SENSORS TO WATCH QUAKES DATA TO GUIDE RESCUES.

Byline: Holly Edwards Staff Writer

SANTA CLARITA - In about 9.5 million years or so, Santa Clarita and Oakland will be neighbors, experts say.

Meanwhile, Southern California residents can expect a bumpy ride as the Pacific Plate inches northward and collides with the North American Plate, generating an average of 30 small earthquakes each day, researchers say.

In future quakes, a network of 600 earthquake sensors placed throughout the region - including in Santa Clarita - will allow experts to determine in minutes where the strongest forces, and the most damage, occurred, said Tony Shakal, a seismologist with the California Department of Conservation.

``After the Northridge Earthquake, emergency responders didn't know where to concentrate their efforts,'' he said. ``Now we'll know where to put them in just a few minutes.''

The $20 million project, dubbed Trinet, is funded primarily by the Federal Emergency Management Agency, and is a collaborative among the state Department of Conservation, the United States Geological Survey and the California Institute of Technology.

In Santa Clarita, the sensors are housed in Fire Station 73 in Newhall, Fire Station 111 in Canyon Country and in two small buildings in Hasley Canyon and along the Old Ridge Route in Castaic, Shakal said.

All of the sensors - one for every ZIP code - are expected to be in place by the end of the year, Shakal said.

Until recently, those who measure the severity of earthquakes were limited by a network of scattered devices that did not allow them to determine quickly where the strongest shaking occurred, officials said.

As a result, it took several days for authorities to realize that Newhall had experienced virtually the full impact of the 6.7 magnitude Northridge temblor, said Shakal.

Encased in plain wooden boxes, the sensors may prove particularly crucial for the Santa Clarita Valley because much of the area is situated in the eastern end of the Ventura Basin - the deepest basin in Southern California, said Dr. Egill Hauksson, a seismologist at Caltech.

``Santa Clarita is a risky area because a lot of it lies within the basin, which can expect stronger shaking because the ground is softer,'' he said. The area is also surrounded by two faults, the Oakridge fault and the San Cayetano fault, he said.

The soft layers of sedimentation beneath much of the valley is one of the reasons the area was hit so hard by the 1994 Northridge Earthquake, which caused an estimated $428 million in damages valleywide, he said.

After an earthquake, the senors will relay the magnitude of the quake via phone lines to computers at the three agencies sponsoring the program.

Rescuers can then dispatch crews to the hardest-hit areas immediately, which could save lives, said Dr. Lucille Jones, a seismologist at USGS.

``If we don't get people out of collapsed buildings on the first day, most of them die,'' Jones said. ``The biggest thing this project will do is reduce the amount of time people are caught in buildings.''

The sensors will also enable researchers to record how the ground moves in an earthquake, which will allow engineers to design safer buildings and bridges, Jones said.

And, she said, faced with the unpredictable nature of earthquakes, designing safer structures is the most important safety step that can be taken.

``Emotionally, it's the unpredictability of earthquakes that makes them frightening,'' she said. ``But would you rather know an earthquake's going to happen five hours in advance, or know the building you're in isn't going to fall down?''

For scientists, the sensors may also hold the key to gaining a better understanding of the most perplexing of natural disasters.

``Because earthquakes occur so deep in the ground, the only information we get is what's recorded on our ground sensors,'' Jones said. ``And what we record is a wave, so what we really want to know is what is the source of the wave and what is its path.''

By recording where the strongest shaking occurred, scientists can learn how earthquake waves travel underground through various types of rock, which can in turn help them learn the waves' source and path, Hauksson said.

Researchers could then predict where the strongest shaking would occur in future quakes, he said.

And, according to Jones, that's about the best that science can do.

``We're pretty close to proving it's impossible to predict earthquakes,'' she said. ``Even if we knew when the 30 or so earthquakes were going to happen each day, as far as we can tell, the size of an earthquake is determined during the earthquake itself. The question now is, how do we live without prediction?''

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Photo:

(color) This earthquake sensor at L.A. County Fire Station 111 is part of a statewide system.

David R. Crane/Staff Photographer