不同采样率水位同震响应能力及其特征分析

分析同种仪器不同采样率水位资料同震响应记录情况,发现存在很大差异,不但形态上明显不同,响应能力及响应幅度上也差别很大.在此基础上认为,秒采样率数据能更好记录同震响应.指出,为了记录到真实完整可靠的同震响应,观测仪器应在采样率、数据存储容量、GPS授时、触发阈值、时值及分钟值取值方式等方面作改进.最后指出,同震响应分析可能是今后地震分析预报有所突破的一个研究方向.     

LN-3A数字地震水位仪故障分析与解决

分析了LN-3A数字地震水位仪在安装及运行过程中,传感器、数据采集器、数据通讯及观测数据曲线出现的各种故障及异常,针对故障及异常进行分析并查找原因,提出了解决办法.为一线台站人员能够在第一时间处理仪器故障、找出观测数据曲线异常原因提供借鉴,为仪器的安全稳定运行和观测资料的连续、准确、可靠打下良好基础.     

Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers”

Citation Abrahart, R.J. & Mount, N.J. (2011) Discussion of “Neuro-fuzzy models employing wavelet analysis for suspended sediment concentration prediction in rivers by S.A. Mirgagheri et al. (2010, Hydrol. Sci. J. 55(7), 1175–1189).” Hydrol. Sci. J. 56(7), 1325–1329.     

Reconstruction of groundwater levels to impute missing values using singular and multichannel spectrum analysis: application to the Ardabil Plain,Iran

ABSTRACT

Groundwater-level time series often have a substantial number of missing values which should be taken into consideration before using them for further analysis, particularly for numerical groundwater flow modelling applications. This study aims to comprehensively compare two data-driven models, singular spectrum analysis (SSA) and multichannel spectrum analysis (MSSA), to reconstruct groundwater-level time series and impute the missing values for 25 piezometric stations in Ardabil Plain, northwest Iran. The reconstructed groundwater-level time series are assessed against the complete observed groundwater time series, while the imputed values are appraised against the artificially created gap values. The results show that both SSA and MSSA demonstrate a solid competency in imputation and reconstruction of groundwater-level data. However, depending on the spatial correlation between the piezometers, and the most suitable probability distribution function (pdf) fitted to the time series of each piezometer, the performance may vary from piezometer to piezometer.     

Simulating and understanding effects of water level fluctuations on thermal regimes in Miyun Reservoir

ABSTRACT

Water temperature dynamics in a reservoir are affected by its bathymetry, climatic conditions and hydrological processes. Miyun Reservoir in China is a large and deep reservoir that experienced a large water level decline in 1999–2004 due to low rainfall and relatively high water supply to Beijing. To study changes of stratification characteristics in Miyun Reservoir from 1998 to 2011, the one-dimensional year-round lake model MINLAKE2010 was modified by adding a new selective withdraw module and a reservoir hydrological model. Simulation results under three scenarios demonstrated that the new MINLAKE2012 model accurately predicted daily water levels and temperature dynamics during the water level fluctuation period. The water level decline led to 7.6 and 3.8°C increases in the maximum and mean bottom temperatures and about 29 days reduction in the stratification days. These simulation results provide an insight into the thermal evolution of Miyun Reservoir during the planned future water filling process.

Editor D. Koutsoyiannis Associate editor M. Acreman     

Dynamic model of mesoscale eddies. Eddy parameterization for coarse resolution ocean circulation models

In the framework of the eddy dynamic model developed in two previous papers (Dubovikov, M.S., Dynamical model of mesoscale eddies, Geophys. Astophys. Fluid Dyn., 2003, 97, 311–358; Canuto, V.M. and Dubovikov, M.S., Modeling mesoscale eddies, Ocean Modelling, 2004, 8, 1–30 referred as I–II), we compute the contribution of unresolved mesoscale eddies to the large-scale dynamic equations of the ocean. In isopycnal coordinates, in addition to the bolus velocity discussed in I–II, the mesoscale contribution to the large scale momentum equation is derived. Its form is quite different from the traditional down-gradient parameterization. The model solutions in isopycnal coordinates are transformed to level coordinates to parameterize the eddy contributions to the corresponding large scale density and momentum equations. In the former, the contributions due to the eddy induced velocity and to the residual density flux across mean isopycnals (so called Σ-term) are derived, both contributions being shown to be of the same order. As for the large scale momentum equation, as well as in isopycnal coordinates, the eddy contribution has a form which is quite different from the down-gradient expression.     

芦山7.0级地震医疗建筑震害与启示

鉴于医疗建筑在防灾救灾中的重要地位和作用,本科考小组对雅安地区医疗建筑在芦山地震中的震害进行了调查,调查包括不同烈度区、不同结构类型和建筑年代、不同级别的医疗卫生机构,对结构构件、非结构构件、医疗设备的震害特征,以及其他影响医疗秩序和使用功能的因素做了阐述和分析,并总结了汶川灾后新建及重建项目的抗震效果.调查表明,雅安地区医疗建筑在建筑结构的抗震安全性及救灾功能的实现方面仍存在很多问题,反映了我国医疗建筑的普遍问题.因此,对医疗建筑的抗震设防,需要作进一步系统的研究.     

Monitoring wetland ditch water levels in the North Kent Marshes,UK, using Landsat TM imagery and ground-based measurements

Abstract

An understanding of hydrology is a prerequisite for ensuring the successful management, conservation and restoration of wetland environments. Frequently, however, little is known about historical hydrological conditions, such as water levels, within wetlands. Moreover, many channel and ditch systems in wetlands are not routinely monitored, except perhaps for research purposes. A methodology is presented herein which makes use of satellite imagery to indirectly provide remotely sensed observations of water levels within channels and ditches. Using multi-temporal Landsat Thematic Mapper (TM) imagery and simultaneous ground-based measurements of water levels, statistical relationships are established between satellite-derived effective wet ditch widths and measured water levels in the drainage system of the Elmley Marshes, southeast England. These relationships can be used subsequently to estimate historical ditch water levels and to monitor contemporary ditch water levels in the wetland. The study shows that satellite imagery has much to offer in monitoring changes in the hydrological regime of wetlands and in providing complimentary approaches to field monitoring.     

龙门山断裂带南段应力状态与强震危险性研究

龙门山断裂带可分为南段、中段和北段,2008年汶川M8.0级地震发生在该断裂带中-北段. 龙门山断裂带南段是否存在发生强震的危险性倍受关注. 利用1977-2012年四川区域地震台网资料,获得了龙门山断裂带南段的地震活动性参数b值图像以及汶川地震前、后b值的差值Δb图像. 同时,根据宽频带数字地震波形资料,计算了2007年以来南段及附近区域M_L≥3.8级地震的视应力. 结果表明,2008年汶川地震后,龙门山断裂带南段天全-芦山、泸定和宝兴北部等区域应力增强,而靠近汶川余震区南端的大邑地区应力水平降低. 天全至宝兴段应力水平相对较高,具有发生中-强地震的条件. 鲜水河断裂带康定以南段应力水平低,短期内发生强震的可能性较小.