重力異常から地下構造を求める一近似式

抄録

A theoretical formula for calculating subterranian mass distribution from the gravity values at the surface is studied on the basis of Tsuboi's method. We are led to an appro ximate formula (7) or (15) expressed by linear equation with gravity value and its first and the second vertical derivatives at the surface. The coefficients of this linear combination can be determined by the way that the response of the Fourier components would be the best and the numerical coefficients are also presented under the consideration of the grid spacing or the wave length and the depth for calculation. Since the derivative calcu lation has the filtering characteristics that can be compared to that of an electric filter, its indication may be quite variable depending on the choice of spacing and pattern of the points or wave length. Then the evaluation of the vertical derivative formulas of gravity introduced in our present formula is examined by the characteristic equation concerning with wave length, with special reference to the formulas given by Elkins, Kato, and others. Thus, the subterranian mass distribution can be obtained within 10 percent errors by our formula.