47 km NNW of San Antonio, Puerto Rico

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 32 km (20 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 750 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 20,000× the energy of this one
2. Magna, Utah 2020 M 5.7 14,000× 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 750 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 4.2 on 2017-08-27 — about 75 times the energy of this one.

Before 2016, the USGS record lists 17 earthquakes of M5 or more within 50 km; the five largest:

1. 7.7 45 km N of San Antonio, Puerto Rico · 16 km E of this epicentre Jul 29, 1943
2. 7.1 24 km NNW of San Antonio, Puerto Rico · 23 km SSE of this epicentre Oct 11, 1918
3. 6.4 32 km NW of Aguadilla, Puerto Rico · 33 km SSW of this epicentre Feb 10, 1920
4. 6.1 15 km WNW of San Antonio, Puerto Rico · 38 km S of this epicentre Oct 11, 1918
5. 6.1 18 km NNW of San Antonio, Puerto Rico · 30 km SSE of this epicentre Nov 12, 1918

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 18.8895, -67.2710. Map © OpenStreetMap contributors.

Nearby places

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. 2.9 45 km NW of Aguadilla, Puerto Rico 08:40 UTC
2. 2.8 48 km SE of San Antonio, Puerto Rico 05:55 UTC
3. 2.9 78 km N of Isabela, Puerto Rico 02:16 UTC
4. 2.4 30 km NW of San Antonio, Puerto Rico 03:50 UTC
5. 2.9 51 km N of Isabela, Puerto Rico 11:29 UTC
6. 2.7 40 km NNW of San Antonio, Puerto Rico 09:08 UTC
7. 3.0 71 km NW of San Antonio, Puerto Rico 21:07 UTC
8. 2.6 35 km NNW of San Antonio, Puerto Rico 10:37 UTC
9. 2.8 37 km NW of Rincón, Puerto Rico 07:46 UTC
10. 2.5 0 km N of San Antonio, Puerto Rico 04:24 UTC
11. 2.5 39 km NNW of San Antonio, Puerto Rico 08:46 UTC
12. 2.9 47 km NNW of San Antonio, Puerto Rico 09:53 UTC
13. 2.8 52 km NW of San Antonio, Puerto Rico 00:51 UTC
14. 2.8 95 km NNW of San Antonio, Puerto Rico 03:06 UTC
15. 2.7 92 km NNW of San Antonio, Puerto Rico 23:54 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 21:21 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.