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Moment Tensor Estimation of Event S1222a and Implications for Tectonics Near the Dichotomy Boundary in Southern Elysium Planitia, Mars
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  • Ross Maguire,
  • Vedran Lekic,
  • Doyeon Kim,
  • Nicholas Charles Schmerr,
  • Jiaqi Li,
  • Caroline Beghein,
  • Quancheng Huang,
  • Jessica Claire Elizabeth Irving,
  • Foivos Georgios Karakostas,
  • Philippe Lognonné,
  • Simon C. Stähler,
  • William Bruce Banerdt
Ross Maguire
University of Illinois at Urbana Champaign

Corresponding Author:rossrm@illinois.edu

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Vedran Lekic
University of Maryland, College Park
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Doyeon Kim
Swiss Federal Institute of Technology in Zürich
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Nicholas Charles Schmerr
University of Maryland, College Park
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Jiaqi Li
University of California, Los Angeles
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Caroline Beghein
University of California Los Angeles
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Quancheng Huang
Department of Geophysics, Colorado School of Mines
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Jessica Claire Elizabeth Irving
University of Bristol
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Foivos Georgios Karakostas
Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Bologna
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Philippe Lognonné
Université Paris Cité, Institute de physique de globe de Paris, CNRS
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Simon C. Stähler
Eidgenössische Technische Hochschule Zürich
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William Bruce Banerdt
Jet Propulsion Laboratory, California Institute of Technology
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On May 4th, 2022 the InSight seismometer SEIS recorded the largest marsquake ever observed, S1222a, with an initial magnitude estimate of Mw 4.7. Understanding the depth and source properties of this event has important implications for the nature of tectonic activity on Mars. Located ~37 degrees to the southeast of InSight, S1222a is one of the few non-impact marsquakes that exhibits prominent ratio surface waves. We use waveform modeling of body waves (P and S) and surface waves (Rayleigh and Love) to constrain the moment tensor and quantify the associated uncertainty. We find that S1222a likely resulted from dip-slip faulting in the mid-crust (source depth ~18 – 28 km) and estimate a scalar moment of 3.51015 – 5.01015 Nm (magnitude Mw 4.3 – 4.4). The best-fitting focal mechanism is sensitive to the choice of phase windows and misfit weights, as well as the structural model of Mars used to calculate Green’s functions. We find that an E-W to SE-NW striking thrust fault can explain the data well, although depending on the choice of misfit weighting, a normal fault solution is also permissible. The orientation of the best-fitting fault plane solutions suggests that S1222a takes place on a fault system near the martian crustal dichotomy accommodating relative motion between the northern lowlands and southern highlands. Independent constraints on the event depth and improved models of the (an)isotropic velocity structure of the martian crust and mantle could help resolve the ambiguity inherent to single-station moment tensor inversions of S1222a and other marsquakes.
28 Feb 2023Submitted to ESS Open Archive
01 Mar 2023Published in ESS Open Archive