GEOL 1 Lecture Notes - Lecture 15: Richter Magnitude Scale, Seismometer, Roman Numerals
2 Dec 2020
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P (primary) waves compressional waves moving through material, causing it to expand/contract (slinky) Move though earth to other parts of world. S (secondary, shear) waves vertical motion. Much slower, 2-3 km/s, come second to primary waves. Move through solids fine, but not liquid. Water gets out of way, the wave runs out of energy. S wave shadow zone areas on earth where s waves don"t occur, can"t get there without passing through liquid layers. L (long, surface) waves motion up/down and also side to side. Causes rolling motion, can cause a lot of damage on surface. Solo machines set up in groups of 3, set to record waves in different directions. Old fashioned machines not a needle moving up/down on paper, digital. Swinging needles needle never moves, paper/equipment moves underneath a (north/south, east/west, up/down) equipment stationary needle. Need to know where to send help. Key to finding focus is that different waves travel at different speeds.
