WaveDemo

Seismic Wave Demonstrations and Animations L. Braile, Purdue Universitybraile@purdue.edu, www.eas.purdue.edu/~braile: 

Seismic Wave Demonstrations and Animations L. Braile, Purdue University braile@purdue.edu, www.eas.purdue.edu/~braile  Copyright 2004. L. Braile. Permission granted for reproduction and use of files and animations for non-commercial uses

Slide2: 

Seismic Body Waves

Slide3: 

Seismic Surface Waves

Slide4: 

3-D Grid for Seismic Wave Animations No attenuation (decrease in amplitude with distance due to spreading out of the waves or absorption of energy by the material) dispersion (variation in velocity with frequency), or anisotropy (velocity depends on direction of propagation) is included.

Slide5: 

Compressional Wave (P-Wave) Animation Deformation propagates. Particle motion consists of alternating compression and dilation. Particle motion is parallel to the direction of propagation (longitudinal). Material returns to its original shape after wave passes.

Slide6: 

Shear Wave (S-Wave) Animation Deformation propagates. Particle motion consists of alternating transverse motion. Particle motion is perpendicular to the direction of propagation (transverse). Transverse particle motion shown here is vertical but can be in any direction. However, Earth’s layers tend to cause mostly vertical (SV; in the vertical plane) or horizontal (SH) shear motions. Material returns to its original shape after wave passes.

Slide7: 

Rayleigh Wave (R-Wave) Animation Deformation propagates. Particle motion consists of elliptical motions (generally retrograde elliptical) in the vertical plane and parallel to the direction of propagation. Amplitude decreases with depth. Material returns to its original shape after wave passes.

Slide8: 

Love Wave (L-Wave) Animation Deformation propagates. Particle motion consists of alternating transverse motions. Particle motion is horizontal and perpendicular to the direction of propagation (transverse). To aid in seeing that the particle motion is purely horizontal, focus on the Y axis (red line) as the wave propagates through it. Amplitude decreases with depth. Material returns to its original shape after wave passes.

Slide9: 

1. What seismic wave type is shown here?

Slide10: 

2. What seismic wave type is shown here?

Slide11: 

3. What seismic wave type is shown here?

Slide12: 

4. What seismic wave type is shown here?

Slide13: 

Comparison of wave animations with wave motion recorded on seismograms Map of west central South America showing historical seismicity (M6+, 1990-1999), epicenter of M6.5 earthquake off the west coast of Chile, and location of GSN seismograph station NNA (Nana, Peru)

Slide14: 

Three-component seismograms for the M6.5 west coast of Chile earthquake recorded at NNA

Slide15: 

Earth cross section and approximate ray path for direct P- and S-waves for a propagation distance of ~18 degrees

Slide16: 

Particle motion diagrams for specific wave arrivals for the NNA seismograms (arrows show approximate propagation [ray path] direction; numbers indicate successive times in the wave arrival)

Slide17: 

3-D particle motion diagram for the first P wave arrival for the NNA seismograms (arrow shows approximate propagation direction [ray path]; numbers indicate successive times in the wave arrival)

Slide18: 

For further information, see the web page: www.eas.purdue.edu/~braile/edumod/waves/WaveDemo.htm or the MS Word document: www.eas.purdue.edu/~braile/edumod/waves/WaveDemo.doc www.eas.purdue.edu/~braile  Copyright 2004. L. Braile. Permission granted for reproduction and use of files and animations for non-commercial uses