Earthquake · reviewed by a seismologist
M 2.8md
Earthquake near Cobb, CA
Yes: an earthquake was likely felt in Cobb in the last 24 hours. M 1.6, 4 km (2 mi) W of Cobb, at 1:30 pm PST on 11 November 2026 (21:30 UTC); the estimated shaking in Cobb was intensity II (weak). Every earthquake near Cobb
This page: a magnitude 2.8 earthquake was recorded 4 km (3 mi) northwest of Cobb, CA, at 10:54 am PDT on 26 May 2021 (17:54 UTC), 1.3 km deep. 1 person has reported feeling it to USGS.
USGS: 4km NW of Cobb, CA
45 km (28 mi) N of Santa Rosa, CA · 122 km (76 mi) NNW of San Francisco, CA
- When
- 10:54 am PDT on 26 May 2021 ()
- Where
- 4 km (3 mi) northwest of Cobb, CA · earthquakes near Cobb
- Magnitude
- M 2.8 (md)
- Depth
- 1.3 km below the surface
- Felt
- 1 report · strongest reported intensity III
- Nearest
- Lake County, 29 km N
- Nearest mapped fault
- Konocti Bay 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 1930 days ago
Earthquake alerts for Cobb, CA
Get a notification in this browser when USGS records an earthquake near Cobb, 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 small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 26 km (16 mi) from the epicentre. In Cobb, 4 km away, the estimate is intensity III (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: Cobb 4 km, intensity III · Clearlake 17 km, intensity II · Cloverdale 23 km, intensity II · Lakeport 26 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 450 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 34,000× the energy of this one
- Magna, Utah 2020 M 5.7 24,000× the energy of this one
- Around the size people start to feel M 3.0 2.1× the energy of this one
- This earthquake M 2.8 about 450 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 2,200 times the energy of this one.
Before 2016, the USGS record lists one earthquake of M5 or more within 50 km:
- 5.2 6 km ESE of Talmage, California · 42 km NW 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 38.8457, -122.7602. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Lake County, CA | 29 km (18 mi) | N | earthquakes near Lake County |
| Sonoma County, CA | 38 km (24 mi) | SSW | earthquakes near Sonoma County |
| Napa County, CA | 53 km (33 mi) | SE | earthquakes near Napa County |
| Colusa County, CA | 58 km (36 mi) | NE | earthquakes near Colusa County |
| Yolo County, CA | 77 km (48 mi) | ESE | earthquakes near Yolo County |
| Mendocino County, CA | 88 km (55 mi) | NW | earthquakes near Mendocino County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
53 earthquakes have been recorded within 50 km since this one.
- 1.8 5km ENE of Talmage, CA
- 2.2 8km NW of The Geysers, CA
- 1.6 7km W of Cobb, CA
- 1.7 11km E of Hidden Valley Lake, CA
- 2.4 7km NW of The Geysers, CA
- 2.4 3km W of Cobb, CA
- 1.6 2km N of The Geysers, CA
- 1.5 12km E of Angwin, CA
- 1.6 7km NW of The Geysers, CA
- 2.3 11km E of Hidden Valley Lake, CA
- 2.1 10km ESE of Angwin, CA
- 1.8 7km NW of The Geysers, CA
- 1.7 3km WSW of Anderson Springs, CA
- 1.5 8km NW of The Geysers, CA
- 3.0 9km WNW 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.