Today's Indian Ocean Tsunami, Small Tsunamis, and The Tsunami Warning System

This is a continuation of a post I wrote (and updated a couple of times) earlier today. Since the tsunami is no longer a possibility - it's an actual event - I thought a new title was probably a good idea. Here's the situation as it currently stands:

The Pacific Tsunami Warning Center issued a final watch statement for the event at 11:05 am Eastern time. They report that a tsunami was generated, and is currently traveling across the Indian Ocean. Based on the data that they have - currently, they have readings from three near-shore tide gauges and one deep-ocean gauge - the tsunami is small, and is not expected to cause damage in distant areas. (It should be noted, however, that PTWC's message also notes that they still only have limited access to sea level data in the Indian Ocean, and that they might be wrong about that.)

The concept of a "small tsunami" might seem strange to some people, but when it comes to figuring out if a wave is a tsunami, size doesn't matter. Most people, when they hear the word 'tsunami', might think of news footage from 2004, with giant waves crashing down over people and buildings. Tsunamis like that do happen (obviously), and the threat of a tsunami in that size range is (obviously) the reason that we're concerned enough to have people constantly alert to the threat of another one. But that doesn't mean that every tsunami is a big wave.

You might be surprised to hear this, but today's Indian Ocean tsunami isn't the first tsunami this year. There have already been three in the Pacific Ocean - one in January that was caused by a quake off the Kuril Islands, on in April caused by a Solomon Islands earthquake, and one in August that resulted from a 7.9 earthquake near the coast of Peru. These events were all small, but if you go to NOAA's National Geophysical Data Center page you'll find maps and water runup data for all three. It'll probably take a while for the information to be collected, but information on this latest one will probably find its way there eventually.

More like this

A few years ago Eos published a series of photos of a small tsunami striking the Costa Rican (?) coast.

The max wave crest was about 6 inches high as far as I recall...

I suspect that lots of "micro-tsunamis" are being generated frequently. By micro-tsunami, I mean very small amplitude waves, but similar in wavelength and amplitude versus depth profile, as their deadly but rare high-amplitude cousins. Being that the noise (short period gravity waves, and tides) is fairly large I suspect we can't readily observe them.

HR Service, the sources of 'noise' are so well-understood they can be subtracted out, and the tsunami observed in what remains.