Earthquakes: The Quake Project

CMU scientists used the PSC's T3E and now up to 3000 processors on our terascale system, Lemieux, for problem sizes up to 100 million elements, to investigate how soil composition affects ground motion during earthquakes.

These first images and animations show their simulation of a 1994 Northridge earthquake aftershock. This area is an alluvial basin- soil and soft rock contained by a bowl shaped space within denser rock.

The following animation shows a surface view of displacement amplitude and is composited over landsat data (provided by Bill Harbert, U of Pittsburgh) to show the local terrain.

This volume rendering shows how the shock wave radiates upwards until it reaches less dense rock, then becomes amplified as it enters the basin.

These next two animations show visualizations of simulated ground motion of an earthquake generated along a vertical (strike-slip) fault. Oblique view from above and below ground, showing horizontal velocity amplitude pattern in the vicinity of the fault, at increasing times after onset of earthquake. Earthquake source originates near the far edge of the computational domain and travels along the fault toward the near edge. Seismic waves travel both perpendicularly to the fault and downstream from the epicenter. At first, ground motion is strongest in the direction parallel to the fault (initial red crescent moving away from fault), and later in the perependicular direction (initial green cresecent becoming red as it moves downstream). Peak fault-normal velocity is twice as large as peak fault-parallel velocity.

The two views below show the results of inversion of synthetic surface seismograms for a portion of the San Fernando Valley, California. The inverse problem is solved on a 129³ grid using an acoustic wave propagation forward model. Each animation compares the Inverted (left) with Target (right) compressional wave velocity. (wave velocity km/s, domain 32x32x16 [depth] km)

This image shows inversion of synthetic surface seismograms for soil stiffness of San Fernando basin model. (read left->right, top->bottom) First three images show progression of inverted models. Final image shows target basin.

Next is animation of surface response from a simulation of the 1994 Northridge earthquake in an 80x80x30 km³ Los Angeles Basin model. Color indicates magnitude of horizontal component of velocity.

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