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Energy Envelope and Attenuation Characteristics of High-Frequency (HF) and Very-High-Frequency (VF) Martian Events

Menina, Sabrina and Margerin, Ludovic and Kawamura, Taïchi and Lognonné, Philippe and Marti, Jules and Drilleau, Mélanie and Calvet, Marie and Compaire, Nicolas and Garcia, Raphaël F. and Karakostas, Foivos and Schmerr, Nicholas and van Driel, Martin and Stähler, Simon C. and Plasman, Matthieu and Giardini, Domenico and Carrasco, Sebastian and Knapmeyer-Endrun, Brigitte and Sainton, Grégory and Banerdt, William Bruce Energy Envelope and Attenuation Characteristics of High-Frequency (HF) and Very-High-Frequency (VF) Martian Events. (2021) Bulletin of the Seismological Society of America, 111 (6). 3016-3034. ISSN 0037-1106

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Official URL: https://doi.org/10.1785/0120210127

Abstract

Since its deployment at the surface of Mars, the Seismic Experiment for Interior Structure (SEIS) instrument of the InSight mission has detected hundreds of small-magnitude seismic events. In this work, we highlight some features of two specific families: high-frequency (HF) and very-high-frequency (VF) events. We characterize the shape of the energy envelopes of HF and VF events with two parameters: (1) the delay time t d between the onset and the peak of the dominant arrival; and (2) the quality factor Qc, which quantifies the energy decay rate in the coda. We observe that the envelope of HF and VF events is frequency indepen- dent. As a consequence, a single delay time suffices to characterize envelope broadening in the 2.5–7.5 Hz band. The typical coda decay time is also frequency independent, as attested by the close to linear increase of Qc with frequency. Finally, we use elastic radiative transfer theory to perform a series of inversion of seismogram envelopes for the attenuation proper- ties of the Martian lithosphere. The good fit between synthetic and observed envelopes confirms that multiple scattering of elastic waves released by internal sources is a plausible explanation of the events characteristics. We quantify scattering and attenuation properties of Mars and highlight the differences and similarities with the Earth and the Moon. The albedo, that is, the contribution of scattering to the total attenuation, derived from VF events is very high, which we interpret as a signature of a mostly dry medium. Our results also suggest a stratification of the scattering and attenuation properties.

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Deposited On:12 Jan 2022 09:14

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