Monday 22 August 2005

G3
1330-1530 hours

055
Coseismic displacement of the 2004, Mw=9.0 Sumatra-Andaman earthquake from GPS measurements
Irwan, Meilano¹, Oota, Yasaku¹, Z. Abidin, Hasannudin², A. Kusuma, Mipi², Sugiyanto, Didik³, Agustan⁴, Ito, Takeo¹, Kimata, Fumiaki¹
1 Research Center For Seismology, Volcanology and Disaster Mitigation Nagoya University, Japan
2 Dept. of Geodetic Eng. Institute of Technology Bandung, Indonesia
3 Dept. of Physics, Syiah Kuala University Aceh, Indonesia
4 Agency for Assessment and Application of Technology, Indonesia
Author email: irwan@seis.nagoya-u.ac.jp
A megathrust earthquake of a magnitude 9.0 struck Aceh in North of Sumatra, Indonesia at 00:58:53 UTC. This devastating megathrust earthquake occurred on the interface of the India and Sunda (Burma) plates. The earthquake ruptured a surface at least 400 km long and 100km, some models use a longer rupture up to 1000 km further north. Most of the aftershock occur in the Andaman area. Whether this part of the fault slipped during mainshock's rupture is difficult to infer from seismic records, because the long period nature of the event. We present GPS measurements of horizontal and vertical coseismic displacements that provide new constrain on the rupture geometry. The inversion shows, slip was larger in the north of epicenter. Subsidence along the west coast of Sumatra indicates the main rupture did not reach the Sumatra Island (down-dip). A few ten centimeter horizontal displacement to the north in Simeulue Island, suggests that the rupture zone of 1861 earthquake did not re-ruptured during 2004 Sumatra Earthquake.

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