Understanding Earthquakes: Magnitude and Intensity, Slides of Geology

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Depth distribution of earthquakes

Earthquake size

1) How damaging is an earthquake: perception at

a given location -> Intensity

2) Energy released in earthquakes:

 Magnitude

Shaking depends on distance from rupture but also on the nature of the ground

Shaking intensity geology Dark color: hard rock Yellow/pink: filled land or recent alluvium Brown: strongest shaking Blue->green->pink->yellow

Wood Anderson seismometer Rotation of a small inertial mass C fixed on thin wire T under tension damped by magnets M Light beam reflected off Mirror attached to the mass writes on photographic paper

1- Measure S-P time-> distance 2- measure amplitude in mm on Wood-Anderson seismometer 3 – Draw line between the two points to obtain magnitude Richter Magnitude