QuakeIndex

Earthquake · reviewed by a seismologist

M 3.4mw

Earthquake near Big Bear City, CA

No earthquake was likely felt in Big Bear City in the 24 hours to 6:23 am PST (14:23 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 3.4 earthquake was recorded 10 km (7 mi) north of Big Bear City, CA, at 6:44 pm PDT on 6 October 2020 (01:44 UTC), 7.8 km deep. 90 people have reported feeling it to USGS.

USGS: 10km N of Big Bear City, CA

70 km (43 mi) NE of Riverside, CA · 40 km (25 mi) ESE of Apple Valley, CA

6:44 pm PDT, Oct 6, 2020 · · 7.8 km deep · released about 2 tons of TNT

10 km30 km60 km120 km N San Bernardino County 81 kmRiverside County 103 kmOrange County 116 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
6:44 pm PDT on 6 October 2020 ()
Where
10 km (7 mi) north of Big Bear City, CA · earthquakes near Big Bear City
Magnitude
M 3.4 (mw)
Depth
7.8 km below the surface
Felt
90 reports · strongest reported intensity IV
Measured shaking
intensity IV (ShakeMap)
Nearest
San Bernardino County, 81 km NE
Nearest mapped fault
North Frontal thrust system, 2 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 2051 days ago

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 58 km (36 mi) from the epicentre. In Big Bear City, 10 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 10 km, intensity III · Big Bear Lake 15 km, intensity III · Lucerne Valley 16 km, intensity III · Lake Arrowhead 35 km, intensity II · Apple Valley 37 km, intensity II · Yucaipa 41 km, intensity II · Morongo Valley 41 km, intensity II · Mentone 42 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 2 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.4 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 83,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 3,700× the energy of this one
  3. Magna, Utah 2020 M 5.7 2,600× the energy of this one
  4. This earthquake M 3.4 about 2 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 4.3× 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 40 times the energy of this one.

Before 2016, the USGS record lists 27 earthquakes of M5 or more within 50 km; the five largest:

  1. 7.3 The 1992 Landers, California Earthquake · 40 km ESE of this epicentre
  2. 6.3 The 1992 Big Bear, California Earthquake · 17 km S of this epicentre
  3. 6.2 3 km SE of San Bernardino, California · 49 km SW of this epicentre
  4. 6.0 The 1986 North Palm Springs, California Earthquake · 44 km SSE of this epicentre
  5. 5.8 3km NE of Yucca Valley, California · 46 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 34.3542, -116.8267. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
San Bernardino County, CA 81 km (51 mi) NE earthquakes near San Bernardino County
Riverside County, CA 103 km (64 mi) SE earthquakes near Riverside County
Orange County, CA 116 km (72 mi) SW earthquakes near Orange County

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

Aftershocks so far

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

  1. 2.5 18km N of Banning, CA
  2. 1.6 17km NNW of Morongo Valley, CA
  3. 1.5 22km N of Yucca Valley, CA
  4. 1.9 12km WSW of Morongo Valley, CA
  5. 1.7 30km WSW of Ludlow, CA
  6. 1.5 10km NE of Running Springs, CA
  7. 2.0 13km WNW of Morongo Valley, CA
  8. 1.7 13km WNW of Morongo Valley, CA
  9. 3.5 13km WNW of Morongo Valley, CA
  10. 1.6 12km E of Yucaipa, CA
  11. 1.8 10km NNW of Cabazon, CA
  12. 1.6 1km ENE of Redlands, CA
  13. 1.5 4km S of Redlands, CA
  14. 1.6 12km ESE of Big Bear City, CA
  15. 1.5 3km WSW of Redlands, 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.