Fig. 5: Observations of second and fourth PKIKP multiples, i.e., PKIKP2 and PKIKP4, respectively, in the seismic wavefield from the 30 Nov 2018, Mw 7.1 Anchorage earthquake.

A Seismic records from the Alaskan network are aligned with the predictions of PKIKP2 arrivals, corrected by the Earth’s ellipticity69. The waveforms are bandpass filtered in the period band of 7–13 s. C Linear stack of individual waveforms. E The spectrograms of stacked waveforms before filtering show the frequency content variation as a function of time. (B, D, F) Similar to (A), (C), and (E) but for the PKIKP4 arrivals.