Seismicity
Santa Rosa lies atop the Healdsburg-Rodgers Creek segment of the Hayward-Rodgers Creek Fault System. The U.S. Geological Survey estimates a 20% chance of a magnitude 6.7 or greater earthquake on this segment by 2030.
On April 14, 2005, the United States Geological Survey released a map detailing the results of a new tool that measures ground shaking during an earthquake. The map determined that the 1906 San Francisco earthquake was most powerful in an area between Santa Rosa and what is now Sebastopol, causing more damage in Santa Rosa (for its size) than any other city affected.
Two earthquakes of magnitudes 5.6 and 5.7 shook Santa Rosa October 1, 1969, damaging about 100 structures. They were the strongest quakes to affect the city since 1906. The epicenters were about two miles (3 km) north of Santa Rosa.
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