This paster was presented at AGU 2002 Fall Meeting, December 6-10, 2002, San
3D Finite-difference Modeling of Strong Ground
Motion in the Upper Rhine Graben - 1356 Basel earthquake
I. Oprsal (1,2), D. Faeh (1), D. Giardini (1),
Swiss Seismological Service,
ETH-Hoenggerberg/HPP, CH-8093 Zuerich, Switzerland.
Department of Geophysics, Charles University,
Ke Karlovu 3, 121 16, Prague, Czech Republic,
The disastrous Basel earthquake of October 18, 1356 (I0=X,
M ≈ 6.9), appeared in, today seismically modest, Basel region (Upper
Rhine Graben). The lack of strong ground motion seismic data can be
effectively supplied by numerical modeling. We applied the 3D finite
differences (FD) to predict ground motions which can be used for
microzonation and hazard assessment studies.
The FD method is formulated for topography models on irregular
rectangular grids. It is a 3D explicit FD formulation of the hyperbolic
differential equation (PDE). Elastodynamic PDE is solved in the time
domain. The Hooke’s isotropic inhomogeneous medium contains
discontinuities and a topographic free surface.
The 3D elastic FD modeling is applied on a newly established P and
S-wave velocities structure model. This complex structure contains main
interfaces and gradients inside some layers. It is adjacent to the
earth surface and includes topography (Kind, Faeh and Giardini, 2002, A
3D Reference Model for the Area of Basel, in prep.). The first attempt
was done for a double-couple point source and relatively simple source
function. Numerical tests are planned for several finite-extent source
histories because the 1356 Basel earthquake source features have not
been well determined, yet. The presumed finite-extent source is adjacent
to the free surface. The results are compared to the macroseismic
information of the Basel area.
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