ACTIVITY FEATURES OF JINGYANG SMALL EARTHQUAKE SWARMS

In this paper,the small earthquake sequence occurred in Jingyang,Shaanxi during 25 April-30 November 1983 are analysed. Using only the data of Jingyang seismograph station,the temporal distribution,the relation between repetition rate and magnitude,the attenuation of aftershocks and the spatial distribution of the hypocenters for the earthquakes in the swarms are studied. This paper also makes an approach to the seismogenic structure of the region. Results show that activity feactures of the low-level micro-earthquake sequence occurring in a small region are similar to those of moderate-strong earthquakes occurring in a large region during a long period of time. Furthermore,it is indicated that the sptial distribution of the earthquake foci is related to the tectonic activity and that the mode of hypocentral displacment is controlled by the stress field in the crust of the whole region.