Thursday, July 16, 2009

Soft Rocks - Saviours In Earthquakes

Article

This is an interesting earthquake article. I'm still chewing over the implications. Are earthquakes started in 'soft rocks' better than the 'hard rock' variety? Is it just a matter of depth? The problem is that 'soft rock' implies lower stress drop, and for a given magnitude, it means the displacement has to be greater. This is not good.

Yet, it didn't wake up the poor schnooks that were camping right on top of it. They were probably camping on 'hard rock', which is good for earthquakes. Doesn't sound like the earthquake ruptured right beside them, or they would have had trouble finding the latrine in the morning!

So, this hard vs. soft thing has me very confused....

2 comments:

Bhuvan Chand said...

Some 80 percent of all the planet’s earthquakes occur along the rim of the Pacific Ocean, called the “Ring of Fire” because of the preponderance of volcanic activity there as well. Most earthquakes occur at fault zones, where tectonic plates—giant rock slabs that make up the Earth’s upper layer—collide or slide against each other. These impacts are usually gradual and unnoticeable on the surface; however, immense stress can build up between plates. When this stress is released quickly, it sends massive vibrations, called seismic waves, often hundreds of miles through the rock and up to the surface. Other quakes can occur far from faults zones when plates are stretched or squeezed.

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