Woods Hole Oceanographic Institution

The Cascadia subduction zone offshore of Northern California, Oregon, Washington and British Columbia had its last major earthquake and tsunami over 300 years ago and has been building up strain for the next earthquake since then.  The majority of this fault, which could produce a Magnitude 9 earthquake at any moment, lies offshore, where there are currently no geodetic instruments set up for monitoring the buildup of strain.  Hence, scientists have relatively little ability to project the details of the next earthquake.  The project will install the first seafloor geodetic observatory above the locked, offshore portion of the Cascadia fault.  It will also mount state-of-the art geodetic instruments (tiltmeters) in an existing borehole offshore of Vancouver Island that will have real-time data availability through the NEPTUNE cabled observatory and will be co-located with already existing sub-seafloor hydrological monitoring equipment.  Together these instruments will enable new interdisciplinary studies of the fluid flow transients within the subduction system.  Additionally, a wider array of instruments for measuring the vertical deformation of the seafloor both at short and long time scales will be installed.  These pressure gauge benchmarks will allow a determination of whether the Cascadia fault is locked to shallow depths, and hence likely to rupture in a manner similar to the recent catastrophic Japanese earthquake.