ITB Lecturer Discusses Complexity of Faults in Central Sulawesi

A magnitude 6.7 earthquake that struck Central Sulawesi on June 16, 2026, has highlighted the region's complex geological fault system. Compounding the issue, different official bodies have identified varying triggers for the tremor, with the Meteorology, Climatology, and Geophysics Agency (BMKG) pointing to the Sausu Fault and the Geological Agency to the Palolo Fault.

This complexity stems from Sulawesi's tectonic history, characterized by its formation from a collection of small plates. The area hosts a significant number of faults, making it challenging to determine which are active. "Many of these plate junctions are faults," explained Astyka Pamumpuni, a geology lecturer at the Bandung Institute of Technology (ITB), on Thursday, June 18, 2026.

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Many of these plate junctions are faults.

Pamumpuni elaborated that the earthquake's occurrence in Sulawesi is influenced by the westward movement of the large Pacific Plate. This movement interacts with the Eurasian Plate, creating the Sorong Fault that extends to the Palu region. "This is what makes the Palu-Koro Fault quite large, due to the rapid plate movement," she noted, referring to one of Central Sulawesi's two main faults.

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This is what makes the Palu-Koro Fault quite large, due to the rapid plate movement.

The recent earthquake occurred east of the Palu-Koro Fault, between Palu City and the east coast of Sausu. Pamumpuni suggested this tremor resulted from pressure from eastern plates on smaller faults, including the Sausu and Palolo faults. "We cannot be certain until it is proven in the field," she stated, emphasizing the need for on-site verification.

The earthquake's impact was most severe in the Sigi Regency, resulting in three fatalities and over a hundred injuries. More than 1,600 homes and dozens of public and government buildings, including the Sigi Regent's office, sustained damage.

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We cannot be certain until it is proven in the field.