iSGTW Feature - Anticipating the big one

Feature - Anticipating "The big one"

Click here or on image to view the animation.

The detailed, perspective views show the ground shaking from a viewpoint two miles (three kilometers) above the earth looking towards each location. The left panel shows a map view of the area with the fault rupture highlighted in red, the epicenter (location where the rupture starts) identified by the red ball, and the location shown in the right panel labeled in yellow. In the right panel the deformation of the ground associated with the propagation of the seismic waves is exaggerated by a factor of 1000. Simulations developed by the Southern California Earthquake Center ShakeOut Simulation workgroup.

Animations courtesy of the U.S Geological Survey and the Southern California Earthquake Center.

At 10 a.m. on November 13, 5.3 million people in Southern California participated in the largest earthquake preparedness activity in U.S. history.

The Great Southern California ShakeOut - an earthquake drill that was a collaboration between the United States Geological Society, the National Science Foundation, and the Southern California Earthquake Center (SCEC), among others - provided detailed information to the public about what would happen in the event of a magnitude 7.8 earthquake.

The effort required hundreds of the nation's top seismologists, thousands of years of collective research, and the combined computational capability of some of the world's most powerful supercomputers, including Ranger at the Texas Advanced Computing Center (TACC), Kraken at the National Institute of Computational Sciences (NICS), and Datastar and Intimidata at the San Diego Supercomputer Center. All three supercomputer sites are part of TeraGrid, the nation's largest open scientific discovery infrastructure.

When the Earth Moves

Over the last decade, SCEC has begun to transform seismic hazard analysis - the art of predicting and mapping the effect of an earthquake - from an empirical backward-looking discipline to a predictive science where researchers actually simulate the earthquake process in advance.

"We model how waves are generated by the fault, and how they travel outward from the fault and interact with complex three-dimensional geological structures, such as the sedimentary basins," said Thomas Jordan, director of SCEC.

Click here or on image to view the animation.

This movie shows a view of southern California with the seismic waves radiating outward from the fault as the rupture propagates towards the northwest along the San Andreas fault.

Animations courtesy of the U.S Geological Survey and the Southern California Earthquake Center.

To create accurate predictions, scientists need both the most inclusive model of earthquake physics and the highest-resolution simulation possible. These two factors determine the computational workload.

Run several times on several different high-performance computing systems, each ShakeOut simulation used increasing physical reality and resolution. The most advanced of these simulations, "ShakeOut D," performed on the Ranger supercomputer at TACC, simulated the rupture and its impact with a 100-meter resolution over a three-dimensional area approximately 600 kilometers long by 300 kilometers wide by 80 kilometers deep. It stands as a milestone for seismology and for computational science generally.

The simulation was not only a milestone in terms of processing power, said Yifeng Cui, senior computational scientist at the San Diego Supercomputer Center. It was also a significant advance in terms of memory usage, input and output, data transfer, and storage, each of which required unique solutions.

The Real Aim

For the next-generation seismic hazard mapping, the team has a much more ambitious goal. They aim for a physics-based, probabilistic seismic hazard analysis that will transform the way scientists and engineers actually use seismic hazard analysis and build buildings.

"We're trying to change the way people think about and live with earthquakes," Jordan said. "In the future, the ShakeOut project is going to save lots of lives and dollars."

-Aaron Dubrow, TACC
Adapted with permission from the original.