索伦-西拉木伦缝合带中段及周边区域面波层析成像  

The Lithospheric Structure of the Middle Solonker-Xar Moron Suture by Surface-wave Tomography

作　　者：冯梅[1] 安美建[1] 侯贺晟[1] 范桃园[1] 臧虎临 FENG Mei;AN Meijian;HOU Hesheng;FAN Taoyuan;ZANG Hulin(Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质科学院,北京100037

出　　处：《CT理论与应用研究（中英文）》2023年第1期1-14,共14页Computerized Tomography Theory and Applications

基　　金：国家自然科学基金(利用高覆盖宽频地震观测研究南美大陆岩石圈三维结构(41974051));中国地质调查项目(黑吉蒙关键区带深部地质调查(DD20221643-2);松嫩地块及周缘关键区带深部地质调查(DD20190010))。

摘　　要：索伦-西拉木伦缝合带中段及周边区域先后经历了古生代古亚洲洋闭合、中生代蒙古鄂霍茨克洋闭合和中新生代太平洋俯冲等构造复合叠加,导致该区深部构造异常复杂。本研究从该区近年来累积的宽频地震探测资料的地震面波和环境噪音互相关格林函数中提取瑞雷波群速度频散,并据此反演区域尺度的三维横波速度。结果发现:区域地壳厚度横向变化不大,松辽盆地和下辽河盆地地壳比大兴安岭薄,地壳厚度与地形吻合表明这些地区基本达到重力均衡状态;而辽东隆起和渤海湾盆地地壳厚度与地形高度呈反相关,表明这些地区可能仍处于构造改造过程中。在80 km深度之下,波速分布则呈现与索伦-西拉木伦缝合带走向近似平行的东西向展布。以索伦-西拉木伦缝合带为界,南北两侧横波速分布复杂程度明显不同且南侧的东西两部分复杂程度也不同。这些结果表明区域受太平洋俯冲体系冲破坏程度存在明显差异,同时索伦-西拉木伦缝合带以南可能仍有古亚洲洋板片残留。The middle section of the Solonker-Xar Moron suture and its surrounding areas have successively been affected by the closure of the Paleo-Asian Ocean during the Paleozoic, the closure of the Mongolian-Okhotsk Ocean during the Mesozoic,and the subduction of the Pacific Ocean plate since the Meso-Cenozoic, resulting in very complex, deep structures in this area.We conducted a regional-scale three-dimensional S-wave velocity tomographic study of the area. To do this, we used surface waves from earthquake data and ambient noise data recorded in recent years. The lithospheric tomographic model shows that the regional crustal thickness does not vary considerably, but the crust in the Songliao and the Lower Liaohe basins is thinner than that in the Daxing’an Mountains. The fact that the crustal thickness remains consistent with changes in topography indicates that these areas have reached gravitational equilibrium. However, the crustal thickness of the Liaodong uplift and the Bohai Bay Basin is inversely related with topography, indicating that these areas may still be in a tectonically active state. At depths greater than 80 km, the S-wave velocities spread in an east-west direction approximately parallel to the Solonker-Xar Moron suture. The complexity of the upper-mantle velocity distribution to the north of the Solonker-Xar Moron suture differs significantly from that to its south. Furthermore, south of the Solonker-Xar Moron suture, the complexity of the velocity distribution in the east differs considerably from that in the west. This implies that the destruction resulting from the Pacific Ocean subduction system varies significantly within the study region, and remnants of the paleo-Asian ocean slab may still exist in the south.

关 键 词：面波层析成像 三维横波速度 索伦-西拉木伦缝合带 华北克拉通 中亚造山带东段 

分 类 号：P315[天文地球—地震学]