Using seismic recordings of event S1222a, we measure dispersion curves of Rayleigh and Love waves, including their first overtones, and invert these for shear velocity (VS) and radial anisotropic structure of the Martian crust. The crustal structure along the topographic dichotomy is characterized by a fairly uniform vertically polarized shear velocity (VSV) of 3.17 km/s between ∼5 and 30 km depth, compatible with the previous study by Kim et al. (2022), https://doi.org/10.1126/science.abq7157. Radial anisotropy as large as 12% (VSH > VSV) is required in the crust between 5 and 40 km depth. At greater depths, we observe a large discontinuity near 63 ± 10 km, below which VSV reaches 4.1 km/s. We interpret this velocity increase as the crust‐mantle boundary along the path. Combined gravimetric modeling suggests that the observed average crustal thickness favors the absence of large‐scale density differences across the topographic dichotomy.
Plain Language Summary
The first detection and analysis of surface waves on Mars (Kim et al., 2022, https://doi.org/10.1126/science.abq7157) revealed that the crustal structure away from the InSight lander is fairly uniform between 5 and 30 km depth in the northern lowlands. This is strikingly different from the crustal structure inferred beneath the lander. The largest marsquake recorded during the InSight mission to Mars, S1222a, provides the first clear signals of both types of...

Structure Along the Martian Dichotomy Constrained by Rayleigh and Love Waves and Their Overtones

10.1029/2022GL101666