An even bigger quake than Tuesday night’s temblor could be in
store for area residents, geologists said.
Gilroy
An even bigger quake than Tuesday night’s temblor could be in store for area residents, geologists said.
On the heels of the 5.6-magnitude earthquake that struck about 9 miles northeast of San Jose, a team of scientists at the California Earthquake Prediction Evaluation Council warned another quake could be on its way. While state geologists said the chances are “tiny,” the U.S. Geological Survey reported there was a 35- to 40-percent increased chance of another earthquake larger than magnitude 5.6 by Tuesday night.
The Bay Area already experienced 40 aftershocks greater than 1.0 magnitude since the initial quake, which occurred at 8:05 p.m. at the intersection of the Hayward and Calaveras faults and was felt as far east as Sacramento and as far north as Sonoma County. The Hayward Fault runs down the East Bay from Oakland to San Jose, while Calaveras Fault runs almost parallel from Danville south along the base of the Diablo Mountains into Hollister.
Most of these aftershocks, the largest of which registered 3.7 on the Richter scale at 3:54 p.m., were located close to Alum Rock. The closest temblor, just 1.1 in magnitude, hit three miles northeast of San Martin.
Though state geologists also said the chance of a “damaging” earthquake – above 5.0 in magnitude – along the faults had “significantly increased,” they also said the overall likelihood was very low.
“It’s as if you had the lottery and you were given one of the seven numbers,” said John Parrish, state geologist with the California Geological Society. “It’s gone from a really tiny thing to a tiny thing.”
While Tuesday’s quake – the strongest in the Bay Area since the 1989 Loma Prieta earthquake – could have relieved stress on the Calaveras Fault, stress could also have been transferred to the Hayward Fault, he said. The period of highest likelihood of a second quake has passed, he added.
Geologist Jim Berkland – who gained notoriety after predicting the 1989 Loma Prieta earthquake in the Dispatch using tidal charts and animal behavior patterns – said the Bay Area is not likely to get another quake until the end of November and December, when tides are at their highest.
Berkland predicted an earthquake between 3.5- and 6.5-magnitude within 140 miles of Mount Diablo during the last week of October. Tuesday’s earthquake fit these parameters.
The magnitude-7.0 quake that experts anticipate will hit one of the region’s seven major faults in the next 25 years will pack 60 times the force of Tuesday’s quake, said Tom Brocher, a senior U.S. Geological Survey seismologist.
When the next quake does come, residents should be prepared, said Cindy Stewart, emergency planning coordinator with the Santa Clara County Office of Emergency Services.
“I think they should always be looking at things like there is a possibility of an earthquake,” she said.
As Stewart does regularly with her three children, residents should walk through the house and decide where they would go in the event of an emergency, she said. County officials discourage taking refuge in door frames as doors sometimes close on people’s hands. Instead, they recommend hiding under tables to protect against falling objects. In addition, having a three-day supply of water could be useful if emergency services are slow to arrive, state officials said.
Though no major damage or injuries were reported, the county inspected dams and gas tanks to check for possible weaknesses, Stewart said. Many Bay Area residents reported land and cell phone service being down for at least 10 minutes – possibly the result of the rush of calls after the quake, she said.
Even if another quake does not hit in the next few days, it’s an opportunity for residents to make sure they have a plan for what to do in an emergency, Parrish said.
“It’s a good time for people to wake up again,” he said. “Remember you live in earthquake country.”
QUAKE BY THE NUMBERS
- Time: 8:05 p.m.
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Magnitude: 5.6 on the Richter scale
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Location: 9 miles northeast of San Jose
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Duration: 1 minute
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Aftershocks: 7, all less than 2.0
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Quakes of note:
1984, 6.2 Morgan Hill, $8 million in property damage;
1989, 6.9 Loma Prieta, 63 dead, 3,737 injured, $6 billion in
property damage
