RENO — Scientists are keeping a close eye on a swarm of dozens of small earthquakes that have been recorded in recent days in Sun Valley north of Reno, along with a larger quake earlier this month south of Reno.
A sequence of 60 earthquakes that began in Sun Valley early Wednesday were too small to be felt, said Graham Kent, a geophysicist who directs the Nevada Seismological Lab at the University of Nevada, Reno.
"These sequences like we are seeing in Sun Valley can either subside or escalate. We've seen it happen both ways in Nevada,'' Kent said. ``Once in a while we've seen them culminate in magnitude 4 and higher earthquakes. It pays to be prepared.''
More than 1,200 people felt the magnitude 3.7 temblor June 6 in Washoe Valley south of Reno.
Kent said it's a gentle reminder that Nevadans live in the third-most seismically active state, behind Alaska and California.
"We hope that this perspective will encourage residents of our area to undertake sensible actions to be prepared for earthquakes,'' added John Anderson, a professor at the university who has authored studies on earthquake hazards in the state.
Nevada has dozens of identified earthquake fault systems, sharing some with California. But they haven't been moving as much as expected compared with the history of quakes in the region the past century.
Scientists said at a 2016 earthquake conference in Reno that the Sierra's eastern front is long overdue for a large earthquake along the California-Nevada line, where a magnitude 7 event expected on average every 30 years hasn't occurred in six decades.
Kent said then that the region's earthquake ``drought'' is likely one of the reasons the public has a misconception there's a low risk a serious quake will strike.
"We've experienced such a long stretch of not having earthquakes, we've sort of built in a sense of complacency,'' he said.
All 13 of Nevada's recorded earthquakes with magnitude 6.5 or greater occurred in the 102-year period ending in 1954.
Of the 44 known earthquakes with magnitude 6.0 or greater, only five have occurred since 1960, while 15 would be more consistent with the prior historical rate, experts say.