HR: 17:15h
AN: S14B-06    [Abstracts]
TI: Slip-Length Scaling in Large Earthquakes: The Role of Deep Penetrating Slip Below the Seismogenic Layer
AU: * Shaw, B E
EM: shaw@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, United States
AU: Wesnousky, S G
EM: stevew@seismo.unr.edu
AF: Center for Neotectonic Studies, University of Nevada Reno, Reno, NV 89557, United States
AB: Coseismic slip is observed to increase with earthquake rupture length for lengths far beyond the lengthscale set by the seismogenic layer. The observation, when interpreted within the realm of static dislocation theory and the imposed limit that slip be confined to the seismogenic layer, implies that earthquake stress drop increases as a function of rupture length for large earthquakes and, hence, that large earthquakes differ from small. Here a three dimensional elastodynamic model is applied to show that the observed increase in coseismic slip with rupture length may be satisfied while maintaining constant stress drop across the entire spectrum of earthquake sizes when slip is allowed to penetrate below the seismogenic layer into an underlying zone characterized by velocity-strengthening behavior. Is this deep coseismic slip happening during large earthquakes? We point to a number of additional associated features of the model behavior which are potentially observable in the Earth. These include the predictions that a substantial fraction, of order a third of total coseismic moment, is due to slip below the seismogenic layer, and that slip below the seismogenic layer should be characterized by long risetimes and a dearth of high frequency motion.
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7218 Lithosphere (1236)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 7250 Transform faults
SC: Seismology [S]
MN: 2007 Fall Meeting