Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Sea Ranch, CA
No earthquake was likely felt in Sea Ranch in the 24 hours to 5:12 am PST (13:12 UTC). The last one was M 3.7, 33 km (21 mi) N, at 8:42 pm PDT on 25 September 2026, estimated intensity III (weak) in town; 134 felt reports to USGS. Every earthquake near Sea Ranch
This page: a magnitude 1.8 earthquake was recorded 36 km (22 mi) northwest of Sea Ranch, CA, at 11:57 am PST on 4 December 2021 (19:57 UTC), 2.6 km deep.
USGS: 5km NW of Point Arena, CA
- When
- 11:57 am PST on 4 December 2021 ()
- Where
- 36 km (22 mi) northwest of Sea Ranch, CA · earthquakes near Sea Ranch
- Magnitude
- M 1.8 (md)
- Depth
- 2.6 km below the surface
- Felt
- no reports yet
- Nearest
- Mendocino County, 60 km NNE
- Nearest mapped fault
- San Andreas fault, 6 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 1797 days ago
Earthquake alerts for Sea Ranch, CA
Get a notification in this browser when USGS records an earthquake near Sea Ranch, 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 13 km (8 mi) from the epicentre. In Sea Ranch, 36 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 5.7 710,000× 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
No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.
Before 2016, the USGS record since 1900 lists no earthquake of M5 or more within 50 km.
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 38.9433, -123.7445. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Mendocino County, CA | 60 km (37 mi) | NNE | earthquakes near Mendocino County |
| Sonoma County, CA | 85 km (53 mi) | ESE | earthquakes near Sonoma County |
| Lake County, CA | 88 km (55 mi) | ENE | earthquakes near Lake County |
| Marin County, CA | 132 km (82 mi) | SE | earthquakes near Marin County |
| Glenn County, CA | 137 km (85 mi) | ENE | earthquakes near Glenn County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
30 earthquakes have been recorded within 50 km since this one.
- 1.6 9km SE of Point Arena, CA
- 1.6 20km SW of Point Arena, CA
- 1.8 9km ENE of Boonville, CA
- 1.6 12km NNE of Point Arena, CA
- 1.8 32km WNW of Point Arena, CA
- 1.7 16km WNW of Boonville, CA
- 1.6 21km WNW of Ukiah, CA
- 1.6 12km W of Ukiah, CA
- 2.0 21km WNW of Ukiah, CA
- 1.8 21km NNW of Boonville, CA
- 1.8 20km SSW of Willits, CA
- 1.8 20km SSW of Willits, CA
- 1.5 8km NE of Boonville, CA
- 1.9 14km S of Talmage, CA
- 2.0 14km WSW of Willits, 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.