青藏高原东北缘及其邻区重力异常小波多尺度特征分析  

Study on the transverse variation characteristics of gravity anomalies in the northeastern margin of the Tibetan Plateau and its adjacent areas,based on wavelet multi-scale analysis

作　　者：张站稳 高国明[1] 王树琴 潘莹 杨滢 ZHANG Zhan-wen;GAO Guo-ming;WANG Shu-qin;PAN Ying;YANG Ying(Department of Geophysics,School of Earth Sciences,Yunnan University,Kunming 650500,Yunnan,China)

机构地区：[1]云南大学地球科学学院地球物理系,云南昆明650500

出　　处：《云南大学学报（自然科学版）》2023年第4期866-874,共9页Journal of Yunnan University(Natural Sciences Edition)

基　　金：云南省教育厅科学研究基金(2022Y013);国家自然科学基金(41964004);云南省科技厅科技计划(202101AT070181).

摘　　要：青藏高原东北缘是青藏高原北东向扩展的前缘部位,研究青藏高原东北缘的重力异常展布特征,对揭示青藏高原的动力学过程有重要意义.基于WGM2012全球重力场模型,利用小波多尺度分析方法对青藏高原东北缘的布格重力异常进行分解,得到了不同深度、不同阶数的布格重力异常分布特征.结果显示:随着分解阶数的增加,对应的等效源深度也增加、低频信息越突出.研究区的布格重力异常异存在明显的东西分区现象,呈现出西部低‒东部高的现象,印证了青藏高原地壳物质的流动与其周边刚性块体的阻挡作用;羌塘地块在4阶细节场中表现为正异常的特征,反映了印度板块俯冲、摩擦作用引起下地壳温度升高使物质熔融上涌至中地壳的动力学过程;阿拉善地块的重力异常在各阶细节场的分布特征与鄂尔多斯块体类似,反映阿拉善地块是从华北古陆上分离出的.结合各阶重力异常分布,分析研究区主要断裂所在的深度位置,其中鄂尔多斯断裂西缘、甘肃断裂带及龙门山断裂是表层断裂带;阿尔金断裂、南祁连缝合带、昆仑山缝合带及海源断裂带穿过上地壳到达地表;巴丹吉林断裂主要存在于上地壳,北祁连缝合带由中地壳延伸到地表.The northeastern margin of the Tibetan Plateau(NETP)is the leading edge of the North-East expansion of the Tibetan Plateau.Studying the distribution characteristics of gravity anomalies in the NETP is of great significance for revealing the dynamic process of the Tibetan Plateau.Based on WGM2012 global gravity field model,in this paper the distribution characteristics of the different depths and different orders of Bouguer gravity anomaly are found by using the method of wavelet multi-scale analysis to analyze Bouguer gravity anomaly of the northeast edge of the Tibetan Plateau.The results show that with the increase of decomposition order numbers,the corresponding equivalent source depths increase,and the low frequency information is more outstanding.The Bouguer gravity anomaly in the study area has an obvious east-west partition phenomenon,showing a low phenomenon in the west and a high one in the east,which confirms the flow of crustal materials and the blocking effect of the rigid blocks around the Tibetan Plateau.The Qiangtang block shows a positive anomaly in the fourth-order detail field,which reflects the dynamic process of material melting and upwelling to the middle crust due to the temperature rise caused by the subduction and friction of the Indian plate.The distribution characteristics of gravity anomaly in each detail field of the Alxa block are similar to those of the Ordos block,indicating that the Alxa block was separated from the North China ancient land.Based on the distribution of the gravity anomaly,the depth-positions of the main fractures of the study area are analyzed,which found out that the western margin of Ordos,Gansu fault,and Longmenshan fault are surface faults;the Altun fault,the South Qilian suture,the Kunlun Mountains suture,and Haiyuan fault go through the upper-crust to the surface;the Badain jaran fracture mainly exists in the upper-crust,and the North Qilian suture extends from the middle crust to the surface.

关 键 词：WGM2012重力场模型 布格重力异常 小波多尺度分析 青藏高原东北缘 

分 类 号：P318[天文地球—固体地球物理学]