As I have a background in building broadband, realtime siesmic networks I will briefly return from self-imposed exile to comment on this tradegy.
The science of tsunamis as presented in this thread is largely accurate. In a nutshell, a tsunami is a fast-moving standing wave caused by crustal displacement after siesmic activity (we will ignore other potential causes for the moment). As has been pointed out, not all undersea earthquakes will cause a tsunami event. The usual cause is a thrust fault in a subduction zone which results in a rise or drop (sometimes both) in the sea floor. This creates a shockwave which radiates out in a circular pattern from the epicenter of the event. The important thing to realize is that the destructive power of the tsunami is not so much the height of the resulting wave, but the extreme velocity of its propagation.
Now, what to do about it. In order to create an early warning system requires three elements.
1. A realtime seismic network, which can detect and localize seismic events hours before any tsunami would reach land.
2. An array of deep-ocean sensors to detect the actual tsunami.
3. An emergency broadcast system to warn coastal communities.
The good news is that 1 and 3 are largely taken care of. There are many realtime seismic nets around the world and most beach communities, even in third world countries, have some sort of rudimentary public alert system. All that is really needed is a few deep ocean sensors and integration with existing emergency broadcast systems. I'm confident that I could deploy an entire system for a single country for less than five million dollars, with a recurring cost of about 500k per annum to cover staffing and maitenence.
Unfortunately, the lack of a realtime alert system is not the root cause of this tradegy. The elephant in the living room, so speak, that no one is talking about is the excessive development of coastal areas, with little attention paid to evironmental issues.
To an earth scientist, beaches are temporary. Anything built on them probably won't be there a hundred years from now. It's just the way it is. At the very least, a reinforced sea wall of at least twenty feet should be built before all dwellings, which themselves should be built only on established coastal terrain.
I am pessimisstic that we have learned anything from this. I'm sure that after the last of the bodies are burned and debris cleaned from the beaches, that the hotels will rebuild their beach bungalows, a hundred feet from high tide with an unobstructed view. And this is all going to happen again.
P.S. One brief addendum, I was laid off last year due primarily to budget cuts for the USGS by the current administration. And there is no tsunami warning system in place for the Atlantic coast.
(or did I miss something?)
