Earthquake · reviewed by a seismologist
M 1.8md
Earthquake near Cobb, CA
USGS: 6 km WSW of Cobb, California
41 km (25 mi) NNW of Santa Rosa, CA · 119 km (74 mi) NNW of San Francisco, CA
- When
- 11:30 pm PDT on 4 August 2016 ()
- Where
- 7 km (4 mi) WSW of Cobb, CA · earthquakes near Cobb
- Magnitude
- M 1.8 (md)
- Depth
- 1.4 km below the surface
- Felt
- no reports yet
- Nearest
- Sonoma County, 33 km SSW
- Nearest mapped fault
- Maacama fault, 11 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 3521 days ago
A magnitude 1.8 earthquake was recorded 7 km (4 mi) WSW of Cobb, CA, at 11:30 pm PDT on 4 August 2016 (06:30 UTC). This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
Earthquakes near other towns within 30 km: Middletown, Clear Lake Riviera, Cloverdale, Kelseyville, Lower Lake, Hidden Valley Lake.
How big was it?
This earthquake released about 16 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 5.8 930,000× the energy of this one
- Magna, Utah 2020 M 5.7 660,000× the energy of this one
- Around the size people start to feel M 3.0 59× the energy of this one
- This earthquake M 1.8 about 16 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 lists one earthquake of M5 or more within 50 km:
- 5.2 6 km ESE of Talmage, California · 43 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 38.8072, -122.8010. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Sonoma County, CA | 33 km (21 mi) | SSW | earthquakes near Sonoma County |
| Lake County, CA | 34 km (21 mi) | N | earthquakes near Lake County |
| Napa County, CA | 53 km (33 mi) | SE | earthquakes near Napa County |
| Colusa County, CA | 64 km (40 mi) | NE | earthquakes near Colusa County |
| Yolo County, CA | 79 km (49 mi) | E | earthquakes near Yolo County |
| Marin County, CA | 84 km (52 mi) | S | earthquakes near Marin County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
60 earthquakes have been recorded within 50 km since this one.
- 2.2 3 km S of Cobb, California
- 1.6 Northern California
- 1.7 7 km ESE of Lower Lake, California
- 2.0 3 km SSW of Cobb, California
- 1.6 8 km W of Cobb, California
- 2.7 2 km NW of Cobb, California
- 2.1 7 km W of Cobb, California
- 1.5 7 km W of Cobb, California
- 2.6 6 km SW of Cobb, California
- 3.0 9 km W of Cobb, California
- 1.7 9 km W of Cobb, California
- 2.0 9 km W of Cobb, California
- 2.1 4 km W of Cobb, California
- 2.4 4 km W of Cobb, California
- 1.9 7 km SSE of Talmage, California
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.