Earthquake near Portola, CA

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 Portola, 7 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: Portola 7 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 37 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 5.8 410,000× the energy of this one
2. Magna, Utah 2020 M 5.7 290,000× the energy of this one
3. Around the size people start to feel M 3.0 26× the energy of this one
4. This earthquake M 2.1 about 37 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 4.7 on 2021-05-07 — about 7,700 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 6.0 6 km WNW of Verdi, California · 50 km SE of this epicentre Dec 29, 1948
2. 5.6 6 km NNE of Doyle, California · 43 km ENE of this epicentre Dec 14, 1950
3. 5.6 5 km NE of Loyalton, California · 30 km SE of this epicentre Apr 1, 1959
4. 5.3 11 km N of Soda Springs, California · 50 km S of this epicentre Mar 30, 1943
5. 5.3 4 km S of Doyle, California · 34 km ENE of this epicentre Feb 22, 1979

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 39.8737, -120.4847. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 2.3 11km NW of Verdi-Mogul, NV 23:48 UTC
2. 1.9 6 km NNW of Verdi, California 20:09 UTC
3. 1.6 6 km NNW of Beckwourth, California 01:41 UTC
4. 1.6 Northern California 23:30 UTC
5. 1.6 8 km SSE of Johnsville, California 02:45 UTC
6. 1.6 7 km S of Plumas Eureka (historical), California 10:02 UTC
7. 1.5 9 km SSE of Beckwourth, California 05:21 UTC
8. 1.6 1 km NNE of Paxton, California 07:30 UTC
9. 1.5 1 km WNW of Keddie, California 07:49 UTC
10. 1.7 1 km W of Keddie, California 13:09 UTC
11. 1.6 0 km E of Paxton, California 11:13 UTC
12. 2.8 3km N of Greenhorn, CA 14:40 UTC
13. 1.6 5 km NNW of Plumas Eureka (historical), California 10:17 UTC
14. 1.5 1 km SW of Spring Garden, California 20:16 UTC
15. 2.2 4km NE of Lake Davis, CA 13:24 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 22:21 UTC. 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.