On how the ergodic assumption influences seismic risk
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On how the ergodic assumption influences seismic risk Zehra Çağnan1 Received: 16 April 2020 / Accepted: 22 October 2020 © Springer Nature B.V. 2020
Abstract The Monte-Carlo (MC) simulation approach has been widely applied to the problem of probabilistic seismic hazard assessment (PSHA) for geographically distributed systems. Although the conventional integral approach is well-established in PSHA, the MC simulation approach is an efficient and flexible alternative when complicated factors, such as spatial correlation of ground shaking are involved. The objective of this study is to assess how the ergodic assumption influences the economic loss results for a region. To meet this objective, MC simulation and multi-scale random fields techniques are used to assess the probabilistic seismic hazard of a region, while incorporating estimated site-terms (δS2Ss) based on available strong-motion records at specific sites and spatially correlated δS2Ss at others in addition to single-station sigma to the PSHA process. The proposed method is applied to the Fatih district of Istanbul in the case of a moment magnitude 7.3 earthquake on the Marmara Fault. Results indicate that the probability for total economic loss being underestimated due to the ergodic assumption by at least 29% is 0.50 in the case of a moment magnitude 7.3 earthquake on the Marmara Fault. Keywords Probabilistic seismic hazard assessment · Probabilistic seismic risk assessment · Monte-carlo simulation · Single-station sigma · Ergodic assumption
1 Introduction When GMPMs are utilized as part of seismic hazard assessment studies, an inherent assumption is made, namely that the ground-motion variability obtained based on a global (or regional) dataset is the same as the variability of ground-motion caused by a single-source at a single-site. This assumption has been referred to as the ergodic assumption (i.e. Anderson and Brune 1999; Douglas 2003; Strasser et al. 2009). Over the last decade, the availability of recorded ground motions at single sites caused by multiple earthquakes originating from the same tectonic sources has allowed researchers to estimate what is referred to as the nonergodic Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1051 8-020-00992-z) contains supplementary material, which is available to authorized users. * Zehra Çağnan [email protected] 1
Engineering Sciences Department, Middle East Technical University, MM Building, Universiteler Mah.Dumlupinar Blvd. No.1, 06800 Ankara, Turkey
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Vol.:(0123456789)
Bulletin of Earthquake Engineering
standard deviation of ground-motion. This is also known as single-source single-station standard deviation. Quantification of the nonergodic standard deviation enables the elimination of epistemic site-to-site, path-to-path and source-to-source variability from the GMPM sigma hence it is a step forward towards quantification of the true aleatory variability of the groundmotion at a specific site. For an ideal PSHA, the standard deviation o
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