TY - JOUR
T1 - Retrieval of source parameters of an event of the 2000 West Bohemia earthquake swarm assuming an anisotropic crust
AU - Rössler, Dirk
AU - Krüger, F.
AU - Psencik, I.
AU - Rümpker, G.
PY - 2007
Y1 - 2007
N2 - 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 MT = 3.2 − 3.8 × 1014 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.
AB - 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 MT = 3.2 − 3.8 × 1014 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.
U2 - 10.1007/s11200-007-0012-9
DO - 10.1007/s11200-007-0012-9
M3 - Journal article
SN - 0039-3169
VL - 51
SP - 231
EP - 254
JO - Studia Geophysica et Geodaetica
JF - Studia Geophysica et Geodaetica
IS - 7
ER -