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。
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.
出处
《大地测量与地球动力学》
CSCD
北大核心
2008年第6期31-37,共7页
Journal of Geodesy and Geodynamics
基金
国家自然科学基金(40841017)
地震科学联合基金(106076)
关键词
龙门山构造带
汶川地震
地球物理探测
深部结构
低速高导层
Longmenshan tectonic belt
Wenchuan earthquake
geophysical probe
deep structure
low velocity -high conductivity layer
