宜川—泰安剖面的密度结构、构造特征和地震活动  

DENSITY STRUCTURE,TECTONIC FEATURES AND SEISMIC ACTIVITY OF THE YICHUAN-TAI AN PROFILE

作　　者：罗翔飞[1] 李忠良[1] 李勇江[1] 王泽源 姬计法[1] 何辛 于博 LUO Xiang-fei;LI Zhong-liang;LI Yong-jiang;WANG Ze-yuan;JI Ji-fa;HE Xin;YU Bo(Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China)

机构地区：[1]中国地震局地球物理勘探中心,郑州450002

出　　处：《地震地质》2023年第6期1385-1399,共15页Seismology and Geology

基　　金：中国地震局地震行业科技专项(102152210360000000015);国家自然科学基金(41274113);中国地震局地球物理勘探中心青年基金(20240731YFGEC2023006)共同资助。

摘　　要：文中利用宜川—泰安重力剖面的相对联测和同址GNSS测量数据获得沿线的布格重力异常、剩余密度相关成像和地壳密度结构,可以看出:剖面的布格异常变化范围为-(161.7~5.5)×10^(-5)m/s^(2),自西向东总体呈上升趋势,在临汾盆地有明显“凹陷”,可能与上地壳存在低密度构造有关;剖面地壳密度分布具有明显的不均匀性,以太行山重力梯级带为界,西部密度较高,东部密度较低,中下地壳存在低密度体,可能是上地幔物质上涌岩石含部分高温流体和熔融岩体所致;不同构造块体的密度差异明显,在断裂带分布区域均存在密度差,说明密度分布与构造有一定关系;地壳介质的不均匀性和地震活动相关:鄂尔多斯断块的地壳介质相对均匀,不容易积累能量,地震活动水平低;山西断陷带和华北平原断块则相反,具有显著的不均匀性,地震活动频繁。We examine the density structure,tectonic features,and seismic activity along the Yichuan-Tai an profile.To do this,we use regional Bouguer gravity anomaly data and analyze the correlation between the Bouguer gravity anomaly,residual density,and density structure distribution along the profile.We also incorporate seismic detection and geological tectonic results to conduct density inversion and residual density correlation imaging studies on the profile.The results show that:(1)The Bouguer anomaly in the profile ranges from-(161.7~5.5)×10-5 m/s 2 and shows an overall upward trend from west to east.The Yichuan-Linfen-Changzhi section has a low background with a gradual upward trend,but the Bouguer anomaly is noticeably“depressed”between the Luoyunshan Fault and the Huoshan Mountain Frontal Fault.This depression could be due to the presence of low-density structures in the upper crust of the Linfen Basin and the density“loss”between the enclosing rocks.The Changzhi-Taihongshan-Linxian section changes from a gentle rise in a low background to a rising trend in a high background.The Bouguer gravity anomaly suddenly drops and then rises again,indicating the existence of pre-Taihang Mountains fractures and the undulations of the Moho interface.The Anyang-Nanle-Tai an section shows a gradually rising trend of high background,with many local anomalies and small-scale gradient zones distributed in the background.These anomalies and zones are related to smaller internal depressions and uplifts.The background anomaly responds to the change in crustal thickness,showing a pattern of deep crust in the west and shallow crust in the east.However,the crustal uplift in the Linfen Basin and North China Fault Basin may be due to the extrusion and expansion uplift of the crust when the upper mantle material invades upward.In the uplifted areas of Luliang Mountains and Taihang Mountains,the crust is depressed,likely due to the splitting between the upper and lower crust,making the uplifted massif thicker than the basin crust.

关 键 词：重力剖面 布格重力异常 剩余密度相关成像 地壳密度结构 地震活动 

分 类 号：P315.726[天文地球—地震学]