SAN FRANCISCO (KPIX 5) — In 1989, a gallon of gas was just less than a dollar, the first episode of “The Simpsons” aired on TV, and the first GPS satellites were launched into orbit. Twenty-five years later, GPS is the key to new technology allowing seismologists to warn us when a big quake is about to hit.

By now, almost all of us use GPS. But instead of measuring our movement, the U.S. Geological Survey uses GPS to measure the ground’s movement, as faults slide past each other.

“Most specifically what we’re trying to get at is at what rates are the faults slipping,” said Keith Knudsen, Deputy Director of the USGS Earthquake Science Center. “The higher the slip rate the greater the hazard.”

Knudsen said that in the 25 years since Loma Prieta, real-time data on fault movement has become a reality.

Whereas three decades ago, Knudsen recalled, “An earthquake would occur and we would have technicians who would have to go out in the field, grab the films, put new films in, come back to the lab, process the films, and then we’d interpret them.”

The process took hours. Now it happens nearly instantaneously.

“Almost real time,” Knudsen said. “Within seconds we’re getting information about what level of shaking and what the shaking looked like from hundreds of points around the Bay Area.”

And that single leap in technology is the heart of the early warning system, a system Knudsen said worked just before the Napa Quake, the first big test since Loma Prieta.

“Because of this increased processing speed, we can calculate the magnitude and know the location. And because we can communicate that information outward faster than the earthquake waves travel through the earth we can warn people of the impending shaking that’s headed their way,” Knudsen said.

Granted, the early warning system is a prototype, there still isn’t funding to use it statewide. But Knudsen said it did provide between five and ten seconds of warning in the East Bay and Peninsula.

And, for stopping BART trains, or letting a surgeon know so the scalpel is put down, that could very well be enough time.

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