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markferg's avatar

Do marine animals suffer in underwater earthquakes?

Asked by markferg (1877points) March 11th, 2011

Very sad about what happens on land, what about fishes and cetaceans. Are they affected too?

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9 Answers

Seelix's avatar

Here‘s an article about the aftermath of the tsunami in Sumatra.

Apparently toads are among the animals that can predict earthquakes!

I would think that there would be some pretty strongly-felt effects underwater as well as on land. It’s tough to find information online about it – maybe there haven’t been a whole lot of studies, maybe I’m just not much of a Googler. But it would make sense for coral reefs to be affected greatly depending on the magnitude, which in turn would change the underwater ecosystem at least somewhat.

the100thmonkey's avatar

The majority of the devastation caused by the Sumatra and Tohoku (the region of Japan most seriously affected by the temblor) earthquakes was caused by the attendant tsunami, which in both instances was basically caused by the edge of the tectonic plate ‘pinging upwards’ as the stress was released. This pushes the water column above the thrust upwards, resulting in a wave.

The wave is so destructive because it has a high amplitude and long wavelength. It’s often barely noticeable in the open ocean as the amplitude of the wave is not as great as the depth of the water column. When the water gets shallower, though, the sea floor reflects the wave back earlier, so the energy has nowhere to go. The amplitude of the wave is deflected upwards, causing it to rear up. The long wavelength ensures that there are millions – possibly billions – of gallons of water pushed up behind the crest which all follows the wavefront inland. This is why it’s so destructive on coastal areas.

Unless whales happened to be close to shore, I don’t think they would suffer any ill-effects – a wave is actually a circular motion of the water, so they might be somewhat confused for a few seconds as they are pushed in a wide circle. As for other marine life, obviously coastal fish and other sea life close to shore would be pushed inland and come into contact with very dirty, muddy water, with implications for their survival. Coral and other sedentary organisms would have to cope with the sheer amount of energy in the wave as it pushed strongly in one direction for several minutes, and then deal with the sludge, and possibly pollutants, flowing in the other direction as the wave recedes.

I wonder how a submarine earthquake sounds. Probably extremely unpleasant.

JLeslie's avatar

@the100thmonkey Your explanation reminds me of a story I once heard in school of small fishing villages in the pacific, where the men would go out early morning to fish, a tsunami passing under their boats, barely noticeable in the deep sea, and returning to their villages near the shore, to find everything destroyed and their families gone, dead.

the100thmonkey's avatar

@JLeslie – I’m pretty sure that the story was repeated today.

Tragic.

Bellatrix's avatar

@markferg what a fascinating question and interesting answers. I never even thought about sea creatures and the impact on them.

ParaParaYukiko's avatar

I just asked my mother who is getting her PhD in marine fisheries this question. She said that marine creatures in the deep ocean probably wouldn’t be largely affected by earthquakes, since not much in the way of tremors is felt at the source of a quake. Same with tsunamis; in the open ocean, tsunami waves are just a couple feet tall at most. They get large in shallow water.

Marine creatures who are more likely to get affected by things like these are those living in intertidal zones (whose habitats would be washed away by a tsunami) or if buildings or something fell into the water and damaged their habitat that way.

Generally, I’d say whales and marine mammals are harmed more by man-made noise than Nature-made disasters.

JLeslie's avatar

Before the big wave comes in there is a large drawback that exposes the ocean floor near shore, so I would guess sea life in shallow water might be beached so to speak, and if out of the water long enough would die. The drawback of the sea is a clue to run fast inland and to higher ground. I can see how some might think the event before the wave is almost miraculous, like a parting of the seas, but it is a warning of a natural disaster being unleashed.

shabbir's avatar

the excess force and pressure cause them to die!

dwms02's avatar

UNDERSEA EARTHQUAKE ARE THE REASON WHALES MASS STRAND!

David Williams, a commercial sea captain, believes he has discovered the answer to the centuries-old mystery of why whales beach en masse. He says the answer is simply! Pods of offshore odontoceti (toothed whales) accidentally run aground because they are lost and have no idea where they are going. They are swimming along with the flow of the surface currents when they go ashore. Said differently, the current is the force that carried each grain of sand to the beach in the first place and is the same force guiding the lost pod of whales. As an example, if a blind person swims in a stream of current, they will be turned by the flow and pointed downstream because to swim upstream or even across the current offers far great resistance than going downstream in the path of least resistance. Capt. Williams says it happens most often on beaches located in areas where large geographical land masses extend out to sea in an opposing fashion to the surface currents. Cape Cod in the USA and Golden Bay in New Zealand are two prime examples. The hook-shaped capes serves as a giant catching arm to trap the lost whales in the sand. Once in the sand, the whales have no idea how to escape since these are deep offshore whales who known nothing about the sandy shoreline.

This sea captain with 50 years of experience at sea says the failure of their biosonar/navigation system is the result of a barotraumatic injury in the air sacs and sinuses of their heads. The accident occurs during a feeding dive when a shallow-focused earthquake suddenly erupts in the seafloor below them.

Seismic waves from the focal center of the quake cross the rock/water interface and enter the water column as low frequency (LF) hydro-acoustic waves at ~7.5 hertz. These pressure waves are identical in nature to powerful LF sonar signals generated by transducers mounted in the hull of naval vessels. Geophysicists and seismologists call these compressional vibrations “T-phase waves” (t-waves for short). T-waves from an earthquake near the Island of Tonga traveled ~3,000 kilometers across the Pacific Ocean, arrive at the drop off edge of Tahiti, reenter the solid earth, and shook the island so furiously that the inhabitants thought a local earthquake had occurred (link). T-waves would be “felted” by the diving pod as a series of sudden increases and decreases in the external water pressure surrounding the diving whales. Such rapid changes in pressure during a dive would result in both compressions and expansions in the volume of air contained within the internal air spaces of the head and lungs in keeping with the principles of Boyle’s law. When the air rapidly expands in volume during the expansion phase, the extra air is vented out of the whale’s mouth in a fashion similar to the wind being knocked out of a man by a powerful blow to his chest. The internal trauma will depend on the intensity of the pressure changes, the depth of water where the accident occurs, and the duration of the exposure. Since the average earthquake might last 30 seconds at a frequency of 7.5 cycles per second, the whales would be exposed on average to (30×7.5) 225 rapid inflation/deflations of the membranes surrounding their sinuses and air sacs. Because air compresses and expands during the passing of earthquake water waves, and bodily tissues, blood, and bones do not, strong pressure differentials develop at air-filled interfaces causing shear forces that tear, bruise, and disrupt tissues, membranes, and small vessels. When the membranes tear, air mixed with blood can escapes into the head forcing the sinuses to collapse.

Said differently for better understanding, earthquake-induced pressure oscillations move vertically from the seafloor toward the surface as low frequency compressional waves (aka: longitudinal waves). When these waves traverse through the organs that contain pockets of gas (air sacs, sinuses, middle ear cavities, lungs, stomach) they cause a sudden implosion of the air space on the positive pressure pulse followed a split second later by a sudden rebound expansion on the negative (rarefaction) pulse. These implosions and expansions in the air sinuses continues at a rate of 7.5 times per second until the earthquake subsides. Such violent disturbances of the membranes of the air spaces result in serious barotraumatic injury. In fact, it is well-known that rapid and excessive changes in the surrounding water pressure is a diver’s worse nightmare come true.

The pterygoid air sacs surrounding the two inner ears are of particular concern. This grouping of small air sacs, depicted in green, isolate each cochlea thereby ensuring that only the sounds traveling through the channel of fat inside the lower jaw bone reach the organs of hearing (link). Toothed whales generate click-like vocalizations using phonic lips (“monkey lips”) and associated air sacs in their nasal passages. The clicks are transmitted through a waxy “melon” that is located on the forehead and contains lipids of different densities. It acts as an acoustic lens and emits a focused beam of sound. The echoes are primarily received through the lower jaw, which is surrounded by complex fatty structures, and conveyed to the ear through a continuous fat-filled canal. Baro-traumatized pterygoid air sacs allow unwanted sounds, especially the animal’s own powerful clicks, to stimulate the inner ear thereby confusing each whale’s biosonar. Injured sinuses will also prevent the whales from diving and feeding. Baro-traumatized odontoceti are still able to hear and generate and respond to sound, but are not able to determine the azimuth of any returning navigational echoes, nor are they able to dive much deeper than 3–4 meters without severe pain.

As just one example of the power of a small underwater earthquake, on 28 August 1997, the front page of the Washington Times reported that seismic stations around the world had detected a powerful underwater explosion offshore near a Russian nuclear test facility on Novaya Zemlya, a small island in the Kara Sea. The first impression of many government scientists was that the Russians had exploded an underwater nuclear device with a yield between 10 to 1,000 tons of TNT in violation of the Comprehensive Test Ban Treaty. CIA geologists insisted that the explosive nature of the event was proof of a nuclear explosion, while others felt the seismic spectrum was that of a magnitude 3.5 shallow-focused earthquake that had erupted in the upper crust of the bottom with explosive characteristics. The argument went back and forth in the newspapers and was finally resolved three months later when two Columbia University seismologists released evidence that indeed a shallow earthquake had ruptured through the brittle layer of the seafloor near the Russian test site. (link)

It turned out to be a false alarm created; however, the point is that the quibbling back and forth by the world’s best experts shows just how tough it is to tell the difference between an explosive volcanic/tectonic earthquake at 3.5 magnitude and a small nuclear device. The difficulty is easy to understand since the energy released during a magnitude 4 event is equal to that released by 1,000 tons on TNT.

The TNT equivalent of Little Boy, the nuclear bomb that destroyed Hiroshima, was 15,000 tons. The energy equivalent of the average earthquake found responsible for mass strandings is ~32,000 tons (link). Common sense will tell you that a seismic event releasing 32,000 tons of TNT ~4 kilometers below seafloor under a pod of diving whales could easily cause barotrauma in their head sinuses, which would indeed result a few weeks later in a mass stranding of the entire pod.

Marine mammal scientists have proven that the air sinuses play a major role in the function of biosonar. Thus, it stands to reason that a whale (or pod of whales) with busted sinuses would be unable to navigate.

Without a sense of direction, the swim path of an earthquake-injured pod, harassed constantly by oceanic sharks, would be directed downstream. Filaments of current that occasionally break off from the main oceanic current would then direct these injured pods toward shore. As they near land, hook-shaped capes and peninsulas with gradually sloping beaches that extend out from the shoreline opposing the prevailing currents would act like giant catching arm systems, trapping the debilitated pod, precipitating a mass stranding event.

source: http://www.deafwhale.com

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