Control of bedrock geology on active structural deformation revealed by changes in geomorphic parameters: A case study of the Fodongmiao-Hongyazi Frontal Thrust, NE Tibet

Abstract

Objective Widely distributed active faults are natural carriers that produce surface-rupture events; multidisciplinary observations have revealed that geometric changes in active faults significantly influence surface-rupture development. However, previous studies on the interaction between the geometric characteristics of active faults and the underlying rock geology have been relatively limited and only confined to observing high-temperature and high-pressure experiments. Methods With the development of high-resolution geographic technology and quantitative research methods for active faults, it is now possible to finely characterize the geometric structure of large-scale faults and recognize multiparameter displaced landform characteristics. In this study, we utilized high-resolution topographic data (0.5 m) from the Fodongmiao-Hongyazi Frontal thrust (FFT) on the northeastern margin of the Tibetan Plateau, spanning approximately 120 km in length to identify and compare the parameters and characteristics of the faulted landform with the underlying bedrock geology. Result The research results indicate that the geometric characteristics of the fault are segmented and synchronized with the geological background of the bedrock. The shallow geometric structures of the eastern and western sections of the FFT are relatively simple and continuous, and the changes in parameters such as the strike, roughness, and deformation zone width of the fault are relatively small. The fault's geometric structure was rougher in the middle section of the fault, where Silurian granite is located, and the shallow deformation zone was broader than that in the eastern and western segments. The step-width distribution also varied more drastically along the fault. Conclusion This study revealed a significant correspondence between faulted landform parameter changes, the boundary of fault segments, and zones of vertical separation attenuation. Additionally, this study suggests that bedrock geology may exert substantial control over the shallow structural deformation of thrust faults. Significance The potential impact of the underlying geology should be considered for thrust faults and when analyzing seismic hazards related to active faults.

Keywords

• active fault
• faulted landform
• bedrock geology
• structural deformation