Geological and geophysical differences between the north and south sections of the Yap trench‐arc system and their relationship with Caroline Ridge subduction

Abstract

The Yap trench‐arc system is divided into north and south sections based on the location of the Yap Trench relative to the Caroline Ridge. Based on a comprehensive analysis and interpretation of new geophysical data and global open access data, the geological and geophysical characteristics of the north and south sections of the Yap trench‐arc system are compared. High‐resolution bathymetric data reveal that the southernmost Parece Vela Basin (PVB) experienced E–W and NE–SW spreading and amagmatic extension after the seafloor spreading that occurred in the main PVB. The gravity anomalies suggest that the southern Yap Arc shows a normal volcanic arc crust, while the northern Yap Arc underwent strong tectonic erosion that may have led to the loss of volcanic arc crust. The shallow earthquakes in the northern part of the Yap subduction zone are more numerous than those in the southern part, indicating that the coupling between the overriding and subducting plates is stronger in the north than in the south. The structural belt of horsts and grabens at the outer edge of the trench and the centroid‐moment tensor mechanism of earthquakes show that the Yap Arc to the north of the Sorol Trough is under extension while the Yap Arc south of the Sorol Trough is under compression. The centroid‐moment tensor solutions in the southernmost Mariana Arc and southernmost Yap Trench show a large strike‐slip component, which is presumed to be a dynamic effect caused by the Caroline Ridge collision. The different frictional surfaces between the obducting and the subducting plates cause different subduction erosion patterns in the north and south sections of the Yap trench‐arc system. Subduction erosion to the west of the Caroline Island Ridge is mainly caused by horsts and grabens, while to the west of the West Caroline Rise, it is caused by seamounts. The subduction of the Caroline Ridge is the main reason for the obvious differences in the geological and geophysical features between the north and south sections of the Yap trench‐arc system. The collision between the Caroline Ridge and Yap Trench played an important role in the formation and evolution of the Yap trench‐arc‐basin system.