A new geodynamic model related to seismicity beneath the southeastern margin of the Tibetan Plateau revealed by regional tomography
A new geodynamic model related to seismicity beneath the southeastern margin of the Tibetan Plateau revealed by regional tomography
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区域层析成像揭示的青藏高原东南缘地震活动新地球动力学模型
DOI：
10.1093/gji/ggy183
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发表时间：
2018
影响因子：
2.8
通讯作者：
Bo Zhang
中科院分区：
文献类型：
--
作者：
Yujin Hua;Shuangxi Zhang;Mengkui Li;Tengfei Wu;Weibing Qin;Fang Wang;Bo Zhang
青藏高原东南缘是中国大陆地震活动最活跃的地区。为了了解该地区的地震活动性，利用云南省49个地震台记录的区域地震的P波和S波到时进行了层析反演的新的地震实验。在这项研究中，我们使用事件组合方法来减少数据分布的极端不确定性，并使用到达时间来构建参考速度模型。为了验证反演结果的可靠性，进行了棋盘格和奇偶数据检验。可靠的P波速度模型揭示了两个低速异常带（LVAZ）的边界主要走滑断层。该地区的大地震几乎都发生在这两个LVAZ中，这两个LVAZ的趋势与基于欧亚固定参考架的全球定位系统速度场一致。我们认为这两个LVAZ是SETP中物质迁移的通道。在垂直方向上，力学性质较弱的地壳物质随刚性块体向南滑动，而下伏地幔物质继续受到碰撞挤压。这一垂直模型与剪切波分裂引起的地壳和岩石圈地幔的地震各向异性基本一致。新的区域地球动力学模型对青藏高原的地震活动性给出了合理的解释，并认为通道带物质的迁移在青藏高原的构造演化中起着重要作用。
The southeastern margin of the Tibetan Plateau (SETP) presents the highest level of seismicity in mainland China. To understand the seismicity in this region, a new seismic experiment is carried out based on the tomographic inversion ofP- andS-wave arrival times from the regional earthquakes recorded by 49 seismic stations in Yunnan Province of Southwest China. In this study, we reduce the extreme disproportionality of the data distribution using an events combination method, and we use arrival times to construct the reference velocity model. Checkerboard tests and odd/even data tests are carried out to assess the reliability of the inversion results. The reliableP-wave velocity model reveals two low-velocity anomaly zones (LVAZs) bounded by major strike-slip faults. Almost all the large earthquakes in this region occurred in the two LVAZs and the trend of the two LVAZs is consistent with a global positioning system velocity field based on the Eurasia-fixed reference frame. We propose that the two LVAZs are material migration passageways in the SETP. In the vertical direction, the mechanically weak crustal materials are sliding southward with the rigid block, while the underlying mantle materials continue to be compressed by the collision. This vertical model is broadly consistent with the seismic anisotropy in the crust and lithospheric mantle from shear-wave splitting. The new regional geodynamic model gives a reasonable interpretation of the seismicity of the SETP, and we suggest that the material migration in the passageway zones plays an important role in the tectonic evolution of the SETP.