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本文根据北京台网、大连、长春、牡丹江、海参威等26个台站的记录,选用了从北京地区到阿留申群岛西端的300多个地震,研究了北京—萨哈林剖面的地幔纵向速度分布。 用Herglotz-Wiechert公式计算得出的V-h作为初始模型,计算理论走时曲线,找出了与实际走时曲线符合较好的速度结构。其特点为:上地幔顶部的速度为7.8公里/秒;高速盖层中有正速度梯度;在约60—120公里深度范围内为低速层;130公里以下速度缓慢增大;在370—440公里、600—740公里有两个速度梯度较大的过渡层,其中以370—440公里的正速度梯度最大,与之相应的震中距为19°。在1060公里以下有微弱的正梯度。 用Kaila方法计算了深度为400公里左右的地震震源深度处的速度值,与上述结果一致。
Based on the records of 26 stations including Beijing, Beijing, Changchun, Mudanjiang and Hailongwei, this paper selected more than 300 earthquakes from Beijing to the western end of the Aleutian Islands. The longitudinal velocity of the mantle in the Beijing-Sakhalin section distributed. Using Vg calculated by Herglotz-Wiechert formula as the initial model, the theoretical travel time curve is calculated, and the velocity structure which is in good agreement with the actual travel time curve is found out. Its characteristics are: the top of the upper mantle velocity of 7.8 km / s; high-speed cover has a positive gradient; depth of about 60-120 km in the low-speed layer; 130 km below the slow increase in speed; 370-440 km There are two transitional layers with large velocity gradient in 600-740 km, of which 370-440 km has the largest positive gradient and the corresponding epicenter distance is 19 °. There is a weak positive gradient below 1060 km. The Kaila method was used to calculate the velocity at the focal depth of about 400 km, consistent with the above results.