For the purpose of extending the urban geological work, our party has conducted since 1986 ground radiometric measurement over an area of 1632 km² in Dalian and, on such a basis, made information conversion for gamma radiation level, thus extending the service of radiometric measurement which was formerly only used in geological work, and raising the effectiveness of ra-diometric measurement.This paper describes in detail the natural environment gamma radiation level of Dalian area and distribution of air-absorbed doses. Two maps, namely. the division of natural eivironment ionizing radiation ra tes in Dalian area and the distribution of air-absorbed doses of natural envi ronment ionizing radiation, have bean compiled.The completion of this work has provided environmental radiogenic ba ckground data for Dalian City and made a gratifying stride in applying geo physical and geochemical prospecting to the study of urban environment.

Through regional investigation of physical properties of rocks in Guangxi, the authors have determined the density, magnetism, electric characteristics and temporal-spatial distribution of regional rocks, disclosed the boundary separating different densities, made clear the existence of magnetic basement, worked out a geophysical model for stratigraphic sequence of rocks, indicated magnetic variation characteristics of granites of different ages, and established a pregnostic model for gravity low of concealed granites. These achievements will be surely of great significance in such aspects as regional structural mapping, concealed granite mapping, study of oil-gas structures in small basins, prognosis of solid ore minerogenic belts and basic geological research.

Based on an integrated analysis of large quantities of outcomes obtainedin such fields as geology, aeromagnetic survey, gratity, telluric electromagneticsounding, seismic exploration and density determination, we have established a geological-geophysical model for Central Sichuan area. With the direct calculation method, we have analysed the Central Sichuan gravity anomaly centering on Dazu. Finally, a new viewpoint is put forward concerning the composite origin of the Dazu gravity high.

With case studies this paper deals with the application of geophysical prospecting to geologic calamity investigation and water exploration.During the leakage investigation of the Wenxiakou reservoir, radio wave penetration method and "mise-a-la-masse" method were successfully used to locate leakage channel; during the investigation of the dirsction of Yemaodong cave at the Pengshui dam site of the Wujiang River, the direction of the karst channel buried some 100 m at depth was found out by means of radio wave penetration method; to look into the leakage that occurred along the batardeau of the upper reaches of the two rivers at Gezhouba dam, self-potential method was used and, as a result, leakage position was accurately located.Concerning water exploration in Quaternary sediments, two examples are presented which deal with the application of D. C. electrical sounding.Finally, the paper mentions some problems that are worth noticing in the application of geophysical prospecting to geologic calamity investigation and water exploration.

The formula of △T anomaly from the 2.5 D polygonal body has been deduced and an optimum procedure that computes the magnetic model is described in detail. As a result of the application of SVD to the solution of Generalized Matrix Inversion, the problem related to the compromise between speed and stability of the convergence has been solved. In this way, the best model in the sense of the least squares can be obtained. With two theoretical models and the data obtained in Xianiu area, this paper illustrates the effecti veness of the method.

This paper makes a fairly systematic study of electromagnetic coupling (EM)phase frequency spectra of (lipole-dipole array in horizontal two-layered earth. It is considered that the electrical parameter μ₂(relative electric con ductivity) and geometric parameter h₁/a(thickness of cover/dipole distance) are major factors affecting properties of EM in two-layered earth. The two-layered earth whose bottom layer has high resistance shows a rather strong EM effect, and such an EM effect only reflects the shallow layer; if the bot tom layer has low resistance, the EM effect reflects the distribution of com paratively-deep-seated electric bodies. An analysis of parameter regularity of EM frequency spectra and inversion shows that the variation in EM cha racteristics might directly indicate the variation in resistivity of underground media.

In geophysical and geochemical oil-gas exploration, uncertainty would cause assessment of prospects to fall into trouble. The use of geophysical and geo chemical data would reduce but could not eliminate the uncertainty. The use of data in different stages of decision making would also help to promote exploration effectiveness and increase the ratio of success. Introduction of pro bability methods would improve the current interpretation status in explora tion and enable the assessment and decision making to be performed on the quantitative basis.

Using quantitative analyses of stream sediment combinatorial samples arranged evenly in network by-MGMk, the authors drew directly on computer diagrams grading pollution indexes, and made snrficial environmental assessment of Quanzhou-Meizhou Bay district nearly 8, 000 km² in area. On such a basis,the types of factors causing environmental pollution were indicated.

Environmental pollution in Kunming City has been studied geochemically. This paper, using geochemical data of bedrock and soil, investigates primary environment and secondary environment of this area as well as their relation ship, discusses assessment indices for soil pollution (pollution indices), divi des this area into subareas with different degrees of pollution and, combined with biologic data, analyzes the influence of pollution on ecologic environment. The data obtained are of practical value to environmental geology and agri cultural geology.