The Role of Sumatera Fault Structures in Appearance of Geothermal Features at Cubadak Area, West Sumatera, Indonesia

Abstract

The Cubadak geothermal area is located in the great Sumatra fault zone. It is important to understand characteristics of this fault zone in connection with the geothermal area.
Geothermal features of Cubadak consist of hotsprings situated at Cubadak and Sawah Mudik with temperatures between 37.10C – 74.80C. The appearance of Cubadak hotspring is controlled by the Cubadak northwest-southeast trending fault. The Sawah Mudik hot spring is controlled by the Botung southwest-northeast trending fault. These structures truncate reservoir rocks underground and enable trapped hydrothermal fluids to flow to the surface along the fractures.
The structures in the Cubadak geothermal area are part of the Sumatera fault zone that spreads along Sumatera Island from Semangko Gulf at the south to Aceh at the north. The fault is still active, the subduction zone along west coast of Sumatera Island is a result of stress caused by the convergence of the Indian-Australian plate and the Eurasian plate. As result of the motion of this structural system, the depression (graben) in several locations occurs especially in en-echelon truncation, is the result of extensional forces in this fault system. Cubadak geothermal area is developed at a depression zone which has a northwest-southeast trending fault structure boundary. This structural zone is facilitating the appearance of geothermal features at Cubadak area and has contributed to the formation of this geothermal system.