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根据中国地震台网和ISC台站提供的P波走时资料,使用差异演化全局优化算法(DE算法)和移动窗方法反演了琉球-台湾-吕宋地区岩石层尺度的P波速度结构.在台站和地震分布较为密集的地区,反演窗口为2°×2°,移动步长为1°;在台站和地震较少的地区,反演窗口为4°×4°左右,移动步长为2°.反演结果揭示出琉球-台湾-吕宋地区壳幔结构的横向差异:琉球岛弧西侧受冲绳海槽地幔热扰动的地壳减薄,东侧由于菲律宾海板决的俯冲挤压地壳略有增厚;欧亚大陆与菲律宾海板块的相互碰撞导致台湾地区地壳及岩石层明显增厚;吕宋及菲律宾北部岩石层受岛弧火山下方热流影响较大.结果表明,非线性全局优化算法和移动窗方法能够用于反演较大尺度速度结构的横向变化. 相似文献
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利用中国大陆东部及台湾地区、日本和琉球群岛的地震观测数据，通过体波地震层析技术反演了中国东部海域及其邻近地区的P波速度结构.以此为依据分析了不同地区的岩石层性质和深部动力学条件，探讨了中朝与扬子块体、扬子与华夏块体在海区的深部边界及其构造属性，揭示出菲律宾海板块与欧亚大陆的碰撞以及板片俯冲下沉、弧后扩张作用对中国东部海域岩石层结构的影响.结果表明，中国东部海域的岩石层地幔存在明显的横向非均匀性，它们与区域构造的形成演化有一定的联系.中国大陆东部的五莲－青岛断裂与朝鲜半岛西缘断裂、济州岛南缘断裂共同构成中朝和扬子块体的边界，江绍断裂向东延伸至朝鲜半岛南端成为分隔扬子和华夏块体的边界；东海陆架与冲绳海槽的岩石层结构差异明显，东海陆架具有中国东部地区的岩石层特征，属于欧亚大陆向海域的延伸；冲绳海槽的岩石层强烈减薄，为大陆向大洋过渡的区域；沿着日本－琉球－台湾俯冲带，菲律宾海板块俯冲下沉引起的地幔扰动对中国东部海域产生了较大的影响，欧亚大陆与菲律宾海板块之间的相互碰撞导致台湾地区岩石层明显增厚. 相似文献
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琉球海沟的构造和运动特征 总被引：3，自引：3，他引：3
琉球海沟是欧亚板块与菲律宾海板块之间的边界，海沟西坡是大陆性质的琉球岛弧，东坡是大洋性质的菲律宾海地壳．海底地震反射探测和地震震源定位表明，菲律宾海板块沿海沟向琉球岛弧下俯冲，俯冲角度与深度沿海沟走向变化．有证据显示，由于俯冲板前缘的横向移动，海沟和岛弧正朝大洋方向后退，弧后盆地-冲绳海槽发生拉张变形．最近一次的海沟后退与冲绳海槽扩张可能是从上新世末(2Ma前)开始的，岛弧的后退移动和弧后拉张在南部与海沟走向垂直，在中部和北部与海沟走向斜交，总体上向南的运动分量占优势、与海沟后退相关的弧后拉张集中在冲绳海槽，没有证据表明对其西侧的中国东海陆架盆地产生影响、海沟后退的原因可能与俯冲板的动力不平衡以及它与周围地幔的相互作用有关． 相似文献
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Receiver functions in northeast China - implications for slab penetration into the lower mantle in northwest Pacific subduction zone 总被引：6，自引：0，他引：6
Seismic studies of the subducting lithosphere and the upper mantle discontinuities in the northwest Pacific subduction zone beneath Japan and northeast China have suggested contrary subduction scenarios. There was little consensus on the issue whether the subducting slab penetrates the upper mantle discontinuities into the lower mantle or it is deflected atop of the 660-km discontinuity over several hundred kilometers. We calculate receiver functions from a recent seismic broadband station network located in northeast China and find topographic variations of the upper mantle discontinuities. A deeper-than-normal 660-km discontinuity is observed over an area of 400 km and it coincides with the stagnant slab imaged by seismic tomography. The 660-km discontinuity is locally depressed by more than 35 km and the transition zone is thickened by more than 20 km in the east of the region where it encounters the slab. These observations provide evidence of the slab accumulating in the mantle transition zone and locally penetrating into the lower mantle. 相似文献
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《Earth and Planetary Science Letters》2006,241(1-2):2-10
Surface heat flows are calculated from elastic lithosphere thicknesses for the heavy cratered highlands of Mars, in terms of the fraction of the surface heat flow derived from crustal heat sources. Previous heat flow estimations for Mars used linear thermal gradients, which is equivalent to ignoring the existence of heat sources within the crust. We compute surface heat flows following a methodology that relates effective thickness and curvature of an elastic plate with the strength envelope of the lithosphere, and assuming crustal heat sources homogeneously distributed in a radioactive element-rich layer 20 or 60 km thick. The obtained results show that the surface heat flow increases with the proportion of heat sources within the crust, and with the decrease of both radioactive element-rich layer thickness and surface temperature. Also, the results permit us to calculate representative temperatures for the crust base, rock strength for the upper mantle, and lower and upper limits to the crustal magnetization depth and intensity, respectively. For Terra Cimmeria, an effective elastic thickness of 12 km implies between 30% and 80% of heat sources located within the crust. In this case the uppermost mantle would be weak at the time of loading, and temperatures in the lower crust cold enough to favor unrelaxed crustal thickness variations and to permit deep Curie depths in the highlands, as suggested by the observational evidence. 相似文献
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Effects of relative plate motion on the deep structure and penetration depth of slabs below the Izu-Bonin and Mariana island arcs 总被引：2，自引：0，他引：2
An increasing number of seismological studies indicate that slabs of subducted lithosphere penetrate the Earth's lower mantle below some island arcs but are deflected, or, rather, laid down, in the transition zone below others. Recent numerical simulations of mantle flow also advocate a hybrid form of mantle convection, with intermittent layering. We present a multi-disciplinary analysis of slab morphology and mantle dynamics in which we account explicitly for the history of subduction below specific island arcs in an attempt to understand what controls lateral variations in slab morphology and penetration depth. Central in our discussion are the Izu-Bonin and Mariana subduction zones. We argue that the differences in the tectonic evolution of these subduction zones—in particular the amount and rate of trench migration—can explain why the slab of subducted oceanic lithosphere seems to be (at least temporarily) stagnant in the Earth's transition zone below the Izu-Bonin arc but penetrates into the lower mantle below the Mariana arc. We briefly speculate on the applicability of our model of the temporal and spatial evolution of slab morphology to other subduction zones. Although further investigation is necessary, our tentative model shows the potential for interpreting seismic images of slab structure by accounting for the plate-tectonic history of the subduction zones involved. We therefore hope that the ideas outlined here will stimulate and direct new research initiatives. 相似文献
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Motoo Ukawa 《Earth and Planetary Science Letters》1979,43(3):434-440
Composite P-wave seismograms are constructed for intermediate earthquakes in the Kurile region using seismic stations in central and western Japan. Ray paths are approximately parallel to the intermediate seismic zone along the Kurile-Japan arc. A compressional velocity structure model is constructed from the travel time and relative amplitude data for the upper mantle involving this intermediate seismic zone. The absence of any significant low-velocity layer below the descending slab of lithosphere can be shown from the data. Instead, the model consistent with the observed data has a non-velocity gradient layer of about 30 km thickness beneath the descending slab. The result suggests that the low-velocity layer beneath the Pacific plate thins landward across the Kurile-Japan trench and does not descend along the base of the descending slab. 相似文献
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基于SIO(Scripps Institute of Oceanography)最新全球重力和高程模型,计算了巴颜喀拉地块东部及邻区的布格重力异常、均衡重力异常、岩石圈有效弹性厚度及荷载比.结合大地热流、地震速度结构、地震活动和断裂构造分布等,分析了地壳均衡状态和岩石圈有效弹性厚度、地质构造单元间的差异及与地震活动的相关性特征.研究结果表明,该区域布格重力变化范围约为-500～0mGal(1mGal=10~(-5)m·s~(-2),下同),在巴颜喀拉块体东部区域形成弧形重力梯度带,近年来的中强地震活动频发于该梯度带不同部位,应与其应力依次释放有关;均衡重力异常结果表明,其变化范围约为-80～+100mGal,且大部分区域处于±20mGal以内的被认为处于重力均衡的状态,重力非均衡(正或负)多出现于块体边界带附近,地震多发生在靠近块体边界的均衡重力异常(正或负,主要为正)区域内;巴颜喀拉地块东部及邻区岩石圈有效弹性厚度(T_e)为10～65km,不同构造单元之间T_e空间分布差异明显,较低的T_e值出现在龙门山构造带附近,T_e值为20km左右,岩石圈荷载加载比为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.进一步分析表明,巴颜喀拉地块东部挤压增生与横向流动同时发生,是造成该区域地震发生与重力均衡异常高值重合、岩石圈有效弹性厚度和大地热流值较低的主要原因.本文获得的地壳均衡特征及岩石圈有效弹性强度结果,加深了对巴颜喀拉东部及邻区岩石圈构造演化过程的认识. 相似文献
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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
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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
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The traditional view of the rheology of the continental lithosphere, sometimes known as the “jelly sandwich model”, consists of a strong upper crust, a weak lower crust, and a strong upper lithospheric mantle. Some authors argue, however, that the lithospheric mantle is weak and contributes little to the total strength and the effective elastic thickness of the lithosphere; this weakness is claimed to be due to the mantle being wet or subjected to temperatures higher than usually believed. This paper uses the relationship between rheology of the lithosphere and heat flow to calculate theoretical effective elastic thicknesses for three regions of the central Iberian Peninsula (the Duero Basin, the Spanish Central System and the Tajo Basin), taking into account the contribution of the crust and the lithospheric mantle, for dry and wet rheologies. We found that a wet peridotite rheology for the lithospheric mantle is generally consistent with independent (based on Bouguer coherence or flexural modeling) estimates of the effective elastic thickness for the study area, whereas a dry peridotite rheology cannot be reconciled with them. Moreover, the contribution of the mantle to the bending moment of the lithosphere, and therefore to both the effective elastic thickness and the total strength of the lithosphere, is important, and it may even be the dominant contribution. Therefore, the jelly sandwich model may be considered valid for the central Iberian Peninsula. 相似文献
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由给定的随时间和空间变化的二维应变速率分布计算速度场,根据速度场计算二维热传导方程,得到岩石圈的热演化结构,然后计算由热扰动引起的密度变化,进而确定加载到岩石圈上的载荷,根据载荷计算挠曲方程,最终得到盆地的沉降.在此基础上讨论了热源对地表热流和沉降的影响以及岩石圈有效弹性厚度对盆地几何形态的影响.结果表明,热源对地表热流影响显著,对沉降影响不大,岩石圈有效弹性厚度则控制盆地的几何形态.二维应变速率正演为下一步的反演奠定了基础. 相似文献
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盆地内快速剧烈的构造作用可导致热异常,在利用盆地热历史揭示深部动力学过程时,需消除热异常的影响. 本文根据瞬时热传导原理,校正了渤海湾盆地渤中坳陷低热异常,准确地约束了盆地深部动力学状态. 对渤中坳陷内3口典型井进行热流校正结果表明,渤中坳陷古近纪以来快速沉积导致其现今（~60.9 mW·m-2）未达到热平衡（低热异常）. 校正后的热流值平均约为67.4 mW·m-2,比现今高5~10 mW·m-2. 利用校正后的热流值计算得到的渤中坳陷的“热”岩石圈的平均厚度约为70 km,比修正前的厚度（82~100 km）减少了13~28 km. 相似文献
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We have determined the elastic thicknessTe of the oceanic lithosphere along two volcanic chains of the South Central Pacific: Cook-Austral and Society islands. We used a three-dimensional spatial method to model the lithospheric flexure assuming a continuous elastic plate. The model was constrained by geoid height data from the SEASAT satellite.Along the Cook-Austral chain the elastic thickness increases westward, from 2–4 km at McDonald hot spot to 14 km at Rarotonga. At McDonald seamount, however, the data are better explained by a local compensation model. The observed trend shows an increase ofTe with age of plate at loading time. However, the elastic layer under the Cook-Austral appears systematically thinner by several kilometers than expected for “normal” seafloor, suggesting that substantial thermal thinning has taken place in this region. Considering the apparent thermal age of the plate instead of crustal age improves noticeably the results. Along the Society chainTe varies from 20 km under Tahiti to 13 km under Maupiti which is located 500 km westward. When plotting together the Society and Cook-AustralTe results versus age of load, we notice that within the first five million years after loading,Te decreases significantly while tending rapidly to an equilibrium value. This may be interpreted as the effect of initial stress relaxation which occurs just after loading inside the lower lithosphere and suggests that the presently measured elastic thickness under the very young Tahiti load ( 0.8 Ma) is not yet the equilibrium thickness. 相似文献
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LIU Shaowen WANG Liangshu GONG Yuling LI Cheng LI Hua & HAN Yongbing . Department of Urban Resources Nanjing University Nanjing China . Department of Earth Sciences Nanjing University Nanjing China 《中国科学D辑(英文版)》2005,48(10)
Thermal regime of the lithosphere is the scenario of the lithospheric thermal evolution, and the thermo-mechanical state of lithosphere definitively controls its deformation style and mechanism. Better understanding of the lithospheric deep thermal-rheo- logical structure of sedimentary basin will shed light on the formation and evolution dynamic process of the basin. Surface tectonics is the response of the deep structure, and is controlled by the lithospheric ther-mal-rheological properties.… 相似文献
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The traditional definition of lithospheric strength is derived from the differential stresses required to form brittle and ductile structures at a constant strain rate. This definition is based on dissipative brittle and ductile deformation and does not take into account the ability of the lithosphere to store elastic strain. Here we show the important role of elasticity in controlling the long-term behaviour of the lithosphere. This is particularly evident when describing deformation in a thermodynamic framework, which differentiates between stored (Helmholtz free energy) and dissipative (entropy) energy potentials. In our model calculations we stretch a continental lithosphere with a wide range of crustal thickness (30–60 km) and heat flow (50–80 mW/m2) at a constant velocity. We show that the Helmholtz free energy, which in our simple calculation describes the energy stored elastically, converges for all models within a 25% range, while the dissipated energy varies over an order of magnitude. This variation stems from complex patterns in the local strain distributions of the different models, which together operate to minimize the Helmholtz free energy. This energy minimization is a fundamental material behaviour of the lithosphere, which in our simple case is defined by its elastic properties. We conclude from this result that elasticity (more generally Helmholtz free energy) is an important regulator of the long-term geological strength of the lithosphere. 相似文献
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S.D. Kogan 《Physics of the Earth and Planetary Interiors》1981,26(3):171-178
An investigation of travel-time residuals of P waves as compared to an average global travel-time curve with a base-line determined shows that about 400–500 km of the upper mantle at the boundary with the crust and a similar thickness of the lower mantle at the boundary with the core are laterally inhomogeneous. The upper mantle both under continents and under oceans consists of crust-mantle blocks distinguished by longitudinal wave velocity, surface tectonics and intensity of the heat flow. It has been revealed that within individual crust-mantle blocks there is an azimuthal relationship of P-wave travel-time indicative of possible anisotropy of upper mantle elastic properties down to depths of the order of several hundred kilometers. 相似文献
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从洋中脊上升的地慢物质带上来的大量热量,使在洋中脊裂谷处的海底热流及温度最高,向海沟逐渐减小．由于热胀冷缩,海底地势在洋中脊处最高．作者根据板块模型由一维运动物体的热传导方程推出裂谷处上升物体的温度分布公式．用此分布公式作为垂直边的边界条件,严格地求解了运动板块的二维运动物体热传导方程．用此方程研究了各参数与观测量之间的关系．通过改变公式中的参数值,使计算的理论曲线与实测海底热流一年龄及海底深度一年龄曲线拟合,从而求出了板块的厚度Ｌ＝９７ｋｍ,地幔上升速度ｕ＝３．ｇｍｍ／ａ,热膨胀系数ａ＝３．３７×１０－５／℃及温度分布．该方法克服了在洋中脊处理论热流值趋于无限大的问题,并可以计算出地幔上升流的速度及宽度． 相似文献