Gravity change observed in a local gravity network and its implication to seasonal precipitation in Dali county,Yunnan province,China

This study investigates data-processing methods and examines the precipitation effect on gravity measurements at the Dali gravity network, established in 2005. High-quality gravity data were collected during four measurement campaigns. To use the gravity data validly, some geophysical corrections must be considered carefully. We first discuss data-processing methods using weighted leastsquares adjustment with the constraint of the absolute gravity datum. Results indicate that the gravity precision can be improved if all absolute gravity data are used as constraints and if calibration functions of relative gravimeters are modeled within the observation function. Using this data-processing scheme, the mean point gravity precision is better than 12 lgal. After determining the best data-processing scheme, we then process the gravity data obtained in the four measurement campaigns, and obtain gravity changes in three time periods. Results show that the gravity has a remarkable change of more than 50 lgal in the first time period from Apr–May of 2005 to Aug–Sept of 2007. To interpret the large gravity change, a mean water mass change(0.6 m in height) is assumed in the ETOPO1 topographic model. Calculations of the precipitation effect on gravity show that it can reach the same order of the observed gravity change. It is regarded as a main source of the remarkable gravity change in the Dali gravity network, suggesting that the precipitation effect on gravity measurements must be considered carefully.     

半径-斜率域加权反假频地震数据重建

为减小地震数据缺失给地震后续处理工作带来的影响,需要对地震数据进行插值重建.针对反假频插值重建这个难点问题,进行了相关研究,并由此提出了一种改进的R-P（半径-斜率）域加权反假频地震数据插值重建方法.该方法将F-K（频率-波数）谱变换到R-P域,在R-P域设计一个权函数并将其作用于每次的迭代插值过程.通过模型数据和实际数据的测试,证明了该方法具有较好的反假频插值重建能力.     

Crustal growth and tectonic evolution of the Tianshan orogenic belt,NW China: A receiver function analysis

The Central Asian Orogenic Belt (CAOB) represents the world's largest Phanerozoic accretionary orogen, the major phase of which was built during the closure of the Paleo-Asian Ocean. The Tianshan orogenic belt forms the southwestern segment of the CAOB and has been the focus of investigations related to the evolution of the CAOB. Here we present results from an analysis of the crustal structure and upper mantle discontinuity beneath the Chinese Tianshan by employing H-k stacking technique as well as depth domain and synthetic receiver functions. Our results identify a double peak of Moho Ps in the Tianshan orogenic belt, suggesting the possibility of insertion of the lower crust of the Tarim Basin into this belt, with the latter retaining its initial crustal architecture. Our results provide insights into the dynamics of northward extrusion and the N–S trending crustal shortening of the Tianshan orogen during the convergence of the India and Eurasia blocks.     

A seismic investigation into the geometry and controls upon alluvial architecture in the Walloon Subgroup,Surat Basin,Queensland

The sedimentology of the Walloon Subgroup (WSG) has been extensively studied; however, gaps exist in our understanding of the succession's alluvial architecture and the mechanisms controlling its complex internal organisation. Successful coal-seam gas development in the Surat Basin requires the construction of predictive facies models, which in turn necessitates a fulsome understanding of the geometry and controls on the spatial and temporal distribution of alluvial sub-environments. To improve our models of WSG facies, this study employs an open-source high-resolution 3D seismic dataset available on the western limb of the Surat Basin. Integration of core, wireline and seismic data has resolved the geometries of four discrete alluvial architectural elements, representing simple channel, channel belt, crevasse splay complexes and peat-mire sub-environments. Channel belts were found to be 1600–2000 m wide, simple channels 400–800 m in width and crevasse splays averaging 3.5 × 5.5 km. Coal bodies mapped from seismic attribute extractions were found to be 4.2 km² on average. The high-resolution dataset has also yielded insight into the geological controls governing the spatial and temporal distribution of these sub-environments, explaining, in part the mechanisms responsible for the complex internal distribution of facies within the WSG. In places within the study area, the WSG's sedimentary organisation appears to be initiated by the rejuvenation of deep-seated tectonic features, the expression of which is propagated upward via the mechanics of compensational stacking.     

华南大陆东部赣闽地区地壳厚度与泊松比研究

通过收集江西省和福建省共58个固定台站记录到的2011-01～2012-12的远震数据,利用接收函数H-κ扫描叠加方法得到台站下方平均地壳厚度和波速比估计,并通过插值得到华南大陆东部赣闽地区整体的地壳厚度变化趋势以及泊松比分布情况。结果表明,研究区地壳厚度约为28～34 km,由内陆向沿海有起伏地逐渐减薄,赣南地区同福建沿海地区地壳厚度较薄,江西东部和福建西北部地壳较厚;泊松比约为0.21～0.28,由内陆向沿海逐渐增加,赣北地区泊松比值最低,低于0.23（波速比低于1.70）,沿海地区泊松比较高,可达0.28（波速比为1.83）。并探讨了造成地壳厚度和泊松比变化的构造因素。     

北京北部上侏罗统辫状河体系沉积特征

根据野外露头的沉积构造和沉积层序特征,对北京北部延庆硅化木国家地质公园上侏罗统后城组进行沉积相研究,认为该地区以辫状河沉积为主,构成辫状河体系的4种沉积微相类型包括河道、心滩、河间湖泊和溢岸沉积,其中的溢岸沉积相当于曲流河中发育的决口河道与决口扇沉积。运用基准面旋回变化原理,识别出了2个中期旋回和构成中期旋回的多个短期旋回。总结了基准面旋回特征,阐明了地层叠加样式随A/S(可容纳空间/沉积物供给)比值的变化规律,认为低A/S比值时,河道砂体的连通性较好,而高A/S比值时,河道较孤立,连通性较差;且溢岸沉积的地层厚度随着A/S比值的增加不断增大,溢岸沉积的厚度可以作为判断可容纳空间大小的一个依据。     

基于接收函数的华南及邻区地壳结构研究

利用华南地块及邻区2007～2012年609个地震台站记录的约900个5.7级以上远震事件,获得各台站的接收函数,通过分析接收函数的形态变化了解各台站下方的地壳结构特征,然后再利用H-κ叠加搜索技术获得各台站下方的地壳厚度和波速比.结果显示,研究区的地壳结构表现为从沿海向内陆逐渐复杂的变化,地壳厚度也表现出由沿海向内陆...     

1979—2019年武汉市重点水体多要素协同的时空演变特征

城市发展对水体多方面要素产生了巨大影响,尤其是对水资源丰富的城市,迫切需要开展相关监测研究。研究以武汉市为例,通过梳理国内外相关研究以及武汉水体保护政策,提出融合水体面积、水质、水体景观、滨水区生态环境4个方面要素的分析技术路线以更为全面的反映城市尺度的水体时空演变特征,具体的,利用随机森林模型基于1979—2019年遥感影像获取武汉67个重点水体信息,并以此获取水体面积和水体景观的变化特征;同时,通过梳理多年水质监测数据分析水质变化特征;另外,基于遥感生态指数（Remote Sensing Ecological Index, RSEI）分析滨水区生态环境变化;最后,采用多尺度地理加权回归模型（Multi-scale Geographically Weighted Regression, MGWR）对重点水体面积变化的影响因素研究,希冀为政府制定差异化的水体保护政策提供科学支撑,并为其他地区水体的多要素分析提供有益借鉴。结果表明：① 武汉市水体面积呈下降趋势,水体总面积、重点水体面积分别减少10.75%及13.12%,中心城区及郊区水体变化存在显著差异;② 水体景观呈退化趋势,周长面积分维数、平均斑块面积、聚合指数及结合指数分别减少了6.43%,79.35%,1.55%及10.94%;③ 重点水体水质总体呈恶化趋势,其中江河及水库多数常年为III类及以上水体,中心城区湖泊多为V类及以下水体,郊区湖泊多为IV类及V类水体;④ 中心城区及郊区滨水区遥感生态指数（RSEI）分析表明滨水区生态环境呈恢复态势,其中中心城区滨水区平均RSEI增长了14.29%;⑤ MGWR分析表明,自然气象因素中,相对湿度的增加对江夏区湖泊恢复影响更为显著,降水对水面较小的水体恢复影响更为显著;社会经济因素中,各行政区GDP的增加有助于水体恢复,对中心城区、黄陂及新洲的水体保护影响更为显著;滨水缓冲区内不透水面占比（IS）的增加导致大多数水体面积的减少,然而,对于少数重点修复水体,IS增加是受相关保护政策影响,IS增加有助于这些水体恢复。     

一种计算区域内气象要素平均值的方法

采用面积分的原理,提出了一种计算区域内气象要素平均值的新方法,通过对湖南全省温度、降水的平均值计算分析,对计算误差进行了检验。结果表明,采用该计算方法可以减少因气象台站分布不均匀对平均值的影响,计算得到的平均值更能反映实际情况。     

多宝山地区岩石反射波谱研究

黑龙江多宝山地区岩石反射波谱研究表明，海西期岩浆岩反射率（ρ）最高，古生代地层次之，火山熔岩最小，岩浆岩中ρ值大则蚀变作用强，ρ值变化大则蚀变类型多，０．７０μｍ谱是岩浆岩蚀变作用显著与否的标志，岩石经热流体后期改造作用后产生强的１．４０、１．９０和２．２０μｍ特征谱。火山熔岩ρ值与ＳｉＯ＿２含量呈正相关，其铜含量高、蚀变作用强则ρ值变化大，ρ值在ＮＩＲ区差异最大并形成三个优选窗口。古生代地层ρ值与碳含量、特征谱数呈负相关，Ｃａ含量、基团与特征谱数、强度呈正相关。据岩石波谱数据及其计算值，文章演绎出地面波谱叠合法并综合其他方法确定了区内ＴＭ图像处理的最佳波段组合。