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Quantitative Assessment of Atmospheric and Teleseismic Excitation of a 2.4 Hz Resonance in Insight Data From Mars

Description: 

InSight landed on Mars in November, 2018, and spent the next few months deploying a sensitive seismometer package (Seismic Experiment for Interior Structure; SEIS) and a heat flow probe to the surface. For more than two Martian years it recorded over 1300 cataloged marsquakes and other seismic events. Among the many signals recorded by SEIS is a prominent mode around 2.4 Hz. Possible explanations for this signal include a specific lander mode due to the solar arrays, or a local ground substructure as described notably in Hobiger et al. (2021). A different approach to modeling the basic observation of the structure of the SEIS background noise Horizontal to Vertical (H/V) ratio was taken by Carrasco et al. (2023), producing a suite of models matching or excluding the prominent 2.4 Hz resonance. Both studies suggest that models explaining the 2.4 Hz resonance using a subsurface structure require a significant Low Velocity Zone (LVZ) within the top 100 m.

In this study, we test the hypothesis that the 2.4 Hz signal in both ambient background noise and teleseismic marsquakes are caused by a seismic LVZ by simulating the amplitude of the 2.4Hz peak observed during marsquakes and during the quiet Martian night. We generate Green’s functions of the ground substructure for high-incidence-angle teleseismic events and for regional surface sources through models derived from both Hobiger et al. (2021) and Carrasco et al. (2023). Subsequently we test the ground response to these excitations by convolving the simulated sources with the appropriate Green’s functions considering sources from above for the atmospheric excitation, or from below for the teleseismic excitation. We demonstrate that a range of models matching the 2.4 Hz H/V ratios can produce reasonable amplitudes of excitation driven by measured pressure fields above noise levels during the night, but not detectable during the day, as well as matching the relative excitation in teleseismic data.

Session: Exploring Planetary Interiors and Seismology: Observations, Models, Experiments and Future Missions - I

Type: Oral

Date: 4/17/2025

Presentation Time: 08:15 AM (local time)

Presenting Author: Mark

Student Presenter: No

Invited Presentation: Yes

Poster Number:

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