51 km N of Brenas, 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 it was probably too small to be felt, even directly above it. 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 680 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 22,000× the energy of this one
2. Magna, Utah 2020 M 5.7 16,000× the energy of this one
3. Around the size people start to feel M 3.0 1.4× the energy of this one
4. This earthquake M 2.9 about 680 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 4.8 on 2017-08-18 — about 710 times the energy of this one.

Before 2016, the USGS record lists 6 earthquakes of M5 or more within 50 km; the five largest:

1. 5.9 78 km N of Arecibo, Puerto Rico · 45 km NW of this epicentre Oct 14, 1918
2. 5.8 12 km N of Garrochales, Puerto Rico · 50 km SW of this epicentre Oct 12, 1918
3. 5.7 78 km N of Tierras Nuevas Poniente, Puerto Rico · 37 km NW of this epicentre Sep 10, 1943
4. 5.5 64 km N of Tierras Nuevas Poniente, Puerto Rico · 22 km WNW of this epicentre Jul 14, 1964
5. 5.1 66 km N of Brenas, Puerto Rico · 17 km NNW of this epicentre Mar 12, 2009

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 18.9336, -66.3018. Map © OpenStreetMap contributors.

Nearby places

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

Aftershocks so far

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

1. 3.2 67 km N of Tierras Nuevas Poniente, Puerto Rico 17:28 UTC
2. 3.4 61 km N of Arecibo, Puerto Rico 16:30 UTC
3. 3.1 68 km N of Arecibo, Puerto Rico 12:56 UTC
4. 3.2 38 km N of San Juan, Puerto Rico 01:20 UTC
5. 3.3 69 km N of Brenas, Puerto Rico 17:04 UTC
6. 3.1 51 km N of Hatillo, Puerto Rico 13:48 UTC
7. 3.5 14 km NNW of Brenas, Puerto Rico 18:41 UTC
8. 3.5 22 km NNE of Tierras Nuevas Poniente, Puerto Rico 06:02 UTC
9. 3.4 85 km N of San Juan, Puerto Rico 19:55 UTC
10. 3.2 80 km N of San Juan, Puerto Rico 19:41 UTC
11. 3.5 79 km N of San Juan, Puerto Rico 19:37 UTC
12. 3.6 82 km N of San Juan, Puerto Rico 19:11 UTC
13. 3.5 77 km N of Tierras Nuevas Poniente, Puerto Rico 06:19 UTC
14. 2.5 19 km N of San Juan, Puerto Rico 06:07 UTC
15. 3.4 6 km N of Tierras Nuevas Poniente, Puerto Rico 12:09 UTC

Counted from the QuakeIndex database, which ingests the USGS feed every 30 seconds · as of 20:16 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.