Introduction to the Special Issue on faulting and fault-related processes on planetary surfaces

Faults have been documented on nearly every solid surface in the solar system, from asteroids to moons to planets, and they provide a remarkable suite of data sets and critical problems for investigation and analysis by structural geologists. The lack of significant atmospheres on Mercury, the Moon, and most outer planet satellites, along with slow erosion rates and a lack of crustal recycling and Earth-like plate tectonics on most planetary bodies, allows for excellent preservation of fault scarp morphologies for study of fault populations and developmental sequences.     

Littoral cells and harbor dredging along the California coast

Beach compartments or littoral cells form the framework for our understanding of the sources, transport, and sinks of sand in the nearshore zone. In general, along the California coast, beach sand is derived from rivers or clifferosion, moves alongshore under the influence of the prevailing waver conditions, and ultimately is lost either to a submarine canyon or a dune field. Marinas or harbors built either between or at the upcoast ends of beach compartments have been relatively maintenance-free, because of a lack of significant littoral drift at these locations. On the other hand, those harbors built in the middle reaches or at the downcoast ends of littoral cells have had expensive annual dredging problems, because of the interruption of large volumes of littoral drift. Although engineers have labored for years on various breakwater, jetty, or entrance channel configurations, the actual design utilized is of secondary importance. The critical factors are harbor location within a littoral cell and annual litoral drift volume.     

Plate motion on Europa and nonrigid behavior of the Icy lithosphere: The Castalia Macula region

We have developed a generalized quantitative technique for determining the finite pole of rotation between two rigid plates and use it to critically examine differing reconstructions of a region surrounding a prominent dark spot on Europa, Castalia Macula. This region is located near the equator of Europa's trailing hemisphere and has been suggested as a site where crustal convergence may have occurred. Previous reconstructions of the region have indicated that a ridge set and/or a band-like complex that define a collection of tectonic plates in the region accommodated surface contraction. However, a critical examination of the differences between these reconstructions has been complicated by the lack of a finite pole of rotation for the plates involved in either reconstruction. We have applied our modeling technique, coupled with a detailed examination of the morphology and cross-cutting relationships involving this ridge set and band-like complex, to determine if a unique reconstruction exists for several tectonic plates in this region. The cross-cutting relationships involving the ridge set also allow us to test the general assumption that plates behave rigidly on Europa. Assuming rigid behavior, our results suggest that a unique reconstruction does exist, indicating the ridge set accommodated surface contraction. However, analysis performed to test the assumption of plate rigidity indicates that one or more of the plates in the region did not behave rigidly. This does not rule out surface contraction along the ridge set but does indicate that a component of nonrigid behavior must be considered.     

Rainwater harvesting: an option for sustainable rural water supply in Ghana

Potable water is a critical for improved health and for the pursuit of various socio-economic activities. Despite its immense usefulness, rural communities in developing countries such as Ghana lack adequate access to potable water. Rainwater harvesting, which has the potential of providing potable water for rural communities in Ghana and can be undertaken largely with local resources is rarely utilized. The purpose of this paper is to present rainwater harvesting as a sustainable water supply strategy for domestic use and is based on research undertaken in two rural communities in Ghana. The paper identifies opportunities such as affordability and user ownership as well as constraining bottlenecks that include poor roofing materials, lack of appropriate harvesting facilities and housing occupancy status as factors influencing rainwater harvesting practices by rural communities. It then proposes measures to resolve these and other difficulties associated with rainwater harvesting and thereby enhance its potential for sustainable rural water supply.     

This isn’t your usual obstacle course: Critical pedagogy with Special Operations Forces

In an effort to practice what we teach, this paper moves beyond a simple academic-military binary and summarizes the efforts of four faculty members to teach critical thinking to US Army Special Operations Forces (SOF) officers. All four of us teach graduate level courses in a non-thesis, interdisciplinary Master’s degree program intended to satisfy military interest in civilian education. We view our work as an effort to think both with security and as an intervention into security. We position this work as an endeavor of public geographies and critical pedagogy. The paper begins by considering public geographies and the supposed academic/military binary and explores subtle and not so subtle interactions between academics and the U.S. national security apparatus. Each of the four co-authors—a geographer, a sociologist, and two political scientists—describes a particular approach to teaching critical thinking and comments on how the SOF students have responded. We conclude the paper by reflecting on the value of this work within the broader context of our shared mission as scholars and teachers.     

The tourism disaster vulnerability framework: an application to tourism in small island destinations

Islands are known to be vulnerable to natural hazards, resulting in substantial risks for their tourism industries. To facilitate the systematic analysis of the underlying vulnerability drivers, a tourism disaster vulnerability framework was developed. The conceptual model then guided qualitative empirical research in three regions: the Caribbean, the South Pacific, and the Indian Ocean. The results from 73 interviews highlight common, as well as idiosyncratic, factors that shape the islands’ hazardscapes and vulnerabilities. Key vulnerabilities included social, economic, political, and environmental dimensions. Probably, the most critical vulnerability driver is the lack of private sector investment in disaster risk reduction. This is interrelated with deficient planning processes, on-going demand for coastal products, lack of political will, and poor environmental conditions. Notwithstanding many barriers, some businesses and organisations engage proactively in addressing disaster risk. The paper’s empirical evidence supports the validity of the framework, and suggestions for further research are made.     

挖掘吉林省水资源潜力，解决水资源紧缺问题

吉林省是一个水资源紧缺的省份。随着社会经济进一步发展，人口不断增加和城市化进程加快，未来水资源的供城矛盾将日趋尖锐，供水紧缺已成为全省经济和社会发展的重要制约因素。为了充分挖掘全省水资源开发的潜力，解决水资源紧缺问题，该文按不同地区，从实际出发，有针对性地提出了现实的，应急的对策，同时也提出了许多对全省有长远战略意义和创新性的技术对策。如洪水资源的开发和修建地下水库等建议即是。     

The constraints of an ‘ironic scholar’: Negotiating critical engagement with indigeneity and nature conservation

This paper examines how contemporary articulations of indigeneity as bound to nature are treated by critical scholarship. I suggest that critical scholarship has done much to interrogate problematic understandings and restrictive positionings of indigeneity but has also lead to a contemporary position of irony, explored here as academic detachment and as a corrective form. I argue that this ironic position can lead to a lack of recognition for the ways that some groups are currently articulating indigeneity as bound to nature - in ways that, in Latin America, are currently opening up new political spaces, across scales, to debate how nature is valued, protected and lived with. In this paper, I firstly outline how past critiques from critical geography and anthropology can create an ironic treatment of indigeneity and nature conservation. Secondly, I adopt a political ecology approach to consider how past histories and experiences of (shifting) indigenous discourse can help to make sense of the claims that groups make on nature in the contemporary period, revealing how shifting identity politics, discursive regimes, policy frameworks and articulations of nature have been co-produced. Thirdly, I draw on examples from contemporary Bolivian indigenous politics and suggest their relevance to contemporary conservation debates.     

Place-based learning and knowing: critical pedagogies grounded in Indigeneity

For Indigenous peoples, knowledge and science are written onto the landscapes our languages ??talk into being?? through the ??individual and collective consciousness of our communities (Cajete 2000, 284).?? Our landscapes are the storied histories, cosmogonies, philosophies and sciences of those Indigenous knowledges which are increasingly being pushed aside by the ??gray uniformity?? of globalization and its progenitor, European colonization. It is within storied places that we can still glimpse alternatives to this gray uniformity of globalization which brings with it a rhetoric of capitalism, modernism, abstract space and Western science. It is this rhetoric produced through globalization which erases the storied landscapes, destroying the libraries embedded within Indigenous toponyms, creating a terra nullius: an empty land awaiting a colonial/neo-colonial history and economy. As Paulo Freire has challenged us to see, critical consciousness requires us to ??read our world,?? decoding the images of our own concrete, situated experiences with the world (Freire and Macedo 1987, 35). A critical pedagogy of place recognizes the concrete experiences of communities grounded in shared histories, stories and challenges based within a politics of place. A critical pedagogy of place seeks to decolonize and reinhabit the storied landscape through ??reading?? the ways in which Indigenous peoples?? places and environment have been injured and exploited. This paper seeks to discuss how through reading the places in the world as ??political texts,?? one may engage in reflection and praxis in order to understand, and where necessary, to change the world.     

An Overview of Electrokinetic Consolidation of Soils

Electrokinetic stabilization is one of the techniques that improve the geotechnical properties of the soils. It was pioneered by Casagrande in late 1940s and has not seen much development since then, especially in large-scale field applications. Some bench scale studies have been carried out during the past two decades and there have been some small scale field studies and limited field applications, mostly on soft soils. Due to lack of understanding of the physiochemical and electrochemical changes in the soil during electrokinetic stabilization, uncertain energy costs, loss of efficiency with time and the corrosion of electrodes, this method is usually considered as a last resort for large-scale practical applications. The objective of this paper is to highlight the critical parameters affecting electrokinetic consolidation, and to discuss their effects on the efficiency of the process. A better understanding of these critical parameters and their effects will enable geotechnical engineers to design the electrokinetic consolidation operation more effectively and make it an economically viable process for many situations.     

Importance of geologic characterization of potential low-level radioactive waste disposal sites

Using the example of the Geff Alternative Site in Wayne County, Illinois, for the disposal of low-level radioactive waste, this paper demonstrates, from a policy and public opinion perspective, the importance of accurately determining site stratigraphy. Complete and accurate characterization of geologic materials and determination of site stratigraphy at potential low-level waste disposal sites provides the frame-work for subsequent hydrologic and geochemical investigations. Proper geologic characterization is critical to determine the long-term site stability and the extent of interactions of groundwater between the site and its surroundings. Failure to adequately characterize site stratigraphy can lead to the incorrect evaluation of the geology of a site, which in turn may result in a lack of public confidence. A potential problem of lack of public confidence was alleviated as a result of the resolution and proper definition of the Geff Alternative Site stratigraphy. The integrity of the investigation was not questioned and public perception was not compromised.     

考虑断裂韧性影响的页岩气储层可压性评价方法

可压性是衡量页岩气储层对压裂改造响应程度的重要依据,目前针对页岩可压性常用脆性指数对其进行评价。但在实际运用中存在脆性指数相近,实际压裂效果却差别甚远的问题。为了弥补利用脆性指数进行页岩气储层可压性评价的不足,在考虑断裂韧性影响的基础上引入临界机械能释放率,综合了Ⅰ型、Ⅱ型断裂韧性对岩石裂缝发育的影响,并定义平均临界机械能释放率。最后结合平均临界机械能释放率和脆性指数,初步建立了以裂缝发育指数为量化指标的页岩气储层可压性评价模型。基于焦石坝龙马溪组焦页48-2HF井测井资料,计算出其弹性模量、泊松比、Ⅰ型及Ⅱ型断裂韧性,并根据构建的裂缝发育指数模型,得出页岩储层可压性随埋深的变化关系。结合现场微震资料,验证了该模型能有效预测页岩气储层可压性随埋深的变化趋势,为页岩气实际开发过程中优选页岩储层压裂段提供可靠方法。      

Estimating Freshwater Acidification Critical Load Exceedance Data for Great Britain Using Space-Varying Relationship Models

In this study, two distinct sets of analyses are conducted on a freshwater acidification critical load dataset, with the objective of assessing the quality of various models in estimating critical load exceedance data. Relationships between contextual catchment and critical load data are known to vary across space; as such, we cater for this in our model choice. Firstly, ordinary kriging (OK), multiple linear regression (MLR), geographically weighted regression (GWR), simple kriging with GWR-derived local means (SKlm-GWR), and kriging with an external drift (KED) are used to predict critical loads (and exceedances). Here, models that cater for space-varying relationships (GWR; SKlm-GWR; KED using local neighbourhoods) make more accurate predictions than those that do not (MLR; KED using a global neighbourhood), as well as in comparison to OK. Secondly, as the chosen predictors are not suited to providing useable estimates of critical load exceedance risk, they are replaced with indicator kriging (IK) models. Here, an IK model that is newly adapted to cater for space-varying relationships performs better than those that are not adapted in this way. However, when site misclassification rates are found using either exceedance predictions or estimates of exceedance risk, rates are intolerably high, reflecting much underlying noise in the data.     

Exploring job centers by accessibility using fuzzy set approach: the case study of the Columbus MSA

When comparing accessibility, the interpretation of results is complex because of lack of standard or universal norm. This uncertainty issue of the distinction from the lack of standard can be solved using the multi-level approach of fuzzy set: universal, relative, and absolute index. Since a fuzzy set approach deals with the vagueness and indiscernibility of accessibility index, the proposed approach suggests a better solution to classify the index than a crisp set or even a single-level fuzzy set approach. In this study, we evaluate job accessibility of locations in the Columbus MSA in Ohio, USA for 18 worker groups. The uncertain distinction between strong/weak, rich/poor, and higher/lower accessibility is improved by the multi-level approach. Moreover, this study attempts to enhance our understanding of spatial structure of job accessibility disaggregated by occupation type and gender.     

Early Diagenetic Dolomite as a Potential Archive of Paleo-redox Fluctuations in an Early Tonian Marine Basin?

The Tonian Period witnessed important environmental changes and critical evolutionary innovations. Published iron speciation data suggest a global redox transition of mid-depth seawaters from euxinic to ferruginous in early Tonian, but details of this transition remain unknown. This study explores Tonian stromatolitic carbonates as a possible archive of paleoenvironmental changes, through the investigation of dolomitic limestones and dolostones associated with stromatolites of the Weiji Formation in the Huaibei region of North China. Three types of dolomitization are recognized on the basis of petrographic and geochemical data. Type I and II dolomitization resulted in dolomitic limestones characterized by LREE depletions, MREE enrichments, positive yttrium anomalies, and a lack of europium anomalies, indicating early diagenetic dolomitization, possibly in the iron reduction zone and under the influence of bottom seawater. The lack of cerium anomalies in these carbonates suggests anoxia in shallow marine environments. The coexistence of ferroan/non-ferroan dolomite crystals and overgrowth bands is interpreted as possible evidence for rapid fluctuations between iron-rich and iron-depleted conditions in pore-waters or seawaters. In contrast, type III dolomitization resulted in pervasively dolomitized stromatolitic carbonates and likely represents late diagenetic processes. This study highlights the potential of early diagenetic dolomite as an archive for paleoenvironmental investigations.     

城市地面沉降设防问题

我国地面沉降地质灾害存在长期蔓延之势,主观原因在于对上海地面沉降的治疗认识不足。通过对地面沉降发生的必要条件的探究,对有关城市地面沉降设防的若干问题,作一初步探讨。     

The definition of urban stormwater tolerance threshold and its conceptual estimation: an example from Taiwan

The combination of climate change and urbanization is worsening urban flooding problems. Estimating the amount of rainfall that a city can tolerate without flooding is a fundamental task that is difficult to perform, although large amounts of resources are invested in urban flood control. The purpose of this study is to determine the tolerance threshold for stormwater in a city. Based on hydrometeorological characteristics and existing flood control facilities, the urban adaptive water capacity is analyzed to determine the critical rainfall loading. Different critical levels are defined. The low critical point represents the beginning of the water accumulation, while the intermediate and high critical points are defined as flooding with heights of 300 and 600 cm, respectively, in low-lying areas. This study adopts a simple conceptual method to illustrate the critical levels instead of applying complex hydrologic and hydraulic modeling, which require high-resolution spatial data. Three cities and one township in Taiwan are used as urban case studies and to verify the conceptual method. As the capital, Taipei City utilizes the highest flood control engineering technology of our case studies; it is also the site in which the lowest rainfall thresholds cause the accumulation of water to reach the intermediate and high critical points because its small ‘internal water areas’ increase the height of floods rapidly. Conversely, Taichung City has a large internal water area that can disperse accumulating waters without increasing flood height. The estimations of urban storm tolerance thresholds increase the understanding of the limitations of water protection facilities. These estimations may be combined with rainfall forecasts to increase early warning functions and provide a reference point for subsequent planning related to urban flood adaptation strategies.     

Regional-scale back-analysis using TRIGRS: an approach to advance landslide hazard modeling and prediction in sparse data regions

Landslides in Kerala, India, have been shown to be preceded not only by critical rainfall over a short period but also a much longer period of elevated pore pressure. Such rainfall-triggered landslides are difficult to monitor due to a lack of adequate data on the locations of failures and precipitation. Here, a method is presented using Transient Rainfall Infiltration and Grid-based Regional Slope stability (TRIGRS) as a tool to model the relationship between critical rainfall and antecedent pore pressure as they relate to slope stability, which can be useful for hazard assessment in sparse data regions. This is demonstrated by parameterizing the model with a combination of regional data sources, remote sensing, and temporal back-analysis based on two known failure events (June 2004 and July 2007). Ranges of possible geotechnical and hydraulic parameters were obtained from various local and regional sources, and soil thickness was modeled as a function of slope angle. Rainfall was estimated using satellite microwave radiometry data. For back-analysis, combinations of cohesion, friction angle, and water table depth were then tested in TRIGRS using trial and error until the predicted and observed failure times coincided for the two failure events. While the spatial prediction accuracy of the model is low and multiple solution sets are expected to exist, the results confirm that information regarding the critical pre-failure conditions and stability changes over time can be derived despite data-poor circumstances. Future studies can be undertaken extending this method to characterize many parameter combinations and incorporate more failure cases to develop probabilistic early-warning thresholds.     

Conceptual issues in dealing with land degradation/conservation problems in developing countries

Among experts in the field, there is general agreement that land degradation/conservation is a matter of life or death to hundreds of millions of people. There is general agreement too that in spite of the great efforts being made to combat desertification in the last 10 years, the problem is growing worse every day. On the other hand the technology and know-how to deal with all sorts of land degradation problems is available everywhere in abundance. Why then do we in the developing world, the most affected by the problem, seem handicapped or not able to deal effectively with it? What do we really lack? Do we lack the knowledge, the experience, the money or do we lack the will to live? This paper, while trying to give at least partial answers to all those questions, assumes that the right way of thinking in dealing with resources degradation is the most serious thing we are lacking. With some examples from Egypt and other developing countries, the paper will point to some aspects that may constitute part of the conceptual framework that is required to save our world and to keep the forthcoming disasters at an acceptable level.     

无循环钻进工艺在易坍塌、缩孔和卵砾石地层的应用

无循环钻进工艺是我国现在和将来桩孔施工领域的主要施工工艺之一,通过对无循环钻进工艺及器具的研究,解决了我国桩孔施工在无水地区和岩石层、卵砾石、淤泥、流沙层进行桩孔钻进的难题,大大减少了孔内事故,提高了无循环钻进工艺在复杂地层中钻进的效率。根据我国目前全套管施工设备少,而旋挖钻机保用量已超过3000多台的现状,通过新的钻具和工艺的结合,用旋挖钻进工艺与全套管跟管钻进、全套管护壁钻进等特殊工法和特殊钻具的配套施工,解决了全套管钻进的成本问题,推动了无循环钻进工艺、机具及全套管配套技术的研究。