Earthquake.now

M3.6 Earthquake near Isabela, Puerto Rico — 20 September 2025

A minor earthquake of magnitude 3.6 was recorded near Isabela, Puerto Rico on , with an epicentre 140 km north of Isabela, at a focal depth of 42.0 km. It ranked as the 10th strongest of 157 earthquakes recorded in Puerto Rico in the preceding 30 days.

3.6 Minor

Time (UTC): 2025-09-20 19:45:18

Time (your timezone): —

Magnitude: 3.6 (minor)

Focal depth: 42.0 km (shallow)

Epicentre: 19.7583, -66.8568

Location: 140 km N of Isabela, Puerto Rico

Country: Puerto Rico

USGS link to NOAA tsunami information: Not linked

Review status: Reviewed

Source: USGS event page

How strong was this earthquake?

Minor earthquakes in this range are felt by people close to the epicentre as a brief jolt or rattle, but they very rarely cause any damage.

A magnitude 3.6 earthquake radiates roughly 3.8 tons of TNT equivalent in seismic energy.

The USGS assigns this earthquake a significance score of 199, which is below the USGS threshold of more than 600 for its significant-earthquake list. The ranking combines magnitude with available Did You Feel It responses and PAGER alert level; it is not a direct measurement of damage.

What the magnitude scale actually measures →

Where was the epicentre?

The epicentre was located at 19.7583, -66.8568 — 140 km north of Isabela. The closest other recorded event was a magnitude 3.1 earthquake 84 km south of here on 16 August 2026.

Why the 42 km depth matters

At 42 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size may be noticed locally, especially close to the epicentre. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.

Read more on how focal depth changes what you feel →

What does the tsunami information flag mean?

The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M3.6 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.

How earthquakes generate tsunamis, and what the alert levels mean →

Aftershocks and local seismic history

11 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 4.2.

95 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.9 event near Punta Cana on 25 February 2025. This M3.6 event released about 2,818 times less energy than that event.

How long aftershock sequences last, and how large they get →

Where this event sits in the record

This earthquake is part of the September 2025 worldwide record, and of earthquakes in Puerto Rico during September 2025. Browse the full monthly archive to compare periods.

Nearest recorded earthquakes to this epicentre

Other recent earthquakes in Puerto Rico

All recorded earthquakes in Puerto Rico →

Other magnitude 3 earthquakes worldwide

All magnitude 3 earthquakes →

Questions about this earthquake

How strong is a magnitude 3.6 earthquake?

Minor earthquakes in this range are felt by people close to the epicentre as a brief jolt or rattle, but they very rarely cause any damage. A magnitude 3.6 earthquake radiates roughly 3.8 tons of TNT equivalent in seismic energy.

How deep was the earthquake near Isabela?

At 42 km this was a shallow earthquake. Shallow events release their energy close to the surface, so for a given magnitude they produce noticeably stronger shaking — and more damage — than deeper ones. Roughly three quarters of all earthquakes worldwide occur at shallow depths.

Was the M3.6 earthquake near Isabela felt?

This catalogue does not ingest eyewitness responses, so it cannot confirm where this earthquake was felt. Based on magnitude alone, an event this size may be noticed locally, especially close to the epicentre. Its shallow focus makes stronger surface shaking more likely than for a deeper event of the same magnitude.

What does the USGS tsunami field mean for this event?

The USGS record does not carry a link to NOAA tsunami information. That field is not an all-clear and does not state whether a tsunami occurred. In this case, a damaging tsunami would be less likely because at M3.6 it falls below the magnitude 6.5 threshold that generally applies before a submarine earthquake displaces enough water to generate a damaging tsunami; it occurred inland rather than beneath the sea floor. For an active coastal alert, use tsunami.gov or your local warning authority.

Have there been aftershocks?

11 further earthquakes have been recorded within about 150 km of the epicentre in the seven days after this event, the largest of them magnitude 4.2.

How often do earthquakes happen near Isabela?

95 earthquakes of magnitude 4 or above have been logged within roughly 200 km of this epicentre in our catalogue. The strongest was a magnitude 5.9 event near Punta Cana on 25 February 2025. This M3.6 event released about 2,818 times less energy than that event.