中文摘要：

为揭示汶川Ms8．0特大地震的深部构造背景，广泛收集整理龙门山地区的深部地球物理探测资料，对龙门山构造带的深部结构与构造特征进行分析讨论。资料表明：龙门山构造带是一地壳厚度陡变带，两侧普遍存在低速高导层，地壳上地幔顶部结构存在较大差异，带内逆掩断层发育，低速高导层缺失，表现为高阻基底。西侧川西高原的Pn波速度较低（7．6～7．8krn／s），东侧四川盆地较高（8．0～8．2krn／s），低的上地幔顶部Pn波速度结构可能意味着川西高原壳幔之间存在较为强烈的热交换过程，中上地壳内的低速高导层有可能成为龙门山L形的滑脱面，为龙门山中上地壳内浅源地震的孕育提供深部构造条件。

英文摘要：

In order to reveal the deep tectonic background of Wenchuan Ms8.0 earthquake, the deep geophysical investigation data were collected and deep structural characteristics beneath Longtnenshan area were discussed. The present results show that the Longmenshan tectonic zone is a steep variation belt of crustal thickness. At its two sides, the layers with low velocity or high conductivity are widely distributed, and there is big difference in structures of crust and uppermost mantle. It means that the Longmenshan tectonic zone has a high resistance basement. In western Sichuan Plateau, the Pn velocity is 7.6 - 7. 8 km/s, which is lower than that of Sichuan Basin, where the Pn velocity is 8.0 - 8.2 km/s. The lower Pn velocity suggests that there is possiblly strong heat exchange between crust and mantle in western Sichuan Plateau. The low velocity-high conductivity layers in middle-upper crust are likely to be an L detachment, which served as the deep tectonic conditions for shallow earthquake development in Longmenshan tectonic belt.