All the tech millions and billions you have in the bank or in stock options owon’t help much when “the big one (earthquake)” once again hits the city of San Francisco any more than the rich and famous will be protected in LA. A new study is showing that there is a massive vertical sinking and rising occurring on either side of the most famous fault line in the United States.
Not just side-to-side movement in new San Andreas modelling
Clearly the San Andreas fault doesn’t just threaten San Francisco in the north of California but nearly all of the state with Southern California also “living in the shadows” of the St. Andreas’ earthquake potential.
The EarthScope Plate Boundary Observatory’s GPS array was used to clearly see that some areas of California are rising a few millimeters each year while others are sinking.
While scientists certainly recognize that this won’t help with real-time warnings being able to be broadcast throughout the state, but they do hope that by looking at this rising and falling could give some understanding when the next big earthquake could occur.
The study was published in the journal Nature Geoscience on Monday and is the first of its kind.
Irrigation and seismic activity
It’s quite possible that a lot of the sinking is a result of pulling out ground water for irrigation in the drought-plagued state as well as seismic activity.
The study shows that large portions of the Los Angeles Basin, Orange County, San Diego County and the Bakersfield are sinking about 2 to 3 millimeters annually while Santa Barbara and San Luis Obispo counties, and a large portion of San Bernardino County are moving at the same rate in the opposite direction, upwards.
“While the San Andreas GPS data has been publicly available for more than a decade, the vertical component of the measurements had largely been ignored in tectonic investigations because of difficulties in interpreting the noisy data. Using this technique, we were able to break down the noisy signals to isolate a simple vertical motion pattern that curiously straddled the San Andreas fault,” said lead author Samuel Howell from the University of Hawaii at Manoa.
Others involved in the study included: Neil Frazer, also of the University of Hawaii; Xiaopeng Tong of the University of Washington; and David Sandwell, of the Scripps Institute of Oceanography at UC San Diego whose work was largely funded by the National Science Foundation.
The areas that are rising and sinking are expected to level in the near future(?). Unfortunately, that will only come once a large earthquake hits the region.
“Once there is a major event, all of that energy gets released,” said Howell.
The last major earthquake that occurred in Southern California along the San Andreas fault was a 7.9 shake that hit Monterey County through Los Angeles County in 1857. Frankly, those areas are due though it should be said that every “150 years” is a bit arbitrary.
“It’s pretty much impossible to say when the next one will happen,” Howell said.
The accomplishment in this study was based on GPS information and a computer code that was able to look past non-seismic factors in the movement.
“We wrote a computer code that could try and find the broad, large-scale signal,” Howell said. “It’s trying to find the smooth trend.”
Even without this study, residents of the area who have been through a 5.5+ earthquake are well aware of the volatility of the region.