Nuclear tests in North Korea triggered 1,399 quakes, affected Earth's crust

A new study says North Korea's underground nuclear tests at Mount Mantap triggered 1,399 local earthquakes between 2008 and 2025. The findings suggest the blasts reactivated faults and altered the crust years after testing ended.

In Short

• Researchers tracked seismic records from stations in China and South Korea
• The team detected far more quakes than earlier catalogues had recorded
• After the 2017 test, seismic activity rose instead of fading away

North Korea's underground nuclear tests at Mount Mantap have had effects on the surrounding Earth's crust that lasted years after the explosions stopped, with seismic activity continuing to increase long after the country's final nuclear test, according to a new study.

The findings shed light on the long-term consequences of underground nuclear explosions and could have implications for monitoring former nuclear test sites.

Researchers say the explosions may reactivate faults that had remained seismically quiet, potentially producing earthquakes that can be difficult to distinguish from naturally occurring tectonic activity.

North Korea's Punggye-ri nuclear test site, located beneath Mount Mantap, hosted six underground nuclear tests between 2006 and 2017.

The final test, conducted in September 2017, was the largest. It produced an estimated yield of 100 to 250 kilotons and triggered a seismic event measured at magnitude 6.3 by the US Geological Survey.

Satellite radar observations also detected substantial deformation of the mountain's summit following the explosion.

While earlier research largely focused on determining the location, timing and size of North Korea's nuclear tests, the longer-term impact of the explosions on surrounding seismic activity remained less understood.

To investigate this, Xingli Fan and colleagues analysed seismic records from stations in China and South Korea, including instruments located between 80 and 200 kilometres from Mount Mantap.

Their analysis identified 1,399 local earthquakes between 2008 and 2025, considerably more than previous earthquake catalogues had recorded.

The researchers found a particularly unusual pattern following the 2017 explosion. Instead of seismic activity gradually declining after the test, as is typically expected from short-lived post-explosion earthquake sequences, activity around Mount Mantap began increasing about three weeks after the detonation.

The earthquakes then continued to increase in both frequency and magnitude through 2025.

High-precision earthquake locations showed that the events were concentrated along two roughly north-northwest-trending fault structures, suggesting that the activity was organised and linked to the reactivation of faults rather than being random seismic activity.

The researchers propose that repeated nuclear explosions progressively damaged the shallow crust and changed the stresses acting within it. This may have allowed faults that were already close to failure to become active gradually over several years.

The study therefore suggests that the seismic footprint of an underground nuclear test may extend well beyond the immediate explosion, potentially reshaping the behaviour of faults long after the testing itself has ended.

- Ends