タイトル:

Tectonic Setting, Historical Subduction Earthquakes, and the 10 August 2026 Mw 7.4 Earthquake in the Northern Colombian Andes

要旨:

Abstract: A strong Mw 7.4 earthquake struck Colombia on August 10, 2026. The earthquake was widely felt across the country, with a reported maximum peak ground acceleration (PGA) of approximately 500 cm/s². To date, 331 fatalities have been reported, together with widespread structural damage across four major cities in the affected region. Approximately 36,226 buildings and dwellings were reported to have collapsed, including hospitals and schools, while extensive damage to roads, airports, and other critical infrastructure was also documented. In this talk, I will review the tectonic setting of northwestern South America and the Caribbean region, with particular emphasis on the complex geometry of the subducting plates beneath the Northern Andes as revealed by seismic tomography studies, and discuss its relationship to the occurrence of the 2026 Mw 7.4 Colombia earthquake. I will also present preliminary observations on the source characteristics of the earthquake based on currently available regional seismic data. Finally, I will summarize my previous work on the source process of the 1906 Colombia–Ecuador earthquake, the largest historical subduction megathrust earthquake known to have occurred in the region, and discuss its relevance to this regional seismo-tectonic setting.