So the ship gradually fills with water, going down steadily by the bow.
Finally, the stern starts to tip upwards. Then the stern breaks off, and the two pieces of Titanic sink beneath the water.
So how long from the moment the ship disappears beneath the water until it hits the ocean floor?
And, suppose such an accident were to happen today: would the impact of the pieces of Titanic on the ocean floor be enough to show up on modern seismographs?
From that same link, the halves of the ship were travelling at an estimated 30 mph when they hit the bottom. In terms of kinetic energy, each half of the Titanic would have about 2 gigajoules of energy, some fraction of which would be transmitted to the sea-bottom when it impacted.
If Wikipedia is to be believed, a earthquake with Richter magnitude 3.0 releases approximately the same amount of kinetic energy as this. However, a 3.0 earthquake isn’t that strong, and I’m not sure whether this would be detectable by a land-based station hundreds of thousands of miles away. (Obviously, there are no seismometers in the North Atlantic Ocean.)
It’s highly variable how far it would be detectable.
But hundreds of thousands of miles? :dubious: You are aware that anything more than 24 000 miles is as far as you can get away from the epicentre and not be on your way back, right? 
Wouldn’t half the circumference (12,000 mi) be as far away as you could get?
That’s what I get for posting too early in the morning. I meant “hundreds or thousands of miles away.”
Don’t feel bad. I make that of/or typo 3x/day. It’s surprisingly hard to spot.
Back to the OP …
If that was to happen today it might not be detected on seismometers. But is sure would be detected by SOSUS (wiki) and its successor systems.
:smack: Doh, yes. That’ll teach me to worry about getting the miles right and forgetting to actually halve it.
Actually it’s worse than that.
Seismic waves don’t travel along the surface, but rather through the interior which can represent a short-cut. They don’t follow a straight line path though. So even though the Earth’s diameter is about 8000 miles and that forms the geometric worst-case minimum, that’s not a practical minimum.
See Seismic wave - Wikipedia for more.
Just FYI, the Richter scale is logarithmic which, if you don’t know anything about math, means it is very non-intuitive. In human terms anything below a 5.0 is essentially nothing, anything above a 5.0 is a small to large catastrophe…
Below 5 is not “essentially nothing”. I’d say 3-5 is the range for “noticeable, but almost certainly not damaging” - and if you’re not used to 'quakes, noticeable is not nothing.
BUMP
I was recently poking around on the wikipedia article for the Kursk sinking, and found the following:
If a seismic event of 1.5 Richter is picked up, then presumably a 3.0 Richter would be picked up, if a similar sinking as Titanic happens today?
How much energy gets coupled to the crust to generate a detectable seismic wave is going to be a very variable thing. There are a lot of factors. Whilst there was a given amount of energy in the falling ship, how it was dissipated is going to be a mixture of mechanisms.
If the ship hits a solid rock sea bottom it is going to be very different to settling into thick mud. The time it takes the ship’s structure to stop matters as well, as this determines the frequency distribution of the impulse. If the ship’s structure buckles on impact, that buckling will absorb some of the energy. As will displacing mud. However the location where the Titanic settled does not have very deep mud.
One metric to consider is the mechanical impedance or often its inverse, the admittance, of the sea floor. This controls how much energy is coupled into the Earth and thus how much might be seen as a seismic wave. It is highly frequency dependant. The problem becomes one of an impedance matching problem, between the hull sections and the seafloor.
I’m going to bet that there will little detectable seismic energy detectable at any useful distance. A lot of the energy will be locally dissipated rather than coupled into the Earth. An underwater explosion may tend to couple a lot better with much higher peak energies.
Interesting. Thank you.
If a person were swimming on the surface and put their head underwater at the moment it hit bottom, would they have heard it?
Well, there’s your problem:. You’re using metric while the shipyard used imperial!
Pay attention here to dropzone, who knows his stuff about dropping objects!
No, not at that ‘moment’ – it would be some time later that the sound would travel back up 3800 meters.
Also, there would be 2 ‘moments’ – the stern section stayed afloat for some minutes after the bow section broke off and headed for the sea floor. Plus the bow section (streamlined) was sinking faster than the stern section.
This may also be of interest: