利用2010—2017年跨断层近场形变观测资料,采用最小二乘法求解川滇菱形块体西侧主要活动断裂近场区域的应变参数,分析各断裂带上最大剪应变、应变率、面应变、面应变率的近场结果。结果 显示:①程海断裂剪切活动北段强于南段,张压活动在2013年前后出现转折变化,具有分段特征,北段由压性转为趋势张性、南段由张压不明显转为压性变化; ②红河断裂剪切活动中段最强、北段次之、南段最弱,面应变结果显示北、中段长期处于压性活动状态,南段目前张压活动不明显; ③曲江断裂表现为弱剪切压性累积增强的活动特征; ④石屏—建水断裂显示出弱剪切压性活动特征。综上分析认为研究区断裂活动特征表现为压性增强且剪切活动强或长期处于压性状态下的弱剪切活动的断裂存在应变积累,因此程海断裂南段、红河断裂北段、曲江、石屏—建水断裂地震危险性值得关注。
Making use of observation data of cross-fault near-field deformation monitoring from 2010 to 2017 at the west side of Sichuan-Yunnan rhombic block,we use the least square method to solve and analyze the near field parameters such as the maximum shear strain and the shear strain rate,the surface strain and the surface strain rate.The results show that:① Shearing activity of the northern section of the Chenghai fault is stronger than that of the southern section,and tension-squeezing activity has a segmental characteristics before and after 2013.The north section of the Chenghai fault changes from compressive activity to tensional activity,and the southern segment changed from weak activity to compressive activity.② The shearing activity of the Honghe fault is the strongest in the middle part,with the northern part weaker,and the southern part is the weakest.The surface strain results show that the northern and middle segments is compressive for a long time,while the current tension-squeezing of southern segment is not obvious.③ The active characteristics of the Qujiang fault appears weak shear and cumulative accumulation pressure.④ The active characteristics shows weak shear and pressure in the Shiping-Jianshui fault.In summary,it is considered that the fault activity is characterized by the existence of strain accumulation in the faults with enhanced pressure and strong shear activity and weak shear activity under long-term compressive state.Therefore,the seismic hazard is worthy of attention in faults of the southern section of the Chenghai fault,the northern section of the Honghe fault,the Qujiang fault and Shiping-Jianshui.
