Characteristics of seismic reflections in central region of the South China Sea and their geological significance

More than 4 000 km 48-channel seismic reflection data from the central region of the South China Sea have been interpreted. Five seismic interfaces have been distinguished, named T1, T2, T4, T6 and Tg respectively Meanwhile, five seismic sequences numbered I - V have been divided with the ages of Quaternary and Pliocene, Later Mocene, Earlier and Middle Miocene, Oligocene and Pre- Oligocene separately. Sequences I-II overlie all parts of the area. In the continental slope and island slope, Sequences III-V are mainly found in the grabens. Sequence III is found at moot profiles of the deep-sea basin, and Sequnce IV is seen not only at the margins of the east subbasin but also at the margins of the southwest subbasin. Strong reflection from Moho is found at most profiles of the deep-sea basin. The depth of Moho varies between 10 and 12 km, with a thickness of 6- 8 km for the crust. Calculated by age-basement depth correlation formula, the age of basaltic basement in the southwest subbasin is 51-39 Ma. It is indicated that the evolution of the southwest subbasin is simultaneous with or earlier than that of the east subbasin.

Study on Fine Crustal Structure of the Sanhe-Pinggu Earthquake (M8.0) Region by Deep Seismic Reflection Profiling

Two near-vertical deep seismic reflection profiles (140km-long, 24-fold) were completed in the 1679 Sanhe-Pinggu earthquake (M8.0) region. The profiles ran through the Xiadian fault and the Ershilichangshan fault. The profiling result shows that the crust in this region is divided into the upper crust, the lower crust and the crust-mantle transitional zone by two powerful laminated reflectors: one at the two-way travel-time of about 7.0s (21km), the other at about 11.0～12.5s (33～37km). Crustal structure varies significantly in vertical direction. The shallow part is characterized by obvious stratification, multilayers and complexity. The upper crust on the whole features reflection “transparency”, while the lower crust features distinct reflectivity. Crustal structure also varies a lot in the lateral direction. The main fracture in this region is the deep fault under the Xiadian fault. This deep fault is steeply inclined (nearly vertical), and is supposed to be the causative fault of the Sanhe-Pinggu M8.0 earthquake. The two profiles respectively reveal the existence of local strong reflectivity in the lower crust and the lower part of the upper crust, which is assumed to be a dike or rock mass formed by the upwelling and cooling down of materials from the upper mantle. Magmatic activity in this part brought about differences in regional stress distribution, which then gave rise to the formation of the deep fault. That is supposed to be the deep structural setting for the Sanhe-Pinggu M8.0 earthquake.

巴基斯坦东部海域中生代地层发现与油气意义

巴基斯坦海域历经60余年油气勘探,长期以新生界为主要目标,对中生代地层展布、构造演化特征等认识不清。巴基斯坦东部海域中—新生代时期经历了复杂的构造—沉积演化过程,新生代受喜马拉雅隆升影响而沉积了巨量陆缘碎屑物质,因此是研究诸多重大基础科学问题的极佳场所。受白垩纪晚期区域火成岩影响,对该区中生代地层是否存在、如何展布等问题一直存在较大争议,这极大限制了区域油气勘探活动的开展。本研究基于新采集的高品质二维地震剖面,突破了火成岩层的屏蔽作用,通过地震反射界面刻画、地震波组特征分析和层速度分析等手段,揭示了中生代地层在巴基斯坦东部海域广泛分布,中生代地层受控于同期活动的强烈伸展断陷作用,被隆坳相间的构造古地理格局分割在多个规模不等的次级凹陷内部。整体厚度800~10000 m,表现为东南厚、西北薄,向北和向西超覆,最大沉积厚度位于研究区东南和西北两个区域,该套地层在陆域下印度河盆地已证实为重要烃源岩层,因此海域中生代地层的发现有效拓展了该区未来油气勘探方向和潜在价值。

基于光谱反射率的寒地水稻叶片氮含量预测

为实现利用水稻叶片光谱指数实时预测叶片群体的氮素含量,采集了不同年份中氮素、品种差异下寒地水稻主要生育期(T_(1)穗分化中期、T_(2)拔节期、T_(3)孕穗期、T_(4)齐穗期、T5蜡熟期)顶部3片全展叶(上1、上2、上3叶分别记作L1、L_(2)、L_(3))的光谱反射率,探究其变化规律以及光谱指数与叶片氮素含量的关系,并用P-k、均方根误差(RMSE)、对称平均绝对百分比误差(SMAPE)、校正均方根误差(RMSEC)、交互验证均方根误差(RMSECV)、相对预测性能(RPD)对模型精度进行验证。结果显示:提高氮肥投入量,叶片反射率在可见光区域内呈降低趋势,在近红外平台叶片反射率上升。随着生育期的推进,在可见光区域内,不同品种L1叶反射率先降低后上升,L_(2)、L_(3)叶的反射率一直上升,与叶片氮素百分含量的敏感波段为500~550和650~700nm。对光谱指标和叶片氮素百分含量进行相关分析,生育前期以下位叶片的光谱指标相关系数高,生育后期则相反,筛选出T_(1)时期L_(2)叶指标FD-NDNI、T_(2)时期L_(2)叶指标GM2、T_(3)时期L_(2)叶指标Lic2、T_(4)时期L1叶指标MRESRI以及T5时期L1叶指标Ctr1适宜作为不同时期预测叶片氮素含量的最佳指标,预测叶片氮素含量的回归方程R2分别0.54^(**)、0.60^(**)、0.66^(**)、0.62^(**)、0.51^(**),均达到极显著水平;验证指标的P-k值分别为0.00、0.04、0.06、0.01、0.04;RMSE分别为0.39、0.58、0.22、0.54、2.56;SMAPE分别为1.11、1.41、1.03、1.64、3.89;RMSEC分别为0.17、0.15、0.13、0.13、0.13;RMSECV分别为0.18、0.14、0.12、0.12、、0.14;RPD分别为2.46、2.19、3.15、1.74、3.01,其中T_(3)时期L_(2)叶指标Lic2的预测效果表现最佳。借助筛选的光谱指标能够实现快捷、无损和实时预测水稻不同生育时期的氮素营养状况,促进高产优质的寒地水稻可持续发展。

Derivation of salt content in salinized soil from hyperspectral reflectance data: A case study at Minqin Oasis, Northwest China

Soil salinization is a serious ecological and environmental problem because it adversely affects sustainable development worldwide, especially in arid and semi-arid regions. It is crucial and urgent that advanced technologies are used to efficiently and accurately assess the status of salinization processes. Case studies to determine the relations between particular types of salinization and their spectral reflectances are essential because of the distinctive characteristics of the reflectance spectra of particular salts. During April 2015 we collected surface soil samples(0–10 cm depth) at 64 field sites in the downstream area of Minqin Oasis in Northwest China, an area that is undergoing serious salinization. We developed a linear model for determination of salt content in soil from hyperspectral data as follows. First, we undertook chemical analysis of the soil samples to determine their soluble salt contents. We then measured the reflectance spectra of the soil samples, which we post-processed using a continuum-removed reflectance algorithm to enhance the absorption features and better discriminate subtle differences in spectral features. We applied a normalized difference salinity index to the continuum-removed hyperspectral data to obtain all possible waveband pairs. Correlation of the indices obtained for all of the waveband pairs with the wavebands corresponding to measured soil salinities showed that two wavebands centred at wavelengths of 1358 and 2382 nm had the highest sensitivity to salinity. We then applied the linear regression modelling to the data from half of the soil samples to develop a soil salinity index for the relationships between wavebands and laboratory measured soluble salt content. We used the hyperspectral data from the remaining samples to validate the model. The salt content in soil from Minqin Oasis were well produced by the model. Our results indicate that wavelengths at 1358 and 2382 nm are the optimal wavebands for monitoring the concentrations of chlorine and sulphate compounds, the predominant salts at Minqin Oasis. Our modelling provides a reference for future case studies on the use of hyperspectral data for predictive quantitative estimation of salt content in soils in arid regions. Further research is warranted on the application of this method to remotely sensed hyperspectral data to investigate its potential use for large-scale mapping of the extent and severity of soil salinity.

Detection of Acid Rain Stress Effect on Plant Using Hyperspectral Data in Three Gorges Region,China

This paper aims to use hyperspectral data to detect the spectral change caused by acid stress to a native forest type in the Three Gorges region of China. For this purpose, a ground-based hyperspectral experiment was conducted at the Three Gorges region to detect acid deposition that caused Masson pine (Pinus massoniana) forest degra-dation. Continuum removal method was used to isolate wavebands more responsive to stress in wavelengths 450-750nm. The differences in chlorophyll concentrations and needle thickness caused by acidic stress are found to be explicable to the different spectral reflectance patterns in the visible and near-infrared wavelengths. Two new chlorotic indices were utilized to explain the stress-caused leaf chlorosis. The comparison of simulated vegetation indices and principal component analysis (PCA) results suggests that it would be possible to monitor acid rain stress effect on forest ecosystem from some wider spectral regions.

Characteristics of crustal variation and extensional break-up in the Western Pacific back-arc region based on a wide-angle seismic profile

The marginal sea and back-arc basins in the Western Pacific Ocean have become the focus of tectonics due to their unique tectonic location.To understand the deep crustal structure in the back-arc region,we present a 545-kmlong active-source ocean bottom seismometer(OBS)wide-angle reflection/refraction profile in the East China Sea.The P wave velocity model shows that the Moho depth rises significantly,from approximately 30 km in the East China Sea shelf to approximately 16 km in the axis of the Okinawa Trough.The lower crustal high-velocity zone(HVZ)in the southern Okinawa Trough,with V_(p) of 6.8-7.3 km/s,is a remarkable manifestation of the mantle material upwelling and accretion to the lower crust.This confirms that the lower crustal high-velocity mantle accretion is developed in the southern Okinawa Trough.During the process of back-arc extension,the crustal structure of the southern Okinawa Trough is completely invaded and penetrated by the upper mantle material in the axis region.In some areas of the southern central graben,the crust may has broken up and entered the initial stage of seafloor spreading.The discontinuous HVZs in the lower crust in the back-arc region also indicate the migration of spreading centers in the back-arc region since the Cenozoic.The asthenosphere material upwelling in the continent-ocean transition zone is constantly driving the lithosphere eastward for episodic extension,and is causing evident tectonic migration in the Western Pacific back-arc region.

基于阴影和周边区域色差的光照条件和光谱反射率计算方法

光照条件和光谱反射率对增强现实和场景渲染任务非常有用,但是通过仪器采集比较困难,因此根据普通图像计算光照条件和光谱反射率是重要的计算机视觉任务.本文设计了一种通过分析场景中的阴影区域和周边区域颜色之间的色差,无需训练数据即可计算场景的光照条件和光谱反射率的算法.在自然场景中,阴影区域由于遮挡只能接收和反射天空光,而其周边的非阴影区域则同时受到太阳光和天空光的影响.当阴影和非阴影区域有着相同的光谱反射率时,两块区域颜色之间的色差反映了被遮挡光源的信息.两块区域之间的颜色差异由光照条件造成,又以光谱反射率为联系.因此,可以利用这两种颜色之间的关系计算光照条件和光谱反射率.本文使用先验知识和模型公式化表达某一区域在光照下呈现在图像中的颜色,然后基于两种颜色以及两者之间的色差设计了一种优化算法,通过计算最优解来计算场景的光照条件以及光谱反射率.通过在多个数据集上的一系列对比实验,以及一个使用光照条件和光谱反射率来去除阴影区域的应用实验,证明了该算法的准确性.

基于Ka波段云雷达观测的中国西天山降雨云宏微观物理特征研究

利用Ka毫米波云雷达与自动气象站降雨资料,研究了西天山地区2019年和2020年5~8月的降雨云宏微观特性。结果表明:(1)降雨主要发生在夜间,累积降雨量集中在21:00(北京时间,下同)至次日07:00,降雨频次和累积降雨量相关系数为0.71。大雨强频次虽最少,但对总累积降雨量贡献较显著。(2)小雨强、中雨强、大雨强平均反射率因子最大值分别为30 dBZ、35.8 dBZ和39.5 dBZ,最大平均液态水含量分别为1.5 g m^(-3)、4.2 g m^(-3)和7.3 g m^(-3)。(3)不同降雨强度对应的反射率因子都有两个集中区域,2.0~4.4 km反射率因子集中在15~26 dBZ,地面附近的小雨强、中雨强、大雨强对应的反射率因子分别集中在24~32 dBZ、29~38 dBZ和31~42 dBZ。1.75 km以下中雨强和大雨强液态含水量小于1gm^(-3)的频率明显少于小雨强,降雨强度的越大降雨粒子径向速度越集中。

代谢综合征患者脏腑红外热成像特征研究

目的:应用红外热成像(IRTI)技术探究代谢综合征(MS)患者脏腑功能反射区红外热成像特征。方法:研究对象为2021年8月至2022年4月在中国中医科学院广安门医院南区内分泌门诊及病房就诊的MS患者和健康受试者,经严格筛查,符合纳入排除标准且实验室指标完整者共120例,其中MS组96例,健康对照组24名。分析受试者躯干部位感兴趣区域(ROI)体表平均温度。结果:MS组患者红外热图呈现明显凉偏离,且分布不均匀、不连续、不对称;与健康对照组比较,MS组青年患者胃脘、大腹、任脉、右腰、左腰及督脉等ROI体表平均温度降低(P<0.01或P<0.05),MS组中年患者ROI体表平均温度降低(P<0.01或P<0.05);不同年龄受试者ROI体表平均温度呈现随代谢异常指标增多而降低的趋势,大腹、右腰明显凉偏离;MS组11例患者ROI体表平均温度与代谢指标腰围负相关(P<0.01或P<0.05)。结论:腰围是MS重要特异指标;MS患者躯干部位脏腑功能反射区红外热图存在凉偏离的特征性表现,尤其在大腹及右腰,提示脾肾阳气不足,脏腑功能低下,代谢障碍是MS红外特征形成的重要原因。

基于改进区域生长法的洞室支护锚杆点云提取方法研究

针对施工期抽水蓄能电站地下厂房支护锚杆点云影响数据处理精度的问题,提出了一种基于反射强度改进区域生长算法提取锚杆点云的方法。通过分析锚杆表面曲率及反射强度特征,推导平滑及曲率阈值对提取结果的影响关系,确定基于反射强度的自适应阈值区域生长的改进方法,并通过采集洞室点云及提取支护锚杆点云分析该算法的提取结果。试验表明,该算法效率高,稳定性好,其提取点云簇准确率达98.09%,各簇锚杆的平均点云误提取率仅为2.61%。

基于不同开源DEM的地形校正模型应用对比研究

复杂地形严重影响光学卫星遥感在山区的定量化应用精度,基于开源DEM的半经验地形校正模型是消除遥感观测地形效应的常用方法,然而对不同开源DEM和不同校正模型的最佳组合方式仍缺乏研究。该文以黄土丘陵区为例,基于Landsat8 OLI影像,使用3种开源DEM(AW3D、SRTM、GDEM)和4种地形校正模型(C模型、SCS+C模型、SE模型、MIN模型)开展地形校正试验,并通过构建地形校正效果评价指标,对由太阳局地入射角引起的光谱异常、坡向引起的光谱异常和同地类光谱变异性的校正效果进行定量评估。结果表明:基于不同开源DEM产品的综合地形校正效果排序为AW3D>SRTM>GDEM,基于AW3D产品的地形校正能最精细刻画遥感影像地表反射率对局地太阳入射角变化的响应规律;所有开源DEM和校正模型组合试验中,AW3D产品和SE校正模型组合的地形校正效果最佳,对太阳局地入射角引起的光谱异常、坡向引起的光谱异常和同地类光谱异常的减少幅度分别为98.2%、38.8%和97.4%。研究成果可为黄土丘陵区遥感影像地形校正提供参考。

地震反射波法在潼关县地热资源勘查中的应用

陕西省潼关地区北部属于深部地热资源勘查开发的空白区,区域内无深部地球物理和钻孔资料,地下地质情况和构造情况不明。为了查明潼关县北部古城景区地热资源分布情况,使用二维地震反射波法进行勘查,查明了各个时代地层的埋深及厚度、热储层位特征和断裂构造空间分布情况。在物探勘查工作基础上,于圈定的地热有利地段布设一眼地热孔,最终成孔深度为2300 m,出水量为63.2 m^(3)/h,温度为74℃。勘探成果表明,地震反射波法在潼关地区地热资源勘查中具有较好的应用效果。

水体红波段反射光谱对叶绿素浓度变化的响应

在不考虑叶绿素荧光效应的前提下，基于水体光学活性因子藻类叶绿素、有色可溶性有机物及非藻类颗粒物的吸收和后向散射系数，根据前向辐射传输模型模拟水面以上遥感反射率，分析了藻类叶绿素红光峰强度和波长位置随浓度的变化规律。结果发现：叶绿素浓度为1～50 μg·L-1时，红光峰强度和叶绿素浓度呈较好的线性关系，随叶绿素浓度的增加，线性关系越来越不明显。当叶绿素浓度为1～1 000 μg·L-1时，则呈现较好的对数关系;随叶绿素浓度的增加，红波段反射峰波长位置按对数规律逐渐向长波方向移动，不同水色组分的水体，其叶绿素在红波段的光谱反射特性随浓度的变化规律是一致的;此外，对比研究显示红波段反射峰特征不同于荧光光谱。

硫化物的映震特征及其映震机理的研究

概述了硫化物监测点的水文地质及硫化物的来源和存在形式 ,并结合近二十多年来的震例 ,分析和总结了硫化物的映震特征。表明硫化物的地震前兆异常基本上都是正异常 ,且具有一定的重复性 ,即硫化物测值遵循背景值 -趋势性上升 (或突升 ) -最高值 -趋势性下降 (或突降 )-恢复至背景值 ,而地震常常发生在硫化物由高变低 (靠近背景值 )的过程中。并对硫化物异常形成原因进行了探讨 ,认为硫化物在生成过程中明显受孔隙压力 (压强 )的影响 。

可可西里BDQ0608钻孔沉积物色度环境意义及其影响因素

通过对青藏高原腹地可可西里边缘地区古湖泊体BDQ0608钻孔岩心分析发现,色度在干样和湿样测试中,它们的变化趋势相同,但值有很大的不同,a*和b*值变化较小,而L*值变化较大,达到了22.48,并且色度值随岩心明暗有很好的变化趋势,说明岩心颜色反映一定的成岩环境,可以作为一个环境指标来恢复过去环境。进一步分析认为,L*值高低变化主要是由于总有机碳含量高低引起的。粒度与L*相关分析表明,沉积环境的改变会影响总有机碳的储存情况,进而影响L*值的变化。通过对彩度Ca*b*与其他环境代用指标的分析,认为引起沉积物彩度Ca*b*值变化的主要原因可能是由于当时的温度和水分所引起的氧化-还原反应所生成的致色矿物。彩度Ca*b*值与磁化率、总有机碳和碳酸盐含量都呈正相关关系,而且高的彩度值通常与高的黏土组分含量变化表现出较好的一致性,说明彩度Ca*b*的高值可能指示了较高的湖面,此时研究区环境相对暖湿。

三河-平谷8.0级大震区震源细结构的深地震反射探测研究

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基于分区的太湖叶绿素a遥感估测模型

以太湖为研究区域，测试水体的反射光谱和表层水质并分析叶绿素的光谱特征，对比MODIS波段并找出与叶绿素a质量浓度相关性较好或对叶绿素a质量浓度变化较为敏感的波段，根据主成分变换后的MODIS图像色调对太湖进行分区并分别用主成分、单波段及波段组合因子建立各区内相应的叶绿素a质量浓度估测模型．结果表明：对太湖合理分区可以提高叶绿素a质量浓度的遥感估测精度；经过主成分变化后的第2主成分，MODIS波段1，3-4，10～14的反射率及波段反射率组合可以较好地估测分区后的叶绿素a质量浓度。

区域雷达网同步观测对比分析

利用长江中游的合肥、宜昌、武汉、常德和长沙雷达周围的1:25万的地形高度数据得到各雷达的混合扫描仰角和等射束高度拼图。选用2004年7月17—19日5部雷达同步观测的雷达体扫资料,分析了各雷达的最低扫描仰角;在尽量排除地物杂波、波束阻挡、距离衰减和波束展宽等因素影响的情况下,对比分析了5部雷达构成的有重叠覆盖区的7个雷达对的反射率因子差异。结果表明:(1)对雷达最低扫描仰角进行分析可以检查雷达的仰角标定,武汉和合肥雷达平均最低观测仰角比VCP21扫描方式规定的要低;(2)用雷达对等距离线上的反射率垂直剖面可以分析雷达对同步观测的回波空间位置和强度差异,常德雷达和其周围雷达同步观测的回波高度明显偏低;(3)用雷达对等距离线上某高度的反射率因子曲线变化的一致程度可以分析雷达的方位标定,这5部雷达没有明显的方位定标偏差;(4)用雷达对等距离线上某高度的平均反射率因子差可以分析雷达对同步观测的系统观测差,宜昌雷达和其周围的雷达相比,观测的回波强度偏强,而武汉和其周围的雷达相比,观测的回波强度偏弱;(5)反射率因子差的时间平均值随着反射率因子的大小变化而变化,当观测的反射率因子越大时雷达对的反射率因子差的时间平均值也越大。

华安汰内井水氡对闽台地震的映震特征差异性分析

通过华安汰内井水氡对1987年以来福建地区ML4.5以上地震、台湾地区MS7.0以上地震的映震特征分析,认为该井水氡对福建和台湾地区地震的映震特征具有一定的差异性,其差异性表现为对福建地区的地震,其异常特征一般表现为突跳及振荡,且异常多发生在震前20天左右,同时异常持续的时间也较短;对台湾地区的地震,其异常特征表现为高值异常且异常持续时间长,异常多发生在震前11个月左右。据此可以在华安汰内井水氡发生异常时对未来的发震地点做出较为准确的判断。