EARTHQUAKEM6.4

M6.4 earthquake near Kainantu, Papua New Guinea

Map: the earthquake near Kainantu, Papua New Guinea, with plate boundaries

A magnitude 6.4 earthquake struck 50 km (31 mi) north-northeast of Kainantu, Papua New Guinea on Sunday, September 20, 2026 at 09:17 UTC, at a depth of 113 km (70 mi), according to the U.S. Geological Survey. At this intermediate depth, shaking spreads out before it reaches the surface.

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

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

MagnitudeM6.4
Depth113 km (70 mi)
Time (UTC)Sep 20 09:17
Location5.90°S 146.11°E
Nearest townKainantu · 50 km
Energy60 kilotons TNT
Aftershocks M2.5+3
Tsunami flagNo
PAGER alertGREEN
Felt reports30
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Why here?

This earthquake struck about 61 km (38 mi) from the boundary between the Australian 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 113 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. About 290,806 people were exposed to moderate shaking or stronger (intensity 5 and up). USGS’s PAGER system estimates it most likely caused no deaths (90 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 6.4 released roughly the energy of 60 kilotons of TNT, about 4 times the Hiroshima atomic bomb. That is about 4,000 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 45,000 times more than this one.

Aftershocks

In the first 30 days after it, USGS recorded 3 smaller earthquakes of magnitude 2.5 or more within 100 km (62 mi). The largest was a magnitude 5.4 on September 20 at 12:45 UTC.

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 204 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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