ANALYSIS ON ACTIVE CHARACTERISTICS OF SMALL EARTHQUAKES AT HUATING IN PINGLIANG AREA

In recently years,the small earthquakes have occurred more frequently at Huating,Pingliang area in the eastern segment of the Qilian Mountains,such as 4.2 magtitude earthquake in Oct.2 2005,and brought some loss of wealth and people.This article deduced the properties of the small earthquakes systematic determinant and discussed the connection of their regional stress field and increased activities by analyzing the distribution intensity characteristics of space-time and the state of regional stress field.The results concluded that,since 2001 the crowd activities about the small earthquakes in Huating district of Pingliang were the earthquakes which induced by the coal mine,the structure of magnitude was primarily composed of 1~2 magtitude and the small earth-quakes were densely located 30~40km area,occurred more frenquently during May to August.Sec-ondly,after the renovation of digital seismograph network,the enhanced ability of regional monitor is also one of reasons of the high small earthquake frequence.