克孜尔水库跨断层形变变化速率的非均匀性特征分析

对克孜尔水库跨断层垂直形变近40年的资料和水平形变近32年的资料进行了分析。研究发现,①跨断层形变的变化速率具有明显的不均匀性,根据数据序列走势,变化速率的不同可分为6个阶段;②水库施工对跨断层形变有一定的影响,水库蓄水对跨断层形变有显著的影响;③水库蓄水达到正常库容量后的新平衡状态下,跨断层形变速率变化几乎是无干扰背景下变化速率的2倍;④区域应力场的增强对跨断层形变趋势性转折有显著性影响。     

准噶尔盆地沙湾凹陷西斜坡二叠系佳木河组物源区构造背景分析*

准噶尔盆地沙湾凹陷西斜坡二叠系佳木河组物源体系一直备受争议,导致沉积体系“众说纷纭”。利用聚类分析、多维尺度分析及主成分分析等方法,对重矿物含量、微量元素进行分析,明确了沙湾凹陷西斜坡二叠系佳木河组砂砾岩碎屑颗粒富石英(35.41%)、长石(43.2%),贫岩屑(18.71%)。稀土元素总量(ΣREE)平均值139×10^-6接近大陆上地壳(UCC)的平均值148.14×10^-6,Hf-La/Th微量元素物源判别图解和La/Sc-Co/Th值表明佳木河组属于酸性岛弧区。稀土配分模式表现为右倾分布模式,整体上具有“轻稀土元素富集、重稀土元素亏损”的特征,指示源岩以长英质火山岩为主,即“一源”。在同一物源下,又可以分为4个物源区:新光1井—中佳6井物源区,车排10井—中佳5井—中佳4井—中佳3井物源区,车排7井—车排005井体系物源区,车排5井物源区,即“四区”。构造背景判别图解揭示了佳木河组形成于大陆岛弧环境。该研究将有助于对沙湾凹陷西斜坡的沉积体系及古水系的准确恢复和远景区油气储集层的准确预测。     

近500年来咸海湖泊沉积记录的环境演变

过去的五十年里,作为曾经世界第四大湖泊的咸海面积急剧萎缩,环境质量严重下降并对大部分中亚地区造成了灾难性的影响.咸海的水位下降过程虽然历时相对较短却变化显著,为了了解这一变化的详细过程,1997年从咸海北部湖盆采集了AS17孔浅钻岩芯.通过对该岩芯的矿物学、介形虫、孢粉等沉积环境指标综合分析,结果表明岩芯在矿物学特征及生物特征上的一系列显著变化,揭示了过去近500年中咸海的沉积环境经历了含盐量增加-下降-再增加三个明显的阶段,并为15世纪咸海的干旱提供了新的证据.     

Sediment and hydrodynamics of the Tauranga entrance to Tauranga harbour

To relate the textural characteristics of the bottom sediments of a tidal inlet to hydrodynamics, 45 sediment samples from the Tauranga Entrance to Tauranga Harbour were analysed for textural parameters, and tidal currents and waves were monitored. Tidal currents dominate sediment transport processes near the Tauranga Entrance although swell waves are significant on the ebb tidal delta, and wind waves may influence intertidal sediments within the harbour. The bulk of the sediment is probably derived from marine sand from the Bay of Plenty continental shelf, but tidal currents and waves have changed its textural character. In areas of swift tidal currents, particularly in the inlet channel itself, sediment is coarser, more poorly sorted, and more coarsely skewed than that in areas of slower currents.     

散乱点云数据的分割方法探究

数据分割是点云数据处理流程中的一项关键技术,本文针对点云数据分割这一问题,分析了基于几何模型的分割法、欧几里德簇分割法和区域生长分割法三种点云数据分割方法的原理和算法流程,并利用实际工程数据检验了三种分割方法的效果。针对以上三种方法的优势及缺陷,本文实现了附条件的欧几里德簇分割法,该算法对欧几里德簇分割法和区域生长分割法进行融合改进,利用同一点云数据对该算法与上述算法进行比较分析,最后用一处复杂建筑物点云数据对该算法的分割效果进行再次检验,分割效果较为明显,再次证实了该算法具有较强的实用性。     

Spring-summer temperatures since AD 1780 reconstructed from stable oxygen isotope ratios in white spruce tree-rings from the Mackenzie Delta,northwestern Canada

High-latitude δ¹⁸O archives deriving from meteoric water (e.g., tree-rings and ice-cores) can provide valuable information on past temperature variability, but stationarity of temperature signals in these archives depends on the stability of moisture source/trajectory and precipitation seasonality, both of which can be affected by atmospheric circulation changes. A tree-ring δ¹⁸O record (AD 1780–2003) from the Mackenzie Delta is evaluated as a temperature proxy based on linear regression diagnostics. The primary source of moisture for this region is the North Pacific and, thus, North Pacific atmospheric circulation variability could potentially affect the tree-ring δ¹⁸O-temperature signal. Over the instrumental period (AD 1892–2003), tree-ring δ¹⁸O explained 29 % of interannual variability in April–July minimum temperatures, and the explained variability increases substantially at lower-frequencies. A split-period calibration/verification analysis found the δ¹⁸O-temperature relation was time-stable, which supported a temperature reconstruction back to AD 1780. The stability of the δ¹⁸O-temperature signal indirectly implies the study region is insensitive to North Pacific circulation effects, since North Pacific circulation was not constant over the calibration period. Simulations from the NASA-GISS ModelE isotope-enabled general circulation model confirm that meteoric δ¹⁸O and precipitation seasonality in the study region are likely insensitive to North Pacific circulation effects, highlighting the paleoclimatic value of tree-ring and possibly other δ¹⁸O records from this region. Our δ¹⁸O-based temperature reconstruction is the first of its kind in northwestern North America, and one of few worldwide, and provides a long-term context for evaluating recent climate warming in the Mackenzie Delta region.     

新疆于田绿洲-荒漠交错带土地利用/覆盖变化的社会驱动力研究

以新疆于田绿洲为例，在遥感手段对图形分析的基础上，根据景观特征为于田绿洲土地利用／覆盖变化（LUCC）的具体表现提供空间分析功能。结合统计资料和调查数据，从经济发展、人口增长、政治经济政策3个方面分析影响研究区LUCC的主要社会影响因子。结果表明：20世纪90年代以来，于田县人口数量增长是研究区LUCC2最主要影响因素，其次是牲畜头数的增长以及采樵量的变化。开荒和撂荒面积对区域的土地利用变化影响也很大。     

Modelling of Tsunamis Generated by Pyroclastic Flows (Ignimbrites)

Pyroclastic flows entering the sea played a major role in generating the largest tsunamiwaves, arising from the 1883 eruption of Krakatau, Indonesia, which caused a considerabledeath toll, most deaths resulting from the tsunamis. The potential exists for similar eventsto occur in Indonesia and New Zealand.Processes leading to tsunami generation by pyroclastic flows, especially those associatedwith Krakatau-type eruptions, are reviewed. The major processes include:1. Deposition at the shoreline causing a lateral displacement as the zone of depositionmoves offshore.2. Upward and lateral displacement of water caused by the propagation of a watersupported mass-flow.3. Downward and lateral displacement of water caused by the sinking of debris from a segregated flow travelling over the water surface.4. Upward displacement of a large volume of water due to the deposition of acaldera-infill ignimbrite or pyroclastic flow deposit.The pyroclastic flow is modelled as a horizontal piston forcingwater displacement. The flow behaves as a wedge of material displacingseawater horizontally and vertically as it moves outwards from the source.Individual pyroclastic flows are treated as linear features that travel alonga specific direction from the volcano, exhibiting limited lateral spreading.The event duration for the formation of a large pyroclastic flow and thedeposition of the ignimbrite is taken as 200–400 s, with flow velocitiesdependent on the volume of material erupted.For simulations it is assumed that the ignimbrite deposit is elliptical with relativelyuniform thickness and the principal axis orientated along the flow direction. Therefore the tsunami is generated by defining an elliptical source region and defining an effective displacement behaviour at each node within that region. The effective displacement is defined by a start time, a finish time and a vertical velocity. These three parameters determine when the seafloor starts to rise and how far it travels during a model time step. The result is a seafloor disturbance that propagates away from the source.The major difficulty with this approach is determination of the appropriate verticalvelocity. With a real pyroclastic flow the effective vertical velocity at any point isvery high. However the model needs to average the displacement spatially andtemporally. Accordingly we apply the model to pyroclastic flows from Mayor Island, New Zealand to examine the influence of model parameters. To further calibrate the numerical model this study is being undertaken in conjunction with physical modelling of the Krakatau 1883 eruption at the Indonesian Tsunami Research Center, BPPT, Jakarta. Historical data will also be used to refine and calibrate the pyroclastic flow model.