Earthquake · reviewed by a seismologist
M 1.6ml
Earthquake near Portola, CA
No earthquake was likely felt in Portola in the 24 hours to 10:01 am PST (18:01 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 11 km (7 mi) southwest of Portola, CA, at 1:08 pm PDT on 26 September 2023 (20:08 UTC), 8.0 km deep.
USGS: 0 km NNE of Clio, California
66 km (41 mi) WNW of Reno, NV
- When
- 1:08 pm PDT on 26 September 2023 ()
- Where
- 11 km (7 mi) southwest of Portola, CA · earthquakes near Portola
- Magnitude
- M 1.6 (ml)
- Depth
- 8.0 km below the surface
- Felt
- no reports yet
- Nearest
- Sierra County, 20 km SSE
- Nearest mapped fault
- Mohawk Valley fault, 2 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 1123 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, 11 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 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 4.7 on 2021-05-07 — about 38,000 times the energy of this one.
Before 2016, the USGS record lists 8 earthquakes of M5 or more within 50 km; the five largest:
- 6.0 6 km WNW of Verdi, California · 48 km ESE of this epicentre
- 5.9 West of Downieville, California · 46 km SW of this epicentre
- 5.9 9 km NW of Truckee, California · 48 km SE of this epicentre
- 5.6 5 km NE of Loyalton, California · 33 km E of this epicentre
- 5.3 11 km N of Soda Springs, California · 39 km SSE 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 39.7505, -120.5777. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Sierra County, CA | 20 km (12 mi) | SSE | earthquakes near Sierra County |
| Plumas County, CA | 34 km (21 mi) | NW | earthquakes near Plumas County |
| Nevada County, CA | 53 km (33 mi) | SSW | earthquakes near Nevada County |
| Placer County, CA | 78 km (48 mi) | S | earthquakes near Placer County |
| Yuba County, CA | 85 km (53 mi) | SW | earthquakes near Yuba County |
| Butte County, CA | 88 km (55 mi) | W | earthquakes near Butte County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
31 earthquakes have been recorded within 50 km since this one.
- 1.5 6 km SE of Beckwourth, California
- 2.3 18 km NNW of Truckee, CA
- 2.9 0 km NNE of Whitehawk, CA
- 2.3 4 km S of Cromberg, CA
- 2.1 12 km W of La Porte, CA
- 2.4 17 km N of Truckee, CA
- 1.5 9 km SSE of Sierraville, California
- 1.7 4 km SW of Sierra Brooks, California
- 1.7 7 km ENE of East Quincy, California
- 2.2 4 km NNW of Spring Garden, CA
- 2.2 5 km NNE of East Quincy, CA
- 1.5 13 km NE of Lake Davis, California
- 3.4 4 km ENE of East Quincy, CA
- 2.0 4 km SW of Whitehawk, California
- 2.2 9 km SE of Meadow Valley, 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.