Non-Ergodic Site Response in Seismic Hazard Analysis

2017 ◽  
Vol 33 (4) ◽  
pp. 1385-1414 ◽  
Author(s):  
Jonathan P. Stewart ◽  
Kioumars Afshari ◽  
Christine A. Goulet
Keyword(s):  
Standard Deviation ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Site Response ◽  
Hazard Analysis ◽  
Specific Site ◽  
Uniform Hazard Spectra ◽  
Motion Models ◽  
Site Term ◽  
Site Variability

Probabilistic seismic hazard analyses are usually performed with semi-empirical ground motion models (GMMs) following the ergodic assumption whereby average source, path, and site effects from global databases apply for a specific site of interest. Site-specific site response is likely to differ from the global average conditional on site parameters used in GMMs (typically V S30 and basin depth). Non-ergodic site response can be evaluated using on-site ground motion recordings and/or one-dimensional wave propagation analyses, and allows site-to-site variability to be removed from the within-event standard deviation. Relative to ergodic, non-ergodic hazard analyses often reduce ground motions at long return periods. We describe procedures for replacing the site term in GMMs with a non-ergodic nonlinear mean over its appropriate range of periods (returning to the ergodic mean outside that range). We also present procedures for computing non-ergodic standard deviation by removing site-to-site variability while considering effects of soil nonlinearity. We illustrate application of these procedures, and their effect on hazard curves and uniform hazard spectra, as implemented in OpenSHA.

Ranking of Ground-Motion Models (GMMs) for Use in Probabilistic Seismic Hazard Analysis for Iran Based on an Independent Data Set

2020 ◽  
Author(s):  
Zoya Farajpour ◽  
Milad Kowsari ◽  
Shahram Pezeshk ◽  
Benedikt Halldorsson
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Selection Process ◽  
Hazard Analysis ◽  
Probabilistic Seismic Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Probabilistic Seismic Hazard ◽  
Data Set ◽  
Motion Models ◽  
Ground Motion Models

ABSTRACT We apply three data-driven selection methods, log-likelihood (LLH), Euclidean distance-based ranking (EDR), and deviance information criterion (DIC), to objectively evaluate the predictive capability of 10 ground-motion models (GMMs) developed from Iranian and worldwide data sets against a new and independent Iranian strong-motion data set. The data set includes, for example, the 12 November 2017 Mw 7.3 Ezgaleh earthquake and the 25 November 2018 Mw 6.3 Sarpol-e Zahab earthquake and includes a total of 201 records from 29 recent events with moment magnitudes 4.5≤Mw≤7.3 with distances up to 275 km. The results of this study show that the prior sigma of the GMMs acts as the key measure used by the LLH and EDR methods in the ranking against the data set. In some cases, this leads to the resulting model bias being ignored. In contrast, the DIC method is free from such ambiguity as it uses the posterior sigma as the basis for the ranking. Thus, the DIC method offers a clear advantage of partially removing the ergodic assumption from the GMM selection process and allows a more objective representation of the expected ground motion at a specific site when the ground-motion recordings are homogeneously distributed in terms of magnitudes and distances. The ranking results thus show that the local models that were exclusively developed from Iranian strong motions perform better than GMMs from other regions for use in probabilistic seismic hazard analysis in Iran. Among the Next Generation Attenuation-West2 models, the GMMs by Boore et al. (2014) and Abrahamson et al. (2014) perform better. The GMMs proposed by Darzi et al. (2019) and Farajpour et al. (2019) fit the recorded data well at short periods (peak ground acceleration and pseudoacceleration spectra at T=0.2  s). However, at long periods, the models developed by Zafarani et al. (2018), Sedaghati and Pezeshk (2017), and Kale et al. (2015) are preferable.

Capturing epistemic uncertainty in site response

2020 ◽  
pp. 875529302097097
Author(s):  
Adrian Rodriguez-Marek ◽  
Julian J Bommer ◽  
Robert R Youngs ◽  
Maria J Crespo ◽  
Peter J Stafford ◽  
...  
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Discrete Distribution ◽  
Seismic Source ◽  
Site Specific ◽  
Underlying Distribution ◽  
Response Characteristics ◽  
Motion Models

The incorporation of local amplification factors (AFs) determined through site response analyses has become standard practice in site-specific probabilistic seismic hazard analysis (PSHA). Another indispensable feature of the current state of practice in site-specific PSHA is the identification and quantification of all epistemic uncertainties that influence the final hazard estimates. Consequently, logic trees are constructed not only for seismic source characteristics and ground-motion models (GMMs) but also for the site AFs, the latter generally characterized by branches for alternative shear-wave velocity ( VS) profiles. However, in the same way that branch weights on alternative GMMs can give rise to unintentionally narrow distributions of predicted ground-motion amplitudes, the distribution of AFs obtained from a small number of weighted VS profiles will often be quite narrow at some oscillator frequencies. We propose an alternative approach to capturing epistemic uncertainty in site response in order to avoid such unintentionally constricted distributions of AFs using more complete logic trees for site response analyses. Nodes are included for all the factors that influence the calculated AFs, which may include shallow VS profiles, deeper VS profiles, depth of impedance contrasts, low-strain soil damping, and choice of modulus reduction and damping curves. Site response analyses are then executed for all branch combinations to generate a large number of frequency-dependent AFs. Finally, these are re-sampled as a discrete distribution with enough branches to capture the underlying distribution of AFs. While this approach improves the representation of epistemic uncertainty in the dynamic site response characteristics, modeling uncertainty in the AFs is not automatically captured in this way, for which reason it is also proposed that a minimum level of epistemic uncertainty should be imposed on the final distribution.

On the Ground‐Motion Models for Chinese Seismic Hazard Mapping

2019 ◽  
Vol 109 (5) ◽  
pp. 2106-2124 ◽  
Author(s):  
Han Ping Hong ◽  
Chao Feng
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Projection Method ◽  
Return Period ◽  
Mainland China ◽  
Hazard Mapping ◽  
Uniform Hazard Spectra ◽  
Motion Models ◽  
Fifth Generation ◽  
Ground Motion Models

Abstract The ground‐motion models (GMMs) used to map seismic hazard in China were developed based on the so‐called projection method, assuming relations of a pair of predicted macrointensities and of a pair of predicted ground‐motion measures in two different regions. The use of such a method is necessary because the ground‐motion records of a large number of strong earthquakes are lacking in mainland China, although the catalog of historical Chinese earthquakes is relatively rich. A critical review of the GMMs adopted to develop the third‐, fourth‐, and fifth‐generation Chinese seismic hazard maps (CSHMs) for mainland China suggests that some of the information used to project these models, such as the earthquake magnitude interpretation and GMM for the macrointensity, may need additional justification, and that the standard deviation (sigma) of the GMMs may be low. Also, new GMMs applicable to mainland China are developed based on the projection method and a set of the GMMs from the Next Generation Attenuation relationships. The results obtained using newly projected GMMs and seismic hazard analysis indicate that the ratio of the return period values of the peak ground acceleration obtained using the newly projected GMMs and using the GMMs adopted for the fifth‐generation CSHM is about 1.35 for a return period range from 50 to 2475 yr. Part of this increase is attributed to the differences in the standard deviations of residuals for the newly projected GMMs and the adopted GMMs used to map seismic hazard for mainland China. The results also suggest that the shape of the adopted seismic design spectrum in Chinese structural design code differs from the uniform hazard spectra obtained based on the newly projected GMMs for simple seismic source zones.

scholarly journals Selection and ranking of ground motion models for seismic hazard analysis in the Pyrenees

2007 ◽  
Vol 11 (1) ◽  
pp. 87-100 ◽  
Author(s):  
Stéphane Drouet ◽  
Frank Scherbaum ◽  
Fabrice Cotton ◽  
Annie Souriau
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Motion Models ◽  
Ground Motion Models ◽  
Selection And Ranking

scholarly journals A ground motion logic tree for seismic hazard analysis in the stable cratonic region of Europe: regionalisation, model selection and development of a scaled backbone approach

2020 ◽  
Vol 18 (14) ◽  
pp. 6119-6148
Author(s):  
Graeme Weatherill ◽  
Fabrice Cotton
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Ground Motion ◽  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Eastern United States ◽  
Logic Tree ◽  
Short Period ◽  
Northeastern Europe

Abstract Regions of low seismicity present a particular challenge for probabilistic seismic hazard analysis when identifying suitable ground motion models (GMMs) and quantifying their epistemic uncertainty. The 2020 European Seismic Hazard Model adopts a scaled backbone approach to characterise this uncertainty for shallow seismicity in Europe, incorporating region-to-region source and attenuation variability based on European strong motion data. This approach, however, may not be suited to stable cratonic region of northeastern Europe (encompassing Finland, Sweden and the Baltic countries), where exploration of various global geophysical datasets reveals that its crustal properties are distinctly different from the rest of Europe, and are instead more closely represented by those of the Central and Eastern United States. Building upon the suite of models developed by the recent NGA East project, we construct a new scaled backbone ground motion model and calibrate its corresponding epistemic uncertainties. The resulting logic tree is shown to provide comparable hazard outcomes to the epistemic uncertainty modelling strategy adopted for the Eastern United States, despite the different approaches taken. Comparison with previous GMM selections for northeastern Europe, however, highlights key differences in short period accelerations resulting from new assumptions regarding the characteristics of the reference rock and its influence on site amplification.

scholarly journals Seismic Hazard Assessment for the Tianshui Urban Area, Gansu Province, China

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Zhenming Wang ◽  
David T. Butler ◽  
Edward W. Woolery ◽  
Lanmin Wang
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Seismic Design ◽  
Hazard Analysis ◽  
Seismic Hazard Assessment ◽  
Gansu Province ◽  
Mitigation Measures ◽  
Peak Ground Velocity ◽  
Ground Acceleration ◽  
Acceleration Time Histories

A scenario seismic hazard analysis was performed for the city of Tianshui. The scenario hazard analysis utilized the best available geologic and seismological information as well as composite source model (i.e., ground motion simulation) to derive ground motion hazards in terms of acceleration time histories, peak values (e.g., peak ground acceleration and peak ground velocity), and response spectra. This study confirms that Tianshui is facing significant seismic hazard, and certain mitigation measures, such as better seismic design for buildings and other structures, should be developed and implemented. This study shows that PGA of 0.3 g (equivalent to Chinese intensity VIII) should be considered for seismic design of general building and PGA of 0.4 g (equivalent to Chinese intensity IX) for seismic design of critical facility in Tianshui.

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