Earthquake near Fontana, CA

No earthquake was likely felt in Fontana in the 24 hours to 9:03 am PST (17:03 UTC). The last one was M 1.6, 5 km (3 mi) W, at 6:17 am PDT on 26 October 2026, estimated intensity II (weak) in town. Every earthquake near Fontana

This page: a magnitude 3.1 earthquake was recorded 4 km (2 mi) northwest of Fontana, CA, at 2:54 am PDT on 19 September 2023 (09:54 UTC), 6.8 km deep. 250 people have reported feeling it to USGS.

USGS: 2 km NW of Fontana, CA

in Fontana, CA · 87 km (54 mi) E of Los Angeles, CA

2:54 am PDT, Sep 19, 2023 · 2023-09-19 09:54 UTC · 6.8 km deep · released about 1,200 lb of TNT

Every earthquake near Fontana Felt it? Tell USGS Check my area

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: 2:54 am PDT on 19 September 2023 (2023-09-19 09:54 UTC)
Where: 4 km (2 mi) northwest of Fontana, CA · earthquakes near Fontana
Magnitude: M 3.1 (ml)
Depth: 6.8 km below the surface
Felt: 250 reports · strongest reported intensity III
Measured shaking: intensity III (ShakeMap)
Nearest: Orange County, 56 km SSW
Nearest mapped fault: Sierra Madre fault, 6 km from its surface trace — near is not the same as on
Status: Reviewed by a seismologist

USGS · last changed by USGS 775 days ago · we first saw it 775 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 39 km (24 mi) from the epicentre. In Fontana, 4 km away, the estimate is intensity III (weak). 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.

Likely felt in: Fontana 4 km, intensity III · Rialto 9 km, intensity III · Rancho Cucamonga 11 km, intensity III · Muscoy 12 km, intensity III · Rubidoux 14 km, intensity III · Colton 15 km, intensity III · Pedley 15 km, intensity III · Upland 17 km, intensity III. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 1,200 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.1 would have released about 32 times as much.

Northridge, California 1994 M 6.7 290,000× the energy of this one
Mineral, Virginia 2011 M 5.8 13,000× the energy of this one
Magna, Utah 2020 M 5.7 9,100× the energy of this one
This earthquake M 3.1 about 1,200 lb of TNT
Around the size people start to feel M 3.0 this one released 1.2× 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 4.4 on 2018-08-29 — about 95 times the energy of this one.

Before 2016, the USGS record lists 12 earthquakes of M5 or more within 50 km; the five largest:

6.2 3 km SE of San Bernardino, California · 20 km E of this epicentre Jul 23, 1923
6.0 The 1910 Lake Elsinore, California Earthquake · 46 km S of this epicentre May 15, 1910
5.6 7km ENE of Running Springs, CA · 42 km ENE of this epicentre Oct 16, 1999
5.5 The 1990 Upland, California Earthquake · 21 km W of this epicentre Feb 28, 1990
5.4 5km S of Chino Hills, CA · 33 km WSW of this epicentre Jul 29, 2008

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
Orange County, CA	56 km (35 mi)	SSW	earthquakes near Orange County
Los Angeles County, CA	73 km (46 mi)	W	earthquakes near Los Angeles County
San Bernardino County, CA	144 km (90 mi)	NE	earthquakes near San Bernardino County

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

Aftershocks so far

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

2.7 12 km WNW of Big Bear Lake, CA 06:14 UTC
1.5 5 km ESE of Yucaipa, CA 06:35 UTC
1.5 7 km SSE of Home Gardens, CA 21:36 UTC
1.5 10 km NE of Running Springs, CA 09:23 UTC
1.7 5 km SE of Home Gardens, CA 19:26 UTC
1.8 12 km SSW of Big Bear Lake, CA 17:48 UTC
1.7 2 km E of Fullerton, CA 06:39 UTC
2.3 2 km E of Fullerton, CA 04:28 UTC
3.3 2 km E of Fullerton, CA 04:09 UTC
1.6 7 km NE of Rancho Cucamonga, CA 03:02 UTC
1.9 6 km NNW of Yorba Linda, CA 08:34 UTC
1.6 4 km W of Yucaipa, CA 00:26 UTC
1.8 3 km NNE of Loma Linda, CA 23:11 UTC
1.8 3 km NNE of Loma Linda, CA 02:09 UTC
1.5 3 km S of Redlands, CA 17:51 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 17:03 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.