HR: 10:20h
AN: S52A-01    [Abstracts]
TI: Dynamic rupture of a fault kink in antiplane model
AU: Adda-Bedia, M
EM: adda@lps.ens.fr
AF: Laboratoire de Physique Statistique, Ecole Normale Superieure 24 rue Lhomond, Paris Cedex 05, 75231 France
AU: * Madariaga, R
EM: madariag@geologie.ens.fr
AF: Laboratoire de Geologie, Ecole Normale Superieure 24 rue Lhomond, Paris Cedex 05, 75231 France
AB: We study the propagation, seismic radiation and energy balance of a two-dimensional antiplane crack that propagates at a constant sub-shear rupture velocity when it encounters a geometric discontinuity on the fault. We solve exactly the case of a kink of arbitrary angle as well as that of a finite unbreakable barrier that serves as a model. The solution obtained by a variation of the Cagniard method can only be computed numerically, but it is complete, so that we can examine the difference between near and far field as well as detailed energy flow, radiation patterns and frequency dependence of the radiation. Before it reaches the kink rupture emits seismic energy continuously at a rate controlled by the load of the fault and rupture speed. When it encounters the kink rupture emits an ω^-2-like wave and seismic energy flow changes abruptly. Later as the rupture propagates along the kink it adjusts its rupture speed and produces continuous radiation at a different rate from which it had before the kink. Radiation pattern from the kink phase is not of double couple type and, curiously, the near and far field of the velocity field have the same r^-1/2 decay with distance r from the tip (Eshelby, 1969). The static stress field around the fault, obtained once rupture has been completed, presents a weak local singularity near the kink. Comparing our results with those of a model with a barrier it is possible to completely identify the origin of seismic radiation with the fault segment that generates it.
DE: 7209 Earthquake dynamics (1242)
SC: Seismology [S]
MN: Fall Meeting 2005