When using Eurocode 8 and the French codes PS92 and AFPS for seismic analysis, click Parameters to open the Spectrum Envelope dialog.
If the assumed structure site is unknown, it is possible to perform calculations taking the spectrum envelope for selected locations into consideration. Select the ground type option Envelope. Click Parameters to define which of the sites are to be considered in the spectrum envelope (for the code PS 92 / AFPS the following selection is possible: S0, S1, S2 or S3, for Eurocode 8: A, B, C, D or E).