Distribution of the low velocity bulk in the middle-to-lower crust of southern Tibet: implications for formation of the north–south trending rift zones
Mingming Jiang1, Yinshuang Ai1, Shiyong Zhou2, Yongshun John Chen2
1 Key Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2 Institute of Theoretical and Applied Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China
Distribution of the low velocity bulk in the middle-to-lower crust of southern Tibet: implications for formation of the north–south trending rift zones
Mingming Jiang1, Yinshuang Ai1, Shiyong Zhou2, Yongshun John Chen2
1 Key Laboratory of the Earth’s Deep Interior, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China 2 Institute of Theoretical and Applied Geophysics, School of Earth and Space Sciences, Peking University, Beijing 100871, China
摘要e conducted the ambient noise tomography to image the shallow crustal structure of southern Tibet. The 2D maps of phase velocity anomalies at the periods of 10–16 s show that the low velocities are mainly confined along or near some of the rift zones. While the maps at the periods of 18–25 s show that the coherent patterns that the low velocities expand outside of the rift zones. It means that the low velocities are prevailing in the middle crust of southern Tibet. According to the previous study of surface wave tomography with teleseismic data, we find that the low velocities from the lower crust to the lithospheric mantle are also restricted to the same rift zones. Thus, the integrated knowledge of the distribution of the low velocities in southern Tibet provides some new insight on the formation of the north–south trending rift zones. Compiling the multidiscipline evidences, we conclude that the rifting was an integrated process of the entire lithosphere in the early stage (~26–10 Ma), but mainly occurred within the upper crust due to the weakening a decoupling in the low velocity middle crust in the late stage (later than ~8 Ma).
Abstract：e conducted the ambient noise tomography to image the shallow crustal structure of southern Tibet. The 2D maps of phase velocity anomalies at the periods of 10–16 s show that the low velocities are mainly confined along or near some of the rift zones. While the maps at the periods of 18–25 s show that the coherent patterns that the low velocities expand outside of the rift zones. It means that the low velocities are prevailing in the middle crust of southern Tibet. According to the previous study of surface wave tomography with teleseismic data, we find that the low velocities from the lower crust to the lithospheric mantle are also restricted to the same rift zones. Thus, the integrated knowledge of the distribution of the low velocities in southern Tibet provides some new insight on the formation of the north–south trending rift zones. Compiling the multidiscipline evidences, we conclude that the rifting was an integrated process of the entire lithosphere in the early stage (~26–10 Ma), but mainly occurred within the upper crust due to the weakening a decoupling in the low velocity middle crust in the late stage (later than ~8 Ma).
基金资助:the National Natural Science Foundation of China (Grant No.: 41274002 and 41125015)
通讯作者:
Yinshuang Ai
E-mail: ysai@mail.iggcas.ac.cn
引用本文:
Mingming Jiang, Yinshuang Ai, Shiyong Zhou, Yongshun John Chen. Distribution of the low velocity bulk in the middle-to-lower crust of southern Tibet: implications for formation of the north–south trending rift zones[J]. 《地震学报》英文版, 2014, 27(2): 149-157.
Mingming Jiang, Yinshuang Ai, Shiyong Zhou, Yongshun John Chen. Distribution of the low velocity bulk in the middle-to-lower crust of southern Tibet: implications for formation of the north–south trending rift zones. Earthquake Science, 2014, 27(2): 149-157.
