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M 3.4 Earthquake Strikes 6 km SE of Ontario, CA

Source: USGS · Southern California

A magnitude 3.4 earthquake was recorded by USGS near 6 km SE of Ontario. On the USGS Earthquake Hazards Program scale, M3.4 is classified "Minor". Among the 1,720 earthquake reports Areazine has published, this M3.4 event ranks stronger than 26% of them (rank #1,179 by magnitude).

30 seconds on this earthquake report

Magnitude
M 3.4
USGS class
Minor
Location
6 km SE of Ontario
Archive rank
#1,179 of 1,720
Source
USGS
Published
September 2, 2026
MINOR

Out of 1,720 earthquake reports Areazine has logged, this one outranks 26% of them — 1,178 recorded a higher magnitude.

Record status: a snapshot from USGS, not a final record. Check USGS's own event page for aftershocks and any later revision to the magnitude shown here.

What Happened

A magnitude 3.4 ml earthquake struck 6 km SE of Ontario, CA, at a depth of 6.16 km. The event occurred at 1788352632720 (Unix timestamp, corresponding to approximately 12:37 UTC on August 3, 2026).

Location Details

The epicenter was located at coordinates 34.0133°N, 117.5907°W. The shallow depth of 6.16 km (less than 20 km) places it in the shallow category, where seismic waves reach the surface more intensely.

Impact Assessment

The earthquake was felt by 44 people, with a maximum reported intensity (CDI) of 4.1 and instrumental intensity (MMI) of 3.94. No tsunami advisory was issued (tsunami: 0) and no alert level was assigned.

What You Should Know

This was a minor earthquake (M 2.5-3.9 range) that is often felt but rarely causes damage. Residents in the area may experience aftershocks.

Source

USGS Event Page

Original source: USGS Official Notice ↗

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Similar notices nationwide by length or severity timing 8

Two cross-category peer sets, both computed from Areazine's own archive: notices with a similar body length, and notices near the same severity and agency date. These are drawn from other categories, not the same-feed Related list above.

Similar body length

Nearest notices by article body length (918 characters here).

Advice Issued for 245-Hectare Grass Fire Near Annie Pyers Dr, Gundagai 918 chars Planned Burn Alert in Kurrajong Heights, Hawkesbury 918 chars Blizzard Warning Issued for Resolute as Conditions Deteriorate 918 chars Yellow Frost Advisory Issued for Burin Peninsula 918 chars

Similar severity timing

Same severity (low) notices issued closest in time to September 2, 2026.

Squall Warning Changed for Southern Georgian Bay low Yellow Frost Advisory in Effect for Western and Central Newfoundland low Squall Watch Changed for Lake Simcoe (Sep 2, 2026) low Squall Watch Changed for Lake St. Clair (Sep 3, 2026) low

Frequently Asked Questions

Questions readers often have about this USGS earthquake report.

What was the magnitude of this event? ▾
A magnitude 3.4 earthquake occurred 6 km southeast of Ontario, California, on August 3, 2026, at 12:37 UTC.
What does a magnitude 3.4 ("Minor") earthquake mean? ▾
The USGS classifies M3.4 as "Minor" on its Earthquake Hazards Program scale. Events in this range are rarely felt beyond the immediate epicenter and typically cause no damage; most are recorded only by seismographs.
Is this earthquake stronger or weaker than others in the archive? ▾
This is the #1,179 strongest of the 1,720 earthquake reports in Areazine's archive by magnitude, stronger than 26% of them and weaker than 1,178 others.
Was Ontario likely to feel this earthquake? ▾
This event was centered 6 km SE of Ontario. Shaking intensity falls off sharply with distance from the epicenter and depends on depth and local geology, so check the USGS "Did You Feel It?" report for this event for real felt-shaking data rather than assuming from magnitude and distance alone.

Primary source data

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AirNow (EPA / NOAA)

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National Weather Service

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CDC Air Quality & Health

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