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03/18/1997 08:00:00

State-of-the-Art Seismic Network Gets First Trial-by-Fire During This Morning's 5.4-magnitude Earthquake

PASADENA—Los Angeles reporters and camera crews responding to a 5.4-magnitude earthquake this morning got their first look at the new Caltech/USGS earthquake monitoring system.

The look was not only new but almost instantaneous. Within 15 minutes of the earthquake, Caltech seismologists had already printed out a full-color poster-sized map of the region to show on live TV, and had already posted the contour map on the Internet. Moreover, they were able to determine the magnitude of the event within five minutes — a tremendous improvement over the time it once took to confirm data.

"Today, we had a much better picture of how the ground responded to the earthquake than we've ever had in the past," said Dr. Lucile Jones, a U.S. Geological Survey seismologist who is stationed at Caltech. "This was the largest earthquake we've had since September of 1995, and was the first time we've been able to use the new instruments that we're still installing."

The new instruments are made possible by the TriNet Project, a $20.75-million initiative for providing a state-of-the-art monitoring network for Southern California. A scientific collaboration between Caltech, the USGS and the California Department of Conservation's Division of Mines and Geology, the project is designed to provide real-time earthquake monitoring and, ultimately, to lead to early-warning technology to save lives and mitigate urban damage after earthquakes occur.

"The idea of Trinet was to get quick locations and magnitudes out, to get quick estimates of the distribution of the ground shaking, and a prototype early-warning system," Caltech seismic analyst Egill Hauksson said an hour after this morning's earthquake. "The first two of those things are already in progress. We are in the midst of deploying hardware in the field and developing data-processing software." TriNet was announced earlier this year when funding was approved by the Federal Emergency Management Agency. The new system relies heavily on recent advances in computer communications technology and data processing.

The map printed out this morning (the ShakeMap) is just a preview of future TriNet products. Caltech seismologist Kate Hutton gave a number of TV interviews in front of the map this morning. The map was noteworthy not only for the speed in which it was produced, but also for the manner in which information about the earthquake was relayed.

Instead of charting magnitudes, the map was drawn in such a way that the velocity the ground moved was shown with contour lines. The most rapid movement in the 5.4 earthquake this morning was about two inches per second at the epicenter, and this was clearly indicated in the innermost circle on the color map. Moving outward from the epicenter of the earthquake, the velocity of ground movement decreased, and this was indicated by lower velocity numbers in the outer circles.

The maps can also be printed out to show ground accelerations, which are especially useful for ascertaining likely damage in an earthquake area, Hutton said.

Later, the TriNet will result in prototype early warnings to distant locations in the Los Angeles area that potentially damaging ground shaking is on the way. After an earthquake occurs, the seismic waves travel a few kilometers per second, while communication transmission can travel the speed of light. Thus, Los Angeles could eventually receive warning of a major earthquake at the San Andreas fault some 30 to 60 seconds before the heavy shaking actually began in the city.

The total cost of the project is $20.75 million. FEMA will provide $12.75 million, the USGS has provided $4.0 million, and the balance is to be matched by Caltech ($2.5 million) and the DOC ($1.75 million). Several private sector partners, including GTE and Pacific Bell, are assisting Caltech with matching funds for its portion of the TriNet balance.

The TriNet Project is being built upon existing networks and collaborations. Southern California's first digital network began with the installation of seismographs known as TERRAscope, and was made possible by a grant from the L.K. Whittier Foundation and the ARCO Foundation. Also, Pacific Bell through its CalREN Program has provided new frame-relay digital communications technology.

A major step in the modernization came in response to the Northridge earthquake, when the USGS received $4.0 million from funds appropriated by Congress to the National Earthquake Hazard Reduction Program. This money was the first step in the TriNet project and the USGS has been working with Caltech for the last 27 months to begin design and implementation. Significant progress has already been made and new instrumentation is now operational:

o Thirty state-of-the-art digital seismic stations are operating with continuous communication to Caltech/USGS

o Twenty strong-motion sites installed near critical structures

o Two high-rise buildings have been instrumented

o Alarming and processing software have been designed and implemented

o Automated maps of contoured ground shaking are available on the Web within a few minutes after felt and damaging earthquakes (http://www-socal.wr.usgs.gov).

DOC's strong motion network in Southern California is a key component of the TriNet Project, contributing 400 of the network's 650 sensing stations. DOC's network expansion and upgrade through the funding of this project will allow much better information about strong shaking than was possible for the Northridge earthquake. This data is the key to improving building codes for more earthquake-resistant structures.

Written by Robert Tindol