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Influence of body waves, instrumentation resonances, and prior assumptions on Rayleigh wave ellipticity inversion for shallow structure at the InSight landing site

Knapmeyer-Endrun, B. and Murdoch, N. and Kenda, B. and Golombek, M. and Knapmeyer, Martin and Witte, Lars and Verdier, N and Kedar, S. and Lognonne, P. and Banerdt, B. (2018) Influence of body waves, instrumentation resonances, and prior assumptions on Rayleigh wave ellipticity inversion for shallow structure at the InSight landing site. Space Science Reviews. Springer. DOI: 10.1007/s11214-018-0529-y ISSN 0038-6308

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Official URL: https://link.springer.com/article/10.1007%2Fs11214-018-0529-y

Abstract

Based on an updated model of the regolith’s elastic properties, we simulate the ambient vibrations background wavefield recorded by InSight’s Seismic Experiment for Interior Structure (SEIS) on Mars to characterise the influence of the regolith and invert SEIS data for shallow subsurface structure. By approximately scaling the synthetics based on seismic signals of a terrestrial dust devil, we find that the high-frequency atmospheric background wavefield should be above the self-noise of SEIS’s SP sensors, even if the signals are not produced within 100–200 m of the station. We compare horizontal-to-vertical spectral ratios and Rayleigh wave ellipticity curves for a surface-wave based simulation on the one hand with synthetics explicitly considering body waves on the other hand and do not find any striking differences. Inverting the data, we find that the results are insensitive to assumptions on density. By contrast, assumptions on the velocity range in the upper-most layer have a strong influence on the results also at larger depth. Wrong assumptions can lead to results far from the true model in this case. Additional information on the general shape of the curve, i.e. single or dual peak, could help to mitigate this effect, even if it cannot directly be included into the inversion. We find that the ellipticity curves can provide stronger constraints on the minimum thickness and velocity of the second layer of the model than on the maximum values. We also consider the effect of instrumentation resonances caused by the lander flexible modes, solar panels, and the SEIS levelling system. Both the levelling system resonances and the lander flexible modes occur at significantly higher frequencies than the expected structural response, i.e. above 35 Hz and 20 Hz, respectively. While the lander and solar panel resonances might be too weak in amplitude to be recorded by SEIS, the levelling system resonances will show up clearly in horizontal spectra, the H/V and ellipticity curves. They are not removed by trying to extract only Rayleigh-wave dominated parts of the data. However, they can be distinguished from any subsurface response by their exceptionally low damping ratios of 1% or less as determined by random decrement analysis. The same applies to lander-generated signals observed in actual data from a Moon analogue experiment, so we expect this analysis will be useful in identifying instrumentation resonances in SEIS data.

Item URL in elib:https://elib.dlr.de/121112/
Document Type:Article
Title:Influence of body waves, instrumentation resonances, and prior assumptions on Rayleigh wave ellipticity inversion for shallow structure at the InSight landing site
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Knapmeyer-Endrun, B.max planck institute for solar system research, göttingen, germanyUNSPECIFIED
Murdoch, N.ISEA-SUPERO, Université de ToulouseUNSPECIFIED
Kenda, B.UNSPECIFIEDUNSPECIFIED
Golombek, M.Jet Propulsion Laboratory, Pasadena, CA, USAUNSPECIFIED
Knapmeyer, MartinMartin.Knapmeyer (at) dlr.dehttps://orcid.org/0000-0003-0319-2514
Witte, LarsLars.Witte (at) dlr.dehttps://orcid.org/0000-0002-3921-2524
Verdier, NUNSPECIFIEDUNSPECIFIED
Kedar, S.jet propulsion laboratory, pasadena, ca, usaUNSPECIFIED
Lognonne, P.Institut de Physique du Globe, Paris, FranceUNSPECIFIED
Banerdt, B.Jet Propulsion Laboratory, Pasadena, CA, USAUNSPECIFIED
Date:August 2018
Journal or Publication Title:Space Science Reviews
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.1007/s11214-018-0529-y
Publisher:Springer
ISSN:0038-6308
Status:Published
Keywords:Mars, InSight, Seismology, Regolith, Rayleigh Waves
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space Science and Exploration
DLR - Research area:Raumfahrt
DLR - Program:R EW - Erforschung des Weltraums
DLR - Research theme (Project):R - Projekt InSight, Project InSight HP3
Location: Berlin-Adlershof , Bremen
Institutes and Institutions:Institute of Planetary Research
Institute of Space Systems > Land and Exploration Technology
Institute of Planetary Research > Planetary Physics
Deposited By: Knapmeyer, Dr. Martin
Deposited On:24 Oct 2018 09:55
Last Modified:15 Jan 2019 12:30

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