Antipodal focusing of seismic waves after larger meteorite impacts

Details Antipodal focusing of seismic waves after larger meteorite impacts Antipodal focusing of seismic waves after larger meteorite impacts

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p33a1747m&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #P33A-1747

Statistics

Computation

[5420] Planetary Sciences: Solid Surface Planets / Impact Phenomena, Cratering, [7290] Seismology / Computational Seismology

Scientific paper

We examine focusing of seismic waves at the antipode of large terrestrial meteorite impacts, using the Chicxulub impact as our case study. Numerical simulations are based on a spectral-element method, representing the impact as a Gaussian force in time and space. Simulating the impact as a point source at the surface of a spherically symmetric Earth model results in deceptively large peak displacements at the antipode. Earth's ellipticity, lateral heterogeneity and a spatially distributed source limit high-frequency waves from constructively interfering at the antipode, thereby reducing peak displacement by a factor of four. Nevertheless, for plausible impact parameters, we observe peak antipodal displacements of ˜ 4~m, dynamic stresses in excess of 15~bar, and strains of 2 ± 10-5 . While these values are significantly lower than prior estimates, mainly based on a point source in a spherically symmetric Earth model, wave interference en route to the antipode induces ``channels'' of peak stress that are 5~times greater than in surrounding areas. Underneath the antipode we observed ``chimneys'' of peak stress, strain and velocity, with peak values exceeding 50~bar, 10-5 and 0.1~m/s, respectively. Our results put quantitative constraints on the feasibility of impact-induced antipodal volcanism and seismicity, as well as mantle plume and hotspot formation.

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