Previously unmapped earthquake faults ruptured during the Aug. 24 magnitude-6.0 South Napa earthquake, surprising both scientists and homeowners. In the Browns Valley neighborhood, one section of the fault cracked through homes, splitting foundations and damaging some houses so severely that they were evacuated. The California Geological Survey is studying the possible fault strands and is working on a regulatory map.
Moderate building damage
Newly discovered faults
Previously mapped faults
Possible fault strands under study
Graphics reporting by Rosanna Xia and Rong-Gong Lin II
Sources: U.S. Geological Survey, California Geological Survey, city of Napa