High-frequency earthquakes at White Island volcano, New Zealand: insights into the shallow structure of a volcano-hydrothermal system

摘要: Abstract Volcano-tectonic earthquakes at White Island are concentrated in a single seismically active zone, southeast of the vents and depths less than 1 km. A few deeper also occur beneath vents. composite focal mechanism indicates that stress regime shallow seismic zone is N-S extensional. Shallow seismicity occurs within main volume volcano-hydrothermal system underlies Main Crater floor, we interpret this as region where rocks have been weakened by past magmatic intrusions, elevated pore fluid pressure physico-chemical effects acid volcanic fluids, thereby allowing preferential failure. Brittle failure requires temperature about 400 °C, implies high horizontal gradients close to craters fumaroles. Spasmodic bursts events result brittle failure, but zones significant permeability response changes local pressure.