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1.
《地球物理学进展》2016,(2)
应用高分辨率GRAIL重力场模型和LOLA激光测高数据,利用两者间重力/地形导纳的统计关系反演月球岩石圈的结构特征是当前的重要手段.在研究区域物理性质各向同性的前提下,可将不同载荷模型引起的岩石圈挠曲量的球谐系数,表示成观测地形球谐系数的函数关系,结合非线性反演算法,可将不同参数的模型导纳谱与观测值进行最优拟合.结果表明导纳方法求解的高地地形平均月壳密度较接近高地地形的平均值2550 kg/m~3.载荷比有正有负,表明内部载荷与表面载荷可能同相也有可能反相,也反映了月球岩石圈较复杂的结构特征.在各向同性的前提下,少部分区域的拟合残差接近其期望值1,可反演出参数的最优解.大部分区域较难反演出最优值,表明月球岩石圈的物理性质大部分并不均一,在各向异性的前提下,在空间域内使用数值计算方法有望对大部分区域的弹性厚度进行最优估计. 相似文献
2.
区域岩石圈有效弹性厚度Te的确定对认识其力学性质及演化等动力学问题具有重要意义.长期以来,大陆地区有效弹性厚度的确定一直存在着争议.尽管Pérez-Gussinyé等2004年的研究消除了不同方法(自由空气导纳法和布格相关法)之间的分歧,但其确定有效弹性厚度的误差仍然非常大.本文提出了利用Moho面起伏及地表地形反演岩石圈有效弹性厚度的Moho地形导纳法(MDDF),并利用合成的地表地形和Moho面起伏模型验证了该方法的可行性.结果表明,与传统的重力地形导纳法相比,使用Moho地形导纳法(MDDF)反演岩石圈有效弹性厚度,能较好地提高反演精度. 相似文献
3.
本文利用三维有限差分方法,基于EIGEN6C4布格重力异常和SIO V15.1地形数据,计算了青藏高原东南缘岩石圈有效弹性厚度.结果表明:青藏高原东南缘岩石圈有效弹性厚度为0~100 km,四川盆地和喜马拉雅东构造结岩石圈有效弹性厚度最大,达50~100 km;巴颜喀拉块体东部、川滇菱形块体大部、滇西等地区岩石圈强度弱,有效弹性厚度一般小于15 km;羌塘块体东部的玉树—德格附近地区岩石圈有效弹性厚度大于40 km;滇南地区岩石圈有效弹性厚度为10~30 km,大于云南北部地区.研究区域有效弹性厚度分布特征与岩石圈结构关系密切.四川盆地、喜马拉雅东构造结地区内部结构稳定,因而岩石圈强度大.川滇菱形块体等岩石圈有效弹性厚度小的地区与壳内低速、低阻/高导层分布有很好的对应关系,推测壳内岩石的部分熔融软化可能是造成高原东南缘岩石圈强度较弱的重要原因.羌塘块体东部的局部高力学强度岩石圈则可能是高原形成过程中的残留克拉通.根据本文计算的岩石圈有效弹性厚度特征,结合地震学、大地电磁等研究成果,认为青藏高原物质向东南缘挤出后受四川盆地等阻挡,造成下地壳软弱物质在理塘—稻城—丽江一带堆积,少部分物质可能穿过鲜水河断裂带的康定—道孚地区向北运动,但大部分物质向南运动,在受到滇南块体阻挡后一支流向西南的腾冲方向,另一支流向东南的攀枝花—东川方向. 相似文献
4.
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
5.
西太平洋地区板块间相互作用强烈,热演化和构造演化过程复杂.为了揭示构造相互作用对岩石圈强度的影响,本文使用自由空气重力异常模型WGM2012和地形模型ETOPO1,基于小波变换的导纳法计算得到了该地区的岩石圈有效弹性厚度(Te).西太平洋区域的Te主要分布在5～85 km之间,南海等张裂环境地区Te普遍小于20 km,俯冲带附近Te一般大于80 km,与俯冲板片年龄呈正相关.参照平板冷却模型,弹性岩石圈底界面主要分布在200～500 ℃等温面之间,随洋壳年龄增大逐渐趋于平稳,热点及年轻洋壳部分地区弹性岩石圈底界面处于200℃等温面之上.西太平洋海山与年轻海盆等区域Te与居里点深度一般呈正相关,与地表热流一般呈负相关,但由于强烈的构造运动、热液循环、岩浆活动、地幔流变性等因素的影响,整体Te与居里点深度和地表热流所反映的岩石圈热结构相关性不高. 相似文献
6.
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
7.
基于二维稳态热传导方程,利用有限元数值模拟方法,选取东西向横穿鄂尔多斯盆地地质与地球物理解释大剖面进行了深部温度场数值模拟研究,得到了华北克拉通西部的鄂尔多斯盆地下伏岩石圈热结构特征.地幔热流变化范围:21.2~24.5mW·m-2,体现为东高西低特征.壳幔热流比(Qc/Qm)介于1.51~1.84之间,为"热壳冷幔".与华北东部地幔热流对比表明,西部的鄂尔多斯盆地相对处于稳定的深部动力学环境.在岩石圈热结构研究基础上,对克拉通地震岩石圈与热岩石圈厚度差异进行了对比,研究表明:鄂尔多斯盆地西部地震岩石圈与热岩石圈厚度差异约达140km,而东部的汾渭地堑,渤海湾盆地二者差异逐渐减小.华北克拉通自西向东,地震岩石圈厚度与热岩石圈厚度差异不断减小,意味着华北克拉通岩石圈下部的软流圈地幔黏性系数自西向东逐渐降低,本文从地热学角度可能印证了太平洋俯冲脱水作用对华北克拉通的影响. 相似文献
8.
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
9.
跨呼和浩特-包头盆地(以下简称"呼包盆地")完成的91.8km长的深地震反射剖面,揭示了呼包盆地的岩石圈精细结构和断裂的深、浅构造特征.结果表明,本区地壳和岩石圈具有清晰的层状反射结构特征,其中,地壳厚度约45~48km,岩石圈厚度约82~87km.莫霍面在大青山之下出现约3.5km的抬升,暗示大青山的隆升不是因为地壳物质增厚所致,即大青山可能不存在"山根".呼包盆地为南浅、北深的"箕状"断陷盆地,盆地沉积层最厚处位于大青山山前,其厚度约为7~8km.鄂尔多斯北缘断裂和大青山山前断裂作为呼包盆地的南、北边界断裂,在剖面上均表现为由3~4条断裂组成的"Y"字形断裂构造,它们对呼包盆地的形成、地层沉积、基底变形和地震活动都有重要的控制作用.剖面揭示的岩石圈深断裂位于大青山山前断裂的下方,该断裂向上进入上地壳,向下切割中-下地壳、莫霍面,进入上地幔.深断裂的存在为深部热物质的上涌与能量强烈交换提供了通道,而上涌的软流层物质与岩石圈地幔发生交代和侵蚀作用导致岩石圈减薄. 相似文献
10.
岩石圈有效弹性厚度(Te)表征岩石圈综合力学强度,对理解区域深部构造孕震环境具有重要意义.青藏高原东北缘地质构造复杂,强烈地震活动频发.为进一步了解该区域深部岩石圈力学性质特征及其与地震活动的关系,本文利用基于Fan小波的谱方法,使用WGM2012重力异常数据、ETOPO1地形数据和CRUST1.0模型,通过导纳和相关联合反演计算了青藏高原东北缘的岩石圈有效弹性厚度(Te)与荷载比(F).结果显示研究区Te整体呈明显的东高西低分布,青藏块体Te变化剧烈,西部高值(>40 km)和东部低值(<20 km)共存;鄂尔多斯地块Te较高(>30 km),变化相对平缓;荷载比F存在局部西南高,巴颜喀拉和羌塘地块荷载比F较高(>0.5),说明以地下荷载为主,其他地块荷载比F较低(<0.2),以地表荷载为主.鄂尔多斯地块结构稳定,岩石圈强度较大,Te值较高;内部构造活动性微弱,深部物质密度横向变化较小,岩石圈所受荷载以地表为主,荷载比F较低... 相似文献
11.
《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
12.
利用双差地震定位方法对鄂尔多斯东缘地区（34°N-41°N,110°E-115°E）2008年1月-2012年12月的中小地震进行了重新定位.重定位后,定位精度得到改善,震中分布更加集中.鄂尔多斯东缘拉张盆地内部震源深度较浅,大多小于13 km,向盆地两端震源深度有加深的趋势,特别是太原盆地北端,临汾盆地北端,以及运城与临汾盆地之间的峨眉台地,震源深度可达20~25 km左右.我们认为盆地内部地壳减薄,上地幔上隆,热作用导致地壳内部脆性层减薄,致使最大震源深度变浅;盆地之间的横向隆起区受区域应力场挤压剪切作用以及盆地内部上地幔上拱产生的水平向挤压力作用等,在横向隆起区与盆地接触带易产生应力集中,导致地震的发生,由于受脆性层厚度变化等的影响,在盆地向横向隆起区过渡部位出现震源深度加深的现象.鄂尔多斯东北缘地区地震分布弥散、震源深度相对较浅,可能与源自地幔的大范围深部热作用以及地壳脆性层厚度减薄有关.根据地震的空间分布特征,对部分盆地内部的断层特征进行了讨论. 相似文献
13.
T. S. Sakoulina S. N. Kashubin G. A. Pavlenkova 《Izvestiya Physics of the Solid Earth》2016,52(4):572-589
Profile 1-AP with a length of 1300 km intersects the Barents Sea from The Kola Peninsula to Franz Josef Land. The combined Common Depth Point (CDP) and Deep Seismic Sounding (DSS) seismic studies were carried out on this profile. The DSS measurements were conducted with the standalone bottom seismic stations with an interval of 5–20 km between them. The stations recorded the signals generated by the large air guns with a step of 250 m. Based on these data, the detailed P-velocity section of the Earth’s crust and uppermost mantle have been constructed for the entire profile and the S-velocity section for its southern part. The use of a variety of methods for constructing the velocity sections enabled us to assess the capabilities of each method from the standpoint of the highest reliability and informativity of the models. The ray tracing method yielded the best results. The 1-PR profile crosses two large basins—the South Barents and North Barents ones, with the thickness of the sediments increasing from 8 to 10 km in the south to 12–15 km in the north. The Earth’s crust pertains to the continental type along the entire profile. Its thickness averages 32 to 36 km and only increases to 43 km at the boundary between the two basins. The distinct change in the wave field at this boundary suggests the presence of a large deep fault in this zone. The high-velocity blocks are revealed in the crust of the South Barents basin, whereas the North Barents crust is characterized by relatively low velocities. 相似文献
14.
T. S. Sakulina Yu. V. Roslov G. A. Pavlenkova 《Izvestiya Physics of the Solid Earth》2009,45(3):231-238
Extensive seismic investigations of the crust and upper mantle have been carried out in the region of the Barents and Kara seas during the past decade. One of the profiles (2-AR) measured by FGU NPP “Sevmorgeo” with the CDP and deep seismic sounding methods was successfully used for comparatively analyzing different technologies of constructing seismic sections and for demonstrating a high information content of the method of mathematical modeling and the constructions of wave sections from supercritical reflected waves. It is shown that the crusts of the North Barents and South Kara basins are different. In the first case, the velocity section changes insignificantly, whereas, in the second case, velocities in the crust increase under the basin and the M boundary rises. The crust of the Novaya Zemlya orogen has a thickness of 48 km, and its average thickness on the profile is 35 km. 相似文献
15.
This paper presents a probable isostatic model of the East Anatolian Region, which lies in a belt of significant plate movements.
Probable locations of the horizontal and vertical discontinuities in the crust structure were determined using the normalized
full gradient (NFG) method. For the purpose of explaining the mechanism that supports topography corresponding to the crust
thickness in the region, calculations of effective elastic thickness (T
e) were carried out initially by utilizing admittance and misfit functions. According to these results, the effective elastic
thickness value obtained was less than the crust thickness, even though the isostatic model does not conform with the Airy
model. Consequently, it was assumed that there could be problems beneath the crust. Hence, the NFG method was applied on
the Bouguer gravity data of the region in order to investigate probable discontinuities in the crust structure. According
to the NFG results, vertical structural transitions were observed at a depth ranging between 10 and 30 km, which begin immediately
north of the Bitlis Zagros Suture Zone (BZSZ) and continue in a northerly direction. The relationship between the effective
elastic thickness (T
e; 13 km in average as determined in the last stage), and the seismogenic zone in the region was investigated. If the T
e value happens to be less then the crustal thickness, then one can say that there are problems in the crustal structure of
the region similar to Eastern Anatolia. Indeed, when NFG results of the study area are examined, numerous vertical and horizontal
discontinuities in the crust can be observed. These discontinuities, which correspond to low Bouguer gravity anomalies and
shallow focal depth-earthquakes, are probably the source of the factors which rule the tectonic mechanism of the region. 相似文献
16.
Titanium concentrations have been derived from measurements with the lunar-orbiting gamma-ray experiment on Apollo 15 and 16 by analyzing a spectral interval in which the titanium signal is relatively enhanced. Landing site soil values provide the reference for a regression curve from which Ti concentrations in 137 regions of adequate counting statistics are calculated. Among the mare regions overflown, the southern portion of Mare Tranquillitatis contains the highest Ti concentration (4.4%), Mare Serenitatis, Mare Fecunditatis, and Mare Smythii have intermediate values corresponding to low-Ti basalts, and Mare Crisium is conspicuously low in Ti (0.9%). Regional values in the western maria range from 1.1% to 4.1%, somewhat higher in the north than in the south, with the highest values seen south and west of Aristarchus. The Aristarchus Plateau appears chemically distinct from the surrounding mare. The younger western basalts mapped by the experiment do not appear to be identical to the Apollo 11 and Apollo 17 high-Ti basalts. Low-Ti basalts predominate in the observed mare regions. Highland Ti concentrations range from undetectable to 1.5% with several exceptions; accuracy is limited by the relatively large uncertainty. Highland results suggest a north-south asymmetry which is not consistent with previously reported results for Fe and Th. Comparisons with telescopic spectral reflectance studies of the maria do not show complete agreement and suggest that effects due to Fe may not have been fully removed from the reflectance data. 相似文献
17.
John D. O&#x;Keefe Thomas J. Ahrens 《Physics of the Earth and Planetary Interiors》1978,16(4):341-351
The axisymmetric distribution of stress, internal energy and particle velocity resulting from the impact of an iron meteoroid with a gabbroic anorthosite lunar crust has been calculated for the regime in which shock-induced melting and vaporization takes place. Comparison of impact flow fields, with phase changes in silicates taken into account, with earlier results demonstrate that in the phase change case when the 15-km/s projectile has penetrated some two projectile radii into the moon, the peak stress in the flow is ～0.66 Mbar at a depth of 66 km, and the stress has decayed to ～66 kbar at a depth of 47 km. Rapid attenuation occurs because of the high rarefaction velocity of the high-pressure phases associated with a 35% (zero-pressure) density increase. This feature of the phase-change flow tends to strongly concentrate the maximum shock pressures along the meteoroid trajectory (axis) and makes the conical zone along which high internal energy deposition occurs, both shallow and narrow. Examination of the gravitational energies required to excavate larger craters on the moon indicates the importance of gravity forces acting during the excavation of craters having radii in the range greater than ～2 – ～140 km. It is observed that the “hydrodynamic” energy vs. crater radius relation approaches those for various “gravitational” energy vs. radius relations at the radii values corresponding to the larger mare basins. Cratering energy values in the range of (1.0 – 9.4) · 1032 erg are inferred on this basis for the Imbrium crater. Using these values and the criteria that all rocks exposed to ～100 kbar or greater shock pressures are included in the ejecta (some of which falls back) implies that the maximum depth of sampling expected to be represented within the Apollo collection lies in the range 148–328 km. 相似文献
18.
19.
发生在地球浅层的2008年汶川地震驱动了龙门山及前陆地区的地表同震垂向位移.根据冲断带-前陆盆地弹性挠曲模型理论,在进行弹性挠曲模拟反演的基础上,结合对深部地球物理特征(泊松比、电性结构)的分析,发现龙门山前陆盆地现今岩石圈有效弹性厚度(T_e)具有自东向西逐渐减薄的趋势,自川中地区的30~40 km减至龙门山地区的10~20 km.在对晚三叠世以来前陆盆地各阶段盆地结构进行刻画的基础上,进行弹性挠曲模拟反演,推断龙门山前陆盆地的前渊地区(四川盆地西部)岩石圈的T_e值自晚三叠世以来具有逐渐减薄的趋势.这可能与松潘一甘孜地块下方广泛存在的软流圈热物质对四川盆地西部岩石圈下部的长期加热而导致的熔融有关,反映了地球深部动力学过程与地球表层盆地演化之间的耦合关系. 相似文献
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N. I. Pavlenkova S. N. Kashubin G. A. Pavlenkova 《Izvestiya Physics of the Solid Earth》2016,52(5):770-784
Several large basins with a depth up to 15–20 km are revealed in the platform regions of Northern Eurasia—the Pre-Caspian, Vilyui, Pur-Gydan, and Kara–Barents platforms. All these basins have two structural features in common: they all have a rounded shape with steep walls and are marked with the reduced thickness of the Earth’s crust. With the basins' depth of 15–20 km, the basement top is flat and has an almost horizontal surface. The basins differ by the average seismic velocities in the crystalline crust which vary from 6.2–64 to 6.8–7.0 km/s. Another distinction is the type of the crystalline crust ranging from continental with a thick granite-gneiss layer to suboceanic, represented by the basite layer. For explaining the formation of these basins, we suggest a combined petrophysical model which includes several geodynamical processes of different intensity: rifting, basification, and eclogitization of the Earth’s crust.The model also takes into account the process of material outflow from beneath a basin through the midcrustal layer of increased porosity and fluid saturation. This accounts for the strong reduction of the granite-gneiss layer with the preservation of the basement’s flat surface and for the formation of significant source areas of clastic material around the basin. The formation of these basins requires an extensive and sufficiently laterally uniform and longoperating energy source. The intrusion of the mantle material saturated with fluids into the bottom portions of the crust or, simply, the long-lasting inflow of the deep fluids are the most probable sources of this kind. 相似文献