Fin whale songs could help map the ocean floor


Researchers say the songs of fin whales -- like the one pictured -- could be used to improve seismic ocean surveys, and in some cases replace the airguns that are generally used by surveyors. Photo by Aqqa Rosing-Asvid/Wikimedia



Feb. 11 (UPI) -- The fin whale is the loudest species in the ocean. The mammal's long, loud, low-frequency vocalizations can travel for hundreds of miles.

Fin whale songs are so strong, in fact, they generate seismic data that can be used to probe the structure and composition of Earth's seafloor.

Scientists described the fin whale's potential as a seismic source in a new paper, published Thursday in the journal Science.

"The idea to study subsurface signals in whale calls was rather a coincidence," lead study author Václav Kuna told UPI in an email.

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"I am a seismologist and I was studying earthquakes at the Blanco Fracture Zone west of the Oregon coast. Accidentally, I found fin whale call recordings in our data and -- given my seismological perspective -- I was wondering whether they could be used similarly as airguns," said Kuna, a geophysicist and graduate research assistant at Oregon State University.

Airguns are the seismic source of choice for scientists mapping the ocean floor, but the massive blasts can be disruptive to marine species, especially whales and dolphins that use sound to communicate with each other and hunt for food.

Conducting seismic surveys using airguns requires time, energy and money -- finite resources. Fin whales all over the world are constantly singing, for free.

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Scientists knew fin whales were quite loud, but until now, it wasn't clear that their songs could generate useful seismic data.

"Seismic stations record all kinds of mechanical waves -- earthquakes, ocean wave noise, engines of ships ... and also whale songs," Kuna said. "In principle, all these sources generate the same kind of mechanical wave that can be picked up by the station."

For the study, Kuna and research partner John Nábelek, a professor of seismology at Oregon State, analyzed fin whale song data recorded by a series of seismometer stations positioned on the floor of the Pacific Ocean.

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What surprised the pair was not the presence of fin whale songs among data collected by seismometers, but the amount of seismic data generated by the songs.

The sound waves are strong enough that they penetrate several feet into the ocean floor, reverberating off layers of rock and sediment.

Kuna and Nábelek found seismic data generated by the songs was sufficient to constrain the thickness and density of oceanic sediment and basaltic rock layers beneath the stations.

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Though fin whale songs won't replace air guns, they can help scientists characterize oceanic crust and gain insights in the composition of oceanic sediments -- information useful to both geologists and climatologists.

The seismic data generated by fin whale songs could also be used for what seismologists call "static corrections," a process that helps scientists more precisely pinpoint the origins of earthquakes.

"Shallow structure -- mainly sediment thickness and velocity -- varies from site to site," said Kuna. "When locating earthquakes, these variations introduce unknown time shifts in arrivals of earthquake waves. If we know the shallow structure, we can correct the records at individual stations, which leads to higher quality of earthquake location."

"The study shows that whale and animal vocalizations carry more information than we thought previously," Kuna said. "I hope that the paper will encourage other scientists to study other animal vocalizations and come up with more potential applications."

Instead of adding more human noises to the ocean, Kuna hopes scientists will take advantage of the sound waves that are already reverberating beneath the ocean surface.