汶川地震汉源县烈度异常区地质构造背景分析

Analysis on Geological Structure Background of Hanyuan Intensity Anomalies in Wenchuan M_S8.0 Earthquake

汉源县是汶川8.0级大地震Ⅵ度区内唯一的Ⅷ度异常区,是十分典型的远震烈度异常区。本文在汉源场地条件科考工作的基础上,对其城区及周边地质构造背景条件进行了分析,内容包括区域地层发育概况、区域主要断裂及其活动性、近场断裂分布状况及其对研究区的影响以及第四纪地质地貌的形态,结果表明研究区处于大渡河与流沙河阶地交汇处,河流阶地发育,地形切割深度差异较大,地质构造条件复杂,新构造运动强烈。对汉源县城区地质构造背景进行分析是对其地震烈度异常做出科学解释的前提和基础,进一步确定烈度异常的原因,因而具有极高的科学价值和重要的工程意义。

Hanyuan County is the only Ⅷ intensity anomalies inVI region of Wenchuan Ms8.0 earthquake, which is a very typical intensity anomaly far from epicenter. In this paper, Hanyuan County and the surrounding geological structure background conditions are analyzed at the basis of our site condition-scientific investigation work in it, and the main contents are the stratigraphic development, major faults, main fault distribution of near-field and its effect on the study area as well as the Quaternary geological features of the morphology; the result indicates that the study area is at the stream terraces Interchange of Liusha River and Dadu River, fiver terrace is in development, cutting depth of the terrain is different, the conditions of the geological structure are complex, the new tectonic movement is strong. Analysis on geological structure background is the foundation and premise of making their scientific explanation to intensity anomaly, and then determining the causes of intensity anomaly, which is a very high scientific value and important engineering significance.