## Retrieval of source parameters for local earthquakes
in anisotropic media

**D. Rössler,
I. Psencik,
F. Krüger & G. Rümpker **
### Summary

An inversion scheme to retrieve the characteristic of seismic point sources in anisotropic media
is proposed.

Moment tensors retrieved from waves generated by point sources in anisotropic media may
be biased if isotropy is assumed during inversion. Apparent volumetric components may be
obtained for shear sources and falsely interpreted in terms of tensile earthquakes. Similarly,
real volumetric components due to tensile faulting may not be visible in retrieved moment
tensors.

Instead of the moment tensor the geometry of the source is retrieved directly in our inversion.
The source geometry is dened by the orientation of the slip vector and the fault normal
as well as the strength of the event given by the length of the slip and the area of the fault. The
source geometry may be used to calculate the moment tensor. Our tests show that approximating
structural inhomogeneity instead of using homogeneous models is important to retrieve the
orientation of the source. However, accounting for inhomogeneity and anisotropy during inversion
yields more complete solutions. This allows accurate interpretation of the source geometry
in terms of shear and tensile faulting to identify volumetric source changes that occur during
rupturing.

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In: Seismic Waves in Complex 3-D Structures, Report 15,
pp. 333-344, Dep. Geophys., Charles Univ., Prague, 2005.

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