M4.9 Earthquake 15 km NNW of Susanville, CA — December 31, 2025
2025-12-31 05:49:32 UTC (2025-12-31) · approx. 9:49 PM UTC-8 local
Felt by 625 people across surrounding communities. Maximum shaking intensity MMI 6.6 (very strong).
On December 31, 2025 at 05:49 UTC, a magnitude 4.9 shallow crustal earthquake struck 15 km NNW of Susanville, CA, at a depth of 5.3 km and coordinates 40.5443°, -120.6923°. The earthquake was reported felt by 625 peopleacross surrounding communities, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 6.6 (very strong). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. This earthquake was detected by 29 seismic stations with excellent location accuracy and was assigned a USGS significance rating of 791, making it a moderate-impact event. The nearest populated place is Johnstonville (population 1,024).
Physical scale: An earthquake of magnitude 4.9 releases seismic energy equivalent to roughly 362 metric tons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 1.5 km — 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
Nearest Populated Places
What the Shaking Felt Like
At MMI 6.6 (very strong), people in the most strongly affected areas would have experienced: Strong shaking felt by everyone. Heavy furniture may move. Books fall from shelves. Plaster and chimneys may crack. Damage is generally slight in well-built structures.
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 625 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
Population exposure (USGS PAGER)
Estimated population that experienced each level of shaking. Based on the USGS PAGER rapid impact assessment, which combines ShakeMap output with global population grids.
| Shaking intensity (MMI) | Description | Population exposed |
|---|---|---|
| MMI 3 | weak | 891,140 |
| MMI 4 | light | 22,772 |
| MMI 5 | moderate | 10,484 |
| MMI 6 | strong | 2 |
Earthquake Details
-120.6923°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 4.9 earthquake near Susanville, CA?
The magnitude 4.9 earthquake that struck 15 km NNW of Susanville, CA on December 31, 2025 at 05:49 UTC had a depth of 5.3 km. It was felt by 625 people with maximum shaking intensity of MMI 6.6 (very strong). For context, this was a light earthquake commonly felt near the epicenter.
Where did the earthquake occur?
The earthquake epicenter was located at 40.5443°, -120.6923°, which is 15 km NNW of Susanville, CA. The nearest populated place is Johnstonville (population 1,024). View all earthquakes in California.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 4.9 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 4.9 event is significantly smaller than that historical record.
What should I do after an earthquake?
If you were in the affected area: check yourself and others for injuries, inspect your home for damage, and be prepared for aftershocks. For detailed guidance, see our earthquake safety guide and emergency planning resources.
Authoritative source: USGS event page (event ID: nc75288851). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2025, December 31, 2025). M4.9 Earthquake 15 km NNW of Susanville, CA — December 31, 2025. Retrieved May 16, 2026 from https://www.earthquaketracker.org/earthquakes/event/nc75288851/