oa Optimization of seismic data processing flow for tunnel detection using energy spectrum and stacking spectral energy peaks of overlapping arrays

Analyses of seismic data demonstrate increasing acoustic energy recorded above an<br>underground tunnel. This is attributed to internal reverberations within the tunnel,<br>reflection (backscattering), and wave conversion. Soil heterogeneity, changes in<br>geophone-to-ground coupling and the shape of the generated signal introduce fluctuations<br>into the trace spectrum.