Mapping structural geometry and tectonics of the continental margin of Vietnam and adjacent areas using an enhanced horizontal gradient of gravity data

Abstract

The exploration of hidden structures beneath complex tectonic regions using potential field edge detection techniques poses a significant challenge. Traditional edge enhancement methods encounter inherent limitations, such as generating low-resolution outcomes or heavily depending on source depth. To overcome these challenges, we introduced an innovative edge detector called the Enhanced Horizontal Gradient (EHG). Through thorough testing on synthetic models (both 2D and 3D), we evaluated its performance against other conventional edge enhancement techniques. Our results demonstrate that the proposed detector effectively generates clear signals along source boundaries, minimizes the introduction of false edges, and operates independently of source depth. Applying the EHG method to Bouguer gravity anomalies, in conjunction with prominent tectonic faults, suture zones, mantle Bouguer anomalies, and Moho structure, provides substantial insights into comprehending the gravity characteristics of the continental margin of Vietnam and adjacent areas. Key findings from our research encompass the identification of discontinuities in the Red River Fault Zone, the absence of the Tam Ky-Phuoc Son (TK-PS) fault, the mapping of the extension of the magmatic zone in the oceanic region toward the northeast part of the Phu Khanh Basin, and a noticeable shift in gravity trends from NNE-SSW in the northeastern region of the East Vietnam Sea (EVS) to NNW-SSE direction. Moreover, the Moho depth obtained from gravity inversion, ranging from 7 to 54 km in the study area, closely corresponds with the intricate tectonics, offering conclusive evidence of a mechanism involving the flow of crustal magmatic material and associated uplift. In conclusion, our study suggests that interactions among tectonic plates likely play a role in shaping complex tectonic settings and the underlying uplift mechanism, ultimately influencing changes in bathymetry and seafloor structure.