QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1ml

Earthquake near Lake Arrowhead, CA

No earthquake was likely felt in Lake Arrowhead in the 24 hours to 6:54 am PST (14:54 UTC). The last one was M 2.0, 11 km (7 mi) SSW, at 3:40 pm PDT on 22 September 2026, estimated intensity II (weak) in town; 14 felt reports to USGS. Every earthquake near Lake Arrowhead

This page: a magnitude 2.1 earthquake was recorded 6 km (4 mi) east-northeast of Lake Arrowhead, CA, at 5:18 pm PDT on 20 October 2017 (00:18 UTC), 5.6 km deep.

USGS: 6km ENE of Lake Arrowhead, CA

18 km (11 mi) N of Highland, CA · 121 km (75 mi) ENE of Los Angeles, CA

5:18 pm PDT, Oct 20, 2017 · · 5.6 km deep · released about 40 lb of TNT

Every earthquake near Lake Arrowhead Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Orange County 89 kmLos Angeles County 104 kmSan Bernardino County 108 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
5:18 pm PDT on 20 October 2017 ()
Where
6 km (4 mi) east-northeast of Lake Arrowhead, CA · earthquakes near Lake Arrowhead
Magnitude
M 2.1 (ml)
Depth
5.6 km below the surface
Felt
no reports yet
Nearest
Orange County, 89 km SW
Nearest mapped fault
Cleghorn fault, 7 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 3304 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 16 km (10 mi) from the epicentre. In Lake Arrowhead, 6 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.

Likely felt in: Lake Arrowhead 6 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 4.4 on 2016-01-06 — about 2,900 times the energy of this one.

Before 2016, the USGS record lists 14 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.3 The 1992 Big Bear, California Earthquake · 29 km ESE of this epicentre
  2. 6.2 3 km SE of San Bernardino, California · 24 km SSW of this epicentre
  3. 5.6 7km ENE of Running Springs, CA · 10 km ESE of this epicentre
  4. 5.5 11km SSE of Big Bear Lake, California · 29 km ESE of this epicentre
  5. 5.3 Near San Bernardino, California · 9 km SSE 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 34.2773, -117.1333. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Orange County, CA 89 km (56 mi) SW earthquakes near Orange County
Los Angeles County, CA 104 km (65 mi) W earthquakes near Los Angeles County
San Bernardino County, CA 108 km (67 mi) NE earthquakes near San Bernardino County
Riverside County, CA 121 km (75 mi) ESE earthquakes near Riverside County

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

Aftershocks so far

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

  1. 2.2 9km SW of Lytle Creek, CA
  2. 2.4 3km SW of San Bernardino, CA
  3. 1.5 3km WSW of Rancho Cucamonga, CA
  4. 2.2 3km NNW of Glen Avon, CA
  5. 2.0 7km SSE of Redlands, CA
  6. 2.4 6km N of Big Bear City, CA
  7. 1.5 8km SSW of Lytle Creek, CA
  8. 2.1 14km NNE of Cabazon, CA
  9. 2.0 6km NNE of Banning, CA
  10. 1.7 2km ESE of Loma Linda, CA
  11. 2.1 2km SE of Mentone, CA
  12. 1.7 7km NE of Beaumont, CA
  13. 1.6 6km NE of San Bernardino, CA
  14. 2.9 6km NE of San Bernardino, CA
  15. 2.1 6km NE of San Bernardino, 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.