HR: 0800h
AN: S11B-1014    [Abstracts]
TI: Inversion for Seismic Moment Tensors in Anisotropic Media Using Standard Isotropic Techniques
AU: R\"o\ss{}ler, D
EM: diroess@rz.uni-potsdam.de
AF: Institute of Geoscience, University of Potsdam, Karl-Liebknecht-Str. 24/H25, Golm, 14476 Germany
AU: Kr\"uger, F
EM: kruegerf@geo.uni-potsdam.de
AF: Institute of Geoscience, University of Potsdam, Karl-Liebknecht-Str. 24/H25, Golm, 14476 Germany
AU: * R\"umpker, G
EM: rumpker@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AB: Although seismic anisotropy is commonly observed in regions of the Earth's crust and mantle, it is usually neglected during the inversion for source parameters of earthquakes. Here, we investigate how this simplification may influence the inversion for seismic moment tensors. Our approach is based on synthetic waveform modeling for moment-tensor sources in anisotropic media. The results are used as an input for the inversion routine. The forward modeling shows that anisotropy may cause apparent volumetric source characteristics. On the other hand, the true nature of tensile sources may be hidden by anisotropic effects. Varying the orientation of the anisotropic elastic tensor in the neighborhood of the source and in the surrounding medium greatly influences the calculated waveforms. Our examples indicate that the fault-plane orientation can be derived accurately if additional constraints are used in the inversion process (such as assuming a zero trace of the moment tensor). However, even if the fault plane is known, non-double-couple components are usually underestimated. The examples further suggest that, if anisotropy is restricted to the near-source region, moment tensors and anisotropic elastic constants may be derived simultaneously form the observed waveforms. The degree of anistropy determined by this method is within 3% of the true value, whereas the orientation of the elastic tensor differs by up to 10$^\circ$.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
SC: Seismology [S]
MN: 2004 AGU Fall Meeting