49 km W of Petrolia, CA

Yes. A magnitude 3.5 earthquake was recorded 49 km W of Petrolia, CA, at 5:23 am PDT on 27 October 2025 (12:23 UTC), less than 1 km deep. 1 person has reported feeling it to USGS. The magnitude and location are an automatic first estimate and may change.

2025-10-27 12:23 UTC · 0.4 km deep · released about 2.3 tons of TNT

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Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.

When: 2025-10-27 12:23 UTC
Magnitude: M 3.5 (ml)
Depth: 0.4 km below the surface
Felt: 1 report · strongest reported intensity II
Nearest: Humboldt County, 86 km ENE
Status: Automatic — a machine’s first estimate, which may change

USGS · last changed by USGS 301 days ago · we first saw it 301 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.

At this magnitude and depth, people at rest would likely notice it out to about 61 km (38 mi) from the epicentre. Estimated from magnitude, depth and distance with the intensity equation USGS Did You Feel It? uses; felt reports, where there are any, are the measurement.

How big was it?

This earthquake released about 2.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.

Northridge, California 1994 M 6.7 75,000× the energy of this one
Mineral, Virginia 2011 M 5.8 3,300× the energy of this one
Magna, Utah 2020 M 5.7 2,400× the energy of this one
This earthquake M 3.5 about 2.3 tons of TNT
Around the size people start to feel M 3.0 this one released 4.7× more

Energy from the Gutenberg–Richter relation (log₁₀E = 1.5M + 4.8), rounded to two figures; bar length is magnitude, which is already a logarithm of energy. Magnitudes of past earthquakes from the USGS catalogue.

For this area

The largest earthquake within 50 km since 2016 was M 7.0 on 2024-12-05 — about 210,000 times the energy of this one.

Before 2016, the USGS record lists 32 earthquakes of M5 or more within 50 km; the five largest:

6.6 32 km SW of Ferndale, California · 25 km E of this epicentre Apr 26, 1992
6.5 30 km WSW of Ferndale, California · 25 km E of this epicentre Apr 26, 1992
6.5 The 2010 Eureka, California Earthquake · 32 km NNE of this epicentre Jan 10, 2010
6.0 Offshore Humboldt County, California · 45 km SSW of this epicentre Mar 19, 1910
6.0 53 km SW of Ferndale, California · 21 km SE of this epicentre Oct 8, 1951

Since 2016: the QuakeIndex catalogue (US, M1.5+), built from the USGS FDSN event service. Before 2016: USGS ComCat, M5+ from 1900. Distances are between epicentres. This is the record, not a forecast.

Where

Map loads when it scrolls into view

Nearby places

Place	Distance	Direction from the epicentre
Humboldt County, CA	86 km (53 mi)	ENE	earthquakes near Humboldt County
Mendocino County, CA	161 km (100 mi)	SE	earthquakes near Mendocino County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

60 earthquakes have been recorded within 50 km since this one.

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 16:45 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

On USGS

The official USGS event page — the source of record for every value above
Did you feel it? Report it to USGS — reports go to USGS, not to us
ShakeMap for this event, when USGS has produced one

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.