Abstract：The method for gradient interpretation of gravity anomaly presented by Stanley,Green and Butler is to first use horizontal gradient-vertical gradient map of gravity anomaly to obtain the dip angle of step and the position of origin of coordi-nate (intersecting line between inclined plane of step and surface),then use horizontal and vertical gradients of gravity anomaly to determine the buried depths of top and bottom of step.These op-erations must be finished by manual activity,and can produce major errors even be failure to be done when dips of step is more than 10°.On the basis of deducing the relationship between first and second derivatives of 2D step gravity anomaly and buried depth,dip and attitude of step,the paper made an important modification for the method presented by Stanley et al:1.using least variance to fit hori-zontal and vertical gradients of gravity by second order curve and automatically computing the dips of step;2.deducing the expression of computing the buried depths of top and bottom of step from second derivative of gravity and automatically com-puting the buried depths of top and bottom of step.Comparison with former methods,the method can more accurately and rapidly compute the atti-tude of step (contact field).The computed case of gravity data in Liupanshang basin is shown in the paper,which proved that the method can effective-ly interpret the gravitational anomaly of step.
