Detection of Mars Normal Modes From S1222a Event and Seismic Hum

Abstract

The inversion of normal mode eigenfrequencies is one of the most efficient ways to determine the physically averaged interior structure of a planet, as illustrated by Dziewonski and Anderson (1981), one of the most cited references in seismology. On Earth, normal mode observations require both large quakes, with magnitude larger than 7, and well-shielded, long-period (LP), low-noise seismic instrumentation (Laske & Widmer-Schnidrig, 2015). This delayed the first observation of Earth normal modes until the great M w = 9.5 Chile earthquake in 1960, several decades after the body wave hodochrone table determined by Jeffreys (1937). See Benioff et al. (1961), Lognonné andClévédé (2002), Laske and Widmer-Schnidrig (2015), among others for reviews of Earth's normal modes.Despite the challenges presented by the effective deployment of a LP seismometer and the expected lack of very large-magnitude marsquakes, normal mode detection was always an ultimate goal for Mars seismology. This was listed in descriptions of the first Mars seismic exploration projects (

Global Crustal Thickness Revealed by Surface Waves Orbiting Mars

“…At much longer periods between 100 and 200 s, a similar group velocity close to 3.8 km/s for the excitation of R2 has been reported by using ambient noise correlations (Deng & Levander, 2022). A normal mode study on Mars has also shown some potential excitation of the fundamental mode surface waves in comparable period ranges between 120 and 300 s (Lognonné et al., 2023).…”

Seismic Autocorrelation Analysis of Deep Mars

“…The ACFs of glitch-only and 80% glitch-only data do not show a prominent response at ∼385 s. We take this as indicating the reflection response at ∼385 s originated from Martian CMB rather than an unfortunate correlation of glitches suggested by Barkaoui et al (2021) and Kim et al (2021). The noise sources to generate this deep Mars reflection signal may come from atmospheric phenomena (Nishikawa et al, 2019) or coda waves of Marsquakes (Lognonné, Schimmel, et al, 2023), which are less attenuated during wave propagation as Mars is a dry, cold and tectonically inactive planet compared with Earth (Menina et al, 2021). In the stacked raw data ACF there is a signal at ∼385 s, but the reflection pulse is much more complicated than in the clean waveform because it is contaminated by the high-amplitude seismic glitches in the raw data.…”

“…(2021). The noise sources to generate this deep Mars reflection signal may come from atmospheric phenomena (Nishikawa et al., 2019) or coda waves of Marsquakes (Lognonné, Schimmel, et al., 2023), which are less attenuated during wave propagation as Mars is a dry, cold and tectonically inactive planet compared with Earth (Menina et al., 2021). In the stacked raw data ACF there is a signal at ∼385 s, but the reflection pulse is much more complicated than in the clean waveform because it is contaminated by the high‐amplitude seismic glitches in the raw data.…”

Applications of Time‐Frequency Domain Polarization Filtering to InSight Seismic Data

“…We downsampled the data from 20 to 0.5 Hz sampling frequency to reduce the number of floating point operations that needs to be performed during the computation of the time‐frequency‐dependent polarization attributes and consequently reduce the computational costs. Deglitching the LF band of the data could, for example, be particularly important for the detection of the normal modes of the planet (Lognonné, Banerdt, et al., 2023; Lognonné, Schimmel, et al., 2023), which are expected to be excited by large marsquakes (Bissig et al., 2018) and for the computation of autocorrelations to study the deep reflectivity structure of Mars (Kim et al., 2021).…”

“…All seismic data analysis is therefore restricted to single-station techniques. Consequently, the estimation of, for example, source locations and the determination of the interior structure of the planet are associated with large uncertainties (Drilleau et al, 2022;Durán et al, 2022;Khan et al, 2016;Lognonné, Banerdt, et al, 2023;Lognonné, Schimmel, et al, 2023) compared to similar investigations on Earth that can usually benefit from the high number of available seismic stations. The limitations of single-station recordings are exacerbated by the fact that most of the recorded seismic events are relatively weak in amplitude because the data are corrupted by relatively high levels of noise (Lognonné et al, 2020;Stott et al, 2023).…”