HR: 11:35h
AN: S42B-06    [Abstracts]
TI: Estimates of Fault Area and Rupture Velocity for Long Duration Subduction Zone Earthquakes
AU: * Bilek, S L
EM: sbilek@ees.nmt.edu
AF: Earth and Environmental Science Dept., New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801 United States
AB: Previous studies of global subduction zone earthquake rupture processes have found examples of shallow earthquakes that exhibit depth dependent durations, with the longest durations observed for the several of the shallowest earthquakes. The long durations, after scaled for earthquake size, are comparable to those durations found for tsunami earthquakes. One model for tsunami earthquakes involves shallow faulting in regions of low fault zone rigidity or other variable friction conditions to explain the observed long earthquake source durations and efficient tsunami generation. A model of variable rigidity, and thus variable rupture velocity, is one end-member explanation for the global earthquake dataset as well. Depth dependent durations can also be explained through a model of variable stress drop. In the case of variable stress drop, rupture velocity and fault zone material properties are constant, suggesting that duration variations indicate variable scaled rupture areas for each earthquake. Here we analyze a subset of the global dataset, including earthquakes in the Alaska-Aleutian, Chile, Kamchatka, Peru, and Mexico subduction zones in an attempt to distinguish between the two end member models. This subset contains the longest duration earthquakes, as well as additional earthquakes with shorter durations for comparison. More refined estimates of the source time functions, durations, and depths are presented with analysis for source finiteness, rupture directivity effects, and variable focal mechanism effects. Fault rupture areas and rupture velocity estimates are also presented in order to describe the observed source duration pattern in terms of either the variable stress drop or rupture velocity models.
DE: 7230 Seismicity and seismotectonics
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting