QuakeIndex

Earthquake · reviewed by a seismologist

M 4.5mw

Earthquake near South El Monte, CA

No earthquake was likely felt in South El Monte in the 24 hours to 1:37 am PST (09:37 UTC). The last one was M 3.2, 32 km (20 mi) SSW, at 12:44 am PDT on 9 October 2026, estimated intensity II (weak) in town; 1,090 felt reports to USGS. Every earthquake near South El Monte

This page: a magnitude 4.5 earthquake was recorded 3 km (2 mi) west-southwest of South El Monte, CA, at 11:38 pm PDT on 18 September 2020 (06:38 UTC), 17 km deep. 21,402 people have reported feeling it to USGS.

USGS: 3km WSW of South El Monte, CA

in Montebello, CA · 31 km (19 mi) E of Los Angeles, CA

11:38 pm PDT, Sep 18, 2020 · · 17 km deep · released about 97 tons of TNT

Every earthquake near South El Monte Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Los Angeles County 24 kmOrange County 49 kmVentura County 103 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
11:38 pm PDT on 18 September 2020 ()
Where
3 km (2 mi) west-southwest of South El Monte, CA · earthquakes near South El Monte
Magnitude
M 4.5 (mw)
Depth
17 km below the surface
Felt
21,402 reports · strongest reported intensity V
Measured shaking
intensity VI (ShakeMap)
USGS impact alert
green
Tsunami
USGS flagged this event for tsunami evaluation. Follow tsunami.gov for official messages.
Nearest
Los Angeles County, 24 km NW
Nearest mapped fault
Puente Hills blind thrust system, 9 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 654 days ago

This was a light earthquake. It is usually felt clearly nearby and can rattle windows and dishes, but damage is uncommon.

At this magnitude and depth, people at rest would likely notice it out to about 142 km (88 mi) from the epicentre. In South El Monte, 3 km away, the estimate is intensity IV (light). 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: South El Monte 3 km, intensity IV · Montebello 4 km, intensity IV · Rosemead 5 km, intensity IV · Monterey Park 5 km, intensity IV · El Monte 6 km, intensity IV · Pico Rivera 6 km, intensity IV · San Gabriel 7 km, intensity IV · West Whittier-Los Nietos 7 km, intensity IV. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 97 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.5 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 1,700× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 78× the energy of this one
  3. Magna, Utah 2020 M 5.7 55× the energy of this one
  4. This earthquake M 4.5 about 97 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 200× 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 (31 mi) since our catalogue begins in 2016. The previous largest was M 4.4 on 2018-08-29.

Before 2016, the USGS record lists 20 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.7 Northridge, California, earthquake · 46 km WNW of this epicentre
  2. 6.6 1971 San Fernando Earthquake, California · 50 km NNW of this epicentre
  3. 6.4 The 1933 Long Beach, California Earthquake · 46 km S of this epicentre
  4. 5.9 The 1987 Whittier Narrows, California Earthquake · 3 km N of this epicentre
  5. 5.9 1km ENE of Granada Hills, California · 46 km NW 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 34.0380, -118.0800. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Los Angeles County, CA 24 km (15 mi) NW earthquakes near Los Angeles County
Orange County, CA 49 km (30 mi) SE earthquakes near Orange County
Ventura County, CA 103 km (64 mi) WNW earthquakes near Ventura County

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

Aftershocks so far

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

  1. 1.6 2km SW of La Habra, CA
  2. 1.7 2km SE of Placentia, CA
  3. 2.7 2km SSE of Placentia, CA
  4. 1.6 3km W of South El Monte, CA
  5. 1.8 2km NNE of Villa Park, CA
  6. 2.8 6km SSW of Pearblossom, CA
  7. 1.6 6km SSW of Pearblossom, CA
  8. 1.7 3km W of Sylmar, CA
  9. 1.7 1km W of Brea, CA
  10. 1.8 1km SE of San Fernando, CA
  11. 1.9 6km ENE of Villa Park, CA
  12. 2.5 1km NW of Bell, CA
  13. 1.7 7km SSW of Pearblossom, CA
  14. 1.7 3km NE of Granada Hills, CA
  15. 1.5 2km S of Granada Hills, 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.