Earthquake · reviewed by a seismologist
M 1.7md
Earthquake near Angwin, CA
No earthquake was likely felt in Angwin in the 24 hours to 12:03 am PST (08:03 UTC). The last one was M 1.6, in Angwin, at 11:57 pm PDT on 10 October 2026, estimated intensity II (weak) in town. Every earthquake near Angwin
This page: a magnitude 1.7 earthquake was recorded 16 km (10 mi) east-southeast of Angwin, CA, at 1:16 am PDT on 11 August 2023 (08:16 UTC), 6.2 km deep.
USGS: 16 km ESE of Angwin, CA
85 km (53 mi) N of San Francisco, CA · 27 km (17 mi) N of Napa, CA
- When
- 1:16 am PDT on 11 August 2023 ()
- Where
- 16 km (10 mi) east-southeast of Angwin, CA · earthquakes near Angwin
- Magnitude
- M 1.7 (md)
- Depth
- 6.2 km below the surface
- Felt
- no reports yet
- Nearest
- Napa County, 6 km SW
- Nearest mapped fault
- Green 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 1189 days ago
Earthquake alerts for Angwin, 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 10 km (6 mi) from the epicentre. In Angwin, 16 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: Deer Park, Yountville, Saint Helena, Winters, Calistoga, Napa.
How big was it?
This earthquake released about 10 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.7 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,500,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,100,000× the energy of this one
- Around the size people start to feel M 3.0 95× the energy of this one
- This earthquake M 1.7 about 10 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 4.4 on 2022-09-14 — about 12,000 times the energy of this one.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 36 km S of this epicentre
- 5.4 South of Elmira, California · 42 km SE 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 38.5395, -122.2748. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Napa County, CA | 6 km (4 mi) | SW | earthquakes near Napa County |
| Yolo County, CA | 36 km (22 mi) | ENE | earthquakes near Yolo County |
| Solano County, CA | 42 km (26 mi) | SE | earthquakes near Solano County |
| Sonoma County, CA | 57 km (35 mi) | W | earthquakes near Sonoma County |
| Marin County, CA | 68 km (42 mi) | SW | earthquakes near Marin County |
| Colusa County, CA | 71 km (44 mi) | N | earthquakes near Colusa County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
24 earthquakes have been recorded within 50 km since this one.
- 1.7 1 km NE of The Geysers, CA
- 1.5 2 km W of Anderson Springs, CA
- 2.2 1 km NW of Green Valley, CA
- 2.4 4 km W of Glen Ellen, CA
- 1.6 7 km WNW of Yountville, CA
- 1.6 3 km NE of The Geysers, CA
- 1.8 3 km WNW of Boyes Hot Springs, CA
- 1.6 1 km NE of The Geysers, CA
- 1.6 5 km NNE of Windsor, CA
- 2.3 8 km ENE of Kenwood, CA
- 2.0 0 km NNE of The Geysers, CA
- 1.8 6 km NE of Kenwood, CA
- 1.6 2 km NW of Anderson Springs, CA
- 1.8 2 km SE of The Geysers, CA
- 1.6 2 km ESE of The Geysers, 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.