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渤海是连接郯庐断裂带辽宁段和山东段的重要区域,利用地震层析成像方法重建三维P波速度模型,展示了渤海海域地壳和上地幔结构的变化,揭示出郯庐断裂带的深部构造特征以及与构造活动的关系.分析表明,渤海海域的地壳结构存在明显的横向非均匀性:在辽东湾及渤海中部,郯庐断裂带附近的地壳具有双层结构,浅部为低速沉积层,地壳中、下部速度偏高,未见壳内低速层,显示了相对稳定的地壳结构特征,与现今较弱的地震活动相吻合.在渤海南部及莱州湾,郯庐断裂带受张家口-蓬莱断裂带的影响较大,全新世以来的构造活动使得这一地区的地壳结构极为复杂,成为地震活动频繁发生的重要原因之一.此外,渤海海域地壳中、下部和上地幔平均速度偏低,推测与华北克拉通破坏及地幔上涌存在一定的联系.地幔热流物质有可能沿郯庐断裂带形成的通道向上侵入,在地壳底部冷却后形成高速薄层,对于强化壳幔边界、减缓断裂带的构造活动起到了一定作用.
The Bohai Sea is an important area connecting the Liaoning section and the Shandong section of the Tancheng-Lujiang fault belt. The three-dimensional P-wave velocity model was reconstructed by seismic tomography to show the structural changes of the crust and upper mantle in the Bohai Sea, revealing the deep structure of the Tanlu fault zone Characteristics and the relationship with tectonic activity.The analysis shows that the crustal structure in the Bohai Sea has obvious lateral heterogeneity: in Liaodong Bay and the central Bohai Sea, the crust near the Tanlu fault zone has a double-layer structure and the shallow part is a low-velocity sedimentary layer, In the middle and lower parts of the Bohai Sea, the Tanlu fault zone is dominated by the Zhangjiakou-Penglai fault, with high velocity in the middle and lower parts of the crust and no low-velocity layer in the crust, showing relatively stable features of the crustal structure, which is consistent with the weaker seismic activity. The tectonic activities since the Holocene make the crustal structure extremely complicated in this area and become one of the important causes of frequent earthquakes. In addition, the average velocity of the middle and lower crust in the Bohai Sea is lower than that of the upper mantle, And North China craton damage and mantle upwelling there is a certain relationship between the mantle plume heat may be formed along the Tancheng fault upwards into the channel After cooling the bottom of the high-speed formation of a thin layer, for strengthening the shell mantle boundary, slow fault of tectonic activity played a role.