Yield estimate of the 2016 DPRK nuclear test based on InSAR and Finite Element Modeling

Abstract:

The Democratic People’s Republic of Korea (DPRK) has performed six underground nuclear tests between 2006 and 2017, and is the only country known to have tested nuclear weapons in this century. A precise and accurate estimate of nuclear yield for these tests is essential, but the established method of using seismic waveforms combined with a magnitude-yield scaling relationship has inherent uncertainties due to local geological heterogeneity, the device’s depth/yield tradeoff, and complex phases in the cavity itself (Zhang & Wen 2013, Chiang et al., 2018, Zhao et al., 2016). Using Interferometric Synthetic Aperture Radar (InSAR) and numerical modeling in tandem with seismic methods can fill this gap, but previous applications of InSAR to this problem are also lacking in reliability for the same reasons as well as added inaccuracy from modeling simplifications (Wei, 2017; Myers et al., 2018; Stevens & O’Brien 2018; Wang et al., 2018). Here we address these limitations by building a finite element model of the test site that includes real topography and mechanical heterogeneity. We use a multi-parameter search to find the nuclear source characteristics that best reproduce ground deformation seen in ALOS-2 InSAR data for the January 2016 DPRK nuclear test and present preliminary results. This model can be later used as a stepping stone to characterizing the more complex explosive deformation associated with a much larger nuclear event, such as the September 2017 DPRK nuclear test.