It's been a year since the release of the American blockbuster hit "San Andreas," and incidentally, the catastrophic event portrayed in the film is bound to happen in the next 30 years, experts say.
GPS Data Detects Fault Movement
The San Andreas Fault System in Southern California has detected large-scale motion in the area. Samuel Howell and his colleagues from the University of Hawaii has found a 125 kilometers of stretch of land experiencing an uplift and subsidence for a few millimeters every year.
"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," says Howell, lead author and resercher from the University of Hawaii. "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."
Earthquakes Still Unpredictable
With the current sophisticated detectors and instruments, horizontal movements are able to be tracked and are deemed to be "largely predictable." However, the vertical motions that came from tectonic activity is still hard to predict. Horizontal movements are caused by a number of things including geology, groundwater pumping and tectonic motion of the Earth's crust.
Howell and his team used a special technique in observing the tectonic motion in order to "break down the noisy signals to isolate a simple vertical motion pattern that curiously straddled the San Andreas fault."
Researcher Bridget Smith-Konter, who had been observing this events, predicted the earthquake cycles. She said, "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."
"The powerful combination of a priori model predictions and a unique analysis of vertical GPS data led us to confirm that the build-up of century-long earthquake cycle forces within the crust are a dominant source of the observed vertical motion signal," she added.
The team sought to find ways to improve the current understandings in the behavior of faults when there's a major gap between earthquakes for decades. The last incident of a major earthquake involving the San Andreas fault was 159 years ago in 1857, hitting California with a 7.9 magnitude earthquake.