GEOL 001 Lecture Notes - Lecture 15: Seismic Wave, Paleoseismology, Dynamo Theory
20 Dec 2020
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Document Summary
Deep-focus earthquakes occur along ocean trenches (subduction) Shallow-focus earthquakes occur along divergent and transform fault boundaries. The center of the earth is about 6400 km below us. Earth"s interior is explored by using information from seismic waves and their passage through the body of the earth. Heat inside the earth drives the core"s geodynamo and the mantle"s convection. Most of our knowledge of earth"s interior comes from the study of earthquake waves. Travel times of p (compressional) and s (shear) waves through the earth vary. Variations in the travel times correspond to changes in the materials depending on the properties of the materials encountered. The nature of seismic waves forming a more compact elastic material. Velocity depends on the density and elasticity of the material. Within a given layer, the speed generally increases with depth due to pressure. Compressional waves (p waves) are able to propagate through liquids as well. Shear waves (s waves) cannot travel through liquids.
