Ground‐Motion Prediction Model for Vertical Response Spectra from Mexican Interplate Earthquakes

Abstract

Abstract We present ground‐motion prediction equations (GMPEs) for vertical response spectra from Mexican interplate earthquakes at rock sites (National Earthquake Hazards Reduction Program B class). Two options to obtain the vertical response spectrum are presented: (1) directly from the vertical‐attenuation model and (2) by multiplying the horizontal spectral ordinates by the vertical‐to‐horizontal ratios. The equations were built as functions of magnitude and distance to the fault surface of the earthquake, using 40 interplate earthquakes. We compared our results with previous attenuation models for inslab and interplate earthquakes in Mexico, and other vertical‐attenuation models in the world. The predicted intensities from the model were found to be in broad agreement with models derived with other models worldwide. Not many vertical and/or vertical‐to‐horizontal attenuation models were found in the literature, although the vertical response of structures is used in practice and included in design codes. Nevertheless, it seems to be a trend to pay more attention to this model. There was also found to be a lack of GMPEs for vertical response spectra applicable to subduction interplate earthquakes for a large range of distances and the region under study. Therefore, an attenuation model for interplate earthquakes was developed for distances up to around 400 km and M w from ∼5 to 8. The model could be useful for probabilistic seismic‐hazard assessment and as an aid for code writers.