西昌地区现今地壳运动及主要断裂活动研究

doi:10.12196/j.issn.1000-3274.2020.01.005

摘要/Abstract

摘要： 利用2009—2017年GPS水平速度场和1990—2018年跨断层短水准资料, 分析西昌地区现今三维地壳活动及主要断裂的活动性。结果表明: 在西昌地区, GPS水平运动场及应变场的大小和方向发生变化。 E向运动速率由北部的平均约8 mm/a减小到南部的平均约4 mm/a; S向运动以安宁河—则木河断裂为界, 西侧点位的运动速率明显大于东侧的点位。相对华南地块的水平形变场也显示西昌地区水平运动的差异性。主应变场在西昌地区以SW—NE向拉张和NW—SE向挤压为主。大凉山次级块体东侧的张应变和压应变均大于西侧; 最大剪应变率在此次级块体以条带形式展布, 条带上的最大剪应变率大于东、西两侧; GPS水平运动速率和变形宽度相比1999—2007年资料得到的结果大, 表明安宁河—则木河断裂带处于剪切应变积累阶段, 闭锁程度有所提高。跨断层水准资料显示, 该断裂存在新的活动迹象, 应力持续积累。综合分析两种资料结果, 推测区域地震危险性将进一步增强。

关键词: 西昌地区, 水平运动, 应变积累, 断裂活动, 地震危险性

Abstract: Using the GPS horizontal velocity field from 2009 to 2017 and the short-level cross-fault data from 1990 to 2018, the current three-dimensional crustal activity and main fault activity in Xichang are analyzed. The results show that the size and direction of GPS horizontal motion field and strain field change in Xichang area. The E-direction movement rate is reduced from an average of about 8 mm/a in the north to an average of about 4 mm/a in the south; the S-direction movement is bounded by the Anning-Zemuhe fault, and the movement rate of the west side point is obvios higher than that of the east side. The horizontal deformation field of the South China block also shows the difference in horizontal movements in Xichang. The main strain field is dominated by SW-NE tensile and NW-SE extrusion in Xichang area. The tensile and compressive strains on the east side of the secondary block of the Daliangshan are larger than the west side; the maximum shear strain rate is distributed in the form of strips in the secondary block, which is larger than the east and west sides; the horizontal horizontal motion velocity is compared with the deformation width. The results obtained from 1999 to 2007 are large, indicating that the Anninghe-Zemuhe fault zone is in the stage of shear strain accumulation, and the degree of occlusion is improved. Cross-fault level data shows that there is new signs of activity in the fracture and the stress continues to accumulate. Based on a comprehensive analysis of the results of the two data, it is speculated that the regional stress continues to accumulate and the seismic risk is further enhanced.

Key words: Xichang area, Horizontal movement, Strain accumulation, Fault activity, Seismic risk

中图分类号:

P315.7

胡亚轩, 曾致, 李长军, 李煜航, 宋尚武. 西昌地区现今地壳运动及主要断裂活动研究[J]. 地震, 2020, 40(1): 62-72.

HU Ya-xuan, ZENG Zhi, LI Chang-jun, LI Yu-hang, SONG Shang-wu. Research on Present-day Crustal Deformation and Fault Activities in Xichang Area[J]. EARTHQUAKE, 2020, 40(1): 62-72.

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