In the nearly three weeks since, as leaders of North Korea and the United States have exchanged insults, the world has braced itself for another show of force by the North. So when the China Earthquake Administration reported a 3.4-magnitude tremor on Saturday afternoon and attributed it to a “suspected explosion,” the news immediately set off alarm bells. Sign Up You agree to receive occasional updates and special offers for The New York Times's products and services. North Korea conducted its six nuclear tests in deep underground tunnels at Punggye-ri. The latest, on Sept. 3, when North Korea claimed it had detonated a hydrogen bomb, generated a tremor measuring at magnitudes of 5.7 to 6.3.

Source: New York Times September 23, 2017 11:48 UTC