QuakeIndex

Earthquake · reviewed by a seismologist

M 2.1md

Earthquake near Patterson, CA

No earthquake was likely felt in Patterson in the 24 hours to 3:22 am PST (11:22 UTC). The last one was M 2.9, 29 km (18 mi) W, at 9:44 am PDT on 31 October 2026, estimated intensity II (weak) in town. Every earthquake near Patterson

This page: a magnitude 2.1 earthquake was recorded 11 km (7 mi) west of Patterson, CA, at 12:09 am PDT on 23 September 2023 (07:09 UTC), less than 1 km deep. 2 people have reported feeling it to USGS.

USGS: 11 km W of Patterson, CA

53 km (33 mi) ENE of San Jose, CA · 30 km (19 mi) SW of Modesto, CA

12:09 am PDT, Sep 23, 2023 · · 0.7 km deep · released about 46 lb of TNT

Every earthquake near Patterson Felt it? Tell USGS Check my area
10 km30 km60 km120 km N Stanislaus County 25 kmSanta Clara County 47 kmSan Joaquin County 53 kmMerced County 55 kmAlameda County 62 kmContra Costa County 80 kmSanta Cruz County 83 kmSan Benito County 95 kmSan Mateo County 99 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
12:09 am PDT on 23 September 2023 ()
Where
11 km (7 mi) west of Patterson, CA · earthquakes near Patterson
Magnitude
M 2.1 (md)
Depth
0.7 km below the surface
Felt
2 reports · strongest reported intensity II
Nearest
Stanislaus County, 25 km ENE
Nearest mapped fault
Great Valley thrust fault system, 6 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 1141 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 17 km (11 mi) from the epicentre. In Patterson, 11 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: Patterson 11 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 46 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.

  1. Mineral, Virginia 2011 M 5.8 330,000× the energy of this one
  2. Magna, Utah 2020 M 5.7 230,000× the energy of this one
  3. Around the size people start to feel M 3.0 21× the energy of this one
  4. This earthquake M 2.1 about 46 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 5.1 on 2022-10-25 — about 26,000 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

  1. 6.2 The 1984 Morgan Hill, California Earthquake · 41 km WSW of this epicentre
  2. 5.8 The 1979 Coyote Lake, California Earthquake · 45 km SSW of this epicentre
  3. 5.7 15 km NE of East Foothills, California · 38 km W of this epicentre
  4. 5.5 6 km NNE of East Foothills, California · 46 km W of this epicentre
  5. 5.3 6 km E of East Foothills, California · 44 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 37.4565, -121.2537. Map © OpenStreetMap contributors.

Nearby places

PlaceDistanceDirection from the epicentre
Stanislaus County, CA 25 km (16 mi) ENE earthquakes near Stanislaus County
Santa Clara County, CA 47 km (29 mi) SW earthquakes near Santa Clara County
San Joaquin County, CA 53 km (33 mi) N earthquakes near San Joaquin County
Merced County, CA 55 km (34 mi) ESE earthquakes near Merced County
Alameda County, CA 62 km (38 mi) WNW earthquakes near Alameda County
Contra Costa County, CA 80 km (50 mi) NW 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.

  1. 1.6 10 km E of San Martin, CA
  2. 2.4 16 km E of Seven Trees, CA
  3. 1.5 9 km E of Alum Rock, CA
  4. 1.9 9 km ENE of San Martin, CA
  5. 1.5 9 km NE of Alum Rock, CA
  6. 1.7 24 km W of Los Banos, CA
  7. 1.5 11 km WSW of Patterson, CA
  8. 2.7 15 km SW of Westley, CA
  9. 2.5 24 km SSW of Gustine, CA
  10. 2.5 24 km SSW of Gustine, CA
  11. 1.7 25 km NE of Hollister, CA
  12. 1.6 15 km N of Morgan Hill, CA
  13. 1.7 20 km WSW of Patterson, CA
  14. 1.6 24 km SW of Gustine, CA
  15. 1.7 9 km ENE of Morgan Hill, 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.