Seismic crustal imaging using fin whale songs

Abstract

Structure from a whale song Probing the structure of the ocean crust requires a wave source. The most common source is an air gun, which is effective but potentially harmful for ocean life and not easy to use everywhere. Kuna and Nábělek found that fin whale songs can also be used as a seismic source for determining crustal structure. Fin whale vocalizations can be as loud as large ships and occur at frequencies useful for traveling through the ocean floor. These properties allow fin whale songs to be used for mapping out the density of ocean crust, a vital part of exploring the seafloor. Science, this issue p. 731 Fin whale songs can be used as a seismic source for investigating seafloor crustal structure. Fin whale calls are among the strongest animal vocalizations that are detectable over great distances in the oceans. We analyze fin whale songs recorded at ocean-bottom seismometers in the northeast Pacific Ocean and show that in addition to the waterborne signal, the song recordings also contain signals reflected and refracted from crustal interfaces beneath the stations. With these data, we constrain the thickness and seismic velocity of the oceanic sediment and basaltic basement and the P-wave velocity of the gabbroic lower crust beneath and around the ocean bottom seismic stations. The abundant and globally available fin whale calls may be used to complement seismic studies in situations where conventional air-gun surveys are not available.