Crustal structure beneath Simeulue Island, Indonesia: Preliminary study from a joint inversion of receiver function and surface wave dispersion

Abstract

Simeulue Island is located on the subduction zone between Indo-Australian and Eurasian plates. The Island is in the forearc basin west of Sumatra Island. Due to subduction process of Indo-Australian plate beneath Eurasian plate, high seismic activities occur around Simeulue Island. Two devastating megathrust earthquakes of 2004 Mw 9.2 Sumatra-Andaman and 2005 Mw 8.7 Nias earthquakes occurred close to the Island. Information of crustal structure may provide better understanding about tectonic characteristics. In this preliminary study, we investigated crustal structure beneath Simeulue Island from three temporary broadband seismometers. Crustal structure was derived from joint inversion of receiver function and surface wave dispersion. S-wave velocity profiles obtained from joint inversion may suggest that the crustal thickness beneath Simeulue Island is at about 20-25 km. S-wave velocity decrease is observed at depth of about 50-60 km depth. This low velocity decrease may be related to the subducting slab of Indo-Australian plate.