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M1.8 Earthquake near Petrolia, United States — 04 September 2026

A micro earthquake of magnitude 1.8 was recorded near Petrolia, United States on , with an epicentre 16 km southeast of Petrolia, at a focal depth of 2.3 km. It ranked as the 2181st strongest of 7950 earthquakes recorded in the United States in the preceding 30 days.

1.8 Micro

Time (UTC): 2026-09-04 05:52:15

Time (your timezone): —

Magnitude: 1.8 (micro)

Focal depth: 2.3 km (shallow)

Epicentre: 40.2233, -124.1550

Location: 16 km SE of Petrolia, CA

Country: United States

USGS link to NOAA tsunami information: Not linked

Review status: Automatic

Source: USGS event page

How strong was this earthquake?

Micro earthquakes are almost never felt at the surface and are recorded only by seismographs.

A magnitude 1.8 earthquake radiates roughly 8.1 kg of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 51, which is below the USGS threshold of more than 600 for its significant-earthquake list. The ranking combines magnitude with available Did You Feel It responses and PAGER alert level; it is not a direct measurement of damage.

What the magnitude scale actually measures →

When it happened locally

That is about 21:35 local solar time at the epicentre, late at night.

This event was shallower than 77% of the 153,430 earthquakes recorded in the United States in our catalogue and stronger than 76% of them.

Where was the epicentre?

The epicentre was located at 40.2233, -124.1550 — 16 km southeast of Petrolia. The closest other recorded event was a magnitude 2.8 earthquake 2 km west of here on 03 September 2026.

The nearest other settlements in our records are Alder Springs (140 km east-southeast), Anderson (170 km east) and Anderson Springs (213 km southeast).

Why the 2 km depth matters

At 2 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, events this small are usually detected by instruments rather than people. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.

Read more on how focal depth changes what you feel →

What does the tsunami information flag mean?

The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M1.8 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.

How earthquakes generate tsunamis, and what the alert levels mean →

Aftershocks and local seismic history

No further earthquakes have been recorded within about 150 km of the epicentre since this event was recorded.

39 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.7 event near Pistol River on 03 June 2026. This M1.8 event released about 660,693 times less energy than that event.

540 earthquakes have been recorded within 100 km of this epicentre in the past year, 47 of them in the past 30 days.

How long aftershock sequences last, and how large they get →

Where this event sits in the record

This earthquake is part of the September 2026 worldwide record, and of earthquakes in the United States during September 2026. Browse the full monthly archive to compare periods.

Nearest recorded earthquakes to this epicentre

Other recent earthquakes in the United States

All recorded earthquakes in the United States →

Other magnitude 1 earthquakes worldwide

Questions about this earthquake

How strong was the earthquake near Petrolia?

It measured magnitude 1.8 — a micro earthquake. A magnitude 1.8 earthquake radiates roughly 8.1 kg of TNT equivalent in seismic energy.

How deep was the earthquake near Petrolia?

The focus was 2 km below the surface, which counts as shallow.

Was the Petrolia earthquake felt at the surface?

At magnitude 1.8 and a focal depth of 2 km, shaking would have been concentrated near the epicentre.

When did the earthquake near Petrolia happen?

04 September 2026 at 05:52 UTC.

Was there a tsunami?

No. The USGS record carries no tsunami-information link for this event.

Have there been aftershocks?

No further earthquakes have been recorded within about 150 km of the epicentre since this event was recorded.

How often do earthquakes happen near Petrolia?

39 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.7 event near Pistol River on 03 June 2026. This M1.8 event released about 660,693 times less energy than that event.