EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

First seismic constraints on the Martian crust – receiver functions for InSight

Brigitte Knapmeyer-Endrun1, Felix Bissig2, Nicolas Compaire3, Raphael Garcia3, Rakshit Joshi4, Amir Khan2, Doyeon Kim5, Vedran Lekic5, Ludovic Margerin6, Mark Panning7, Martin Schimmel8, Nicolas Schmerr5, Eleonore Stutzmann9, Benoit Tauzin10, Saikiran Tharimena7, Simon Stähler2, Paul Davis11, Baptiste Pinot3, John-Robert Scholz4, and the InSight crustal structure team*
Brigitte Knapmeyer-Endrun et al.
  • 1Bensberg Observatory, University of Cologne, Germany
  • 2Institute of Geophysics, ETH Zurich, Switzerland
  • 3Institut Supérieur de l'Aéronautique et de l'Espace SUPAERO, Toulouse, France
  • 4MPI for Solar System Research, Göttingen, Germany
  • 5University of Maryland, College Park, USA
  • 6Institut de Recherche en Astrophysique et Planétologie, Université Toulouse III Paul Sabatier, France
  • 7Jet Propulsion Laboratory, Caltech, Pasadena, USA
  • 8Institute of Earth Sciences Jaume Almera – CSIC, Barcelona, Spain
  • 9Université de Paris, Institut de physique du globe de Paris, France
  • 10Université de Lyon, France
  • 11UCLA, USA
  • *A full list of authors appears at the end of the abstract

NASA’s InSight mission arrived on Mars in November 2018 and deployed the first very broad-band seismometer, SEIS, on the planet’s surface. SEIS has been collecting data continuously since early February 2019, by now recording more than 400 events of different types. InSight aims at enhancing our understanding of the internal structure and dynamics of Mars, including better constraints on its crustal thickness. Various models based on topography and gravity observed from the orbit currently vary in average crustal thickness from 30 km to more than 100 km, with important implications for Mars’ thermal evolution, and the partitioning of silicates and heat-producing elements between different layers of Mars.

We present P-to-S and S-to-P receiver functions, which are available for 4 and 3 marsquakes, respectively, up to now. Out of all of the marsquakes recorded to date, these are the only ones with clear enough P- or S-arrivals not dominated by scattering to make them suitable for the analysis. All of the quakes are located at comparatively small epicentral distances, between 25° and 40°. We observe three consistent phases within the first 10 seconds of the P-to-S receiver functions. The S-to-P receiver functions also show a consistent first phase. Later arrivals are harder to pinpoint, which could be due to the comparatively shallow incidence of the S-waves at the considered distances, which prevents the generation of converted waves. Identification of later multiple phases in the P-to-S receiver functions likewise remains inconclusive. To obtain better constraints on velocity, we also calculated apparent velocity curves from the P-to-S receiver functions, but these provide meaningful results for only one event so far, implying a large uncertainty. Due to difficulties in clearly identifying multiples, the receiver functions can currently be explained by either two crustal layers and a thin (25-30 km) crust or three crustal layers and a thicker (40-45 km) crust at the landing site. This model range already improves the present constraints by providing a new maximum value of less than 70 km for the average crustal thickness. Information from noise autocorrelations as a complementary method, identification of P-reverberations and S-precursors in the event recordings, and more extensive modeling, ultimately including 3D-effects, are considered to further our understanding of the waveforms and tighten the constraints on the crust.

InSight crustal structure team:

E. Bozdag, D. Peter, A.-C. Plesa, M. Wieczorek, D. Antonangeli, L. Pan, C. Perrin, D. Giardini, P. Lognonné, S. Smrekar, W. B. Banerdt

How to cite: Knapmeyer-Endrun, B., Bissig, F., Compaire, N., Garcia, R., Joshi, R., Khan, A., Kim, D., Lekic, V., Margerin, L., Panning, M., Schimmel, M., Schmerr, N., Stutzmann, E., Tauzin, B., Tharimena, S., Stähler, S., Davis, P., Pinot, B., and Scholz, J.-R. and the InSight crustal structure team: First seismic constraints on the Martian crust – receiver functions for InSight, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22525,, 2020