IGPP is pleased to invite you to join its Winter 2023 Seminar Series presentation featuring USC's John Vidale. Dr. Vidale's talk, "The Confusing Gyrations of Earth’s Inner Core" will be available on January 31, 2023 in the Revelle conference room, with a Zoom option: https://ucsd.zoom.us/j/95589623414?pwd=eVVsTDByU2VRTWxDWTZDOTlsRkhWdz09 Password: igpp
Time: 12:00 pm, Pacific Time
Location: Zoom
Abstract: With passing time, there is ever less agreement whether and how Earth inner core moves. From repeated explosions in Alaska, we find that the inner core subrotated at least 0.1° from 1969 to 1971, in contrast to super-rotation of ~0.29° from 1971 to 1974. These observations contradict models of steady inner core rotation and models that posit much faster rotation rates. The reversal of polarity, timing, and rotation rates is consistent with a model of six-year oscillations about an equilibrium with gravitational locking of the mantle and inner core due to lateral density variations. The model can also explain variations in the length of day during past decades.
We also analyze changes in 99 repeating earthquake pairs captured on the ILAR and YKA arrays. Unexpected clock errors on YKA required unravelling to extend our findings. We confirm the observation of strong changes in PKIKP around the year 2003, and also note other PKIKP changes that are sporadic and asynchronous between the two arrays. Taken together, the data may suggest both rotation and local inner core changes, with a so-far-unresolved physical mechanism.