Autocorrelation Reflectivity of the Martian Interior from Insight Data
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: 11:00 AM
Room: 115
Description:
Determining Martian seismic structure contributes to understanding the formation and evolution of the inner planets in the solar system. The Martian subsurface has been studied at different scales by gravity anomaly inversion, solar tide detection, high-pressure experiments and mineralogic model calculations. Mars, having an internal structure similar to Earth, can be divided into crust, mantle and core (Smrekar et al., 2018). The Viking 2 seismic recordings provided modest information on the Martian interior structure (Anderson et al, 1977) which led to numerical and theoretical estimation of seismic parameters prior to the InSight mission (Panning et al., 2017; Lognonne et al., 2019). Crustal thickness has been estimated from gravity observations (Zuber, 2001). Evidence that Mars’ core is largely liquid comes from the large Love number (Yoder et al., 2003), and from high-pressure experiments using assumed core properties (Stewart et al., 2007), while existence of a solid inner core is still undetermined.
Here we use autocorrelation reflectivity imaging (Claerbout, 1968) together with prior estimates of Martian seismic velocity structure to identify major seismic boundaries within Mars. We calculated and stacked the autocorrelograms of the available SEIS data, ~4000 hours, to construct the reflection response beneath the InSight lander. We identify noise that is approximately periodic with the Martian sol, some of which we associate with lander operations and some to diurnal variation in Martian weather. The data are cut into ~2000 2-hour-long windows, and temporally balanced to remove the features related to the lander and weather conditions. To identify signals at different depths, the autocorrelation reflectivity is filtered in different bands. We identify signals in the autocorrelations as reflections from the Martian Moho, a deep mantle discontinuity at a depth appropriate for the olivine-spinel transition, and prominent signals at the expected depth of the core-mantle boundary. Bootstrap calculations suggest the signals we identify are robust.
Presenting Author: Alan Levander
Authors
Sizhuang Deng sd62@rice.edu Rice University, Houston, Texas, United States |
Alan Levander alan@rice.edu Rice University, Houston, Texas, United States Presenting Author
Corresponding Author
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Autocorrelation Reflectivity of the Martian Interior from Insight Data
Category
Insight Seismology on Mars: Results From the First (Earth) Year of Data and Prospects for the Future