Structure of the Upper Mantle and Transition Zone Beneath the South China Block Imaged by Finite Frequency Tomography
Structure of the Upper Mantle and Transition Zone Beneath the South China Block Imaged by Finite Frequency Tomography
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有限频率层析成像的上地幔结构及华南地块下方过渡带结构
DOI：
10.1111/1755-6724.12807
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发表时间：
2016-10
期刊：
影响因子：
--
通讯作者：
Chen Bo
中科院分区：
文献类型：
--
作者：
Sun Ya;Liu Jianxin;Tang Youcai;Chen Jiawei;Zhou Keping;Chen Bo
利用有限频率层析成像方法，对2007年7月至2010年7月华南地块（SCB）及其周边地区350个宽带台站记录的地震S波资料进行了分析，以更好地了解上地幔形变。在反演中使用对每个站具有适当权重的一对站中的差分旅行时。我们的研究结果与以前的层析成像显示，在四川盆地下的高速度异常和高速度异常的过渡带下扬子江是一致的。然而，地幔不均匀性的解决提供了新的见解，在研究区西部的缅甸岩石圈俯冲和东部的大洋岩石圈俯冲的构造格架。在107°E以西的俯冲区，四川盆地东南部有一个明显的快S波异常。在107°E以东，华南块体中部400-600 km深度处出现两个窄而不连续的快S波异常，其上覆有明显的100和400 km深度的低S波异常。如果位于地幔过渡带的快速异常代表停滞板，则其破碎的性质可能表明它们可能是由西太平洋岛屿下方的不同俯冲事件产生的，而上述慢速异常可能与正在进行的俯冲的弧后区域有关。此外，层析成像还揭示了一个异常高的S波速度大陆根向东延伸到四川盆地东部以下400 km的深度。这种异常可能与印度-欧亚大陆碰撞引起的印度岩石圈向东挤压有关。此外，我们的研究结果还表明，大的缓慢异常下方的红河断裂区连接到更深的异常下方的华南褶皱带和南海。这与华南地块是由古太平洋板块俯冲和缅甸微板块向东俯冲共同作用形成的观点是一致的。
We applied the finite frequency tomography method to S wave data recorded by 350 broadband stations beneath the South China Block (SCB) and its surroundings from earthquakes occurring between July 2007 and July 2010, to better understand upper mantle deformation. Differential travel‐times in the pair of stations with appropriate weighting for each station are used in the inversion. Our results are consistent with previous tomography that show a high velocity anomaly beneath the Sichuan basin and a high velocity anomaly in the transition zone beneath the Yangtze Craton. However, the resolution of mantle heterogeneity provides new insight into the tectonic framework of subduction of Burmese lithosphere in the west part of the study region and subduction of oceanic lithosphere in the east. In the subduction realm, west of 107°E, a significant fast S‐wave anomaly is located on the southeast of Sichuan Basin. East of 107°E, and two narrow and discontinuous fast S‐wave anomalies occur at a depth of 400–600 km beneath the middle of the South China block overlain by the pronounced low S‐wave anomalies at a depth of 100 and 400 km. If the fast anomalies located in the mantle transition zone represent stagnant slabs, their fragmented nature may suggest that they could be produced by different episodes of subduction beneath western Pacific island and the above slow velocity anomaly may associated with the back‐arc regions of ongoing subduction. In addition, tomography also reveals an anomalously high S‐wave velocity continental root extends eastward to a depth 400 km beneath the eastern Sichuan Basin. This anomaly may be related to eastern extrusion of Indian lithosphere associated with the collision of India and Eurasia. Moreover, our results also show large slow anomalies beneath the Red River fault region connected to deeper anomalies beneath the South China Fold Belt and South China Sea. All these observations are consistent with the scenario that the South China block has been built by both of subduction of Paleo‐pacific plate and eastward subduction of Burma microplate.
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作者：
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通讯作者：
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