This earthquake occurred approximately 35 km WNW of Ferndale, CA in a deformation zone of the southernmost Juan de Fuca plate that is commonly referred to as the Gorda plate. The earthquake’s epicenter is northwest of the Mendocino Triple Junction, which is formed by the intersection of the Mendocino fracture zone, the San Andreas fault and the Cascadia subduction zone. The Gorda plate is subducting beneath the North America plate at about 2.5-3 cm/year in the direction N50E. The Gorda plate is also subjected to intense compressive stresses by oblique-convergence of the northwestward migrating Pacific Plate as well as localized eastward spreading at the Gorda Ridge. The resulting internal deformation of the Gorda plate is manifested primarily by intraplate strike-slip events on vertical NE-oriented faults.
I wish I was a geology nerd so I understood half of this. About the earthquake yesterday in Northern California.
Source: earthquake.usgs.gov