龙门山构造带南段向西南延伸的遥感影像证据及地震地质意义

在系统总结活动断裂遥感影像解译标志的基础上,利用Landsat ETM、Google Earth及ASTER GDEM等影像资料,结合前人研究成果,重点分析了龙门山构造带南段主要活动断裂的空间展布及几何学与运动学特征。研究结果表明,龙门山构造带在向南延伸过程中发生了明显的断裂分散现象,整个断裂带逐渐展宽,主要包括5条断裂带且其中包含多条次级断裂,至最南端被北西向鲜水河左旋走滑断裂带阻挡。其中活动性较为明显的断裂自西向东主要有4条:泸定断裂、天全断裂、芦山断裂和大邑—名山断裂,前两者是北川—映秀断裂的南延分支,而后两者是安县—灌县断裂的南延部分。由于龙门山构造带南段的构造变形被分解至多条次级断裂上,导致单条断裂错断地表的活动迹象明显变弱,因此单条断裂的潜在发震频率和强度也将相应变小,但潜在震源区会更为分散。结合已有的地震地质资料认为,未来应注意泸定和雅安2个地区的地壳稳定性及未来强震危险性问题。

REMOTE SENSING EVIDENCE OF THE SOUTH SEGMENT OF LONGMENSHAN FAULT ZONE EXTENDING TO SOUTHWEST AND ITS SEISMIC GEOLOGICAL SIGNIFICANCE

Combining remote sensing imagery interpretation of active faults with Landsat ETM, Google Earth and ASTER GDEM image data, this paper analysed the spatial distribution and geometry and motion characteristics of the south section of Longmenshan tectonic belt. The results showed that Longmenshan tectonic belt occurred obvious fracture dispersion in the process of extending to the south. The tectonic zone gradually widened, developing 5 faults and many secondary faults. The southernmost of Longmenshan tectonic zone was stopped by Xianshuihe sinistral strike-slip fault. Activities of Luding fault, Tianquan fault, Lushan fault and Dayi-Mingshan fault are more obvious. The former two are south-extending branches of Beichuan-Yingxiu fault, the latter two are south-extending branches of Anxian-Guanxian fault. The tectonic deformation of south Longmenshan tectonic belt was dispersed to a plurality of secondary faults, resulting in surface activity signs of single fault weaken significantly. So the potential earthquake frequency and intensity of single fault will also be correspondingly smaller, but potential seismic source region will be more dispersed. According to the existing seismic geological data, we should pay attention to the crustal stability and strong earthquake risk in Ya''an and Luding areas in the future.