Two geological faults in northern California are linked, meaning that the risk of a large earthquake in the eastern San Francisco Bay Area is greater than was thought.

A team led by Estelle Chaussard of the University of California, Berkeley, used satellite radar to study ground deformation along the Hayward fault, east of San Francisco. The scientists found that it connected with the Calaveras fault. Both are part of the San Andreas system and were considered to be separate.

The combined fault system could unleash an earthquake greater than magnitude 7, bigger than had been expected.

Geophys. Res. Lett. http://doi.org/3hh (2015)