Re: What type of stress is happening to cause the earthquakes in Turkey?

First, let me apologize for taking so long to respond to your question.  I 
was out of town when it arrived and just returned.

As far as earthquakes, in general, go, you can have them due to 
compression, tension, lateral motion, or a combination.  You'll see quakes 
due to compression in places like the Himalaya, where the Indian 
subcontinent is pushing into Asia and compressing the crust in the 
collision zone.  In these cases, one block of rock will ride up and over 
another.  You see this a lot in most mountain ranges because this is how 
most mountains form.

Tensional faults occur where the crust is pulling apart.  This sort of 
faulting happened, for example, Europe, Africa, and the Americas split 
apart to form the Atlantic Ocean.  Currently we see this sort of faulting 
in the Red Sea and the African Rift Valley.

Lateral movement occurs near what are called transform faults.  This is 
where one tectonic plate is moving alongside another, but the motion takes 
place in fits and starts.  We see this in California, where the 
western-most part of the state is moving northward on the Pacific Plate and 
the rest of the state is on the North American Plate.  So ground on the 
west side of the San Andreas Fault is slowly moving to the north in small 
jumps of a few meters or so at a time.

In the case of Turkey, it's in a seismically active area.  Typically, as 
you can guess from the mountains, the stress is compressional because the 
mountains are still building.

For more information about earthquakes and faulting you should try the WWW 
page of the United States Geological Survey (USGS) at http://www.usgs.gov - 
they have a lot of good information.  You can also try to contact a local 
college or university (for example, in the Boston area, MIT has some 
excellent geophysicists) and the USGS may have an office, too.