地震孕育过程的宏-细观力学模拟

由于多种原因 ,地震预测仍然没有取得突破性进展。固体材料损伤破坏预测理论是固体力学中非常困难的问题之一 ,这也正是地震预测困难的科学根源。随着计算机技术的发展 ,用计算机进行数值模拟可能会加深对这类复杂现象的理解。本文重点研究了地震孕育和破坏的力学过程 ,提出了适合于研究地震破坏的数值模型 ,从细观及宏观的尺度模拟研究了材料破坏和地震的一些基本特征和起作用的因素 ,得到了下面的主要结果 :在链网模型的基础上 ,我们研究了一种能模拟材料破坏各向异性特征的模型。该模型由几个不同方向的承载机制 (纤维 )构成 ,在给出各方…     

国际地震预测研究进展与动向

地震预测是世界公认的科学难题，本文对地震预测的难点作了简要分析，并指出其实质在于缺乏对地震发生规律性的认识。文中较详细地介绍了近些年来欧洲、日本、美国和俄罗斯在地震预测研究方面的进展。实际情况表明，国际上虽对地震预测研究还存在着种种不同意见，但地震预测研究仍在扎扎实实地取得进展，然而，要期望取得突破，尚需做出长期不懈的努力。     

对地震预测有关问题的看法

文中对地震预测的一些问题提出了看法,认为影响地震预测的诸多因素中,最为关键的问题在于地震成因。利用新的观测技术,发展新的地震成因理论,或将成为地震预测研究取得突破性进展的必经之路。     

基于时间相依地震活动性模型的地震时间序列模拟

模拟地震时间序列在地震危险性分析和地震灾害预测等领域中具有重要作用,地震活动性模型是模拟地震序列的重要理论基础.本文以时间相依地震活动性模型为理论模型,系统梳理了现有时间相依地震活动性模型理论与方法,研究了断层(震源)上最新地震发生时间已知、未知以及地震历史开放间隔已知三种情况下地震发生概率的计算方法,分析了地震复发间隔的变异系数对时间相依地震发生概率的影响.研究了基于布朗模型的特征地震准周期发生的物理原理,建立了时间相依地震时间序列的模拟方法.研究结果表明,在地震离逝时间较长的情况下,基于时间相依地震活动性模型计算的地震发生概率要显著大于泊松模型;在地震历史开放时间已知情况下,计算的地震发生概率要高于地震离逝时间未知的情况.地震复发间隔的变异系数越小,模拟的地震时间序列越呈现周期性.本文研究结果可提高长期地震概率预测水平,模拟的具有时间相依特征的地震时间序列可用于地震预测、概率地震危险性分析以及地震灾害预测等领域.     

地震巨灾模型中的随机地震事件集模拟

地震巨灾保险是降低地震灾害风险的有效手段之一,而地震危险性分析是地震巨灾模型的主要分析模块之一。传统的概率地震危险性分析主要是基于潜在震源模型、地震活动性模型和地震动衰减模型等并采用概率方法得到场点的地震危险性值,该危险性表示的是未来所有地震对场点的综合影响。然而,在使用地震巨灾模型进行地震风险分析时需要用到单个地震事件对场点的影响,这就需要根据潜在震源区生成一系列单个地震事件,并计算每个事件对场点的影响。本研究采用蒙特卡洛方法,基于第五代中国地震动参数区划图中所采用的地震活动性模型(潜在震源区及其地震活动性参数),模拟符合我国地震活动时间、空间和强度分布特征的地震事件集。模拟时遵从的基本理论为:地震发生在时间上符合泊松分布,震级分布可用古登堡-里克特定律来描述,空间分布特征则用潜在震源区及其地震发生率来描述。模拟得到的地震事件包含以下参数:时间(年、月、日)、地点(经度、纬度)、深度、震级、断层走向以及衰减特征等。该模拟地震事件集可满足地震巨灾模型中地震风险分析的需求,已应用于我国地震巨灾模型中。     

日本广岛6．4级地震及地震工作概述

综合介绍了2001年3月24日日本广岛发生6．4级地震的破坏情况，发震和构造背景及历史地震记录；概述了日本的地震灾害，地震观测技术和“地震预计计划”的进展，并阐述了日本未来10年地震调查研究的方针政策。     

地震预测：回顾与展望

本文概要回顾自20世纪60年代以来国际地震预测研究与地震预报实践的进展情况,指出地震预测这一既紧迫要求予以回答、又需要通过长期探索方能解决的地球科学难题目前尚处于初期的科学探索阶段,虽然总体水平仍然不高,特别是短期与临震预测的水平与社会需求相距甚远,但是近半个世纪以来并非毫无进展．文中以板块边界大“地震空区”的确认、“应力影区”、地震活动性图像、图像识别等方法以及美国帕克菲尔德（Parkfield）的地震预报实践为例,说明在中期与长期地震预测方面,地震预测研究均取得了一些有意义的进展．文中分析了地震预测在科学上面临的困难,阐述了为解决这些困难所应当采取的科学途径,展望了地震预测的前景,指出地震预测的进展主要受到地球内部的“不可入性”、大地震的“非频发性”以及地震物理过程的复杂性等困难的制约;地震预测虽然困难,但并不是不可能的;依靠科技进步,强化对地震及其前兆的观测,选准地点、开展并坚持以地震预测试验场为重要方式的地震预测科学试验,坚持不懈地、系统地进行基础性的对地球内部及对地震震源区的观测、探测与研究,对实现地震预测的前景是可以审慎地乐观的．     

混杂地震复发模型及其对地震危险性分析结果的影响

为了考虑某一给定断层特征地震的影响，提出了地震危险性分析混杂地震复发模型并进行了深入的研究。该模型综合考虑了大地震的更新时间、特征震级模型和中小地震的传统指数－时间及指数－震级模型。     

中国大陆地震构造研究回顾

简要回顾了近4年来(1999～2002年)我国在地震构造方面研究的进展，重点介绍了在地壳上地幔结构、活动断裂和大地震构造背景、地壳形变和数值模拟方面的工作．在我国境内发生的绝大多数地震都属于大陆地震的范畴，因此,中国地震学家把研究的重点放在大陆地震上．中国在九五期间完成的中国数字地震观测系统和中国地壳运动观测网络重大科学工程为地震构造的研究提供了大量的基础资料．因此，４年来的地震构造研究取得了相当大的进展．      

澜沧—耿马地震前地震熵异常研究

本文将地震系统作为开放系统进行研究,认为系统和外界有物质和能量的交流,导致孕震区滑向不稳定的非平衡态,然后在各种涨落扰动下发生地震。本文研究1988年澜沧——耿马地震、1976年龙陵、宁蒗地震、1974年昭通地震、1970年通海地震孕震区,得到大震孕育调整模型,大震前地震开放系统熵值曲线变化特征,可作为大震预报指标应用于日常监测工作中。     

Bayesian spatial modeling of Lavaca Bay pollutants

Locational risk of increased mercury and PAH concentrations in Lavaca Bay, Texas sediments and eastern oysters (Crassostrea virginica) harvested from Lavaca Bay, Texas were analysed. Chemical analysis results were evaluated utilizing Bayesian geo-statistical methods for comparison of the model fit of a random effects model versus a convoluted model which included both random and spatial effects. For those results fit best with the convoluted model, continuous surface maps of predicted parameter values were created. Sediment and oyster concentrations of mercury and the majority of measured PAHs were fit best with the convoluted model. The locational risks of encountering elevated concentrations of these pollutants in Lavaca Bay sediments and oysters were highest in close proximity to industrial facilities.     

A modified subsurface stormflow model of hillsides in forest catchment

Subsurface flow plays an important role in forest catchment hydrological processes, for which a modified model is established in this paper. Firstly, by taking soil samples from Natural Preserve Forests of Changbai Mountain, two crucial parameters for subsurface flow, the saturated hydraulic conductivity and effective porosity, were measured in the laboratory. Secondly, submodels of the two parameters varying logarithmically with soil depth were established through regressive analysis. Then a modified subsurface stormflow model (Modified model) was founded by substituting the submodels into a storage–discharge model (Sloan's model), established by Sloan in 1983. Finally, to verify the Modified model, five rainfall events on a simulated hillside were carried out. The subsurface flow processes were simulated using the Modified model, Sloan's model and Robinson's model. The comparison of simulated subsurface stormflow processes using the three models respectively with measured ones showed that the Modified model obtained better accuracy for peak flow and total amount of subsurface stormflow than the other two models. Copyright © 2005 John Wiley & Sons, Ltd.     

Investigating the effect of complexity on groundwater flow modeling uncertainty

Considering complexity in groundwater modeling can aid in selecting an optimal model, and can avoid over parameterization, model uncertainty, and misleading conclusions. This study was designed to determine the uncertainty arising from model complexity, and to identify how complexity affects model uncertainty. The Ajabshir aquifer, located in East Azerbaijan, Iran, was used for comprehensive hydrogeological studies and modeling. Six unique conceptual models with four different degrees of complexity measured by the number of calibrated model parameters (6, 10, 10, 13, 13 and 15 parameters) were compared and characterized with alternative geological interpretations, recharge estimates and boundary conditions. The models were developed with Model Muse and calibrated using UCODE with the same set of observed data of hydraulic head. Different methods were used to calculate model probability and model weight to explore model complexity, including Bayesian model averaging, model selection criteria, and multicriteria decision-making (MCDM). With the model selection criteria of AIC, AICc and BIC, the simplest model received the highest model probability. The model selection criterion, KIC, and the MCDM method, in addition to considering the quality of model fit between observed and simulated data and the number of calibrated parameters, also consider uncertainty in parameter estimates with a Fisher information matrix. KIC and MCDM selected a model with moderate complexity (10 parameters) and the best parameter estimation (model 3) as the best models, over another model with the same degree of complexity (model 2). The results of these comparisons show that in choosing between models, priority should be given to quality of the data and parameter estimation rather than degree of complexity.     

Regionalization of hydrologic parameters of Nash mode

hydrologic models are important tools to estimate runoff from a catchment. Identification of broad based parameters of a hydrologic model for development of direct runoff hydrograph is a key issue for the modelers. Optimization and regionalization of hydrologic parameters for application of Nash’s model is investigated in this paper. Six catchments dominated by hill torrent flows were selected for this purpose. Fifty seven rainfall events were used for regionalization of parameters and about 55 events were used for validation of the results. The hydrologic parameters of the Nash Model, number of linear cascades (N) and storage coefficient (k) were determined using optimization based upon Downhill Simplex method. The data was collected by field measurements and from Water and Power Development Authority (WAPDA) Pakistan. The physical parameters of the catchments were derived from the satellite images of the watersheds with the help of ERDAS software. The performance of the model was assessed by the model efficiency. It is concluded that the conceptual Nash model can simulate direct runoff hydrograph using regional hydrologic parameters with model efficiency of 67%.     

The effect of forcing and landscape distribution on performance and consistency of model structures

It is often challenging to determine the appropriate level of spatial model forcing and model distribution in conceptual rainfall‐runoff modelling. This paper compares the value of incorporating both spatially distributed forcing data and spatially distributed model conceptualisations based on landscape heterogeneity, applied to the Ourthe catchment in Belgium. Distributed forcing data were used to create a spatial distribution of model states. Eight different configurations were tested: a lumped and distributed model structure, each with four levels of model state distribution. The results show that in the study catchment the distributed model structure can in general better reproduce the dynamics of the hydrograph, and furthermore, that the differences in performance and consistency between calibration and validation are smallest for the distributed model structure with distributed model states. For the Ourthe catchment, it can be concluded that the positive effect of incorporating a distributed model structure is larger than that of incorporating distributed model states. Distribution of model structure increases both model performance and consistency. Copyright © 2015 John Wiley & Sons, Ltd.     

基于响应面的预应力混凝土桥动力有限元模型研究

建立了基于正交实验的响应面模型和精细有限元模型,并将其用于中华大桥的有限元模型修正,通过实测动力数据对修正后的有限元模型计算结果进行了验证。基于修正后的有限元模型,分析了预应力对预应力钢筋混凝土桥梁模态信息（频率和振型）的影响,以及单元类型对桥梁模态频率的影响。结果表明,修正后的有限元模型能够比较准确地反映桥梁实际结构的动力特性,基于响应面模型和遗传算法的修正方法可有效地用于大桥的健康监测和状态评估;预应力对预应力钢筋混凝土桥梁模态信息的影响较小,建模时可不予精确考虑;对于由多根预应力混凝土梁组成的桥梁体系,采用实体单元分析较好。     

A comparative modeling study of a dual tracer experiment in a large lysimeter under atmospheric conditions

In this paper, five model approaches with different physical and mathematical concepts varying in their model complexity and requirements were applied to identify the transport processes in the unsaturated zone. The applicability of these model approaches were compared and evaluated investigating two tracer breakthrough curves (bromide, deuterium) in a cropped, free-draining lysimeter experiment under natural atmospheric boundary conditions. The data set consisted of time series of water balance, depth resolved water contents, pressure heads and resident concentrations measured during 800 days. The tracer transport parameters were determined using a simple stochastic (stream tube model), three lumped parameter (constant water content model, multi-flow dispersion model, variable flow dispersion model) and a transient model approach. All of them were able to fit the tracer breakthrough curves. The identified transport parameters of each model approach were compared. Despite the differing physical and mathematical concepts the resulting parameters (mean water contents, mean water flux, dispersivities) of the five model approaches were all in the same range. The results indicate that the flow processes are also describable assuming steady state conditions. Homogeneous matrix flow is dominant and a small pore volume with enhanced flow velocities near saturation was identified with variable saturation flow and transport approach. The multi-flow dispersion model also identified preferential flow and additionally suggested a third less mobile flow component. Due to high fitting accuracy and parameter similarity all model approaches indicated reliable results.     

Usefulness of the Modified NRCS-CN Method for the Assessment of Direct Runoff in a Mountain Catchment

The aim of this study was to evaluate the usefulness of modified methods, developed on the basis of NRCS-CN method, in determining the size of an effective rainfall (direct runoff). The analyses were performed for the mountain catchment of the Kamienica river, right-hand tributary of the Dunajec. The amount of direct runoff was calculated using the following methods: (1) Original NRCS-CN model, (2) Mishra—Singh model (MS model), (3) Sahu Mishra Eldho model (SME model), (4) Sahu 1-p model, (5) Sahu 3-p model, and (6) Q_base model. The study results indicated that the amount of direct runoff, determined on the basis of the original NRCS-CN method, may differ significantly from the actually observed values. The best results were achieved when the direct runoff was determined using the SME and Sahu 3-p model.     

Integrated numerical modeling for basin-wide water management: The case of the Rattlesnake Creek basin in south-central Kansas

The objective of this article is to develop and implement a comprehensive computer model that is capable of simulating the surface-water, ground-water, and stream-aquifer interactions on a continuous basis for the Rattlesnake Creek basin in south-central Kansas. The model is to be used as a tool for evaluating long-term water-management strategies. The agriculturally-based watershed model SWAT and the ground-water model MODFLOW with stream-aquifer interaction routines, suitably modified, were linked into a comprehensive basin model known as SWATMOD. The hydrologic response unit concept was implemented to overcome the quasi-lumped nature of SWAT and represent the heterogeneity within each subbasin of the basin model. A graphical user-interface and a decision support system were also developed to evaluate scenarios involving manipulation of water rights and agricultural land uses on stream-aquifer system response. An extensive sensitivity analysis on model parameters was conducted, and model limitations and parameter uncertainties were emphasized. A combination of trial-and-error and inverse modeling techniques were employed to calibrate the model against multiple calibration targets of measured ground-water levels, streamflows, and reported irrigation amounts. The split-sample technique was employed for corroborating the calibrated model. The model was run for a 40 y historical simulation period, and a 40 y prediction period. A number of hypothetical management scenarios involving reductions and variations in withdrawal rates and patterns were simulated. The SWATMOD model was developed as a hydrologically rational low-flow model for analyzing, in a user-friendly manner, the conditions in the basin when there is a shortage of water.     

黄土场地地铁车站振动台试验方案设计与研究

为得到可靠的试验数据,对黄土场地典型断面地铁车站大型振动台试验方案进行设计与研究.根据试验目的和特点,提出黄土场地与地铁车站动力相互作用模型体系相似设计原则,并基于Bockingham的π定理对模型结构进行相似设计;通过室内试验研究模型材料配合比、力学特性及模型制作技术;采用有限元-无限元耦合数值建模方法,分析黄土场地...