QuakeIndex

Earthquake · reviewed by a seismologist

M 3.7md

134 km N of San Juan, Puerto Rico

Yes. A magnitude 3.7 earthquake was recorded 134 km N of San Juan, Puerto Rico, at 8:40 am AST on 24 July 2023 (12:40 UTC), 33 km deep.

· 33 km deep · released about 5.9 tons of TNT

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Distance rings around the epicentre, with the nearest towns at their true direction and later quakes as coloured dots. Not a shaking map — see the USGS ShakeMap for that.
When
Magnitude
M 3.7 (md)
Depth
33 km below the surface
Felt
no reports yet
Status
Reviewed by a seismologist

USGS · last changed by USGS · we first saw it 1206 days ago

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 70 km (43 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 5.9 tons of TNT. Magnitude is logarithmic: each whole step up releases about 32 times more energy, so a magnitude 4.7 would have released about 32 times as much.

  1. Northridge, California 1994 M 6.7 29,000× the energy of this one
  2. Mineral, Virginia 2011 M 5.8 1,300× the energy of this one
  3. Magna, Utah 2020 M 5.7 900× the energy of this one
  4. This earthquake M 3.7 about 5.9 tons of TNT
  5. Around the size people start to feel M 3.0 this one released 12× more

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 2016-10-23 — about 10 times the energy of this one.

Before 2016, the USGS record lists 2 earthquakes of M5 or more within 50 km:

  1. 5.4 106 km N of Brenas, Puerto Rico · 43 km SW of this epicentre
  2. 5.0 113 km N of Brenas, Puerto Rico · 34 km SW 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 19.6771, -66.0668. Map © OpenStreetMap contributors.

Aftershocks so far

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

  1. 4.0 110 km N of Brenas, Puerto Rico
  2. 3.4 112 km N of San Juan, Puerto Rico
  3. 3.2 105 km N of San Juan, Puerto Rico
  4. 3.6 105 km N of Suárez, Puerto Rico
  5. 3.9 123 km N of Suárez, Puerto Rico
  6. 3.6 123 km N of Suárez, Puerto Rico
  7. 3.7 97 km N of Brenas, Puerto Rico
  8. 3.6 108 km NNE of San Juan, Puerto Rico
  9. 3.6 119 km N of San Juan, Puerto Rico
  10. 3.8 127 km N of Suárez, Puerto Rico
  11. 3.6 124 km N of Suárez, Puerto Rico
  12. 3.6 118 km N of Suárez, Puerto Rico
  13. 3.7 133 km N of Tierras Nuevas Poniente, Puerto Rico
  14. 3.5 106 km N of San Juan, Puerto Rico
  15. 3.7 111 km N of San Juan, Puerto Rico

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

QuakeIndex does not issue warnings. For earthquake early warning see ShakeAlert.