QLg tomography in Colombia

The crustal attenuation of Lg waves in Colombia was estimated and analyzed using local seismological data from the National Seismological Network of Colombia (RSNC). The selected dataset comprises 510 crustal earthquakes with a total of 2928 ray paths. This large dataset allowed us to invert for a regional average of QLg, tomographic images for Colombia, and simultaneously, source size for each event and site term at the seismological stations. The computed regional average for QLg in the frequency band 0.5–5.0 Hz was found to agree with the previously reported values in neighboring regions. In order to resolve the lateral variation in the attenuation of Lg waves in the crust, independent tomographic inversions for 26 frequencies between 0.5 and 5.0 Hz were conducted. The resulting maps confirm that heterogeneities in the crust exist and that they are related to the large-scale tectonic features in the country. The highest attenuation in the region is linked to the presence of active volcanic arcs, where the crust is weakened by partial melting. Relatively high attenuation is also found in zones where the crust is composed of accreted oceanic rocks and in regions with near-surface low-velocity sedimentary layers.