Antipodal focusing of seismic waves due to large meteorite impacts on Earth

Abstract

S U M M A R YWe 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 spectralelement 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 4. 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 . Although 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 five 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 −1 , respectively. Our results put quantitative constraints on the feasibility of impact-induced antipodal volcanism and seismicity, as well as mantle plume and hotspot formation.

Temporal Changes of the Inner Core From Globally Distributed Repeating Earthquakes

“…The earlier event of the pairs in Figures 13b–f is right after the 2004 Indian Ocean earthquake (Mw 9.1) on 26 December. A large earthquake can amplify disturbances along antipodal directions at the top of the inner core and near the center of the Earth (Meschede et al, 2011). Thus, we conjure a possible scenario that the small‐scale iron patches in the mushy zone of the inner core near the region beneath Sumatra are disturbed by the waves of the great Sumatra earthquakes, which were sampled by steep incident DF phase at relatively large distances.…”

Subsurface failure in spherical bodies: A formation scenario for linear troughs on Vesta’s surface

“…It is known that seismic stresses can be enhanced at the antipode to large impacts, which can result in increased damage formation (e.g., Schultz and Gault, 1975;Asphaug et al, 1996;Schultz and Crawford, 2011;Meschede et al, 2011). Numerical studies by Asphaug et al (1996) and Benz and Asphaug (1994) reveal that the grooves (troughs) in Pola Regio, a region of the asteroid Ida, and the grooves on Phobos may have formed by large impacts (Fujiwara and Asada, 1983;Asphaug and Melosh, 1993).…”

Upheavals during the Late Maastrichtian: Volcanism, climate and faunal events preceding the end-Cretaceous mass extinction

“…and references therein) based on biostratigraphy, magnetostratigraphy, sedimentology and geochemistry of numerous sequences in NE Mexico and Texas Meschede et al (2011). investigated the global seismic effects of the Chicxulub impact and found that the shock waves would have to be bundled to their greatest effect at the precise opposite side of the planet, the antipode.…”