During the VISIONS'13 expedition, low frequency hydrophones, coupled with broadband seismometers, will be deployed at the base of the Cascadia Margin (Slope Base), and at the base of and summit of Axial Volcano.
Real-time detection of seismic events along the Cascadia subduction zone and Juan de Fuca Plate is a powerful capability provided by the OOI Regional Cabled Observatory. Part of this detection and monitoring capability is provided by an array of low-frequency hydrophones (2 Hz to 20 KHz) that are well suited to detect the hydroacoustic tertiary phase of T waves of oceanic earthquakes. These sensors also detect solid-earth P waves from regional and teleseismic earthquakes. Coupled with the Ocean Bottom Seismometers, the low-frequency hydrophones will increase our ability to detect offshore earthquakes in real-time, determine their magnitude, and enable better location accuracy.
During the April 24th, 2015 eruption of Axial Seamount the hydrophones "heard" what is believe to be explosions from the eruption.