DI024-0011
Detecting the Mantle Transition Zone of Mars From Seismic Triplicated and Reflected Waves

Tuesday, 15 December 2020
Poster
Quancheng Huang1, Nicholas C. Schmerr2, Ross Maguire1, Daniele Antonangeli3, Benjamin Fernando4, Kuangdai Leng4, Tarje Nissen-Meyer5, Scott D King6, Attilio Rivoldini7, Ana-Catalina Plesa8, Carolina R Lithgow-Bertelloni9, Tamara Gudkova10, Henri Samuel11, Domenico Giardini12, Philippe Henri Lognonné11 and William Bruce Banerdt13, (1)University of Maryland, Department of Geology, College Park, MD, United States, (2)University of Maryland College Park, Department of Geology, College Park, MD, United States, (3)Sorbonne Université - MNHN - CNRS - IMPMC, Paris, France, (4)University of Oxford, Oxford, United Kingdom, (5)University of Oxford, Department of Earth Sciences, Oxford, United Kingdom, (6)Virginia Polytechnic Institute and State University, Blacksburg, VA, United States, (7)Royal Observatory of Belgium, Brussels, Belgium, (8)German Aerospace Center (DLR), Berlin, Germany, (9)University of California Los Angeles, Los Angeles, CA, United States, (10)Schmidt Institute of Physics of the Earth RAS, Moscow, Russia, (11)Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, France, (12)Swiss Federal Institute of Technology (ETH), Zurich, Switzerland, (13)JPL/NASA/Caltech, Pasadena, CA, United States
Abstract:
The mantle transition zone (MTZ) of Mars is associated with the mineral phase transition from olivine to wadsleyite, and this phase change can produce a seismic discontinuity at ~1,100-km depth. Constraints on the depth of the 1,100-km discontinuity can shed light on the composition and temperature of the Martian interior. The InSight Mission provides a unique opportunity to detect the Martian MTZ with a single station approach. Here, we identified the triplicated and reflected waves (topside + underside) as candidate body waves to investigate the Martian MTZ. We used AxiSEM to compute high frequency synthetics (1 Hz) based on the EH45TcoldCrust1 model. We quantified the detectability of candidate phases by calculating the signal-to-noise ratios (SNR) with respect to the SEIS VBB noise level. The triplications only require Mw 3 events to be detectable, whereas the reflections require at least Mw 5 events which have not been observed yet. We also investigated the effects of regolith layer and crustal scattering on the detectability of Martian MTZ. To search for triplications in InSight data, we applied a polarization filter to enhance the SNR of body waves and aligned all the low-frequency and broadband events on P and S waves. We constrained the back-azimuths of these events from the polarizations of P waves and then rotated seismograms to radial and transverse components. We found 5 candidate events for triplications in the target distance range (60-85 degrees). We discovered a phase after S waves with a “bow-tie” shape of move-out, which could be associated with the S wave triplication. However, the P waves did not show such a phase likely due to the lower SNR. Our next step is to use the deglitched dataset and 1-D synthetics to validate if this new phase is the S wave triplication. Our goal is to determine the depth of olivine-to-wadsleyite phase transition from the triplications.
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