Ice flow physical processes derived from the ERS-1 high-resolution map of the Antarctica and Greenland ice sheets

The ERS-1 satellite, launched in 1991, has provided altimetric observations of the Greenland Ice Sheet and 80 per cent of the Antarctica Ice Sheet north of 82°S. It was placed in a geodetic (168-day repeat) orbit between April 1994 and March 1995, yielding a 1.5  km across-track spacing at latitude 70° with a higher along-track sampling of 350  m. We have analysed the waveform altimetric data from this period to compute maps with a 1/30° grid size. Data processing consists of correcting for environmental factors and editing and retracking the waveforms. A further step consists of reducing the radial orbit error through crossover analysis and correcting the slope error to second order. The high-resolution topography of both ice sheets reveals numerous details. A kilometre-scale surface roughness running at 45° from the flow direction is the dominant topographic characteristic of both continents. Antarctica also exhibits many scars due to local flow anomalies. Several physical processes can be identified: abrupt transitions from deformation to sliding and vice versa, and impressive strike-slip phenomena, inducing en echelon folds.     

Study the elastic properties and the anisotropy of rocks using different machine learning methods

This paper aims to demonstrate that the elastic stiffnesses and the anisotropic parameters of rocks can be accurately predicted from geophysical features such as the porosity, the density, the compression stress, the pore pressure and the burial depth using relevant machine learning methods. It also suggests that the extreme gradient boosting method is the best method for this purpose. It is more accurate, extremely faster to train and more robust than the artificial neural networks and the support vector machine methods. Very high R-squared scores was obtained for the predicted elastic stiffnesses of a relevant dataset that is available in the literature. This dataset contains different types of rocks, and the values of the features are in large ranges. An optimal set of parameters was obtained by considering an appropriate sensitivity analysis. The optimized model is very easy to implement in Python for practical applications.     

线性石蜡基钻井液高温高压性能的研究

为了评价近期研制出的新型线性石蜡基钻井液的高温高压性能,对优选出的线性石蜡基钻井液开展了一系列的实验研究。评价试验包括：高温老化试验、高温流变性试验以及温度压力共同作用下钻井液的流变参数的测定。在试验研究的基础上,建立了预测高温高压条件流变参数的回归模型。该回归模型可用来预测限定条件下某一井深处的流变参数。研究结果表明,优选出的线性石蜡基钻井液可用作深井钻井的钻井液。     

岩石破裂电磁辐射频率与弹性参数的关系

为进一步研究岩石破裂电磁辐射特征,本文根据岩石破裂电磁辐射是由岩石破裂时产生带电粒子扰动引起的假说,通过断裂力学理论中的张开位移法计算岩石破裂过程中的裂纹宽度,由电磁辐射频率与破裂宽度之间的关系,研究电磁辐射频率与弹性参数之间的关系,并给出了它们之间的关系表达式.通过建立具有中心贯穿裂纹的无限大平板模型,根据破裂宽度计算了在该模型条件下几种岩石破裂过程中产生电磁辐射频率范围.理论模型计算出来的频率范围主要集中在实验观测的中高频段,并体现出频率随弹性参数的变化.     

Deformation, high-pressure metamorphism and exhumation of ultramafic rocks in a deep subduction/collision setting (Cabo Ortegal, NW Spain)

New petrological and microstructural data from various metaperidotite 'boudins' within large ductile shear zones in the Cabo Ortegal allochthonous complex in NW Spain have important implications for the tectonic models of the area. The peridotites (mylonitic garnet harzburgite, Ti-clinohumite and magnesite–olivine orthopyroxenite) contain mineral assemblages that equilibrated at high- to ultra-high-pressure metamorphic conditions as well as microstructures of tectonic origin formed at temperatures well above 800  °C. Olivine and orthopyroxene fabrics resulted from flow at high temperature (>1000  °C) and solid-state non-coaxial plastic flow at intermediate temperature (800–900  °C). Flow caused dynamic recrystallization and formation of moderate to strong lattice preferred orientations under low to moderate differential stresses and strain rates characteristic of upper mantle and deep crustal deformation. The microstructures and textural relationships suggest that the mylonitic garnet harzburgite represents mantle fragments with lithospheric and asthenospheric imprints, whereas the olivine orthopyroxenite resulted from serpentinite burial to depths where it acquired a characteristic high/ultra-high-pressure metamorphic signature. Both types of ultramafites converged to a common site in a subduction zone that was later incorporated during continental collision to the NW Iberian Massif as exotic, allochthonous complexes that record structural and metamorphic evidence of the earliest phases of the Hercynian orogeny.     

地球内部物理和演化的几个核心论题：Ⅲ微观地球物理概要

微地球物理是一正处酝酿阶段,以微物理学为基础,以地球内部及地质休和冉石物理特性搂研究对象,以理论、实验、数据和计算机模拟为手段的新兴学科。其研究内容涉及地球内部受多种微物理机制所制约的岩石圈和地幔流变,岩石动力摩擦与地壳脆－塑性转换,地震和断裂力学问题,流体－岩石相互作用,声发射／微震活动与声波／超声波理论和地质应用等。结合其动力学和相互耦合关系,是微地球物理学的一个重要研究方向。其应用结果将导致环境地球物理和环境地球化学并行发展。关于地球内部的认识存在相当的不确定性,有些问题如板块和地幔涌运动,以致微破裂和断层滑移运动等都可能涉及随机和无序理论的应用。微观与宏观方法的结合,并使两者相一致,是最终解决问题的必要途径和工作目标。     

超越板块构造——我国构造地质学要做些什么?

对近十年来全球构造学和构造地质学的重要进展进行了简要评述.30年前建立的全球构造理论改变了人们对地球及其演化的认识.作为固体地球统一理论的板块构造主要涉及刚性板块边界之间的变形、地震活动和火山作用.至今还没有完整理论阐明板块运动的驱动力和地幔对流机制.板块边界和板内变形等许多问题仍然无法回答.大陆岩石圈和大洋岩石圈在成分、厚度和力学强度方面有明显的差别, 因此现有板块构造不完全适合于大陆构造.大陆地壳和地幔流变学的综合研究是认识大陆构造和超越板块构造的最佳途径.流变学是大陆造山带几何学和动力学的桥梁.大陆岩石圈对构造作用、重力作用和热作用的响应在很大程度上取决于其流变强度.岩石圈流变性质是岩石圈分层和塑性流动的主导因素.大量透入性变形和巨型大陆造山带内部构造显示非刚性特征.大陆构造和力学行为主要由地壳强度而不是地幔强度所控制.从大陆岩石圈多层性和力学强度不均匀性表征看, 现在是抛弃传统“三明治”构造模式的时候了.面对地球系统科学和地球动力学新思维发展趋势, 多学科综合研究大陆构造(造山带)和加速高水平构造地质学人才的培养是我国构造地质学发展的最紧迫任务      

双相横向各向同性介质分界面上弹性波反射与透射问题研究

从双相横向各向同性介质弹性波波动方程出发 ,利用边界上的 4个连续性条件 ,计算双相横向各向同性介质分界面上弹性波反射和透射系数 .计算表明 ,快纵波在双相横向各向同性介质分界面上 ,要产生反射快纵波、反射转换 qSV波、反射转换慢纵波和透射快纵波、透射转换qSV波、透射转换慢纵波 .反射转换慢纵波振幅和透射转换慢纵波振幅均较小 .频率、耗散和各向异性大小影响着快纵波反射系数的大小 .     

Molecular dynamics study of pressure-induced transformation of quartz-type GeO2

We simulated quartz-type GeO₂ and investigated its high-pressure transformation using the molecular dynamics (MD) simulation method with a model potential. The calculated results under hydrostatic compression indicated that a pressure-induced amorphization of quartz-type GeO₂ originated from the mechanical instability of the quartz lattice as, in previous theoretical studies of SiO₂. Furthermore, quartz-type GeO₂ directly transformed to a rutile-like structure with only subtle displacements of ions under σ _{x y} imposed shear stressed decompression. This is the first reproduction of the quartz-to-rutile transformation. A possible pathway of this transition is proposed in this study. Received: 14 April 1999 / Revised, accepted: 11 August 1999