Earthquake · reviewed by a seismologist
M 3.5mw
Earthquake near Borrego Springs, CA
No earthquake was likely felt in Borrego Springs in the 24 hours to 12:56 pm PST (20:56 UTC). The last one was M 4.9, 145 km (90 mi) SE, at 10:27 am PST on 3 November 2026, estimated intensity II (weak) in town; 321 felt reports to USGS. Every earthquake near Borrego Springs
This page: a magnitude 3.5 earthquake was recorded 10 km (6 mi) south of Borrego Springs, CA, at 3:50 am PDT on 28 April 2021 (10:50 UTC), 7.3 km deep. 283 people have reported feeling it to USGS.
USGS: 10km S of Borrego Springs, CA
80 km (50 mi) ENE of San Diego, CA
- When
- 3:50 am PDT on 28 April 2021 ()
- Where
- 10 km (6 mi) south of Borrego Springs, CA · earthquakes near Borrego Springs
- Magnitude
- M 3.5 (mw)
- Depth
- 7.3 km below the surface
- Felt
- 283 reports · strongest reported intensity III
- Measured shaking
- intensity IV (ShakeMap)
- Nearest
- San Diego County, 40 km WSW
- Nearest mapped fault
- Elsinore fault, 9 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 1765 days ago
Earthquake alerts for Borrego Springs, CA
Get a notification in this browser when USGS records an earthquake near Borrego Springs, CA. No account or email needed.
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 60 km (37 mi) from the epicentre. In Borrego Springs, 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: Borrego Springs 10 km, intensity III · Julian 23 km, intensity III · Pine Valley 40 km, intensity II · San Diego Country Estates 41 km, intensity II · Salton City 42 km, intensity II · Ramona 47 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 2.3 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.5 would have released about 32 times as much.
- Northridge, California 1994 M 6.7 75,000× the energy of this one
- Mineral, Virginia 2011 M 5.8 3,300× the energy of this one
- Magna, Utah 2020 M 5.7 2,400× the energy of this one
- This earthquake M 3.5 about 2.3 tons of TNT
- Around the size people start to feel M 3.0 this one released 4.7× 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 410 times the energy of this one.
Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:
- 6.6 The 1968 Borrego Mountain, California Earthquake · 26 km E of this epicentre
- 6.4 The 1954 San Jacinto Fault, California Earthquake · 32 km ENE of this epicentre
- 6.0 16km WSW of Oasis, CA · 29 km NNE of this epicentre
- 5.7 Eastern San Diego County, California · 27 km E of this epicentre
- 5.5 8km NNE of Ocotillo Wells, CA · 27 km E 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 33.1628, -116.3817. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Diego County, CA | 40 km (25 mi) | WSW | earthquakes near San Diego County |
| Riverside County, CA | 72 km (45 mi) | NNE | earthquakes near Riverside County |
| Imperial County, CA | 97 km (60 mi) | E | earthquakes near Imperial County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
43 earthquakes have been recorded within 50 km since this one.
- 1.6 21km E of Ocotillo Wells, CA
- 1.7 13km NNW of Borrego Springs, CA
- 2.0 10km S of Borrego Springs, CA
- 1.5 8km SW of Salton City, CA
- 1.7 9km E of San Diego Country Estates, CA
- 1.9 16km ESE of Anza, CA
- 3.1 12km NNE of Borrego Springs, CA
- 1.6 6km WSW of Salton City, CA
- 1.7 12km SSW of Oasis, CA
- 1.9 4km NW of Borrego Springs, CA
- 3.0 10km NNE of Ocotillo Wells, CA
- 1.8 21km ESE of Anza, CA
- 1.7 15km SE of Ocotillo Wells, CA
- 1.6 18km N of Borrego Springs, CA
- 1.6 18km N 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.