Soil–structure interaction in the time domain using halfspace Green's functions

A time-domain formulation is proposed for the transient response analysis of general, three-dimensional structures resting on a homogeneous, elastic halfspace subjected to either external loads or seismic motions. The formulation consists of two parts: (a) the time domain formulation of the soil behaviour and (b) the coupling of the corresponding soil algorithms to the Finite Element Code ANSYS. As far as the structure is concerned, this coupling opens the way for the analysis of non-linear soil–structure interaction. The approach is based on halfspace Green's functions for displacements elicited by Heaviside time-dependent surface point loads. Hence, the spatial discretisation can be confined to the contact area between the foundation and the soil, i.e. no auxiliary grid beyond the foundation as for conventional boundary element formulations is required. The method is applied to analyse the dynamic response of a railway track due to a moving wheel set by demonstrating the influence of ‘through-the-soil coupling’.     

k-nn方法在热带气旋路径预报中的应用

引入k-nn方法，结合经过预报实践检验、应用证明效果较好的预报因子，制作热带气旋路径预报系统，运行效果良好，可以应用到日常预报业务中。     

Thermicité et déformation de la marge continentale dans le Sud de la Tasmanie (Australie) : résultats préliminaires d'une analyse par traces de fission et d'une étude microstructuraleFission track reconnaissance of the thermal and tectonic settings of the South Tasman rise

We present and discuss a few fission track data, and microstructural observations, from rock samples dredged along the western and southwestern continental margin of Tasmania. The results allow assessing the thermal and tectonic regimes that were active prior to and during the margin creation. The different ages, as provided by fission tracks, and deformational styles, as evidenced from microstructures, are then tentatively correlated with the two main rifting episodes, in Late Jurassic–Cretaceous times and Eocene–Oligocene respectively, deduced from kinematical reconstructions, that have led to the present- day southern margin of Tasmania. To cite this article: M. Sélo et al., C. R. Geoscience 334 (2002) 59–66     

The thermal history of the eastern Officer Basin (South Australia): evidence from apatite fission track analysis and organic maturity data

The eastern Officer Basin in South Australia contains a Neoproterozoic to Devonian succession overlain by relatively thin (<500 m) Permian, Mesozoic and Tertiary deposits. Within the basin fill, there are several major unconformities representing uncertain amounts of erosion. Three of these surfaces are associated with regional deformational events. Regional unconformities formed between 560 and 540 Ma (Petermann Ranges Orogeny), approximately 510–490 Ma (Delamerian Orogeny), 370–300 Ma (Alice Springs Orogeny), 260–150 Ma; and 95–40 Ma. AFTA® results from 13 samples of Neoproterozoic, Cambrian and Permian sedimentary rocks in five wells (Giles-1, Manya-2, -5 and -6 and Lake Maurice West-1) show clear evidence for a number of distinct thermal episodes. Results from all samples are consistent with cooling from the most recent thermal episode beginning at some time between 70 and 20 Ma (Maastrichtian–Miocene). AFTA results from Giles-1 indicate at least two pre-Cretaceous thermal episodes with cooling beginning between 350 and 250 Ma (Carboniferous–Permian) and between 210 and 110 Ma (Late Triassic–Albian). Results from Manya-2, -5 and -6 and Lake Maurice West-1 show evidence for at least one earlier higher temperature event, with cooling from elevated paleotemperatures beginning between 270 and 200 Ma (Late Permian to Late Triassic). These episodes can be correlated with other cooling/erosional events outside the study area, and the AFTA-derived paleotemperatures are consistent with kilometre-scale erosion for each of the episodes identified. Integration of the AFTA data with organic thermal maturation indicators (MPI) in the Manya and Giles-1 wells suggests that the Cambrian and Neoproterozoic successions in the northern part of the study area reached peak maturation prior to the Permian, while limited data from Lake Maurice West-1 allows peak maturation to have occurred as young as the Late Permian to Late Triassic thermal episode revealed by AFTA. The approach outlined in this study is relevant to all ancient basins as it emphasises the importance of understanding events associated with neighbouring regions. The thermal history of the Officer Basin, as with most other ancient basins, has been strongly affected by significant tectonic events throughout its history, even though younger deposits are not preserved in the basin itself. The recognition of these younger events, and the implications of these events for the depositional history, is important as it allows identification of the best regions for preservation of early generated hydrocarbons, and in some cases, suggests areas where generation of hydrocarbons could have occurred more recently than previously thought.     

Thermotectonic evolution of the western fold-and-thrust belt, southern Uralides, Russia, as revealed by apatite fission track data

The Uralides, a linear N–S trending Palaeozoic fold belt, reveals an intact, well-preserved orogen with a deep crustal root within a stable continental interior. In the western fold-and-thrust belt of the southern Uralides, Devonian to Carboniferous siliciclastic and carbonate rocks overlay Mesoproterozoic to Neoproterozoic sedimentary rocks. Deformation in the Devonian, Carboniferous and Permian caused thick-skinned tectonic features in the western and central parts of the western fold-and-thrust belt. A stack of several nappes characterizes the deformation in the eastern part. Along the E–W transect AC-TS'96 that crosses the western fold-and-thrust belt, apatite fission track data record various stages of the geodynamic evolution of the Uralide orogeny such as basin evolution during the Palaeozoic, synorogenic movements along major thrusts, synorogenic to postorogenic exhumation and a change in the regional stress field during the Upper Jurassic and Lower Cretaceous. The Palaeozoic sedimentary cover and the Neoproterozoic basement of the Ala-Tau anticlinorium never exceed the upper limit of the PAZ since the Devonian. A temperature gradient similar to the recent one (20 °C/km) would account for the FT data. Reactivation of the Neoproterozoic Zilmerdak thrust was time equivalent to the onset of the Devonian and Carboniferous collision-related deformation in the east. West-directed movement along the Tashli thrust occurred in the Lower Permian. The Devonian and Carboniferous exhumation path of the Neoproterozoic siliciclastic units of the Tirlyan synclinorium mirrors the onset of the Uralian orogeny, the emplacement of the Tirlyan nappe and the continuous west-directed compression. The five main tectonic segments Inzer Synclinorium, Beloretzk Terrane, Ala-Tau anticlinorium, Yamantau anticlinorium and Zilair synclinorium were exhumed one after another to a stable position in the crust between 290 and 230 Ma. Each segment has its own t–T path but the exhumation rate was nearly the same. Final denudation of the western fold-and-thrust belt and exhumation to the present surface probably began in Late Tertiary. In Jurassic and Cretaceous, south-directed movements along W–E trending normal faults indicate a change in the tectonic regime in the southern Uralides.     

影响我国北方热带气旋的若干统计特征

利用中国气象局出版的１９４９—１９９４年台风年鉴资料，在大量普查的基础上，定义进入３０°Ｎ以北、１２５°Ｅ以西热带气旋为影响我国北方的热带气旋。根据其后期移动路径的不同划分为：沿海北上、沿海转向、登陆北上、登陆填塞、登陆转向及西折６类。最后，对各类不同路径的热带气旋的气候特征及产生的暴雨区和暴雨强度做了详细的分析     

热带气旋运动曲率的数学模型与路径异常的月尖突变判据

采用运动曲率数学模型，研究热带气旋异常路径的成因，得到的主要结果是：热带气旋路径曲率及其变化与科氏力参数、环境场气压分布、热带气旋的移速及涡旋动力结构、下垫面摩擦力等因子有关；当各类影响因子渐变至满足月尖突变判据时，出现演变曲线的折叠区，随着外源参数变化，一旦解移出折叠区，热带气旋便可发生移间突变，出现各类异常轨迹。     

SPECTRUM-90时期大气10—20天准周期振荡对热带气旋转向路径的影响

本文研究了SPECTRUM-90时期，大气10—20天周期振荡对西北太平洋转向台风路径的影响，结果表明，这种影响是显著的。在SPECTRUM-90时期，10—20天周期振荡比较活跃，西北太平洋副热带高压的周期性退缩现象是来自中、高纬和热带的10—20天周期低压扰动共同影响所致，这也是导致热带气旋转向运动的一个重要原因。进一步研究还发现，在SPECTRUM-90时期，存在着一支源于热带西北太平洋上呈经向排列的纬向风波列，热带波动沿此波列向北传播，在一定程度上，可以推动热带气旋北上转向。     

利用磷灰石裂变径迹资料反演合肥盆地古地温和估计沉降率与剥蚀率

利用合肥盆地内６个磷灰石裂变径迹样品资料，反演模拟了该盆地自侏罗纪晚期以来各时代地层古地温变化，估算了沉降率与剥蚀率．模拟结果与其他地质资料推论一致，它揭示出该盆地南北两地存在不同的构造变化和受热史，反映了大别山构造发展对盆地南北两地区影响的差异．盆地南部靠近大别山地区的晚侏罗世地层在白垩纪早期埋藏温度曾大于１２０℃；早白垩世后期的构造抬升（剥蚀率约１３０ｍ／Ｍａ）使温度降至３０—４０℃；自白垩纪后期始，该地区一直处于动荡的但总体为持续抬升的构造环境中．盆地北部地区晚侏罗世与早白垩世早期地层在白垩纪期间埋藏温度曾达到和超过１００℃，但随后的大幅度构造抬升（剥蚀率约１９０ｍ／Ｍａ）使其温度降至３０—６０℃；第三纪早期，局部区域的裂陷（沉降率约６０ｍ／Ｍａ）使温度又升至８０℃左右．指出合肥盆地构造演化大体可分形成、隆升、局部裂陷和再隆升４个阶段．     

Fission track ages of Hymalayan muscovites (Kathmandu Valley,Nepal)

Summary Himalayan muscovites from pegmatites of Kathmandu Valley, Nepal yield an age of 2–23 m. y. by fission track (f.t.) method. The uranium concentration is estimated to be 10^–10 atom/atom.