I think that the antipode idea regarding the Deccan Trappes may be true, and that the angle the asteroid came in could effect the area of exact maximum shock. However, the Hawaiian Chain started about 70 mya with the Emperor Seamount Chain which was trending south from the Aleutian Trench until around 44 mya when it started to trend more eastward. The cause is suggested to be a magma hot spot which was moving for a time and then stood still and let the crust move over it. See the link below with ocean map clearly showing the two series of volcanic mounds, the significant change of direction, and the final point in the Hawaiian Islands.
http://geology.com/usgs/hawaiian-hot-spot/
Antipodal Hotspot Pairs
http://www.science-frontiers.com/sf088/sf088g12.htm
Glitches In The Terrestrial Conveyor Belt
http://www.science-frontiers.com/sf118/sf118p11.htm
Do the continents really drift?
http://www.science-frontiers.com/sf026/sf026p08.htm