The U.S. Geological Survey has released a new estimate saying that the chance of an 8.0 magnitude or greater earthquake striking California is 7%, up from 4.7%.

The USGS said the increase in the percentage is due to new understanding that quakes aren’t always limited to separate faults.  A quake could start on one fault and jump to another causing a simultaneous mega-quake.

“The new likelihoods are due to the inclusion of possible multi-fault ruptures, where earthquakes are no longer confined to separate, individual faults, but can occasionally rupture multiple faults simultaneously,” USGS seismologist Ned Field, the lead author of the report, told the L.A. Times.

“This is a significant advancement in terms of representing a broader range of earthquakes throughout California’s complex fault system.”

Data for the report included the April 4, 2010 quake that triggered aftershocks in at least six different fault lines. The report also found quakes jumping over a gap in the fault of over seven miles, more than double the previously observed three miles.

“As the inventory of California faults has grown over the years, it has become increasingly apparent that we are not dealing with a few well-separate faults, but with a vast interconnected fault system,” the report said. “In fact, it has become difficult to identify where some faults end and others begin, implying many more opportunities for multifault ruptures.”