Detection and tracking of fin whales during seismic exploration in the Gulf of California

The fin whale (Balaenoptera physalus) commonly produces low-frequency and high-intensity downswept sounds centered at 20 Hz, named “20 Hz pulses.” The frequency bandwidth associated with seismic exploration (using airguns) overlaps with these signals. The data analyzed in this work came from a geophysics project conducted in the Gulf of California in October 2002. In several locations across the Gulf, a series of Ocean Bottom Seismometers (OBS) were deployed on the seafloor. This study focused on 60 OBSs deployed in Guaymas Basin. The instruments had two data channels, a hydrophone and a vertical geophone, recording at 125 samples per second. The array continuously recorded data over a period of ∼11 days, during which airgun surveys were conducted over 6 days during daylight hours only. Abundant vocalizations of numerous fin whales were recorded. The OBSs were spaced ∼12 km apart from each other, allowing localization and tracking of individual whales. Algorithms were developed to automatically detect wha...