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Seismic Velocities Distribution in a 3D Mantle: Implications for InSight Measurements
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  • Ana-Catalina Plesa,
  • Ebru Bozdag,
  • Attilio Rivoldini,
  • Martin Knapmeyer,
  • Scott McLennan,
  • Sebastiano Padovan,
  • Nicola Tosi,
  • Doris Breuer,
  • Daniel Peter,
  • Simon Staehler,
  • Mark Wieczorek,
  • Martin van Driel,
  • Amir Khan,
  • Tilman Spohn,
  • Caio Ciardelli,
  • Scott King
Ana-Catalina Plesa
German Aerospace Center DLR Berlin

Corresponding Author:ana.plesa@dlr.de

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Ebru Bozdag
Colorado School of Mines
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Attilio Rivoldini
Royal Observatory of Belgium
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Martin Knapmeyer
German Aerospace Center DLR Berlin
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Scott McLennan
Stony Brook University
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Sebastiano Padovan
German Aerospace Center DLR Berlin
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Nicola Tosi
German Aerospace Center DLR Berlin
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Doris Breuer
German Aerospace Center DLR Berlin
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Daniel Peter
King Abdullah University of Science and Technology
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Simon Staehler
ETH Zurich
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Mark Wieczorek
Observatoire de la Côte d'Azur
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Martin van Driel
ETH Zurich
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Amir Khan
ETH Zurich
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Tilman Spohn
German Aerospace Center DLR Berlin
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Caio Ciardelli
Colorado School of Mines
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Scott King
Virginia Polytechnic Institute and State University
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Abstract

The InSight mission [1] landed in November 2018 in the Elysium Planitia region [2] bringing the first geophysical observatory to Mars. Since February 2019 the seismometer SEIS [3] has continuously recorded Mars’ seismic activity, and a list of the seismic events is available in the InSight Marsquake Service catalog [4]. In this study, we predict present-day seismic velocities in the Martian interior using the 3D thermal evolution models of [5]. We then use the 3D velocity distributions to interpret seismic observations recorded by InSight. Our analysis is focused on the two high quality events S0173a and S0235b. Both have distinguishable P- and S-wave arrivals and are thought to originate in Cerberus Fossae [6], a potentially active fault system [7]. Our results show that models with a crust containing more than half of the total amount of heat producing elements (HPE) of the bulk of Mars lead to large variations of the seismic velocities in the lithosphere. A seismic velocity pattern similar to the crustal thickness structure is observed at depths larger than 400 km for cases with cold and thick lithospheres. Models, with less than 20% of the total HPE in the crust have thinner lithospheres with shallower but more prominent low velocity zones. The latter, lead to shadow zones that are incompatible with the observed P- and S-wave arrivals of seismic events occurring in Cerberus Fossae, in 20° - 40° epicentral distance. We therefore expect that future high-quality seismic events have the potential to further constrain the amount of HPE in the Martian crust. Future work will combine the seismic velocities distribution calculated in this study with modeling of seismic wave propagation [8, 9]. This will help to assess the effects of a 3D thermal structure on the waveforms and provide a powerful framework for the interpretation of InSight’s seismic data. [1] Banerdt et al., Nat. Geo. 2020; [2] Golombek et al., Nat. Comm. 2020, [3] Lognnoné et al., Nat. Geo. 2020, [4] InSight MQS, Mars Seismic Catalogue, InSight Mission V3, 2020, https://doi.org/10.12686/A8, [5] Plesa et al., GRL 2018, [6] Giardini et al., Nat. Geo. 2020, [7] Taylor et al., JGR 2013, [8] Bozdag et al., SSR 2017, [9] Komatitsch & Tromp, GJI 2002.