Fault Model of the 1995 North Sakhalin Earthquake Based on SAR Interferogram

Abstract

A large (Mw=7.0) earthquake occurred on May 27, 1995 at the northern part of Sakhalin Island. Field workers reported right-lateral, strike-slip seismic fault as long as 35km, running NNE on the surface, which maximum lateral displacement is about 8.1m.

We report crustal deformations associated with the earthquake using SAR interferometry (InSAR) and a fault model we constructed from this result. JERS-1 L-band (24cm) SAR data of one month (April 28 before and two weeks after (June 11) the mainshock were used to detect the crustal deformation. The fringes due to topographic component were removed from the interferogram by using 3-pass method. A fault model was constructed by non-linear least square method using this crustal deformation data.

The resulting interferogram shows characteristic features. First, around the eastern side of the southern end of the fault, the uplift with a pair of adjacent peaks clearly appears, one of which is as large as 70 cm. Second, the eastern side of the north end of the fault subsided about 1m. These structures could not be observed in detail by any other means than InSAR, such as GPS observation Data.

A model of the seismic fault was analyzed from the SAR interferogram. The model indicates that the southern end of the seismic fault extends more than the one that appears on the ground surface.