Correlation of the backscatter analysis of surface waves method (BASW) for anomaly detection

• DOI: 10.1190/segam2014-1684.1
• Publication Date: 2014-08-05T22:07:51Z
• Authors: J. Tyler Schwenk*; Steven D. Sloan; Richard D. Miller; Julian Ivanov
• Keywords: 01 natural sciences; 0105 earth and related environmental sciences

We use the multichannel analysis of surface waves (MASW) approach to study Rayleigh waves and the backscatter analysis of surface waves (BASW) to detect anomalies in the subsurface. Waves incident upon these discontinuities generate diffracted, reflected, or ‘backscattered’ waves. F-k filtering enhances backscattered energy, while dynamic linear moveout corrections and a common receiver stack place the locus of these events at time zero. Separate moveout functions are designed around the fundamental and higher-mode dispersion trends. Synthetic data demonstrates that both velocity corrections result in proper location of a subsurface air-filled void. Correlation of the two moved-out gathers further constrained the lateral position of the void. This added localization and use of higher-mode dispersion is seen as the major discovery of this research. These conclusions were further tested, and shown repeatable, across several field data sets of known tunnel sites. Our correlation technique allows greater interpretability and localization of anomalies in realworld scenarios. We suggest the optimized workflow of the BASW method for future anomaly-detection applications.