短潮位序列系统误差的探测及修复方法研究

提出了一种基于最小二乘潮位序列分段匹配方法。通过系统误差类型分析、分段段长确定、沉降发生具体时刻确定、系统误差类型探测和修复等算法研究,实现了临时潮位站潮位资料不同系统误差的准确探测和高精度修复。     

GZCORS在广州轨道交通水下地形测量中的应用

水下地形图是轨道交通工程规划、设计、施工的重要基础资料,本文以广州轨道交通三号线流溪河水下地形测量为例,阐述了广州市连续运行参考站城市3维定位系统(GZCORS)在水下地形测量中的作业模式、方法及精度。该种作业模式在河道、沿海港口等水下地形测量中有着广阔的应用前景。     

Observation on height changes of chinese tide gauges by GPS

IntroductionBecause of global temperature rising and glacierthawing,the sea level has risen about 10-25 cmin the past century[1]. The sea level change isone of the main ai ms in global change monito-ring. Presently the basic tool used in sea levelmonitori…     

Phases Representing Source Lengths of Tsunami in Tide Gauge Records

We identified a phase representing the source length of tsunami's in the tide gauge records around Japan. This phase was observed at tide stations, located in the direction of the long axis of the sources, for four large tsunamis: 1964 Niigata, 1968 Tokachi-oki, 1983 Nihonkaichubu, and 1993 Hokkaido-nanseioki. The phase consists of two continuous crests starting as the initial arrival and has a time length of 15–47 minutes. This is the time required to propagate across the source area along the long axis. Strong evidence that the phase is generated at the source is the good correlation between waveform observed at one side and time-inversed waveform at another side. The correlation results from the instantaneous generation of the source. The source lengths of 74–254 km were obtained under an assumption of sea depths at the sources and verified to coincide with ones within a relative error of 15% that were previously obtained by other methods.     

电导率各向异性的海洋电磁三维有限单元法正演

本文提出了一种基于非结构化网格的海洋电磁有限单元正演算法.为了回避场源奇异性, 文中选用二次场算法, 将背景电阻率设置为水平层状且各向异性, 场源在水平层状各向异性介质中所激发的一次场通过汉克尔积分得到.基于Coulomb规范得到二次矢量位和标量位所满足的Maxwell方程组, 通过Galerkin加权余量法形成大型稀疏有限元方程, 采用不完全LU分解(ILU)预条件因子的quasi-minimum residual(QMR)迭代解法对有限元方程进行求解得到二次矢量位和标量位; 进而, 利用滑动平均方法得到二次矢量位和标量位在空间的导数, 由此得到二次电磁场; 通过一维模型对算法的可靠性进行验证, 与此同时, 针对实际复杂海洋电磁模型, 比较有限元模拟结果与积分方程模拟结果, 进一步验证算法精度.若干计算结果均表明, 文中算法具有良好的通用性, 适用于井中电磁、航空电磁, 环境地球物理等非均匀且各向异性介质中的电磁感应基础研究.     

Levee effects upon flood levels: an empirical assessment

This study used stream gauge records to assess the impact of levees on flood levels, providing an empirical test of theoretical and model predictions of the effects on local flood response. Focusing upon a study area in Illinois and Iowa for which levee records were available, we identified 203 gauges with ≥ 50 years hydrological record, including 15 gauges where a levee was constructed during the period of record. At these sites, step‐change analysis utilizing regression residuals tested levee‐related stage changes and levels of significance and quantified the magnitudes of stage changes. Despite large differences in stream sizes, levee alignments, and degree of floodplain constriction, the post‐levee rating‐curve adjustments showed consistent signatures. For all the study sites, stages for below bankfull (non‐flood) conditions were unaffected by levee construction. For above bankfull (flood) conditions, stages at sites downstream of their associated levees also were statistically indistinguishable before versus after levee construction. However, at all sites upstream of levees or within leveed reaches, stages increased for above bankfull conditions. These increases were abrupt, statistically significant, and generally large in magnitude – ranging up to 2.3 m (Wabash River at Mt. Carmel, IL). Stage increases began when discharge increased above bankfull flow and generally increased in magnitude with discharge until the associated levee(s) were overtopped. Detailed site assessments and supplementary data available from some sites helped document the dominant mechanisms by which levees can increase flood levels. Levee construction reduces the area of the floodplain open to storage of flood waters and reduces the width of the floodplain open to conveyance of flood flow. Floodplain conveyance often is underestimated or ignored, but Acoustic Doppler Current Profiler (ADCP) measurements analysed here confirm previous studies that up to 70% or more of the total discharge during large floods (~3% chance flood) can move over the floodplain. Upstream of levees and levee‐related floodplain constriction, backwater effects reduce flow velocities relative to pre‐levee conditions and, thus, increase stages for a given discharge. The empirical results here confirm a variety of theoretical predictions of levee effects but suggest that many one‐dimensional model‐based predictions of levee‐related stage changes may underestimate actual levee impacts. Copyright © 2011 John Wiley & Sons, Ltd.     

集成奇异谱分析和自回归滑动平均预测日本近海海平面变化

本文从日本沿岸选取了28个验潮站及联测的GPS站,利用奇异谱分析（Singular Spectrum Analysis,SSA）和SSA+自回归滑动平均（Auto Regression Moving Average,ARMA）方法预测了2014—2018年的近海海平面变化和地壳垂直变化.并用同时段的验潮及GPS的实际测量值进行验证,结果显示,SSA+ARMA预测的相对海平面精度为0.0357~0.0607 m,地壳垂直运动的精度为0.0049~0.0077 m,绝对海平面的精度为0.0433~0.0683 m,且三者SSA+ARMA的预测结果均优于只用SSA预测的结果.在此基础上本文利用SSA+ARMA预测了日本沿岸2019—2023年的近海绝对海平面变化,结果显示,2019—2023年的平均海面高较往年（2014—2018）升高0.0353 m,2003—2023年绝对海平面的变化率为0.0039 m·a^-1,预测结果较为理想.

     

Comparison of observed and theoretically calculated seiches of Heda Bay,Japan

We carried out observations of sea-level fluctuations simultaneously at three stations on the coast of Heda Bay, Honshu, Japan, using supersonic-type water level gauges controlled by a personal computer. Analyses of the obtained data showed predominant spectral peaks at periods of 7.6, 2.0 and 1.3 minutes for all three stations. Comparison of the observed data with numerically calculated normal oscillation modes of the bay indicates that these three spectral peaks correspond to the theoretical first, third and seventh normal modes of the basin respectively, judging from the results of cross-spectral analyses. The reason for the absence of the remaining normal modes, especially of the second or the lateral first mode of the basin, is briefly considered.     

A Reanalysis and Reinterpretation of Geodetic and Geological Evidence of Glacial-Isostatic Adjustment in the Churchill Region, Hudson Bay

We review the historical, geological, tide-gauge, GPS and gravimetric evidence advanced in favour of, or against, continuing land uplift around Hudson Bay, Canada. We also reanalyse the tide-gauge and GPS data for Churchill using longer time series than those available to previous investigators. The dependence of the mean rate of relative sea-level change obtained from the tide-gauge record on the length and mid-epoch of the observation interval considered is investigated by means of a newly developed linear-trend analysis diagram. For studying the shorter-period variability of the tide-gauge record, the wavelet transform is used. The mean rate of land uplift obtained from GPS is based on a new analysis using IGS solutions of GFZ. To include the post-glacial land uplift, sea-level indicators from the Churchill region representing the relative sea-level history during the past 8000 years are also used. Finally, the values of the four observables are jointly inverted in terms of mantle viscosity. The optimum values are ~3.2 × 10²⁰ Pa s and ~1.6 × 10²² Pa s for the upper- and lower-mantle viscosities, respectively.