华北断块区均衡重力异常、构造特征及地震活动  

ISOSTATIC GRAVITY ANOMALY,STRUCTURAL FEATURES AND SEISMICITY OF NORTH CHINA CRATON

作　　者：黎哲君[1] 徐如刚[1] 张玮晶[2] 张毅[1] 李辉[3] 杨光亮[3] 龙剑锋[1] 

机构地区：[1]安徽省地震局,合肥230031 [2]中国地震局应急搜救中心,北京100049 [3]中国地震局地震研究所,武汉430071

出　　处：《地震地质》2015年第2期496-509,共14页Seismology and Geology

基　　金：地震科技星火计划项目(XH14028Y);中国地震局地震行业科研专项(201308004);安徽省地震科研基金(20130701);安徽省地震局科研合同制项目(201323)共同资助

摘　　要：均衡重力异常是地壳均衡状态的标志,地壳均衡状态与构造特征及地震活动密切相关。文中基于高阶地球重力场模型EGM2008自由空气异常,采用高精度数字地形模型(DEM)ASTER GDEM 2009和ETOPO1分别作为陆地和海底地形数据,通过基于DEM的严密地形-均衡改正方法计算得到华北断块区5'×5'网格分辨率的Airy均衡重力异常。根据计算结果讨论了华北断块区均衡重力异常分布特征,并探讨了区内均衡重力异常与构造特征、地震活动的关系。结果表明,华北断块区均衡重力异常空间分布极不均匀,表现出明显的断块差异性;区内均衡重力异常大小主要受新构造运动控制,是地壳表层物质密度横向变化和深部构造差异共同作用的结果,构造运动对均衡重力异常的显著影响说明华北断块区地壳均衡调整尚未完成;华北断块区地震活动和均衡重力异常之间有一定的联系,地震活动在显著的均衡重力异常高值区或低值区周围及正负均衡重力异常区过渡部位分布较为集中。Isostatic gravity anomaly is considered a sign of the isostatic state of the crust, and studies show that the isostatic state of crust is closely connected with the structural features and seismicity in many areas. In order to investigate the isostatic state of crust and to understand its relation to structural features and seismicity in North China Craton, a new isostatic residual gravity map of North China Craton has been computed using recently released earth gravitational model and digital terrain models. Free-air gravity anomalies of North China Craton have been prepared using the gravity data set of Earth Gravitational Model 2008 （EGM2008）. EGM2008 data set is believed to be reliable and studies show that EGM2008 free-air gravity anomalies have a general accuracy of 10.5mGal（ 1mGal--10^-3 cm/s^2）in China. The topographie-isostatic corrections were computed based on an Airy-Heiskanen model of local compensation using a strict algorithm based on digital elevation model （DEM） , the average crust thickness of the study area was derived from CRUST2.0, and the topographic and bathymetric data sets were derived from digital elevation model ASTER GDEM 2009 （larc second resolution） and ETOPO1 （larc minute resolution）respectively. Topographic-isostatic corrections were then added to the free-air gravity anomalies to determine the isostatic gravity anomalies of North China Craton with a gridding resolution of 5arc minutes. According to the results of calculations, distribution of isostatic gravity anomalies and its relations to structural features and seismicity of North China Craton were discussed. The results indicate that the spatial distribution of isostatic gravity anomalies is remarkably uneven in North China Craton, and isostatic gravity anomalies are very different between different fault blocks. Isostatic gravity anomalies of North China Craton are mainly controlled by neo- tectonic movements, and are significantly influenced both by lateral variations in crust density and deep structures.

关 键 词：均衡重力异常 华北断块区 地震活动 构造特征 地球重力场模型 

分 类 号：P315.726[天文地球—地震学]