I did a small project about impact events on Earth as part of my physics degree. The Tunguska event was most likely a meteorite which exploded in the atmosphere producing a pressure wave which knocked down trees and what not at ground level, other attempted explanations I have seen have just been nonsense.
Just a sidenote, antimatter is real and there is plenty of evidence for it's existence. It is not even theoretical, antimatter exists without any shadow of any scientific doubt. Also, matter-antimatter annihilations are not "nuclear" reactions because, say a positron annihilates with an electron, there is no nucleus involved. An explosion resulting from annihilation of a large anti matter body (which has never been observed btw) and matter would not be like a thermonuclear weapon because it is a completely different process. The only similarity would be my indisposition to standing underneath it.
tweehonderd graden, dat is waarom ze me mr. fahrenheit noemen, ik reis aan de snelheid van het licht, ik ga een supersonische man van u maken