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<p>The southeastern margin of the Tibetan Plateau lies within the oblique convergence zone of the India-Eurasia collision. Since the Cenozoic, this region has experienced intense crust-mantle interactions, active tectono-magmatic processes, and complex focal mechanisms, reflecting a crustal structure with pronounced vertical layering and lateral segmentation. To better understand the regional stress regime and fault activity, we compiled a comprehensive database of focal mechanism solutions for the southeastern Tibetan Plateau. We collected and integrated earthquake data from 1950 to 2023 across the Sichuan-Yunnan region and adjacent areas. After data cleaning and integration, a database of 9902 high-quality focal mechanism solutions was established. Using a damped stress inversion method, we derived regional stress field models on 1°×1° and 0.2°×0.2° grids. The results reveal that: (1) focal mechanism types exhibit significant spatial heterogeneity; strike-slip events dominate the region, thrust events concentrate along the Longmenshan fault zone, and normal faulting prevails along the western boundary of the Sichuan-Yunnan block. (2) The large-scale stress field shows a systematic clockwise rotation of the maximum compressive stress axis (<i>σ</i><sub>1</sub>) from north to south, consistent with the far-field effect of the ongoing India-Eurasia collision. (3) The high-resolution results reveal multi-scale stress variations, with strong horizontal continuity of <i>σ</i><sub>1</sub> across the plateau, supporting a long-term stable compressional regime. In contrast, higher three-dimensional complexity occurs along the block boundaries and southern Yunnan, particularly across the Lijiang-Xiaojinhe fault, where a clear north-south stress gradient is observed. This study provides the first systematic stress field characterization based on a unified focal mechanism database for the southeastern Tibetan Plateau, offering refined constraints on crustal deformation and insights into the geodynamic processes governing continental earthquake generation.</p>

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Compilation of a focal mechanism solution database and investigation of the regional crustal stress field in the southeastern margin of the Tibetan Plateau

  • 期刊论文

  • 发表日期：

    2026年2月5日

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  • Bocong Li,
  • Xiaohui He,
  • Yipeng Zhang,
  • Yang Wang,
  • Peizhen Zhang

摘要

The southeastern margin of the Tibetan Plateau lies within the oblique convergence zone of the India-Eurasia collision. Since the Cenozoic, this region has experienced intense crust-mantle interactions, active tectono-magmatic processes, and complex focal mechanisms, reflecting a crustal structure with pronounced vertical layering and lateral segmentation. To better understand the regional stress regime and fault activity, we compiled a comprehensive database of focal mechanism solutions for the southeastern Tibetan Plateau. We collected and integrated earthquake data from 1950 to 2023 across the Sichuan-Yunnan region and adjacent areas. After data cleaning and integration, a database of 9902 high-quality focal mechanism solutions was established. Using a damped stress inversion method, we derived regional stress field models on 1°×1° and 0.2°×0.2° grids. The results reveal that: (1) focal mechanism types exhibit significant spatial heterogeneity; strike-slip events dominate the region, thrust events concentrate along the Longmenshan fault zone, and normal faulting prevails along the western boundary of the Sichuan-Yunnan block. (2) The large-scale stress field shows a systematic clockwise rotation of the maximum compressive stress axis (σ1) from north to south, consistent with the far-field effect of the ongoing India-Eurasia collision. (3) The high-resolution results reveal multi-scale stress variations, with strong horizontal continuity of σ1 across the plateau, supporting a long-term stable compressional regime. In contrast, higher three-dimensional complexity occurs along the block boundaries and southern Yunnan, particularly across the Lijiang-Xiaojinhe fault, where a clear north-south stress gradient is observed. This study provides the first systematic stress field characterization based on a unified focal mechanism database for the southeastern Tibetan Plateau, offering refined constraints on crustal deformation and insights into the geodynamic processes governing continental earthquake generation.