Retrieval of source parameters for local earthquakes in anisotropic media

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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