Thursday, April 8, 2010

Earthquakes on the rise in 2010?

There's no news like the bad news, and earthquakes surely fall into that category. And so the news media world over has been reporting earthquakes like there was no tomorrow. Is it really that bad? Has the earth started shaking a little too frequently to be cause for concern?

The answers to that line of questioning is overwhelmingly NO. There has been no increase in either the frequency  or the magnitude of earthquakes. The earth is behaving in it's old pattern. The earth consists of seven major and seven minor plates. These plates consist of entire continent in some cases to entire water bodies, or a part of both. And all these plates have been in motion since time immemorial ( Thanks to wagner for pointing this out.). So it is natural that when plates move they interact in any of the following three ways:

1. They drift apart from each other allowing the lava or magma from the depths below to come up. They are very stable in the sense that they do not lead to any  earth tremors, just slow upwelling of lavas. This is pretty commonplace in Iceland. And these plate boundaries are called divergent plate boundaries.

2. They slide past each other leading to faults. Also not dangerous ( in terms of EQ's)

3. And the final one is convergent plate boundaries wherein two plates collide face to face ( ah don't take it too literally). This is the reason for so many violent shakings of  the earth. When two plates collide something has to give. [ Himalayas are the creation of one such plate collision. The highest mountains in the world are remnants of  some river valley propped up by the collision] The denser of the two plates subducts beneath the lesser denser plate and the plate boundaries experience incidence of vulcanism and EQ's.

The pacific ring of fire is one such hot zone. It accounts for 90% of all EQ's encountered annually. And we record thousands of EQ's every year.Let’s take a look at how many earthquakes occur each year on average. The USGS has a fascinating page of earthquake facts and statistics, with the following table:



MagnitudeAverage Annually
8 and higher1 ¹
7 – 7.917 ²
6 – 6.9134 ²
5 – 5.91319 ²
4 – 4.913,000
(estimated)
3 – 3.9130,000
(estimated)
2 – 2.91,300,000
(estimated)
¹ Based on observations since 1900.

² Based on observations since 1990.

So it seems that the EQ's are commonplace after all. It is only due to the widely networked world that EQ's are getting published more regularly and we have started noticing them. When we see the news of Haiti, Chile and California earthquakes at a frequent interval we tend to draw associations where none exist. It is all a part of our psyche- where we try to make meaning of the world by some simple rule of thumb. We read more about the EQ's so they must be happening more often. Alas the real world is more complex and more random. [ Despite all the progress made by science we can't still predict when and where will an EQ occur. It is still in the realms of psychics, fortune tellers and animals.]

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