2500 earthquakes in the last several decades near California , Fresno . Swarms of earthquakes not uncommon in the region . David Shelly , a seismologist with California Volcano Observatory , said this swarm is `` bigger than we 've seen recently , but normal in the area . '' Last swarm of earthquakes produced over Three dozen between 1997-98 .
2500 earthquakes in the last several decades near California , Fresno . Swarms of earthquakes not uncommon in the region . Last swarm of earthquakes produced over Three dozen between 1997-98 .