Fig. 9

Input model of COMMEMI 3D-2. a Two adjacent rectangular blocks (A, B) with dimensions of \(20 \times 40 \times 10\) \(\text {km}^3\) are embedded in a horizontally layered background and located at the center of the top layer. Resistivities are \(A=1\,\Omega \, \text {m}\), \(B=100\,\Omega \, \text {m}\), \(C=10\,\Omega \, \text {m}\), and \(D=0.1\,\Omega \, \text {m}\). Thickness of the first two layers is 10 km and 20 km from top to bottom. This model has overall dimensions of \(x,y\in [-40,40]\) km, and \(z\in [0,-50]\) km. Horizontal (left) and vertical (right) cross-sections. b Computational domain, including grid structure, air layer, and boundary extension zones. Horizontal (left) and vertical (right) cross-sections. Air height is set to 10 km, the spacing is \(\text{d}x=\text{d}y=\text{d}z=3\) km. The inner domain was extended 175.5 km in all directions, and the computational grid dimensions are \(x,y\in [-215.5, 213.5]\) km and \(z\in [-205.5,205.5]\) km