3. Note: at this point, the wave hits an “edge” from it’s perspective. This is where the “diffracted” term comes from

6. Instrument response?

10. Seismic wave velocities Wave equation: –Part 1: Force = stress x area –Part 2: Force = mass x acceleration Also need: –Hooke’s law: F = -k x Deep breath (lower stress)…..

11. Deriving wave equation 1.Go over some tools 2.Relate stress and displacement 3.Simplify as much as possible 4.Substitute into F=ma equation 5.Apply some vector identities 6.Show that there are only two solutions, which have the velocities of the P- and S- waves

12. Stress & Strain Stress –Force/unit area Strain (1-dimension) –Here =  L/L –Finite strain Whole history >few % Shape/relationships change –Infinitesimal strain Less than few % Allows some simplifications (L’-L)/L =  L/L =  xx =du x /dx

14. Vector fields Divergence of a vector field: –No rotation –Just volume change –Which body wave?

15. Vector fields Curl: –No volume change –Just rotation –Which body wave?