The Effect of Mars Impact Crater Topography on Seismic Signals

Meteoroid impacts on Mars have been reported to result in small seismic surface-wave amplitudes, compared to body-wave amplitudes. We hypothesize that Mars’ topography could be responsible for preferential attenuation of surface waves. We use a spectral element method to simulate 3D seismic wave propagation from impact events. The model topography is based on Mars’ digital elevation model, and the crustal structure is based on published works. We also vary the craters’ effective depth to further investigate their influence on seismic signals. Results show that surface waves traveling through a crater lose energy proportional to the crater depth via scattering. The scattered surface waves are partially converted to body waves and scatter in other directions. The energy loss from scattering gradually recovers via multiple scattering, but still results in a net loss. The multiple scattered surface waves from distant craters arrive late, adding energy to the recorded coda waves. P-waves, however, arriving at steep incidence angles are almost unaffected by topography. The difference of how topographic scattering affects body and surface waves could explain the weak or lack of surface waves recorded by the InSight’s seismometer.