Slow San Andreas Fault Movements May Trigger Big California Earthquakes

A new study warns that slow movements on the San Andreas fault line could trigger bigger earthquakes. The research was detailed in a newly published study out of Arizona State University, where a pair of geophysicists found that so-called "slow earthquake" activity can result in larger — and potentially destructive — earthquakes.

The San Andreas Fault is the large fault line that runs through California. Major movement along this fault line could one day result in "the Big One," a term used to refer to an anticipated major future California earthquake that could have devastating effects on major cities in the state, including Los Angeles and San Francisco.

Researchers have known for a long while that San Andreas experiences a "creeping" movement, which has been thought to provide a safe and unnoticeable release of energy. However, the newly published study warns that over months, the fault has also experienced a sequence of what is referred to as "stick-and-slip movements," perhaps better known as slow earthquakes.

These movements cannot be felt by people in the area, but the researchers warn that they may trigger big and destructive quakes in nearby regions. Explaining this is the study's lead author, graduate researcher assistant Mostafa Khosmanesh, who said, "What looked like steady, continuous creep was actually made of episodes of acceleration and deceleration along the fault."

The slow earthquakes are described as episodic, having been found to occur every year or two with several months of activity each time. Rather than releasing energy in a safe way, these slow earthquakes may be causing stress to build in parts of the fault, some sections of which have historically suffered severe earthquakes, including the 7.9 quake of 1857.

SOURCE: Arizona State University