Evaluation of S1222a Source Parameters Based on Site Effect Simulation and Implication for the Event Origin.

Estimating the rupture process of a quake constrains the tectonic setting of its source region. In terrestrial seismology, the rupture process can be described with a classical ω2 model. In this study, we focus on one key source parameter of S1222a, the corner frequency, to investigate its origin. However, estimating the corner frequency of S1222a is complicated by S1222a's non‐classical spectra which deviate from the ω2 model. To explain S1222a's spectra, we take into account the site effect at the InSight landing site. Through numerical simulation, we demonstrate that the spectral fitting is greatly improved after considering the site effect. We further estimated the source spectrum and stress drop of S1222a. The obtained stress drop resembles the values for regional tectonic earthquakes and shallow moonquakes but differs from the Cerberus Fossae marsquakes, which favors a different tectonic origin from the Cerberus Fossae marsquakes for S1222a. Plain Language Summary: The source of a quake is a key piece of information to uncover the dynamic process at the source region. In terrestrial seismology, the source of a quake can be described with a classical model in which the spectra decay with frequency at a certain speed. In this study, we focus on one key source parameter of S1222a, the corner frequency, to explore the generating process of S1222a. However, S1222a exhibits non‐classical spectra which cannot be explained by the classical model, making it difficult to estimate S1222a's source spectrum. To explain S1222a's spectra, we hypothesized that the seismic records are contaminated by wave reverberations in the subsurface layers, namely site effect. We validated our hypothesis with a numerical method. After considering site effect, S1222a's source spectrum and stress drop can be better estimated. The obtained stress drop value is close to those for regional tectonic earthquakes and shallow moonquakes but differs from the values observed for some marsquakes located at Cerberus Fossae, a seismically active region on Mars. Thus, we conclude that S1222a has a different tectonic origin from the Cerberus Fossae marsquakes. Key Points: We constructed a numerical model to simulate the site effect at the InSight landing site to better explain the spectra of S1222aWe estimated the corner frequency of S1222a to be 0.76 (0.58–1.07) Hz, which corresponds to a stress drop of 3.62 (0.80–20.26) MPaThe corner frequency and stress drop estimation favor that S1222a has a different tectonic origin from the Cerberus Fossae marsquakes [ABSTRACT FROM AUTHOR]