higher order modes while using 2D axisymmetric model

If a 2D axisymmetric model is used to simulate the behavior of CMUT, then the FFT of the surface pressure is calculated after applying a ricker wavelet. Will we be able to detect the frequency of the 2nd and 3rd mode using the FFT of the surface pressure?

If yes, then how did this happen while the axisymmetric model assumes that the left and right halves of the membrane will go up and down together?. For example, for the second mode, half of the membrane is up while the other half is down.