scholarly journals The effect of spatial dependence on hazard validation

2017 ◽  
Vol 209 (3) ◽  
pp. 1363-1368 ◽  
Author(s):  
Iunio Iervolino ◽  
Massimiliano Giorgio ◽  
Pasquale Cito
Keyword(s):  
Ground Motion ◽  
Spatial Dependence ◽  
Best Practice ◽  
Hazard Analysis ◽  
Time Span ◽  
Probabilistic Seismic Hazard ◽  
Monitoring Networks ◽  
Hazard Maps ◽  
Intensity Measures ◽  
Seismic Networks

Summary In countries where best-practice probabilistic hazard studies and seismic monitoring networks are available, there is increasing interest in direct validation of hazard maps. It usually means trying to quantitatively understand whether probabilities estimated via hazard analysis are consistent with observed frequencies of exceedance of ground motion intensity thresholds. Because the exceedance events of interest are typically rare with respect to the time span covered by data from seismic networks, a common approach underlying these studies is to pool observations from different sites. The main reason for this is to collect a sample large enough to convincingly perform a statistical analysis. However, this requires accounting for the dependence among the stochastic processes counting exceedances of ground motion intensity measures thresholds at different sites. Neglecting this dependence may lead to potentially fallacious conclusions about inadequateness of probabilistic seismic hazard. This study addresses this issue revisiting a hazard validation exercise for Italy, showing that accounting for this kind of spatial dependence can change the results of formal testing.

scholarly journals Probabilistic seismic hazard analysis using a new ground motion intensity measure

DYNA ◽  
2016 ◽  
Vol 83 (195) ◽  
pp. 206-215 ◽  
Author(s):  
Robespiere Chávez López ◽  
Edén Bojórquez-Mora
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Probabilistic Seismic Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Probabilistic Seismic Hazard ◽  
Intensity Measure ◽  
Intensity Measures ◽  
First Time ◽  
Ground Motion Intensity Measure

The main objective of this work is to compute the probabilistic seismic hazard analysis for a region of Mexico using a new ground motion intensity measure which is based on the spectral acceleration and a parameter proxy of the spectral shape named Np. The motivation of using this new ground motion intensity measure is because recently it has demonstrated its potential in predicting the response of buildings subjected to earthquakes. In fact, it was demonstrated that intensity measures based on Np are more efficient compared with other parameter of the literature. It is important to mention that this is the first time that a probabilistic seismic hazard analysis is performed using this new intensity measurement.

Probabilities and Fallacies: Why Hazard Maps Cannot be Validated by Individual Earthquakes

2013 ◽  
Vol 29 (3) ◽  
pp. 1125-1136 ◽  
Author(s):  
Iunio Iervolino
Keyword(s):  
Ground Motion ◽  
Best Practice ◽  
Short Note ◽  
Response Spectra ◽  
Current Approach ◽  
Elastic Response ◽  
Hazard Maps ◽  
Intensity Measures ◽  
Elastic Response Spectra ◽  
Type Of Exercise

In countries with an advanced seismic technical culture, where best-practice hazard studies (which are therefore necessarily probabilistic) are available, the occurrence of a damaging event often triggers a debate, which is as understandable as it is delicate, aimed toward the verification and/or validation of the ground motion intensity estimates provided by the official hazard maps. Evaluations such as these are typically based either on the comparison of elastic response spectra derived from records of the event in question with uniform hazard (design) spectra, or on superimposing ground motion intensity measures on available hazard curves to retrieve the return period to which they correspond. This short note, using the recent 2012 Mw 6.0 Emilia (Italy) earthquake, discusses a few arguments, according to which this type of exercise should take into account the implications inherent in the probabilistic nature of hazard analyses, in order to avoid the risk of drawing conclusions that may be misleading or that may be likely to cause misconceptions about rationality of the current approach to seismic hazard.

Probabilistic seismic hazard maps for California do not perform better relative to historical shaking data when site-specific VS30 is considered

2021 ◽  
Author(s):  
Molly Gallahue ◽  
Leah Salditch ◽  
Madeleine Lucas ◽  
James Neely ◽  
Susan Hough ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Tall Buildings ◽  
Historical Period ◽  
Probabilistic Seismic Hazard ◽  
Hazard Maps ◽  
Site Specific ◽  
Seismic Hazard Maps ◽  
Intensity Mapping ◽  
Aleatory Variability

<div> <p>Probabilistic seismic hazard assessments forecast levels of earthquake shaking that should be exceeded with only a certain probability over a given period of time are important for earthquake hazard mitigation. These rely on assumptions about when and where earthquakes will occur, their size, and the resulting shaking as a function of distance as described by ground-motion models (GMMs) that cover broad geologic regions. Seismic hazard maps are used to develop building codes.</p> </div><div> <p>To explore the robustness of maps’ shaking forecasts, we consider how maps hindcast past shaking. We have compiled the California Historical Intensity Mapping Project (CHIMP) dataset of the maximum observed seismic intensity of shaking from the largest Californian earthquakes over the past 162 years. Previous comparisons between the maps for a constant V<sub>S30</sub> (shear-wave velcoity in the top 30 m of soil) of 760 m/s and CHIMP based on several metrics suggested that current maps overpredict shaking.</p> <p>The differences between the V<sub>S30</sub> at the CHIMP sites and the reference value of 760 m/s could amplify or deamplify the ground motions relative to the mapped values. We evaluate whether the V<sub>S30 </sub>at the CHIMP sites could cause a possible bias in the models. By comparison with the intensity data in CHIMP, we find that using site-specific V<sub>S30</sub> does not improve map performance, because the site corrections cause only minor differences from the original 2018 USGS hazard maps at the short periods (high frequencies) relevant to peak ground acceleration and hence MMI. The minimal differences reflect the fact that the nonlinear deamplification due to increased soil damping largely offsets the linear amplification due to low V<sub>S30</sub>. The net effects will be larger for longer periods relevant to tall buildings, where net amplification occurs. </p> <div> <p>Possible reasons for this discrepancy include limitations of the dataset, a bias in the hazard models, an over-estimation of the aleatory variability of the ground motion or that seismicity throughout the historical period has been lower than the long-term average, perhaps by chance due to the variability of earthquake recurrence. Resolving this discrepancy, which is also observed in Italy and Japan, could improve the performance of seismic hazard maps and thus earthquake safety for California and, by extension, worldwide. We also explore whether new nonergodic GMMs, with reduced aleatory variability, perform better than presently used ergodic GMMs compared to historical data.</p> </div> </div>

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.

scholarly journals Seismic hazard maps of Peshawar District for various return periods

2020 ◽  
Vol 20 (6) ◽  
pp. 1639-1661
Author(s):  
Khalid Mahmood ◽  
Naveed Ahmad ◽  
Usman Khan ◽  
Qaiser Iqbal
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Target Location ◽  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Source Parameters ◽  
Seismic Source ◽  
Return Periods ◽  
Hazard Maps ◽  
Seismic Hazard Maps

Abstract. Probabilistic seismic hazard analysis of Peshawar District has been performed for a grid size of 0.01∘. The seismic sources for the target location are defined as the area polygon with uniform seismicity. The earthquake catalogue was developed based on the earthquake data obtained from different worldwide seismological networks and historical records. The earthquake events obtained at different magnitude scales were converted into moment magnitude using indigenous catalogue-specific regression relationships. The homogenized catalogue was subdivided into shallow crustal and deep-subduction-zone earthquake events. The seismic source parameters were obtained using the bounded Gutenberg–Richter recurrence law. Seismic hazard maps were prepared for peak horizontal acceleration at bedrock level using different ground motion attenuation relationships. The study revealed the selection of an appropriate ground motion prediction equation is crucial for defining the seismic hazard of Peshawar District. The inclusion of deep subduction earthquakes does not add significantly to the seismic hazard for design base ground motions. The seismic hazard map developed for shallow crustal earthquakes, including also the epistemic uncertainty, was in close agreement with the map given in the Building Code of Pakistan Seismic Provisions (2007) for a return period of 475 years on bedrock. The seismic hazard maps for other return periods i.e., 50, 100, 250, 475 and 2500 years, are also presented.

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