Macroseismic and seismotectonic analysis of the Mw 6.1 August 17, 2023 earthquake in the central region of Colombia

Abstract

This study conducts a complementary analysis of instrumental and macroseismic data regarding the August 17, 2023, earthquake in the central region of Colombia. This event is part of a historical earthquake sequence in the region, with an intensity higher than VII EMS‑98, which has caused considerable material damage in the area. This earthquake had a magnitude of 6.1 Mw. The application of the attenuation model calibrated in magnitude Mw and the BW97 method allows for precise modeling of the location and magnitude from macroseismic data within an acceptable margin of uncertainty for both magnitudes (Mw±0.2) and location (±13 km). Using valid empirical regressions, we determine the parameters of the seismic focus size: horizontal extension L = 9.62 km, vertical extension lz = 15.76 km, rupture area A = 97.3 km2 , and deformed volume V = 1533.45 km3. Within the first five days, at least 90 aftershocks were located by the Red Sismológica Nacional de Colombia (RSNC), supporting the source-area geometry inferred in this study. With these parameters and applying Kostrov’s model to the seismic flow of the rock mass, it was found that the maximum compressional strain rate is ε̇yy=1.22 x 10-6 yr-1, which is produced at an average velocity of 11.7 in the E-W direction.