2015年尼泊尔强震序列对中国大陆的应力影响

基于2015年尼泊尔地震序列的破裂模型及均匀弹性半空间模型,计算了该地震序列传递到中国西藏境内发生在定日县地震和聂拉木县地震的应力.2015年尼泊尔地震序列导致定日县地震和聂拉木地震节面和滑动方向的库仑应力增加(2~3)×103 Pa和(2.4~3.1)×105 Pa, 表明这两个地震受到尼泊尔地震序列的触发.其次,我们计算了2015年尼泊尔地震序列在中国大陆及其附近主要活动断层上产生的库仑应力变化.喜马拉雅主山前逆冲断裂和青藏高原内部的拉张正断层上的库仑应力有较大的增加,而青藏高原的走滑断裂,如阿尔金断裂、东昆仑断裂、玉树玛曲断裂、班公错断裂西部、嘉黎断裂的库仑应力有较大的降低.天山南北两侧的断裂库仑应力降低.而华北及东北、华南地区的库仑应力变化几乎可以忽略不计.最后,计算了该地震序列造成的水平应力变化.水平面应力在2015年尼泊尔地震序列北向(青藏高原大部和新疆区域)增加(拉张),而在地震序列东侧的西藏南部和川滇地区南部降低(压缩),在华北和东北仅有少许增加,在华南地区有少许降低.在中国西部,主压应力表现为以2015年地震序列为圆心的向外辐射状,而主张应力方向与同心圆切线方向大体一致.水平主压应力方向在东北地区为北东向,在华北地区为北东东向,在华南地区为南东东向.这种模式与现今构造应力场方向相似,表现了2015尼泊尔地震序列所代表的印度板块和欧亚板块的碰撞是中国大陆构造变形的主要动力来源.

Stress influence of the 2015 Nepal earthquake sequence on Chinese mainland

Based on the rupture models of the 2015 Nepal earthquake sequence and half space homogeneous elastic model, the Coulomb stress changes are calculated on nodal planes and slip directions of the Tingri and Nyalam earthquakes which occurred in Tibet, China. The results show that the Coulomb stresses on the Tingri and Nyalam earthquakes transferred by the 2015 Nepal earthquake sequence are (2~3)×10³ Pa and (2.4~3.1)×10⁵ Pa, respectively. It implies that the Tingri and Nyalam earthquakes are triggered by the 2015 Nepal earthquake sequence. #br#Then, we projected the stress changes generated by the 2015 Nepal earthquake sequence on the fault planes and slip directions of the active faults near the source region and in Chinese mainland. The Coulomb stress largely increases on the Himalayan main frontal thrust fault and the extensional normal faults in the interior of the Tibet plateau, such as the Kyêbxang Co-Xainza-Dinggyê fault zone, the fault zone of the southeast foot of the Nyaiqêntanglha Mountains, the Yibug Caka-Dawa Co-Gyêsar Co fault zone,the Cam Co-Palung Co fault zone. While it decreases on the strike-slip faults in Tibet plateau, such as the Altyn Tagh fault, the East Kunlun fault, the Yushu-Maqu fault, west of the Pangong Tso fault, the Lhari fault. The Coulomb stress also decreases on the faults on the north and south side of the Tienshan Mountains. Little Coulomb stress changes appear on the faults in northern Xinjiang, North China, Northeast China and South China. #br#Lastly, we calculated horizontal stress changes generated by the 2015 Nepal earthquake sequence. The horizontal area stress increases in the north direction of the 2015 Nepal earthquake sequence (most of the Tibet plateau and Xinjiang region), and decreases in southern Tibet to the east side of the earthquake sequence and south part of the Sichuan-Yunnan region. Little horizontal area stress increase took place in North China and Northeast China. Little horizontal area stress decreases are seen in South China. The principal compressive stress shows an outward radiation centered on the 2015 Nepal earthquake sequence with the principal extensional stress along the direction of concentric circles in western China. The principal compressive stress shows NE direction in Northeast China, NEE in North China and SEE in South China, respectively. The direction of the horizontal stress change generated by the 2015 Nepal earthquake sequence presents a similar pattern of the contemporary stress field, which means that collision between the India and Eurasia plates associated with the 2015 Nepal earthquake sequence is the major dynamic source for tectonic deformation in Chinese mainland.