Variable Daily Autocorrelation Functions of High-Frequency Seismic Data on Mars

Abstract High-frequency seismic data on Mars are dominated by wind-generated lander vibrations, which radiated partially to the subsurface. Autocorrelation functions (ACFs) of filtered between 1 and 5 Hz show clear phases at ∼1.3, ∼2.6, ∼3.9 s. Daily temporal changes their arrival times (dt/t) correlate well with daily ground temperature, ∼5% variation ∼50 min apparent phase delay. The following two mechanisms could explain observations: (1) interference predominant spectral peaks ∼3.3 ∼4.1 Hz, assumed be both resonance modes, generate arrivals in ACFs; (2) vibration its reflection from an interface ∼200 m below 3.3 peak ∼1.3 s ACFs. driving mechanism resolved dt/t that most likely explains delay is thermoelastic strain a near-surface layer, affecting lander–ground coupling subsurface structures. outlined suggest, respectively, up ∼10% stiffness 1–5 ∼15% velocity top ∼20 layer. These upper bound values considering also other possible contributions. presented methodology results contribute analysis ACFs limited understanding materials Mars.