Earthquake · reviewed by a seismologist
M 3.6mw
Earthquake near Fontana, CA
No earthquake was likely felt in Fontana in the 24 hours to 5:56 am PST (13:56 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 3.6 earthquake was recorded 14 km (9 mi) north-northwest of Fontana, CA, at 2:28 am PST on 8 December 2021 (10:28 UTC), 5.0 km deep. 994 people have reported feeling it to USGS.
USGS: 7km S of Lytle Creek, CA
10 km (6 mi) NE of Rancho Cucamonga, CA · 86 km (53 mi) ENE of Los Angeles, CA
- When
- 2:28 am PST on 8 December 2021 ()
- Where
- 14 km (9 mi) north-northwest of Fontana, CA · earthquakes near Fontana
- Magnitude
- M 3.6 (mw)
- Depth
- 5.0 km below the surface
- Felt
- 994 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Orange County, 63 km SSW
- Nearest mapped fault
- San Jacinto fault, 3 km from its surface trace — near is not the same as on
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1022 days ago
Earthquake alerts for Fontana, CA
Get a notification in this browser when USGS records an earthquake near Fontana, CA. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 70 km (43 mi) from the epicentre. In Fontana, 14 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: Rancho Cucamonga 13 km, intensity III · Fontana 14 km, intensity III · Muscoy 16 km, intensity III · Rialto 16 km, intensity III · Upland 17 km, intensity III · Ontario 20 km, intensity III · Wrightwood 21 km, intensity III · Montclair 22 km, intensity III. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 4.1 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.6 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 42,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 1,900× the energy of this one
- Magna, Utah 2020 M 5.7 1,300× the energy of this one
- This earthquake M 3.6 about 4.1 tons of TNT
- Around the size people start to feel M 3.0 this one released 8.5× 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 14 times the energy of this one.
Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:
- 6.2 3 km SE of San Bernardino, California · 26 km ESE of this epicentre
- 5.8 The 1991 Sierra Madre, California Earthquake · 45 km W of this epicentre
- 5.6 7km ENE of Running Springs, CA · 43 km E of this epicentre
- 5.5 The 1990 Upland, California Earthquake · 19 km WSW of this epicentre
- 5.4 5km S of Chino Hills, CA · 37 km SW of this epicentre
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
Epicentre 34.2005, -117.5068. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Orange County, CA | 63 km (39 mi) | SSW | earthquakes near Orange County |
| Los Angeles County, CA | 69 km (43 mi) | W | earthquakes near Los Angeles County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
52 earthquakes have been recorded within 50 km since this one.
- 1.5 2km NW of Loma Linda, CA
- 1.8 3km SSW of San Bernardino, CA
- 1.6 10km NE of Lake Arrowhead, CA
- 1.5 3km ESE of Loma Linda, CA
- 2.0 7km NE of Lake Arrowhead, CA
- 1.7 10km WNW of Big Bear Lake, CA
- 1.7 10km WNW of Big Bear Lake, CA
- 1.8 8km N of Glendora, CA
- 2.6 2km S of Redlands, CA
- 1.5 4km SSW of Redlands, CA
- 1.6 2km NNW of Fontana, CA
- 1.5 2km E of Home Gardens, CA
- 1.5 4km SE of Home Gardens, CA
- 1.7 6km WNW of Fontana, CA
- 1.6 3km E of Yucaipa, CA
Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of . 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.