We discuss the question whether inner core (IC) differential rotation or temporal change of the IC surface provides a consistent interpretation for temporal changes of the IC‐related phases and their coda. While temporal change of the IC surface is required and provides a consistent explanation to all the seismic observations, we present three lines of seismic evidence showing that IC differential rotation cannot provide a consistent or reasonable interpretation for the observed temporal change of seismic waves from repeating earthquakes in the South Sandwich Islands (SSI) and the Middle America subduction zone.

1. We present high-precision locations and detailed source information of four small seismic events following North Korea’s 2017 nuclear test.
2. The first event is an on-site collapse 440 m northwest of the test site and best explained by a near vertical single force.
3. The later events are an earthquake swarm located 8.4 km north of the test site with a focal depth of at least 2.4 km.