QuakeIndex

Earthquake · reviewed by a seismologist

M 2.8ml

Earthquake near Fontana, CA

No earthquake was likely felt in Fontana in the 24 hours to 4:31 am PST (12:31 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 2.8 earthquake was recorded 5 km (3 mi) northwest of Fontana, CA, at 2:41 pm PDT on 10 August 2018 (21:41 UTC), 17 km deep. 17 people have reported feeling it to USGS.

USGS: 3km NW of Fontana, CA

in Fontana, CA · 86 km (54 mi) E of Los Angeles, CA

2:41 pm PDT, Aug 10, 2018 · · 17 km deep · released about 460 lb of TNT

Every earthquake near Fontana Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Orange County 57 kmLos Angeles County 72 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
2:41 pm PDT on 10 August 2018 ()
Where
5 km (3 mi) northwest of Fontana, CA · earthquakes near Fontana
Magnitude
M 2.8 (ml)
Depth
17 km below the surface
Felt
17 reports · strongest reported intensity III
Nearest
Orange County, 57 km SSW
Nearest mapped fault
Sierra Madre fault, 5 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 3015 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 21 km (13 mi) from the epicentre. In Fontana, 5 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: Fontana 5 km, intensity II · Rialto 10 km, intensity II · Rancho Cucamonga 10 km, intensity II · Muscoy 13 km, intensity II · Rubidoux 16 km, intensity II · Upland 16 km, intensity II · Pedley 16 km, intensity II · Colton 16 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 460 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 33,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 23,000× the energy of this one
  3. Around the size people start to feel M 3.0 2.1× the energy of this one
  4. This earthquake M 2.8 about 460 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

No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.

Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.2 3 km SE of San Bernardino, California · 21 km E of this epicentre
  2. 6.0 The 1910 Lake Elsinore, California Earthquake · 47 km S of this epicentre
  3. 5.8 The 1991 Sierra Madre, California Earthquake · 50 km WNW of this epicentre
  4. 5.6 7km ENE of Running Springs, CA · 43 km ENE of this epicentre
  5. 5.5 The 1990 Upland, California Earthquake · 20 km W 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 34.1215, -117.4808. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Orange County, CA 57 km (35 mi) SSW earthquakes near Orange County
Los Angeles County, CA 72 km (45 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

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

  1. 1.5 7km SSE of Home Gardens, CA
  2. 3.0 9km WSW of Wrightwood, CA
  3. 1.6 12km SSE of Corona, CA
  4. 1.7 7km SSW of Redlands, CA
  5. 1.9 4km N of La Verne, CA
  6. 2.1 7km WSW of Calimesa, CA
  7. 1.7 4km ENE of Calimesa, CA
  8. 3.5 4km ENE of Calimesa, CA
  9. 2.1 9km ENE of North Tustin, CA
  10. 1.7 9km E of Running Springs, CA
  11. 3.6 4km ENE of Calimesa, CA
  12. 1.8 8km E of Yorba Linda, CA
  13. 2.1 7km W of Calimesa, CA
  14. 1.9 2km WNW of Orange, CA
  15. 2.0 2km ESE of Loma Linda, 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.