POSTSEISMIC CRUSTAL DEFORMATION ASSOCIATED WITH THE 1995 HYOGO-KEN-NANBU EARTHQUAKE DERIVED FROM GPS OBSERVATION - PRELIMINARY-ANALYSIS OF TRIMBLE DATA

Within 1 to 4 days following the 1995 Hyogo-ken Nanbu earthquake (M 7. 2) that occurred on January 17, 1995, the Japanese University Consorti um for GPS Research deployed more than 30 GPS receivers in the hypocen tral area to investigate post-seismic activity. Of these stations, we analyzed data from 8 sites that were placed near the hypocentral area; six in Kobe and two in Awaji. Two methods of analysis were employed: 1) change of absolute geocentric coordinates were estimated by assumin g Usuda global site, which is about 300 km northeast of the hypocentra l area, as fixed, 2) analyses for short baselines were conducted withi n the hypocentral area using the automatic processing technique. Resul ts suggest that 1) rapid displacements toward the southeast of more th an 4 cm/year were found at all of the analyzed sites, which might be p art of a post-seismic deformation process, 2) largest of which was fou nd at Rokko Farm site, at which displacement amounted to about 3 cm un til the end of February, though its cause were not specified, and 3) l ocal straining seems to be taking place al both Kobe and Awaji areas.