SEISMIC OCEANOGRAPHY IN THE ”JUAN DE FUCA RIDGE TO TRENCH ” SURVEY

Seismic oceanography (SO) is a discipline that studies physical properties of the oceanic water from mul-tichannel seismic reflection data (Holbrook et al., 2003). Multichannel seismic reflection data can be used to image mesoscale structures in the ocean like fronts, eddies (Biescas et al., 2008) and currents (Buffett et al., 2009). These data reveal the lateral coherence of thermohaline oceanic structures as well as the interactions with the topography. This discipline uses the same instrumentation and software for data ac-quisition and processing that marine geophysics, but it uses the first 5-6 seconds of the seismic records, which travel through the water column. Therefore, it can be a complementary study to the one done by marine geophysicists. The ”Juan de Fuca Ridge to Trench ” survey has been carried out in the Cascadia Basin (Figure 1). The water column above Cascadia Basin is affected by several currents that influence regional patterns. As the North Pacific Current approaches North America from the central Pacific, it splits into the north-flowing Alaskan Current and the south-directed California Current (Figure 2). Different water masses can be identified in the water column: the California Current up tp 500 m; the Subartic Intermediate Water, between 900 m and 1900 m deep and the Cascadia Basin Bottom Water and the Cascadia Deep Water below 2000 m. These water masses have different properties of temperature and salinity. It was expected tha