From 1990, the Commission on Exploration Geophysics, Geological Societyof China would write a review every year to report some major advances inexploration geophysics in the previous year, and this paper is the second one.In 1990, the application of various major exploration methods to variousfields prodeeded approximately on the same scale as that in 1989, with lotsof technical advances made. Quite a few new China-made seismic instrumentsand equipments passed appraisal, including remote measuring data-collectingsystems, seismic sources and detectors. The application of 3D, high sensiti-vity, S wave and Rayleigh wave seismic exploration and vertical seismicprofile was further broadened. Varied new China-made logging and undergro-und geophysical instruments and equipments passed appraisal, which includednumerical control logging systems and microcomputerized borehole and galleryelectromagnetic wave systems. A number of new microcomputer logging dataprocessing and interpretation systems were developed. In addtiion, several newChina-made microcomputerized instruments for electrical method began to beproduced in 1990. The ground radar system began to be used in engineeringsurvey. In cooperation with Soviet geophysicists, a new electrical method,i. e.,differential normalized method, was tested in oil fields of China with initialresults obtained. Drill holes for the first time arranged directly on the basisof high-precision gravity survey revealed industrial oil flows in 1990. As 1990 was the last year of the 7 th Five-Year Plan in China, this paper has alsomade a brief review on the progress of exploration geophysics gained in vari-ous major fields in the past five years.

For the purpose of performing direct continuation of high-precision gravityand magnetic potential field on the three-dimensional irregularly undulateobservational curved surface, this paper puts forward two continuation methodsfor potential field curved surface, i. e. trigonometric function method and evenposition method, which are characterized by high precision, strong adaptabili-ty, high computation speed, negligible error in block processing and easy reali-zation on microcomputer. Tentative calculations on theoretical models andprocessing of practical data prove the correctness and reliability of these twomethods and their softwares.

There usually exists significant correlation between such radioactive para-meters as K, U and Th in airborne gamma-ray spectrometric data, whichcovers up some useful information. Using principal component analysis, we canextract a few new variables uncorrelated to each otber from a number ofhighly correlated observed data, thus getting rid of this trouble.The interpretation of airborne gamma-ray spectrometric data by usingprincipal component analysis in the middle of CDM basin shows that thismethod can be used to help lithologic and structural mapping, recognize envi-ronments favorable for uranium and sylvite deposition, establish minerogenicmodels for these two types of deposit, and make minerogenic perspective pro-gnosis for them. It is hence conceivable that principal component analysis islikely to be a new potential technique in the interpretation of airborne gamma-ray spectrometric data.

In non-uranium geology, there often exists one sort or several sorts of faint radon anomalies, such as ²²²Rn and ²³⁰Rn. To detect these anomalies, themethods chosen for radon survey must be characterized by high sensitivity,high precision and multiparameters. For this reason, techniques of multipara-meter survey such as electrostatic a-card method and a-cup method wereemployed to delimit dykes, distinguish dykes of different properties, search forwater storage structures and determine limits of oil fields. The esultsr obtain-ed obvious1y prove these techniques to be effective.

This paper has given the expression for the anomalous magnetic field ofpipeline current under the condition of clinoform, calculated theoretical profilecurves of various magnetic field components over the underground pipeline,described the distribution regularity of various magnetic field camponents andcharacteristics of their anomalies, and suggested a simple and convenientmethod for horizontal location and depth determination of the undergronudpipeline by using the dumb point and peak point on the H_z profile curve.

This paper deals with a method for solving the problem of drilling coreorientation under the specific condition of stable stratigraphie attitude anddistinct bedding in the core, with data from drill hole inclination survey avai-lable.

This paper describes distribution chatacteristics of soil gas CO₂ anomaliesand thermally-released CO₂ anomalies from rocks and ores. Based on the studyof relationship between the distribution of CO₂ anomalies and the occurren-ce of ore bodies, the authors make a preliminary discussion on the formationmechanism of anomalies, and recount the distribution regularity of CO₂ ano-malies in areas with thick overburden as well as the role of these anomaliesin prospecting for concealed ore deposits and looking for regional ore-control-ling structures.

Through a comparison of various indices of adsorbed hydrocarbon: it isfound that index of C₈⁺ is not affected by surface interfering factors, and itsanomalies might indicate the information of underground oil and gas. Using theC₈⁺ index, we have delineated five anomalies, of which No. I anomaly has ledto the discovery of oil flow of industrial significance through drilling, No. Ⅱtal No.Ⅲ anomalies show very great oil-gas exploration value, No. Ⅳ anomalyalso has certain exploration significance, but No. V seems of no explorationvalue. In addition, No. V geothermal anomaly has developed into an oil fieldcalled the Sanchunji oil field. Industrial oil flow was revealed through drillingat a 2nd grade hydrochemical anomaly (No. 2). These data provide convincingevidence for the effectiveness of the geochemical method in the explorationof oil-gas field.