Even though Danville resident David Schwartz spends every work day thinking about little else, he knows that most Bay Area residents don't dwell on earthquakes.

"When you don't have an earthquake for four or five years, you don't think about it affecting you," he said. "It would be different if we had a magnitude 5.2 or 5.5 every day for a month or two. There'd be quite a bit more public consciousness then."

Schwartz is an earthquake geologist for the U.S. Geological Survey in Menlo Park who can recite the names of faults the same way a first-grader spits out the alphabet.

Seismologist John Cassidy reads the seismograph chart at the Pacific Geoscience Center of the Pacific from the earthquake that shook Victoria on Wednesday
Seismologist John Cassidy reads the seismograph chart at the Pacific Geoscience Center of the Pacific from the earthquake that shook Victoria on Wednesday morning Feb. 28, 2001. (AP Photo/VIctoria Times Colonist, Ian McKain)

"The Bay Area has the highest density of active faults per square mile of any urban area in the country," he said, sounding like a proud parent. "You have the San Gregorio, the San Andreas, the Calaveras, the Hayward, the Rodgers Creek, the Greenville and the Concord/Green Valley -- and that's just from Half Moon Bay out to Livermore. There's also a thrust fault beneath Mount Diablo that's still active."

What spurred this conversation was the recent flurry of temblors in the Los Angeles basin -- a magnitude-4.4 quake that rattled Westwood on March 17 and a 5.1 that made for jittery nerves in La Habra just 11 days later.

Is this recent activity in Southern California a precursor to shaking to the north? Not likely, Schwartz said. A rupture on one fault line seldom affects another, unless it's quite large. "When we have a really large quake, then it can change the stress around it."

The classic example, he said, was the monster 7.9 quake that leveled San Francisco in 1906 and relieved the tectonic pressure for miles around.

"It was so large," he said, "that it released essentially all of the stress in the crust of the Bay Area and Northern California. It relaxed everything, and we've had very few earthquakes since. We call this a stress shadow. The question is whether we're still in that shadow or transitioning out of it."

Our period of "quiescence," as Schwartz calls it, can't last forever. The USGS says there is 63 percent probability of a magnitude-6.7 quake or larger in the Bay Area in the next 30 years. A more specific forecast would be nice, he acknowledged, but predicting earthquakes is a fool's mission.

That hasn't stopped the regulars Schwartz sees at Piatti restaurant in Danville from hounding him for a date. The requests became so frequent that he finally relented recently.

"I wrote down Jan. 7, 2015, for the next big earthquake and gave it to the bartender. I just wanted to get everyone off my back."

The best thing about the recent temblors in L.A., he said, is that they remind us that we need to be prepared for a jolt from out of the blue. Lay in supplies, keep a flashlight handy, have a place to seek shelter, secure heavy bookcases and know how to turn off the gas.

"Everybody gets tired of hearing that," Schwartz said, "but most people are unprepared. We can't tell you when, but we can tell you there certainly will be big earthquakes in the future. Some people will get it, and some people won't until it actually happens.

"Only 10 percent of homeowners in the state have earthquake insurance. That's a sign of being unprepared."

Does Schwartz have a policy?

"I do," he said.

Here's betting it's paid through at least Jan. 7.

Contact Tom Barnidge at tbarnidge@bayareanewsgroup.com.