January 7, 2005
Off Sumatra Earthquake and Tsunami Survey Group
IFREE/DSR: Wonn Soh, Masa Kinoshita
Tel +81+46-867-9323 fax +81-46-867-9315
Public Relations: Kenichi Takahashi
Tel +81+46-867-9066 fax +81-46-867-9055
Japan Agency for Marine-Earth Science and Technology (JAMSTEC: President Yasuhiro Kato) hereby announces its plan to conduct an offshore survey in immediate response to the gigantic Earthquake of December 26, 2004 occurred off the western coast of Sumatra, which accompanied huge tsunamis causing unprecedented damages around the Indian Ocean.
Aim of the survey
The extraordinary event (M 9.0) has caused unprecedented tsunami disasters. Numerous aftershocks are still occurring in the area and it will be a while before this sequence following the main event dies down. Considering the circumstances and responding to international request, JAMSTEC decides to conduct an offshore survey in the epicenter area in February and March, 2005.
Outline of the survey
JAMSTECfs R/V Natsushima and ROV (Remotely Operated Vehicle) : gHyper Dolphinh or Deep Tow will be engaged in this cruise (Plate 1) in the epicentral area (Plate 2). The survey will include collecting swath bathymetry and side scan sonar image, making ROV dives to view the possible sea floor deformation, and deploying and retrieving ocean bottom seismometers (OBSs) to obtain the aftershocks distribution (details of each observation are not fixed yet).
Significance and deliverables of the survey
The in situ observations of the sea floor deformation (seismic fault traces and foldings) and aftershocks are critical in determining the location, mechanism and the magnitude of the main faulting. This is the only way to obtain near-field data to link the cause (what exactly happened) and consequences (tremendous calamity) in a scientific manner to be applicable in the future and in other areas including adjacent southern extension of the Sunda Trench. The survey area will be targeted where large offsets are estimated by teleseismic (seismic observations at far distances) observations. The results from this survey and following surveys will be put into the public domain as immediately as possible.