BAY AREA QUAKE : BART’s Underwater Tunnel Withstands Test

Traveling under San Francisco Bay proved to be safer than over it during Tuesday’s earthquake. Riders made it safely through BART’s four-mile long underwater tunnel linking San Francisco and Oakland.

But there were harrowing moments for passengers all along the 71.5-mile Bay Area Rapid Transit system.

James Herron Zamora was a passenger on an above-ground BART station in Oakland when the quake hit. “Our train bounced in the air off the tracks and landed again,” he said. “I felt like I was going to throw up. People next to me were crying. One woman started praying in Spanish.

“It was chaotic, it was crazy,” Zamora said. “No one knew what to do.”

Zamora said the train operator shouted, “There is an earthquake and I don’t know what to do.”

The train stopped for five to 10 minutes and proceeded to the next station, where frantic passengers got off, joining about 300 passengers from other trains, he said.

BART’s shutdown stalled another train for several minutes in the four-mile tube beneath the bay. “There was a train stopped in the tunnel, but they got it out without a problem,” said Susan Cowan-Scott, commander of the California Highway Patrol’s public affairs office.

After the quake, which struck during the afternoon rush hour, hundreds of people were streaming out of BART stations along Market Street in San Francisco, reversing the normal order of events at that time of day, when commuters normally are pouring into the stations.

During the first few hours after the temblor, there were no reports of injuries or serious trouble elsewhere along the BART system that runs in San Francisco, Alameda, San Mateo and Contra Costa counties. However, one train in a tunnel through the Berkeley hills was reported evacuated.

The CHP’s Cowan-Scott said that, while BART’s trans-bay service to San Francisco would be shut down today, the Fremont and Richmond lines on the eastern or Oakland side of the bay will be operating.

The $1.5-billion Bay Area subway system was largely completed in 1973, with the route under the bay opening a year later.

BART tracks cross several earthquake fault lines, but transit officials said as recently as last month that most of the system was designed to withstand quakes approaching the power of the 1906 San Francisco quake, which was a magnitude 8.0 temblor.

A number of studies have been done on what could happen to BART during a severe earthquake. Most of them concluded that some elevated structures would be damaged and that the track in the Berkeley hills tunnel could become misaligned.

But BART officials said that the studies indicated that it is unlikely that the trans-bay tube would be damaged.

The tube, running 132 feet under the bay, is submerged in soft mud and has flexible earthquake joints at each end.

The moment a mild earthquake begins trembling in the Bay Area, sensors at eight locations are supposed to trigger alarms, and part or all of the BART system is designed to shut down.

If an earthquake is strong, the system’s operators are to be instructed by radio to stop their trains and wait for orders.

Times staff writer Irene Chang contributed to this story