Analysis of Source Rupture Process of the September 2, 2009 Tasikmalaya Earthquake by Using the Joint Inversion Method of Near Field and Teleseismic Data

Abstract

In order to enhance our understanding of the earthquake mechanism and seismotectonic characteristics of the September 2, 2009 Tasikmalaya earthquake, we have performed the joint inversion method to the near field data from the MCGA regional network and teleseismic body wave data from the IRIS-DMC seismic network. To make the stable inversion, we adapted the Akaike's Bayesian Information Criterion (ABIC) method by applying the smoothness constraint with respect to time and space on the slip distribution. The results of joint inversion show that there are four asperities. The maximum slip amount is 1.20 m in the first asperity near epicenter. The source parameters are obtained i.e. the total seismic moment Mo = 0.3521x1020 Nm (Mw = 7.0), and the source duration time = 17 seconds. In general, the rupture propagates along the dip direction on the fault plane, and trending in a southeast and northwest direction of the epicenter. The slip directions are mainly towards the surface (the up dip direction). The slip and rupture propagation trending dip direction is probably one of the main causes of the aftershocks laid above the plate interface. We also estimated the shear stress change caused by mainshock in and around the fault zone. We found that a lot of aftershocks around the plate boundaries are triggered by increasing stress due to the rupture of the mainshock, and there is a tendency for the aftershocks distribution leads to appear north of the epicenter. The strike almost perpendicular to the trench may be related to a strong slab pull beneath the region, which generates the stress along the Java trench. So the stress parallel to the trench line is estimated to play a major role in the source mechanism of the September 2, 2009 Tasikmalaya earthquake.