Crustal Structure of the Jurassic Quiet Zone in the West Pacific Ocean: Insights from 2D Multichannel Seismic Reflection Profiles

The Jurassic oceanic crust is the oldest existing oceanic crust on earth, and although distributed sparsely, carries essential information about the earth’s evolution. The area around the Pigafetta Basin in the west Pacific Ocean (also known as the Jurassic Quiet Zone, JQZ) is one of a few areas where the Jurassic oceanic crust is present. This study takes full advantage of high-resolution multichannel seismic reflection profiles in combination with bathymetry, magnetic, and gravity data from the JQZ to examine the structure, deformation, and morphology of the Jurassic oceanic crust. Our results show the following insights: 1) The Moho lies at 2–3s in two-way travel time beneath the seafloor with the segmented feature. The gaps between the Moho segments well correspond to the seamounts on the seafloor, suggesting the upward migration of magma from the mantle has interrupted the pre-existing Moho. 2) The oceanic crust is predominantly deformed by crustal-scale thrust faults, normal faults cutting through the top of basement, and vertical seismic disturbance zones in association with migration of thermal fluids. The thrust faults are locally found and interpreted as the results of tectonic inversion. 3) Seafloor morphology in the JQZ is characterized by fault scarps, fold scarps, seamounts, and small hills, indicating the occurrence of active faults. 4) The oceanic crust in the JQZ and East Pacific Rise has many structural and geometrical variations, such as the thickness of sediments, seafloor topography, basement morphology, fault size and type.