QuakeIndex

Earthquake · reviewed by a seismologist

M 1.8md

5km ESE of St. Helena, CA

· 12 km deep · released about 13 lb of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Napa County 8 kmSonoma County 45 kmSolano County 48 kmYolo County 50 kmMarin County 56 kmContra Costa County 75 kmLake County 75 kmColusa County 79 kmSutter County 87 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
Magnitude
M 1.8 (md)
Depth
12 km below the surface
Felt
1 report · strongest reported intensity II
Nearest
Napa County, 8 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 2033 days ago

This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 1 person has reported feeling it to USGS.

How big was it?

This earthquake released about 13 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.

  1. Mineral, Virginia 2011 M 5.8 1,200,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 840,000× the energy of this one
  3. Around the size people start to feel M 3.0 75× the energy of this one
  4. This earthquake M 1.8 about 13 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.

Where

Epicentre 38.4818, -122.4172. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Napa County, CA 8 km (5 mi) WSW of here earthquakes near Napa County
Sonoma County, CA 45 km (28 mi) E of here earthquakes near Sonoma County
Solano County, CA 48 km (30 mi) WNW of here earthquakes near Solano County
Yolo County, CA 50 km (31 mi) WSW of here earthquakes near Yolo County
Marin County, CA 56 km (35 mi) NNE of here earthquakes near Marin County
Contra Costa County, CA 75 km (46 mi) NNW of here earthquakes near Contra Costa County

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

Aftershocks so far

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

  1. 1.6 10km WNW of Calistoga, CA
  2. 1.5 1km WNW of The Geysers, CA
  3. 1.7 5km W of Cobb, CA
  4. 1.8 3km NNW of The Geysers, CA
  5. 1.9 3km NNW of The Geysers, CA
  6. 3.1 5km W of Cobb, CA
  7. 2.0 4km NW of The Geysers, CA
  8. 2.0 4km SSW of Anderson Springs, CA
  9. 1.5 4km WNW of The Geysers, CA
  10. 1.9 4km SW of Anderson Springs, CA
  11. 1.8 6km WNW of The Geysers, CA
  12. 1.7 5km NW of The Geysers, CA
  13. 1.8 11km ENE of Yountville, CA
  14. 2.8 10km ENE of Yountville, CA
  15. 1.8 4km SSW 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.

For this area

The largest earthquake within 50 km in our catalogue was M 4.2 on 2018-01-18 — it released about 5,100 times the energy of this one.

From the QuakeIndex catalogue, built from the USGS FDSN event service.

On USGS

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