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Tag: Irrigation

  • San Andreas Fault Affected by Irrigation

    The San Andreas Fault, a continental transform that runs roughly 810 miles through California, is being affected by irrigation practices in the area, according to a study by Geologist Colin Amos from Western Washington University.

    Readings from GPS technology have shown that water levels in the San Joaquin Valley aquifer have lowered and that the mountains nearby have simultaneously risen, which has caused the San Andreas Fault to undergo changes in pressure levels. Though, Amos points out that stress changed due to lower water levels are minuscule compared to pressure-changes seen on the fault before a major earthquake.

    The San Andreas Fault forms a tectonic boundary between the Pacific Plate and the North American Plate, and a study in 2006 concluded that the fault has achieved a level of stress sufficient to facilitate the next “big one”, or an earthquake greater than magnitude 7.0. In 1906, a rupture in the San Andreas Fault caused a magnitude 7.7-8.25 earthquake in San Francisco that destroyed almost 80% of the city and killed 3,000 people. The earthquake and resulting fire are regarded as one of the worst natural disasters in the history of the United States.

    Here is a small documentary on San Andreas:

    Amos’ study, which was published in Nature journal on Wednesday, suggests that human-related activities can cause the San Andreas Fault to unclamp, resulting in the possibility of greater future volatility. At present, seismologists have found that the San Andreas Fault produces a magnitude 6.0 earthquake approximately once every 22 years. The last occurred in the Parkfield area in 2004.

    Satellite data has shown that groundwater in and near the California Central Valley has been depleted more quickly than it can be re-filled over the past decade, and Amos’ study related the water in association to the mountains in the area as being akin to a weight sitting atop a piece of bendable wood. As the water is depleted, its weight is lifted, which in turn pushes the mountains to rise from the Earth’s crust.

    Amos confirmed that seasonal fluctuations in water usage have coincided with minor earthquakes around the San Andreas Fault, and that new developments for water usage and natural groundwater retention need to be implemented.

    Image via Wikimedia Commons

  • San Andreas Fault Stressed By Irrigation

    On Wednesday, the journal of Nature released their most recent findings regarding the San Andreas Fault.

    According to the study, excessive irrigation could be aggravating the fault, causing more frequent earthquakes. GPS readings have shown that parts of the floor of the San Joaquin Valley have been diminishing while the nearby mountains are being lifted higher. These motions are causing stress on the nearby faults, including the San Andreas.

    Colin Amos, the lead researcher and a geologist at Western Washington University, wrote an email about their findings. “The magnitude of these stress changes is exceedingly small compared to the stresses relieved during a large earthquake,” he said.

    Paul Lundgren of the NASA Jet Propulsion Laboratory, who did not take part in the research, explained that human activities “can cause significant unclamping of the nearby San Andreas Fault system.”

    Shockingly, in the past 100 years, the amount of groundwater that has been lost through irrigation in the Central Valley is equivalent to the amount of water in Lake Tahoe. The current drought that has bombarded California has also contributed to the loss of groundwater, as the community is having to tap into their supply.

    The San Andreas Fault is one of the largest in California, running approximately 800 miles from just north of San Francisco to the Salton Sea near the United States/Mexico border.

    Scientists have revealed that if a magnitude 7.8 earthquake were to occur near the southern part of the fault, it could cause the deaths of nearly 1,800 people and $200 billion in damages.

    Image via Wikimedia Commons