HR: 15:15h
AN: U43C-07    [Abstracts]
TI: Communicating an uncertain increase in earthquake hazard: a case study from Sumatra
AU: * Steacy, S
EM: s.steacy@ulster.ac.uk
AF: Geophysics Research Group School of Environmental Sciences, University of Ulster Cromore Road, Coleraine, BT52 1SA Ireland
AU: McCloskey, J
EM: j.mccloskey@ulster.ac.uk
AF: Geophysics Research Group School of Environmental Sciences, University of Ulster Cromore Road, Coleraine, BT52 1SA Ireland
AU: Nalbant, S
EM: ss.nalbant@ulster.uk
AF: Geophysics Research Group School of Environmental Sciences, University of Ulster Cromore Road, Coleraine, BT52 1SA Ireland
AB: Immediately after the 26 Dec. 2004 Sumatra - Andaman Islands earthquake, we computed the stress changes due to it on the Sunda Trench to the south of the Dec. rupture plane and on the Sumatra Fault which runs down the center of the island. Our results clearly showed a significant increase in stress of up to 9 bars on both structures; stress changes of about 0.1 bars had been shown to trigger large earthquakes in other regions. Additionally, evidence from the Nankai Trough offshore Japan demonstrated that subduction zone earthquakes are often linked, with many events apparently triggering neighboring earthquakes in the following 1-2 years, and an earthquake on the Sunda Trench had the clear potential to generate another tsunami. These results led to a serious discussion about our responsibilities as scientists, on the one hand we were certain that the seismic risk on the island of Sumatra had increased, on the other we were very aware of the uncertainties in the application of the results, particularly with respect to timing. We also expected that publication would lead to considerable media attention and we were concerned that our results would be misinterpreted as a "prediction"; this indeed turned out to be the case. The research was published on 17 March and a triggered M=8.7 event occurred on the Sunda Trench, in the area of concern, 11 days later. Although the timescale in this instance was clearly too short to affect preparedness, its occurrence strongly suggested that our decision to publish was correct. We have since shown that the March event, in turn, increased stress farther south along the subduction zone, again leading to an unquantifiable increase in seismic hazard. The media response to this work has been mixed, with international organizations echoing our call for urgent moves towards improving preparedness and local ones (e.g. the Jakarta Post) debunking the work.
DE: 4564 Tsunamis and storm surges
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Union [U]
MN: Fall Meeting 2005