Physically based ground motion prediction and validation: a case study medium-size magnitude Marmara Sea earthquakes

The evaluation of realistic time histories for various locations around Marmara Region is aimed to provide reliable input for performance-based seismic design, hazard or risk management studies and developing new seismic standards. The applicability of empirical Green’s functions methodology and physics-based solution of earthquake rupture have been assessed in terms of modeling complex geologic structures. This paper has two main objectives. The first one is to simulate five medium-size magnitude earthquakes (M_w ≈ 5.0) recorded in the Marmara Region. A series of synthetic ground motion waveforms for three components are evaluated with a ‘physics-based’ solution of earthquake rupture. The simulation methodology is based on the studies of Hutchings and Wu (J Geophys Res 95:1187–1214, 1990), Hutchings (Seismol Soc Am 81:88–121, 1991; Seismol Soc Am 84:1028–1050, 1994), Hutchings et al. (Geophys J Int 168:569–680, 2007), and Scognamiglio and Hutchings (Tectonophysics 476:145–158, 2009). For each earthquake, we calculate synthetic seismograms by using 500 different rupture scenarios that are generated by Monte Carlo method for a selection of parameters within a range based on prior knowledge of where the earthquakes will occur. The second objective is to validate synthetic seismograms with real seismograms. To improve the credibility of synthetic seismograms from an engineering point of view, the methodology presented by Anderson (in 13th world conference on earthquake engineering, Vancouver, 2003) is followed. This methodology proposes a similarity score based on averages of the quality of fit measuring ground motion characteristics and uses a suite of measurements. In order to compute goodness of fit, ten different ground motion parameters were compared on a scale from 0 to 100, where 100 means perfect agreement. Because the methodology produces source- and site-specific synthetic ground motion time histories, and the goodness-of-fit scores of obtained synthetics are between ‘good’ and ‘excellent’ range (61.128–82.164) based on the Anderson’s score, we conclude that it can be used to produce reliable ground motion time histories for seismic risk regions to develop or improve seismic codes and standards.