Great subduction zone earthquakes, such as the Alaska earthquake in 1964) and tsunamis originate in seismogenic (earthquake generating) zones of subduction zones, where vast tracts of seafloor slide beneath adjacent continental margins. One such region is the Cascadia Subduction Zone, which extends from northernmost California to southern British Columbia, Canada. Great earthquakes occur along this margin at interval of several hundred years; the last was in 1700. Given the population density of the region today, the next is likely to cause considerable damage and loss of life. Learning a much as possible about seismogenic processes in Cascadia is clearly imperative. Much has been learned in recent years about how energy is stored and released in seismogenic zones. Among the most interesting phenomona are episodic tremor and slip (ETS) and very low frequency events (VLFE). These are not earthquakes; instead, the Earth groans, but these processes are not well understood. This deployment of ocean bottom seismometers is part of an international collaboration aimed at investigating these seismic processes. Aside from its obvious societal relevance, the broader impacts of this effort include the international collaboration and its contribution to upcoming broader Cascadia initiative.
