宁夏及其邻区地震活动带与小区域构造应力场

本文利用宁夏及其邻区地震台网记录的18099个初动符号,以单个地震震源机制解和小震综合解的平均解,求得7个小区的区域构造应力场。全区主压应力场的平均方位为39°左右。各小区的平均主压应力方位为:西(吉)、海(原)、固(原)地区60°;银川平原及石咀山地区42°;石咀山以北、以西地区26°;(中)卫、(中)宁地区17°。各区均以来自西南方向的压应力为主。并认为当弱震活动带走向与主压应力方位成25°—30°夹角时,未来在这些条带上发生中强地震的可能性较大

SEISMIC ACTIVITY AND LOCAL TECTONIC STRESS FIELD IN NINGXIA AND NEARBY REGIONS

From the recorded 18099 first motion symbols by the seismic station network in Ningxia and nearby regions and using the average of single earthquake source mechanism solutions and the average of small earthquake synthetic solutions, the local tectonic stress fields in 7 small areas are determined. The average direction of maximum com-pressive stress in the entire region is approximately N 30°E with local variations as N 60°E in Xi-Hai-Gu area; N 42°E in Yinchuan plain and Shizhuishan area; N 26°E in the north or west to the Shizhuishan as well as NE 17° in Wei-Ning area. The stress source of the areas are mainly from the southwest compression. It is also concluded that if the strike of weak seismic belts intersect in 25°-30° with the maximum compressive stress, the probability of moderate or large earthquake occurrence along these belts is relatively high