Evolution of cumulative Coulomb failure stress in northeastern Qinghai-Xizang （Tibetan） Plateau and its effect on large earthquake occurrence

We simulate accumulative Coulomb failure stress change in a layered Maxwell viscoelastic media in the north-eastern Qinghai-Xizang(Tibetan)Plateau since 1920.Lithospheric stress/strain evolution is assumed to be drivenby dislocations of large earthquakes(M≥7.0)and secular tectonic loading.The earthquake rupture parameters suchas the fault rupture length,width,and slip are either adopted from field investigations or estimated from their sta-tistic relationships with the earthquake magnitudes and seismic moments.Our study shows that among 20 largeearthquakes(M≥7.0)investigated,17 occurred in areas where the Coulomb failure stress change is positive,with atriggering rate of 85%.This study provides essential data for the intermediate to long-term likelihood estimation oflarge earthquakes in the northeastern Tibetan Plateau.     

Numerical study of circulation and temperature-salinity distributions in the Bras d’Or Lakes

The Bras d’Or Lakes (BdOL) are a large, complex and virtually land-locked estuary in central Cape Breton Island of Nova Scotia and one of Canada’s charismatic ecosystems, sustaining ecological and cultural communities unique in many aspects. The BdOL comprise two major basins, many deep and shallow bays, several narrow channels and straits and a large, geologically complex watershed. Predictive knowledge of the water movement within the estuary is a key requirement for effective management and sustainable development of the BdOL ecosystem. A three-dimensional (3D) primitive-equation ocean circulation model is used to examine the estuary’s response to tides, winds and buoyancy forcing associated with freshwater runoff in a series of numerical experiments validated with empirical data. The model results generate intense, jet-like tidal flows of about 1 m s^?1 in the channels between the basins and connecting them to the ocean and relatively weak tidal currents in other regions, which agrees well with previous observations and numerical results. Wind forcing and buoyancy forcing associated with river runoff play important roles in generating the significant sub-tidal circulations in the estuary, including narrow channels, deep basins and shallow bays. The circulation model is also used to reconstruct the 3D circulation and temperature-salinity distributions in the summer months of 1974, when current and hydrographic measurements were made at several locations. The sub-tidal circulation in the estuary produced by the model is characterised by wind and barometric set-up and set-down in different sections of the system, and a classic two-layer estuarine circulation in which brackish, near-surface waters flow seaward from the estuary into the Atlantic Ocean, and deep salty waters flow landward through the major channel. The model results reproduce reasonably well the overall features of observed circulation and temperature-salinity fields made in the BdOL in 1974 but generally underestimate the observed currents and density stratification. The model discrepancies reflect the use of spatially mean wind forcing and spatially and monthly mean surface heat flux and the inability of the coarse model horizontal resolution (～500 m) to resolve narrow channels and straits.     

Crossover from capillary fingering to compact invasion for two-phase drainage with stable viscosity ratios

Motivated by a wide range of applications from enhanced oil recovery to carbon dioxide sequestration, we have developed a two-dimensional, pore-level model of immiscible drainage, incorporating viscous, capillary, and gravitational effects. This model has been validated quantitatively, in the very different limits of zero viscosity ratio and zero capillary number; flow patterns from modeling agree well with experiment. For a range of stable viscosity ratios (μ_injected/μ_displaced ? 1), we have increased the capillary number, N_c, and studied the way in which the flows deviate from capillary fingering (the fractal flow of invasion percolation) and become compact for realistic capillary numbers. Results exhibiting this crossover from capillary fingering to compact invasion are presented for the average position of the injected fluid, the fluid–fluid interface, the saturation and fractional flow profiles, and the relative permeabilities. The agreement between our results and earlier theoretical predictions [Blunt M, King MJ, Scher H. Simulation and theory of two-phase flow in porous media. Phys Rev A 1992;46:7680–99; Lenormand R. Flow through porous media: limits of fractal patterns. Proc Roy Soc A 1989;423:159–68; Wilkinson D. Percolation effects in immiscible displacement. Phys Rev A 1986;34:1380–90; Xu B, Yortsos YC, Salin D. Invasion Percolation with viscous forces. Phys Rev E 1998;57:739–51] supports the validity of these general theoretical arguments, which were independent of the details of the porous media in both two and three dimensions.     

近45a长江中下游地区夏季降水的区域特征

利用旋转经验正交函数(Rotated Empirical Orthogonal Function,REOF)展开方法,分析了长江中下游地区六省一市1960—2004年78站夏季(6—8月)降水场,并将降水场分为5个主要区域,在此基础上揭示了长江中下游5个区域夏季降水的时间演变特征。5个区域夏季降水序列的Mann-Kendall突变检验表明,各区代表站中只有衢州和南通发生了突变,且突变时间不同;5个区域夏季降水长期变化呈现增加趋势,Ⅰ区和Ⅴ区表现出较强的增加趋势,Ⅲ区次之,Ⅱ区和Ⅳ区较弱;5个区域夏季降水的周期振荡差异明显。     

公路交通事故与气象条件关系及其气象预警模型

以西安地区为例, 分析该地区2002年1月—2004年12月连续3年逐日公路交通事故资料1096个样本, 以及该地区、对应的逐日13个气象要素资料, 并将样本数据划分为春夏和秋冬两个半年, 来考虑气象要素在不同时段的不同影响, 建立合理有效的公路气象预警模型。通过2005年3月—2006年4月交通事故发生起数共365个测试样本的检验, 发现这个模型具有较高的预测准确性, 运用该地区气象要素建立公路交通事故的预警模型是可行而有效的。研究表明:西安地区气象要素中包含着影响和可以预测当地公路交通的信息, 按照在logistic方程中的显著性大小和因子负载的大小, 在春夏半年 (4—9月), 影响西安地区公路交通事故相关因素依次为:能见度因子、相对湿度因子和降水因子; 而在秋冬半年 (10月—次年3月), 依次为温度因子、能见度因子、降水因子。     

城市物业管理信息平台初步解决方案

从实际项目出发,为城市物业管理信息平台建设提出初步的解决方案。信息平台包括两个主要部分:数字社区系统、网络系统。对平台的设计思路、组织结构、实现功能等进行阐述。     

城市加密高程控制测量若干问题的探讨

探讨了加密高程控制测量的路线长度和发展次数,并阐述了在实际工作中掌握的基本原则和施测方法。     

The effects of climatic variability on estimates of recharge from temperature profiles

Using heat as a tracer allows for estimation of ground water recharge rates based on subsurface temperature measurements. While possible in theory, it may be difficult in practice to discriminate the effects of climate from the effects of ground water advection. This study uses synthetic simulations to determine the influence of variability of ground surface temperature (GST) on the ability to estimate vertical specific discharge from temperature profiles. Results suggest that in cases where temperature measurements are sufficiently deep and specific discharge is sufficiently high, estimates of specific discharges will be reasonably accurate. Increasing the number of times temperatures are measured, or producing models that incorporate variations in GST, will increase the reliability of any studies using temperatures to estimate specific discharge. Furthermore, inversions of temperature measurements should be combined with other methods of estimating recharge rates to improve the reliability of recharge estimates.     

Understanding and managing the stressed Mexico-USA transboundary Hueco bolson aquifer in the El Paso del Norte region as a complex system

As the latest drought has swept over the southwestern United States, most local and regional water providers have had to rely on ground water to meet their water demands as surface water supplies have diminished. In areas near major population centers this situation has continued to put strain and stress on already over-drafted regional aquifers. Metropolitan centers throughout the southwestern United States, as exemplified by Las Vegas, Nevada; Phoenix and Tucson, Arizona; and El Paso, Texas, have a history of over drafting their available ground water resources. How these stressed aquifers should be managed is an urgent issue. In El Paso, Texas long-term groundwater mining in the transboundary Hueco bolson aquifer has resulted in large water level drawdowns within the basin, particularly in several well fields. This situation has promoted the intrusion of brackish water into fresh water zones, and consequently reduced the volume of fresh water stored in the aquifer. Management of this aquifer is made more complex as the water resources of the region are shared across the United States/Mexico boundary and the transboundary region continues to grow rapidly. This paper describes the current situation within the Hueco bolson due to over drafting and continued reliance on the fresh water in storage and describes how understanding the dynamics of the aquifer as a complex system can offer managerial perspectives that can be used to establish operational procedures and programs for bringing drawdowns into equilibrium, increasing the longevity of the aquifer, gradually restoring water quality, and offering the hope of utilization of the resource in a sustainable manner.

---

Resumen A medida que la última sequía ha pasado ligeramente sobre el suroeste de Estados Unidos la mayoría de abastecedores locales y regionales de agua han tenido que depender del agua subterránea para satisfacer sus demandas de agua debido a que las fuentes de agua superficial han disminuido. En áreas cerca de centros poblados principales esta situación ha continuado ejerciendo presión en los ya sobre explotados acuíferos regionales. Los centros metropolitanos en todo el suroeste de Estados Unidos, por ejemplo Las Vegas, Nevada; Fénix y Tucson, Arizona; y El Paso, Texas tienen una historia de sobre explotar los recursos de agua subterránea disponibles.La gestión de estos acuíferos estresados constituye un problema urgente. En El Paso, Texas el minado de agua subterránea a largo plazo en el acuífero transnacional Hueco bolsón ha resultado en varios campos de pozos. Esta situación ha promovido la intrusión de agua salobre hacia zonas con agua fresca y reducido consecuentemente el volumen de agua fresca almacenado en el acuífero. El manejo de este acuífero se hace más complejo debido a que los recursos hídricos de la región son compartidos a través del límite Estados Unidos/México y la región transnacional continúa creciendo rápidamente. Este artículo describe la situación actual dentro del Hueco bolsón debido a la sobre explotación y continua dependencia en el agua fresca almacenada y describe como el entendimiento de la dinámica del acuífero como un sistema complejo puede ofrecer perspectivas de gestión que pueden utilizarse para establecer procedimientos operacionales y programas que conduzcan al equilibrio de los descensos, aumentando la longevidad del acuífero, gradualmente restaurando la calidad del agua, y ofreciendo la esperanza de utilizar el recurso de manera sostenible.

---

Résumé Alors que la dernière sécheresse a atteint toute la partie Sud-Ouest des Etats-Unis, la plus part des distributeurs deau, locaux et régionaux, doivent sapprovisionner en eau souterraine dés lors que les niveaux des eaux de surface ont diminués. Dans les zones proches des grands centres densément peuplés, cette situation a continuée a altérée des aquifères déjà surexploités. Les centres métropolitains du Sud-Ouest des Etats-Unis (Las Vegas dans le Nevada, Phoenix et Tucson dans lArizona, El Paso au Texas) sont connus historiquement pour surexploités leurs ressources en eaux souterraines. Il devient urgent de définir un mode de gestion de ses aquifères surexploités. A El Paso dans le Texas, le minage de laquifère transfrontalier engendre un rabattement important dans le bassin, et plus particulièrement autour des zones de captage. Cette situation a induit lintrusion deaux saumâtres dans des zones deaux douces, et a par conséquent réduit le volume deau douce stockée et exploitable dans laquifère. La gestion de cet aquifère est par ailleurs complexifiée par la situation transfrontalière, dautant que la zone frontalière connaît une croissance rapide. Cet article décrit la situation actuelle dans la vallée fermée du Hueco, due au sur-rabattement et à lexploitation continue des eaux douces, et décrit comment la compréhension de laquifère, vu comme un système complexe, peut offrir des perspectives de gestion amenant à des procédures opérationnelles et à des programmes à long terme permettant de ramener à léquilibre la baisse des niveaux deau. Ainsi la longévité de laquifère sera mieux garantie, la qualité de leau sera graduellement restaurée et lutilisation de leau respectera le souci de développement durable.