Earthquake · reviewed by a seismologist
M 2.1md
Earthquake near Penngrove, CA
No earthquake was likely felt in Penngrove in the 24 hours to 11:45 pm PST (07:45 UTC). The last one was M 1.9, 15 km (9 mi) NE, at 3:31 am PDT on 11 October 2026, estimated intensity II (weak) in town. Every earthquake near Penngrove
This page: a magnitude 2.1 earthquake was recorded 6 km (4 mi) northeast of Penngrove, CA, at 3:50 am PDT on 4 September 2018 (10:50 UTC), 6.4 km deep.
USGS: 6km NE of Penngrove, CA
13 km (8 mi) SSE of Santa Rosa, CA · 11 km (7 mi) N of Petaluma, CA
- When
- 3:50 am PDT on 4 September 2018 ()
- Where
- 6 km (4 mi) northeast of Penngrove, CA · earthquakes near Penngrove
- Magnitude
- M 2.1 (md)
- Depth
- 6.4 km below the surface
- Felt
- no reports yet
- Nearest
- Napa County, 32 km NE
- Nearest mapped fault
- Bennett Valley fault, 5 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 2988 days ago
Earthquake alerts for Penngrove, CA
Get a notification in this browser when USGS records an earthquake near Penngrove, 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 16 km (10 mi) from the epicentre. In Penngrove, 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.
Likely felt in: Rohnert Park 6 km, intensity II · Kenwood 11 km, intensity II · Petaluma 12 km, intensity II · Agua Caliente 12 km, intensity II · Santa Rosa 13 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 40 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 380,000× the energy of this one
- Magna, Utah 2020 M 5.7 270,000× the energy of this one
- Around the size people start to feel M 3.0 24× the energy of this one
- This earthquake M 2.1 about 40 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 3 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 31 km ESE of this epicentre
- 5.3 3 km E of Bloomfield, California · 16 km W of this epicentre
- 5.3 Northern California · 17 km W 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 38.3428, -122.6275. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Napa County, CA | 32 km (20 mi) | NE | earthquakes near Napa County |
| Sonoma County, CA | 33 km (20 mi) | NW | earthquakes near Sonoma County |
| Marin County, CA | 34 km (21 mi) | SSW | earthquakes near Marin County |
| Solano County, CA | 61 km (38 mi) | E | earthquakes near Solano County |
| Yolo County, CA | 73 km (46 mi) | ENE | earthquakes near Yolo County |
| Contra Costa County, CA | 76 km (47 mi) | SE | earthquakes near Contra Costa County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
48 earthquakes have been recorded within 50 km since this one.
- 2.7 2km NW of Crockett, CA
- 3.5 2km NW of Crockett, CA
- 1.7 10km SW of The Geysers, CA
- 1.6 3km SW of Anderson Springs, CA
- 1.5 8km SW of Calistoga, CA
- 2.4 2km E of The Geysers, CA
- 1.7 2km W of Anderson Springs, CA
- 1.7 8km ENE of Larkfield-Wikiup, CA
- 1.7 2km SSW of Anderson Springs, CA
- 1.6 4km NE of Vallejo, CA
- 1.5 4km NE of Saint Helena, CA
- 1.5 2km WSW of Anderson Springs, CA
- 1.8 9km SSW of Calistoga, CA
- 1.6 4km SSW of Anderson Springs, CA
- 2.1 12km E of Angwin, 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.