Earthquake · reviewed by a seismologist
M 1.5md
Earthquake near Santa Rosa, CA
No earthquake was likely felt in Santa Rosa in the 24 hours to 9:33 am PST (17:33 UTC). The last one was M 1.9, 5 km (3 mi) NE, at 2:01 pm PDT on 23 October 2026, estimated intensity II (weak) in town. Every earthquake near Santa Rosa
This page: a magnitude 1.5 earthquake was recorded 16 km (10 mi) east-northeast of Santa Rosa, CA, at 11:27 am PDT on 27 August 2021 (18:27 UTC), 8.7 km deep.
USGS: 7km WSW of St. Helena, CA
15 km (9 mi) ENE of Santa Rosa, CA
- When
- 11:27 am PDT on 27 August 2021 ()
- Where
- 16 km (10 mi) east-northeast of Santa Rosa, CA · earthquakes near Santa Rosa
- Magnitude
- M 1.5 (md)
- Depth
- 8.7 km below the surface
- Felt
- no reports yet
- Nearest
- Napa County, 19 km E
- Nearest mapped fault
- Maacama fault, 3 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 1900 days ago
Earthquake alerts for Santa Rosa, CA
Get a notification in this browser when USGS records an earthquake near Santa Rosa, 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 6 km (4 mi) from the epicentre. In Santa Rosa, 16 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: Saint Helena, Kenwood, Deer Park, Calistoga, Angwin, Eldridge.
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 · 35 km SE of this epicentre
- 5.3 3 km E of Bloomfield, California · 30 km SW of this epicentre
- 5.3 Northern California · 31 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 38.4788, -122.5392. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Napa County, CA | 19 km (12 mi) | E | earthquakes near Napa County |
| Sonoma County, CA | 34 km (21 mi) | W | earthquakes near Sonoma County |
| Marin County, CA | 51 km (32 mi) | SSW | earthquakes near Marin County |
| Solano County, CA | 57 km (36 mi) | ESE | earthquakes near Solano County |
| Yolo County, CA | 60 km (37 mi) | ENE | earthquakes near Yolo County |
| Lake County, CA | 72 km (45 mi) | NNW | earthquakes near Lake County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
56 earthquakes have been recorded within 50 km since this one.
- 1.6 3km SE of The Geysers, CA
- 1.6 3km SW of Anderson Springs, CA
- 2.7 1km SSE of Vallejo, CA
- 1.7 3km NNW of The Geysers, CA
- 1.7 6km NW of The Geysers, CA
- 1.7 6km NW of The Geysers, CA
- 1.7 3km SW of Anderson Springs, CA
- 2.6 3km NW of The Geysers, CA
- 1.6 10km NE of Healdsburg, CA
- 1.8 3km SE of Larkfield-Wikiup, CA
- 1.5 0km WNW of The Geysers, CA
- 2.0 9km WNW of The Geysers, CA
- 1.5 5km NW of The Geysers, CA
- 1.6 2km NW of Anderson Springs, CA
- 2.4 5km 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.