| 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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| 引用本文：龙锋,倪四道,闻学泽.2011.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[J].地球学报,32(4):438-446. |
| DOI：10.3975/cagsb.2011.04.07 |
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| 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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| 中文摘要:利用龙门山断裂带及其邻近地区地震台站的远震波形记录, 采用时间域迭代反褶积技术求取接收函数, 并用H-Kappa叠加方法计算出各台站下方的莫霍面深度和波速比及其相应的误差。结果除了获得与前人研究大体相同的莫霍面深度分布轮廓外, 还获得一些新的细节与认识: (1)莫霍面深度在四川盆地内为41~48 km, 在四川盆地西缘存在一个NNE向的“舌状”莫霍面隆起带, 对应了龙门山逆冲构造带的前陆拗陷地带。(2)莫霍面深度从龙门山断裂带东缘的约42 km向西很快增加到56 km以上, 形成一个总体展布为NE-NNE向的莫霍面深度的梯度带; 该梯度带在龙门山断裂带北段和中段的走向大体与断裂带平行; 然而, 在龙门山断裂带南段地区, 莫霍面深度梯度带展布转为NNE向, 与断裂带走向呈15°~20°的交角, 且梯度显著增高。(3)龙门山断裂带及青藏高原一侧各台站之下的莫霍面深度误差较大, 可能与那里较复杂的地壳-幔结构、构造有关。(4)波速比的空间差异不明显, 初步认为四川盆地一侧和青藏高原一侧的中-高波速比异常可能分别与台站下方存在含水沉积层以及壳内低速层(或通道流)有关。 |
| 中文关键词:龙门山断裂带 接收函数 H-Kappa叠加方法 莫霍面深度 波速比 |
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| Variations of Moho Depth and Velocity Ratio along and surrounding the Longmenshan Fault Zone from Tele-seismic Receiver Functions |
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| Abstract: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. |
| keywords:Longmenshan fault zone receiver function H-Kappa stacking method Moho depth wave-velocity ratio |
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