NONDESTRUCTIVE METHOD OF DETECTING VOIDS IN UPPER SECTION OF EARTH'S CRUST Russian patent published in 2013 - IPC G01V1/00 

FIELD: radio engineering, communication.

SUBSTANCE: disclosed is a method of detecting voids in the upper section of the earth's crust, involving measurement and detection of acoustic emission on the profile in the 0.01-500 Hz frequency range, with distance between measurement points in accordance with survey scale. Profiling is performed based on natural acoustic noise. Acoustic emission is detected at each point for at least 1 minute; acoustic emission spectra are calculated in 3-10 s in multiple time intervals; the average dominant experimental spectrum Se(f) and the mean-square deviation (σ_s) of the average from the three-second spectra are found. The theoretical shape of the desired objects is set and theoretical spectra S₀(f) thereof are calculated. Resonance frequencies f_m are determined from the function Se(f); curves of intensity of the spectral function Se at resonance frequencies f_m (m=1, 2, 3) are plotted. Probable boundaries of desired objects on the profile are determined from intensity anomalies indicated by intensity of the spectral function S(f_m) on the profile exceeding its average value by +Kσ, and gradients of the function S(f_m). Preliminary dimensions and shape of said objects are determined from said boundaries and the given shape. Theoretical spectra are calculated, compared with experimental spectra; the most similar theoretical spectrum is found from the mean-square difference which does not exceed +Kσ_s (K=1-3) and the selected theoretical spectrum is identified with voids of a given shape and size.

EFFECT: detecting voids without breaching the integrity of the earth's surface.