Earthquake · reviewed by a seismologist
M 2.1md
Earthquake near Hillsborough, CA
No earthquake was likely felt in Hillsborough in the 24 hours to 1:36 am PST (09:36 UTC). The last one was M 2.7, 10 km (6 mi) NW, at 5:17 pm PDT on 28 October 2026, estimated intensity III (weak) in town; 526 felt reports to USGS. Every earthquake near Hillsborough
This page: a magnitude 2.1 earthquake was recorded 5 km (3 mi) west of Hillsborough, CA, at 3:51 pm PDT on 18 June 2023 (22:51 UTC), 11 km deep. 1 person has reported feeling it to USGS.
USGS: 5km W of Hillsborough, CA
24 km (15 mi) S of San Francisco, CA · 11 km (7 mi) W of San Mateo, CA
- When
- 3:51 pm PDT on 18 June 2023 ()
- Where
- 5 km (3 mi) west of Hillsborough, CA · earthquakes near Hillsborough
- Magnitude
- M 2.1 (md)
- Depth
- 11 km below the surface
- Felt
- 1 report · strongest reported intensity II
- Nearest
- San Mateo County, 18 km SSE
- Nearest mapped fault
- San Andreas fault, 3 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 1241 days ago
Earthquake alerts for Hillsborough, 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 13 km (8 mi) from the epicentre. In Hillsborough, 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: Millbrae 6 km, intensity II · Burlingame 7 km, intensity II · Pacifica 7 km, intensity II · San Bruno 7 km, intensity II · San Mateo 10 km, intensity II · South San Francisco 10 km, intensity II · Half Moon Bay 11 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 40 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 5.8 380,000× the energy of this one
- Magna, Utah 2020 M 5.7 270,000× the energy of this one
- Around the size people start to feel M 3.0 24× the energy of this one
- This earthquake M 2.1 about 40 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 4.4 on 2018-01-04 — about 2,800 times the energy of this one.
Before 2016, the USGS record lists 3 earthquakes of M5 or more within 50 km:
- 7.9 The 1906 San Francisco, California Earthquake · 23 km NNW of this epicentre
- 5.8 7 km NNW of Boulder Creek, California · 49 km SSE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 12 km NNW 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 37.5663, -122.4372. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Mateo County, CA | 18 km (11 mi) | SSE | earthquakes near San Mateo County |
| Alameda County, CA | 47 km (29 mi) | E | earthquakes near Alameda County |
| San Francisco County, CA | 55 km (34 mi) | WNW | earthquakes near San Francisco County |
| Contra Costa County, CA | 58 km (36 mi) | NE | earthquakes near Contra Costa County |
| Marin County, CA | 60 km (38 mi) | NNW | earthquakes near Marin County |
| Santa Cruz County, CA | 72 km (45 mi) | SSE | earthquakes near Santa Cruz County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
52 earthquakes have been recorded within 50 km since this one.
- 2.0 2 km ENE of Berkeley, CA
- 1.8 3 km W of Orinda, CA
- 2.2 1 km NE of San Leandro, CA
- 1.7 7 km WNW of San Francisco Zoo, CA
- 2.5 3 km NNW of Piedmont, CA
- 1.9 4 km WSW of Cupertino, CA
- 1.8 6 km ESE of Santa Venetia, CA
- 1.5 6 km NNE of Orinda, CA
- 1.6 4 km WSW of Cupertino, CA
- 2.1 10 km WSW of San Lorenzo, CA
- 1.7 2 km ENE of San Leandro, CA
- 1.9 4 km WSW of Cupertino, CA
- 2.0 7 km NW of San Francisco Zoo, CA
- 1.9 3 km ESE of South San Francisco, CA
- 1.7 4 km WSW of Cupertino, 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.