12 Seconds Apart: Twin Seismic Pulses In China That Set Off US Nuclear Alarm

A small tremor rippled through a remote corner of Central Asia in June 2020. It registered at 2.75 on the seismic scale. The signal was picked up by a monitoring station in Kazakhstan operated by the Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO). Within seconds, analysts began tracing its origin.

The United States now says that the tremor was not an earthquake.

Senior American officials claim it was a secret underground nuclear test carried out by China at Lop Nur, its long-standing nuclear test site in the Xinjiang region. The allegation comes amid US President Donald Trump's preparations to expand the US nuclear arsenal.

Christopher Yeaw, an assistant secretary of state, said the June 22, 2020, signal was traced back to Lop Nur, over 700 km from the monitoring station that detected it. “There is very little possibility that it is anything other than an explosion,” he said at a policy event in Washington, as per NPR.

Another senior official, Thomas DiNanno, said China tried to hide the blast by using a method known as “decoupling,” which reduces the seismic signature of an underground explosion. According to him, the People's Liberation Army masked the test because it knew such activity would breach international commitments. He called the event a “yield-producing” nuclear explosion, Reuters reported.

China has denied the accusation. A spokesperson for its embassy in Washington described the claim as political manipulation, saying the US was creating a pretext for restarting its own nuclear testing. Beijing insists it remains committed to restraint as per The Times.

Between these two positions sits the CTBTO. The organisation confirmed that its International Monitoring System detected two small seismic events, 12 seconds apart, at 9:18 am that day.

It also said the signals were “very small”, far below the threshold at which its system can confidently identify a nuclear explosion. With that data alone, the body said, it cannot determine the cause.

The disagreement exposes that the global nuclear order is under strain.

The Comprehensive Nuclear Test Ban Treaty (CTBT), agreed in 1998, was meant to ban all nuclear tests. It never took effect. The US, Russia and China signed but did not ratify it. India, Pakistan, Israel and North Korea are outside it. Without full approval, the monitoring body cannot enforce tougher checks.

The last US-Russia arms treaty, New START, has also expired. The Trump administration says any new deal must include China. Beijing refuses, saying its arsenal is far smaller.

Russia has about 5,580 warheads. The US has around 5,200. China has about 600 but is expanding fast.