Citation: Oprsal, I., Brokesova, J., Faeh, D., Giardini, D., 2002. 3D
Hybrid Ray-FD and DWN-FD Seismic Modeling For Simple Models Containing
Complex Local Structures, Stud. Geophys. Geod., 46, 711-730.
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3D Hybrid ray-FD and DWN-FD Seismic Modeling For
Simple Models Containing Complex Local Structures
I. Oprsal (1,2), J. Brokesova (2), D. Faeh(1), D. Giardini (1),
Swiss Seismological Service,
ETH-Hoenggerberg/HPP, CH-8093 Zuerich, Switzerland.
e-mail: email@example.com, firstname.lastname@example.org
Department of Geophysics, Charles University,
Ke Karlovu 3, 121 16, Prague, Czech Republic,
Hybrid approaches find broad applications wherever
all-in-one modeling of source, path, and site effects is too
expensive. Our new 3D hybrid approach allows to compute the seismic
wavefield in elastic isotropic models containing a complex local
structure embedded in a large, but considerably simpler, regional
structure. The hybrid modeling is realized in two successive steps.
In the 1st step, the ray or discrete wave number (DWN) method is used
to compute the seismic wavefield due to the source and simple regional
structure. The complex local structure is not present. Thus, the
excitation contains the source and regional path effects. The time
history of this wavefield (excitation), recorded at the points of so
called excitation box, is stored on a disk. The excitation box
envelopes a small portion of a computational domain.
The 2nd step of the hybrid method, now containing the complex local
structure, is computed by ﬁnite diﬀerences (FD) inside the excitation
box and its close vicinity. The excitation from the 1st step is now
used to inject the 1st step waveﬁeld into the 2nd step computation.
After that, the hybrid combination of the 1st and 2nd steps contains
the source, regional path, and local structure eﬀects at reasonably
lower computational costs than in case of all-in-one modeling. The
3D ray-FD method is tested on models in which the locally complex
structure is the well-known Volvi lake basin, embedded in various 1D
structures. The waveﬁeld is excited by the point source situated
outside the basin. Although the structure outside the excitation box
may be less dimensional (2D, 1D, homogeneous), the whole problem is
actually 3D due to the 3D features of the structure inside the
excitation box, 3D shape of the excitation box, and arbitrary source -
excitation-box conﬁguration. Simple (1D) structures outside the
excitation box allow for comparison with the alternative hybrid DWN-FD
results. However the ray method is suitable for computation of 3D
regional structures outside the excitation box. The results from both
approaches show a very good agreement for realistic crustal and local
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