to researchers contributing earthquake forecast models applied to Japan. Now more than 100 earthquake forecast models were submitted on the prospective experiment. The models are separated into 4 testing classes (1 day, 3 months, 1 year and 3 years) and 3 testing regions covering an area of Japan including sea area, Japanese mainland and Kanto district. We evaluate the performance of the models in the official suite of tests defined by CSEP. The total number of experiments was implemented for approximately 300 rounds. These results provide new knowledge concerning statistical forecasting models. We started a study for constructing a 3-dimensional earthquake forecasting model for Kanto district in Japan based on CSEP experiments under the Special Project for Reducing Vulnerability for Urban Mega Earthquake Disasters. Because seismicity of the area ranges from shallower part to a depth of 80 km due to subducting Philippine Sea plate and Pacific plate, we need to study effect of depth distribution. We will develop models for forecasting based on the results of 2-D modeling. We defined the 3D - forecasting area in the Kanto region with test classes of 1 day, 3 months, 1 year and 3 years, and magnitudes from 4.0 to 9.0 as in CSEP-Japan. In the first step of the study, we will install RI10K model (Nanjo, 2011) and the HISTETAS models (Ogata, 2011) to know if those models have good performance as in the 3 months 2-D CSEP-Japan experiments in the Kanto region before the 2011 Tohoku event (Yokoi et al., in preparation). We use CSEP

  9. Lessons of L'Aquila for Operational Earthquake Forecasting

    Science.gov (United States)

    Jordan, T. H.

    2012-12-01

    The L'Aquila earthquake of 6 Apr 2009 (magnitude 6.3) killed 309 people and left tens of thousands homeless. The mainshock was preceded by a vigorous seismic sequence that prompted informal earthquake predictions and evacuations. In an attempt to calm the population, the Italian Department of Civil Protection (DPC) convened its Commission on the Forecasting and Prevention of Major Risk (MRC) in L'Aquila on 31 March 2009 and issued statements about the hazard that were widely received as an "anti-alarm"; i.e., a deterministic prediction that there would not be a major earthquake. On October 23, 2012, a court in L'Aquila convicted the vice-director of DPC and six scientists and engineers who attended the MRC meeting on charges of criminal manslaughter, and it sentenced each to six years in prison. A few weeks after the L'Aquila disaster, the Italian government convened an International Commission on Earthquake Forecasting for Civil Protection (ICEF) with the mandate to assess the status of short-term forecasting methods and to recommend how they should be used in civil protection. The ICEF, which I chaired, issued its findings and recommendations on 2 Oct 2009 and published its final report, "Operational Earthquake Forecasting: Status of Knowledge and Guidelines for Implementation," in Aug 2011 (www.annalsofgeophysics.eu/index.php/annals/article/view/5350). As defined by the Commission, operational earthquake forecasting (OEF) involves two key activities: the continual updating of authoritative information about the future occurrence of potentially damaging earthquakes, and the officially sanctioned dissemination of this information to enhance earthquake preparedness in threatened communities. Among the main lessons of L'Aquila is the need to separate the role of science advisors, whose job is to provide objective information about natural hazards, from that of civil decision-makers who must weigh the benefits of protective actions against the costs of false alarms

  10. Amplitude of foreshocks as a possible seismic precursor to earthquakes

    Science.gov (United States)

    Lindh, A.G.

    1978-01-01

    In recent years, we have made significant progress in being able to recognize the long-range pattern of events that precede large earthquakes. For example, in a recent issue of the Earthquake Information Bulletin, we saw how the pioneering work of S.A. Fedotov of the U.S.S.R in the Kamchatka-Kurile Islands region has been applied worldwide to forecast where large, shallow earthquakes might occur in the next decades. Indeed, such a "seismic gap" off the coast of Alaska was filled by the 1972 Sitka earthquake. Promising results are slowly accumulating from other techniques that suggest that intermediate-term precursors might also be seen: among these are tilt and geomagnetic anomalies and anomalous land uplift. But the crucial point remains that short-term precursors (days to hours) will be needed in many cases if there is to be a significant saving of lives. 

  11. Gambling scores for earthquake predictions and forecasts

    Science.gov (United States)

    Zhuang, Jiancang

    2010-04-01

    This paper presents a new method, namely the gambling score, for scoring the performance earthquake forecasts or predictions. Unlike most other scoring procedures that require a regular scheme of forecast and treat each earthquake equally, regardless their magnitude, this new scoring method compensates the risk that the forecaster has taken. Starting with a certain number of reputation points, once a forecaster makes a prediction or forecast, he is assumed to have betted some points of his reputation. The reference model, which plays the role of the house, determines how many reputation points the forecaster can gain if he succeeds, according to a fair rule, and also takes away the reputation points betted by the forecaster if he loses. This method is also extended to the continuous case of point process models, where the reputation points betted by the forecaster become a continuous mass on the space-time-magnitude range of interest. We also calculate the upper bound of the gambling score when the true model is a renewal process, the stress release model or the ETAS model and when the reference model is the Poisson model.

  12. Retrospective evaluation of the five-year and ten-year CSEP-Italy earthquake forecasts

    Directory of Open Access Journals (Sweden)

    Stefan Wiemer

    2010-11-01

    Full Text Available On August 1, 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP launched a prospective and comparative earthquake predictability experiment in Italy. The goal of this CSEP-Italy experiment is to test earthquake occurrence hypotheses that have been formalized as probabilistic earthquake forecasts over temporal scales that range from days to years. In the first round of forecast submissions, members of the CSEP-Italy Working Group presented 18 five-year and ten-year earthquake forecasts to the European CSEP Testing Center at ETH Zurich. We have considered here the twelve time-independent earthquake forecasts among this set, and evaluated them with respect to past seismicity data from two Italian earthquake catalogs. We present the results of the tests that measure the consistencies of the forecasts according to past observations. As well as being an evaluation of the time-independent forecasts submitted, this exercise provides insight into a number of important issues in predictability experiments with regard to the specification of the forecasts, the performance of the tests, and the trade-off between robustness of results and experiment duration. We conclude with suggestions for the design of future earthquake predictability experiments.

  13. Forecasting of future earthquakes in the northeast region of India considering energy released concept

    Science.gov (United States)

    Zarola, Amit; Sil, Arjun

    2018-04-01

    This study presents the forecasting of time and magnitude size of the next earthquake in the northeast India, using four probability distribution models (Gamma, Lognormal, Weibull and Log-logistic) considering updated earthquake catalog of magnitude Mw ≥ 6.0 that occurred from year 1737-2015 in the study area. On the basis of past seismicity of the region, two types of conditional probabilities have been estimated using their best fit model and respective model parameters. The first conditional probability is the probability of seismic energy (e × 1020 ergs), which is expected to release in the future earthquake, exceeding a certain level of seismic energy (E × 1020 ergs). And the second conditional probability is the probability of seismic energy (a × 1020 ergs/year), which is expected to release per year, exceeding a certain level of seismic energy per year (A × 1020 ergs/year). The logarithm likelihood functions (ln L) were also estimated for all four probability distribution models. A higher value of ln L suggests a better model and a lower value shows a worse model. The time of the future earthquake is forecasted by dividing the total seismic energy expected to release in the future earthquake with the total seismic energy expected to release per year. The epicentre of recently occurred 4 January 2016 Manipur earthquake (M 6.7), 13 April 2016 Myanmar earthquake (M 6.9) and the 24 August 2016 Myanmar earthquake (M 6.8) are located in zone Z.12, zone Z.16 and zone Z.15, respectively and that are the identified seismic source zones in the study area which show that the proposed techniques and models yield good forecasting accuracy.

  14. Applying Binary Forecasting Approaches to Induced Seismicity in the Western Canada Sedimentary Basin

    Science.gov (United States)

    Kahue, R.; Shcherbakov, R.

    2016-12-01

    The Western Canada Sedimentary Basin has been chosen as a focus due to an increase in the recent observed seismicity there which is most likely linked to anthropogenic activities related to unconventional oil and gas exploration. Seismicity caused by these types of activities is called induced seismicity. The occurrence of moderate to larger induced earthquakes in areas where critical infrastructure is present can be potentially problematic. Here we use a binary forecast method to analyze past seismicity and well production data in order to quantify future areas of increased seismicity. This method splits the given region into spatial cells. The binary forecast method used here has been suggested in the past to retroactively forecast large earthquakes occurring globally in areas called alarm cells. An alarm cell, or alert zone, is a bin in which there is a higher likelihood for earthquakes to occur based on previous data. The first method utilizes the cumulative Benioff strain, based on earthquakes that had occurred in each bin above a given magnitude over a time interval called the training period. The second method utilizes the cumulative well production data within each bin. Earthquakes that occurred within an alert zone in the retrospective forecast period contribute to the hit rate, while alert zones that did not have an earthquake occur within them in the forecast period contribute to the false alarm rate. In the resulting analysis the hit rate and false alarm rate are determined after optimizing and modifying the initial parameters using the receiver operating characteristic diagram. It is found that when modifying the cell size and threshold magnitude parameters within various training periods, hit and false alarm rates are obtained for specific regions in Western Canada using both recent seismicity and cumulative well production data. Certain areas are thus shown to be more prone to potential larger earthquakes based on both datasets. This has implications

  15. Multiscale seismicity analysis and forecasting: examples from the Western Pacific and Iceland

    International Nuclear Information System (INIS)

    Eberhard, A. J.

    2014-01-01

    Seismicity forecasting has three major challenges: (1) the development of models or algorithms to forecast of seismicity, (2) the evaluation and testing of the forecasts and (3) the need for an appropriate software package. The goal of my thesis is to improve seismicity forecasting. I do this by contributing to a solution for all of the three challenges, using data from the West Pacific and from Iceland. The thesis is split into three chapters, each focusing on one of the challenges and each chapter will be (or already is) published in a peer-reviewed scientific journal. This first chapter (chapter 2 in this thesis) is about testing of seismic forecasts. The Collaboratory for the Study of Earthquake Predictability (CSEP, www.cseptesting.org; Jordan, 2006) has been conducting an earthquake forecast experiment in the western Pacific. The data and forecasts of this experiment serve as example for this chapter. For the three participating statistical models, I analyze the first four years of this experiment. I use likelihood-based metrics to evaluate the consistency of the forecasts with the observed target earthquakes, and I apply measures based on Student’s t-test and the Wilcoxon signed-rank test to compare the forecasts. I estimate also the uncertainties of the test results resulting from uncertainties in earthquake location and seismic moment. The estimated uncertainties are relatively small and suggest that the evaluation metrics are relatively robust. In chapter 3 I focus on the forecast itself with an Operational Earthquake Forecasting (OEF) experiment–forecasting seismicity in near real-time–for Iceland. The goal is to estimate the feasibility of OEF with the state-of-the-art models. I use the period between 2007 and 2010 and a sparsely processed catalogue as basis for a retrospective forecasting experiment with next-day forecasts. To better understand the effect of updating cycle on the probability gain I also use scheme in which the forecasts are

  16. Multiscale seismicity analysis and forecasting: examples from the Western Pacific and Iceland

    Energy Technology Data Exchange (ETDEWEB)

    Eberhard, A. J.

    2014-07-01

    Seismicity forecasting has three major challenges: (1) the development of models or algorithms to forecast of seismicity, (2) the evaluation and testing of the forecasts and (3) the need for an appropriate software package. The goal of my thesis is to improve seismicity forecasting. I do this by contributing to a solution for all of the three challenges, using data from the West Pacific and from Iceland. The thesis is split into three chapters, each focusing on one of the challenges and each chapter will be (or already is) published in a peer-reviewed scientific journal. This first chapter (chapter 2 in this thesis) is about testing of seismic forecasts. The Collaboratory for the Study of Earthquake Predictability (CSEP, www.cseptesting.org; Jordan, 2006) has been conducting an earthquake forecast experiment in the western Pacific. The data and forecasts of this experiment serve as example for this chapter. For the three participating statistical models, I analyze the first four years of this experiment. I use likelihood-based metrics to evaluate the consistency of the forecasts with the observed target earthquakes, and I apply measures based on Student’s t-test and the Wilcoxon signed-rank test to compare the forecasts. I estimate also the uncertainties of the test results resulting from uncertainties in earthquake location and seismic moment. The estimated uncertainties are relatively small and suggest that the evaluation metrics are relatively robust. In chapter 3 I focus on the forecast itself with an Operational Earthquake Forecasting (OEF) experiment–forecasting seismicity in near real-time–for Iceland. The goal is to estimate the feasibility of OEF with the state-of-the-art models. I use the period between 2007 and 2010 and a sparsely processed catalogue as basis for a retrospective forecasting experiment with next-day forecasts. To better understand the effect of updating cycle on the probability gain I also use scheme in which the forecasts are

  17. Retrospective Evaluation of the Long-Term CSEP-Italy Earthquake Forecasts

    Science.gov (United States)

    Werner, M. J.; Zechar, J. D.; Marzocchi, W.; Wiemer, S.

    2010-12-01

    On 1 August 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP) launched a prospective and comparative earthquake predictability experiment in Italy. The goal of the CSEP-Italy experiment is to test earthquake occurrence hypotheses that have been formalized as probabilistic earthquake forecasts over temporal scales that range from days to years. In the first round of forecast submissions, members of the CSEP-Italy Working Group presented eighteen five-year and ten-year earthquake forecasts to the European CSEP Testing Center at ETH Zurich. We considered the twelve time-independent earthquake forecasts among this set and evaluated them with respect to past seismicity data from two Italian earthquake catalogs. Here, we present the results of tests that measure the consistency of the forecasts with the past observations. Besides being an evaluation of the submitted time-independent forecasts, this exercise provided insight into a number of important issues in predictability experiments with regard to the specification of the forecasts, the performance of the tests, and the trade-off between the robustness of results and experiment duration.

  18. Are seismic hazard assessment errors and earthquake surprises unavoidable?

    Science.gov (United States)

    Kossobokov, Vladimir

    2013-04-01

    Why earthquake occurrences bring us so many surprises? The answer seems evident if we review the relationships that are commonly used to assess seismic hazard. The time-span of physically reliable Seismic History is yet a small portion of a rupture recurrence cycle at an earthquake-prone site, which makes premature any kind of reliable probabilistic statements about narrowly localized seismic hazard. Moreover, seismic evidences accumulated to-date demonstrate clearly that most of the empirical relations commonly accepted in the early history of instrumental seismology can be proved erroneous when testing statistical significance is applied. Seismic events, including mega-earthquakes, cluster displaying behaviors that are far from independent or periodic. Their distribution in space is possibly fractal, definitely, far from uniform even in a single segment of a fault zone. Such a situation contradicts generally accepted assumptions used for analytically tractable or computer simulations and complicates design of reliable methodologies for realistic earthquake hazard assessment, as well as search and definition of precursory behaviors to be used for forecast/prediction purposes. As a result, the conclusions drawn from such simulations and analyses can MISLEAD TO SCIENTIFICALLY GROUNDLESS APPLICATION, which is unwise and extremely dangerous in assessing expected societal risks and losses. For example, a systematic comparison of the GSHAP peak ground acceleration estimates with those related to actual strong earthquakes, unfortunately, discloses gross inadequacy of this "probabilistic" product, which appears UNACCEPTABLE FOR ANY KIND OF RESPONSIBLE SEISMIC RISK EVALUATION AND KNOWLEDGEABLE DISASTER PREVENTION. The self-evident shortcomings and failures of GSHAP appeals to all earthquake scientists and engineers for an urgent revision of the global seismic hazard maps from the first principles including background methodologies involved, such that there becomes: (a) a

  19. Seismicity map tools for earthquake studies

    Science.gov (United States)

    Boucouvalas, Anthony; Kaskebes, Athanasios; Tselikas, Nikos

    2014-05-01

    We report on the development of new and online set of tools for use within Google Maps, for earthquake research. We demonstrate this server based and online platform (developped with PHP, Javascript, MySQL) with the new tools using a database system with earthquake data. The platform allows us to carry out statistical and deterministic analysis on earthquake data use of Google Maps and plot various seismicity graphs. The tool box has been extended to draw on the map line segments, multiple straight lines horizontally and vertically as well as multiple circles, including geodesic lines. The application is demonstrated using localized seismic data from the geographic region of Greece as well as other global earthquake data. The application also offers regional segmentation (NxN) which allows the studying earthquake clustering, and earthquake cluster shift within the segments in space. The platform offers many filters such for plotting selected magnitude ranges or time periods. The plotting facility allows statistically based plots such as cumulative earthquake magnitude plots and earthquake magnitude histograms, calculation of 'b' etc. What is novel for the platform is the additional deterministic tools. Using the newly developed horizontal and vertical line and circle tools we have studied the spatial distribution trends of many earthquakes and we here show for the first time the link between Fibonacci Numbers and spatiotemporal location of some earthquakes. The new tools are valuable for examining visualizing trends in earthquake research as it allows calculation of statistics as well as deterministic precursors. We plan to show many new results based on our newly developed platform.

  20. Applications of the gambling score in evaluating earthquake predictions and forecasts

    Science.gov (United States)

    Zhuang, Jiancang; Zechar, Jeremy D.; Jiang, Changsheng; Console, Rodolfo; Murru, Maura; Falcone, Giuseppe

    2010-05-01

    This study presents a new method, namely the gambling score, for scoring the performance earthquake forecasts or predictions. Unlike most other scoring procedures that require a regular scheme of forecast and treat each earthquake equally, regardless their magnitude, this new scoring method compensates the risk that the forecaster has taken. Starting with a certain number of reputation points, once a forecaster makes a prediction or forecast, he is assumed to have betted some points of his reputation. The reference model, which plays the role of the house, determines how many reputation points the forecaster can gain if he succeeds, according to a fair rule, and also takes away the reputation points bet by the forecaster if he loses. This method is also extended to the continuous case of point process models, where the reputation points betted by the forecaster become a continuous mass on the space-time-magnitude range of interest. For discrete predictions, we apply this method to evaluate performance of Shebalin's predictions made by using the Reverse Tracing of Precursors (RTP) algorithm and of the outputs of the predictions from the Annual Consultation Meeting on Earthquake Tendency held by China Earthquake Administration. For the continuous case, we use it to compare the probability forecasts of seismicity in the Abruzzo region before and after the L'aquila earthquake based on the ETAS model and the PPE model.

  1. Portals for Real-Time Earthquake Data and Forecasting: Challenge and Promise (Invited)

    Science.gov (United States)

    Rundle, J. B.; Holliday, J. R.; Graves, W. R.; Feltstykket, R.; Donnellan, A.; Glasscoe, M. T.

    2013-12-01

    Earthquake forecasts have been computed by a variety of countries world-wide for over two decades. For the most part, forecasts have been computed for insurance, reinsurance and underwriters of catastrophe bonds. However, recent events clearly demonstrate that mitigating personal risk is becoming the responsibility of individual members of the public. Open access to a variety of web-based forecasts, tools, utilities and information is therefore required. Portals for data and forecasts present particular challenges, and require the development of both apps and the client/server architecture to deliver the basic information in real time. The basic forecast model we consider is the Natural Time Weibull (NTW) method (JBR et al., Phys. Rev. E, 86, 021106, 2012). This model uses small earthquakes (';seismicity-based models') to forecast the occurrence of large earthquakes, via data-mining algorithms combined with the ANSS earthquake catalog. This method computes large earthquake probabilities using the number of small earthquakes that have occurred in a region since the last large earthquake. Localizing these forecasts in space so that global forecasts can be computed in real time presents special algorithmic challenges, which we describe in this talk. Using 25 years of data from the ANSS California-Nevada catalog of earthquakes, we compute real-time global forecasts at a grid scale of 0.1o. We analyze and monitor the performance of these models using the standard tests, which include the Reliability/Attributes and Receiver Operating Characteristic (ROC) tests. It is clear from much of the analysis that data quality is a major limitation on the accurate computation of earthquake probabilities. We discuss the challenges of serving up these datasets over the web on web-based platforms such as those at www.quakesim.org , www.e-decider.org , and www.openhazards.com.

  2. 2017 One‐year seismic‐hazard forecast for the central and eastern United States from induced and natural earthquakes

    Science.gov (United States)

    Petersen, Mark D.; Mueller, Charles; Moschetti, Morgan P.; Hoover, Susan M.; Shumway, Allison; McNamara, Daniel E.; Williams, Robert; Llenos, Andrea L.; Ellsworth, William L.; Rubinstein, Justin L.; McGarr, Arthur F.; Rukstales, Kenneth S.

    2017-01-01

    We produce a one‐year 2017 seismic‐hazard forecast for the central and eastern United States from induced and natural earthquakes that updates the 2016 one‐year forecast; this map is intended to provide information to the public and to facilitate the development of induced seismicity forecasting models, methods, and data. The 2017 hazard model applies the same methodology and input logic tree as the 2016 forecast, but with an updated earthquake catalog. We also evaluate the 2016 seismic‐hazard forecast to improve future assessments. The 2016 forecast indicated high seismic hazard (greater than 1% probability of potentially damaging ground shaking in one year) in five focus areas: Oklahoma–Kansas, the Raton basin (Colorado/New Mexico border), north Texas, north Arkansas, and the New Madrid Seismic Zone. During 2016, several damaging induced earthquakes occurred in Oklahoma within the highest hazard region of the 2016 forecast; all of the 21 moment magnitude (M) ≥4 and 3 M≥5 earthquakes occurred within the highest hazard area in the 2016 forecast. Outside the Oklahoma–Kansas focus area, two earthquakes with M≥4 occurred near Trinidad, Colorado (in the Raton basin focus area), but no earthquakes with M≥2.7 were observed in the north Texas or north Arkansas focus areas. Several observations of damaging ground‐shaking levels were also recorded in the highest hazard region of Oklahoma. The 2017 forecasted seismic rates are lower in regions of induced activity due to lower rates of earthquakes in 2016 compared with 2015, which may be related to decreased wastewater injection caused by regulatory actions or by a decrease in unconventional oil and gas production. Nevertheless, the 2017 forecasted hazard is still significantly elevated in Oklahoma compared to the hazard calculated from seismicity before 2009.

  3. Study on the Forecast of Ground Motion Parameters from Real Time Earthquake Information Based on Wave Form Data at the Front Site

    OpenAIRE

    萩原, 由訓; 源栄, 正人; 三辻, 和弥; 野畑, 有秀; Yoshinori, HAGIWARA; Masato, MOTOSAKA; Kazuya, MITSUJI; Arihide, NOBATA; (株)大林組 技術研究所; 東北大学大学院工学研究科; 山形大学地域教育文化学部生活総合学科生活環境科学コース; (株)大林組 技術研究所; Obayashi Corporation Technical Research Institute; Graduate School of Eng., Tohoku University; Faculty of Education, Art and Science, Yamagata University

    2011-01-01

    The Japan Meteorological Agency(JMA) provides Earthquake Early Warnings(EEW) for advanced users from August 1, 2006. Advanced EEW users can forecaste seismic ground motion (example: Seismic Intensity, Peak Ground Acceleration) from information of the earthquake in EEW. But there are limits to the accuracy and the earliness of the forecasting. This paper describes regression equation to decrease the error and to increase rapidity of the forecast of ground motion parameters from Real Time Earth...

  4. Robust seismicity forecasting based on Bayesian parameter estimation for epidemiological spatio-temporal aftershock clustering models.

    Science.gov (United States)

    Ebrahimian, Hossein; Jalayer, Fatemeh

    2017-08-29

    In the immediate aftermath of a strong earthquake and in the presence of an ongoing aftershock sequence, scientific advisories in terms of seismicity forecasts play quite a crucial role in emergency decision-making and risk mitigation. Epidemic Type Aftershock Sequence (ETAS) models are frequently used for forecasting the spatio-temporal evolution of seismicity in the short-term. We propose robust forecasting of seismicity based on ETAS model, by exploiting the link between Bayesian inference and Markov Chain Monte Carlo Simulation. The methodology considers the uncertainty not only in the model parameters, conditioned on the available catalogue of events occurred before the forecasting interval, but also the uncertainty in the sequence of events that are going to happen during the forecasting interval. We demonstrate the methodology by retrospective early forecasting of seismicity associated with the 2016 Amatrice seismic sequence activities in central Italy. We provide robust spatio-temporal short-term seismicity forecasts with various time intervals in the first few days elapsed after each of the three main events within the sequence, which can predict the seismicity within plus/minus two standard deviations from the mean estimate within the few hours elapsed after the main event.

  5. Romanian earthquakes analysis using BURAR seismic array

    International Nuclear Information System (INIS)

    Borleanu, Felix; Rogozea, Maria; Nica, Daniela; Popescu, Emilia; Popa, Mihaela; Radulian, Mircea

    2008-01-01

    Bucovina seismic array (BURAR) is a medium-aperture array, installed in 2002 in the northern part of Romania (47.61480 N latitude, 25.21680 E longitude, 1150 m altitude), as a result of the cooperation between Air Force Technical Applications Center, USA and National Institute for Earth Physics, Romania. The array consists of ten elements, located in boreholes and distributed over a 5 x 5 km 2 area; nine with short-period vertical sensors and one with a broadband three-component sensor. Since the new station has been operating the earthquake survey of Romania's territory has been significantly improved. Data recorded by BURAR during 01.01.2005 - 12.31.2005 time interval are first processed and analyzed, in order to establish the array detection capability of the local earthquakes, occurred in different Romanian seismic zones. Subsequently a spectral ratios technique was applied in order to determine the calibration relationships for magnitude, using only the information gathered by BURAR station. The spectral ratios are computed relatively to a reference event, considered as representative for each seismic zone. This method has the advantage to eliminate the path effects. The new calibration procedure is tested for the case of Vrancea intermediate-depth earthquakes and proved to be very efficient in constraining the size of these earthquakes. (authors)

  6. Moment-ration imaging of seismic regions for earthquake prediction

    Science.gov (United States)

    Lomnitz, Cinna

    1993-10-01

    An algorithm for predicting large earthquakes is proposed. The reciprocal ratio (mri) of the residual seismic moment to the total moment release in a region is used for imaging seismic moment precursors. Peaks in mri predict recent major earthquakes, including the 1985 Michoacan, 1985 central Chile, and 1992 Eureka, California earthquakes.

  7. Short- and Long-Term Earthquake Forecasts Based on Statistical Models

    Science.gov (United States)

    Console, Rodolfo; Taroni, Matteo; Murru, Maura; Falcone, Giuseppe; Marzocchi, Warner

    2017-04-01

    The epidemic-type aftershock sequences (ETAS) models have been experimentally used to forecast the space-time earthquake occurrence rate during the sequence that followed the 2009 L'Aquila earthquake and for the 2012 Emilia earthquake sequence. These forecasts represented the two first pioneering attempts to check the feasibility of providing operational earthquake forecasting (OEF) in Italy. After the 2009 L'Aquila earthquake the Italian Department of Civil Protection nominated an International Commission on Earthquake Forecasting (ICEF) for the development of the first official OEF in Italy that was implemented for testing purposes by the newly established "Centro di Pericolosità Sismica" (CPS, the seismic Hazard Center) at the Istituto Nazionale di Geofisica e Vulcanologia (INGV). According to the ICEF guidelines, the system is open, transparent, reproducible and testable. The scientific information delivered by OEF-Italy is shaped in different formats according to the interested stakeholders, such as scientists, national and regional authorities, and the general public. The communication to people is certainly the most challenging issue, and careful pilot tests are necessary to check the effectiveness of the communication strategy, before opening the information to the public. With regard to long-term time-dependent earthquake forecast, the application of a newly developed simulation algorithm to Calabria region provided typical features in time, space and magnitude behaviour of the seismicity, which can be compared with those of the real observations. These features include long-term pseudo-periodicity and clustering of strong earthquakes, and a realistic earthquake magnitude distribution departing from the Gutenberg-Richter distribution in the moderate and higher magnitude range.

  8. Seismic quiescence in a frictional earthquake model

    Science.gov (United States)

    Braun, Oleg M.; Peyrard, Michel

    2018-04-01

    We investigate the origin of seismic quiescence with a generalized version of the Burridge-Knopoff model for earthquakes and show that it can be generated by a multipeaked probability distribution of the thresholds at which contacts break. Such a distribution is not assumed a priori but naturally results from the aging of the contacts. We show that the model can exhibit quiescence as well as enhanced foreshock activity, depending on the value of some parameters. This provides a generic understanding for seismic quiescence, which encompasses earlier specific explanations and could provide a pathway for a classification of faults.

  9. Forecasting Italian seismicity through a spatio-temporal physical model: importance of considering time-dependency and reliability of the forecast

    Directory of Open Access Journals (Sweden)

    Amir Hakimhashemi

    2010-11-01

    Full Text Available We apply here a forecasting model to the Italian region for the spatio-temporal distribution of seismicity based on a smoothing Kernel function, Coulomb stress variations, and a rate-and-state friction law. We tested the feasibility of this approach, and analyzed the importance of introducing time-dependency in forecasting future events. The change in seismicity rate as a function of time was estimated by calculating the Coulomb stress change imparted by large earthquakes. We applied our approach to the region of Italy, and used all of the cataloged earthquakes that occurred up to 2006 to generate the reference seismicity rate. For calculation of the time-dependent seismicity rate changes, we estimated the rate-and-state stress transfer imparted by all of the ML≥4.0 earthquakes that occurred during 2007 and 2008. To validate the results, we first compared the reference seismicity rate with the distribution of ML≥1.8 earthquakes since 2007, using both a non-declustered and a declustered catalog. A positive correlation was found, and all of the forecast earthquakes had locations within 82% and 87% of the study area with the highest seismicity rate, respectively. Furthermore, 95% of the forecast earthquakes had locations within 27% and 47% of the study area with the highest seismicity rate, respectively. For the time-dependent seismicity rate changes, the number of events with locations in the regions with a seismicity rate increase was 11% more than in the regions with a seismicity rate decrease.

  10. Interevent times in a new alarm-based earthquake forecasting model

    Science.gov (United States)

    Talbi, Abdelhak; Nanjo, Kazuyoshi; Zhuang, Jiancang; Satake, Kenji; Hamdache, Mohamed

    2013-09-01

    This study introduces a new earthquake forecasting model that uses the moment ratio (MR) of the first to second order moments of earthquake interevent times as a precursory alarm index to forecast large earthquake events. This MR model is based on the idea that the MR is associated with anomalous long-term changes in background seismicity prior to large earthquake events. In a given region, the MR statistic is defined as the inverse of the index of dispersion or Fano factor, with MR values (or scores) providing a biased estimate of the relative regional frequency of background events, here termed the background fraction. To test the forecasting performance of this proposed MR model, a composite Japan-wide earthquake catalogue for the years between 679 and 2012 was compiled using the Japan Meteorological Agency catalogue for the period between 1923 and 2012, and the Utsu historical seismicity records between 679 and 1922. MR values were estimated by sampling interevent times from events with magnitude M ≥ 6 using an earthquake random sampling (ERS) algorithm developed during previous research. Three retrospective tests of M ≥ 7 target earthquakes were undertaken to evaluate the long-, intermediate- and short-term performance of MR forecasting, using mainly Molchan diagrams and optimal spatial maps obtained by minimizing forecasting error defined by miss and alarm rate addition. This testing indicates that the MR forecasting technique performs well at long-, intermediate- and short-term. The MR maps produced during long-term testing indicate significant alarm levels before 15 of the 18 shallow earthquakes within the testing region during the past two decades, with an alarm region covering about 20 per cent (alarm rate) of the testing region. The number of shallow events missed by forecasting was reduced by about 60 per cent after using the MR method instead of the relative intensity (RI) forecasting method. At short term, our model succeeded in forecasting the

  11. Dynamic evaluation of seismic hazard and risks based on the Unified Scaling Law for Earthquakes

    Science.gov (United States)

    Kossobokov, V. G.; Nekrasova, A.

    2016-12-01

    We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing seismic hazard maps based on the Unified Scaling Law for Earthquakes (USLE), i.e. log N(M,L) = A + B•(6 - M) + C•log L, where N(M,L) is the expected annual number of earthquakes of a certain magnitude M within an seismically prone area of linear dimension L, A characterizes the average annual rate of strong (M = 6) earthquakes, B determines the balance between magnitude ranges, and C estimates the fractal dimension of seismic locus in projection to the Earth surface. The parameters A, B, and C of USLE are used to assess, first, the expected maximum magnitude in a time interval at a seismically prone cell of a uniform grid that cover the region of interest, and then the corresponding expected ground shaking parameters. After a rigorous testing against the available seismic evidences in the past (e.g., the historically reported macro-seismic intensity or paleo data), such a seismic hazard map is used to generate maps of specific earthquake risks for population, cities, and infrastructures. The hazard maps for a given territory change dramatically, when the methodology is applied to a certain size moving time window, e.g. about a decade long for an intermediate-term regional assessment or exponentially increasing intervals for a daily local strong aftershock forecasting. The of dynamical seismic hazard and risks assessment is illustrated by applications to the territory of Greater Caucasus and Crimea and the two-year series of aftershocks of the 11 October 2008 Kurchaloy, Chechnya earthquake which case-history appears to be encouraging for further systematic testing as potential short-term forecasting tool.

  12. Web-Based Real Time Earthquake Forecasting and Personal Risk Management

    Science.gov (United States)

    Rundle, J. B.; Holliday, J. R.; Graves, W. R.; Turcotte, D. L.; Donnellan, A.

    2012-12-01

    Earthquake forecasts have been computed by a variety of countries and economies world-wide for over two decades. For the most part, forecasts have been computed for insurance, reinsurance and underwriters of catastrophe bonds. One example is the Working Group on California Earthquake Probabilities that has been responsible for the official California earthquake forecast since 1988. However, in a time of increasingly severe global financial constraints, we are now moving inexorably towards personal risk management, wherein mitigating risk is becoming the responsibility of individual members of the public. Under these circumstances, open access to a variety of web-based tools, utilities and information is a necessity. Here we describe a web-based system that has been operational since 2009 at www.openhazards.com and www.quakesim.org. Models for earthquake physics and forecasting require input data, along with model parameters. The models we consider are the Natural Time Weibull (NTW) model for regional earthquake forecasting, together with models for activation and quiescence. These models use small earthquakes ('seismicity-based models") to forecast the occurrence of large earthquakes, either through varying rates of small earthquake activity, or via an accumulation of this activity over time. These approaches use data-mining algorithms combined with the ANSS earthquake catalog. The basic idea is to compute large earthquake probabilities using the number of small earthquakes that have occurred in a region since the last large earthquake. Each of these approaches has computational challenges associated with computing forecast information in real time. Using 25 years of data from the ANSS California-Nevada catalog of earthquakes, we show that real-time forecasting is possible at a grid scale of 0.1o. We have analyzed the performance of these models using Reliability/Attributes and standard Receiver Operating Characteristic (ROC) tests. We show how the Reliability and

  13. Bridge seismic retrofit measures considering subduction zone earthquakes.

    Science.gov (United States)

    2015-07-01

    Over the years, earthquakes have exposed the vulnerability of reinforced concrete structures under : seismic loads. The recent occurrence of highly devastating earthquakes near instrumented regions, e.g. 2010 Maule, Chile : and 2011 Tohoku, Japan, ha...

  14. Operational Earthquake Forecasting and Decision-Making in a Low-Probability Environment

    Science.gov (United States)

    Jordan, T. H.; the International Commission on Earthquake ForecastingCivil Protection

    2011-12-01

    Operational earthquake forecasting (OEF) is the dissemination of authoritative information about the time dependence of seismic hazards to help communities prepare for potentially destructive earthquakes. Most previous work on the public utility of OEF has anticipated that forecasts would deliver high probabilities of large earthquakes; i.e., deterministic predictions with low error rates (false alarms and failures-to-predict) would be possible. This expectation has not been realized. An alternative to deterministic prediction is probabilistic forecasting based on empirical statistical models of aftershock triggering and seismic clustering. During periods of high seismic activity, short-term earthquake forecasts can attain prospective probability gains in excess of 100 relative to long-term forecasts. The utility of such information is by no means clear, however, because even with hundredfold increases, the probabilities of large earthquakes typically remain small, rarely exceeding a few percent over forecasting intervals of days or weeks. Civil protection agencies have been understandably cautious in implementing OEF in this sort of "low-probability environment." The need to move more quickly has been underscored by recent seismic crises, such as the 2009 L'Aquila earthquake sequence, in which an anxious public was confused by informal and inaccurate earthquake predictions. After the L'Aquila earthquake, the Italian Department of Civil Protection appointed an International Commission on Earthquake Forecasting (ICEF), which I chaired, to recommend guidelines for OEF utilization. Our report (Ann. Geophys., 54, 4, 2011; doi: 10.4401/ag-5350) concludes: (a) Public sources of information on short-term probabilities should be authoritative, scientific, open, and timely, and need to convey epistemic uncertainties. (b) Earthquake probabilities should be based on operationally qualified, regularly updated forecasting systems. (c) All operational models should be evaluated

  15. Seismic dynamics in advance and after the recent strong earthquakes in Italy and New Zealand

    Science.gov (United States)

    Nekrasova, A.; Kossobokov, V. G.

    2017-12-01

    We consider seismic events as a sequence of avalanches in self-organized system of blocks-and-faults of the Earth lithosphere and characterize earthquake series with the distribution of the control parameter, η = τ × 10B × (5-M) × L C of the Unified Scaling Law for Earthquakes, USLE (where τ is inter-event time, B is analogous to the Gutenberg-Richter b-value, and C is fractal dimension of seismic locus). A systematic analysis of earthquake series in Central Italy and New Zealand, 1993-2017, suggests the existence, in a long-term, of different rather steady levels of seismic activity characterized with near constant values of η, which, in mid-term, intermittently switch at times of transitions associated with the strong catastrophic events. On such a transition, seismic activity, in short-term, may follow different scenarios with inter-event time scaling of different kind, including constant, logarithmic, power law, exponential rise/decay or a mixture of those. The results do not support the presence of universality in seismic energy release. The observed variability of seismic activity in advance and after strong (M6.0+) earthquakes in Italy and significant (M7.0+) earthquakes in New Zealand provides important constraints on modelling realistic earthquake sequences by geophysicists and can be used to improve local seismic hazard assessments including earthquake forecast/prediction methodologies. The transitions of seismic regime in Central Italy and New Zealand started in 2016 are still in progress and require special attention and geotechnical monitoring. It would be premature to make any kind of definitive conclusions on the level of seismic hazard which is evidently high at this particular moment of time in both regions. The study supported by the Russian Science Foundation Grant No.16-17-00093.

  16. Nonlinear time series modeling and forecasting the seismic data of the Hindu Kush region

    Science.gov (United States)

    Khan, Muhammad Yousaf; Mittnik, Stefan

    2018-01-01

    In this study, we extended the application of linear and nonlinear time models in the field of earthquake seismology and examined the out-of-sample forecast accuracy of linear Autoregressive (AR), Autoregressive Conditional Duration (ACD), Self-Exciting Threshold Autoregressive (SETAR), Threshold Autoregressive (TAR), Logistic Smooth Transition Autoregressive (LSTAR), Additive Autoregressive (AAR), and Artificial Neural Network (ANN) models for seismic data of the Hindu Kush region. We also extended the previous studies by using Vector Autoregressive (VAR) and Threshold Vector Autoregressive (TVAR) models and compared their forecasting accuracy with linear AR model. Unlike previous studies that typically consider the threshold model specifications by using internal threshold variable, we specified these models with external transition variables and compared their out-of-sample forecasting performance with the linear benchmark AR model. The modeling results show that time series models used in the present study are capable of capturing the dynamic structure present in the seismic data. The point forecast results indicate that the AR model generally outperforms the nonlinear models. However, in some cases, threshold models with external threshold variables specification produce more accurate forecasts, indicating that specification of threshold time series models is of crucial importance. For raw seismic data, the ACD model does not show an improved out-of-sample forecasting performance over the linear AR model. The results indicate that the AR model is the best forecasting device to model and forecast the raw seismic data of the Hindu Kush region.

  17. Nonlinear acoustic/seismic waves in earthquake processes

    International Nuclear Information System (INIS)

    Johnson, Paul A.

    2012-01-01

    Nonlinear dynamics induced by seismic sources and seismic waves are common in Earth. Observations range from seismic strong ground motion (the most damaging aspect of earthquakes), intense near-source effects, and distant nonlinear effects from the source that have important consequences. The distant effects include dynamic earthquake triggering—one of the most fascinating topics in seismology today—which may be elastically nonlinearly driven. Dynamic earthquake triggering is the phenomenon whereby seismic waves generated from one earthquake trigger slip events on a nearby or distant fault. Dynamic triggering may take place at distances thousands of kilometers from the triggering earthquake, and includes triggering of the entire spectrum of slip behaviors currently identified. These include triggered earthquakes and triggered slow, silent-slip during which little seismic energy is radiated. It appears that the elasticity of the fault gouge—the granular material located between the fault blocks—is key to the triggering phenomenon.

  18. Measuring the effectiveness of earthquake forecasting in insurance strategies

    Science.gov (United States)

    Mignan, A.; Muir-Wood, R.

    2009-04-01

    Given the difficulty of judging whether the skill of a particular methodology of earthquake forecasts is offset by the inevitable false alarms and missed predictions, it is important to find a means to weigh the successes and failures according to a common currency. Rather than judge subjectively the relative costs and benefits of predictions, we develop a simple method to determine if the use of earthquake forecasts can increase the profitability of active financial risk management strategies employed in standard insurance procedures. Three types of risk management transactions are employed: (1) insurance underwriting, (2) reinsurance purchasing and (3) investment in CAT bonds. For each case premiums are collected based on modelled technical risk costs and losses are modelled for the portfolio in force at the time of the earthquake. A set of predetermined actions follow from the announcement of any change in earthquake hazard, so that, for each earthquake forecaster, the financial performance of an active risk management strategy can be compared with the equivalent passive strategy in which no notice is taken of earthquake forecasts. Overall performance can be tracked through time to determine which strategy gives the best long term financial performance. This will be determined by whether the skill in forecasting the location and timing of a significant earthquake (where loss is avoided) is outweighed by false predictions (when no premium is collected). This methodology is to be tested in California, where catastrophe modeling is reasonably mature and where a number of researchers issue earthquake forecasts.

  19. Lower bound earthquake magnitude for probabilistic seismic hazard evaluation

    International Nuclear Information System (INIS)

    McCann, M.W. Jr.; Reed, J.W.

    1990-01-01

    This paper presents the results of a study that develops an engineering and seismological basis for selecting a lower-bound magnitude (LBM) for use in seismic hazard assessment. As part of a seismic hazard analysis the range of earthquake magnitudes that are included in the assessment of the probability of exceedance of ground motion must be defined. The upper-bound magnitude is established by earth science experts based on their interpretation of the maximum size of earthquakes that can be generated by a seismic source. The lower-bound or smallest earthquake that is considered in the analysis must also be specified. The LBM limits the earthquakes that are considered in assessing the probability that specified ground motion levels are exceeded. In the past there has not been a direct consideration of the appropriate LBM value that should be used in a seismic hazard assessment. This study specifically looks at the selection of a LBM for use in seismic hazard analyses that are input to the evaluation/design of nuclear power plants (NPPs). Topics addressed in the evaluation of a LBM are earthquake experience data at heavy industrial facilities, engineering characteristics of ground motions associated with small-magnitude earthquakes, probabilistic seismic risk assessments (seismic PRAs), and seismic margin evaluations. The results of this study and the recommendations concerning a LBM for use in seismic hazard assessments are discussed. (orig.)

  20. On one approach to an earthquakes forecasting problems solution

    International Nuclear Information System (INIS)

    Khugaev, A.V.; Koblik, Yu.N.; Rakhmanov, T.T.

    2007-01-01

    The problem of earthquake forecasting is practically important one but it is extremely complex and so it does not solved yet. In the report the problem of data analysis obtained in measurements of radioactive gases emission (for example, radon, thoron, action) from the earth surface, data in magnetic fields anomalies measurement and their correlation in accordance of seismic activity is considered. In a general case the problem has an unlikely total solution in an analytic meaning due to it nonlinearity, multi-parametration and influence of random factors. It is suggested that useful solution could be found only at reasonable combination of empiric knowledge got at a long observations, its generalization and numerical simulation. In the base of the offered calculation method the correlation analysis between seismic activity and , for example, radioactive gases emission variations of earthquake signs one can present in form of two components, one of which is regular component, and the second one is irregular one. The key interest presents the analysis of irregular component reasoned by random factors. At problem solution of irregular component of the Earth magnetic fields determination which with high precise could measured with help of magnetic sensors is determined. At that time in the base of mathematical apparatus for analysis the approach for irregular component determination applied at determination of irregular component of galactic magnet field. Hear values of irregular component and field size in which they play considerable role are obtained. Besides, the work the approach allowing solving problem about complex surface oscillation with necessary precision for practical requirements is discussed

  1. Network similarity and statistical analysis of earthquake seismic data

    OpenAIRE

    Deyasi, Krishanu; Chakraborty, Abhijit; Banerjee, Anirban

    2016-01-01

    We study the structural similarity of earthquake networks constructed from seismic catalogs of different geographical regions. A hierarchical clustering of underlying undirected earthquake networks is shown using Jensen-Shannon divergence in graph spectra. The directed nature of links indicates that each earthquake network is strongly connected, which motivates us to study the directed version statistically. Our statistical analysis of each earthquake region identifies the hub regions. We cal...

  2. Physics-based forecasting of induced seismicity at Groningen gas field, the Netherlands

    Science.gov (United States)

    Dempsey, David; Suckale, Jenny

    2017-08-01

    Earthquakes induced by natural gas extraction from the Groningen reservoir, the Netherlands, put local communities at risk. Responsible operation of a reservoir whose gas reserves are of strategic importance to the country requires understanding of the link between extraction and earthquakes. We synthesize observations and a model for Groningen seismicity to produce forecasts for felt seismicity (M > 2.5) in the period February 2017 to 2024. Our model accounts for poroelastic earthquake triggering and rupture on the 325 largest reservoir faults, using an ensemble approach to model unknown heterogeneity and replicate earthquake statistics. We calculate probability distributions for key model parameters using a Bayesian method that incorporates the earthquake observations with a nonhomogeneous Poisson process. Our analysis indicates that the Groningen reservoir was not critically stressed prior to the start of production. Epistemic uncertainty and aleatoric uncertainty are incorporated into forecasts for three different future extraction scenarios. The largest expected earthquake was similar for all scenarios, with a 5% likelihood of exceeding M 4.0.

  3. Earthquake experience suggests new approach to seismic criteria

    International Nuclear Information System (INIS)

    Knox, R.

    1983-01-01

    Progress in seismic qualification of nuclear power plants as reviewed at the 4th Pacific Basin Nuclear Conference in Vancouver, September 1983, is discussed. The lack of experience of earthquakes in existing nuclear plants can be compensated by the growing experience of actual earthquake effects in conventional power plants and similar installations. A survey of the effects on four power stations, with a total of twenty generating units, in the area strongly shaken by the San Fernando earthquake in California in 1971 is reported. The Canadian approach to seismic qualification, international criteria, Canadian/Korean experience, safety related equipment, the Tadotsu test facility and seismic tests are discussed. (U.K.)

  4. Calibration and validation of earthquake catastrophe models. Case study: Impact Forecasting Earthquake Model for Algeria

    Science.gov (United States)

    Trendafiloski, G.; Gaspa Rebull, O.; Ewing, C.; Podlaha, A.; Magee, B.

    2012-04-01

    Calibration and validation are crucial steps in the production of the catastrophe models for the insurance industry in order to assure the model's reliability and to quantify its uncertainty. Calibration is needed in all components of model development including hazard and vulnerability. Validation is required to ensure that the losses calculated by the model match those observed in past events and which could happen in future. Impact Forecasting, the catastrophe modelling development centre of excellence within Aon Benfield, has recently launched its earthquake model for Algeria as a part of the earthquake model for the Maghreb region. The earthquake model went through a detailed calibration process including: (1) the seismic intensity attenuation model by use of macroseismic observations and maps from past earthquakes in Algeria; (2) calculation of the country-specific vulnerability modifiers by use of past damage observations in the country. The use of Benouar, 1994 ground motion prediction relationship was proven as the most appropriate for our model. Calculation of the regional vulnerability modifiers for the country led to 10% to 40% larger vulnerability indexes for different building types compared to average European indexes. The country specific damage models also included aggregate damage models for residential, commercial and industrial properties considering the description of the buildings stock given by World Housing Encyclopaedia and the local rebuilding cost factors equal to 10% for damage grade 1, 20% for damage grade 2, 35% for damage grade 3, 75% for damage grade 4 and 100% for damage grade 5. The damage grades comply with the European Macroseismic Scale (EMS-1998). The model was validated by use of "as-if" historical scenario simulations of three past earthquake events in Algeria M6.8 2003 Boumerdes, M7.3 1980 El-Asnam and M7.3 1856 Djidjelli earthquake. The calculated return periods of the losses for client market portfolio align with the

  5. Seismicity and earthquake risk in western Sicily

    Directory of Open Access Journals (Sweden)

    P. COSENTINO

    1978-06-01

    Full Text Available The seismicity and the earthquake risk in Western Sicily are here
    evaluated on the basis of the experimental data referring to the historical
    and instrumentally recorded earthquakes in this area (from 1248
    up to 1968, which have been thoroughly collected, analyzed, tested and
    normalized in order to assure the quasi-stationarity of the series of
    events.
    The approximated magnitude values — obtained by means of a compared
    analysis of the magnitude and epicentral intensity values of the
    latest events — have allowed to study the parameters of the frequency-
    magnitude relation with both the classical exponential model and
    the truncated exponential one previously proposed by the author.
    So, the basic parameters, including the maximum possible regional
    magnitude, have been estimated by means of different procedures, and
    their behaviours have been studied as functions of the threshold magnitude.

  6. Magnitudes and frequencies of earthquakes in relation to seismic risk

    International Nuclear Information System (INIS)

    Sharma, R.D.

    1989-01-01

    Estimating the frequencies of occurrence of earthquakes of different magnitudes on a regional basis is an important task in estimating seismic risk at a construction site. Analysis of global earthquake data provides an insight into the magnitudes frequency relationship in a statistical manner. It turns out that, whereas a linear relationship between the logarithm of earthquake occurrence rates and the corresponding earthquake magnitudes fits well in the magnitude range between 5 and 7, a second degree polynomial in M, the earthquake magnitude provides a better description of the frequencies of earthquakes in a much wider range of magnitudes. It may be possible to adopt magnitude frequency relation for regions, for which adequate earthquake data are not available, to carry out seismic risk calculations. (author). 32 refs., 8 tabs., 7 figs

  7. Seismic methodology in determining basis earthquake for nuclear installation

    International Nuclear Information System (INIS)

    Ameli Zamani, Sh.

    2008-01-01

    Design basis earthquake ground motions for nuclear installations should be determined to assure the design purpose of reactor safety: that reactors should be built and operated to pose no undue risk to public health and safety from earthquake and other hazards. Regarding the influence of seismic hazard to a site, large numbers of earthquake ground motions can be predicted considering possible variability among the source, path, and site parameters. However, seismic safety design using all predicted ground motions is practically impossible. In the determination of design basis earthquake ground motions it is therefore important to represent the influences of the large numbers of earthquake ground motions derived from the seismic ground motion prediction methods for the surrounding seismic sources. Viewing the relations between current design basis earthquake ground motion determination and modem earthquake ground motion estimation, a development of risk-informed design basis earthquake ground motion methodology is discussed for insight into the on going modernization of the Examination Guide for Seismic Design on NPP

  8. Earthquake hazard in Northeast India – A seismic microzonation ...

    Indian Academy of Sciences (India)

    microzonation approach with typical case studies from .... the other hand, Guwahati city represents a case of well-formed basin with ... earthquake prone regions towards developing its ... tonic network and the observed seismicity has been.

  9. 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

  10. Mechanism of Post-seismic Floods after the Wenchuan Earthquake ...

    Indian Academy of Sciences (India)

    23

    multiple post-seismic floods in the upper reaches of Minjiang river causing huge loss ...... out, and conference communication should be strengthen with large and ... forecast accuracy and scientific and foresight of decision-making in the flood ...

  11. A spatiotemporal clustering model for the Third Uniform California Earthquake Rupture Forecast (UCERF3‐ETAS): Toward an operational earthquake forecast

    Science.gov (United States)

    Field, Edward; Milner, Kevin R.; Hardebeck, Jeanne L.; Page, Morgan T.; van der Elst, Nicholas; Jordan, Thomas H.; Michael, Andrew J.; Shaw, Bruce E.; Werner, Maximillan J.

    2017-01-01

    We, the ongoing Working Group on California Earthquake Probabilities, present a spatiotemporal clustering model for the Third Uniform California Earthquake Rupture Forecast (UCERF3), with the goal being to represent aftershocks, induced seismicity, and otherwise triggered events as a potential basis for operational earthquake forecasting (OEF). Specifically, we add an epidemic‐type aftershock sequence (ETAS) component to the previously published time‐independent and long‐term time‐dependent forecasts. This combined model, referred to as UCERF3‐ETAS, collectively represents a relaxation of segmentation assumptions, the inclusion of multifault ruptures, an elastic‐rebound model for fault‐based ruptures, and a state‐of‐the‐art spatiotemporal clustering component. It also represents an attempt to merge fault‐based forecasts with statistical seismology models, such that information on fault proximity, activity rate, and time since last event are considered in OEF. We describe several unanticipated challenges that were encountered, including a need for elastic rebound and characteristic magnitude–frequency distributions (MFDs) on faults, both of which are required to get realistic triggering behavior. UCERF3‐ETAS produces synthetic catalogs of M≥2.5 events, conditioned on any prior M≥2.5 events that are input to the model. We evaluate results with respect to both long‐term (1000 year) simulations as well as for 10‐year time periods following a variety of hypothetical scenario mainshocks. Although the results are very plausible, they are not always consistent with the simple notion that triggering probabilities should be greater if a mainshock is located near a fault. Important factors include whether the MFD near faults includes a significant characteristic earthquake component, as well as whether large triggered events can nucleate from within the rupture zone of the mainshock. Because UCERF3‐ETAS has many sources of uncertainty, as

  12. Data base and seismicity studies for Fagaras, Romania crustal earthquakes

    International Nuclear Information System (INIS)

    Moldovan, I.-A.; Enescu, B. D.; Pantea, A.; Constantin, A.; Bazacliu, O.; Malita, Z.; Moldoveanu, T.

    2002-01-01

    Besides the major impact of the Vrancea seismic region, one of the most important intermediate earthquake sources of Europe, the Romanian crustal earthquake sources, from Fagaras, Banat, Crisana, Bucovina or Dobrogea regions, have to be taken into consideration for seismicity studies or seismic hazard assessment. To determine the characteristics of the seismicity for Fagaras seismogenic region, a revised and updated catalogue of the Romanian earthquakes, recently compiled by Oncescu et al. (1999) is used. The catalogue contains 471 tectonic earthquakes and 338 induced earthquakes and is homogenous starting with 1471 for I>VIII and for I>VII starting with 1801. The catalogue is complete for magnitudes larger than 3 starting with 1982. In the studied zone only normal earthquakes occur, related to intracrustal fractures situated from 5 to 30 km depth. Most of them are of low energy, but once in a century a large destructive event occurs with epicentral intensity larger than VIII. The maximum expected magnitude is M GR = 6.5 and the epicenter distribution outlines significant clustering in the zones and on the lines mentioned in the tectonic studies. Taking into account the date of the last major earthquake (1916) and the return periods of severe damaging shocks of over 85 years it is to be expected very soon a large shock in the area. That's why a seismicity and hazard study for this zone is necessary. In the paper there are studied the b parameter variation (the mean value is 0.69), the activity value, the return periods, and seismicity maps and different histograms are plotted. At the same time there are excluded from the catalogue the explosions due to Campulung quarry. Because the catalogue contains the aftershocks for the 1916 earthquake for the seismicity studies we have excluded these shocks. (authors)

  13. Earthquake Forecasting Methodology Catalogue - A collection and comparison of the state-of-the-art in earthquake forecasting and prediction methodologies

    Science.gov (United States)

    Schaefer, Andreas; Daniell, James; Wenzel, Friedemann

    2015-04-01

    Earthquake forecasting and prediction has been one of the key struggles of modern geosciences for the last few decades. A large number of approaches for various time periods have been developed for different locations around the world. A categorization and review of more than 20 of new and old methods was undertaken to develop a state-of-the-art catalogue in forecasting algorithms and methodologies. The different methods have been categorised into time-independent, time-dependent and hybrid methods, from which the last group represents methods where additional data than just historical earthquake statistics have been used. It is necessary to categorize in such a way between pure statistical approaches where historical earthquake data represents the only direct data source and also between algorithms which incorporate further information e.g. spatial data of fault distributions or which incorporate physical models like static triggering to indicate future earthquakes. Furthermore, the location of application has been taken into account to identify methods which can be applied e.g. in active tectonic regions like California or in less active continental regions. In general, most of the methods cover well-known high-seismicity regions like Italy, Japan or California. Many more elements have been reviewed, including the application of established theories and methods e.g. for the determination of the completeness magnitude or whether the modified Omori law was used or not. Target temporal scales are identified as well as the publication history. All these different aspects have been reviewed and catalogued to provide an easy-to-use tool for the development of earthquake forecasting algorithms and to get an overview in the state-of-the-art.

  14. 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.

  15. 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.

  16. Integrated study of geophysical and biological anomalies before earthquakes (seismic and non-seismic), in Austria and Indonesia

    Science.gov (United States)

    Straka, Wolfgang; Assef, Rizkita; Faber, Robert; Ferasyi, Reza

    2015-04-01

    Earthquakes are commonly seen as unpredictable. Even when scientists believe an earthquake is likely, it is still hard to understand the indications observed, as well as their theoretical and practical implications. There is some controversy surrounding the concept of using animals as a precursor of earthquakes. Nonetheless, several institutes at University of Natural Resources and Life Sciences, and Vienna University of Technology, both Vienna, Austria, and Syiah Kuala University, Banda Aceh, as well as Terramath Indonesia, Buleleng, both Indonesia, cooperate in a long-term project, funded by Red Bull Media House, Salzburg, Austria, which aims at getting some decisive step forward from anecdotal to scientific evidence of those interdependencies, and show their possible use in forecasting seismic hazard on a short-term basis. Though no conclusive research has yet been published, an idea in this study is that even if animals do not respond to specific geophysical precursors and with enough notice to enable earthquake forecasting on that basis, they may at least enhance, in conjunction with other indications, the degree of certainty we can get of a prediction of an impending earthquake. In Indonesia, indeed, before the great earthquakes of 2004 and 2005, ominous geophysical as well as biological phenomena occurred (but were realized as precursors only in retrospect). Numerous comparable stories can be told from other times and regions. Nearly 2000 perceptible earthquakes (> M3.5) occur each year in Indonesia. Also, in 2007, the government has launched a program, focused on West Sumatra, for investigating earthquake precursors. Therefore, Indonesia is an excellent target area for a study concerning possible interconnections between geophysical and biological earthquake precursors. Geophysical and atmospheric measurements and behavioral observation of several animal species (elephant, domestic cattle, water buffalo, chicken, rat, catfish) are conducted in three areas

  17. International Aftershock Forecasting: Lessons from the Gorkha Earthquake

    Science.gov (United States)

    Michael, A. J.; Blanpied, M. L.; Brady, S. R.; van der Elst, N.; Hardebeck, J.; Mayberry, G. C.; Page, M. T.; Smoczyk, G. M.; Wein, A. M.

    2015-12-01

    Following the M7.8 Gorhka, Nepal, earthquake of April 25, 2015 the USGS issued a series of aftershock forecasts. The initial impetus for these forecasts was a request from the USAID Office of US Foreign Disaster Assistance to support their Disaster Assistance Response Team (DART) which coordinated US Government disaster response, including search and rescue, with the Government of Nepal. Because of the possible utility of the forecasts to people in the region and other response teams, the USGS released these forecasts publicly through the USGS Earthquake Program web site. The initial forecast used the Reasenberg and Jones (Science, 1989) model with generic parameters developed for active deep continental regions based on the Garcia et al. (BSSA, 2012) tectonic regionalization. These were then updated to reflect a lower productivity and higher decay rate based on the observed aftershocks, although relying on teleseismic observations, with a high magnitude-of-completeness, limited the amount of data. After the 12 May M7.3 aftershock, the forecasts used an Epidemic Type Aftershock Sequence model to better characterize the multiple sources of earthquake clustering. This model provided better estimates of aftershock uncertainty. These forecast messages were crafted based on lessons learned from the Christchurch earthquake along with input from the U.S. Embassy staff in Kathmandu. Challenges included how to balance simple messaging with forecasts over a variety of time periods (week, month, and year), whether to characterize probabilities with words such as those suggested by the IPCC (IPCC, 2010), how to word the messages in a way that would translate accurately into Nepali and not alarm the public, and how to present the probabilities of unlikely but possible large and potentially damaging aftershocks, such as the M7.3 event, which had an estimated probability of only 1-in-200 for the week in which it occurred.

  18. Forecasting characteristic earthquakes in a minimalist model

    DEFF Research Database (Denmark)

    Vázquez-Prada, M.; Pacheco, A.; González, Á.

    2003-01-01

    -dimensional numerical exploration of the loss function. This first strategy is then refined by considering a classification of the seismic cycles of the model according to the presence, or not, of some factors related to the seismicity observed in the cycle. These factors, statistically speaking, enlarge or shorten...

  19. 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

  20. Earthquake predictions using seismic velocity ratios

    Science.gov (United States)

    Sherburne, R. W.

    1979-01-01

    Since the beginning of modern seismology, seismologists have contemplated predicting earthquakes. The usefulness of earthquake predictions to the reduction of human and economic losses and the value of long-range earthquake prediction to planning is obvious. Not as clear are the long-range economic and social impacts of earthquake prediction to a speicifc area. The general consensus of opinion among scientists and government officials, however, is that the quest of earthquake prediction is a worthwhile goal and should be prusued with a sense of urgency. 

  1. Fractals and Forecasting in Earthquakes and Finance

    Science.gov (United States)

    Rundle, J. B.; Holliday, J. R.; Turcotte, D. L.

    2011-12-01

    It is now recognized that Benoit Mandelbrot's fractals play a critical role in describing a vast range of physical and social phenomena. Here we focus on two systems, earthquakes and finance. Since 1942, earthquakes have been characterized by the Gutenberg-Richter magnitude-frequency relation, which in more recent times is often written as a moment-frequency power law. A similar relation can be shown to hold for financial markets. Moreover, a recent New York Times article, titled "A Richter Scale for the Markets" [1] summarized the emerging viewpoint that stock market crashes can be described with similar ideas as large and great earthquakes. The idea that stock market crashes can be related in any way to earthquake phenomena has its roots in Mandelbrot's 1963 work on speculative prices in commodities markets such as cotton [2]. He pointed out that Gaussian statistics did not account for the excessive number of booms and busts that characterize such markets. Here we show that both earthquakes and financial crashes can both be described by a common Landau-Ginzburg-type free energy model, involving the presence of a classical limit of stability, or spinodal. These metastable systems are characterized by fractal statistics near the spinodal. For earthquakes, the independent ("order") parameter is the slip deficit along a fault, whereas for the financial markets, it is financial leverage in place. For financial markets, asset values play the role of a free energy. In both systems, a common set of techniques can be used to compute the probabilities of future earthquakes or crashes. In the case of financial models, the probabilities are closely related to implied volatility, an important component of Black-Scholes models for stock valuations. [2] B. Mandelbrot, The variation of certain speculative prices, J. Business, 36, 294 (1963)

  2. Seismicity and seismic hazard in Sabah, East Malaysia from earthquake and geodetic data

    Science.gov (United States)

    Gilligan, A.; Rawlinson, N.; Tongkul, F.; Stephenson, R.

    2017-12-01

    While the levels of seismicity are low in most of Malaysia, the state of Sabah in northern Borneo has moderate levels of seismicity. Notable earthquakes in the region include the 1976 M6.2 Lahad Datu earthquake and the 2015 M6 Ranau earthquake. The recent Ranau earthquake resulted in the deaths of 18 people on Mt Kinabalu, an estimated 100 million RM ( US$23 million) damage to buildings, roads, and infrastructure from shaking, and flooding, reduced water quality, and damage to farms from landslides. Over the last 40 years the population of Sabah has increased to over four times what it was in 1976, yet seismic hazard in Sabah remains poorly understood. Using seismic and geodetic data we hope to better quantify the hazards posed by earthquakes in Sabah, and thus help to minimize risk. In order to do this we need to know about the locations of earthquakes, types of earthquakes that occur, and faults that are generating them. We use data from 15 MetMalaysia seismic stations currently operating in Sabah to develop a region-specific velocity model from receiver functions and a pre-existing surface wave model. We use this new velocity model to (re)locate earthquakes that occurred in Sabah from 2005-2016, including a large number of aftershocks from the 2015 Ranau earthquake. We use a probabilistic nonlinear earthquake location program to locate the earthquakes and then refine their relative locations using a double difference method. The recorded waveforms are further used to obtain moment tensor solutions for these earthquakes. Earthquake locations and moment tensor solutions are then compared with the locations of faults throughout Sabah. Faults are identified from high-resolution IFSAR images and subsequent fieldwork, with a particular focus on the Lahad Datau and Ranau areas. Used together, these seismic and geodetic data can help us to develop a new seismic hazard model for Sabah, as well as aiding in the delivery of outreach activities regarding seismic hazard

  3. Earthquake forecasting studies using radon time series data in Taiwan

    Science.gov (United States)

    Walia, Vivek; Kumar, Arvind; Fu, Ching-Chou; Lin, Shih-Jung; Chou, Kuang-Wu; Wen, Kuo-Liang; Chen, Cheng-Hong

    2017-04-01

    For few decades, growing number of studies have shown usefulness of data in the field of seismogeochemistry interpreted as geochemical precursory signals for impending earthquakes and radon is idendified to be as one of the most reliable geochemical precursor. Radon is recognized as short-term precursor and is being monitored in many countries. This study is aimed at developing an effective earthquake forecasting system by inspecting long term radon time series data. The data is obtained from a network of radon monitoring stations eastblished along different faults of Taiwan. The continuous time series radon data for earthquake studies have been recorded and some significant variations associated with strong earthquakes have been observed. The data is also examined to evaluate earthquake precursory signals against environmental factors. An automated real-time database operating system has been developed recently to improve the data processing for earthquake precursory studies. In addition, the study is aimed at the appraisal and filtrations of these environmental parameters, in order to create a real-time database that helps our earthquake precursory study. In recent years, automatic operating real-time database has been developed using R, an open source programming language, to carry out statistical computation on the data. To integrate our data with our working procedure, we use the popular and famous open source web application solution, AMP (Apache, MySQL, and PHP), creating a website that could effectively show and help us manage the real-time database.

  4. Induced seismicity provides insight into why earthquake ruptures stop

    KAUST Repository

    Galis, Martin

    2017-12-21

    Injection-induced earthquakes pose a serious seismic hazard but also offer an opportunity to gain insight into earthquake physics. Currently used models relating the maximum magnitude of injection-induced earthquakes to injection parameters do not incorporate rupture physics. We develop theoretical estimates, validated by simulations, of the size of ruptures induced by localized pore-pressure perturbations and propagating on prestressed faults. Our model accounts for ruptures growing beyond the perturbed area and distinguishes self-arrested from runaway ruptures. We develop a theoretical scaling relation between the largest magnitude of self-arrested earthquakes and the injected volume and find it consistent with observed maximum magnitudes of injection-induced earthquakes over a broad range of injected volumes, suggesting that, although runaway ruptures are possible, most injection-induced events so far have been self-arrested ruptures.

  5. Seismic Margin of 500MWe PFBR Beyond Safe Shutdown Earthquake

    International Nuclear Information System (INIS)

    Sajish, S.D.; Chellapandi, P.; Chetal, S.C.

    2012-01-01

    Summary: • Seismic design aspects of safety related systems and components of PFBR is discussed with a focus on reactor assembly components. • PFBR is situated in a low seismic area with a peak ground acceleration value of 0.156 g. • The design basis ground motion parameters for the seismic design are evaluated by deterministic method and confirmed by probabilistic seismic hazard analysis. • Review of the seismic design of various safety related systems and components indicate that margin is available to meet any demand due to an earthquake beyond SSE. • Reactor assembly vessels are the most critical components w.r.t seismic loading. • Minimum safety margin is 1.41 for plastic deformation and 1.46 against buckling. • From the preliminary investigation we come to the conclusion that PFBR can withstand an earthquake up to 0.22 g without violating any safety limits. • Additional margin can be estimated by detailed fragility analysis and seismic margin assessment methods

  6. Hysteresis behavior of seismic isolators in earthquakes near a fault ...

    African Journals Online (AJOL)

    Seismic performance and appropriate design of structures located near the faults has always been a major concern of design engineers. Because during an earthquake; the effects of plasticity will make differences in characteristics of near field records. These pulsed movements at the beginning of records will increase the ...

  7. Building configuration and seismic design: The architecture of earthquake resistance

    Science.gov (United States)

    Arnold, C.; Reitherman, R.; Whitaker, D.

    1981-05-01

    The architecture of a building in relation to its ability to withstand earthquakes was determined. Aspects of round motion which are significant to building behavior are discussed. Results of a survey of configuration decisions that affect the performance of buildings with a focus on the architectural aspects of configuration design are provided. Configuration derivation, building type as it relates to seismic design, and seismic design, and seismic issues in the design process are examined. Case studies of the Veterans' Administration Hospital in Loma Linda, California, and the Imperial Hotel in Tokyo, Japan, are presented. The seismic design process is described paying special attention to the configuration issues. The need is stressed for guidelines, codes, and regulations to ensure design solutions that respect and balance the full range of architectural, engineering, and material influences on seismic hazards.

  8. Evidence for strong Holocene earthquake(s) in the Wabash Valley seismic zone

    International Nuclear Information System (INIS)

    Obermeier, S.

    1991-01-01

    Many small and slightly damaging earthquakes have taken place in the region of the lower Wabash River Valley of Indiana and Illinois during the 200 years of historic record. Seismologists have long suspected the Wabash Valley seismic zone to be capable of producing earthquakes much stronger than the largest of record (m b 5.8). The seismic zone contains the poorly defined Wabash Valley fault zone and also appears to contain other vaguely defined faults at depths from which the strongest earthquakes presently originate. Faults near the surface are generally covered with thick alluvium in lowlands and a veneer of loess in uplands, which make direct observations of faults difficult. Partly because of this difficulty, a search for paleoliquefaction features was begun in 1990. Conclusions of the study are as follows: (1) an earthquake much stronger than any historic earthquake struck the lower Wabash Valley between 1,500 and 7,500 years ago; (2) the epicentral region of the prehistoric strong earthquake was the Wabash Valley seismic zone; (3) apparent sites have been located where 1811-12 earthquake accelerations can be bracketed

  9. Initiation process of earthquakes and its implications for seismic hazard reduction strategy.

    Science.gov (United States)

    Kanamori, H

    1996-04-30

    For the average citizen and the public, "earthquake prediction" means "short-term prediction," a prediction of a specific earthquake on a relatively short time scale. Such prediction must specify the time, place, and magnitude of the earthquake in question with sufficiently high reliability. For this type of prediction, one must rely on some short-term precursors. Examinations of strain changes just before large earthquakes suggest that consistent detection of such precursory strain changes cannot be expected. Other precursory phenomena such as foreshocks and nonseismological anomalies do not occur consistently either. Thus, reliable short-term prediction would be very difficult. Although short-term predictions with large uncertainties could be useful for some areas if their social and economic environments can tolerate false alarms, such predictions would be impractical for most modern industrialized cities. A strategy for effective seismic hazard reduction is to take full advantage of the recent technical advancements in seismology, computers, and communication. In highly industrialized communities, rapid earthquake information is critically important for emergency services agencies, utilities, communications, financial companies, and media to make quick reports and damage estimates and to determine where emergency response is most needed. Long-term forecast, or prognosis, of earthquakes is important for development of realistic building codes, retrofitting existing structures, and land-use planning, but the distinction between short-term and long-term predictions needs to be clearly communicated to the public to avoid misunderstanding.

  10. LASSCI2009.2: layered earthquake rupture forecast model for central Italy, submitted to the CSEP project

    Directory of Open Access Journals (Sweden)

    Francesco Visini

    2010-11-01

    Full Text Available The Collaboratory for the Study of Earthquake Predictability (CSEP selected Italy as a testing region for probabilistic earthquake forecast models in October, 2008. The model we have submitted for the two medium-term forecast periods of 5 and 10 years (from 2009 is a time-dependent, geologically based earthquake rupture forecast that is defined for central Italy only (11-15˚ E; 41-45˚ N. The model took into account three separate layers of seismogenic sources: background seismicity; seismotectonic provinces; and individual faults that can produce major earthquakes (seismogenic boxes. For CSEP testing purposes, the background seismicity layer covered a range of magnitudes from 5.0 to 5.3 and the seismicity rates were obtained by truncated Gutenberg-Richter relationships for cells centered on the CSEP grid. Then the seismotectonic provinces layer returned the expected rates of medium-to-large earthquakes following a traditional Cornell-type approach. Finally, for the seismogenic boxes layer, the rates were based on the geometry and kinematics of the faults that different earthquake recurrence models have been assigned to, ranging from pure Gutenberg-Richter behavior to characteristic events, with the intermediate behavior named as the hybrid model. The results for different magnitude ranges highlight the contribution of each of the three layers to the total computation. The expected rates for M >6.0 on April 1, 2009 (thus computed before the L'Aquila, 2009, MW= 6.3 earthquake are of particular interest. They showed local maxima in the two seismogenic-box sources of Paganica and Sulmona, one of which was activated by the L'Aquila earthquake of April 6, 2009. Earthquake rates as of August 1, 2009, (now under test also showed a maximum close to the Sulmona source for MW ~6.5; significant seismicity rates (10-4 to 10-3 in 5 years for destructive events (magnitude up to 7.0 were located in other individual sources identified as being capable of such

  11. Vrancea earthquakes. Courses for specific actions to mitigate seismic risk

    International Nuclear Information System (INIS)

    Marmureanu, Gheorghe; Marmureanu, Alexandru

    2005-01-01

    Earthquakes in the Carpathian-Pannonian region are confined to the crust, except the Vrancea zone, where earthquakes with focal depth down to 200 Km occur. For example, the ruptured area migrated from 150 km to 180 km (November 10,1940, M w = 7.7) from 90 km to 110 km (March 4, 1977, M w 7.4), from 130 km to 150 km (August 30, 1986, M w = 7.1) and from 70 km to 90 km (May 30, 1990, M w = 6.9) depth. The depth interval between 110 km and 130 km remains not ruptured since 1802, October 26, when it was the strongest earthquake occurred in this part of Central Europe. The magnitude is assumed to be M w = 7.9 - 8.0 and this depth interval is a natural candidate for the next strong Vrancea event. While no country in the world is entirely safe, the lack of capacity to limit the impact of seismic hazards remains a major burden for all countries and while the world has witnessed an exponential increase in human and material losses due to natural disasters given by earthquakes, there is a need to reverse trends in seismic risk mitigation to future events. Main courses for specific actions to mitigate the seismic risk given by strong deep Vrancea earthquakes should be considered as key for development actions: - Early warning system for industrial facilities. Early warning is more than a technological instrument to detect, monitor and submit warnings. It should become part of a management information system for decision-making in the context of national institutional frameworks for disaster management and part of national and local strategies and programmers for risk mitigation; - Prediction program of Vrancea strong earthquakes of short and long term; - Hazard seismic map of Romania. The wrong assessment of the seismic hazard can lead to dramatic situations as those from Bucharest or Kobe. Before the 1977 Vrancea earthquake, the city of Bucharest was designed to intensity I = VII (MMI) and the real intensity was I = IX1/2-X (MMI); - Seismic microzonation of large populated

  12. Vrancea earthquakes. Specific actions to mitigate seismic risk

    International Nuclear Information System (INIS)

    Marmureanu, Gheorghe; Marmureanu, Alexandru

    2005-01-01

    Earthquakes have been known in Romania since Roman times, when Trajan's legionnaires began the colonization of the rich plains stretching from the Carpathian Mountains to the Danube River. Since readings from seismographic stations became available, after 1940, it has been established that the most frequent largest earthquakes arise from deep Vrancea sources at the bend of the Carpathians Earthquakes in the Carpathian-Pannonian region are confined to the crust, except for the Vrancea zone, where earthquakes with focal depth down to 200 km occur. For example, the ruptured area migrated in depth from 150 km to 180 km (November 10, 1940, M w =7.7), from 90 to 110 km (March 4, 1977, M w =7.4), from 130 to 150 km (August 30, 1986, M w =7.1), and from 70 to 90 km (May 30, 1990, M w =6.9). The depth interval between 110 km and 130 km has remained unruptured since 1802, October 26, when the strongest known earthquake occurred in this part of Central Europe. The magnitude is assumed to have been M w =7.9 - 8.0, and this depth interval is a natural candidate for the next strong Vrancea event. The maximum intensity for strong deep Vrancea earthquakes is quite distant from the actual epicenter and greater than the epicentral intensity. For the 1977 strong earthquake (M w =7.4), the estimated intensity at its Vrancea region epicenter was only VII (MMI scale), while some 170 km away, in the capital city of Bucharest, the estimated maximum intensity was IX1/2 -X (MMI). The intensely deforming Vrancea zone shows a quite enigmatic seismic pattern (peak ground accelerations/intensity one, characteristic response spectra with large periods of 1.5 seconds, no significant attenuations on Romanian territory, large amplifications away, etc.). While no country in the world is entirely safe, the lack of capacity to limit the impact of seismic hazards remains a major burden for all countries and while the world has witnessed an exponential increase in human and material losses due to

  13. Temporal properties of seismicity and largest earthquakes in SE Carpathians

    Directory of Open Access Journals (Sweden)

    S. Byrdina

    2006-01-01

    Full Text Available In order to estimate the hazard rate distribution of the largest seismic events in Vrancea, South-Eastern Carpathians, we study temporal properties of historical and instrumental catalogues of seismicity. First, on the basis of Generalized Extreme Value theory we estimate the average return period of the largest events. Then, following Bak et al. (2002 and Corral (2005a, we study scaling properties of recurrence times between earthquakes in appropriate spatial volumes. We come to the conclusion that the seismicity is temporally clustered, and that the distribution of recurrence times is significantly different from a Poisson process even for times largely exceeding corresponding periods of foreshock and aftershock activity. Modeling the recurrence times by a gamma distributed variable, we finally estimate hazard rates with respect to the time elapsed from the last large earthquake.

  14. The seismic cycles of large Romanian earthquake: The physical foundation, and the next large earthquake in Vrancea

    International Nuclear Information System (INIS)

    Purcaru, G.

    2002-01-01

    The occurrence patterns of large/great earthquakes at subduction zone interface and in-slab are complex in the space-time dynamics, and make even long-term forecasts very difficult. For some favourable cases where a predictive (empirical) law was found successful predictions were possible (eg. Aleutians, Kuriles, etc). For the large Romanian events (M > 6.7), occurring in the Vrancea seismic slab below 60 km, Purcaru (1974) first found the law of the occurrence time and magnitude: the law of 'quasicycles' and 'supercycles', for large and largest events (M > 7.25), respectively. The quantitative model of Purcaru with these seismic cycles has three time-bands (periods of large earthquakes)/century, discovered using the earthquake history (1100-1973) (however incomplete) of large Vrancea earthquakes for which M was initially estimated (Purcaru, 1974, 1979). Our long-term prediction model is essentially quasideterministic, it predicts uniquely the time and magnitude; since is not strict deterministic the forecasting is interval valued. It predicted the next large earthquake in 1980 in the 3rd time-band (1970-1990), and which occurred in 1977 (M7.1, M w 7.5). The prediction was successful, in long-term sense. We discuss the unpredicted events in 1986 and 1990. Since the laws are phenomenological, we give their physical foundation based on the large scale of rupture zone (RZ) and subscale of the rupture process (RP). First results show that: (1) the 1940 event (h=122 km) ruptured the lower part of the oceanic slab entirely along strike, and down dip, and similarly for 1977 but its upper part, (2) the RZ of 1977 and 1990 events overlap and the first asperity of 1977 event was rebroken in 1990. This shows the size of the events strongly depends on RZ, asperity size/strength and, thus on the failure stress level (FSL), but not on depth, (3) when FSL of high strength (HS) larger zones is critical largest events (eg. 1802, 1940) occur, thus explaining the supercyles (the 1940

  15. Seismic Regionalization of Michoacan, Mexico and Recurrence Periods for Earthquakes

    Science.gov (United States)

    Magaña García, N.; Figueroa-Soto, Á.; Garduño-Monroy, V. H.; Zúñiga, R.

    2017-12-01

    Michoacán is one of the states with the highest occurrence of earthquakes in Mexico and it is a limit of convergence triggered by the subduction of Cocos plate over the North American plate, located in the zone of the Pacific Ocean of our country, in addition to the existence of active faults inside of the state like the Morelia-Acambay Fault System (MAFS).It is important to make a combination of seismic, paleosismological and geological studies to have good planning and development of urban complexes to mitigate disasters if destructive earthquakes appear. With statistical seismology it is possible to characterize the degree of seismic activity as well as to estimate the recurrence periods for earthquakes. For this work, seismicity catalog of Michoacán was compiled and homogenized in time and magnitude. This information was obtained from world and national agencies (SSN, CMT, etc), some data published by Mendoza and Martínez-López (2016) and starting from the seismic catalog homogenized by F. R. Zúñiga (Personal communication). From the analysis of the different focal mechanisms reported in the literature and geological studies, the seismic regionalization of the state of Michoacán complemented the one presented by Vázquez-Rosas (2012) and the recurrence periods for earthquakes within the four different seismotectonic regions. In addition, stable periods were determined for the b value of the Gutenberg-Richter (1944) using the Maximum Curvature and EMR (Entire Magnitude Range Method, 2005) techniques, which allowed us to determine recurrence periods: years for earthquakes upper to 7.5 for the subduction zone (A zone) with EMR technique and years with MAXC technique for the same years for earthquakes upper to 5 for B1 zone with EMR technique and years with MAXC technique; years for earthquakes upper to 7.0 for B2 zone with EMR technique and years with MAXC technique; and the last one, the Morelia-Acambay Fault Sistem zone (C zone) years for earthquakes

  16. Deeper penetration of large earthquakes on seismically quiescent faults.

    Science.gov (United States)

    Jiang, Junle; Lapusta, Nadia

    2016-06-10

    Why many major strike-slip faults known to have had large earthquakes are silent in the interseismic period is a long-standing enigma. One would expect small earthquakes to occur at least at the bottom of the seismogenic zone, where deeper aseismic deformation concentrates loading. We suggest that the absence of such concentrated microseismicity indicates deep rupture past the seismogenic zone in previous large earthquakes. We support this conclusion with numerical simulations of fault behavior and observations of recent major events. Our modeling implies that the 1857 Fort Tejon earthquake on the San Andreas Fault in Southern California penetrated below the seismogenic zone by at least 3 to 5 kilometers. Our findings suggest that such deeper ruptures may occur on other major fault segments, potentially increasing the associated seismic hazard. Copyright © 2016, American Association for the Advancement of Science.

  17. Seismic hazard maps for earthquake-resistant construction designs

    International Nuclear Information System (INIS)

    Ohkawa, Izuru

    2004-01-01

    Based on the idea that seismic phenomena in Japan varying in different localities are to be reflected in designing specific nuclear facilities in specific site, the present research program started to make seismic hazard maps representing geographical distribution of seismic load factors. First, recent research data on historical earthquakes and materials on active faults in Japan have been documented. Differences in character due to different localities are expressed by dynamic load in consideration of specific building properties. Next, hazard evaluation corresponding to seismic-resistance factor is given as response index (spectrum) of an adequately selected building, for example a nuclear power station, with the help of investigation results of statistical analysis. (S. Ohno)

  18. Earthquake clustering in modern seismicity and its relationship with strong historical earthquakes around Beijing, China

    Science.gov (United States)

    Wang, Jian; Main, Ian G.; Musson, Roger M. W.

    2017-11-01

    Beijing, China's capital city, is located in a typical intraplate seismic belt, with relatively high-quality instrumental catalogue data available since 1970. The Chinese historical earthquake catalogue contains six strong historical earthquakes of Ms ≥ 6 around Beijing, the earliest in 294 AD. This poses a significant potential hazard to one of the most densely populated and economically active parts of China. In some intraplate areas, persistent clusters of events associated with historical events can occur over centuries, for example, the ongoing sequence in the New Madrid zone of the eastern US. Here we will examine the evidence for such persistent clusters around Beijing. We introduce a metric known as the `seismic density index' that quantifies the degree of clustering of seismic energy release. For a given map location, this multi-dimensional index depends on the number of events, their magnitudes, and the distances to the locations of the surrounding population of earthquakes. We apply the index to modern instrumental catalogue data between 1970 and 2014, and identify six clear candidate zones. We then compare these locations to earthquake epicentre and seismic intensity data for the six largest historical earthquakes. Each candidate zone contains one of the six historical events, and the location of peak intensity is within 5 km or so of the reported epicentre in five of these cases. In one case—the great Ms 8 earthquake of 1679—the peak is closer to the area of strongest shaking (Intensity XI or more) than the reported epicentre. The present-day event rates are similar to those predicted by the modified Omori law but there is no evidence of ongoing decay in event rates. Accordingly, the index is more likely to be picking out the location of persistent weaknesses in the lithosphere. Our results imply zones of high seismic density index could be used in principle to indicate the location of unrecorded historical of palaeoseismic events, in China and

  19. Retrospective Evaluation of the Five-Year and Ten-Year CSEP-Italy Earthquake Forecasts

    OpenAIRE

    Werner, M. J.; Zechar, J. D.; Marzocchi, W.; Wiemer, S.

    2010-01-01

    On 1 August 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP) launched a prospective and comparative earthquake predictability experiment in Italy. The goal of the CSEP-Italy experiment is to test earthquake occurrence hypotheses that have been formalized as probabilistic earthquake forecasts over temporal scales that range from days to years. In the first round of forecast submissions, members of the CSEP-Italy Working Group presented eighteen five-year and ten...

  20. Earthquake prediction in Japan and natural time analysis of seismicity

    Science.gov (United States)

    Uyeda, S.; Varotsos, P.

    2011-12-01

    M9 super-giant earthquake with huge tsunami devastated East Japan on 11 March, causing more than 20,000 casualties and serious damage of Fukushima nuclear plant. This earthquake was predicted neither short-term nor long-term. Seismologists were shocked because it was not even considered possible to happen at the East Japan subduction zone. However, it was not the only un-predicted earthquake. In fact, throughout several decades of the National Earthquake Prediction Project, not even a single earthquake was predicted. In reality, practically no effective research has been conducted for the most important short-term prediction. This happened because the Japanese National Project was devoted for construction of elaborate seismic networks, which was not the best way for short-term prediction. After the Kobe disaster, in order to parry the mounting criticism on their no success history, they defiantly changed their policy to "stop aiming at short-term prediction because it is impossible and concentrate resources on fundamental research", that meant to obtain "more funding for no prediction research". The public were and are not informed about this change. Obviously earthquake prediction would be possible only when reliable precursory phenomena are caught and we have insisted this would be done most likely through non-seismic means such as geochemical/hydrological and electromagnetic monitoring. Admittedly, the lack of convincing precursors for the M9 super-giant earthquake has adverse effect for us, although its epicenter was far out off shore of the range of operating monitoring systems. In this presentation, we show a new possibility of finding remarkable precursory signals, ironically, from ordinary seismological catalogs. In the frame of the new time domain termed natural time, an order parameter of seismicity, κ1, has been introduced. This is the variance of natural time kai weighted by normalised energy release at χ. In the case that Seismic Electric Signals

  1. National Earthquake Information Center Seismic Event Detections on Multiple Scales

    Science.gov (United States)

    Patton, J.; Yeck, W. L.; Benz, H.; Earle, P. S.; Soto-Cordero, L.; Johnson, C. E.

    2017-12-01

    The U.S. Geological Survey National Earthquake Information Center (NEIC) monitors seismicity on local, regional, and global scales using automatic picks from more than 2,000 near-real time seismic stations. This presents unique challenges in automated event detection due to the high variability in data quality, network geometries and density, and distance-dependent variability in observed seismic signals. To lower the overall detection threshold while minimizing false detection rates, NEIC has begun to test the incorporation of new detection and picking algorithms, including multiband (Lomax et al., 2012) and kurtosis (Baillard et al., 2014) pickers, and a new bayesian associator (Glass 3.0). The Glass 3.0 associator allows for simultaneous processing of variably scaled detection grids, each with a unique set of nucleation criteria (e.g., nucleation threshold, minimum associated picks, nucleation phases) to meet specific monitoring goals. We test the efficacy of these new tools on event detection in networks of various scales and geometries, compare our results with previous catalogs, and discuss lessons learned. For example, we find that on local and regional scales, rapid nucleation of small events may require event nucleation with both P and higher-amplitude secondary phases (e.g., S or Lg). We provide examples of the implementation of a scale-independent associator for an induced seismicity sequence (local-scale), a large aftershock sequence (regional-scale), and for monitoring global seismicity. Baillard, C., Crawford, W. C., Ballu, V., Hibert, C., & Mangeney, A. (2014). An automatic kurtosis-based P-and S-phase picker designed for local seismic networks. Bulletin of the Seismological Society of America, 104(1), 394-409. Lomax, A., Satriano, C., & Vassallo, M. (2012). Automatic picker developments and optimization: FilterPicker - a robust, broadband picker for real-time seismic monitoring and earthquake early-warning, Seism. Res. Lett. , 83, 531-540, doi: 10

  2. Variations of Background Seismic Noise Before Strong Earthquakes, Kamchatka.

    Science.gov (United States)

    Kasimova, V.; Kopylova, G.; Lyubushin, A.

    2017-12-01

    The network of broadband seismic stations of Geophysical Service (Russian Academy of Science) works on the territory of Kamchatka peninsula in the Far East of Russia. We used continuous records on Z-channels at 21 stations for creation of background seismic noise time series in 2011-2017. Average daily parameters of multi-fractal spectra of singularity have been calculated at each station using 1-minute records. Maps and graphs of their spatial distribution and temporal changes were constructed at time scales from days to several years. The analysis of the coherent behavior of the time series of the statistics was considered. The technique included the splitting of seismic network into groups of stations, taking into account the coastal effect, the network configuration and the main tectonic elements of Kamchatka. Then the time series of median values of noise parameters from each group of stations were made and the frequency-time diagrams of the evolution of the spectral measure of the coherent behavior of four time series were analyzed. The time intervals and frequency bands of the maximum values showing the increase of coherence in the changes of all statistics were evaluated. The strong earthquakes with magnitudes M=6.9-8.3 occurred near the Kamchatka peninsula during the observations. The synchronous variations of the background noise parameters and increase in the coherent behavior of the median values of statistical parameters was shown before two earthquakes 2013 (February 28, Mw=6.9; May 24, Mw=8.3) within 3-9 months and before earthquake of January 30, 2016, Mw=7.2 within 3-6 months. The maximum effect of increased coherence in the range of periods 4-5.5 days corresponds to the time of preparation of two strong earthquakes in 2013 and their aftershock processes. Peculiarities in changes of statistical parameters at stages of preparation of strong earthquakes indicate the attenuation in high-amplitude outliers and the loss of multi-fractal properties in

  3. The Great Maule earthquake: seismicity prior to and after the main shock from amphibious seismic networks

    Science.gov (United States)

    Lieser, K.; Arroyo, I. G.; Grevemeyer, I.; Flueh, E. R.; Lange, D.; Tilmann, F. J.

    2013-12-01

    The Chilean subduction zone is among the seismically most active plate boundaries in the world and its coastal ranges suffer from a magnitude 8 or larger megathrust earthquake every 10-20 years. The Constitución-Concepción or Maule segment in central Chile between ~35.5°S and 37°S was considered to be a mature seismic gap, rupturing last in 1835 and being seismically quiet without any magnitude 4.5 or larger earthquakes reported in global catalogues. It is located to the north of the nucleation area of the 1960 magnitude 9.5 Valdivia earthquake and to the south of the 1928 magnitude 8 Talca earthquake. On 27 February 2010 this segment ruptured in a Mw=8.8 earthquake, nucleating near 36°S and affecting a 500-600 km long segment of the margin between 34°S and 38.5°S. Aftershocks occurred along a roughly 600 km long portion of the central Chilean margin, most of them offshore. Therefore, a network of 30 ocean-bottom-seismometers was deployed in the northern portion of the rupture area for a three month period, recording local offshore aftershocks between 20 September 2010 and 25 December 2010. In addition, data of a network consisting of 33 landstations of the GeoForschungsZentrum Potsdam were included into the network, providing an ideal coverage of both the rupture plane and areas affected by post-seismic slip as deduced from geodetic data. Aftershock locations are based on automatically detected P wave onsets and a 2.5D velocity model of the combined on- and offshore network. Aftershock seismicity analysis in the northern part of the survey area reveals a well resolved seismically active splay fault in the accretionary prism of the Chilean forearc. Our findings imply that in the northernmost part of the rupture zone, co-seismic slip most likely propagated along the splay fault and not the subduction thrust fault. In addition, the updip limit of aftershocks along the plate interface can be verified to about 40 km landwards from the deformation front. Prior to

  4. The Strain Energy, Seismic Moment and Magnitudes of Large Earthquakes

    Science.gov (United States)

    Purcaru, G.

    2004-12-01

    The strain energy Est, as potential energy, released by an earthquake and the seismic moment Mo are two fundamental physical earthquake parameters. The earthquake rupture process ``represents'' the release of the accumulated Est. The moment Mo, first obtained in 1966 by Aki, revolutioned the quantification of earthquake size and led to the elimination of the limitations of the conventional magnitudes (originally ML, Richter, 1930) mb, Ms, m, MGR. Both Mo and Est, not in a 1-to-1 correspondence, are uniform measures of the size, although Est is presently less accurate than Mo. Est is partitioned in seismic- (Es), fracture- (Eg) and frictional-energy Ef, and Ef is lost as frictional heat energy. The available Est = Es + Eg (Aki and Richards (1980), Kostrov and Das, (1988) for fundamentals on Mo and Est). Related to Mo, Est and Es, several modern magnitudes were defined under various assumptions: the moment magnitude Mw (Kanamori, 1977), strain energy magnitude ME (Purcaru and Berckhemer, 1978), tsunami magnitude Mt (Abe, 1979), mantle magnitude Mm (Okal and Talandier, 1987), seismic energy magnitude Me (Choy and Boatright, 1995, Yanovskaya et al, 1996), body-wave magnitude Mpw (Tsuboi et al, 1998). The available Est = (1/2μ )Δ σ Mo, Δ σ ~=~average stress drop, and ME is % \\[M_E = 2/3(\\log M_o + \\log(\\Delta\\sigma/\\mu)-12.1) ,\\] % and log Est = 11.8 + 1.5 ME. The estimation of Est was modified to include Mo, Δ and μ of predominant high slip zones (asperities) to account for multiple events (Purcaru, 1997): % \\[E_{st} = \\frac{1}{2} \\sum_i {\\frac{1}{\\mu_i} M_{o,i} \\Delta\\sigma_i} , \\sum_i M_{o,i} = M_o \\] % We derived the energy balance of Est, Es and Eg as: % \\[ E_{st}/M_o = (1+e(g,s)) E_s/M_o , e(g,s) = E_g/E_s \\] % We analyzed a set of about 90 large earthquakes and found that, depending on the goal these magnitudes quantify differently the rupture process, thus providing complementary means of earthquake characterization. Results for some

  5. Spatial Distribution of the Coefficient of Variation and Bayesian Forecast for the Paleo-Earthquakes in Japan

    Science.gov (United States)

    Nomura, Shunichi; Ogata, Yosihiko

    2016-04-01

    We propose a Bayesian method of probability forecasting for recurrent earthquakes of inland active faults in Japan. Renewal processes with the Brownian Passage Time (BPT) distribution are applied for over a half of active faults in Japan by the Headquarters for Earthquake Research Promotion (HERP) of Japan. Long-term forecast with the BPT distribution needs two parameters; the mean and coefficient of variation (COV) for recurrence intervals. The HERP applies a common COV parameter for all of these faults because most of them have very few specified paleoseismic events, which is not enough to estimate reliable COV values for respective faults. However, different COV estimates are proposed for the same paleoseismic catalog by some related works. It can make critical difference in forecast to apply different COV estimates and so COV should be carefully selected for individual faults. Recurrence intervals on a fault are, on the average, determined by the long-term slip rate caused by the tectonic motion but fluctuated by nearby seismicities which influence surrounding stress field. The COVs of recurrence intervals depend on such stress perturbation and so have spatial trends due to the heterogeneity of tectonic motion and seismicity. Thus we introduce a spatial structure on its COV parameter by Bayesian modeling with a Gaussian process prior. The COVs on active faults are correlated and take similar values for closely located faults. It is found that the spatial trends in the estimated COV values coincide with the density of active faults in Japan. We also show Bayesian forecasts by the proposed model using Markov chain Monte Carlo method. Our forecasts are different from HERP's forecast especially on the active faults where HERP's forecasts are very high or low.

  6. Short-term volcano-tectonic earthquake forecasts based on a moving mean recurrence time algorithm: the El Hierro seismo-volcanic crisis experience

    Science.gov (United States)

    García, Alicia; De la Cruz-Reyna, Servando; Marrero, José M.; Ortiz, Ramón

    2016-05-01

    Under certain conditions, volcano-tectonic (VT) earthquakes may pose significant hazards to people living in or near active volcanic regions, especially on volcanic islands; however, hazard arising from VT activity caused by localized volcanic sources is rarely addressed in the literature. The evolution of VT earthquakes resulting from a magmatic intrusion shows some orderly behaviour that may allow the occurrence and magnitude of major events to be forecast. Thus governmental decision makers can be supplied with warnings of the increased probability of larger-magnitude earthquakes on the short-term timescale. We present here a methodology for forecasting the occurrence of large-magnitude VT events during volcanic crises; it is based on a mean recurrence time (MRT) algorithm that translates the Gutenberg-Richter distribution parameter fluctuations into time windows of increased probability of a major VT earthquake. The MRT forecasting algorithm was developed after observing a repetitive pattern in the seismic swarm episodes occurring between July and November 2011 at El Hierro (Canary Islands). From then on, this methodology has been applied to the consecutive seismic crises registered at El Hierro, achieving a high success rate in the real-time forecasting, within 10-day time windows, of volcano-tectonic earthquakes.

  7. Physics-based and statistical earthquake forecasting in a continental rift zone: the case study of Corinth Gulf (Greece)

    Science.gov (United States)

    Segou, Margarita

    2016-01-01

    I perform a retrospective forecast experiment in the most rapid extensive continental rift worldwide, the western Corinth Gulf (wCG, Greece), aiming to predict shallow seismicity (depth statistics, four physics-based (CRS) models, combining static stress change estimations and the rate-and-state laboratory law and one hybrid model. For the latter models, I incorporate the stress changes imparted from 31 earthquakes with magnitude M ≥ 4.5 at the extended area of wCG. Special attention is given on the 3-D representation of active faults, acting as potential receiver planes for the estimation of static stress changes. I use reference seismicity between 1990 and 1995, corresponding to the learning phase of physics-based models, and I evaluate the forecasts for six months following the 1995 M = 6.4 Aigio earthquake using log-likelihood performance metrics. For the ETAS realizations, I use seismic events with magnitude M ≥ 2.5 within daily update intervals to enhance their predictive power. For assessing the role of background seismicity, I implement a stochastic reconstruction (aka declustering) aiming to answer whether M > 4.5 earthquakes correspond to spontaneous events and identify, if possible, different triggering characteristics between aftershock sequences and swarm-type seismicity periods. I find that: (1) ETAS models outperform CRS models in most time intervals achieving very low rejection ratio RN = 6 per cent, when I test their efficiency to forecast the total number of events inside the study area, (2) the best rejection ratio for CRS models reaches RN = 17 per cent, when I use varying target depths and receiver plane geometry, (3) 75 per cent of the 1995 Aigio aftershocks that occurred within the first month can be explained by static stress changes, (4) highly variable performance on behalf of both statistical and physical models is suggested by large confidence intervals of information gain per earthquake and (5) generic ETAS models can adequately

  8. 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

  9. Natural Time, Nowcasting and the Physics of Earthquakes: Estimation of Seismic Risk to Global Megacities

    Science.gov (United States)

    Rundle, John B.; Luginbuhl, Molly; Giguere, Alexis; Turcotte, Donald L.

    2018-02-01

    Natural Time ("NT") refers to the concept of using small earthquake counts, for example of M > 3 events, to mark the intervals between large earthquakes, for example M > 6 events. The term was first used by Varotsos et al. (2005) and later by Holliday et al. (2006) in their studies of earthquakes. In this paper, we discuss ideas and applications arising from the use of NT to understand earthquake dynamics, in particular by use of the idea of nowcasting. Nowcasting differs from forecasting, in that the goal of nowcasting is to estimate the current state of the system, rather than the probability of a future event. Rather than focus on an individual earthquake faults, we focus on a defined local geographic region surrounding a particular location. This local region is considered to be embedded in a larger regional setting from which we accumulate the relevant statistics. We apply the nowcasting idea to the practical development of methods to estimate the current state of risk for dozens of the world's seismically exposed megacities, defined as cities having populations of over 1 million persons. We compute a ranking of these cities based on their current nowcast value, and discuss the advantages and limitations of this approach. We note explicitly that the nowcast method is not a model, in that there are no free parameters to be fit to data. Rather, the method is simply a presentation of statistical data, which the user can interpret. Among other results, we find, for example, that the current nowcast ranking of the Los Angeles region is comparable to its ranking just prior to the January 17, 1994 Northridge earthquake.

  10. Seismic demand evaluation based on actual earthquake records

    International Nuclear Information System (INIS)

    Jhaveri, D.P.; Czarnecki, R.M.; Kassawara, R.P.; Singh, A.

    1990-01-01

    Seismic input in the form of floor response spectra (FRS) are needed in seismic design and evaluation of equipment in nuclear power plants (NPPs). These are typically determined by analytical procedures using mathematical models of NPP structures and are known to be very conservative. Recorded earthquake data, in the form of acceleration response spectra computed from the recorded acceleration time histories, have been collected from NPP structures located in seismically active areas. Statistics of the ratios, or amplification factors, between the FRS at typical floors and the acceleration response spectra at the basemat or in the freefield, are obtained for typical NPP structures. These amplification factors are typically in terms of the peak spectral and zero period values, as well as a function of frequency. The average + 1σ values of these ratios, for those cases where enough data are available, are proposed to be used as limits to analytically calculated FRS, or for construction of simplified FRS for determining seismic input or demand in equipment qualification. (orig.)

  11. Seismic ground motion modelling and damage earthquake scenarios: A bridge between seismologists and seismic engineers

    International Nuclear Information System (INIS)

    Panza, G.F.; Romanelli, F.; Vaccari. F.; . E-mails: Luis.Decanini@uniroma1.it; Fabrizio.Mollaioli@uniroma1.it)

    2002-07-01

    The input for the seismic risk analysis can be expressed with a description of 'roundshaking scenarios', or with probabilistic maps of perhaps relevant parameters. The probabilistic approach, unavoidably based upon rough assumptions and models (e.g. recurrence and attenuation laws), can be misleading, as it cannot take into account, with satisfactory accuracy, some of the most important aspects like rupture process, directivity and site effects. This is evidenced by the comparison of recent recordings with the values predicted by the probabilistic methods. We prefer a scenario-based, deterministic approach in view of the limited seismological data, of the local irregularity of the occurrence of strong earthquakes, and of the multiscale seismicity model, that is capable to reconcile two apparently conflicting ideas: the Characteristic Earthquake concept and the Self Organized Criticality paradigm. Where the numerical modeling is successfully compared with records, the synthetic seismograms permit the microzoning, based upon a set of possible scenario earthquakes. Where no recordings are available the synthetic signals can be used to estimate the ground motion without having to wait for a strong earthquake to occur (pre-disaster microzonation). In both cases the use of modeling is necessary since the so-called local site effects can be strongly dependent upon the properties of the seismic source and can be properly defined only by means of envelopes. The joint use of reliable synthetic signals and observations permits the computation of advanced hazard indicators (e.g. damaging potential) that take into account local soil properties. The envelope of synthetic elastic energy spectra reproduces the distribution of the energy demand in the most relevant frequency range for seismic engineering. The synthetic accelerograms can be fruitfully used for design and strengthening of structures, also when innovative techniques, like seismic isolation, are employed. For these

  12. Monitoring Seismic Velocity Change to Explore the Earthquake Seismogenic Structures

    Science.gov (United States)

    Liao, C. F.; Wen, S.; Chen, C.

    2017-12-01

    Vp/Vs ratio) structures in high seismic potential zones is an important task which can lead to reduce seismic hazard for a future large earthquake.

  13. The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard

    Science.gov (United States)

    Malagnini, Luca; Herrmann, Robert B.; Munafò, Irene; Buttinelli, Mauro; Anselmi, Mario; Akinci, Aybige; Boschi, E.

    2012-10-01

    Inadequate seismic design codes can be dangerous, particularly when they underestimate the true hazard. In this study we use data from a sequence of moderate-sized earthquakes in northeast Italy to validate and test a regional wave propagation model which, in turn, is used to understand some weaknesses of the current design spectra. Our velocity model, while regionalized and somewhat ad hoc, is consistent with geophysical observations and the local geology. In the 0.02-0.1 Hz band, this model is validated by using it to calculate moment tensor solutions of 20 earthquakes (5.6 ≥ MW ≥ 3.2) in the 2012 Ferrara, Italy, seismic sequence. The seismic spectra observed for the relatively small main shock significantly exceeded the design spectra to be used in the area for critical structures. Observations and synthetics reveal that the ground motions are dominated by long-duration surface waves, which, apparently, the design codes do not adequately anticipate. In light of our results, the present seismic hazard assessment in the entire Pianura Padana, including the city of Milan, needs to be re-evaluated.

  14. Earthquake and nuclear explosion location using the global seismic network

    International Nuclear Information System (INIS)

    Lopez, L.M.

    1983-01-01

    The relocation of nuclear explosions, aftershock sequence and regional seismicity is addressed by using joint hypocenter determination, Lomnitz' distance domain location, and origin time and earthquake depth determination with local observations. Distance domain and joint hypocenter location are used for a stepwise relocation of nuclear explosions in the USSR. The resulting origin times are 2.5 seconds earlier than those obtained by ISC. Local travel times from the relocated explosions are compared to Jeffreys-Bullen tables. P times are found to be faster at 9-30 0 distances, the largest deviation being around 10 seconds at 13-18 0 . At these distances S travel times also are faster by approximately 20 seconds. The 1977 Sumba earthquake sequence is relocated by iterative joint hypocenter determination of events with most station reports. Simultaneously determined station corrections are utilized for the relocation of smaller aftershocks. The relocated hypocenters indicate that the aftershocks were initially concentrated along the deep trench. Origin times and depths are recalculated for intermediate depth and deep earthquakes using local observations in and around the Japanese Islands. It is found that origin time and depth differ systematically from ISC values for intermediate depth events. Origin times obtained for events below the crust down to 100 km depth are earlier, whereas no general bias seem to exist for origin times of events in the 100-400 km depth range. The recalculated depths for earthquakes shallower than 100 km are shallower than ISC depths. The depth estimates for earthquakes deeper than 100 km were increased by the recalculations

  15. Earthquake and nuclear explosion location using the global seismic network

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, L.M.

    1983-01-01

    The relocation of nuclear explosions, aftershock sequence and regional seismicity is addressed by using joint hypocenter determination, Lomnitz' distance domain location, and origin time and earthquake depth determination with local observations. Distance domain and joint hypocenter location are used for a stepwise relocation of nuclear explosions in the USSR. The resulting origin times are 2.5 seconds earlier than those obtained by ISC. Local travel times from the relocated explosions are compared to Jeffreys-Bullen tables. P times are found to be faster at 9-30/sup 0/ distances, the largest deviation being around 10 seconds at 13-18/sup 0/. At these distances S travel times also are faster by approximately 20 seconds. The 1977 Sumba earthquake sequence is relocated by iterative joint hypocenter determination of events with most station reports. Simultaneously determined station corrections are utilized for the relocation of smaller aftershocks. The relocated hypocenters indicate that the aftershocks were initially concentrated along the deep trench. Origin times and depths are recalculated for intermediate depth and deep earthquakes using local observations in and around the Japanese Islands. It is found that origin time and depth differ systematically from ISC values for intermediate depth events. Origin times obtained for events below the crust down to 100 km depth are earlier, whereas no general bias seem to exist for origin times of events in the 100-400 km depth range. The recalculated depths for earthquakes shallower than 100 km are shallower than ISC depths. The depth estimates for earthquakes deeper than 100 km were increased by the recalculations.

  16. A model of characteristic earthquakes and its implications for regional seismicity

    DEFF Research Database (Denmark)

    López-Ruiz, R.; Vázquez-Prada, M.; Pacheco, A.F.

    2004-01-01

    Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size-frequency relationship, the Gutenberg-Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from...... active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez-Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show...... that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non-characteristic events triggered in the faults...

  17. Ergodicity and Phase Transitions and Their Implications for Earthquake Forecasting.

    Science.gov (United States)

    Klein, W.

    2017-12-01

    Forecasting earthquakes or even predicting the statistical distribution of events on a given fault is extremely difficult. One reason for this difficulty is the large number of fault characteristics that can affect the distribution and timing of events. The range of stress transfer, the level of noise, and the nature of the friction force all influence the type of the events and the values of these parameters can vary from fault to fault and also vary with time. In addition, the geometrical structure of the faults and the correlation of events on different faults plays an important role in determining the event size and their distribution. Another reason for the difficulty is that the important fault characteristics are not easily measured. The noise level, fault structure, stress transfer range, and the nature of the friction force are extremely difficult, if not impossible to ascertain. Given this lack of information, one of the most useful approaches to understanding the effect of fault characteristics and the way they interact is to develop and investigate models of faults and fault systems.In this talk I will present results obtained from a series of models of varying abstraction and compare them with data from actual faults. We are able to provide a physical basis for several observed phenomena such as the earthquake cycle, thefact that some faults display Gutenburg-Richter scaling and others do not, and that some faults exhibit quasi-periodic characteristic events and others do not. I will also discuss some surprising results such as the fact that some faults are in thermodynamic equilibrium depending on the stress transfer range and the noise level. An example of an important conclusion that can be drawn from this work is that the statistical distribution of earthquake events can vary from fault to fault and that an indication of an impending large event such as accelerating moment release may be relevant on some faults but not on others.

  18. Forecasting probabilistic seismic shaking for greater Tokyo from 400 years of intensity observations (Invited)

    Science.gov (United States)

    Bozkurt, S.; Stein, R. S.; Toda, S.

    2009-12-01

    The long recorded history of earthquakes in Japan affords an opportunity to forecast seismic shaking exclusively from past shaking. We calculate the time-averaged (Poisson) probability of severe shaking by using more than 10,000 intensity observations recorded since AD 1600 in a 350-km-wide box centered on Tokyo. Unlike other hazard assessment methods, source and site effects are included without modeling, and we do not need to know the size or location of any earthquake or the location and slip rate of any fault. The two key assumptions are that the slope of the observed frequency-intensity relation at every site is the same; and that the 400-year record is long enough to encompass the full range of seismic behavior. Tests we conduct here suggest that both assumptions are sound. The resulting 30-year probability of IJMA≥6 shaking (~PGA≥0.9 g or MMI≥IX) is 30-40% in Tokyo, Kawasaki, and Yokohama, and 10-15% in Chiba and Tsukuba. This result means that there is a 30% chance that 4 million people would be subjected to IJMA≥6 shaking during an average 30-year period. We also produce exceedance maps of peak ground acceleration for building code regulations, and calculate short-term hazard associated with a hypothetical catastrophe bond. Our results resemble an independent assessment developed from conventional seismic hazard analysis for greater Tokyo. Over 10000 intensity observations stored and analyzed using geostatistical tools of GIS. Distribution of historical data is shown on this figure.

  19. Volcano-tectonic earthquakes: A new tool for estimating intrusive volumes and forecasting eruptions

    Science.gov (United States)

    White, Randall; McCausland, Wendy

    2016-01-01

    We present data on 136 high-frequency earthquakes and swarms, termed volcano-tectonic (VT) seismicity, which preceded 111 eruptions at 83 volcanoes, plus data on VT swarms that preceded intrusions at 21 other volcanoes. We find that VT seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more, and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from VEI 0 to ultraplinian VEI 6 at such previously long-dormant volcanoes. Because large eruptions occur most commonly during resumption of activity at long-dormant volcanoes, VT seismicity is an important precursor for the Earth's most dangerous eruptions. VT seismicity precedes all explosive eruptions of VEI ≥ 5 and most if not all VEI 4 eruptions in our data set. Surprisingly we find that the VT seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption, and rarely if ever starts beneath the eruption site itself. The distal VT swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance, beyond which hypocenter depths level out. We summarize several important characteristics of this distal VT seismicity including: swarm-like nature, onset days to years prior to the beginning of magmatic eruptions, peaking of activity at the time of the initial eruption whether phreatic or magmatic, and large non-double couple component to focal mechanisms. Most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the VT seismicity from: Log10 V = 0.77 Log ΣMoment - 5.32, with volume, V, in cubic meters and seismic moment in Newton meters. Because the cumulative seismic moment can be approximated from the size of just the few largest events, and is quite insensitive to precise locations

  20. Students, earthquakes, media: does a seismic crisis make a difference?

    Directory of Open Access Journals (Sweden)

    Gemma Musacchio

    2016-12-01

    Full Text Available How do students use the big data flow of information form the Internet? What is their opinion and trust of scientists? How far is the influence of catastrophic earthquakes and environmental disasters on their opinion? In this study we present the results of a poll conducted on high school students (age 13-20 to assess young Italian citizens trust on geoscientists and theirs science. The sample of about 700 students is collected in areas prone to natural hazards from low to moderate intensity. The poll included only a very few questions to allow a fast compilation that could be held directly at school. Questions assessed the source from which information on catastrophes and natural phenomena is usually retrieved by the students, the role of scientists in everyday life and scientists ethical integrity. Although limited, this is the first poll of this kind and the collected up to now can be used for a rough picture of the present situation, compare results with recent disasters and project future results of on-going analysis. All information will also help us in a future analysis to understand if and how much a recent earthquake or environmental local crisis can affect the perception. Students do not completely trust that scientists are independent from outer urges. They also believe that media manipulate information with willful misconduct, to hide inconvenient realities or to get economic advantages.   Answers from our Emilia sample of students were unexpected: they did not show any specific bias after the 2012 seismic sequence. They show less skepticism towards scientists and scientific integrity in comparison to students from other regions. This suggests that the perception towards science and scientists might be driven by cultural and social background and not necessarily affected by recent seismic crisis. In this perspective this on-going study will be challenged as soon as poll after the Amatrice 2016 seismic sequence will be awailable.

  1. Connection with seismic networks and construction of real time earthquake monitoring system

    International Nuclear Information System (INIS)

    Chi, Heon Cheol; Lee, H. I.; Shin, I. C.; Lim, I. S.; Park, J. H.; Lee, B. K.; Whee, K. H.; Cho, C. S.

    2000-12-01

    It is natural to use the nuclear power plant seismic network which have been operated by KEPRI(Korea Electric Power Research Institute) and local seismic network by KIGAM(Korea Institute of Geology, Mining and Material). The real time earthquake monitoring system is composed with monitoring module and data base module. Data base module plays role of seismic data storage and classification and the other, monitoring module represents the status of acceleration in the nuclear power plant area. This research placed the target on the first, networking the KIN's seismic monitoring system with KIGAM and KEPRI seismic network and the second, construction the KIN's Independent earthquake monitoring system

  2. Composite Earthquake Catalog of the Yellow Sea for Seismic Hazard Studies

    Science.gov (United States)

    Kang, S. Y.; Kim, K. H.; LI, Z.; Hao, T.

    2017-12-01

    The Yellow Sea (a.k.a West Sea in Korea) is an epicontinental and semi-closed sea located between Korea and China. Recent earthquakes in the Yellow Sea including, but not limited to, the Seogyuckryulbi-do (1 April 2014, magnitude 5.1), Heuksan-do (21 April 2013, magnitude 4.9), Baekryung-do (18 May 2013, magnitude 4.9) earthquakes, and the earthquake swarm in the Boryung offshore region in 2013, remind us of the seismic hazards affecting east Asia. This series of earthquakes in the Yellow Sea raised numerous questions. Unfortunately, both governments have trouble in monitoring seismicity in the Yellow Sea because earthquakes occur beyond their seismic networks. For example, the epicenters of the magnitude 5.1 earthquake in the Seogyuckryulbi-do region in 2014 reported by the Korea Meteorological Administration and China Earthquake Administration differed by approximately 20 km. This illustrates the difficulty with seismic monitoring and locating earthquakes in the region, despite the huge effort made by both governments. Joint effort is required not only to overcome the limits posed by political boundaries and geographical location but also to study seismicity and the underground structures responsible. Although the well-established and developing seismic networks in Korea and China have provided unprecedented amount and quality of seismic data, high quality catalog is limited to the recent 10s of years, which is far from major earthquake cycle. It is also noticed the earthquake catalog from either country is biased to its own and cannot provide complete picture of seismicity in the Yellow Sea. In order to understand seismic hazard and tectonics in the Yellow Sea, a composite earthquake catalog has been developed. We gathered earthquake information during last 5,000 years from various sources. There are good reasons to believe that some listings account for same earthquake, but in different source parameters. We established criteria in order to provide consistent

  3. UCERF3: A new earthquake forecast for California's complex fault system

    Science.gov (United States)

    Field, Edward H.; ,

    2015-01-01

    With innovations, fresh data, and lessons learned from recent earthquakes, scientists have developed a new earthquake forecast model for California, a region under constant threat from potentially damaging events. The new model, referred to as the third Uniform California Earthquake Rupture Forecast, or "UCERF" (http://www.WGCEP.org/UCERF3), provides authoritative estimates of the magnitude, location, and likelihood of earthquake fault rupture throughout the state. Overall the results confirm previous findings, but with some significant changes because of model improvements. For example, compared to the previous forecast (Uniform California Earthquake Rupture Forecast 2), the likelihood of moderate-sized earthquakes (magnitude 6.5 to 7.5) is lower, whereas that of larger events is higher. This is because of the inclusion of multifault ruptures, where earthquakes are no longer confined to separate, individual faults, but can occasionally rupture multiple faults simultaneously. The public-safety implications of this and other model improvements depend on several factors, including site location and type of structure (for example, family dwelling compared to a long-span bridge). Building codes, earthquake insurance products, emergency plans, and other risk-mitigation efforts will be updated accordingly. This model also serves as a reminder that damaging earthquakes are inevitable for California. Fortunately, there are many simple steps residents can take to protect lives and property.

  4. Seismic gaps previous to certain great earthquakes occurring in North China

    Energy Technology Data Exchange (ETDEWEB)

    Wei, K H; Lin, C H; Chu, H C; Chao, Y H; Chao, H L; Hou, H F

    1978-07-01

    The epicentral distributions of small and moderate earthquakes preceding nine great earthquakes (M greater than or equal to 7.0) in North China are analyzed. It can be seen that most of these earthquakes are preceded by gaps in the regions surrounding their epicenters. The relations between the parameters of the seismic gaps, such as the lengths of their long and short axes, the areas of the gaps, etc., and the parameters of the corresponding earthquakes are discussed.

  5. Forecasting the Rupture Directivity of Large Earthquakes: Centroid Bias of the Conditional Hypocenter Distribution

    Science.gov (United States)

    Donovan, J.; Jordan, T. H.

    2012-12-01

    Forecasting the rupture directivity of large earthquakes is an important problem in probabilistic seismic hazard analysis (PSHA), because directivity is known to strongly influence ground motions. We describe how rupture directivity can be forecast in terms of the "conditional hypocenter distribution" or CHD, defined to be the probability distribution of a hypocenter given the spatial distribution of moment release (fault slip). The simplest CHD is a uniform distribution, in which the hypocenter probability density equals the moment-release probability density. For rupture models in which the rupture velocity and rise time depend only on the local slip, the CHD completely specifies the distribution of the directivity parameter D, defined in terms of the degree-two polynomial moments of the source space-time function. This parameter, which is zero for a bilateral rupture and unity for a unilateral rupture, can be estimated from finite-source models or by the direct inversion of seismograms (McGuire et al., 2002). We compile D-values from published studies of 65 large earthquakes and show that these data are statistically inconsistent with the uniform CHD advocated by McGuire et al. (2002). Instead, the data indicate a "centroid biased" CHD, in which the expected distance between the hypocenter and the hypocentroid is less than that of a uniform CHD. In other words, the observed directivities appear to be closer to bilateral than predicted by this simple model. We discuss the implications of these results for rupture dynamics and fault-zone heterogeneities. We also explore their PSHA implications by modifying the CyberShake simulation-based hazard model for the Los Angeles region, which assumed a uniform CHD (Graves et al., 2011).

  6. A forecast experiment of earthquake activity in Japan under Collaboratory for the Study of Earthquake Predictability (CSEP)

    Science.gov (United States)

    Hirata, N.; Yokoi, S.; Nanjo, K. Z.; Tsuruoka, H.

    2012-04-01

    One major focus of the current Japanese earthquake prediction research program (2009-2013), which is now integrated with the research program for prediction of volcanic eruptions, is to move toward creating testable earthquake forecast models. For this purpose we started an experiment of forecasting earthquake activity in Japan under the framework of the Collaboratory for the Study of Earthquake Predictability (CSEP) through an international collaboration. We established the CSEP Testing Centre, an infrastructure to encourage researchers to develop testable models for Japan, and to conduct verifiable prospective tests of their model performance. We started the 1st earthquake forecast testing experiment in Japan within the CSEP framework. We use the earthquake catalogue maintained and provided by the Japan Meteorological Agency (JMA). The experiment consists of 12 categories, with 4 testing classes with different time spans (1 day, 3 months, 1 year, and 3 years) and 3 testing regions called "All Japan," "Mainland," and "Kanto." A total of 105 models were submitted, and are currently under the CSEP official suite of tests for evaluating the performance of forecasts. The experiments were completed for 92 rounds for 1-day, 6 rounds for 3-month, and 3 rounds for 1-year classes. For 1-day testing class all models passed all the CSEP's evaluation tests at more than 90% rounds. The results of the 3-month testing class also gave us new knowledge concerning statistical forecasting models. All models showed a good performance for magnitude forecasting. On the other hand, observation is hardly consistent in space distribution with most models when many earthquakes occurred at a spot. Now we prepare the 3-D forecasting experiment with a depth range of 0 to 100 km in Kanto region. The testing center is improving an evaluation system for 1-day class experiment to finish forecasting and testing results within one day. The special issue of 1st part titled Earthquake Forecast

  7. Seismic Hazard Assessment for a Characteristic Earthquake Scenario: Probabilistic-Deterministic Method

    Science.gov (United States)

    mouloud, Hamidatou

    2016-04-01

    The objective of this paper is to analyze the seismic activity and the statistical treatment of seismicity catalog the Constantine region between 1357 and 2014 with 7007 seismic event. Our research is a contribution to improving the seismic risk management by evaluating the seismic hazard in the North-East Algeria. In the present study, Earthquake hazard maps for the Constantine region are calculated. Probabilistic seismic hazard analysis (PSHA) is classically performed through the Cornell approach by using a uniform earthquake distribution over the source area and a given magnitude range. This study aims at extending the PSHA approach to the case of a characteristic earthquake scenario associated with an active fault. The approach integrates PSHA with a high-frequency deterministic technique for the prediction of peak and spectral ground motion parameters in a characteristic earthquake. The method is based on the site-dependent evaluation of the probability of exceedance for the chosen strong-motion parameter. We proposed five sismotectonique zones. Four steps are necessary: (i) identification of potential sources of future earthquakes, (ii) assessment of their geological, geophysical and geometric, (iii) identification of the attenuation pattern of seismic motion, (iv) calculation of the hazard at a site and finally (v) hazard mapping for a region. In this study, the procedure of the earthquake hazard evaluation recently developed by Kijko and Sellevoll (1992) is used to estimate seismic hazard parameters in the northern part of Algeria.

  8. Predicting earthquakes by analyzing accelerating precursory seismic activity

    Science.gov (United States)

    Varnes, D.J.

    1989-01-01

    During 11 sequences of earthquakes that in retrospect can be classed as foreshocks, the accelerating rate at which seismic moment is released follows, at least in part, a simple equation. This equation (1) is {Mathematical expression},where {Mathematical expression} is the cumulative sum until time, t, of the square roots of seismic moments of individual foreshocks computed from reported magnitudes;C and n are constants; and tfis a limiting time at which the rate of seismic moment accumulation becomes infinite. The possible time of a major foreshock or main shock, tf,is found by the best fit of equation (1), or its integral, to step-like plots of {Mathematical expression} versus time using successive estimates of tfin linearized regressions until the maximum coefficient of determination, r2,is obtained. Analyzed examples include sequences preceding earthquakes at Cremasta, Greece, 2/5/66; Haicheng, China 2/4/75; Oaxaca, Mexico, 11/29/78; Petatlan, Mexico, 3/14/79; and Central Chile, 3/3/85. In 29 estimates of main-shock time, made as the sequences developed, the errors in 20 were less than one-half and in 9 less than one tenth the time remaining between the time of the last data used and the main shock. Some precursory sequences, or parts of them, yield no solution. Two sequences appear to include in their first parts the aftershocks of a previous event; plots using the integral of equation (1) show that the sequences are easily separable into aftershock and foreshock segments. Synthetic seismic sequences of shocks at equal time intervals were constructed to follow equation (1), using four values of n. In each series the resulting distributions of magnitudes closely follow the linear Gutenberg-Richter relation log N=a-bM, and the product n times b for each series is the same constant. In various forms and for decades, equation (1) has been used successfully to predict failure times of stressed metals and ceramics, landslides in soil and rock slopes, and volcanic

  9. Earthquake Ground Motion Measures for Seismic Response Evaluation of Structures

    Energy Technology Data Exchange (ETDEWEB)

    Cho, In-Kil; Ahn, Seong-Moon; Choun, Young-Sun; Seo, Jeong-Moon

    2007-03-15

    This study used the assessment results of failure criteria - base shear, story drift, top acceleration and top displacement - for a PSC containment building subjected to 30 sets of near-fault ground motions to evaluate the earthquake ground motion intensity measures. Seven intensity measures, peak ground acceleration(PGA), peak ground velocity(PGV), spectral acceleration(Sa), velocity(Sv), spectrum intensity for acceleration(SIa), velocity(SIv) and displacement(SId), were used to represent alternative ground motion. The regression analyses of the failure criteria for a PSC containment building were carried out to evaluate a proper intensity measure by using two regression models and seven ground motion parameters. The regression analysis results demonstrate the correlation coefficients of the failure criteria in terms of the candidate IM. From the results, spectral acceleration(Sa) is estimated as the best parameter for a evaluation of the structural safety for a seismic PSA.

  10. Original earthquake design basis in light of recent seismic hazard studies

    International Nuclear Information System (INIS)

    Petrovski, D.

    1993-01-01

    For the purpose of conceiving the framework within which efforts have been made in the eastern countries to construct earthquake resistant nuclear power plants, a review of the development and application of the seismic zoning map of USSR is given. The normative values of seismic intensity and acceleration are discussed from the aspect of recent probabilistic seismic hazard studies. To that effect, presented briefly in this paper is the methodology of probabilistic seismic hazard analysis. (author)

  11. Social Media as Seismic Networks for the Earthquake Damage Assessment

    Science.gov (United States)

    Meletti, C.; Cresci, S.; La Polla, M. N.; Marchetti, A.; Tesconi, M.

    2014-12-01

    The growing popularity of online platforms, based on user-generated content, is gradually creating a digital world that mirrors the physical world. In the paradigm of crowdsensing, the crowd becomes a distributed network of sensors that allows us to understand real life events at a quasi-real-time rate. The SoS-Social Sensing project [http://socialsensing.it/] exploits the opportunistic crowdsensing, involving users in the sensing process in a minimal way, for social media emergency management purposes in order to obtain a very fast, but still reliable, detection of emergency dimension to face. First of all we designed and implemented a decision support system for the detection and the damage assessment of earthquakes. Our system exploits the messages shared in real-time on Twitter. In the detection phase, data mining and natural language processing techniques are firstly adopted to select meaningful and comprehensive sets of tweets. Then we applied a burst detection algorithm in order to promptly identify outbreaking seismic events. Using georeferenced tweets and reported locality names, a rough epicentral determination is also possible. The results, compared to Italian INGV official reports, show that the system is able to detect, within seconds, events of a magnitude in the region of 3.5 with a precision of 75% and a recall of 81,82%. We then focused our attention on damage assessment phase. We investigated the possibility to exploit social media data to estimate earthquake intensity. We designed a set of predictive linear models and evaluated their ability to map the intensity of worldwide earthquakes. The models build on a dataset of almost 5 million tweets exploited to compute our earthquake features, and more than 7,000 globally distributed earthquakes data, acquired in a semi-automatic way from USGS, serving as ground truth. We extracted 45 distinct features falling into four categories: profile, tweet, time and linguistic. We run diagnostic tests and

  12. Using Dynamic Fourier Analysis to Discriminate Between Seismic Signals from Natural Earthquakes and Mining Explosions

    Directory of Open Access Journals (Sweden)

    Maria C. Mariani

    2017-08-01

    Full Text Available A sequence of intraplate earthquakes occurred in Arizona at the same location where miningexplosions were carried out in previous years. The explosions and some of the earthquakes generatedvery similar seismic signals. In this study Dynamic Fourier Analysis is used for discriminating signalsoriginating from natural earthquakes and mining explosions. Frequency analysis of seismogramsrecorded at regional distances shows that compared with the mining explosions the earthquake signalshave larger amplitudes in the frequency interval ~ 6 to 8 Hz and significantly smaller amplitudes inthe frequency interval ~ 2 to 4 Hz. This type of analysis permits identifying characteristics in theseismograms frequency yielding to detect potentially risky seismic events.

  13. Earthquakes from peninsular India : data from the Gauribidanur seismic array

    International Nuclear Information System (INIS)

    Gangrade, B.K.; Prasad, A.G.V.; Sharma, R.D.

    1987-01-01

    Arrival times of the P and S wave signals recorded at the Gauribidanur seismic array from earthquakes in the neighbouring areas in peninsular India have been analysed to estimate their locations (latitudes and longitudes of the epicenters), magnitudes and origin times. Considering typical inaccuracies in the observed data, uncertainties in the estimated epicentral parameters have been illustrated. Using a crustal model, which has been specifically derived for the region around the array, expected arrival times of these signals at other important seismic stations (Kodaikanal, Hyderabad, Poona, New Delhi and Shillong) have been computed for identifying events at these stations in order to determine accurate arrival times at these stations. Due to a higher signal detection capability of the Gauribidanur array, the number of events given in this catalogue is much greater than that detected by these stations. The M S magnitude estimates of events detected at the Hyderabad station have been used to obtain a magnitude scale for Gauribidanur. Origin times, epicentral locations and magnitudes of these events are listed in this report. 10 refs., 3 figures, 3 tables. (author)

  14. The Wenchuan, China M8.0 Earthquake: A Lesson and Implication for Seismic Hazard Mitigation

    Science.gov (United States)

    Wang, Z.

    2008-12-01

    The Wenchuan, China M8.0 earthquake caused great damage and huge casualty. 69,197 people were killed, 374,176 people were injured, and 18,341 people are still missing. The estimated direct economic loss is about 126 billion U.S. dollar. The Wenchuan earthquake again demonstrated that earthquake does not kill people, but the built environments and induced hazards, landslides in particular, do. Therefore, it is critical to strengthen the built environments, such buildings and bridges, and to mitigate the induced hazards in order to avoid such disaster. As a part of the so-called North-South Seismic Zone in China, the Wenchuan earthquake occurred along the Longmen Shan thrust belt which forms a boundary between the Qinghai-Tibet Plateau and the Sichuan basin, and there is a long history (~4,000 years) of seismicity in the area. The historical records show that the area experienced high intensity (i.e., greater than IX) in the past several thousand years. In other words, the area is well-known to have high seismic hazard because of its tectonic setting and seismicity. However, only intensity VII (0.1 to 0.15g PGA) has been considered for seismic design for the built environments in the area. This was one of the main reasons that so many building collapses, particularly the school buildings, during the Wenchuan earthquake. It is clear that the seismic design (i.e., the design ground motion or intensity) is not adequate in the Wenchuan earthquake stricken area. A lesson can be learned from the Wenchuan earthquake on the seismic hazard and risk assessment. A lesson can also be learned from this earthquake on seismic hazard mitigation and/or seismic risk reduction.

  15. Seismic fragility analyses of nuclear power plant structures based on the recorded earthquake data in Korea

    International Nuclear Information System (INIS)

    Joe, Yang Hee; Cho, Sung Gook

    2003-01-01

    This paper briefly introduces an improved method for evaluating seismic fragilities of components of nuclear power plants in Korea. Engineering characteristics of small magnitude earthquake spectra recorded in the Korean peninsula during the last several years are also discussed in this paper. For the purpose of evaluating the effects of the recorded earthquake on the seismic fragilities of Korean nuclear power plant structures, several cases of comparative studies have been performed. The study results show that seismic fragility analysis based on the Newmark's spectra in Korea might over-estimate the seismic capacities of Korean facilities. (author)

  16. Lessons learned from the 2016 Kumamoto earthquake: Building damages and behavior of seismically isolated buildings

    Science.gov (United States)

    Morita, Keiko; Takayama, Mineo

    2017-10-01

    Powerful earthquakes stuck Kumamoto and Oita Prefectures in Kyushu, Japan. It began with the Magnitude 6.5 foreshock at 21:26 JST 14 April, followed by the Magnitude 7.3 mainshock at 1:25 JST 16 April, 2016. The sequence earthquakes also involved more than 1700 perceptible earthquakes as of 13 June. The entire sequence was named the 2016 Kumamoto earthquake by the Japan Meteorological Agency. Thousands of buildings and many roads were damaged, and landslides occurred. The Japanese building standard law is revised in 1981. Structural damages were concentrated on buildings constructed prior to 1981. The area of Mashiki and Southern Aso were most badly affected, especially wooden houses extremely damaged. In Japan, Prof. Hideyuki Tada (title at the time) undertook research on laminated rubber bearings in 1978, and put it into practical use in 1981. The single family house at Yachiyodai, Chiba Prefecture is completed in 1983, it's the first seismically isolated building which is installed laminated rubber bearings in Japan. Afterward, this system is gradually adopted to mainly office buildings, like a research laboratory, a hospital, a computer center and other offices. In the 1994 Northridge earthquake, the 1995 Kobe earthquake and 2011 Tohoku earthquake, seismically isolated buildings improve these good performances, and recently number of the buildings have increased, mainly high risk area of earthquakes. Many people believed that Kumamoto was a low risk area. But there were 24 seismically isolated buildings in Kumamoto Prefecture at the time. The seismically isolated buildings indicated excellent performances during the earthquakes. They protected people, buildings and other important facilities from damages caused by the earthquake. The purpose of this paper is to discuss lessons learned from the 2016 Kumamoto earthquake and behavior of seismically isolated buildings in the earthquake.

  17. The earthquake of January 13, 1915 and the seismic hazard of the area

    International Nuclear Information System (INIS)

    Scarascia Mugnozza, Gabriele; Hailemikael, Salomon; Martini, Guido

    2015-01-01

    The January 13, 1915, magnitude 7.0 Marsica Earthquake devastated the Fucino basin and surroundings, causing about 30,000 casualties and entirely destroying several towns, among which the major municipality of the area, the town of Avezzano. In this paper, we briefly review the main characteristics of the earthquake and its effects on the environment. Furthermore, based on the Italian building code and ongoing seismic microzonation investigations, we describe the seismic hazard of the area struck by the earthquake in terms of both probabilistic seismic hazard assessment and contribution of site effects on the seismic hazard estimate. All the studies confirm the very high level of seismic hazard of the Fucino territory [it

  18. 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)

  19. Estimation of co-seismic stress change of the 2008 Wenchuan Ms8.0 earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Sun Dongsheng; Wang Hongcai; Ma Yinsheng; Zhou Chunjing [Key laboratory of Neotectonic movement and Geohazard, Ministry of Land and Resources, Beijing 100081 (China) and Institute of Geomechanics, Chinese academy of Geological Sciences, Beijing 100081 (China)

    2012-09-26

    In-situ stress change near the fault before and after a great earthquake is a key issue in the geosciences field. In this work, based on the 2008 Great Wenchuan earthquake fault slip dislocation model, the co-seismic stress tensor change due to the Wenchuan earthquake and the distribution functions around the Longmen Shan fault are given. Our calculated results are almost consistent with the before and after great Wenchuan earthquake in-situ measuring results. The quantitative assessment results provide a reference for the study of the mechanism of earthquakes.

  20. Earthquake potential in California-Nevada implied by correlation of strain rate and seismicity

    Science.gov (United States)

    Zeng, Yuehua; Petersen, Mark D.; Shen, Zheng-Kang

    2018-01-01

    Rock mechanics studies and dynamic earthquake simulations show that patterns of seismicity evolve with time through (1) accumulation phase, (2) localization phase, and (3) rupture phase. We observe a similar pattern of changes in seismicity during the past century across California and Nevada. To quantify these changes, we correlate GPS strain rates with seismicity. Earthquakes of M > 6.5 are collocated with regions of highest strain rates. By contrast, smaller magnitude earthquakes of M ≥ 4 show clear spatiotemporal changes. From 1933 to the late 1980s, earthquakes of M ≥ 4 were more diffused and broadly distributed in both high and low strain rate regions (accumulation phase). From the late 1980s to 2016, earthquakes were more concentrated within the high strain rate areas focused on the major fault strands (localization phase). In the same time period, the rate of M > 6.5 events also increased significantly in the high strain rate areas. The strong correlation between current strain rate and the later period of seismicity indicates that seismicity is closely related to the strain rate. The spatial patterns suggest that before the late 1980s, the strain rate field was also broadly distributed because of the stress shadows from previous large earthquakes. As the deformation field evolved out of the shadow in the late 1980s, strain has refocused on the major fault systems and we are entering a period of increased risk for large earthquakes in California.

  1. Seismic Hazard characterization study using an earthquake source with Probabilistic Seismic Hazard Analysis (PSHA) method in the Northern of Sumatra

    International Nuclear Information System (INIS)

    Yahya, A.; Palupi, M. I. R.; Suharsono

    2016-01-01

    Sumatra region is one of the earthquake-prone areas in Indonesia because it is lie on an active tectonic zone. In 2004 there is earthquake with a moment magnitude of 9.2 located on the coast with the distance 160 km in the west of Nanggroe Aceh Darussalam and triggering a tsunami. These events take a lot of casualties and material losses, especially in the Province of Nanggroe Aceh Darussalam and North Sumatra. To minimize the impact of the earthquake disaster, a fundamental assessment of the earthquake hazard in the region is needed. Stages of research include the study of literature, collection and processing of seismic data, seismic source characterization and analysis of earthquake hazard by probabilistic methods (PSHA) used earthquake catalog from 1907 through 2014. The earthquake hazard represented by the value of Peak Ground Acceleration (PGA) and Spectral Acceleration (SA) in the period of 0.2 and 1 second on bedrock that is presented in the form of a map with a return period of 2475 years and the earthquake hazard curves for the city of Medan and Banda Aceh. (paper)

  2. Seismic-resistant design of nuclear power stations in Japan, earthquake country. Lessons learned from Chuetsu-oki earthquake

    International Nuclear Information System (INIS)

    Irikura, Kojiro

    2008-01-01

    The new assessment (back-check) of earthquake-proof safety was being conducted at Kashiwazaki-Kariwa Nuclear Power Plants, Tokyo Electric Co. in response to a request based on the guideline for reactor evaluation for seismic-resistant design code, revised in 2006, when the 2007 Chuetsu-oki Earthquake occurred and brought about an unexpectedly huge tremor in this area, although the magnitude of the earthquake was only 6.8 but the intensity of earthquake motion exceeded 2.5-fold more than supposed. This paper introduces how and why the guideline for seismic-resistant design of nuclear facilities was revised in 2006, the outline of the Chuetsu-oki Earthquake, and preliminary findings and lessons learned from the Earthquake. The paper specifically discusses on (1) how we may specify in advance geologic active faults as has been overlooked this time, (2) how we can make adequate models for seismic origin from which we can extract its characteristics, and (3) how the estimation of strong ground motion simulation may be possible for ground vibration level of a possibly overlooked fault. (S. Ohno)

  3. Uniform California earthquake rupture forecast, version 3 (UCERF3): the time-independent model

    Science.gov (United States)

    Field, Edward H.; Biasi, Glenn P.; Bird, Peter; Dawson, Timothy E.; Felzer, Karen R.; Jackson, David D.; Johnson, Kaj M.; Jordan, Thomas H.; Madden, Christopher; Michael, Andrew J.; Milner, Kevin R.; Page, Morgan T.; Parsons, Thomas; Powers, Peter M.; Shaw, Bruce E.; Thatcher, Wayne R.; Weldon, Ray J.; Zeng, Yuehua; ,

    2013-01-01

    In this report we present the time-independent component of the Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3), which provides authoritative estimates of the magnitude, location, and time-averaged frequency of potentially damaging earthquakes in California. The primary achievements have been to relax fault segmentation assumptions and to include multifault ruptures, both limitations of the previous model (UCERF2). The rates of all earthquakes are solved for simultaneously, and from a broader range of data, using a system-level "grand inversion" that is both conceptually simple and extensible. The inverse problem is large and underdetermined, so a range of models is sampled using an efficient simulated annealing algorithm. The approach is more derivative than prescriptive (for example, magnitude-frequency distributions are no longer assumed), so new analysis tools were developed for exploring solutions. Epistemic uncertainties were also accounted for using 1,440 alternative logic tree branches, necessitating access to supercomputers. The most influential uncertainties include alternative deformation models (fault slip rates), a new smoothed seismicity algorithm, alternative values for the total rate of M≥5 events, and different scaling relationships, virtually all of which are new. As a notable first, three deformation models are based on kinematically consistent inversions of geodetic and geologic data, also providing slip-rate constraints on faults previously excluded because of lack of geologic data. The grand inversion constitutes a system-level framework for testing hypotheses and balancing the influence of different experts. For example, we demonstrate serious challenges with the Gutenberg-Richter hypothesis for individual faults. UCERF3 is still an approximation of the system, however, and the range of models is limited (for example, constrained to stay close to UCERF2). Nevertheless, UCERF3 removes the apparent UCERF2 overprediction of

  4. Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: earthquake locations and source parameters

    Science.gov (United States)

    Ruppert, Natalia G.; Prejean, Stephanie G.; Hansen, Roger A.

    2011-01-01

    An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field.

  5. Earthquake Early Warning: New Strategies for Seismic Hardware

    Science.gov (United States)

    Allardice, S.; Hill, P.

    2017-12-01

    Implementing Earthquake Early Warning System (EEWS) triggering algorithms into seismic networks has been a hot topic of discussion for some years now. With digitizer technology now available, such as the Güralp Minimus, with on average 40-60ms delay time (latency) from earthquake origin to issuing an alert the next step is to provide network operators with a simple interface for on board parameter calculations from a seismic station. A voting mechanism is implemented on board which mitigates the risk of false positives being communicated. Each Minimus can be configured to with a `score' from various sources i.e. Z channel on seismometer, N/S E/W channels on accelerometer and MEMS inside Minimus. If the score exceeds the set threshold then an alert is sent to the `Master Minimus'. The Master Minimus within the network will also be configured as to when the alert should be issued i.e. at least 3 stations must have triggered. Industry standard algorithms focus around the calculation of Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), Peak Ground Displacement (PGD) and C. Calculating these single station parameters on-board in order to stream only the results could help network operators with possible issues, such as restricted bandwidth. Developments on the Minimus allow these parameters to be calculated and distributed through Common Alert Protocol (CAP). CAP is the XML based data format used for exchanging and describing public warnings and emergencies. Whenever the trigger conditions are met the Minimus can send a signed UDP packet to the configured CAP receiver which can then send the alert via SMS, e-mail or CAP forwarding. Increasing network redundancy is also a consideration when developing these features, therefore the forwarding CAP message can be sent to multiple destinations. This allows for a hierarchical approach by which the single station (or network) parameters can be streamed to another Minimus, or data centre, or both, so that there is no

  6. Seismicity Pattern and Fault Structure in the Central Himalaya Seismic Gap Using Precise Earthquake Hypocenters and their Source Parameters

    Science.gov (United States)

    Mendoza, M.; Ghosh, A.; Rai, S. S.

    2017-12-01

    The devastation brought on by the Mw 7.8 Gorkha earthquake in Nepal on 25 April 2015, reconditioned people to the high earthquake risk along the Himalayan arc. It is therefore imperative to learn from the Gorkha earthquake, and gain a better understanding of the state of stress in this fault regime, in order to identify areas that could produce the next devastating earthquake. Here, we focus on what is known as the "central Himalaya seismic gap". It is located in Uttarakhand, India, west of Nepal, where a large (> Mw 7.0) earthquake has not occurred for over the past 200 years [Rajendran, C.P., & Rajendran, K., 2005]. This 500 - 800 km long along-strike seismic gap has been poorly studied, mainly due to the lack of modern and dense instrumentation. It is especially concerning since it surrounds densely populated cities, such as New Delhi. In this study, we analyze a rich seismic dataset from a dense network consisting of 50 broadband stations, that operated between 2005 and 2012. We use the STA/LTA filter technique to detect earthquake phases, and the latest tools contributed to the Antelope software environment, to develop a large and robust earthquake catalog containing thousands of precise hypocentral locations, magnitudes, and focal mechanisms. By refining those locations in HypoDD [Waldhauser & Ellsworth, 2000] to form a tighter cluster of events using relative relocation, we can potentially illustrate fault structures in this region with high resolution. Additionally, using ZMAP [Weimer, S., 2001], we perform a variety of statistical analyses to understand the variability and nature of seismicity occurring in the region. Generating a large and consistent earthquake catalog not only brings to light the physical processes controlling the earthquake cycle in an Himalayan seismogenic zone, it also illustrates how stresses are building up along the décollment and the faults that stem from it. With this new catalog, we aim to reveal fault structure, study

  7. 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

  8. 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

  9. MyShake: A smartphone seismic network for earthquake early warning and beyond.

    Science.gov (United States)

    Kong, Qingkai; Allen, Richard M; Schreier, Louis; Kwon, Young-Woo

    2016-02-01

    Large magnitude earthquakes in urban environments continue to kill and injure tens to hundreds of thousands of people, inflicting lasting societal and economic disasters. Earthquake early warning (EEW) provides seconds to minutes of warning, allowing people to move to safe zones and automated slowdown and shutdown of transit and other machinery. The handful of EEW systems operating around the world use traditional seismic and geodetic networks that exist only in a few nations. Smartphones are much more prevalent than traditional networks and contain accelerometers that can also be used to detect earthquakes. We report on the development of a new type of seismic system, MyShake, that harnesses personal/private smartphone sensors to collect data and analyze earthquakes. We show that smartphones can record magnitude 5 earthquakes at distances of 10 km or less and develop an on-phone detection capability to separate earthquakes from other everyday shakes. Our proof-of-concept system then collects earthquake data at a central site where a network detection algorithm confirms that an earthquake is under way and estimates the location and magnitude in real time. This information can then be used to issue an alert of forthcoming ground shaking. MyShake could be used to enhance EEW in regions with traditional networks and could provide the only EEW capability in regions without. In addition, the seismic waveforms recorded could be used to deliver rapid microseism maps, study impacts on buildings, and possibly image shallow earth structure and earthquake rupture kinematics.

  10. Contributions to the Chile’s Seismic History: the Case of the Great Earthquake of 1730

    Directory of Open Access Journals (Sweden)

    María X. Urbina Carrasco

    2016-12-01

    Full Text Available According to the new and previously known documents it is concluded the earthquake of Chile in 1730 was composed by two independent earthquakes, each associated to a tsunami. Considering the latitudinal extension of the damage and the size of the tsunamis, it can be taken as the largest seismic event occurred in the history of Metropolitan or Central Chile. These conclusions allow to know better the seismic sequence of Central Chile, the Seismic History of the country, and contribute to the knowledge of the colonial history of the kingdom of Chile.

  11. A procedure for the determination of scenario earthquakes for seismic design based on probabilistic seismic hazard analysis

    International Nuclear Information System (INIS)

    Hirose, Jiro; Muramatsu, Ken

    2002-03-01

    This report presents a study on the procedures for the determination of scenario earthquakes for seismic design of nuclear power plants (NPPs) based on probabilistic seismic hazard analysis (PSHA). In the recent years, the use of PSHA, which is a part of seismic probabilistic safety assessment (PSA), to determine the design basis earthquake motions for NPPs has been proposed. The identified earthquakes are called probability-based scenario earthquakes (PBSEs). The concept of PBSEs originates both from the study of US NRC and from Ishikawa and Kameda. The assessment of PBSEs is composed of seismic hazard analysis and identification of dominant earthquakes. The objectives of this study are to formulate the concept of PBSEs and to examine the procedures for determining the PBSEs for a domestic NPP site. This report consists of three parts, namely, procedures to compile analytical conditions for PBSEs, an assessment to identify PBSEs for a model site using the Ishikawa's concept and the examination of uncertainties involved in analytical conditions. The results obtained from the examination of PBSEs using Ishikawa's concept are as follows. (a) Since PBSEs are expressed by hazard-consistent magnitude and distance in terms of a prescribed reference probability, it is easy to obtain a concrete image of earthquakes that determine the ground response spectrum to be considered in the design of NPPs. (b) Source contribution factors provide the information on the importance of the earthquake source regions and/or active faults, and allows the selection of a couple of PBSEs based on their importance to the site. (c) Since analytical conditions involve uncertainty, sensitivity analyses on uncertainties that would affect seismic hazard curves and identification of PBSEs were performed on various aspects and provided useful insights for assessment of PBSEs. A result from this sensitivity analysis was that, although the difference in selection of attenuation equations led to a

  12. 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)

  13. Seismic response analysis of Wolsung NPP structure and equipment subjected to scenario earthquakes

    Energy Technology Data Exchange (ETDEWEB)

    Choi, In Kil; Ahn, Seong Moon; Choun, Young Sun; Seo, Jeong Moon

    2005-03-15

    The standard response spectrum proposed by US NRC has been used as a design earthquake for the design of Korean nuclear power plant structures. However, it does not reflect the characteristic of seismological and geological of Korea. In this study, the seismic response analysis of Wolsung NPP structure and equipment were performed. Three types of input motions, artificial time histories that envelop the US NRC Regulatory Guide 1.60 spectrum and the probability based scenario earthquake spectra developed for the Korean NPP site and a typical near-fault earthquake recorded at thirty sites, were used as input motions. The acceleration, displacement and shear force responses of Wolsung containment structure due to the design earthquake were larger than those due to the other input earthquakes. But, considering displacement response increases abruptly as Wolsung NPP structure does nonlinear behavior, the reassessment of the seismic safety margin based on the displacement is necessary if the structure does nonlinear behavior; although it has adequate the seismic safety margin within elastic limit. Among the main safety-related devices, electrical cabinet and pump showed the large responses on the scenario earthquake which has the high frequency characteristic. This has great effects of the seismic capacity of the main devices installed inside of the building. This means that the design earthquake is not so conservative for the safety of the safety related nuclear power plant equipments.

  14. Probabilistic Seismic Hazard Assessment for Himalayan-Tibetan Region from Historical and Instrumental Earthquake Catalogs

    Science.gov (United States)

    Rahman, M. Moklesur; Bai, Ling; Khan, Nangyal Ghani; Li, Guohui

    2018-02-01

    The Himalayan-Tibetan region has a long history of devastating earthquakes with wide-spread casualties and socio-economic damages. Here, we conduct the probabilistic seismic hazard analysis by incorporating the incomplete historical earthquake records along with the instrumental earthquake catalogs for the Himalayan-Tibetan region. Historical earthquake records back to more than 1000 years ago and an updated, homogenized and declustered instrumental earthquake catalog since 1906 are utilized. The essential seismicity parameters, namely, the mean seismicity rate γ, the Gutenberg-Richter b value, and the maximum expected magnitude M max are estimated using the maximum likelihood algorithm assuming the incompleteness of the catalog. To compute the hazard value, three seismogenic source models (smoothed gridded, linear, and areal sources) and two sets of ground motion prediction equations are combined by means of a logic tree on accounting the epistemic uncertainties. The peak ground acceleration (PGA) and spectral acceleration (SA) at 0.2 and 1.0 s are predicted for 2 and 10% probabilities of exceedance over 50 years assuming bedrock condition. The resulting PGA and SA maps show a significant spatio-temporal variation in the hazard values. In general, hazard value is found to be much higher than the previous studies for regions, where great earthquakes have actually occurred. The use of the historical and instrumental earthquake catalogs in combination of multiple seismogenic source models provides better seismic hazard constraints for the Himalayan-Tibetan region.

  15. Seismic response analysis of Wolsung NPP structure and equipment subjected to scenario earthquakes

    International Nuclear Information System (INIS)

    Choi, In Kil; Ahn, Seong Moon; Choun, Young Sun; Seo, Jeong Moon

    2005-03-01

    The standard response spectrum proposed by US NRC has been used as a design earthquake for the design of Korean nuclear power plant structures. However, it does not reflect the characteristic of seismological and geological of Korea. In this study, the seismic response analysis of Wolsung NPP structure and equipment were performed. Three types of input motions, artificial time histories that envelop the US NRC Regulatory Guide 1.60 spectrum and the probability based scenario earthquake spectra developed for the Korean NPP site and a typical near-fault earthquake recorded at thirty sites, were used as input motions. The acceleration, displacement and shear force responses of Wolsung containment structure due to the design earthquake were larger than those due to the other input earthquakes. But, considering displacement response increases abruptly as Wolsung NPP structure does nonlinear behavior, the reassessment of the seismic safety margin based on the displacement is necessary if the structure does nonlinear behavior; although it has adequate the seismic safety margin within elastic limit. Among the main safety-related devices, electrical cabinet and pump showed the large responses on the scenario earthquake which has the high frequency characteristic. This has great effects of the seismic capacity of the main devices installed inside of the building. This means that the design earthquake is not so conservative for the safety of the safety related nuclear power plant equipments

  16. Atlas of Wenchuan-Earthquake Geohazards : Analysis of co-seismic and post-seismic Geohazards in the area affected by the 2008 Wenchuan Earthquake

    NARCIS (Netherlands)

    Tang, Chuan; van Westen, C.J.

    2018-01-01

    This atlas provides basic information and overviews of the occurrence of co-seismic landslides, the subsequent rainstorm-induced debris flows, and the methods used for hazard and risk assessment in the Wenchuan-earthquake affected area. The atlas pages are illustrated with maps, photos and graphs,

  17. Deep seismic transect across the Tonankai earthquake area obtained from the onshore- offshore wide-angle seismic study

    Science.gov (United States)

    Nakanishi, A.; Obana, K.; Kodaira, S.; Miura, S.; Fujie, G.; Ito, A.; Sato, T.; Park, J.; Kaneda, Y.; Ito, K.; Iwasaki, T.

    2008-12-01

    In the Nankai Trough subduction seismogenic zone, M8-class great earthquake area can be divided into three segments; they are source regions of the Nankai, Tonankai and presumed Tokai earthquakes. The Nankai and Tonankai earthquakes had often occurred simultaneously, and caused a great event. Hypocenters of these great earthquakes were usually located off the cape Shiono, Kii Peninsula, and the rupture propagated westwards and eastwards, respectively. To obtain the deep structure of the down-dip limit of around the Nankai Trough seismogenic zone, the segment boundary and first break area off the Kii Peninsula, the onshore-offshore wide-angle seismic studies was conducted in the western and eastern part of the Kii Peninsula and their offshore area in 2004 and 2006, respectively. The result of the seismic study in 2004 is mainly shown here. Structural images along the onshore and offshore profiles have already been separately obtained. In this study, an onshore-offshore integrated image of the western part of the Kii Peninsula, ~400km in a total length, is obtained from first arrival tomography and traveltime mapping of reflection phases by combining dataset of 13 land explosions, 2269 land stations, 36 OBSs and 1806 offshore airgun shots. The subduction angle of the Philippine Sea plate (PSP) gradually increases landward up to ~20-25 degree. Beneath the onshore part, the subducting PSP is estimated at ~5km shallower than that previously derived from seismicity. Low frequency earthquakes (identified and picked by Japan Meteorological Agency) are relocated around the plate interface of the subducting PSP by using the deep seismic transect obtained in this study. The offshore research is part of 'Structure research on plate dynamics of the presumed rupture zone of the Tonankai-Nankai Earthquakes' funded by Ministry of Education, Culture, Sports, Science and Technology (MEXT). The onshore research carried by the Kyoto University is part of 'Special Project for

  18. Earthquake and failure forecasting in real-time: A Forecasting Model Testing Centre

    Science.gov (United States)

    Filgueira, Rosa; Atkinson, Malcolm; Bell, Andrew; Main, Ian; Boon, Steven; Meredith, Philip

    2013-04-01

    Across Europe there are a large number of rock deformation laboratories, each of which runs many experiments. Similarly there are a large number of theoretical rock physicists who develop constitutive and computational models both for rock deformation and changes in geophysical properties. Here we consider how to open up opportunities for sharing experimental data in a way that is integrated with multiple hypothesis testing. We present a prototype for a new forecasting model testing centre based on e-infrastructures for capturing and sharing data and models to accelerate the Rock Physicist (RP) research. This proposal is triggered by our work on data assimilation in the NERC EFFORT (Earthquake and Failure Forecasting in Real Time) project, using data provided by the NERC CREEP 2 experimental project as a test case. EFFORT is a multi-disciplinary collaboration between Geoscientists, Rock Physicists and Computer Scientist. Brittle failure of the crust is likely to play a key role in controlling the timing of a range of geophysical hazards, such as volcanic eruptions, yet the predictability of brittle failure is unknown. Our aim is to provide a facility for developing and testing models to forecast brittle failure in experimental and natural data. Model testing is performed in real-time, verifiably prospective mode, in order to avoid selection biases that are possible in retrospective analyses. The project will ultimately quantify the predictability of brittle failure, and how this predictability scales from simple, controlled laboratory conditions to the complex, uncontrolled real world. Experimental data are collected from controlled laboratory experiments which includes data from the UCL Laboratory and from Creep2 project which will undertake experiments in a deep-sea laboratory. We illustrate the properties of the prototype testing centre by streaming and analysing realistically noisy synthetic data, as an aid to generating and improving testing methodologies in

  19. Seismic evaluation of a diesel generator system at the Savannah River Site using earthquake experience data

    International Nuclear Information System (INIS)

    Griffin, M.J.; Tong, Wen H.; Rawls, G.B.

    1990-01-01

    New equipment and systems have been seismically qualified traditionally by either two methods, testing or analysis. Testing programs are generally expensive and their input loadings are conservative. It is generally recognized that standard seismic analysis techniques produce conservative results. Seismic loads and response levels for equipment that are typically calculated exceed the values actually experienced in earthquakes. An alternate method for demonstrating the seismic adequacy of equipment has been developed which is based on conclusions derived from studying the performance of equipment that has been subjected to actual earthquake excitations. The conclusion reached from earthquake experience data is that damage or malfunction to most types of equipment subjected to earthquakes is less than that predicted by traditional testing and analysis techniques. The use of conclusions derived from experience data provides a realistic approach in assessing the seismic ruggedness of equipment. By recognizing the inherently higher capacity that exists in specific classes of equipment, commercial ''off-the-shelf'' equipment can be procured and qualified without the need to perform expensive modifications to meet requirements imposed by traditional conservative qualification analyses. This paper will present the seismic experience data methodology applied to demonstrate the seismic adequacy of several commercially supplied 800KW diesel powered engine driven generator sets with peripheral support components installed at the Savannah River Site (SRS)

  20. Memory effect in M ≥ 6 earthquakes of South-North Seismic Belt, Mainland China

    Science.gov (United States)

    Wang, Jeen-Hwa

    2013-07-01

    The M ≥ 6 earthquakes occurred in the South-North Seismic Belt, Mainland China, during 1901-2008 are taken to study the possible existence of memory effect in large earthquakes. The fluctuation analysis technique is applied to analyze the sequences of earthquake magnitude and inter-event time represented in the natural time domain. Calculated results show that the exponents of scaling law of fluctuation versus window length are less than 0.5 for the sequences of earthquake magnitude and inter-event time. The migration of earthquakes in study is taken to discuss the possible correlation between events. The phase portraits of two sequent magnitudes and two sequent inter-event times are also applied to explore if large (or small) earthquakes are followed by large (or small) events. Together with all kinds of given information, we conclude that the earthquakes in study is short-term correlated and thus the short-term memory effect would be operative.

  1. Characterization of tsunamigenic earthquake in Java region based on seismic wave calculation

    International Nuclear Information System (INIS)

    Pribadi, Sugeng; Afnimar,; Puspito, Nanang T.; Ibrahim, Gunawan

    2014-01-01

    This study is to characterize the source mechanism of tsunamigenic earthquake based on seismic wave calculation. The source parameter used are the ratio (Θ) between the radiated seismic energy (E) and seismic moment (M o ), moment magnitude (M W ), rupture duration (T o ) and focal mechanism. These determine the types of tsunamigenic earthquake and tsunami earthquake. We calculate the formula using the teleseismic wave signal processing with the initial phase of P wave with bandpass filter 0.001 Hz to 5 Hz. The amount of station is 84 broadband seismometer with far distance of 30° to 90°. The 2 June 1994 Banyuwangi earthquake with M W =7.8 and the 17 July 2006 Pangandaran earthquake with M W =7.7 include the criteria as a tsunami earthquake which distributed about ratio Θ=−6.1, long rupture duration To>100 s and high tsunami H>7 m. The 2 September 2009 Tasikmalaya earthquake with M W =7.2, Θ=−5.1 and To=27 s which characterized as a small tsunamigenic earthquake

  2. Characterization of tsunamigenic earthquake in Java region based on seismic wave calculation

    Energy Technology Data Exchange (ETDEWEB)

    Pribadi, Sugeng, E-mail: sugengpribadimsc@gmail.com [Badan Meteorologi Klimatologi Geofisika, Jl Angkasa I No. 2 Jakarta (Indonesia); Afnimar,; Puspito, Nanang T.; Ibrahim, Gunawan [Institut Teknologi Bandung, Jl. Ganesha 10, Bandung 40132 (Indonesia)

    2014-03-24

    This study is to characterize the source mechanism of tsunamigenic earthquake based on seismic wave calculation. The source parameter used are the ratio (Θ) between the radiated seismic energy (E) and seismic moment (M{sub o}), moment magnitude (M{sub W}), rupture duration (T{sub o}) and focal mechanism. These determine the types of tsunamigenic earthquake and tsunami earthquake. We calculate the formula using the teleseismic wave signal processing with the initial phase of P wave with bandpass filter 0.001 Hz to 5 Hz. The amount of station is 84 broadband seismometer with far distance of 30° to 90°. The 2 June 1994 Banyuwangi earthquake with M{sub W}=7.8 and the 17 July 2006 Pangandaran earthquake with M{sub W}=7.7 include the criteria as a tsunami earthquake which distributed about ratio Θ=−6.1, long rupture duration To>100 s and high tsunami H>7 m. The 2 September 2009 Tasikmalaya earthquake with M{sub W}=7.2, Θ=−5.1 and To=27 s which characterized as a small tsunamigenic earthquake.

  3. Modeling Seismic Cycles of Great Megathrust Earthquakes Across the Scales With Focus at Postseismic Phase

    Science.gov (United States)

    Sobolev, Stephan V.; Muldashev, Iskander A.

    2017-12-01

    Subduction is substantially multiscale process where the stresses are built by long-term tectonic motions, modified by sudden jerky deformations during earthquakes, and then restored by following multiple relaxation processes. Here we develop a cross-scale thermomechanical model aimed to simulate the subduction process from 1 min to million years' time scale. The model employs elasticity, nonlinear transient viscous rheology, and rate-and-state friction. It generates spontaneous earthquake sequences and by using an adaptive time step algorithm, recreates the deformation process as observed naturally during the seismic cycle and multiple seismic cycles. The model predicts that viscosity in the mantle wedge drops by more than three orders of magnitude during the great earthquake with a magnitude above 9. As a result, the surface velocities just an hour or day after the earthquake are controlled by viscoelastic relaxation in the several hundred km of mantle landward of the trench and not by the afterslip localized at the fault as is currently believed. Our model replicates centuries-long seismic cycles exhibited by the greatest earthquakes and is consistent with the postseismic surface displacements recorded after the Great Tohoku Earthquake. We demonstrate that there is no contradiction between extremely low mechanical coupling at the subduction megathrust in South Chile inferred from long-term geodynamic models and appearance of the largest earthquakes, like the Great Chile 1960 Earthquake.

  4. Widespread seismicity excitation following the 2011 M=9.0 Tohoku, Japan, earthquake and its implications for seismic hazard

    Science.gov (United States)

    Toda, S.; Stein, R. S.; Lin, J.

    2011-12-01

    The 11 March 2011 Tohoku-chiho Taiheiyo-oki earthquake (Tohoku earthquake) was followed by massive offshore aftershocks including 6 M≧7 and 94 M≧6 shocks during the 4.5 months (until July 26). It is also unprecedented that a broad increase in seismicity was observed over inland Japan at distances of up to 425 km from the locus of high seismic slip on the megathrust. Such an increase was not seen for the 2004 M=9.1 Sumatra or 2010 M=8.8 Chile earthquakes, but they lacked the seismic networks necessary to detect such small events. Here we explore the possibility that the rate changes are the product of static Coulomb stress transfer to small faults. We use the nodal planes of M≧3.5 earthquakes as proxies for such small active faults, and find that of fifteen regions averaging ˜80 by 80 km in size, 11 show a positive association between calculated stress changes and the observed seismicity rate change, 3 show a negative correlation, and for one the changes are too small to assess. This work demonstrates that seismicity can turn on in the nominal stress shadow of a mainshock as long as small geometrically diverse active faults exist there, which is likely quite common in areas having complex geologic background like Tohoku. In Central Japan, however, there are several regions where the usual tectonic stress has been enhanced by the Tohoku earthquake, and the moderate and large faults have been brought closer to failure, producing M˜5 to 6 shocks, including Nagano, near Mt. Fuji, Tokyo metropolitan area and its offshore. We confirmed that at least 5 of the seven large, exotic, or remote aftershocks were brought ≧0.3 bars closer to failure. Validated by such correlations, we evaluate the effects of the Tohoku event on the other subduction zones nearby and major active faults inland. The majorities of thrust faults inland Tohoku are brought farther from failure by the M9 event. However, we found that the large sections of the Japan trench megathrust, the outer

  5. Connection with seismic networks and construction of real time earthquake monitoring system

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Heon Cheol; Lee, H. I.; Shin, I. C.; Lim, I. S.; Park, J. H.; Lee, B. K.; Whee, K. H.; Cho, C. S. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2000-12-15

    It is natural to use the nuclear power plant seismic network which have been operated by KEPRI(Korea Electric Power Research Institute) and local seismic network by KIGAM(Korea Institute of Geology, Mining and Material). The real time earthquake monitoring system is composed with monitoring module and data base module. Data base module plays role of seismic data storage and classification and the other, monitoring module represents the status of acceleration in the nuclear power plant area. This research placed the target on the first, networking the KIN's seismic monitoring system with KIGAM and KEPRI seismic network and the second, construction the KIN's Independent earthquake monitoring system.

  6. Seismic fragility analyses of nuclear power plant structures based on the recorded earthquake data in Korea

    International Nuclear Information System (INIS)

    Cho, Sung Gook; Joe, Yang Hee

    2005-01-01

    By nature, the seismic fragility analysis results will be considerably affected by the statistical data of design information and site-dependent ground motions. The engineering characteristics of small magnitude earthquake spectra recorded in the Korean peninsula during the last several years are analyzed in this paper. An improved method of seismic fragility analysis is evaluated by comparative analyses to verify its efficiency for practical application to nuclear power plant structures. The effects of the recorded earthquake on the seismic fragilities of Korean nuclear power plant structures are also evaluated from the comparative studies. Observing the obtained results, the proposed method is more efficient for the multi-modes structures. The case study results show that seismic fragility analysis based on the Newmark's spectra in Korea might over-estimate the seismic capacities of Korean facilities

  7. Seismic fragility analyses of nuclear power plant structures based on the recorded earthquake data in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Sung Gook [Department of Civil and Environmental System Engineering, University of Incheon, 177 Dohwa-dong, Nam-gu, Incheon 402-749 (Korea, Republic of)]. E-mail: sgcho@incheon.ac.kr; Joe, Yang Hee [Department of Civil and Environmental System Engineering, University of Incheon, 177 Dohwa-dong, Nam-gu, Incheon 402-749 (Korea, Republic of)

    2005-08-01

    By nature, the seismic fragility analysis results will be considerably affected by the statistical data of design information and site-dependent ground motions. The engineering characteristics of small magnitude earthquake spectra recorded in the Korean peninsula during the last several years are analyzed in this paper. An improved method of seismic fragility analysis is evaluated by comparative analyses to verify its efficiency for practical application to nuclear power plant structures. The effects of the recorded earthquake on the seismic fragilities of Korean nuclear power plant structures are also evaluated from the comparative studies. Observing the obtained results, the proposed method is more efficient for the multi-modes structures. The case study results show that seismic fragility analysis based on the Newmark's spectra in Korea might over-estimate the seismic capacities of Korean facilities.

  8. 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

  9. 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

  10. Seismic quiescence before the 2016 Mw 6.0 Amatrice earthquake, central Italy

    Science.gov (United States)

    Di Giovambattista, R.; Gentili, S.; Peresan, A.

    2017-12-01

    Seismic quiescence before major worldwide earthquakes has been reported by many authors. We have analyzed the seismicity preceding the last damaging 2016-2017 seismic sequence occurred in central Italy, and we have characterized the temporal and spatial extension of the foregoing seismic quiescence. The multiple mainshock sequence (24/08/2016, Mw 6.0; 26/10/2016 Mw 5.4 and 5.9; 30/10/2016, Mw 6.5), which occurred in central Italy, caused the death of nearly 300 people and widespread destruction of entire villages. The Mw 6.5 earthquake was the most powerful recorded in Italy since the 1980 M 6.9 Irpinia earthquake. The Region-Time-Length (RTL) method has been used to quantitatively analyze the seismic quiescence preceding the first Mw 6.0 Amatrice mainshock. This analysis was performed using the earthquake catalogue maintained by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) declustered using a novel statistical approach, which is based on the "nearest-neighbor" distances between pairs of earthquakes in the space-time-energy domain. A well-evident quiescence that preceded the sequence was detected. The quiescence extended throughout a broad region north of the epicenter. The largest event of the sequence and its aftershocks covered most of the quiescence region, except for a small area to the west. The quiescence started from the beginning of September 2015 and lasted for approximately 1 year, up to the Amatrice mainshock. The results obtained have been compared with those of previous seismic sequences occurred in Italy. A similar analysis applied to the 1997-1998, Mw 5.7 Umbria-Marche earthquakes located at the northern termination of the Amatrice sequence, showed a decrease in RTL corresponding to a seismic quiescence, followed by a foreshock activation in the epicentral area before the occurrence of the mainshock.

  11. 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.

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

    Science.gov (United States)

    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.

  13. Failures and suggestions in Earthquake forecasting and prediction

    Science.gov (United States)

    Sacks, S. I.

    2013-12-01

    Seismologists have had poor success in earthquake prediction. However, wide ranging observations from earlier great earthquakes show that precursory data can exist. In particular, two aspects seem promising. In agreement with simple physical modeling, b-values decrease in highly loaded fault zones for years before failure. Potentially more usefully, in high stress regions, breakdown of dilatant patches leading to failure can yield expelled water-related observations. The volume increase (dilatancy) caused by high shear stresses decreases the pore pressure. Eventually, water flows back in restoring the pore pressure, promoting failure and expelling the extra water. Of course, in a generally stressed region there may be many small patches that fail, such as observed before the 1975 Haicheng earthquake. Only a few days before the major event will most of the dilatancy breakdown occur in the fault zone itself such as for the Tangshan, 1976 destructive event. Observations of 'water release' effects have been observed before the 1923 great Kanto earthquake, the 1984 Yamasaki event, the 1975 Haicheng and the 1976 Tangshan earthquakes and also the 1995 Kobe earthquake. While there are obvious difficulties in water release observations, not least because there is currently no observational network anywhere, historical data does suggest some promise if we broaden our approach to this difficult subject.

  14. Seismic hazard assessment based on the Unified Scaling Law for Earthquakes: the Greater Caucasus

    Science.gov (United States)

    Nekrasova, A.; Kossobokov, V. G.

    2015-12-01

    Losses from natural disasters continue to increase mainly due to poor understanding by majority of scientific community, decision makers and public, the three components of Risk, i.e., Hazard, Exposure, and Vulnerability. Contemporary Science is responsible for not coping with challenging changes of Exposures and their Vulnerability inflicted by growing population, its concentration, etc., which result in a steady increase of Losses from Natural Hazards. Scientists owe to Society for lack of knowledge, education, and communication. In fact, Contemporary Science can do a better job in disclosing Natural Hazards, assessing Risks, and delivering such knowledge in advance catastrophic events. We continue applying the general concept of seismic risk analysis in a number of seismic regions worldwide by constructing regional seismic hazard maps based on the Unified Scaling Law for Earthquakes (USLE), i.e. log N(M,L) = A - B•(M-6) + C•log L, where N(M,L) is the expected annual number of earthquakes of a certain magnitude M within an seismically prone area of linear dimension L. The parameters A, B, and C of USLE are used to estimate, first, the expected maximum magnitude in a time interval at a seismically prone cell of a uniform grid that cover the region of interest, and then the corresponding expected ground shaking parameters including macro-seismic intensity. After a rigorous testing against the available seismic evidences in the past (e.g., the historically reported macro-seismic intensity), such a seismic hazard map is used to generate maps of specific earthquake risks (e.g., those based on the density of exposed population). The methodology of seismic hazard and risks assessment based on USLE is illustrated by application to the seismic region of Greater Caucasus.

  15. 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.

  16. Thermal alteration of pyrite to pyrrhotite during earthquakes : New evidence of seismic slip in the rock record

    NARCIS (Netherlands)

    Yang, Tao; Dekkers, Mark J.; Chen, Jianye

    Seismic slip zones convey important information on earthquake energy dissipation and rupture processes. However, geological records of earthquakes along exhumed faults remain scarce. They can be traced with a variety of methods that establish the frictional heating of seismic slip, although each has

  17. Scenarios for local seismic effects of Tulcea (Romania) crustal earthquakes, preliminary approach for the seismic microzoning of Tulcea city

    Science.gov (United States)

    Florin Bǎlan, Å.žTefan; Apostol, Bogdan; Chitea, F.; Anghelache, Mirela Adriana; Cioflan, Carmen O.; Serban, A.

    2010-05-01

    The discussed area, Tulcea, is delimitated by the Scythian Platform in the North and Moessian Platform in the South, not far from the Black Sea coast. Natural disasters in the city could occur due to Vrancea intermediate-depth (subcrustal) earthquakes and crustal earthquakes caused by active faults. In the last 30 years three important seismic events affected the region of interest with the following recorded magnitudes: MW = 5.1 (13.11.1981) followed in the same day by 6 aftershocks (at depth 0-9 km) with MW = 2.9-3.3; MW = 5 (27.04.1986) and MW = 4.9 (3.10.2004) followed by two aftershocks. Information about the seismic zone of Tulcea is from three seismic catalogues made by Florinescu (1958), Constantinescu and Mârza (1980) and ROMPLUS (2008), but for urban planning of Tulcea city is very important to be better understood the effect of active faults (Măcin-Cerna, Tulcea-Isaccea, Peceneaga-Camena etc) located in the Pre-Dobrogean Depression (our interest area) in the two parts of the city. Regarding the effects of Vrancea subcrustal earthquakes, as the Tulcea city is situated relatively at a large distance from the epicenters, there is necessary to improve the actual method of microzonation based on Medvedev's method. In order to discuss the local seismic site effects we have considered two scenarios, which take into account the characteristics of the seismogenic area. The first one considers the city exposed to a seismic event with magnitude Mw = 5.1 from Sf. Gheorghe fault and the second one considers the city exposed to an earthquake from the EV zone (superficial). The earthquake epicentres are located in very active seismic areas. The absolute response spectra at the bedrock and at surface will be calculated and the characteristic transfer functions, as well. Nonlinear effects induced by significant deformations need a certain method - linear equivalent - for a multistratified zone, as we considered for the Tulcea superficial area. Therefore, important

  18. Induced earthquakes. Sharp increase in central Oklahoma seismicity since 2008 induced by massive wastewater injection.

    Science.gov (United States)

    Keranen, K M; Weingarten, M; Abers, G A; Bekins, B A; Ge, S

    2014-07-25

    Unconventional oil and gas production provides a rapidly growing energy source; however, high-production states in the United States, such as Oklahoma, face sharply rising numbers of earthquakes. Subsurface pressure data required to unequivocally link earthquakes to wastewater injection are rarely accessible. Here we use seismicity and hydrogeological models to show that fluid migration from high-rate disposal wells in Oklahoma is potentially responsible for the largest swarm. Earthquake hypocenters occur within disposal formations and upper basement, between 2- and 5-kilometer depth. The modeled fluid pressure perturbation propagates throughout the same depth range and tracks earthquakes to distances of 35 kilometers, with a triggering threshold of ~0.07 megapascals. Although thousands of disposal wells operate aseismically, four of the highest-rate wells are capable of inducing 20% of 2008 to 2013 central U.S. seismicity. Copyright © 2014, American Association for the Advancement of Science.

  19. Co-seismic Earth’s rotation change caused by the 2012 Sumatra earthquake

    Directory of Open Access Journals (Sweden)

    Xu Changyi

    2012-11-01

    Full Text Available Earthquakes heavily deform the crust in the vicinity of the fault, which leads to mass redistribution in the earth interior. Then it will produce the change of the Earth’s rotation (polar motion and length of day due to the change of Earth inertial moment. This paper adopts the elastic dislocation to compute the co-seismic polar motion and variation in length of day (LOD caused by the 2011 Sumatra earthquake. The Earth’s rotational axis shifted about 1 mas and this earthquake decreased the length of day of 1 μs, indicating the tendency of earthquakes make the Earth rounder and to pull the mass toward the centre of the Earth. The result of variation in length of day is one order of magnitude smaller than the observed results that are available. We also compared the results of three fault models and find the co-seismic change is depended on the fault model.

  20. Seismic-electromagnetic precursors of Romania's Vrancea earthquakes

    International Nuclear Information System (INIS)

    Enescu, B.D.; Enescu, C.; Constantin, A. P.

    1999-01-01

    Diagrams were plotted from electromagnetic data that were recorded at Muntele Rosu Observatory during December 1996 to January 1997, and December 1997 to September 1998. The times when Vrancea earthquakes of magnitudes M ≥ 3.9 occurred within these periods are marked on the diagrams.The parameters of the earthquakes are given in a table which also includes information on the magnetic and electric anomalies (perturbations) preceding these earthquakes. The magnetic data prove that Vrancea earthquakes are preceded by magnetic perturbations that may be regarded as their short-term precursors. Perturbations, which could likewise be seen as short-term precursors of Vrancea earthquakes, are also noticed in the electric records. Still, a number of electric data do cast a doubt on their forerunning nature. Some suggestions are made in the end of the paper on how electromagnetic research should go ahead to be of use for Vrancea earthquake prediction. (authors)

  1. Tectonic styles of future earthquakes in Italy as input data for seismic hazard

    Science.gov (United States)

    Pondrelli, S.; Meletti, C.; Rovida, A.; Visini, F.; D'Amico, V.; Pace, B.

    2017-12-01

    In a recent elaboration of a new seismogenic zonation and hazard model for Italy, we tried to understand how many indications we have on the tectonic style of future earthquake/rupture. Using all available or recomputed seismic moment tensors for relevant seismic events (Mw starting from 4.5) of the last 100 yrs, first arrival focal mechanisms for less recent earthquakes and also geological data on past activated faults, we collected a database gathering a thousands of data all over the Italian peninsula and regions around it. After several summations of seismic moment tensors, over regular grids of different dimensions and different thicknesses of the seismogenic layer, we applied the same procedure to each of the 50 area sources that were designed in the seismogenic zonation. The results for several seismic zones are very stable, e.g. along the southern Apennines we expect future earthquakes to be mostly extensional, although in the outer part of the chain strike-slip events are possible. In the Northern part of the Apennines we also expect different, opposite tectonic styles for different hypocentral depths. In several zones, characterized by a low seismic moment release, defined for the study region using 1000 yrs of catalog, the next possible tectonic style of future earthquakes is less clear. It is worth to note that for some zones the possible greatest earthquake could be not represented in the available observations. We also add to our analysis the computation of the seismic release rate, computed using a distributed completeness, identified for single great events of the historical seismic catalog for Italy. All these information layers, overlapped and compared, may be used to characterize each new seismogenic zone.

  2. Predicting the Maximum Earthquake Magnitude from Seismic Data in Israel and Its Neighboring Countries.

    Science.gov (United States)

    Last, Mark; Rabinowitz, Nitzan; Leonard, Gideon

    2016-01-01

    This paper explores several data mining and time series analysis methods for predicting the magnitude of the largest seismic event in the next year based on the previously recorded seismic events in the same region. The methods are evaluated on a catalog of 9,042 earthquake events, which took place between 01/01/1983 and 31/12/2010 in the area of Israel and its neighboring countries. The data was obtained from the Geophysical Institute of Israel. Each earthquake record in the catalog is associated with one of 33 seismic regions. The data was cleaned by removing foreshocks and aftershocks. In our study, we have focused on ten most active regions, which account for more than 80% of the total number of earthquakes in the area. The goal is to predict whether the maximum earthquake magnitude in the following year will exceed the median of maximum yearly magnitudes in the same region. Since the analyzed catalog includes only 28 years of complete data, the last five annual records of each region (referring to the years 2006-2010) are kept for testing while using the previous annual records for training. The predictive features are based on the Gutenberg-Richter Ratio as well as on some new seismic indicators based on the moving averages of the number of earthquakes in each area. The new predictive features prove to be much more useful than the indicators traditionally used in the earthquake prediction literature. The most accurate result (AUC = 0.698) is reached by the Multi-Objective Info-Fuzzy Network (M-IFN) algorithm, which takes into account the association between two target variables: the number of earthquakes and the maximum earthquake magnitude during the same year.

  3. Seismic margin analysis for Kashiwazaki Kariwa ABWR plant considering the Niigataken Chuetsu-oki earthquake

    International Nuclear Information System (INIS)

    Matsuo, Toshihiro; Nagasawa, Kazuyuki; Kawamura, Shinichi; Ueki, Takashi; Higuchi, Tomokazu; Sakaki, Isao

    2009-01-01

    Seismic Margin Analysis (SMA) study was conducted for Kashiwazaki Kariwa (KK) ABWR representative plant (unit 6). Considering that the installation behaved in a safe manner during and after the Niigataken Chuetsu-oki (NCO) Earthquake which significantly exceeded the level of the seismic input taken into account in the design of the plant, the study to find out how much margin the ABWR plant had toward the same seismic motion was conducted. In this study fragility analyses were conducted for SSCs that were included in the accident sequences and that were considered to have relatively small margin taking EPRI margin analysis method into consideration. In order to calculate plant level seismic margin Min-Max method was adopted. As the result of this study, the plant level High Confidence Low Probability of Failure (HCLPF) acceleration for unit 6 was calculated more than tripled NCO earthquake motion. (author)

  4. Double seismic zone for deep earthquakes in the izu-bonin subduction zone.

    Science.gov (United States)

    Iidaka, T; Furukawa, Y

    1994-02-25

    A double seismic zone for deep earthquakes was found in the Izu-Bonin region. An analysis of SP-converted phases confirms that the deep seismic zone consists of two layers separated by approximately 20 kilometers. Numerical modeling of the thermal structure implies that the hypocenters are located along isotherms of 500 degrees to 550 degrees C, which is consistent with the hypothesis that deep earthquakes result from the phase transition of metastable olivine to a high-pressure phase in the subducting slab.

  5. Seismological database for Banat seismic region (Romania) - Part 1: The parametric earthquake catalogue

    International Nuclear Information System (INIS)

    Oros, E.; Popa, M.; Moldovan, I. A.

    2008-01-01

    The most comprehensive seismological database for Banat seismic region (Romania) has been achieved. This paper refers to the essential characteristics of the first component of this database, namely the Parametric Earthquakes Catalogue for the Banat Seismic Region (PECBSR). PECBSR comprises 7783 crustal earthquakes (3 ≤ h ≤ 25 km) with 0.4 ≤ M i ≥ 5.6 (M i is M L , M D , M S , M W , Mm and/or mb from compiled sources) occurred in the Banat region and its surroundings between years 1443 and 2006. Different magnitude scales were converted into moment magnitude scale, Mw. The completeness of PECBSR strongly depends on the time. (authors)

  6. Seismicity Pattern Changes before the M = 4.8 Aeolian Archipelago (Italy Earthquake of August 16, 2010

    Directory of Open Access Journals (Sweden)

    Salvatore Gambino

    2014-01-01

    Full Text Available We investigated the seismicity patterns associated with an M=4.8 earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the M=4.8 earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics.

  7. Can Vrancea earthquakes be accurately predicted from unusual bio-system behavior and seismic-electromagnetic records?

    International Nuclear Information System (INIS)

    Enescu, D.; Chitaru, C.; Enescu, B.D.

    1999-01-01

    The relevance of bio-seismic research for the short-term prediction of strong Vrancea earthquakes is underscored. An unusual animal behavior before and during Vrancea earthquakes is described and illustrated in the individual case of the major earthquake of March 4, 1977. Several hypotheses to account for the uncommon behavior of bio-systems in relation to earthquakes in general and strong Vrancea earthquakes in particular are discussed in the second section. It is reminded that promising preliminary results concerning the identification of seismic-electromagnetic precursor signals have been obtained in the Vrancea seismogenic area using special, highly sensitive equipment. The need to correlate bio-seismic and seismic-electromagnetic researches is evident. Further investigations are suggested and urgent steps are proposed in order to achieve a successful short-term prediction of strong Vrancea earthquakes. (authors)

  8. Seismic Barrier Protection of Critical Infrastructure from Earthquakes

    Science.gov (United States)

    2017-05-01

    We observe that such barrier structures reduce seismic wave powers by 10 – 40 dB that would otherwise reach the foundation location. Moreover, the... structure composed of opposing boreholes or trenches to mitigate seismic waves from diffracting and traveling in the vertical plane. Computational...seismic wave propagation models suggest that air or fluid filled subsurface V- shaped muffler structures are critical to the redirection and self

  9. Research in historical earthquakes in the Korean peninsula and its circumferential regions

    Institute of Scientific and Technical Information of China (English)

    翟文杰; 吴戈; 韩绍欣

    2004-01-01

    @@ The historical earthquake data is one of the important foundations for seismic monitoring, earthquake fore-cast and seismic safety evaluation. However, the recognition of earthquake is limited by the scientific and techno-logical level. Therefore, the earthquake can only be described using perfect earthquake catalogue after the seismo-graph is invented. Before this time, the earthquake parameters were determined according to the earthquake disas-ter on the surface and the written records in history, and the earthquake level was measured using earthquake in-tensity.

  10. The earthquake/seismic risk, vulnerability and capacity profile for ...

    African Journals Online (AJOL)

    The study was carried out to understand the risks posed by earthquakes in Karonga based on roles and perception of stakeholders. Information was collected from several stakeholders who were found responding to earthquakes impacts in Karonga Town. The study found that several stakeholders, governmental and ...

  11. Why Earthquake Effects are to be Reduced Conventional seismic ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 10; Issue 11. Learning Earthquake Design and Construction – 24. How to Reduce Earthquake Effects on Buildings? C V R Murty. Classroom Volume 10 Issue 11 November 2005 pp 89-92 ...

  12. Seismic hazard in Hawaii: High rate of large earthquakes and probabilistics ground-motion maps

    Science.gov (United States)

    Klein, F.W.; Frankel, A.D.; Mueller, C.S.; Wesson, R.L.; Okubo, P.G.

    2001-01-01

    The seismic hazard and earthquake occurrence rates in Hawaii are locally as high as that near the most hazardous faults elsewhere in the United States. We have generated maps of peak ground acceleration (PGA) and spectral acceleration (SA) (at 0.2, 0.3 and 1.0 sec, 5% critical damping) at 2% and 10% exceedance probabilities in 50 years. The highest hazard is on the south side of Hawaii Island, as indicated by the MI 7.0, MS 7.2, and MI 7.9 earthquakes, which occurred there since 1868. Probabilistic values of horizontal PGA (2% in 50 years) on Hawaii's south coast exceed 1.75g. Because some large earthquake aftershock zones and the geometry of flank blocks slipping on subhorizontal decollement faults are known, we use a combination of spatially uniform sources in active flank blocks and smoothed seismicity in other areas to model seismicity. Rates of earthquakes are derived from magnitude distributions of the modem (1959-1997) catalog of the Hawaiian Volcano Observatory's seismic network supplemented by the historic (1868-1959) catalog. Modern magnitudes are ML measured on a Wood-Anderson seismograph or MS. Historic magnitudes may add ML measured on a Milne-Shaw or Bosch-Omori seismograph or MI derived from calibrated areas of MM intensities. Active flank areas, which by far account for the highest hazard, are characterized by distributions with b slopes of about 1.0 below M 5.0 and about 0.6 above M 5.0. The kinked distribution means that large earthquake rates would be grossly under-estimated by extrapolating small earthquake rates, and that longer catalogs are essential for estimating or verifying the rates of large earthquakes. Flank earthquakes thus follow a semicharacteristic model, which is a combination of background seismicity and an excess number of large earthquakes. Flank earthquakes are geometrically confined to rupture zones on the volcano flanks by barriers such as rift zones and the seaward edge of the volcano, which may be expressed by a magnitude

  13. Studying geodesy and earthquake hazard in and around the New Madrid Seismic Zone

    Science.gov (United States)

    Boyd, Oliver Salz; Magistrale, Harold

    2011-01-01

    Workshop on New Madrid Geodesy and the Challenges of Understanding Intraplate Earthquakes; Norwood, Massachusetts, 4 March 2011 Twenty-six researchers gathered for a workshop sponsored by the U.S. Geological Survey (USGS) and FM Global to discuss geodesy in and around the New Madrid seismic zone (NMSZ) and its relation to earthquake hazards. The group addressed the challenge of reconciling current geodetic measurements, which show low present-day surface strain rates, with paleoseismic evidence of recent, relatively frequent, major earthquakes in the region. The workshop presentations and conclusions will be available in a forthcoming USGS open-file report (http://pubs.usgs.gov).

  14. Urban MEMS based seismic network for post-earthquakes rapid disaster assessment

    Science.gov (United States)

    D'Alessandro, Antonino; Luzio, Dario; D'Anna, Giuseppe

    2014-05-01

    Life losses following disastrous earthquake depends mainly by the building vulnerability, intensity of shaking and timeliness of rescue operations. In recent decades, the increase in population and industrial density has significantly increased the exposure to earthquakes of urban areas. The potential impact of a strong earthquake on a town center can be reduced by timely and correct actions of the emergency management centers. A real time urban seismic network can drastically reduce casualties immediately following a strong earthquake, by timely providing information about the distribution of the ground shaking level. Emergency management centers, with functions in the immediate post-earthquake period, could be use this information to allocate and prioritize resources to minimize loss of human life. However, due to the high charges of the seismological instrumentation, the realization of an urban seismic network, which may allow reducing the rate of fatalities, has not been achieved. Recent technological developments in MEMS (Micro Electro-Mechanical Systems) technology could allow today the realization of a high-density urban seismic network for post-earthquakes rapid disaster assessment, suitable for the earthquake effects mitigation. In the 1990s, MEMS accelerometers revolutionized the automotive-airbag system industry and are today widely used in laptops, games controllers and mobile phones. Due to their great commercial successes, the research into and development of MEMS accelerometers are actively pursued around the world. Nowadays, the sensitivity and dynamics of these sensors are such to allow accurate recording of earthquakes with moderate to strong magnitude. Due to their low cost and small size, the MEMS accelerometers may be employed for the realization of high-density seismic networks. The MEMS accelerometers could be installed inside sensitive places (high vulnerability and exposure), such as schools, hospitals, public buildings and places of

  15. Spatial organization of foreshocks as a tool to forecast large earthquakes.

    Science.gov (United States)

    Lippiello, E; Marzocchi, W; de Arcangelis, L; Godano, C

    2012-01-01

    An increase in the number of smaller magnitude events, retrospectively named foreshocks, is often observed before large earthquakes. We show that the linear density probability of earthquakes occurring before and after small or intermediate mainshocks displays a symmetrical behavior, indicating that the size of the area fractured during the mainshock is encoded in the foreshock spatial organization. This observation can be used to discriminate spatial clustering due to foreshocks from the one induced by aftershocks and is implemented in an alarm-based model to forecast m > 6 earthquakes. A retrospective study of the last 19 years Southern California catalog shows that the daily occurrence probability presents isolated peaks closely located in time and space to the epicenters of five of the six m > 6 earthquakes. We find daily probabilities as high as 25% (in cells of size 0.04 × 0.04deg(2)), with significant probability gains with respect to standard models.

  16. Seismic experience in power and industrial facilities as it relates to small magnitude earthquakes

    International Nuclear Information System (INIS)

    Swan, S.W.; Horstman, N.G.

    1987-01-01

    The data base on the performance of power and industrial facilities in small magnitude earthquakes (M = 4.0 - 5.5) is potentially very large. In California alone many earthquakes in this magnitude range occur every year, often near industrial areas. In 1986 for example, in northern California alone, there were 76 earthquakes between Richter magnitude 4.0 and 5.5. Experience has shown that the effects of small magnitude earthquakes are seldom significant to well-engineered facilities. (The term well-engineered is here defined to include most modern industrial installations, as well as power plants and substations.) Therefore detailed investigations of small magnitude earthquakes are normally not considered worthwhile. The purpose of this paper is to review the tendency toward seismic damage of equipment installations representative of nuclear power plant safety systems. Estimates are made of the thresholds of seismic damage to certain types of equipment in terms of conventional means of measuring the damage potential of an earthquake. The objective is to define thresholds of damage that can be correlated with Richter magnitude. In this manner an earthquake magnitude might be chosen below which damage to nuclear plant safety systems is not considered credible

  17. A model of seismic focus and related statistical distributions of earthquakes

    International Nuclear Information System (INIS)

    Apostol, Bogdan-Felix

    2006-01-01

    A growth model for accumulating seismic energy in a localized seismic focus is described, which introduces a fractional parameter r on geometrical grounds. The model is employed for deriving a power-type law for the statistical distribution in energy, where the parameter r contributes to the exponent, as well as corresponding time and magnitude distributions for earthquakes. The accompanying seismic activity of foreshocks and aftershocks is discussed in connection with this approach, as based on Omori distributions, and the rate of released energy is derived

  18. The smart cluster method. Adaptive earthquake cluster identification and analysis in strong seismic regions

    Science.gov (United States)

    Schaefer, Andreas M.; Daniell, James E.; Wenzel, Friedemann

    2017-07-01

    Earthquake clustering is an essential part of almost any statistical analysis of spatial and temporal properties of seismic activity. The nature of earthquake clusters and subsequent declustering of earthquake catalogues plays a crucial role in determining the magnitude-dependent earthquake return period and its respective spatial variation for probabilistic seismic hazard assessment. This study introduces the Smart Cluster Method (SCM), a new methodology to identify earthquake clusters, which uses an adaptive point process for spatio-temporal cluster identification. It utilises the magnitude-dependent spatio-temporal earthquake density to adjust the search properties, subsequently analyses the identified clusters to determine directional variation and adjusts its search space with respect to directional properties. In the case of rapid subsequent ruptures like the 1992 Landers sequence or the 2010-2011 Darfield-Christchurch sequence, a reclassification procedure is applied to disassemble subsequent ruptures using near-field searches, nearest neighbour classification and temporal splitting. The method is capable of identifying and classifying earthquake clusters in space and time. It has been tested and validated using earthquake data from California and New Zealand. A total of more than 1500 clusters have been found in both regions since 1980 with M m i n = 2.0. Utilising the knowledge of cluster classification, the method has been adjusted to provide an earthquake declustering algorithm, which has been compared to existing methods. Its performance is comparable to established methodologies. The analysis of earthquake clustering statistics lead to various new and updated correlation functions, e.g. for ratios between mainshock and strongest aftershock and general aftershock activity metrics.

  19. The typical seismic behavior in the vicinity of a large earthquake

    Science.gov (United States)

    Rodkin, M. V.; Tikhonov, I. N.

    2016-10-01

    The Global Centroid Moment Tensor catalog (GCMT) was used to construct the spatio-temporal generalized vicinity of a large earthquake (GVLE) and to investigate the behavior of seismicity in GVLE. The vicinity is made of earthquakes falling into the zone of influence of a large number (100, 300, or 1000) of largest earthquakes. The GVLE construction aims at enlarging the available statistics, diminishing a strong random component, and revealing typical features of pre- and post-shock seismic activity in more detail. As a result of the GVLE construction, the character of fore- and aftershock cascades was examined in more detail than was possible without of the use of the GVLE approach. As well, several anomalies in the behavior exhibited by a variety of earthquake parameters were identified. The amplitudes of all these anomalies increase with the approaching time of the generalized large earthquake (GLE) as the logarithm of the time interval from the GLE occurrence. Most of the discussed anomalies agree with common features well expected in the evolution of instability. In addition to these common type precursors, one earthquake-specific precursor was found. The decrease in mean earthquake depth presumably occurring in a smaller GVLE probably provides evidence of a deep fluid being involved in the process. The typical features in the evolution of shear instability as revealed in GVLE agree with results obtained in laboratory studies of acoustic emission (AE). The majority of the anomalies in earthquake parameters appear to have a secondary character, largely connected with an increase in mean magnitude and decreasing fraction of moderate size events (mw5.0-6.0) in the immediate GLE vicinity. This deficit of moderate size events could hardly be caused entirely by their incomplete reporting and can presumably reflect some features in the evolution of seismic instability.

  20. Mechanism of post-seismic floods after the Wenchuan earthquake in ...

    Indian Academy of Sciences (India)

    Ding Hairong

    2017-10-06

    Oct 6, 2017 ... development of devastating post-seismic floods. Thirdly, the ... The segment from. Dujiangyan city to the upstream source of the river is known .... trends downward in the region. ..... quake: A case study in the upper reaches of the Min River,. Sichuan .... the digital strong earthquake network in Sichuan and.

  1. Induced seismicity provides insight into why earthquake ruptures stop

    KAUST Repository

    Galis, Martin; Ampuero, Jean Paul; Mai, Paul Martin; Cappa, Fré dé ric

    2017-01-01

    the perturbed area and distinguishes self-arrested from runaway ruptures. We develop a theoretical scaling relation between the largest magnitude of self-arrested earthquakes and the injected volume and find it consistent with observed maximum magnitudes

  2. Seismic response of the EBR-II to the Mt. Borah earthquake

    International Nuclear Information System (INIS)

    Gale, J.G.; Lehto, W.K.

    1985-01-01

    On October 28, 1983, an earthquake of magnitude 7.3 occurred in the mountains of central Idaho at a distance of 114-km from the ANL-West site. The earthquake tripped the seismic sensors in the EBR-II reactor shutdown system causing a reactor scram. Visual and operability checks of structures, components, and systems showed no indication of damage or system abnormalities and reactor restart was initiated. As a result of the earthquake, questions arose as to the magnitude of the actual stress levels in critical components and what value of ground acceleration could be experienced without damage to reactor structures. EBR-II was designed prior to implementation of present day requirements for seismic qualification and appropriate analyses had not been conducted. A lumped-mass, finite element model of the primary tank, support structure, and the reactor was generated and analyzed using the response spectrum technique. The analysis showed that the stress levels in the primary tank system were very low during the Mount Borah earthquake and that the system could experience seismic loadings three to four times those of the Mount Borah earthquake without exceeding yield stresses in any of the components

  3. Minimum of the order parameter fluctuations of seismicity before major earthquakes in Japan.

    Science.gov (United States)

    Sarlis, Nicholas V; Skordas, Efthimios S; Varotsos, Panayiotis A; Nagao, Toshiyasu; Kamogawa, Masashi; Tanaka, Haruo; Uyeda, Seiya

    2013-08-20

    It has been shown that some dynamic features hidden in the time series of complex systems can be uncovered if we analyze them in a time domain called natural time χ. The order parameter of seismicity introduced in this time domain is the variance of χ weighted for normalized energy of each earthquake. Here, we analyze the Japan seismic catalog in natural time from January 1, 1984 to March 11, 2011, the day of the M9 Tohoku earthquake, by considering a sliding natural time window of fixed length comprised of the number of events that would occur in a few months. We find that the fluctuations of the order parameter of seismicity exhibit distinct minima a few months before all of the shallow earthquakes of magnitude 7.6 or larger that occurred during this 27-y period in the Japanese area. Among the minima, the minimum before the M9 Tohoku earthquake was the deepest. It appears that there are two kinds of minima, namely precursory and nonprecursory, to large earthquakes.

  4. Triggered seismicity and deformation between the Landers, California, and Little Skull Mountain, Nevada, earthquakes

    Science.gov (United States)

    Bodin, Paul; Gomberg, Joan

    1994-01-01

    This article presents evidence for the channeling of strain energy released by the Ms = 7.4 Landers, California, earthquake within the eastern California shear zone (ECSZ). We document an increase in seismicity levels during the 22-hr period starting with the Landers earthquake and culminating 22 hr later with the Ms = 5.4 Little Skull Mountain (LSM), Nevada, earthquake. We evaluate the completeness of regional seismicity catalogs during this period and find that the continuity of post-Landers strain release within the ECSZ is even more pronounced than is evident from the catalog data. We hypothesize that regional-scale connectivity of faults within the ECSZ and LSM region is a critical ingredient in the unprecedented scale and distribution of remotely triggered earthquakes and geodetically manifest strain changes that followed the Landers earthquake. The viability of static strain changes as triggering agents is tested using numerical models. Modeling results illustrate that regional-scale fault connectivity can increase the static strain changes by approximately an order of magnitude at distances of at least 280 km, the distance between the Landers and LSM epicenters. This is possible for models that include both a network of connected faults that slip “sympathetically” and realistic levels of tectonic prestrain. Alternatively, if dynamic strains are a more significant triggering agent than static strains, ECSZ structure may still be important in determining the distribution of triggered seismic and aseismic deformation.

  5. Landslide maps and seismic noise: Rockmass weakening caused by shallow earthquakes

    Science.gov (United States)

    Uchida, Tara; Marc, Odin; Sens-Schönfelder, Christoph; Sawazaki, Kaoru; Hobiger, Manuel; Hovius, Niels

    2015-04-01

    Some studies have suggested that the shaking and deformation associated with earthquake would result in a temporary increased hillslope erodibility. However very few data have been able to clarify such effect. We present integrated geomorphic data constraining an elevated landslide rate following 4 continental shallow earthquakes, the Mw 6.9 Finisterre (1993), the Mw 7.6 ChiChi (1999), the Mw 6.6 Niigata (2004) and the Mw 6.8 Iwate-Miyagi (2008) earthquakes. We constrained the magnitude, the recovery time and somewhat the mechanism at the source of this higher landslide risk. We provide some evidences excluding aftershocks or rain forcing intensity as possible mechanism and leaving subsurface weakening as the most likely. The landslide data suggest that this ground strength weakening is not limited to the soil cover but also affect the shallow bedrock. Additionally, we used ambient noise autocorrelation techniques to monitor shallow subsurface seismic velocity within the epicentral area of three of those earthquakes. For most stations we observe a velocity drop followed by a recovery processes of several years in fair agreement with the recovery time estimated based on landslide observation. Thus a common processes could alter the strength of the first 10m of soil/rock and simultaneously drive the landslide rate increase and the seismic velocity drop. The ability to firmly demonstrate this link require additional constraints on the seismic signal interpretation but would provide a very useful tool for post-earthquake risk managment.

  6. First-passage Probability Estimation of an Earthquake Response of Seismically Isolated Containment Buildings

    International Nuclear Information System (INIS)

    Hahm, Dae-Gi; Park, Kwan-Soon; Koh, Hyun-Moo

    2008-01-01

    The awareness of a seismic hazard and risk is being increased rapidly according to the frequent occurrences of the huge earthquakes such as the 2008 Sichuan earthquake which caused about 70,000 confirmed casualties and a 20 billion U.S. dollars economic loss. Since an earthquake load contains various uncertainties naturally, the safety of a structural system under an earthquake excitation has been assessed by probabilistic approaches. In many structural applications for a probabilistic safety assessment, it is often regarded that the failure of a system will occur when the response of the structure firstly crosses the limit barrier within a specified interval of time. The determination of such a failure probability is usually called the 'first-passage problem' and has been extensively studied during the last few decades. However, especially for the structures which show a significant nonlinear dynamic behavior, an effective and accurate method for the estimation of such a failure probability is not fully established yet. In this study, we presented a new approach to evaluate the first-passage probability of an earthquake response of seismically isolated structures. The proposed method is applied to the seismic isolation system for the containment buildings of a nuclear power plant. From the numerical example, we verified that the proposed method shows accurate results with more efficient computational efforts compared to the conventional approaches

  7. Earthquakes and forecast reliability: thermoactivation and mesomechanics of the focal zone

    Science.gov (United States)

    Kalinnikov, I. I.; Manukin, A. B.; Matyunin, V. P.

    2017-06-01

    According to our data, the involvement of the fundamental laws of physics, in particular, consideration of an earthquake as a particular macroprocess with a peak together with the thermofluctuational activation of mechanical stresses in some environments, makes it possible to move beyond the traditional idea of the issue of earthquake prediction. Many formal parameters of statistical processing of the geophysical data can be provided with a physical sense related to the mesomechanics of structural changes in a stressed solid body. Measures for improving the efficiency of observations and their mathematical processing to solve the forecasting issues have been specified.

  8. Probabilistic seismic hazard assessments of Sabah, east Malaysia: accounting for local earthquake activity near Ranau

    Science.gov (United States)

    Khalil, Amin E.; Abir, Ismail A.; Ginsos, Hanteh; Abdel Hafiez, Hesham E.; Khan, Sohail

    2018-02-01

    Sabah state in eastern Malaysia, unlike most of the other Malaysian states, is characterized by common seismological activity; generally an earthquake of moderate magnitude is experienced at an interval of roughly every 20 years, originating mainly from two major sources, either a local source (e.g. Ranau and Lahad Dato) or a regional source (e.g. Kalimantan and South Philippines subductions). The seismicity map of Sabah shows the presence of two zones of distinctive seismicity, these zones are near Ranau (near Kota Kinabalu) and Lahad Datu in the southeast of Sabah. The seismicity record of Ranau begins in 1991, according to the international seismicity bulletins (e.g. United States Geological Survey and the International Seismological Center), and this short record is not sufficient for seismic source characterization. Fortunately, active Quaternary fault systems are delineated in the area. Henceforth, the seismicity of the area is thus determined as line sources referring to these faults. Two main fault systems are believed to be the source of such activities; namely, the Mensaban fault zone and the Crocker fault zone in addition to some other faults in their vicinity. Seismic hazard assessments became a very important and needed study for the extensive developing projects in Sabah especially with the presence of earthquake activities. Probabilistic seismic hazard assessments are adopted for the present work since it can provide the probability of various ground motion levels during expected from future large earthquakes. The output results are presented in terms of spectral acceleration curves and uniform hazard curves for periods of 500, 1000 and 2500 years. Since this is the first time that a complete hazard study has been done for the area, the output will be a base and standard for any future strategic plans in the area.

  9. The fine structure of the dynamics of seismicity before earthquakes in the area of Reggio Emilia (Northern Italy

    Directory of Open Access Journals (Sweden)

    Y. Tyupki

    1999-06-01

    Full Text Available We present the results of studies of seismicity in the Reggio Emilia area (Northern Italy. The Istituto Nazionale di Geofisica instrumental earthquake catalogue (1975-1996 reported about three moderate-size earthquakes with M ³ 4.5 that occurred in this area (November 1983, May 1987, October 1996. The RTL prognostic parameter proposed by Sobolev and Tyupkin (1996a was used for analysis. This parameter is designed in such a way that a seismic quiescence produces negative anomaly of the RTL parameter in comparison to its perennial background level and an activation of seismicity initiates the growth of its value. The RTL prognostic parameter indicates that all three earthquakes are preceded by activation of the seismicity. The interval between the commencement of the activation identified by RTL parameter and the event itself was about one year for the 1987 and 1996 earthquakes, and about three months for the 1983 earthquake.

  10. Earthquake recurrence and magnitude and seismic deformation of the northwestern Okhotsk plate, northeast Russia

    Science.gov (United States)

    Hindle, D.; Mackey, K.

    2011-02-01

    Recorded seismicity from the northwestern Okhotsk plate, northeast Asia, is currently insufficient to account for the predicted slip rates along its boundaries due to plate tectonics. However, the magnitude-frequency relationship for earthquakes from the region suggests that larger earthquakes are possible in the future and that events of ˜Mw 7.5 which should occur every ˜100-350 years would account for almost all the slip of the plate along its boundaries due to Eurasia-North America convergence. We use models for seismic slip distribution along the bounding faults of Okhotsk to conclude that relatively little aseismic strain release is occurring and that larger future earthquakes are likely in the region. Our models broadly support the idea of a single Okhotsk plate, with the large majority of tectonic strain released along its boundaries.

  11. Opto-mechanical lab-on-fibre seismic sensors detected the Norcia earthquake.

    Science.gov (United States)

    Pisco, Marco; Bruno, Francesco Antonio; Galluzzo, Danilo; Nardone, Lucia; Gruca, Grzegorz; Rijnveld, Niek; Bianco, Francesca; Cutolo, Antonello; Cusano, Andrea

    2018-04-27

    We have designed and developed lab-on-fibre seismic sensors containing a micro-opto-mechanical cavity on the fibre tip. The mechanical cavity is designed as a double cantilever suspended on the fibre end facet and connected to a proof mass to tune its response. Ground acceleration leads to displacement of the cavity length, which in turn can be remotely detected using an interferometric interrogation technique. After the sensors characterization, an experimental validation was conducted at the Italian National Institute of Geophysics and Volcanology (INGV), which is responsible for seismic surveillance over the Italian country. The fabricated sensors have been continuously used for long periods to demonstrate their effectiveness as seismic accelerometer sensors. During the tests, fibre optic seismic accelerometers clearly detected the seismic sequence that culminated in the severe Mw6.5 Norcia earthquake that struck central Italy on October 30, 2016. The seismic data provided by the optical sensors were analysed by specialists at the INGV. The wave traces were compared with state-of-the-art traditional sensors typically incorporated into the INGV seismic networks. The comparison verifies the high fidelity of the optical sensors in seismic wave detection, indicating their suitability for a novel class of seismic sensors to be employed in practical scenarios.

  12. 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

  13. Characterizing potentially induced earthquake rate changes in the Brawley Seismic Zone, southern California

    Science.gov (United States)

    Llenos, Andrea L.; Michael, Andrew J.

    2016-01-01

    The Brawley seismic zone (BSZ), in the Salton trough of southern California, has a history of earthquake swarms and geothermal energy exploitation. Some earthquake rate changes may have been induced by fluid extraction and injection activity at local geothermal fields, particularly at the North Brawley Geothermal Field (NBGF) and at the Salton Sea Geothermal Field (SSGF). We explore this issue by examining earthquake rate changes and interevent distance distributions in these fields. In Oklahoma and Arkansas, where considerable wastewater injection occurs, increases in background seismicity rate and aftershock productivity and decreases in interevent distance were indicative of fluid‐injection‐induced seismicity. Here, we test if similar changes occur that may be associated with fluid injection and extraction in geothermal areas. We use stochastic epidemic‐type aftershock sequence models to detect changes in the underlying seismogenic processes, shown by statistically significant changes in the model parameters. The most robust model changes in the SSGF roughly occur when large changes in net fluid production occur, but a similar correlation is not seen in the NBGF. Also, although both background seismicity rate and aftershock productivity increased for fluid‐injection‐induced earthquake rate changes in Oklahoma and Arkansas, the background rate increases significantly in the BSZ only, roughly corresponding with net fluid production rate increases. Moreover, in both fields the interevent spacing does not change significantly during active energy projects. This suggests that, although geothermal field activities in a tectonically active region may not significantly change the physics of earthquake interactions, earthquake rates may still be driven by fluid injection or extraction rates, particularly in the SSGF.

  14. Measuring co-seismic deformation of the Sichuan earthquake by satellite differential INSAR

    Science.gov (United States)

    Zhang, Yonghong; Gong, Wenyu; Zhang, Jixian

    2008-12-01

    The Sichuan Earthquake, occurred on May 12, 2008, is the strongest earthquake to hit China since the 1976 Tangshan earthquake. The earthquake had a magnitude of M 8.0, and caused surface deformation greater than 3 meters. This paper presents the research work of measuring the co-seismic deformations of the earthquake with satellite differential interferometric SAR technique. Four L-band SAR images were used to form the interferogram with 2 pre- scenes imaged on Feb 17, 2008 and 2 post- scenes on May 19, 2008. The Digital Elevation Models extracted from 1:50,000-scale national geo-spatial database were used to remove the topographic contribution and form a differential interferogram. The interferogram presents very high coherence in most areas, although the pre- and post- images were acquired with time interval of 92 days. This indicates that the L-band PALSAR sensor is very powerful for interferometry applications. The baseline error is regarded as the main phase error source in the differential interferogram. Due to the difficulties of doing field works immediately after the earthquake, only one deformation measurement recorded by a permanent GPS station is obtained for this research. An approximation method is proposed to eliminate the orbital phase error with one control point. The derived deformation map shows similar spatial pattern and deformation magnitude compared with deformation field generated by seismic inversion method.

  15. The MCE (Maximum Credible Earthquake) - an approach to reduction of seismic risk

    International Nuclear Information System (INIS)

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

    1979-01-01

    It is the responsibility of the Regulatory Body (in Canada, the AECB) to ensure that radiological risks resulting from the effects of earthquakes on nuclear facilities, do not exceed acceptable levels. In simplified numerical terms this means that the frequency of an unacceptable radiation dose must be kept below 10 -6 per annum. Unfortunately, seismic events fall into the class of external events which are not well defined at these low frequency levels. Thus, design earthquakes have been chosen, at the 10 -3 - 10 -4 frequency level, a level commensurate with the limits of statistical data. There exists, therefore, a need to define an additional level of earthquake. A seismic design explicitly and implicitly recognizes three levels of earthquake loading; one comfortably below yield, one at or about yield, and one at ultimate. The ultimate level earthquake, contrary to the first two, has been implicitly addressed by conscientious designers by choosing systems, materials and details compatible with postulated dynamic forces. It is the purpose of this paper to discuss the regulatory specifications required to quantify this third level, or Maximum Credible Earthquake (MCE). (orig.)

  16. Stress development in heterogenetic lithosphere: Insights into earthquake processes in the New Madrid Seismic Zone

    Science.gov (United States)

    Zhan, Yan; Hou, Guiting; Kusky, Timothy; Gregg, Patricia M.

    2016-03-01

    The New Madrid Seismic Zone (NMSZ) in the Midwestern United States was the site of several major M 6.8-8 earthquakes in 1811-1812, and remains seismically active. Although this region has been investigated extensively, the ultimate controls on earthquake initiation and the duration of the seismicity remain unclear. In this study, we develop a finite element model for the Central United States to conduct a series of numerical experiments with the goal of determining the impact of heterogeneity in the upper crust, the lower crust, and the mantle on earthquake nucleation and rupture processes. Regional seismic tomography data (CITE) are utilized to infer the viscosity structure of the lithosphere which provide an important input to the numerical models. Results indicate that when differential stresses build in the Central United States, the stresses accumulating beneath the Reelfoot Rift in the NMSZ are highly concentrated, whereas the stresses below the geologically similar Midcontinent Rift System are comparatively low. The numerical observations coincide with the observed distribution of seismicity throughout the region. By comparing the numerical results with three reference models, we argue that an extensive mantle low velocity zone beneath the NMSZ produces differential stress localization in the layers above. Furthermore, the relatively strong crust in this region, exhibited by high seismic velocities, enables the elevated stress to extend to the base of the ancient rift system, reactivating fossil rifting faults and therefore triggering earthquakes. These results show that, if boundary displacements are significant, the NMSZ is able to localize tectonic stresses, which may be released when faults close to failure are triggered by external processes such as melting of the Laurentide ice sheet or rapid river incision.

  17. A preliminary regional assessment of earthquake-induced landslide susceptibility for Vrancea Seismic Region

    Science.gov (United States)

    Micu, Mihai; Balteanu, Dan; Ionescu, Constantin; Havenith, Hans; Radulian, Mircea; van Westen, Cees; Damen, Michiel; Jurchescu, Marta

    2015-04-01

    In seismically-active regions, earthquakes may trigger landslides enhancing the short-to-long term slope denudation and sediment delivery and conditioning the general landscape evolution. Co-seismic slope failures present in general a low frequency - high magnitude pattern which should be addressed accordingly by landslide hazard assessment, with respect to the generally more frequent precipitation-triggered landslides. The Vrancea Seismic Region, corresponding to the curvature sector of the Eastern Romanian Carpathians, represents the most active sub-crustal (focal depth > 50 km) earthquake province of Europe. It represents the main seismic energy source throughout Romania with significant transboundary effects recorded as far as Ukraine and Bulgaria. During the last 300 years, the region featured 14 earthquakes with M>7, among which seven events with magnitude above 7.5 and three between 7.7 and 7.9. Apart from the direct damages, the Vrancea earthquakes are also responsible for causing numerous other geohazards, such as ground fracturing, groundwater level disturbances and possible deep-seated landslide occurrences (rock slumps, rock-block slides, rock falls, rock avalanches). The older deep-seated landslides (assumed to have been) triggered by earthquakes usually affect the entire slope profile. They often formed landslide dams strongly influencing the river morphology and representing potential threats (through flash-floods) in case of lake outburst. Despite the large potential of this research issue, the correlation between the region's seismotectonic context and landslide predisposing factors has not yet been entirely understood. Presently, there is a lack of information provided by the geohazards databases of Vrancea that does not allow us to outline the seismic influence on the triggering of slope failures in this region. We only know that the morphology of numerous large, deep-seated and dormant landslides (which can possibly be reactivated in future

  18. Recent Earthquakes Mark the Onset of Induced Seismicity in Northeastern Pennsylvania

    Science.gov (United States)

    Martone, P.; Nikulin, A.; Pietras, J.

    2017-12-01

    The link between induced seismicity and injection of hydraulic fracturing wastewater has largely been accepted and corroborated through case studies in Colorado, Arkansas, Texas, and Oklahoma. To date, induced seismicity has largely impacted hydrocarbon-producing regions in the Central United States, while the seismic response in Eastern states, like Pennsylvania, has been relatively muted. In recent years, Pennsylvania exponentially increased hydrocarbon production from the Marcellus and Utica Shales and our results indicate that this activity has triggered an onset of induced seismicity in areas of the state where no previous seismic activity was reported. Three recent earthquakes in Northeastern Pennsylvania directly correlate to hydraulic fracturing activity, though USGS NEIC earthquake catalog locations have vertical errors up to 31km. We present signal analysis results of recorded waveforms of the three identified events and results of a high-precision relocation effort and improvements to the regional velocity model aimed at constraining the horizontal and vertical error in hypocenter position. We show that at least one event is positioned directly along the wellbore track of an active well and correlate its timing to the hydraulic fracturing schedule. Results show that in the absence of wastewater disposal in this area, it is possible to confidently make the connection between the hydraulic fracturing process and induced seismicity.

  19. Romanian crustal earthquake sequences: evidence for space and time clustering in correlation with seismic source properties

    International Nuclear Information System (INIS)

    Popescu, E.; Popa, M.; Radulian, M.

    2002-01-01

    The study of seismic sequences is important from both scientific point of view, and its socio-economical impact on human society. In this paper we analyze the crustal earthquake sequences in correlation with the seismogenic zones delimited on the Romanian territory using geological and tectonic information available. We consider on one hand the sequences typical for the Carpathians foreland region (Ramnicu Sarat, Vrancioaia and Sinaia seismic zones), which are associated with the Vrancea subduction process and, on the other hand the sequences typical for the contact between the Pannonian Basin and Carpathians orogen (Banat seismic zone). To analyze the seismicity and source properties, we applied the fractal statistics and relative methods such as spectral ratio and deconvolution with the empirical Green's functions. On the basis of the retrieved source parameters for small and moderate size events the scaling relations for the characteristic properties of the seismic source are estimated. The scaling and earthquake clustering properties are correlated with the geological and rheological properties of the studied seismic areas. (authors)

  20. Effects of Strike-Slip Fault Segmentation on Earthquake Energy and Seismic Hazard

    Science.gov (United States)

    Madden, E. H.; Cooke, M. L.; Savage, H. M.; McBeck, J.

    2014-12-01

    Many major strike-slip faults are segmented along strike, including those along plate boundaries in California and Turkey. Failure of distinct fault segments at depth may be the source of multiple pulses of seismic radiation observed for single earthquakes. However, how and when segmentation affects fault behavior and energy release is the basis of many outstanding questions related to the physics of faulting and seismic hazard. These include the probability for a single earthquake to rupture multiple fault segments and the effects of segmentation on earthquake magnitude, radiated seismic energy, and ground motions. Using numerical models, we quantify components of the earthquake energy budget, including the tectonic work acting externally on the system, the energy of internal rock strain, the energy required to overcome fault strength and initiate slip, the energy required to overcome frictional resistance during slip, and the radiated seismic energy. We compare the energy budgets of systems of two en echelon fault segments with various spacing that include both releasing and restraining steps. First, we allow the fault segments to fail simultaneously and capture the effects of segmentation geometry on the earthquake energy budget and on the efficiency with which applied displacement is accommodated. Assuming that higher efficiency correlates with higher probability for a single, larger earthquake, this approach has utility for assessing the seismic hazard of segmented faults. Second, we nucleate slip along a weak portion of one fault segment and let the quasi-static rupture propagate across the system. Allowing fractures to form near faults in these models shows that damage develops within releasing steps and promotes slip along the second fault, while damage develops outside of restraining steps and can prohibit slip along the second fault. Work is consumed in both the propagation of and frictional slip along these new fractures, impacting the energy available

  1. Multi-Parameter Observation and Detection of Pre-Earthquake Signals in Seismically Active Areas

    Science.gov (United States)

    Ouzounov, D.; Pulinets, S.; Parrot, M.; Liu, J. Y.; Hattori, K.; Kafatos, M.; Taylor, P.

    2012-01-01

    The recent large earthquakes (M9.0 Tohoku, 03/2011; M7.0 Haiti, 01/2010; M6.7 L Aquila, 04/2008; and M7.9 Wenchuan 05/2008) have renewed interest in pre-anomalous seismic signals associated with them. Recent workshops (DEMETER 2006, 2011 and VESTO 2009 ) have shown that there were precursory atmospheric /ionospheric signals observed in space prior to these events. Our initial results indicate that no single pre-earthquake observation (seismic, magnetic field, electric field, thermal infrared [TIR], or GPS/TEC) can provide a consistent and successful global scale early warning. This is most likely due to complexity and chaotic nature of earthquakes and the limitation in existing ground (temporal/spatial) and global satellite observations. In this study we analyze preseismic temporal and spatial variations (gas/radon counting rate, atmospheric temperature and humidity change, long-wave radiation transitions and ionospheric electron density/plasma variations) which we propose occur before the onset of major earthquakes:. We propose an Integrated Space -- Terrestrial Framework (ISTF), as a different approach for revealing pre-earthquake phenomena in seismically active areas. ISTF is a sensor web of a coordinated observation infrastructure employing multiple sensors that are distributed on one or more platforms; data from satellite sensors (Terra, Aqua, POES, DEMETER and others) and ground observations, e.g., Global Positioning System, Total Electron Content (GPS/TEC). As a theoretical guide we use the Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) model to explain the generation of multiple earthquake precursors. Using our methodology, we evaluated retrospectively the signals preceding the most devastated earthquakes during 2005-2011. We observed a correlation between both atmospheric and ionospheric anomalies preceding most of these earthquakes. The second phase of our validation include systematic retrospective analysis for more than 100 major earthquakes (M>5

  2. Crustal structure and Seismic Hazard studies in Nigeria from ambient noise and earthquakes

    Science.gov (United States)

    Kadiri, U. A.

    2016-12-01

    The crust, upper Mantle and seismic hazard studies have been carried out in Nigeria using noise and earthquake data. The data were acquired from stations in Nigeria and international Agencies. Firstly, known depths of sediments in the Lower Benue Trough (LBT) were collected from wells; Resonance frequency (Fo) and average shear-wave velocities (Vs) were then computed using Matlab. Secondly, average velocities were estimated from noise cross-correlation along seismic stations. Thirdly, the moho depths beneath Ife, Kaduna and Nsukka stations were estimated, as well as Vp/Vs ratio using 2009 earthquake with epicenter in Nigeria. Finally, Statistical and Probabilistic Seismic Hazard Assessment (PSHA) were used to compute seismic hazard parameters in Nigeria and its surroundings. The results showed that, soils on the LBT with average shear wave velocity of about 5684m/s would experience more amplification in case of an earthquake, compared to the basement complex in Nigeria. The Vs beneath the seismic stations in Nigeria were also estimated as 288m/s, 1019m/s, 940.6m/s and 255.02m/s in Ife, Nsukka, Awka, and Abakaliki respectively. The average velocity along the station paths was 4.5km/secs, and the Vp, Vs for depths 100-500km profile in parts of South West Nigeria increased from about 5.83-6.42Km/sec and 3.48-6.31km/s respectively with Vp/Vs ratio decreasing from 1.68 to 1.02. Statistical analysis revealed a trend of increasing earthquake occurrence along the Mid-Atlantic Ridge and tending to West African region. The analysis of PSHA shows the likelihood of earthquakes with different magnitudes occurring in Nigeria and other parts West Africa in future. This work is aimed at addressing critical issues regarding sites effect characterization, improved earthquake location and robust seismic hazards assessment for planning in the choice of sites for critical facilities in Nigeria. Keywords: Sediment thickness, Resonance Frequency, Average Velocity, Seismic Hazard, Nigeria

  3. ON STRUCTURED AND DIFFUSE SEISMICITY, STIFFNESS OF EARTHQUAKE FOCI, AND NONLINEARITY OF MAGNITUDE RECURRENCE GRAPHS

    Directory of Open Access Journals (Sweden)

    Evgeny G. Bugaev

    2011-01-01

    Full Text Available Geological, geophysical and seismogeological studies are now conducted in a more detail and thus provide for determining seismic sources with higher accuracy, from the first meters to first dozens of meters [Waldhauser, Schaff, 2008]. It is now possible to consider uncertainty ellipses of earthquake hypocenters, that are recorded in the updated Earthquake Catalogue, as surfaces of earthquake focus generators. In our article, it is accepted that a maximum horizontal size of an uncertainty ellipse corresponds to an area of a focus generator, and seismic events are thus classified into two groups, earthquakes with nonstiff and stiff foci. Criteria of such a classification are two limits of elastic strain and brittle strain in case of uniaxial (3⋅10–5 or omnidirectional (10–6 compression. The criteria are established from results of analyses of parameters of seismic dislocations and earthquake foci with regard to studies of surface parameters and deformation parameters of fault zones. It is recommendable that the uniaxial compression criterion shall be applied to zones of interaction between tectonic plates, and the unilateral compression criterion shall be applied to low active (interplate areas. Sample cases demonstrate the use of data sets on nonstiff and stiff foci for separate evaluation of magnitude reoccurrence curves, analyses of structured and dissipated seismicity, review of the physical nature of nonlinearity of recurrence curves and conditions of preparation of strong earthquakes. Changes of parameters of the recurrence curves with changes of data collection square areas are considered. Reviewed are changes of parameters of the recurrence curves during preparation for the Japan major earthquake of 11 March 2011 prior to and after the major shock. It is emphasized that it is important to conduct even more detailed geological and geophysical studies and to improve precision and sensitivity of local seismological monitoring networks

  4. Pattern recognition methodologies and deterministic evaluation of seismic hazard: A strategy to increase earthquake preparedness

    International Nuclear Information System (INIS)

    Peresan, Antonella; Panza, Giuliano F.; Gorshkov, Alexander I.; Aoudia, Abdelkrim

    2001-05-01

    Several algorithms, structured according to a general pattern-recognition scheme, have been developed for the space-time identification of strong events. Currently, two of such algorithms are applied to the Italian territory, one for the recognition of earthquake-prone areas and the other, namely CN algorithm, for earthquake prediction purposes. These procedures can be viewed as independent experts, hence they can be combined to better constrain the alerted seismogenic area. We examine here the possibility to integrate CN intermediate-term medium-range earthquake predictions, pattern recognition of earthquake-prone areas and deterministic hazard maps, in order to associate CN Times of Increased Probability (TIPs) to a set of appropriate scenarios of ground motion. The advantage of this procedure mainly consists in the time information provided by predictions, useful to increase preparedness of safety measures and to indicate a priority for detailed seismic risk studies to be performed at a local scale. (author)

  5. Volcano-tectonic earthquakes: A new tool for estimating intrusive volumes and forecasting eruptions

    Science.gov (United States)

    White, Randall A.; McCausland, Wendy

    2016-01-01

    We present data on 136 high-frequency earthquakes and swarms, termed volcano-tectonic (VT) seismicity, which preceded 111 eruptions at 83 volcanoes, plus data on VT swarms that preceded intrusions at 21 other volcanoes. We find that VT seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more, and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from VEI 0 to ultraplinian VEI 6 at such previously long-dormant volcanoes. Because large eruptions occur most commonly during resumption of activity at long-dormant volcanoes, VT seismicity is an important precursor for the Earth's most dangerous eruptions. VT seismicity precedes all explosive eruptions of VEI ≥ 5 and most if not all VEI 4 eruptions in our data set. Surprisingly we find that the VT seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption, and rarely if ever starts beneath the eruption site itself. The distal VT swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance, beyond which hypocenter depths level out. We summarize several important characteristics of this distal VT seismicity including: swarm-like nature, onset days to years prior to the beginning of magmatic eruptions, peaking of activity at the time of the initial eruption whether phreatic or magmatic, and large non-double couple component to focal mechanisms. Most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the VT seismicity from:

  6. Seismic hazard and seismic risk assessment based on the unified scaling law for earthquakes: Himalayas and adjacent regions

    Science.gov (United States)

    Nekrasova, A. K.; Kossobokov, V. G.; Parvez, I. A.

    2015-03-01

    For the Himalayas and neighboring regions, the maps of seismic hazard and seismic risk are constructed with the use of the estimates for the parameters of the unified scaling law for earthquakes (USLE), in which the Gutenberg-Richter law for magnitude distribution of seismic events within a given area is applied in the modified version with allowance for linear dimensions of the area, namely, log N( M, L) = A + B (5 - M) + C log L, where N( M, L) is the expected annual number of the earthquakes with magnitude M in the area with linear dimension L. The spatial variations in the parameters A, B, and C for the Himalayas and adjacent regions are studied on two time intervals from 1965 to 2011 and from 1980 to 2011. The difference in A, B, and C between these two time intervals indicates that seismic activity experiences significant variations on a scale of a few decades. With a global consideration of the seismic belts of the Earth overall, the estimates of coefficient A, which determines the logarithm of the annual average frequency of the earthquakes with a magnitude of 5.0 and higher in the zone with a linear dimension of 1 degree of the Earth's meridian, differ by a factor of 30 and more and mainly fall in the interval from -1.1 to 0.5. The values of coefficient B, which describes the balance between the number of earthquakes with different magnitudes, gravitate to 0.9 and range from less than 0.6 to 1.1 and higher. The values of coefficient C, which estimates the fractal dimension of the local distribution of epicenters, vary from 0.5 to 1.4 and higher. In the Himalayas and neighboring regions, the USLE coefficients mainly fall in the intervals of -1.1 to 0.3 for A, 0.8 to 1.3 for B, and 1.0 to 1.4 for C. The calculations of the local value of the expected peak ground acceleration (PGA) from the maximal expected magnitude provided the necessary basis for mapping the seismic hazards in the studied region. When doing this, we used the local estimates of the

  7. The Spitak (Armenia, USSR) Earthquake: Residential Building Typology and Seismic Behaviour.

    Science.gov (United States)

    Pomonis, A

    1990-06-01

    The 1988 earthquake in Armenia was the most serious seismic disaster since the 1976 earthquake in Tangshan, China. At least 25,000 people lost their lives in a tremor of moderate magnitude and the USSR suffered a loss of more than 2.5 per cent of 1988's GDP. Research at the Martin Centre on the effects of earthquakes on human lives has shown an increase in global earthquake mortality rate, despite the well known improvements in some countries. The Armenian disaster was a warning to all of us concerned with natural or man-made disasters. Areas of potential high hazard are pointed out for the sub-Caucasian region. Construction practices similar to those in Armenia are certainly found in many other parts of the world, with some regional variations, and the fast assimilation of the lessons is an important target. The structural characteristics of all the residential building types existing in the affected area are presented in terms of their seismic vulnerability. Vulnerable points are discussed with a view to low cost interventions that will drastically improve the seismic safety of new buildings.

  8. On seismic intensities of questionnaires for 1996 earthquake near Akita-Miyagi prefecture

    Energy Technology Data Exchange (ETDEWEB)

    Nogoshi, M; Sasaki, N [Akita University, Akita (Japan). College of Education; Nakamura, M [Nippon Geophysical Prospecting Co. Ltd., Tokyo (Japan)

    1997-05-27

    The earthquake occurred in 1996 near the border of Akita and Miyagi Prefectures was a seismic activity in mountainous area with low population density. However, since a necessity was felt to make a seismic intensity survey, a questionnaire investigation was carried out. The investigation placed a focus on the following points: (1) to learn seismic intensity distribution in the vicinity of the epicenter by using replies to the questionnaire and (2) to learn what evacuation activities the residents have taken to avoid disasters from the earthquake, which is an inland local earthquake occurred first since the Hyogoken-nanbu earthquake in 1995. Because the main shock has occurred in the Akita prefecture side, the shocks were concentrated at Akinomiya, Takamatsu, Sugawa and Koyasu areas where the intensities were 4.0 to 4.5 in most cases. The largest aftershocks were concentrated to the Miyagi prefecture side, with an intensity of 6.0 felt most, followed by 5.5. The questionnaire on evacuation actions revealed a result of about 37% of the reply saying, ``I have jumped out of my house before I knew what has happened`` and ``I remember nothing about what I did because I was acting totally instinctively``. The answers show how intense the experience was. This result indicates how to make the unconscious actions turned into conscious actions is an important issue in preventing disasters. 11 figs.

  9. 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 ...

  10. Crustal seismicity and the earthquake catalog maximum moment magnitudes (Mcmax) in stable continental regions (SCRs): correlation with the seismic velocity of the lithosphere

    Science.gov (United States)

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-01-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  11. Crustal seismicity and the earthquake catalog maximum moment magnitude (Mcmax) in stable continental regions (SCRs): Correlation with the seismic velocity of the lithosphere

    Science.gov (United States)

    Mooney, Walter D.; Ritsema, Jeroen; Hwang, Yong Keun

    2012-12-01

    A joint analysis of global seismicity and seismic tomography indicates that the seismic potential of continental intraplate regions is correlated with the seismic properties of the lithosphere. Archean and Early Proterozoic cratons with cold, stable continental lithospheric roots have fewer crustal earthquakes and a lower maximum earthquake catalog moment magnitude (Mcmax). The geographic distribution of thick lithospheric roots is inferred from the global seismic model S40RTS that displays shear-velocity perturbations (δVS) relative to the Preliminary Reference Earth Model (PREM). We compare δVS at a depth of 175 km with the locations and moment magnitudes (Mw) of intraplate earthquakes in the crust (Schulte and Mooney, 2005). Many intraplate earthquakes concentrate around the pronounced lateral gradients in lithospheric thickness that surround the cratons and few earthquakes occur within cratonic interiors. Globally, 27% of stable continental lithosphere is underlain by δVS≥3.0%, yet only 6.5% of crustal earthquakes with Mw>4.5 occur above these regions with thick lithosphere. No earthquakes in our catalog with Mw>6 have occurred above mantle lithosphere with δVS>3.5%, although such lithosphere comprises 19% of stable continental regions. Thus, for cratonic interiors with seismically determined thick lithosphere (1) there is a significant decrease in the number of crustal earthquakes, and (2) the maximum moment magnitude found in the earthquake catalog is Mcmax=6.0. We attribute these observations to higher lithospheric strength beneath cratonic interiors due to lower temperatures and dehydration in both the lower crust and the highly depleted lithospheric root.

  12. Catalogue of European earthquakes and an atlas of European seismic maps

    International Nuclear Information System (INIS)

    Van Gils, J.M.

    1988-01-01

    The Catalogue of European earthquakes and an atlas of European seismic maps has been prepared in the framework of the activities of the CEC Working Group on the safety of ligh-water reactors. Seismic hazards are considered to be an important element of possible external accidents to be taken into account in the design, construction, and operation of nuclear power plants. The report relies on the data base available, the historical as well as the present-day data. After a short historical review, actually-used intensity scales are discussed. The scale applied in European countries and the one proposed in the United States of America are compared. The different seismic maps of interest are explained and a mathematical procedure presented which allows, under certain conditions, to draw seismic maps by computer facilities

  13. Seismic margin assessment and earthquake experience based methods for WWER-440/213 type NPPs

    International Nuclear Information System (INIS)

    Masopust, R.

    1996-01-01

    This report covers the review of the already completed studies, namely, safe shutdown system identification and classification for Bohunice NPP and the comparative study of standards and criteria. It contains a report on currently ongoing studies concerning seismic margin assessment and earthquake experience based methods in application for seismic evaluation and verification of structures and equipment components of the operating WWER-440/213 type NPPs. This is based on experiences obtained from Paks NPP. The work plan for the remaining period of Benchmark CRP and the new proposals are included. These are concerned with seismic evaluation of selected safety related mechanical equipment and pipes of Paks NPP, and the actual seismic issues of the Temelin WWER-1000 type NPP

  14. Earthquake Hazard in the New Madrid Seismic Zone Remains a Concern

    Science.gov (United States)

    Frankel, A.D.; Applegate, D.; Tuttle, M.P.; Williams, R.A.

    2009-01-01

    There is broad agreement in the scientific community that a continuing concern exists for a major destructive earthquake in the New Madrid seismic zone. Many structures in Memphis, Tenn., St. Louis, Mo., and other communities in the central Mississippi River Valley region are vulnerable and at risk from severe ground shaking. This assessment is based on decades of research on New Madrid earthquakes and related phenomena by dozens of Federal, university, State, and consulting earth scientists. Considerable interest has developed recently from media reports that the New Madrid seismic zone may be shutting down. These reports stem from published research using global positioning system (GPS) instruments with results of geodetic measurements of strain in the Earth's crust. Because of a lack of measurable strain at the surface in some areas of the seismic zone over the past 14 years, arguments have been advanced that there is no buildup of stress at depth within the New Madrid seismic zone and that the zone may no longer pose a significant hazard. As part of the consensus-building process used to develop the national seismic hazard maps, the U.S. Geological Survey (USGS) convened a workshop of experts in 2006 to evaluate the latest findings in earthquake hazards in the Eastern United States. These experts considered the GPS data from New Madrid available at that time that also showed little to no ground movement at the surface. The experts did not find the GPS data to be a convincing reason to lower the assessment of earthquake hazard in the New Madrid region, especially in light of the many other types of data that are used to construct the hazard assessment, several of which are described here.

  15. Correlation between Earthquakes and AE Monitoring of Historical Buildings in Seismic Areas

    Directory of Open Access Journals (Sweden)

    Giuseppe Lacidogna

    2015-12-01

    Full Text Available In this contribution a new method for evaluating seismic risk in regional areas based on the acoustic emission (AE technique is proposed. Most earthquakes have precursors, i.e., phenomena of changes in the Earth’s physical-chemical properties that take place prior to an earthquake. Acoustic emissions in materials and earthquakes in the Earth’s crust, despite the fact that they take place on very different scales, are very similar phenomena; both are caused by a release of elastic energy from a source located in a medium. For the AE monitoring, two important constructions of Italian cultural heritage are considered: the chapel of the “Sacred Mountain of Varallo” and the “Asinelli Tower” of Bologna. They were monitored during earthquake sequences in their relative areas. By using the Grassberger-Procaccia algorithm, a statistical method of analysis was developed that detects AEs as earthquake precursors or aftershocks. Under certain conditions it was observed that AEs precede earthquakes. These considerations reinforce the idea that the AE monitoring can be considered an effective tool for earthquake risk evaluation.

  16. 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)

  17. Volcanic Eruption Forecasts From Accelerating Rates of Drumbeat Long-Period Earthquakes

    Science.gov (United States)

    Bell, Andrew F.; Naylor, Mark; Hernandez, Stephen; Main, Ian G.; Gaunt, H. Elizabeth; Mothes, Patricia; Ruiz, Mario

    2018-02-01

    Accelerating rates of quasiperiodic "drumbeat" long-period earthquakes (LPs) are commonly reported before eruptions at andesite and dacite volcanoes, and promise insights into the nature of fundamental preeruptive processes and improved eruption forecasts. Here we apply a new Bayesian Markov chain Monte Carlo gamma point process methodology to investigate an exceptionally well-developed sequence of drumbeat LPs preceding a recent large vulcanian explosion at Tungurahua volcano, Ecuador. For more than 24 hr, LP rates increased according to the inverse power law trend predicted by material failure theory, and with a retrospectively forecast failure time that agrees with the eruption onset within error. LPs resulted from repeated activation of a single characteristic source driven by accelerating loading, rather than a distributed failure process, showing that similar precursory trends can emerge from quite different underlying physics. Nevertheless, such sequences have clear potential for improving forecasts of eruptions at Tungurahua and analogous volcanoes.

  18. The 2014, MW6.9 North Aegean earthquake: seismic and geodetic evidence for coseismic slip on persistent asperities

    Science.gov (United States)

    Konca, Ali Ozgun; Cetin, Seda; Karabulut, Hayrullah; Reilinger, Robert; Dogan, Ugur; Ergintav, Semih; Cakir, Ziyadin; Tari, Ergin

    2018-05-01

    We report that asperities with the highest coseismic slip in the 2014 MW6.9 North Aegean earthquake persisted through the interseismic, coseismic and immediate post-seismic periods. We use GPS and seismic data to obtain the source model of the 2014 earthquake, which is located on the western extension of the North Anatolian Fault (NAF). The earthquake ruptured a bilateral, 90 km strike-slip fault with three slip patches: one asperity located west of the hypocentre and two to the east with a rupture duration of 40 s. Relocated pre-earthquake seismicity and aftershocks show that zones with significant coseismic slip were relatively quiet during both the 7 yr of interseismic and the 3-month aftershock periods, while the surrounding regions generated significant seismicity during both the interseismic and post-seismic periods. We interpret the unusually long fault length and source duration, and distribution of pre- and post-main-shock seismicity as evidence for a rupture of asperities that persisted through strain accumulation and coseismic strain release in a partially coupled fault zone. We further suggest that the association of seismicity with fault creep may characterize the adjacent Izmit, Marmara Sea and Saros segments of the NAF. Similar behaviour has been reported for sections of the San Andreas Fault, and some large subduction zones, suggesting that the association of seismicity with creeping fault segments and rapid relocking of asperities may characterize many large earthquake faults.

  19. The April 2017 M6.7 Botswana Earthquake: Implications for African Intraplate Seismicity.

    Science.gov (United States)

    Gardonio, B.; Calais, E.; Jolivet, R.

    2017-12-01

    The last decades have seen a rapidly increasing number of studies of interplate seismicity, revealing for instance the fundamental relationship between seismic and aseismic slip along plate boundary faults. To the contrary, intraplate earthquakes, occurring far from plate boundaries are still misunderstood and by far less studied. Key questions are the mechanisms through which elastic strain builds up and is released in the seismogenic crust in such contexts, in the absence of (yet) measurable intraplate strain rates. The April 2017 M6.7 Botswana earthquake was a surprise in many ways. This is the largest recorded event that struck this ordinarily seismically quiet region, West to the East-African Rift system where most of the usual southern seismicity occurs. It may also be the largest intraplate event recorded since the 1988 Tennant Creek earthquake in central Australia. No active structure can be mapped at the surface. Active extension related to the east African rifting may occur several hundreds of kilometers to the north-east with low rates of a few mm per year. Closer to the event, the Okavango delta, located at 20° of latitude and 23° of longitude is considered by some as an incipient rift with very low deformation rates, similar to a large part of the southern African continent. Interestingly, seismic activity in the area of the recent Botswana earthquake is more important than the world average intraplate activity, potentially due to rifting to the east and/or large stresses induced by lateral gradients in gravitational potential energy (this part of the world has an altitude of 1000 to 2000 m.). The aim of this study is to better constrain the tectonic setting and the dynamics of the Botswana earthquake area. To do so, we analyze a Sentinel 1 interferogram of the event to constrain the strike, dip, depth, magnitude and location of the earthquake. We also analyze continuous teleseismic signals during two months centered on the mainshock using a template

  20. Seismic waves and earthquakes in a global monolithic model

    Science.gov (United States)

    Roubíček, Tomáš

    2018-03-01

    The philosophy that a single "monolithic" model can "asymptotically" replace and couple in a simple elegant way several specialized models relevant on various Earth layers is presented and, in special situations, also rigorously justified. In particular, global seismicity and tectonics is coupled to capture, e.g., (here by a simplified model) ruptures of lithospheric faults generating seismic waves which then propagate through the solid-like mantle and inner core both as shear (S) or pressure (P) waves, while S-waves are suppressed in the fluidic outer core and also in the oceans. The "monolithic-type" models have the capacity to describe all the mentioned features globally in a unified way together with corresponding interfacial conditions implicitly involved, only when scaling its parameters appropriately in different Earth's layers. Coupling of seismic waves with seismic sources due to tectonic events is thus an automatic side effect. The global ansatz is here based, rather for an illustration, only on a relatively simple Jeffreys' viscoelastic damageable material at small strains whose various scaling (limits) can lead to Boger's viscoelastic fluid or even to purely elastic (inviscid) fluid. Self-induced gravity field, Coriolis, centrifugal, and tidal forces are counted in our global model, as well. The rigorous mathematical analysis as far as the existence of solutions, convergence of the mentioned scalings, and energy conservation is briefly presented.

  1. Aftershock Forecasting: Recent Developments and Lessons from the 2016 M5.8 Pawnee, Oklahoma, Earthquake

    Science.gov (United States)

    Michael, A. J.; Field, E. H.; Hardebeck, J.; Llenos, A. L.; Milner, K. R.; Page, M. T.; Perry, S. C.; van der Elst, N.; Wein, A. M.

    2016-12-01

    After the Mw 5.8 Pawnee, Oklahoma, earthquake of September 3, 2016 the USGS issued a series of aftershock forecasts for the next month and year. These forecasts were aimed at the emergency response community, those making decisions about well operations in the affected region, and the general public. The forecasts were generated manually using methods planned for automatically released Operational Aftershock Forecasts. The underlying method is from Reasenberg and Jones (Science, 1989) with improvements recently published in Page et al. (BSSA, 2016), implemented in a JAVA Graphical User Interface and presented in a template that is under development. The methodological improvements include initial models based on the tectonic regime as defined by Garcia et al. (BSSA, 2012) and the inclusion of both uncertainty in the clustering parameters and natural random variability. We did not utilize the time-dependent magnitude of completeness model from Page et al. because it applies only to teleseismic events recorded by NEIC. The parameters for Garcia's Generic Active Continental Region underestimated the modified-Omori decay parameter and underestimated the aftershock rate by a factor of 2. And the sequence following the Mw 5.7 Prague, Oklahoma, earthquake of November 6, 2011 was about 3 to 4 times more productive than the Pawnee sequence. The high productivity for these potentially induced sequences is consistent with an increase in productivity in Oklahoma since 2009 (Llenos and Michael, BSSA, 2013) and makes a general tectonic model inapplicable to sequences in this region. Soon after the mainshock occurred, the forecasts relied on the sequence specific parameters. After one month, the Omori decay parameter p is less than one, implying a very long-lived sequence. However, the decay parameter is known to be biased low at early times due to secondary aftershock triggering, and the p-value determined early in the sequence may be inaccurate for long-term forecasting.

  2. Inverse Problem for 3D coupled Flow-Geomechanics Models and Induced Seismicity: Application to Subsurface Characterization and Seismicity Forecasting in Geologic CO2 Storage

    Science.gov (United States)

    Castineira, D.; Jha, B.; Juanes, R.

    2016-12-01

    Carbon Capture and Sequestration (CCS) is regarded as a promising technology to mitigate rising CO2 concentrations in the atmosphere from industrial emissions. However, as a result of the inherent uncertainty that is present in geological structures, assessing the stability of geological faults and quantifying the potential for induced seismicity is a fundamental challenge for practical implementation of CCS. Here we present a formal framework for the solution of the inverse problem associated with coupled flow and geomechanics models of CO2 injection and subsurface storage. Our approach builds from the application of Gaussian Processes, MCMC and posterior predictive analysis to evaluate relevant earthquake attributes (earthquake time, location and magnitude) in 3D synthetic models of CO2 storage under geologic, observational and operational uncertainty. In our approach, we first conduct hundreds of simulations of a high-fidelity 3D computational model for CO2 injection into a deep saline aquifer, dominated by an anticline structure and a fault. This ensemble of realizations accounts for uncertainty in the model parameters (including fault geomechanical and rock properties) and observations (earthquake time, location and magnitude). We apply Gaussian processes (GP) to generate a valid surrogate that closely approximates the behavior of the high fidelity (and computationally intensive) model, and apply hyperparameter optimization and cross-validation techniques in the solution of this multidimensional data-fit problem. The net result of this process is the generation of a fast model that can be effectively used for Bayesian analysis. We then implement Markov chain Monte Carlo (MCMC) to determine the posterior distribution of the model uncertain parameters (given some prior distributions for those parameters and given the likelihood defined in this case by the GP model). Our results show that the resulting posterior distributions correctly converge towards the "true

  3. A seismic analysis of nuclear power plant components subjected to multi-excitations of earthquakes

    International Nuclear Information System (INIS)

    Ichiki, T.; Matsumoto, T.; Gunyasu, K.

    1977-01-01

    In this analysis, the modal analysis methods are used to determine the seismic responses of structural systems instead of the direct integration method. These results have been compared with some kinds of other analytical methods, and investigated the accuracy of numerical results of these analysis, applying to such components as Reactor Pressure Vessel and Reactor Internals of an actual plant. The results of this method of analysis are summarized as follows: (1) one of the seismic analysis methods concerning systems subjected to multi-excitations of earthquakes has been presented to the conference of JSME. Although the analytical theory presented to that conference is correct, it has a serious problem about the accuracy of numerical results. This computer program and theory cannot be used practically due to the time necessary to calculate. However, the method described in this paper overcomes those serious problems stated above and has no problem about the computer time and precision. So, it is possible to apply this method to the seismic design of an actual nuclear power plant practically. (2) The feed back effects of the seismic responses of Reactor Internals to Reactor Building are considered so small that we can separate the model of Reactor Internals from Reactor Building. (3) The results of seismic response of Reactor Internals are fairly consistent with those obtained from the model coupled with Reactor Building. (4) This analysis method can be extended to the model of Reactor Internals subjected to more than two random excitations of earthquakes. (5) It is possible that this analysis method is also applied to the seismic analysis of such three-dimensional systems as piping systems subjected to multi-excitations of earthquakes

  4. EMSE: Synergizing EM and seismic data attributes for enhanced forecasts of reservoirs

    KAUST Repository

    Katterbauer, Klemens

    2014-10-01

    New developments of electromagnetic and seismic techniques have recently revolutionized the oil and gas industry. Time-lapse seismic data is providing engineers with tools to more accurately track the dynamics of multi-phase reservoir fluid flows. With the challenges faced in distinguishing between hydrocarbons and water via seismic methods, the industry has been looking at electromagnetic techniques in order to exploit the strong contrast in conductivity between hydrocarbons and water. Incorporating this information into reservoir simulation is expected to considerably enhance the forecasting of the reservoir, hence optimizing production and reducing costs. Conventional approaches typically invert the seismic and electromagnetic data in order to transform them into production parameters, before incorporating them as constraints in the history matching process and reservoir simulations. This makes automatization difficult and computationally expensive due to the necessity of manual processing, besides the potential artifacts. Here we introduce a new approach to incorporate seismic and electromagnetic data attributes directly into the history matching process. To avoid solving inverse problems and exploit information in the dynamics of the flow, we exploit petrophysical transformations to simultaneously incorporate time lapse seismic and electromagnetic data attributes using different ensemble Kalman-based history matching techniques. Our simulation results show enhanced predictability of the critical reservoir parameters and reduce uncertainties in model simulations, outperforming with only production data or the inclusion of either seismic or electromagnetic data. A statistical test is performed to confirm the significance of the results. © 2014 Elsevier B.V. All rights reserved.

  5. Report on the seismic safety examination of nuclear facilities based on the 1995 Hyogoken-Nanbu earthquake

    International Nuclear Information System (INIS)

    2001-01-01

    Just after the Hyogoken-Nanbu Earthquake occurred, Nuclear Safety Commission of Japan established a committee to examine the validity or related guidelines on the seismic design to be used for the safety examination. After the 8 months study, the committee confirmed that the validity of guidelines regulating the seismic design of nuclear facilities is not impaired even though on the basis of the Hyogoken-Nanbu earthquake. This report is the outline of the Committee's study results. (author)

  6. Experience with seismic instrumentation and real earthquake data at nuclear power plant Beznau Switzerland

    International Nuclear Information System (INIS)

    Sahgal, S.; Tinic, S.

    2005-01-01

    This paper deals with the aspects of design specification, bid evaluation and, seismic criteria used for the generation of seismic alarms etc. The paper also describes how the recorded data is utilized to check the various assumptions made in conjunction with the seismic plant design and seismic load generation. Out of some 8 seismic events registered so far only one event had the maximum recorded acceleration of approximately 28% of OBE Peak Ground Acceleration (PGA). From the real earthquakes experienced and the in-situ free-field ground accelerations recorded, the free-field response spectra were calculated. The calculated spectra are compared to the Regulatory Guide 1.60 Design Response Spectra scaled linearly to the site peak ground acceleration. The free field data recording units on the weathered rock and at the top of the soil provided a real data to calculate the site amplification factors. The in-situ amplification calculated is then compared to that used in the seismic design. The recorded acceleration time history at various plant grades were used to generate response spectra. The calculated response spectra were in turn compared to the spectra used in the seismic design. (authors)

  7. 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

  8. Seismic waves and acoustic waves: from earthquake to music

    OpenAIRE

    D'Addezio, Giuliana; Marsili, Antonella; Ingrid Hunstad, Ingrid; Burrato, Pierfrancesco; Casale, Paolo; Vallocchia, Massimiliano; Fracassi, Umberto; Ventura, Guido

    2011-01-01

    INGV is currently the largest European scientific institution dealing with Earth Sciences research and real-time surveillance, early warning, and forecast activities in geophysics and volcanology. The Laboratorio Didattica e Divulgazione Scientifica of INGV organizes every year rich educational and outreach activities with schools of different levels and with general public to convey scientific knowledge and to promote research on science and nature, focusing on volcanic and s...

  9. Keeping focus on earthquakes at school for seismic risk mitigation of the next generations

    Science.gov (United States)

    Saraò, Angela; Barnaba, Carla; Peruzza, Laura

    2013-04-01

    The knowledge of the seismic history of its own territory, the understanding of physical phenomena in response to an earthquake, the changes in the cultural heritage following a strong earthquake, the learning of actions to be taken during and after an earthquake, are piece of information that contribute to keep focus on the seismic hazard and to implement strategies for seismic risk mitigation. The training of new generations, today more than ever subject to rapid forgetting of past events, becomes therefore a key element to increase the perception that earthquakes happened and can happen at anytime and that mitigation actions are the only means to ensure the safety and to reduce damages and human losses. Since several years our institute (OGS) is involved in activities to raise awareness of education on earthquake. We aim to implement education programs with the goal of addressing a critical approach to seismic hazard reduction, differentiating the types of activities according to the age of the students. However, being such kind of activity unfunded, we can act at now only on a very limited number of schools per year. To be effective, the inclusion of the seismic risk issues in school curricula requires specific time and appropriate approaches when planning activities. For this reason, we involve also the teachers as proponents of activities and we encourage them to keep alive memories and discussion on earthquake in the classes. During the past years we acted mainly in the schools of the Friuli Venezia Giulia area (NE Italy), that is an earthquake prone area struck in 1976 by a destructive seismic event (Ms=6.5). We organized short training courses for teachers, we lectured classes, and we led laboratory activities with students. Indeed, being well known that students enjoy classes more when visual and active learning are joined, we propose a program that is composed by seminars, demonstrations and hands-on activities in the classrooms; for high school students

  10. REGIONAL SEISMIC AMPLITUDE MODELING AND TOMOGRAPHY FOR EARTHQUAKE-EXPLOSION DISCRIMINATION

    Energy Technology Data Exchange (ETDEWEB)

    Walter, W R; Pasyanos, M E; Matzel, E; Gok, R; Sweeney, J; Ford, S R; Rodgers, A J

    2008-07-08

    We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S in a variety of frequency bands. Empirically we demonstrate that such ratios separate explosions from earthquakes using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world (e.g. Nevada, Novaya Zemlya, Semipalatinsk, Lop Nor, India, Pakistan, and North Korea). We are also examining if there is any relationship between the observed P/S and the point source variability revealed by longer period full waveform modeling (e. g. Ford et al 2008). For example, regional waveform modeling shows strong tectonic release from the May 1998 India test, in contrast with very little tectonic release in the October 2006 North Korea test, but the P/S discrimination behavior appears similar in both events using the limited regional data available. While regional amplitude ratios such as P/S can separate events in close proximity, it is also empirically well known that path effects can greatly distort observed amplitudes and make earthquakes appear very explosion-like. Previously we have shown that the MDAC (Magnitude Distance Amplitude Correction, Walter and Taylor, 2001) technique can account for simple 1-D attenuation and geometrical spreading corrections, as well as magnitude and site effects. However in some regions 1-D path corrections are a poor approximation and we need to develop 2-D path corrections. Here we demonstrate a new 2-D attenuation tomography technique using the MDAC earthquake source model applied to a set of events and stations in both the Middle East and the Yellow Sea Korean Peninsula regions. We believe this new 2-D MDAC tomography has the potential to greatly improve earthquake-explosion discrimination, particularly in tectonically complex regions such as the Middle East. Monitoring the world for potential nuclear explosions requires characterizing seismic

  11. Seismic design technology for breeder reactor structures. Volume 1. Special topics in earthquake ground motion

    International Nuclear Information System (INIS)

    Reddy, D.P.

    1983-04-01

    This report is divided into twelve chapters: seismic hazard analysis procedures, statistical and probabilistic considerations, vertical ground motion characteristics, vertical ground response spectrum shapes, effects of inclined rock strata on site response, correlation of ground response spectra with intensity, intensity attenuation relationships, peak ground acceleration in the very mean field, statistical analysis of response spectral amplitudes, contributions of body and surface waves, evaluation of ground motion characteristics, and design earthquake motions

  12. 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.

  13. Evaluation and optimization of seismic networks and algorithms for earthquake early warning – the case of Istanbul (Turkey)

    OpenAIRE

    Oth, Adrien; Böse, Maren; Wenzel, Friedemann; Köhler, Nina; Erdik, Mustafa

    2010-01-01

    Earthquake early warning (EEW) systems should provide reliable warnings as quickly as possible with a minimum number of false and missed alarms. Using the example of the megacity Istanbul and based on a set of simulated scenario earthquakes, we present a novel approach for evaluating and optimizing seismic networks for EEW, in particular in regions with a scarce number of instrumentally recorded earthquakes. We show that, while the current station locations of the existing Istanbul EEW system...

  14. Coulomb Failure Stress Accumulation in Nepal After the 2015 Mw 7.8 Gorkha Earthquake: Testing Earthquake Triggering Hypothesis and Evaluating Seismic Hazards

    Science.gov (United States)

    Xiong, N.; Niu, F.

    2017-12-01

    A Mw 7.8 earthquake struck Gorkha, Nepal, on April 5, 2015, resulting in more than 8000 deaths and 3.5 million homeless. The earthquake initiated 70km west of Kathmandu and propagated eastward, rupturing an area of approximately 150km by 60km in size. However, the earthquake failed to fully rupture the locked fault beneath the Himalaya, suggesting that the region south of Kathmandu and west of the current rupture are still locked and a much more powerful earthquake might occur in future. Therefore, the seismic hazard of the unruptured region is of great concern. In this study, we investigated the Coulomb failure stress (CFS) accumulation on the unruptured fault transferred by the Gorkha earthquake and some nearby historical great earthquakes. First, we calculated the co-seismic CFS changes of the Gorkha earthquake on the nodal planes of 16 large aftershocks to quantitatively examine whether they were brought closer to failure by the mainshock. It is shown that at least 12 of the 16 aftershocks were encouraged by an increase of CFS of 0.1-3 MPa. The correspondence between the distribution of off-fault aftershocks and the increased CFS pattern also validates the applicability of the earthquake triggering hypothesis in the thrust regime of Nepal. With the validation as confidence, we calculated the co-seismic CFS change on the locked region imparted by the Gorkha earthquake and historical great earthquakes. A newly proposed ramp-flat-ramp-flat fault geometry model was employed, and the source parameters of historical earthquakes were computed with the empirical scaling relationship. A broad region south of the Kathmandu and west of the current rupture were shown to be positively stressed with CFS change roughly ranging between 0.01 and 0.5 MPa. The maximum of CFS increase (>1MPa) was found in the updip segment south of the current rupture, implying a high seismic hazard. Since the locked region may be additionally stressed by the post-seismic relaxation of the lower

  15. Generation of artificial earthquake time histories for seismic design at Hanford, Washington

    International Nuclear Information System (INIS)

    Salmon, M.W.; Kuilanoff, G.

    1991-01-01

    The purpose of the development of artificial time-histories is to provide the designer with ground motion estimates which will meet the requirements of the design guidelines at the Hanford site. In particular, the artificial time histories presented in this paper were prepared to assist designers of the Hanford Waste Vitrification Plant (HWVP) with time histories that envelop the requirements for both a large magnitude earthquake (MI > 6.0) and a small magnitude, near-field earthquake (MI < 5. 0). A background of the requirements for both the large magnitude and small magnitude events is presented in this paper. The work done in generating time histories which produce response spectra matching those of the design seismic events is also presented. Finally, some preliminary results from studies performed using the small-magnitude near-filed earthquake time-history are presented

  16. Co-seismic deformation and gravity changes of the 2011 India-Nepal and Myanmar earthquakes

    Directory of Open Access Journals (Sweden)

    Liu Chengli

    2012-02-01

    Full Text Available Co-seismic deformation and gravity field changes caused by the 2011 Mw6. 8 Myanmar and Mw6. 9 India-Nepal earthquakes are calculated with a finite-element model and an average-slip model, respectively, based on the multi-layered elastic half-space dislocation theory. The calculated maximum horizontal displacement of the Myanmar earthquake is 36 cm, which is larger than the value of 9. 5 cm for the India-Nepal earthquake. This difference is attributed to their different focal depths and our use of different models. Except certain differences in the near field, both models give similar deformation and gravity results for the Myanmar event.

  17. 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)

  18. Intensity estimation of historical earthquakes through seismic analysis of wooden house

    International Nuclear Information System (INIS)

    Choi, I. K.; Soe, J. M.

    1999-01-01

    The intensity of historical earthquake records related with house collapses are estimated by the seismic analyses of traditional three-bay-straw-roof house. Eighteen artificial time histories for magnitudes 6-8, epicentral distances 5 km - 350 km and hard and soft soil condition were generated for the analyses. Nonlinear dynamic analyses were performed for a traditional three-bay-roof house. Damage level of the wooden house according to the input earthquake motions and the MM intensity were estimated by maximum displacement response at the top of columns. Considering the structural characteristics of the three-bay-straw-roof house, the largest historical earthquake record related to the house collapse is about MMI VIII

  19. NRIAG's Effort to Mitigate Earthquake Disasters in Egypt Using GPS and Seismic Data

    Science.gov (United States)

    Mahmoud, Salah

    It has been estimated that, during historical time more than 50 million people have lost their lives in earthquakes during ground shaking, such as soil amplification and/or liquefaction, landslides and tsunamis or its immediate aftereffects, as fires. The distribution of population takes generally no account of earthquake risk, at least on a large scale. An earthquake may be large but not destructive, on the other hand, an earthquake may be destructive but not large. The absence of correlation is due to the fact that, great number of other factors entering into consideration: first of all, the location of the earthquake in relation to populated areas, also soil conditions and building constructions. Soil liquefaction has been identified as the underlying phenomenon for many ground failures, settlements and lateral spreads, which are a major cause of damage to soil structures and building foundations in many events. Egypt is suffered a numerous of destructive earthquakes as well as Kalabsha earthquake (1981, Mag 5.4) near Aswan city and the High dam, Dahshour earthquake (1992, Mag 5.9) near Cairo city and Aqaba earthquake (1995, Mag 7.2). As the category of earthquake damage includes all the phenomena related to the direct and indirect damages, the Egyptian authorities do a great effort to mitigate the earthquake disasters. The seismicity especially at the zones of high activity is investigated in details in order to obtain the active source zones not only by the Egyptian National Seismic Network (ENSN) but also by the local seismic networks at, Aswan, Hurghada, Aqaba, Abu Dabbab and Dabbaa. On the other hand the soil condition, soil amplification, soil structure interaction, liquefaction and seismic hazard are carried out in particular the urbanized areas and the region near the source zones. All these parameters are integrated to obtain the Egyptian building code which is valid to construct buildings resist damages and consequently mitigate the earthquake

  20. [Engineering aspects of seismic behavior of health-care facilities: lessons from California earthquakes].

    Science.gov (United States)

    Rutenberg, A

    1995-03-15

    The construction of health-care facilities is similar to that of other buildings. Yet the need to function immediately after an earthquake, the helplessness of the many patients and the high and continuous occupancy of these buildings, require that special attention be paid to their seismic performance. Here the lessons from the California experience are invaluable. In this paper the behavior of California hospitals during destructive earthquakes is briefly described. Adequate structural design and execution, and securing of nonstructural elements are required to ensure both safety of occupants, and practically uninterrupted functioning of equipment, mechanical and electrical services and other vital systems. Criteria for post-earthquake functioning are listed. In view of the hazards to Israeli hospitals, in particular those located along the Jordan Valley and the Arava, a program for the seismic evaluation of medical facilities should be initiated. This evaluation should consider the hazards from nonstructural elements, the safety of equipment and systems, and their ability to function after a severe earthquake. It should not merely concentrate on safety-related structural behavior.

  1. Slow Earthquakes in the Alaska-Aleutian Subduction Zone Detected by Multiple Mini Seismic Arrays

    Science.gov (United States)

    LI, B.; Ghosh, A.; Thurber, C. H.; Lanza, F.

    2017-12-01

    The Alaska-Aleutian subduction zone is one of the most seismically and volcanically active plate boundaries on earth. Compared to other subduction zones, the slow earthquakes, such as tectonic tremors (TTs) and low frequency earthquakes (LFEs), are relatively poorly studied due to the limited data availability and difficult logistics. The analysis of two-months of continuous data from a mini array deployed in 2012 shows abundant tremor and LFE activities under Unalaska Island that is heterogeneously distributed [Li & Ghosh, 2017]. To better study slow earthquakes and understand their physical characteristics in the study region, we deployed a hybrid array of arrays, consisting of three well-designed mini seismic arrays and five stand alone stations, in the Unalaska Island in 2014. They were operational for between one and two years. Using the beam back-projection method [Ghosh et al., 2009, 2012], we detect continuous tremor activities for over a year when all three arrays are running. The sources of tremors are located south of the Unalaska and Akutan Islands, at the eastern and down-dip edge of the rupture zone of the 1957 Mw 8.6 earthquake, and they are clustered in several patches, with a gap between the two major clusters. Tremors show multiple migration patterns with propagation in both along-strike and dip directions and a wide range of velocities. We also identify tens of LFE families and use them as templates to search for repeating LFE events with the matched-filter method. Hundreds to thousands of LFEs for each family are detected and their activities are spatiotemporally consistent with tremor activities. The array techniques are revealing a near-continuous tremor activity in this area with remarkable spatiotemporal details. It helps us to better recognize the physical properties of the transition zone, provides new insights into the slow earthquake activities in this area, and explores their relation with the local earthquakes and the potential slow

  2. Application of seismic isolation for seismic strengthening of buildings damaged by the earthquake of L’Aquila

    International Nuclear Information System (INIS)

    Corsetti, Daniele

    2015-01-01

    The earthquake of 6 April 2009 destroyed the social and economic network fabric of the town of 'L'Aquila'. Since then, many buildings have been restored and some designers have taken the opportunity of rebuilding the town applying innovative technologies. In this context, despite the inevitable bureaucratic hurdles and economic constraints, added to the death of Mr. Mancinelli in 2012 (GLIS Member), several projects were carried out on existing buildings with the idea of applying base seismic isolation. A decade after the first application of this solution on an existing building in Fabriano by Mr. Mancinelli, the experience has proved to be a success, both in terms of achieved results and ease of management. For L’Aquila earthquake the idea was to replicate the positive experience of the “Marche earthquake”, though the problems and obstacles to face often were substantially different. The experience outlined below is a summary of the issues faced and resolved in two projects, taking into account that any solution can be further improved and refined depending on the ability and sensitivity of the designer. We have come to the conclusion that the projects of a base seismic isolation of existing buildings are 'tailor-made' projects, and that the solutions have to be analysed a case by case, even if the main concepts are simple and applicable to a wide range of buildings [it

  3. Earthquake response spectra for seismic design of nuclear power plants in the UK

    International Nuclear Information System (INIS)

    Bommer, Julian J.; Papaspiliou, Myrto; Price, Warren

    2011-01-01

    Highlights: → Seismic design of UK nuclear power plants usually based on PML response spectra. → We review derivation of PML spectra in terms of earthquake data used and procedure. → The data include errors and represent a small fraction of what is now available. → Seismic design loads in current practice are derived as mean uniform hazard spectra. → The need to capture epistemic uncertainty makes use of single equation indefensible. - Abstract: Earthquake actions for the seismic design of nuclear power plants in the United Kingdom are generally based on spectral shapes anchored to peak ground acceleration (PGA) values obtained from a single predictive equation. Both the spectra and the PGA prediction equation were derived in the 1980s. The technical bases for these formulations of seismic loading are now very dated if compared with the state-of-the-art in this field. Alternative spectral shapes are explored and the options, and the associated benefits and challenges, for generating uniform hazard response spectra instead of fixed shapes anchored to PGA are discussed.

  4. DEPENDENCE OF DISTRIBUTION FUNCTION OF COMMERCIAL DAMAGES DUE TO POSSIBLE EARTHQUAKES ON THE CLASS OF SEISMIC RESISTANCE OF A BUILDING

    OpenAIRE

    Hanzada R. Zajnulabidova; Alexander M. Uzdin; Tatiana M. Chirkst

    2017-01-01

    Abstract. Objectives To determine the damage probability of earthquakes of different intensities on the example of a real projected railway station building having a framework design scheme based on the density function of damage distribution. Methods Uncertainty, always existing in nature, invalidates a deterministic approach to the assessment of territorial seismic hazards and, consequently, seismic risk. In this case, seismic risk assessment can be carried out on a probabilistic basis. Thu...

  5. EVALUATION ON THE SEISMIC RESPONSE CHARACTERISTICS OF A ROAD EMBANKMENT BASED ON THE MODERATE EARTHQUAKE OBSERVATION AND THE MICROTREMOR MEASUREMENT

    Science.gov (United States)

    Hata, Yoshiya; Ichii, Koji; Yamada, Masayuki; Tokida, Ken-Ichi; Takezawa, Koichiro; Shibao, Susumu; Mitsushita, Junji; Murata, Akira; Furukawa, Aiko; Koizumi, Keigo

    Accurate evaluation on the seismic response characteristics of a road embankment is very important for the rational seismic assessment. However, in a lot of previous studies, the seismic response characteristics of an embankment were evaluated based on the results of shaking table test, centrifuge model test and dynamic FEM analysis. In this study, the transfer function and the shear wave velocity of a road embankment were evaluated based on the in-situ records of moderate earthquake observation and microtremor measurement. Test results show the possibility that the shear wave velocity of an embankment can be estimated by the earthquake observation or the microtremor measurement and the dynamic linear FEM analysis.

  6. Disaggregated seismic hazard and the elastic input energy spectrum: An approach to design earthquake selection

    Science.gov (United States)

    Chapman, Martin Colby

    1998-12-01

    The design earthquake selection problem is fundamentally probabilistic. Disaggregation of a probabilistic model of the seismic hazard offers a rational and objective approach that can identify the most likely earthquake scenario(s) contributing to hazard. An ensemble of time series can be selected on the basis of the modal earthquakes derived from the disaggregation. This gives a useful time-domain realization of the seismic hazard, to the extent that a single motion parameter captures the important time-domain characteristics. A possible limitation to this approach arises because most currently available motion prediction models for peak ground motion or oscillator response are essentially independent of duration, and modal events derived using the peak motions for the analysis may not represent the optimal characterization of the hazard. The elastic input energy spectrum is an alternative to the elastic response spectrum for these types of analyses. The input energy combines the elements of amplitude and duration into a single parameter description of the ground motion that can be readily incorporated into standard probabilistic seismic hazard analysis methodology. This use of the elastic input energy spectrum is examined. Regression analysis is performed using strong motion data from Western North America and consistent data processing procedures for both the absolute input energy equivalent velocity, (Vsbea), and the elastic pseudo-relative velocity response (PSV) in the frequency range 0.5 to 10 Hz. The results show that the two parameters can be successfully fit with identical functional forms. The dependence of Vsbea and PSV upon (NEHRP) site classification is virtually identical. The variance of Vsbea is uniformly less than that of PSV, indicating that Vsbea can be predicted with slightly less uncertainty as a function of magnitude, distance and site classification. The effects of site class are important at frequencies less than a few Hertz. The regression

  7. General discrimination technique to determine between earthquake and nuclear test with seismic data

    International Nuclear Information System (INIS)

    Bashillah Baharuddin; Alawiah Musa; Roslan Mohd Ali

    2007-01-01

    The Comprehensive Nuclear-Test-Ban Treaty (CTBT) was developed to ban of any nuclear weapon test explosion moreover will restrict the development and qualitative improvement of nuclear weapons and end the development of advanced new types of these weapons. The Treaty provides for a comprehensive global verification regime, which includes an International Monitoring System (IMS). The IMS comprises a network of 321 monitoring stations and 16 radionuclide laboratories that monitor the Earth for evidence of nuclear explosions, which cover underground, underwater and atmosphere environments. Presently, Malaysia receives seismic, infrasound, hydroacoustic and radionuclide data from the International Data Centre (IDC) of the CTBT. In order to maximise the use of the data for the purposes of the CTBT, the Malaysian Nuclear Agency is developing capability to analyse the data in order to detect nuclear weapon test, with an initial focus on the seismic data. Through the CTBT IMS, seismic data is constantly being obtained to monitor and detect nuclear explosions. However, in the process, other natural and man-made activities that generate seismic waves, especially earthquakes and large man-made explosions, are also detectable through the IMS, and need to be differentiated and discriminated before any nuclear explosions can be identified. The detection capability by using seismological methods was proven through simulated explosion tests at selected nuclear weapon test sites. This is supported by data previously collected from a total of 2089 nuclear weapon tests that have been carried out globally, out of which 1567 were underground, 514 in the atmosphere, including outer space, and 8 underwater. The discrimination of seismic data to detect nuclear explosions from natural earthquake and explosions can be undertaken through the identification of the epicentre location, hypocentre depth, magnitude and short-period discrimination of the seismic events. (Author)

  8. Seismogenic Tectonic Environment of 1976 Great Tangshan Earthquake: Results from Dense Seismic Array Observations

    Science.gov (United States)

    LIU, Qiyuan; WANG, Jun; CHEN, Jiuhui; LI, Shuncheng; GUO, Biao

    On July 28, 1976, the great Tangshan earthquake that shook the whole world took place in the Tangshan area of the Hebei Province, China. A big incomprehensible question is why such a tremendous earthquake took place in the Paleo-craton area in North China? It would be worth considering whether a similar event will reoccur in the Tangshan region. In this study, using the receiver function inversion technique and teleseismic P waveform data recorded at the Capital Circle Seismic network and our movable seismic array, we investigated the 3-D S-wave velocity structure of the crust and upper mantle down to 60 km beneath Tangshan area. Our results manifest that (1) the media beneath the Tangshan block cut by active faults are very different from the adjacent area, and all of the active faults surrounding the Tangshan block was through the whole crust; (2) in the upper and middle crust, there exist obvious heterogeneous low-velocity media beneath the Tangshan earthquake region; the crust-mantle boundary has an obvious block uplift and, in comparison with both sides, the top anomalous uplift of the upper mantle beneath the Tangshan block reaches to 10 km, and the upper mantle beneath has an anomalous heterogeneous structure; (4) beneath the Tangshan earthquake region, there are probably massive intrusions derived from the upper mantle, which form the low-velocity body in the upper and middle crust. Because of our results having much higher resolution than previous results, some new features of the crust and upper mantle velocity structure could be shown in this study; (5) the locations of destructive earthquakes are not random and are related closely to their deep structure of the crust and upper mantle. This provides a possibility of correctly estimating the location of destructive earthquakes. On the basis of our results, we discuss the dynamic genesis of the Tangshan earthquake. We consider that the main dynamic source for the Tangshan earthquake is the vertical

  9. Swedish National Seismic Network (SNSN). A short report on recorded earthquakes during the fourth quarter of the year 2010

    Energy Technology Data Exchange (ETDEWEB)

    Boedvarsson, Reynir (Uppsala Univ. (Sweden), Dept. of Earth Sciences)

    2011-01-15

    According to an agreement with Swedish Nuclear Fuel and Waste Management Company (SKB) and Uppsala Univ., the Dept. of Earth Sciences has continued to carry out observations of seismic events at seismic stations within the Swedish National Seismic Network (SNSN). This short report gives brief information about the recorded seismicity during October through December 2010. The Swedish National Seismic Network consists of 62 stations. During October through December, 2,241 events were located whereof 158 are estimated as real earthquakes, 1,457 are estimated as explosions, 444 are induced earthquakes in the vicinity of the mines in Kiruna and Malmberget and 182 events are still considered as uncertain but these are most likely explosions and are mainly located outside the network. One earthquake had a magnitude above M{sub L} = 2.0 during the period. In November one earthquake was located 13 km SW of Haernoesand with a magnitude of M{sub L} = 2.1. The largest earthquake in October had a magnitude of M{sub L} = 1.7 and was located 12 km NE of Eksjoe and in December an earthquake with a magnitude of M{sub L} = 1.8 was located 19 km north of Motala

  10. Incorporating Low-Cost Seismometers into the Central Weather Bureau Seismic Network for Earthquake Early Warning in Taiwan

    Directory of Open Access Journals (Sweden)

    Da-Yi Chen

    2015-01-01

    Full Text Available A dense seismic network can increase Earthquake Early Warning (EEW system capability to estimate earthquake information with higher accuracy. It is also critical for generating fast, robust earthquake alarms before strong-ground shaking hits the target area. However, building a dense seismic network via traditional seismometers is too expensive and may not be practical. Using low-cost Micro-Electro Mechanical System (MEMS accelerometers is a potential solution to quickly deploy a large number of sensors around the monitored region. An EEW system constructed using a dense seismic network with 543 MEMS sensors in Taiwan is presented. The system also incorporates the official seismic network of _ Central Weather Bureau (CWB. The real-time data streams generated by the two networks are integrated using the Earthworm software. This paper illustrates the methods used by the integrated system for estimating earthquake information and evaluates the system performance. We applied the Earthworm picker for the seismograms recorded by the MEMS sensors (Chen et al. 2015 following new picking constraints to accurately detect P-wave arrivals and use a new regression equation for estimating earthquake magnitudes. An off-line test was implemented using 46 earthquakes with magnitudes ranging from ML 4.5 - 6.5 to calibrate the system. The experimental results show that the integrated system has stable source parameter results and issues alarms much faster than the current system run by the CWB seismic network (CWBSN.

  11. Multiscale assessment of micro-seismicity and slow earthquakes

    Science.gov (United States)

    Yuen, David A.; Ni, Sidao; Wang, Yibo; Xu, Chang; Veveakis, Manny

    2017-03-01

    Today we witness the economical throes and uncertainties created by the dramatic cratering of oil prices in 2014 from 115 dollars per barrel to 38 dollars. This dramatic nonlinear phenomenon reminds earth scientists of the disintegration of the Laurentide ice sheet, some 14,000 years ago. One of the contributing factors of the precipitous drop in oil prices is super-fracking. This is used for oil as well as for gas production and became economically feasible about .twenty years ago. Thanks to this technological breakthrough Americans had enjoyed a renaissance in oil production since 2005. This process, however, has some drawbacks, such as the induced earthquakes occurring in rejuvenated or new fields (Fig. 1).

  12. Co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake

    Science.gov (United States)

    Yagi, Yuji; Kikuchi, Masayuki; Nishimura, Takuya

    2003-11-01

    We analyzed continuous GPS data to investigate the spatio-temporal distribution of co-seismic slip, post-seismic slip, and largest aftershock associated with the 1994 Sanriku-haruka-oki, Japan, earthquake (Mw = 7.7). To get better resolution for co-seismic and post-seismic slip distribution, we imposed a weak constraint as a priori information of the co-seismic slip determined by seismic wave analyses. We found that the post-seismic slip during 100 days following the main-shock amount to as much moment release as the main-shock, and that the sites of co-seismic slip and post-seismic slip are partitioning on a plate boundary region in complimentary fashion. The major post-seismic slip was triggered by the mainshock in western side of the co-seismic slip, and the extent of the post-seismic slip is almost unchanged with time. It rapidly developed a shear stress concentration ahead of the slip area, and triggered the largest aftershock.

  13. Local amplification of seismic waves from the Denali earthquake and damaging seiches in Lake Union, Seattle, Washington

    Science.gov (United States)

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

    2004-01-01

    The Mw7.9 Denali, Alaska earthquake of 3 November, 2002, caused minor damage to at least 20 houseboats in Seattle, Washington by initiating water waves in Lake Union. These water waves were likely initiated during the large amplitude seismic surface waves from this earthquake. Maps of spectral amplification recorded during the Denali earthquake on the Pacific Northwest Seismic Network (PNSN) strong-motion instruments show substantially increased shear and surface wave amplitudes coincident with the Seattle sedimentary basin. Because Lake Union is situated on the Seattle basin, the size of the water waves may have been increased by local amplification of the seismic waves by the basin. Complete hazard assessments require understanding the causes of these water waves during future earthquakes. Copyright 2004 by the American Geophysical Union.

  14. Strain Anomalies during an Earthquake Sequence in the South Iceland Seismic Zone

    Science.gov (United States)

    Arnadottir, T.; Haines, A. J.; Geirsson, H.; Hreinsdottir, S.

    2017-12-01

    The South Iceland Seismic Zone (SISZ) accommodates E-W translation due to oblique spreading between the North American/Hreppar microplate and Eurasian plate, in South Iceland. Strain is released in the SISZ during earthquake sequences that last days to years, at average intervals of 80-100 years. The SISZ is currently in the midst of an earthquake sequence that started with two M6.5 earthquakes in June 2000, and continued with two M6 earthquakes in May 2008. Estimates of geometric strain accumulation, and seismic strain release in these events indicate that they released at most only half of the strain accumulated since the last earthquake cycle in 1896-1912. Annual GPS campaigns and continuous measurements during 2001-2015 were used to calculate station velocities and strain rates from a new method using the vertical derivatives of horizontal stress (VDoHS). This new method allows higher resolution of strain rates than other (older) approaches, as the strain rates are estimated by integrating VDoHS rates obtained by inversion rather than differentiating interpolated GPS velocities. Estimating the strain rates for eight 1-2 year intervals indicates temporal and spatial variation of strain rates in the SISZ. In addition to earthquake faulting, the strain rates in the SISZ are influenced by anthropogenic signals due to geothermal exploitation, and magma movements in neighboring volcanoes - Hekla and Eyjafjallajökull. Subtle signals of post-seismic strain rate changes are seen following the June 2000 M6.5 main shocks, but interestingly, much larger strain rate variations are observed after the two May 2008 M6 main shocks. A prominent strain anomaly is evident in the epicentral area prior to the May 2008 earthquake sequence. The strain signal persists over at least 4 years in the epicentral area, leading up to the M6 main shocks. The strain is primarily extension in ESE-WNW direction (sub-parallel to the direction of plate spreading), but overall shear across the N

  15. Statistical analysis of seismicity rate change in the Tokyo Metropolitan area due to the 2011 Tohoku Earthquake

    Science.gov (United States)

    Ishibe, T.; Sakai, S.; Shimazaki, K.; Satake, K.; Tsuruoka, H.; Nakagawa, S.; Hirata, N.

    2012-12-01

    We examined a relationship between the Coulomb Failure Function (ΔCFF) due to the Tohoku earthquake (March 11, 2011; MJMA 9.0) and the seismicity rate change in Tokyo Metropolitan area following March 2011. Because of large variation in focal mechanism in the Kanto region, the receiver faults for the ΔCFF were assumed to be two nodal planes of small (M ≥ 2.0) earthquakes which occurred before and after the Tohoku earthquake. The seismicity rate changes, particularly the rate increase, are well explained by ΔCFF due to the gigantic thrusting, while some other possible factors (e.g., dynamic stress changes, excess of fluid dehydration) may also contribute the rate changes. Among 30,746 previous events provided by the National Research Institute for Earth Science and Disaster Prevention (M ≥ 2.0, July 1979 - July 2003), we used as receiver faults, almost 16,000 events indicate significant increase in ΔCFF, while about 8,000 events show significant decrease. Positive ΔCFF predicts seismicity rate increase in southwestern Ibaraki and northern Chiba prefectures where intermediate-depth earthquakes occur, and in shallow crust of the Izu-Oshima and Hakone regions. In these regions, seismicity rates significantly increased after the Tohoku earthquake. The seismicity has increased since March 2011 with respect to the Epidemic Type of Aftershock Sequence (ETAS) model (Ogata, 1988), indicating that the rate change was due to the stress increase by the Tohoku earthquake. The activated seismicity in the Izu and Hakone regions rapidly decayed following the Omori-Utsu formula, while the increased rate of seismicity in the southwestern Ibaraki and northern Chiba prefectures is still continuing. We also calculated ΔCFF due to the 2011 Tohoku earthquake for the focal mechanism solutions of earthquakes between April 2008 and October 2011 recorded on the Metropolitan Seismic Observation network (MeSO-net). The ΔCFF values for the earthquakes after March 2011 show more

  16. 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

  17. Empirical relations between instrumental and seismic parameters of some strong earthquakes of Colombia

    International Nuclear Information System (INIS)

    Marin Arias, Juan Pablo; Salcedo Hurtado, Elkin de Jesus; Castillo Gonzalez, Hardany

    2008-01-01

    In order to establish the relationships between macroseismic and instrumental parameters, macroseismic field of 28 historical earthquakes that produced great effects in the Colombian territory were studied. The integration of the parameters was made by using the methodology of Kaussel and Ramirez (1992), for great Chilean earthquakes; Kanamori and Anderson (1975) and Coppersmith and Well (1994) for world-wide earthquakes. Once determined the macroseismic and instrumental parameters it was come to establish the model of the source of each earthquake, with which the data base of these parameters was completed. For each earthquake parameters related to the local and normal macroseismic epicenter were complemented, depth of the local and normal center, horizontal extension of both centers, vertical extension of the normal center, model of the source, area of rupture. The obtained empirical relations from linear equations, even show behaviors very similar to the found ones by other authors for other regions of the world and to world-wide level. The results of this work allow establishing that certain mutual non compatibility exists between the area of rupture and the length of rupture determined by the macroseismic methods, with parameters found with instrumental data like seismic moment, Ms magnitude and Mw magnitude.

  18. Have recent earthquakes exposed flaws in or misunderstandings of probabilistic seismic hazard analysis?

    Science.gov (United States)

    Hanks, Thomas C.; Beroza, Gregory C.; Toda, Shinji

    2012-01-01

    In a recent Opinion piece in these pages, Stein et al. (2011) offer a remarkable indictment of the methods, models, and results of probabilistic seismic hazard analysis (PSHA). The principal object of their concern is the PSHA map for Japan released by the Japan Headquarters for Earthquake Research Promotion (HERP), which is reproduced by Stein et al. (2011) as their Figure 1 and also here as our Figure 1. It shows the probability of exceedance (also referred to as the “hazard”) of the Japan Meteorological Agency (JMA) intensity 6–lower (JMA 6–) in Japan for the 30-year period beginning in January 2010. JMA 6– is an earthquake-damage intensity measure that is associated with fairly strong ground motion that can be damaging to well-built structures and is potentially destructive to poor construction (HERP, 2005, appendix 5). Reiterating Geller (2011, p. 408), Stein et al. (2011, p. 623) have this to say about Figure 1: The regions assessed as most dangerous are the zones of three hypothetical “scenario earthquakes” (Tokai, Tonankai, and Nankai; see map). However, since 1979, earthquakes that caused 10 or more fatalities in Japan actually occurred in places assigned a relatively low probability. This discrepancy—the latest in a string of negative results for the characteristic model and its cousin the seismic-gap model—strongly suggest that the hazard map and the methods used to produce it are flawed and should be discarded. Given the central role that PSHA now plays in seismic risk analysis, performance-based engineering, and design-basis ground motions, discarding PSHA would have important consequences. We are not persuaded by the arguments of Geller (2011) and Stein et al. (2011) for doing so because important misunderstandings about PSHA seem to have conditioned them. In the quotation above, for example, they have confused important differences between earthquake-occurrence observations and ground-motion hazard calculations.

  19. Forecasting of Energy Expenditure of Induced Seismicity with Use of Artificial Neural Network

    Science.gov (United States)

    Cichy, Tomasz; Banka, Piotr

    2017-12-01

    Coal mining in many Polish mines in the Upper Silesian Coal Basin is accompanied by high levels of induced seismicity. In mining plants, the methods of shock monitoring are improved, allowing for more accurate localization of the occurring phenomena and determining their seismic energy. Equally important is the development of ways of forecasting seismic hazards that may occur while implementing mine design projects. These methods, depending on the length of time for which the forecasts are made, can be divided into: longterm, medium-term, short-term and so-called alarm. Long-term forecasts are particularly useful for the design of seam exploitations. The paper presents a method of predicting changes in energy expenditure of shock using a properly trained artificial neural network. This method allows to make long-term forecasts at the stage of the mine’s exploitation design, thus enabling the mining work plans to be reviewed to minimize the potential for tremors. The information given at the input of the neural network is indicative of the specific energy changes of the elastic deformation occurring in the selected, thick, resistant rock layers (tremor-prone layers). Energy changes, taking place in one or more tremor-prone layers are considered. These indicators describe only the specific energy changes of the elastic deformation accumulating in the rock as a consequence of the mining operation, but does not determine the amount of energy released during the destruction of a given volume of rock. In this process, the potential energy of elastic strain transforms into other, non-measurable energy types, including the seismic energy of recorded tremors. In this way, potential energy changes affect the observed induced seismicity. The parameters used are characterized by increases (declines) of specific energy with separation to occur before the hypothetical destruction of the rock and after it. Additional input information is an index characterizing the rate of

  20. Global earthquake catalogs and long-range correlation of seismic activity (Invited)

    Science.gov (United States)

    Ogata, Y.

    2009-12-01

    In view of the long-term seismic activity in the world, homogeneity of a global catalog is indispensable. Lately, Engdahl and Villaseñor (2002) compiled a global earthquake catalog of magnitude (M)7.0 or larger during the last century (1900-1999). This catalog is based on the various existing catalogs such as Abe catalog (Abe, 1981, 1984; Abe and Noguchi, 1983a, b) for the world seismicity (1894-1980), its modified catalogs by Perez and Scholz (1984) and by Pacheco and Sykes (1992), and also the Harvard University catalog since 1975. However, the original surface wave magnitudes of Abe catalog were systematically changed by Perez and Scholz (1984) and Pacheco and Sykes (1992). They suspected inhomogeneity of the Abe catalog and claimed that the two seeming changes in the occurrence rate around 1922 and 1948 resulted from magnitude shifts for some instrumental-related reasons. They used a statistical test assuming that such a series of large earthquakes in the world should behave as the stationary Poisson process (uniform occurrences). It is obvious that their claim strongly depends on their a priori assumption of an independent or short-range dependence of earthquake occurrence. We question this assumption from the viewpoint of long-range dependence of seismicity. We make some statistical analyses of the spectrum, dispersion-time diagrams and R/S for estimating and testing of the long-range correlations. We also attempt to show the possibility that the apparent rate change in the global seismicity can be simulated by a certain long-range correlated process. Further, if we divide the globe into the two regions of high and low latitudes, for example, we have different shapes of the cumulative curves to each other, and the above mentioned apparent change-points disappear from the both regions. This suggests that the Abe catalog shows the genuine seismic activity rather than the artifact of the suspected magnitude shifts that should appear in any wide enough regions

  1. Three-dimensional seismic velocity structure and earthquake relocations at Katmai, Alaska

    Science.gov (United States)

    Murphy, Rachel; Thurber, Clifford; Prejean, Stephanie G.; Bennington, Ninfa

    2014-01-01

    We invert arrival time data from local earthquakes occurring between September 2004 and May 2009 to determine the three-dimensional (3D) upper crustal seismic structure in the Katmai volcanic region. Waveforms for the study come from the Alaska Volcano Observatory's permanent network of 20 seismic stations in the area (predominantly single-component, short period instruments) plus a densely spaced temporary array of 11 broadband, 3-component stations. The absolute and relative arrival times are used in a double-difference seismic tomography inversion to solve for 3D P- and S-wave velocity models for an area encompassing the main volcanic centers. The relocated hypocenters provide insight into the geometry of seismogenic structures in the area, revealing clustering of events into four distinct zones associated with Martin, Mageik, Trident-Novarupta, and Mount Katmai. The seismic activity extends from about sea level to 2 km depth (all depths referenced to mean sea level) beneath Martin, is concentrated near 2 km depth beneath Mageik, and lies mainly between 2 and 4 km depth below Katmai and Trident-Novarupta. Many new features are apparent within these earthquake clusters. In particular, linear features are visible within all clusters, some associated with swarm activity, including an observation of earthquake migration near Trident in 2008. The final velocity model reveals a possible zone of magma storage beneath Mageik, but there is no clear evidence for magma beneath the Katmai-Novarupta area where the 1912 eruptive activity occurred, suggesting that the storage zone for that eruption may have largely been evacuated, or remnant magma has solidified.

  2. Long-term earthquake forecasts based on the epidemic-type aftershock sequence (ETAS model for short-term clustering

    Directory of Open Access Journals (Sweden)

    Jiancang Zhuang

    2012-07-01

    Full Text Available Based on the ETAS (epidemic-type aftershock sequence model, which is used for describing the features of short-term clustering of earthquake occurrence, this paper presents some theories and techniques related to evaluating the probability distribution of the maximum magnitude in a given space-time window, where the Gutenberg-Richter law for earthquake magnitude distribution cannot be directly applied. It is seen that the distribution of the maximum magnitude in a given space-time volume is determined in the longterm by the background seismicity rate and the magnitude distribution of the largest events in each earthquake cluster. The techniques introduced were applied to the seismicity in the Japan region in the period from 1926 to 2009. It was found that the regions most likely to have big earthquakes are along the Tohoku (northeastern Japan Arc and the Kuril Arc, both with much higher probabilities than the offshore Nankai and Tokai regions.

  3. Efficient blind search for similar-waveform earthquakes in years of continuous seismic data

    Science.gov (United States)

    Yoon, C. E.; Bergen, K.; Rong, K.; Elezabi, H.; Bailis, P.; Levis, P.; Beroza, G. C.

    2017-12-01

    Cross-correlating an earthquake waveform template with continuous seismic data has proven to be a sensitive, discriminating detector of small events missing from earthquake catalogs, but a key limitation of this approach is that it requires advance knowledge of the earthquake signals we wish to detect. To overcome this limitation, we can perform a blind search for events with similar waveforms, comparing waveforms from all possible times within the continuous data (Brown et al., 2008). However, the runtime for naive blind search scales quadratically with the duration of continuous data, making it impractical to process years of continuous data. The Fingerprint And Similarity Thresholding (FAST) detection method (Yoon et al., 2015) enables a comprehensive blind search for similar-waveform earthquakes in a fast, scalable manner by adapting data-mining techniques originally developed for audio and image search within massive databases. FAST converts seismic waveforms into compact "fingerprints", which are efficiently organized and searched within a database. In this way, FAST avoids the unnecessary comparison of dissimilar waveforms. To date, the longest duration of continuous data used for event detection with FAST was 3 months at a single station near Guy-Greenbrier, Arkansas, which revealed microearthquakes closely correlated with stages of hydraulic fracturing (Yoon et al., 2017). In this presentation we introduce an optimized, parallel version of the FAST software with improvements to the fingerprinting algorithm and the ability to detect events using continuous data from a network of stations (Bergen et al., 2016). We demonstrate its ability to detect low-magnitude earthquakes within several years of continuous data at locations of interest in California.

  4. Criteria for Seismic Splay Fault Activation During Subduction Earthquakes

    Science.gov (United States)

    Dedontney, N.; Templeton, E.; Bhat, H.; Dmowska, R.; Rice, J. R.

    2008-12-01

    As sediment is added to the accretionary prism or removed from the forearc, the material overlying the plate interface must deform to maintain a wedge structure. One of the ways this internal deformation is achieved is by slip on splay faults branching from the main detachment, which are possibly activated as part of a major seismic event. As a rupture propagates updip along the plate interface, it will reach a series of junctions between the shallowly dipping detachment and more steeply dipping splay faults. The amount and distribution of slip on these splay faults and the detachment determines the seafloor deformation and the tsunami waveform. Numerical studies by Kame et al. [JGR, 2003] of fault branching during dynamic slip-weakening rupture in 2D plane strain showed that branch activation depends on the initial stress state, rupture velocity at the branching junction, and branch angle. They found that for a constant initial stress state, with the maximum principal stress at shallow angles to the main fault, branch activation is favored on the compressional side of the fault for a range of branch angles. By extending the part of their work on modeling the branching behavior in the context of subduction zones, where critical taper wedge concepts suggest the angle that the principal stress makes with the main fault is shallow, but not horizontal, we hope to better understand the conditions for splay fault activation and the criteria for significant moment release on the splay. Our aim is to determine the range of initial stresses and relative frictional strengths of the detachment and splay fault that would result in seismic splay fault activation. In aid of that, we conduct similar dynamic rupture analyses to those of Kame et al., but use explicit finite element methods, and take fuller account of overall structure of the zone (rather than focusing just on the branching junction). Critical taper theory requires that the basal fault be weaker than the overlying

  5. Evaluation and summary of seismic response of above ground nuclear power plant piping to strong motion earthquakes

    International Nuclear Information System (INIS)

    Stevenson, J.D.

    1985-01-01

    The purpose of this paper is to summarize the observations and experience which has been developed relative to the seismic behavior of above-ground, building-supported, industrial type piping (similar to piping used in nuclear power plants) in strong motion earthquakes. The paper also contains observations regarding the response of piping in experimental tests which attempted to excite the piping to failure. Appropriate conclusions regarding the behavior of such piping in large earthquakes and recommendations as to future design of such piping to resist earthquake motion damage are presented based on observed behavior in large earthquakes and simulated shake table testing

  6. Consideration on the relation between dynamic seismic motion and static seismic coefficient for the earthquake proof design of slope around nuclear power plant

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Kitahara, Yoshihiro; Hirata, Kazuta

    1986-01-01

    When the large cutting slopes are constructed closed to around nuclear power plants, it is important to evaluate the stability of the slopes during the strong earthquake. In the evaluation, it may be useful to clarify relationship between the static seismic coefficient and dynamic seismic force corresponded to the basic seismic motion which is specified for designing the nuclear power facilities. To investigate this relation some numerical analyses are conducted in this paper. As the results, it is found that dynamic forces considering the amplified responses of the slopes subjected to the basic seismic motion with a peak acceleration of 500 gals at the toe of the slopes, are approximately equal to static seismic force which generates in the slopes when the seismic coefficients of k = 0.3 is applied. (author)

  7. Surface-seismic imaging for nehrp soil profile classifications and earthquake hazards in urban areas

    Science.gov (United States)

    Williams, R.A.; Stephenson, W.J.; Odum, J.K.

    1998-01-01

    We acquired high-resolution seismic-refraction data on the ground surface in selected areas of the San Fernando Valley (SFV) to help explain the earthquake damage patterns and the variation in ground motion caused by the 17 January 1994 magnitude 6.7 Northridge earthquake. We used these data to determine the compressional- and shear-wave velocities (Vp and Vs) at 20 aftershock recording sites to 30-m depth ( V??s30, and V??p30). Two other sites, located next to boreholes with downhole Vp and Vs data, show that we imaged very similar seismic-vefocity structures in the upper 40 m. Overall, high site response appears to be associated with tow Vs in the near surface, but there can be a wide rangepf site amplifications for a given NEHRP soil type. The data suggest that for the SFV, if the V??s30 is known, we can determine whether the earthquake ground motion will be amplified above a factor of 2 relative to a local rock site.

  8. 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

  9. Approaches that use seismic hazard results to address topics of nuclear power plant seismic safety, with application to the Charleston earthquake issue

    International Nuclear Information System (INIS)

    Sewell, R.T.; McGuire, R.K.; Toro, G.R.; Stepp, J.C.; Cornell, C.A.

    1990-01-01

    Plant seismic safety indicators include seismic hazard at the SSE (safe shut-down earthquake) acceleration, seismic margin, reliability against core damage, and reliability against offsite consequences. This work examines the key role of hazard analysis in evaluating these indicators and in making rational decisions regarding plant safety. The paper outlines approaches that use seismic hazard results as a basis for plant seismic safety evaluation and applies one of these approaches to the Charleston earthquake issue. This approach compares seismic hazard results that account for the Charleston tectonic interpretation, using the EPRI-Seismicity Owners Group (SOG) methodology, with hazard results that are consistent with historical tectonic interpretations accepted in regulation. Based on hazard results for a set of 21 eastern U.S. nuclear power plant sites, the comparison shows that no systematic 'plant-to-plant' increase in hazard accompanies the Charleston hypothesis; differences in mean hazards for the two interpretations are generally insignificant relative to current uncertainties in seismic hazard. (orig.)

  10. Seismic properties of the Longmen Shan complex: Implications for the moment magnitude of the great 2008 Wenchuan earthquake in China

    Science.gov (United States)

    Sun, Shengsi; Ji, Shaocheng; Wang, Qian; Wang, Hongcai; Long, Changxing; Salisbury, Matthew

    2012-09-01

    The 12 May 2008 Wenchuan earthquake is the largest active tectonic event reported to date in Sichuan (China). We have experimentally calibrated, up to 800 MPa, seismic and elastic properties of 12 representative samples from the Longmen Shan complex in which this great earthquake took place and its coseismic ruptures nucleated and propagated. Most of the samples show little Vp or Vs anisotropy at pressures above the microcrack-closure pressure (Pc = 200-300 MPa), and so the variation of anisotropy with pressure provides important hints for the preferred orientation of microcracks in the nonlinear poroelastic regime below Pc. Geothermal and rheological profiles indicate that the focal depth (~ 19 km) corresponds to the base of the schizosphere, below which the Longmen Shan complex switches from the brittle to ductile behavior. The investigation reveals that the crust of the Longmen Shan range consists of 4 layers from the surface to the Moho: Layer 1: Vp < 4.88 km/s (0-3 km thick, sedimentary rocks such as limestone, sandstone, conglomerate, and mudstone); Layer 2: Vp = 5.95-6.25 km/s (25-28 km thick, felsic rocks); Layer 3: Vp = 6.55 km/s (10 km thick, 67.5% felsic and 32.5% mafic rocks); and Layer 4: Vp = 6.90 km/s (8 km thick, 20.0% felsic and 80.0% mafic rocks). The average Vp/Vs ratio of 1.71 or Poisson's ratio of 0.24 calculated for the whole crust is consistent with the results measured using teleseismic receiver function techniques. This study also offers necessary information for broadband simulations of strong ground motions in the assessment and forecast of earthquake hazards in the region. Furthermore, the study, which yields a moment magnitude of 7.9-8.0 given the variation in the dip of the coseismic ruptures and the uncertainty in the depth to which the coseismic rupture may propagate downwards below the depth of the mainshock hypocenter, presents the first accurate quantification of the 2008 Wenchuan earthquake's size.

  11. PROBABILISTIC SEISMIC ASSESSMENT OF BASE-ISOLATED NPPS SUBJECTED TO STRONG GROUND MOTIONS OF TOHOKU EARTHQUAKE

    Directory of Open Access Journals (Sweden)

    AHMER ALI

    2014-10-01

    Full Text Available The probabilistic seismic performance of a standard Korean nuclear power plant (NPP with an idealized isolation is investigated in the present work. A probabilistic seismic hazard analysis (PSHA of the Wolsong site on the Korean peninsula is performed by considering peak ground acceleration (PGA as an earthquake intensity measure. A procedure is reported on the categorization and selection of two sets of ground motions of the Tohoku earthquake, i.e. long-period and common as Set A and Set B respectively, for the nonlinear time history response analysis of the base-isolated NPP. Limit state values as multiples of the displacement responses of the NPP base isolation are considered for the fragility estimation. The seismic risk of the NPP is further assessed by incorporation of the rate of frequency exceedance and conditional failure probability curves. Furthermore, this framework attempts to show the unacceptable performance of the isolated NPP in terms of the probabilistic distribution and annual probability of limit states. The comparative results for long and common ground motions are discussed to contribute to the future safety of nuclear facilities against drastic events like Tohoku.

  12. Probabilistic seismic assessment of base-isolated NPPs subjected to strong ground motions of Tohoku earthquake

    Energy Technology Data Exchange (ETDEWEB)

    Ali, Ahmer; Hayah, Nadin Abu; Kim, Doo Kie [Dept. of Civil and Environmental Engineering, Kunsan National University, Kunsan (Korea, Republic of); Cho, Sung Gook [R and D Center, JACE KOREA Company, Gyeonggido (Korea, Republic of)

    2014-10-15

    The probabilistic seismic performance of a standard Korean nuclear power plant (NPP) with an idealized isolation is investigated in the present work. A probabilistic seismic hazard analysis (PSHA) of the Wolsong site on the Korean peninsula is performed by considering peak ground acceleration (PGA) as an earthquake intensity measure. A procedure is reported on the categorization and selection of two sets of ground motions of the Tohoku earthquake, i.e. long-period and common as Set A and Set B respectively, for the nonlinear time history response analysis of the base-isolated NPP. Limit state values as multiples of the displacement responses of the NPP base isolation are considered for the fragility estimation. The seismic risk of the NPP is further assessed by incorporation of the rate of frequency exceedance and conditional failure probability curves. Furthermore, this framework attempts to show the unacceptable performance of the isolated NPP in terms of the probabilistic distribution and annual probability of limit states. The comparative results for long and common ground motions are discussed to contribute to the future safety of nuclear facilities against drastic events like Tohoku.

  13. Earthquake location determination using data from DOMERAPI and BMKG seismic networks: A preliminary result of DOMERAPI project

    Energy Technology Data Exchange (ETDEWEB)

    Ramdhan, Mohamad [Study Program of Earth Science, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung, 40132 (Indonesia); Agency for Meteorology, Climatology and Geophysics of Indonesia (BMKG) Jl. Angkasa 1 No. 2 Kemayoran, Jakarta Pusat, 10720 (Indonesia); Nugraha, Andri Dian; Widiyantoro, Sri [Global Geophysics Research Group, Faculty of Mining and Petroleum Engineering, Institut TeknologiBandung, Jl. Ganesa 10, Bandung, 40132 (Indonesia); Métaxian, Jean-Philippe [Institut de Recherche pour le Développement (IRD) (France); Valencia, Ayunda Aulia, E-mail: mohamad.ramdhan@bmkg.go.id [Study Program of Geophysical Engineering, Institut Teknologi Bandung, Jl. Ganesa 10, Bandung, 40132 (Indonesia)

    2015-04-24

    DOMERAPI project has been conducted to comprehensively study the internal structure of Merapi volcano, especially about deep structural features beneath the volcano. DOMERAPI earthquake monitoring network consists of 46 broad-band seismometers installed around the Merapi volcano. Earthquake hypocenter determination is a very important step for further studies, such as hypocenter relocation and seismic tomographic imaging. Ray paths from earthquake events occurring outside the Merapi region can be utilized to delineate the deep magma structure. Earthquakes occurring outside the DOMERAPI seismic network will produce an azimuthal gap greater than 180{sup 0}. Owing to this situation the stations from BMKG seismic network can be used jointly to minimize the azimuthal gap. We identified earthquake events manually and carefully, and then picked arrival times of P and S waves. The data from the DOMERAPI seismic network were combined with the BMKG data catalogue to determine earthquake events outside the Merapi region. For future work, we will also use the BPPTKG (Center for Research and Development of Geological Disaster Technology) data catalogue in order to study shallow structures beneath the Merapi volcano. The application of all data catalogues will provide good information as input for further advanced studies and volcano hazards mitigation.

  14. Discrimination of DPRK M5.1 February 12th, 2013 Earthquake as Nuclear Test Using Analysis of Magnitude, Rupture Duration and Ratio of Seismic Energy and Moment

    Science.gov (United States)

    Salomo Sianipar, Dimas; Subakti, Hendri; Pribadi, Sugeng

    2015-04-01

    On February 12th, 2013 morning at 02:57 UTC, there had been an earthquake with its epicenter in the region of North Korea precisely around Sungjibaegam Mountains. Monitoring stations of the Preparatory Commission for the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO) and some other seismic network detected this shallow seismic event. Analyzing seismograms recorded after this event can discriminate between a natural earthquake or an explosion. Zhao et. al. (2014) have been successfully discriminate this seismic event of North Korea nuclear test 2013 from ordinary earthquakes based on network P/S spectral ratios using broadband regional seismic data recorded in China, South Korea and Japan. The P/S-type spectral ratios were powerful discriminants to separate explosions from earthquake (Zhao et. al., 2014). Pribadi et. al. (2014) have characterized 27 earthquake-generated tsunamis (tsunamigenic earthquake or tsunami earthquake) from 1991 to 2012 in Indonesia using W-phase inversion analysis, the ratio between the seismic energy (E) and the seismic moment (Mo), the moment magnitude (Mw), the rupture duration (To) and the distance of the hypocenter to the trench. Some of this method was also used by us to characterize the nuclear test earthquake. We discriminate this DPRK M5.1 February 12th, 2013 earthquake from a natural earthquake using analysis magnitude mb, ms and mw, ratio of seismic energy and moment and rupture duration. We used the waveform data of the seismicity on the scope region in radius 5 degrees from the DPRK M5.1 February 12th, 2013 epicenter 41.29, 129.07 (Zhang and Wen, 2013) from 2006 to 2014 with magnitude M ≥ 4.0. We conclude that this earthquake was a shallow seismic event with explosion characteristics and can be discriminate from a natural or tectonic earthquake. Keywords: North Korean nuclear test, magnitude mb, ms, mw, ratio between seismic energy and moment, ruptures duration

  15. Intermediate-term earthquake prediction and seismic zoning in Northern Italy

    International Nuclear Information System (INIS)

    Panza, G.F.; Orozova Stanishkova, I.; Costa, G.; Vaccari, F.

    1993-12-01

    The algorithm CN for intermediate earthquake prediction has been applied to an area in Northern Italy, which has been chosen according to a recently proposed seismotectonic model. Earthquakes with magnitude ≥ 5.4 occur in the area with a relevant frequency and their occurrence is predicted by algorithm CN. Therefore a seismic hazard analysis has been performed using a deterministic procedure, based on the computation of complete synthetic seismograms. The results are summarized in a map giving the distribution of peak ground acceleration, but the complete time series are available, which can be used by civil engineers in the design of new seismo-resistant constructions and in the retrofitting of the existing ones. This risk reduction action should be intensified in connection with warnings issued on the basis of the forward predictions made by CN. (author). Refs, 7 figs, 1 tab

  16. Effects of seismic intensity and socioeconomic status on injury and displacement after the 2007 Peru earthquake.

    Science.gov (United States)

    Milch, Karen; Gorokhovich, Yuri; Doocy, Shannon

    2010-10-01

    Earthquakes are a major cause of displacement, particularly in developing countries. Models of injury and displacement can be applied to assist governments and aid organisations in effectively targeting preparedness and relief efforts. A stratified cluster survey was conducted in January 2008 to evaluate risk factors for injury and displacement following the 15 August 2007 earthquake in southern Peru. In statistical modelling, seismic intensity, distance to rupture, living conditions, and educational attainment collectively explained 54.9 per cent of the variability in displacement rates across clusters. Living conditions was a particularly significant predictor of injury and displacement, indicating a strong relationship between risk and socioeconomic status. Contrary to expectations, urban, periurban, and rural clusters did not exhibit significantly different injury and displacement rates. Proxies of socioeconomic status, particularly the living conditions index score, proved relevant in explaining displacement, likely due to unmeasured aspects of housing construction practices and building materials. © 2010 The Author(s). Journal compilation © Overseas Development Institute, 2010.

  17. Re-evaluation Of The Shallow Seismicity On Mt Etna Applying Probabilistic Earthquake Location Algorithms.

    Science.gov (United States)

    Tuve, T.; Mostaccio, A.; Langer, H. K.; di Grazia, G.

    2005-12-01

    A recent research project carried out together with the Italian Civil Protection concerns the study of amplitude decay laws in various areas on the Italian territory, including Mt Etna. A particular feature of seismic activity is the presence of moderate magnitude earthquakes causing frequently considerable damage in the epicentre areas. These earthquakes are supposed to occur at rather shallow depth, no more than 5 km. Given the geological context, however, these shallow earthquakes would origin in rather weak sedimentary material. In this study we check the reliability of standard earthquake location, in particular with respect to the calculated focal depth, using standard location methods as well as more advanced approaches such as the NONLINLOC software proposed by Lomax et al. (2000) using it with its various options (i.e., Grid Search, Metropolis-Gibbs and Oct-Tree) and 3D velocity model (Cocina et al., 2005). All three options of NONLINLOC gave comparable results with respect to hypocenter locations and quality. Compared to standard locations we note a significant improve of location quality and, in particular a considerable difference of focal depths (in the order of 1.5 - 2 km). However, we cannot find a clear bias towards greater or lower depth. Further analyses concern the assessment of the stability of locations. For this purpose we carry out various Monte Carlo experiments perturbing travel time reading randomly. Further investigations are devoted to possible biases which may arise from the use of an unsuitable velocity model.

  18. Contribution of Satellite Gravimetry to Understanding Seismic Source Processes of the 2011 Tohoku-Oki Earthquake

    Science.gov (United States)

    Han, Shin-Chan; Sauber, Jeanne; Riva, Riccardo

    2011-01-01

    The 2011 great Tohoku-Oki earthquake, apart from shaking the ground, perturbed the motions of satellites orbiting some hundreds km away above the ground, such as GRACE, due to coseismic change in the gravity field. Significant changes in inter-satellite distance were observed after the earthquake. These unconventional satellite measurements were inverted to examine the earthquake source processes from a radically different perspective that complements the analyses of seismic and geodetic ground recordings. We found the average slip located up-dip of the hypocenter but within the lower crust, as characterized by a limited range of bulk and shear moduli. The GRACE data constrained a group of earthquake source parameters that yield increasing dip (7-16 degrees plus or minus 2 degrees) and, simultaneously, decreasing moment magnitude (9.17-9.02 plus or minus 0.04) with increasing source depth (15-24 kilometers). The GRACE solution includes the cumulative moment released over a month and demonstrates a unique view of the long-wavelength gravimetric response to all mass redistribution processes associated with the dynamic rupture and short-term postseismic mechanisms to improve our understanding of the physics of megathrusts.

  19. Seismic damage to structures in the M s6.5 Ludian earthquake

    Science.gov (United States)

    Chen, Hao; Xie, Quancai; Dai, Boyang; Zhang, Haoyu; Chen, Hongfu

    2016-03-01

    On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1) ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2) the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete (RC) frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the `strong column, weak beam' design target. Traditional timber frame structures with a light infill wall showed good aseismic performance.

  20. Tectonic Divisions Based on Gravity Data and Earthquake Distribution Characteristics in the North South Seismic Belt, China

    Science.gov (United States)

    Tian, T.; Zhang, J.; Jiang, W.

    2017-12-01

    The North South Seismic Belt is located in the middle of China, and this seismic belt can be divided into 12 tectonic zones, including the South West Yunnan (I), the Sichuan Yunnan (II), the Qiang Tang (III), the Bayan Har (IV), the East Kunlun Qaidam (V), the Qi Lian Mountain (VI), the Tarim(VII), the East Alashan (VIII), the East Sichuan (IX), the Ordos(X), the Middle Yangtze River (XI) and the Edge of Qinghai Tibet Block (XII) zone. Based on the Bouguer Gravity data calculated from the EGM2008 model, the Euler deconvolution was used to obtain the edge of tectonic zone to amend the traditional tectonic divisions. In every tectonic zone and the whole research area, the logarithm of the total energy of seismic was calculated. The Time Series Analysis (TSA) for all tectonic zones and the whole area were progressed in R, and 12 equal divisions were made (A1-3, B1-3, C1-3, D1-3) by latitude and longitude as a control group. A simple linear trend fitting of time was used, and the QQ figure was used to show the residual distribution features. Among the zones according to Gravity anomalies, I, II and XII show similar statistical characteristic, with no earthquake free year (on which year there was no earthquake in the zone), and it shows that the more seismic activity area is more similar in statistical characteristic as the large area, no matter how large the zone is or how many earthquakes are in the zone. Zone IV, V, IX, III, VII and VIII show one or several seismic free year during 1970s (IV, V and IX) and 1980s (III, VII and VIII), which may implicate the earthquake activity were low decades ago or the earthquake catalogue were not complete in these zones, or both. Zone VI, X and XI show many earthquake free years even in this decade, which means in these zones the earthquake activity were very low even if the catalogue were not complete. In the control group, the earthquake free year zone appeared random and independent of the seismic density, and in all equal

  1. Recorded earthquake responses from the integrated seismic monitoring network of the Atwood Building, Anchorage, Alaska

    Science.gov (United States)

    Celebi, M.

    2006-01-01

    An integrated seismic monitoring system with a total of 53 channels of accelerometers is now operating in and at the nearby free-field site of the 20-story steel-framed Atwood Building in highly seismic Anchorage, Alaska. The building has a single-story basement and a reinforced concrete foundation without piles. The monitoring system comprises a 32-channel structural array and a 21-channel site array. Accelerometers are deployed on 10 levels of the building to assess translational, torsional, and rocking motions, interstory drift (displacement) between selected pairs of adjacent floors, and average drift between floors. The site array, located approximately a city block from the building, comprises seven triaxial accelerometers, one at the surface and six in boreholes ranging in depths from 15 to 200 feet (???5-60 meters). The arrays have already recorded low-amplitude shaking responses of the building and the site caused by numerous earthquakes at distances ranging from tens to a couple of hundred kilometers. Data from an earthquake that occurred 186 km away traces the propagation of waves from the deepest borehole to the roof of the building in approximately 0.5 seconds. Fundamental structural frequencies [0.58 Hz (NS) and 0.47 Hz (EW)], low damping percentages (2-4%), mode coupling, and beating effects are identified. The fundamental site frequency at approximately 1.5 Hz is close to the second modal frequencies (1.83 Hz NS and 1.43 EW) of the building, which may cause resonance of the building. Additional earthquakes prove repeatability of these characteristics; however, stronger shaking may alter these conclusions. ?? 2006, Earthquake Engineering Research Institute.

  2. Variations of local seismic response in Benevento (Southern Italy) using earthquakes and ambient noise recordings

    Science.gov (United States)

    Improta, Luigi; di Giulio, Giuseppe; Rovelli, Antonio

    The city of Benevento (Southern Italy) has been repeatedly struck by large historical earthquakes. A heterogeneous geologic structure and widespread soft soil conditions make the estimation of site effects crucial for the seismic hazard assessment of the city. From 2000 until 2004, we installed seismic stations to collect earthquake data over zones with different geological conditions. Despite the high level of urban noise, we recorded more than 150 earthquakes at twelve sites. This data set yields the first, well documented experimental evidence for weak to moderate local amplifications. We investigated site effects primarily by the classical spectral ratio technique (CSR) using a rock station placed on the Benevento hill as reference. All sites in the Calore river valley and in the eastern part of the Benevento hill show a moderate high-frequency (f > 4 Hz) amplification peak. Conversely, sites in the Sabato river valley share weak-to-moderate amplification in a wide frequency band (from 1-2 to 7-10 Hz), without evident frequency peaks. Application of no-reference-site techniques to earthquake and noise data confirms the results of the CSRs in the sites of the Calore river valley and of the eastern part of the Benevento hill, but fails in providing indications for site effects in the Sabato river valley, being the H/V ratios nearly flat. One-dimensional modeling indicates that the ground motion amplification can be essentially explained in terms of a vertically varying geologic structure. High-frequency narrow peaks are caused by the strong impedance contrast existing between near-surface soft deposits and stiff cemented conglomerates. Conversely, broad-band amplifications in the Sabato river valley are likely due to a more complex layering with weak impedance contrasts both in the shallow and deep structure of the valley.

  3. Numerical simulation of co-seismic deformation of 2011 Japan Mw9. 0 earthquake

    Directory of Open Access Journals (Sweden)

    Zhang Keliang

    2011-08-01

    Full Text Available Co-seismic displacements associated with the Mw9. 0 earthquake on March 11, 2011 in Japan are numerically simulated on the basis of a finite-fault dislocation model with PSGRN/PSCMP software. Compared with the inland GPS observation, 90% of the computed eastward, northward and vertical displacements have residuals less than 0.10 m, suggesting that the simulated results can be, to certain extent, used to demonstrate the co-seismic deformation in the near field. In this model, the maximum eastward displacement increases from 6 m along the coast to 30 m near the epicenter, where the maximum southward displacement is 13 m. The three-dimensional display shows that the vertical displacement reaches a maximum uplift of 14.3 m, which is comparable to the tsunami height in the near-trench region. The maximum subsidence is 5.3 m.

  4. Local magnitude, duration magnitude and seismic moment of Dahshour 1992 earthquakes

    Directory of Open Access Journals (Sweden)

    M. F. Abdelwahed

    2000-06-01

    Full Text Available Local magnitudes ML have been calculated for 56 earthquakes of the Dahshour 1992 sequence using simulated records of the KEG broadband station and the estimated calibration function of the Dahshour area. These were compared with their corresponding values of duration magnitudes obtained from the analog short period seismograms of the HLW station. The local magnitudes M L and the duration magnitudes M D for this region imply a linear relation as follows: M L = 1.2988 (± 0.04 M D – 0.9032 (± 0.14. Seismic moment has also been estimated for these events using simple measurements from the time domain records. These measurements based on the simulated Wood Anderson seismograms are used for the local magnitude (ML estimation. The derived relationship between seismic moment (M 0 and magnitude (M L is: log (M 0 = 0.954 (± 0.019 M L + 17.258 (± 0.075.

  5. From Seismic Scenarios to Earthquake Risk Assessment: A Case Study for Iquique, Chile.

    Science.gov (United States)

    Aguirre, P.; Fortuno, C.; Martin, J. C. D. L. L.; Vasquez, J.

    2015-12-01

    Iquique is a strategic city and economic center in northern Chile, and is located in a large seismic gap where a megathrust earthquake and tsunami is expected. Although it was hit by a Mw 8.2 earthquake on April 1st 2014, which caused moderate damage, geophysical evidence still suggests that there is potential for a larger event, so a thorough risk assessment is key to understand the physical, social, and economic effects of such potential event, and devise appropriate mitigation plans. Hence, Iquique has been selected as a prime study case for the implementation of a risk assessment platform in Chile. Our study integrates research on three main elements of risk calculations: hazard evaluation, exposure model, and physical vulnerabilities. To characterize the hazard field, a set of synthetic seismic scenarios have been developed based on plate interlocking and the residual slip potential that results from subtracting the slip occurred during the April 1st 2014 rupture fault mechanism, obtained using InSAR+GPS inversion. Additional scenarios were developed based of the fault rupture model of the Maule 2010 Mw 8.8 earthquake and on the local plate locking models in northern Chile. These rupture models define a collection of possible realizations of earthquake geometries parameterized in terms of critical variables like slip magnitude, rise time, mean propagation velocity, directivity, and other, which are propagated to obtain a hazard map for Iquique (e.g. PGA, PGV, PDG). Furthermore, a large body of public and local data was used to construct a detailed exposure model for Iquique, including aggregated building count, demographics, essential facilities, and lifelines. This model together with the PGA maps for the April 1st 2014 earthquake are used to calibrate HAZUS outputs against observed damage, and adjust the fragility curves of physical systems according to more detailed analyses of typical Chilean building types and their structural properties, plus historical

  6. 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.

  7. Micro-seismic earthquakes characteristics at natural and exploited hydrothermal systems in West Java, Indonesia

    Science.gov (United States)

    Jousset, P. G.; Jaya, M. S.; Sule, R.; Diningrat, W.; Gassner, A.; Akbar, F.; Ryannugroho, R.; Hendryana, A.; Kusnadi, Y.; Syahbana, D.; Nugraha, A. D.; Umar, M.; Indrinanto, Y.; Erbas, K.

    2013-12-01

    The assessment of geothermal resources requires the understanding of the structure and the dynamics of geothermal reservoirs. We deployed a multidisciplinary geophysical network around geothermal areas in the south of Bandung, West Java, Indonesia. The first deployment included a network of 30 broadband and 4 short-period seismic stations with Güralp and Trillium sensors (0.008 - 100 Hz) since October 2012. In a second step, we extended the network in June 2013 with 16 short-period (1 Hz) seismometers. We describe the set-up of the seismic networks and discuss first observations and results. The co-existence of a large variety of intense surface manifestations like geysers, hot-steaming grounds, hot water pools, and active volcanoes suggest an intimate coupling between volcanic, tectonic and hydrothermal processes in this area. Preliminary location of earthquakes is performed using a non-linear algorithm, which allows us to define at least 3 seismic clusters. We discuss this seismic pattern within the geothermal fields.

  8. 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)

  9. Post-seismic velocity changes following the 2010 Mw 7.1 Darfield earthquake, New Zealand, revealed by ambient seismic field analysis

    Science.gov (United States)

    Heckels, R. EG; Savage, M. K.; Townend, J.

    2018-05-01

    Quantifying seismic velocity changes following large earthquakes can provide insights into fault healing and reloading processes. This study presents temporal velocity changes detected following the 2010 September Mw 7.1 Darfield event in Canterbury, New Zealand. We use continuous waveform data from several temporary seismic networks lying on and surrounding the Greendale Fault, with a maximum interstation distance of 156 km. Nine-component, day-long Green's functions were computed for frequencies between 0.1 and 1.0 Hz for continuous seismic records from immediately after the 2010 September 04 earthquake until 2011 January 10. Using the moving-window cross-spectral method, seismic velocity changes were calculated. Over the study period, an increase in seismic velocity of 0.14 ± 0.04 per cent was determined near the Greendale Fault, providing a new constraint on post-seismic relaxation rates in the region. A depth analysis further showed that velocity changes were confined to the uppermost 5 km of the subsurface. We attribute the observed changes to post-seismic relaxation via crack healing of the Greendale Fault and throughout the surrounding region.

  10. GRACE gravity data help constraining seismic models of the 2004 Sumatran earthquake

    Science.gov (United States)

    Cambiotti, G.; Bordoni, A.; Sabadini, R.; Colli, L.

    2011-10-01

    The analysis of Gravity Recovery and Climate Experiment (GRACE) Level 2 data time series from the Center for Space Research (CSR) and GeoForschungsZentrum (GFZ) allows us to extract a new estimate of the co-seismic gravity signal due to the 2004 Sumatran earthquake. Owing to compressible self-gravitating Earth models, including sea level feedback in a new self-consistent way and designed to compute gravitational perturbations due to volume changes separately, we are able to prove that the asymmetry in the co-seismic gravity pattern, in which the north-eastern negative anomaly is twice as large as the south-western positive anomaly, is not due to the previously overestimated dilatation in the crust. The overestimate was due to a large dilatation localized at the fault discontinuity, the gravitational effect of which is compensated by an opposite contribution from topography due to the uplifted crust. After this localized dilatation is removed, we instead predict compression in the footwall and dilatation in the hanging wall. The overall anomaly is then mainly due to the additional gravitational effects of the ocean after water is displaced away from the uplifted crust, as first indicated by de Linage et al. (2009). We also detail the differences between compressible and incompressible material properties. By focusing on the most robust estimates from GRACE data, consisting of the peak-to-peak gravity anomaly and an asymmetry coefficient, that is given by the ratio of the negative gravity anomaly over the positive anomaly, we show that they are quite sensitive to seismic source depths and dip angles. This allows us to exploit space gravity data for the first time to help constraining centroid-momentum-tensor (CMT) source analyses of the 2004 Sumatran earthquake and to conclude that the seismic moment has been released mainly in the lower crust rather than the lithospheric mantle. Thus, GRACE data and CMT source analyses, as well as geodetic slip distributions aided

  11. Stress Field Variation after the 2001 Skyros Earthquake, Greece, Derived from Seismicity Rate Changes

    Science.gov (United States)

    Leptokaropoulos, K.; Papadimitriou, E.; Orlecka-Sikora, B.; Karakostas, V.

    2012-04-01

    The spatial variation of the stress field (ΔCFF) after the 2001 strong (Mw=6.4) Skyros earthquake in North Aegean Sea, Greece, is investigated in association with the changes of earthquake production rates. A detailed slip model is considered in which the causative fault is consisted of several sub-faults with different coseismic slip onto each one of them. First the spatial distribution of aftershock productivity is compared with the static stress changes due to the coseismic slip. Calculations of ΔCFF are performed at different depths inside the seismogenic layer, defined from the vertical distribution of the aftershocks. Seismicity rates of the smaller magnitude events with M≥Mc for different time increments before and after the main shock are then derived from the application of a Probability Density Function (PDF). These rates are computed by spatially smoothing the seismicity and for this purpose a normal grid of rectangular cells is superimposed onto the area and the PDF determines seismicity rate values at the center of each cell. The differences between the earthquake occurrence rates before and after the main shock are compared and used as input data in a stress inversion algorithm based upon the Rate/State dependent friction concept in order to provide an independent estimation of stress changes. This model incorporates the physical properties of the fault zones (characteristic relaxation time, fault constitutive parameters, effective friction coefficient) with a probabilistic estimation of the spatial distribution of seismicity rates, derived from the application of the PDF. The stress patterns derived from the previously mentioned approaches are compared and the quantitative correlation between the respective results is accomplished by the evaluation of Pearson linear correlation coefficient and its confidence intervals to quantify their significance. Different assumptions and combinations of the physical and statistical parameters are tested for

  12. The Augustine magmatic system as revealed by seismic tomography and relocated earthquake hypocenters from 1994 through 2009

    Science.gov (United States)

    Syracuse, E.M.; Thurber, C.H.; Power, J.A.

    2011-01-01

    We incorporate 14 years of earthquake data from the Alaska Volcano Observatory with data from a 1975 controlled-source seismic experiment to obtain the three-dimensional P and S wave velocity structure and the first high-precision earthquake locations at Augustine Volcano to be calculated in a fully three-dimensional velocity model. Velocity tomography shows two main features beneath Augustine: a narrow, high-velocity column beneath the summit, extending from ???2 km depth to the surface, and elevated velocities on the south flank. Our relocation results allow a thorough analysis of the spatio-temoral patterns of seismicity and the relationship to the magmatic and eruptive activity. Background seismicity is centered beneath the summit at an average depth of 0.6 km above sea level. In the weeks leading to the January 2006 eruption of Augustine, seismicity focused on a NW-SE line along the trend of an inflating dike. A series of drumbeat earthquakes occurred in the early weeks of the eruption, indicating further magma transport through the same dike system. During the six months following the onset of the eruption, the otherwise quiescent region 1 to 5 km below sea level centered beneath the summit became seismically active with two groups of earthquakes, differentiated by frequency content. The deep longer-period earthquakes occurred during the eruption and are interpreted as resulting from the movement of magma toward the summit, and the post-eruptive shorter-period earthquakes may be due to the relaxation of an emptied magma tube. The seismicity subsequently returned to its normal background rates and patterns. Copyright 2011 by the American Geophysical Union.

  13. The forecast of mining-induced seismicity and the consequent risk of damage to the excavation in the area of seismic event

    Directory of Open Access Journals (Sweden)

    Jan Drzewiecki

    2017-01-01

    Full Text Available The Central Mining Institute has developed a method for forecasting the amount of seismic energy created by tremors induced by mining operations. The results of geophysical measurements of S wave velocity anomalies in a rock mass or the results of analytic calculations of the values of pressure on the horizon of the elastic layers are used in the process of calculating the energy. The calculation program which has been developed and adopted has been modified over recent years and it now enables not only the prediction of the energy of dynamic phenomena induced by mining but also the forecasting of the devastating range of seismic shock. The results obtained from this calculation, usually presented in a more readable graphic form, are useful for the macroscopic evaluation of locations that are potential sources of seismic energy. Forecasting of the maximum energy of seismic shock without prior knowledge of the location of the shock's source, does not allow shock attenuation that results from, for example, a distance of tremor source from the excavation which will be affected by seismic energy, to be taken into consideration. The phenomena of energy dissipation, which is taken into account in the forecasts, create a new quality of assessment of threat to the excavation. The paper presents the principle of a method of forecasting the seismic energy of a shock and the risk of damage to the excavation as a result of the impact of its energy wave. The solution assumes that the source of the energy shock is a resilient layer in which the sum of the gravitational stresses, resulting from natural disturbances and those induced by the conducted or planned mining exploitation, is estimated. The proposed solution assumes a spherical model for the tremor source, for which seismic energy is forecasted as a function of the longwall advance and the elementary value of seismic energy destroying the excavation. Subsequently, the following are calculated for the

  14. Changes and challenges following the 1997 Colfiorito earthquake: the evolution of the use of the Internet for large seismic events

    Directory of Open Access Journals (Sweden)

    R. Camassi

    2008-06-01

    Full Text Available The September 26, 1997 Central Italy earthquake represents the first Italian large seismic event on the occasion of which Internet was intensively exploited to exchange and disseminate data, information and news. The paper illustrates how national and international seismological institutions disseminate information about earthquakes ten years ago. A web evolution is sketched, and some features that can be of interest today in the seismological community are presented.

  15. Transient postseismic mantle relaxation following 2004 Sumatra earthquake: implications of seismic vulnerability in the Andaman-Nicobar region

    Directory of Open Access Journals (Sweden)

    C. D. Reddy

    2012-02-01

    Full Text Available Throughout the world, the tsunami generation potential of some large under-sea earthquakes significantly contributes to regional seismic hazard, which gives rise to significant risk in the near-shore provinces where human settlements are in sizeable population, often referred to as coastal seismic risk. In this context, we show from the pertinent GPS data that the transient stresses generated by the viscoelastic relaxation process taking place in the mantle is capable of rupturing major faults by stress transfer from the mantle through the lower crust including triggering additional rupture on the other major faults. We also infer that postseismic relaxation at relatively large depths can push some of the fault segments to reactivation causing failure sequences. As an illustration to these effects, we consider in detail the earthquake sequence comprising six events, starting from the main event of Mw = 7.5, on 10 August 2009 and tapering off to a small earthquake of Mw = 4.5 on 2 February 2011 over a period of eighteen months in the intensely seismic Andaman Islands between India and Myanmar. The persisting transient stresses, spatio-temporal seismic pattern, modeled Coulomb stress changes, and the southward migration of earthquake activity has increased the probability of moderate earthquakes recurring in the northern Andaman region, particularly closer to or somewhat south of Diglipur.

  16. 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.

  17. Earthquake Monitoring: SeisComp3 at the Swiss National Seismic Network

    Science.gov (United States)

    Clinton, J. F.; Diehl, T.; Cauzzi, C.; Kaestli, P.

    2011-12-01

    The Swiss Seismological Service (SED) has an ongoing responsibility to improve the seismicity monitoring capability for Switzerland. This is a crucial issue for a country with low background seismicity but where a large M6+ earthquake is expected in the next decades. With over 30 stations with spacing of ~25km, the SED operates one of the densest broadband networks in the world, which is complimented by ~ 50 realtime strong motion stations. The strong motion network is expected to grow with an additional ~80 stations over the next few years. Furthermore, the backbone of the network is complemented by broadband data from surrounding countries and temporary sub-networks for local monitoring of microseismicity (e.g. at geothermal sites). The variety of seismic monitoring responsibilities as well as the anticipated densifications of our network demands highly flexible processing software. We are transitioning all software to the SeisComP3 (SC3) framework. SC3 is a fully featured automated real-time earthquake monitoring software developed by GeoForschungZentrum Potsdam in collaboration with commercial partner, gempa GmbH. It is in its core open source, and becoming a community standard software for earthquake detection and waveform processing for regional and global networks across the globe. SC3 was originally developed for regional and global rapid monitoring of potentially tsunamagenic earthquakes. In order to fulfill the requirements of a local network recording moderate seismicity, SED has tuned configurations and added several modules. In this contribution, we present our SC3 implementation strategy, focusing on the detection and identification of seismicity on different scales. We operate several parallel processing "pipelines" to detect and locate local, regional and global seismicity. Additional pipelines with lower detection thresholds can be defined to monitor seismicity within dense subnets of the network. To be consistent with existing processing

  18. Earthquake source parameter and focal mechanism estimates for the Western Quebec Seismic Zone in eastern Canada

    Science.gov (United States)

    Rodriguez Padilla, A. M.; Onwuemeka, J.; Liu, Y.; Harrington, R. M.

    2017-12-01

    The Western Quebec Seismic Zone (WQSZ) is a 160-km-wide band of intraplate seismicity extending 500 km from the Adirondack Highlands (United States) to the Laurentian uplands (Canada). Historically, the WQSZ has experienced over fifteen earthquakes above magnitude 5, with the noteworthy MN5.2 Ladysmith event on May 17, 2013. Previous studies have associated seismicity in the area to the reactivation of Early Paleozoic normal faults within a failed Iapetan rift arm, or strength contrasts between mafic intrusions and felsic rocks due to the Mesozoic track of the Great Meteor hotspot. A good understanding of seismicity and its relation to pre-existing structures requires information about event source properties, such as static stress drop and fault plane orientation, which can be constrained via spectral analysis and focal mechanism solutions. Using data recorded by the CNSN and USArray Transportable Array, we first characterize b-value for 709 events between 2012 and 2016 in WQSZ, obtaining a value of 0.75. We then determine corner frequency and seismic moment values by fitting S-wave spectra on transverse components at all stations for 35 events MN 2.7+. We select event pairs with highly similar waveforms, proximal hypocenters, and magnitudes differing by 1-2 units. Our preliminary results using single-station spectra show corner frequencies of 15 to 40 Hz and stress drop values between 7 and 130 MPa, typical of intraplate seismicity. Last, we solve focal mechanism solutions of 35 events with impulsive P-wave arrivals at a minimum of 8 stations using the hybridMT moment tensor inversion algorithm. Our preliminary results suggest predominantly thrust faulting mechanisms, and at times oblique thrust faulting. The P-axis trend of the focal mechanism solutions suggests a principal stress orientation of NE-SW, which is consistent with that derived from focal mechanisms of earthquakes prior to 2013. We plan to fit the event pair spectral ratios to correct for attenuation

  19. A novel tree-based algorithm to discover seismic patterns in earthquake catalogs

    Science.gov (United States)

    Florido, E.; Asencio-Cortés, G.; Aznarte, J. L.; Rubio-Escudero, C.; Martínez-Álvarez, F.

    2018-06-01

    A novel methodology is introduced in this research study to detect seismic precursors. Based on an existing approach, the new methodology searches for patterns in the historical data. Such patterns may contain statistical or soil dynamics information. It improves the original version in several aspects. First, new seismicity indicators have been used to characterize earthquakes. Second, a machine learning clustering algorithm has been applied in a very flexible way, thus allowing the discovery of new data groupings. Third, a novel search strategy is proposed in order to obtain non-overlapped patterns. And, fourth, arbitrary lengths of patterns are searched for, thus discovering long and short-term behaviors that may influence in the occurrence of medium-large earthquakes. The methodology has been applied to seven different datasets, from three different regions, namely the Iberian Peninsula, Chile and Japan. Reported results show a remarkable improvement with respect to the former version, in terms of all evaluated quality measures. In particular, the number of false positives has decreased and the positive predictive values increased, both of them in a very remarkable manner.

  20. Study on Repaired Earthquake-Damaged Bridge Piers under Seismic Load

    Directory of Open Access Journals (Sweden)

    Jun Deng

    2015-01-01

    Full Text Available The concrete bridge pier damaged during earthquakes need be repaired to meet the design standards. Steel tube as a traditional material or FRP as a novel material has become popular to repair the damaged reinforced concrete (RC bridge piers. In this paper, experimental and finite element (FE studies are employed to analyze the confinement effectiveness of the different repair materials. The FE method was used to calculate the hysteretic behavior of three predamaged circle RC bridge piers repaired with steel tube, basalt fiber reinforced polymer (BFRP, and carbon fiber reinforced polymer (CFRP, respectively. Meanwhile, the repaired predamaged circle concrete bridge piers were tested by pseudo-static cyclic loading to study the seismic behavior and evaluate the confinement effectiveness of the different repair materials and techniques. The FE analysis and experimental results showed that the repaired piers had similar hysteretic curves with the original specimens and all the three repair techniques can restore the seismic performance of the earthquake-damaged piers. Steel tube jacketing can significantly improve the lateral stiffness and peak load of the damaged pier, while the BFRP and CFRP sheets cannot improve these properties due to their thin thickness.

  1. Seismicity Precursors of the M6.0 2004 Parkfield and M7.0 1989Loma Prieta Earthquakes

    Energy Technology Data Exchange (ETDEWEB)

    Korneev, Valeri A.

    2006-03-09

    The M6.0 2004 Parkfield and M7.0 1989 Loma Prietastrike-slip earthquakes on the San Andreas Fault (SAF) were preceded byseismicity peaks occurring several months prior to the main events.Earthquakes directly within the SAF zone were intentionally excluded fromthe analysis because they manifest stress-release processes rather thanstress accumulation. The observed increase in seismicity is interpretedas a signature of the increasing stress level in the surrounding crust,whereas the peaks and the subsequent decrease in seismicity areattributed to damage-induced softening processes. Furthermore, in bothcases there is a distinctive zone of low seismic activity that surroundsthe epicentral region in the pre-event period. The increase of seismicityin the crust surrounding a potential future event and the development ofa low-seismicity epicentral zone can be regarded as promising precursoryinformation that could help signal the arrival of large earthquakes. TheGutenberg-Richter relationship (GRR) should allow extrapolation ofseismicity changes down to seismic noise level magnitudes. Thishypothesis is verified by comparison of seismic noise at 80 Hz with theParkfield M4 1993-1994 series, where noise peaks 5 months before theseries to about twice the background level.

  2. Consideration on the applicability of the design seismic coefficient of a large cutting slope under the strong earthquake

    International Nuclear Information System (INIS)

    Ito, Hiroshi; Sawada, Yoshihiro; Satou, Kiyotaka

    1989-01-01

    In this study, the characteristic of equivalent seismic coefficient and the applicability of the design seismic coefficient of a large cutting rock slope around Nuclear Power Plant were examined by analytical parameter survey. As the results, the equivalent seismic coefficient by dynamic analysis become great with increase of transverse elastic wave velocity and the case of long period motion. That is, as the wave length of rock mass become longer, the equivalent seismic coefficient become great parabolically. Moreover, there is a inverse proportion relation between the ratio (dynamic safety factor/static safety factor) and wave length. In addition, the graph to forecast the dynamic sliding safety factor under the input seismic motion of the max. Acceleration 500 gal from the result of static simple method was proposed and the applicable range of design seismic coefficient of rock slope was indicated. (author)

  3. Interpretation of interseismic deformations and the seismic cycle associated with large subduction earthquakes

    Science.gov (United States)

    Trubienko, Olga; Fleitout, Luce; Garaud, Jean-Didier; Vigny, Christophe

    2013-03-01

    The deformations of the overriding and subducting plates during the seismic cycle associated with large subduction earthquakes are modelled using 2D and 3D finite element techniques. A particular emphasis is put on the interseismic velocities and on the impact of the rheology of the asthenosphere. The distance over which the seismic cycle perturbs significantly the velocities depends upon the ratio of the viscosity in the asthenosphere to the period of the seismic cycle and can reach several thousand km for rheological parameters deduced from the first years of deformation after the Aceh earthquake. For a same early postseismic velocity, a Burger rheology of the asthenosphere implies a smaller duration of the postseismic phase and thus smaller interseismic velocities than a Maxwell rheology. A low viscosity wedge (LVW) modifies very significantly the predicted horizontal and vertical motions in the near and middle fields. In particular, with a LVW, the peak in vertical velocity at the end of the cycle is predicted to be no longer above the deep end of the locked section of the fault but further away, above the continentward limit of the LVW. The lateral viscosity variations linked to the presence at depth of the subducting slab affect substantially the results. The north-south interseismic compression predicted by this preliminary 2D model over more than 1500 km within the Sunda block is in good agreement with the pre-2004 velocities with respect to South-China inferred from GPS observations in Thailand, Malaysia and Indonesia. In Japan, before the Tohoku earthquake, the eastern part of northern Honshu was subsiding while the western part was uplifting. This transition from subsidence to uplift so far away from the trench is well fitted by the predictions from our models involving a LVW. Most of the results obtained here in a 2D geometry are shown to provide a good estimate of the displacements for fault segments of finite lateral extent, with a 3D spherical

  4. Pre-, Co-, and Post-Seismic Fault Slip in the Northern Chile Seismic Gap Associated with the April 1, 2014 (Mw 8.2) Pisagua Earthquake.

    Science.gov (United States)

    Simons, M.; Duputel, Z.; Fielding, E. J.; Galetzka, J.; Genrich, J. F.; Jiang, J.; Jolivet, R.; Kanamori, H.; Moore, A. W.; Ortega Culaciati, F. H.; Owen, S. E.; Riel, B. V.; Rivera, L. A.; Carrizo, D.; Cotte, N.; Jara, J.; Klotz, J.; Norabuena, E. O.; Ortega, I.; Socquet, A.; Samsonov, S. V.; Valderas Bermejo, M.

    2014-12-01

    The April 1, 2014 (Mw 8.2) Pisagua Earthquake occurred in Northern Chile, within a long recognized seismic gap in the Central Andean region that last experienced major megathrust events in 1868 and 1877. We built a continuous GPS network starting in 2005, with the ultimate goal of understanding the kinematics and dynamics of this portion of the subduction zone. Using observations from this network, as well as others in the region, combined with InSAR, seismic and tsunami observations, we obtain estimates of inter-seismic, co-seismic and initial post-seismic fault slip using an internally consistent Bayesian unregularized approach. We evaluate the extent of spatial overlap between regions of fault slip during this different time periods. Of particular interest to this event is the extent and nature of any geodetic evidence for transient slow fault slip preceding the Pisagua Earthquake mainshock. To this end, we compare daily and high rate GPS solutions, the former of which shows long period transient motion started about 15 days before the mainshock and with maximum registered amplitude of 14.2 +/- 2 [mm] at site PSGA. Contrary to published findings, we find that pre-seismic deformation seen by the GPS network can be explained as coseismic motion associated with the multiple foreshocks.

  5. Uncertainties for seismic moment tensors and applications to nuclear explosions, volcanic events, and earthquakes

    Science.gov (United States)

    Tape, C.; Alvizuri, C. R.; Silwal, V.; Tape, W.

    2017-12-01

    When considered as a point source, a seismic source can be characterized in terms of its origin time, hypocenter, moment tensor, and source time function. The seismologist's task is to estimate these parameters--and their uncertainties--from three-component ground motion recorded at irregularly spaced stations. We will focus on one portion of this problem: the estimation of the moment tensor and its uncertainties. With magnitude estimated separately, we are left with five parameters describing the normalized moment tensor. A lune of normalized eigenvalue triples can be used to visualize the two parameters (lune longitude and lune latitude) describing the source type, while the conventional strike, dip, and rake angles can be used to characterize the orientation. Slight modifications of these five parameters lead to a uniform parameterization of moment tensors--uniform in the sense that equal volumes in the coordinate domain of the parameterization correspond to equal volumes of moment tensors. For a moment tensor m that we have inferred from seismic data for an earthquake, we define P(V) to be the probability that the true moment tensor for the earthquake lies in the neighborhood of m that has fractional volume V. The average value of P(V) is then a measure of our confidence in our inference of m. The calculation of P(V) requires knowing both the probability P(w) and the fractional volume V(w) of the set of moment tensors within a given angular radius w of m. We apply this approach to several different data sets, including nuclear explosions from the Nevada Test Site, volcanic events from Uturuncu (Bolivia), and earthquakes. Several challenges remain: choosing an appropriate misfit function, handling time shifts between data and synthetic waveforms, and extending the uncertainty estimation to include more source parameters (e.g., hypocenter and source time function).

  6. Time-lapse imaging of fault properties at seismogenic depth using repeating earthquakes, active sources and seismic ambient noise

    Science.gov (United States)

    Cheng, Xin

    2009-12-01

    The time-varying stress field of fault systems at seismogenic depths plays the mort important role in controlling the sequencing and nucleation of seismic events. Using seismic observations from repeating earthquakes, controlled active sources and seismic ambient noise, five studies at four different fault systems across North America, Central Japan, North and mid-West China are presented to describe our efforts to measure such time dependent structural properties. Repeating and similar earthquakes are hunted and analyzed to study the post-seismic fault relaxation at the aftershock zone of the 1984 M 6.8 western Nagano and the 1976 M 7.8 Tangshan earthquakes. The lack of observed repeating earthquakes at western Nagano is attributed to the absence of a well developed weak fault zone, suggesting that the fault damage zone has been almost completely healed. In contrast, the high percentage of similar and repeating events found at Tangshan suggest the existence of mature fault zones characterized by stable creep under steady tectonic loading. At the Parkfield region of the San Andreas Fault, repeating earthquake clusters and chemical explosions are used to construct a scatterer migration image based on the observation of systematic temporal variations in the seismic waveforms across the occurrence time of the 2004 M 6 Parkfield earthquake. Coseismic fluid charge or discharge in fractures caused by the Parkfield earthquake is used to explain the observed seismic scattering properties change at depth. In the same region, a controlled source cross-well experiment conducted at SAFOD pilot and main holes documents two large excursions in the travel time required for a shear wave to travel through the rock along a fixed pathway shortly before two rupture events, suggesting that they may be related to pre-rupture stress induced changes in crack properties. At central China, a tomographic inversion based on the theory of seismic ambient noise and coda wave interferometry

  7. Earthquake stand-by instruction device for nuclear power plant

    International Nuclear Information System (INIS)

    Nakagawa, Masaki; Ijima, Tadashi

    1998-01-01

    The magnitude of earthquakes is forecast at a high accuracy by disposing seismic detectors to a plurality of points distant from an object plant. The accuracy of the judgement for the magnitude of earthquakes can be improved by processing seismic movements by using seismic movements observed along with elapse of time. The measured seismic waveforms are always stored even during the processing time. With such procedures, when one processing is completed, processing can be conducted successively by using stored data, by which processing can be conducted by using all the data from the occurrence of the earthquakes. Then, the seismic movements can be estimated from an early stage of the occurrence of the earthquakes, and since the seismic movement can be judged based on a great amount of data with lapse of time, an appropriate stand-by instruction can be provided. (N.H.)

  8. The Geological Susceptibility of Induced Earthquakes in the Duvernay Play

    Science.gov (United States)

    Pawley, Steven; Schultz, Ryan; Playter, Tiffany; Corlett, Hilary; Shipman, Todd; Lyster, Steven; Hauck, Tyler

    2018-02-01

    Presently, consensus on the incorporation of induced earthquakes into seismic hazard has yet to be established. For example, the nonstationary, spatiotemporal nature of induced earthquakes is not well understood. Specific to the Western Canada Sedimentary Basin, geological bias in seismogenic activation potential has been suggested to control the spatial distribution of induced earthquakes regionally. In this paper, we train a machine learning algorithm to systemically evaluate tectonic, geomechanical, and hydrological proxies suspected to control induced seismicity. Feature importance suggests that proximity to basement, in situ stress, proximity to fossil reef margins, lithium concentration, and rate of natural seismicity are among the strongest model predictors. Our derived seismogenic potential map faithfully reproduces the current distribution of induced seismicity and is suggestive of other regions which may be prone to induced earthquakes. The refinement of induced seismicity geological susceptibility may become an important technique to identify significant underlying geological features and address induced seismic hazard forecasting issues.

  9. Analysis of recorded earthquake response data at the Hualien large-scale seismic test site

    International Nuclear Information System (INIS)

    Hyun, C.H.; Tang, H.T.; Dermitzakis, S.; Esfandiari, S.

    1997-01-01

    A soil-structure interaction (SSI) experiment is being conducted in a seismically active region in Hualien, Taiwan. To obtain earthquake data for quantifying SSI effects and providing a basis to benchmark analysis methods, a 1/4-th scale cylindrical concrete containment model similar in shape to that of a nuclear power plant containment was constructed in the field where both the containment model and its surrounding soil, surface and sub-surface, are extensively instrumented to record earthquake data. In between September 1993 and May 1995, eight earthquakes with Richter magnitudes ranging from 4.2 to 6.2 were recorded. The author focuses on studying and analyzing the recorded data to provide information on the response characteristics of the Hualien soil-structure system, the SSI effects and the ground motion characteristics. An effort was also made to directly determine the site soil physical properties based on correlation analysis of the recorded data. No modeling simulations were attempted to try to analytically predict the SSI response of the soil and the structure. These will be the scope of a subsequent study

  10. Real-time seismic monitoring of the integrated cape girardeau bridge array and recorded earthquake response

    Science.gov (United States)

    Celebi, M.

    2006-01-01

    This paper introduces the state of the art, real-time and broad-band seismic monitoring network implemented for the 1206 m [3956 ft] long, cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (MO), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811-1812 New Madrid earthquakes. The bridge was designed for a strong earthquake (magnitude 7.5 or greater) during the design life of the bridge. The monitoring network comprises a total of 84 channels of accelerometers deployed on the superstructure, pier foundations and at surface and downhole free-field arrays of the bridge. The paper also presents the high quality response data obtained from the network. Such data is aimed to be used by the owner, researchers and engineers to assess the performance of the bridge, to check design parameters, including the comparison of dynamic characteristics with actual response, and to better design future similar bridges. Preliminary analyses of ambient and low amplitude small earthquake data reveal specific response characteristics of the bridge and the free-field. There is evidence of coherent tower, cable, deck interaction that sometimes results in amplified ambient motions. Motions at the lowest tri-axial downhole accelerometers on both MO and IL sides are practically free from any feedback from the bridge. Motions at the mid-level and surface downhole accelerometers are influenced significantly by feedback due to amplified ambient motions of the bridge. Copyright ASCE 2006.

  11. Shaking Table Tests on the Seismic Behavior of Steel Frame Structures Subjected to Various Earthquake Ground Motions

    International Nuclear Information System (INIS)

    Choi, In Kil; Kim, Min Kyu; Choun, Young Sun; Seo, Jeong Moon

    2004-05-01

    The standard response spectrum proposed by US NRC has been used as a design earthquake for the design of Korean nuclear power plant structures. Recent large earthquakes occurred in near-fault zone have done significant damage and loss of life to earthquake area. A survey on some of the Quaternary fault segments near the Korean nuclear power plants is ongoing. If the faults are confirmed as active ones, it will be necessary to reevaluate the seismic safety of the nuclear power plants located near the fault. In this study, the shaking table tests of three steel frame structures were performed. Three types of input motions, artificial time histories that envelop the US NRC Regulatory Guide 1.60 spectrum and the probability based scenario earthquake spectra developed for the Korean nuclear power plant site and a typical near-fault earthquake recorded at Chi-Chi earthquake, were used as input motions. The acceleration and displacement responses of the structure due to the design earthquake were larger than those due to the other input earthquakes. It seems that the design earthquake for the Korean nuclear power plants is conservative, and that the near-fault earthquake and scenario earthquake are not so damageable for the nuclear power plant structures, because the fundamental frequencies of the nuclear power plant structures are generally greater than 5 Hz. The high frequency ground motions that appeared in the scenario earthquake can be more damageable for the equipment installed on the high floors in a building. This means that the design earthquake is not so conservative for the safety of the safety related nuclear power plant equipment

  12. Comparison Of Seismic Performance Of Erciş Cultural Center Building With Observed And Calculated By Turkish Earthquake Code-2007

    Directory of Open Access Journals (Sweden)

    Recep Ali Dedecan

    2013-08-01

    Full Text Available The goal of this paper is to review the validity of seismic assessment procedure given in the Turkish Earthquake Code by comparing the assessment results with real structures from Eastern Turkey, where the 2011 Van earthquake occurred. To test the analysis methods for a typically suitable structure, the cultural center building at Erciş with 3 stories, is selected. In order to compare the results of the three different analysis techniques, for an identical earthquake, the ground motion used in analysis was characterized by equivalent elastic earthquake spectra, which were developed from available time history at the nearest construction site. It was found that the damage predictions by using the by Turkish Earthquake Code procedures point out the different level of damages. But, it is concluded that nonlinear time history analysis calculated the best estimation of the damage observed in the site.

  13. Seismic displacements monitoring for 2015 Mw 7.8 Nepal earthquake with GNSS data

    Science.gov (United States)

    Geng, T.; Su, X.; Xie, X.

    2017-12-01

    The high-rate Global Positioning Satellite System (GNSS) has been recognized as one of the powerful tools for monitoring ground motions generated by seismic events. The high-rate GPS and BDS data collected during the 2015 Mw 7.8 Nepal earthquake have been analyzed using two methods, that are the variometric approach and Precise point positioning (PPP). The variometric approach is based on time differenced technique using only GNSS broadcast products to estimate velocity time series from tracking observations in real time, followed by an integration procedure on the velocities to derive the seismic event induced displacements. PPP is a positioning method to calculate precise positions at centimeter- or even millimeter-level accuracy with a single GNSS receiver using precise satellite orbit and clock products. The displacement motions with accuracy of 2 cm at far-field stations and 5 cm at near-field stations with great ground motions and static offsets up to 1-2 m could be achieved. The multi-GNSS, GPS + BDS, could provide higher accuracy displacements with the increasing of satellite numbers and the improvement of the Position Dilution of Precision (PDOP) values. Considering the time consumption of clock estimates and the precision of PPP solutions, 5 s GNSS satellite clock interval is suggested. In addition, the GNSS-derived displacements are in good agreement with those from strong motion data. These studies demonstrate the feasibility of real-time capturing seismic waves with multi-GNSS observations, which is of great promise for the purpose of earthquake early warning and rapid hazard assessment.

  14. Parametric time series analysis of geoelectrical signals: an application to earthquake forecasting in Southern Italy

    Directory of Open Access Journals (Sweden)

    V. Tramutoli

    1996-06-01

    Full Text Available An autoregressive model was selected to describe geoelectrical time series. An objective technique was subsequently applied to analyze and discriminate values above (below an a priorifixed threshold possibly related to seismic events. A complete check of the model and the main guidelines to estimate the occurrence probability of extreme events are reported. A first application of the proposed technique is discussed through the analysis of the experimental data recorded by an automatic station located in Tito, a small town on the Apennine chain in Southern Italy. This region was hit by the November 1980 Irpinia-Basilicata earthquake and it is one of most active areas of the Mediterranean region. After a preliminary filtering procedure to reduce the influence of external parameters (i.e. the meteo-climatic effects, it was demonstrated that the geoelectrical residual time series are well described by means of a second order autoregressive model. Our findings outline a statistical methodology to evaluate the efficiency of electrical seismic precursors.

  15. The April 16th 2016 Pedernales Earthquake and Instituto Geofisico efforts for improving seismic monitoring in Ecuador

    Science.gov (United States)

    Ruiz, M. C.; Alvarado, A. P.; Hernandez, S.; Singaucho, J. C.; Gabriela, P.; Landeureau, A.; Perrault, M.; Acero, W.; Viracucha, C.; Plain, M.; Yepes, H. A.; Palacios, P.; Aguilar, J.; Mothes, P. A.; Segovia, M.; Pacheco, D. A.; Vaca, S.

    2016-12-01

    On April 16th, 2016, Ecuador's coastal provinces were struck by a devastating earthquake with 7.8 Mw magnitude. This event caused the earthquake-related largest dead toll in Ecuador (663 fatalities) since 1987 inland event. It provoked also a widespread destruction of houses, hotels, hospitals, affecting economic activities. Damaged was very worthy in the city of Pedernales, one of the nearest localities to the epicenter. Rupture area extended about a 100 km from the southern limit marked by the aftershock area of the 1998, 7.1 Mw earthquake to its northern limit controlled by the Punta Galera-Mompiche seismic zone, which is one of the several elongated swarms oriented perpendicular to the trench that occurred since 2007. Historical accounts of the Ecuador Colombia subduction zone have few mentions of felt earthquakes in the XVIII and XIX century likely related to poor communication and urban settlements in this area. A cycle of noticeable earthquakes began in 1896, including the 1906 8.8 Mw event and three earthquakes with magnitudes larger than 7.7 in the period 1942-1979, that preceded the 2016 earthquake. The Instituto Geofiísico of the Escuela Politécnica Nacional (IGEPN) has been monitoring the coastal area through the National Seismic Network (RENSIG) since 30 years back and recently enhanced through SENASCYT and SENPLADES supported projects. International collaboration from Japanese JICA and French IRD also contributed to expand the network and implement research projects in the area. Nowadays, the RENSIG has 135 seismic stations including 105 broadband and 5 strong motion velocimeters. Processing performed by Seiscomp3 software allows an automatic distribution of seismic parameters. A joint cooperation between IGEPN, the Navy Oceanographic Institute and the National Department for Risk Management is in charge of tsunami monitoring.

  16. The ANSS response to the Mw 5.8 Central Virginia Seismic Zone earthquake of August 23, 2011

    Science.gov (United States)

    McNamara, D. E.; Horton, S.; Benz, H.; Earle, P. S.; Withers, M. M.; Hayes, G. P.; Kim, W. Y.; Chapman, M. C.; Herrmann, R. B.; Petersen, M. D.; Williams, R. A.

    2011-12-01

    An Mw 5.8 earthquake (depth=6km) occurred on August 23, 2011 (17:51:04 UTC) near Mineral, Virginia, which was widely felt from Maine to Georgia along the eastern seaboard and west to Chicago and western Tennessee. The USGS tallied nearly 142,000 felt reports submitted to the Did You Feel It (DYFI) internet community intensity system, making it the most widely felt earthquake since the web-site began, and demonstrating that more people felt this earthquake than any other in U.S. history. Significant damage was reported in the epicentral area and as far away as Washington D.C. (135 km away); minor damage was reported in Baltimore (200 km). The reverse faulting earthquake occurred on a northeast-striking plane within a region of diffuse seismicity known as the Central Virginia Seismic Zone. Within the first week, the mainshock was followed by 17 aftershocks with magnitude greater than 2, including Mw 4.5, 4.2, and 3.8 events. In the days following the mainshock, 46 portable seismic stations were deployed by several organizations, making this among the best-recorded aftershock sequence in the eastern U.S. Within 24 hours of the mainshock, 8 portable stations were deployed in time to record the largest aftershock to date (M4.5). We will present the results of our post-earthquake response, including attenuation and site amplification observations using portable aftershock station data, details on the initial USGS NEIC post earthquake response products and an assessment of the seismotectonics of the Central Virginia Seismic Zone based on aftershock locations and source parameter modeling of the larger earthquakes.

  17. 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

  18. Lessons Learned about Best Practices for Communicating Earthquake Forecasting and Early Warning to Non-Scientific Publics

    Science.gov (United States)

    Sellnow, D. D.; Sellnow, T. L.

    2017-12-01

    Earthquake scientists are without doubt experts in understanding earthquake probabilities, magnitudes, and intensities, as well as the potential consequences of them to community infrastructures and inhabitants. One critical challenge these scientific experts face, however, rests with communicating what they know to the people they want to help. Helping scientists translate scientific information to non-scientists is something Drs. Tim and Deanna Sellnow have been committed to for decades. As such, they have compiled a host of data-driven best practices for communicating effectively to non-scientific publics about earthquake forecasting, probabilities, and warnings. In this session, they will summarize what they have learned as it may help earthquake scientists, emergency managers, and other key spokespersons share these important messages to disparate publics in ways that result in positive outcomes, the most important of which is saving lives.

  19. Influence of crustal layering and thickness on co-seismic effects of Wenchuan earthquake

    Directory of Open Access Journals (Sweden)

    Tan Hongbo

    2011-02-01

    Full Text Available Using the PSGRN/PSCMP software and the fault model offered by USGS and on the basis of finite rectangular dislocation theory and the local layered wave velocity structures of the crust-upper-mantle, the influences of crustal layering and thickness on co-seismic gravity changes and deformation of Wenchuan earthquake have been simulated. The results indicate that; the influences have a relationship with the attitude of faults and the relative position between calculated points and fault. The difference distribution form of simulated results between the two models is similar to that of co-seismic effect. For the per centum distribution, it’s restricted by the zero line of the co-seismic effects obviously. Its positive is far away from the zero line. For the crustal thickness, the effect is about 10% – 20%. The negative and the effect over 30% focus around the zero line. The average influences of crustal layering and thickness for the E-W displacement, N-S displacement, vertical displacement and gravity changes are 18.4%,18.0%, 15.8% and 16.2% respectively, When the crustal thickness is 40 km, they are 4.6%, 5.3%, 3.8% and 3.8%. Then the crustal thickness is 70 km, the average influences are 3.5%, 4.6%, 3.0% and 2.5% respectively.

  20. Passive seismic monitoring of natural and induced earthquakes: case studies, future directions and socio-economic relevance

    Science.gov (United States)

    Bohnhoff, Marco; Dresen, Georg; Ellsworth, William L.; Ito, Hisao; Cloetingh, Sierd; Negendank, Jörg

    2010-01-01

    An important discovery in crustal mechanics has been that the Earth’s crust is commonly stressed close to failure, even in tectonically quiet areas. As a result, small natural or man-made perturbations to the local stress field may trigger earthquakes. To understand these processes, Passive Seismic Monitoring (PSM) with seismometer arrays is a widely used technique that has been successfully applied to study seismicity at different magnitude levels ranging from acoustic emissions generated in the laboratory under controlled conditions, to seismicity induced by hydraulic stimulations in geological reservoirs, and up to great earthquakes occurring along plate boundaries. In all these environments the appropriate deployment of seismic sensors, i.e., directly on the rock sample, at the earth’s surface or in boreholes close to the seismic sources allows for the detection and location of brittle failure processes at sufficiently low magnitude-detection threshold and with adequate spatial resolution for further analysis. One principal aim is to develop an improved understanding of the physical processes occurring at the seismic source and their relationship to the host geologic environment. In this paper we review selected case studies and future directions of PSM efforts across a wide range of scales and environments. These include induced failure within small rock samples, hydrocarbon reservoirs, and natural seismicity at convergent and transform plate boundaries. Each example represents a milestone with regard to bridging the gap between laboratory-scale experiments under controlled boundary conditions and large-scale field studies. The common motivation for all studies is to refine the understanding of how earthquakes nucleate, how they proceed and how they interact in space and time. This is of special relevance at the larger end of the magnitude scale, i.e., for large devastating earthquakes due to their severe socio-economic impact.

  1. Performance of USGS one-year earthquake hazard map for natural and induced seismicity in the central and eastern United States

    Science.gov (United States)

    Brooks, E. M.; Stein, S.; Spencer, B. D.; Salditch, L.; Petersen, M. D.; McNamara, D. E.

    2017-12-01

    Seismicity in the central United States has dramatically increased since 2008 due to the injection of wastewater produced by oil and gas extraction. In response, the USGS created a one-year probabilistic hazard model and map for 2016 to describe the increased hazard posed to the central and eastern United States. Using the intensity of shaking reported to the "Did You Feel It?" system during 2016, we assess the performance of this model. Assessing the performance of earthquake hazard maps for natural and induced seismicity is conceptually similar but has practical differences. Maps that have return periods of hundreds or thousands of years— as commonly used for natural seismicity— can be assessed using historical intensity data that also span hundreds or thousands of years. Several different features stand out when assessing the USGS 2016 seismic hazard model for the central and eastern United States from induced and natural earthquakes. First, the model can be assessed as a forecast in one year, because event rates are sufficiently high to permit evaluation with one year of data. Second, because these models are projections from the previous year thus implicitly assuming that fluid injection rates remain the same, misfit may reflect changes in human activity. Our results suggest that the model was very successful by the metric implicit in probabilistic hazard seismic assessment: namely, that the fraction of sites at which the maximum shaking exceeded the mapped value is comparable to that expected. The model also did well by a misfit metric that compares the spatial patterns of predicted and maximum observed shaking. This was true for both the central and eastern United States as a whole, and for the region within it with the highest amount of seismicity, Oklahoma and its surrounding area. The model performed least well in northern Texas, over-stating hazard, presumably because lower oil and gas prices and regulatory action reduced the water injection volume

  2. Monitoring the West Bohemian earthquake swarm in 2008/2009 by a temporary small-aperture seismic array

    DEFF Research Database (Denmark)

    Hiemer, Stefan; Rössler, Dirk; Scherbaum, Frank

    2012-01-01

    The most recent intense earthquake swarm in West Bohemia lasted from 6 October 2008 to January 2009. Starting 12 days after the onset, the University of Potsdam monitored the swarm by a temporary small-aperture seismic array at 10 km epicentral distance. The purpose of the installation...

  3. Some possible correlation between electro-magnetic emission and seismic activity during West Bohemia 2008 earthquake swarm

    Czech Academy of Sciences Publication Activity Database

    Kolář, Petr

    2010-01-01

    Roč. 1, č. 1 (2010), s. 93-98 ISSN 1869-9510 R&D Projects: GA AV ČR(CZ) IAA300120805 Institutional research plan: CEZ:AV0Z30120515 Keywords : electromagnetic emission * seismic activity * West Bohemia 2008 earthquake swarm Subject RIV: DC - Siesmology, Volcanology, Earth Structure

  4. The detection of weak earthquakes in the western Bohemian swarm area through the deployment of seismic arrays

    Czech Academy of Sciences Publication Activity Database

    Štrunc, Jaroslav; Brož, Milan

    2011-01-01

    Roč. 8, č. 4 (2011), s. 469-477 ISSN 1214-9705 Institutional research plan: CEZ:AV0Z30460519 Keywords : weak earthquakes * seismic array * small aperture Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.530, year: 2011 http://www.irsm.cas.cz/abstracts/AGG/04_11/8_Strunc.pdf

  5. Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada

    Energy Technology Data Exchange (ETDEWEB)

    Eisses, A.; Kell, A.; Kent, G. [UNR; Driscoll, N. [UCSD; Karlin, R.; Baskin, R. [USGS; Louie, J. [UNR; Pullammanappallil, S. [Optim

    2016-08-01

    Amy Eisses, Annie M. Kell, Graham Kent, Neal W. Driscoll, Robert E. Karlin, Robert L. Baskin, John N. Louie, Kenneth D. Smith, Sathish Pullammanappallil, 2011, Marine and land active-source seismic investigation of geothermal potential, tectonic structure, and earthquake hazards in Pyramid Lake, Nevada: presented at American Geophysical Union Fall Meeting, San Francisco, Dec. 5-9, abstract NS14A-08.

  6. Co-seismic luminescence in Lima, 150 km from the epicenter of the Pisco, Peru earthquake of 15 August 2007

    Directory of Open Access Journals (Sweden)

    J. A. Heraud

    2011-04-01

    Full Text Available The first photographs of Co-seismic Luminescence, commonly known as Earthquake lights (EQLs, were reported in 1968 in Japan. However, there have been documented reports of luminescence associated with earthquakes since ancient times in different parts of the world. Besides this, there is modern scientific work dealing with evidence of and models for the production of such lights. During the Peru 15 August 2007 Mw=8.0 earthquake which occurred at 06:40 p.m. LT, hence dark in the southern wintertime, several EQLs were observed along the Peruvian coast and extensively reported in the capital city of Lima, about 150 km northwest of the epicenter. These lights were video-recorded by a security camera installed at the Pontificia Universidad Catolica del Peru (PUCP campus and time-correlated with seismic ground accelerations registered at the seismological station on campus, analyzed and related to highly qualified eyewitness observations of the phenomena from other parts of the city and to other video recordings. We believe the evidence presented here contributes significantly to sustain the hypothesis that electromagnetic phenomena related to seismic activity can occur, at least during an earthquake. It is highly probable that continued research in luminescence and the use of magnetometers in studying electromagnetic activity and radon gas emanation detectors will contribute even more towards determining their occurrence during and probably prior to seismic activity.

  7. Quantifying capability of a local seismic network in terms of locations and focal mechanism solutions of weak earthquakes

    Czech Academy of Sciences Publication Activity Database

    Fojtíková, Lucia; Kristeková, M.; Málek, Jiří; Sokos, E.; Csicsay, K.; Zahradník, J.

    2016-01-01

    Roč. 20, č. 1 (2016), 93-106 ISSN 1383-4649 R&D Projects: GA ČR GAP210/12/2336 Institutional support: RVO:67985891 Keywords : Focal-mechanism uncertainty * Little Carpathians * Relative location uncertainty * Seismic network * Uncertainty mapping * Waveform inversion * Weak earthquake s Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.089, year: 2016

  8. Risk Management in Earthquakes, Financial Markets, and the Game of 21: The role of Forecasting, Nowcasting, and Timecasting

    Science.gov (United States)

    Rundle, J. B.

    2017-12-01

    Earthquakes and financial markets share surprising similarities [1]. For example, the well-known VIX index, which by definition is the implied volatility of the Standard and Poors 500 index, behaves in very similar quantitative fashion to time series for earthquake rates. Both display sudden increases at the time of an earthquake or an announcement of the US Federal Reserve Open Market Committee [2], and both decay as an inverse power of time. Both can be regarded as examples of first order phase transitions [1], and display fractal and scaling behavior associated with critical transitions, such as power-law magnitude-frequency relations in the tails of the distributions. Early quantitative investors such as Edward Thorpe and John Kelly invented novel methods to mitigate or manage risk in games of chance such as blackjack, and in markets using hedging techniques that are still in widespread use today. The basic idea is the concept of proportional betting, where the gambler/investor bets a fraction of the bankroll whose size is determined by the "edge" or inside knowledge of the real (and changing) odds. For earthquake systems, the "edge" over nature can only exist in the form of a forecast (probability of a future earthquake); a nowcast (knowledge of the current state of an earthquake fault system); or a timecast (statistical estimate of the waiting time until the next major earthquake). In our terminology, a forecast is a model, while the nowcast and timecast are analysis methods using observed data only (no model). We also focus on defined geographic areas rather than on faults, thereby eliminating the need to consider specific fault data or fault interactions. Data used are online earthquake catalogs, generally since 1980. Forecasts are based on the Weibull (1952) probability law, and only a handful of parameters are needed. These methods allow the development of real time hazard and risk estimation using cloud-based technologies, and permit the application of

  9. Types of damage that could result from a great earthquake in the New Madrid, Missouri, seismic zone

    Science.gov (United States)

    Hopper, M.G.; Algermissen, S.T.

    1984-01-01

    In the winter of 1811–1812 a series of three great earthquakes occurred in the New Madrid seismic zone. In addition to the three principal shocks, at least 15 other earthquakes, Io ≥ VIII, occurred within a year of the first large earthquake on December 16, 1811. The three main shocks were felt over the entire eastern United States. They were strong enough to cause minor damage as far away as Indiana and Ohio on the north, the Carolinas on the east, and southern Mississippi on the south. They were strong enough to cause severe or structural damage in parts of Missouri, Illinois, Indiana, Kentucky, Tennessee, Mississippi, and Arkansas. The section of this poster titled "Seismic history of the New Madrid region" describes what happened in the epicentral region. Fortunately, few people lived in the severely shaken area in 1811; that is not the case today. What would happen if a series of earthquakes as large and numerous as the "New Madrid" earthquakes were to occur in the New Madrid seismic zone today?

  10. The source parameters of 2013 Mw6.6 Lushan earthquake constrained with the restored local clipped seismic waveforms

    Science.gov (United States)

    Hao, J.; Zhang, J. H.; Yao, Z. X.

    2017-12-01

    We developed a method to restore the clipped seismic waveforms near epicenter using projection onto convex sets method (Zhang et al, 2016). This method was applied to rescue the local clipped waveforms of 2013 Mw 6.6 Lushan earthquake. We restored 88 out of 93 clipped waveforms of 38 broadband seismic stations of China Earthquake Networks (CEN). The epicenter distance of the nearest station to the epicenter that we can faithfully restore is only about 32 km. In order to investigate if the source parameters of earthquake could be determined exactly with the restored data, restored waveforms are utilized to get the mechanism of Lushan earthquake. We apply the generalized reflection-transmission coefficient matrix method to calculate the synthetic seismic records and simulated annealing method in inversion (Yao and Harkrider, 1983; Hao et al., 2012). We select 5 stations of CEN with the epicenter distance about 200km whose records aren't clipped and three-component velocity records are used. The result shows the strike, dip and rake angles of Lushan earthquake are 200o, 51o and 87o respectively, hereinafter "standard result". Then the clipped and restored seismic waveforms are applied respectively. The strike, dip and rake angles of clipped seismic waveforms are 184o, 53o and 72o respectively. The largest misfit of angle is 16o. In contrast, the strike, dip and rake angles of restored seismic waveforms are 198o, 51o and 87o respectively. It is very close to the "standard result". We also study the rupture history of Lushan earthquake constrained with the restored local broadband and teleseismic waves based on finite fault method (Hao et al., 2013). The result consists with that constrained with the strong motion and teleseismic waves (Hao et al., 2013), especially the location of the patch with larger slip. In real-time seismology, determining the source parameters as soon as possible is important. This method will help us to determine the mechanism of earthquake

  11. 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.

  12. The 2011 Mineral, Virginia, earthquake and its significance for seismic hazards in eastern North America: overview and synthesis

    Science.gov (United States)

    Horton, J. Wright; Chapman, Martin C.; Green, Russell A.

    2015-01-01

    The 23 August 2011 Mw (moment magnitude) 5.7 ± 0.1, Mineral, Virginia, earthquake was the largest and most damaging in the central and eastern United States since the 1886 Mw 6.8–7.0, Charleston, South Carolina, earthquake. Seismic data indicate that the earthquake rupture occurred on a southeast-dipping reverse fault and consisted of three subevents that progressed northeastward and updip. U.S. Geological Survey (USGS) "Did You Feel It?" intensity reports from across the eastern United States and southeastern Canada, rockfalls triggered at distances to 245 km, and regional groundwater-level changes are all consistent with efficient propagation of high-frequency seismic waves (∼1 Hz and higher) in eastern North America due to low attenuation.

  13. GPS-determined Crustal Deformation of South Korea after the 2011 Tohoku-Oki Earthquake: Straining Heterogeneity and Seismicity

    Science.gov (United States)

    Ree, J. H.; Kim, S.; Yoon, H. S.; Choi, B. K.; Park, P. H.

    2017-12-01

    The GPS-determined, pre-, co- and post-seismic crustal deformations of the Korean peninsula with respect to the 2011 Tohoku-Oki earthquake (Baek et al., 2012, Terra Nova; Kim et al., 2015, KSCE Jour. of Civil Engineering) are all stretching ones (extensional; horizontal stretching rate larger than horizontal shortening rate). However, focal mechanism solutions of earthquakes indicate that South Korea has been at compressional regime dominated by strike- and reverse-slip faultings. We reevaluated the velocity field of GPS data to see any effect of the Tohoku-Oki earthquake on the Korean crustal deformation and seismicity. To calculate the velocity gradient tensor of GPS sites, we used a gridding method based on least-square collocation (LSC). This LSC method can overcome shortcomings of the segmentation methods including the triangulation method. For example, an undesirable, abrupt change in components of velocity field occurs at segment boundaries in the segmentation methods. It is also known that LSC method is more useful in evaluating deformation patterns in intraplate areas with relatively small displacements. Velocity vectors of South Korea, pointing in general to 113° before the Tohoku-Oki earthquake, instantly changed their direction toward the epicenter (82° on average) during the Tohoku-Oki earthquake, and then gradually returned to the original position about 2 years after the Tohoku-Oki earthquake. Our calculation of velocity gradient tensors after the Tohoku-Oki earthquake shows that the stretching and rotating fields are quite heterogeneous, and that both stretching and shortening areas exist in South Korea. In particular, after the post-seismic relaxation ceased (i.e., from two years after the Tohoku-Oki earthquake), regions with thicker and thinner crusts tend to be shortening and stretching, respectively, in South Korea. Furthermore, the straining rate is larger in the regions with thinner crust. Although there is no meaningful correlation between

  14. The impact of earthquakes on the city of Aigio in Greece. Urban planning as a factor in mitigating seismic damage

    International Nuclear Information System (INIS)

    Athanasopoulou, Evanthia; Despoiniadou, Varvara; Dritsos, Stefanos

    2008-01-01

    This paper examines the effects of the mortal earthquake on the city of Aigio in Greece in 1995, with particular focus on urbanization and planning policies. It is based on interviews with experts and surveys on damage to buildings following this earthquake. The analysis takes into account several factors, such as exact location, land use, construction period and the height of damaged buildings. Furthermore, the relationship between the seismic damage and the postseismic construction development of Aigio is examined and the conclusion is reached that the Greek urban planning system needs to be better organized to prepare for seismic damage. To this end, the paper recommends a five-point discussion agenda for applying local planning to seismic mitigation

  15. The impact of earthquakes on the city of Aigio in Greece. Urban planning as a factor in mitigating seismic damage.

    Science.gov (United States)

    Athanasopoulou, Evanthia; Despoiniadou, Varvara; Dritsos, Stefanos

    2008-07-01

    This paper examines the effects of the mortal earthquake on the city of Aigio in Greece in 1995, with particular focus on urbanization and planning policies. It is based on interviews with experts and surveys on damage to buildings following this earthquake. The analysis takes into account several factors, such as exact location, land use, construction period and the height of damaged buildings. Furthermore, the relationship between the seismic damage and the postseismic construction development of Aigio is examined and the conclusion is reached that the Greek urban planning system needs to be better organized to prepare for seismic damage. To this end, the paper recommends a five-point discussion agenda for applying local planning to seismic mitigation.

  16. Absolute earthquake locations using 3-D versus 1-D velocity models below a local seismic network: example from the Pyrenees

    Science.gov (United States)

    Theunissen, T.; Chevrot, S.; Sylvander, M.; Monteiller, V.; Calvet, M.; Villaseñor, A.; Benahmed, S.; Pauchet, H.; Grimaud, F.

    2018-03-01

    Local seismic networks are usually designed so that earthquakes are located inside them (primary azimuthal gap 180° and distance to the first station higher than 15 km). Errors on velocity models and accuracy of absolute earthquake locations are assessed based on a reference data set made of active seismic, quarry blasts and passive temporary experiments. Solutions and uncertainties are estimated using the probabilistic approach of the NonLinLoc (NLLoc) software based on Equal Differential Time. Some updates have been added to NLLoc to better focus on the final solution (outlier exclusion, multiscale grid search, S-phases weighting). Errors in the probabilistic approach are defined to take into account errors on velocity models and on arrival times. The seismicity in the final 3-D catalogue is located with a horizontal uncertainty of about 2.0 ± 1.9 km and a vertical uncertainty of about 3.0 ± 2.0 km.

  17. Archiving and Distributing Seismic Data at the Southern California Earthquake Data Center (SCEDC)

    Science.gov (United States)

    Appel, V. L.

    2002-12-01

    The Southern California Earthquake Data Center (SCEDC) archives and provides public access to earthquake parametric and waveform data gathered by the Southern California Seismic Network and since January 1, 2001, the TriNet seismic network, southern California's earthquake monitoring network. The parametric data in the archive includes earthquake locations, magnitudes, moment-tensor solutions and phase picks. The SCEDC waveform archive prior to TriNet consists primarily of short-period, 100-samples-per-second waveforms from the SCSN. The addition of the TriNet array added continuous recordings of 155 broadband stations (20 samples per second or less), and triggered seismograms from 200 accelerometers and 200 short-period instruments. Since the Data Center and TriNet use the same Oracle database system, new earthquake data are available to the seismological community in near real-time. Primary access to the database and waveforms is through the Seismogram Transfer Program (STP) interface. The interface enables users to search the database for earthquake information, phase picks, and continuous and triggered waveform data. Output is available in SAC, miniSEED, and other formats. Both the raw counts format (V0) and the gain-corrected format (V1) of COSMOS (Consortium of Organizations for Strong-Motion Observation Systems) are now supported by STP. EQQuest is an interface to prepackaged waveform data sets for select earthquakes in Southern California stored at the SCEDC. Waveform data for large-magnitude events have been prepared and new data sets will be available for download in near real-time following major events. The parametric data from 1981 to present has been loaded into the Oracle 9.2.0.1 database system and the waveforms for that time period have been converted to mSEED format and are accessible through the STP interface. The DISC optical-disk system (the "jukebox") that currently serves as the mass-storage for the SCEDC is in the process of being replaced

  18. Co-seismic deformation of the August 27, 2012 Mw 7.3 El Salvador and September 5, 2012 Mw 7.6 Costa Rica earthquakes

    Science.gov (United States)

    Geirsson, H.; La Femina, P. C.; DeMets, C.; Mattioli, G. S.; Hernández, D.

    2013-05-01

    We investigate the co-seismic deformation of two significant earthquakes that occurred along the Middle America trench in 2012. The August 27 Mw 7.3 El Salvador and September 5 Mw 7.6 Nicoya Peninsula, Costa Rica earthquakes, were examined using a combination of episodic and continuous Global Positioning System (GPS) data. USGS finite fault models based on seismic data predict fundamentally different characteristics for the two ruptures. The El Salvador event occurred in a historical seismic gap and on the shallow segment of the Middle America Trench main thrust, rupturing a large area, but with a low magnitude of slip. A small tsunami was observed along the coast in Nicaragua and El Salvador, additionally indicating near-trench rupture. Conversely, the Nicoya, Costa Rica earthquake was predicted to have an order of magnitude higher slip on a spatially smaller patch deeper on the main thrust. We present results from episodic and continuous geodetic GPS measurements made in conjunction with the two earthquakes, including data from newly installed COCONet (Continuously Operating Caribbean GPS Observational Network) sites. Episodic GPS measurements made in El Salvador, Honduras, and Nicaragua following the earthquakes, allow us to estimate the co-seismic deformation field from both earthquakes. Because of the small magnitude of the El Salvador earthquake and its shallow rupture the observed co-seismic deformation is small (earthquake occurred directly beneath a seismic and geodetic network specifically designed to capture such events. The observed displacements exceeded 0.5 m and there is a significant post-seismic transient following the earthquake. We use our estimated co-seismic offsets for both earthquakes to model the magnitude and spatial variability of slip for these two events.

  19. Studies of the seismic coda using an earthquake cluster as a deeply buried seismograph array

    Science.gov (United States)

    Spudich, Paul; Bostwick, Todd

    1987-09-01

    Loosely speaking, the principle of Green's function reciprocity means that the source and receiver positions in a seismic experiment can be exchanged without affecting the observed seismograms. Consequently, the seismograms observed at a single observation location o and caused by a cluster of microearthquakes at locations {ei} are identical to the time series that would be measured by an array of stress meters emplaced at positions {ei}, recording waves generated by a source acting at o. By applying array analysis techniques like slant stacking and frequency-wave number analysis to these seismograms, we can determine the directions and velocities of the component waves as they travel in the earthquake focal region rather than at the surface. We have developed a computationally rapid plane-wave decomposition which we have applied to single-station recordings of aftershocks of the 1984 Morgan Hill, California, earthquake. The analysis is applied to data from three seismic stations having considerably different site geologies. One is a relatively hard rock station situated on Franciscan metamorphics, one is within the Calaveras fault zone, and one is on semiconsolidated sand and gravels. We define the early coda to be the part of the coda initiating immediately after the direct S wave and ending at twice the S wave lapse time. The character of the S wave and early coda varies from being impulsive at the first station to highly reverberative at the last. We examine waves in sequential time windows starting at the S wave and continuing through the early part of the coda. At all seismic stations the early coda is dominated by a persistent signal that must be caused by multiple scattering, probably within 2 km of each seismic station. Despite clear station-to-station differences in the character of the early coda, coda Q values measured in the late coda (greater than twice the S lapse time) agree well among stations, implying that the mechanisms causing the varying

  20. Satellite Geodetic Constraints On Earthquake Processes: Implications of the 1999 Turkish Earthquakes for Fault Mechanics and Seismic Hazards on the San Andreas Fault

    Science.gov (United States)

    Reilinger, Robert

    2005-01-01

    Our principal activities during the initial phase of this project include: 1) Continued monitoring of postseismic deformation for the 1999 Izmit and Duzce, Turkey earthquakes from repeated GPS survey measurements and expansion of the Marmara Continuous GPS Network (MAGNET), 2) Establishing three North Anatolian fault crossing profiles (10 sitedprofile) at locations that experienced major surface-fault earthquakes at different times in the past to examine strain accumulation as a function of time in the earthquake cycle (2004), 3) Repeat observations of selected sites in the fault-crossing profiles (2005), 4) Repeat surveys of the Marmara GPS network to continue to monitor postseismic deformation, 5) Refining block models for the Marmara Sea seismic gap area to better understand earthquake hazards in the Greater Istanbul area, 6) Continuing development of models for afterslip and distributed viscoelastic deformation for the earthquake cycle. We are keeping close contact with MIT colleagues (Brad Hager, and Eric Hetland) who are developing models for S. California and for the earthquake cycle in general (Hetland, 2006). In addition, our Turkish partners at the Marmara Research Center have undertaken repeat, micro-gravity measurements at the MAGNET sites and have provided us estimates of gravity change during the period 2003 - 2005.

  1. Seismic safety reexaminations to NPPs in Taiwan. Lessons learned from 20061226 Taiwan Hengchun and 20070716 Japan Niigata-Chuetsu oki earthquakes

    International Nuclear Information System (INIS)

    Chow Ting; Wu Yuanchieh; Gau Yunchau

    2008-01-01

    On December 26 2006, a strong earthquake with a local magnitude M L of 7.0 hit the most southern part of Taiwan, Hengchun village, where the Maanshan Nuclear Power Station is located. This is a historic high earthquake ever been experienced to Taiwan's existing nuclear power units, and it raised high public concerns about the seismic safety of the nuclear power plants operation. More recently on July 16 2007, in Japan, where the earthquake focal mechanisms are very similar to those in Taiwan, all 7 nuclear power units in Kashiwazaki-Kariwa site were struck by a more devastating earthquake and as the result, the design earthquakes for all the nuclear units have been exceeded. Therefore, the assurance of good seismic design and the appropriateness of associated post-earthquake actions to the nuclear power units in Taiwan become very urgent topics. Based on the experiences learned from the above mentioned two earthquakes, this paper will focus on the seismic safety reexamination of Taiwan's existing nuclear power plants of the following aspects: (1) current US orientated seismic designs/regulations from earthquake probabilistic risk point of view, (2) earthquake shut-down criterion, especially the CAV parameter and its threshold value, and (3) current post earthquake actions. (author)

  2. Non-Invasive Seismic Methods for Earthquake Site Classification Applied to Ontario Bridge Sites

    Science.gov (United States)

    Bilson Darko, A.; Molnar, S.; Sadrekarimi, A.

    2017-12-01

    How a site responds to earthquake shaking and its corresponding damage is largely influenced by the underlying ground conditions through which it propagates. The effects of site conditions on propagating seismic waves can be predicted from measurements of the shear wave velocity (Vs) of the soil layer(s) and the impedance ratio between bedrock and soil. Currently the seismic design of new buildings and bridges (2015 Canadian building and bridge codes) requires determination of the time-averaged shear-wave velocity of the upper 30 metres (Vs30) of a given site. In this study, two in situ Vs profiling methods; Multichannel Analysis of Surface Waves (MASW) and Ambient Vibration Array (AVA) methods are used to determine Vs30 at chosen bridge sites in Ontario, Canada. Both active-source (MASW) and passive-source (AVA) surface wave methods are used at each bridge site to obtain Rayleigh-wave phase velocities over a wide frequency bandwidth. The dispersion curve is jointly inverted with each site's amplification function (microtremor horizontal-to-vertical spectral ratio) to obtain shear-wave velocity profile(s). We apply our non-invasive testing at three major infrastructure projects, e.g., five bridge sites along the Rt. Hon. Herb Gray Parkway in Windsor, Ontario. Our non-invasive testing is co-located with previous invasive testing, including Standard Penetration Test (SPT), Cone Penetration Test and downhole Vs data. Correlations between SPT blowcount and Vs are developed for the different soil types sampled at our Ontario bridge sites. A robust earthquake site classification procedure (reliable Vs30 estimates) for bridge sites across Ontario is evaluated from available combinations of invasive and non-invasive site characterization methods.

  3. Numerical modeling of the deformations associated with large subduction earthquakes through the seismic cycle

    Science.gov (United States)

    Fleitout, L.; Trubienko, O.; Garaud, J.; Vigny, C.; Cailletaud, G.; Simons, W. J.; Satirapod, C.; Shestakov, N.

    2012-12-01

    A 3D finite element code (Zebulon-Zset) is used to model deformations through the seismic cycle in the areas surrounding the last three large subduction earthquakes: Sumatra, Japan and Chile. The mesh featuring a broad spherical shell portion with a viscoelastic asthenosphere is refined close to the subduction zones. The model is constrained by 6 years of postseismic data in Sumatra area and over a year of data for Japan and Chile plus preseismic data in the three areas. The coseismic displacements on the subduction plane are inverted from the coseismic displacements using the finite element program and provide the initial stresses. The predicted horizontal postseismic displacements depend upon the thicknesses of the elastic plate and of the low viscosity asthenosphere. Non-dimensionalized by the coseismic displacements, they present an almost uniform value between 500km and 1500km from the trench for elastic plates 80km thick. The time evolution of the velocities is function of the creep law (Maxwell, Burger or power-law creep). Moreover, the forward models predict a sizable far-field subsidence, also with a spatial distribution which varies with the geometry of the asthenosphere and lithosphere. Slip on the subduction interface does not induce such a subsidence. The observed horizontal velocities, divided by the coseismic displacement, present a similar pattern as function of time and distance from trench for the three areas, indicative of similar lithospheric and asthenospheric thicknesses and asthenospheric viscosity. This pattern cannot be fitted with power-law creep in the asthenosphere but indicates a lithosphere 60 to 90km thick and an asthenosphere of thickness of the order of 100km with a burger rheology represented by a Kelvin-Voigt element with a viscosity of 3.1018Pas and μKelvin=μelastic/3. A second Kelvin-Voigt element with very limited amplitude may explain some characteristics of the short time-scale signal. The postseismic subsidence is

  4. Co-Seismic Effect of the 2011 Japan Earthquake on the Crustal Movement Observation Network of China

    Directory of Open Access Journals (Sweden)

    Shaomin Yang

    2013-01-01

    Full Text Available Great earthquakes introduce measurable co-seismic displacements over regions of hundreds and thousands of kilometers in width, which, if not accounted for, may significantly bias the long-term surface velocity field constrained by GPS observations performed during a period encompassing that event. Here, we first present an estimation of the far-field co-seismic off-sets associated with the 2011 Japan Mw 9.0 earthquake using GPS measurements from the Crustal Movement Observation Network of China (CMONOC in North China. The uncertainties of co-seismic off-set, either at cGPS stations or at campaign sites, are better than 5 - 6 mm on average. We compare three methods to constrain the co-seismic off-sets at the campaign sites in northeastern China 1 interpolating cGPS coseismic offsets, 2 estimating in terms of sparsely sampled time-series, and 3 predicting by using a well-constrained slip model. We show that the interpolation of cGPS co-seismic off-sets onto the campaign sites yield the best co-seismic off-set solution for these sites. The source model gives a consistent prediction based on finite dislocation in a layered spherical Earth, which agrees with the best prediction with discrepancies of 2 - 10 mm for 32 campaign sites. Thus, the co-seismic off-set model prediction is still a reasonable choice if a good coverage cGPS network is not available for a very active region like the Tibetan Plateau in which numerous campaign GPS sites were displaced by the recent large earthquakes.

  5. 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 ...

  6. EVALUATION OF SEISMIC PERFORMANCE OF RAMP TUNNEL STRUCTURE DURING LEVEL-2 EARTHQUAKE BY MASSIVE 3D NUMERICAL COMPUTATION

    Science.gov (United States)

    Yamada, Takemine; Ichimura, Tsuyoshi; Hori, Muneo; Dobashi, Hiroshi; Ohbo, Naoto

    Quasi non-linear 3D FEM earthquake response analysises with level-2 earthquake are conducted for a ramp tunnel structure of Tokyo metropolitan express way central circular line the Yamate tunnel. Large-scale numerical computation with solid elements is highly required for examination of seismic response of large tunnel in case of level-2 earthquake. The results are obtained as follows: i) In level-2 earthquake, stress concentration in ramp tunnel becomes great near geological interface between two layers of high impedance contrast. ii) The response is not obtained as a superposition of two-dimensional responses which is an assumption in conventional design methods because the distribution of displacements in the direction of tunnel axis at cross-section of ramp tunnel structure near geological interface does not linearly distribute. iii) Evaluation of stress in addition to section force is desirable for the correct evaluation of the three-dimensional response of tunnel structure.

  7. Outline of the report on the seismic safety examination of nuclear facilities based on the 1995 Hyogoken-Nanbu earthquake (tentative translation) - September 1995

    International Nuclear Information System (INIS)

    2003-01-01

    From the standpoint of thoroughly confirming the seismic safety of nuclear facilities, Nuclear Safety Commission established an Examination Committee on the Seismic Safety of Nuclear Power Reactor Facilities (hereinafter called Seismic Safety Examination Committee) based on the 1995 Hyogoken-Nanbu Earthquake on January 19, 1995, two days after the occurrence of the earthquake, in order to examine the validity of related guidelines on the seismic design to be used for the safety examination. This report outlines the results of the examinations by the Seismic Safety Examination Committee: basic principle of examinations at the seismic safety examination committee, overview on the related guidelines of the seismic design, information and knowledge obtained on the 1995 Hyogoken-Nanbu earthquake, examination of validity of the guidelines based on various information of the Hyogoken-Nanbu earthquake. The Seismic Design Examination Committee surveyed the related guidelines on seismic design, selected the items to be examined, and examined on those items based on the knowledge obtained from the Hyogoken-Nanbu Earthquake. As a result, the Committee confirmed that the validity of the guidelines regulating the seismic design of nuclear facilities is not impaired even though on the basis of the Hyogoken-Nanbu Earthquake. However, the people related to the nuclear facilities may not be content with the above result, but continuously put efforts in doing the following matters to improve furthermore the reliability of seismic design of nuclear facilities by always reflecting the latest knowledge on the seismic design. 1) - The people related to nuclear facilities must seriously accept the fact that valuable knowledge could be obtained from the Hyogoken-Nanbu Earthquake, try to study and analyze the obtained data, and reflect the results of investigations, studies, and examinations conducted appropriately to the seismic design of nuclear facilities referring to the investigations

  8. 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)

  9. Input parameters for the statistical seismic hazard assessment in central part of Romania territory using crustal earthquakes

    International Nuclear Information System (INIS)

    Moldovan, A.I.; Bazacliu, O.; Popescu, E.

    2004-01-01

    The seismic hazard assessment in dense-populated geographical regions and subsequently the design of the strategic objectives (dams, nuclear power plants, etc.) are based on the knowledge of the seismicity parameters of the seismic sources which can generate ground motion amplitudes above the minimum level considered risky at the specific site and the way the seismic waves propagate between the focus and the site. The purpose of this paper is to provide a set of information required for a probabilistic assessment of the seismic hazard in the central Romanian territory relative to the following seismic sources: Fagaras zone (FC), Campulung zone (CP), and Transilvania zone (TD) all of them in the crust domain. Extremely vulnerable objectives are present in the central part of Romania, including cities of Pitesti and Sibiu and the 'Vidraru' dam. The analysis that we propose implies: (1) geometrical definition of the seismic sources, (2) estimation of the maximum possible magnitude, (3) estimation of the frequency - magnitude relationship and (4) estimation of the attenuation laws. As an example, the obtained input parameters are used to evaluate the seismic hazard distribution due to the crustal earthquakes applying the McGuire's procedure (1976). These preliminary results are in good agreement with the previous research based on deterministic approach (Radulian et al., 2000). (authors)

  10. Evaluation of Seismic Rupture Models for the 2011 Tohoku-Oki Earthquake Using Tsunami Simulation

    Directory of Open Access Journals (Sweden)

    Ming-Da Chiou

    2013-01-01

    Full Text Available Developing a realistic, three-dimensional rupture model of the large offshore earthquake is difficult to accomplish directly through band-limited ground-motion observations. A potential indirect method is using a tsunami simulation to verify the rupture model in reverse because the initial conditions of the associated tsunamis are caused by a coseismic seafloor displacement correlating to the rupture pattern along the main faulting. In this study, five well-developed rupture models for the 2011 Tohoku-Oki earthquake were adopted to evaluate differences in simulated tsunamis and various rupture asperities. The leading wave of the simulated tsunamis triggered by the seafloor displacement in Yamazaki et al. (2011 model resulted in the smallest root-mean-squared difference (~0.082 m on average from the records of the eight DART (Deep-ocean Assessment and Reporting of Tsunamis stations. This indicates that the main seismic rupture during the 2011 Tohoku earthquake should occur in a large shallow slip in a narrow range adjacent to the Japan trench. This study also quantified the influences of ocean stratification and tides which are normally overlooked in tsunami simulations. The discrepancy between the simulations with and without stratification was less than 5% of the first peak wave height at the eight DART stations. The simulations, run with and without the presence of tides, resulted in a ~1% discrepancy in the height of the leading wave. Because simulations accounting for tides and stratification are time-consuming and their influences are negligible, particularly in the first tsunami wave, the two factors can be ignored in a tsunami prediction for practical purposes.

  11. SEISMIC PERFORMANCE OF MOMENT-RESISTING CONCRETE FRAMES SUBJECTED TO EARTHQUAKE EXCITATION

    Directory of Open Access Journals (Sweden)

    FADZLI MOHAMED NAZRI

    2014-12-01

    Full Text Available In this study, moment-resisting concrete frames (MRCFs were designed based on Eurocodes 2 and 8, which indicate the seismic provisions and requirements for building design and construction. This study aims to investigate the damage measure of MRCFs subjected to earthquake excitation by pushover analysis (POA and incremental dynamic analysis (IDA. In POA, inverted triangular lateral load and uniform lateral load patterns were used to produce a base shear–drift curve. In IDA, seven far-field and seven near-field ground motion records were selected to establish the base shear–drift relationship. Structural response and damage measures were examined by the performance-based seismic design limit states. Vision 2000 proposed four performance states, namely, fully operational, operational, life safety (LS, and near collapse. The results showed that the designed structures have low stiffness because all MRCFs failed to meet the LS limit state. The base shear–drift relationship produced a higher demand in IDA than in POA. In POA, the lateral uniform load pattern produced higher demand than the lateral inverted triangular load pattern. In IDA, the farfield effect produced higher demand than the near-field effect. POA approximated IDA accurately at the elastic stage, but the approximation failed after the yield point.

  12. Nonlinear Seismic Behavior of Different Boundary Conditions of Transmission Line Systems under Earthquake Loading

    Directory of Open Access Journals (Sweden)

    Li Tian

    2016-01-01

    Full Text Available Nonlinear seismic behaviors of different boundary conditions of transmission line system under earthquake loading are investigated in this paper. The transmission lines are modeled by cable element accounting for the nonlinearity of the cable. For the suspension type, three towers and two span lines with spring model (Model 1 and three towers and four span lines’ model (Model 2 are established, respectively. For the tension type, three towers and two span lines’ model (Model 3 and three towers and four span lines’ model (Model 4 are created, respectively. The frequencies of the transmission towers and transmission lines of the suspension type and tension type are calculated, respectively. The responses of the suspension type and tension type are investigated using nonlinear time history analysis method, respectively. The results show that the responses of the transmission tower and transmission line of the two models of the suspension type are slightly different. However, the responses of transmission tower and transmission line of the two models of the tension type are significantly different. Therefore, in order to obtain accurate results, a reasonable model should be considered. The results could provide a reference for the seismic analysis of the transmission tower-line system.

  13. Monitoring the West Bohemian earthquake swarm in 2008/2009 by a temporary small-aperture seismic array

    Science.gov (United States)

    Hiemer, Stefan; Roessler, Dirk; Scherbaum, Frank

    2012-04-01

    The most recent intense earthquake swarm in West Bohemia lasted from 6 October 2008 to January 2009. Starting 12 days after the onset, the University of Potsdam monitored the swarm by a temporary small-aperture seismic array at 10 km epicentral distance. The purpose of the installation was a complete monitoring of the swarm including micro-earthquakes ( M L 0.0). In the course of this work, the main temporal features (frequency-magnitude distribution, propagation of back azimuth and horizontal slowness, occurrence rate of aftershock sequences and interevent-time distribution) of the recent 2008/2009 earthquake swarm are presented and discussed. Temporal changes of the coefficient of variation (based on interevent times) suggest that the swarm earthquake activity of the 2008/2009 swarm terminates by 12 January 2009. During the main phase in our studied swarm period after 19 October, the b value of the Gutenberg-Richter relation decreases from 1.2 to 0.8. This trend is also reflected in the power-law behavior of the seismic moment release. The corresponding total seismic moment release of 1.02×1017 Nm is equivalent to M L,max = 5.4.

  14. Automatic recognition of seismic intensity based on RS and GIS: a case study in Wenchuan Ms8.0 earthquake of China.

    Science.gov (United States)

    Zhang, Qiuwen; Zhang, Yan; Yang, Xiaohong; Su, Bin

    2014-01-01

    In recent years, earthquakes have frequently occurred all over the world, which caused huge casualties and economic losses. It is very necessary and urgent to obtain the seismic intensity map timely so as to master the distribution of the disaster and provide supports for quick earthquake relief. Compared with traditional methods of drawing seismic intensity map, which require many investigations in the field of earthquake area or are too dependent on the empirical formulas, spatial information technologies such as Remote Sensing (RS) and Geographical Information System (GIS) can provide fast and economical way to automatically recognize the seismic intensity. With the integrated application of RS and GIS, this paper proposes a RS/GIS-based approach for automatic recognition of seismic intensity, in which RS is used to retrieve and extract the information on damages caused by earthquake, and GIS is applied to manage and display the data of seismic intensity. The case study in Wenchuan Ms8.0 earthquake in China shows that the information on seismic intensity can be automatically extracted from remotely sensed images as quickly as possible after earthquake occurrence, and the Digital Intensity Model (DIM) can be used to visually query and display the distribution of seismic intensity.

  15. Automatic Recognition of Seismic Intensity Based on RS and GIS: A Case Study in Wenchuan Ms8.0 Earthquake of China

    Directory of Open Access Journals (Sweden)

    Qiuwen Zhang

    2014-01-01

    Full Text Available In recent years, earthquakes have frequently occurred all over the world, which caused huge casualties and economic losses. It is very necessary and urgent to obtain the seismic intensity map timely so as to master the distribution of the disaster and provide supports for quick earthquake relief. Compared with traditional methods of drawing seismic intensity map, which require many investigations in the field of earthquake area or are too dependent on the empirical formulas, spatial information technologies such as Remote Sensing (RS and Geographical Information System (GIS can provide fast and economical way to automatically recognize the seismic intensity. With the integrated application of RS and GIS, this paper proposes a RS/GIS-based approach for automatic recognition of seismic intensity, in which RS is used to retrieve and extract the information on damages caused by earthquake, and GIS is applied to manage and display the data of seismic intensity. The case study in Wenchuan Ms8.0 earthquake in China shows that the information on seismic intensity can be automatically extracted from remotely sensed images as quickly as possible after earthquake occurrence, and the Digital Intensity Model (DIM can be used to visually query and display the distribution of seismic intensity.

  16. Probabilistic model to forecast earthquakes in the Zemmouri (Algeria) seismoactive area on the basis of moment magnitude scale distribution functions

    Science.gov (United States)

    Baddari, Kamel; Makdeche, Said; Bellalem, Fouzi

    2013-02-01

    Based on the moment magnitude scale, a probabilistic model was developed to predict the occurrences of strong earthquakes in the seismoactive area of Zemmouri, Algeria. Firstly, the distributions of earthquake magnitudes M i were described using the distribution function F 0(m), which adjusts the magnitudes considered as independent random variables. Secondly, the obtained result, i.e., the distribution function F 0(m) of the variables M i was used to deduce the distribution functions G(x) and H(y) of the variables Y i = Log M 0,i and Z i = M 0,i , where (Y i)i and (Z i)i are independent. Thirdly, some forecast for moments of the future earthquakes in the studied area is given.

  17. Radiated Seismic Energy of Earthquakes in the South-Central Region of the Gulf of California, Mexico

    Science.gov (United States)

    Castro, Raúl R.; Mendoza-Camberos, Antonio; Pérez-Vertti, Arturo

    2018-05-01

    We estimated the radiated seismic energy (ES) of 65 earthquakes located in the south-central region of the Gulf of California. Most of these events occurred along active transform faults that define the Pacific-North America plate boundary and have magnitudes between M3.3 and M5.9. We corrected the spectral records for attenuation using nonparametric S-wave attenuation functions determined with the whole data set. The path effects were isolated from the seismic source using a spectral inversion. We computed radiated seismic energy of the earthquakes by integrating the square velocity source spectrum and estimated their apparent stresses. We found that most events have apparent stress between 3 × 10-4 and 3 MPa. Model independent estimates of the ratio between seismic energy and moment (ES/M0) indicates that this ratio is independent of earthquake size. We conclude that in general the apparent stress is low (σa < 3 MPa) in the south-central and southern Gulf of California.

  18. St. Louis area earthquake hazards mapping project; seismic and liquefaction hazard maps

    Science.gov (United States)

    Cramer, Chris H.; Bauer, Robert A.; Chung, Jae-won; Rogers, David; Pierce, Larry; Voigt, Vicki; Mitchell, Brad; Gaunt, David; Williams, Robert; Hoffman, David; Hempen, Gregory L.; Steckel, Phyllis; Boyd, Oliver; Watkins, Connor M.; Tucker, Kathleen; McCallister, Natasha

    2016-01-01

    We present probabilistic and deterministic seismic and liquefaction hazard maps for the densely populated St. Louis metropolitan area that account for the expected effects of surficial geology on earthquake ground shaking. Hazard calculations were based on a map grid of 0.005°, or about every 500 m, and are thus higher in resolution than any earlier studies. To estimate ground motions at the surface of the model (e.g., site amplification), we used a new detailed near‐surface shear‐wave velocity model in a 1D equivalent‐linear response analysis. When compared with the 2014 U.S. Geological Survey (USGS) National Seismic Hazard Model, which uses a uniform firm‐rock‐site condition, the new probabilistic seismic‐hazard estimates document much more variability. Hazard levels for upland sites (consisting of bedrock and weathered bedrock overlain by loess‐covered till and drift deposits), show up to twice the ground‐motion values for peak ground acceleration (PGA), and similar ground‐motion values for 1.0 s spectral acceleration (SA). Probabilistic ground‐motion levels for lowland alluvial floodplain sites (generally the 20–40‐m‐thick modern Mississippi and Missouri River floodplain deposits overlying bedrock) exhibit up to twice the ground‐motion levels for PGA, and up to three times the ground‐motion levels for 1.0 s SA. Liquefaction probability curves were developed from available standard penetration test data assuming typical lowland and upland water table levels. A simplified liquefaction hazard map was created from the 5%‐in‐50‐year probabilistic ground‐shaking model. The liquefaction hazard ranges from low (60% of area expected to liquefy) in the lowlands. Because many transportation routes, power and gas transmission lines, and population centers exist in or on the highly susceptible lowland alluvium, these areas in the St. Louis region are at significant potential risk from seismically induced liquefaction and associated

  19. Detecting earthquakes over a seismic network using single-station similarity measures

    Science.gov (United States)

    Bergen, Karianne J.; Beroza, Gregory C.

    2018-06-01

    New blind waveform-similarity-based detection methods, such as Fingerprint and Similarity Thresholding (FAST), have shown promise for detecting weak signals in long-duration, continuous waveform data. While blind detectors are capable of identifying similar or repeating waveforms without templates, they can also be susceptible to false detections due to local correlated noise. In this work, we present a set of three new methods that allow us to extend single-station similarity-based detection over a seismic network; event-pair extraction, pairwise pseudo-association, and event resolution complete a post-processing pipeline that combines single-station similarity measures (e.g. FAST sparse similarity matrix) from each station in a network into a list of candidate events. The core technique, pairwise pseudo-association, leverages the pairwise structure of event detections in its network detection model, which allows it to identify events observed at multiple stations in the network without modeling the expected moveout. Though our approach is general, we apply it to extend FAST over a sparse seismic network. We demonstrate that our network-based extension of FAST is both sensitive and maintains a low false detection rate. As a test case, we apply our approach to 2 weeks of continuous waveform data from five stations during the foreshock sequence prior to the 2014 Mw 8.2 Iquique earthquake. Our method identifies nearly five times as many events as the local seismicity catalogue (including 95 per cent of the catalogue events), and less than 1 per cent of these candidate events are false detections.

  20. Significance test for seismicity rate changes before the 1987 Chiba-toho-oki earthquake ({mu} 6.7) Japan

    Energy Technology Data Exchange (ETDEWEB)

    Maeda, K.; Wiemer, S. [Meteorologial Research Institute, Tsukuba, Ibaraki (Japan). Dept. of Seismology and Volcanology Research

    1999-10-01

    The paper discusses a quantitative analysis of the seismicity rates, using two independent catalogs provided by the NIED (National Research Institute for Earth Science and Disaster Prevention) and JMA (Japan Meteorological Agency) networks and shows that the precursory seismic quiescence is centered in the shallower part of the rupture zone of the subsequent main shock, at the depth of 20-40 km. At the hypocenter of 1987 Chiba-toho-oki earthquake, a 50% increase in the seismicity rate was detected in the NIED data, coinciding in time with the onset of quiescence. For the aid of real time monitoring of seismicity rate changes, the method to calculate the 95-percentile of confidence level for the significant rate changes has been introduced.

  1. Earthquake forecast for the Wasatch Front region of the Intermountain West

    Science.gov (United States)

    DuRoss, Christopher B.

    2016-04-18

    The Working Group on Utah Earthquake Probabilities has assessed the probability of large earthquakes in the Wasatch Front region. There is a 43 percent probability of one or more magnitude 6.75 or greater earthquakes and a 57 percent probability of one or more magnitude 6.0 or greater earthquakes in the region in the next 50 years. These results highlight the threat of large earthquakes in the region.

  2. Combining Real-Time Seismic and GPS Data for Earthquake Early Warning (Invited)

    Science.gov (United States)

    Boese, M.; Heaton, T. H.; Hudnut, K. W.

    2013-12-01

    Scientists at Caltech, UC Berkeley, the Univ. of SoCal, the Univ. of Washington, the US Geological Survey, and ETH Zurich have developed an earthquake early warning (EEW) demonstration system for California and the Pacific Northwest. To quickly determine the earthquake magnitude and location, 'ShakeAlert' currently processes and interprets real-time data-streams from ~400 seismic broadband and strong-motion stations within the California Integrated Seismic Network (CISN). Based on these parameters, the 'UserDisplay' software predicts and displays the arrival and intensity of shaking at a given user site. Real-time ShakeAlert feeds are currently shared with around 160 individuals, companies, and emergency response organizations to educate potential users about EEW and to identify needs and applications of EEW in a future operational warning system. Recently, scientists at the contributing institutions have started to develop algorithms for ShakeAlert that make use of high-rate real-time GPS data to improve the magnitude estimates for large earthquakes (M>6.5) and to determine slip distributions. Knowing the fault slip in (near) real-time is crucial for users relying on or operating distributed systems, such as for power, water or transportation, especially if these networks run close to or across large faults. As shown in an earlier study, slip information is also useful to predict (in a probabilistic sense) how far a fault rupture will propagate, thus enabling more robust probabilistic ground-motion predictions at distant locations. Finally, fault slip information is needed for tsunami warning, such as in the Cascadia subduction-zone. To handle extended fault-ruptures of large earthquakes in real-time, Caltech and USGS Pasadena are currently developing and testing a two-step procedure that combines seismic and geodetic data; in the first step, high-frequency strong-motion amplitudes are used to rapidly classify near-and far-source stations. Then, the location and

  3. An innovative view to the seismic hazard from strong Vrancea intermediate-depth earthquakes: the case studies of Bucharest (Romania) and Russe (Bulgaria)

    International Nuclear Information System (INIS)

    Panza, G.F.; Cioflan, C.; Marmureanu, G.; Kouteva, M.; Paskaleva, I.; Romanelli, F.

    2003-04-01

    An advanced procedure for ground motion modelling, capable of synthesizing the seismic ground motion from basic understanding of fault mechanism and seismic wave propagation, is applied to compute seismic signals at Bucharest (Romania) and Russe, NE Bulgaria, due to the seismic hazard from intermediate-depth Vrancea earthquakes. The theoretically obtained signals are successfully compared with the available observations. For both case studies site response estimates along selected geological cross sections are provided for three recent, strong and intermediate-depth, Vrancea earthquakes: August 30, 1986 and May 30 and 31, 1990. The applied ground motion modelling technique has proved that it is possible to investigate the local effects, taking into account both the seismic source and the propagation path effects. The computation of realistic seismic input, utilising the huge amount of geological, geophysical and geotechnical data, already available, goes well beyond the conventional deterministic approach and gives an economically valid scientific tool for seismic microzonation. (author)

  4. Irregularities in Early Seismic Rupture Propagation for Large Events in a Crustal Earthquake Model

    Science.gov (United States)

    Lapusta, N.; Rice, J. R.; Rice, J. R.

    2001-12-01

    We study early seismic propagation of model earthquakes in a 2-D model of a vertical strike-slip fault with depth-variable rate and state friction properties. Our model earthquakes are obtained in fully dynamic simulations of sequences of instabilities on a fault subjected to realistically slow tectonic loading (Lapusta et al., JGR, 2000). This work is motivated by results of Ellsworth and Beroza (Science, 1995), who observe that for many earthquakes, far-field velocity seismograms during initial stages of dynamic rupture propagation have irregular fluctuations which constitute a "seismic nucleation phase". In our simulations, we find that such irregularities in velocity seismograms can be caused by two factors: (1) rupture propagation over regions of stress concentrations and (2) partial arrest of rupture in neighboring creeping regions. As rupture approaches a region of stress concentration, it sees increasing background stress and its moment acceleration (to which velocity seismographs in the far field are proportional) increases. After the peak in stress concentration, the rupture sees decreasing background stress and moment acceleration decreases. Hence a fluctuation in moment acceleration is created. If rupture starts sufficiently far from a creeping region, then partial arrest of rupture in the creeping region causes a decrease in moment acceleration. As the other parts of rupture continue to develop, moment acceleration then starts to grow again, and a fluctuation again results. Other factors may cause the irregularities in moment acceleration, e.g., phenomena such as branching and/or intermittent rupture propagation (Poliakov et al., submitted to JGR, 2001) which we have not studied here. Regions of stress concentration are created in our model by arrest of previous smaller events as well as by interactions with creeping regions. One such region is deep in the fault zone, and is caused by the temperature-induced transition from seismogenic to creeping

  5. Imaging 2015 Mw 7.8 Gorkha Earthquake and Its Aftershock Sequence Combining Multiple Calibrated Global Seismic Arrays

    Science.gov (United States)

    LI, B.; Ghosh, A.

    2016-12-01

    The 2015 Mw 7.8 Gorkha earthquake provides a good opportunity to study the tectonics and earthquake hazards in the Himalayas, one of the most seismically active plate boundaries. Details of the seismicity patterns and associated structures in the Himalayas are poorly understood mainly due to limited instrumentation. Here, we apply a back-projection method to study the mainshock rupture and the following aftershock sequence using four large aperture global seismic arrays. All the arrays show eastward rupture propagation of about 130 km and reveal similar evolution of seismic energy radiation, with strong high-frequency energy burst about 50 km north of Kathmandu. Each single array, however, is typically limited by large azimuthal gap, low resolution, and artifacts due to unmodeled velocity structures. Therefore, we use a self-consistent empirical calibration method to combine four different arrays to image the Gorkha event. It greatly improves the resolution, can better track rupture and reveal details that cannot be resolved by any individual array. In addition, we also use the same arrays at teleseismic distances and apply a back-projection technique to detect and locate the aftershocks immediately following the Gorkha earthquake. We detect about 2.5 times the aftershocks recorded by the Advance National Seismic System comprehensive earthquake catalog during the 19 days following the mainshock. The aftershocks detected by the arrays show an east-west trend in general, with majority of the aftershocks located at the eastern part of the rupture patch and surrounding the rupture zone of the largest Mw 7.3 aftershock. Overall spatiotemporal aftershock pattern agrees well with global catalog, with our catalog showing more details relative to the standard global catalog. The improved aftershock catalog enables us to better study the aftershock dynamics, stress evolution in this region. Moreover, rapid and better imaging of aftershock distribution may aid rapid response

  6. Using the automized system ''section'' to forecast velocity sections using data on borehole velocity measurement and seismic field prospecting

    Energy Technology Data Exchange (ETDEWEB)

    Dorman, M.I.; Gein, F.F.; Zubairov, F.B.

    1981-01-01

    A system of automated processing of seismic data is examined which makes it possible to set up rate functions at arbitrary points of a seismic prospecting section or at points conciding with boreholes in which rate measurements have not been completed. The basis for the forecasting method is data on seismic well logging investigations, seismic prospecting and some indirect observations on sections. The bases of a procedure realizing a forecasting method are set forth, as are those requirements which satisfy the system as a whole. The results of using the ''section'' system in a terrestrial section of Western Siberia are set forth.

  7. InSAR Analysis of Post-Seismic Deformation Following the 2013 Mw 7.7 Balochistan, Pakistan Earthquake

    Science.gov (United States)

    Peterson, K.; Barnhart, W. D.

    2017-12-01

    On September 24th, 2013, a Mw 7.7 earthquake ruptured a 200 km portion of the Hoshab fault, a reverse fault in the Makran accretionary prism of southern Pakistan. This earthquake is notable because it ruptured a reverse fault with a predominantly strike-slip sense of displacement, and it ruptured a mechanically weak accretionary prism. Here, we present initial analysis of ongoing post-seismic deformation imaged with the Sentinel-1 interferometric synthetic aperture radar (InSAR) mission with the goals of a) determining the dominant post-seismic deformation processes active, b) characterizing the rigidity and rheological structure of a flat-slab subduction zone, and c) elucidating whether post-seismic deformation may account for or exacerbate the 4-6 m fault convergence deficit left by the 2013 earthquake. We first present InSAR time series analysis of the post-seismic transient derived from ongoing Sentinel-1 SAR acquisitions, including a comparison of atmosphere-corrected and uncorrected time series. Interferograms spanning December 2014 to the present reveal an ongoing post-seismic deformation transient in the region surrounding the Hoshab fault. Additionally, fault creep signals on and adjacent to the Hoshab fault are present. Second, we present a suite of forward models that explore the potential contributions of viscoelastic relaxation and frictional afterslip to the recorded displacement signal. These models, conducted using the semi-analytical solutions of RELAX and compared to InSAR line-of-sight time series displacements, explore a range of candidate rheological descriptions of the Makran subduction zone that are designed to probe the rheological structure of a region where current knowledge of the subsurface geology is highly limited. Our preliminary results suggest that post-seismic displacements arise from a combination of viscoelastic deformation and frictional afterslip, as opposed to one single mechanism. Additionally, our preliminary results suggest

  8. Studies of crustal structure, seismic precursors to volcanic eruptions and earthquake hazard in the eastern provinces of the Democratic Republic of Congo

    CSIR Research Space (South Africa)

    Mavonga, T

    2010-11-01

    Full Text Available In recent decades, civil wars in the eastern provinces of the Democratic Republic of Congo have caused massive social disruptions, which have been exacerbated by volcanic and earthquake disasters. Seismic data were gathered and analysed as part...

  9. Application of bounding spectra to seismic design of piping based on the performance of above ground piping in power plants subjected to strong motion earthquakes

    International Nuclear Information System (INIS)

    Stevenson, J.D.

    1995-02-01

    This report extends the potential application of Bounding Spectra evaluation procedures, developed as part of the A-46 Unresolved Safety Issue applicable to seismic verification of in-situ electrical and mechanical equipment, to in-situ safety related piping in nuclear power plants. The report presents a summary of earthquake experience data which define the behavior of typical U.S. power plant piping subject to strong motion earthquakes. The report defines those piping system caveats which would assure the seismic adequacy of the piping systems which meet those caveats and whose seismic demand are within the bounding spectra input. Based on the observed behavior of piping in strong motion earthquakes, the report describes the capabilities of the piping system to carry seismic loads as a function of the type of connection (i.e. threaded versus welded). This report also discusses in some detail the basic causes and mechanisms for earthquake damages and failures to power plant piping systems

  10. Earthquake and Tsunami: a movie and a book for seismic and tsunami risk reduction in Italy.

    Science.gov (United States)

    Nostro, C.; Baroux, E.; Maramai, A.; Graziani, L.; Tertulliani, A.; Castellano, C.; Arcoraci, L.; Casale, P.; Ciaccio, M. G.; Frepoli, A.

    2009-04-01

    Italy is a country well known for the seismic and volcanic hazard. However, a similarly great hazard, although not well recognized, is posed by the occurrence of tsunami waves along the Italian coastline. This is testified by a rich catalogue and by field evidence of deposits left over by pre- and historical tsunamis, even in places today considered safe. This observation is of great importance since many of the areas affected by tsunamis in the past are today touristic places. The Italian tsunamis can be caused by different sources: 1- off-shore or near coast in-land earthquakes; 2- very large earthquakes on distant sources in the Mediterranean; 3- submarine volcanic explosion in the Tyrrhenian sea; 4- submarine landslides triggered by earthquakes and volcanic activity. The consequence of such a wide spectrum of sources is that an important part of the more than 7000 km long Italian coast line is exposed to the tsunami risk, and thousands of inhabitants (with numbers increasing during summer) live near hazardous coasts. The main historical tsunamis are the 1783 and 1908 events that hit Calabrian and Sicilian coasts. The recent tsunami is that caused by the 2002 Stromboli landslide. In order to reduce this risk and following the emotional impact of the December 2004 Sumatra earthquake and tsunami, we developed an outreach program consisting in talks given by scientists and in a movie and a book, both exploring the causes of the tsunami waves, how do they propagate in deep and shallow waters, and what are the effects on the coasts. Hints are also given on the most dangerous Italian coasts (as deduced by scientific studies), and how to behave in the case of a tsunami approaching the coast. These seminars are open to the general public, but special programs are developed with schools of all grades. In this talk we want to present the book and the movie used during the seminars and scientific expositions, that was realized from a previous 3D version originally

  11. FSI effects and seismic performance evaluation of water storage tank of AP1000 subjected to earthquake loading

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Chunfeng, E-mail: zhaowindy@126.com [Institute of Earthquake Engineering, Dalian University of Technology, Dalian 116024 (China); School of Civil Engineering, Hefei University of Technology, Anhui Province 230009 (China); Chen, Jianyun; Xu, Qiang [Institute of Earthquake Engineering, Dalian University of Technology, Dalian 116024 (China)

    2014-12-15

    Graphical abstract: - Highlights: • Water sloshing and oscillation of water tank under earthquake are simulated by FEM. • The influences of various water levels on seismic response are investigated. • ALE algorithm is applied to study the fluid–structure interaction effects. • The effects of different water levels in reducing seismic response are compared. • The optimal water level of water tank under seismic loading is obtained. - Abstract: The gravity water storage tank of AP1000 is designed to cool down the temperature of containment vessel by spray water when accident releases mass energy. However, the influence of fluid–structure interaction between water and water tank of AP1000 on dynamic behavior of shield building is still a hot research question. The main objective of the current study is to investigate how the fluid–structure interaction affects the dynamic behavior of water tank and whether the water sloshing and oscillation can reduce the seismic response of the shield building subjected to earthquake. For this purpose, a fluid–structure interaction algorithm of finite element technique is employed for the seismic analysis of water storage tank of AP1000. In the finite element model, 8 cases height of water, such as 10.8, 9.8, 8.8, 7.8, 6.8, 5.8, 4.8, and 3.8 m, are established and compared with the empty water tank in order to demonstrate the positive effect in mitigating the seismic response. An Arbitrary Lagrangian Eulerian (ALE) algorithm is used to simulate the fluid–structure interaction, fluid sloshing and oscillation of water tank under the El-Centro earthquake. The correlation between seismic response and parameters of water tank in terms of height of air (h{sub 1}), height of water (h{sub 2}), height ratio of water to tank (h{sub 2}/H{sub w}) and mass ratio of water to total structure (m{sub w}/m{sub t}) is also analyzed. The numerical results clearly show that the optimal h{sub 2}, h{sub 2}/H{sub w} and m{sub w}/m{sub t

  12. Earthquake source imaging by high-resolution array analysis at regional distances: the 2010 M7 Haiti earthquake as seen by the Venezuela National Seismic Network

    Science.gov (United States)

    Meng, L.; Ampuero, J. P.; Rendon, H.

    2010-12-01

    Back projection of teleseismic waves based on array processing has become a popular technique for earthquake source imaging,in particular to track the areas of the source that generate the strongest high frequency radiation. The technique has been previously applied to study the rupture process of the Sumatra earthquake and the supershear rupture of the Kunlun earthquakes. Here we attempt to image the Haiti earthquake using the data recorded by Venezuela National Seismic Network (VNSN). The network is composed of 22 broad-band stations with an East-West oriented geometry, and is located approximately 10 degrees away from Haiti in the perpendicular direction to the Enriquillo fault strike. This is the first opportunity to exploit the privileged position of the VNSN to study large earthquake ruptures in the Caribbean region. This is also a great opportunity to explore the back projection scheme of the crustal Pn phase at regional distances,which provides unique complementary insights to the teleseismic source inversions. The challenge in the analysis of the 2010 M7.0 Haiti earthquake is its very compact source region, possibly shorter than 30km, which is below the resolution limit of standard back projection techniques based on beamforming. Results of back projection analysis using the teleseismic USarray data reveal little details of the rupture process. To overcome the classical resolution limit we explored the Multiple Signal Classification method (MUSIC), a high-resolution array processing technique based on the signal-noise orthognality in the eigen space of the data covariance, which achieves both enhanced resolution and better ability to resolve closely spaced sources. We experiment with various synthetic earthquake scenarios to test the resolution. We find that MUSIC provides at least 3 times higher resolution than beamforming. We also study the inherent bias due to the interferences of coherent Green’s functions, which leads to a potential quantification

  13. Spatial Evaluation and Verification of Earthquake Simulators

    Science.gov (United States)

    Wilson, John Max; Yoder, Mark R.; Rundle, John B.; Turcotte, Donald L.; Schultz, Kasey W.

    2017-06-01

    In this paper, we address the problem of verifying earthquake simulators with observed data. Earthquake simulators are a class of computational simulations which attempt to mirror the topological complexity of fault systems on which earthquakes occur. In addition, the physics of friction and elastic interactions between fault elements are included in these simulations. Simulation parameters are adjusted so that natural earthquake sequences are matched in their scaling properties. Physically based earthquake simulators can generate many thousands of years of simulated seismicity, allowing for a robust capture of the statistical properties of large, damaging earthquakes that have long recurrence time scales. Verification of simulations against current observed earthquake seismicity is necessary, and following past simulator and forecast model verification methods, we approach the challenges in spatial forecast verification to simulators; namely, that simulator outputs are confined to the modeled faults, while observed earthquake epicenters often occur off of known faults. We present two methods for addressing this discrepancy: a simplistic approach whereby observed earthquakes are shifted to the nearest fault element and a smoothing method based on the power laws of the epidemic-type aftershock (ETAS) model, which distributes the seismicity of each simulated earthquake over the entire test region at a decaying rate with epicentral distance. To test these methods, a receiver operating characteristic plot was produced by comparing the rate maps to observed m>6.0 earthquakes in California since 1980. We found that the nearest-neighbor mapping produced poor forecasts, while the ETAS power-law method produced rate maps that agreed reasonably well with observations.

  14. Automatic Event Detection and Picking of P, S Seismic Phases for Earthquake Early Warning: A Case Study of the 2008 Wenchuan Earthquake

    Science.gov (United States)

    WANG, Z.; Zhao, B.

    2015-12-01

    We develop an automatic seismic phase arrival detection and picking algorithm for the impending earthquakes occurred with diverse focal mechanisms and depths. The polarization analysis of the three-component seismograms is utilized to distinguish between P and S waves through a sliding time window. When applying the short term average/long term average (STA/LTA) method to the polarized data, we also construct a new characteristics function that can sensitively reflect the changes of signals' amplitude and frequency, providing a better detection for the phase arrival. Then an improved combination method of the higher order statistics and the Akaike information criteria (AIC) picker is applied to the refined signal to lock on the arrival time with a higher degree of accuracy. We test our techniques to the aftershocks of the Ms8.0 Wenchuan earthquake, where hundreds of three-component acceleration records with magnitudes of 4.0 to 6.4 are treated. In comparison to the analyst picks, the results of the proposed detection algorithms are shown to perform well and can be applied from a single instrument within a network of stations for the large seismic events in the Earthquake Early Warning System (EEWS).

  15. The analysis of historical seismograms: an important tool for seismic hazard assessment. Case histories from French and Italian earthquakes

    International Nuclear Information System (INIS)

    Pino, N.A.

    2011-01-01

    Seismic hazard assessment relies on the knowledge of the source characteristics of past earthquakes. Unfortunately, seismic waveform analysis, representing the most powerful tool for the investigation of earthquake source parameters, is only possible for events occurred in the last 100-120 years, i.e., since seismographs with known response function were developed. Nevertheless, during this time significant earthquakes have been recorded by such instruments and today, also thanks to technological progress, these data can be recovered and analysed by means of modern techniques. In this paper, aiming at giving a general sketch of possible analyses and attainable results in historical seismogram studies, I briefly describe the major difficulties in processing the original waveforms and present a review of the results that I obtained from previous seismogram analysis of selected significant historical earthquakes occurred during the first decades of the 20. century, including (A) the December 28, 1908, Messina straits (southern Italy), (B) the June 11, 1909, Lambesc (southern France) - both of which are the strongest ever recorded instrumentally in their respective countries - and (C) the July 13, 1930, Irpinia (southern Italy) events. For these earthquakes, the major achievements are represented by the assessment of the seismic moment (A, B, C), the geometry and kinematics of faulting (B, C), the fault length and an approximate slip distribution (A, C). The source characteristics of the studied events have also been interpreted in the frame of the tectonic environment active in the respective region of interest. In spite of the difficulties inherent to the investigation of old seismic data, these results demonstrate the invaluable and irreplaceable role of historical seismogram analysis in defining the local seismo-genic potential and, ultimately, for assessing the seismic hazard. The retrieved information is crucial in areas where important civil engineering works

  16. Estimation of recurrence interval of large earthquakes on the central Longmen Shan fault zone based on seismic moment accumulation/release model.

    Science.gov (United States)

    Ren, Junjie; Zhang, Shimin

    2013-01-01

    Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9) occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF) and the Guanxian-Jiangyou fault (GJF). However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS) and Interferometric Synthetic Aperture Radar (InSAR) data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3) × 10¹⁷ N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  17. Estimation of Recurrence Interval of Large Earthquakes on the Central Longmen Shan Fault Zone Based on Seismic Moment Accumulation/Release Model

    Directory of Open Access Journals (Sweden)

    Junjie Ren

    2013-01-01

    Full Text Available Recurrence interval of large earthquake on an active fault zone is an important parameter in assessing seismic hazard. The 2008 Wenchuan earthquake (Mw 7.9 occurred on the central Longmen Shan fault zone and ruptured the Yingxiu-Beichuan fault (YBF and the Guanxian-Jiangyou fault (GJF. However, there is a considerable discrepancy among recurrence intervals of large earthquake in preseismic and postseismic estimates based on slip rate and paleoseismologic results. Post-seismic trenches showed that the central Longmen Shan fault zone probably undertakes an event similar to the 2008 quake, suggesting a characteristic earthquake model. In this paper, we use the published seismogenic model of the 2008 earthquake based on Global Positioning System (GPS and Interferometric Synthetic Aperture Radar (InSAR data and construct a characteristic seismic moment accumulation/release model to estimate recurrence interval of large earthquakes on the central Longmen Shan fault zone. Our results show that the seismogenic zone accommodates a moment rate of (2.7 ± 0.3 × 1017 N m/yr, and a recurrence interval of 3900 ± 400 yrs is necessary for accumulation of strain energy equivalent to the 2008 earthquake. This study provides a preferred interval estimation of large earthquakes for seismic hazard analysis in the Longmen Shan region.

  18. Spatially dependent seismic anisotropy in the Tonga subduction zone: A possible contributor to the complexity of deep earthquakes

    Czech Academy of Sciences Publication Activity Database

    Vavryčuk, Václav

    2006-01-01

    Roč. 155, 1/2 (2006), s. 63-72 ISSN 0031-9201 R&D Projects: GA AV ČR IAA3012309; GA ČR GA205/02/0383 Institutional research plan: CEZ:AV0Z30120515 Keywords : deep-focus earthquakes * seismic anisotropy * subduction zones Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.440, year: 2006

  19. Structure of the Koyna-Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

    Science.gov (United States)

    Catchings, Rufus D.; Dixit, M.M.; Goldman, Mark R.; Kumar, S.

    2015-01-01

    The Koyna-Warna area of India is one of the best worldwide examples of reservoir-induced seismicity, with the distinction of having generated the largest known induced earthquake (M6.3 on 10 December 1967) and persistent moderate-magnitude (>M5) events for nearly 50 years. Yet, the fault structure and tectonic setting that has accommodated the induced seismicity is poorly known, in part because the seismic events occur beneath a thick sequence of basalt layers. On the basis of the alignment of earthquake epicenters over an ~50 year period, lateral variations in focal mechanisms, upper-crustal tomographic velocity images, geophysical data (aeromagnetic, gravity, and magnetotelluric), geomorphic data, and correlation with similar structures elsewhere, we suggest that the Koyna-Warna area lies within a right step between northwest trending, right-lateral faults. The sub-basalt basement may form a local structural depression (pull-apart basin) caused by extension within the step-over zone between the right-lateral faults. Our postulated model accounts for the observed pattern of normal faulting in a region that is dominated by north-south directed compression. The right-lateral faults extend well beyond the immediate Koyna-Warna area, possibly suggesting a more extensive zone of seismic hazards for the central India area. Induced seismic events have been observed many places worldwide, but relatively large-magnitude induced events are less common because critically stressed, preexisting structures are a necessary component. We suggest that releasing bends and fault step-overs like those we postulate for the Koyna-Warna area may serve as an ideal tectonic environment for generating moderate- to large- magnitude induced (reservoir, injection, etc.) earthquakes.

  20. On Strong Positive Frequency Dependencies of Quality Factors in Local-Earthquake Seismic Studies

    Science.gov (United States)

    Morozov, Igor B.; Jhajhria, Atul; Deng, Wubing

    2018-03-01

    Many observations of seismic waves from local earthquakes are interpreted in terms of the frequency-dependent quality factor Q( f ) = Q0 f^{η } , where η is often close to or exceeds one. However, such steep positive frequency dependencies of Q require careful analysis with regard to their physical consistency. In particular, the case of η = 1 corresponds to frequency-independent (elastic) amplitude decays with time and consequently requires no Q-type attenuation mechanisms. For η > 1, several problems with physical meanings of such Q-factors occur. First, contrary to the key premise of seismic attenuation, high-frequency parts of the wavefield are enhanced with increasing propagation times relative to the low-frequency ones. Second, such attenuation cannot be implemented by mechanical models of wave-propagating media. Third, with η > 1, the velocity dispersion associated with such Q(f) occurs over unrealistically short frequency range and has an unexpected oscillatory shape. Cases η = 1 and η > 1 are usually attributed to scattering; however, this scattering must exhibit fortuitous tuning into the observation frequency band, which appears unlikely. The reason for the above problems is that the inferred Q values are affected by the conventional single-station measurement procedure. Both parameters Q 0 and are apparent, i.e., dependent on the selected parameterization and inversion method, and they should not be directly attributed to the subsurface. For η ≈ 1, parameter Q 0 actually describes the frequency-independent amplitude decay in access of some assumed geometric spreading t -α , where α is usually taken equal one. The case η > 1 is not allowed physically and could serve as an indicator of problematic interpretations. Although the case 0 < η < 1 is possible, its parameters Q 0 and may also be biased by the measurement procedure. To avoid such difficulties of Q-based approaches, we recommend measuring and interpreting the amplitude-decay rates

  1. Seismicity of Romania: fractal properties of earthquake space, time and energy distributions and their correlation with segmentation of subducted lithosphere and Vrancea seismic source

    International Nuclear Information System (INIS)

    Popescu, E.; Ardeleanu, L.; Bazacliu, O.; Popa, M.; Radulian, M.; Rizescu, M.

    2002-01-01

    For any strategy of seismic hazard assessment, it is important to set a realistic seismic input such as: delimitation of seismogenic zones, geometry of seismic sources, seismicity regime, focal mechanism and stress field. The aim of the present project is a systematic investigation focused on the problem of Vrancea seismic regime at different time, space and energy scales which can offer a crucial information on the seismogenic process of this peculiar seismic area. The departures from linearity of the time, space and energy distributions are associated with inhomogeneities in the subducting slab, rheology, tectonic stress distribution and focal mechanism. The significant variations are correlated with the existence of active and inactive segments along the seismogenic zone, the deviation from linearity of the frequency-magnitude distribution is associated with the existence of different earthquake generation models and the nonlinearities showed in the time series are related with the occurrence of the major earthquakes. Another important purpose of the project is to analyze the main crustal seismic sequences generated on the Romanian territory in the following regions: Ramnicu Sarat, Fagaras-Campulung, Banat. Time, space and energy distributions together with the source parameters and scaling relations are investigated. The analysis of the seismicity and clustering properties of the earthquakes generated in both Vrancea intermediate-depth region and Romanian crustal seismogenic zones, achieved within this project, constitutes the starting point for the study of seismic zoning, seismic hazard and earthquake prediction. The data set consists of Vrancea subcrustal earthquake catalogue (since 1974 and continuously updated) and catalogues with events located in the other crustal seimogenic zones of Romania. To build up these data sets, high-quality information made available through multiple international cooperation programs is considered. The results obtained up to

  2. Seismic Hazard Analysis based on Earthquake Vulnerability and Peak Ground Acceleration using Microseismic Method at Universitas Negeri Semarang

    Science.gov (United States)

    Sulistiawan, H.; Supriyadi; Yulianti, I.

    2017-02-01

    Microseismic is a harmonic vibration of land that occurs continuously at a low frequency. The characteristics of microseismic represents the characteristics of the soil layer based on the value of its natural frequency. This paper presents the analysis of seismic hazard at Universitas Negeri Semarang using microseismic method. The data acquisition was done at 20 points with distance between points 300 m by using three component’s seismometer. The data was processed using Horizontal to Vertical Spectral Ratio (HVSR) method to obtain the natural frequency and amplification value. The value of the natural frequency and amplification used to determine the value of the earthquake vulnerability and peak ground acceleration (PGA). The result shows then the earthquake vulnerability value range from 0.2 to 7.5, while the value of the average peak ground acceleration (PGA) is in the range 10-24 gal. Therefore, the average peak ground acceleration equal to earthquake intensity IV MMI scale.

  3. Assessment of seismic hazard for NPP sites in France analysis of several aftershocks of November 8, 1983, Liege earthquake

    International Nuclear Information System (INIS)

    Mohammadioun, B.; Mohammadioun, G.; Bresson, A.

    1984-03-01

    Current French practice for assessing seismic hazard on the sites of nuclear facilities is outlined. The procedure calls for as rich and varied an assortment of actual earthquake recordings as can be procured, including earthquakes in France itself and in nearby countries, recorded by the CEA/IPSN's own staff. Following the November 8, 1983, Liege earthquake, suitably equipped, temporary recording stations were set up in the epicentral area in order to record its aftershocks. Ground motion time histories and response spectra were computed for several of these, and a quality factor Q was derived from these data for the most superficial sedimentary layers of the area. The values obtained show reasonable agreement with ones found for similar materials in other regions

  4. Earthquake chemical precursors in groundwater: a review

    Science.gov (United States)

    Paudel, Shukra Raj; Banjara, Sushant Prasad; Wagle, Amrita; Freund, Friedemann T.

    2018-03-01

    We review changes in groundwater chemistry as precursory signs for earthquakes. In particular, we discuss pH, total dissolved solids (TDS), electrical conductivity, and dissolved gases in relation to their significance for earthquake prediction or forecasting. These parameters are widely believed to vary in response to seismic and pre-seismic activity. However, the same parameters also vary in response to non-seismic processes. The inability to reliably distinguish between changes caused by seismic or pre-seismic activities from changes caused by non-seismic activities has impeded progress in earthquake science. Short-term earthquake prediction is unlikely to be achieved, however, by pH, TDS, electrical conductivity, and dissolved gas measurements alone. On the other hand, the production of free hydroxyl radicals (•OH), subsequent reactions such as formation of H2O2 and oxidation of As(III) to As(V) in groundwater, have distinctive precursory characteristics. This study deviates from the prevailing mechanical mantra. It addresses earthquake-related non-seismic mechanisms, but focused on the stress-induced electrification of rocks, the generation of positive hole charge carriers and their long-distance propagation through the rock column, plus on electrochemical processes at the rock-water interface.

  5. Temporal b-Value Variations through out a Seismic Faulting Process: The 2008 Taoyuan Earthquake in Taiwan

    Directory of Open Access Journals (Sweden)

    Cheng-Horng Lin

    2010-01-01

    Full Text Available Temporal b-value variations have been completely obtained for the seismic faulting process of the 4 March 2008 Taoyuan earthquake (ML = 5.2, southern Taiwan. In addition to triggering several hundred after shocks, the mainshock was preceded by two groups of foreshocks (64 events that clustered along the narrow major fault zone. A high b-value of ~1.25, estimated from the foreshock series, representing fault growth, was significantly larger than the b-values of 0.80 and 0.81, obtained respectively from after shocks and back ground seismicity. Also there were some pre-shocks (i.e., micro-earth quakes that occurred one month before the earthquake sequence, with an extremely high b-value of ~2.1. This number might successfully indicate pre-nucleation seismic features in the vicinity of the fault zone. These seismic characteristics are fundamentally very similar to general features such as fracture nucleation and growth observed in rock samples under controlled stress in laboratory experiments, and thus ought to be considered to improve our understanding of crustal fault growth.

  6. Longitudinal Seismic Behavior of a Single-Tower Cable-Stayed Bridge Subjected to Near-Field Earthquakes

    Directory of Open Access Journals (Sweden)

    J. Yi

    2017-01-01

    Full Text Available Cable-stayed bridges are quite sensitive to large amplitude oscillations from earthquakes and seismic damage was observed for Shipshaw Bridge and Chi-Lu Bridge during past earthquakes. In order to investigate seismic damage of cable-stayed bridges, a 1 : 20 scale model of a single-tower cable-stayed bridge with A-shaped tower was designed, constructed, and tested on shake tables at Tongji University, China. One typical near-field ground motion was used to excite the model from low to high intensity. Test result showed that severe structural damage occurred at the tower of the model including parallel concrete cracks from bottom to nearly half height of the tower, concrete spalling, and exposed bars at top tower 0.2 m above the section where two skewed legs intersect. Posttest analysis was conducted and compared with test results. It is revealed that the numerical model was able to simulate the seismic damage of the test model by modeling nonlinearity of different components for cable-stayed bridges, namely, the tower, bents, superstructure, cables, and bearings. Numerical analysis also revealed that cable relaxation, which was detected during the test, had limited influence on the overall seismic response of the bridge with maximum error of 12%.

  7. DEPENDENCE OF DISTRIBUTION FUNCTION OF COMMERCIAL DAMAGES DUE TO POSSIBLE EARTHQUAKES ON THE CLASS OF SEISMIC RESISTANCE OF A BUILDING

    Directory of Open Access Journals (Sweden)

    Hanzada R. Zajnulabidova

    2017-01-01

    Full Text Available Abstract. Objectives To determine the damage probability of earthquakes of different intensities on the example of a real projected railway station building having a framework design scheme based on the density function of damage distribution. Methods Uncertainty, always existing in nature, invalidates a deterministic approach to the assessment of territorial seismic hazards and, consequently, seismic risk. In this case, seismic risk assessment can be carried out on a probabilistic basis. Thus, the risk will always be there, but it must be minimised. The task of optimising the reinforcement costs is solved by using the density distribution function for seismic effects of varying intensity, taking into account the degree of building responsibility. Results The distribution functions of the expected damage for a building with a reinforced concrete frame located in a highly seismic region with a repetition of 9-point shocks every 500 years and 10-point shocks once every 5000 years are constructed. A significant effect of the seismic resistance class of a building on the form of the distribution functions is shown. For structures of a high seismic resistance class, not only is the seismic risk reduced, but also the variance of the expected damage. From the graphs obtained, it can be seen that the seismic resistance class significantly affects the damage distribution. At a probability of 0.997, the expected damage for a non-reinforced building will exceed 43%; for a reinforced one it is only 10%. It also follows from the graphs that the variance of the damage magnitude decreases with the growth of the seismic resistance class of the building. This fact is an additional incentive for investing in antiseismic reinforcement of buildings. Conclusion The study shows the expediency of working with the damage density distribution function when managing seismic risk. In this case, it becomes possible to strengthen the building with a specified probability of

  8. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    Science.gov (United States)

    Anggraeni, Novia Antika

    2015-04-01

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano's inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 - 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between -2.86 up to 5.49 days.

  9. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    International Nuclear Information System (INIS)

    Anggraeni, Novia Antika

    2015-01-01

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano’s inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 – 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between −2.86 up to 5.49 days

  10. Seismic energy data analysis of Merapi volcano to test the eruption time prediction using materials failure forecast method (FFM)

    Energy Technology Data Exchange (ETDEWEB)

    Anggraeni, Novia Antika, E-mail: novia.antika.a@gmail.com [Geophysics Sub-department, Physics Department, Faculty of Mathematic and Natural Science, Universitas Gadjah Mada. BLS 21 Yogyakarta 55281 (Indonesia)

    2015-04-24

    The test of eruption time prediction is an effort to prepare volcanic disaster mitigation, especially in the volcano’s inhabited slope area, such as Merapi Volcano. The test can be conducted by observing the increase of volcanic activity, such as seismicity degree, deformation and SO2 gas emission. One of methods that can be used to predict the time of eruption is Materials Failure Forecast Method (FFM). Materials Failure Forecast Method (FFM) is a predictive method to determine the time of volcanic eruption which was introduced by Voight (1988). This method requires an increase in the rate of change, or acceleration of the observed volcanic activity parameters. The parameter used in this study is the seismic energy value of Merapi Volcano from 1990 – 2012. The data was plotted in form of graphs of seismic energy rate inverse versus time with FFM graphical technique approach uses simple linear regression. The data quality control used to increase the time precision employs the data correlation coefficient value of the seismic energy rate inverse versus time. From the results of graph analysis, the precision of prediction time toward the real time of eruption vary between −2.86 up to 5.49 days.

  11. Seismic‐hazard forecast for 2016 including induced and natural earthquakes in the central and eastern United States

    Science.gov (United States)

    Petersen, Mark D.; Mueller, Charles; Moschetti, Morgan P.; Hoover, Susan M.; Llenos, Andrea L.; Ellsworth, William L.; Michael, Andrew J.; Rubinstein, Justin L.; McGarr, Arthur F.; Rukstales, Kenneth S.

    2016-01-01

    The U.S. Geological Survey (USGS) has produced a one‐year (2016) probabilistic seismic‐hazard assessment for the central and eastern United States (CEUS) that includes contributions from both induced and natural earthquakes that are constructed with probabilistic methods using alternative data and inputs. This hazard assessment builds on our 2016 final model (Petersen et al., 2016) by adding sensitivity studies, illustrating hazard in new ways, incorporating new population data, and discussing potential improvements. The model considers short‐term seismic activity rates (primarily 2014–2015) and assumes that the activity rates will remain stationary over short time intervals. The final model considers different ways of categorizing induced and natural earthquakes by incorporating two equally weighted earthquake rate submodels that are composed of alternative earthquake inputs for catalog duration, smoothing parameters, maximum magnitudes, and ground‐motion models. These alternatives represent uncertainties on how we calculate earthquake occurrence and the diversity of opinion within the science community. In this article, we also test sensitivity to the minimum moment magnitude between M 4 and M 4.7 and the choice of applying a declustered catalog with b=1.0 rather than the full catalog with b=1.3. We incorporate two earthquake rate submodels: in the informed submodel we classify earthquakes as induced or natural, and in the adaptive submodel we do not differentiate. The alternative submodel hazard maps both depict high hazard and these are combined in the final model. Results depict several ground‐shaking measures as well as intensity and include maps showing a high‐hazard level (1% probability of exceedance in 1 year or greater). Ground motions reach 0.6g horizontal peak ground acceleration (PGA) in north‐central Oklahoma and southern Kansas, and about 0.2g PGA in the Raton basin of Colorado and New Mexico, in central Arkansas, and in

  12. Seismic Attenuation Tomography of the Rupture Zone of the 2010 Maule, Chile, Earthquake

    Science.gov (United States)

    Torpey, M. E.; Russo, R. M.; Panning, M. P.

    2014-12-01

    We used measurements of differential S to P seismic attenuation in the rupture zone of the 2010 Mw 8.8 Maule, Chile earthquake (33°S-38°S) to characterize the seismic attenuation structure of the South American crust and upper mantle wedge. We used data obtained from the IRIS CHAMP rapid-response temporary seismic network, filtered between 0.7-20 Hz. For events with large signal to noise ratios, we visually identified the P and S arrivals on the seismograms and used an evolving time window to determine 400 individual Qs and t* values and their uncertainties using a spectral ratio method. Using a phase pair method allows us to neglect the source-time function and instrument response of each P-S phase pair. Assuming a constant Qp/Qs ratio for a given P-S phase pair, we evaluated the 400 spectral ratios and discarded portions of the evolving time window that incorporate multipathed phases. We recalculated the Qs and standard deviation of the retained window and excluded measurements with standard deviations larger than half of the Qs value. We also excluded measurements that span frequency windows longer than 10 Hz as they contain noise that contaminates Qs measurements. We examined ~200 local events yielding a total of 1,076 path-integrated Q­s measurements. Qs values are low (100-400) for the majority of ray paths evaluated, however we observe a spatial distribution of low path-integrated Qs values (100-300) in the northeastern portion of the rupture zone and higher values (300-600) in the southwest. We divided the rupture zone into cubes and implemented a bounded linear inequality least squares inversion (0

  13. Long-term seismic observations along Myanmar-Sunda subduction margin: insights for 2004 M w > 9.0 earthquake

    Science.gov (United States)

    Khan, Prosanta Kumar; Banerjee, Jayashree; Shamim, Sk; Mohanty, Manoranjan

    2018-03-01

    The present study investigates the temporal variation of few seismic parameters between the Myanmar (Zone I), Andaman-Nicobar-Northwest Sumatra (Zone II), Southeast Sumatra-West Indonesia (Zone III) and East Indonesia (Zone IV) converging boundaries in reference to the generation of 26 December 2004 M w > 9.0 off-Sumatra mega-earthquake event. The four segments are distinguished based on tectonics parameters, distinct geological locations, great earthquake occurrences, and the Wadati-Benioff zone characteristics. Two important seismic parameters such as seismic energy and b values are computed over a time-window of 6-month period during the entire 1976-2013 period for these segments. The b values show a constant decrease in Zones II, III, and IV, whereas the Zone I does not show any such pattern prior to the 2004 mega-event. The release of seismic energy was also gradually decreasing in Zones II and III till the 2004 event, and little similar pattern was also noted in Zone IV. This distinct observation might be indicating that the stress accumulation was dominant near the Sumatra-Java area located towards southeast of Zone II and northwest of Zone III. The released strain energy during the 2004 event was subsequently migrated towards north, rupturing 1300 km of the boundary between the Northwest Sumatra and the North Andaman. The occurrence of 2004 mega-event was apparently concealed behind the long-term seismic quiescence existing near the Sumatra and Nicobar margin. A systematic study of the patterns of seismic energy release and b values, and the long-term observation of collective behaviour of the margin tectonics might have had given clues to the possibility of the 2004 mega-event.

  14. Postseismic deformation following the June 2000 earthquake sequence in the south Iceland seismic zone

    Science.gov (United States)

    Arnadottir, T.; Jonsson, Sigurjon; Pollitz, F.F.; Jiang, W.; Feigl, K.L.

    2005-01-01

    We observe postseismic deformation on two spatiotemporal scales following Mw = 6.5 earthquakes in the south Iceland seismic zone on 17 and 21 June 2000. We see a rapidly decaying deformation transient lasting no more than 2 months and extending about 5 km away from the two main shock ruptures. This local, month-scale transient is captured by several radar interferograms and is also observed at a few campaign GPS sites located near the faults. A slower transient with a characteristic timescale of about a year is detected only by GPS measurements. The month-scale deformation pattern has been explained by poroelastic rebound due to postearthquake pore pressure changes. In contrast, the year-scale deformation can be explained by either afterslip at 8-14 km depth or viscoelastic relaxation of the lower crust and upper mantle in response to the coseismic stress changes. The optimal viscoelastic models have lower crustal viscosities of 0.5-1 ?? 1019 Pa s and upper mantle viscosity of ???3 ?? 1018 Pa s. Because of the limitations of our GPS campaign data, we consider both afterslip and viscoelastic relaxation as plausible mechanisms explaining the deformation field. Both types of postseismic deformation models suggest that the areas of large coseismic stress increase east of the 17 June and west of the 21 June ruptures continue to be loaded by the postseismic deformation. Copyright 2005 by the American Geophysical Union.

  15. Pre-seismic geomagnetic and ionosphere signatures related to the Mw5.7 earthquake occurred in Vrancea zone on September 24, 2016

    Science.gov (United States)

    Stanica, Dragos Armand; Stanica, Dumitru; Błęcki, Jan; Ernst, Tomasz; Jóźwiak, Waldemar; Słomiński, Jan

    2018-02-01

    To emphasize the relationship between the pre-seismic geomagnetic signals and Vrancea seismicity, in this work it is hypothesized that before an earthquake initiation, the high stress reached into seismogenic volume generates dehydration of the rocks and fracturing processes followed by release of electric charges along the faulting systems, which lead to resistivity changes. These changes were explored on September 2016 by the normalized function Bzn obtained from the geomagnetic data recorded in ULF range (0.001-0.0083 Hz). A statistical analysis was also performed to discriminate on the new Bzn* time series a pre-seismic signature related to the Mw5.7 earthquake. Significant anomalous behavior of Bzn* was identified on September 21, with 3 days prior to the onset of the seismic event. Similar information is provided by registrations of the magnetic and electron concentration variations in the ionosphere over the Vrancea zone, by Swarm satellites, 4 days and 1 day before the earthquake.

  16. Evaluation of Fourier and Response Spectra at Ichihasama and Koromogawa Seismic Intensity Observation Sites During the Iwate-Miyagi Nairiku Earthquake in 2008

    Science.gov (United States)

    Nishikawa, Hayato; Miyajima, Masakatsu

    In this study, we evaluate an acceleration Fourier and response spectra at Ichihasama and Koromogawa seismic intensity observation sites which observed JMA seismic intensity of 6 upper but seismic waveform records don't exist during the Iwate-Miyagi Nairiku earthquake in 2008. Firstly, formula to evaluate acceleration Fourier and response spectra are developed using peak ground acceleration, JMA seismic intensity and predominant period of earthquake spectra based on records obtained from crustal earthquakes with Magnitude of 6 to 7. Acceleration Fourier and response spectra are evaluated for another local government site which are not chosen for development of the formula. The evaluated values mostly agree with the observed ones. Finally, acceleration Fourier and response spectra are evaluated for Ichihasama and Koromogawa observation sites. It is clarified that short period below 1 second was predominated in the evaluated spectra.

  17. Numerical Modeling on Co-seismic Influence of Wenchuan 8.0 Earthquake in Sichuan-Yunnan Area, China

    Science.gov (United States)

    Chen, L.; Li, H.; Lu, Y.; Li, Y.; Ye, J.

    2009-12-01

    In this paper, a three dimensional finite element model for active faults which are handled by contact friction elements in Sichuan-Yunnan area is built. Applying the boundary conditions determined through GPS data, a numerical simulations on spatial patterns of stress-strain changes induced by Wenchuan Ms8.0 earthquake are performed. Some primary results are: a) the co-seismic displacements in Longmen shan fault zone by the initial cracking event benefit not only the NE-direction expanding of subsequent fracture process but also the focal mechanism conversions from thrust to right lateral strike for the most of following sub-cracking events. b) tectonic movements induced by the Wenchuan earthquake are stronger in the upper wall of Longmen shan fault belt than in the lower wall and are influenced remarkably by the northeast boundary faults of the rhombic block. c) the extrema of stress changes induced by the main shock are 106Pa and its spatial size is about 400km long and 100km wide. The total stress level is reduced in the most regions in Longmen shan fault zone, whereas stress change is rather weak in its southwest segment and possibly result in fewer aftershocks in there. d) effects induced by the Wenchuan earthquake to the major active faults are obviously different from each other. e) triggering effect of the Wenchuan earthquake to the following Huili 6.1 earthquake is very weak.

  18. Short-Term Forecasting of Taiwanese Earthquakes Using a Universal Model of Fusion-Fission Processes

    Science.gov (United States)

    Cheong, Siew Ann; Tan, Teck Liang; Chen, Chien-Chih; Chang, Wu-Lung; Liu, Zheng; Chew, Lock Yue; Sloot, Peter M. A.; Johnson, Neil F.

    2014-01-01

    Predicting how large an earthquake can be, where and when it will strike remains an elusive goal in spite of the ever-increasing volume of data collected by earth scientists. In this paper, we introduce a universal model of fusion-fission processes that can be used to predict earthquakes starting from catalog data. We show how the equilibrium dynamics of this model very naturally explains the Gutenberg-Richter law. Using the high-resolution earthquake catalog of Taiwan between Jan 1994 and Feb 2009, we illustrate how out-of-equilibrium spatio-temporal signatures in the time interval between earthquakes and the integrated energy released by earthquakes can be used to reliably determine the times, magnitudes, and locations of large earthquakes, as well as the maximum numbers of large aftershocks that would follow. PMID:24406467

  19. Pre-earthquake multiparameter analysis of the 2016 Amatrice-Norcia (Central Italy) seismic sequence: a case study for the application of the SAFE project concepts

    Science.gov (United States)

    De Santis, A.

    2017-12-01

    The SAFE (Swarm for Earthquake study) project (funded by European Space Agency in the framework "STSE Swarm+Innovation", 2014-2016) aimed at applying the new approach of geosystemics to the analysis of Swarm satellite (ESA) electromagnetic data for investigating the preparatory phase of earthquakes. We present in this talk the case study of the most recent seismic sequence in Italy. First a M6 earthquake on 24 August 2016 and then a M6.5 earthquake on 30 October 2016 shocked almost in the same region of Central Italy causing about 300 deaths in total (mostly on 24 August), with a revival of other significant seismicity on January 2017. Analysing both geophysical and climatological satellite and ground data preceding the major earthquakes of the sequence we present results that confirm a complex solid earth-atmosphere coupling in the preparation phase of the whole sequence.

  20. Seismic soil structure interaction analysis for asymmetrical buildings supported on piled raft for the 2015 Nepal earthquake

    Science.gov (United States)

    Badry, Pallavi; Satyam, Neelima

    2017-01-01

    Seismic damage surveys and analyses conducted on modes of failure of structures during past earthquakes observed that the asymmetrical buildings show the most vulnerable effect throughout the course of failures (Wegner et al., 2009). Thus, all asymmetrical buildings significantly fails during the shaking events and it is really needed to focus on the accurate analysis of the building, including all possible accuracy in the analysis. Apart from superstructure geometry, the soil behavior during earthquake shaking plays a pivotal role in the building collapse (Chopra, 2012). Fixed base analysis where the soil is considered to be infinitely rigid cannot simulate the actual scenario of wave propagation during earthquakes and wave transfer mechanism in the superstructure (Wolf, 1985). This can be well explained in the soil structure interaction analysis, where the ground movement and structural movement can be considered with the equal rigor. In the present study the object oriented program has been developed in C++ to model the SSI system using the finite element methodology. In this attempt the seismic soil structure interaction analysis has been carried out for T, L and C types piled raft supported buildings in the recent 25th April 2015 Nepal earthquake (M = 7.8). The soil properties have been considered with the appropriate soil data from the Katmandu valley region. The effect of asymmetry of the building on the responses of the superstructure is compared with the author's research work. It has been studied/observed that the shape or geometry of the superstructure governs the response of the superstructure subjected to the same earthquake load.

  1. Some possible correlations between electro-magnetic emission and seismic activity during West Bohemia 2008 earthquake swarm

    Directory of Open Access Journals (Sweden)

    P. Kolář

    2010-10-01

    Full Text Available A potential link between electromagnetic emission (EME and seismic activity (SA has been the subject of scientific speculations for a long time. EME versus SA relations obtained during the 2008 earthquake swarm which occurred in West Bohemia are presented. First, a brief characterisation of the seismic region and then the EME recording method and data analysis will be described. No simple direct link between EME and SA intensity was observed, nevertheless a deeper statistical analysis indicates: (i slight increase of EME activity in the time interval 60 to 30 min before a seismic event with prevalent periods about 10 min, (ii some gap in EME activity approximately 2 h after the event, and (iii again a flat maximum about 4 h after the seismic events. These results qualitatively correspond with the observations from other seismically active regions (Fraser-Smith et al., 1990. The global decrease of EME activity correlating with the swarm activity decay was also observed. Due to the incomplete EME data and short observation time, these results are limited in reliability and are indicative only.

  2. An innovative assessment of the seismic hazard from Vrancea intermediate-depth earthquakes: Case studies in Romania and Bulgaria

    International Nuclear Information System (INIS)

    Panza, G.F.; Cioflan, C.; Marmureanu, G.; Kouteva, M.; Paskaleva, I.; Romanelli, F.

    2002-02-01

    An advanced procedure for ground motion, capable of synthesizing the seismic ground motion from basic understanding of fault mechanism and seismic wave propagation, is applied to the case studies of Bucharest (Romania) and Russe, NE Bulgaria, exposed to the seismic hazard from Vrancea events. Synthetic seismic signals along representative geological cross sections in Bucharest and Russe and been computed and the energetic input spectra have been derived both from the synthetic signals and the few existing records. The theoretical signals are successfully compared with the available observations. The site response has been calculated for three recent, strong and intermediate-depth, Vrancea earthquakes: August 30, 1986 and May 30 and 31, 1990. The used approach differs significantly from today's engineering practice that relays upon rock-site hazard maps and applies the site correction at a later stage. The obtained results show that it is very useful to estimate the site effect via waveform modelling, considering simultaneously the geotechnical properties of the site, the position and geometry of the seismic source and the mechanical properties of the propagation medium. (author)

  3. Constraining the Long-Term Average of Earthquake Recurrence Intervals From Paleo- and Historic Earthquakes by Assimilating Information From Instrumental Seismicity

    Science.gov (United States)

    Zoeller, G.

    2017-12-01

    Paleo- and historic earthquakes are the most important source of information for the estimationof long-term recurrence intervals in fault zones, because sequences of paleoearthquakes cover more than one seismic cycle. On the other hand, these events are often rare, dating uncertainties are enormous and the problem of missing or misinterpreted events leads to additional problems. Taking these shortcomings into account, long-term recurrence intervals are usually unstable as long as no additional information are included. In the present study, we assume that the time to the next major earthquake depends on the rate of small and intermediate events between the large ones in terms of a ``clock-change'' model that leads to a Brownian Passage Time distribution for recurrence intervals. We take advantage of an earlier finding that the aperiodicity of this distribution can be related to the Gutenberg-Richter-b-value, which is usually around one and can be estimated easily from instrumental seismicity in the region under consideration. This allows to reduce the uncertainties in the estimation of the mean recurrence interval significantly, especially for short paleoearthquake sequences and high dating uncertainties. We present illustrative case studies from Southern California and compare the method with the commonly used approach of exponentially distributed recurrence times assuming a stationary Poisson process.

  4. Recent research in earth structure, earthquake and mine seismology, and seismic hazard evaluation in South Africa

    CSIR Research Space (South Africa)

    Wright, C

    2003-07-01

    Full Text Available of earthquakes, earthquake hazard and earth structure in South Africa was prepared for the centennial handbook of the Interna- tional Association of Seismology and the Physics of the Earth?s Interior(IASPEI).3 Referencestothesescompletedinthelastfour...

  5. 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.

  6. Spatiotemporal seismic velocity change in the Earth's subsurface associated with large earthquake: contribution of strong ground motion and crustal deformation

    Science.gov (United States)

    Sawazaki, K.

    2016-12-01

    It is well known that seismic velocity of the subsurface medium changes after a large earthquake. The cause of the velocity change is roughly attributed to strong ground motion (dynamic strain change), crustal deformation (static strain change), and fracturing around the fault zone. Several studies have revealed that the velocity reduction down to several percent concentrates at the depths shallower than several hundred meters. The amount of velocity reduction correlates well with the intensity of strong ground motion, which indicates that the strong motion is the primary cause of the velocity reduction. Although some studies have proposed contributions of coseismic static strain change and fracturing around fault zone to the velocity change, separation of their contributions from the site-related velocity change is usually difficult. Velocity recovery after a large earthquake is also widely observed. The recovery process is generally proportional to logarithm of the lapse time, which is similar to the behavior of "slow dynamics" recognized in laboratory experiments. The time scale of the recovery is usually months to years in field observations, while it is several hours in laboratory experiments. Although the factor that controls the recovery speed is not well understood, cumulative strain change due to post-seismic deformation, migration of underground water, mechanical and chemical reactions on the crack surface could be the candidate. In this study, I summarize several observations that revealed spatiotemporal distribution of seismic velocity change due to large earthquakes; especially I focus on the case of the M9.0 2011 Tohoku earthquake. Combining seismograms of Hi-net (high-sensitivity) and KiK-net (strong motion), geodetic records of GEONET and the seafloor GPS/Acoustic ranging, I investigate contribution of the strong ground motion and crustal deformation to the velocity change associated with the Tohoku earthquake, and propose a gross view of

  7. Short-Term Forecasting of Taiwanese Earthquakes Using a Universal Model of Fusion-Fission Processes

    NARCIS (Netherlands)

    Cheong, S.A.; Tan, T.L.; Chen, C.-C.; Chang, W.-L.; Liu, Z.; Chew, L.Y.; Sloot, P.M.A.; Johnson, N.F.

    2014-01-01

    Predicting how large an earthquake can be, where and when it will strike remains an elusive goal in spite of the ever-increasing volume of data collected by earth scientists. In this paper, we introduce a universal model of fusion-fission processes that can be used to predict earthquakes starting

  8. Nowcasting Earthquakes and Tsunamis

    Science.gov (United States)

    Rundle, J. B.; Turcotte, D. L.

    2017-12-01

    The term "nowcasting" refers to the estimation of the current uncertain state of a dynamical system, whereas "forecasting" is a calculation of probabilities of future state(s). Nowcasting is a term that originated in economics and finance, referring to the process of determining the uncertain state of the economy or market indicators such as GDP at the current time by indirect means. We have applied this idea to seismically active regions, where the goal is to determine the current state of a system of faults, and its current level of progress through the earthquake cycle (http://onlinelibrary.wiley.com/doi/10.1002/2016EA000185/full). Advantages of our nowcasting method over forecasting models include: 1) Nowcasting is simply data analysis and does not involve a model having parameters that must be fit to data; 2) We use only earthquake catalog data which generally has known errors and characteristics; and 3) We use area-based analysis rather than fault-based analysis, meaning that the methods work equally well on land and in subduction zones. To use the nowcast method to estimate how far the fault system has progressed through the "cycle" of large recurring earthquakes, we use the global catalog of earthquakes, using "small" earthquakes to determine the level of hazard from "large" earthquakes in the region. We select a "small" region in which the nowcast is to be made, and compute the statistics of a much larger region around the small region. The statistics of the large region are then applied to the small region. For an application, we can define a small region around major global cities, for example a "small" circle of radius 150 km and a depth of 100 km, as well as a "large" earthquake magnitude, for example M6.0. The region of influence of such earthquakes is roughly 150 km radius x 100 km depth, which is the reason these values were selected. We can then compute and rank the seismic risk of the world's major cities in terms of their relative seismic risk

  9. Evaluation of Soil-Structure Interaction on the Seismic Response of Liquid Storage Tanks under Earthquake Ground Motions

    Directory of Open Access Journals (Sweden)

    Mostafa Farajian

    2017-03-01

    Full Text Available Soil-structure interaction (SSI could affect the seismic response of structures. Since liquid storage tanks are vital structures and must continue their operation under severe earthquakes, their seismic behavior should be studied. Accordingly, the seismic response of two types of steel liquid storage tanks (namely, broad and slender, with aspect ratios of height to radius equal to 0.6 and 1.85 founded on half-space soil is scrutinized under different earthquake ground motions. For a better comparison, the six considered ground motions are classified, based on their pulse-like characteristics, into two groups, named far and near fault ground motions. To model the liquid storage tanks, the simplified mass-spring model is used and the liquid is modeled as two lumped masses known as sloshing and impulsive, and the interaction of fluid and structure is considered using two coupled springs and dashpots. The SSI effect, also, is considered using a coupled spring and dashpot. Additionally, four types of soils are used to consider a wide variety of soil properties. To this end, after deriving the equations of motion, MATLAB programming is employed to obtain the time history responses. Results show that although the SSI effect leads to a decrease in the impulsive displacement, overturning moment, and normalized base shear, the sloshing (or convective displacement is not affected by such effects due to its long period.

  10. Seismic tomography of Basse-Terre volcanic island, Guadeloupe, Lesser Antilles, using earthquake travel times and noise correlations

    Science.gov (United States)

    Barnoud, Anne; Coutant, Olivier; Bouligand, Claire; Massin, Frédérick; Stehly, Laurent

    2015-04-01

    We image the volcanic island of Basse-Terre, Guadeloupe, Lesser Antilles, using both earthquake travel times and noise correlations. (1) A new earthquake catalog was recently compiled for the Lesser Antilles by the CDSA/OVSG/IPGP (Massin et al., EGU General Assembly 2014) and allows us to perform classical travel time tomography to obtain smooth 3D body wave velocity models. The geometrical configuration of the volcanic arc controls the resolution of the model in our zone of interest. (2) Surface wave tomography using noise correlations was successfully applied to volcanoes (Brenguier et al., Geophys. Res. Lett. 2007). We use seismic noise recorded at 16 broad-band stations and 9 short-period stations from Basse-Terre over a period of six years (2007-2012). For each station pair, we extract a dispersion curve from the noise correlation to get surface wave velocity models. The inversion of the dispersion curves produces a 3D S-wave velocity model of the island. The spatial distribution of seismic stations accross the island is highly heterogeneous, leading to higher resolution near the dome of the Soufrière of Guadeloupe volcano. Resulting velocity models are compared with densities obtained by 3D inversion of gravimetric data (Barnoud et al., AGU Fall Meeting 2013). Further work should include simultaneous inversion of seismic and gravimetric datasets to overcome resolution limitations.

  11. Waveform through the subducted plate under the Tokyo region in Japan observed by a ultra-dense seismic network (MeSO-net) and seismic activity around mega-thrust earthquakes area

    Science.gov (United States)

    Sakai, S.; Kasahara, K.; Nanjo, K.; Nakagawa, S.; Tsuruoka, H.; Morita, Y.; Kato, A.; Iidaka, T.; Hirata, N.; Tanada, T.; Obara, K.; Sekine, S.; Kurashimo, E.

    2009-12-01

    In central Japan, the Philippine Sea plate (PSP) subducts beneath the Tokyo Metropolitan area, the Kanto region, where it causes mega-thrust earthquakes, such as the 1703 Genroku earthquake (M8.0) and the 1923 Kanto earthquake (M7.9) which had 105,000 fatalities. A M7 or greater earthquake in this region at present has high potential to produce devastating loss of life and property with even greater global economic repercussions. The Central Disaster Management Council of Japan estimates the next great earthquake will cause 11,000 fatalities and 112 trillion yen (1 trillion US$) economic loss. This great earthquake is evaluated to occur with a probability of 70 % in 30 years by the Earthquake Research Committee of Japan. We had started the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan area (2007-2012). Under this project, the construction of the Metropolitan Seismic Observation network (MeSO-net) that consists of about 400 observation sites was started [Kasahara et al., 2008; Nakagawa et al., 2008]. Now, we had 178 observation sites. The correlation of the wave is high because the observation point is deployed at about 2 km intervals, and the identification of the later phase is recognized easily thought artificial noise is very large. We also discuss the relation between a deformation of PSP and intra-plate M7+ earthquakes: the PSP is subducting beneath the Honshu arc and also colliding with the Pacific plate. The subduction and collision both contribute active seismicity in the Kanto region. We are going to present a high resolution tomographic image to show low velocity zone which suggests a possible internal failure of the plate; a source region of the M7+ intra-plate earthquake. Our study will contribute a new assessment of the seismic hazard at the Metropolitan area in Japan. Acknowledgement: This study was supported by the Earthquake Research Institute cooperative research program.

  12. Coseismic and postseismic deformation associated with the 2016 Mw 7.8 Kaikoura earthquake, New Zealand: fault movement investigation and seismic hazard analysis

    Science.gov (United States)

    Jiang, Zhongshan; Huang, Dingfa; Yuan, Linguo; Hassan, Abubakr; Zhang, Lupeng; Yang, Zhongrong

    2018-04-01

    The 2016 moment magnitude (Mw) 7.8 Kaikoura earthquake demonstrated that multiple fault segments can undergo rupture during a single seismic event. Here, we employ Global Positioning System (GPS) observations and geodetic modeling methods to create detailed images of coseismic slip and postseismic afterslip associated with the Kaikoura earthquake. Our optimal geodetic coseismic model suggests that rupture not only occurred on shallow crustal faults but also to some extent at the Hikurangi subduction interface. The GPS-inverted moment release during the earthquake is equivalent to a Mw 7.9 event. The near-field postseismic deformation is mainly derived from right-lateral strike-slip motions on shallow crustal faults. The afterslip did not only significantly extend northeastward on the Needles fault but also appeared at the plate interface, slowly releasing energy over the past 6 months, equivalent to a Mw 7.3 earthquake. Coulomb stress changes induced by coseismic deformation exhibit complex patterns and diversity at different depths, undoubtedly reflecting multi-fault rupture complexity associated with the earthquake. The Coulomb stress can reach several MPa during coseismic deformation, which can explain the trigger mechanisms of afterslip in two high-slip regions and the majority of aftershocks. Based on the deformation characteristics of the Kaik