Evidence for crustal seismic anisotropy at the InSight lander site

Jiaqi Li*, Caroline Begheim, James M Wookey, Paul Davis, Philippe Lognonne, Martin Schimmel, Eléonore Stutzmann, Matt Golombek, Jean-Paul Montagner, William B. Banerdt

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

19 Citations (Scopus)

Abstract

We analyzed broadband and low-frequency events recorded on Mars and made the first detection of horizontally polarized shear wave reflections, which help constrain the crustal structure at NASA's InSight lander site. Coherent signals from five well-recorded marsquakes appear to be independent of the focal depth and are consistent with SH-wave reflections off the topmost crustal interface (8 ± 2 km). This phase confirms the existence of the ∼8 km interface in the crust and the large wave speed (or impedance) contrast across it. The range of acceptable parameters determined from the detected SH-wave reflections differs from the majority of the vertically polarized shear wave models resulting from a previous receiver function study, indicating that the velocity of the vertically polarized waves is larger than that of horizontally polarized waves. We propose that this inconsistency results from the presence of seismic anisotropy within the top crustal layer at the lander site. Modeling results show that dry- or liquid-filled cracks/fractures and igneous intrusions can reproduce the observed radial anisotropy.
Original languageEnglish
Article number117654
JournalEarth and Planetary Science Letters
Volume593
Early online date17 Jun 2022
DOIs
Publication statusPublished - 1 Sept 2022

Bibliographical note

Funding Information:
J.L. and C.B. were supported by NASA InSight PSP grant # 80NSSC18K1679 . J.W. was supported by a UKSA Aurora Grant ( ST/T002972/1 ). P.L., E.S., and J.P.M. are supported by Agence Nationale de la Recherche (MAGIS, ANR-19-CE31-0008-08 ; IdEx Université Paris Cité, ANR-18-IDEX-0001 ), and by CNES for SEIS science support. M.S. thanks SANIMS ( RTI2018-095594-B-I00 ).

Funding Information:
J.L. thanks Tong Zhou (from the InSightSeers program) for assistance in the anisotropy modeling and benchmarks for the synthetic waveforms calculation. J.L. thanks Ross Maguire for providing the Marsquakes downloading script (InSight SEIS Data Bundle, 2021). We thank reviewer Martha Savage and another anonymous reviewer for their helpful reviews. J.L. and C.B. were supported by NASA InSight PSP grant #80NSSC18K1679. J.W. was supported by a UKSA Aurora Grant (ST/T002972/1). P.L. E.S. and J.P.M. are supported by Agence Nationale de la Recherche (MAGIS, ANR-19-CE31-0008-08; IdEx Université Paris Cité, ANR-18-IDEX-0001), and by CNES for SEIS science support. M.S. thanks SANIMS (RTI2018-095594-B-I00). This is InSight Contribution Number 237. InSight seismic data presented here (http://dx.doi.org/10.18715/SEIS.INSIGHT.XB_2016) is publicly available through the Planetary Data System (PDS) Geosciences node, the Incorporated Research Institutions for Seismology (IRIS) Data Management Center under network code XB, and through the data center of Institut de Physique du Globe, Paris (http://seis-insight.eu). We acknowledge NASA, CNES, their partner agencies and Institutions (UKSA, SSO, DLR, JPL, IPGP-CNRS, ETHZ, IC, MPS-MPG) and the flight operations team at JPL, SISMOC, MSDS, IRIS-DMC and PDS for providing SEED SEIS data. A portion of the work was supported by the InSight Project at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • Martian crust
  • SH-wave reflections
  • negative radial anisotropy

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