Seismological Laboratory, University of Patras, Greece
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The Basel earthquake of October 18, 1356 is
considered to be one of the most serious earthquakes in Europe (I0=IX,
M ≈ 6.5-6.9). The ground motion is modeled for the area of the city of
Basel and it’s vicinity. The numerical modeling consists of the
ﬁnite-extent source combined with the complex local structure in a
two-step hybrid 3D ﬁnite-difference (FD) method. The synthetic
seismograms are accurate in the frequency band 0-2.2 Hz. The 3D FD is
linear explicit displacement formulation using an irregular rectangular
grid including the topography.
The ﬁnite-extent source is adjacent to the free surface, because the fault has been recognized through trenching on the Reinach fault. For the 1356 Basel earthquake (Mw = 6.5), two rupture histories are computed by a pseudo-dynamic approach. Another source is a hypothetical earthquake with the characteristics of the 1999 Athens earthquake (Mw = 5.9), modeled by kinematic approach. The scenario includes the sources located to the East, South and West from the city. The local structure computational model is determined from the recently established P and S-wave velocity structure of the Basel area, including the topography. The results are compared to recently established 2D simulations. The ampliﬁcations with respect to a bedrock site are given for the various earthquake scenarios. The 3D modeling gives, in some areas, reasonably different behavior from the 2D computations. The existence of the edge effect proved to be strongly dependent on the position of the source.
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