QuakeIndex

Earthquake · reviewed by a seismologist

M 4.0mw

14 km SSW of Westley, CA

· 0.1 km deep · released about 14 tons of TNT

Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Stanislaus County 28 kmSanta Clara County 43 kmSan Joaquin County 55 kmMerced County 57 kmAlameda County 60 kmContra Costa County 79 kmSanta Cruz County 80 kmSan Benito County 94 kmSan Mateo County 96 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 4.0 (mw)
Depth
0.1 km below the surface
Felt
364 reports · strongest reported intensity IV
Measured shaking
intensity V (ShakeMap)
USGS impact alert
green
Nearest
Stanislaus County, 28 km ENE
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 877 days ago

This was a small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage. 364 people have reported feeling it to USGS.

How big was it?

This earthquake released about 14 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 5.0 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 12,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 560× the energy of this one
  3. Magna, Utah 2020 M 5.7 390× the energy of this one
  4. This earthquake M 4.0 about 14 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 29× more

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 37.4418, -121.2848. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection
Stanislaus County, CA 28 km (18 mi) WSW of here earthquakes near Stanislaus County
Santa Clara County, CA 43 km (27 mi) NE of here earthquakes near Santa Clara County
San Joaquin County, CA 55 km (34 mi) S of here earthquakes near San Joaquin County
Merced County, CA 57 km (35 mi) WNW of here earthquakes near Merced County
Alameda County, CA 60 km (37 mi) ESE of here earthquakes near Alameda County
Contra Costa County, CA 79 km (49 mi) SE 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

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

  1. 2.0 14 km ESE of Alum Rock, CA
  2. 2.5 25 km SSW of Gustine, CA
  3. 2.1 11 km ESE of Alum Rock, CA
  4. 2.8 11 km ESE of Alum Rock, CA
  5. 1.6 24 km SSW of Gustine, CA
  6. 1.7 24 km SSW of Gustine, CA
  7. 2.6 8 km ENE of Alum Rock, CA
  8. 2.6 24 km SSW of Gustine, CA
  9. 1.9 24 km ENE of Alum Rock, CA
  10. 2.1 16 km E of Seven Trees, CA
  11. 2.7 8 km ENE of Alum Rock, CA
  12. 2.2 9 km NE of Alum Rock, CA
  13. 2.0 9 km NE of Alum Rock, CA
  14. 1.6 25 km NE of Hollister, CA
  15. 1.5 25 km NE of Hollister, 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 5.1 on 2022-10-25 — it released about 43 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.