M2.7 Earthquake 3km NW of Palomar Observatory, CA — December 21, 2021
2021-12-21 22:38:38 UTC (2021-12-21) · approx. 2:38 PM UTC-8 local
Felt by 53 people across nearby locations.
On December 21, 2021 at 22:38 UTC, a magnitude 2.7 shallow crustal earthquake struck 3km NW of Palomar Observatory, CA, at a depth of 4.8 km and coordinates 33.3747°, -116.8803°. This earthquake was detected by 93 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 133, placing it among routine seismic activity.
Physical scale: An earthquake of magnitude 2.7 releases seismic energy equivalent to roughly 163 kg of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 43 m — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in California, a region characterized by the San Andreas transform fault system, where the Pacific and North American plates slide past each other at roughly 46 mm per year. The nearest mapped fault system is the San Andreas Fault. View all earthquakes in California.
Learn more: San Andreas Fault · Magnitude scale · Aftershock sequences
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 53 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Earthquake Details
-116.8803°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 2.7 earthquake near Palomar Observatory, CA?
The magnitude 2.7 earthquake that struck 3km NW of Palomar Observatory, CA on December 21, 2021 at 22:38 UTC had a depth of 4.8 km. For context, this was a minor earthquake typically detected only by instruments.
Where did the earthquake occur?
The earthquake epicenter was located at 33.3747°, -116.8803°, which is 3km NW of Palomar Observatory, CA. View all earthquakes in California.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 2.7 earthquakes can continue for several days and gradually diminish over time.
Has California had earthquakes this big before?
The largest recorded earthquake in California was the M7.9 Fort Tejon earthquake of January 9, 1857. Today's magnitude 2.7 event is significantly smaller than that historical record.
Actions
Authoritative source: USGS event page (event ID: ci39892903). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, December 21, 2021). M2.7 Earthquake 3km NW of Palomar Observatory, CA — December 21, 2021. Retrieved March 1, 2022 from https://www.earthquaketracker.org/earthquakes/event/ci39892903/