摘要:
基于青藏高原东南缘空间数据库及系统建立成果的基础上，综合整理青藏高原东南缘地区的1980—2013年地震信息、地震地质资料及国家基础地理信息，通过Arcgis软件及其脚本编写应用，利用空间模型初步实现了区域内1980—2013年地震活动信息的地统计分析。依据区域地震b值与地壳内部应力分布状态的负相关原理，利用b值进行大面积空间与时间扫描方法对青藏高原东南缘当前应力分布特点进行研究。以2°×2°为单元网格将研究区分为若干区，分别对其进行分时间、分单元b值计算，针对重点低b值区形成时空曲线总结大地震发生前b值曲线的时空规律，并结合之前划出的地震围空区对本区地震危险性进行综合性的中长期预测，结果表明：①汶川地震、芦山地震验证大震发生前后b值时间曲线会有水平—负增长—正增长—负增长—水平的曲线变化；②地震震级越大b值负增长的低值危险区形成时间越早，持续时间越久；③汶川大地震前川北出现大面积低b值异常区；④目前b值低值区持续时间较长的区域有：东喜马拉雅构造结、玉树—甘孜断裂、安宁河断裂—则木河断裂—鲜水河断裂—小江断裂和畹町断裂—南汀河断裂，澜沧断裂—景洪断裂与地震空区危险性预测有较多重叠。
Abstract:
Based on the establishment of the spatial databases and its system for the southeastern active tectonic zone of the Tibetan Plateau, the authors gathered earthquake information of this region from 1980 to 2013 and geohazards as well as national fundamental geographic information. Using the script writing and spatial model, the authors made a statistic analysis of the seismic activity information in this region from 1980 to 2013. Based on the principle of negative correlation between regional seismic b-value and crust internal stress distribution, the authors employed a large-area temporal-spatial scanning method based on b-value to detect current stress state of the southeastern margin of the Tibetan Plateau and, in combination with the study of active structure, to provide a clue to seismic hazard discussion. Considering the spatial difference of the seismic statistical samples, the authors divided the study area into several districts of 2°×2° grid cells, and then calculated the b-value for every unit and every year. The study focused on low b-value areas, summarized b-value temporal-spatial regularity and curves and, in combination with the former study of seismic gap, made a comprehensive mid-long-term seismic hazard prediction. Some conclusions have been reached:①Wenchuan earthquake and Lushan earthquake demonstrate that before and after the marcoquake the b-value time curve will change in order of horizontal-negative growth-positive growth-negative growth-horizontal; ② the greater the earthquake magnitude, the earlier the formation of the low value dangerous area of the b-value negative growth and the longer the duration; ③ before Wenchuan earthquake, a large area of low b-value anomaly appeared in northern Sichuan; ④ at present, the low b-value areas that have lasted for quite a long time include eastern Himalayan syntaxis, Yushu-Garze fault, Anninghe fault-Zemuhe fault-Xianshuihe-fault-Xiaojing fault and Wanting fault-Nantinghe fault, and there exists quite a lot of overlapping between Lancang fault-Jinghong fault and the predicted seismic open risk area.
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