Issues

Front: On 3 September 2017, North Korea carried out its sixth declared underground nuclear explosion. The resulting seismic event immediately drew the attention of the global geophysical community because it was an order of magnitude larger than any of North Korea’s five previous declared nuclear tests, and because it was followed by several smaller seismic events. The SRL Focus Section on North Korea’s September 2017 Nuclear Test and Its Aftermath (this issue) comprises 17 articles covering a full range of topics, from surface and acoustic observations through detailed seismological investigations of the nuclear test, the post-test collapse of Mt. Mantap, and the additional seismic events, including event detection, location, depth and yield estimation, and source-type discrimination. Here a map indicates the location, geography, and topography of the test area (upper left, from Schaff et al., this issue); detections resulting from some of the events are also shown (upper right, from Dodge, this issue). Locations of the Mt. Mantap collapse and a resulting earthquake swarm are plotted on a Google Earth map and events in the swarm are located in detail (lower left and right, respectively; both from Yao Tian, Lu et al., this issue).

Back: Qaysi et al. (this issue) present a uniform database of teleseismic shearwave splitting parameters for the Arabian plate. The parameters, including the fast polarization orientation and splitting time, are measured based on a procedure that minimizes the energy on the transverse component. Above, a map of the Arabian plate shows the individual shear-wave splitting measurements (blue, green, and red) plotted above the 200 km depth ray-piercing points; dashed yellow line indicates the Afro-Arabian dome. Below, a map shows distribution of spatially averaged splitting times in radius = 1° circles.