ALAMO (CBS SF) — An early morning earthquake measuring 3.3 rattled through the Danville area along the Calaveras fault system Monday, according to the U.S. Geological Survey.
The temblor was felt strongly enough to have BART stop commuter trains briefly to check its tracks for any damage.
The quake was centered near Alamo and struck at 4:55 a.m. It hit in the same area where a swarm of small quakes ranging from 3.0 to 1.5 struck on Sunday.
The USGS said a 3.0 magnitude quake struck at 10:34 a.m Sunday followed quickly by a 2.7 magnitude quake at 10:38 a.m. and another 3.0 at 3:25 p.m. Several smaller temblors followed.
All were epicentered in the Danville-Diablo area along an active area of the Calaveras fault system. While the quakes grabbed the attention of local residents, there was no damage reported.
Back in February, more than 55 small quakes rattled the area with the largest measuring a 3.3. Other swarms have rattled along the fault system for the aseveral years.
USGS Seismologist Anne Marie Baltay said during the February swarm that the small temblors are not a sign that a larger quake was was coming.
“We don’t expect this to grow into anything really large,” she said.”This swarm is very typical of what we see in this region. It’s happened seven times in this area since 1970.