Shear-Wave Seismic Reflection Exploration for Cavities and Tunnels. Volume 2. Appendices.

摘要

A theoretical analysis of horizontally polarized shear (SH) waves was performed to determine the seismic reflection characteristics and practical seismic frequency for detecting cylindrical cavities representative of man-made tunnels. The analytical model consists of an SH-wave line source in an absorptive layered half-space containing a cylindrical cavity in a high-quality bedrock underlying a lossy low-velocity surface layer. Seismic wave scattering patterns of synthetic reflection seismograms were computed to illustrate the reflection response of SH waves polarized parallel to the cavity axis. The influence of the lossy surface layer on the reflected SH waves was found to be significant enough to require the use of subsurface-coupled source and detectors for practical detection of the cavity. Based upon these analytical model results, technical specifications were developed for a high-resolution SH-wave seismic exploration system designed specifically for search and detection of tunnels.