Determination of telesesimic finite-fault models for the 19 August 1966 Varto (Ms=6.8) and 6 September 1975 Lice (Ms=6.6) earthquakes

The August 19, 1966 Varto (Ms=6.8) and the September 6, 1975 Lice earthquakes (Ms=6.6) are the damaging large earthquakes that occurred in Eastern Turkey with discontinuous surface ruptures. The former took place along the North Anatolian Fault Zone while the latter along the Bitlis Thrust Zone. In the present study, teleseismically recorded long period P body waveforms of both earthquakes are inverted to obtain the finite-fault source properties using a finite-fault inversion methodology developed by Kikuchi et al. (2003). The rupture planes of both earthquakes are represented by point source grids which are placed in the source regions with reference to their hypocenters. After several inversion trials with different model fault parameterisations, the parameters that give best fit to the data are determined. The rupture of the 1966 Varto earthquake is found to be mainly unilateral to northwest with failure of three asperities over a southwest dipping fault plane. The peak slip amplitude is determined to be 196 cm at a location 8 km west of the hypocentre. The slip model corresponds to a seismic moment of 1.5 x 1019 Nt m (MW≈6.7). For the 1975 Lice earthquake the inversion trials have shown that the rupture almost unilateral to the southwest over a rupture plane striking 254o and dipping 54o NW. The rupture has been mainly controlled by a failure of large asperity with 60 cm peak slip in the hypocentral region. The total seismic moment and rake angle are calculated as 8.7 x 1018 Nt m (MW≈6.6) and 24o, respectively. The rake angle suggests that the rupture is oblique with larger left-lateral component in accordance with the seismotectonics of the source region controlled by the Bitlis Thrust Zone and East Anatolian Fault Zone.