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.

Knowledge regarding the characteristics of soils in Bogotá basin has been possible to get through previous microzonation studies. However, there is still insufficient knowledge of the crustal velocity structure of the region. Bogotá is located in a region prone to a significant seismic hazard. Historically, the city has been affected by strong earthquakes, reaching moment magnitudes greater than or equal to 7. Furthermore, the city was built on a lacustrine basin, with soft soils of considerable depth that may strongly amplify the ground motion during an earthquake. In this article, we describe the development of a first crustal structure and material properties model for the region of Bogotá, Colombia, covering an area of about 130 km by 102 km. This effort aims at constructing a realistic 3D seismic velocity model using geological and geotechnical information from several sources. Major geological units have been identified and mapped into the model. The Inverse Distance Weighted (IDW) interpolation was used to create continuous surfaces delimiting the geological units. Seismic-wave properties are assigned to any point in the domain using a location-based approach. We expect this model to be useful for a wide range of applications, including dynamic ground motion simulations and fault system modeling.

Este artículo presenta el conjunto de datos de terremotos denominado Catálogo Sísmico Integrado (CSI) para Colombia y territorios limítrofes (fronteras con Costa Rica, Ecuador, Nicaragua, Panamá, Perú y Venezuela). El CSI contiene soluciones denominadas preferidas, construidas con base en catálogos sísmicos globales y regionales. Cada solución preferida incluye las mejores alternativas disponibles para magnitud y localización, seleccionadas de entre las candidatas provenientes de los diferentes catálogos recopilados siguiendo matrices de priorización. Los eventos sísmicos que componen el CSI se encuentran en un cuadrante entre los −84° y −66° de longitud y −5° y 16° de latitud, en el sistema geográfico WGS84, y cubre el periodo desde 1610 (apoyado en catálogos de sismos históricos con magnitudes estimadas a partir de intensidades macrosísmicas) hasta el 31 de diciembre de 2020. Las soluciones preferidas incluidas en el CSI tienen valores de magnitud homogeneizados a magnitud de momento (Mw), utilizando transformaciones en los casos en donde este valor no se estimó por su fuente original, y en su lugar se calculó un tipo de magnitud diferente. Se espera que el CSI sirva como insumo o referencia para generar modelos de amenaza y caracterizar fuentes sismogénicas, puesto que busca integrar diferentes soluciones de localización y magnitud, estandarizadas a los parámetros más utilizados en la actualidad.