Seismic and acoustic excitation for shallow void detection: Examples from a known tunnel site

Authors: BAKHTIARA, RAD - University Of Mississippi; WODAJO, LETI - University Of Mississippi; SAMAD, MD - University Of Mississippi; HICKEY, CRAIG - University Of Mississippi

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/3/2022
Publication Date: 9/1/2021
Citation: Bakhtiara, R.P., Wodajo, L., Samad, M., Hickey, C. 2021. Seismic and acoustic excitation for shallow void detection: Examples from a known tunnel site. First International Meeting for Applied Geoscience & Energy. https://doi.org/10.1190/segam2021-3595017.1.
DOI: https://doi.org/10.1190/segam2021-3595017.1

Interpretive Summary: Abstract Only

Technical Abstract: Near-surface voids, tunnels or high-contrast anomalies, if properly excited can produce scattering energy coming to the surface in the form of resonant emission. Several mechanisms for the resonant energy observed in the data are proposed in the literature; acoustics modes in the void, circumferential waves at the void/tunnel interface, and waves trapped within the overburden. In this work, we focus on the effect of acoustic modes in the air-filled void and report insights for data collected inside and outside of a buried pipe. The hypothesis is that an incoming seismic wave excites an acoustic resonance in the pipe which radiates energy back to the surface. Accordingly, we performed several experiments with different sources and sensors placed inside and outside of the pipe, and compare their frequency spectra with theoretical acoustic modes. The test results confirmed that the acoustic modes of the pipe account for the frequency spectra of the surface measurements. The multichannel active test also reveals that the acoustic modes of the pipe can appear in time domain and spectral domain and can be helpful in detection of the pipe.