QuakeIndex

Earthquake · reviewed by a seismologist

M 2.5md

Earthquake near Mammoth Lakes, CA

No earthquake was likely felt in Mammoth Lakes in the 24 hours to 2:29 pm PST (22:29 UTC). The last one was M 2.9, 26 km (16 mi) SSE, at 3:54 am PDT on 24 October 2026, estimated intensity II (weak) in town. Every earthquake near Mammoth Lakes

This page: a magnitude 2.5 earthquake was recorded 39 km (24 mi) south-southeast of Mammoth Lakes, CA, at 6:20 am PDT on 22 September 2020 (13:20 UTC), 20 km deep. 1 person has reported feeling it to USGS.

USGS: 19km WSW of Round Valley, CA

6:20 am PDT, Sep 22, 2020 · · 20 km deep · released about 160 lb of TNT

10 km30 km60 km120 km N Mono County 65 kmMadera County 86 kmFresno County 100 kmMariposa County 103 kmEsmeralda County 113 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
6:20 am PDT on 22 September 2020 ()
Where
39 km (24 mi) south-southeast of Mammoth Lakes, CA · earthquakes near Mammoth Lakes
Magnitude
M 2.5 (md)
Depth
20 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Mono County, 65 km N
Nearest mapped fault
Round Valley fault, 14 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 1648 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 Mammoth Lakes, 39 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: West Bishop.

How big was it?

This earthquake released about 160 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.5 would have released about 32 times as much.

  1. Mineral, Virginia 2011 M 5.8 92,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 65,000× the energy of this one
  3. Around the size people start to feel M 3.0 5.8× the energy of this one
  4. This earthquake M 2.5 about 160 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 4.8 on 2016-02-16 — about 2,600 times the energy of this one.

Before 2016, the USGS record lists 36 earthquakes of M5 or more within 50 km; the five largest:

  1. 6.4 The 1986 Chalfant Valley, California Earthquake · 38 km NE of this epicentre
  2. 6.2 9 km SW of Aspen Springs, California · 19 km N of this epicentre
  3. 6.1 11 km WNW of Aspen Springs, California · 29 km N of this epicentre
  4. 6.1 8 km W of Aspen Springs, California · 25 km N of this epicentre
  5. 6.1 4 km NNW of Round Valley, California · 21 km NE 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 37.3323, -118.7875. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Mono County, CA 65 km (41 mi) N earthquakes near Mono County
Madera County, CA 86 km (54 mi) W earthquakes near Madera County
Fresno County, CA 100 km (62 mi) SW earthquakes near Fresno County
Mariposa County, CA 103 km (64 mi) WNW earthquakes near Mariposa County
Esmeralda County, NV 113 km (70 mi) ENE earthquakes near Esmeralda County
Tuolumne County, CA 129 km (80 mi) NW earthquakes near Tuolumne 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. 2.7 11km SW of Toms Place, CA
  2. 1.8 9km ESE of Mammoth Lakes, CA
  3. 1.7 9km E of Mammoth Lakes, CA
  4. 2.3 6km ESE of Round Valley, CA
  5. 2.9 19km NNW of Toms Place, CA
  6. 1.7 12km E of Mammoth Lakes, CA
  7. 1.9 11km E of Mammoth Lakes, CA
  8. 2.0 15km SW of Toms Place, CA
  9. 1.6 4km E of Mammoth Lakes, CA
  10. 2.1 4km E of Mammoth Lakes, CA
  11. 1.7 4km E of Mammoth Lakes, CA
  12. 1.6 4km E of Mammoth Lakes, CA
  13. 2.2 4km E of Mammoth Lakes, CA
  14. 2.9 4km E of Mammoth Lakes, CA
  15. 1.8 4km E of Mammoth Lakes, 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.