利用Lg波Q值反双台层析成像方法研究青藏高原南部地区的地壳衰减  

Crustal attenuation in the southern Tibetan Plateau by reverse two-station Lg-wave Q value tomography

作　　者：鲁志楠 边银菊[1] 王婷婷[1] 刘森 Lu Zhinan;Bian Yinju;Wang Tingting;Liu Sen(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Sichuan Earthquake Agency,Chengdu 610041,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]四川省地震局,成都610041

出　　处：《地震学报》2021年第3期287-302,I0001,共17页Acta Seismologica Sinica

基　　金：核查项目(075440)资助。

摘　　要：首次基于2017—2019年西藏自治区区域台网27个宽频带固定台站记录的757次地震的波形资料,利用反双台法开展了青藏高原南部地区1 Hz的Lg波Q值层析成像研究。研究中采用3.5—2.4 km/s的速度窗截取了1981条Lg波,计算得到13543条路径上的Q值,测试了1°×1°和0.5°×0.5°网格下的棋盘格恢复情况,得到了0.5°×0.5°分辨率的Lg波Q0值层析成像。反演结果显示:青藏高原南部地壳整体的Lg波呈高衰减、低Q值,与P波速度负异常、地热分布及东部的两条裂谷系对应良好,因此推断青藏高原南部地壳存在广泛的熔融物质;两条可能存在的流体-熔融物质通道中,主通道位于亚东—谷露裂谷与桑日—错那裂谷之间,副通道沿雅鲁藏布江缝合带分流而出。此外,还对亚东—谷露裂谷两侧熔融物质的分布差异予以分析,结果表明,印度板块与欧亚板块碰撞前端存在不同的动力?学演化模式,亚东—谷露裂谷以西符合缩短增厚理论,以东符合"水泵"模式。Based on the seismic waveform data of 757 earthquakes recorded by 27 broadband stations of Tibet Autonomous Region seismic network from 2017 to 2019,it is for the first time that the reverse two-station method has been applied to 1 Hz Lg-wave Q value tomography study in the southern Tibetan Plateau.In this research,total 1981 Lg-waves were intercepted from the velocity window of 3.5-2.4 km/s and the Q values of 13543 paths were calculated.After testing the checkerboard recovery of 1°×1°and 0.5°×0.5°grids respectively,we got the tomography of the Lg-wave Q0 value of the southern Tibetan Plateau with 0.5°×0.5°resolution.The inversion result shows that there exhibits high attenuation and low Q values of Lg-wave in the southern Tibetan Plateau crust,which is highly consistent with the negative anomaly of P-wave velocity,the geothermal distribution and two rift valleys in the east of the Tibet.Therefore it is inferred that there may be widespread molten material in the crust of the southern Tibetan Plateau and two fluid-melting channels.The main channel is located between the Yadong-Gulu rift and the Sangri-Cona rift,and the secondary channel flows out along the Yarlung Zangbo suture zone.By analyzing the differences of molten material distribution on both sides of the Yadong-Gulu rift,it is considered that there are different dynamical evolution models in the front-end of collision between Indian Plate and Eurasian Plate,the dynamical evolution to the west of Yadong-Gulu rift is in accordance with the theory of shortening and thickening,and that to the east of Yadong-Gulu rift is consistent with the"pump"mode.

关 键 词：青藏高原 Lg波衰减QLg 反双台法 层析成像 

分 类 号：P315.31[天文地球—地震学]