# A Fully Automatic DEXP Method for Gravity Data and Its Application on a Potash Salt Deposit
## 4 Application on Real Gravity Data
The gravity gradient zone predominantly follows a near NW trend, with the subsidiary trend in the NE and NNE direction. Near Nase and Nazhanpa, a linear structure is well developed with an NW trend, with subsidiary structures primarily developing in NE and trending NNE. The distribution of fault structure plays a significant role in the formation and occurrence of the potash salt deposit. Additionally, gravity prospecting offers distinct advantages in providing high-resolution information about the horizonal changes in the geological body. To detect the edge of the study area, we used the multidirectional standard difference method (CCMS method), which was proposed by [PERSON] et al. [40]. This algorithm exhibits notable characteristics, including simplicity and stability, effective feature identification, accurate detection of the edges of geological bodies at various depths, robust preservation of edge shape, and low sensitivity to noise. The calculated result of the CCMS method is presented in Figure 12a, while the inferred fault structure is displayed in Figure 12b. It is evident that the tectonic structure is well-developed within the study area. The NW trending faults exert significant control near Wells Jx4 and Jx5, while sub-faults are observed in close proximity to Wells Jx4 and Jx5, with a near NE trending orientation. These fault structures play a crucial role in facilitating the formation and accumulation of potash salt. Figure 10: The borehole data for Wells Jx4 and Jx5. With the analysis of known borehole data, the center depth of the Jx5 target layers is about 226.5 m, and the center depth of the Jx4 target layers is about 140.7 m.  
The imaging result of the improved DEXP method is shown in Figure 13. Figure 13b displays the combination of inferred faults and low-density rock, which is inverted using the improved DEXP method. It is evident that the location of low-density rock is significantly controlled by the faults, indicating the crucial role of fault structure functions in the  
Figure 11: **(a)** The elevation of the study area. **(b)** The residual gravity anomaly that was obtained. The study area is outlined with a white rectangle. Well Jx4 and Well Jx5 are known boreholes whose data are characterized by the potash salt deposit layers. To test the validity of the proposed method, Profile I (shown as the red line) is extracted and travels through Well Jx4 and Well Jx5, which is used for a comparison with the imaging result. The white rectangle is the range of gravity data. Figure 12: **(a)** The inversion result of the CCMS method. **(b)** The distribution of the inferred fault (shown as red line) and the base map is the residual gravity (Figure 11b). sedimentary processes. Figure 13c illustrates the combination of the residual gravity anomaly, the lower value portion of the imaging result obtained using the improved DEXP method, and the inferred faults. The lower-value part of the imaging result represents relatively low-density rock. Furthermore, Figure 13d shows the extracted Profile I result from Figure 13c. In the Profile I result, it can be inferred that the depth of the low-extreme point in Well Jx5 is approximately 235.8 m (with an explored center depth of about 226.5 m). Similarly, the depth of the low-extreme point in Well Jx4 is estimated to be around 142.3 m (with an explored center depth of 140.7 m). By comparing these depths with the explored center depth, it is observed that the deviation in Well Jx4 is 0.7 m, resulting in an error ratio of 4.2% (error ratio = error/thickness). On the other hand, the deviation in Well Jx5 is 1.6 m, leading to an error ratio of 1.8%. Considering the objective of locating the potash salt layer,  
Figure 13: The residual gravity anomaly, inferred faults, and imaging results obtained with the improved DEXP method. (**a**) The inversed result of the improved DEXP method. (**b**) The combination of the inferred faults and low-density rock.