Ecological Indicators (Aug 2023)
Calculation of precipitation and seismicity thresholds as triggers for mass movements in the region of Bucaramanga, Colombia
Abstract
The triggers of mass movements such as rainfall and seismic activity are an important point in the evaluation of spatiotemporal or hazard scenarios since they include within the study of the susceptible or inherent elements of the terrain a temporal or frequency relationship. Being able to estimate this relationship provides a base parameter within the more global analysis that involves the understanding and planning of both natural and anthropic resources, since they have an impact on decision-making at a political and/or social level. To this end, in the present study, these triggers are correlated through the proposed methodology with the historical record of mass movements to estimate the limits or thresholds of the probability of occurrence of a mass movement. From this correlation it was established that, from the characterization of the rainfall, the defined threshold is 53 mm for 24-hour rainfalls and 158 mm for previous rainfalls, where the months of May and October are more feasible to exceed this threshold. These thresholds are defined for a Return Period (Tr) of 5 and 25 years that can change to Tr of 3 and 10 years depending on climate change conditions. At the same time, there was a considerable increase in rainfall for the station named Piedecuesta (southeast of the city of Bucaramanga), where the highest rates of IDF are also appreciated, especially for the return periods of 25, 50 and 100 years. For the earthquake trigger, a combined relationship between seismic activity and later rainfall was estimated, since no points of convergence were found between the two databases, but it was reached that magnitudes 4 Mw within the seismic productivity would generate unstable areas, as well, a high number of unstable points was evidenced for the region of the Piedecuesta station where it has the highest PGA record.
