Earthquake · reviewed by a seismologist
M 3.3ml
Earthquake near San Francisco, CA
No earthquake was likely felt in San Francisco in the 24 hours to 2:56 am PST (10:56 UTC). The last one was M 2.6, 18 km (11 mi) ENE, at 6:23 pm PST on 1 November 2026, estimated intensity II (weak) in town; 114 felt reports to USGS. Every earthquake near San Francisco
This page: a magnitude 3.3 earthquake was recorded 16 km (10 mi) west of San Francisco, CA, at 5:41 am PST on 31 December 2020 (13:41 UTC), 13 km deep. 3,865 people have reported feeling it to USGS.
USGS: 7km S of Muir Beach, CA
15 km (10 mi) W of San Francisco, CA
- When
- 5:41 am PST on 31 December 2020 ()
- Where
- 16 km (10 mi) west of San Francisco, CA · earthquakes near San Francisco
- Magnitude
- M 3.3 (ml)
- Depth
- 13 km below the surface
- Felt
- 3,865 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Marin County, 31 km NNW
- Nearest mapped fault
- San Andreas 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 699 days ago
Earthquake alerts for San Francisco, 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 small earthquake. Shaking like this is often felt indoors nearby and very rarely causes damage.
At this magnitude and depth, people at rest would likely notice it out to about 52 km (32 mi) from the epicentre. In San Francisco, 16 km away, the estimate is intensity III (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: Tamalpais-Homestead Valley 10 km, intensity III · San Francisco 16 km, intensity III · Daly City 16 km, intensity III · San Rafael 20 km, intensity II · Bayview-Hunters Point 20 km, intensity II · Pacifica 23 km, intensity II · South San Francisco 23 km, intensity II · San Bruno 25 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 1.5 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.3 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 110,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 5,100× the energy of this one
- Magna, Utah 2020 M 5.7 3,600× the energy of this one
- This earthquake M 3.3 about 1.5 tons of TNT
- Around the size people start to feel M 3.0 this one released 3.1× more
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 50 times the energy of this one.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 7.9 The 1906 San Francisco, California Earthquake · 7 km SE of this epicentre
- 5.3 The 1957 San Francisco, California Earthquake · 18 km SSE 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 37.7995, -122.5937. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Marin County, CA | 31 km (19 mi) | NNW | earthquakes near Marin County |
| San Francisco County, CA | 39 km (24 mi) | WSW | earthquakes near San Francisco County |
| San Mateo County, CA | 47 km (29 mi) | SSE | earthquakes near San Mateo County |
| Contra Costa County, CA | 58 km (36 mi) | ENE | earthquakes near Contra Costa County |
| Alameda County, CA | 62 km (39 mi) | ESE | earthquakes near Alameda County |
| Solano County, CA | 77 km (48 mi) | NE | earthquakes near Solano County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
46 earthquakes have been recorded within 50 km since this one.
- 1.6 1km NE of Berkeley, CA
- 2.0 1km NNW of Pleasant Hill, CA
- 1.5 2km ESE of Berkeley, CA
- 1.5 4km E of Moraga, CA
- 1.8 7km S of Muir Beach, CA
- 1.9 4km SSW of Colma, CA
- 1.7 2km E of Berkeley, CA
- 2.1 8km S of Muir Beach, CA
- 1.6 8km S of Muir Beach, CA
- 1.6 3km NNW of Piedmont, CA
- 2.1 2km ENE of Berkeley, CA
- 1.7 3km WNW of Castro Valley, CA
- 1.9 1km NNW of Crockett, CA
- 3.9 3km N of San Lorenzo, CA
- 1.8 2km ESE of Berkeley, 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.