Identification of underground nuclear events in Lop Nur area (China) and blast source modeling using SAR interferometry

We aim to accurately identify underground nuclear events (UNEs) and estimate the source’s physical properties using synthetic aperture radar interferometry (InSAR). Two explosions at Lop Nur, the Chinese nuclear weapons test site, were investigated. Two SAR images were processed interferometrically to produce a differential two-pass interferogram and a relative coherence image of the area. The interferometric products were then corrected for tropospheric atmospheric disturbances using the generic atmospheric correction online service for InSAR method (GACOS). Because the time span between the event and the satellite image acquisition was very short, we were able to accurately determine the epicenter of a UNE. This determination was based on the deformations (induced uplift) caused by the blast, which allowed us to estimate the explosion’s depth and magnitude. However, four other explosions from the past were also identified. We show that it is possible to characterize some of the most important blast parameters based on the ground displacements calculated with InSAR. We also demonstrate the ability of the InSAR method to detect UNEs based on their impact on terrain from underground detonations, and estimate that the method will become increasingly important as China has prepared to resume nuclear testing in the Lop Nur region.