Different Martian Crustal Seismic Velocities Across the Dichotomy Boundary From Multi-Orbiting Surface Waves

We have observed both minor-arc (R1) and major-arc (R2) Rayleigh waves for the largest marsquake (magnitude of 4.7 +/- 0.2) ever recorded. Along the R1 path (in the lowlands), inversion results show that a simple, two-layer model with an interface located at 21-29 km and an upper crustal shear-wave velocity of 3.05-3.17 km/s can fit the group velocity measurements. Along the R2 path, observations can be explained by upper crustal thickness models constrained from gravity data and upper crustal shear-wave velocities of 2.61-3.27 and 3.28-3.52 km/s in the lowlands and highlands, respectively. The shear-wave velocity being faster in the highlands than in the lowlands indicates the possible existence of sedimentary rocks, and relatively higher porosity in the lowlands.

Automated summary

We have observed both minor-arc (R1) and major-arc (R2) Rayleigh waves for the largest marsquake (magnitude of 4.7 +/- 0.2) ever recorded. Along the R1 path (in the lowlands), a simple, two-layer model with an interface located at 21-29 km and an upper crustal shear-wave velocity of 3.05-3.17 km/s can fit the group velocity measurements. Along the R2 path, observations can be explained by upper crustal thickness models constrained from gravity data and upper crustal shear-wave velocities of 2.61-3.27 and 3.28-3.52 km/s in the lowlands and highlands, respectively. The shear-wave velocity being faster in the highlands than in the lowlands indicates the possible existence of sedimentary rocks and relatively higher porosity in the lowlands.