Investigation of Martian Regional Crustal Structure Near the Dichotomy Using S1222a Surface-Wave Group Velocities

Knowledge of Martian crust and uppermost mantle aid us studying the planet's evolution. NASA's InSight mission provides seismic data being used to reveal the interior structure. Most studies have focused on the crustal structure beneath InSight lander, but the seismic structure of other regions has remained poorly known. We use surface-wave data to investigate the crustal structure of a large region along the Medusa Fossae Formation and the dichotomy. We adopt the largest-magnitude marsquake (S1222a) that has been recorded, which provides both Rayleigh- and Love-wave signals. We measure and jointly invert these surface-wave fundamental-mode group velocities from similar to 15 to 40 s to estimate the average 1D isotropic velocity models. These models includes a high-velocity layer at similar to 7-km depth, which could be due to a regional basaltic activity or regional stress. Our models also indicate that a common intra-crustal structure (similar to 12-40 km depth) may exist in this region along the dichotomy.