S1222a—The Largest Marsquake Detected by InSight

Abstract

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

“…On the 1222nd Martian day (sol) of the InSight mission, the largest marsquake (S1222a) ever recorded occurred with a magnitude of 4.7 ± 0.2, which corresponds to energy five times greater than the second‐largest event (InSight Marsquake Service, 2022; Kawamura et al., 2022). For the first time, both Rayleigh and Love waves were observed on a planet other than Earth (Beghein et al., 2022; Kawamura et al., 2022; Xu et al., 2022).…”

“…The epicentral distance of event S1222a is 37.0° ± 1.6°, and the back azimuth is estimated to be between 96° and 112° (Kawamura et al., 2022), placing the location of S1222a in the lowlands and near the dichotomy boundary. The dichotomy boundary separates the northern lowlands and southern highlands and has highly debated origins (Andrews‐Hanna et al., 2008; Frey, 2006; Marinova et al., 2008; Zhong & Zuber, 2001).…”

“… (a) Mars Orbiter Laser Altimeter (Smith et al., 2001) map. The red star marks the optimal hypocenter of event S1222a (Kawamura et al., 2022), and the black triangle indicates the broadband seismometer of the InSight mission. The red and blue curves denote the great‐circle paths of R1 and R2, respectively.…”

Constraints on the martian crust away from the InSight landing site

“…Constraining the crustal structure at other locations is, however, crucial to fully understand the formation and evolution of the crust, and to improve global models of crustal thickness based on gravity data 17 . Although surface waves have been recently detected for the first time from two meteorite impacts 18 , 19 and the largest marsquake ever recorded 20 , surface waves constrain the average structures along the event-lander path 19 , 21 , 22 and are less sensitive to subsurface discontinuities. The present work aims at providing seismic constraints on the crustal structure at a location far from the InSight lander.…”

“…Although surface waves have been recently detected for the first time from two meteorite impacts 18,19 and the largest marsquake ever recorded 20 , surface waves constrain the average structures along the event-lander path 19,21,22 and are less sensitive to subsurface discontinuities. The present work aims at providing seismic constraints on the crustal structure at a location far from the InSight lander.…”