Earthquake · reviewed by a seismologist
M 2.1md
Earthquake near Pacheco, CA
No earthquake was likely felt in Pacheco in the 24 hours to 6:04 pm PST (02:04 UTC). The last one was M 2.1, 5 km (3 mi) S, at 4:05 am PST on 8 November 2026, estimated intensity II (weak) in town; 3 felt reports to USGS. Every earthquake near Pacheco
This page: a magnitude 2.1 earthquake was recorded in Pacheco, CA, at 12:32 am PDT on 23 October 2023 (07:32 UTC), 16 km deep. 1 person has reported feeling it to USGS.
USGS: 2 km E of Pacheco, CA
in Concord, CA
- When
- 12:32 am PDT on 23 October 2023 ()
- Where
- in Pacheco, CA · earthquakes near Pacheco
- Magnitude
- M 2.1 (md)
- Depth
- 16 km below the surface
- Felt
- 1 report · strongest reported intensity II
- Nearest
- Contra Costa County, 11 km SE
- Nearest mapped fault
- Concord fault, under 1 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 1114 days ago
Earthquake alerts for Pacheco, 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 7 km (4 mi) from the epicentre. 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: Concord in town, intensity II · Pacheco in town, intensity II · Pleasant Hill 4 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 44 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.
- Mineral, Virginia 2011 M 5.8 340,000× the energy of this one
- Magna, Utah 2020 M 5.7 240,000× the energy of this one
- Around the size people start to feel M 3.0 22× the energy of this one
- This earthquake M 2.1 about 44 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 4.5 on 2019-10-15 — about 3,300 times the energy of this one.
Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:
- 6.0 The 2014 South Napa, California Earthquake · 35 km NW of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 29 km ESE of this epicentre
- 5.4 South of Elmira, California · 38 km NNE of this epicentre
- 5.4 9 km NE of Livermore, California · 40 km SE of this epicentre
- 5.1 11 km E of Blackhawk, California · 31 km SE 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 37.9803, -122.0530. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 11 km (7 mi) | SE | earthquakes near Contra Costa County |
| Solano County, CA | 33 km (21 mi) | NNE | earthquakes near Solano County |
| Alameda County, CA | 39 km (24 mi) | SSE | earthquakes near Alameda County |
| Marin County, CA | 61 km (38 mi) | W | earthquakes near Marin County |
| Napa County, CA | 63 km (39 mi) | NNW | earthquakes near Napa County |
| San Joaquin County, CA | 69 km (43 mi) | E | earthquakes near San Joaquin County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
47 earthquakes have been recorded within 50 km since this one.
- 1.6 6 km S of Alameda, CA
- 1.5 6 km E of Santa Venetia, CA
- 1.6 1 km SSE of Pacheco, CA
- 1.5 2 km N of Pleasant Hill, CA
- 1.6 2 km ENE of Oakland, CA
- 1.8 0 km SW of Crockett, CA
- 1.7 8 km NW of Bayview-Montalvin, CA
- 2.0 3 km SSE of Vacaville, CA
- 1.8 1 km N of Pacheco, CA
- 1.6 6 km SSE of Moraga, CA
- 1.5 7 km ENE of Black Point-Green Point, CA
- 2.0 0 km E of Pacheco, CA
- 2.2 2 km NE of El Cerrito, CA
- 1.8 0 km NNW of Pacheco, CA
- 2.0 2 km ENE of Pleasant 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
- 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.