Earthquake · reviewed by a seismologist
M 2.1ml
Earthquake near Norco, CA
No earthquake was likely felt in Norco in the 24 hours to 3:11 am PST (11:11 UTC). The last one was M 1.8, 11 km (7 mi) SSE, at 11:31 am PST on 5 November 2026, estimated intensity II (weak) in town. Every earthquake near Norco
This page: a magnitude 2.1 earthquake was recorded 3 km (2 mi) east of Norco, CA, at 2:09 am PDT on 20 September 2017 (09:09 UTC), 3.1 km deep. 137 people have reported feeling it to USGS.
USGS: 3km E of Norco, CA
8 km (5 mi) ESE of Eastvale, CA · 83 km (52 mi) E of Los Angeles, CA
- When
- 2:09 am PDT on 20 September 2017 ()
- Where
- 3 km (2 mi) east of Norco, CA · earthquakes near Norco
- Magnitude
- M 2.1 (ml)
- Depth
- 3.1 km below the surface
- Felt
- 137 reports · strongest reported intensity IV
- Nearest
- Orange County, 37 km SW
- Nearest mapped fault
- Elsinore fault, 13 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 3304 days ago
Earthquake alerts for Norco, CA
Get a notification in this browser when USGS records an earthquake near Norco, 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, people at rest would likely notice it out to about 17 km (11 mi) from the epicentre. In Norco, 3 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: Norco 3 km, intensity II · Pedley 6 km, intensity II · Eastvale 6 km, intensity II · Corona 8 km, intensity II · Riverside 11 km, intensity II · Rubidoux 12 km, intensity II. Estimated for each town centre; each link is that town's own record.
How big was it?
This earthquake released about 47 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.1 would have released about 32 times as much.
- Mineral, Virginia 2011 M 5.8 320,000× the energy of this one
- Magna, Utah 2020 M 5.7 230,000× the energy of this one
- Around the size people start to feel M 3.0 20× the energy of this one
- This earthquake M 2.1 about 47 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 12 earthquakes of M5 or more within 50 km; the five largest:
- 6.2 3 km SE of San Bernardino, California · 29 km NE of this epicentre
- 6.0 The 1910 Lake Elsinore, California Earthquake · 28 km SSE of this epicentre
- 5.5 The 1990 Upland, California Earthquake · 29 km NW of this epicentre
- 5.4 5km S of Chino Hills, CA · 24 km W of this epicentre
- 5.3 Near San Bernardino, California · 48 km NE 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 33.9292, -117.5120. Map © OpenStreetMap contributors.
Nearby places
| Place | Distance | Direction from the epicentre | |
|---|---|---|---|
| Orange County, CA | 37 km (23 mi) | SW | earthquakes near Orange County |
| Los Angeles County, CA | 75 km (47 mi) | WNW | earthquakes near Los Angeles County |
| San Diego County, CA | 122 km (76 mi) | SE | earthquakes near San Diego County |
Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.
Aftershocks so far
48 earthquakes have been recorded within 50 km since this one.
- 1.8 2km NE of Redlands, CA
- 1.6 8km ESE of Yorba Linda, CA
- 1.6 3km SE of Loma Linda, CA
- 2.6 3km SE of Loma Linda, CA
- 1.6 3km ESE of Loma Linda, CA
- 2.7 5km E of Calimesa, CA
- 2.7 2km ESE of Loma Linda, CA
- 1.5 5km ENE of Rancho Cucamonga, CA
- 1.5 3km ESE of Loma Linda, CA
- 2.5 10km N of Lytle Creek, CA
- 1.7 5km NE of Yorba Linda, CA
- 2.3 1km NNW of Colton, CA
- 1.9 5km SSE of Home Gardens, CA
- 2.2 4km SE of Yucaipa, CA
- 2.4 4km SSW of Yorba Linda, 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.