Earthquake near Charter Oak, CA

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.

At this magnitude and depth it was probably too small to be felt, even directly above it. 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.

Earthquakes near other towns within 30 km: Covina, San Dimas, Glendora, Citrus, Azusa, La Verne.

How big was it?

This earthquake released about 0.65 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 1.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 23,000,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000,000× the energy of this one
3. Around the size people start to feel M 3.0 1,500× the energy of this one
4. This earthquake M 0.9 about 0.65 lb of TNT

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 4.5 on 2020-09-19 — about 300,000 times the energy of this one.

Before 2016, the USGS record lists 10 earthquakes of M5 or more within 50 km; the five largest:

1. 5.9 The 1987 Whittier Narrows, California Earthquake · 22 km WSW of this epicentre Oct 1, 1987
2. 5.8 The 1991 Sierra Madre, California Earthquake · 23 km NW of this epicentre Jun 28, 1991
3. 5.5 The 1990 Upland, California Earthquake · 15 km ENE of this epicentre Feb 28, 1990
4. 5.4 5km S of Chino Hills, CA · 19 km SSE of this epicentre Jul 29, 2008
5. 5.2 3km W of Lytle Creek, CA · 34 km ENE of this epicentre Sep 12, 1970

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 34.1008, -117.8497. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 1.6 3 km S of Fontana, CA 00:04 UTC
2. 1.1 4 km SE of Littlerock, CA 11:27 UTC
3. 1.1 3 km S of Fontana, CA 03:06 UTC
4. 1.5 7 km SSE of Home Gardens, CA 21:51 UTC
5. 1.7 5 km SE of Ontario, CA 21:48 UTC
6. 1.7 5 km SW of Lytle Creek, CA 11:13 UTC
7. 0.8 3 km W of Fontana, CA 10:21 UTC
8. 0.7 5 km SE of Ontario, CA 08:22 UTC
9. 3.2 2 km SW of Signal Hill, CA 07:44 UTC
10. 0.8 2 km W of Fontana, CA 16:39 UTC
11. 0.9 2 km W of Fontana, CA 16:30 UTC
12. 0.5 1 km WNW of Fontana, CA 16:27 UTC
13. 0.7 3 km W of Fontana, CA 15:23 UTC
14. 1.1 2 km W of Fontana, CA 14:30 UTC
15. 0.6 7 km N of Rancho Cucamonga, CA 12:24 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 09:22 UTC. QuakeIndex does not forecast aftershocks. When USGS issues an operational aftershock forecast it appears on the USGS event page.

Revisions

USGS refines a solution as more stations report. Every change we have seen is listed here.

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.