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Riding that wave

VISUAL | December 7, 2011

Image of ground motion 75 seconds after the Magnitude 8 earthquake has initiated on the San Andreas fault near Parkfield (northern terminus of the dashed line, not shown). The waves are still shaking in the Ventura, Los Angeles, and San Bernardino areas (due to reverberations in their underlying soft sedimentary basins) while the rupture is still in progress, and the wave fronts are rapidly approaching San Diego. Click on the image to watch the simulation video. Image courtesy Amit Chourasia, San Diego Supercomputer Center, UC San Diego.

Advanced computer simulations and high-performance computers are helping to save the lives of people in earthquake prone areas. The adjacent video was created by the South California Earthquake Center in the U.S., and visualizes how the ground shakes from shock waves after a magnitude 8.0 earthquake has occurred.

The simulation follows the rapid expansion of an earthquake wave front on the San Andreas fault as it approaches the city of San Diego. The strongest motions correspond to a white color and the weakest, a red color, with the ground motion magnitude represented as a height field.

The leading edge of the rupture is a ‘cone like’ distribution of ground motions called a ‘Mach cone’. A Mach cone is the same effect when an aircraft exceeds the speed of sound or Mach 1, and a large pressure difference causes a shock wave called a Mach cone, which in turn creates a sonic boom.

Earthquake mach cones are difficult to observe, because they are rare, but essential in large earthquake ground motions. This visualization is being used to understand how buildings respond in large-scale earthquakes and eventually help engineers make safer structures.

This magnitude 8 simulation represents computation at the petascale level with over one quadrillion floating point calculations per second and 223,074 cores used in the analysis. Researchers at the earthquake institute created a parallel and scalable wave propagation software code called AWP-ODC for their research.

“It’s the largest and most detailed simulation of a major earthquake ever performed in terms of floating point operations, and opens up new territory for earthquake science and engineering with the goal of reducing the potential for loss of life and property,” said Yifeng Cui, a computational scientist at the South California Earthquake Center.

The project was funded by the U.S. National Science Foundation (NSF), and the simulation was performed using the NSF’s Kraken and the Department of Energy’s Jaguar high-performance computers.

The simulation was one of 10 winners of the ‘visualization night’ at the Scientific Discovery through Advanced Computing Program (SciDAC) event held in Denver, Colorado, in July 2011, supported by the U.S. Department of Energy Office of Science. More project winners can be seen here.