# GEOL 106 Lecture Notes - Seismogram, Seismometer, Epicenter

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23 Nov 2011
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## Document Summary

To locate the quake focus: need a minimum of 3 seismometer stations. Where do earthquakes occur: at what depth, less than 700 km, 90% are less than 100 km deep, note: radius of earth is 6370 km. How do we estimate energy released from a quake: 1. Measure the intensity: based on observed damage (eg. the mercalli scale, subjective, varies with distance from epicenter, a quantitative measure of energy released, 2. Determined from the maximum s-wave amplitude on a seismogram (corrected for distance) The lines on a skwigale is an open ended scale. we don"t know how high it could go: the largest earthquakes ever recorder are 9 on the richter scale. Quakes <2. 5 magnitude are not felt by humans. Each magnitude integer step corresponds to approx. a 30-fold difference in energy release. What do the richter numbers mean in terms of actual energy released: how would you figure that out, compare to known explosions (eg nuclear blasts)