First Focal Mechanisms of Marsquakes

Nienke Brinkman*, Simon C. Stähler, D. Giardini, C. Schmelzbach, Amir Khan, Alice Jacob, Nobuaki Fuji, Clément Perrin, P. Lognonné, Éric Beucler, Maren Böse, Savas Ceylan, C. Charalambous, John Clinton, Martin van Driel, Fabian Euchner, Anna C Horleston, Taichi Kawamura, Brigitte Knapmeyer-Endrun, Guenolé Orhand-MainsantM. P. Panning, W. T. Pike, John-Robert Scholz, J. Robertsson, W. B. Banerdt

*Corresponding author for this work

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

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Abstract

Since February 2019, NASA's InSight lander is recording seismic signals on the planet Mars, which, for the first time, allows to observe ongoing tectonic processes with geophysical methods. A number of Marsquakes have been located in the Cerberus Fossae graben system in Elysium Planitia and further west, in the Orcus Patera depression. We present a first study of the focal mechanisms of three well-recorded events (S0173a, S0183a, S0235b) to determine the processes dominating in the source region. We infer for all three events a predominantly extensional setting. Our method is adapted to the case of a single, multicomponent receiver and based on fitting waveforms of P and S waves against synthetic seismograms computed for the initial crustal velocity model derived by the InSight team. We explore the uncertainty due to the single-station limitation and find that even data recorded by one station constrains the mechanisms (reasonably) well. For the events in the Cerberus Fossae region (S0173a, S0235b) normal faulting with a relatively steep dipping fault plane is inferred, suggesting an extensional regime mainly oriented E-W to NE-SW. The fault regime in the Orcus Patera region is not determined uniquely because only the P wave can be used for the source inversion. However, we find that the P and weak S waves of the S0183a event show similar polarities to the event S0173, which indicates similar fault regimes.
Original languageEnglish
Article numbere2020JE006546
Number of pages22
JournalJournal of Geophysical Research: Planets
Volume126
Issue number4
Early online date13 Feb 2021
DOIs
Publication statusPublished - 1 Apr 2021

Bibliographical note

Funding Information:
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. Nienke Brinkman was funded for this research by ETH Grant 1‐003285‐000. Amir Khan, Domenico Giardini, John F. Clinton, and Simon C. Stähler acknowledge support from ETHZ through the ETH + funding scheme (ETH+02 19‐1: “Planet Mars”). The French coauthors acknowledge CNES and ANR (ANR‐19‐CE31‐0008‐08). Numerical simulations were supported by a grant from the Swiss National Supercomputing Centre (CSCS) under project ID s922. We thank the developers of Instaseis for sharing the broadband waveform databases, which was essential for this work. Finally, we wish to thank Editor‐in‐Chief Laurent Montesi, and reviewers Goran Ekström and Luis Rivera for their careful and critical review that have significantly improved the manuscript. This is InSight Contribution Number 180.

Funding Information:
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. Nienke Brinkman was funded for this research by ETH Grant 1-003285-000. Amir Khan, Domenico Giardini, John F. Clinton, and Simon C. St?hler acknowledge support from ETHZ through the ETH?+?funding scheme (ETH+02 19-1: ?Planet Mars?). The French coauthors acknowledge CNES and ANR (ANR-19-CE31-0008-08). Numerical simulations were supported by a grant from the Swiss National Supercomputing Centre (CSCS) under project ID s922. We thank the developers of Instaseis for sharing the broadband waveform databases, which was essential for this work. Finally, we wish to thank Editor-in-Chief Laurent Montesi, and reviewers Goran Ekstr?m and Luis Rivera for their careful and critical review that have significantly improved the manuscript. This is InSight Contribution Number 180.

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

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