Earthquake · reviewed by a seismologist
M 2.1md
4km WSW of Alamo, CA
- When
- Magnitude
- M 2.1 (md)
- Depth
- 15 km below the surface
- Felt
- 3 reports · strongest reported intensity II
- Nearest
- Contra Costa County, 14 km NE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 1815 days ago
This was a minor earthquake. Quakes this small are rarely felt and do not cause damage. 3 people have reported feeling it to USGS.
How big was it?
This earthquake released about 49 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 5.8 310,000× the energy of this one
- Magna, Utah 2020 M 5.7 220,000× the energy of this one
- Around the size people start to feel M 3.0 19× the energy of this one
- This earthquake M 2.1 about 49 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.
Where
Epicentre 37.8340, -122.0682. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction | |
|---|---|---|---|
| Contra Costa County, CA | 14 km (9 mi) | SW of here | earthquakes near Contra Costa County |
| Alameda County, CA | 25 km (15 mi) | NNW of here | earthquakes near Alameda County |
| Solano County, CA | 49 km (31 mi) | SSW of here | earthquakes near Solano County |
| San Mateo County, CA | 54 km (33 mi) | NNE of here | earthquakes near San Mateo County |
| Marin County, CA | 64 km (40 mi) | ESE of here | earthquakes near Marin County |
| San Joaquin County, CA | 71 km (44 mi) | W of here | earthquakes near San Joaquin 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.
- 1.9 6km E of Vallejo, CA
- 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
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 4.5 on 2019-10-15 — it released about 3,000 times the energy of this one.
From the QuakeIndex catalogue, built from the USGS FDSN event service.
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.