A new study of the Bay Area's fault lines set to be published today in the Bulletin of the Seismological Society of America once again reminds us, as many experts have reminded us for most of the last decade and a half, that we are due for a big earthquake any day. And by the way, later this week, we'll be marking the 25th anniversary of Loma Prieta.
As the Wall Street Journal and every local newscast last night reported, four faults around the Bay are "locked and loaded" and ready to rupture tomorrow, or in the next 30 years. This basically upgrades the likelihood of such a rupture from 63 percent, according to the USGS a few years ago, to 70 percent, with the Hayward Fault being the most overdue, and the most likely to give us our next big earthquake.
The Hayward Fault, which runs beneath the East Bay from Hayward, along the Oakland and Berkeley Hills and under Richmond and Suisun Bay, has not had a significant rupture since the not-much-discussed earthquake of 1868, when the Bay Area was not as densely populated as it was by 1906. The fault shows a history of rupturing about every 160 years, which means it's due now, and a major earthquake here would effect the entire Bay Area, and potentially disrupt San Francisco's water supply.
The new study's lead author, USGS research physicist Jim Lienkaemper, gave multiple interviews saying that we don't know, of course, when Mother Nature's "going to pull the trigger," but preparations need to continue to shore up infrastructure and residential buildings in the meantime.
The other three faults that are also likely to rupture next in the San Andreas Fault Zone are the Calaveras Fault, which runs from about Hollister to Danville; the Rodgers Creek Fault which runs from about Petaluma to Healdsburg (and is basically an extension of the Hayward Fault); and the Green Valley Fault in Solano County, which the study suggests "is likely to have a larger earthquake than people previously thought." In fact, based on the observed "creep rate" of these faults and the subsequent buildup of tension below ground, the Rodgers Creek and Green Valley Faults could produce earthquakes in the range of 7.1 magnitude.
As the Chron notes, in addition to the Hayward Fault not rupturing since 1868, "the Rodgers Creek Fault last broke in 1745, according to evidence uncovered by trenches scientists have dug in the area. The last known major earthquake on the Calaveras Fault struck about 1740, and on the Green Valley Fault, the last rupture occurred about 1609."
Anyway, none of this changes what we already knew: We live in earthquake country, and we all need earthquake kits. Like tomorrow. Like, go to the store tonight even. And get one of those hand-crank radios, and make sure you've got a stash of cash in small bills somewhere handy.
Also, if one of these signs appeared on your building, tell your landlord to get their shit together. Fast.