Analytical and semi-analytical physical models for MEMS are derived from nonlinear mechanics. By taking into account system characteristics and assumptions, system identification enables the derivation of a mathematical model that is tailored to the effect and the MEMS under analysis. Such an adapted model can successfully emulate and explain the nonlinear dynamics of individual MEMS, including resonant actuation of parasitic modes. The performed analyses also confirm that small deviations in the mode spectrum between devices influence the occurrence of nonlinear effects.