青藏高原松潘—西秦岭—临夏盆地深地震反射剖面——采集、处理与初步解释

Deep seismic reflection profiling in the Songpan-west Qinling-Linxia basin of the Qinghai-Tibet plateau:data acquisition,data processing and preliminary interpretations

由于印度洋板块向亚欧板块俯冲使青藏高原不断隆起,其形成不仅导致了亚洲大陆内部强烈的晚新生代构造变形,还对其边缘地区的地貌格局产生重大影响.青藏高原东北缘是青藏高原向北东方向扩展的前缘部位,是印度与欧亚两大板块碰撞作用由近南北方向向北东、东方向转换的重要场所.本文利用2004年和2008年完成的深地震反射剖面资料,采用关键处理技术和参数开展唐克-合作剖面与合作-临夏剖面联线处理,获得总长约400km的深地震反射剖面,完整揭示了西秦岭造山带及其两侧盆地的地壳结构和构造变形样式.结果显示西秦岭造山带下地壳向若尔盖逆冲推覆的深部构造特征;西秦岭下地壳北倾的强反射及其北侧南倾的强反射特征揭示出扬子与华北两个大陆板块在西秦岭造山带下的汇聚行为.Moho的埋深和起伏形态表明青藏高原东北缘地壳经历了高原隆升后强烈的伸展减薄作用.

Subduction of the Indian plate underneath the Eurasian plate results in continuous uplift of the Qinghai-Tibet Plateau, whose formation not only led to tectonic deformation of the Asian continent in the late Cenozoic, but also affects landscape patterns of its peripheral areas. The northeast margin of Qinghai Tibet Plateau is the front position where the Qinghai Tibet plateau grows northeastward, and is also an important place of conversion where the India and Eurasia plate collision changes its direction from nearly north-south to northeast and east. In this study, we used deep seismic reflection profiles completed in 2004 and 2008, respectively. We spliced original shot gathers and used some key processing techniques and parameters to obtain a 400 km-long reliable section. This section reveals overall crustal structure and deformation style of the West Qinling orogenic belt and basins on its both sides. The results display the deep tectonic characteristics about the West Qinling orogenic thrust-napping toward the Ruoergai basin. The north-dipping and south-dipping strong reflections in the lower crust of the West Qinling and its south are considered as reflective patterns of the Yangtze and North China plate convergence under the West Qinling orogenic. Moho geometry and depth indicate the northeast margin of the Tibetan Plateau has experienced intense extension and thinning after the plateau strongly uplifted.