A strange movement was detected near the San Andreas Fault

Geoscientists have detected unexpected movements in the San Bernardino basin, near the San Andreas and San Jacinto faults. The vertical movement, called Deep Creek, occurs 10 km below the surface of the Earth and is likely to cause unusual ruptures in the area.

The researchers came to this conclusion based on data that included the analysis of thousands of very small earthquakes in the San Bernardino basin. Although small earthquakes are often overlooked by people, researchers say they can lead to larger and more destructive earthquakes.

"These small earthquakes are a very useful dataset, and if we pay more attention than in the past to the details they tell us, we can learn more about active fault behaviors that will help us better understand. loading that leads to devastating large earthquakes, "said geoscience professor Michele Cooke of the University of Massachusetts at Amherst.

The San Bernardino Basin in southern California has been intensively studied over the years. The data show that many earthquakes less than 10 km deep have a very different deformation style than other deformations in the region. Rather than showing the expected horizontal glide, many sections slide vertically.

To understand the phenomenon, researchers have developed models of deformation of the crust. The modeling has shown that a vertical movement can be produced in the basin if the North San Jacinto Fault located nearby moves in depth. In addition, this part of the fault is constantly moving rather than locked, as should be the case between large earthquakes. This implies that small earthquakes that occur near active faults may have a very different deformation style than large earthquakes.

"The typical way we look for creep is to use GPS stations on either side of the fault. Over time, you may notice that there is movement; the defects are slowly diverging. The problem here is that the San Andreas and San Jacinto faults are so close together that GPS can not solve creep problems. That's why no one had seen this before. The traditional way of detecting it could not do it, "Cooke said. "In this article, we showed that there was a way to have these tiny earthquakes quite next to the San Jacinto Fault below 10 km, where deep creep occurs."