Eastern Frontal Fault System  The Eastern Frontal Fault System () is a megaregional system of oblique and thrust faults cross-cutting Colombia from Ecuador in the south to Venezuela in the north. The system from south to north covers ten out of 32 departments of Colombia; Nariño, Putumayo, Cauca, Huila, Caquetá, Cundinamarca, Meta, Boyacá, Casanare and Arauca. The Eastern Frontal Fault System underlies and affects the capitals of Putumayo, Mocoa, Caquetá, Florencia, Meta, Villavicencio and Casanare, Yopal. The fault system has a total length of with a cumulative length of the faults of and runs along an average northeast to southwest strike of 042.1 ± 19 bordering and crossing the Eastern Ranges of the Colombian Andes. The fault system forms the boundary between the North Andes microplate and the South American Plate. Several segments of the fault system are active, with major earthquakes occurring in historical times. The 1827 Timaná (Mw 7.7), 1834 Sibundoy (Mw 7.0), 1917 Sumapaz (Mw 7.3), 1967 Neiva (Mw 7.2), 1995 Tauramena (Mw 6.5) and 2008 El Calvario earthquakes (Mw 5.6) are associated with movement of the fault system. The fault system is named after the Eastern Ranges, forming the front with the Llanos and Caguán-Putumayo Basins. The Eastern Frontal Fault System is one of the most active and continuous fault systems in Colombia. Several names have been given to it according to where it has been studied along its length. Local common fault names or "sections" from north to south are the Guaicáramo, Yopal, San José, Servitá-Santa Maria, Guayuriba, Algeciras, Mocoa, Florencia and Afiladores Faults. Other less common names include the Pajarito, Colepato, Acacías, and Colonia Faults. The fault system is probably an extension of the Boconó Fault and associated faults of the Mérida Andes in Venezuela and likely continues south as a dextral fault in the Republic of Ecuador. The Eastern Frontal Fault System is the main fault system bounding the Andean Ranges in the west and the lowlands or "Llanos Orientales" plains in the east.