The majority of faults in the County are located in the Cobb Mountain area and Hopland Grade area running southeasterly to the southern County line. The southeastern portion of the County also appears to have considerable earthquake faults. There are also active faults within the vicinity of the City of Lakeport, including the San Andreas Fault which is to the west, and the Healdsburg Fault which is to the west. These faults have been responsible for moderate to major earthquakes in the past. The maximum creditable earthquake magnitudes are 8.25 for the San Andreas fault and 6.75 for the Healdsburg fault.