Indonesian Geological Agency Links Palu M6.7 Quake to Palolo Fault Movement

A magnitude 6.7 earthquake struck Central Sulawesi, Indonesia, on June 16, 2026, leaving a trail of destruction. Three people died, over 100 were injured, and buildings across Sigi Regency suffered extensive damage.

The Indonesian Geological Agency has concluded that the earthquake's origin lies in the movement of the Palolo Graben fault. This conclusion is supported by their analysis of aftershock distribution, surface geological conditions, observed damage patterns, and subsurface geophysics.

"Our analysis shows that tectonic activity in the Palolo Graben area is the main factor controlling this earthquake," said Lana Saria, acting head of the Geological Agency, during an online briefing on June 19, 2026. The earthquake's epicenter was located inland, approximately 42 kilometers southeast of Palu, at a depth of 10 kilometers.

Saria noted that the earthquake's parameters indicate a shallow event with significant energy release, leading to its substantial impact. She acknowledged that interpretations of the earthquake's source can vary based on analytical methods and data. However, she stated that mechanisms reported by the Meteorology, Climatology, and Geophysics Agency (BMKG), the U.S. Geological Survey (USGS), and Germany's GFZ all point to a normal fault.

This mechanism aligns with the Palolo fault, according to Saria. She contrasted this with BMKG's identification of the Sausu fault as the epicenter, which she described as a strike-slip fault, thus unrelated to the current event. As of June 18, over 150 aftershocks ranging from magnitude 2.5 to 5.1 had been recorded. Saria explained that the main shock followed by numerous aftershocks indicates complex geological conditions with varied lithology and intensive geological structures in the affected region. The soil classification in the impacted areas, ranging from very dense to soft, also influences the shaking intensity, with soft soils amplifying ground motion and increasing damage potential.

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Our analysis shows that tectonic activity in the Palolo Graben area is the main factor controlling this earthquake.