Abstract: The environment shear stress τ₀ for 64 smaller shocks form February 2002 to May 2003, recorded by Heyuan station, is calculated by using peak acceleration (a_p), peak velocity (v_p) and peak displacement (d_p). We found that error of τ_0v and τ_0d mainly came from seismic moment M₀. So, if M₀ cannot be calculated from source spectrum, the error of τ₀, calculated by use of peak acceleration, was small. Shear stress provided the specific physical foundation for analyzing the earthquake tendency by use of magnitude sequence. When many shocks with high magnitude occurred, the stress field is situated in a reinforced background, which reminds possibility of lager earthquake occurrence, or vise verse. A linear correlation was got by means of formula analyzing and data fitting between lg(τ₀) and M_L. Therefore, the efficiency of earthquake prediction seems to be basically same when compared the magnitude with shear stress sequence. But the method of calculating τ₀ is complicated, and its error probability is also higher than that of magnitude calculation.

Key words: Heyuan earthquake sequence, Environment shear stress, Linear relation, Efficiency of earthquake prediction