Morning Quake Rattles The East Bay

SAN RAMON, CA — An earthquake rattled residents in the East Bay out of bed Tuesday morning.

The magnitude 3.1 quake struck at 5:53 a.m. Tuesday just southeast of San Ramon, according to the U.S. Geological Survey.

SEE ALSO: Why Does San Ramon Get So Many Earthquakes?

There were no immediate reports of damage. Residents from Alameda to Half Moon Bay reported the shaking.

Over the past two months, the city has been the epicenter of more than 21 earthquakes over 2.0, ranging from 2.9 to 4.0 in magnitude, according to USGS research geophysicist Annemarie Baltay. There have been dozens more smaller quakes in San Ramon this month alone.

The city sits along the Calaveras Fault, and several micro-faults along the main fault result in swarms of quakes. When fluids like water or gas move through a complex web of cracks in tiny faults, this can trigger many dozens of small quakes in quick succession.

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Patch Staffer Michael Wittner contributed to this report.