QOCA和GLOBK软件处理高精度GNSS网结果对比分析

分别利用GLOBK和QOCA软件对陆态网络260个基准站的GNSS观测数据进行处理,获得站点在ITRF2008框架下的坐标和速度。通过比较分析两个软件的解算结果,证明了QOCA 软件能更好地处理测站位移的非线性变化,并通过拟合周年、半年项、剔除共模误差等手段提高解算精度。结果表明,相比于GLOBK软件,QOCA软件得到的拟合残差序列的RMS在E、N、U 3个方向上分别减小70%、80%和70%。     

Variational analysis of dynamics of fissured poroelastic rocks

Rocks can be modeled in a continuum framework as fissured, poroelastic materials, i.e., materials with two degrees of porosity, one due to the fissures and another one due to the pores. The governing equations of motion of fissured poroelastic rocks established by Beskos are rederived here by establishing a variational statement which also provides the boundary conditions of the problem. This is accomplished by considering strain, dissipation and kinetic energies as well as the work of external forces. The above statement is also derived here by employing the method of weighted residuals.     

联邦滤波的改进算法

分析并综述了联邦滤波算法,以及该算法存在的问题.针对观测信息不足的情况下,结合抗差估计和自适应估计理论对联邦滤波算法进行了改进,给出了联邦滤波在局部传感器观测信息不足情况下的改进算法.由模拟计算结果可知,在局部传感器观测信息不足的情况下,改进的联邦滤波器能较好地抑制载体观测异常和状态扰动异常对动态系统参数估值的影响,具有很强的的抗差性和自适应性.     

基于船载ADCP观测对罗源湾湾口断面潮流及余流的分析

基于对罗源湾可门水道的25 h连续走航ADCP观测,成功构建了沿走航断面共12个站位的连续海流时间序列,并对这些站位的潮流、余流以及潮通量等进行了分析。结果表明可门水道内的潮流为正规半日潮流,驻波性质明显,涨潮首先出现在水道中下层而退潮则首先发生在水道上层。水道内的潮流为往复流,水道南部M₂分潮流流速较大,并且其倾角自北向南逐渐增加。此外,水道两端的浅水区域内浅水分潮M₄振幅较显著。可门水道内余流呈现出两层结构,20 m以浅余流沿东北向流出海湾,并且出流的核心位置偏南,而20 m以深的余流沿西南向流入湾内,入流的流核位于偏北的近底层区域。对潮通量的积分计算表明通过可门水道进入罗源湾的潮通量约为4.81×108 m3。     

Truncation of the distribution of ground-motion residuals

Recent studies to assess very long-term seismic hazard in the USA and in Europe have highlighted the importance of the upper tail of the ground-motion distribution at the very low annual frequencies of exceedance required by these projects. In particular, the use of an unbounded lognormal distribution to represent the aleatory variability of ground motions leads to very high and potentially unphysical estimates of the expected level of shaking. Current practice in seismic hazard analysis consists of truncating the ground-motion distribution at a fixed number (ε _max) of standard deviations (σ). However, there is a general lack of consensus regarding the truncation level to adopt. This paper investigates whether a physical basis for choosing ε _max can be found, by examining records with large positive residuals from the dataset used to derive one of the ground-motion models of the Next Generation Attenuation (NGA) project. In particular, interpretations of the selected records in terms of causative physical mechanisms are reviewed. This leads to the conclusion that even in well-documented cases, it is not possible to establish a robust correlation between specific physical mechanisms and large values of the residuals, and thus obtain direct physical constraints on ε _max. Alternative approaches based on absolute levels of ground motion and numerical simulations are discussed. However, the choice of ε _max is likely to remain a matter of judgment for the foreseeable future, in view of the large epistemic uncertainties associated with these alternatives. Additional issues arise from the coupling between ε _max and σ, which causes the truncation level in terms of absolute ground motion to be dependent on the predictive equation used. Furthermore, the absolute truncation level implied by ε _max will also be affected if σ is reduced significantly. These factors contribute to rendering a truncation scheme based on a single ε _max value impractical.     

Calibration of paired watersheds: Utility of moving sums in presence of externalities

Historically, paired watershed studies have been used to quantify the hydrological effects of land use and management practices by concurrently monitoring 2 similar watersheds during calibration (pretreatment) and post‐treatment periods. This study characterizes seasonal water table and flow response to rainfall during the calibration period and tests a change detection technique of moving sums of recursive residuals (MOSUM) to select calibration periods for each control–treatment watershed pair when the regression coefficients for daily water table elevation were most stable to minimize regression model uncertainty. The control and treatment watersheds were 1 watershed of 3–4‐year‐old intensely managed loblolly pine (Pinus taeda L.) with natural understory, 1 watershed of 3–4‐year‐old loblolly pine intercropped with switchgrass (Panicum virgatum), 1 watershed of 14–15‐year‐old thinned loblolly pine with natural understory (control), and 1 watershed of switchgrass only. The study period spanned from 2009 to 2012. Silvicultural operational practices during this period acted as external factors, potentially shifting hydrologic calibration relationships between control and treatment watersheds. MOSUM results indicated significant changes in regression parameters due to silvicultural operations and were used to identify stable relationships for water table elevation. None of the calibration relationships developed using this method were significantly different from the classical calibration relationship based on published historical data. We attribute that to the similarity of historical and 2010–2012 leaf area index on control and treatment watersheds as moderated by the emergent vegetation. Although the MOSUM approach does not eliminate the need for true calibration data or replace the classic paired watershed approach, our results show that it may be an effective alternative approach when true data are unavailable, as it minimizes the impacts of external disturbances other than the treatment of interest.     

依兰-伊通断裂带地表温度变化分析

GPS结果显示,2011年3月11日日本MW9.0大地震引起了我国东北地区的拉张活动增强,其中,依兰——伊通断裂带最显著．这个变化在温度场中是否也有所响应是一个值得探讨的问题,也是一个利用地表温度进行现今构造活动探索的机会．本文利用2000——2011年的中分辨率成像光谱仪(MODIS)地表温度产品对东北地区地表温度进行了分析,以去除稳定年周期变化的年变残差作为研究对象, 通过空间和时间分析,排除地形、纬度、气象等干扰因素的影响,寻找与构造活动相关的热信息．结果表明, 2001年初和2010年初依兰——伊通断裂北段曾经出现了显著的降温现象,且降温过程持续约两个月．通过气象资料分析,初步认为上述现象并非由气象因素引起．这与GPS远场同震位移结果所显示的依兰——伊通断裂带在日本地震后出现相对比较明显的张性应变相吻合. 初步认为上述降温现象与依兰——伊通断裂的拉张增强有关．      

Water temperature modelling: comparison between the generalized additive model,logistic, residuals regression and linear regression models

Water temperature has a significant influence on aquatic organisms, including stenotherm fish such as salmonids. It is thus of prime importance to build reliable tools to forecast water temperature. This study evaluated a statistical scheme to model average water temperature based on daily average air temperature and average discharge at the Sainte-Marguerite River, Northern Canada. The aim was to test a non-parametric water temperature generalized additive model (GAM) and to compare its performance to three previously developed approaches: the logistic, residuals regression and linear regression models. Due to its flexibility, the GAM was able to capture some of the nonlinear response between water temperature and the two explanatory variables (air temperature and flow). The shape of these effects was determined by the trends shown in the collected data. The four models were evaluated annually using a cross-validation technique. Three comparison criteria were calculated: the root mean square error (RMSE), the bias error and the Nash-Sutcliffe coefficient of efficiency (NSC). The goodness of fit of the four models was also compared graphically. The GAM was the best among the four models (RMSE = 1.44°C, bias = ?0.04 and NSC = 0.94).     

Travel time residuals in southeastern Europe

The Pn travel time relative residuals, in respect to a crustal model of the Aegean area, have been determined for 103 permanent seismological stations in southeastern Europe, western Turkey and the Middle East. The values of these residuals are considered to depend mainly on the crustal thickness beneath the seismological stations. Based on these values seven regions with different crustal thickness, varying between 31 Km and 42 Km, have been defined. The crust in these regions is continental. A region with very high negative residuals has been defined in the Middle East (Egypt, Israel, Lebanon). These negative residuals are attributed to different crustal structure of the eastern Mediterranean (oceanic crust with an extra thick sedimentary layer) and not the crustal thickness at the station sites.Independently from the interpretation, these Pn residuals can be used successfully to considerably improve (up to 2 Km) the determination of the earthquake foci locations.