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**Table 1:** Source characteristics.

**Table 2:** Characteristics of San Fernando Basin meshes.

**Figure 1:** The Archimedes system.

Click to take a close look (Same for figures below)

**Figure 2:**
Near-surface distribution of shear-wave velocity in the San Fernando Valley; actual depth is 1m.

**Figure 3:** Nodal distribution for the San Fernando Valley. Node
generation is based on an octree method that locally resolves the
elastic wavelength. The node distribution shown here is a factor of 12
coarser in each direction than the real one used for simulation, which
is too fine to be shown, and appears solid black when displayed.
However, the relative resolution between soft soil regions and rock
illustrated here is similar to that of the 13 million node model we
use for simulations.

**Figure 4:** Tetrahedral element mesh of the San Fernando Valley. Maximum
tetrahedral aspect ratio is 5.5. Again, for illustration purposes,
the mesh shown is much coarser than those used for simulation.

**Figure 5:** Mesh partitioned for 64 subdomains.

**Figure 6:** Communication graph for the partitioned element mesh
depicted in Fig. 5.

**Figure 7:**
Horizontal surface velocity seismogram of the E-W component along
the d-d axis shown in Fig. 2.

**Figure 8:**
Horizontal surface velocity seismogram of the N-S component along
the d-d axis shown in Fig. 2.

**Figure 9:**
Distribution of maximum horizontal surface displacement.

**Figure 10:**
Surface distribution of the amplitude of the Fourier Transform of the E-W displacement component for a frequency of 1.45Hz.

**Figure 11:**
Displacement response spectrum for a simple oscillator with Hz and 5% critical damping.

**Figure 12:**
Displacement response spectrum for a simple oscillator with Hz
and 5% critical damping.

**Figure 13:** Timings in seconds
on a Cray T3D as a function of number of processors (PEs), excluding
I/O. The breakdown of computation and communication is shown. The mesh
is `sf2`, and 6000 time steps are carried out.

**Figure 14:** Aggregate performance on Cray T3D
as a function of number of processors (PEs). Rate measured for
matrix-vector (MV) product operations (which account for 80% of the
total running time and all of the communication) during 6000 times
steps.

**Figure 15:** T3D wall-clock time in microseconds per time step per
average number of nodes per processor (PE), as a function of number of
processors. This figure is based on an entire 6000 time step
simulation, exclusive of I/O. The `sf1b` result is based on a
damping scheme in which in Eq. 6 so
that only one matrix-vector product is performed at each time step.

Wed Apr 2 16:22:44 EST 1997