HR: 11:35h
AN: S32B-06 INVITED     [Abstracts]
TI: 3D non-Planar Finite Difference Dynamic Rupture: Application to the Landers Earthquake
AU: * Cruz-Atienza, V M
EM: cruz@geoazur.unice.fr
AF: Geosciences Azur, 250 rue A. Einstein, Sophia Antipolis, Valbonne, 06560 France
AU: Virieux, J
EM: virieux@geoazur.unice.fr
AF: Geosciences Azur, 250 rue A. Einstein, Sophia Antipolis, Valbonne, 06560 France
AU: Aochi, H
EM: H.Aochi@brgm.fr
AF: BRGM/ARN/MAS, 3 avenue Claude Guillemin, BP6009 Cedex 2, ORLEANS, 45060 France
AU: Peyrat, S
EM: peyrat@geoazur.unice.fr
AF: Geosciences Azur, 250 rue A. Einstein, Sophia Antipolis, Valbonne, 06560 France
AB: Many aspects of seismic complexity have been explained in the last thirty years thanks to the development of numerical approaches allowing seismologists to simulate the dynamic rupture of earthquakes. Heterogeneities in both the initial stress field and the surrounding medium are extremely important elements. The constitutive law describing the physics of the breakdown process which relates the fault friction to fault kinematics is also determinant. However, given the increasing amount of high quality seismological data, more sophisticated approaches are needed to explain observations so that others important physical factors, such as the real fault geometry, could be integrated into simulations. Bearing in mind these new high quality observations along with the current computational power, a great interest has arisen in the last five years to develop 3D numerical codes to simulate earthquakes with real fault geometries. Recently, Cruz-Atienza and Virieux (2004) have introduced a 2D finite difference (FD) approach for modeling the dynamic rupture of non-planar faults. In this work we analyze the 3D extension of such an approach. On that account, the new 3D code may consider arbitrary heterogeneous media, composite friction laws and non-planar fault geometries. The numerical criteria for rupture boundary conditions to model rupture processes accurately were determined experimentally finding consistency with those determined for the 2D case: the source is discretized by a set of numerical cells. Given a spatial grid step for wave propagation, the number of grid nodes contained in each cell should be adapted accordingly. The smaller the spatial step the greater the number of nodes. We have performed dynamic rupture simulations for different curved 3D faults and compared results with those given by a BIE method (Aochi et al., 2000). Consistency between solutions yielded by different numerical approaches is essential since it is the only way to have confidence in these kinds of complex simulations for which no theoretical solutions are available. This benchmarking exercise has also allowed us to better understand and quantify the effect of fault curvature on near-source seismograms and fault solutions. Finally, we applied our numerical approach to model the 1992 Landers earthquake (Mw=7.3). Several simulations were carried out including a heterogeneous initial stress field, layered elastic medium and the non-planar fault trace geometry. Complexity in near-field seismograms enhances the importance of both a heterogeneous surrounding medium and non-planar fault geometry due to their intimate interaction during rupture process. Aochi, H., E. Fukuyama and M. Matsu'ura, 2000, Pure. Appl. Geophys., 157, 2003-2027. Cruz-Atienza, V.M. and J. Virieux, 2004, Geophys. J. Int., 158, 939-954.
DE: 7260 Theory and modeling
DE: 7209 Earthquake dynamics and mechanics
DE: 7212 Earthquake ground motions and engineering
DE: 3230 Numerical solutions
SC: Seismology [S]
MN: 2004 AGU Fall Meeting