Earthquake · reviewed by a seismologist
M 1.6ml
Earthquake near Portola, CA
No earthquake was likely felt in Portola in the 24 hours to 6:11 am PST (14:11 UTC). The last one was M 2.7, 8 km (5 mi) N, at 8:16 am PST on 10 November 2026, estimated intensity III (weak) in town; 9 felt reports to USGS. Every earthquake near Portola
This page: a magnitude 1.6 earthquake was recorded 15 km (9 mi) west-northwest of Portola, CA, at 8:03 pm PDT on 31 May 2023 (03:03 UTC), 7.8 km deep.
USGS: Northern California
76 km (47 mi) WNW of Reno, NV
- When
- 8:03 pm PDT on 31 May 2023 ()
- Where
- 15 km (9 mi) west-northwest of Portola, CA · earthquakes near Portola
- Magnitude
- M 1.6 (ml)
- Depth
- 7.8 km below the surface
- Felt
- no reports yet
- Nearest
- Plumas County, 21 km NW
- Nearest mapped fault
- Mohawk Valley fault, 6 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 1260 days ago
Earthquake alerts for Portola, CA
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Alerts are on for .
Not a warning. An alert comes after USGS publishes a quake, usually minutes after the shaking. For early warning use ShakeAlert, through your phone's Wireless Emergency Alerts or the MyShake app.
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 8 km (5 mi) from the epicentre. In Portola, 15 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: East Quincy, Quincy.
How big was it?
This earthquake released about 7.6 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.6 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,000,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,400,000× the energy of this one
- Around the size people start to feel M 3.0 130× the energy of this one
- This earthquake M 1.6 about 7.6 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 2016-08-04 — about 21,000 times the energy of this one.
Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:
- 5.6 5 km NE of Loyalton, California · 40 km ESE of this epicentre
- 5.3 4 km S of Doyle, California · 45 km ENE of this epicentre
- 5.2 3 km N of Blairsden, California · 8 km S 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 39.8822, -120.6191. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Plumas County, CA | 21 km (13 mi) | NW | earthquakes near Plumas County |
| Sierra County, CA | 35 km (22 mi) | SSE | earthquakes near Sierra County |
| Nevada County, CA | 66 km (41 mi) | SSW | earthquakes near Nevada County |
| Butte County, CA | 87 km (54 mi) | WSW | earthquakes near Butte County |
| Placer County, CA | 92 km (57 mi) | S | earthquakes near Placer County |
| Yuba County, CA | 92 km (57 mi) | SW | earthquakes near Yuba County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
7 earthquakes have been recorded within 50 km since this one.
- 1.6 6 km SW of Cromberg, California
- 1.8 4 km NW of Spring Garden, California
- 2.5 13 km SSW of Loyalton, CA
- 1.5 7 km SSE of Canyondam, California
- 2.5 2km S of Canyondam, CA
- 2.4 9km NNW of Loyalton, CA
- 1.6 9 km SSE of Sierraville, California
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
- 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.