If a country wants to keep a nuclear bomb test secret, it’ll probably do it deep underground. But even if you bury the bomb, some clues will reach the surface. So says a study in the journal Geophysical Research Letters. [P. Vincent et al., "Anomalous transient uplift observed at the Lop Nor, China nuclear test site using satellite radar interferometry time‐series analysis"]
Scientists analyzed radar satellite data of a spot in western China, where three nukes were detonated underground in the ‘90s. And they found that after the blasts, the land above the test chambers gradually swelled one inch higher in elevation.
Here’s why: shock waves from the explosion left cracks in rock near the surface. Years later, plumes of underground water, still steamy from the blast, trickled up and infiltrated those cracks, causing the rock to expand and rise—forensic evidence that could be used to infer the bomb’s explosive energy.
The International Atomic Energy Agency won’t be busting nuclear rebels with this method anytime soon—it took four years for this bulge in the Chinese desert to appear.* But since seismic analysis—the other tool for studying bomb blasts—can be foiled by a cleverly designed detonation chamber, this trick gives nuclear detectives one more way to study blasts from the past.
[The above text is a transcript of this podcast.]
*Clarification (1/13/12): Although the IAEA monitors the use of fissile materials, verification that no nation has violated the ban on nuclear testing is done by the Preparatory Commission for the Comprehensive Nuclear Test Ban Organization.