quarry blast · reviewed by a seismologist
M 1.9mh
5km S of Portola Valley, CA
- When
- Magnitude
- M 1.9 (mh)
- Depth
- -0.3 km below the surface
- Felt
- no reports yet
- Nearest
- San Mateo County, 15 km NW
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 2609 days ago
This was a minor earthquake. Quakes this small are rarely felt and do not cause damage.
USGS catalogues this as quarry blast, not an earthquake.
How big was it?
This earthquake released about 21 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 5.8 710,000× the energy of this one
- Magna, Utah 2020 M 5.7 500,000× the energy of this one
- Around the size people start to feel M 3.0 45× the energy of this one
- This earthquake M 1.9 about 21 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 37.3395, -122.2302. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction | |
|---|---|---|---|
| San Mateo County, CA | 15 km (9 mi) | ESE of here | earthquakes near San Mateo County |
| Santa Cruz County, CA | 41 km (26 mi) | NNW of here | earthquakes near Santa Cruz County |
| Alameda County, CA | 44 km (27 mi) | SW of here | earthquakes near Alameda County |
| Santa Clara County, CA | 50 km (31 mi) | WNW of here | earthquakes near Santa Clara County |
| Contra Costa County, CA | 69 km (43 mi) | SSW of here | earthquakes near Contra Costa County |
| San Francisco County, CA | 83 km (51 mi) | ESE of here | earthquakes near San Francisco County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
33 earthquakes have been recorded within 50 km since this one.
- 2.5 8km NNE of Alum Rock, CA
- 2.8 8km NNE of Alum Rock, CA
- 1.6 8km E of Sunol, CA
- 1.8 4km W of Dublin, CA
- 2.0 8km ENE of Alum Rock, CA
- 2.2 3km NNW of Pacifica, CA
- 1.6 6km WNW of Dublin, CA
- 2.7 3km W of Cupertino, CA
- 1.7 2km NE of Union City, CA
- 3.3 8km ENE of Alum Rock, CA
- 2.0 9km ENE of Milpitas, CA
- 1.8 6km WSW of Colma, CA
- 1.9 6km WSW of Colma, CA
- 1.6 6km WSW of Colma, CA
- 3.5 5km WSW of Colma, 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.