QuakeIndex

Earthquake · reviewed by a seismologist

M 2.6ml

Earthquake near Rancho Cucamonga, CA

No earthquake was likely felt in Rancho Cucamonga in the 24 hours to 4:04 am PST (12:04 UTC). The last one was M 2.0, 10 km (6 mi) E, at 2:35 am PDT on 23 October 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Rancho Cucamonga

This page: a magnitude 2.6 earthquake was recorded 12 km (8 mi) north-northwest of Rancho Cucamonga, CA, at 10:00 pm PDT on 4 August 2020 (05:00 UTC), 9.2 km deep. 116 people have reported feeling it to USGS.

USGS: 11km NW of Rancho Cucamonga, CA

10 km (6 mi) N of Upland, CA · 72 km (45 mi) ENE of Los Angeles, CA

10:00 pm PDT, Aug 4, 2020 · · 9.2 km deep · released about 250 lb of TNT

Every earthquake near Rancho Cucamonga Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Los Angeles County 56 kmOrange County 60 km
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
10:00 pm PDT on 4 August 2020 ()
Where
12 km (8 mi) north-northwest of Rancho Cucamonga, CA · earthquakes near Rancho Cucamonga
Magnitude
M 2.6 (ml)
Depth
9.2 km below the surface
Felt
116 reports · strongest reported intensity V
Nearest
Los Angeles County, 56 km W
Nearest mapped fault
San Jacinto fault, 4 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 2213 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 22 km (14 mi) from the epicentre. In Rancho Cucamonga, 12 km away, the estimate is intensity II (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: Upland 12 km, intensity II · Rancho Cucamonga 12 km, intensity II · Claremont 13 km, intensity II · Montclair 14 km, intensity II · La Verne 15 km, intensity II · Ontario 15 km, intensity II · San Dimas 17 km, intensity II · Wrightwood 18 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 250 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.6 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 61,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 43,000× the energy of this one
  3. Around the size people start to feel M 3.0 3.8× the energy of this one
  4. This earthquake M 2.6 about 250 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 4.4 on 2018-08-29 — about 450 times the energy of this one.

Before 2016, the USGS record lists 9 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 3 km SE of San Bernardino, California · 39 km ESE of this epicentre
  2. 5.9 The 1987 Whittier Narrows, California Earthquake · 42 km WSW of this epicentre
  3. 5.8 The 1991 Sierra Madre, California Earthquake · 32 km WNW of this epicentre
  4. 5.5 The 1990 Upland, California Earthquake · 7 km SSW of this epicentre
  5. 5.4 5km S of Chino Hills, CA · 30 km SSW 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 34.2018, -117.6572. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Los Angeles County, CA 56 km (35 mi) W earthquakes near Los Angeles County
Orange County, CA 60 km (37 mi) S earthquakes near Orange County

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

Aftershocks so far

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

  1. 1.5 3km SW of La Mirada, CA
  2. 2.5 8km NNW of Rancho Cucamonga, CA
  3. 1.6 4km SSW of Lytle Creek, CA
  4. 1.6 11km NW of Rancho Cucamonga, CA
  5. 2.3 3km WSW of South El Monte, CA
  6. 3.2 11km NW of Rancho Cucamonga, CA
  7. 1.7 4km SE of Home Gardens, CA
  8. 1.6 3km W of South El Monte, CA
  9. 1.5 1km N of Redlands, CA
  10. 1.9 1km NNE of Redlands, CA
  11. 1.8 3km W of South El Monte, CA
  12. 1.6 3km W of South El Monte, CA
  13. 2.1 3km WSW of South El Monte, CA
  14. 1.6 3km WSW of South El Monte, CA
  15. 1.9 4km W of South El Monte, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.