A detailed slip model for the 1995, October 1, Dinar, Turkey, earthquake (M-S=6.1) determined from inversion of teleseismic P and SH waveforms

Abstract

Teleseismically recorded P and SH waveforms of the 1995, October 1 Dinar, Turkey, earthquake are inverted to find detailed coseismic slip distribution on the ruptured part of the Dinar-Civril fault. For this purpose a linear finite-fault inversion procedure with time window approach is used to allow variable rise time and rupture velocity on the model fault. The source is represented by a 24 x 21 km rectangle fault plane, which is divided into 56 equal size subfaults. The strike and the dip of the fault plane are assumed as determined by a previous study. The amount of slip and the rake angle on each subfault is retrieved through fitting the observed and synthetic seismograms in a least-squares sense. The previous inversion studies indicated that the earthquake was associated with two subevents, with a 6 stime lag of the NW subevent. Therefore, the model fault plane is also divided into two separate equal-area segments, the SE and the NW segments, to delay the rupture propagation over the NW segment. We tried several models to fix the delay time and hypocentral depth and to explain the waveforms. The smallest misfit error resulted from a model with 5 s delay time and 7.5 km hypocentral depth. The preferred solution suggests that the earthquake is associated with breaking of two asperities and the coseismic slip occurred mostly above the depth of 10 km. The smaller asperity is located to the SE just beneath Dinar town with peak slip of 26 cm while the larger one is located to the NW with peak slip of 41 cm. The observed surface rupture coincides with the location of the smaller asperity. The seismic moment for our slip model is 2 8 x 10(18) N m. The modelling yields an average rake angle of -102degrees and almost no difference between the average rake angles of the two asperities.