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Importance of Bimaterial Interfaces for Earthquake Dynamics and Strong Ground Motion

Brietzke, Gilbert B., Alain Cochard, and Heiner Igel (2009), Importance of Bimaterial Interfaces for Earthquake Dynamics and Strong Ground Motion, Geophys. J. Int., doi:10.1111/j.1365-246X.2009.04209.x, in press.

Abstract
We perform a numerical investigation of dynamic ruptures on a bimaterial interface in
3D with regularized slip-weakening friction and a heterogeneous initial shear stress, and
discuss the resulting strong ground motion. To isolate effects introduced by the mate-
rial contrast we perform pairs of simulations with opposite material orientations as it has
been done by Andrews & Harris (2005). We show that for many parameter sets the dy-
namics of rupture propagation are significantly influenced by the broken symmetry due to
the material discontinuity during rupture propagation. The resulting slip histories of two
events with reversed orientations of the material contrast can deviate such that the ema-
nating waves lead to large differences in peak ground motion (PGV & PGA) even when
slip-distribution of the individual events are very similar and therefore their moment mag-
nitudes are basically identical. We also show that the wrinkle-like slip pulse specific to
the bimaterial mechanism can be nucleated naturally from an initially crack-like mode of
rupture when the initial stress allows for large propagation distances. Once such a pulse
has been nucleated it travels at a dominant propagation speed close to the generalized
Rayleigh velocity. The dynamic weakening of the fault due to the normal stress alteration
during slip allows nucleating ruptures to overcome asperities of low initial shear stress in
the preferred direction, which is the direction of slip on the seismically slower side of the
fault. In such situations the orientation of the material contrast determines rupture extent
and therefore the size of the earthquake, potentially by orders of magnitude.
Further information
BibTeX
@article{id1329,
  author = {Gilbert B. Brietzke and Alain Cochard and Heiner Igel},
  journal = {Geophys. J. Int.},
  note = {in press},
  title = {{Importance of Bimaterial Interfaces for Earthquake Dynamics and Strong Ground Motion}},
  year = {2009},
  language = {en},
  url = {http://www.geophysik.uni-muenchen.de/~brietzke/pubs/GJI-08-0394{\_}R1.pdf},
  doi = {10.1111/j.1365-246X.2009.04209.x},
}
EndNote
%0 Journal Article
%A Brietzke, Gilbert B.
%A Cochard, Alain
%A Igel, Heiner
%D 2009
%J Geophys. J. Int.
%T Importance of Bimaterial Interfaces for Earthquake Dynamics and Strong Ground Motion
%U http://www.geophysik.uni-muenchen.de/~brietzke/pubs/GJI-08-0394_R1.pdf
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