It is the plane of intersection between the Wadati seismic waves and the Benioff suture between continents

The same as Moho or Mohorovicic that marks the crust-mantle boundary

It is the seismic surface that separates two different continents that have collided and is especially active in the India-Asia collision

It is the surface defined by earthquake hypocentres that form as an oceanic lithosphere subducts, it marks the surface of the subducting plate