Earthquake · reviewed by a seismologist
M 3.4mw
Earthquake near Anza, CA
No earthquake was likely felt in Anza in the 24 hours to 8:35 am PST (16:35 UTC). The last one was M 2.6, 17 km (10 mi) S, at 10:44 pm PST on 5 November 2026, estimated intensity II (weak) in town; 7 felt reports to USGS. Every earthquake near Anza
This page: a magnitude 3.4 earthquake was recorded 10 km (6 mi) north-northwest of Anza, CA, at 3:41 pm PDT on 21 September 2021 (22:41 UTC), 13 km deep. 296 people have reported feeling it to USGS.
USGS: 10km NNW of Anza, CA
99 km (62 mi) NNE of San Diego, CA · 28 km (18 mi) ESE of Hemet, CA
- When
- 3:41 pm PDT on 21 September 2021 ()
- Where
- 10 km (6 mi) north-northwest of Anza, CA · earthquakes near Anza
- Magnitude
- M 3.4 (mw)
- Depth
- 13 km below the surface
- Felt
- 296 reports · strongest reported intensity IV
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- Riverside County, 67 km E
- Nearest mapped fault
- San Jacinto 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 1759 days ago
Earthquake alerts for Anza, 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 57 km (35 mi) from the epicentre. In Anza, 10 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: Anza 10 km, intensity III · Idyllwild 12 km, intensity III · Valle Vista 21 km, intensity III · Aguanga 25 km, intensity II · Palm Springs 27 km, intensity II · Hemet 27 km, intensity II · San Jacinto 28 km, intensity II · Cathedral City 28 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 2 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.4 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 83,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 3,700× the energy of this one
- Magna, Utah 2020 M 5.7 2,600× the energy of this one
- This earthquake M 3.4 about 2 tons of TNT
- Around the size people start to feel M 3.0 this one released 4.3× 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 5.2 on 2016-06-10 — about 450 times the energy of this one.
Before 2016, the USGS record lists 13 earthquakes of M5 or more within 50 km; the five largest:
- 6.7 The 1918 San Jacinto, California Earthquake · 28 km WNW of this epicentre
- 6.0 The 1986 North Palm Springs, California Earthquake · 42 km NNE of this epicentre
- 5.4 20km NNW of Borrego Springs, CA · 33 km SE of this epicentre
- 5.3 4km NNE of Desert Hot Springs, CA · 45 km NNE of this epicentre
- 5.3 6km SSE of Hemet, CA · 22 km WNW 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 33.6348, -116.7148. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Riverside County, CA | 67 km (41 mi) | E | earthquakes near Riverside County |
| San Diego County, CA | 68 km (42 mi) | S | earthquakes near San Diego County |
| Orange County, CA | 98 km (61 mi) | W | earthquakes near Orange County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
44 earthquakes have been recorded within 50 km since this one.
- 1.5 8km SSE of Banning, CA
- 1.9 10km NNW of Borrego Springs, CA
- 1.6 15km NNE of Banning, CA
- 1.8 5km NE of Anza, CA
- 1.6 9km NE of Aguanga, CA
- 1.7 9km ENE of Aguanga, CA
- 2.3 17km SE of Anza, CA
- 1.5 10km N of Cabazon, CA
- 1.7 11km S of Idyllwild, CA
- 1.7 3km SSW of Calimesa, CA
- 1.6 9km NNW of Anza, CA
- 1.7 6km NE of Cabazon, CA
- 1.8 1km SE of Anza, CA
- 1.5 9km NE of Aguanga, CA
- 1.7 16km NNE of Borrego Springs, 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.