Fig. 3: Comparative analysis of P-wave attenuation on Mars and Earth, and marsquake spectra.
From: Evidence for weak seismic attenuation in Mars’ deep mantle
a P-wave attenuation \({Q}_{P}(r)\) profiles for Earth and Mars. The Earth profile (dashed gray line) is derived from the Preliminary Reference Earth Model53 (PREM) at intermediate periods100 (>10 s). Mars’ profiles (solid red lines) represent attenuation profiles at a short period (1 s), corresponding to different grain size ratios between Mars and Earth (1.0, 1.6, 2.0, 3.0; from left to right) or their equivalent water content ratios (100%, 24%, 13%, 4%). Mars’ profiles are calculated based on Earth’s PREM model, with corrections to account for differences in period, temperature, and pressure (see “Methods”). b Grid search results for Mars from various combinations of water content ratios and grain size ratios relative to Earth. Models within the red-filled region exhibit excessive attenuation compared to the observed marsquake spectra shown in (d, e) and are thus rejected, either due to small grain sizes or high water content. c Cross-section (upper panel) of Mars highlighting the seismic ray paths for marsquakes S1102a and S1415a, with their maximum penetration depths into the upper mantle and transition zone. The paths are calculated based on 1000 mantle models85. Waveforms (lower panel) for marsquakes S1415a and S1102a. d Spectral analysis for marsquake S1102a. The logarithm of the waveform amplitude is plotted against frequency. The dark blue curve represents the P-wave spectrum used for fitting, and the light blue curve shows data excluded due to smaller amplitude or site amplification effects (see “Methods”). The gray curve indicates noise levels. The red synthetic curves correspond to the \({Q}_{P}(r)\) profiles of Mars shown in (a), with grain size ratios of 1.0, 1.6, 2.0, and 3.0 assuming the same water content (or equivalent to water content ratios of 100%, 24%, 13%, and 4% assuming the same grain size), and solid curves indicate the best-fitting models. e Similar spectral analysis for marsquake S1415a, following the same framework as (d).
