MODELING SUPPORTS GPS-SHIELD CONCEPT FOR A TSUNAMI EARLY WARNING SYSTEM

The catastrophic December 2004 Indian Ocean tsunami has strongly emphasized the need for efficient and reliable early-warning systems for tsunamis. This is particularly important, but also particularly complicated, for regions located close to subduction zones, such as the city of Padang on Sumatra where giant earthquake is expected in the near future. By modeling various potential tsunami sources, together with wave propagation, and employing non-linear 2D and 3D inversion techniques, we confirm that the problem of the early warning of near-field tsunami can be solved using special types of near-field GPS arrays operating in real time (GPS-Shield arrays) as suggested by Sobolev et al. (JGR in press). We demonstrate that these arrays, which measure both vertical and horizontal displacements, can resolve higher order features of the slip distribution on the fault than seismic moment, already during or only few minutes after a rupture, if they are placed less than some 100 km away of the rupture zone. Stations in the arrays are aligned perpendicular to the trench, i.e., parallel to the expected gradient of surface coseismic displacement and are placed as close as possible to the source. In the case of Sumatra the GPS-Shield arrays should be placed at Mentawai Islands, located between the trench and Sumatra and directly at the Sumatra western coast where no islands are present. We demonstrate that the 'GPS Shield' can also be applied to northern Chile, where giant earthquake may also occur in the near future. Moreover, this concept may be applied globally, to many other tsunamigenic active margins where the land is located above or close to seismogenic zones.