## Retrieval of source parameters of an event
of the 2000 West Bohemia earthquake swarm
assuming an anisotropic crust

**Dirk Rössler** ** , **
**Frank Krüger** ** , **
**Ivan Psencik** ** & **
**Georg Rümpker**
### Summary

We propose an inversion scheme for retrieval
of characteristics of seismic point
sources, which in contrast to common practice,
takes into account anisotropy. If
anisotropy is neglected during inversion,
the moment tensors retrieved from seismic
waves generated by sources situated in
anisotropic media may be biased. Instead of the
moment tensor, the geometry of the source
is retrieved directly in our inversion; if
necessary, the moment tensor can be then
determined from the source geometry
aposteriori. The source geometry is defined
by the orientation of the slip vector and the
fault normal as well as the strength of the
event given by the size of the slip and the area
of the fault. This approach allows direct
interpretation of the source geometry in terms of
shear and tensile faulting. It also makes
possible to identify volumetric source changes
that occur during rupturing.

We apply the described algorithm to one event
of the 2000 West Bohemia earthquake
swarm episode. For inversion we use information
of the direct P waves. The structure is
approximated by three different models
determined from travel-time observations. The
models are inhomogeneous isotropic,
inhomogeneous anisotropic, and homogeneous
anisotropic. For these models we obtain seismic
moments *M*_{T} = 3.2-3.8×10^{14} Nm and
left-lateral near-vertical oblique normal
faulting on a N-S trending rupture surface. The
orientation of the rupture surface is consistent
with fault-plane solutions of earlier studies
and with the spatial distribution of other
events during this swarm. The studied event
seems to be accompanied by a small amount
of crack opening. The amount of crack
opening is slightly reduced when the
inhomogeneous anisotropic model is assumed, but it
persists. These results and additional
independent observations seem to indicate that
tensile faulting occurs as a result of high
fluid pressure.

### Keywords

Seismic source, tensile faulting, seismic anisotropy, West Bohemia.

### Whole paper

The reprint is available in
PDF (3515 kB !).

*Stud. geophys. geod.*, **51** (2007), 231-254.

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