36km SSE of Santa Cruz Is. (E end), CA

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 25 km (16 mi) from the epicentre. 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.

How big was it?

This earthquake released about 720 lb of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 3.9 would have released about 32 times as much.

1. Mineral, Virginia 2011 M 5.8 21,000× the energy of this one
2. Magna, Utah 2020 M 5.7 15,000× the energy of this one
3. Around the size people start to feel M 3.0 1.3× the energy of this one
4. This earthquake M 2.9 about 720 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 5.3 on 2018-04-05 — about 3,600 times the energy of this one.

Before 2016, the USGS record lists 5 earthquakes of M5 or more within 50 km:

1. 5.5 30 km SW of Channel Islands Beach, California · 32 km NNW of this epicentre Feb 18, 1926
2. 5.5 11km NNW of Santa Barbara Is., CA · 32 km SE of this epicentre Sep 4, 1981
3. 5.3 The 1973 Point Mugu, California Earthquake · 44 km NE of this epicentre Feb 21, 1973
4. 5.2 9 km SW of Channel Islands Beach, California · 43 km NNE of this epicentre Apr 18, 1928
5. 5.1 9km SSE of Santa Cruz Is. (E end), CA · 27 km NNW of this epicentre Aug 6, 1973

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 33.7203, -119.4090. Map © OpenStreetMap contributors.

Nearby places

Places and coordinates from the US Census Bureau Gazetteer (2024). Distances are from the epicentre.

Aftershocks so far

26 earthquakes have been recorded within 50 km since this one.

1. 1.8 18 km S of Port Hueneme, CA 12:04 UTC
2. 1.6 19 km SSW of Port Hueneme, CA 05:09 UTC
3. 2.7 27 km SSW of Port Hueneme, CA 01:10 UTC
4. 2.6 17km SE of Santa Cruz Is. (E end), CA 21:27 UTC
5. 1.8 31km NE of Santa Barbara Is., CA 12:27 UTC
6. 1.7 14km SSE of Port Hueneme, CA 08:25 UTC
7. 3.6 15km SSE of Port Hueneme, CA 20:24 UTC
8. 2.8 26km SE of Santa Cruz Is. (E end), CA 06:05 UTC
9. 2.3 15km SSE of Port Hueneme, CA 22:39 UTC
10. 1.5 15km NNE of Santa Cruz Is. (E end), CA 11:45 UTC
11. 2.8 33km NW of Santa Barbara Is., CA 05:23 UTC
12. 2.8 31km NNW of Santa Barbara Is., CA 14:58 UTC
13. 2.9 35km NW of Santa Barbara Is., CA 07:19 UTC
14. 1.8 20km SSE of Port Hueneme, CA 03:58 UTC
15. 2.5 19km SSE of Port Hueneme, CA 17:25 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 20:54 UTC. 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.