Earthquake · reviewed by a seismologist
M 1.5md
Earthquake near Saint Helena, CA
No earthquake was likely felt in Saint Helena in the 24 hours to 5:05 pm PST (01:05 UTC). The last one was M 1.7, 11 km (7 mi) SSW, at 12:33 am PDT on 25 October 2026, estimated intensity II (weak) in town. Every earthquake near Saint Helena
This page: a magnitude 1.5 earthquake was recorded 6 km (4 mi) west-northwest of Saint Helena, CA, at 2:20 am PST on 31 December 2017 (10:20 UTC), 9.6 km deep.
USGS: 6km WNW of Saint Helena, CA
17 km (11 mi) ENE of Santa Rosa, CA
- When
- 2:20 am PST on 31 December 2017 ()
- Where
- 6 km (4 mi) west-northwest of Saint Helena, CA · earthquakes near Saint Helena
- Magnitude
- M 1.5 (md)
- Depth
- 9.6 km below the surface
- Felt
- no reports yet
- Nearest
- Napa County, 18 km E
- Nearest mapped fault
- Maacama fault, 4 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 3233 days ago
Earthquake alerts for Saint Helena, 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 4 km (2 mi) from the epicentre. In Saint Helena, 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.
Earthquakes near other towns within 30 km: Deer Park, Calistoga, Angwin, Kenwood, Santa Rosa, Larkfield-Wikiup.
How big was it?
This earthquake released about 5.9 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.5 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 2,500,000× the energy of this one
- Magna, Utah 2020 M 5.7 1,800,000× the energy of this one
- Around the size people start to feel M 3.0 160× the energy of this one
- This earthquake M 1.5 about 5.9 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 5.0 on 2016-12-14 — about 170,000 times the energy of this one.
Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 39 km SSE of this epicentre
- 5.3 3 km E of Bloomfield, California · 33 km SW of this epicentre
- 5.3 Northern California · 33 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 38.5163, -122.5337. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Napa County, CA | 18 km (11 mi) | E | earthquakes near Napa County |
| Sonoma County, CA | 34 km (21 mi) | W | earthquakes near Sonoma County |
| Marin County, CA | 55 km (34 mi) | SSW | earthquakes near Marin County |
| Yolo County, CA | 58 km (36 mi) | ENE | earthquakes near Yolo County |
| Solano County, CA | 59 km (36 mi) | ESE | earthquakes near Solano County |
| Lake County, CA | 68 km (42 mi) | NNW | earthquakes near Lake County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
58 earthquakes have been recorded within 50 km since this one.
- 2.2 4km W of Glen Ellen, CA
- 2.3 6km WNW of The Geysers, CA
- 2.3 10km WNW of The Geysers, CA
- 1.8 5km WNW of The Geysers, CA
- 1.9 2km ENE of The Geysers, CA
- 2.4 6km NW of The Geysers, CA
- 1.9 6km NW of The Geysers, CA
- 2.0 4km WNW of Lower Lake, CA
- 2.0 4km WNW of Lower Lake, CA
- 1.8 4km SSW of Clearlake, CA
- 2.6 4km WNW of Lower Lake, CA
- 1.9 11km WNW of The Geysers, CA
- 2.0 1km NE of The Geysers, CA
- 1.6 7km NW of The Geysers, CA
- 1.6 1km NNE 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.