RECENT TECTONIC STRESS FIELD AND SEISMICITY IN YIHE-SHUHE FAULT BELT

In this paper, by use of focal mechanism solutions of 31 small shocks and 15 single stations(average result), the characteristics of stress fields of Yihe-Shuhe fault belt and its adjacent region are studied. The results have shown that the directions of principal stress axes, P and T, in Yihe-Shuhe fault belt are 72° and 342°, respectively, which agree with that in Jiangsud Shandong-Anhui-Henan region; the stress field difference at vertical variant segments in the fault belt is obvious. The statistical result of mechanism of earthquakes at different depth has shown that the focal mechanism of earth quakes in depth more than 17km appers to reflect crustal stress field more really. The mechanical model of Yihe-Shuhe fault belt is given. Finally, the recent characters of seismicity in this fault belt and its relation to active fault, stress state and fracture angle have been discussed.