PSHA for Strong Ground-Motion Hazards in Marmara Region, Turkey with Physically-based Ground Motion Prediction Methodology

Wednesday, 17 December 2014
Aydin Mert, Kandilli Observatory, Istanbul, Turkey, Yasin Fahjan, Gebze Institute of Technology, Kocaeli, Turkey and Lawrence J Hutchings, LBNL-Earth Sciences, Berkeley, CA, United States
We perform a probabilistic seismic hazard analysis (PSHA) for strong ground motion within the Marmara region, Turkey, from potential earthquakes along the North Anatolian fault segments in and around Marmara Sea. Because of the increasing awareness of earthquake threat in the Marmara Region, the need for seismic hazard studies has become progressively more important for planning risk reduction actions. We perform the PSHA utilizing empirical Green’s functions (EGFs) along with models of finite rupture in place of standard “attenuation relations”. The important aspect of this study is that we combined the basic PSHA with ground motion simulations and obtained hazard analysis for all significant magnitude earthquakes, and provide the necessary full-waveform simulated ground motions to calculate building response, and thus risk. Recordings of small earthquakes from a local seismic array operated by Kandilli Observatory and Earthquake Research Institute (KOERI) were used as EGFs.

Over the past 50 years, probabilistic seismic hazard analysis (PSHA) has been based upon estimating annual frequency of exceedance for a ground-motion parameter at a particular site (i.e., a hazard curve, Cornell, 1968). In the present study, we estimated the seismic hazard in Marmara Region and we expand and utilize the “physically based” approach proposed by Hutchings et al. (2007), Scognamiglio and Hutchings (2009). This approach replaces the aleatory uncertainty that current PSHA studies estimate by regression of empirical parameters with epistemic uncertainty that is expressed by the variability in the physical parameters of earthquake rupture. Epistemic uncertainty can be reduced by further research. By ‘physically based’ we refer to ground motion synthesized with quasi-dynamic rupture models derived from physics and an understanding of earthquake process. This methodology provides source- and site-specific calculations of full-waveform ground motion time histories, which is important for nonlinear dynamic analysis of structures, and reduce uncertainties in estimating standard engineering parameters. Further, based on these calculations, PSHA results are presented 2%, 10% and 50% hazards for all investigated sites in Marmara Region.