基于互联网的地震信息精准与定向传播研究

当互联网的移动时代来临时,数量众多的个人成为信息传播的载体,尤其是在地震灾难事件发生后,信息的不确定性、虚假性也陡然猛增。面对大量繁杂的信息,即使在相对准确的信息面前,人们往往因自身的判断失误而无法做出正确的选择,不少准确的信息也因为失去有效的传播途径而被忽视和湮没。精准与定向这个概念自然而然便浮现出来,精准与定向成为互联网信息传播的发展趋势。本文结合地震信息传播的特点,提出基于互联网的地震信息精准与定向传播研究思路,最大限度地发挥地震信息传播在防震减灾中的作用。     

Well-balanced numerical modelling of non-uniform sediment transport in alluvial rivers

The last two decades have witnessed the development and application of well-balanced numerical models for shallow flows in natural rivers.However,until now there have been no such models for flows with non-uniform sediment transport.This paper presents a 1D well-balanced model to simulate flows and non-capacity transport of non-uniform sediment in alluvial rivers.The active layer formulation is adopted to resolve the change of bed sediment composition.In the framework of the finite volume Slope Llmiter Centred(SLIC) scheme,a surface gradient method is incorporated to attain well-balanced solutions to the governing equations.The proposed model is tested against typical cases with irregular topography,including the refilling of dredged trenches,aggradation due to sediment overloading and flood flow due to landslide dam failure.The agreement between the computed results and measured data is encouraging.Compared to a non-well-balanced model,the well-balanced model features improved performance in reproducing stage,velocity and bed deformation.It should find general applications for non-uniform sediment transport modelling in alluvial rivers,especially in mountain areas where the bed topography is mostly irregular.     

输入界面对场地地表地震动参数的影响

本文以江淮地区典型场地资料为原型,选取不同深度的岩层位置作为地震动输入界面,构造多种场地土层模型,选择Taft、Kobe和E1centro 3条强震记录作为地震输入,采用一维频域等效线性化波动方法重点分析了地震动输入界面对场地地表地震动参数的影响。研究结果表明,随着输入界面深度的增加,场地地表的峰值加速度逐渐增加,且增加的幅度呈逐渐减小的趋势,但输入界面深度对地表加速度反应谱特征周期的影响较小;输入界面剪切波速值对反应谱特征周期影响有限,但对地表峰值加速度影响较为显著,地表峰值加速度随着输入界面剪切波速的增大而增大,且两者的增幅呈现近似的线性关系。     

云南彝良“9?7地震”前异常特点

对2012年9月7日云南省昭通市彝良县洛泽河一带5.7、5.6级地震前地震活动和前兆异常分析,其地震活动特征、流体和形变动态变化及预测指标,发现：地震前4级地震活动水平增强、出现小震活动空区;前兆异常开始于震前1年左右;短期异常有由外围向震中迁移的现象;临震异常出现的时间较为集中,震前一周内。对该地区5.0级以上强震的预报和研究具有一定的指示意义。     

Evaluating actual evapotranspiration and impacts of groundwater storage change in the North China Plain

As a critical water discharge term in basin‐scale water balance, accurate estimation of evapotranspiration (ET) is therefore important for sustainable water resources management. The understanding of the relationship between ET and groundwater storage change can improve our knowledge on the hydrological cycle in such regions with intensive agricultural land usage. Since the 1960s, the North China Plain (NCP) has experienced groundwater depletion because of overexploitation of groundwater for agriculture and urban development. Using meteorological data from 23 stations, the complementary relationship areal evapotranspiration model is evaluated against estimates of ET derived from regional water balance in the NCP during the period 1993–2008. The discrepancies between calculated ET and that derived by basin water balance indicate seasonal and interannual variations in model parameters. The monthly actual ET variations during the period from 1960 to 2008 are investigated by the calibrated model and then are used to derive groundwater storage change. The estimated actual ET is positively correlated with precipitation, and the general higher ET than precipitation indicates the contributions of groundwater irrigation to the total water supply. The long term decreasing trend in the actual ET can be explained by declining in precipitation, sunshine duration and wind speed. Over the past ~50 years, the calculated average annual water storage change, represented by the difference between actual ET and precipitation, was approximately 36 mm, or 4.8 km³; and the cumulative groundwater storage depletion was approximately 1700 mm, or 220 km³ in the NCP. The significantly groundwater storage depletion conversely affects the seasonal and interannual variations of ET. Irrigation especially during spring cause a marked increase in seasonal ET, whereas the rapid increasing of agricultural coverage over the NCP reduces the annual ET and is the primary control factor of the strong linear relationship between actual and potential ET. Copyright © 2013 John Wiley & Sons, Ltd.     

A statistical framework of data fusion for spatial prediction of categorical variables

With rapid advances of geospatial technologies, the amount of spatial data has been increasing exponentially over the past few decades. Usually collected by diverse source providers, the available spatial data tend to be fragmented by a large variety of data heterogeneities, which highlights the need of sound methods capable of efficiently fusing the diverse and incompatible spatial information. Within the context of spatial prediction of categorical variables, this paper describes a statistical framework for integrating and drawing inferences from a collection of spatially correlated variables while accounting for data heterogeneities and complex spatial dependencies. In this framework, we discuss the spatial prediction of categorical variables in the paradigm of latent random fields, and represent each spatial variable via spatial covariance functions, which define two-point similarities or dependencies of spatially correlated variables. The representation of spatial covariance functions derived from different spatial variables is independent of heterogeneous characteristics and can be combined in a straightforward fashion. Therefore it provides a unified and flexible representation of heterogeneous spatial variables in spatial analysis while accounting for complex spatial dependencies. We show that in the spatial prediction of categorical variables, the sought-after class occurrence probability at a target location can be formulated as a multinomial logistic function of spatial covariances of spatial variables between the target and sampled locations. Group least absolute shrinkage and selection operator is adopted for parameter estimation, which prevents the model from over-fitting, and simultaneously selects an optimal subset of important information (variables). Synthetic and real case studies are provided to illustrate the introduced concepts, and showcase the advantages of the proposed statistical framework.     

Crust and upper mantle structures beneath Northeast China from receiver function studies

P-wave and S-wave receiver function analyses have been performed along a profile consisted of 27 broadband seismic stations to image the crustal and upper mantle discontinuities across Northeast China. The results show that the average Moho depth varies from about 37 km beneath the Daxing’anling orogenic belt in the west to about 33 km beneath the Songliao Basin, and to about 35 km beneath the Changbai mountain region in the east. Our results reveal that the Moho is generally flat beneath the Daxing’anling region and a remarkable Moho offset (about 4 km) exists beneath the basin-mountain boundary, the Daxing’anling-Taihang Gravity Line. Beneath the Tanlu faults zone, which seperates the Songliao Basin and Changbai region, the Moho is uplift and the crustal thickness changes rapidly. We interpret this feature as that the Tanlu faults might deeply penetrate into the upper mantle, and facilitate the mantle upwelling along the faults during the Cenozoic era. The average depth of the lithosphere-asthenosphere boundary (LAB) is ~80 km along the profile which is thinner than an average thickness of a continental lithosphere. The LAB shows an arc-like shape in the basin, with the shallowest part approximately beneath the center of the basin. The uplift LAB beneath the basin might be related to the extensive lithospheric stretching in the Mesozoic. In the mantle transition zone, a structurally complicated 660 km discontinuity with a maximum 35 km depression beneath the Changbai region is observed. The 35 km depression is roughly coincident with the location of the stagnant western pacific slab on top of the 660 km discontinuity revealed by the recent P wave tomography.     

云南鲁甸6.5级地震灾害特点浅析

通过对2014年8月3日云南鲁甸6.5级地震震害开展实地调查,对灾区破坏情况进行总体介绍,并就各烈度区特征和建筑物震害、地震地质灾害、工程结构震害进行分析,初步得出本次地震的一些震害特点.一是灾区人口密度大,人员死亡较集中.人员死亡主要集中在Ⅷ和Ⅸ度区.二是地震振动强,灾区破坏严重.本次地震震源深度12km,极震区烈度高达Ⅸ度,震源破裂在11s内集中释放.三是抗震能力弱,房屋破坏严重.灾区属国家级贫困区,农村民居抗震能力弱,且多数民房坐落在河谷陡坡上,边坡效应加重房屋震害,重灾区砖木和土木房屋成片损毁、倒塌.四是灾区条件恶劣,救灾难度大.震区活动断裂密集发育、地质破碎疏松、地形崎岖不平,又恰值雨季,诱发极其严重次生地质灾害,导致人员伤亡,造成灾区大面积交通、通信、电力中断,救援物资与救援力量无法及时发挥作用.     

河流附近非水平初始面潜水渗流分析

考虑初始面非水平条件,建立河流边界控制下的半无限含水层渗流模型,提出非水平初始面及其相关参数（a、t_N）的简易计算方法,并探讨模型的适用条件。分析表明,该法适用于观测数据较少、地下水水位变幅相对于潜水含水层厚度较小、且观测孔距河岸较近条件下河流附近潜水含水层渗流计算。结合实例,采用查表法和配线法求解模型。计算结果表明:参数a和t_N的计算值不同,水位计算误差在0.02 m以内,较原公式精度有明显提高。新模型为初始面非水平条件下的潜水渗流计算提供一种简易方法。     

The influence of topography and land use on water quality of Xiangxi River in Three Gorges Reservoir region

A self-organizing map (SOM) was used to cluster the water quality data of Xiangxi River in the Three Gorges Reservoir region. The results showed that 81 sampling sites could be divided into several groups representing different land use types. The forest dominated region had low concentrations of most nutrient variables except COD, whereas the agricultural region had high concentrations of NO₃N, TN, Alkalinity, and Hardness. The sites downstream of an urban area were high in NH₃N, NO₂N, PO₄P and TP. Redundancy analysis was used to identify the individual effects of topography and land use on river water quality. The results revealed that the watershed factors accounted for 61.7% variations of water quality in the Xiangxi River. Specifically, topographical characteristics explained 26.0% variations of water quality, land use explained 10.2%, and topography and land use together explained 25.5%. More than 50% of the variation in most water quality variables was explained by watershed characteristics. However, water quality variables which are strongly influenced by urban and industrial point source pollution (NH₃N, NO₂N, PO₄P and TP) were not as well correlated with watershed characteristics.