Uncertainty analysis of 3D Quaternary geological structural model under a shallow cover, with the discrete boreholes in Yuncao map as an example

The Confidence Index of geostatistic method is used to quantitatively evaluate the uncertainty of Quaternary geological structural model that is established mainly based on discrete boreholes. The geological complexity information was obtained using trend analysis of the top surface of the target strata, and the data accuracy information was obtained according to the spatial autocorrelation of the top surface of the target stratum with semi-variance function analysis. Expert experience was also considered for comprehensively assessing the uncertainty in the form of confidence coefficient. The three-dimensional(3D)Quaternary geological structural model of the Yuncao area was taken as an example, and the elevation and Confidence Index maps of the top surfaces of Qp^1-2qy and Qp^2-3d were plotted in this study. The results show that the Confidence Index in the areas near boreholes or with dense boreholes is obviously high, and low in the areas near map edge or in stratum absence. The Confidence Index is positively correlated with borehole data accuracy, and is negatively with geological complexity. The Confidence Index provides a tool for quantitatively assessing the uncertainty of 3D Quaternary geological structural model established with discrete boreholes.