Apollo Seismic Station
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Current Work
InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is a Mars lander designed to give the Red Planet its first thorough checkup since it formed 4 billion years ago. It is the first outer space robotic explorer to study in-depth the "inner space" of Mars: its crust, mantle, and core. An introduction to the mission is available from NASA.
I am currently interested in studying the interior of Mars using seismic data from InSight to recover seismic signals related to the deep interior of Mars.
Finished Works
Receiver Function Velocity Analysis Technique and Its Application to Remove Multiples
Shi, J., Wang, T., & Chen, L. (2020).Receiver function velocity analysis technique and its application to remove multiples. Journal of Geophysical Research - Solid Earth, [Full paper].
Results of P wave receiver function (RF) analysis (e.g., H‐κ stacking, common conversion point (CCP) stacking, and migration) depend on the velocity models employed. Converted phases of crustal and upper mantle discontinuities are often interfered by multiple reflections from shallower structures, adding further complexity to the interpretation of P wave RF images. In this study, we propose a receiver function velocity analysis technique (RFVAT) that can constrain the velocity structure above discontinuities and remove multiple reflections arising from target discontinuities. By applying the proposed RFVAT to real P wave RF data from the northeastern part of the North China Craton, we achieve an improvement in CCP stacking image of lithospheric discontinuities, especially for the lithosphere‐asthenosphere boundary (LAB).
In addition to ground motions, earthquakes generate low-frequency inaudible sound (<20Hz), called infrasound, which propagates through the atmosphere and can be recorded by microphones far from the epicenter (up to thousands of kilometers). This infrasound results from the coupling of the solid Earth and the atmosphere. Our study finds that, depending on the topographic relief scale, only ground motions at special frequencies are transferred efficiently to pressure fluctuations in the atmosphere. Earthquake waves also vary according to the receiver position, much like the tone of a horn varies with a listener's position; accordingly, seismologists can infer fault parameters using seismic data. Our results reveal that infrasound data have a similar distribution to the seismic data. This study illustrates the potential of air-based earthquake monitoring, especially on other terrestrial planets, such as Venus.
Repeating Infrasound From an Earthquake Doublet in Alaska
Yang, M.H., Wang, T., & Shi, J. (2021).Repeating infrasound from an earthquake doublet in Alaska. Geophysical Researh Letters, [Full paper].
High-Frequency Receiver Functions With Event S1222a Reveal a Discontinuity in the Martian Shallow Crust
Shi, J., Plasman, M., Knapmeyer-Endrun, B., Xu, Z., Kawamura, T., Lognonné, P., et al. (2023). High-frequency receiver functions with event S1222a reveal a discontinuity in the Martian shallow crust. Geophysical Research Letters, [Full paper].
The Martian shallow crustal structure is essential for understanding the geological evolution of Mars. The InSight lander successfully deployed a seismic station on Mars in late 2018, aiming to investigate the internal structure of Mars. Since most marsquakes detected previously have a low signal-to-noise ratio (SNR) at high frequencies, most seismic analyses do not focus on the shallow structure of Mars (1–5 km). However, when the InSight seismometer was near the end of its observational lifetime, a large marsquake occurred on sol 1222 with significant high-frequency energy, far more than the noise level, allowing us to study the Martian shallow structure. We calculate the high-frequency P-wave receiver function (RF) of S1222a and extract a converted S-wave at approximately 1 s after the direct P-wave. To confirm the result, we also compute P-wave RFs for high SNR events that occurred before. We observe this ∼1-s signal in the high-frequency P-wave RFs of two additional large events as well. Combined with the geological analysis adjacent to the InSight lander, we attribute this 1-s converted S-wave to a discontinuity at approximately 2 km depth, probably corresponding to the bottom of highly fractured crustal materials beneath the InSight landing site.
The scattering properties of terrestrial planetary bodies can provide valuable insights into their shallow seismic structure, meteoritic impact history, and geological activity. In this study, we investigate the scattering properties of the shallow crusts of Earth, Mars, and the Moon by constructing P-wave receiver functions (PRFs) from teleseismic waveforms with high signal-to-noise ratios. Our analysis reveals that strong coda waves lead to significant variations in the PRF waveforms calculated using different time windows, and the stability of the PRF is primarily influenced by the fractional velocity fluctuation. Synthetic PRFs for various scattering media confirm these observations. Comparing the observed and synthetic PRFs, we find that the fractional velocity fluctuation in the shallow crust is greater than ~0.2 for the Moon, but less than ~0.2 for Earth and Mars. We further discuss possible mechanisms that could have affected the fractional velocity fluctuation and suggest that the distinct fractional velocity fluctuation between the Moon and Earth/Mars is mainly due to differences in the water content of the crustal rocks of the three planetary bodies.
Shi, J., et al., Differences in Scattering Properties of the Shallow Crusts of Earth, Mars, and the Moon Revealed by P-Wave Receiver Functions. Journal of Geophysical Research - Planets, [Full paper].
Differences in Scattering Properties of the Shallow Crusts of Earth, Mars, and the Moon Revealed by P-Wave Receiver Functions
Structure of the Martian Crust Below InSight From Surface Waves and Body Waves Generated by Nearby Meteoroid Impacts
Mélanie Drilleau, Éric Beucler, Jing Shi, et al., Structure of the Martian Crust Below InSight From Surface Waves and Body Waves Generated by Nearby Meteoroid Impacts. Geophysical Research Letters, [Full paper].
The knowledge of the crustal structure of Mars is essential for understanding the formation and evolution of the planet. Thanks to the Very Broadband Seismometer of the InSight mission which landed on the surface of Mars (its operational life lasted almost four terrestrial years), seismic signals generated by meteoroid impacts have been recorded. Five craters have been identified by orbital imaging to be located within a circle of ∼250 km radius around the lander. For two of these meteoroid impacts, we measured surface waves for the first time, which are mostly sensitive to the crustal structure in the first kilometers below the InSight lander. Our surface wave analysis, in combination with other measurements, are compatible with a crustal model in the vicinity of the InSight lander made of four layers, with a shallow low velocity layer ∼1.2 km thick. We verified the compatibility of our results with independent observations from previous studies.
Martian seismic anisotropy underneath Elysium Planitia revealed by direct S wave splitting
Jing Shi, Cunrui Han, Tao Wang, Chao Qi, Han Chen, Zhihan Yu, Jiaqi Geng, Minghan Yang, Xu Wang, Ling Chen, Hejiu Hui. Letters Earth and Planetary Science Letters, [Full paper].
Seismic anisotropy, arising from the crystallographic/lattice-preferred orientation of anisotropic minerals or the shape-preferred orientation of melts or cracks, can establish a critical link between Mars's past evolution and its current state. So far, seismic anisotropy in Mars has been proposed due to different velocities of vertically and horizontally polarized shear waves in the Martian crust, obtained from crustal converted waves, multiples, and surface waves recorded by the InSight seismometer. However, the shear wave splitting, which stands out as a straightforward indicator of seismic anisotropy, has not been reported using marsquake records. In this study, we employ low-frequency marsquakes detected by the InSight seismometer to reveal shear wave splitting in marsquake recordings. We find that the direct S waves of three marsquake recordings (S0173a, S0235b, and S1133c) with high signal-to-noise ratios exhibit the splitting phenomenon. We rule out the possibility of apparent anisotropy through synthetic tests, affirming the presence of seismic anisotropy in Mars. The delay time measured from the direct S wave splitting is too large to be solely attributed to the seismic anisotropy in the upper crust (0 – 10 km) beneath the InSight. Thus, seismic anisotropy in the deeper region of Mars is required. Combined with other geophysical evidence near the InSight landing site, the seismic anisotropy observed in this study implies the aligned cracks in the crust are greater than 10 km beneath the InSight and/or the existence of mantle flow underneath the Elysium Planitia of Mars.
An Indoor Positioning Research Based On The Least Square Method Of Monte Carlo
With the development of wireless communication technology in our country, the research of positioning system becomes more and more mature. The traditional positioning is mainly through the satellite navigation system, the accurate positioning in the outdoor is better, but in the indoor or high-rise buildings, shelter more cases, the positioning accuracy is poor. Correspondingly, the methods of location based on TOA, T DOA and RSSI are derived. However, in the actual operation process, the computation time is longer. To solve this problem, a Monte Carlo based least squares indoor location model is proposed. Make full use of the Monte Carlo randomness, to avoid the complex calculations, making the positioning accuracy in the three-dimensional room higher.
L. Li, J. Shi*, Y. Kang, J. Duan and P. Sun, An Indoor Positioning Research Based On The Least Square Method Of Monte Carlo, 2018 Ubiquitous Positioning, Indoor Navigation and Location-Based Services (UPINLBS), Wuhan, 2018, pp. 1-6. [Full paper]
Patent: L. Li, J. Shi, J. Duan and Y. Kang. An Indoor Positioning model And Its Construction Method And Application Based On The Least Square Method Of Monte Carlo [P]. Sichuan: CN107786939B,2020-08-14
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