The Bay Area earthquake last night got my attention, but as felt in Berkeley in a house built on bedrock, it was not that big a deal. One fairly big shock, followed by an extended (news reports say one minute) period of modest shaking. The epicenter was roughly 40 miles away in San Jose, and structures built on sedimentary soil may well have been much more noticeably affected.
Of more concern is the possibility that the stresses released on one fault might add to stresses on a really worrisome earthquake fault line: the Hayward Fault, which runs through much of the East Bay, including Memorial Stadium at UC Berkeley, where the Cal Bears play Washington State Saturday night. The San Francisco Chronicle reports:
Fox Sports Network is televising the Cal-Washington State game, at least regionally and maybe nationally, since it starts at 10 PM Eastern time.
Whenever a quake occurs and a fault slips, it releases pent-up stress, [David] Oppenheimer [of the United States Geological Survey] said. And that shaking also triggers changes in the stresses built up along nearby faults, he said.
"There's always the possibility of a significant quake along those faults or another one on the Calaveras," Oppenheimer said. "But we don't have a crystal ball, and there's no way of knowing whether the one on Tuesday was a foreshock of another there or whether it was the main event. Nor do we know how much it might affect the threat on the Hayward."