There apparently is a large impact crater on the exact opposite side of the earth from the Siberian Traps. It is called the Falklands Crater, and it is west of the Falklans. See the following Link:
Massive impact crater may be hiding near the Falklands
The Chicxulub Crater that wiped out the non-avian dinosaurs about 65 million years ago is about 110 miles (180 kilometers) wide. The suspected Falklands Crater is estimated to be 155 miles (250 kilometers) wide and may be the second largest impact crater know on earth. The age of the Falklands Crater is estimated to be 250 to 270 million years old (in the ballpark of the mass extinction at the end of the Permian), but the crater has not been drilled into yet to give a better date estimate.
I've often wondered how such large impacts would affect the earth. Would the earth ring like a bell such that something like the Siberian Traps or volcanoes might occur on the opposite side of the earth where large tectonic (?) waves resulting from the impact might converge? The Deccan Traps in India are about the same age as the Chicxulub Crater. They are on the opposite side of the earth from Chicxulub but not the exact opposite location.
I'm no geologist, as you probably can tell. My sister is a PhD geophysicist though. I'll bounce it off of her.
Thanks, no geologist either. Off the West coast of India is the Shiva impact (370x250 miles). No link, have to google it. Jury is still out on exactly what it is, may not be an impact site. But it dates from about the time of the Chicxulub crater and the Deccan Traps.
I would think that the Siberian Traps would have had bad impact on life. Almost a million cubic miles of basalt poured onto the surface of the planet is a little over a million years.
But imagine you are standing exactly opposite of the impact site.
The shock wave rushes out from the impact at the speed of sound in rock in all directions.
Your first clue is a problem in this scenario is when that shock wave comes at you over the curve of the earth from all directions at once.
In terms of delivered energy, you are at the focal point like an ant under a magnifying glass!
You and the ground under your feet get slammed so hard that the surrounding rock is shattered all the way down to the mantle, the energy is sufficient to slam you and pressure-liquified rock into space! (not to worry, what's left of your remains will fall back to earth).
I don't doubt that magma would flow up through the shattered rock for centuries.
All in all, a pretty bad day...