According to a new study, earthquake and tsunami risks are associated with seven major faults off the coast of Southern California.

The study suggests that the vertical fault zones have displaced the sea floor, upping the risk of 7.9 to 8.0 earthquakes and tsunami waves, this magnitude of disaster could damage cities such as Los Angeles and San Diego.

Mark Legg, geologist of Legg Geophysical in Huntington Beach, California said “We’re dealing with continental collision,” in reference to the cause of the offshore danger. “That’s fundamental. That’s why we have this mess of a complicated logjam.”

The logjam is created by blocks of Earth’s crust that are involved in a tectonic battle between the North America tectonic plate and the Pacific plate. As the pacific plate slides away from California, the blocks get moves and squeezed together.

To determine how many faults have slipped over time and whether it was causing the seafloor to pucker upwards, researchers have combined the seafloor data and digital seismic data.

The data has confirmed both the upward and sideways movement of the seafloor along the Santa Cruz-Catalina Ridge Fault. Regions around the Ferrelo Fault zone showed signs of thrust faulting, which is an upward movement on one side of the fault. This data suggests that the blocks of crust are being compressed and sliding horizontally in what is called as transpression.

The plate movement is building up seismic stress on San Andreas, Santa Cruz-Catalina Ridge, and Ferrelo Faults.

Christopher Sorlien, geologists of the University of California at Santa Barbara and the co-author of the study said, “Such large faults could even have the potential of a magnitude 8 quake. This continental shelf off California is not like other continental shelves – like in the Eastern U.S.”

The findings of the study are published in Journal of Geophysical Research: Earth Surface.