共查询到20条相似文献，搜索用时 328 毫秒
1.
Imen Hamdi-Nasr Mohamed Hédi Inoubli Abdelhamid Ben Salem Saïd Tlig Abdelbaki Mansouri 《Geophysical Prospecting》2009,57(4):719-728
Detailed gravity measurements integrated with geological data were computed to constrain the mechanisms that were active during the emplacement of the Triassic evaporite-bearing folds of Jebel Cheid from the salt-dome zone in the Atlassic region. The gravity analysis consists in mapping the contrasting gravity responses: complete Bouguer anomaly, residual anomaly and derivative maps; the main results display a positive amplitude gravity anomaly as the response of Triassic evaporite bodies and important NE–SW-trending features at the boundaries between the Triassic outcrops and their enveloping strata. In contrast with gravity calculations of a salt dome structure usually resulting in negative gravity anomaly models, the Jebel Cheid clearly expresses a positive gravity anomaly; furthermore, this result is supported by synthetic gravity interpretation. 相似文献
2.
Mohamed Arfaoui Mohamed Hdi Inoubli Saïd Tlig Rabeh Alouani 《Geophysical Prospecting》2011,59(3):576-591
Triassic outcrops in the Atlassic zone of northern Tunisia may be modelled in two ways: salt bodies piercing through Cretaceous terrains or Triassic salt flows stratified within an Albian series. Both models find support from gravity data and are debatable. To evaluate the mass distribution changes with depth, the Bouguer anomaly of the El Kef‐Ouargha region was successively decomposed into regional and residual components to construct multiple pseudo‐depth slices and apparent density maps. Analyses of gravity lows clearly show a vertical continuity of less dense materials below the Triassic salt outcrops. These features can be explained by salt diapirism during Mesozoic and Cenozoic. Further, gravity data tend to indicate less dense materials below Aptian outcropping in Jebel Aite (Oued Bou Adila); thus suggesting Triassic materials occurring at depth. In addition, dense entities were recognized under Mio‐Pliocene and Quaternary deposits, which are thought to correspond to Cretaceous paleoshoals currently collapsed by non‐outcropping faults. Our findings lend support to a diapir model intruding overburden rather than the salt glacier model stratified in the Albian series proposed by some authors as the genetic structural model for Triassic material‐bearing series in the north of Tunisia. 相似文献
3.
以河北省流动重力测点覆盖区域内邢台地区4条断裂为例,将卫星布格重力异常与实测布格重力异常进行对比,发现流动重力资料可更为详细地反映测点周围构造的空间分布特征,为精细刻画华北平原地区深部构造背景提供可靠资料。采用向上延拓方法,对实测布格重力异常进行处理,获得不同上延高度的布格重力异常图像,结合当地地震地质与构造资料进行分析,并对流动重力资料在构造解释上的应用前景进行展望,认为该方法可提高现有资料的利用价值,适合在流动重力测量地区推广。 相似文献
4.
Sub-ice geology inland of the Transantarctic Mountains in light of new aerogeophysical data 总被引：3，自引：0，他引：3
Michael Studinger Robin E. Bell W.Roger Buck Garry D. Karner Donald D. Blankenship 《Earth and Planetary Science Letters》2004,220(3-4):391-408
The Transantarctic Mountains are a major geologic boundary that bisects the Antarctic continent, separating the low-lying, tectonically active terrains of West Antarctica from the East Antarctic craton. A new comprehensive aerogeophysical data set, extending 1150 km from the Ross Sea into the interior of East Antarctica provides insights into the complex structure inland of the Transantarctic Mountains. Geophysical maps, compiled from 21 000 km of gravity, magnetic and subglacial topography data, outline the boundaries of several geologic and tectonic segments within the survey area. The coherent pattern in magnetic data and mesa topography suggests a subglacial extent of the Transantarctic Mountains 400–500 km inland the last exposed rock outcrops. We estimate the maximum thickness of a potential sediment infill in the Wilkes Subglacial Basin to be less than 1 km, based on gravity modeling and source depth estimates from magnetic data. The coherent nature of the potential field and topography data, together with the northwest–southeast trends, define the Adventure Subglacial Trench and the Resolution Subglacial Highlands as a tectonic unit. The crustal structure and the strong similarity of the observed gravity with fold-and-thrust belts suggest a compressional scenario for the origin of the Adventure Subglacial Trench and the Resolution Subglacial Highlands. The complexity and apparent structural control of the Wilkes Subglacial Basin raise the issue of what influence pre-existing structures may have played in the formation of the Transantarctic Mountains system. The previous hypothesis of a thermal boundary beneath the mountains is difficult to reconcile with our new gravity data. The apparent difficulties to match our new data with certain key aspects of previous models suggests that a reassessment of the existing uplift models is necessary. We have modeled the prominent gravity anomaly over the Transantarctic Mountains with thicker crust. 相似文献
5.
有研究表明从中国北部经黄海、朝鲜半岛、日本海至日本本州岛存在一个大型断裂带,被称为“北纬40°断裂带”.为了验证该断裂带的存在性,本文通过GRACE和CHAMP卫星的位场数据中的大尺度区域重力和磁力异常来研究该区的大型构造特征.区域性研究范围为24°N~56°N,90°E~150°E,详细研究范围为32°N~42°N,122°E~132°E.2008年Taylor等利用CHAMP卫星2005年6月至12月收集的轨道数据,从测量数据中消除地核和外部产生磁场效应,经化磁极之后得到磁异常图,从中来追踪构造特征,并根据地质和地球物理资料建立了数学模型来进行解释.本文在此基础上,增加了GRACE卫星2003年10月份测量的重力异常场数据.实测差分位场数据利用高斯-勒让德求积法转换为垂向重力异常值,通过减去最新地球重力场模型（EGM96）的场值来去除波长超过1100 km的长波长异常,所得的重力异常数据和磁场数据进行比较.为了能从中得到研究区的共同构造特征,建立一个球面棱柱模型进行正演模拟、并进行重、磁异常场的波数相关性分析.研究发现在重、磁异常中均发现一个呈负相关的纬向构造特征,东亚地区“北纬40°断裂带”横穿了整个朝鲜半岛. 相似文献
6.
在云南省西部，跨越中、缅两国交界的横断山系地区（97°E~102°E，24°N~30°N）有近一半的面积尚没有重力测点、即重力数据空白区和重力测点稀少的普查级测区.以前的有关文献、图集中所给出对此地区的重力场都是十分模糊的结果与图件.因此应用这些资料无法详细地研究该地区重力场特征与深部地壳结构（构造）.本文应用卫星重力异常资料作为“近似空间重力异常”，经中间层改正后给出的“计算布格重力异常”，其分布特征与该地区的地形高程呈很好的镜像相关.对相应山脉、河谷以及断裂构造都有所反映.特别是在横断山系地区该布格重力异常呈现为近南北的走向.为此，据该“计算布格重力异常”,并选定对该区有代表性的一条重力异常剖面作正反演计算，以得到其地壳深部结构剖面.结果表明，在横断山脉地区的地壳厚度在51~56 km间起伏变化；滇西北云岭山系以及玉龙山区的地壳厚度约在60 km以上. 最后，对所得结果与图件进行了讨论，并提出了几点认识和纠正的建议. 相似文献
7.
Pedro Del Río Antonio Casas Juan J. Villalaín Tania Mochales Ruth Soto Belén Oliva-Urcia 《Studia Geophysica et Geodaetica》2013,57(3):442-459
Outstanding potential field anomalies (gravimetric and magnetic) in the Cameros Basin (N Spain) follow a WNW-ESE trend, parallel to the geological structures resulting from Mesozoic extension and Tertiary basin inversion. The positive Bouguer gravity anomaly (15 mGal) is interpreted as the result of a strong contrast between the density of Tertiary rocks of the foreland basin and the Paleozoic and Mesozoic rocks, combined with crustal thickening in the Iberian Chain with respect to the Ebro Basin. The dipolar magnetic anomaly, slightly shifted to the south with respect to the relative maximum of the Bouguer anomaly, can be interpreted as related to volcanic rocks within the basement, which are linked to Triassic rifting as witnessed by outcrops of basalts along the basin margins. An exhaustive analysis of rock properties (density, magnetic susceptibility and remanence) and basin geometry from other sources (seismic reflection profiles) allow to constrain variations in crustal thickness and the location of large-scale basement faults. 相似文献
8.
泾阳4.8级地震前后重力变化探析 总被引：2，自引：0，他引：2
系统分析了泾阳Ms4．8地震前后陕西关中地区流动重力观测资料，探讨了重力场的时空变化及其映震特征。结果表明：①震前在震中区附近形成较显著地重力负异常区，且与沉降区基本吻合。②泾阳地震震中区既是重力变化梯度带，也是重力异常的正值区到负值区的过度带。③由于震源区应力作用方式是以水平为主的左旋走滑运动，震前局部重力异常不显著。 相似文献
9.
Located between eastern segments of the Atlas and Tell-Rif oro-genic belts, the “Dome zone” of northern Tunisia is characterized by the juxtaposition of various structures that mainly controlled the long geody-namic history of this part of the south-Tethyan Margin. To better understand the organization and deep extension of these structures, gravity data from the Teboursouk key area are proposed. These data include the plotting of Bouguer anomaly map and related parameters such as vertical and horizontal gradients, upward continuation and Euler solution. Compared to geological and structural maps available, they allow the identification of new deep structures and greater precision regarding the characteristics and organization of known ones; consequently, an updated structural pattern is proposed. 相似文献
10.
用于监测四川地区重力场随时间变化的流动重力测网于2008年5月12日汶川MS8.0地震后进行了全面改造, 形成了新的闭合环线并对整网点位每年实施2次重力观测工作. 该文以2010—2012年获取的5期流动重力资料为基础, 分别采用小波多尺度分解和三维视密度反演等位场分离方法, 对测区内重力场的动态变化进行多层次分解及异常特征提取, 以探求四川测区范围内重力异常动态变化特征以及地震前后不同深度范围内密度变化情况与重力场响应之间的关系. 结果表明, 对同一期资料进行小波分解得到不同阶次的细节图像, 揭示了不同深度处重力异常动态变化特征; 分解结果同时也表明了四川测区范围内重力场的变化形态与川内特有的断裂构造格架和深部结构环境及过渡带特征密切相关. 通过对不同时期的差分重力异常资料进行三维视密度反演对比研究发现, 在地震前后四川测区范围内由浅到深密度变化呈现出不同程度的差异, 震区附近出现较为明显的横向密度变化特征且浅层物质密度局部性的异常变化差异较为突出, 测区范围内中上地壳深度层密度反演切片显示出的趋势性差异基本上反映了地震前后测区内地下物质的动态变化趋势, 因此, 深刻认识不同深度范围内重力场的动态演化特征, 对研究壳内物质密度变化以及与地震的孕育和发展有关的深部介质环境具有积极的意义. 相似文献
11.
利用重力异常反演测试三维地震波速度结构,存在解不唯一、可靠性不高的问题。将面波反演充分融合到重力异常反演方程中,降低传统反演方法的非唯一性,并提升可靠性。以川滇地区为例,采用融合后的重力异常反演方法分析三维地震波速度结构。通过速度和密度的关系转换,得到对应的重力异常数据。由于面波频射数据主要对地震波横波速度敏感,因此将重力异常数据和初始横波速度相连,依据地震波速度和岩石密度之间的关系,获取重力异常反演方程,用于分析速度结构。选取21.6°~34.2°N、97.1°~105.9°E范围内的川滇地区活动块体作为实验数据,经过实验分析发现：使用该方法迭代反演川滇地区地壳上地幔顶部横波速度,重力异常数据和面波频射数据的残差值分别是6.24 mGal和0.027 km/s,实际拟合效果较好;分析该地区不同深度切面横波速度发现,在24 km深度处,上地壳中含有相对低速层,在44 km深度处,中下地壳中存在低速层;且该方法分析川滇地区三维地震波速度结构解的分辨率较高。 相似文献
12.
跨越中、印、缅三国交界的青藏高原东南的喜玛拉雅“东构造结”地区（92°E~97°E，26°N~30°N）一半以上的面积尚没有重力测点，是重力数据空白区,故无法直接研究其重力场特征与深部地壳结构（构造）.本文分析了卫星重力异常的特性，提出应用卫星重力异常作为近似空间重力异常，并作布格改正后，得到的布格重力异常具有与该地区地形高程呈镜像相关的特征，可用以研究深部地壳结构.据三条重力剖面计算得到该地区三个地壳深部结构剖面的结果，给出青藏高原地壳厚度>70 km；喜马拉雅造山带为55 km左右；布拉马普特拉河谷盆地为33~35 km；那加山山脉地区为40~45 km，显示出三者为三个不同的构造单元.同时给出布拉马普特拉构造单元为相对高密度的刚性物质构成，随着印度洋板块向北运移，在碰撞、挤压下，插入青藏高原东南缘一带.导致该地带的强烈构造运动，和频发大、小地震.最后提出了几点认识和建议. 相似文献
13.
Shallow structure beneath the Central Volcanic Complex of Tenerife from new gravity data: Implications for its evolution and recent reactivation 总被引：1，自引：0，他引：1
J. Gottsmann A.G. Camacho J. Martí L. Wooller J. Fernndez A. García H. Rymer 《Physics of the Earth and Planetary Interiors》2008,168(3-4):212-230
We present a new local Bouguer anomaly map of the Central Volcanic Complex (CVC) of Tenerife, Spain, constructed from the amalgamation of 323 new high precision gravity measurements with existing gravity data from 361 observations. The new anomaly map images the high-density core of the CVC and the pronounced gravity low centred in the Las Cañadas caldera in greater detail than previously available. Mathematical construction of a sub-surface model from the local anomaly data, employing a 3D inversion based on “growing” the sub-surface density distribution via the aggregation of cells, enables mapping of the shallow structure beneath the complex, giving unprecedented insights into the sub-surface architecture. We find the resultant density distribution in agreement with geological and other geophysical data. The modelled sub-surface structure supports a vertical collapse origin of the caldera, and maps the headwall of the ca. 180 ka Icod landslide, which appears to lie buried beneath the Pico Viejo–Pico Teide stratovolcanic complex. The results allow us to put into context the recorded ground deformation and gravity changes at the CVC during its reactivation in spring 2004 in relation to its dominant structural building blocks. For example, the areas undergoing the most significant changes at depth in recent years are underlain by low-density material and are aligned along long-standing structural entities, which have shaped this volcanic ocean island over the past few million years. 相似文献
14.
Ravi Prakash Srivastava Nimisha Vedanti V. P. Dimri 《Pure and Applied Geophysics》2007,164(10):2009-2022
Fractal dimension analysis was carried out for optimal designing of 2-D gravity survey network and to determine an optimum
range of gridding interval to generate least aliased Bouguer anomaly maps. As a test case, this method has been successfully
applied to the Jabera-Damoh region of the Vindhyan Basin, which is considered as a potential hydrocarbon bearing area. In
particular, we aim to delineate accurately the lateral extent of a possible hydrocarbon bearing structure. To achieve this
aim, fractal dimension of survey network was computed using 2-D distributions of observation points in the planning phase
of the survey so that the optimum station spacing for gravity survey can be obtained. A range of optimum gridding interval
for the gravity data set was suggested using the box-counting method of fractal dimension determination. Bouguer anomaly maps
of the region are prepared utilizing the optimum gridding interval. For the first time, these anomaly maps clearly outline
the gravity evidence of an anomalous rifted structure, which is bounded by parallel faults on either side. This structure
is interpreted as a favorable basin for the occurrence of hydrocarbons. Another finding of this study has been the delineation
of an apparently small ridge-like structure running east-west, dividing this basin in two parts. A subsurface geological model
along a profile across the Jabera structure has also been presented. 相似文献
15.
16.
文中通过多源数据融合、模型构建、数据试验、二维离散小波变换和功率谱分析等方法获取了大别造山带东段深、浅部场源布格异常及其场源似深度,并结合地壳结构、地质构造、岩石圈有效弹性厚度和地震活动等资料,讨论了地壳深、浅部的结构特征及地震活动构造背景。结果表明,低频布格异常显示大别造山带东段与华北地块间深部构造缝合带在东部应位于青山-晓天断裂前缘,在落儿岭-土地岭断裂和商城-麻城断裂之间向N偏移至梅山-龙河口断裂之下,造山带南侧与扬子地块间深部构造缝合带位于襄樊-广济断裂以北约20km,造山带东侧与扬子地块间的深部构造转换带位于郯庐断裂带之下,造山带东段腹地显著的低频布格异常低值表明对应部位的莫霍面存在明显下凹,造山带内部的布格异常高梯度带表明其深部结构不完整;高频布格异常揭示肥中断裂、六安-合肥断裂、肥西-韩摆渡断裂和郯庐断裂带等主要断裂对地壳中上部密度结构的影响明显,落儿岭-土地岭断裂对地壳中上部密度结构的影响范围向N延伸至肥西-韩摆渡断裂前缘。结合地震活动资料进一步分析认为,大别造山带东段与华北地块在青山-晓天断裂前缘附近接触和相互作用,且大别造山带东段地壳深、浅部结构均不完整,不利于应力积累,趋向于在断裂交错的脆弱部位频繁释放应力,是霍山地区小地震活动频繁的主要原因。 相似文献
17.
青藏高原东北缘重力异常多尺度横向构造分析 总被引：8，自引：6，他引：2
本文研究了青藏高原东北缘地区布格重力异常特征,采用优化滤波法和归一化总水平梯度垂直导数法对研究区重力异常进行多尺度分离和横向构造分析.分离出的多尺度重力异常特征表明:1) 青藏高原东北缘地区大致以东经106°线为界,有一条醒目的重力异常梯级带,即贺兰山-六盘山-川滇南北构造带的北段,其东西两侧布格重力异常特征在形态和走向上截然不同,意味着两侧密度结构和构造特征存在明显差异. 2) 鄂尔多斯地块内部定边以北,重力异常高带走向由北东向转为近南北向,推测定边附近存在一个密度或构造界面,其两侧物质组成和构造特征具有差异,对比大尺度重力异常和中尺度重力异常,表明异常特征的这种差异主要是由上地幔深部结构引起的. 3) 青藏高原东北部各块体深部边界位置与地表构造分布不同,反映出该区构造复杂,深浅构造差异大. 4) 由于印度-欧亚板块碰撞及随后印度板块持续向北的挤压作用,造成青藏高原东北缘中、下地壳物质在巨大的北东向推挤力和鄂尔多斯刚性块体阻挡的共同作用下,沿着相对软弱的秦岭造山带方向蠕动.依据多尺度重力异常及其横向构造特征,综合推断出研究区内五条断裂带,即秦岭地轴北缘断裂带、海原-六盘山断裂带、香山-天景山断裂带、烟筒山断裂带和青铜峡-固原断裂带,并分析了它们在地壳深部的可能展布特征. 相似文献
18.
The National Survey and Cadastre - Denmark (KMS) has for several years produced gravity anomaly maps over the oceans derived from satellite altimetry. During the last four years, KMS has also conducted airborne gravity surveys along the coast of Greenland dedicated to complement the existing onshore gravity coverage and fill in new data in the very-near coastal area, where altimetry data may contain gross errors. The airborne surveys extend from the coastline to approximately 100 km offshore, along 6000 km of coastline. An adequate merging of these different data sources is important for the use of gravity data especially, when computing geoid models in coastal regions.The presence of reliable marine gravity data for independent control offers an opportunity to study procedures for the merging of airborne and satellite data around Greenland. Two different merging techniques, both based on collocation, are investigated in this paper. Collocation offers a way of combining the individual airborne gravity observation with either the residual geoid observations derived from satellite altimetry or with gravity derived from these data using the inverse Stokes method implemented by Fast Fourier Transform (FFT). 相似文献
19.
A parameter-estimation technique based on existing hydrological, geophysical, and geological data was developed to approximate transmissivity values for use in a ground-water flow model of the Animas Valley, southwest New Mexico. Complete Bouguer gravity anomaly maps together with seismic-refraction profiles, geologic maps, geologic, geophysical, and drillers' logs, water levels, and pumping-test data provide insight into the transmissivity of bolson deposits throughout the basin. The transmissivity distribution was primarily based on reported pumping and specific-capacity tests in conjunction with complete Bouguer gravity anomaly maps and well log data. Reported transmissivity values were characterized by gravity values and well log data. In grid blocks lacking pumping and specific-capacity tests, transmissivity values were assigned based on the relationship of gravity values and well log data within the grid block to gravity values and well log data within other grid blocks for which transmissivity values are available. A two-dimensional, finite-difference, ground-water flow computer code was used to evaluate the effectiveness of the parameter-estimation technique. Although the trial-and-error method of calibration was employed, the actual computer time necessary for model calibration was minimal. The conceptually straightforward approach for parameter estimation utilizing existing hydrological, geophysical, and geological data provides realistic parameter estimates. 相似文献
20.
Merzouk Ouyed Mouloud Idres Amar Bourmatte Mohamed Salah Boughacha Sadek Samai Abdelkrim Yelles Abderrahmene Haned Chafik Aidi 《Journal of Seismology》2011,15(2):173-189
In order to try to identify the seismogenic sources in the epicentral area, we interpreted data collected from gravity and
aftershocks in the eastern part of the Mitidja basin after the occurrence of the 21 May 2003 Boumerdes earthquake (Mw = 6.8).
The residual gravity anomaly and the horizontal gradient maps revealed the basement shape and density discontinuities. A seismotectonic
model obtained from the aftershocks distribution and gravity data is proposed. This model highlights three active faults:
one offshore and two onshore. The offshore reverse fault striking NE-SW, parallel to the coast, is consistent with the USGS
focal mechanism of the main event, which is assumed to have the most moment release. The two onshore dipping blind active
faults are postulated at crossing angles near the SW tip of the main fault. The interpretation is based mainly on the re-location
and distribution of aftershocks, and their focal solutions. It is also supported by the basin structures obtained from the
inversion and interpretation of residual gravity anomalies, as well as by additional compiled information such as the pattern
of coastal co-seismic uplift. This configuration puts forward the failure mode complexity during the main shock. The topography
of the basement obtained from 3D gravity inversion shows that all the onshore located aftershocks occurred in the basement,
and the area between the two onshore faults rose as a consequence of their sliding. 相似文献