Origin of the in situ stress field in south-eastern Australia   总被引：3，自引：0，他引：3  

Mike Sandiford  Malcolm Wallace  David Coblentz† 《Basin Research》2004,16(3):325-338

The in situ stress field of south‐eastern Australia inferred from earthquake focal mechanisms and bore‐hole breakouts is unusual in that it is characterised by large obliquity between the maximum horizontal compressive stress orientation (S_Hmax) and the absolute plate motion azimuth. The evolution of the neotectonic strain field deduced from historical seismicity and both onshore and offshore faulting records is used to address the origin of this unusual stress field. Strain rates derived from estimates of the seismic moment release rate (up to ～10^?16 s^?1) are compatible with Quaternary fault–slip rates. The record of more or less continuous tectonic activity extends back to the terminal Miocene or early Pliocene (10–5 Ma). Terminal Miocene tectonic activity was characterised by regional‐scale tilting and local uplift and erosion, now best preserved by unconformities in offshore basins. Plate‐scale stress modelling suggests the in situ stress field reflects increased coupling of the Australian and Pacific Plate boundary in the late Miocene, associated with the formation of the Southern Alps in New Zealand.  相似文献   

Editorial     

Mike Bradshaw Editor 《Area》2004,36(2):99-100

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Editorial: Earth Surface Exchanges (ESEX)     

Mike Kirkby  Stuart Lane 《地球表面变化过程与地形》2004,29(10):1171-1172

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The significance of European high mountain lakes in critical load distributions at the EMEP grid scale     

Chris J. Curtis  Max Posch  Pilar Casals-Carrasco  Jordi Catalan  Mike Hughes  Martin Kernan  Marc Ventura 《Aquatic Sciences - Research Across Boundaries》2005,67(3):252-262

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Relative contributions of silicate and carbonate rocks to riverine Sr fluxes in the headwaters of the Ganges   总被引：1，自引：0，他引：1  

Mike J. Bickle  Hazel J. Chapman  Nigel B.W. Harris  Talat Ahmad 《Geochimica et cosmochimica acta》2005,69(9):2221-2240

Exhumation of the Himalayan-Tibetan orogen is implicated in the marked rise in seawater ⁸⁷Sr/⁸⁶Sr ratios since 40 Ma. However both silicate and carbonate rocks in the Himalaya have elevated ⁸⁷Sr/⁸⁶Sr ratios and there is disagreement as to how much of the ⁸⁷Sr flux is derived from silicate weathering. Most previous studies have used element ratios from bedrock to constrain the proportions of silicate- and carbonate-derived Sr in river waters. Here we use arrays of water compositions sampled from the head waters of the Ganges in the Indian and Nepalese Himalaya to constrain the end-member element ratios. The compositions of tributaries draining catchments restricted to a limited range of geological units can be described by two-component mixing of silicate and carbonate-derived components and lie on a plane in multicomponent composition space. Key elemental ratios of the carbonate and silicate components are determined by the intersection of the tributary mixing plane with the planes Na = 0 for carbonate and constant Ca/Na for silicate. The fractions of Sr derived from silicate and carbonate sources are then calculated by mass-balance in Sr-Ca-Mg-Na composition space. Comparison of end-member compositions with bedrock implies that secondary calcite deposition may be important in some catchments and that dissolution of low-Mg trace calcite in silicate rocks may explain discrepancies in Sr-Ca-Na-Mg covariation. Alternatively, composition-dependent precipitation or incongruent dissolution reactions may rotate mixing trends on cation-ratio diagrams. However the calculations are not sensitive to transformations of the compositions by incongruent dissolution or precipitation processes provided that the transformed silicate and carbonate component vectors are constrained. Silicates are calculated to provide ∼50% of the dissolved Sr flux from the head waters of the Ganges assuming that discrepancies between Ca-Mg-Na covariation and the silicate rock compositions arise from addition of trace calcite. If the Ca-Mg-Na mixing plane is rotated by composition-dependent secondary calcite deposition, this estimate would be increased. Moreover, when ⁸⁷Sr/⁸⁶Sr ratios of the Sr inputs are considered, silicate Sr is responsible for 70 ± 16% (1σ) of the ⁸⁷Sr flux forcing changes in seawater Sr-isotopic composition. Since earlier studies predict that silicate weathering generates as little as 20% of the total Sr flux in Himalayan river systems, this study demonstrates that the significance of silicate weathering can be greatly underestimated if the processes that decouple the water cation ratios from those of the source rocks are not properly evaluated.  相似文献   

用ANUDEM建立水文地貌关系正确DEM的方法研究   总被引：4，自引：0，他引：4  

杨勤科  Tim R. McVicar  Mike Hutchinson  李领涛 《测绘科学》2006,31(6):155-157,148

针对区域尺度的径流、水土流失定量评价和植被适宜性评价等研究工作需要,利用1∶25万数字地形图和ANUDEM软件,对黄土丘陵区中等分辨率水文地貌关系正确DEM建立方法进行了研究。结果表明该方法所建立的DEM,可以正确反映地貌梁、沟结构及其与流水线网络的关系,对地形描述的能力优于TIN方法建立的DEM;利用ANUDEM和1∶25万地形图插值建立黄土丘陵区DEM的三个主要参数分别为分辨率50或100,计算迭代次数40,第二糙率系数0.8。  相似文献   

A Climate Change Scenario for the Tropics   总被引：1，自引：1，他引：0  

Mike Hulme  David Viner 《Climatic change》1998,39(2-3):145-176

This paper describes the construction of a climate change scenario for a region representing the extended Tropics – 30° N to 30° S – using a methodology that combines results from a simple climate model and a Global Climate Model (GCM) transient climate change experiment. The estimated date by which this climate change scenario might be realized ranges from as early as the end of the 2030s to as late as well into the 22nd century. The central estimate is for this scenario to describe the climate of the 2060s, which would represent a global warming rate of about 0.2 °C per decade, with associated atmospheric CO₂ concentrations estimated to be about 560 ppmv, 55% higher than 1990 levels. The role of anthropogenic aerosols in offsetting part of this future global warming and altering the regional character of the changes has not been considered. The paper presents changes in mean temperature; mean rainfall; rainfall seasonality, variability, frequency, and intensity and soil moisture. These patterns of change derive from only one GCM climate change experiment; different experiments would yield different patterns for the same global warming. There is also some discussion about possible changes in tropical cyclone (TC) activity, although since TCs remain poorly modelled in GCMs, the full range of possibilities (from reduced activity, through no change, to increased activity) should be considered in any impact assessment.  相似文献   

On the asphericity of nova remnants caused by rotating white dwarf envelopes     

John M. Porter  O'Brien  & Mike F. Bode 《Monthly notices of the Royal Astronomical Society》1998,296(4):943-948

The effect of rotating white dwarf envelopes in determining the structure of nova shells is examined. This is achieved by numerical hydrodynamic simulations of the flows around a binary star system. In previous studies of remnant formation, this rotation has not been included.
It is found that the structures formed in the flow are more consistent with observations of nova shells than the previous theoretical studies. The shells produced by the nova become more prolate with increasing white dwarf envelope rotation. Hence the rotation of white dwarf envelopes must be included in any future discussion of remnant formation.
A possible method of identifying the dominant process by which mixing of accreted and white dwarf matter takes place is suggested.  相似文献   

藏南深反射测线附近地表地质观察研究成果   总被引：3，自引：0，他引：3  

岳永君  蒋忠惕  武长得  李冀湘  William S.F.  Kidd Mike Edward 《地球学报》1996,17(2):177-186

本文简要介绍了ＩＮＤＥＰＴＨ项目地质组１９９４年和１９９５年间沿ＩＮＤＥＰＴＨ—Ｉ路线进行的野外填图工作的初步研究成果。它们是：①在帕里西北确定了高喜马拉雅与特提斯喜马拉雅之间拆离带的存在；③在帕里北发现了一套特提斯沉积，从而提出帕里西北的拆离带有可能穿过南北方向的亚东－谷露裂谷，而没有大规模错开；③在特提斯喜马拉雅带中确定了两条具一定规模的逆冲断裂；④发现康马穹窿存在两期构造变形，早期为上盘向北运动，晚期为横弯造穹作用。最后，结合深反射资料进一步讨论了康马穹窿与藏南拆离带之间的关系。  相似文献   

Modelling the links between vegetation and landforms     

Mike Kirkby 《Geomorphology》1995,13(1-4)

Vegetation is the most important intermediate through which climate and land use modify geomorphological processes and landforms. In this paper we explore three types of model which attempt to simulate the links to uncultivated vegetation, all sharing a common basis in hydrology. The first simulates the relationship between climate, vegetation and erosion rates for a fixed topography and soil cover. The second group of models takes into account longer term interactions with soil properties, which are thought to be important on the times scales of current concern with global change. An expanded illustration of this interaction is the relationship between wash erosion processes, vegetation cover and the evolution of microtopography. The third group of models looks at geological time spans, for which consistent differences in vegetation and landform between climatic areas create responses in the pattern of erosion rates, jointly to a combination of past and present climates.  相似文献