PREPARATION STRESSED, NOT TREMOR PREDICTIONS.

Byline: Phil Davis Daily News Staff Writer

When the Northridge Earthquake struck along a previously unknown fault on Jan. 17, 1994, it demolished scientists' longtime hopes of predicting the Big One.

Within just seconds, the most costly temblor to strike an American city had forced seismologists to re-examine their goals and assumptions. Yet today, as Los Angeles approaches the quake's five-year anniversary, seismologists report there is good news.

Information gleaned from the quake is helping shape crude forecasts of impending trouble, useful in preparing structures for an eventual strike.

And the temblor's abruptness prompted government and scientists to spend nearly $30 million lacing Southern California with sensors that can instantly pinpoint quakes and eventually will issue alerts to outlying communities that a shock wave is on its way.

Seismologists say that despite billions of dollars spent, that is the best they can do with existing technology - fortifying the scientific school of thought that learning how to prepare for disaster is more prudent than trying to predict one.

``Predictions are not in our near future,'' said Tom Henyey, director of the USC Southern California Earthquake Center. ``The Northridge Earthquake gave us our first extensive set of ground motion readings in the L.A. Basin - possibly the all-time best readings.

``This enables us to predict what ground motion might be like in a certain area. We can plan for these things. This will save lots of money, and it's not going to cause panic like a prediction,'' Henyey said.

The magnitude 6.7 Northridge Earthquake struck at 4:31 a.m., killing 57 people as it destroyed more than 114,000 buildings and wrought havoc as far away as Santa Monica. The quake caused an estimated $13 billion to $20 billion in damage, making it the most expensive temblor to hit an American city, according to the Insurance Information Institute.

Seismologists later determined it occurred on a fault 12 miles beneath Reseda, despite the Northridge designation bestowed in the days after the quake.

New questions

Although the information gathered in the 30 seconds of shaking was the best ever recorded in centuries of earthquake study, the Northridge Quake still invited more questions than answers about how earthquakes work.

``It actually made things more complicated. Everyone would like to predict an earthquake, and many people are working in that area, but it's very difficult,'' said Paul Davis, a University of California, Los Angeles, professor of geophysics. ``If anything, Northridge sort of reinforced that belief because it happened in a place where we didn't expect a big earthquake.''

Among the many tidbits of progress science can claim: In October, seismologists found that wedges of rock buried beneath Santa Monica may help explain why the city suffered so much damage during the Northridge Earthquake, despite its distance from the epicenter.

The report stated that the immense rock structures separating the Santa Monica Mountains from the Los Angeles Basin amplified shaking and battered buildings more than scientists could easily explain.

And in 1994, scientists studying data from the Northridge Quake arrived at an unprecedented consensus that a temblor at least the size of the Northridge Quake will occur once every 40 years - but no one could say yet when or where.

Shaking up priorities

If Lucy Jones has her way, Southern California won't be caught entirely off-guard, largely because of a new, massive web of ground motion-mapping sensors and sophisticated computer equipment that was installed after the Northridge Quake.

It took the quake to refine the technology and prompt the purchase of better computers, triggering a fundamental shift in the philosophy of funding earthquake studies, said Jones, scientist in charge of the U.S. Geological Survey in Pasadena.

Before Northridge, quake-study funds came out of research grants. But after the quake and its unprecedented cost, the California Institute of Technology convinced Federal Emergency Management officials that some disaster-relief money would be well-spent building a network that can pinpoint vulnerable areas and better direct rescue efforts in the next major quake.

When the Northridge Quake hit, it overwhelmed the aging U.S. Geological Survey computer network, which mistook the main shock for a massive microwave burst.

``It was so much information, so rapidly, it confused our systems,'' Jones said. ``We couldn't talk to the computer. It was so busy recording the aftershocks, it took us half an hour to get the information.''

The glitch delayed rescue efforts.

The solution: TriNet, a $20.75 million ground motion-mapping system uses a network of 600 sensor stations that monitor Los Angeles' daily rumblings - most too small to be felt by humans. TriNet will also enable emergency officials to pinpoint the hardest-hit areas within five minutes of the disaster. Installation of the network began in 1997 and should continue through 2004. It will be maintained by the USGS, California Polytechnic State University, the state Office of Emergency Services and the state Division of Mines and Geology.

Jones said TriNet should eventually be able to provide a warning of a major quake if the fault lies outside the city. A quake at the San Andreas Fault, for instance, would be felt in downtown Los Angeles within about 30 seconds.

``There are a lot of things you can do in 30 seconds, if you have already planned what you're going to do,'' Jones said. ``You could stop nuclear reactions, stop trains and stop the handling of hazardous waste. You could move people away from open windows.''

The downside: The closer the quake, the less warning. There would have been no warning of Northridge, but rescuers would at least have known where to go.

Emergency response

``None of this was there when Northridge happened,'' Jones said. ``If we were to have Northridge today, we would be able to have information available for emergency responders within five minutes - if the Internet stays up. Five years from now, we'll be more reliable. We'll be able to get rid of the ifs.''

But, Jones added, one big question lingers: Will all this knowledge be used wisely?

Most of the buildings destroyed in the Northridge Quake - and in the temblor in Kobe, Japan, exactly a year later - did not meet current earthquake safety codes.

``There were surprises in the Northridge Earthquake, of course, but 95 percent of the damage was, we told you so,'' Jones said. ``Just understanding the problem doesn't make it disappear. No building code in the world is retroactive. That's the lesson learned from the earthquake, but I'm not sure how far the learning has gone.''

CAPTION(S):

4 photos

PHOTO Voices

(1 -- color) ``It was so difficult to rebuild. It took a day to reassemble each room. I would start off in one corner so it wouldn't be so overwhelming. I had a sliding glass door on my living room floor. It was crazy, absolutely crazy.

- Ray Barnes

record producer

Tarzana

(2 -- color) ``I've taken precautions such as fastening things to walls. I have an emergency kit and change of clothes in my car.''

- Jackie Harris

account manager

Valley Village

(3 -- color) ``It makes you understand how fragile life is. It teaches you respect for life, and to live day by day and appreciate your family. That could have been the end.

- Leon Gilbert

attorney

Encino

(4 -- color) ``The guy who ran a convenience store near my house was telling people to come in and get (supplies) free...It was nice to see the good side of human nature come out.''

- Gloria Ghaffari

account manager

Saugus