USGS: Repeat of Tuesday's Alameda Earthquake Is Unlikely

Alameda's 2.2 magnitude "micro quake" Tuesday morning was only the second earthquake with an epicenter under the Island in the past 43 years — and it's not likely to be repeated anytime soon, according to David Oppenheimer, a seismologist with the U.S. Geological Survey (USGS) in Menlo Park.

The small quake was recorded at 7:17 a.m. Nov. 12, with an epicenter beneath Alameda Point.

The only other local temblor since 1970 was a 2.3 magnitude earthquake recorded on Dec. 28, 2008, Oppenheimer said. The epicenter of that quake was near the corner of Third Street and Pacific Avenue.

A large earthquake on the Hayward Fault is much more likely to cause damage in Alameda than one closer to home, Oppenheimer said.

"We see these small quakes all the time in the East Bay — especially a cluster around the Caldecott Tunnel in Oakland and the Berkeley campus [on the Hayward Fault]," he said.

"But for a big quake, you need a big fault," he said.

The Hayward Fault, of course, qualifies as "big." But USGS maps don't show any fault near the site of Tuesday's Alameda quake. That's in part because the land beneath Alameda Point is basically mud, Oppenheimer said.

"Shaking levels would be significant in Alameda for a large earthquake on the Hayward Fault, though," he said, since parts of the city are built on landfill or formerly marshy ground.

"That's exactly the kind of situation that brought down the Cypress Freeway in the 1989 Loma Prieta earthquake," Oppenheimer said.

Several West End residents have reported experiencing Tuesday's quake mainly as a loud booming noise.

Oppenheimer said that's relatively unusual in an earthquake at this depth (about five miles), although common in shallow temblors.

In a quake, sound waves (20-30 Hz per second) excite the surface of the ground and create a rumbling sound, he said.

People may also hear the sound of buildings — including their homes — moving during a quake, he said.

Oppenheimer said he hopes Tuesday's micro quake will serve as a reminder to people to prepare for the possibility of a larger earthquake. Find information about the steps you can take to protect yourself and to survive the aftermath of a quake at the Bay Area Earthquake Alliance website.

See details and maps of Tuesday's quake here: "Yes, That Was an Earthquake This Morning — Right Under Alameda."

'Like' Alameda Patch on Facebook / Follow us on Twitter @AlamedaPatch / Share your thoughts in the comments section below