THE FOCAL MECHANISMS IN NORTH CHINA

The authors obtianed the focal mechanisms of moderately strong earthquakes in North China since 1980, and analyzed and sorted out the data of the focal mechanisms of 85 earthquakes in North China since 1937. The results indicated that since more than half a century the earthquakes in this area mainly are the type of strike-slip faults. The strikes of the two nodal sections of these focal mechanisms are north northeast and northwestwest repectively. Most of the compressive principal stress axes p strike northeast east-southwestwest. Most of the tensile stress principal axes T strike north-northwest——southsoutheast. By means of studying and inferring for different time intervals, the focal mechanisms of earthquakes in North China are not only consistent in space but also stable in time.