鄂尔多斯盆地北缘南北向剖面上地幔远震P波层析成像  

Teleseismic P-wave tomography of the upper mantle along the north-south profile under the northern Ordos basin

作　　者：毛慧慧[1,2] 雷建设[3] 滕吉文[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]中国科学院大学,北京100049 [3]中国地震局地壳应力研究所(地壳动力学重点实验室),北京100085

出　　处：《地球物理学报》2016年第6期2056-2065,共10页Chinese Journal of Geophysics

基　　金：国家自然科学基金重点项目(90914012;41530212)和面上项目(41274059)资助

摘　　要：为深入理解华北克拉通破坏机理,本研究通过鄂尔多斯盆地北缘南北向宽频带线性高密度流动地震台观测记录的远震波形数据,获得了1985条高质量到时资料,进而利用FMTT（Fast Marching Teleseismic Tomography）快速行进层析成像方法获得了华北克拉通西部鄂尔多斯盆地北缘深至300km范围的P波速度模型.结果显示,鄂尔多斯盆地下方呈现出深至150-200km的高波速异常,说明华北克拉通其西部岩石圈保存完好尚未遭到明显破坏.河套地堑下方存在向鄂尔多斯盆地下方延伸的明显低波速异常,其深度可达300km深度,而阴山造山带下方上地幔存在深至100km左右的弱高波速异常,说明鄂尔多斯盆地周边地区的岩石圈均遭到一定程度破坏并减薄,可能与新生代时期太平洋板块的俯冲引起深部热物质上涌等作用密切相关.这些研究结果说明,华北克拉通在构造演化过程中不同块体经历了不同的破坏演化历史,这对于认识克拉通破坏减薄机制具有重要意义.In the present study we used the seismic waveform data from 215 teleseismic events（MW≥5.3and epicentral distances between 30°and 90°）recorded at the north-south linearly portable seismic array composed of 54 stations along-110°E to hand-picked the 1985high-quality seismic arrival times.The teleseismic events have a good azimuthal distribution around the study region.To avoid the influence of the uncertainties in the source parameters and seismic structure outside the modeling space,we adopted the relative travel time residuals that are calculated in the AK135 earth model.The FMTT（Fast Marching Teleseismic Tomography）method was applied to invert for the 3-D P-wave upper mantle structure down to 300 km depth under the Ordos basin（western North China Craton）and surrounding areas.Our results show that a high-velocity anomaly down to 150-200km depth exists under the Ordos basin,suggesting that the lithosphere of western Craton is preserved well and has not been obviously destructed yet.The Hetao graben is imaged as an obvious low-velocity anomaly extending obliquely southward to around 300 km depth beneath the Ordos block,whereas the Yinshan orogenic belt shows a weak high-velocity anomaly,perhaps indicating that the lithosphere around the Ordos basin may have been destructed to some extent,which is related to some dynamic processes such as the hot material upwelling caused by the deep subduction of the western Pacific slab in the Cenozoic times.These results suggest that different blocks may have experienced different evolutional histories,which is of great significance to understand the destruction and thinning mechanism of the North China Craton.

关 键 词：南北向流动观测 P波 速度结构 鄂尔多斯盆地北缘 深层动力过程 

分 类 号：P237[天文地球—摄影测量与遥感] P315[天文地球—测绘科学与技术]