Abstract:The paper theoretically analyzed Hausdorff fractal dimension and Divider fractal dimension algorithms and presented uniform simplified algorithm for Hausdorff fractal dimension and Divider fractal dimension algorithms—Length fractal dimension algorithm.The realizations of the method are follows:①defining a window width on a seismic trace,computing fractal dimension of sampled seismic data sequence within the window and labeling the value at the sample of right edge of working window;②moving the window forward along the seismic trace with step-length of one sample interval and computing fractal dimension at each window,then resulted in one variance track of fractal dimension;③the local track appeals a clear “V” form along with first break gradually enters the window,zooming regionally the local apex in left branch of “V” track,the first rapidly-dropping point is symbol of first break entering window,which corresponds the arrival of first break.The theoretical analysis and practical test showed that the Length fractal dimension method characterized by small computational efforts,without setting measure (fold) scale,removing inconsistent coordinate scale,sensitive to first break of seismic wave,small influence of window width on stability and precision of computed results and strong anti-noise ability,meanwhile,there is no limit to wave mode of first break when computing fractal dimension.