Multiphase Tectonic Process With Slab Dynamics in the Northern East China Sea Shelf Basin

ABSTRACT The northern East China Sea Shelf Basin (ECSSB) is a structurally complex and geodynamically active region formed through interactions among the Eurasian, Pacific and Philippine Sea plates. This study reconstructs the tectonic evolution of the ECSSB through an integrated analysis of 2D/3D seismic reflection profiles and regional gravity anomalies. MS1 represents a syn‐rift stage characterised by graben and half‐graben structures bounded by NE to ENE‐trending basement‐involved normal faults. Internally, localised folding and weak angular unconformities are observed. This sequence is characterised by Palaeocene extension and differential subsidence driven by the rollback of the subducting Izanagi Plate. MS2 shows wedge‐shaped geometries and is structurally characterised by SE‐dipping reverse faults and fault‐related folds. This sequence records a kinematic reorganisation of the East Asian margin, transitioning from a rifting to a compressional regime. MS3 consists of thick sedimentary sequences bounded by an angular unconformity with the overlying sequence. This sequence exhibits a regional syncline and significant decrease in fault density. This phase reflects the transition from Pacific Plate to Philippine Sea Plate subduction, which resulted in the development of reactivated reverse faults, flower structures and synclines in the southern part of the study area. Although the MS4 sequence is generally characterised by regionally stable subsidence, it exhibits distinct evidence of fault reactivation. These features are attributed to slab tearing/detachment and horizontal slab movement beneath the East Asian margin. The gravity anomalies are different: low anomalies in the ECSSB reflect thick sedimentary accumulation, high anomalies in the Taiwan‐Sinzi Uplift and Okinawa Trough that indicate basement uplift and crustal thinning, respectively. This study provides a developed tectonic framework with sedimentary sequence to deep seated slab dynamics in the East China Sea.