The findings are a result of a new radar imaging system created by NASA that can detect how land moves after earthquakes and has been scanning the California landscape since 2009, the Los Angeles Times reported Friday.
Comparing old maps with new images after the April 4 Easter Sunday quake, scientists could see where the earth moved and how earthquake tension shifted northward toward Los Angeles.
The radar system found the quake and its aftershocks triggered movement on at least six faults that run close to heavily populated areas in eastern Los Angeles County and the Inland Empire, researchers say.
"There's a number of activities at the southern parts of these long, dangerous faults that indicate there is a changing stress environment," geophysicist Jay Parker, acting chief of the imaging program, said.
"And because these faults are considered hazardous and potentially may have an earthquake that breaks along their length, this brings the whole picture of activity closer to the Los Angeles area."
One of those faults, the Elsinore fault, could generate a magnitude 7 earthquake if its entire length were to rupture in a single event, "which would be bad news for Los Angeles," Eric Fielding, a geophysicist at NASA's Jet Propulsion Laboratory, said.
The pattern of the northward advance of seismic stress may have triggered the 5.4 magnitude earthquake of July 7 south of Palm Springs, Calif., which was felt as far away as Los Angeles, scientists say.