Thursday, November 29, 2007

The fun of deep earthquakes

If you must have an earthquake go off near you, pray that it is deep! One such earthquake has just happened in the Caribbean. These earthquakes tend to be very large in terms of Magnitude (this one's an M7.3), but just a big rumbler at the surface. Old, crappy buildings may collapse, and people will feel it in high-rises far away.

In fact, this earthquake was such a good transmitter that is set off all the phony earthquake alarms in California! If you look at all the seismograms of the North American seismometers, you will see a very strong signal.

Deep earthquakes are born along the subducted oceanic crust, when it goes for it's big plate-tectonics recycling. After the crust gets crunched up and compacted, it moves along the conveyor belt to get melted. This factory belches out any waste through its chimneys conveniently disguised as the numerous volcanoes in the Caribbean.

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