RAPID SOURCE PARAMETER DETERMINATION AND EARTHQUAKE SOURCE PROCESS IN INDONESIA REGION

We proposed a magnitude determination method for the regional network of the Meteorological and Geophysical Agency (MGA), Badan Meteorologi dan Geofisika (BMG). This method was developed from the empirical formula from Richter's magnitude by using least square method. We use accelerogram from regional accelerometer network of BMG for one month range. The magnitude formula of BMG is as follows: M BMGj = log 10 A D + 2.15 log 10 R -1.88 where A D is the maximum displacement amplitude (μm), and R is hypocentral distance (km), respectively. The comparisons in magnitudes among this formula, Tsuboi's formula (1954), and M w from Global CMT indicate that this formula could be improved after seismic records are accumulated in BMG. Also we determined the moment tensor for the earthquakes by using program written by Kikuchi for calculating Green's function and inversion program coded by Yagi. To understand the state of tectonic stress field of area around epicenters, we investigated the tectonic feature by analyzing the focal mechanism obtained by moment tensor inversion.