滇西南地区主要活动断裂的b值空间分布特征

滇西南地区地处青藏高原东南边缘, 是我国大陆构造活动强烈且强震频发地区之一.通过分析b值与地壳应力分布状态的负相关关系, 采用最大似然法对该区进行b值空间扫描, 并结合区域地震构造背景以及活动断裂特征, 分析该区b值空间分布沿各断裂带的空间差异性, 反映区内不同断裂带以及同一断裂带不同现今应力积累水平与活动习性的差异, 从而反映出地震危险性的空间差异.研究结果表明: 滇西南地区b值处于0.3~1.2之间, 平均b值为0.576, δb值为0.046;区内断裂带与断裂带不同段落的b值分布极其不均匀, 澜沧江断裂南段、怒江断裂带等断裂处于研究区低b值区域, 目前处于相对较高的应力状态, 未来发生强震的可能性较大; 而哀牢山断裂带、龙陵-瑞丽断裂带的西段和东段等断裂处于研究区高b值区域, 目前处于相对较低的应力积累水平, 未来以小震活动为主.该研究方法和结论可供工程场地地震安全性评价和地震活动性中长期预测研究时参考. 

b Values Spatial Distribution Characteristics of the Main Active Faults in Southwestern Yunnan

Southwestern Yunnan is located in the southeast edge of the Tibetan plateau, is one of strong continental tectonic activities and frequent earthquake area in our country. In this paper, based on the principle of negative correlation between regional seismic b-value and crust internal stress distribution, we made the b values map by the maximum likelihood method and combined with the feature of regional seism tectonic background and active faults, analysis spatial difference of distribution b values along the fault belt, reflect the level of stress accumulation and activity habits in the different fault belt and the same fault different section, which reflects the spatial difference of seismic risk. The research result shows that the b value of the study area is 0.3 to 1.2, the average value of b is 0.576, δb is 0.046; the distribution b value and different sections in the Fault belt and fracture belt are uneven. The southern section of the LANCANG river fault, NU river fault etc in the low b value area of the study area, it suggests that this region is at a relatively high stress state and the possibility of strong earthquake in the future. On the contrary, Ailaoshan fault belt、the eastern and western section of the Longling-Ruili fault belt etc. in the high b value area of the study area, it suggests that this region is at a relatively low stress state and the possibility of small earthquake in the next few years. The researching methods of this article and its conclusion are available for risk evaluation research and long-term seismicity prediction research as a reference.