December 20, 2021 M 6.2 Petrolia, CA Earthquake

Event response pages are a service to help coordinate community science after an earthquake or other notable geophysical event by collecting relevant data. Findings and figures are preliminary and subject to revision.

At 20:10:18 (UTC) on December 20, 2021 a magnitude 6.2 earthquake occurred off the coast of Northern California. For more information about the earthquake, see the USGS Earthquake Hazards Program event page.

UPDATE Jan. 26: After we initially published this page, USGS updated the location of the earthquake: “The 12/20/21 M6.2 earthquake near Petrolia is a complicated sequence, with a magnitude 5.7 event occurring 11 seconds before the main energy release. Our analysis shows that the M5.7 was located offshore along the Mendocino transform fault, while the location of the M6.2 is located approximately 30 km to the East and onshore, near Petrolia.”

New maps and magnitude estimate figures have been added below, but the initial figures are also preserved. Notably, the revised location results in a lower magnitude estimate for the event.

The event occurred within the footprint of the Network of the Americas (NOTA), a network of continuous GPS/GNSS stations and borehole instruments operated by UNAVCO that monitors plate motion and transient deformation, in addition to other applications.

These data are provided by the Geodetic Facility for the Advancement of Geoscience (GAGE) Facility, operated by UNAVCO, Inc. with support from the National Science Foundation and the National Aeronautics and Space Administration under NSF Cooperative Agreement EAR-1724794. NOTA is a core component of the NSF GAGE Facility. To acknowledge use of these data please follow the acknowledgment guidelines.