Determination of earthquake source parameters for the Elazığ earthquake of March 8, 2010 based on source spectra

Abstract

Elazığ province was experienced a moment magnitude of 6.0 (Mw=6.0) earthquake on March 8th, 2010 which was followed by a sequence of earthquakes ranging from moderate to large scale near the source of main shock, Başyurt-Karakoçan. Seismic source parameters and scaling relations were determined by using a data set of 29 earthquakes which were recorded by broadband seismic network whose epicentral distances vary between 10 - 600 km and magnitudes are ranging from 3.3 to 6.0 between March 8th and March 29th. In this thesis, the source processes of these earthquakes are analyzed in terms of focal mechanism solutions, moment magnitude, seismic moment, corner frequency, stress drop and fault dimensions. Source parameters are computed by Moment Tensor Inversion method (MTI) represented by a point source model. Focal mechanism solutions are computed by using ZSACWIN software package (Yılmazer, 2011). Fault parameters (strike, dip, and rake angles), and seismic moment are calculated using the technique introduced by Dreger and Helmberger (1993), Dreger (2002). The focal mechanisms of 29 earthquakes are mostly strike-slip fault type, and the seismic moment of main shock determined as Mo=7.21×1024 dyne-cm. The displacement source spectra are determined by applying ω-2 spectral fitting procedure to classical Brune’s (1970) model using SEISAN software package (Ottemöller, 2011). The corrected spectra for S-waves within 5 sec are scaled to compute moment at the long period asymptote corresponding to the spectral plateau. Using the spectral amplitude (Ωo) for 0 Hz, seismic moment (Mo) and corner frequency (fc) which controls the shape of the spectra are derived from the fitted model based on the Brune’s model by implementing Converging Grid Search (CGS) technique. The source dimension of a circular fault area, the average stress drop, and the Mw are calculated with respect to empirical relations proposed by Hanks and Kanamori (1979). For the mainshock of Elazığ earthquake, seismic moment is calculated as Mo =1.80×1025 dyne-cm in agreement with similar studies’ results in the region and Mo from MTI method’s results.