Earthstrike Quake p. 82
You swing your weapon in a wild arc, slamming it into the ground at your feet. Energy surges out from you, causing the ground to shudder with a sharp tremor.
You channel ki into the earth with your mighty strike, causing the ground to rumble and shake briefly. Anyone standing on the ground in this maneuver's area must make a successful Reflex save (DC 18 + your Str modifier) or be knocked prone. Any creature standing on the ground in this area that is currently casting a spell must succeed on a Concentration check (DC 20 + spell level) or lose the spell.
You are immune to the effects of your own earthstrike quake maneuver. Your allies must still save as normal against its effect.
Walls and similar barriers don't block the line of effect of an earthstrike quake.