Real-time Earth and Moon phase

Thursday, July 20, 2006

Semblance with earthquakes

I read an interesting blog post from the May 30th blog of the New Scientist magazine. (I know it's July now and I am talking about a post back in May since I did not follow their blog very closely. But it’s not a timely post anyway.) Here’s the post:

Another earthquake, this time in Indonesia, and the story follows a familiar, tragic arc: the tremor, the casualties, the call for aid, the ending of hope for finding survivors.

What stands out to me, in a gruesome way, is how many people have died – over 5000 as of today – for a relatively small earthquake. The quake measured 6.3 on the Richter Scale (there are about 120 tremors between 6.0 and 6.9 worldwide every year). By comparison, on 28 March 2005, a quake of magnitude 8.7 hit Sumatra. The logarithmic scale means this quake released about 250 times more energy and it killed more than 1000 people. In November 2002, a magnitude 7.9 earthquake struck Alaska and killed no one.

The reason for the discrepancy is location. Huge earthquakes can rock the planet but if they are far from populated areas, they will cause little damage. But smaller, and especially shallow, earthquakes can cause devastation if they occur right under towns and villages. The other key factor is of course the quality of buildings – a seismologist once told me "earthquakes don't kill people – badly constructed buildings do".

I think there is an analogy with freaque waves here. If a very large freaque wave of 60 m or higher can happen, but there is no ship snarled nearby it, then there is no damages happen and no one would really care much about it. But if a minor freaque wave of a few feet high came out of nowhere that capsized a small boat full of people, that would be a dreadful tragic event nevertheless. On the other hand, every earthquake that occurs, large or small, get recorded and noted, but we still can not predict earthquake yet. Now we have no idea where or when freaque waves might happen out there and how high, and no one cares about making measurements, and there’s still this glowing talks about freaque waves prediction in a few years?!

No comments: