The Geology of Indonesia/Major Suture

The tectonics processes in Indonesia formed major structures. The most prominent fault in the west of Indonesia is the Semangko Fault or also called the Great Sumatran Fault, a 1900 km dextral strike-slip fault along Sumatra Island. The fault offset is more than 20 km in the northern part of the island. The formation of this fault zone is related to the subduction zone in the west of Sumatra. . This great fault system is parallel to the Bukit Barisan Mountain range, which is formed by a chain of volacnoes. Palu-Koro fault is another major structural feature formed in the central part of Indonesia, located within the triple junction area between the Pacific, Indo-Australian and Eurasian plates. This fault has similar orientation as the Semangko fault, extend from Koro in central part of Sulawesi, to Palu in the west coast of Sulawesi. Left lateral displacement is more than 350 meters. The slip rate is is about 35 mm/year. This fault is extended across the Makassar strait to Mangkalihat Peninsula, East Kalimantan.

Sorong Fault is located in the eastern part of Indonesia, named after Sorong city in Papua. The fault is a major east-west -trending left-lateral fault system separating Australia from the Philippine Sea Plate and the Molucca Sea Plate. The fault zone juxtaposes Mesozoic-Tertiary continental and arc/ophiolitic rocks. Continental crust was derived from the Australian margin. Crust of Philippine Sea Plate origin has a basement of ophiolitic and/or arc origin.