The Caroline Ridge fault system and implications for the bending-related faulting of incoming oceanic plateaus

Abstract

The latest multichannel seismic data from the Yap subduction zone is presented to investigate the Caroline Ridge fault system, developed by faulting and bending processes within the incoming oceanic plateau. We reveal that horst and graben structures exist along the entire incoming Caroline Ridge adjacent to the trench and that pervasive bending-related faults trending ~N30°E have developed subparallel to the trench. However, the widths of the horst and graben structures decrease gradually from north to south. The two-stage ancient abyssal hill fabrics overlap the incoming Caroline Ridge. Abyssal hill faults trending ~N65°W present large trench-ridge angles (85–90°); in the southern segment, abyssal hill faults trending ~N70°E have relatively low trench-ridge angles (~35–40°). From the Caroline Ridge to the horst and graben structures, the topography decreases, and slump bodies with deformed internal reflections have developed above an irregular reflector. Little stable pelagic sediment with horizontal reflectors accumulates on the horst and graben structures, suggesting that the faulting and bending processes involve long and intense tectonic processes that affect the sedimentary environment. The sedimentary strata and fault distributions differ between the North and South Caroline Ridge, which is primarily attributable to the different rifting processes. Furthermore, we propose that N65°W-trending ancient faults sufficiently decrease the yield strength of the incoming Caroline Ridge to facilitate the bending-related faulting. During subduction, the incoming North Caroline Ridge that has a large degree of rifting and the Sorol Trough, which has a thin crust, may resist less flexural bending and generate the wide horst and graben structures. The ancient faults and rifting model of incoming oceanic plateaus play a significant role in bending-related faulting