He is employed by NASA, for what I don't know. Yes, if you hit a rock with a projectile at 6 km/s some energy will go into all kinds of waves. That is near the speed that the Earth is orbiting the Sun, i.e., extrordinarily fast. What does this have to do with earthquakes? Particle velocity (the speed at which the sides of the fault slip) is about 1 m/s, almost four orders of magnitude less.

Do you realize rock vaporizes at those impact velocities? Probably turns entirely to plasma for all I know.