Reviewing the characteristics of slip behaviour for megathrust earthquake at Sumatera using vertical derivative of GOCE satellite gravity field

Abstract

The review of the seismogenic zone characteristics associated with the earthquake rupture process in the Sumatra Subduction Zone has been carried out by various methods. This zone has experienced several major earthquakes; Aceh 2004 Mw=9,1, Nias-Simeulue 2005 Mw=8,6, Bengkulu 2007 Mw=8,5, and Enggano 2000 Mw=7,9. This study focuses on the relationship between density contrast analysis based on gravity data from the GOCE satellite and the slip distribution in four major earthquake rupture zones. Satellite gravity data processing is carried out to obtain data for Gravity disturbance (Gd) and vertical gravity derivatives (Tzz), corrected by topography and sediment effects with different spectrum decomposition to get gravity maps with different depths. Based on the Tzz analysis, the maximum slip of the earthquake rupture is correlated with the minimum Tzz pattern and low-density contrast. In contrast, the rupture ends at the maximum Tzz pattern and high-density contrast. Tzz pattern and Gravity disturbance can describe the barrier and asperity of the Sumatra subduction zone. The schematic maps portray the seismic segmentation of Sumatra Subduction, which have asperities zone along the subduction strike associated with the minimum Tzz and associated with the forearc zone, as well as the barrier related to the maximum Tzz, which is a manifestation of structures (fracture zone and seamount) that are subducted to the oceanic plate.