A rational delineation method for active land blocks on the southeastern margin of the Tibetan Plateau based on high-precision GNSS horizontal velocity fields

Abstract

As one of the most geologically active regions on Earth, accurate delineation of active land blocks and analysis of crustal deformation characteristics in the southeastern margin of the Tibetan Plateau are crucial for understanding regional tectonic movements and assessing seismic hazards. Current studies in this region are limited and predominantly rely on single clustering methods. In this study, we proposed a general pipeline for active block delineation, which aggregated three clustering methods (K-means clustering, hierarchical clustering (HC), and density peak clustering (DPC)) to cluster the GNSS horizontal velocity field sites in the southeast margin of the Tibetan Plateau, and assessed the outcomes using the Davies–Bouldin Index (DBI) and Silhouette Coefficient to determine the optimal result. Subsequently, we calculated strain field parameters using GNSS horizontal velocity field data and analyzed seismic hazard combining historical earthquake data. By considering the stress and activity of fault zones, we refined the boundaries of active blocks and verified the reasonableness of the division. Finally, we divided the southeastern margin of the Tibetan Plateau into six land blocks: Bayan Kola, Qiangtang, South China, Southwest Yunnan, North Chuandian Subblock and South Chuandian Subblock. Analysis of strain field parameters revealed that the region is predominantly dilatational, transitioning from compressive to extensional states from west to east. The active zones of plate motion are mainly concentrated around specific fault zones around the Sichuan–Yunnan rhombic massif. Furthermore, we validated the generalization of the proposed pipeline in the other region, namely the Kazakhstan-Tienshan region. The clustering results were also consistent with the geologically determined block delineation model.

Keywords

• GNSS
• Southeastern margin of the Tibetan Plateau
• Active land block delineation
• Cluster analysis
• Crustal strain rate