2-D Elastic Isotropic Finite Difference Modeling Lab and Radiation Pattern

OBJECTIVE: Model radiation patterns by a 2-D Finite Difference solution to the isotropic elastic wave equation. Discover nature of radiation patterns for different types of point sources and the component you record. Monitoring of hydrofracs and EOR experiments require identification of fracture zone evolution and its nature. This understanding is assisted by identifying source mechanisms of fractures (double couple, tensile, explosive?).

PROCEDURE:

Load all files into your working directory. Important MATLAB scripts for modeling are (fdps1.m), Ricker wavelet generator (calrick.m), parameter file (param.m), and plotting (plotit.m and plt.m). ). Name each file by their names given above.

In MATLAB, type "fdps1" to generate synthetic data for a 320x120 2-layer model with a centered point source buried beneath the free sirface. Display will show you movie of snapshots of Pressure field for a line source below free surface. Examine the fdps1.m code and convince yourself that it honors the FD algorithm.

Model the radiation pattern of a double couple earthquake source. Determine the radiation pattern of the P waves and S waves. Do they agree with the theoretical prediction.

Same question as the previous one, except now replace the source with a single couple source (e.g., landlside). How does this radiation pattern compare to that of the double couple?

Insert an explosive point source that is rich in P wave arrivals and poor in S-wave arrivals. Compare this radiation pattern to that of the double couple.

Insert tensile crack source point source (two displacement sources pulling in opposite directions. Compare this radiation pattern to that of the double couple.