In a previous episode, we talked about how geologists use Global Navigation Satellite Systems to measure changes in the surface of the Earth, especially in areas that have regular earthquakes. There is an entire system called the Network of the Americas (NOTA) that has GPS and GNSS stations all along the west coast of the United States and down into the Caribbean, and the data taken from these stations is collected continuously. This process allows scientists to understand the interactions between various plate boundaries, such as the San Andreas Fault in California.

Now scientists have taken all of that data collected between 2007 and 2019 in much of California and compared the results to meteorological data from the same time period. The question the team was seeking to answer was if long-term weather pattern changes, such as the multi-year drought from 2012 to 2015, had an effect on the amount of deformation the region experienced. And the short answer was “yes.”

Prior to this study, published in JGR Solid Earth, scientists had come to understand that short-term, seasonal changes in the weather had an effect on crustal deformation and even impacted the local earthquakes. Basically, the ground compacts during wet, winter months, like now, and rebounds during the dryer, summer months. So what happens when the area doesn’t get much rain for three years? The usual rebound, or dilation of the crust, was half what it was in normal wet years.

Apparently, you can’t get a pull without much of a push first. More research is needed to understand just how these long-term variations in the weather actually affect the earthquakes in the region, though. We’ll keep you informed of any new developments.

More Information

Eos article

“Crustal Strain Patterns Associated With Normal, Drought, and Heavy Precipitation Years in California,” Jeonghyeop Kim, Alireza Bahadori, and William E. Holt, 2020 December 2, Journal of Geophysical Research: Solid Earth