Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Portola, CA
No earthquake was likely felt in Portola in the 24 hours to 11:50 am PST (19:50 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 1.8 earthquake was recorded 18 km (11 mi) north of Portola, CA, at 5:46 am PST on 18 December 2025 (13:46 UTC), 11 km deep.
USGS: 11 km N of Lake Davis, CA
72 km (45 mi) NW of Reno, NV
- When
- 5:46 am PST on 18 December 2025 ()
- Where
- 18 km (11 mi) north of Portola, CA · earthquakes near Portola
- Magnitude
- M 1.8 (md)
- Depth
- 11 km below the surface
- Felt
- no reports yet
- Nearest
- Plumas County, 29 km W
- Nearest mapped fault
- Mohawk Valley fault, 21 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 318 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 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, 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.
How big was it?
This earthquake released about 15 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,000,000× the energy of this one
- Magna, Utah 2020 M 5.7 730,000× the energy of this one
- Around the size people start to feel M 3.0 65× the energy of this one
- This earthquake M 1.8 about 15 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 11,000 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 · 38 km ENE of this epicentre
- 5.6 5 km NE of Loyalton, California · 37 km SE of this epicentre
- 5.3 4 km S of Doyle, California · 32 km E of this epicentre
- 5.2 3 km N of Blairsden, California · 21 km SSW 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 39.9692, -120.4883. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Plumas County, CA | 29 km (18 mi) | W | earthquakes near Plumas County |
| Sierra County, CA | 44 km (27 mi) | S | earthquakes near Sierra County |
| Nevada County, CA | 79 km (49 mi) | SSW | earthquakes near Nevada County |
| Lassen County, CA | 84 km (52 mi) | N | earthquakes near Lassen County |
| Butte County, CA | 101 km (63 mi) | WSW | earthquakes near Butte County |
| Storey County, NV | 101 km (63 mi) | SE | earthquakes near Storey County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
47 earthquakes have been recorded within 50 km since this one.
- 2.7 1 km N of Lake Davis, CA
- 2.3 6 km N of East Quincy, CA
- 2.4 10 km N of Greenhorn, CA
- 1.8 23 km NNW of Chilcoot-Vinton, CA
- 2.3 2 km ENE of Keddie, CA
- 2.2 9 km S of Johnsville, CA
- 2.1 7 km NE of Lake Davis, CA
- 2.4 8 km NW of Honey Lake, CA
- 2.6 8 km NE of Lake Davis, CA
- 2.2 15 km SE of Honey Lake, CA
- 2.3 8 km NE of Lake Davis, CA
- 2.2 8 km NE of Lake Davis, CA
- 2.0 5 km SSW of Cromberg, CA
- 3.0 4 km WSW of Johnsville, CA
- 2.4 5 km NW of Johnsville, 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
- 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.