华北克拉通地区基于程函方程的面波层析成像

利用布设在华北克拉通地区的流动和固定地震台站记录到的地震波数据，使用基于程函方程的面波成像方法获得了整个华北克拉通地区瑞利波15~150 s周期的相速度，并反演了研究区S波速度结构.中长周期相速度结果显示，在上地幔及岩石圈深度范围内，燕山地区表现为高速特征，华北克拉通中部大同盆地及其以南地区、太行山等区域的低速体与华北盆地的低速体相连，呈现大面积的低速异常，低速体的速度值比青藏高原东北缘的速度值更低；S波速度显示鄂尔多斯岩石圈厚度较厚，克拉通中部和华北盆地岩石圈厚度相差不大，燕山地区岩石圈厚度要厚于华北盆地.本文认为华北克拉通岩石圈破坏存在分区性，克拉通中部和燕山地区均存在一定的克拉通破坏，但破坏程度不同，鄂尔多斯地块北部存在局部克拉通改造，但克拉通稳定性特征依然存在；破坏的主要动力学来源更可能是太平洋板块的西向俯冲.研究发现克拉通中部和东部的强震分布区与克拉通破坏区域重合，大部分强震发生在岩石圈强度边界上，分析认为岩石圈强度的差异是岩石圈强度边界上显示出较高的强震活动性的原因.

Surface wave tomography based on Eikonal equation in North China Craton

Utilizing the seismic wave data recorded by temporary and permanent seismic stations deployed in the North China Craton, we obtained the phase velocity images of Rayleigh wave with 15~150 s period in the entire North China Craton by surface wave tomography based on the Eikonal equation, and inverted the S wave velocity structure in the study area. It shows that in the depth range of the upper mantle and lithosphere, the Yanshan area is characterized by high velocity, whereas low-velocity zones are found in the Datong Basin in the central North China Craton and to the south of it, as well as in the Taihang Mountains, which are connected to the low-velocity zone of the North China Basin, showing a large area of low velocity anomaly with the velocity lower than that of the northeastern margin of the Tibetan Plateau. The S-wave velocity shows that the lithospheric thickness of the Ordos block is large; it is close between the central North China Craton and the North China Basin, while larger in the Yanshan area than that in the North China Basin. This study suggests that the lithospheric destruction of the North China Craton is partitioned. There are cratonic destruction in the central North China Craton and the Yanshan area, but the degree of destruction is different. Local destruction is also found in the northern Ordos block, which, however, has little influence on the stability of the craton. The main dynamic source of craton destruction is more likely to be the westward subduction of the Pacific plate. It is found that the distribution of strong earthquakes in the central and eastern parts of the craton coincides with the craton destruction areas, and most of the strong earthquakes occur on the lithospheric strength boundary. The difference in lithospheric strength may be the reason why strong earthquake activity of the lithospheric strength boundary is higher than that of other areas.