Application of the two-station spatial autocorrelation method in engineering exploration

The use of two-station seismic records to calculate phase velocity is a very fast seismic exploration method, but its sensitivity to interference severely limits its applications in engineering. This study investigates the suppression and amplification characteristics of noise disturbances by calculating the velocity dispersion curve, using the spatial autocorrelation method. The results showed that in the first monotonic interval of the correlation coefficient, when the phase velocity with a correlation coefficient close to 1 is calculated, the disturbance of the noise is significantly amplified, and the phase velocity with a correlation coefficient of zero is suppressed. The overall relative error was suppressed in other monotonic intervals. The influence of seismic records with different noise levels and correlation coefficients of different radii on the phase velocity was analyzed as well. By combining the correlation coefficients of different radii and the zero point of the correlation coefficient, one can effectively suppress the noise disturbance, which can ensure the lateral resolution of different depths and widen the detection frequency range. Using this method, we processed the active source data of the pavement that collapsed in the cities of Sichuan province (China). We found that the velocity dispersion curves and velocity profiles obtained using a single radius were only consistent with the local results of the surface wave multichannel analysis calculated using the surface waves method. The results of the multi-radius autocorrelation coefficient combined with the zero-autocorrelation coefficient agreed well with the results of the multi-channel analysis and showed high lateral resolution.