A scientific analysis of regional seismic records concludes that underground nuclear detonations beneath Mount Mantap in North Korea were followed by a prolonged increase in local earthquakes and measurable changes to the mountain's crust, continuing years after the last recorded test, researchers said.
Key findings from the seismic analysis
The study, led by Xingli Fan and colleagues, examined waveforms from seismic stations in China and South Korea located roughly 80–200 km from the Punggye‑ri test site beneath Mount Mantap. Their processing identified 1,399 local earthquakes between 2008 and 2025, substantially more events than appear in conventional earthquake catalogues for the area.
- The Punggye‑ri complex hosted six known underground nuclear tests between 2006 and 2017.
- The final test, in September 2017, was the largest and is estimated to have yielded between 100 and 250 kilotons; it generated a seismic signal that the US Geological Survey measured at magnitude 6.3.
- Satellite radar observations recorded significant summit deformation of Mount Mantap after the 2017 detonation, consistent with large subsurface disturbance.
The analysis reveals an unusual post‑2017 pattern of seismicity: rather than returning to background levels after the explosions ceased, the region displayed continuing and in some intervals increasing numbers of small local earthquakes. The authors suggest the explosions may have reactivated faults that were previously quiescent.
Methods, interpretation and limitations
To reach their conclusions the team reprocessed continuous seismic data from nearby national networks and applied detection and location algorithms that can recover smaller events often missed in routine catalogues. The spatial distribution of the newly identified events suggests a link to stress changes induced by the underground explosions and subsequent subsurface collapse and deformation.
However, the researchers emphasise caution in interpretation. Small earthquakes in this distance band can be of tectonic origin; distinguishing explosion‑triggered or induced events from natural tectonic activity requires detailed source characterisation, which remains challenging at low magnitudes. Furthermore, the inference that blasts "reactivated" dormant faults is based on statistical and spatial associations rather than direct measurement of fault slip at depth.
Implications for monitoring and policy
The findings carry implications for both geophysics and arms‑control monitoring. If underground nuclear blasts can produce lingering seismicity and alter crustal structure, that may complicate efforts to discriminate between natural earthquakes and human‑caused events at former test sites. Long‑term seismic surveillance and complementary remote‑sensing — such as interferometric radar that detects surface deformation — can provide additional constraints on subsurface changes.
| Item | Detail |
|---|---|
| Number of tests at Punggye‑ri | 6 (2006–2017) |
| Largest test yield (Sept 2017) | 100–250 kilotons |
| Seismic magnitude recorded (USGS) | 6.3 |
| Events identified by the study | 1,399 local earthquakes (2008–2025) |
Authors note that deploying denser local seismic networks and integrating geodetic data would improve discrimination of induced versus natural events and clarify the mechanical processes that sustain post‑test seismicity. Such data are also valuable for hazard assessment around former test sites.
Beyond monitoring, the research underscores a broader scientific point: large underground explosions can do more than produce an isolated seismic pulse. They may change stress conditions and fracture networks in ways that persist, with consequences for how crustal systems evolve in the years after testing has ended.
The study adds to previous work that documented summit subsidence at Mount Mantap after the 2017 explosion and provides a longer temporal view of seismic activity in the region. While further analysis is required to pin down causal mechanisms, the record assembled by Fan and colleagues will inform both geophysical understanding and international efforts to track remnants of past nuclear testing.
