Borehole seismic observations from the Chicxulub impact drilling: implications for seismic reflectivity and impact damage

Abstract

Seismic profiling over geological features reveal to us both the geometry of the structure and the speeds of the seismic waves within it. Calibrating these profiles using only data from the surface, however, remains challenging, but this can be accomplished by making direct seismic measurements in a borehole with a technique called vertical seismic profiling (VSP). Here, we describe the analysis of such a VSP acquired during drilling into the Chicxulub Impact Structure during International Ocean Discovery Program Expedition 364. Special processing of the waves confirm that the strong seismic reflection seen in surface data originates from abrupt changes in the rock properties related to the juxtaposition of hardened sediments, weak suevites, and melt rock. No seismic reflections could be found originating deeper in the uplifted and highly damaged granitoids of the structures's peak ring. As noted in earlier studies, the seismic wave speeds are anomalously low in these lower materials. These speeds were converted into damage indexes and as such this information may provide a means toward constraining advanced numerical impact modeling and in assessing levels of damage in the subsurface in advance of construction on the surfaces of the Moon and Mars.