The Seismic Signatures of Recently Formed Impact Craters on Mars

Abstract

We investigated the seismic signatures of recent impact crater clusters on Mars that would be recorded by the InSight Seismic Experiment for Interior Structure (SEIS) seismometers. We used a database of 77 measured and dated impact sites, with craters with effective diameters between 2.1 and 33.8 m, along with inferred impact angle, bolide trajectory, and varying target material properties to empirically scale for the momentum, expected seismic source function, and radiation pattern of impacts. The impact source is simulated in a local 3-D finite difference wave propagation code and coupled to teleseismic distances by scaling the spectra of 1-D global synthetic seismograms. We use the SEIS noise floors to estimate seismic detectability of impact(s) across azimuth and distance. Our experiments reveal that impact clusters have a higher peak corner frequency resulting from energy contributed by smaller craters to the power spectrum. We also find that the time separation between individual impacts in a cluster is small (< 10-15 milliseconds) and a require a seismometer closely situated to the source (< 10 km) and a high sampling rate (> 100 Hz) to resolve individual impacts within the cluster. Two of the clusters in our database (> 20 m effective diameter) would have been detectable by InSight, with the assumptions that the martian background noise and background attenuation are both low. Joint detection of surface changes from newly formed crater(s) in images and by SEIS will provide precise source locations that are crucial for constraining the internal structure of Mars.