When all of these earthquake waves are overlaid they reveal the position and general contours of a large irregular object, approximately 2,000 km wide, lodged in the mantle, underneath South America. I believe this is the object which entered through the Indian plate, creating the hole in my pre-cambrian shield reconstruction.

This object could actually be found by conventional seismology, if it was still there. But it has probably long since dissolved, since its entry between 600 million and 4.5 billion years ago, and perhaps centred itself with the Earth's rotation ( Idea: It is now the core )