The echoes of fin whale songs can penetrate sediment and volcanic rock on the ocean floor, according to new research.
Why it matters: Fin whale songs could be used to map the Earth's crust when conventional — and in some cases, controversial — methods like firing seismic air guns from ships may not be available.
- “It’s never going to replace air guns,” study co-author Václav Kuna of the Institute of Geophysics in Prague told the NYT.
- “But it is a complement. And it’s free.”
Fin whales are loud — their low-frequency calls can generate more than 185 decibels underwater, on par with a large ship.
- Researchers typically use the endangered whales' low-frequency vocalizations to study the distribution of the species (Balaenoptera physalus) in the oceans.
What they did: Kuna and John Nábelek of Oregon State University analyzed six whale songs, each with 212–593 calls that were 30–40 seconds apart.
- The calls were picked up by a network of seismometers on the ocean floor that monitor for earthquakes off the coast of Oregon. (The researchers suggest machine learning algorithms could be used to locate and analyze calls.)
- Part of the energy in the whales' calls is "transmitted in the ground as a seismic wave. The seismic wave travels through the oceanic crust, where it is reflected and refracted by layers within the crust," the researchers write today in the journal Science.
- They were able to use those signals to map the thickness of sediment and rock on the ocean floor.
Yes, but: It has its limits — for example, the method worked best in relatively flat regions and the resolution of seismic images constructed from the whales' low-frequency signals was lower than the conventional air gun method.
- The broader-frequency calls of sperm whales may produce higher-resolution imaging, the researchers suggest.
The big picture: "Our study demonstrates that animal vocalizations are useful not only for studying the animals themselves but also for investigating the environment that they inhabit," the researchers write.