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-1724794NOTA is a core component of the NSF GAGE Facility. To acknowledge use of these data please follow the acknowledgment guidelines.

Stations Downloaded


StationDistance (km)1Hz5Hz
P15737partialpartial
P15944XX
P15855XX
P16157XX
P16058XX
P16359XX
P16260XX
P16676XX
P16576XX
P16777XX
P15678XX
P16883XX
P05884XX
P16984XX
P16492XX
P32492XX
P32693XX
TRND96XX
P17097XX
P793101XX
P327101XX
P325118XX
P321124XX
P312125XX
P331129XX
P313131XX
P343135XX
P332135XX
P322138XX
P319141XX
P185144XX
P187145XX
P316149XX
P318151XX
P337159XX
P184160XX
P794160XX
P320161partialX
P338161XX
P186166XX
PTSG168XX
P155169XX
P333169XX
P335172XX
P059177XX
P190177XX
P192178XX
P339179XX
P786182XX
P205183XX
P341185XX
P189190XX
P734199XX
P154202XX
P207209XX
P345210XX
P349210XX
P060211XX
P362215X
P336216XX
P179217XX
P188224XX
P203224XX
P344235XX
P191237partialX
P657238XX
P733238XX
P195239XX
P182243XX
P656243partialpartial
P208248XX
P206252XX
P204253XX
P348255XX
AGNS255XX
P784257XX
P270259XX
Last update: Dec. 27

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The USGS collects information from people who felt an earthquake and creates maps that show what people experienced and the extent of the damage

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Written by:

  • Scott K. Johnson
  • Posted: 20 December 2021
  • Last updated: 26 January 2022

Did you feel it?

The USGS collects information from people who felt an earthquake and creates maps that show what people experienced and the extent of the damage

Submit a response

Response Data

Please contact archive-gps@unavco.org for information on data availability. To request access to these and other RT-GPS stations operated by UNAVCO please send an email request to rtgps@unavco.org.

NOTA GPS/GNSS Data

Standard-rate and high-rate data can be accessed via the Data Archive Interface.

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Borehole Strain Data

High-rate data from borehole strainmeters can be accessed here.

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