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Propagation of a Plane Wave. Plane Wave Approximation from a Spherical Front. Displacements for P and S waves. Radial and Transverse Motion of P and S Waves. Radial and Transverse Energy. N-S and EW components have nearly equal amplitude and energy (BAZ is 323 o )
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Radial and Transverse Energy • N-S and EW components have nearly equal amplitude and energy (BAZ is 323o) • Rotate the seismogram to produce Radial and Transverse components • SKS and SKKS are P to Sv converted phases and are strongest on Radial • Sdiff has mostly Sh energy and is strongest on Transverse
Particle Motion If we plot the particle motion for the Radial versus the Transverse component The SKS phase shows the most energy on the Radial The Sdiff phase shows the most energy on the Transverse
S wave delays Note the S wave arrival times on the N-S and the E-W components. Are they coincident ? Why or Why not ? If you see a time delay or offset, what is causing this ?
Effects of Ground Composition on Seismic Energy Seismometer ground displacements from 1989 Loma Prieta earthquake Magnitude 5 aftershock Seismometer on solid bedrock (above) Seismometer on filled land (below)