A magnitude 5.6 earthquake struck off Guatemala’s Pacific coast with no tsunami threat

An offshore earthquake of magnitude 5.6 hit the sea south of Guatemala at 14:54 UTC on Nov. 10, or 8:54 a.m. local time. The epicenter sat 43 km south of Puerto San José, the port town on the Pacific coast of Escuintla department. The U.S. Geological Survey rated the event green for expected impact, and its tsunami flag stayed at 0.

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Only a few people had logged how it felt when the first automatic solution posted, and 19 felt reports were on file by the time the record was last revised that afternoon. The agency’s alert and intensity fields, covered below, point to light-to-moderate shaking rather than damaging motion.

A moment magnitude of 5.6 and a depth near 35 km

The USGS event record gives the size as a moment magnitude, the scale seismologists prefer for moderate and large earthquakes because it is tied to the physical area and slip of the rupture, with a stated uncertainty of about 0.05. The event page for us7000txb8 lists the preferred depth as 35 km. The moment-tensor solution behind the magnitude reports a slightly shallower derived depth of 30.5 km, so the rupture began deep beneath the seabed rather than near the surface.

Depth shaped the shaking people experienced. A rupture some 30 to 35 km down and 43 km from the nearest port has a long path to travel before its energy reaches the coast, and both distances work to lower the shaking that people on land experience. The tectonic setting is the one that governs this entire coastline, where the Cocos plate descends beneath the Caribbean plate.

Intensity near 4 on shore and a green alert

The agency’s detail feed for the event, updated at 20:59 UTC, shows a ShakeMap intensity of about 4.2, a community-reported intensity of 3.8 and a green alert, the lowest of its color-coded tiers. Intensity is a separate quantity from magnitude, and the USGS explainer on magnitude and shaking intensity states that an earthquake has a single magnitude but a different intensity at every location, depending mostly on distance from the rupture.

A modeled intensity of roughly 4 on the Modified Mercalli scale corresponds to shaking that is noticed by many people but rarely does damage. The gap between the modeled 4.2 and the 3.8 drawn from questionnaires is small and expected, since each comes from a different method and the reported figure rests on very few responses.

Those responses came through the agency’s felt-report system, known as DYFI. The DYFI background documentation says an intensity assigned from more questionnaires is more reliable, and it also says unchecked raw answers vary with local ground conditions. The count of 19 was therefore a thin base for the 3.8, and an early query of the same record showed just 3 reports, so the number grew as people in Guatemala and nearby countries submitted replies after the morning shock.

Size still deserves some perspective. On the USGS rule of thumb that each whole-number step in magnitude means about 32 times more energy, a magnitude 5.6 shock releases roughly 32 times the energy of a magnitude 4.6 event and about a thousand times that of a 3.6 one. It is a strong earthquake by the standards of daily seismic logs, yet well below the magnitudes that wreck buildings across a region, and the green alert reflects that gap.

Tsunami flag 0 and the scope of the record

The record carries a tsunami flag of 0 and a green alert, and the USGS data show no sign of a tsunami product tied to the event. Those two entries are the basis for describing the quake as free of a tsunami threat in this account. A separate warning-center bulletin was not part of the material reviewed, so the statement rests on the agency’s own flags.

The USGS review status on the record reads reviewed, so an analyst has checked the automatic solution, and the data pull from the agency’s event web service confirmed the 5.6 value, the 14:54:17 origin time and the 35 km depth. Nothing in that record speaks to damage, injuries or the response of Guatemala’s disaster agencies, which publish their own tallies separately and were not part of the USGS data.

The sequence of updates shows how quickly a record matures. The origin time is 14:54:17 UTC, a first revision posted by 15:23 UTC with 3 felt reports on file, and the later revision at 20:59 UTC carried 19. Every other value, from the 5.6 magnitude to the 35 km depth, was already present in the early solution and held through the later one, which indicates that the automatic and reviewed calculations agreed closely on the size and position of the event.

Whether the felt-report count settles near 19 or keeps climbing is the loose end in the file. The record was last revised at 20:59 UTC on Nov. 10, about six hours after the earthquake, and the agency treats intensity maps as living products that shift as more reports arrive.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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