Maacama Fault

The Maacama Fault is mostly a right-lateral strike-slip fault that lies north of Santa Rosa and the immediate San Francisco Bay Area and extends as far north as Ukiah. It connects to the Rodgers Creek Fault through a complex set of faults between Santa Rosa and Healdsburg, and is thought to be the northward continuation of the Hayward-Rodgers Creek Fault System. The 2007 Working Group for California Earthquake Probability assigned a total slip rate on the Maacama Fault of approximately 9 mm/yr (1/3 inches/yr), based on the assumption that it continues the slip on the Hayward-Rodgers Creek Fault northward. The central and northern sections of the fault have been observed to accommodate approximately 7 mm/yr (1/4 inch/year) of creep along it.

The Maacama Fault parallels and overlaps the Rodgers Creek Fault, in a geometry that is causing the ground between the faults to subside.

In Sonoma County north of Healdsburg, the Maacama Fault is largely obscured by massive landslides where it passes east of Alexander Valley.

The 2007 Working Group for California Earthquake Probability combined the Maacama and the Garberville Faults into single a 181-km (110 mile) long fault and determined M7.5 as the maximum magnitude for this combined fault system.

There is very little known about the seismic history or earthquake cycle of the Maacama Fault, and as such recurrence intervals are uncertain.