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Primary Author Information
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| Name |
Ivo Oprsal |
| Affiliation |
Swiss Seismological Service, ETH Zurich, Switzerland, on leave from
Faculty of Mathematics and Physics, Charles University in Prague, Czech
Republic |
| Co-Author
Information |
| Co-Author
- 1 |
Name |
Johana Brokesova |
| Affiliation |
Faculty of Mathematics and Physics, Charles University in Prague, Czech Republic |
| Co-Author
- 2 |
Name |
Jiri Zahradnik |
| Affiliation |
Faculty of Mathematics and Physics, Charles University in Prague, Czech Republic |
| Co-Author
- 3 |
Name |
Domenico Giardini |
| Affiliation |
Swiss Seismological Service, ETH Zurich, Switzerland |
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Abstract Information
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| Abstract Number |
3 |
| Abstract Title |
3D FINITE-DIFFERENCE SEISMIC MODELING - COMBINED EFFECTS BY HYBRID METHODS |
| Presentation Style |
ORAL |
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Abstract Submission
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| Speaker |
Primary Author
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| Abstract Body Preview |
| Complex interactions resulting in the earthquake ground motions can be, in
many cases, efficiently modelled by hybrid methods. Our two-step hybrid
method combines an arbitrary 3D method evaluating the source and path
effects, and the 3D finite differences (FD) to incorporate the site
features. In the 1st step we use ray, discrete wavenumber
(DWN), or FD method to simulate the source and path effects in a
background regional structure. The regional model is considerably simpler
than the local structure which is absent in the 1st-step model.
The complex local structure is enveloped in a formal box of receivers
called 'excitation box' (EB). The wavefield, due to the source and path,
is recorded at EB and stored on a disk as so-called excitation. In the
2nd step, the wavefield in a relatively small model containing
only the EB and its vicinity is computed. At this step, the local site
structure is included inside the EB. The wavefield from the 1st
step is injected at the EB into the 2nd-step model. The
2nd step is based on 3D FD performing on irregular rectangular
grid. The FD approximation is of a second-order accuracy, the boundary
conditions at the material interfaces are approximated via treatment of
effective (geometrically averaged) material parameters. The EB is fully
permeable in both steps and the result comprises all effects of the
source, path, and site. The computational cost and memory requirements are
significantly reduced compared to the case of all-in-one FD method. In our
examples, the 1st-step crustal structure is 1D and the source
is represented by a point double couple. The free surface is non-planar,
the example of a local structure is a modified Volvi-Lake site with Vp/Vs
~ 4 and maximum ratio of the velocities Vpmax/Vsmin
~ 10. The maximum frequency of the synthetics is 5Hz and the distance of
the site from the source is ~ 10km. The comparison of the results for the
ray-FD, DWN-FD, and FD-FD hybrid solutions shows a very good agreement, in
spite of the fact that the ray excitation contains less complete wavefield
than the DWN and FD excitations. The whole 2nd-step FD modeling
needs only 6 hours on P3 1Ghz, and this makes the hybrid method an
effective and competitive tool for the earthquake ground motion
computations.
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Symposium or Workshop (First Preference)
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| Symposium or Workshop (First Preference) |
SS04 |
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Symposium or Workshop (Second Preference)
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| Symposium or Workshop (Second Preference) |
SS02 |
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Keyword One
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| Keyword One |
7212 |
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Keyword Two
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| Keyword Two |
7260 |
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Keyword Three
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| Keyword Three |
0902 |
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Is a Student Author presenting the paper?
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| Student Paper |
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Equipment Requested for Presentation
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| Equipment Requested for Presentation |
Projector for PC presentation |
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Notes
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| Notes |
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