Earthquake near Union City, CA

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 15 km (9 mi) from the epicentre. In Union City, 5 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: Union City 5 km, intensity II · Fremont 5 km, intensity II · Newark 9 km, intensity II · Pleasanton 11 km, intensity II · Dublin 13 km, intensity II · Hayward 13 km, intensity II. Estimated for each town centre; each link is that town's own record.

How big was it?

This earthquake released about 40 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.

1. Mineral, Virginia 2011 M 5.8 380,000× the energy of this one
2. Magna, Utah 2020 M 5.7 270,000× the energy of this one
3. Around the size people start to feel M 3.0 24× the energy of this one
4. This earthquake M 2.1 about 40 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 4.4 on 2018-01-04 — about 2,800 times the energy of this one.

Before 2016, the USGS record lists 15 earthquakes of M5 or more within 50 km; the five largest:

1. 6.2 Near San Jose, California · 35 km SSE of this epicentre Aug 3, 1903
2. 6.2 The 1984 Morgan Hill, California Earthquake · 40 km SE of this epicentre Apr 24, 1984
3. 6.1 Near San Jose, California · 46 km SSE of this epicentre Jun 11, 1903
4. 5.8 7 km NNW of Boulder Creek, California · 47 km SSW of this epicentre Sep 5, 1955
5. 5.8 The 1980 Livermore, California Earthquake · 33 km NNE of this epicentre Jan 24, 1980

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 37.5898, -121.9672. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 2.5 3km ENE of Oakland, CA 19:07 UTC
2. 1.8 10km E of Alum Rock, CA 02:42 UTC
3. 1.6 8km NE of Alum Rock, CA 08:51 UTC
4. 1.6 11km S of Portola Valley, CA 06:05 UTC
5. 1.7 6km NE of Blackhawk, CA 05:16 UTC
6. 1.7 3km S of Loyola, CA 21:23 UTC
7. 1.6 6km WNW of Mountain House, CA 22:57 UTC
8. 1.7 4km SSW of Los Altos Hills, CA 08:19 UTC
9. 2.8 6km WNW of Mountain House, CA 01:58 UTC
10. 1.6 2km NW of Pacifica, CA 01:14 UTC
11. 2.5 3km ESE of San Leandro, CA 19:28 UTC
12. 2.1 15km E of Seven Trees, CA 12:50 UTC
13. 1.5 16km SSE of Livermore, CA 21:16 UTC
14. 1.7 2km E of Hayward, CA 06:24 UTC
15. 1.9 11km SSE of Portola Valley, CA 04:58 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 10:37 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.