The San Andreas Fault traverses Marin County running north and south in the western quarter of the county. It enters Marin on the Pacific Coast near Bolinas, follows the path of Highway 1, and Tomales Bay, exiting Marin at sea just west of Dillon Beach. In addition, the eastern, more heavily populated part of Marin is less than ten miles from the northern section of the Hayward/Rogers Creek fault.
These two faults are most likely to create major ground shaking in Marin. The combined chances are 52% of a major (6.7 or greater magnitude) earthquake occurring on one of these faults between now and 2036. For the San Andreas Fault, the probability is 21 percent, while the Hayward/Rodgers Creek has a probability of 31%. Rupture of the San Andreas Fault could severely impact the county’s coastal communities of Bolinas, Point Reyes Station, Stinson Beach and Muir Beach.
The San Andreas Fault was the source of the magnitude of 7.8 earthquake in 1906. Marin was sparsely inhabited at that time and experienced relatively moderate property loss and only two deaths. The epicenter was just two miles west of San Francisco and West Marin experienced some pronounced earthquake effects. This included a horizontal earth displacement of 21 feet near the head of Tomales Bay. In an earthquake, subsidence and differential settlement can occur along Bay Mud and Marshland areas of Marin, leading to damage of any structures sited on those lands due to liquefaction.
Marin County Hazard Map
Locate the area where you live and click to determine the most damaging earthquake scenario for your area.
Source: USGS, 2013.