HR: 17:15h
AN: S34A-06    [Abstracts]
TI: Supershear Slip Pulse and Off-Fault Damage
AU: * Bhat, H S
EM: hbhat@fas.harvard.edu
AF: Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Dmowska, R
EM: dmowska@esag.harvard.edu
AF: Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Dmowska, R
EM: dmowska@esag.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: King, G
EM: king@ipgp.jussieu.fr
AF: Laboratoire de Tectonique, Institut de Physique du Globe de Paris, 4, Place Jussieu, Cedex 05, Paris, 75252 France
AU: Klinger, Y
EM: klinger@ipgp.jussieu.fr
AF: Laboratoire de Tectonique, Institut de Physique du Globe de Paris, 4, Place Jussieu, Cedex 05, Paris, 75252 France
AU: Rice, J R
EM: rice@esag.harvard.edu
AF: Division of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AU: Rice, J R
EM: rice@esag.harvard.edu
AF: Department of Earth and Planetary Sciences, Harvard University, 29 Oxford Street, Cambridge, MA 02138 United States
AB: We extend a model of a two-dimensional self-healing slip pulse, propagating dynamically in steady-state with a slip-weakening failure criterion, to the supershear regime, in order to study the off-fault stressing induced by such a slip pulse and investigate features unique to the supershear range. Specifically, we show that there exists a non-attenuating stress field behind the Mach front which radiates high stresses arbitrarily far from the fault (practically this would be limited to distances comparable to the depth of the seismogenic zone), thus being capable of creating fresh damage or inducing Coulomb failure in known structures at large distances away from the main fault. We allow for both strike-slip and dip-slip failure induced by such a slip pulse by evaluating Coulomb stress changes on both known and optimally oriented structures. In particular we look for features of supershear slip pulse that could nucleate a slip-partitioning event at places where reverse or normal faults exist near a major strike-slip feature. We apply this model to study damage features induced during the 2001 Kokoxili (Kunlun) event in Tibet, for which it has been suggested that much of the rupture was supershear. We argue that an interval of simultaneous induced normal faulting is more likely due to a slip partitioning mechanism suggested previously than to the special features of supershear rupture. However, those features do provide an explanation for otherwise anomalous ground cracking at several kilometers from the main fault. In the big bend region of the San Andreas Fault there is active thrust faulting nearby which might be activated by a supershear event. The most vulnerable locations would be those for which part of the presumably seismogenic thrust surface is within ~15-20 km of the SAF, which (considering dip directions) may include the Pleito, Wheeler Ridge, Cucamonga, Clearwater, Frazier Mountain, Alamo, Dry Creek, Arrowhead, Santa Ana, Waterman Canyon, and San Gorgonio faults, and reverse or minor right-reverse sections of the Banning and San Jacinto fault systems. Many nearby strike slip segments could be vulnerable to the distant stressing too, at least if not oriented too close to perpendicular or parallel to the SAF. The degree of vulnerability has a strong dependence, to be documented, on directivity of the rupture on the SAF and orientation of the considered fault segment. We also compare the damage induced by supershear slip pulse with their sub-Rayleigh analogues to look for unique signature left behind by such slip pulses in terms of off-fault damage. We show that off-fault damage is controlled by the speed of the slip-pulse, scaled stress drop, and principal stress orientation of the pre-stress field. We also make some estimates of fracture energy which, for a given net slip and dynamic stress drop, is lower than for a sub-Rayleigh slip pulse, because part of the energy fed by the far-field stress is radiated back along the Mach fronts.
DE: 4455 Nonlinear waves, shock waves, solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, DE: 7205 Continental crust (1219)
DE: 7209 Earthquake dynamics (1242)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7260 Theory
SC: Seismology [S]
MN: Fall Meeting 2005