QuakeIndex

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 6:28 pm PST (02:28 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 33 km (20 mi) north-northwest of Santa Rosa, CA, at 11:39 am PDT on 20 August 2021 (18:39 UTC), 6.3 km deep.

USGS: 11km SW of The Geysers, CA

32 km (20 mi) NNW of Santa Rosa, CA · 111 km (69 mi) NNW of San Francisco, CA

11:39 am PDT, Aug 20, 2021 · · 6.3 km deep · released about 6.2 lb of TNT

Every earthquake near Santa Rosa Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Sonoma County 22 kmLake County 45 kmNapa County 51 kmMarin County 74 kmColusa County 74 kmYolo County 83 kmSolano County 94 kmMendocino County 95 kmSutter County 106 km
Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
11:39 am PDT on 20 August 2021 ()
Where
33 km (20 mi) north-northwest of Santa Rosa, CA · earthquakes near Santa Rosa
Magnitude
M 1.5 (md)
Depth
6.3 km below the surface
Felt
no reports yet
Nearest
Sonoma County, 22 km SSW
Nearest mapped fault
Maacama fault, 2 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 1905 days ago

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 8 km (5 mi) from the epicentre. In Santa Rosa, 33 km away, the estimate is intensity I (not felt). 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: Healdsburg, Cobb, Cloverdale, Windsor, Middletown, Larkfield-Wikiup.

How big was it?

This earthquake released about 6.2 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.

  1. Mineral, Virginia 2011 M 5.8 2,500,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 1,700,000× the energy of this one
  3. Around the size people start to feel M 3.0 150× the energy of this one
  4. This earthquake M 1.5 about 6.2 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 160,000 times the energy of this one.

Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:

  1. 5.3 3 km E of Bloomfield, California · 44 km S of this epicentre
  2. 5.3 Northern California · 44 km S of this epicentre
  3. 5.2 6 km ESE of Talmage, California · 50 km NNW 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 38.7128, -122.8532. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Sonoma County, CA 22 km (14 mi) SSW earthquakes near Sonoma County
Lake County, CA 45 km (28 mi) NNE earthquakes near Lake County
Napa County, CA 51 km (32 mi) ESE earthquakes near Napa County
Marin County, CA 74 km (46 mi) S earthquakes near Marin County
Colusa County, CA 74 km (46 mi) NE earthquakes near Colusa County
Yolo County, CA 83 km (51 mi) E earthquakes near Yolo County

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

54 earthquakes have been recorded within 50 km since this one.

  1. 1.8 3km SE of Larkfield-Wikiup, CA
  2. 1.5 0km WNW of The Geysers, CA
  3. 2.0 9km WNW of The Geysers, CA
  4. 1.5 5km NW of The Geysers, CA
  5. 1.6 2km NW of Anderson Springs, CA
  6. 2.4 5km WNW of The Geysers, CA
  7. 1.8 3km ENE of The Geysers, CA
  8. 1.6 10km WNW of Calistoga, CA
  9. 2.5 5km NW of The Geysers, CA
  10. 1.7 6km WNW of Cobb, CA
  11. 2.3 6km W of Cobb, CA
  12. 2.1 5km NW of The Geysers, CA
  13. 1.7 7km NW of The Geysers, CA
  14. 1.5 7km W of Cobb, CA
  15. 1.8 3km SW of Anderson Springs, 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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.