[null and void]

A number of moons show shattered zones opposite of major impacts. It’s similar to a coup contrecoup brain injury

[rustbucket]

When I found this thread about the Permian extinction, I looked at a chart I bought 12-14 years ago I have hanging on the wall. The chart contains extinctions, geology maps of the earth, large impact craters, plants, animals plotted against a time scale going back 4 billion years. The mass or partial extinctions correlate well with large crater impacts.

When I looked at the Permian extinction on the chart, two possible large craters were mentioned, Bedoubt and Falklands. I looked up both of them. Current thinking is that Bedoubt is not an impact crater, but Falklands might be.

I highly recommend this fascinating chart. Here is a picture of it online:

Chart

And how to obtain a current version: How to obtain chart

[rustbucket]

My sister, who is retired, passed my question to a friend at her old office. The friend came up with a short summary news article and an abstract to a paper, both of which I link to below.

https://www.princeton.edu/news/2011/10/19/impact-study-princeton-model-shows-fallout-giant-meteorite-strike

and

https://www.researchgate.net/publication/215948949_Antipodal_focusing_of_seismic_waves_due_to_large_meteorite_impacts_on_Earth

The Princeton work in the top link indicates that a model that accounts for the elliptical shape of the earth, the presence of continents, and other inhomogeneities reduces the ground motion at the antipodal point on the opposite side of the earth from 15 meters for a spherical model of the earth to about 4 meters. (Still seems like pretty big ground motion to me.)

There are interesting links in the Princeton summary news article to other findings about extinctions. And, the Princeton article makes the obvious point that continents were at different locations in the past, and that would need to be considered in estimating where the antipodal point was at the time of the impact.