Hydrogeological survey and slope erosion analysis for the preservation of Mogao cavas/World Heritage

年轻的多孔层理岩石，如狮身人面像遗址的始新世灰岩和莫高窟的更新世砾岩，在盐的重结晶、风化和风活动的作用下，被迅速风化和侵蚀。为了促进天然石碑的保护工作，调查人员通过监测蒸发蒸腾作用，阐明了水和水分通过多孔介质和裂缝的传输。通过地质调查、小气候调查和卫星遥感，可以分析遗产地的水文地质特征。电阻率法在干旱地区的吉萨和敦煌都有较好的应用，并能提供合理的含水量分布。马高石窟位于鸣沙山东麓，距敦煌市东南25公里。东向三危山，大泉河在其前奔流，洞穴开凿于大泉河西岸的山崖中。洞穴的出露地层为酒泉冲积、洪积砾岩，其中有泥质、钙质胶结物。石窟壁画因盐的重结晶而严重变质。它与水/水分在岩层中的运动有关。莫高地区基底为前寒武纪形成的花岗岩和片麻岩。通过卫星图像分析和地质调查，阐明了地下水运动受断裂系统控制，其地理性质是由南来的侵略性构造运动所决定的。

Young porous bedding rocks such as Eocene limestone at the Great Sphinx site and Pleistocene conglomerate at the Mogao Grottos are weathered and eroded rapidly by recrystallization of salt, slaking and wind activity. In order to contribute to the preservation work for natural stone monuments the investigators clarified the transport of water and moisture through porous media and fissures by monitoring evapotranspiration action in situ. Hydrogeological feature at heritage sites can be analyzed by geological and micro-climatic survey and remote sensing with satellite images. The electric resistivity measure could be applied well to both Giza and Dunhuang in aridity and provided the reasonable distribution of moisture content.Magao Grottos are located at the eastern foot of the Mingsha Dunes, 25km southeast of Dunhuang Town. It faces east toward Sanwei Mountain, and Daquan River runs in front of it.The caves were excavated into the cliff on the west bank of the Daquan River. The strata in which the caves were excavated are the alluvial and pluvial Jiuquan conglomerate in which there is argillaceous and calcareous cementation. The wall paintings in the caves are subject to the severe deterioration generated by recrystallization of salt. It relates with the movement of water/moisture in rock formation. The basement of Mogao Area consists of granite and gneiss formed in the Pre-Cambrian Age. Through the satellite image analysis and geological survey, it has been clarified that the movement of ground water is governed by the fault system and the geographical nature is specified by the aggressive tectonic movement from the south.