A high-resolution broadband crustal Lg attenuation model beneath Colombia and its implication for triple-junction tectonics

The existence of a typical triple junction in Colombia is crucial for understanding plate convergence and coupling among the South American Plate, the subducting Nazca Plate, and the Caribbean Plate. However, locating this triple junction is challenging due to complex geodynamic evolution and uncertainty in the slab boundaries. Here, we developed a high-resolution Lg-wave attenuation model for Colombia and surrounding areas to constrain crustal magmatic activity, link deep processes with surface volcanism, and identify potential slab boundaries. The area encompassing Central America, western Colombia, and Ecuador exhibits strong Lg attenuation and a concentration of volcanoes, indicating thermal anomalies in the crust. In line with the velocity structure, volcanism, seismicity, and isotopic dating, the thermal anomalies associated with the subducting Nazca and Caribbean slabs suggest the presence of three subducting slabs beneath the South American Plate, with a triple junction located at approximately 7.5°N, 77°W. This research was supported by the National Natural Science Foundation of China (42430306).