Friday, June 16, 2017

Rain and snow help stress out earthquake faults A little bit.

[Popular Science] Natural forces shape every inch of our globe, but in California, the two big players are water falling out of the sky (or the lack thereof) and earthquakes.
For a long time, many researchers figured that the two were unrelated. Earthquakes can mess with groundwater levels and aquifers, but not rain, and for the most part, it was assumed that rain and snow didn’t make enough of an impression on the Earth to really affect earthquakes either.
But a study published today in Science found a connection between seasonal precipitation and earthquakes, especially some of the very small ones.
Much of California has two distinct seasons—wet and dry. During the wet season, reservoirs fill, snowpacks build up on mountaintops, and the ground fills with moisture. In drier months, all that water starts moving, melting, and evaporating. This massive amount of water concentrated in the region collectively weighs so much that it can push down on the Earth by a fraction of an inch.
Earth scientists Christopher Johnson and Roland Bürgmann of UC Berkeley were able to measure those seasonal flexes in the Earth using a network of sensors called EarthScope that tracks tiny movements of the ground under our feet. The network includes GPS measurements (like you have in your phone) that record how the Earth’s surface moves in response to stress. For instance, a bunch of water being dumped on it every season. Read More