ERS120H5 Lecture 16: ERS120 - Lecture 17
23 Oct 2017
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Document Summary
Movement of tectonic plates build up elastic energy along a fault. Then frictional resistance is overcome, the accumulated energy is released as seismic waves. Before the earthquake, the seismograph is in place, ready to take measurements: there is a reference line in place above the ground, to measure with. During the earthquake, the ground and frame will both sink and rise, placing the seismograph above and below the reference line while also rotating. The time between arrival depends on distance from the focus. Surface waves arrive later, and they"re even bigger. The s-p interval increases as distance from the epicenter increases. Can be measured using the richter scale: not suitable for larger earthquakes. Can also be measured using moment magnitude (mw), which factors in: rock rigidity, displacement, rupture area, an increase of 1 in mw = 32x increase in energy released. Long-term forecasting: identify hazardous areas and probability of major quake, e. g.
