Water from melting snow sets off swarms of small earthquakes in California’s Sierra Nevada mountains.
Emily Montgomery-Brown at the US Geological Survey in Menlo Park, California, and her colleagues analysed records of earthquakes near Long Valley Caldera, in the eastern part of the state. The scientists compared the seismic patterns with streamflow in the area.
Since 1984, small earthquakes have rattled the ground 37 times more often when streamflow has been very high than when it has been very low. Water percolating into the ground as snow melts in spring seemingly changes the pressure in the ground, triggering the quakes.
After a record snowfall in the Sierra Nevada area between late 2016 and early 2017, for example, the region experienced a swarm of minor quakes, including more than 3,000 such events between 28 May and 1 August 2017.
The work represents one of only a few examples of a documented link between precipitation and earthquakes.