A magnitude 5.3 quake shook Guam, and USGS logged 40 felt reports from the island

A magnitude 5.3 earthquake struck 41 km north-northeast of Yigo Village, Guam, at 03:58 UTC on October 10, 2026, which was 1:58 p.m. on the island. The U.S. Geological Survey counts 40 felt reports from the event. The shaking came from deep below the surface, which is the main reason it stayed a notable event instead of a damaging one.

A Quake Under the Mariana Arc

Guam sits on the Mariana island arc, the chain that marks where the Pacific plate descends beneath the Mariana plate along the Mariana Trench. That subduction is the source of most earthquakes in the region, and it produces them at a wide range of depths, from shallow ruptures near the trench to events tens or hundreds of kilometres down the sinking slab.

The U.S. Geological Survey’s current catalogue record, read on October 13, carries the magnitude at 5.3 and counts 40 felt reports from the event. The USGS record places this shock at a depth of about 111.6 km, at 13.859 degrees north and 145.089 degrees east, in the open water north-northeast of the island rather than beneath it. The magnitude type is listed as mb, a body-wave measure commonly used for moderate and large events, and the record has been marked as reviewed by USGS analysts, with the magnitude and location unchanged from the weekly feed. A depth of that size sits in the intermediate range inside the descending slab, not in the crust that Guam is built on. Energy released at that depth travels a long way to reach the surface, so the shaking is spread over a broad area and tends to be weaker at any single spot than a shallow quake of the same magnitude would produce.

What 40 Felt Reports Actually Measured

The felt count comes from the USGS felt-report questionnaire program, known as DYFI, a citizen science project in which people who noticed an earthquake describe what they experienced, and the agency turns the responses into maps of perceived shaking and damage. For this event the catalogue lists 40 reports, with a community intensity value of 4.2 on the scale that DYFI responses produce.

Forty reports is a small number in absolute terms, and it measures participation as much as shaking. It reflects how many residents, workers and visitors found the reporting form and chose to fill it in, which depends heavily on population and on how many people were awake, indoors and paying attention at 2 p.m. on a Saturday.

The figure confirms the quake was widely noticed on the island. It does not rank the shaking against other events.

The 4.2 intensity value points to light shaking. Reports at that level typically describe rattling windows and swaying objects, the kind of motion people notice indoors without reaching for emergency supplies. The catalogue’s instrumental shaking field, which would come from measured ground motion, is empty for this event, so the DYFI number is the only intensity estimate it carries.

PAGER, Tsunami and the Hazard Picture for the Island

The USGS PAGER system is the agency’s automated estimate of likely fatalities and economic losses after significant earthquakes, expressed as a colour-coded alert. For this event the alert field in the catalogue is empty, meaning no PAGER level is attached to the record. The tsunami flag is set to zero, and the event is not marked as having generated a tsunami.

The agency scores the event at a significance of 449 on its internal scale, which blends magnitude, reported intensity and estimated impact. That puts it well above routine background activity without placing it among the region’s major disasters. In practical terms, the combination of a magnitude in the low fives, an intermediate depth and an epicentre offshore points to a quake that people felt, not one that damaged buildings, though the catalogue does not itself report damage or injuries.

For Guam, a U.S. territory with more than 150,000 residents and several military bases, the larger lesson is the setting. Moderate quakes at depth are a recurring feature of life beside a subduction zone, and each one is a reminder of the exposure that comes with it, from building standards to tsunami readiness when a rupture is shallow and large.

Where It Ranks in the Week’s Feed

The quake appears in the USGS past-week feed of magnitude 4.5 and larger earthquakes, where it stands as the largest event on U.S. soil in that window. It is not the largest event in the feed overall: a magnitude 6.2 quake struck 79 km south-southeast of Panguna, Papua New Guinea, on October 11, outside U.S. territory. The full record, including the felt count, depth and review status, is also published on the USGS event page for us6000u1cd, which carries the shaking maps and any later revisions. The catalogue entry was last updated on October 12 at about 08:08 UTC, and magnitudes and felt counts can still move as more reports arrive, so the figures here reflect the record as it stood on October 13.

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

More from Morning Overview