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 ∼15 to 40 s to estimate the average 1D isotropic velocity models. These models includes a high‐velocity layer at ∼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 (∼12–40 km depth) may exist in this region along the dichotomy. Plain Language Summary: NASA's Mars exploration mission, InSight, brought a seismometer module that recorded numerous marsquakes. These marsquake recordings reveal the crustal structure beneath the InSight lander. To study the crustal structure of other regions, one can utilize a type of seismic waves, the surface waves. The largest marsquake event observed during InSight provides surface‐wave signals with a high signal‐to‐noise ratio. By analyzing these signals, we investigate the average crustal structure between the epicenter and the InSight landing site in a region near the equator and along the planet's dichotomy. We find a high‐velocity layer at about 7 km depth compared to the layers above and below, which could be due to a regional flood basalt or the regional crustal compressional stress. Our result also exhibits the similar crustal structure (from around 12 to 40 km depth) as the structure beneath the InSight lander, which indicates the possibility of a similar intra‐crustal structure existing along the Martian dichotomy. Key Points: Joint inversion of the S1222a Rayleigh‐ and Love‐wave group velocities provides 1D isotropic velocity models of the regional Martian crustThese models indicate a high‐velocity layer at ∼7 km depth which could be due to the regional basaltic activity or the regional stress fieldExcept for the high‐velocity layer, these models are similar to the crustal structure beneath InSight lander from ∼12 to 40 km depth [ABSTRACT FROM AUTHOR]