Earthquake · reviewed by a seismologist
M 1.9md
Earthquake near Modesto, CA
No earthquake was likely felt in Modesto in the 24 hours to 9:53 pm PST (05:53 UTC). The last one was M 3.5, 47 km (29 mi) WSW, at 7:21 am PDT on 27 September 2026, estimated intensity II (weak) in town; 8 felt reports to USGS. Every earthquake near Modesto
This page: a magnitude 1.9 earthquake was recorded 31 km (19 mi) southwest of Modesto, CA, at 6:56 am PDT on 20 September 2023 (13:56 UTC), less than 1 km deep.
USGS: 11 km SSW of Westley, CA
51 km (32 mi) ENE of San Jose, CA · 31 km (19 mi) SW of Modesto, CA
- When
- 6:56 am PDT on 20 September 2023 ()
- Where
- 31 km (19 mi) southwest of Modesto, CA · earthquakes near Modesto
- Magnitude
- M 1.9 (md)
- Depth
- -0.1 km below the surface
- Felt
- no reports yet
- Nearest
- Stanislaus County, 26 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
Earthquake alerts for Modesto, CA
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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 15 km (9 mi) from the epicentre. In Modesto, 31 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 13 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 22 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.9 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 680,000× the energy of this one
- Magna, Utah 2020 M 5.7 480,000× the energy of this one
- Around the size people start to feel M 3.0 43× the energy of this one
- This earthquake M 1.9 about 22 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 53,000 times the energy of this one.
Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:
- 6.2 Near San Jose, California · 50 km WSW of this epicentre
- 6.2 The 1984 Morgan Hill, California Earthquake · 40 km WSW of this epicentre
- 5.8 The 1979 Coyote Lake, California Earthquake · 45 km SSW of this epicentre
- 5.7 15 km NE of East Foothills, California · 37 km W of this epicentre
- 5.5 6 km NNE 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 37.4628, -121.2728. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Stanislaus County, CA | 26 km (16 mi) | ENE | earthquakes near Stanislaus County |
| Santa Clara County, CA | 46 km (28 mi) | SW | earthquakes near Santa Clara County |
| San Joaquin County, CA | 53 km (33 mi) | N | earthquakes near San Joaquin County |
| Merced County, CA | 57 km (35 mi) | ESE | earthquakes near Merced County |
| Alameda County, CA | 60 km (37 mi) | WNW | earthquakes near Alameda County |
| Contra Costa County, CA | 78 km (49 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
51 earthquakes have been recorded within 50 km since this one.
- 1.9 9 km ENE of San Martin, CA
- 1.5 9 km NE of Alum Rock, CA
- 1.5 11 km WSW of Patterson, CA
- 2.7 15 km SW of Westley, CA
- 2.5 24 km SSW of Gustine, CA
- 2.5 24 km SSW of Gustine, CA
- 1.7 25 km NE of Hollister, CA
- 1.6 15 km N of Morgan Hill, CA
- 1.7 20 km WSW of Patterson, CA
- 1.6 24 km SW of Gustine, CA
- 1.7 9 km ENE of Morgan Hill, CA
- 1.5 24 km W of Los Banos, CA
- 1.5 15 km E of Alum Rock, CA
- 2.4 7 km ENE of Alum Rock, CA
- 1.5 10 km SSW of Westley, 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.