Characterization and geophysical evaluation of the recent 2023 Alausí landslide in the northern Andes of Ecuador

Abstract

The province of Chimborazo located in the northern Andes of Ecuador presents many intrinsic factors, which contribute to the occurrence of mass movements, leaving in many of the cases registered damages of materials and loss of life. The recent landslide of March 26, 2023, in the Alausí canton is an event of great interest due to the magnitude of the occurred destruction and the corresponding fatalities. Therefore, there are two predominant objectives of the current study, of which the first has been to determine the most relevant characteristics of this mass movement by identifying and analyzing the geomorphology of the recorded slope movement and the lithological units involved, by field work and through geophysical surveys. Secondly, we performed a preliminary study of the possible triggers of the movement by means of the historical analysis of the precipitations during the months of January to March of the last decade and the study of the recent seismic series. However, through the obtained analysis, it is determined that the study site is composed of three distinctive lithological units. The observed mass movement is of the rotational type, as result of the intense rainfall that occurred during the first quarter of 2023, being hereby the most probable triggering factor. This corresponds to a 600% increase in the average monthly rainfall compared to the period from 2010 to 2022.