摘要
为了研究中国红河断裂带近年的活动特性,利用块体模型对红河断裂带周围块体内1999—2014年的GPS水平速度场进行建模,反演得到块体的刚体旋转、内部应变率以及断层的滑动速率与三维闭锁程度。结果表明,考虑内部应变的块体模型可以显著提升速度场的拟合效果,反演得到的红河断裂带滑动速率与二维速度剖面的结果吻合较好。红河断裂带的闭锁程度大致呈现中段闭锁较强、南段与北段闭锁较弱的对称分布,南段、中段与北段在地表以下15 km深度范围内的断层闭锁程度分别约为0.34~0.52、0.67~0.75、0.26~0.53,右旋滑动亏损速率分别为1.7、3.0、1.4 mm/a。利用最小二乘配置方法计算了研究区域的应变场分布,发现红河断裂带从南至北由压缩转换为拉张,中段处于压缩与拉张的交界带,剪应变率低于南北两段,这可能是由于中段闭锁较强、断层错动量较小造成的。
In order to study the activity characteristics of the Red River fault zone in recent years, the GPS measurements from 1999 to 2014 in the surrounding blocks of the Red River fault zone are modeled by block model, and the rigid block rotations, internal strain rates, fault slip rates and three-dimensional locking degree are obtained. The inversion results show that the block model considering the internal strain can significantly improve the fitting effect to the GPS velocities, the inverted slip rates of the Red River fault are in good agreement with the results of the velocity profiles. The locking degree of the Red River fault is roughly symmetrical that the middle section is relatively strong, and the southern and northern segments are weak. The locking degree of the southern, middle and northern sections are about 0.34-0.52, 0.67-0.75 and0.26-0.53 respectively from the surface to 15 km depth, and the dextral slip rate deficit were 1.7, 3.0 and1.4 mm/a, respectively. The distribution of strain field in the study area is calculated by the least squares collocation, it is found that the Red River fault zone is converted from compression in the south to tension in the north. The middle section is in the transfer zone of compression and tension, and its shear strain is lower than the northern and southern sections, which may be due to the stronger locking degree of the middle, so that the fault dislocation is smaller.
引文
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