Structural deformation characteristics of active anticline and their implications for seismogeological disaster effect under compression setting in the Late Cenozoic

Abstract

Objective Thrust faults and their associated folds are important structures of continental tectonic deformation, widely distributed at plate boundaries and within plates. The activity of these thrust faults can trigger severe seismic disasters, such as the 1999 Chi-Chi earthquake in Taiwan and the 2008 Wenchuan earthquake. However, research on surface ruptures and associated disasters caused by thrust faulting is relatively limited, mainly due to the complexity of their fault propagation processes. Studying thrust faults and their associated folds could enhance the capability of seismic hazard risk assessment and better predict earthquakes and potential secondary disasters. Methods This paper first introduces the meanings of fold-related faults and fold scarps and explains the impacts of surface uplift and lateral extension deformations on topography. Taking the Tian Shan active fold zone as an example, the paper focuses on analyzing the structural characteristics and landform deformation patterns of the Hejing thrust-and-fold belt in the northern margin of the Yanchi Basin and the Mingyaole anticline in the southern piedmont of the Tian Shan. It also discusses various types of structures, such as thrust faults, fold-related faults (flexural faults, flexural slip faults, and conjugate shear faults), and their effects on landforms. Based on this, the paper explores the relationship between the growth process of active folds and the formation of seismic geological disasters. Results and Conclusion It is believed that in a compressive tectonic environment, the growth of active folds and the formation of fault-related folds cause building displacement, tilting, and damage, thereby generating geological disasters. In particular, it emphasizes that the tilting of the ground on both sides and the footwall of active anticlines during the process of crustal shortening, vertical uplift, and lateral expansion poses a threat to the safe operation of major engineering structures. Simultaneously, the bending deformation caused by regional crustal shortening presents potential seismic risks and triggers geological hazards for significant linear engineering projects spanning active anticlines, warranting attention.

Keywords

• fold-related fault
• fold scarp
• fold growth
• lateral propagation
• seismogeological disasters