Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤  Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

Crustal earthquakes are some of the main contributors to the seismic hazard in northern South America (NoSAm). There is evidence of historical crustal events with epicenters near populated cities, such as the 1999 Mw 6.2 Coffee Region earthquake, whose damages added up to 1.9% of Colombia’s gross domestic product and reported about 1200 deaths. Because the global crustal ground-motion models (GMMs) routinely used in seismic hazard assessments of the region are biased with respect to the available ground-motion records, this article presents a regional GMM developed using local data from earthquakes in Colombia, Ecuador, and Venezuela. The filtered database contains 709 triaxial records from 56 earthquakes, recorded at 92 stations between 1994 and 2020 by the Colombian Geological Survey. The moment magnitudes of the events range between 4.5 and 6.8, with hypocentral depths ≤60 km. The model covers rupture distances ≤350 km. The model site amplification is based on a categorization approach relying on the predominant site period, identified through the horizontal-to-vertical response ratios of 5%-damped response spectra. The proposed GMM is developed as a regionalization of the global Next Generation Attenuation-West2 Project ASK14 model. Our model corrects the misfit of the ASK14 GMM with respect to the observed ground-motion data in NoSAm for moderate magnitudes and intermediate to large distances while keeping the extrapolation capabilities. The proposed GMM considers the added attenuation for ray paths crossing the volcanic arc. Analysis of the variance components allows approximating plausible reductions of the standard deviation in future nonergodic models.

This article proposes a semiempirical model to estimate seismic site effects based on a predominant-period classification scheme for application in earthquake ground-motion models (GMMs). The proposed model introduces the use of the peak amplitude of the average horizontal-to-vertical ratio of the spectral response of the site obtained from earthquake records. The site effects model is implemented within a GMM estimated using ground-motion records from northern South America. The research compares the performance of the proposed site function with other formulations based on VS30 or site predominant period. This approach yields a smaller within-event variability than alternative methodologies, providing confidence for the reliability of the proposed site classification scheme as a viable alternative for the estimation of site effects, especially for sites for which VS30 measurements are not available.

The response of mid-rise reinforced concrete (RC) buildings in Mexico City after the 2017 Puebla Earthquake is assessed through combined field and computational investigation. The Mw 7.1 earthquake damaged more than 500 buildings where most of them are classified as mid-rise RC frames with infill walls. A multinational team from Colombia, Mexico, and the United States was rapidly deployed within a week of the occurrence of the event to investigate the structural and nonstructural damage levels of over 60 RC buildings with 2–12 stories. The results of the study confirmed that older mid-rise structures with limited ductility capacity may have been shaken past their capacity. To elucidate the widespread damage in mid-rise RC framed structures, the post-earthquake reconnaissance effort is complemented with inelastic modeling and simulation of several representative RC framing systems with and without masonry infill walls. It was confirmed that the addition of non-isolated masonry infills significantly impacts the ductility capacity and increases the potential for a soft-story mechanism formation in RC frames originally analyzed and designed to be bare systems.

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