CompuServe Messages

I am no geophysicist. However, I know solid state physics fairly well. }iSome of your reasoning is based, it appears, on the presumption that straight line cracks and defaults only occur it rapid, catastrophic events. Not true. The reason straight line defects occur is because they relieve stress most efficiently, whether or not the motion is fast or slow. When mud dries, the cracks are straight even though that is a slow process. Experiment, try to attach an adhesive label to a small ball whose diameter is about the size of the adhesive label. Try to attach it so that every little bit of area on the label is in contact with the ball. You will see wrinkles, straight line folds, and other shapes you say are impossible for a solid. Try to flatten these folds with a hammer. That is analogous to the catastrophic event you feel took place. Doesn't solve the problem, does it? In the region of the subduction zone, the stress is relieved. Cracks, straight line cracks, do that. Of course that region is almost crack free other than the big one. The two models you claim contradict don't. One is an approximation of the other. If you have a region with many pieces moving around, the average motion can be simple. Just a scaling proble,m. The region areas move without cracking is because material is sinking, and the big crack (the subduction zone) relieves the stress. What do you mean britle? Do you mean the shear strength of the material is greater than all the other forces? Not on this distance scale. Even the empire state building needed steel girders because stone wasn't "brittle" or strong enough to support it. These plates are much larger. I don't know GPS itself, but workers claim it can have a resolution in centimeters under the right conditions. My knowledge of optical interferometry, a small scale version of the same thing, suggests that is plausible. Optical interferometry can measure a 1 micron displacement between two object 1 meter away. Or more. On what do you base the "fact" that GPS "can't." The GPS method is improving, so you may not be able to make that claim forever, it is questionable now. Furthermore, the forces for subduction are qualitatively known. What is the energy source for your great catastrophe? From previous discussions, I think your answer could be very interesting but not what I would call science. Anyway, thank y~rou for making me }iresearch these things. I find tha{_t thesis particularly good reading.