抄録
Fast computation of focal mechanism is achieved with the use of Fourier analysis for a P-wave polarity distribution on a focal sphere. If the focal sphere is rotated so as to give a vertical null axis, the polarity becomes a function of azimuth only. Let every positive and negative polarities be given a value of +1 and -1, respectively, then the polarity distribution is approximated by a periodic square function of period π, which provides a new technique for the focal mechanism solution. The direction of a nodal plane is fundamentally constrained by the phase angle of Fourier component at period π for the function. However, the null axis should systematically be sought on the focal sphere till the best fit to the polarity data is obtained.
