In September , for example , about 500 miniquakes struck southeastern California in about two days . Hundreds of mainly low - magnitude earthquakes have been recorded . Such groups of earthquakes are called tornadoes . They are common in and around a national wildlife refuge in Nevada . Seismologists observe swarms on a regular basis ; in September there was one in Nevada .
Hundreds of mainly low - magnitude earthquakes have been recorded . Such groups of earthquakes are called tornadoes . They are common in and around a national wildlife refuge in Nevada . Seismologists observe swarms on a regular basis ; in September there was one in Nevada .