Fault Patterns in the South Yellow Sea Revealed by Integrated Geophysical Observations

Abstract:

The South Yellow Sea (SYS) is located along the boundary between the North China Block (NCB) and the South China Block (SCB). Hence, studying the geologic structure of the SYS is significant for understanding the collision process between the NCB and SCB and for exploring natural resources in the region. The South Yellow Sea is composed of four main geologic units: the Qianliyan Uplift Zone, the Northern Basin, the Central Uplift Zone, and the Southern Basin. To interpret the basin structure of the SYS, the density and the basement depth were inverted using regional gravity and magnetic data. Due to the low resolution of the gravity and magnetic data, there are much uncertainties in the detail branches, distribution and mechanisms of the faults in the South Yellow Sea. In this study, we interpreted the major faults and their branches in SYS using a wide angle seismic profile data. The interpreted faults are mapped onto the gravity and magnetic maps to further constrain the interpretation of major faults. The result shows that the South Yellow Sea Basin was initiated and controlled by a serial of strike-slip faults. Those faults were generated at the time when the SCB and NCB collided with each other, and were re-activated at the time when the Pacific Plate subducted beneath the East Asia. Our approach of jointly interpreting seismic, gravity and magnetic data is applicable for better delineation of the crustal structure in other regions.