The transition from a passive margin to a subduction zone is a key process in plate tectonics. However, our understanding of the dynamic mechanism behind this process remains ambiguous. The North Sulawesi subduction zone provides unique opportunities to study this phenomenon, since it is a young subduction zone (approximately 5 million years old) without any corresponding arc volcano. 

To investigate this, a research team led by Prof HAO Tianyao from IGG, in collaboration with Prof. Nick Rawlinson and Dr. LYU ChuanChuan from the University of Cambridge, along with Indonesian scientists led by Prof. Sri Widiyantoro from Institut Teknologi Bandung, conducted the deployment and recovery of Ocean Bottom Seismometers (OBS) in 2020 and 2021 respectively. The dataset can be used for earthquake seismology and geophysical dynamic simulations. 

The researchers found that the initial subduction mechanism of Sulawesi is dominated by external forces, suggesting it may be a case of subduction polarity reversal. It appears that shallow earthquakes are largely controlled by dehydration, and that little water reaches the mantle wedge, resulting in a lack of arc magmatism. These findings have been published in GRL, Tectonophysics, and JGR. 

Researchers from China, UK and Indonesia jointly deployed OBSs in the Celebes Sea and Makassar Strait. (Image by HAO's group)