Effects of plate and slab viscosities on the geoid

The effects of plate rheology (strong plate interiors and weak plate margins) and stiff subducted lithosphere (slabs) on the geoid and plate motions, considered jointly, are examined with three-dimensional spherical models of mantle flow. Buoyancy forces are based on the internal distribution of subducted lithosphere estimated from the last 160 Ma of subduction history. While the ratio of the lower mantle/upper mantle viscosity has a strong effect on the long-wavelength geoid, as has been shown before, we find that plate rheology is also significant and that its inclusion yields a better geoid model while simultaneously reproducing basic features of observed plate motion. Slab viscosity can strongly affect the geoid, depending on whether a slab is coupled to the surface. In particular, deep, high-viscosity slabs beneath the northern Pacific that are disconnected from the surface as a result of subduction history produce significant long-wavelength geoid highs that differ from the observation. This suggests that slabs in the lower mantle may be not as stiff as predicted from a simple thermally activated rheology, if the slab model is accurate.     

Formation of small scale folds and faults in northern Ohio

Folds and faults in the Devonian shales of the Berea area, Ohio have been analyzed on a small scale (several meters) to determine their method of formation. A simple elastic model has been developed to account for stress concentration due to lithostatic pressures induced by local relief. This analytical model is then coupled to the beam–column buckling stability theory. The possibility of failure due to faulting is also examined using the Coulomb criterion. Initial results indicate that local stresses due to topography are a probable cause of these structures, though the possible role of regional tectonic effects cannot be eliminated. The state of the local stress field and the possibility of seismic events have important implications for surface and subsurface design problems.     

低信噪比海底多分量地震数据波场分离方法

以多分量地震观测为基础,联合纵波和转换横波数据能更有效地估计地下介质的弹性和物性参数,提升地质构造成像与油气储层描述的精度.在海底多分量地震数据处理过程中,观测记录的上-下行波分解和P/S波分离可压制水层鸣震以及P与S波之间的串扰,对偏移成像和纵横波速度建模至关重要.但受海底环境、仪器与观测因素共同影响,许多海底多分量...     

Rheological properties and structural changes in different sections of boiled abalone meat

1　Introduction　AbaloneHaliotisdiscusisaverypopularfoodthrough outtheworld .WhenAsianpeoples ,notablyJapaneseandChinese ,eatabalonedishes ,theyenjoythefirmtextureoftherawmeatandthetendernessoftheboiledmeat .InJapan ,thetoughervarietiesoftherawabalonemeatareenjoyedandtheabaloneisoftenthin lyslicedandservedraw (sashimi) ,whileinchina ,thetendernessandsoftervarietiesoflesscollagenofboiledmeatareconsideredsuitableforeating ,sotheabaloneisoftenservedbyheating .Infoodscience ,manyreportshavebeen …     

金川矿区地下巷道围岩应力场特征及演化机制

金川矿区位于高地应力区，岩性坚硬但岩体较为破碎，其地下巷道围岩压力在时间上和空间上的分布具有矛盾统一的双重性特征，这种双重性特征在国内外许多同类型地下工程中均存在。从应场演化角度，对该类围岩的应力场特征及其演化机制进行了探讨，人为围岩应力的特殊时间和空间分布特征的根本原因是结构面在围岩动态演化过程中发生一系列复杂的时间相关性力学行为和力学响应。据此提出围岩结构性流变的观点，并给出其理论解，它较好地反映了该类围岩变形破坏过程中应力场的演化特征。     

岩石变形机制与流变学研究的近期发展--显微构造、变形机制与流变学国际会议简介

结合显微构造,变形机制与流学国际会议讨论的有关为形机制与流学的几个主要方面,阐述了目前在该学科领域与研究方向上的研究现状与进展;地壳岩石脆－韧性转变变形机制,强调脆性变形机制与韧性变形机制之间的反应及由此引起的岩石强度降低;应变局部化机理与主要影响因素,应变局部化可以由是软化或硬化机制引起的。     

Rheological Regime of the Upper Mantle beneath the Taiwan Strait and Its Tectonic Significance1

Abstract This paper deals with deformation textures and fabrics of mantle-derived xenoliths and dislocation microstructures of olivine in the upper mantle in the Penghu Islands, Taiwan. According to the calculation of the chemical composition of xenolith minerals (pyroxene), the equilibrium temperatures and pressures were 986-1116°C and 1.50-2.60 GPa, respectively. Deformation events in the upper mantle may fall into three sequences: (1) uniform steady-state flow deformation with high temperatures and low stresses, (2) shear flow deformation with high temperatures and relatively high stresses on diapiric margins of the upper mantle, and (3) extraction deformation of {110} glide bands with low temperatures and high strain rates. Deformation events and thermal structure of the upper mantle in the study area show that eastern Fujian and the Penghu Islands are characterized by very similar rheological properties of the upper mantle. Volcanism of basalts in the Penghu Islands is related to hot spots of the upper mantle under neath the Taiwan Strait, and diapirism and upwelling of the upper mantle are the dominant factors responsible for rifting of the continental margins in eastern China.     

大别—苏鲁区UHP变质岩构造学及流变学演化

在大别—苏鲁区的30个关键位置,对UHP/HP变质岩进行详细构造解析、大比例尺(1∶10000)制图并在区域尺度上进行观察和对比,以便揭示它们的构造几何学、变形条件和流变学演化。初步的研究结果指出,广泛出露的UHP/HP榴辉岩相岩石形成一个巨大的UHP/HP变质带,提供了一个观察中朝与扬子克拉通之间三叠纪大陆深俯冲-碰撞带过程的窗口。观察的显微构造及组构指出,UHP/HP变质带内岩石变形机制,无论是在榴辉岩相阶段还是在榴辉岩相后阶段,都是以塑性流变为主,其力学行为和组构特征都受组成矿物的强度、强度差等流变学特征,以及变形物理环境如压力、温度、应变速率、差异应力和流体含量等的制约。在俯冲/碰撞带内的变形分解作用于岩石圈不同层次及不同的构造阶段都曾发生,而且,在不同尺度上,应变局部化形成具高应变的剪切带网络,且一般显示典型的布丁-基质或碎斑-基质构造及流变学型式。根据构造、岩石、变质作用及地质年代学资料,借助于岩石圈流变学基本原理,提出一个大别—苏鲁区UHP/HP变质岩石流变学演化的工作模式,它涉及早期扬子与中朝克拉通间三叠纪(~250~230Ma)大陆深俯冲/碰撞、UHP/HP变质岩形成,相继深埋岩石的多期折返。特别强调UHP/HP岩石向地壳表层的折返,主要是构造过程,地面侵蚀作用是次要的。     

岩石流变力学的研究现状及其发展方向

从岩石单轴压缩流变试验、多轴压缩流变试验、拉伸断裂流变试验、岩体及结构面的剪切流变试验、以及流变试验中的各种影响因素等来评述岩石流变试验的研究进展。同时从经验模型、元件模型、损伤断裂模型、基于内时理论的流变模型以及弹粘塑性模型等来对岩石流变本构模型的发展进行了回顾。最后, 指出复杂应力路径下岩石的非线性流变、水力-应力耦合情况下的岩石流变、考虑各向异性的岩石流变等方面是今后需要进一步深入研究的问题。