Seismic Autocorrelation Analysis of Deep Mars

Abstract

The InSight mission deployed one seismic station on Mars, providing a chance to apply single-station-based autocorrelation analysis to investigate Martian subsurface structures. However, recent analysis indicated the low-frequency autocorrelation signals may originate from quasi-periodic high-amplitude instrumental “glitches” rather than the reflection response of deep Mars. In this study, we detected and removed these high-amplitude glitches in raw seismic data and employed autocorrelation on the clean vertical component waveforms filtered between 0.05 and 0.1 Hz. We observed signals at the expected times for the olivine-wadsleyite transition and core-mantle boundary (CMB) as estimated by other methods. This result suggests that the low-frequency autocorrelation signals are the reflection response from the olivine-wadsleyite transition in the mantle and the Martian CMB region, rather than a noise phenomena. A grid search method to fit the observed PcP waveform was used to identify a layer intermediate in velocity between the Martian mantle and core at the Martian CMB.