PreliminaryCalifornia5d ago
M3.0 earthquake 21 km WSW of Petrolia, CA
Monday, September 21, 2026, 18:54:41 UTC · 40.276°N, 124.530°W
A magnitude 3.0 earthquake struck 21 km WSW of Petrolia, CA on Monday, September 21, 2026, 18:54:41 UTC, at a depth of 5.7 km (shallow). USGS received 2 “Did You Feel It?” reports, with a maximum reported intensity of II (weak).
- Magnitude
- 3.0
- Minor · md
- Depth
- 6 km
- Shallow
- Felt reports
- 2
- Max intensity II
- Est. shaking
- —
- No ShakeMap
- PAGER alert
- None
- Not issued
- Tsunami
- No flag
- USGS feed
Outlined circle: this earthquakeDashed circle: 50 km aftershock search area
In context
How big was it, and why here?
Energy released
415 kg of TNT
That is about 1/36,253 of the Hiroshima bomb. A magnitude 5.0 releases about 1,148 times more energy.
Tectonic setting
4 km
from the nearest mapped plate boundary, between the North American and Pacific plates. Earthquakes cluster along boundaries like this one, where plates collide, pull apart or slide past each other.
Depth: shallow
6 km
Shallow earthquakes (under 70 km) produce the strongest surface shaking for their size, so they are the ones most likely to cause damage near the epicenter.
Did You Feel It?
Where it was felt
Reports sent by people to USGS, grouped by place (most reports first). Intensity uses the Modified Mercalli scale (I–X): what people felt, not the magnitude.
| Place | Intensity | Reports | Distance |
|---|---|---|---|
| 95540<br>0.330 | II · Weak | 1 | 48 km |
| 95618<br>0.330 | I · Not felt | 1 | 312 km |
USGS PAGER estimate
Who was exposed to shaking
USGS publishes PAGER impact estimates for significant earthquakes, usually within an hour. No PAGER estimate is available for this event.
After the main event
Aftershocks within 50 km
USGS lists 3 M2.5+ earthquakes within 50 km since this event; the largest was M2.6 on September 22, 2026. Most nearby activity right after a large earthquake is aftershocks, which usually become less frequent over days and weeks.
Regional history
Past M5+ earthquakes within 300 km
USGS lists 249 M5.0+ earthquakes within 300 km before this one (catalog from 1900; older records are less complete). The strongest:
- 7.4123 km W of Big Lagoon, CaliforniaJanuary 31, 1922 · 136 km NW of this epicenter
- 7.2The 1992 Petrolia, California EarthquakeApril 25, 1992 · 26 km E of this epicenter
- 7.2The 1980 Eureka, California EarthquakeNovember 8, 1980 · 96 km N of this epicenter
- 7.2153 km W of Big Lagoon, CaliforniaJune 15, 2005 · 165 km NW of this epicenter
- 7.1The 1923 Humboldt County, California EarthquakeJanuary 22, 1923 · 48 km NW of this epicenter
- 7.1121 km W of Ferndale, CaliforniaSeptember 1, 1994 · 98 km W of this epicenter
- 7.02024 Offshore Cape Mendocino, California EarthquakeDecember 5, 2024 · 43 km W of this epicenter
- 7.0136 km WSW of Brookings, OregonAugust 17, 1991 · 192 km NW of this epicenter
History · NOAA
Deadliest earthquakes in this area
NOAA’s significant-earthquake database lists 28 damaging, deadly or tsunami-generating earthquakes within 300 km of this epicenter since 1700, which together caused about 6 recorded deaths. The most severe:
- 2022M6.4
Humboldt County
20 Dec 2022 · 29 km away · intensity VIII
2 deaths$250 million damage
- 2014M6.0
Napa, Vallejo
24 Aug 2014 · 298 km away · intensity VIII
1 death$700 million damage
- 1969M4.8
Santa Rosa
2 Oct 1969 · 256 km away · intensity VIII
1 death$8 million damage
- 1954M6.6
Humboldt County
21 Dec 1954 · 83 km away
1 death$2 million damage
- 1932M6.5
Eureka
6 Jun 1932 · 54 km away · intensity VIII
1 deathModerate damage ($1–5M)
- 1992M7.1
Humboldt County: Ferndale, Petrolia
25 Apr 1992 · 21 km away · intensity VIII
$75 million damagetsunami
NOAA NCEI Global Significant Earthquake Database. Historical figures are estimates; older records are incomplete.