Seismic hazard estimation: directly using observations versus applying seismic hazard model

Seismic hazard evaluation for a site can be carried out based on direct observations such as ground motion records at the site or based on an adopted seismic hazard model, including the distribution of earthquake intensity, the spatio-temporal occurrence model of earthquakes in a region, and the ground motion prediction equations. The former is adequate if sufficient records at the site are available, while the latter is capable to incorporate information from similar tectonic regions. This study compares the seismic hazard estimated using these two approaches for a recording site in Mexico City. The comparison is carried out in terms of uniform hazard spectra by considering interplate earthquakes alone, inslab earthquakes alone, and both interplate and inslab earthquakes. Up to date ground motion records obtained at the site are employed for the analysis. The results showed quantitatively the differences between the uniform hazard spectrum (UHS) obtained by the two approaches and the differences between the estimated UHS and the design spectrum, which is important for seismic risk assessment and design code making. The results are also used to identify the differences between the standard deviation of the residuals for GMPEs developed using records from a single station and that obtained considering a broad network of stations.