California Scientists Join Earthquake Coalition

Early morning on Jan. 17, 1994, UC Berkeley psychology major Kevin Jeung was jolted from his sleepover in Northridge, California, awakened by the screams of his friend's parents and the shaking of the earth beneath him.

"I felt as if I were going to throw up, as if I were on some malfunctioning rollercoaster," Jeung said.

The Northridge earthquake killed 51 people, injured thousands and cost billions in property damage.

While other states face hurricanes, tornadoes, floods and avalanches, California's most dangerous natural disaster is the earthquake.

Recently, teams of California seismologists, UC Berkeley scientists among them, joined forces to create the California Integrated Seismic Network (CISN).

"The CISN was formed to provide a reliable, modern, statewide system for earthquake monitoring, research, archiving and distribution of information for the benefit of public safety, emergency response and loss mitigation," said William Ellsworth, the chief scientist of the U.S. Geological Survey in Menlo Park, California.

One task of the CISN has been the production of ShakeMaps, color-coded maps which show the intensity of recent seismic events of Richter scale magnitude 3.5 and greater.

ShakeMaps can be used to direct emergency workers to areas where they are most needed.

To create these maps, the CISN operates approximately 1000 seismic sensor stations throughout California, including a network of about 50 stations owned by UC Berkeley.

Courtesy/UC Berkeley A sample shakemap displays, through different colors, the seismic intensities recorded throughout California during the Loma Prieta Earthquake.

One sensor station was located 75 meters underneath Memorial Stadium, monitoring the Hayward Fault, an earthquake fault that runs straight through the stadium.

"A large earthquake on the Hayward fault would significantly damage the football stadium," said Lind Gee, a seismologist at the Berkeley Seismology Laboratory. "Fortunately, the stadium is only filled a few Saturdays every fall."

Each sensor station occupies about 50 square feet, including the sensors, the power supplies, the data loggers and other equipment, Gee said.

Not all sensor stations are created equal, however.

"Berkeley operates a sparse network of extremely high quality instruments," said David Oppenheimer, the project chief of the Northern California Seismic Network, operated by the U.S. Geological Survey. "We operate about 470, but they're lower quality."

Typical UC Berkeley stations can measure motion in three directions rather than just one, Oppenheimer said.

Processing computers at UC Berkeley and the U.S. Geological Survey at Menlo Park take data from the sensors and produce ShakeMaps for Northern California, accounting for factors such as geology.

"The geology in the Bay Area is very complex," Gee said. "Geology will strongly affect the amount of shaking from an earthquake."

Beyond emergency response, the CISN also had a promising role in providing research data.

"The Integrated Seismic Network is the standard tool in California to study earthquakes," said John Vidale, a professor of geophysics at UCLA. "It's letting us do things that we couldn't do before."

The CISN could also be used for some initially unintended purposes.

"It lets us develop the techniques to enforce the (nuclear Comprehensive) Test Ban Treaty," said Vidale. "We can see big explosions anywhere in the world from the U.S. using the California seismic array."

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