Evidence for crustal seismic anisotropy at the InSight lander site

We analyzed broadband and low-frequency events recorded on Mars made the first detection of horizontally polarized shear wave reflections, which help constrain crustal structure at NASA's InSight lander site. Coherent signals from five well-recorded marsquakes appear to be independent focal depth are consistent with SH-wave reflections off topmost interface (8 ± 2 km). This phase confirms existence ∼8 km in crust large speed (or impedance) contrast across it. The range acceptable parameters determined detected differs majority vertically models resulting a previous receiver function study, indicating that velocity waves is larger than waves. propose this inconsistency results presence seismic anisotropy within top layer Modeling show dry- or liquid-filled cracks/fractures igneous intrusions can reproduce observed radial anisotropy. • Detection SH-reflections under lander. Constraints km) SEIS. Seismic 8 Martian Elysium Planitia. Presence East-West oriented horizontal inclusions, fluid-filled cracks.