Characteristics and influencing factors of the shallow geothermal field in Beijing plain area

Abstract：Based on a large number of borehole temperature data，the authors systematically studied the distribution characteristics of the shallow geothermal field in Beijing plain area and several influencing factors. The average geothermal gradient of this area（0~300 m） is 7.2℃/100 m，higher than that of deep bedrock whose geothermal gradient ranges from 2.5 to 3.0℃/100 m. Terrestrial heat flow values range from 66.35 to 84.14 mw2/m2. The relatively high level of heat flow values indicates that the lithosphere is relatively thin and hidden faults are existent. There is a close relationship between the current shallow geothermal field and the deep geothermal field in this area. The distribution of the shallow geothermal field is basically consistent with the strike of major hidden active faults in the plain area，mainly controlled by new tectonic movement. In addition，groundwater and the lithology and structure of rock and soil are also important influencing factors.