Skip to main content

M6.4 Petrolia, Dec 20, 2022 California Earthquake


On December 20, 2021, an M6.2 earthquake occurred offshore of northern California near Petrolia. The earthquake was located in the vicinity of the Mendocino triple junction, where the Pacific, North America, and Juan de Fuca plates meet. It was preceded by an M5.7 earthquake 30 km to the west, which likely occurred on the east-west trending Mendocino transform fault. 

Earthquakes are common in this region due to oblique motion between the plates. In the past century, there have been 40 other earthquakes of M6 or larger, including six earthquakes M7 or larger, within 250 km of the December 20 earthquakes. These prior earthquakes primarily occurred along the Mendocino transform fault, in the Cascadia subduction zone, or within the Juan de Fuca/Gorda plate. The M6.2 earthquake occurred approximately 8 km later of the April 25, 1992, M7.2 earthquake, which caused significant shaking and damage. 

The M6.2 earthquake was predicted a few days in advance and more than 50 specialists in financial risk management were informed before it occurred. Such technology can improve resiliency and speed up recovery efforts in the forthcoming earthquakes.