QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

Earthquake near Signal Hill, CA

No earthquake was likely felt in Signal Hill in the 24 hours to 6:50 pm PST (02:50 UTC). The last one was M 2.5, 15 km (9 mi) SSW, at 6:11 pm PST on 12 November 2026, estimated intensity II (weak) in town; 16 felt reports to USGS. Every earthquake near Signal Hill

This page: a magnitude 2.1 earthquake was recorded in Signal Hill, CA, at 1:54 am PDT on 31 May 2023 (08:54 UTC), 7.0 km deep. 95 people have reported feeling it to USGS.

USGS: 2km NW of Signal Hill, CA

in Long Beach, CA · 31 km (19 mi) SE of Los Angeles, CA

1:54 am PDT, May 31, 2023 · · 7.0 km deep · released about 40 lb of TNT

Every earthquake near Signal Hill Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Orange County 41 kmLos Angeles County 43 kmVentura County 106 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
1:54 am PDT on 31 May 2023 ()
Where
in Signal Hill, CA · earthquakes near Signal Hill
Magnitude
M 2.1 (ml)
Depth
7.0 km below the surface
Felt
95 reports · strongest reported intensity IV
Nearest
Orange County, 41 km ESE
Nearest mapped fault
Puente Hills blind thrust system, 10 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 1254 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 15 km (9 mi) from the epicentre. 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: Signal Hill in town, intensity II · Long Beach 6 km, intensity II · Lakewood 6 km, intensity II · Paramount 8 km, intensity II · Bellflower 9 km, intensity II · Compton 9 km, intensity II · Carson 9 km, intensity II · Seal Beach 11 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 40 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 380,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 270,000× the energy of this one
  3. Around the size people start to feel M 3.0 24× the energy of this one
  4. This earthquake M 2.1 about 40 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 4,900 times the energy of this one.

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

  1. 6.4 The 1933 Long Beach, California Earthquake · 27 km SE of this epicentre
  2. 5.9 The 1987 Whittier Narrows, California Earthquake · 29 km NNE of this epicentre
  3. 5.4 5km S of Chino Hills, CA · 41 km ENE of this epicentre
  4. 5.3 2 km SSW of Santa Monica, California · 36 km NW of this epicentre
  5. 5.3 7km W of Newport Beach, CA · 27 km SE 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 33.8180, -118.1812. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Orange County, CA 41 km (25 mi) ESE earthquakes near Orange County
Los Angeles County, CA 43 km (27 mi) N earthquakes near Los Angeles County
Ventura County, CA 106 km (66 mi) NW earthquakes near Ventura County

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

Aftershocks so far

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

  1. 1.9 6 km NNW of Yorba Linda, CA
  2. 2.6 0 km NNW of View Park-Windsor Hills, CA
  3. 1.8 0 km N of View Park-Windsor Hills, CA
  4. 1.6 20 km S of San Pedro, CA
  5. 1.6 22 km SSW of Seal Beach, CA
  6. 1.6 2 km NNE of Placentia, CA
  7. 2.5 5 km ESE of Inglewood, CA
  8. 1.6 0 km W of View Park-Windsor Hills, CA
  9. 1.6 4 km ESE of Gardena, CA
  10. 1.9 10 km WSW of Newport Beach, CA
  11. 2.0 3 km NW of Placentia, CA
  12. 2.0 1 km WNW of Huntington Park, CA
  13. 2.1 1 km SSE of View Park-Windsor Hills, CA
  14. 2.0 3 km S of Encino, CA
  15. 2.6 23 km SSW of Newport Beach, 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.