Asteroseismology is a very powerful technique to study the interior of pulsating stars like the ZZ Ceti white dwarfs (DAV), because the driving mechanism is strongly correlated with the chemical composition of the layers in the star. The necessary first step is the identification of the pulsation mode. In contrast to our sun most DA variables (H-rich atmospheres) have only few pulsation modes, making standard mode-identification techniques difficult or even impossible. In order to understand the exact nature of the mode excitation and to improve the identification Brickhill (1983) did semi-analytical calculations and Wu (1998) & Wu (2001) performed a pertubation analysis of the mode driving zones and the layers above. However, numerical simulations of light curves (Ising & Koester, 2001) did not confirm all results. The most important difference is that even for the fundamental mode the surface distribution of the flux amplitudes is different from the spherical harmonics of the pulsation mode in deeper layers. As a consequence normalized amplitude spectra depend not only on the mode number l but also on pulsation amplitude and inclination. Following the work of J. Ising on DAV the main goal of this research is to extend the range of effective temperatures and chemical compositions. Futhermore the effects of non-linearity and multiple pulsation frequencies on mode-identification are studied, aiming towards the comparison with observations.