Earthquake · reviewed by a seismologist
M 1.8ml
Earthquake near Portola, CA
No earthquake was likely felt in Portola in the 24 hours to 7:54 pm PST (03:54 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 6 km (4 mi) north of Portola, CA, at 2:36 am PDT on 9 June 2021 (09:36 UTC), 7.2 km deep.
USGS: 0 km S of Lake Davis, California
64 km (40 mi) WNW of Reno, NV
- When
- 2:36 am PDT on 9 June 2021 ()
- Where
- 6 km (4 mi) north of Portola, CA · earthquakes near Portola
- Magnitude
- M 1.8 (ml)
- Depth
- 7.2 km below the surface
- Felt
- no reports yet
- Nearest
- Sierra County, 32 km S
- Nearest mapped fault
- Mohawk Valley fault, 16 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 1983 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 11 km (7 mi) from the epicentre. In Portola, 6 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 6 km, intensity II. Estimated for each town centre; each link is that town's own record.
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 5.7 710,000× the energy of this one
- Around the size people start to feel M 3.0 63× 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 4.7 on 2021-05-07 — about 19,000 times the energy of this one.
Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:
- 6.0 6 km WNW of Verdi, California · 49 km SE of this epicentre
- 5.6 6 km NNE of Doyle, California · 42 km NE of this epicentre
- 5.6 5 km NE of Loyalton, California · 29 km SE of this epicentre
- 5.3 11 km N of Soda Springs, California · 49 km S of this epicentre
- 5.3 4 km S of Doyle, California · 34 km ENE 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 39.8666, -120.4774. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Sierra County, CA | 32 km (20 mi) | S | earthquakes near Sierra County |
| Plumas County, CA | 33 km (20 mi) | WNW | earthquakes near Plumas County |
| Nevada County, CA | 68 km (42 mi) | SSW | earthquakes near Nevada County |
| Placer County, CA | 92 km (57 mi) | SSW | earthquakes near Placer County |
| Storey County, NV | 94 km (59 mi) | ESE | earthquakes near Storey County |
| Lassen County, CA | 95 km (59 mi) | N | earthquakes near Lassen County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
52 earthquakes have been recorded within 50 km since this one.
- 1.5 9 km SSE of Beckwourth, California
- 1.6 1 km NNE of Paxton, California
- 1.5 1 km WNW of Keddie, California
- 1.7 1 km W of Keddie, California
- 1.6 0 km E of Paxton, California
- 2.8 3km N of Greenhorn, CA
- 1.6 5 km NNW of Plumas Eureka (historical), California
- 1.5 1 km SW of Spring Garden, California
- 2.2 4km NE of Lake Davis, CA
- 3.1 10km ESE of Loyalton, CA
- 1.5 4 km N of Greenhorn, California
- 2.8 15km WSW of Loyalton, CA
- 1.7 4 km WNW of Sierra City, California
- 1.5 3 km WNW of Sierra City, California
- 2.2 16km WSW of Loyalton, 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.