The Structure and Evolution of the Sorong Fault Zone, Indonesia using Multibeam and Seismic Datasets

The Sorong Fault Zone (SFZ) is a left-lateral strike-slip fault zone located in eastern Indonesia, extending westwards from the Bird’s Head Peninsula of West Papua towards Sulawesi. High
resolution multibeam bathymetry maps of the seafloor, onshore SRTM imagery, and a grid of 2D seismic lines were used in this study to review and interpret the structure and tectonics of the SFZ.
The multibeam data provides the first opportunity to map in detail and identify strands of the SFZ offshore in the largely submarine area between New Guinea and Sulawesi, and then link them to
onshore structures. A regional reconstruction of motions of fragments along the fault zone from 20 to 0 Ma between Borneo and New Guinea has been produced using kinematic analysis of the
structures visible in the dataset, together with geological observations in the fault zone. The fault zone trends E-W through the north of the Bird’s Head, with sinistral deformation taken
up on a number of sub-parallel strands such as the Sorong and Koor faults. Offshore of the Bird’s Head to the northwest, some strands terminate in a series of thrusts forming the Waigeo Basin fold
and thrust belt. The SFZ diverts to a WNW-ESE trending zone of faulting on its most prominent strand – the Salawati-Obi strand – west of the Bird’s Head. The Molucca-Sorong strand diverges
from the Salawati-Obi strand near the island of Kofiau and trends NW-SE, running between the islands of Obi and Halmahera, passing through Bacan. The Salawati-Obi strand diverges again at the
Sula Islands into the North and South Sula Strands before terminating in the Sula Thrust Zone to the north of Mangole and terminating in the northernmost of a series of extensional faults in the
Buru Basin to the south. The clockwise rotation of the Philippine Sea plate has controlled the formation of the Ayu Trough north of the Bird’s Head peninsula. A possible spreading centre in this region, as well as left-lateral
strike-slip motion recorded along the New Guinea Trench and the SFZ, may have contributed to the westward translation of Halmahera, the island of Obi, and the generation of the different strands of
the SFZ. The interaction of the fragments generated by the creation of this zone of faulting has implications for the formation of the Banda Arc and Sulawesi. This reconstruction will help to further
unravel the complex tectonic history of SE Asia, in particular the convoluted four-way intersection between the Philippine Sea, Australian, Caroline, and Eurasian plates.