位场各阶垂向导数的ISVD算法及其应用

位场垂向导数广泛应用于位场数据处理与解释当中,目前求取位场各阶垂向导数方法大致可以分为两类：①在频率域进行;②在空间域进行。针对这两类方法存在着稳定性较差的问题,这里介绍了计算位场各阶垂向导数的ISVD算法,并通过对单一地质体模型和地质体组合模型产生的布格重力异常进行处理分析,证明了ISVD算法在计算位场各阶垂向导数时,特别是在计算位场高阶垂向导数时,比在频率域及空间域计算结果具有较好的稳定性,ISVD算法能够有效地识别出浅层小尺度地质体边界。为了验证该方法对实际资料的处理效果,对某区块实际布格重力异常数据应用ISVD算法试算各阶垂向导数,结合地质背景等资料划分出断裂体系。结果证明,应用ISVD算法计算的位场各阶垂向导数,对于确定浅层小尺度地质体边界有较好的效果。     

盐源盆地重力场与断裂构造特征研究

以盐源盆地1∶5万实测重力数据为基础,对该区重力场进行了解释推断。由研究区大部分为第四系所覆盖,进行了深层重力异常的提取,即利用钻井资所料确定的新近系密度界面深度,采用"剥皮"技术提取古近系及以下地层的重力异常,根据剥皮后的区域布格重力异常图进行了重力异常分区,将研究区划分为三个重力异常区。研究区内已知断裂出露较少,为查明区内隐伏断裂构造,以布格重力异常、剩余重力异常、方向导数等异常图为依据,根据断裂构造所具有的重力异常特征标志划分断裂构造,推断断裂17条,其中大断裂2条,一般断裂15条,并在断裂构造的解释方面获得了新的认识。为了确定盆地内中、新生界的分布和各地层的接触关系,选择了兴隆公社-北门场东西向长剖面进行了剖面拟合计算,推测出了沿剖面方向沉积层的纵横向分布特征。     

利用重力异常的小波模方法识别断层

利用小波特性可以提取航空重力异常的重要信息,笔者采用小波分析方法建立三维地质体模型,讨论了小波模与地质体边界的对应关系。以我国某海域航空重力资料为例,利用小波模极大值识别了断裂信息,并与航空布格重力异常及其方向导数识别的断裂进行对比分析。结果表明,利用小波模不仅可以识别断裂构造,在航空布格异常和方向导数识别模糊的地区效果更为明显。     

中国境内沿北纬40°剖面的重力异常正演拟合及地质解释

在中国境内沿北纬40°截取了长剖面,对布格重力异常和卫星重力异常进行了正演拟合计算,并结合新的大地构造划分作了初步的地质解释。结果表明:古老的陆核、原地台、地台和地块等稳定地区内部的密度值横向变化小,年轻的褶皱带等活动地区内部的密度值横向变化大。各个构造域边界的地壳消减对接带,布格重力异常反映不明显,而卫星重力异常对应较好。布格重力异常与卫星重力异常的正演拟合结果不同的地区,其地壳和上地幔的密度分布有较大的差异。这些重要结论有助于寻求卫星重力异常与布格重力异常的在机制和应用上的共性与差异,以便达到对两种重力异常的本质有更进一步认识的目的。     

青藏高原西部重力异常剖面拟合及其地质解释

在青藏高原西部地区沿东经80°和83°选择了2条剖面,在地质资料、物性资料和布格重力异常、航磁异常研究的基础上,结合深部地球物理, 建立了剖面的地质-地球物理模型。通过重力联合人机交互正演模拟,求解地下地质体的模型,并依此对剖面通过地段的地壳结构、断裂带深部特征和构造单元的深部格架进行了解释推断。     

凤凰─茶陵地学断面重力异常机制分析

对凤凰─茶陵地学断面重力异常,根据爆炸地震测深资料,确定密度分层,用变密度水平梯形体构制剖面密度模型,计算理论重力异常和实测布格重力异常吻合较好。根据剖面密度模型,可以合理地解释布格重力异常。并将地壳划分为沉积盖层、变质岩层、麻粒岩层三层结构,分别计算三层的重力效应曲线及上地幔低密度体重力效应曲线。还计算了莫霍面起伏引起的重力异常曲线,分析了引起地壳重力异常的各种因素及特点。     

凤凰─茶陵地学断面重力异常机制分析

对凤凰─茶陵地学断面重力异常，根据爆炸地震测深资料，确定密度分层，用变密度水平梯形体构制剖面密度模型，计算理论重力异常和实测布格重力异常吻合较好。根据剖面密度模型，可以合理地解释布格重力异常。并将地壳划分为沉积盖层、变质岩层、麻粒岩层三层结构，分别计算三层的重力效应曲线及上地幔低密度体重力效应曲线。还计算了莫霍面起伏引起的重力异常曲线，分析了引起地壳重力异常的各种因素及特点。     

东昆仑东段深大断裂的新认识

青海东昆仑东段在地质上已划定有东昆中、东昆南、东昆北、布青山南缘、温泉-哇洪山等多条深大断裂构造.以东昆仑东段开展的10个图幅1:20万区域重力调查成果--布格重力异常为基础,依据窗口平均法、水平导数等数据处理方法提取的区域场及剩余场等丰富的重力异常信息,结合航磁异常等资料,对东昆中、东昆北等断裂构造的展布位置提出了新的看法,并根据重力资料新推断断裂构造12条,提出尖山-哈莉哈德山断裂为2个一级构造单元的分界,同时通过拟合布格重力异常长剖面的定量计算方法,获取了部分深大断裂构造在东昆仑东段的产状参数.     

火山岩区重力高异常组合的空间地质特征——以内蒙古东北部地区为例

以布格重力异常的地质成因为指导,针对区域重力异常、布格重力异常、剩余重力异常中的局部重力高异常的空间分布,结合区域地质、路线地质调查成果,从三维角度认识重力高异常组合所反映的地质体主成分相构造地质特点,探讨重力高异常的成因机制,以揭示地质体的空间成生、演化规律,为区域地质调查中局部重力异常的解释提供借鉴.     

火山岩区重力高异常组合的空间地质特征——以内蒙古东北部地区为例

以布格重力异常的地质成因为指导，针对区域重力异常、布格重力异常、剩余重力异常中的局部重力高异常的空间分布，结合区域地质、路线地质调查成果，从三维角度认识重力高异常组合所反映的地质体主成分相构造地质特点，探讨重力高异常的成因机制，以揭示地质体的空间成生、演化规律，为区域地质调查中局部重力异常的解释提供借鉴.     

利用重力场研究东北地区断裂分布及构造分区

为了深入研究东北地区断裂分布及构造分区,利用全国1∶2 500 000布格重力异常图,分析了泛东北地区（包括东北3省及内蒙古自治区的东北部分地区）的区域重力场特征。利用布格异常变化形态,并参考地质资料,在研究区内划分出岩石圈断裂14条,壳内断裂11条。根据大兴安岭和依兰—伊通两条明显的重力异常梯级带把研究区划分出兴安、松嫩以及张广才岭等三大重力异常区,在划分断裂和分析重力场特征的基础上进行了构造分区。其研究成果为认识和研究泛东北地区油气与矿产分布提供了重力场方面的依据。     

Evidence for Triassic salt domes in the Tunisian Atlas from gravity and geological data

Detailed gravity data were analyzed to constrain two controversial geological models of evaporitic structures within the Triassic diapiric zone (Triassic massifs of Jebel Debadib and Ben Gasseur) of the northern Tunisian Atlas. Based on surface observations, two geological models have been used to explain the origin of the Triassic evaporitic bodies: (1) salt dome/diapiric structure or (2) a “salt glacier”. The gravity analysis included the construction of a complete Bouguer gravity anomaly map, horizontal gravity gradient (HGG) map and two and a half-dimensional (2.5D) forward models. The complete Bouguer gravity anomaly map shows a prominent negative anomaly over the Triassic evaporite outcrops. The HGG map showed the location of the lateral density changes along northeast structural trends caused by Triassic/Cretaceous lithological differences. The modeling of the complete Bouguer gravity anomaly data favored the diapiric structure as the origin of the evaporitic bodies. The final gravity model constructed over Jebel Debadib indicates that the Triassic evaporitic bodies are thick and deeply rooted involving a dome/diapiric structure and that the Triassic material has pulled upward the younger sediment cover by halokinesis. Taking in account kinematic models and the regional tectonic events affecting the northern margin of Africa, the above diapirs formed during the reactive to active to passive stages of continental margin evolution with development of sinks. Otherwise, this study shows that modeling of detailed gravity data adds useful constraints on the evolution of salt structures that may have an important impact on petroleum exploration models.     

数字图像技术在重力异常地形校正中的应用

通过对地形体及其密度信息数字图像化,利用计算机仿真能较精确地计算出地形体在任意一点的重力场强度。在重力异常地形校正时,用各测点的实测数据减去相应测点的地形体重力场强度,即得到地形改正和中间层改正后的重力场强度。这样,重力异常校正中的地形改正和中间层改正可一并完成,既简化了校正的工作步骤,又提高了准确性。通过地形体实例,分别用数字图像仿真计算和积分精确计算其重力场强度,结果表明,二者计算结果十分相近。用数字图像仿真计算地形体重力场强度,误差较小,准确性较高,该方法完全适合重力异常地形校正。     

Geological evaluation of EIGEN-6C4 and GOCE derived gravity models in and around Karakoram shear zone,Leh, India

New generation high resolution gravity models derived from space-borne gravity data, integrated with land based surveys, have enabled understanding of regional gravity field over regions, which are till date considered to be inaccessible for land surveys, especially in mountainous terrains. In this study, we evaluate two high resolution gravity models EIGEN-6C4 and GO_CONS_GCF_2_TIM_R5 in order to understand its usability in identification of meso-scale regional geological features and lithological boundaries around the Karakoram shear zone, in Leh, India. The EIGEN-6C4 is a “hybrid” model integrating data from space-borne sensors and terrestrial data, whereas GO_CONS_GCF_2_TIM_R5 is a model derived from the latest space-borne GOCE sensor. Bouguer gravity anomaly has been derived for both the models and compared. It is seen that, the GOCE derived model pertains to the regional gravity field of the region and compares well with the regional derivative of the EIGEN-6C4 model. Further, the EIGEN-6C4 has been analyzed using horizontal derivatives (dx, dy), analytical signal (ANS) and tilt derivative (TDR) techniques. These, derived maps are then overlain on published geological map of the area to understand the correlation between sub-surface geology vis a vis gravitational signal. The major and distinct geological signatures as derived from the various derivative maps correlate well with the existing geological map. The source boundaries derived from the TDR map agrees reasonably well with the lithological boundaries. Further, the anomaly and derivative maps from EIGEN-6C4 indicates towards a possible continuation of the Shyok suture zone in the region. Therefore, for the given spatial extent of the area under consideration, the GOCE derived model represents the regional field, whereas the EIGEN-6C4 data and derivatives are of sufficient resolution for understanding the geological variability in and around the Karakoram shear zone.     

位场多尺度导数分析法识别线性构造-以新疆卡拉塔格地区重力解译断裂构造为例

本文介绍了一种新的地质体边界识别方法-位场多尺度导数分析法。在基本原理介绍及理论模型试验的基础上,对该方法在地质体边界识别中的有效性进行了论证。然后,利用该方法对新疆卡拉塔格地区1:5万重力数据进行了多尺度导数处理,识别出了不同尺度和走向的断裂构造,进一步证明多尺度导数分析方法能够对位场数据进行有效的分离和信息增强,进而识别出不同尺度场源体的边界。     

月球风暴洋地区玄武岩厚度的重力研究

利用剩余布格重力异常进行月球表层玄武岩厚度的推断,为月球地质填图提供了一定的证据。文中利用美国GRAIL卫星660阶布格重力异常,采用巴特沃斯（Butterworth）滤波方法,参考Grant H. Herken等的研究成果（即对月球面向地球一面的玄武岩厚度研究推断）,以此作为控制条件,提取了风暴洋地区的剩余布格重力异常,参考遥感光谱反映出的玄武岩范围,然后利用边界元方法反复模拟修正,最终得出该区的玄武岩厚度分布,玄武岩的厚度不超过1.5 km。     

Regional gravity analysis of Burkina Faso: Implications for the location of metallic ore deposits

Gravity data were analyzed in conjunction with available geological data to determine the origin of observed gravity anomalies and their possible relationship to metallic ore deposits. The gravity data analysis included the construction of a Bouguer gravity anomaly, isostatic residual gravity anomaly and enhanced horizontal gravity gradient maps, and two and one-half dimensional gravity models. The isostatic residual gravity anomaly field could be broken down into five distinct regions based on anomaly amplitude, trend and wavelength. The analysis of these regions showed that both the Birimian and granitoid provinces consist mainly of a series of short wavelength gravity maxima and minima with a few large scale anomalies which suggests that the subsurface geology is more complicated than is currently known. Two gravity models roughly oriented north-south also implied this complicated subsurface geology and showed that most source bodies have depths up to 5 km. The known base metal deposits occur on the edge of small-scale gravity maxima within the Birimian province with the exceptions of the deposits within the Bouroum-Yalogo belt which occur next to a large amplitude gravity maximum related to an ultramafic complex.