San Diego Supercomputer Center at UC San Diego. Photo by Alan Decker.

ASKING NOT IF, BUT WHEN?
SAN DIEGO SUPERCOMPUTER CENTER EARTHQUAKE SIMULATIONS

Snapshot of the ground motion after the magnitude 8 simulation has initiated on the San Andreas fault near Parkfield, California (the northern terminus of the dashed line). The waves (orange and yellow) shake through the Ventura, Los Angeles, and San Bernardino areas due to reverberations in their underlying soft sedimentary basins while the rupture is still in progress, spreading out toward the coast and the San Diego area. Image by Amit Chourasia, San Diego Supercomputer Center, UC San Diego.

Seismologists have long been asking not if, but when the Big One will strike Southern California. Simulating the magnitude and variations of the shaking throughout the region could guide emergency planning in the Golden State.

In 2010, researchers at the San Diego Supercomputer Center (SDSC) at UC San Diego and San Diego State University created the largest-ever earthquake simulation, for a magnitude 8.0 (M8) rupture of the entire southern San Andreas fault. The simulation provided more accurate insight into the nature of the shaking anticipated from a large earthquake on the fault. About 25 million people reside in that area, which extends as far south as Yuma, Arizona, and Ensenada, Mexico, and runs up through California as far north as Fresno. Similar large-scale earthquake simulations can be used to evaluate earthquake early-warning planning systems, and help engineers, emergency response teams, and geophysicists better understand seismic hazards in California and around the world.

The simulation project, led by the Southern California Earthquake Center (SCEC), was selected as a finalist for the Gordon Bell Prize, awarded annually for outstanding achievement in high-performance computing applications at the annual International Conference for High Performance Computing, Networking, Storage, and Analysis. Funded through a number of National Science Foundation grants, the SDSC simulation was the most detailed ever performed of a major earthquake in terms of floating point operations, or calculations per second. The project opens up new ways for earthquake science and engineering to reduce the potential for loss of life and property.

As a follow-up to the simulation, the research team will analyze potential damage to buildings, including high-rises in Los Angeles, based on simulated ground motions. High-rise buildings are more susceptible to the low-frequency shaking, a roller-coaster-like motion, while smaller structures usually suffer more damage from the higher-frequency shaking, which feels more like a series of sudden jolts.