Application Of Noise Imaging Technology In Urban Underground Space Exploration In Jinan City

With the rapid development of China's urbanization,the development and utilization of underground space in important cities and city circle has become the main goal of urban development and construction in the next stage.However,the fundamental information of geological conditions and underground space resources is not clear,which has greatly affected and delayed the development and utilization of underground space.The City Jinan is located in the central part of Shandong Province,south of the Taishan-Lushan terrain bulge,and north of the Qihe-Guangrao fault.It is the central city of the southern wing of the Bohai Sea region and is a famous fountain city.For many years,due to the lack of effective detection technology,it is impossible to determine the “source,transportation and storage” of fountain water,thus restricting the construction of subways and other underground space utilization.It is necessary to find out the spatial distribution of faults,rock masses and main strata that control spring water,which can provide a basis for the development of underground space.The background noise tomography method is a passive tomography technique developed in recent years.Compared with the traditional underground space detection method,background noise tomography of dense arrays does not require a specific source.By extracting the Green's function between the station,the 2 km underground shallow S-wave velocity structure can be quickly obtained,which has many advantages such as low cost,low pollution,reliable results,etc.,especially in the environment with serious human disturbance.Underground structure information is increasingly favored by geophysical workers.87 short-period three-component EPS portable digital seismographs were deployed in the downtown area of Jinan City.The dynamic range of the instrument is 120 db,which can measure the medium better even with relatively poor reflection.The sampling rate is 100 Hz,and the data is continuously collected for about one month.The first block is composed of 49 stations and the second block is 38 stations.The grid station layout and the linear station deploy are adopted respectively(the station spacing is 1-2km and 0.15-1km).Firstly,the data is preprocessed,cross-correlated and superimposed,and the surface wave information with higher signal-to-noise ratio is obtained.Then,the base-group velocity dispersion curve inversion method is used to acquired the shallow shear wave velocity structure above 1km in the study area.The background noise tomography technique effectively identified two faults in the study area and analyzes the shear wave velocity structure characteristics of the lower part of the faults,and initially determines the structural pattern of the study area,and depicts the spatial distribution of the main rock mass and stratum in the study area.Happening.The shear wave velocity structure in the research area obtained by the noise imaging technology provides a direct basis for the development of underground space in Jinan.The research results show that the noise imaging technology can obtain underground structure information in urban areas with serious human disturbance,and overcome the shortcomings of traditional geophysical methods that it is difficult to obtain effective information in cities.It is expected to become the main method for city underground space survey.It provides reference and instructions for city underground space surveys across the country.