Earthquake

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Seismic waves – p 529 ,[object Object],[object Object],[object Object],[object Object]

Body waves ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Smaller amplitude than surface (L) waves, but faster, P arrives first P and S waves

Two Types of Surface Waves Most of the destruction Larger amplitude than body waves

Why do P waves reach stations before S? ,[object Object]

Surface waves ,[object Object],[object Object],[object Object]

Seismology ,[object Object],[object Object]

A seismograph designed to record vertical ground motion The heavy mass doesn’t move much The drum moves

Lateral Movement Detector In reality, copper wire coils move around magnets, generating current which is recorded.

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Earthquake focus and epicenter

Note how much bigger the surface waves are Body Waves Delay between P and S arrivals gives distance to epicenter

Graph to find distance to epicenter

Epicenter located using three seismographs

Locations of earthquakes from 1980 to 1990 Broad bands are subduction zone earthquakes, narrow are MOR 80% of seismic energy around Pacific Rim

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