| 用远震接收函数研究龙门山断裂带与其邻区的莫霍面深度及波速比分布 |
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| 关键词:Longmenshan fault zone receiver function H-Kappa stacking method Moho depth wave-velocity ratio |
| 基金项目:地震动力学国家重点实验室开放课题(编号: LED2008B01); 中国地震局M7工作专项 |
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| Variations of Moho Depth and Velocity Ratio along and surrounding the Longmenshan Fault Zone from Tele-seismic Receiver Functions |
| Using tele-seismograms from stations in the region along and surrounding the Longmenshan fault zone, the authors stacked receiver functions by means of time-domain iterative deconvolution, further estimated Moho depths beneath the stations through the H-Kappa stacking method, and finally derived the distribution of both the Moho depth and the wave-to-velocity ratio (Vp/Vs), and their errors for the region. The result suggests that the Moho depth distribution has an outline similar to that from previous studies. Some new details and understanding of the Moho depth distribution are as follows: (1) The Moho depth is between 41 and 48 km in the Sichuan basin, and a NNE-trending “tongue-shaped” uplift of Moho exists beneath the western Sichuan basin, which corresponds to the foreland depression of the Longmenshan thrust zone. (2) The Moho depth is about 42 km along the eastern edge of the Longmenshan fault zone, but increases rapidly to more than 56 km further westward, resulting in a NE- to NNE-trending gradient belt of Moho depth. The gradient belt is NE-SW-trending along the northern and middle segments of the Longmenshan fault zone and is roughly parallel with the two segments of the fault zone. However, the gradient belt trends in NNE-SSW direction in the southern segment of the fault zone, being oblique to the strike of the southern segment at an angle of 15° to 20°, with higher gradient existent there. (3) Relatively big errors exist in the estimated Moho depths for the stations on the side of the Tibetan plateau and the Longmenshan fault zone, which is probably attributed to the relatively complicated crustal-mantle structure and deformation there. (4) The difference in the spatial distribution of the wave-to-velocity ratios Vp/Vs is not significant. A preliminary explanation is that the abnormalities of the medium to high Vp/Vs ratios on the Sichuan basin side and on the Tibetan plateau side are related to the water-bearing stratigraphic formations beneath the basin and to the low-velocity layers (or the channel flow) in the crust of the plateau, respectively. |
| LONG Feng,NI Si-dao,WEN Xue-ze.2011.Variations of Moho Depth and Velocity Ratio along and surrounding the Longmenshan Fault Zone from Tele-seismic Receiver Functions[J].Acta Geoscientica Sinica,32(4):438-446. |
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