折射Pg波层析成像揭示兴蒙造山带及其邻区上地壳结构  

Refraction Pg tomographic imaging reveals the upper crustal structure of the Xing-Meng Orogenic Belt and its adjacent areas

作　　者：曹力夫 王海燕[1,2] 李文辉[1,2] 侯贺晟[2,3] 王光文 庞永香 CAO Lifu;WANG Haiyan;LI Wenhui;HOU Hesheng;WANG Guangwen;PANG Yongxiang(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;SinoProbe Laboratory of Ministry of Natural Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;Chinese Academy of Geological Sciences,Beijing 100037,China;Tianjin Branch,CNPC Logging Company Limited,Tianjin 300280,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质科学院自然资源部深地科学与探测技术实验室,北京100037 [3]中国地质科学院,北京100037 [4]中国石油集团测井有限公司天津分公司,天津300280

出　　处：《地学前缘》2025年第2期346-356,共11页Earth Science Frontiers

基　　金：国家自然科学基金项目(42074115);中国地质调查项目(DD20230217,DD20221647);国家重点研发计划项目(2107YFC0601301)。

摘　　要：兴蒙造山带是由众多微陆块、岛弧、增生楔和蛇绿岩(洋壳残片)等构成,经历了复杂的构造演化历史,记录了古亚洲洋俯冲、西伯利亚和华北板块最终拼合等重要信息,其演化一直是国内外地学界研究的热点。研究兴蒙造山带及邻区各地质体之间的联系对其构造演化有着重要意义,获取精细的上地壳结构成为厘定兴蒙造山带不同块体之间接触关系和揭示中新生代构造演化过程的关键。本文对一条南北向跨越松辽盆地、兴蒙造山带和二连盆地总长为503 km的宽角反射和折射地震剖面数据进行了初至波层析成像研究。本研究使用有限差分算法对16个大炮数据693个初至走时拾取数据进行计算,采用变网格尺度和平滑参数的反演策略,经40次迭代反演,将RMS降至0.103 s,获得上地壳(7 km以上)精细速度结构。成像结果精细刻画了研究区地下的速度结构:北部二连盆地存在低速特征,是一个南深北浅的断陷盆地,最深处可达5.1 km,其发育主要由两侧倾向相背的正断层控制;中部兴蒙造山带(嫩江断裂与贺根山缝合带之间)上地壳呈高速特征,横向变化剧烈,存在3个山间盆地,因其多为中新生代沉积少有第四系沉积,导致其沉积层速度较造山带两侧盆地高;南部松辽盆地为典型箕状断陷盆地,受后期NWW SEE向水平挤压引起的正断层逆向运动致使结晶基底顶界面与沉积层褶皱变形基本一致,沿测线盆地最深处可达5.5 km。基于速度异常厘定出研究区断裂带的位置和上地壳展布形态。多数断裂、断层浅处为大角度陡立状,在向深部延展过程中倾角逐渐减小,演变为铲式。The Xing-Meng Orogenic Belt is composed of many microcontinents,island arcs,accretionary wedges and ophiolite(oceanic crust fragments).It has experienced a complex tectonic evolution history and recorded important information such as the subduction of the Paleo-Asian Ocean and the final assembly of the Siberian and North China Plates.Its evolution has always been a hot topic in the field of geosciences at home and abroad.It is of great significance to study the relationship between the geological bodies in the Xing-Meng Orogenic Belt and its adjacent areas for its tectonic evolution.Obtaining fine upper crustal structure is the key to determine the contact relationship between different blocks in the Xing-Meng Orogenic Belt and reveal the Mesozoic-Cenozoic tectonic evolution process.In this paper,a wide-angle reflection and refraction seismic profile data with a total length of 503 km across Songliao Basin,Xing-Meng Orogenic Belt and Erlian Basin is studied by first-arrival wave tomography.In this study,the finite difference algorithm is used to calculate 693 first arrival traveltime picking data of 16 artillery data.The inversion strategy of variable grid scale and smoothing parameters is adopted.After 40 iterations of inversion,the RMS is reduced to 0.103 s,and the fine velocity structure of the upper crust(more than 7 km)is obtained.The imaging results describe the underground velocity structure of the study area in detail:the northern Erlian Basin has low velocity characteristics,which is a deep south and shallow north fault basin,with a maximum depth of 5.5 km,and its development is mainly controlled by normal faults with opposite tendencies on both sides.The upper crust of the Xing-Meng Orogenic Belt(between the Nenjiang Fault and the Hegenshan Suture Zone)is characterized by high velocity and dramatic lateral changes.There are three mountain basins,most of which are Mesozoic-Cenozoic sediments with few Quaternary sediments,the velocity of the sedimentary layer is higher than that of the basins on both side

关 键 词：宽角反射与折射 兴蒙造山带 松辽盆地 二连盆地 地震层析成像 

分 类 号：P315[天文地球—地震学]