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根据华北地区61次中、小地震(3.0≤M≤5.5)和10次M≥6.0大地震的震源机制结果的统计分析,得到地震释能应力场的优势方向,主压应力轴为70°—80°,主张应力轴为340°—350°,它们的仰角基本上小于45°。这表明,华北地区处于以北东东向水平压应力和北北西向水平张应力为主的现代构造应力场中。指出了这一地区6级以上地震和震源深度大于17公里的中、小地震应力场方向一致性较好,可能更接近构造应力场方向。华北地区一致性应力场的南缘,可能在秦岭、大别山及长江下游一带。
According to the statistical analysis of the focal mechanism results of 61 moderate and small earthquakes (3.0 ≤ M ≤ 5.5) and 10 M ≥ 6.0 earthquakes in North China, the dominant direction of seismic energy release stress field is obtained, and the principal compressive stress axis is 70 ° - 80 °, the stress axis is 340 ° -350 °, and their elevation angle is substantially less than 45 °. This indicates that the North China region is in a modern tectonic stress field dominated by horizontal compressional stress in the NE direction and horizontal stress at the NW level. It is pointed out that the directions of the stress field of the medium and small earthquakes with better than 6 earthquakes of magnitude 6 and above and the focal depth greater than 17 km in this area have better consistency and may be closer to the tectonic stress field. The southern margin of the consistent stress field in North China may be in the Qinling Mountains, the Dabie Mountains and the lower reaches of the Yangtze River.