The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Didier Sornette - One of the best experts on this subject based on the ideXlab platform.
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solution of the nonlinear theory and tests of Earthquake Recurrence times
Physical Review E, 2008Co-Authors: Didier Sornette, S G Utkin, A SaichevAbstract:We develop an efficient numerical scheme to solve accurately the set of nonlinear integral equations derived previously in [A. Saichev and D. Sornette, J. Geophys. Res. 112, B04313 (2007)], which describes the distribution of interevent times in the framework of a general model of Earthquake clustering with long memory. Detailed comparisons between the linear and nonlinear versions of the theory and direct synthetic catalogs show that the nonlinear theory provides an excellent fit to the synthetic catalogs, while there are significant biases resulting from the use of the linear approximation. We then address the suggestions proposed by some authors to use the empirical distribution of interevent times to obtain a better determination of the so-called clustering parameter. Our theory and tests against synthetic and empirical catalogs find a rather dramatic lack of power for the distribution of interevent times to distinguish between quite different sets of parameters, casting doubt on the usefulness of this statistic for the specific purpose of identifying the clustering parameter.
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theory of Earthquake Recurrence times
Journal of Geophysical Research, 2007Co-Authors: A Saichev, Didier SornetteAbstract:[1] The statistics of Recurrence times in broad areas have been reported to obey universal scaling laws, both for single homogeneous regions and when averaged over multiple regions. These unified scaling laws are characterized by intermediate power law asymptotics. On the other hand, Molchan (2005) has presented a mathematical proof that if such a universal law exists, it is necessarily an exponential, in obvious contradiction with the data. First, we generalize Molchan's argument to show that an approximate unified law can be found which is compatible with the empirical observations when incorporating the impact of the Omori-Utsu law of Earthquake triggering. We then develop the theory of the statistics of interevent times in the framework of the Epidemic-Type Aftershock Sequence (ETAS) model of triggered seismicity and show that the empirical observations can be fully explained. Our theoretical expression well fits the empirical statistics over the whole range of Recurrence times, accounting for different regimes by using only the physics of triggering quantified by the Omori-Utsu law. The description of the statistics of Recurrence times over multiple regions requires an additional subtle statistical derivation that maps the fractal geometry of Earthquake epicenters onto the distribution of the average seismic rates in multiple regions. This yields a prediction in excellent agreement with the empirical data for reasonable values of the fractal dimension d ≈ 1.8, the average clustering ratio n ≈ 0.9, and the productivity exponent α ≈ 0.9 times the b value of the Gutenberg-Richter law.
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theory of Earthquake Recurrence times
arXiv: Geophysics, 2006Co-Authors: A Saichev, Didier SornetteAbstract:The statistics of Recurrence times in broad areas have been reported to obey universal scaling laws, both for single homogeneous regions (Corral, 2003) and when averaged over multiple regions (Bak et al.,2002). These unified scaling laws are characterized by intermediate power law asymptotics. On the other hand, Molchan (2005) has presented a mathematical proof that, if such a universal law exists, it is necessarily an exponential, in obvious contradiction with the data. First, we generalize Molchan's argument to show that an approximate unified law can be found which is compatible with the empirical observations when incorporating the impact of the Omori law of Earthquake triggering. We then develop the full theory of the statistics of inter-event times in the framework of the ETAS model of triggered seismicity and show that the empirical observations can be fully explained. Our theoretical expression fits well the empirical statistics over the whole range of Recurrence times, accounting for different regimes by using only the physics of triggering quantified by Omori's law. The description of the statistics of Recurrence times over multiple regions requires an additional subtle statistical derivation that maps the fractal geometry of Earthquake epicenters onto the distribution of the average seismic rates in multiple regions. This yields a prediction in excellent agreement with the empirical data for reasonable values of the fractal dimension $d \approx 1.8$, the average clustering ratio $n \approx 0.9$, and the productivity exponent $\alpha \approx 0.9$ times the $b$-value of the Gutenberg-Richter law.
Yiben Tsai - One of the best experts on this subject based on the ideXlab platform.
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study on probabilistic seismic hazard maps of taiwan after chi chi Earthquake
Journal of GeoEngineering, 2007Co-Authors: Chintung Cheng, Shianjin Chiou, Chyityi Lee, Yiben TsaiAbstract:Probabilistic seismic hazard maps are widely used for engineering design, land use planning, and disaster mitigation etc. This study conducted a review of readily available information on tectonic setting, geology, and seismicity, and the attenuation of peak ground acceleration (PGA) of Taiwan for completing the revised probabilistic seismic hazard maps by the state-of-the-art probabilistic seismic hazard analysis (PSHA) method. The mainshocks from the Earthquake catalog of 1900 to 1999 were used to evaluate the Earthquake Recurrence rate for regional sources and subduction - intraslab sources from Truncated-Exponential model. The fault-slip rates for estimating the Earthquake Recurrence rates of faults and subduction interface sources by Characteristic-Earthquake model were adopted. The revised PSHA in this study takes into consideration the fact that subduction plate sources induce higher ground-motion levels than crustal sources, and active faults induce the hanging-wall effect in attenuation relationships. After considering the fault activity and hanging wall effects in our revised PSHA, it was found that the peak ground acceleration (PGA) levels of near-field in Taiwan always exceed 0.4 g in a 475-year return period. This situation is clearly obvious in central Taiwan, the Miaoli Taichung region, Chyiayi - Tainan region and eastern longitudinal valley.
Olaf Zielke - One of the best experts on this subject based on the ideXlab platform.
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Earthquake Recurrence and the resolution potential of tectono geomorphic records
Bulletin of the Seismological Society of America, 2018Co-Authors: Olaf ZielkeAbstract:The author would like to thank James Dolan for his encouragement to finalize this study. The author also wants to thank the reviewers, Editor-in-Chief Thomas Pratt, and Associate Editor Richard Briggs for their valuable comments that helped further strengthen this contribution. This study was supported by the P. M. Mai and Computational Earthquake Seismology Group, with funding from King Abdullah University of Science and Technology (KAUST).
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fault slip and Earthquake Recurrence along strike slip faults contributions of high resolution geomorphic data
Tectonophysics, 2015Co-Authors: Olaf Zielke, Yann Klinger, Ramon J ArrowsmithAbstract:article i nfo Understanding Earthquake (EQ) Recurrence relies on information about the timing and size of past EQ ruptures along a given fault. Knowledge of a fault's rupture history provides valuable information on its potential future behavior, enabling seismic hazard estimates and loss mitigation. Stratigraphic and geomorphic evidence of faulting is used to constrain the Recurrence of surface rupturing EQs. Analysis of the latter data sets culminated during the mid-1980s in the formulation of now classical EQ Recurrence models, now routinely used to assess seismic hazard. Within the last decade, Light Detection and Ranging (lidar) surveying technology and other high-resolution data sets became increasingly available to tectono-geomorphic studies, promising to contribute to better-informed models of EQ Recurrence and slip-accumulation patterns. After reviewing motivation and background, we outline requirements to successfully reconstruct a fault's offset accumulation pattern from geomorphic evidence. We address sources of uncertainty affecting offset measure- ment and advocate approaches to minimize them. A number of recent studies focus on single-EQ slip distribu- tions and along-fault slip accumulation patterns. We put them in context with paleoseismic studies along the respective faults by comparing coefficients of variation CV for EQ inter-event time and slip-per-event and find that a) single-event offsets vary over a wide range of length-scales and the sources for offset variability differ with length-scale, b) at fault-segment length-scales, single-event offsets are essentially constant, c) along-fault offset accumulation as resolved in the geomorphic record is dominated by essentially same-size, large offset in- crements, and d) there is generally no one-to-one correlation between the offset accumulation pattern constrained in the geomorphic record and EQ occurrence as identified in the stratigraphic record, revealing the higher resolution and preservation potential of the latter. While slip accumulation along a fault segment may be dominated by repetition of large, nearly constant offset increments, timing of surface-rupture is less regular.
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high resolution topography derived offsets along the 1857 fort tejon Earthquake rupture trace san andreas fault
Bulletin of the Seismological Society of America, 2012Co-Authors: Olaf Zielke, Ramon J Arrowsmith, Lisa Grant Ludwig, S O AkcizAbstract:The great Fort Tejon Earthquake of 1857, with an ∼350‐km‐long surface rupture, was the most recent major Earthquake along the south‐central San Andreas fault (SAF). Prior reconstruction of its surface‐slip distribution and reconstruction of preceding Earthquakes along the 1857 rupture trace have contributed to formulation of the characteristic Earthquake (CEM) and uniform‐slip models (USM) for Earthquake Recurrence that find wide application in seismic hazard assessment and Earthquake forecasting. We used the high‐resolution B4 light detection and ranging (LiDAR) topographic data set—sufficient for depiction of meter‐scale tectonic landforms—to reevaluate the distribution of surface displacement along the 1857 rupture trace. We present ∼450 offset measurements with displacements below 60 m, increasing observation density relative to previous studies by a factor of 2. Our results show that the 1857 Earthquake had overall an average displacement below 3.5 m with 4–6 m released along the northwestern half of the rupture. Its along‐fault slip distribution is smooth at >10‐km length scales. At (∼28% less than prior estimates) assuming a 10‐km rupture depth and a 30‐GPa shear modulus. Reconstruction of pre‐1857 Earthquakes is impeded by an exponential decrease in observation density with increasing displacement amount. Offset observation density soon reaches a level where only tentative and nonunique reconstructions are permitted. The results of this study question prior surface‐slipreconstructions of pre‐1857 rupture(s) that were based on a distinctly lower number of offset observations, challenging the applicability of the aforementioned Earthquake Recurrence models to explain SAF rupture behavior. Online Material: Catalog of offset measurements along the 1857 surface rupture trace, as well as an annotated map. [1]: /embed/inline-graphic-1.gif
Gerald P Roberts - One of the best experts on this subject based on the ideXlab platform.
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stress loading history of Earthquake faults influenced by fault shear zone geometry and coulomb pre stress
Scientific Reports, 2020Co-Authors: Claudia Sgambato, Joanna Faure Walker, Zoe Mildon, Gerald P RobertsAbstract:Whether the stress-loading of faults to failure in Earthquakes appears to be random or to an extent explainable, given constraints on fault/shear-zone interaction and the build-up and release of stress over many Earthquake cycles, is a key question for seismic hazard assessment. Here we investigate Earthquake Recurrence for a system of 25 active normal faults arranged predominantly along strike from each other, allowing us to isolate the effects of stress-loading due to regional strain versus across- and along-strike fault interaction. We calculate stress changes over 6 centuries due to interseismic loading and 25 > Mw 5.5 Earthquakes. Where only one fault exists across strike, stress-loading is dominated by the regional tectonics through slip on underlying shear zones and fault planes have spatially smooth stress with predominantly time-dependent stress increase. Conversely, where faults are stress-loaded by across-strike fault interactions, fault planes have more irregular stress patterns and interaction-influenced stress loading histories. Stress-loading to failure in Earthquakes is not the same for all faults and is dependent on the geometry of the fault/shear-zone system.
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relationships between fault geometry slip rate variability and Earthquake Recurrence in extensional settings
Geophysical Journal International, 2012Co-Authors: P A Cowie, Gerald P Roberts, Jonathan M Bull, Francesco VisiniAbstract:Field observations and modelling indicate that elastic interaction between active faults can lead to variations in Earthquake Recurrence intervals measured on timescales of 102–104 yr. Fault geometry strongly influences the nature of the interaction between adjacent structures as it controls the spatial redistribution of stress when rupture occurs. In this paper, we use a previously published numerical model for elastic interaction between spontaneously growing faults to investigate the relationships between fault geometry, fault slip rate variations and the statistics of Earthquake Recurrence. These relationships develop and become systematic as a long-term consequence of stress redistribution in individual rupture events even though on short timescales Earthquake activity appears to be stochastic. We characterize fault behaviour using the coefficient of variation (CV) of Earthquake Recurrence intervals and introduce a new measure, slip-rate variability (SRV) that takes into account the size and time ordering of slip events. CV generally increases when the strain is partitioned on more than one fault but the relationship between long-term fault slip rate (SRmean) and CV is poorly defined. In contrast, SRV increases systematically where faulting is more distributed and SRmean is lower. To first order, SRV is inversely proportional to SRmean. We also extract Earthquake Recurrence statistics and compare these to previously published probability density functions used in Earthquake forecasting. The histograms of Earthquake Recurrence vary systematically as a function of fault geometry and are best characterized by a Weibull distribution with fitting parameters that vary from site to site along the fault array. We explain these phenomena in terms of a time-varying, geometrical control on stress loading of individual faults arising from the history of elastic interactions and compare our results with published data on SRV and Earthquake Recurrence along normal faults in New Zealand and in the Italian Apennines. Our results suggest that palaeoseismic data should be collected and analysed with structural geometry in mind and that information on SRV, CV and SRmean should be integrated with data from Earthquake catalogues when evaluating seismic hazard.
Tom Parsons - One of the best experts on this subject based on the ideXlab platform.
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Earthquake Recurrence on the south hayward fault is most consistent with a time dependent renewal process
Geophysical Research Letters, 2008Co-Authors: Tom ParsonsAbstract:[1] Elastic rebound and stress renewal are important components of Earthquake forecasting because if large Earthquakes can be shown to be periodic, then rupture probability is time dependent. While renewal models are used in formal forecasts, it has not been possible to exclude the alternate view that repeated large Earthquakes can happen in rapid succession without requiring time for stress regeneration. Here a consistency test between time dependent and time independent Recurrence distributions is made using a Monte Carlo method to replicate the paleoseismic series on the south Hayward fault. Time dependent distributions with Recurrence interval of 210 years and coefficient of variation of 0.6 reproduce the event series on the south Hayward 5 times more often than any exponential distribution: a highly significant difference as determined using a two-tailed Z-test for relative proportions. Therefore large Hayward fault Earthquakes are quasi-periodic, and are most consistent with a stress renewal process.
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monte carlo method for determining Earthquake Recurrence parameters from short paleoseismic catalogs example calculations for california
Journal of Geophysical Research, 2008Co-Authors: Tom ParsonsAbstract:[1] PaleoEarthquake observations often lack enough events at a given site to directly define a probability density function (PDF) for Earthquake Recurrence. Sites with fewer than 10–15 intervals do not provide enough information to reliably determine the shape of the PDF using standard maximum-likelihood techniques (e.g., Ellsworth et al., 1999). In this paper I present a method that attempts to fit wide ranges of distribution parameters to short paleoseismic series. From repeated Monte Carlo draws, it becomes possible to quantitatively estimate most likely Recurrence PDF parameters, and a ranked distribution of parameters is returned that can be used to assess uncertainties in hazard calculations. In tests on short synthetic Earthquake series, the method gives results that cluster around the mean of the input distribution, whereas maximum likelihood methods return the sample means (e.g., NIST/SEMATECH, 2006). For short series (fewer than 10 intervals), sample means tend to reflect the median of an asymmetric Recurrence distribution, possibly leading to an overestimate of the hazard should they be used in probability calculations. Therefore a Monte Carlo approach may be useful for assessing Recurrence from limited paleoEarthquake records. Further, the degree of functional dependence among parameters like mean Recurrence interval and coefficient of variation can be established. The method is described for use with time-independent and time-dependent PDFs, and results from 19 paleoseismic sequences on strike-slip faults throughout the state of California are given.