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

Abstract

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.

Focal Mechanism Determination of Event S1222a and Implications for Tectonics Near the Dichotomy Boundary in Southern Elysium Planitia, Mars

“…The resolved positive radial anisotropy in the crust (V SH > V SV ) in the model of Beghein et al (2022) is representative of the path average structure, although negative radial anisotropy has been observed near the InSight landing site (Li, Beghein, Wookey, et al, 2022). Isotropic models with strong crustal layering have also been shown to fit the observed Rayleigh and Love dispersion data of S1222a (Xu et al, 2023). The shear attenuation quality factor Q μ is assumed to be 600 in the crust and mantle (e.g., Giardini et al, 2020).…”

Constraints for the Martian Crustal Structure From Rayleigh Waves Ellipticity of Large Seismic Events

“…On 4 May 2022, the InSight lander recorded the S1222a event, which had a moment magnitude estimated as M W 4.7 and thus corresponds to the largest seismic event ever recorded on Mars (Kawamura et al., 2022). This event exhibits clear surface waves (both Love and Rayleigh) that can be used for studying lithospheric properties along the source‐receiver path (e.g., Beghein et al., 2022; J. Li, Beghein, Lognonné, et al., 2022; Kim, Stähler, et al., 2022; Xu et al., 2023), but is also a unique opportunity to investigate the local crustal structure through ellipticity analysis of Rayleigh waves. Similarly, the events S1000a and S1094b are two other good‐quality seismic events, which are related to the impact of meteorites on the Martian surface, 126° and 58° away from the InSight lander, and had magnitudes estimated as M W 4.1 and 4.0, respectively (Posiolova et al., 2022).…”

Differences in Scattering Properties of the Shallow Crusts of Earth, Mars, and the Moon Revealed by P‐Wave Receiver Functions

“…For the $$\varepsilon $$ value of the Martian shallow crust, although not previously reported, a different method of multiscattering analysis of earthquakes, marsquakes, and moonquakes confirms that the strength of the crustal seismic scattering of Mars is Earth‐like (Menina et al., 2021), but is weaker than that of the Moon (Lognonné et al., 2020). This can also be verified by surface waves, which have been observed in the event waveforms of marsquakes (Charalambous et al., 2022; Kim et al., 2022; Z. Xu et al., 2023) but have never been detected in moonquakes. This is because strong scattering results in the rapid diffusion of surface‐wave energy to that of scattered body waves, leading to the absence of surface waves (e.g., Onodera et al., 2022).…”