The earthquake swarm that has rattled San Ramon for over two months is showing signs of dwindling activity, according to scientists. Starting from November 9, a total of 91 earthquakes of magnitude 2.0 and above were registered in the East Bay region, including a notable 4.0 quake on December 19. However, the last significant trembles occurred on January 10, indicating a possible end to the swarm.

“There’s been a gap for about two weeks,” stated Sarah Minson, a research geophysicist with the U.S. Geological Survey (USGS). “It looks like the swarm may be done.” Despite this, she noted the inherent uncertainties in defining the start and end of earthquake swarms.

David Schwartz, a geologist and scientist emeritus with the USGS, corroborated Minson’s observations, saying, “The swarm has subsided. It appears to have quieted down.” However, he emphasized that earthquake swarms differ from traditional quakes and are subject to mystery and unpredictability.

Many residents of San Ramon, a suburban town in Contra Costa County with a population of about 85,000, have been largely unaffected by the minor earthquakes, which have produced little to no damage or injuries. Mayor Mark Armstrong recounted, “A lot of people who never experienced earthquakes were worried… But it was just a short jolt, and it was over.”

The USGS recorded 471 earthquakes, including some as minor as magnitude 0.3, between November 9 and January 22 within a mile of San Ramon. The geological layout of the area, characterized by small unnamed faults, leads to these occasional flurries of quakes.

This is not the first time San Ramon has experienced such activity; there have been five significant earthquake swarms since 1970, none of which have caused major damage or injuries. Prof. Roland Bürgmann from UC Berkeley reiterated that while swarms can slightly elevate the chance of a larger earthquake, there are currently no indications of a significant fault being activated.

With heartening reassurances, the San Ramon community has taken the swarm in stride, viewing it as a novelty rather than cause for alarm. As Mayor Armstrong aptly noted, “It was something to talk about. But it really wasn’t anything to be worried about.”