July 21--At least a dozen smaller earthquakes rattled the Bay Area on Tuesday after a magnitude 4.0-temblor shook residents and triggered a brief delay on the region's rail system, according to the U.S. Geological Survey.
The first quake, initially reported as a magnitude 4.1, occurred at 2:41 a.m. PDT at a depth of 7.5 miles.
According to the USGS, the epicenter was a mile from Fremont, four miles from Newark, and seven miles from Fairview. Bay Area residents as far as 15 miles away reported feeling the shaking.
The temblor briefly caused 15- to 20-minute delays on the Bay Area Rapid Transit system while maintenance crews inspected the tracks, officials said. There was no reported damage, and trains were back on schedule by about 5:30 a.m., the agency tweeted.
San Francisco's police and fire departments did not report any significant damage or injuries.
In the hours that followed, at least 13 smaller earthquakes were detected in the area, ranging in size from magnitude 1.0 to 2.7, all of them centered in Fremont. The latest small quake came about 6:40 a.m., USGS reported.
In the last 10 days, there have been no earthquakes of magnitude 3.0 or greater centered nearby, according to the USGS.
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UPDATE
8:37 a.m.: This article has been updated with at least a dozen smaller quakes shaking the area.
6:37 a.m.: This article has been updated to reflect that the earthquake was downgraded from magnitude 4.1 to 4.0.
This article was originally published at 5:09 a.m.
