Temporal and spatial variability of Chl-a and SST on the South Atlantic Bight: Revisiting with cloud-free reconstructions of MODIS satellite imagery

Daily, cloud-free data interpolating empirical orthogonal function (DINEOF) reconstructions of sea-surface temperature (SST) and chlorophyll (Chl-a) satellite imagery are compiled into monthly mean images for a six-year period (2003–2008) and used to identify their spatial and temporal variability on the South Atlantic Bight. Monthly-mean SST has the highest variability on the inner-shelf, decreasing seaward approaching the more stable temperatures of the Gulf Stream (GS). Monthly-mean Chl-a concentrations are similarly highest on the inner shelf throughout the year and decrease cross-shelf toward the nutrient depleted open ocean. Empirical orthogonal function (EOF) analyses on SST and Chl-a show a clear seasonal cycle in their 1st mode of variability, with SST lagging behind Chl-a by approximately one month. The 1st EOF modes account for 95.8% and 46.4% variance of SST and Chl-a, respectively. Chl-a EOF mode 1 in particular shows a highly regionalized spatial pattern with values on the central SAB clearly out of phase with the southern and northern SAB. This regional difference is likely a result of shelf geometry and stratification, which modulate GS influence on the shelf. SST EOF mode 2 exhibits a seasonal cycle as well, which previous studies have shown to be a function of local wind. Chl-a EOF mode 2 is well correlated with the cumulative river transport onto the SAB, but accounts for a relatively small 10.8% of Chl-a variability.     

2009年阿合奇M_S5.5、阿图什M_S5.0地震前后重力场变化分析

计算分析了近2期流动重力资料,对2009年4月19日阿合奇发生的MS5.5地震和2009年4月22日阿图什发生的MS5.0地震进行了初步分析。结果表明,这两次地震的孕育与发生,都伴随着重力异常的出现,且地震发生在重力场变化的零线附近和重力场反向回跳的转折线附近。     

国家地震应急指挥技术系统建设中的关键技术及应用

地震应急指挥系统是国家公共安全平台的一个重要组成部分,同时也是地震应急指挥技术系统为国家与各级地方政府进行地震应急指挥服务的专业技术支持系统。本文以数字观测网络项目为背景,全面归纳和总结了国家地震应急指挥技术系统建设中的关键技术及具体应用。     

2000国家重力基本网部分站的最新绝对重力测量

为分析部分2000国家重力基本网点的长期稳定性,应用FG5/240绝对重力仪在该网的永兴岛和郑州站进行了绝对测量。对观测结果的处理表明,观测精度优于5×10 ^-8 ms ^-2 ;同时对观测值及其对应的2000国家重力基本网点的重力值进行了比较,得出两者之间重力值差异变化。     

Frozen subduction in the Yangtze block: insights from the deep seismic profiling and gravity anomaly in east Sichuan fold belt

The Sichuan basin is the main part of the middle-upper Yangtze block, which has been experienced a long-term tectonic evolution since Archean. The Yangtze block was regarded as a stable block until the collision with the Cathaysia block in late Neoproterozoic. A new deep seismic reflection profile conducted in the eastern Sichuan fold belt (ESFB) discovered a serials of south-dipping reflectors shown from lower crust to the mantle imply a frozen subduction zone within the Yangtze block. In order to prove the speculation, we also obtain the middle-lower crustal gravity anomalies by removing the gravity anomalies induced by the sedimentary rocks and the mantle beneath the Moho, which shows the mid-lower crustal structure of the Sichuan basin can be divided into eastern and western parts. Combined with the geochronology and Aeromagnetic anomalies, we speculated the Yangtze block was amalgamated by the West Sichuan and East Sichuan blocks separated by the Huayin-Chongqing line. The frozen subduction zone subsequently shifted to a shear zone accommodated the lower crustal shortening when the decollement at the base of the Nanhua system functioned in the upper plate.     

Geodetic Analysis inside the South Korean Peninsula and Impact of the 2011 Tohoku–Oki (TO) Earthquake

The most powerful Tohoku–Oki (TO) earthquake that occurred in Japan on 11 March 2011 affected Japan as well as South Korea. In the current study, we investigated contemporary geodetic deformation inside South Korea before and after the TO earthquake using Global Navigation Satellite System (GNSS) measurements from 01 January 2008 to 31 December 2017. Measured velocities of GNSS sites are modeled by Auto-regressive moving average (ARMA) method to analyze the long-term GNSS time-series variation and to investigate the secular tectonic crustal deformation. We found that the maximum co-seismic displacements during the TO earthquake reached up to 36.82 ± 0.21 mm in the east and 5.90 ± 0.08 mm in the north directions. The geometric model of the co-seismic thrust surface was characterized by a rectangular plane with a dip of 12.0° and strike 200°. The thrust is situated at 25 km hypocenter depth, with an area roughly ~470 km long and ~120 km wide. The seismicity pattern after the earthquake indicated that the compressional strain started to be replaced by the extensional strain during the post TO earthquake period from 2011 to 2014. Further, the strain became predominantly extensional during the period 2015 to 2017, revealing an effective rotational change that occurred inside the Korean Peninsula.     

资源三号卫星全色影像的姿态角常差检测

根据资源三号卫星传感器的成像原理,构建严格几何模型进行直接定位。通过对不同时间的资源三号全色影像进行实验,验证了姿态角常差的存在,并建立校正模型对其进行改正。利用少量控制点改正姿态角常差后,影像立体定位精度可显著提高。不同地区的实验结果表明,姿态角常差不是恒定不变的,需要根据长期观测建立其变化模型。     

重力式挡土墙结构体系可靠度的Monte Carlo模拟

建立了重力式挡土墙倾覆、基底滑移、地基承载力、墙体自身强度等几个失效模式的可靠度分析模型,采用逐步等效平面法计算结构体系的可靠度。假定设计参数为正态分布的随机变量,利用MATLAB软件的库函数normrnd实现随机样本的抽取。选择重力式挡土墙的实际算例对挡土墙改建后的几个失效模式及结构体系的可靠度进行分析,并与作者所做的其它理论分析结果进行了对比。数值模拟表明两种方法的结果能较好相符。     

Photogrammetric Bathymetry for the Canadian Arctic

Abstract

Remote sensing is becoming common in the estimation of bathymetry for navigational charting through a process known as Satellite Derived Bathymetry (SDB). Most SDB techniques currently used by hydrographic offices employ an empirical approach, requiring the use of in-situ data to calibrate a relationship between spectral information and coincident depths. This article reports on a multi-site test of an alternative SDB method which uses photogrammetry to extract depths from stereo WorldView-2 imagery. In areas with heterogeneous seafloors, the empirical approach faces difficulties in establishing the relationship between colour and depth, while the photogrammetric approach uses the contrasting seafloor features for triangulation. Additionally, the photogrammetric method may be applied in areas lacking previous survey data. Five study areas in Nunavut, Canada were selected to test the robustness of the method in different environments and under different imaging conditions. Study areas were (with resulting RMSE/Bias given in metres) Coral Harbour (0.84/?0.47), Cambridge Bay (1.16/?0.15), Queen Maud Gulf (0.97/0.06), Arviat (0.99/?0.009), and Frobisher Bay, where extraction largely failed due to environmental conditions. Accuracies demonstrated here are similar to those seen using the empirical approach, suggesting that these two methods may be used in conjunction, each applied to regions where they are better suited.     

利用重力方法圈定巨野煤田成矿远景区

重力方法是研究区域构造的重要方法,通过重力正演能准确地计算出具有一定密度差的地层分界面深度。通过收集巨野煤田早期的岩石密度资料以及钻孔资料,利用2.5D剖面重力正演计算方法,圈定了巨野煤田-1 000m以浅成矿远景区。该方法对其他地区盆地内沉积矿产找矿具有借鉴意义。