More than 100 earthquakes have shaken up the San Francisco Bay area in the last four days.
Scientists at the U-S Geological Survey are calling it the “San Ramon swarm.”
Seven earthquakes of magnitude three or higher have hit the area since a 3.9 struck on Sunday morning.
Seismologists say they don´t know if the sequence will trigger a larger quake. They say it´s likely the earthquake swarm will persist for a few weeks and earthquakes as large as magnitude four could occur.