SYNTHETIC-APERTURE RADAR INTERFEROGRAM OF THE 1995 KOBE EARTHQUAKE AND ITS GEODETIC INVERSION

Crustal deformation from the Mw=6.9 January 17 (JST), 1995, Kobe, Japa n earthquake was detected by synthetic aperture radar interferometry ( SAR). More than four fringes with ellipsoidal shape were observed surr ounding the Nojima fault on northern Awaji island suggesting a shorten ing in the range of more than 11.75 x 4 cm on the east side of this fa ult. The SAR sensor shows ellipsoidal fringes with an uplift zone in t he Rokko mountain range and sharp subsidence around the Kobe area. In addition to SAR interferometry, leveling and GPS surveys were conducte d by the Geographical Survey Institute of Japan (GSI). The permanent G PS observation sites of the GSI monitored ground displacements from th is earthquake with daily updates. Based on these geodetic data, we est imated the faulting mechanism of the earthquake. The analytical proced ure was an iterative linearized least squares method. A multi-fault sy stem consisting of six subfaults was constructed. The locations of til e estimated model faults were close to those of the active faults in t his area, running from the Nojima fault on Awaji island to the Rokko f aults in the Kobe area with a change in strike angle near the Ohtsuki fault in the Kobe area. The slip vectors of the Nojima fault on Awaji island had a large component of reverse dip-slip of about 2 m and stri ke slip of about 2 m. In the Kobe area, the amount of slip ranged from 0.3 to 1.2 m and was small compared with the slip on the Nojima fault . The results of these slip vectors agreed well with tile results of o ther seismic, geodetic, and field studies.