Assessing the Feasibility of Detecting Water-Filled Cavities Along Seismic Reflection Profiles: A Synthetic Study

The detection of underground cavities is important for geotechnical safety, groundwater assessment, and subsurface characterization. Fluid-filled cavities in karst areas can strongly influence seismic wavefields due to the contrast between the cavity contents and the surrounding rock. Interaction between seismic waves and cavities can lead to partial trapping of energy, producing reverberations and resonant signals that extend beyond the primary arrivals and appear as characteristic spectral peaks in the frequency domain.

In this study, we investigate the potential of seismic reflection data to identify deep (200m-800m) water-filled cavities (conduits) based on these characteristic responses observed along a seismic profile. Numerical simulations of seismic wave propagation are used to examine the development of cavity-induced resonances and their sensitivity to cavity properties and subsurface conditions. The results indicate that although cavity-induced resonance signatures are strongest at traces located directly above the cavity, they can still be used to determine the lateral position of the cavity along a seismic profile. We are using these numerical studies as a prelude to investigating deep ground water resources in Ireland’s extensive limestones, many of which exhibit karstification. In particular, we are developing spectral and other templates based on numerical simulations for expected deep conduit structures. These templates will be matched with real observations by re-examining existing deep reflection seismic data bases, in the search for deep water-bearing karst structures.