Crustal thickness from seismic noise correlations in preparation for the InSight mission to Mars

The formation of terrestrial planets is still poorly understood. Studying the interior of Mars by analysing seismic waves can help to answer questions about that process. In the absence of plate tectonics, Mars has retained much of its crust from early stages of the planet‘s evolution. Knowledge of its crustal thickness and structure can therefore contribute to the understanding of terrestrial planet formation and evolution. In preparation for the InSight seismometer installation on Mars, a method is developed to image the reflectivity of the subsurface and extract the crustal thickness from ambient seismic noise. The developed method makes use of passive seismic interferometry by calculating auto- and single-station cross-correlations to obtain the reflection response of the subsurface. It is then tested on seismic stations across Central and Eastern Europe with varying crustal thicknesses, comparable to estimates for the InSight landing site. The determined crustal thicknesses compare well with results obtained from other studies using different methods and are consistent across vertical and horizontal component correlations. Furthermore, it is possible to identify additional deeper and shallower reflectors. In conclusion, crustal thickness can be extracted from seismic noise correlations for a single station, for different seismometer types, when only moderate amounts of data are available, without the need for strong seismic sources, and independent of the structure of the subsurface. All this makes the introduced method a promising tool for the InSight mission.