The seismic imaging is via cross-correlation between a source wavefield and a receiver wavefield. Mathematically, it can be expressed as Equation 4.
\[I(\mathbf{x}) = \sum_{i=1}^{N_s}\sum_{t_n=1}^{N_t}p_s^i(\mathbf{x}, t_n)p_r^i(\mathbf{x}, t_n)\hspace{40mm}(4)\]
where \(N_s\) is the total number of shots, \(p_s^i(\mathbf{x}, t_n)\) is a source wavefield and \(p_r^i(\mathbf{x}, t_n)\) is a receiver wavefield.