HR: 14:00h
AN: U53A-02 INVITED    [Abstracts]
TI: THE 2007 BENGKULU EARTHQUAKE SERIES IN THE CONTEXT OF MEGA-RUPTURES OFF SOUTH SUMATRA
AU: * Okal, E A
EM: emile@earth.northwestern.edu
AF: Dept. Earth Planet. Sci., Northwestern University, Evanston, IL 60208, United States
AU: Ebeling, C W
AF: Dept. Earth Planet. Sci., Northwestern University, Evanston, IL 60208, United States
AU: Stein, S
AF: Dept. Earth Planet. Sci., Northwestern University, Evanston, IL 60208, United States
AU: Synolakis, C E
AF: Dept. Civil Engin., Univ. Southern Calif., Los Angeles, CA 90089, United States
AB: We present a seismological and tectonic study of the 2007 Bengkulu series, including an evaluation of the source characteristics of the main three events based on quasi-real time estimators, including the Energy-to-Moment parameter THETA, which suggests a trend towards slowness for the main shock at 11:10 UTC. While the earthquakes took place within the fault area of the great 1833 earthquake, in the probable context of Coulomb stress transfer from the 2004 and 2005 events, the mainshock and its immediate aftershocks define a faulting area significantly smaller than that of the 1833 event, and a preliminary review of plate kinematic models also suggests that the 2007 shock did not release the full strain accumulated since 1833. This is also supported by the seismic moment of the Bengkulu event (5E28 dyn*cm), and by preliminary modeling of the moderate near field tsunami (see Borrero et al., this session). In this context, we address the question of how much slip remains to be released along the 1833 rupture zone and to the South of it, and more generally of the ability for a large, but not gigantic event, to act as a barrier to the propagation of rupture during a future mega-earthquake. Namely, do the 2007 events preclude the future occurrence of a mega-earthquake whose rupture would over-ride the Bengkulu fault area? Historical records in Central and South Peru, as well as the over-riding by the 2004 Sumatra rupture of the 1881 Car Nicobar fault zone, would suggest a "cautiously negative" answer, casting a pessimistic note on far-field tsunami risk for the Southwestern Indian Ocean. ~
DE: 4564 Tsunamis and storm surges
DE: 7215 Earthquake source observations (1240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Union [U]
MN: 2007 Fall Meeting