Internet Puts Quake Data at Fingertips

The 7.0 Hector Mine earthquake, which jolted awake the electronic village of Southern California on Saturday, may be considered the world’s first cyberquake.

Scientists, emergency officials and citizens alike were almost instantly wired together through interactive Internet Web sites and online data networks to exchange damage reports and to assess ground-shaking intensities and shock wave readings.

As spasms of aftershocks made the Mojave Desert tremble, earthquake experts quickly assembled real-time electronic readings from hundreds of ground motion sensors, seismographs and online reports filed by people living in the quake zone to produce a detailed picture of potential damage to guide rescue workers.

“It is the first time we have been able to provide truly high-quality information within minutes of an earthquake,” said Caltech seismologist Egill Hauksson.

Before first light, more than 3,000 people filed their own firsthand reports through a community response Web site, detailing local damage and aftershock patterns from 673 ZIP Code areas in Southern California affected by the temblor.

By 11 a.m., there were 9,000 eyewitness reports filed online, said David Wald, the U.S. Geological Survey scientist responsible for new online seismic intensity maps, which are based on the information.

Overall, these agile online emergency reflexes show just how thoroughly earthquake experts have adopted automated electronic monitoring techniques to track the hundreds of potentially damaging faults in Southern California since the 1994 Northridge quake--despite limited budgets and an impending federal funding squeeze. As fast as such data are available, they are appearing online.

The heart of the online activity Saturday was an expanding network of 200 seismographic stations called TriNet--a joint enterprise of Caltech, the U.S. Geological Survey and the California Division of Mines and Geology. The system is expected to number 670 stations by 2001.

Even at partial capacity, the system allowed earthquake experts to produce detailed maps of ground-shaking intensity--the surest barometer of where quake damage is likely to be most severe--within minutes of the temblor.

The maps automatically showed how intensely the quake affected many locales at the exact moment.

Although such shake maps have been routinely displayed for many Southland quakes as small as magnitude 4.0 for months, Saturday marked the first day they were available for a major quake.

The maps were on the Internet within five minutes, posted online at the Web site https://www.trinet.org/shake.html.

“Before, we were only able to pinpoint the epicenter of an earthquake,” said Hauksson, a supervisor of the TriNet system. “Now, with TriNet, within minutes we know where it shook the hardest, and that facilitates deployment of emergency response resources.”

To buttress the automated sensors, people in the quake zone were able to offer electronically their own observations of shaking and damage in their neighborhoods. Those observations were then used to produce a second set of online maps.

Those community responses, filed through a Web site located at https://www-socal.wr.usgs.gov, were available for others to assess within minutes.

In the immediate aftermath of the quake, the experts also drew on one of the largest and most automated seismic networks in the world: the 350 automated seismographs of the Southern California Seismic Network. That system feeds its readings directly into a central computer facility in the Seismological Laboratory on the Caltech campus.

In addition, there are 291 ground motion sensors scattered throughout the state that also feed data electronically to seismologists. And in the days to come, dozens of sensors linked to the orbiting Global Positioning System will continuously measure the slightest deformations of the quake zone.

Like the shake maps, those data are being made available on the Internet for rapid analysis by scientists and the public.

All this contrasts sharply with the old ways of conveying information about a quake, which often left emergency authorities in the dark for long periods about where the heaviest shaking occurred.

For example, it took days after the 1994 Northridge quake for it to be realized that the most intense shaking was actually not at the epicenter near the Northridge-Reseda border in the San Fernando Valley, but north of the Valley in the less-populated Santa Susana mountains and the western part of the Santa Clarita Valley.

The USGS shake maps were developed by a scientific team led by Wald, assisted by graduate student Vince Quitoriano. The maps rate an earthquake’s power by a measure called the Mercalli Intensity scale.

Unlike more conventional measures of an earthquake’s magnitude, the Mercalli Intensity scale is based on descriptions of a quake’s effects, depending on how it felt to those who experienced it and any damage reported.

The number used to describe the scale at each point is rendered in Roman numerals, and various colors ranging from white to deepest red correspond to the appropriate numerals. A weak I is white and a devastating X is deep red.

For the many common magnitude 3 to 4 quakes, maximum intensities are shown in blues and greens.

On Saturday, the magnitude 7.0 quake in the desert showed up as reds as high as VIII near the epicenter and blues, a IV in metropolitan Los Angeles and Orange counties.

The observations collected from the thousands of people who felt the quake and responded on the interactive site were coded by ZIP Code in the same numerals.

By simply looking at it, emergency authorities, the news media, and ordinary citizens could get a fairly clear idea of how strong the quake was at any given point. So the people reporting helped shape the perception of the quake.

“Anybody who has Web access can get all of this,” Wald emphasized.

But he added that some more complicated information, such as preliminary casualty estimates generated by the state Office of Emergency Services, goes only to the authorities, not to the public.

An emergency backup power system allows the USGS shake maps to be produced even if power failures are widespread, and work is proceeding on dedicated communications to the Emergency Services office to provide the information to the responding authorities.

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STUDYING DAMAGE

Hoping to get insight into quake processes, scientists flock to Mojave epicenter. A35

* LITTLE DISRUPTION

An Amtrak train is derailed, but that is the only major disruption to rail traffic. A35

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Generating a “Shake Map”

Intensity maps were generated within minutes of the Hector Mine quake and then posted on the World Wide Web. Caltech and USGS researchers weaved together real-time electronic readings from ground motion sensors and TriNet seismographical stations to produce the detailed seismic intensity maps, called shake maps. For updates, check www.trinet.org/shake.html. *

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Sources: David J. Wald, Caltech and U.S. Geological Survey; California Division of MInes and Geology

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Did You Feel It?

A new system developed by USGS, Caltech and the Division of Mines and Geology uses reports from Internet users to pinpoint quake intensity. Within hours of the Hector Mine earthquake, thousands of citizens had filed first hand reports on local damage and aftershock patterns from hundreds of ZIP code areas affected by the temblor. Shown here are intensities by ZIP code based on 12,649 responses. For updates, check www-socal.wr.usgs.gov.

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Sources: David J. Wald, Caltech and U.S. Geological Survey; California Division of MInes and Geology