Earthquake · reviewed by a seismologist
M 2.2ml
Earthquake near Altadena, CA
No earthquake was likely felt in Altadena in the 24 hours to 3:54 am PST (11:54 UTC). The last one was M 3.8, 62 km (39 mi) WNW, at 8:00 pm PDT on 29 September 2026, estimated intensity II (weak) in town; 199 felt reports to USGS. Every earthquake near Altadena
This page: a magnitude 2.2 earthquake was recorded 4 km (2 mi) east-southeast of Altadena, CA, at 1:24 am PST on 4 January 2021 (09:24 UTC), 6.7 km deep. 79 people have reported feeling it to USGS.
USGS: 4km ESE of Altadena, CA
in Pasadena, CA · 34 km (21 mi) ENE of Los Angeles, CA
- When
- 1:24 am PST on 4 January 2021 ()
- Where
- 4 km (2 mi) east-southeast of Altadena, CA · earthquakes near Altadena
- Magnitude
- M 2.2 (ml)
- Depth
- 6.7 km below the surface
- Felt
- 79 reports · strongest reported intensity V
- Nearest
- Los Angeles County, 15 km W
- Nearest mapped fault
- Sierra Madre 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 2115 days ago
Earthquake alerts for Altadena, CA
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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 18 km (11 mi) from the epicentre. In Altadena, 4 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: Altadena 4 km, intensity II · Sierra Madre 4 km, intensity II · Pasadena 6 km, intensity II · Arcadia 7 km, intensity II · South Pasadena 8 km, intensity II · Temple City 9 km, intensity II · San Gabriel 9 km, intensity II · Monrovia 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 67 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.2 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 230,000× the energy of this one
- Magna, Utah 2020 M 5.7 160,000× the energy of this one
- Around the size people start to feel M 3.0 14× the energy of this one
- This earthquake M 2.2 about 67 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 2020-09-19 — about 2,900 times the energy of this one.
Before 2016, the USGS record lists 19 earthquakes of M5 or more within 50 km; the five largest:
- 6.7 Northridge, California, earthquake · 41 km W of this epicentre
- 6.6 1971 San Fernando Earthquake, California · 37 km NW of this epicentre
- 5.9 The 1987 Whittier Narrows, California Earthquake · 13 km S of this epicentre
- 5.9 1km ENE of Granada Hills, California · 38 km WNW of this epicentre
- 5.8 10km SSW of Agua Dulce, CA · 37 km NW 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 34.1772, -118.0960. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Los Angeles County, CA | 15 km (10 mi) | W | earthquakes near Los Angeles County |
| Orange County, CA | 63 km (39 mi) | SSE | earthquakes near Orange County |
| Ventura County, CA | 97 km (61 mi) | WNW | earthquakes near Ventura County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
55 earthquakes have been recorded within 50 km since this one.
- 1.5 1km NW of Inglewood, CA
- 1.6 1km WSW of Inglewood, CA
- 2.3 1km ENE of Lennox, CA
- 1.8 1km S of Inglewood, CA
- 1.6 2km ENE of Lennox, CA
- 2.4 1km SSE of Inglewood, CA
- 2.3 2km E of Lennox, CA
- 1.9 1km SSE of Inglewood, CA
- 1.5 1km SE of Inglewood, CA
- 1.6 1km ESE of Inglewood, CA
- 1.7 1km WSW of Inglewood, CA
- 1.6 1km W of Inglewood, CA
- 1.6 1km SW of Inglewood, CA
- 1.9 2km W of Inglewood, CA
- 1.7 1km N of Lennox, 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.