Minor M 3.7 Earthquake Reported 25 km West of Petrolia, California

Source: USGS · Northern California

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A minor 3.7 magnitude earthquake occurred offshore near Petrolia, California, on March 20, 2026. The shallow quake resulted in no tsunami warnings.

What this USGS earthquake report tells you, and what most readers miss

This notice was issued by USGS on April 3, 2026 and geographically references Northern California. Its severity classification of "low" signals how the issuing agency weighs the risk of harm if no action is taken — "critical" and "high" tier alerts typically carry direct consumer actions, while "medium" and "low" tend toward informational guidance or monitoring advisories. The category it belongs to — Earthquakes — determines the regulatory framework behind it, which shapes what remedies (refunds, replacements, recalls, evacuations) are available to affected individuals and who holds statutory responsibility for enforcement.

Most readers skim a notice like this, check whether they are personally affected, and move on. The more useful lens is to read it as a data point about the issuing system: how quickly USGS detected the hazard, how precise the geographic or product-identifier scope is, and whether similar notices have clustered in the same category or region in the last 90 days. Cluster patterns frequently precede a broader regulatory action — a single localized USGS earthquake report is isolated; three of them within a quarter often indicate a supply-chain, infrastructure, or seasonal driver that will keep producing notices until something structural changes.

For decision-making, Areazine pairs each alert with the original agency URL, the full agency name, and a timestamp so you can verify the notice against the primary source before acting on it. Tags on this item (earthquake, seismic, usgs, Northern California) map to related alerts in the same area of risk — browsing them together gives a clearer picture than any single notice alone, because the shape of an ongoing issue only becomes visible across multiple sequential alerts.

What Happened

A minor earthquake with a magnitude of 3.7 mw was recorded on March 20, 2026, at 12:56 UTC (5:56 AM PDT). The event was centered approximately 25 km west of Petrolia, California, according to data from the U.S. Geological Survey (USGS).

Location Details

The earthquake occurred at a depth of 19.33 km, which is classified as a shallow event. Shallow earthquakes, occurring at depths of less than 20 km, are often more noticeable to those nearby than deeper seismic activity. The epicenter was located at coordinates 40.3065°N and 124.5845°W, positioned off the coast of Northern California.

Impact Assessment

There is no tsunami advisory, watch, or warning in effect for this event. The USGS reported a Modified Mercalli Intensity (MMI) of 2.583, suggesting weak shaking near the epicenter. No felt reports were logged at the time of the report, and no damage or injuries have been documented in connection with this routine seismic activity.

What You Should Know

Earthquakes with magnitudes between 2.5 and 3.9 are classified as minor. While they are frequently felt by residents, they rarely cause damage to buildings or infrastructure. Residents in the region should remain aware that aftershocks are a possibility following any seismic event, though they are typically smaller than the initial quake.

Source

Data provided by the USGS Earthquake Hazards Program.

Original source: USGS Official Notice ↗

All Earthquakes →

Frequently Asked Questions

Common questions about this USGS earthquake report.

What is this USGS earthquake report about?
A minor 3.7 magnitude earthquake occurred offshore near Petrolia, California, on March 20, 2026. The shallow quake resulted in no tsunami warnings.
Which agency issued this alert?
This alert was issued by USGS. The original notice is available at the source link at the bottom of this article.
How severe is this alert?
This alert is classified as "low" severity. No immediate action required, but stay aware.
What area is affected?
This alert affects Northern California. Check with USGS for the most current geographic scope.
Where can I find more Earthquakes updates?
Browse the full Earthquakes feed on Areazine at areazine.com/earthquakes/ for the latest updates from USGS and other agencies.