## 8 Conclusions  
The initial inputs required to obtain seismic elastic design spectra are the seismic hazard maps of each country or region, with the seismic intensities determined by applying deterministic and probabilistic methods according to the earthquake records of the zones. Without these maps showing the spectral values in the rock layer as available inputs, the seismic spectra cannot be determined, which affects the design of earthquake-resistant structures and procedures. According to the Mexican, U.S., and international codes described in this review article, by obtaining the seismic elastic design spectra of common structures we can select the constant acceleration and regional spectrum criteria, offering a simple procedure without the need for specialized programs. However, these procedures apply pre-established factors related to the dynamic amplification factors of the soil, which have high and conservative values; this is a disadvantage for structures of high importance because it overestimates the spectral values, affecting the project costs. Therefore, site-specific and deterministic spectrum criteria are applied mainly to structures of high importance, due to the extensive mathematical process required to obtain the spectral acceleration, which reduces conservatism compared with the regional spectrum. The dynamic behavior of the ground is obtained by creating a 1D model of the soil layers with the aid of specialized software, showing fewer conservative values and offering good structural safety. If we compare the procedures described in the MDOC Sismo CFE 2015 and ASCE/SEI 7-16 codes, there are differences related to the initial inputs used to obtain the seismic response spectra, mainly in terms of the constant acceleration and regional spectrum criteria. First, the Mexican code used accelerations in the rock layer \(a_{0r}\) as input, provided by PRODISIS with an optimal return period. On the other hand, the U.S. code used the spectral accelerations \(S_{S}\) and \(S_{1}\) related to short and long structural periods, using an \(MCE_{R}\) with a return period of \(T_{r}=4975\) years. To obtain the soil class of the site, the Mexican  
Figure 19: Example of ADRS response spectra used on several designs. code requires the fundamental period of the soil, \(T_{s}\), with the values of \(v_{s}\) and \(H_{s}\), whereas the U.S. code required the values of \(\overline{v}_{s}\), \(\overline{N}\), and \(\overline{s}_{u}\). Both codes used different parametric factors related to the dynamic behavior of the ground, depending on the soil class. Now, for the site-specific spectrum criteria, the procedure is similar between the codes, using a series of steps to modify the response spectrum in the rock layer, obtained from simulations or real earthquakes with the dynamic properties of the soil according to the transfer function, \(F(\omega)\). Both codes offer the option to start the procedure with the response spectra in the rock layer as an input to obtain the simulated accelerograms, according to the hazard maps. The deterministic spectrum criteria offer the option to obtain response spectra in the rock layer for a specific earthquake, substituting the hazard maps provided by the codes. However, this procedure requires knowledge of the local seismicity, a proper GMPE selection according to the seismic zone, the magnitude of the selected earthquake, and the focal length between the source and the site. With the previous inputs available, both codes provide the option to apply a log-normal distribution process with 84% to obtain the deterministic spectral acceleration. The procedures provided on the Mexican, U.S., and international codes to obtain the elastic design spectrum, from the constant acceleration to site-specific criteria, require an understanding of the structural project needs, where the location, use, size, and importance are required factors for proper criteria selection.