A joint South Korean and Chinese research team has found that North Korea's final and most powerful underground nuclear detonation, carried out in 2017 at the Punggye-ri test site, appears to have triggered more than 1,330 earthquakes concentrated along a fault zone roughly 24 kilometres wide. Unlike seismic activity that followed earlier tests — which was brief — the tremors linked to the 2017 blast have grown in both frequency and intensity through 2025, according to the study published in the journal Science. Researchers warn the region could face an earthquake of up to magnitude 6.4 if the fault zone becomes fully active.