Fig. 8

Model of a checkerboard structure with resistivities of 10 and 100 \(\Omega \,{\text {m}}\) and a size of 80 km \(\times\) 80 km embedded in the lower crust layer (from the depth of 14.8 to 33.3 km of the layered-earth model shown in Fig. 2a). An array of 25 irregularly distributed MT stations (crosses) covers the area of interest, which is 160 km \(\times\) 160 km (dashed frame). Here, one MT station represents an area of 32 \(\times\) 32 km (dash-dotted frames)