Analysis Reveals Large-scale Motion Near San Andreas Fault System

In a new finding utilizing GPS data, the San Andreas Fault has a 125-mile-wide “lobe” of “uplift and subsidence”.  For years, vertical motion had been ignored because of the difficulty in interpreting the “noisy data” in tectonic investigations.

Crustal movement has been predicted using computer models simulating the San Andreas Fault System, but this new data shows vertical lift.  EarthSpope Plate Boundary Observatory GPS data showed that over the past several years, the lobes that are on either side of the fault line have annual movement of a few millimeters.

Researcher Samuel Howell described it, “We were able to break down the noisy signals to isolate a simple vertical motion pattern that curiously straddled the San Andreas fault.”

With the recent seismic activity in California and Yellowstone, this type of modeling will be helpful in determining when and perhaps where along the San Andreas, the Big One could hit.

The 5.2-magnitude quake in Borrego Springs,  woke up many sleepy Southern California homes.  This quake was followed by 800 aftershocks.  This number is abnormally high for aftershocks.

Head northeast, toward Yellowstone National Park and Montana, where just this past week, several quakes have hit the region.  A magnitude 3.7 quake hit on June 9th, magnitude 4.3 on June 13th and on June 15th, a magnitude 4.0 shook the region.

Though Yellowstone is hit by earthquakes all the time, as it sits upon the Yellowstone super volcano, most of these quakes are extremely small.  These higher magnitude quakes are unusual and disconcerting.

Drills are being conducted in the Pacific Northwest to prepare the area for an unprecedented earthquake disaster.

To prepare the Pacific Northwest for such an enormous disaster, the U.S. government has developed alongside the military and state and local emergency personnel a readiness drill the second week of June, a dress rehearsal for the prophesied massive earthquake and tsunami.

Cascadia Rising is what this readiness drill is being called, named after the 600-mile-long fault, the Cascadian Subduction Zone, which runs from Northern California to Southern British Columbia.  The drill will involve 20,000 people, utilizing a wide range of governmental agencies, with the goal to test how well these agencies will work to decrease the loss of life and the destruction such an earthquake would leave.

Earthquake readiness is of great import in recent news, with Cascadia Rising drills that occurred early in June utilizing multi-government cooperation in the Pacific Northwest and into Canada.  Perhaps the data coming out of University of Hawaii’s School of Ocean and Earth Science and Technology and the uptick in activity around the Ring of Fire has caused a needed stir in governmental readiness for a Big One disaster.

The Ring of Fire is going through an alarming uptick in activity right now with 34 volcanoes erupting at the same time. The Ring of Fire a is 25,000-mile, horseshoe-shaped string of volcanoes and seismic activity sites around the edges of the Pacific Ocean. About 90% of all earthquakes and 75% of all active volcanoes are on the Ring of Fire.”

This new model, using GPS data which revealed “new areas of motions around the San Andreas Fault System”, used in conjuncture with previous predictive earthquake models, confirmed the “buildup of century-long earthquake cycle forces within the crust”.

Using data collected by the EarthScope Plate Boundary Observatory’s GPS array, researchers identified 125-mile-wide “lobes” of uplift and subsidence. Over the last several years, the lobes, which straddle the fault line, have hosted a few millimeters of annual movement.

Computer models simulating the San Andreas Fault System have predicted such crustal movement, but the areas of motion hadn’t been physically identified until now.

Researchers used advanced statistical modeling to identify the movement among the inevitable statistical noise that comes with monitoring minute movements in the Earth’s crust.

“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,” lead author Samuel Howell, a researcher at the University of Hawaii at Manoa, explained in a news release. “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.”

The validity of the vertical patterns was confirmed by the fact that similar motions were predicted by an earthquake model designed by researchers at the University of Hawaii’s School of Ocean and Earth Science and Technology.

“We were surprised and thrilled when this statistical method produced a coherent velocity field similar to the one predicted by our physical earthquake cycle models,” said researcher Bridget Smith-Konter. “The powerful combination of a priori model predictions and a unique analysis of vertical GPS data led us to confirm that the buildup of century-long earthquake cycle forces within the crust are a dominant source of the observed vertical motion signal.”

This research could help scientists utilize the lesser lobes of vertical motion to help “predict more significant ruptures”.   With the many earthquake zones across the United States and the consequential damage that is predicted with 8.0 magnitude quakes, being able to predict ruptures utilizing these lobes could be life saving.  From the San Andreas, to the CSZ which on average produces magnitude 9.0 quakes every 500 years, to the The New Madrid seismic zone , the United States is in for a rocky future, should the predictions of enormous seismic activity come to fruition.


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