San Andreas Fault Affected by Water Removal

San Andreas Fault

The over-800-mile-long break of rock in California has formed a dangerous reputation for itself over the years, particularly since 1906 when an earthquake leveled most of San Francisco. The earthquake measured at a magnitude of 7.8 and killed about 3,000 people. A new film, San Andreas, is even being produced around the fault, an action thriller starring Dwayne “The Rock” Johnson that will release in 2015. But the latest finding about the San Andreas Fault is that it can be negatively affected by the removal of water for irrigation or other purposes.

Readings from GPS technology revealed that water levels in the San Joaquin Valley aquifer have lowered and the mountains nearby have simultaneously risen. This has led the San Andreas Fault to undergo changes in pressure levels. Geologist Colin Amos from Western Washington University noted in his studies that the stress changes received from fluctuating water levels are minute compared to the pressure changes on a fault before a major earthquake.

While information like this may not indicate an immediate danger through water level changes, it does not mean business, agriculture and human activity can all necessarily proceed unaltered. Nature journal published the findings from Amos’ study on Wednesday, and suggest that other human-related activities can cause the San Andreas Fault to unclamp, resulting in the possibility of greater future volatility.

Data retrieved from satellites over the past decade show that much of the groundwater in and near the California Central Valley has been depleted more quickly than it can be re-filled. Amos and his colleagues used this information to discover that water removal and the changes affecting the San Andreas Fault are linked to even more variables.

The research group found that the heights of mountains in the Sierra Nevada and the Coastal Ranges increase during late summer and early fall, when people are using more water. The group also discovered that over increments of years at a time, the same mountains are growing as groundwater levels are slowly dropping.

Amos and his team were able to relate water to mountains in the same way that a weight has on a sheet of bendable wood. As water is displaced, or the weight is lifted, the mountains start to rise as the Earth’s crust, or the sheet of wood, bends back to its original position.

The San Andreas Fault is a line that signifies where two of the Earth’s tectonic plates meet. The plate on the eastern side of the Fault, or the side of most of the U.S. states, is pushing toward the southeast. The plate on the western side, towards the Pacific Ocean and Asia, is pushing toward the northwest. The only force keeping the plates where they are is friction, and earthquakes can happen any time the plates temporarily lose balance.

Paul Lundgren, a geophysicist at NASA’s Jet Propulsion Lab in Pasadena, California was not involved with Amos’ study, but offered comments on the work. He noted that the likelihood of earthquakes could be advanced by stress on the San Andreas Fault being decreased, which in turn is caused by long-term depletion of water.

An additional discovery made by Amos’ research team revealed that mini-earthquakes followed the same seasonal patterns as water use. This further solidified the findings that in order to lessen the risk of at least minor earthquakes and pressure changes, it means new developments for water usage and natural groundwater retention will have to take place. The movie involving the San Andreas Fault will likely prove to be a thrilling ride, but with seasonal water removal affecting the real thing, it is likely time for scientists and businesses to team up for a new solution.

By Brad Johnson

SF Public Press
Oklahoma’s Own