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 quakes have been recorded . Such groups of quakes are called swarms . They are happening in and around a national wildlife refuge in Nevada . Seismologists record swarms on a regular basis ; in September there was one in California .