隆尧地裂缝活动特征的定量分析

QUANTITATIVE ANALYSIS OF ACTIVITY CHARACTERISTICS OF LONG-YAO GROUND FISSURE

隆尧地裂缝是华北平原中规模大、活动强的典型地裂缝之一,对跨地裂缝建筑造成水平拉张、走滑剪切与垂直位错等形式的破坏。为了给地裂缝沿线工程建筑的灾害防治提供依据,本文基于野外地质调查及探槽工程揭露,总结了地裂缝的平面展布及剖面结构特征,同时根据探槽剖面分析了地裂缝活动对不同深度土层造成的水平走滑、拉张和垂直活动量,并结合地层光释光测年结果,计算了不同时段地裂缝活动速率。结果表明,隆尧地裂缝平面上分为东段与西段两段展布,其中西段从周村至西店子村,近东西走向,长17.7 km;东段从东店马村至毛儿寨,近北东走向,长15.3km;地裂缝活动具有拉张走滑与差异沉降特征,且西段活动强度大于东段;裂缝两侧垂直差异沉降速率最大,剪切走滑错动速率次之,水平拉张速率最小;在时间轴上,8kaB.-P.至今,地裂缝活动速率逐渐增大,且多次出现活动速率骤升期。

Longyao ground fissure is one of the large and hyperactive ground fissures in North China plain.The activity of the fissure has caused damages such as slip dislocation,vertical subsidence and horizontal tension to buildings and highways over the fissure.In order to provide essential data for disaster prevention and mitigation of engineering buildings along the fissure,we carried out field geological survey and OSL dating experiment to ascertain the accurate activity value of Longyao ground fissure.We summarized the horizontal distribution and sectional structure characteristics of Longyao ground fissure at the beginning.Then we determined the strike-slip displacement,vertical dislocation and horizontal tensile width of the ground fissure based on the exploratory trench profile.Finally,we estimated the slip rates of Longyao ground fissure during different periods.Our study results show that the vertical differential settlement rate is the largest on both sides of the fissure,the horizontal strike-slip dislocation rate is the second,and the horizontal tension rate is the smallest.According to the OSL experiment,from 8ka B.P.to present,the displacement rate of Longyao ground fissure has been increasing.Since the Holocene,the ground fissures have been continuously active and the intensity has been raised constantly.We also found that there were three periods of rapid rise in activity rate.