Jiaqi Li

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Li

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Jiaqi

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0000-0003-4211-9299

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Publications 1 - 5 of 5

The Global Seismic Moment Rate of Mars After Event S1222a
Knapmeyer, Martin; Stähler, Simon Christian; Plesa, Ana-Catalina; et al. (2023)
Geophysical Research Letters
The seismic activity of a planet can be described by the corner magnitude, events larger than which are extremely unlikely, and the seismic moment rate, the long-term average of annual seismic moment release. Marsquake S1222a proves large enough to be representative of the global activity of Mars and places observational constraints on the moment rate. The magnitude-frequency distribution of relevant Marsquakes indicates a b-value of 1.06. The moment rate is likely between 1.55×1015Nm∕a and 1.97×1018Nm∕a, with a marginal distribution peaking at 4.9×1016Nm∕a. Comparing this with pre-InSight estimations shows that these tended to overestimate the moment rate, and that 30% or more of the tectonic deformation may occur silently, whereas the seismicity is probably restricted to localized centers rather than spread over the entire planet.
Focal Mechanism Determination of Event S1222a and Implications for Tectonics Near the Dichotomy Boundary in Southern Elysium Planitia, Mars
Maguire, Ross; Lekić, Vedran; Kim, Doyeon; et al. (2023)
Journal of Geophysical Research: Planets
On 4 May 2022 the InSight seismometer SEIS-VBB recorded the largest marsquake ever observed, S1222a, with an initial magnitude estimate of (Figure presented.) 4.6. Understanding the depth and source properties of this event has important implications for the nature of tectonic activity on Mars. Located ∼37° to the southeast of InSight, S1222a is one of the few non-impact marsquakes that exhibits prominent surface waves. We use waveform modeling of body waves (P and S) and surface waves (Rayleigh and Love) to constrain the focal mechanism, assuming a double-couple source, and find that S1222a likely resulted from reverse faulting in the crust (source depth near 22 km). We estimate the scalar moment to be 2.5 × 1015–3.5 × 1015 Nm (magnitude MW 4.2–4.3). Our results suggest active compressional tectonics near the dichotomy boundary on Mars, likely due to thermal contraction from planetary cooling.
Interactions between temperature and energy supply drive microbial communities in hydrothermal sediment
Lagostina, Lorenzo; Frandsen, Søs; MacGregor, Barbara J.; et al. (2021)
Communications Biology
Temperature and bioavailable energy control the distribution of life on Earth, and interact with each other due to the dependency of biological energy requirements on temperature. Here we analyze how temperature-energy interactions structure sediment microbial communities in two hydrothermally active areas of Guaymas Basin. Sites from one area experience advective input of thermogenically produced electron donors by seepage from deeper layers, whereas sites from the other area are diffusion-dominated and electron donor-depleted. In both locations, Archaea dominate at temperatures >45 °C and Bacteria at temperatures <10 °C. Yet, at the phylum level and below, there are clear differences. Hot seep sites have high proportions of typical hydrothermal vent and hot spring taxa. By contrast, high-temperature sites without seepage harbor mainly novel taxa belonging to phyla that are widespread in cold subseafloor sediment. Our results suggest that in hydrothermal sediments temperature determines domain-level dominance, whereas temperature-energy interactions structure microbial communities at the phylum-level and below.
Crustal Structure Constraints From the Detection of the SsPp Phase on Mars
Li, Jiaqi; Beghein, Caroline; Davis, Paul; et al. (2023)
Earth and Space Science
The shallowest intracrustal layer (extending to 8 +/- 2 km depth) beneath the Mars InSight Lander site exhibits low seismic wave velocity, which is likely related to a combination of high porosity and other lithological factors. The SsPp phase, an SV- to P-wave reflection on the receiver side, is naturally suited for constraining the seismic structure of this top crustal layer since its prominent signal makes it observable with a single station without the need for stacking. We have analyzed six broadband and low-frequency seismic events recorded on Mars and made the first coherent detection of the SsPp phase on the red planet. The timing and amplitude of SsPp confirm the existence of the similar to 8 km interface in the crust and the large wave speed (or impedance) contrast across it. With our new constraints from the SsPp phase, we determined that the average P-wave speed in the top crustal layer is between 2.5 and 3.2 km/s, which is a more precise and robust estimate than the previous range of 2.0-3.5 km/s obtained by receiver function analysis. The low velocity of Layer 1 likely results from the presence of relatively low-density lithified sedimentary rocks and/or aqueously altered igneous rocks that also have a significant amount of porosity, possibly as much as 22%-30% by volume (assuming an aspect ratio of 0.1 for the pore space). These porosities and average P-wave speeds are compatible with our current understanding of the upper crustal stratigraphy beneath the InSight Lander site.
Surface waves and crustal structure on Mars
Kim, Doyeon; Banerdt, William Bruce; Ceylan, Savas; et al. (2022)
Science
We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.

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Jiaqi Li

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