海原地区黄土的微观结构及地脉动特征分析

Microstructure and Microtremor Characteristics of Loess in Haiyuan Area

摘要:

1920年8.5级地震诱发了大量的黄土滑坡，对研究黄土地区的滑坡灾害、土层地脉动特征分析具有重要意义。基于高精度电子扫描显微镜（SEM）分析发现海原地震现场表层黄土为架空孔隙弱胶结微观结构，且该黄土是以粉粒为主的低黏性粉土，有震陷和地震滑坡的高风险。基于地脉动测试得到滑坡场地15个地脉动数据，采用傅里叶变换法对苏堡村滑坡土层的脉动特征进行分析，获得地脉动频谱特征曲线。研究表明场地卓越周期建议值为0.126 s，将其划分为坚硬场地，可为该滑坡场地类别划分作为参考，同时发现滑坡体与未滑体的地脉动特征有较大差异，可为海原地震滑坡的脉动特性分析提供依据。

Abstract:

The 1920 Haiyuan M8.5 earthquake caused numerous landslide disasters, which is of great significance to the study of landslide disasters in loess areas and the analysis of soil microtremor characteristics. The results of high-precision scanning electron microscopy (SEM) showed that the surface loess in the Haiyuan earthquake site is a microstructure with weakly consolidated overhead pores and a strong risk of seismic collapse and seismic landslide occurrence. The microtremor data of 15 landslide sites were obtained via a microtremor test. Fourier-transform was used to analyze the microtremor characteristics of soils in the Subaocun landslide, and then the microtremor spectrum characteristic curves were obtained. The results showed that the recommended value of predominant period of the site is 0.126 s, and it is classified as a hard site. The recommended value of the site predominant period in this area can be used as a reference for landslide site classification. The study shows that the microtremor characteristics of landslide and non-sliding body are very different, which can provide the basis for the analysis of microtremor characteristics of landslides induced by the Haiyuan earthquake.