Seismic Waves
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 projectsofme Active In SP Posts: 1,124 Joined: Jun 2010 12-10-2010, 02:40 PM   Seismic Waves.ppt (Size: 333.5 KB / Downloads: 129) Seismic Waves Topics Wave phenomenon What is a wave, types of waves Measure a wave Wave speed, period, wavelength, amplitude Wave propagations Ray path, reflection, refraction, diffraction Types of seismic waves P and S waves; body waves and surface waves Reading seismograms Identify different waves by their arrival times, amplitudes and periods. What is a Wave ? A wave is a disturbance or variation that transfers energy progressively from point to point in a medium. Examples: Sound wave: variation of pressure in the air Radio wave: variation of EM intensity Water wave: variation of water surface Seismic wave: variation of elastic deformation in rocks Note that the medium doesn’t travel along with the wave. Waves like the EM wave do not even need a medium to propagate. Wave Speed It is the speed that the wave travels. The wave speed is a material property. No matter how big the wave is, it travels at the same speed. Sound wave speed in dry air v = 331 + 0.6 T (m/s) where T is temperature in Celsius Elastic wave speeds in rocks are 1 ~ 10 km/s, depends mainly upon temperature, pressure, and composition.