2-D Elastic Isotropic Finite Difference Modeling Lab and Analysis of PSV Reflections

OBJECTIVE: Model elastic data by a 2-D Finite Difference solution to the isotropic elastic wave equation. Discover nature of PS, SS, PS, PP reflections associated with different types of point sources and the component you record.

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.

Construct a 2-layer model where the PP, PS, SS, reflections can be identified in shot gather (each one will have a different moveout velocity). Point out these arivals in horizontal and vertical component seismograms. Show seismograms and identify these arrivals and explain your reasoning. Perhaps show snapshots. Explain any switching of polarity in horizontal records across on either side of the center of the shot record.

Same question as the previous one, except now replace the vertical particle velocity source with a horizontal particle velocity source. Explain the polarity behavior of the vertical and horizontal particle velocity seismograms.

Insert an explosive point source that is rich in P wave arrivals and poor in S-wave arrivals. Show results and explain your reasoning.