Searching for Seismic Sources Around the Insight Landing Site: Focus on Sol 173 and 235 Marsquakes
Session: InSight Seismology on Mars: Results From the First (Earth) Year of Data and Prospects for the Futur
Type: Oral
Date: 4/28/2020
Time: 10:45 AM
Room: 115
Description:
The NASA InSight mission is dedicated to study the seismic activity and to propose the first internal models of Mars. Since February 2019, it has detected more than 300 seismic events, of which about 30 are interpreted as more than a 1000 km away. On sols 173 (S0173a, May 23rd 2019) and 235 (S0235b, July 27th 2019) the two largest seismic events have been recorded with Mw > 3 and showing clear P and S waves. The InSight MarsQuake Service has estimated their locations: S0173a probability density function (PDF) is at 28±3° distance and 91±10°N azimuth and S0235b, at 26±3° distance and 74±10°N azimuth. Both PDFs are located in the vicinity of the Cerberus Fossae fault system (CF), which is one of the largest tectonic structure on Mars of about 1200 km long.
From orbital imagery of MRO CTX and HiRISE cameras, we study the morphology and the lateral segmentation of the CF. We expect that marsquakes are more likely to initiate in intersegment zones, as they usually correspond to structural discontinuities where stress concentrates along faults on Earth. Besides, assuming the scaling law existing between the rupture length and the seismic moment, fault segments of 1 to 10 km long should be involved during such events. Our tectonic analysis shows that small inter-segments at several eastern graben tips of CF are good candidates for marsquakes locations.
We represent the moment tensor of the two events as it is a robust visualization of the source geometry. The source mechanism is seismically constrained from fitting waveforms of body waves against synthetic data. For this, it is necessary to go beyond fitting the polarity of the first P- and S-wave motion, as it is usually done on Earth, since the take-off angle of both phases is virtually identical. We find that using plausible structural models based on geophysical modeling, the first 10-15 seconds of the waveforms can be fit, constraining the source mechanism and depth, but that the estimation of the uncertainty remains challenging.
Presenting Author: Alice Jacob
Authors
Alice Jacob ajacob@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France Presenting Author
Corresponding Author
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Nienke Brinkman nienke.brinkman@erdw.ethz.ch ETH Zürich, Zürich, , Switzerland |
Clément Perrin perrin@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France |
Nobuaki Fuji nobuaki@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France |
Simon Stähler simon.staehler@erdw.ethz.ch ETH Zürich, Zürich, , Switzerland |
Cedric Schmelzbach cedric.schmelzbach@erdw.ethz.ch ETH Zürich, Zürich, , Switzerland |
Philippe Lognonné lognonne@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France |
Antoine Lucas lucas@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France |
William B Banerdt william.b.banerdt@jpl.nasa.gov Jet Propulsion Laboratory, Pasadena, California, United States |
Alexey Batov batovalex@yandex.ru Schmidt Institute of Physics of the Earth, Moscow, , Russian Federation |
Maren Böse maren@sed.ethz.ch ETH Zürich, Zürich, , Switzerland |
John Clinton jclinton@sed.ethz.ch Institute of Geophysics, ETH Zürich, Zürich, , Switzerland |
Ingrid Daubar ingrid_daubar@brown.edu Brown University, Providence, Rhode Island, United States |
Mélanie Drilleau drilleau@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France |
Domenico Giardini domenico.giardini@erdw.ethz.ch ETH Zürich, Zürich, , Switzerland |
Tamara Gudkova gudkova@ifz.ru Schmidt Institute of Physics of the Earth, Moscow, , Russian Federation |
Sébastien Rodriguez rodriguez@ipgp.fr Institut de Physique du Globe de Paris, Paris, , France |
Jennifer Stevanovic taylorjennifer63@gmail.com AWE Blacknest, Brimpton, , United Kingdom |
Searching for Seismic Sources Around the Insight Landing Site: Focus on Sol 173 and 235 Marsquakes
Category
Insight Seismology on Mars: Results From the First (Earth) Year of Data and Prospects for the Future