Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near Portola, CA
No earthquake was likely felt in Portola in the 24 hours to 10:14 am PST (18:14 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 2.8 earthquake was recorded 18 km (11 mi) north of Portola, CA, at 9:54 pm PDT on 2 September 2021 (04:54 UTC), 12 km deep. 13 people have reported feeling it to USGS.
USGS: 11km NNE of Lake Davis, CA
69 km (43 mi) NW of Reno, NV
- When
- 9:54 pm PDT on 2 September 2021 ()
- Where
- 18 km (11 mi) north of Portola, CA · earthquakes near Portola
- Magnitude
- M 2.8 (md)
- Depth
- 12 km below the surface
- Felt
- 13 reports · strongest reported intensity III
- Nearest
- Plumas County, 33 km W
- Nearest mapped fault
- Mohawk Valley fault, 24 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 1821 days ago
Earthquake alerts for Portola, CA
Get a notification in this browser when USGS records an earthquake near Portola, CA. No account or email needed.
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 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 25 km (16 mi) from the epicentre. In Portola, 18 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 18 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 510 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 30,000× the energy of this one
- Magna, Utah 2020 M 5.7 21,000× the energy of this one
- Around the size people start to feel M 3.0 1.9× the energy of this one
- This earthquake M 2.8 about 510 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 310 times the energy of this one.
Before 2016, the USGS record lists 4 earthquakes of M5 or more within 50 km:
- 5.6 6 km NNE of Doyle, California · 34 km ENE of this epicentre
- 5.6 5 km NE of Loyalton, California · 35 km SE of this epicentre
- 5.3 4 km S of Doyle, California · 28 km E of this epicentre
- 5.2 3 km N of Blairsden, California · 23 km SW 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 39.9665, -120.4418. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Plumas County, CA | 33 km (20 mi) | W | earthquakes near Plumas County |
| Sierra County, CA | 44 km (27 mi) | S | earthquakes near Sierra County |
| Nevada County, CA | 80 km (49 mi) | SSW | earthquakes near Nevada County |
| Lassen County, CA | 85 km (53 mi) | N | earthquakes near Lassen County |
| Storey County, NV | 98 km (61 mi) | SE | earthquakes near Storey County |
| Placer County, CA | 103 km (64 mi) | SSW | earthquakes near Placer County |
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.
- 1.6 Northern California
- 1.6 Northern California
- 1.5 5 km SSW of Cromberg, California
- 2.2 17km WSW of Loyalton, CA
- 1.5 4 km SSW of Greenville, California
- 2.4 6km NW of Johnsville, CA
- 1.6 5 km WNW of Plumas Eureka, California
- 2.0 5 km NNW of Plumas Eureka (historical), California
- 1.6 6 km NNW of Beckwourth, California
- 1.6 Northern California
- 1.6 8 km SSE of Johnsville, California
- 1.6 7 km S of Plumas Eureka (historical), California
- 1.5 9 km SSE of Beckwourth, California
- 1.6 1 km NNE of Paxton, California
- 1.5 1 km WNW of Keddie, 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.