Between 04:03 UTC on Nov. 6 and 21:47 UTC on Nov. 7, the U.S. Geological Survey’s catalog recorded five earthquakes of magnitude 3.0 or higher in the waters and hills around Puerto Rico, a stretch of about 42 hours. The largest was a magnitude 3.45 beneath Moca and the smallest a magnitude 3.02 at La Parguera, and none of the five is large enough to cause serious damage.
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They did not form one neat swarm. Depths run from 8 kilometers to more than 70, and the epicenters range from the island’s northwest corner to the sea north of Culebra, so the group reads as ordinary background activity in a region where several fault systems meet.
Five magnitude 3 events in order
The first, and the strongest, was the magnitude 3.45 near Moca, located 1 kilometer northwest of the town at a depth of 59 kilometers at 04:03 UTC on Nov. 6. Roughly seven hours later, at 10:59 UTC, came a magnitude 3.15 about 62 kilometers north-northeast of Luquillo, offshore at a depth near 60 kilometers. Both are deep enough that surface shaking would be faint.
On Nov. 7 the pace picked up. At 08:38 UTC the USGS logged a magnitude 3.23 about 70 kilometers north-northwest of San Antonio at a depth of 21 kilometers. Two and a half minutes later, at 08:40 UTC, a magnitude 3.1 followed 33 kilometers north-northwest of Culebra, deeper at 71 kilometers. The two sit well apart, one off the northwest coast and the other off the northeast, so their near-simultaneous timing looks coincidental rather than a mainshock and aftershock.
The fifth arrived late that day. At 21:47 UTC, a magnitude 3.02 hit 1 kilometer west-southwest of La Parguera on the south coast, at a shallow 8 kilometers.
Reading the five as a time series shows gaps of about 7 hours, 22 hours, 2.5 minutes and 13 hours. Only one pair is close together in time, and the pair is separated by a large distance. A real swarm would cluster in space as well as time, which these do not, and that supports the reading of ordinary background activity spread across the island region.
Depths from 8 to 71 kilometers
Four of the five sit between roughly 21 and 71 kilometers down, which puts them in or near the descending slab and the plate-boundary zone north of the island, where the North American plate slides beneath the Caribbean. The La Parguera event, at about 8 kilometers, belongs to a different category: a shallow crustal quake on the southern side of the island. The USGS event records give depths but do not assign each quake to a fault, so that grouping is an interpretation of depth rather than a finding.
Depth shapes what residents notice. A magnitude 3.0 at 8 kilometers can be felt as a sharp jolt close to the epicenter, while a 3.45 at 59 kilometers spreads its energy through more rock and registers more softly at the surface. The island’s seismic network, run from the University of Puerto Rico in Mayaguez, publishes its own solutions at the Puerto Rico Seismic Network site, and its local magnitudes can differ by a few tenths from the USGS numbers.
Counting what the feed leaves out
A total of five depends on where the line is drawn. USGS’s weekly list of M2.5-plus events shows more Puerto Rico quakes in the surrounding week, including a 2.95 south of Santa Isabel on Nov. 5, a 2.78 near Orocovis, a 2.68 near Sabana Grande and a 2.5 at Magas Arriba on Nov. 7. Those fall below magnitude 3 and are not part of the five, though they would raise the tally to at least nine events if the cutoff moved to 2.5.
The strongest of the five, the 3.45 under Moca, is also the one that most plausibly was felt on land, since the town sits directly above the epicenter, even at a depth of 59 kilometers. The three offshore events sit tens of kilometers from the coast, and the USGS catalog gives no felt-report totals for them in the feed excerpt read here. Residents who noticed any shaking can compare with the agency’s event pages, which update as new reports arrive.
The cutoff matters for interpretation. Nine small shocks in a week is a busier picture than five, but it remains consistent with the long-running low-level activity around the island, which the USGS and the local network both track continuously. Counting with a 3.0 cutoff, as the USGS feed allows, gives the five described here, and the same listing is the place to check for any new entries. The unresolved question is whether the shallow La Parguera event is the start of a southern sequence or a one-off; the USGS feed will show that quickly if more shocks follow near that spot.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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