1. One or more processor-readable storage media storing computer-executable instructions for causing one or more processors to perform a method, the method comprising: receiving integrated circuit manufacturing process information and layout information of a layout design, the integrated circuit manufacturing process information comprising electrical characteristics of multi-layer substrates in or through which through-silicon vias in the layout design are to be fabricated; performing a function fitting process to generate parameters of a representation for electro-quasi-static potential Green's functions at a plurality of frequencies of interest based on the integrated circuit manufacturing process information, the representation using a summation involving Hankel functions to represent an integral involving the electro-quasi-static potential Green's functions; computing matrix elements of a matrix for each frequency in the plurality of frequencies of interest based on the generated parameters, a set of electric potential basis functions, a set of electric displacement basis functions and the layout information, the matrix being a part of a linear system that formulates a relationship of electric displacement fields and electric potentials in various regions associated with the through-silicon vias; computing admittance values associated with the through-silicon vias based on the matrix; and outputting the admittance values.