A revised lunar interior based on new P and S wave identifications: evidence for deep mantle layers

According to the reevaluation of the deep moonquake data collected by Apollo Passive Seismic Experiment (APSE), new P and S wave identifications were obtained by the method of multi-component cross-correlation. Combined with Double Array Stacking (DAS), the algorithm of Velocity Spectrum Scanning was applied to pick and stack the four different seismic phases (P-to-P, P-to-S, S-to-P and S-to-S) reflected from the deep lunar mantle and the lunar core. Our data set is expanded in comparison to the earlier effort of Weber et al. [2011]. Detection of deep internal interfaces was not consistent from stacked energy of these phases, but analysis of internal P and S velocities was still possible.

Our results suggest that an interface atop the low velocity zone (just above the lunar core) exists at a radius of 560 km, which is consistent with previous studies obtained by the constraints of gravity and planetary dynamics. Moreover, a discontinuity is also detected within this low velocity zone, and some interpretations are possible. In the process, a liquid lunar outer core and a solid inner core are also estimated, which are close to previous studies.