Different Martian Crustal Seismic Velocities Across the Dichotomy Boundary From Multi‐Orbiting Surface Waves. Issue 1 (10th January 2023)

• Record Type: Journal Article
• Authors: Li, Jiaqi; Beghein, Caroline; Lognonné, Philippe; McLennan, Scott M.; Wieczorek, Mark A.; Panning, Mark P.; Knapmeyer‐Endrun, Brigitte; Davis, Paul; Banerdt, W. Bruce
• Is Part Of: Geophysical research letters. Volume 50:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-10
• Subjects: surface wave -- marsquake -- Rayleigh wave -- porosity -- Mars -- dichotomy; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL101243
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: 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. Plain Language Summary: The largest marsquake ever recorded occurred recently and waves propagating at the surface, called surface waves, have been observed. Owing to the relatively large magnitude (i.e., 4.7 ± 0.2) of this event, surface wave energy is still clearly visible after one orbit around the red planet. The shortest path taken by the wave propagating between the source and the receiver is located in the northern lowlands, near the boundary with the southern highlands (called dichotomy). The surface wave traveling in the opposite direction, following the longer distance between the quake and the seismic station, mostly passes through the highlands. Analyses of these two paths reveal that the average shear‐wave velocity is faster in the highlands than in the lowlands near the dichotomy boundary. This lower velocity in the lowlands may be due to the presence of thick accumulations of sedimentary rocks and relatively higher porosity. Key Points: Analyses of the minor‐arc and major‐arc Rayleigh waves reveal different Martian crustal structures across the dichotomy boundary The average shear‐wave velocity is faster in the highlands than in the lowlands near the dichotomy boundary The lower shear‐wave velocity in the lowlands may be due to the presence of sedimentary rocks and relatively higher porosity