http://pnsn.org/volcanoes/mount-st-helens#seismicity-
Discovered?
Look roughly 2 km down, the fluids travel up, then stop about 2 km down where they collect for awhile before moving upwards upon reaching critical pressure.
Forgive me, for I am but a lowly 'murican. I can't think with metric measurements. Is that like a mile or so?