THE BAY AREA QUAKE : What Next? : PONDERING THE LESSONS, HEALING THE SCARS : Seismologist’s Dream: Data on a Live Quake : Geophysics: Sensors in high-rises and forests capture information that may be helpful in determining future of millions living in temblor zones.

Shovels at their sides and geophysical lust in their hearts, seismologists were tramping through the redwood-studded beauty of the Santa Cruz Mountains this week in search of answers.

In cluttered offices, others can tap into computer networks to look at what the earthquake wrought. Still others were anticipating reviewing data captured by ground-motion detectors placed in the basements of high-rises that swayed like metronomes but survived.

The geophysics research community even dispatched a seismology SWAT team to aim a new, smarter generation of earth monitors at the spot where the Earth shuddered.

All because the 6.9-magnitude quake on the San Francisco Peninsula promises answers that can only be found in the rubble of yesterday’s tragedies--and the sooner the data can be gathered, the better.

Learning how the rupture near Santa Cruz occurred could offer scientists the best clues ever on the seismic future of the millions of people who live within shaking distance of potentially more destructive quakes.

The relative primitiveness of much of the earthquake monitoring network--the legacy of a decade of federal budget cuts, scientists grumble--means it will take weeks for much of the data to be gathered by hand. But, for men and women accustomed to spinning geophysical theory from a few tufts of geologic history, this is the chance of a lifetime.

“There’s great excitement. I hate to say this is a seismologist’s dream, but this quake is essentially what front-line seismology is all about,” said Art Lerner-Lam, a seismologist at Lamont-Doherty Geological Observatory in New York. “The opportunity for getting data that can really begin to address some of the problems (in seismology) just can’t be missed.”

What some might view as morbidly detached scientific interest is actually a quiet conviction that meticulous studies will save lives.

For Southern California, perhaps the biggest scientific boon from the quake is likely to come from the comparisons that can be made between that section of the San Andreas Fault and similar sections near the Los Angeles area.

One of the first geophysicists to pack his hiking boots and go to Santa Cruz this week was Kerry Sieh of Caltech. In the past, Sieh has used a backhoe to dig up evidence that the portion of the southern San Andreas in the Mojave Desert moved less than adjoining sections during the last large earthquake there, in 1857. This is pertinent to Tuesday’s quake, because a similar “slip deficit” had been noted in the Santa Cruz section of the San Andreas.

Indeed, it was for this reason that a 1985 research paper by Christopher Scholz of Lamont-Doherty predicted a 6.9-magnitude earthquake would occur in the Santa Cruz segment because, during the 1906 San Francisco earthquake, the fault slipped only a third as much there as it did elsewhere. The two sides of the fault moved only about three feet past each other; in San Francisco, there was eight to nine feet of movement.

Many scientists believe such “slip deficits” occur where there are slight bends in the fault--as is the case just southwest of Palo Alto on the Santa Cruz segment, and all along the San Andreas in Southern California.

A geophysicist at USC, Egill Hauksson, was ready this week to declare the Santa Cruz quake as evidence buttressing Sieh’s work, and as an indicator of size for the next big quake on the southern part of the San Andreas.

“In my mind, what it suggests is that, when we have the great earthquake on the southern San Andreas, if it starts in the Coachella Valley (near Indio), maybe that earthquake is going to continue up into the Mojave segment and maybe all the way into the Cajon Pass,” Hauksson said. That covers nearly 200 miles.

The slip deficit along the southern San Andreas has been one of the reasons that earthquake forecasters believe there is at least a 60% chance of a quake of 7.5 or 8 magnitude somewhere along the southern San Andreas within the next 30 years. The subsection considered at highest risk of a quake that size is the Coachella Valley segment.

Indeed, Tuesday’s quake lent support to these figures, contained in a July, 1988, report that was the U.S. Geological Survey’s first attempt at issuing formal earthquake forecasts.

“I think the one good thing that’s come out of this whole disaster is that it did happen where we had expected it to happen,” said Stuart Nishenko of the National Earthquake Information Center in Colorado, one of a fledgling group of federal earthquake forecasters.

“By getting these successes--if you want to use such a morbid term for it--we’re slowly building up a case history so we can evaluate the methods we have been using. We’ve made the hypothesis and now we’re letting nature verify that hypothesis,” Nishenko said.

In an office at the information center, the woman in charge of evaluating hazards for the Geological Survey, Kaye Shedlock, was seeing the Santa Cruz quake as her best chance yet to get the subtle data needed to tell residents why some buildings shake to pieces and others remain standing.

Why, for instance, was the San Francisco Marina District badly damaged but the Embarcadero District relatively unscathed, when both are built on fill that vibrates like gelatin during a quake? The answers are important because the East Bay area along the Hayward Fault and Southern California have areas that could face similar shaking in a quake.

“We’re looking, at this point, at subtle differences,” Shedlock said. “We need to get in there and be able to say X percent of brick buildings on rock fell down, X percent of brick buildings, wood frame, steel frame. . . . “

Like other seismologists, Shedlock is acutely aware of the human tragedy that shadows her research. But she takes heart in just how well the hazard analysis and retrofitting of buildings over the last two decades worked Tuesday.

“Face it, this earthquake was roughly the same energy level as the one in Armenia,” where about 25,000 people died and an entire region was leveled Dec. 7, Shedlock said.

“Given the fact that California had given some thought to responses to an earthquake and Armenia had not, the difference is graphic. Our death toll is in the low one hundreds. Our building loss is certainly nowhere near the almost complete devastation in Armenia,” she said.

Her group will be searching for specific answers to cut the hazards to California residents and their property even further, by mapping the Bay Area and looking for specific damage patterns. Aiding them will be a network of 60 strong-ground-motion detectors the state has installed in basements of skyscrapers and on bridges and dams in the Bay Area, she said. Unfortunately, the data must be gathered by hand from each machine over several days, she noted, and analyzing it will take even longer.

Stephen R. McNutt, senior seismologist for the state Division of Mines and Geology, noted that the analysis of ground motion during the Whittier earthquake two years ago was only recently issued, because the analysis process is so time-consuming.

The studies of Tuesday’s earthquake also will mark the first use of a new generation of portable seismic instruments that were developed for just such situations, Lerner-Lam said.

Under a National Science Foundation cooperative program, Lamont-Doherty sent a team to the Santa Cruz site Wednesday to install 20 portable seismographs for monitoring aftershocks. The machines not only are 100 times more sensitive than previous portable seismographs, but also formats the data for instantaneous analysis on portable computers in a hotel room, Lerner-Lam said.

Such equipment is expensive, however, and its scarcity points out what seismologists say is the biggest problem associated with quake research: You get what you pay for.

The right equipment just wasn’t in place during the Santa Cruz quake to give scientists good, fast answers, scientists say, and they blamed the budget-cutting fever of the ‘80s. In many cases of the last several years, monitors of fault motion and strain had to be removed because there was no money to maintain them, they say.

There also was a lack of quick information from the monitors that were in place, because centralized seismic systems have not been modified with computer hookups that would allow researchers all over the country to have instantaneous access to their data.

Two small systems like that are in place at Caltech and at Harvard University, but they cost $100,000 each, versus roughly $3,000 for a conventional seismic setup, said Thomas Heaton of Geological Survey’s Pasadena office.

“The people who run the seismic instruments in the Bay Area are basically the U.S. Geological Survey Western Region Office (in Menlo Park), the largest concentration of seismologists in this country by far. And yet we find that, the day after the earthquake, there’s really considerable lack of information about what happened in this quake,” Heaton said.

Over the next days and weeks, geophysicists will be filling that information gap as best they can with the hope that the next time around the scientific import will outweigh the human tragedy.