EESA06H3 Lecture Notes - Lecture 3: Plate Tectonics, Seismic Wave, Subduction
18 Jun 2017
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Document Summary
Earthquakes generate seismic energy, which then can be used to map earth"s deep interior. Epicenter = up at the surface where to damage occurs. Earth quakes can happen as far as 700 km down, after around 799 km, the rocks aren"t brittle, but too soft. Cascade earthquakes: earthquakes that change position along a fault in one direction. - primary waves they travel very fast (7km per second). - secondary waves they travel little less quickly (5km per second). Their velocity depends on the material they"re going through. (through a high density rock -> fast) - wave paths can be complicated; direct and refracted. - p waves arrive first, then s waves. But if the monitoring station is fairly close to the focus, then the p and s will arrive almost at the same time. We can use that gap (time lag), to measure how far away we are from the focus.
