Earthquake · reviewed by a seismologist
M 3.3ml
Earthquake near Big Bear City, CA
No earthquake was likely felt in Big Bear City in the 24 hours to 6:32 am PST (14:32 UTC). The last one was M 1.5, 10 km (6 mi) ESE, at 12:11 pm PST on 3 November 2026, estimated intensity II (weak) in town. Every earthquake near Big Bear City
This page: a magnitude 3.3 earthquake was recorded 9 km (6 mi) north-northwest of Big Bear City, CA, at 12:21 am PDT on 20 August 2023 (07:21 UTC), 1.9 km deep. 32 people have reported feeling it to USGS.
USGS: 9 km NNW of Big Bear City, CA
37 km (23 mi) NE of Highland, CA · 146 km (91 mi) ENE of Los Angeles, CA
- When
- 12:21 am PDT on 20 August 2023 ()
- Where
- 9 km (6 mi) north-northwest of Big Bear City, CA · earthquakes near Big Bear City
- Magnitude
- M 3.3 (ml)
- Depth
- 1.9 km below the surface
- Felt
- 32 reports · strongest reported intensity IV
- Nearest
- San Bernardino County, 85 km NE
- Nearest mapped fault
- Helendale-South Lockhart fault, 3 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 1022 days ago
Earthquake alerts for Big Bear City, CA
Get a notification in this browser when USGS records an earthquake near Big Bear City, CA. No account or email needed.
Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 52 km (32 mi) from the epicentre. In Big Bear City, 9 km away, the estimate is intensity III (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: Big Bear City 9 km, intensity III · Big Bear Lake 12 km, intensity III · Lucerne Valley 14 km, intensity III · Lake Arrowhead 31 km, intensity II · Apple Valley 34 km, intensity II · Yucaipa 38 km, intensity II · Mentone 39 km, intensity II · Highland 39 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 1.4 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 120,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 5,400× the energy of this one
- Magna, Utah 2020 M 5.7 3,800× the energy of this one
- This earthquake M 3.3 about 1.4 tons of TNT
- Around the size people start to feel M 3.0 this one released 2.9× 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 since 2016 was M 4.5 on 2018-05-08 — about 59 times the energy of this one.
Before 2016, the USGS record lists 25 earthquakes of M5 or more within 50 km; the five largest:
- 7.3 The 1992 Landers, California Earthquake · 43 km ESE of this epicentre
- 6.3 The 1992 Big Bear, California Earthquake · 16 km SSE of this epicentre
- 6.2 3 km SE of San Bernardino, California · 46 km SW of this epicentre
- 6.0 The 1986 North Palm Springs, California Earthquake · 45 km SSE of this epicentre
- 5.8 3km NE of Yucca Valley, California · 49 km ESE 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 34.3425, -116.8698. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Bernardino County, CA | 85 km (53 mi) | NE | earthquakes near San Bernardino County |
| Riverside County, CA | 105 km (65 mi) | SE | earthquakes near Riverside County |
| Orange County, CA | 112 km (69 mi) | SW | earthquakes near Orange County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
48 earthquakes have been recorded within 50 km since this one.
- 1.5 11 km N of Banning, CA
- 1.6 9 km NE of Cabazon, CA
- 2.2 4 km S of Big Bear City, CA
- 1.8 22 km N of Yucca Valley, CA
- 1.5 4 km ENE of Calimesa, CA
- 2.0 40 km SW of Ludlow, CA
- 2.3 10 km NNW of Big Bear City, CA
- 2.3 9 km NNW of Big Bear City, CA
- 2.1 8 km NE of Yucaipa, CA
- 1.7 33 km ENE of Big Bear City, CA
- 1.8 35 km NE of Lucerne Valley, CA
- 1.8 39 km WSW of Ludlow, CA
- 1.7 9 km SW of Morongo Valley, CA
- 1.9 5 km ESE of Beaumont, CA
- 2.5 3 km E of Devore, 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
- The official USGS event page — the source of record for every value above
- Did you feel it? Report it to USGS — reports go to USGS, not to us
- ShakeMap for this event, when USGS has produced one
QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.