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After the Mw 9.3 Sumatra-Andaman Earthquake on 26 December 2004, a temporary broadband seismic station was set up at the Khao Chang Telecommunication Station in Phang nga Province, Southern Thailand, in order to monitor aftershocks in an area bounded by 0o-20o N, and 90o-100o E. Altogether 98 events were identified during the study period from 1st to 12th January 2005; but six of these events are not listed in the catalog of the United States Geological Survey (USGS/ NEIC). Body wave magnitudes (mb) and moment magnitudes (Mw) of the events were determined and compared with USGS magnitudes. For mb, the PSU values are 0.215 higher than the USGS values, whereas for Mw, the PSU values are 0.268 lower than the USGS values. Differences in mb may result from differences in time windows chosen for the maximum amplitude determination, or from accuracy of the Q-value. Differences in Mw may result from assumptions made on velocity, attenuation and determination of the low-frequency part of the seismic spectrum. However, these differences are comparatively small considering that the USGS data are network values whereas the PSU data are from a single station.

Residual gravity anomaly with a minimum of about -140 mm s-2 with approximately NS trend and a limited axial length was observed over Hat Yai Basin in Peninsular Thailand. The modeled Hat Yai basin is about 1 km deep at its deepest, 60 km long and 20 km wide. The porosity of basin sediment and the amount of potential ground water reserves within the basin are estimated to be 39% and 121.7±0.8 km3 respectively, assuming full saturation. Within the topmost 80 m of ground where the present extraction is concentrated, the estimated ground water reserve is 12.5±0.5 km3.