Earthquakes and Ground Motions - Earthquake Engineering for Structural Design - page 265

source. But this information was not enough to underline the differences between
the two earthquake types, knowing that the Northridge earthquake was produced
by a thrust fault source, while the Kobe earthquake by a strike-slip fault source.
The solution for this complex problem is based on the use of computational
methods in seismology in order to model the fault rupture and the propagation of
seismic waves. Seismology and Engineering Seismology have been strongly
affected by the set-up of high-performance computing tools (Bielak and Ghattas,
1999), especially related to the activity for searching for petroleum. During the first
step, only some supercomputers were used. Now, the developing software for
parallel supercomputers allows an increase in the amount of obtained data.
Simulation involving hundreds of thousands to millions degree of freedom requires
hundreds of megabytes to gigabytes of memory and billions of floating point
operations. Luckily, only the parallel computer provides a suitable environment for
solving such problems by distributing both the storage and computing among many
processors (Bao et al, 1996). Therefore, only by using the computing centers
equipped with a large number of supercomputers (such as Caltech Center,
Advanced Computing Research, CACR, at the California Institute of Technology,
Pasadena) are able to solve this huge computational problem.
Using the 256 processors of Caltech Center, the simulation of dynamic fault
ruptures was performed by Aagaard (2000). The discretization of the considered
volume of soil (Fig. 7.43) is using a hexahedral (six-sided) and tetrahedral (four-
sided) finite-element mesh with special elements for fault plane, which impose a
dislocation in finite-element model.
Figure 7.43 FE model for simulating the wave propagation:
Finite element, element for fault plane and soil mesh
(after Aagaard et al, 2001a)