QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8ml

Earthquake near Charter Oak, CA

No earthquake was likely felt in Charter Oak in the 24 hours to 7:57 am PST (15:57 UTC). The last one was M 3.6, 64 km (40 mi) WSW, at 8:40 am PDT on 27 September 2026, estimated intensity II (weak) in town; 1,735 felt reports to USGS. Every earthquake near Charter Oak

This page: a magnitude 1.8 earthquake was recorded 4 km (3 mi) south of Charter Oak, CA, at 5:23 pm PDT on 31 July 2017 (00:23 UTC), 11 km deep.

USGS: 4km S of Charter Oak, CA

5 km (3 mi) E of West Covina, CA · 52 km (32 mi) E of Los Angeles, CA

5:23 pm PDT, Jul 31, 2017 · · 11 km deep · released about 14 lb of TNT

Every earthquake near Charter Oak Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Los Angeles County 41 kmOrange County 44 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
5:23 pm PDT on 31 July 2017 ()
Where
4 km (3 mi) south of Charter Oak, CA · earthquakes near Charter Oak
Magnitude
M 1.8 (ml)
Depth
11 km below the surface
Felt
no reports yet
Nearest
Los Angeles County, 41 km WNW
Nearest mapped fault
Sierra Madre fault, 8 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 3304 days ago

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

At this magnitude and depth, people at rest would likely notice it out to about 8 km (5 mi) from the epicentre. In Charter Oak, 4 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: Covina 5 km, intensity II · Walnut 5 km, intensity II · Diamond Bar 5 km, intensity II · San Dimas 6 km, intensity II · West Covina 8 km, intensity II · Glendora 8 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 14 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,100,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 760,000× the energy of this one
  3. Around the size people start to feel M 3.0 68× the energy of this one
  4. This earthquake M 1.8 about 14 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 12 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 The 1933 Long Beach, California Earthquake · 50 km SSW of this epicentre
  2. 5.9 The 1987 Whittier Narrows, California Earthquake · 21 km W of this epicentre
  3. 5.8 The 1991 Sierra Madre, California Earthquake · 26 km NNW of this epicentre
  4. 5.5 The 1990 Upland, California Earthquake · 17 km ENE of this epicentre
  5. 5.4 5km S of Chino Hills, CA · 15 km SSE 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 34.0635, -117.8510. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Los Angeles County, CA 41 km (25 mi) WNW earthquakes near Los Angeles County
Orange County, CA 44 km (27 mi) S earthquakes near Orange County
Ventura County, CA 122 km (76 mi) WNW earthquakes near Ventura County
San Diego County, CA 153 km (95 mi) SE earthquakes near San Diego 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. 1.5 5km ENE of Rancho Cucamonga, CA
  2. 3.1 5km WNW of Willowbrook, CA
  3. 2.1 5km WNW of Willowbrook, CA
  4. 1.6 4km N of Gardena, CA
  5. 2.5 10km N of Lytle Creek, CA
  6. 1.8 3km WSW of East Los Angeles, CA
  7. 1.7 5km NE of Yorba Linda, CA
  8. 2.3 1km NNW of Colton, CA
  9. 1.9 5km SSE of Home Gardens, CA
  10. 2.4 4km SSW of Yorba Linda, CA
  11. 1.6 7km WSW of Huntington Beach, CA
  12. 2.1 4km SSW of Yorba Linda, CA
  13. 1.6 4km ESE of Placentia, CA
  14. 1.6 4km SSW of Yorba Linda, CA
  15. 2.4 4km SSW of Yorba 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.