Just in case you might be one of many awakened in your sleep or jolted at the dinner table by the Bay Area’s flurry of recent seismic activity, rest assured experts say the tremblers aren’t leading up to the “Big One.”
“In California, there are usually 30 to 50 small-scale earthquakes recorded per day, so basically, the recent series of earthquakes have justbeen large enough to feel,” explained John Bellini, a geophysicist with the United States Geological Survey.
The most recent earthquake, whose epicenter was in Piedmont, hit Thursday morning at 5:37 a.m. with a magnitude of 2.8 on the Richter scale — but the Bay Area has been rattling since Dec. 20, when the first of five small-scale quakes hit.</p>
The Dec. 20 quake’s epicenter was about two miles southeast of Berkeley and had a magnitude of 3.7. Two more quakes followed with relatively close epicenters, one on Dec. 22 that also registered a 3.7 magnitude, and another on Dec. 23 with a magnitude of 3.5. Union City was also shaken up Christmas Day by a tiny, magnitude 2.6 temblor.
All the quakes reported were along the Hayward fault, an 80-mile stretch that runs from Richmond to Fremont, according to records from the National Earthquake Information Center in Denver.
“The Hayward fault is part of the boundary between the North American plate and the Pacific plate — which move past each other using the [Bay Area’s] San Andreas fault system as their boundary. Along the boundary, the plates tend to stick together and not move for periods of time, resulting in the pressure release [that is causing the earthquakes],” said Michael Reichele, chief seismologist with the California Geological Survey.
Bellini said the Bay Area is a highly active area, pointing to the three major fault lines that run through six counties of the Bay Area. Quakes measuring above 4.5 on the Richter scale could potentially cause some mild damage, such as knocked-over objects and cracks in plaster.
Bruce Burtch, spokesman for the Red Cross’ Bay Area chapter, said being proactive and taking precautions before the next big quake hits is the best option for anyone worried about the threat.
“It’s important to have an emergency plan and an emergency kit — we always advise people to think of their daily routine and things they might need. Also, to use common sense,” Burtch said.
To track recent seismic activity, visit earthquake.usgs.gov/eqcenter