Abstract: On the hypothesis that there is a sing le fo rce →_F in the homo geneously elastic half space, and thro ugh so lving elastic sta tics equation, wegot the analytic expression of the 3 component s (u,v,w) of displacement solution on the surface of the ea rth. The basic cha racter of the theo reticv ertical defo rmatio n field is also di scussed. The extent of deforma tion is di rectly propo rtio nal to the st reng th of the force, and is inversely pro portional to the depth of the origin of the force. When the dip ang le of the fo rce is no rmal (dow nw ard), the central defo rmation a rea descends. In the cont ra ry, the cent ral deformation arearises. The dip angle is amain factor to decide the image shape of crustal deformation field. Using the leveling data of Da tong region (1984-1987) and Zhang bei region (1984-1991) weinv ersed the dy namic parameters of the tworegion. The resul tsshow the dif ference betw een the center of the fo rce system and the realepicenter is less than 40 km. Dip angle of force is nearly horizo ntal. Theo retical crustal deformation imageis basically similar to the observed defo rmation image.

Key words: Seismic precursor, Crustal deformation field, Inversion, Dynamic parameter