Headline: Earthquake Season? A new study has something to say about that.
A new study by seismologists at the University of California, Berkeley revealed that California’s Winter snow and rain causes seasonal rises in small earthquakes.
The study found that the weight of winter snow and rain pushes down on the Sierra Nevada mountains and Coastal Ranges. When the snow melts away and water has flowed downhill in the Summer, the Earth’s crust rebounds leading to small quakes along the state’s faults — including California’s San Andreas Fault.
In the late Summer and early Fall, the central San Andreas Fault sees a rise in small quakes greater than a magnitude 2 and faults along the eastern side of the Sierra Nevada see a rise in the late Spring and early Summer due to the melting and down flow stream of the rainwater, researchers found.
“It’s not that all earthquakes happen in September. There is no earthquake season,” said Roland Bürgmann, a UC Berkeley professor of earth and planetary science and one of the authors of the study. “It all depends on details of the loading, the location of the fault and the geometry of the fault.”
The impact coming from the up and down flexing of the mountains surrounding the Central Valley increases the chance of earthquakes by a few percentage points, but the study gives seismologists insight on how faults rupture and what kinds of stresses are important in triggering quakes.