Tracking fin and blue whales above the Juan de Fuca Ridge with a local seafloor seismic network.

Abstract

The Endeavour segment of the Juan de Fuca mid-ocean ridge hosts several high-temperature hydrothermal fields. Previous analysis of bio-acoustical data shows that zooplankton are enhanced at all depths above the hydrothermal vent fields compared with sites ⩾10 km away. From 2003–2006, a seafloor seismic network was deployed around the hydrothermal vent fields to monitor earthquakes and it also recorded an extensive data set of fin and blue whale calls. As part of an investigation of a potential correlation between whale tracks, enhanced zooplankton concentrations, and hydrothermal vents above the Juan de Fuca Ridge, an automatic algorithm is being developed to track vocalizing whales that swim near the network. Events are detected by triggering with the ratio of short-term to long-term running RMS averages and whale calls are distinguished from earthquakes based on their spectra. For fin whales each 1-s arrival is identified based on its instantaneous amplitude and frequency and a pick is made at the mid-energy point. A grid search method is used to localize calls using direct and multipath arrivals. The algorithm and preliminary results will be presented. [The Keck Foundation supported the seismic network and the Office of Naval Research is supporting this study.]