EARTHQUAKEM4.9

M4.9 earthquake in the Pagan region, Northern Mariana Islands

Map: the earthquake in the Pagan region, Northern Mariana Islands, with plate boundaries

A magnitude 4.9 earthquake struck in the Pagan region, Northern Mariana Islands on Tuesday, October 20, 2026 at 07:09 UTC, at a depth of 250 km (155 mi), according to the U.S. Geological Survey. At this intermediate depth, shaking spreads out before it reaches the surface. The epicenter was about 404 km (251 mi) north of Capitol Hill.

MagnitudeM4.9
Depth250 km (155 mi)
Time (UTC)Oct 20 07:09
Location18.84°N 145.52°E
Nearest townCapitol Hill · 404 km
Energy338 tons TNT
Aftershocks M2.5+0
Tsunami flagNo
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Why here?

This earthquake struck about 97 km (60 mi) from the boundary between the Philippine Sea and Mariana plates. Most earthquakes happen along plate boundaries like this one, where the pieces of Earth’s outer shell collide, pull apart or grind past each other. Stress builds up over years until the rock suddenly slips. At 250 km down, it most likely broke inside a plate that is sinking into the mantle beneath its neighbor, in what geologists call a subduction zone.

The red lines on the map are plate boundaries.

How strong was it?

Magnitude is logarithmic: each whole step releases about 32 times more energy. This magnitude 4.9 released roughly the energy of 338 tons of TNT. That is about 22 times the energy of a magnitude 4.0, a quake people nearby feel but that rarely causes damage. The strongest earthquake ever recorded, magnitude 9.5 in Chile in 1960, released about 7,900,000 times more than this one.

Aftershocks

In the first 6 days after it, USGS recorded no smaller earthquakes of magnitude 2.5 or more within 100 km (62 mi).

Outside the United States, USGS mainly lists quakes of about magnitude 4 and up, so smaller aftershocks there are undercounted.

Earthquake history here

Before this earthquake, USGS had recorded 63 earthquakes of magnitude 6 or larger within 300 km (186 mi) since 1900. The strongest:

Official details, updates and the shaking map: USGS event page.

See every earthquake on October 20, 2026 or earthquakes by day.

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