EARTHQUAKEM6.5

M6.5 earthquake near Nikolski, Alaska

Map: the earthquake near Nikolski, Alaska, with plate boundaries

A magnitude 6.5 earthquake struck 106 mi (170 km) west of Nikolski, Alaska on Thursday, September 17, 2026 at 14:19 UTC, at a depth of 61 mi (98 km), according to the U.S. Geological Survey. At this intermediate depth, shaking spreads out before it reaches the surface.

USGS set its tsunami flag for this earthquake. The flag is set automatically for large earthquakes at sea and is not a warning. For official tsunami information, see tsunami.gov and your national warning center.

USGS’s PAGER impact estimate is GREEN: little or no damage expected.

8 people reported feeling it to USGS “Did You Feel It?”.

MagnitudeM6.5
Depth61 mi (98 km)
Time (UTC)Sep 17 14:19
Location52.88°N 171.40°W
Nearest townNikolski · 170 km
Energy85 kilotons TNT
Aftershocks M2.5+23
Tsunami flagSet (not a warning)
PAGER alertGREEN
Felt reports8
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Why here?

This earthquake struck about 123 mi (198 km) from the boundary between the North American and Pacific 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 98 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.

What kind of fault?

USGS’s analysis of the seismic waves shows it was an oblique earthquake: the fault slipped partly sideways and partly as one block dropped down as the crust stretched.

Shaking and impact

The strongest shaking USGS estimates was intensity 5 on the Modified Mercalli scale: moderate. USGS’s PAGER system estimates it most likely caused no deaths (99 percent probability). Early estimates are revised as reports come in.

How strong was it?

Magnitude is logarithmic: each whole step releases about 32 times more energy. This magnitude 6.5 released roughly the energy of 85 kilotons of TNT, about 5.7 times the Hiroshima atomic bomb. That is about 5,600 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 32,000 times more than this one.

Aftershocks

In the first 30 days after it, USGS recorded 23 smaller earthquakes of magnitude 2.5 or more within 62 mi (100 km). The largest was a magnitude 4.5 on September 20 at 13:55 UTC.

Earthquake history here

Before this earthquake, USGS had recorded 153 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.

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