Use of macroseismic and instrumental data to reassess earthquake locations: Examples from pre-digital earthquakes in Colombia

Abstract We reconcile the instrumental locations and corresponding macroseismic data for nine earthquakes that occurred in the first half of the last century in Colombia. We use the instrumental data available thanks to the ISC-GEM Catalogue (Version 7 released in April 2020) and the macroseismic intensities from the Sismicidad Historica de Colombia database of the Servicio Geologico Colombiano. We show that in most of the cases analysed we improved the earthquake instrumental locations by using the information provided by the macroseismic intensities. Not surprisingly, the largest discrepancies between macroseismic and instrumental locations were found for earthquakes in the early years of instrumental seismology (i.e., up to the mid-1920s). Such discrepancies are likely due to the low number of instrumental observations and their accuracy, as well as the unbalanced geometry of the global network in the early years of the last century, which was characterized by a scarcity of seismic stations outside Europe.