Investigation of the rupture properties of the June 27, 1998 Adana earthquake (Mw=6.2) from the teleseismic waveforms

The moderate-sized June 27, 1998 Adana earthquake (Mw=6.2) occurred in the Clicia Basin, where a possible extent of the Eastern Anatolian fault is under question. In the present study point-source and finite-fault inversions of the earthquake source are carried out using the teleseismic P and SH waveform in order to determine the source parameters and discuss the rupture properties.In the point source modeling stage nearly the same fit is achieved between the observed and the synthetic waveforms for the single and multiple source inversions. Therefore a single subevent rupture process, is considered for the earthquake rupture process. It is also found in the point source modeling trials that the data is requires a deep lower crust rupture with a source location at 24 km depth. The NE-SW trending nodal plane (strike=57o, dip=70o and rake=20o) of the source mechanism is subparallel to the nearby Göksu fault zone and is considered as the fault plane. A seismic moment of 2.24X1018 Nm (Mw=6.2) is calculated for the point source model.The Finite fault modeling of the earthquake is carried out using the same data and the grid scheme (model fault plane) used in the point source modeling. It is found that the rupture of the earthquake is controlled by the rupture of two asperities. The larger asperity is located updip of the hypocenter and centered at a depth of approximately 26 km depth with a peak displacement of 0.5 m. The smaller asperity is located close to the NE edge of the model fault plane at a depth of 32 km with a peak slip of about 0.25 m. The finite fault inversion of the data is resulted in a seismic moment of 1.91X1018 (Mw=6.1), about three fourth of which is released by the larger asperity.As a whole the teleseismic modeling suggests that the earthquake rupture occurred on a branch fault within the GFZ that do not reach the free surface, dips SE and strikes differently from the surface trace of the GFZ.