# What happens to submarines during the Sendai event? **URL:** \ **Category:** Factual Questions\ **Created:** [March 15, 2011, 2:15am UTC](https://boards.straightdope.com/t/what-happens-to-submarines-during-the-sendai-event/574735 "2011-03-15T02:15:11Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [March 15, 2011, 2:15am UTC](https://boards.straightdope.com/t/what-happens-to-submarines-during-the-sendai-event/574735/1 "2011-03-15T02:15:11Z")
Say a big boomer was lurking around a) an earthquake epicenter and b) tsunami waves (whose (the force at varying depth), distance and other hydrological events about which I have no clue. (Perhaps can choose Sendai event as example)? What does it do? I know there’s a lot of variables that could be proposed, but I have no clue even to what people would do to think this through. BTW, my WAG is that no boomer would be 75 miles off-coast of anything. ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [March 15, 2011, 2:36am UTC](https://boards.straightdope.com/t/what-happens-to-submarines-during-the-sendai-event/574735/2 "2011-03-15T02:36:53Z")
In deep water there’s not much impact from a tsunami. Ships in deep water wouldn’t notice much. ---
**Author:** ![Slc84103](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@Slc84103](https://boards.straightdope.com/u/Slc84103)\ **Post date:** [March 15, 2011, 2:49am UTC](https://boards.straightdope.com/t/what-happens-to-submarines-during-the-sendai-event/574735/3 "2011-03-15T02:49:19Z")
If close enough the sonar guys might hear something like this [http://nickstutorials.com/field-sample-download-underwater-recording-of-an-earthquake/](http://nickstutorials.com/field-sample-download-underwater-recording-of-an-earthquake/) After that maybe a “Crazy Ivan”. ---
**Author:** ![rbroome](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbroome](https://boards.straightdope.com/u/rbroome)\ **Post date:** [March 15, 2011, 12:07pm UTC](https://boards.straightdope.com/t/what-happens-to-submarines-during-the-sendai-event/574735/4 "2011-03-15T12:07:07Z")
> [@Leo\_Bloom](#): > > Say a big boomer was lurking around a) an earthquake epicenter and b) tsunami waves (whose (the force at varying depth), distance and other hydrological events about which I have no clue. (Perhaps can choose Sendai event as example)? What does it do? > I know there’s a lot of variables that could be proposed, but I have no clue even to what people would do to think this through. > > BTW, my WAG is that no boomer would be 75 miles off-coast of anything. It is actually an interesting question. For a large submarine, probably not serious. But it depends on the water conditions. The issue is internal waves. The internal wave amplitude is a function of the density gradient. At the air-sea interface the density gradient is very large, the amplitude is (relatively) small. Think of it as a measure of energy moving through the water-at the surface moving the water surface up a meter or six takes a lot of energy. Down at the bottom of the mixed layer, the same amount of energy moves the water a lot further. So the internal wave amplitudes are much higher. Again it depends on the density gradient. But internal wave amplitudes of 100 meters are not unusual under normal conditions-in some parts of the world. With a large earthquake, the amplitudes would be very large. However, note that the effects of an internal wave are not the same as a surface wave. Again, it is the density gradient. The sub will experience a change in density, but it will be managable. Might be a rough ride though. Certainly a very surprising one. And distance isn’t much of a protection. Any submarine in the pacific almost certainly detected the internal wave. A large submarine would probably notice an excursion. Now if you were a small submarine, or a diver or an autonomous underwater vehicle-those might be in trouble. It is unlikely a diver would ever be in an area where internal waves are significant, but any diver that goes from say 20 to 200 meters in a minute or two would be in very serious trouble. Well, by the time the diver got to 600 ft I doubt he would be in trouble any longer… I have never heard of any underwater vehicles being damaged/lost due to internal waves, but there is always a first time. The factors are the density gradient and the energy of the wave. We understand the gradient. That earthquake pumped in a LOT of energy. Things are bad enough without a nuclear powered submarine running into trouble somewhere.