Modeling patterns of coral bleaching at a remote Central Pacific atoll

A mild bleaching event (9.2% prevalence) at Palmyra Atoll occurred in response to the 2009 ENSO, when mean water temperature reached 29.8-30.1 °C. Prevalence among both abundant and sparse taxa varied with no clear pattern in susceptibility relating to coral morphology. Seven taxon-specific models showed that turbidity exacerbated while prior exposure to higher background temperatures alleviated bleaching, with these predictors explaining an average 16.3% and 11.5% variation in prevalence patterns, respectively. Positive associations occurred between bleaching prevalence and both immediate temperature during the bleaching event (average 8.4% variation explained) and increased sand cover (average 3.7%). Despite these associations, mean unexplained variation in prevalence equalled 59%. Lower bleaching prevalence in areas experiencing higher background temperatures suggests acclimation to temperature stress among several coral genera, while WWII modifications may still be impacting the reefs via shoreline sediment re-distribution and increased turbidity, exacerbating coral bleaching susceptibility during periods of high temperature stress.     

Landslide intelligent prediction using object-oriented method

Landslides are one of the most serious geological disasters in the world and happen quite frequently in the Three Gorges. Landslide prediction is a very important measure of landslide prevention and cure in the Three Gorges. Traditional methods lack in sufficiently mining the various complex information from a landslide system. They often need much manual intervention and possess poor intelligence and accuracy. An intelligent method proposed in this paper for landslide prediction based on an object-oriented method and knowledge driving is hopeful to solve the above problem. The method adopted Landsat ETM+ images, 1:50,000 geological map and 1:10,000 relief map in the Three Gorges as the data origins. It firstly produced the key factors influencing landslide development and used multi-resolution segmentation algorithm to segment the image objects based on the key landslide factors of engineering rock group, reservoir water fluctuation, slope structure and slope level. Secondly, the method chose some sample objects and adopted the decision tree algorithm C5.0 to mine the landslide forecast criteria according to the factor values of each sample object. Finally, under knowledge driving the method classified the image objects and realized landslide susceptibility analysis and intelligent prediction in the Three Gorges. The method proposed in this paper is object-oriented. Results of a real-world example show that: (1) the object-oriented method possesses much more compact knowledge representation, higher efficiency, more continuous classifying result and higher prediction accuracy compared with the pixel-oriented method; (2) it possesses the overall accuracy of 87.64% and kappa coefficient of 0.8305 and is more accurate than the other seven methods (such as the pixel-oriented methods of Parallelpiped, Minimum Distance, Maximum Likelihood, Mahalanobis Distance, K-means and Isodata and the object-oriented method of Nearest Neighbor); (3) about 46.97% landslides lie in the high susceptibility region, 24.24% landslides lie in the moderate susceptibility region, 27.27% landslides lie in the low susceptibility region and 1.52% landslides lie in the very low susceptibility region. Therefore the method can effectively realize landslide susceptibility analysis and provides a new idea for landslide intelligent and accurate prediction.     

Fast and dynamic generation of linear octrees for geological bodies under hardware acceleration

In the application of 3D Geoscience Modeling,we often need to generate the volumetric representations of geological bodies from their surface representations.Linear octree,as an efficient and easily operated volumetric model,is widely used in 3D Geoscience Modeling.This paper proposes an algorithm for fast and dynamic generation of linear octrees of geological bodies from their surface models under hardware acceleration.The Z-buffers are used to determine the attributes of octants and voxels in a fast way,a...     

Simulating bed evolution following the Barlin Dam (Taiwan,China) failure with implications for sediment dynamics modeling of dam removal

The failure of the Barlin Dam in Taiwan, China offers an important case study for evaluating concepts in modeling the rapid erosion and channel recovery following intentional and unplanned dam removals. We present a modeling effort that applied a 1D and quasi-2D uncoupled hydraulics and sediment model (NETSTARS) to evaluate how discretization and parameterization influence thefitofbed elevationpredic-tions to observations following dam failure. Our analysis evaluated the model sensitivity to sediment transport function, active layer thickness, and number of stream tubes used to define the cross-section. Results indicate that a) the model is more sensitive to active layer thickness and sediment transport function than to the number of stream tubes, b) development of dam removal models are likely to benefit from varying the active layer thickness in time, and c) increased lateral discretization does not appear to improve model fit in the steep and rapidly changing river environment at our site. We conclude with discussion on differences between, identifying the need for, and general use of 1D, quasi-2D, and fully 2D models in dam removal and failure analysis.     

Integrating landscape connectivity into the evaluation of ecosystem services for biodiversity conservation and its implications for landscape planning

This paper examines the integration of landscape connectivity and ecosystem services. It is based on the assumption that if a habitat within a landscape has a more significant role in connecting with other habitats, it would have a higher ecosystem services value for biodiversity conservation. The Shenzhen River watershed, a cross-border region shared by the city of Shenzhen and the Hong Kong Special Administrative Region in China, was used as a case study. An area-based functional connectivity index, known as the possibility of connectivity (PC), was implemented to examine the temporal and spatial dynamics of the value of ecosystem services for biodiversity conservation over the period from 1988 to 2008. To evaluate the effectiveness of the PC index, a comparison was made between the conventional assessment method for ecosystem services and the proposed method. Results suggest that our proposed method can identify significant reduction of ecosystem services that was not only due to the decrease of habitat size, but also caused by the damage of connectivity among habitat patches. Also, it can identify sites which should have a high priority in restoring the ecosystem services for biodiversity conservation. In conclusion, this study provides a way to consider landscape connectivity in the evaluation of ecosystem services which is essential for landscape planning and nature conservation.     

单排微型桩加固碎石土滑坡物理模型试验

微型桩因其自身优势被广泛使用,但有关其抗滑机理的理论研究相对较少.首先对模型桩的力学特性进了标定试验,获得其弹塑性工作阶段的弹性模量,分别为0.69×104 MPa和0.04×104 MPa;再通过不同桩间距下单排微型桩加固碎石土滑坡室内模型试验,研究微型桩抗滑机理.试验结果表明:不同桩间距下单排微型桩桩后土压力主要集中在滑面以上1/3桩身范围内;桩间距较小,土拱效应越明显,微型桩抗滑失效的最大临界弯矩越大,微型桩能承受的滑坡推力越大,抗滑效果越好.     

Structural geomorphology,active faulting and slope deformations in the epicentre area of the MW 7.0, 1857, Southern Italy earthquake

In tectonically active domains, fault propagation processes are revealed by landforms. A characteristic morphological feature of exposed active faults is the occurrence of triangular facets. Triangle-shaped landforms morphologically similar to fault-related triangular facets result from erosion of moderately-to-steeply dipping strata or layered successions along fold limbs and are known as flatirons. Triangular facets and flatirons may commonly coexist in mountain chains resulting from the superposition of recent extensional faulting on inherited fold-and-thrust architecture. In these settings analysis of flatirons and triangular facets is not trivial and may result in geomorphologic misinterpretations, hence undermine the interpretations of the geological structure and related deformation history. Here we show that active fault lineaments can be discriminate by inherited morpho-structure. We present the combined results of photo-geological and field survey carried out along well-exposed triangular shaped landforms located in the seismically active Upper Agri River Valley of the Southern Apennine. We found that triangular shaped landforms develop along a major fold back-limb, the Mt. Lama western slope, making it possible to unequivocally interpret these as flatirons. Downslope, Mt. Lama back limb is affected by a large deep-sited landslide whose scarp bound the flatirons and mimics a Holocene fault scarp. This inference appears significant, since the investigated landforms were interpreted by many authors as triangular facets related to an active normal fault, located at its foot, responsible for large historical earthquakes (i.e., the 1857 earthquake). We provide new criteria to discriminate morphologic convergence in tectonically active domains, with consequences for the regional geological interpretation, and for the assessment of geological hazards.     

Multiphysics modeling of CO2 sequestration in a faulted saline formation in Italy

The present work describes the results of a modeling study addressing the geological sequestration of carbon dioxide (CO₂) in an offshore multi-compartment reservoir located in Italy. The study is part of a large scale project aimed at implementing carbon capture and storage (CCS) technology in a power plant in Italy within the framework of the European Energy Programme for Recovery (EEPR). The processes modeled include multiphase flow and geomechanical effects occurring in the storage formation and the sealing layers, along with near wellbore effects, fault/thrust reactivation and land surface stability, for a CO₂ injection rate of 1 × 10⁶ ton/a. Based on an accurate reproduction of the three-dimensional geological setting of the selected structure, two scenarios are discussed depending on a different distribution of the petrophysical properties of the formation used for injection, namely porosity and permeability. The numerical results help clarify the importance of: (i) facies models at the reservoir scale, properly conditioned on wellbore logs, in assessing the CO₂ storage capacity; (ii) coupled wellbore-reservoir flow in allocating injection fluxes among permeable levels; and (iii) geomechanical processes, especially shear failure, in constraining the sustainable pressure buildup of a faulted reservoir.     

Temperature–salinity modeling for Ruwais coastal area in United Arab Emirates

A three dimensional rectangular grid model is applied to resolve the temperature–salinity dynamics of Ruwais, a segment of the UAE coast which is well known as dense water formation zone. The model employs a heat flux module and a turbulence closure scheme that facilitate realistic calculation of temperature–salinity dynamics. A field survey campaign is carried out to support the modeling study, involving measurements of tide, currents, temperature, and salinity. Investigation is done for two meteorologically extreme conditions, i.e. summer and winter. The model study showed that the western flux develops an anticlockwise circulation in the study area. The water industrial discharges elevated the temperature and salinity of the water near the southeastern shoreline. This water mass propagated towards north under the influence of gravity.