Using Moment Tensor Inversions for Rapid Seismic Source Detection and Characterization: Application to the North Korean Nuclear Tests

The rapid detection and source characterization of any type of seismic events including earthquakes and nuclear explosions is one of the missions of many seismological laboratories. Most often, the techniques used are based on phase picking and amplitude measurements for detecting and locating events, and for estimating magnitudes. From these parameters, especially for anthropogenic sources, event screening is then done empirically, and this may lead to misinterpretations of the source nature. However, it is known that seismic waveform inversion for the determination of the moment tensor has proven to be a reliable source physics-based method for event characterization. Here, we present a technique already used for earthquake monitoring in tectonically active regions, and we test it on very shallow natural and anthropogenic events recorded in the vicinity of the Democratic People's Republic of Korea (DPRK). From a grid of potential locations and by scanning continuous seismic waveforms, it is possible to implement a rapid detector of seismic events providing the full information of the sources (origin time, location, magnitude, mechanism, and source decomposition). We show its overall performances on all past DPRK nuclear tests and regional earthquakes. From such an approach fast complete event screening is achieved. Source uncertainties can also be estimated. This stand-alone detector and identifier of seismic events may help monitoring seismological agencies to provide a rapid and complete alert for any events within a region of interest before more in-depth discrimination analysis can be run.