Earthquake Fault Zones
- The Healdsburg Fault (green) runs west of Highway 101 from central Santa Rosa to south of Healdsburg.
- The Maacama Fault (blue) runs from north of Mark West Spring to Cloverdale, also west of Highway 101.
- Rodgers Creek Fault (dark purple) runs from south of Highway 12 to central Santa Rosa, west of Highway 101.
- The San Andreas Fault (bright pink) intersects land in Sonoma County at Doran Beach and Bodega Bay as well as south of Fort Ross traveling north to the county line just east of the coastline.
Areas of Liquefaction
Many of the populace areas in the county have some degree of liquefaction hazard. Liquefaction describes the reduction of soil robustness and strength when an earthquake occurs. Buildings on susceptible soil may lose integrity due to liquefaction causing stress on foundations.
- The areas of Very High Susceptibility (red) to liquefaction include parts of Dry Creek Rd north of Healdsburg and smaller parts of Westside and Eastside Roads through to Guerneville and Forestville., east of Highway 101 from Cloverdale south to east of Healdsburg, areas near Jenner and Duncan Mills, off of Cazadero Road, and a small area near Sonoma.
- Areas of High Susceptibility (orange) to liquefaction include many areas east of Highway 116, as well as locations adjacent to the Very High Susceptibility (red) areas. Additionally, areas of High Susceptibility (orange) far west county locations such as Salmon Creek, some areas in Bodega Bay, off of Valley Ford Rd, Tomales Rd, a small portion of southeast Rohnert Park, a small portion of central west Petaluma, and north of Sebastopol.
- Moderate Susceptibility (yellow) to liquefaction is adjacent to areas of High Susceptibility (orange) as well as large portions of land either side of Highway 12, large portions of land on either side of Highway 101 throughout the county which includes much of Santa Rosa, Petaluma, Windsor, and Healdsburg. Sonoma south to the county line and areas south of Petaluma are also in the Moderate Susceptibility (yellow) zones.