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1.
James R. Cochran 《Earth and Planetary Science Letters》1980,46(2):266-274
The interpretation of linear transfer function (admittance) studies of the relationship between gravity anomalies and topography depends on what assumptions are made in limiting the acceptable set of solutions. However, whatever assumptions are made, the value of the flexural rigidity determined from admittance studies of Australia and the continental United States is less than about 1028 dyne-cm (5-km plate thickness). This is much less than values determined from other studies of the loading of continental lithosphere which consistently give values in the range of 4 × 1030 to 2 × 1031 dyne-cm (elastic plate thickness of 35–60 km). It is argued that the latter values represent the long-term rigidity of the continental lithosphere and that the rigidity does not change greatly with age of loading. 相似文献
2.
《Earth and Planetary Science Letters》2003,205(3-4):211-224
We investigate the Tibet–Quinghai plateau and the Tarim basin in terms of spatial variations of the elastic thickness (Te) in the frame of the thin plate flexure model. The method of investigation makes use of a convolutive method, which allows high spatial resolution of the flexure properties and overcomes some of the problems tied to the spectral admittance/coherence methodologies. We study the relation between the topographic and subsurface loads and the observed crust–mantle interface (CMI) undulations, the latter having been obtained from gravity inversion. The gravity data used for the inversion are a unique set of high quality data available over the Chinese part of the plateau, and constitute the highest resolution grid today available in this impervious area. The gravity inversion is constrained by results from the study of the propagation of seismic waves. The two extensive sedimentary basins, the Tarim and the Qaidam basins, are modeled by forward gravity modeling. The oscillations of the CMI obtained from the gravity inversion agree well with those expected by loading the thin plate model of spatially variably elastic thickness with the surface and subsurface loads. It is found that the modeling of the sedimentary basins is essential in the flexure analysis. The spatial variations of elastic thickness correlate with the extensions of the different terrains that constitute the plateau. Most of the Tibet plateau has low Te, varying in the bounds 10–30 km, with lower values in the Qiangtang terrain, where the Te reaches 8 km. The Tarim and the Qaidam basins, Precambrian platforms overlain by sediments, are rigid and have a Te of up to 110 km and 70 km, respectively. The flexural analysis distinctly discerns the Tibet plateau, with thick crust, part of which is molten, from the cratonic areas, the Tarim and Qaidam basins, which though of thinner crust, act as undeformable rigid blocks. 相似文献
3.
在频域使用多窗口(Multitaper)方法来计算月球正面四个形成于不同历史时期月海区(Smythii, Crisium, Imbrium, Orientale)的重力地形导纳,然后将其与月球弹性岩石圈的理论导纳模型相比较,由最小二乘法得出四个月海区的月球岩石圈的平均弹性厚度约为8 km,月壳的厚度分别为：Smythii 盆地,72 km; Crisium 盆地 70 km;Orientale 盆地 60 km;Imbrium 盆地57 km.随着月球的演化,月壳厚度呈现变厚的趋势. 相似文献
4.
利用中国大陆以及最近与俄罗斯拼接的中亚地区的布格重力和地形数据，采用响应函数和互相关函数技术，结合弹性板挠曲理论，研究了中国大陆及其邻近地区（２５°Ｎ－７０°Ｎ，５０°Ｅ－１４０°Ｅ）的岩石层强度，用现代均衡的观点探讨了研究区的均衡补偿机制．研究结果表明，整个中国大陆及其邻近地区的有效弹性厚度Ｔｅ值为３５ｋｍ．其中，青藏地区Ｔｅ值为８５ｋｍ．西伯利亚西部至乌拉尔Ｔｅ值为７５ｋｍ，天山、塔里木盆地Ｔｅ值为４０ｋｍ，帕米尔高原Ｔｅ值为２５ｋｍ左右，西伯利亚中部、蒙古以及中国东北北部Ｔｅ值为４０ｋｍ，华北Ｔｅ值为２５ｋｍ，华南Ｔｅ值为４０ｋｍ．均衡补偿对于波长大于几千米的地形负荷为局部补偿，对几百公里到１１００ｋｍ的地形负荷为局部补偿和岩石层强度所支持，短波长地形负荷基本上由岩石层强度所支持． 相似文献
5.
The effective elastic thickness of the lithosphere has an important role in constraining compositional structure, geothermal gradient and tectonic forces within the lithosphere and the thickness of this layer can be used to evaluate the earthquakes’ focal depth. Hence, assessment of the elastic thickness of the lithosphere by gravitational admittance method in Iran is the main objective of this paper. Although the global geopotential models estimated from the satellite missions and surface data can portray the Earth’s gravity field in high precision and resolution, there are some debates about using them for lithosphere investigations. We used both the terrestrial data which have been provided by NCC (National Cartographic Center of Iran) and BGI (Bureau Gravimetrique International), and the satellite-derived gravity and topography which are generated by EIGEN-GL04C and ETOPO5, respectively. Finally, it is concluded that signal content of the satellite-derived data is as rich as the terrestrial one and it can be used for the determination of the lithosphere bending. 相似文献
6.
本文引入滑动窗口导纳技术(MWAT),计算西北太平洋岩石圈有效弹性厚度(Te).首先,基于SIO V15.1海底地形模型,模拟研究了MWAT法计算Te的精度,表明当Te5km时,误差在±1km以内,当Te≥5km时,相对误差在10%以内.分别采用GEBCO、SIO V15.1和BAT_VGG海底地形模型,构建了西北太平洋Te,通过对获得的洋壳密度参数和实测导纳与模型导纳之差的均方根进行分析,结果表明,BAT_VGG模型更适用于Te计算.西北太平洋Te均值为13.2km,标准差为6.9km,以板块冷却模型为参考,主要分布在150℃~450℃等温线深度范围内.白垩纪和侏罗纪时期岩石圈Te分布在150℃~300℃等温线深度范围内,且未随海山加载时岩石圈年龄增大而增大,说明海山加载时岩石圈年龄不是影响其强度的唯一因素.南太平洋超级海隆活动,以及研究区域广泛存在的断裂带构造,都曾对本区域岩石圈演化产生过重要影响,可能是本地区岩石圈Te较小的构造原因. 相似文献
7.
依据EIGEN-6C4重力模型和ETOPO1高程模型数据,围绕新疆精河6.6级地震展开岩石圈均衡与挠曲机理研究,得到如下结论：（1）震中附近的布格与自由空气重力异常分别为-221和-92mGal(10~(-5 )m·s~(-2)）,震中位于重力异常高梯度带上;（2）震中周边地区地壳厚度约为50km,密度结构总体变化平缓,东西方向地壳厚度变化较小,但自南向北地壳厚度逐渐变薄,精河6.6级地震初始破裂发生在上中地壳分界面附近;（3）震中附近岩石圈承载的垂向构造应力为20MPa左右,震中位于岩石圈垂向构造应力极大值附近的高梯度带上;（4）地震周边地区岩石圈有效弹性厚度最优解为26km,加载比最优解为F_1=1,F_2=F_3=0,表明该区域岩石圈相对坚硬,且导致岩石圈变形的初始加载全部来自地表． 相似文献
8.
本文用数值实验方法验证了,在Moho地形导纳法(MDDF)中使用先由重力数据反演的Moho面相对起伏数据,能较传统的重力地形导纳法获得更高的反演精度.之后作者应用Moho地形导纳法(MDDF)反演获得了精度较高的中国大陆区域岩石圈有效弹性厚度.结果显示:(1)中国地区岩石圈有效弹性厚度Te从东向西大体上呈阶梯状上升;(2)Te与岩石圈地震-热厚度、地表热流、上地幔顶部的地震波速度等数据密切相关;(3)在中国中东部, Te较低的区域以及Te的高低值转换带对应较强的地震活动性.但在西部,Te与地震活动性的相关性并不明显. 相似文献
9.
Abstract Using topography and observed gravity anomalies, we have estimated the effective elastic thickness as a measure of strength of Japanese island arc lithosphere. The thickness is found to range from about 3 km to >20 km. The thickness seems to be controlled primarily by the thermal state of the lithosphere. The higher the heat flow, the thinner is the elastic plate. However, several areas show significant deviations. The smaller effective elastic thickness in the northern Ryukyu arc than that inferred from heat flow may be attributed to the stress regime. In Japan, extensional tectonics are going on only in the Ryukyu arc region. Shallow subducting slab under the south-western Japan frontal arc probably increases the effective thickness by several kilometers. The determined effective elastic thickness suggests that when we consider vertical movements in the volcanic arc, we should take account of topographic and subsurface loading over a few hundred kilometers. However, if the dip of the slab is shallow, the flexural responses of the underlying slab, not only that of the island arc lithosphere, should be taken into account for the compensation, as is the case of the south-western Japan frontal arc. 相似文献
10.
岩石圈有效弹性厚度是表征岩石圈力学性质的参数,其反映了岩石圈挠曲变形的特征.本文在传统二维挠曲模型的基础上,提出了适用于俯冲及碰撞带的三维薄板挠曲模型.并发展了基于粒子群算法的俯冲带三维有效弹性厚度反演方法.该方法适用于挠曲参数存在横向差异的俯冲-碰撞带.最后利用该方法反演了马尼拉海沟处岩石圈的有效弹性厚度,结果显示:南海中央海盆岩石圈的有效弹性厚度随着距洋中脊距离的增加而增大;马尼拉海沟轴部弯矩在洋中脊两侧呈分段性变化,这表明南海俯冲板片在深部撕裂可能对浅部的挠曲形态产生影响. 相似文献
11.
本文给出了在球层模型下,地球岩石层对表面荷载响应的解析解。计算了地球岩石层对圆盘形荷载和正弦型荷载的响应,及由此产生的重力异常。结果表明:1.岩石层弯曲不仅与其厚度有密切关系,而且与荷载尺度有关。当岩石层厚度与荷载尺度相比很小时,其弯曲与厚度关系不大,并呈现薄板效应。2.弹性模型岩石层在外加荷载下能承受数千巴的弯曲应力。3.弯曲应力在岩石层中的分布较为规则。由于大尺度荷载下岩石层出现薄板效应,传统的由弯曲刚度估算等效岩石层厚度的部分结果需要重新估价。 相似文献
12.
Ashutosh Chamoli Anand K. Pandey V. P. Dimri P. Banerjee 《Pure and Applied Geophysics》2011,168(5):827-844
The gravity response and crustal shortening in the Himalayan belt are modeled in detail for the first time in the NW Himalaya.
The Bouguer gravity anomaly along a ~450-km-long (projected) transect from the Sub-Himalaya in the south to the Karakoram
fault in the north across the Indus-Tsangpo Suture Zone is modeled using spectral analysis, wavelet transform and forward
modeling. The spectral analysis suggests three-layer interfaces in the lithosphere at 68-, 34- and 11-km depths corresponding
to the Moho, the Conrad discontinuity and the Himalayan decollement thrust, respectively. The coherence, admittance and cross
spectra suggest crustal shortening because of convergence compensated by lithospheric folding at 536- and 178-km wavelength
at the Moho and the upper-crustal level. An average effective elastic thickness of around 31 km is calculated using the coherence
method. The gravity data are modeled to demarcate intracrustal to subcrustal regional thrust/fault zones. The geometrical
constraints of these faults are obtained in the space scale domain using the wavelet transform, showing good correlation with
the major tectonic boundaries. The crustal configuration along the transect shows how the Moho depth increases from 45 to
80 km towards the north with the locus of flexure of the Indian crust beneath the Higher Himalayan zone. The combination of
forward modeling and wavelet analysis gives insight into the subsurface extent and geometry of regional structures across
the NW Himalaya. 相似文献
13.
本文在前人研究大陆岩石圈板块有效弹性厚度的基础上,建立研究海洋岩石圈板块有效弹性厚度的理论模型,推导出与大陆岩石圈不同的海洋岩石圈板块响应函数 Z(k,Te) 理论计算公式.并分析海洋岩石圈板块响应函数 Z(k,Te) 的特点.文中对实际的海洋测量数据的响应函数 Z(k,Te) 进行计算和分析,估算我国南海南沙海域和南海中央海盆岩石圈板块有效弹性厚度分别约为10 km和6~7 km. 相似文献
14.
研究中国大陆强震区岩石圈力学特性对理解该区强震孕育环境及发生机理具有重要意义。 岩石圈有效弹性厚度(Te)及初始载荷比(F)与大陆岩石圈力学特征紧密相关。 本文利用导纳和相关函数联合反演方法以及贝叶斯最优参数估计方法, 基于全球最新的WGM2012重力异常数据、 ETOPO1地形数据和CRUST1.0 模型的Moho面深度数据, 计算中国大陆岩石圈有效弹性厚度 (Te) 和初始载荷比 (F)。 通过对比分析, 探索该地区岩石圈Te、 F、 Te梯度和F梯度对强震孕育环境的影响作用。 本文发现, 强震构造区岩石圈一般具有较低的Te值、 较高的Te和F梯度值。 结果表明, 岩石圈综合力学强度较低且力学强度和内部载荷变化剧烈的地区, 往往更有利于强震的孕育。 相似文献
15.
本文利用三个高阶重力场模型LP150Q、GLGM-3和SGM150j以及嫦娥地形模型CLTM-s01,在频率域内使用固定窗口的方法,研究了不同重力场模型的重力/地形局部导纳谱与局部相关谱的全球分布,以及典型质量瘤盆地重力/地形局部导纳谱与局部相关谱分布的特征.结果表明:加入远月面重力场信息有助于增强重力场模型在中高频段的信号强度;三个重力场模型LP150Q、GLGM-3和SGM150j均适合于作近月面重力/地形局部导纳与局部相关性的分析和近月面地球物理参数的估计;重力场模型LP150Q和GLGM-3较适合作远月面大范围的研究,不适合于作远月面重力/地形局部导纳谱与局部相关谱的分析以及作远月面局部区域地球物理参数的估计,SGM150j较适合于作远月面局部区域地球物理参数的估计;近月面大型质量瘤盆地异常质量的尺度比远月面质量瘤盆地异常质量的大,而深度也比远月面的深. 相似文献
16.
华北地区中东部涵盖北京、天津以及即将建设的雄安新区等大型城市,区内发育了张渤地震带等多条大型活动断裂,地震活动性较强,历史上发生过多次6级以上地震.本文利用Fan小波的布格重力异常一致性方法研究该区的岩石圈有效弹性厚度和均衡调整初始加载比分布,同时基于均衡调整方法计算该区垂向构造应力分布,并将以上结果与历史地震活动进行统计分析.岩石圈挠曲分析表明,华北地区中东部的岩石圈有效弹性厚度为10~65 km,分布特征为自东南向西北逐渐减小.均衡调整初始加载比为0.5~0.8,表明现今的岩石圈挠曲状态主要由莫霍面加载形成.该区地壳承载的垂向构造应力约为-20~20 MPa,中西部地区垂向构造应力向上,东北和西南地区向下.统计分析结果显示,华北地区中东部的地震活动性随着岩石圈有效弹性厚度和均衡调整初始加载比的增加而减弱,垂向构造应力零值区域地震活动性较弱.雄安新区的岩石圈有效弹性厚度大约为15 km,均衡调整初始加载比为0.5~0.6,垂向构造应力为15~20 MPa,岩石圈参数对应的地震活动性较强,相关结果对于新区建设具有一定参考价值. 相似文献
17.
J.G. Caldwell W.F. Haxby D.E. Karig D.L. Turcotte 《Earth and Planetary Science Letters》1976,31(2):239-246
Using thin elastic plate theory and neglecting horizontal applied forces, a universal deflection profile applicable to many oceanic trenches is derived. This theoretical profile is compared with bathymetric profiles from the central Aleutian, Kuril, Bonin, and Mariana trench-outer rise regions. The profiles were corrected for sediment thickness and age variation of the lithosphere. Good agreement between theory and observation is found. The distance from the first point of zero deflection seaward of the trench to the point of maximum height of the outer rise is directly related to the flexural rigidity of the lithosphere. The thickness of the elastic lithosphere is found to vary between 20 and 29 km for the trench profiles considered. The good agreement obtained shows that horizontal forces may be neglected and that the bending lithosphere behaves elastically in the cases considered. The analysis shows that only unreasonably large horizontal forces would affect the universal deflection curve. It is concluded that although the near-surface lithosphere may be subject to brittle fracture, the deeper lithosphere is capable of transmitting elastic stresses as high as 9 kbar. 相似文献
18.
An analysis of the relationship between the bathymetry and the gravity field has been carried out both in the frequency domain (admittance technique) and in the space domain over the Del Cano Rise and the Crozet Bank (southern Indian Ocean). A bathymetric map, contoured from original shipboard data and a geoid anomaly map, computed from a merged set of SEASAT and GEOS3 data were used. The inversion of admittances for water depth, crustal thickness, crustal density and elastic plate thickness shows that the isostatic response of the lithosphere supporting the Del Cano Rise differs very much from that of the one situated beneath the Crozet Bank. The Del Cano Rise appears to have been formed near the active Southwest Indian Ridge before Early Eocene and is locally supported by a thickened crust. Shallow thermal processes contribute to the present topography of the Crozet Bank, emplaced further away from the Southeast Indian Ridge on older crust. 相似文献
19.
Topographic and associated gravity signals often result from the interference of several phenomena. In the present paper, an admittance function for the superposition of several physical mechanisms acting in the same waveband is derived. If the processes are not phase related, the resulting admittance function is the average of the individual admittance functions weighted by the squared amplitude of the topography for each process.We use this concept of superposition of different processes to understand the compensation of the Atlantic ridge valley. Classical transfer function studies applied to slow-spreading ridges have concluded that the topography was emplaced on an elastic plate about 10 km thick. These analyses of gravity and topography seem to contradict the physical models explaining the median rift valley, which is thought to be due to dynamical effects and thus to be uncompensated. We obtain an “average axial valley” gravity and topography profile by stacking several profiles perpendicular to the Mid-Atlantic Ridge and subtracting a long-wavelength thermal effect. We find that the gravity over topography spectral ratio of the “average axial valley signal” is consistent with an uncompensated process. Our study thus confirms that the mode of formation of the axial valley of a slow-spreading ridge involves an uncompensated mechanism. The presence of an additional process characterized by low admittance values, uncorrelated from one profile to the other, is also suggested in order to explain the observed admittance function. The study of the long wavelength (λ > 300 km) gravity and topography signal leads us to invoke the cooling of the upper portion of the crust by water circulation and to exclude the presence of a large amount of partial melt at depth (more than 5% over a 20 km thick layer at a mean depth of 60 km). 相似文献
20.
During recent gravity surveys in Patagonia, we were unable to acquire data on the North Patagonian Icecap, which is completely inaccessible for land surveying. The Icecap is clearly of tectonic significance, but, because of its tectonic history, it is uplifted and rugged, and consequently inaccessible. Therefore the distribution of geophysical observations which can be acquired in a rugged field area is dependent on the tectonic history. This suggests that a tectonic history which is reconstructed from geophysical data may be systematically biased. We use models of local and flexural isostasy to estimate the gravity errors associated with interpolation across inaccessible topography. The gravity error is largest for Pratt isostasy, where the mass deficit which supports the topography is at relatively shallow depths. The gravity error is least for flexural isostasy, because in this case the inaccessible topography is supported regionally by a mass deficit which extends beyond the inaccessible region. An analytical flexural interpolation scheme is proposed for interpolation across data gaps associated with inaccessible topography. Flexural theory and Gauss’s theorem are used to predict the gravity anomaly due to the mass excess of the inaccessible topography. We apply this scheme to the North Patagonian Icecap, to demonstrate that flexural interpolation predicts a relative gravity low at the site of the Icecap, which would not be predicted by purely geometrical interpolation schemes. 相似文献