Earthquake · reviewed by a seismologist
M 1.8ml
Earthquake near Alpine, CA
No earthquake was likely felt in Alpine in the 24 hours to 12:16 pm PST (20:16 UTC). The last one was M 4.9, 155 km (96 mi) ESE, at 10:27 am PST on 3 November 2026, estimated intensity II (weak) in town; 321 felt reports to USGS. Every earthquake near Alpine
This page: a magnitude 1.8 earthquake was recorded 10 km (6 mi) north-northwest of Alpine, CA, at 1:41 pm PDT on 3 May 2021 (20:41 UTC), 15 km deep. 12 people have reported feeling it to USGS.
USGS: 10km NNW of Alpine, CA
31 km (20 mi) ENE of San Diego, CA · 17 km (10 mi) ENE of Santee, CA
- When
- 1:41 pm PDT on 3 May 2021 ()
- Where
- 10 km (6 mi) north-northwest of Alpine, CA · earthquakes near Alpine
- Magnitude
- M 1.8 (ml)
- Depth
- 15 km below the surface
- Felt
- 12 reports · strongest reported intensity III
- Nearest
- San Diego County, 13 km NNE
- Status
- Reviewed by a seismologist
USGS · last changed by USGS · we first saw it 2018 days ago
Earthquake alerts for Alpine, CA
Get a notification in this browser when USGS records an earthquake near Alpine, 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 minor earthquake. Quakes this small are rarely felt and do not cause damage.
At this magnitude and depth it was probably too small to be felt, even directly above it. In Alpine, 10 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.
Earthquakes near other towns within 30 km: San Diego Country Estates, Harbison Canyon, Lakeside, Eucalyptus Hills, Crest, Winter Gardens.
How big was it?
This earthquake released about 14 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 2.8 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 1,100,000× the energy of this one
- Magna, Utah 2020 M 5.7 790,000× the energy of this one
- Around the size people start to feel M 3.0 70× the energy of this one
- This earthquake M 1.8 about 14 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
No earthquake of M4 or more has been recorded within 50 km since our catalogue begins in 2016.
Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:
- 5.0 16 km NW of Julian, California · 34 km NNE of this epicentre
- 5.0 26km NE of Pine Valley, CA · 48 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 32.9162, -116.8218. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| San Diego County, CA | 13 km (8 mi) | NNE | earthquakes near San Diego County |
| Riverside County, CA | 118 km (73 mi) | NE | earthquakes near Riverside County |
| Orange County, CA | 123 km (76 mi) | NW | earthquakes near Orange County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
39 earthquakes have been recorded within 50 km since this one.
- 1.6 5km SE of Chula Vista, CA
- 1.6 11km NE of Julian, CA
- 1.6 6km NNW of Lakeside, CA
- 1.6 6km NE of Rancho San Diego, CA
- 1.8 3km ESE of Julian, CA
- 1.6 6km NNW of Lakeside, CA
- 2.6 10km S of Borrego Springs, CA
- 1.5 11km NW of Julian, CA
- 1.8 5km NNE of San Ysidro, CA
- 1.6 10km S of Borrego Springs, CA
- 1.6 18km NNE of Pine Valley, CA
- 1.6 4km SE of Chula Vista, CA
- 1.7 21km E of Julian, CA
- 2.7 2km WNW of Lake Henshaw, CA
- 1.6 6km NNW of Lakeside, 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.