Surface wave time-shift maps for the 2017 DPRK best-fitting moment tensor. A subset of the corresponding waveforms is shown in Fig. 9. The azimuthal pattern in time-shifts reflects differences between the Earth structure in the assumed 1-D model (MDJ2) and the actual Earth structure. The significant negative time-shifts toward Japan indicate that the MDJ2 model—designed for the continental path to station MDJ—is too slow to accurately model fast propagation through oceanic paths. (a) Rayleigh wave time-shifts measured on the vertical and radial components. (b) Love wave time-shifts measured on the transverse component.