Hybrid GPS-Seismic System Aims to Accelerate Earthquake Hazard Response

Japanese seismologists required approximately 20 minutes to accurately determine the full magnitude of last March's massive earthquake off Japan, precious moments for disaster response activation. Now scientists at Scripps Institution of Oceanography at UC San Diego are developing a next-generation detection system they believe could drastically shrink that assessment time down to two to three minutes.

Traditional seismic instruments charged with determining vital earthquake information for rapid hazard assessment have relied on devices that measure ground motions with exquisite precision, but lack the ability to produce rapid views of large seismic events because they do not directly measure ground motion. GPS networks do and therefore are complementary to the more precise seismic data.

At the 2011 American Geophysical Union Fall Meeting in San Francisco, Scripps research geodesist Yehuda Bock, director of the Scripps Orbit and Permanent Array Center (SOPAC), and Scripps graduate students Brendan Crowell and Diego Melgar, will present plans to combine the best of both worlds. The researchers hope to have a new system in place in six months to forecast, assess and even mitigate large natural hazard events as part of a new information system that could benefit first responders, other public safety decision makers and eventually the public. (IN42A-01 · Thursday, Dec. 8, 10:20 a.m. · Moscone Room 102)

Bock and his team are retroactively testing the system on the devastating March 11 magnitude 9 Tohoku-Oki earthquake as well as other large earthquakes such as the 2010 7.2 quake in Baja California's El Mayor-Cucapah region.

"Early warning systems are typically done with seismic instruments, which detect the primary wave that hits the monitoring stations and then there's somewhat of a prediction about when the secondary waves will arrive and how intense they will be," said Bock. However, seismic instruments alone are not suitable for responding to large earthquakes, he said, since they cannot rapidly distinguish between a magnitude 6.5 and a magnitude 9 event.

"For tsunamis and emergency alerts to major cities, there's a window of opportunity to provide a warning," he said. "Our approach using both GPS and seismic instruments can characterize events within two to three minutes-a significant improvement since the first devastating tsunami waves in Japan arrived 30 minutes after the earthquake."

In the tectonically active Western United States, hundreds of real-time GPS stations are now transmitting earthquake data from Southern California, throughout the San Andreas Fault, the San Francisco Bay area and the Pacific Northwest.

Bock and his team are incorporating individual seismic stations featuring earthquake-detecting accelerometer instruments into a real-time "geodetic sensor web" in which instruments pool information, thereby enhancing the fidelity of the entire seismic/GPS system. He and Melgar are working with Mexican authorities to upgrade their national seismic network with real-time GPS technology developed at Scripps.

The research is being funded by NASA's Advanced Information Systems Technology (AIST) program through its Earth Science Technology Office (ESTO).

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