A Seismic Crustal Stratigraphy on Mars Constrained by Seismic Waveforms and Receiver Functions

ABSTRACT

Seismic crustal stratigraphy of Mars is one of the key features that can be used to infer the internal composition of Mars and decipher the evolution of the planet. Here, we construct a detailed seismic stratigraphy of Mars from the source region of a marsquake (event S0235b) in Cerberus Fossae to the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport landing site. Seismic velocity structures are constrained by waveforms recorded for event S0235b and receiver functions extracted from the seismic data of four quality-A marsquakes. The inferred crustal stratigraphy consists of four layers on the landing site and three layers on the source side. Models on the both sides have a low-velocity layer sandwiched between the high-velocity layers at the top and the bottom, with the low-velocity layer on the source side situated at a depth range of 2.7–4.3 km having an SH–SV shear-wave anisotropy of −16% and the low-velocity layer on the landing site situated at a depth range of 3.9–6.2 km having an SH–SV shear-wave anisotropy of −18%. The low-velocity layers overlay a layer with similar seismic velocities, but they are overlain by two distinct layers on the landing site and a single layer on the source side. The inferred crust–mantle discontinuity has a depth of 29.5 km on the source side and 23.0 km on the landing site. The major advancements of this study from the existing crustal-scale models include the discovery of the low-velocity layer sandwiched between the high-velocity layers and well-constrained both P- and S-wave velocities in the individual layers; both are attributed to the waveform data that are first employed in this study. Synthetic tests indicate that our model features are well resolved by the waveform data, and so are the differences from the existing models.