Earthquake · reviewed by a seismologist
M 1.9md
Earthquake near Pacheco, CA
No earthquake was likely felt in Pacheco in the 24 hours to 4:46 am PST (12:46 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 1.9 earthquake was recorded 5 km (3 mi) southwest of Pacheco, CA, at 7:33 am PDT on 6 October 2021 (14:33 UTC), 9.7 km deep. 1 person has reported feeling it to USGS.
USGS: 5km SW of Pacheco, CA
9 km (6 mi) NW of Walnut Creek, CA · 33 km (20 mi) NE of San Francisco, CA
- When
- 7:33 am PDT on 6 October 2021 ()
- Where
- 5 km (3 mi) southwest of Pacheco, CA · earthquakes near Pacheco
- Magnitude
- M 1.9 (md)
- Depth
- 9.7 km below the surface
- Felt
- 1 report · strongest reported intensity IV
- Nearest
- Contra Costa County, 15 km ESE
- Nearest mapped fault
- Concord fault, 7 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 1862 days ago
Earthquake alerts for Pacheco, CA
Get a notification in this browser when USGS records an earthquake near Pacheco, CA. No account or email needed.
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 10 km (6 mi) from the epicentre. In Pacheco, 5 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: Pacheco 5 km, intensity II · Pleasant Hill 5 km, intensity II · Martinez 7 km, intensity II · Walnut Creek 7 km, intensity II · Lafayette 8 km, intensity II · Concord 8 km, intensity II · Orinda 10 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 18 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 5.8 840,000× the energy of this one
- Magna, Utah 2020 M 5.7 600,000× the energy of this one
- Around the size people start to feel M 3.0 53× the energy of this one
- This earthquake M 1.9 about 18 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 8,200 times the energy of this one.
Before 2016, the USGS record lists 7 earthquakes of M5 or more within 50 km; the five largest:
- 7.9 The 1906 San Francisco, California Earthquake · 44 km WSW of this epicentre
- 6.0 The 2014 South Napa, California Earthquake · 33 km NNW of this epicentre
- 5.8 The 1980 Livermore, California Earthquake · 34 km ESE of this epicentre
- 5.4 South of Elmira, California · 43 km NNE of this epicentre
- 5.4 9 km NE of Livermore, California · 43 km ESE 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 37.9568, -122.1207. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Contra Costa County, CA | 15 km (10 mi) | ESE | earthquakes near Contra Costa County |
| Solano County, CA | 38 km (24 mi) | NNE | earthquakes near Solano County |
| Alameda County, CA | 39 km (24 mi) | SSE | earthquakes near Alameda County |
| Marin County, CA | 56 km (35 mi) | W | earthquakes near Marin County |
| Napa County, CA | 64 km (40 mi) | NNW | earthquakes near Napa County |
| San Mateo County, CA | 64 km (40 mi) | SSW | earthquakes near San Mateo County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
56 earthquakes have been recorded within 50 km since this one.
- 1.6 3km SE of Concord, CA
- 2.2 2km E of Pacheco, CA
- 1.6 6km WSW of Colma, CA
- 2.5 4km N of San Leandro, CA
- 1.8 1km NE of San Ramon, CA
- 2.0 1km W of Kensington, CA
- 2.5 1km W of Kensington, CA
- 1.7 5km ENE of Vallejo, CA
- 1.9 7km ESE of Bethel Island, CA
- 1.9 8km SSW of Brentwood, CA
- 1.7 5km E of Fremont, CA
- 1.7 8km WSW of Mountain House, CA
- 1.6 8km E of Vallejo, CA
- 1.9 1km NE of San Ramon, CA
- 1.7 1km NE of San Ramon, 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.