QuakeIndex

Earthquake · reviewed by a seismologist

M 1.7ml

Earthquake near Big Bear Lake, CA

No earthquake was likely felt in Big Bear Lake in the 24 hours to 8:58 am PST (16:58 UTC). The last one was M 2.6, 7 km (4 mi) NE, at 1:40 am PDT on 6 October 2026, estimated intensity III (weak) in town; 18 felt reports to USGS. Every earthquake near Big Bear Lake

This page: a magnitude 1.7 earthquake was recorded 11 km (7 mi) south-southeast of Big Bear Lake, CA, at 8:06 am PDT on 4 August 2021 (15:06 UTC), 6.9 km deep.

USGS: 11km SSE of Big Bear Lake, CA

20 km (12 mi) NE of Yucaipa, CA · 142 km (88 mi) E of Los Angeles, CA

8:06 am PDT, Aug 4, 2021 · · 6.9 km deep · released about 11 lb of TNT

Every earthquake near Big Bear Lake Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Riverside County 93 kmOrange County 98 kmSan Bernardino County 101 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
8:06 am PDT on 4 August 2021 ()
Where
11 km (7 mi) south-southeast of Big Bear Lake, CA · earthquakes near Big Bear Lake
Magnitude
M 1.7 (ml)
Depth
6.9 km below the surface
Felt
no reports yet
Nearest
Riverside County, 93 km ESE
Nearest mapped fault
San Andreas 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 1926 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 10 km (6 mi) from the epicentre. In Big Bear Lake, 11 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.

Earthquakes near other towns within 30 km: Big Bear City, Yucaipa, Cherry Valley, Running Springs, Calimesa, Banning.

How big was it?

This earthquake released about 11 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 1,400,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,000,000× the energy of this one
  3. Around the size people start to feel M 3.0 89× the energy of this one
  4. This earthquake M 1.7 about 11 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 2018-05-08 — about 15,000 times the energy of this one.

Before 2016, the USGS record lists 32 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.3 The 1992 Landers, California Earthquake · 41 km E of this epicentre
  2. 6.7 The 1918 San Jacinto, California Earthquake · 44 km SSW of this epicentre
  3. 6.3 The 1992 Big Bear, California Earthquake · 8 km NE of this epicentre
  4. 6.2 3 km SE of San Bernardino, California · 36 km W of this epicentre
  5. 6.0 The 1986 North Palm Springs, California Earthquake · 30 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 34.1498, -116.8788. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Riverside County, CA 93 km (58 mi) ESE earthquakes near Riverside County
Orange County, CA 98 km (61 mi) WSW earthquakes near Orange County
San Bernardino County, CA 101 km (63 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

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

  1. 2.4 7km S of Redlands, CA
  2. 1.7 6km NW of San Jacinto, CA
  3. 1.6 9km SW of Morongo Valley, CA
  4. 2.1 11km NE of Yucaipa, CA
  5. 1.8 8km ENE of Moreno Valley, CA
  6. 1.6 12km ESE of Lucerne Valley, CA
  7. 3.1 3km NNW of Yucca Valley, CA
  8. 1.9 7km NNW of Cabazon, CA
  9. 2.2 16km ENE of Yucaipa, CA
  10. 2.0 6km SW of Banning, CA
  11. 1.8 13km NNE of Banning, CA
  12. 1.8 13km SE of Big Bear City, CA
  13. 2.4 5km SE of Valle Vista, CA
  14. 1.7 13km SE of Big Bear City, CA
  15. 2.7 6km N of Beaumont, 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.