In addition to these significant quakes , hundreds of smaller events have also occurred in the same area . This swarm is significant because no known dominant fault line has been responsible for the earthquake swarm occurring in the region . It is also highly unusual because the quakes have , for the most part , been limited to a three-mile area . The United States Geological Survey ( USGS ) estimates that over 620 earthquakes have occurred in the general three mile vicinity since the swarm has been monitored . Seismologists with the USGS as well as the Nevada Seismological Laboratory expressed concern that the increasing magnitude of the felt quakes may indicate that a larger earthquake was imminent . As yet , they have not identified the particular tectonics involved with these earthquakes . However , they have stated categorically that volcanic activity is not involved . The last strong earthquake ( M6 .1 ) in the Reno area in occurred on April 24 , 1914 , and the state 's most powerful quake to date was the M7 .4 1915 Pleasant Valley earthquake south of Winnemucca
1915 Pleasant Valley earthquake
1915 Pleasant Valley earthquake
2008 Reno earthquakes