Thursday, February 7, 2013

Faults and earthquakes!

At a rock outcrop, the main things we look for are bedding planes (that were originally flat) and faults. Faults are cracks in the rock where the rocks have moved. Huge faults can produce huge earthquakes. Little faults can help us learn about tectonic forces and buried faults that we can't access.

We were really excited to find some big faults on this trip in India. These faults cut through basalt, which is a really hard igneous rock. Igneous rock forms from magma or lava instead of sand and mud.

This fault had a layer of crushed up rock almost three feet thick. We were able to climb inside the fault zone to take our measurements!

There are three main kinds of faults: normal, reverse and strike-slip. Normal faults happen when plate tectonic forces pull apart and reverse faults happen when the forces push together. Strike-slip faults are where plates move past each other, like the San Andreas fault in California. The main fault I'm studying is a kind of reverse fault and the tectonic forces push one plate over the other.

Sometimes it can be hard to figure out which kind of fault you're looking at, so I have to make careful observations (even if that means climbing into the fault zone!)

On January 9th there was an earthquake nearby, but we didn't feel it. It was an interesting earthquake because it was really deep and east of the Dauki fault that I'm studying. Maybe the Dauki fault continues farther than everyone thought!
Here's a link to a summary of the earthquake (it has a map so you can see the earthquake location):

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