A Numerical–Analytical Approach to Modeling the Axial Rotation of the Earth

A model for the non-uniform axial rotation of the Earth is studied using a celestial-mechanical approach and numerical simulations. The application of an approximate model containing a small number of parameters to predict variations of the axial rotation velocity of the Earth over short time intervals is justified. This approximate model is obtained by averaging variable parameters that are subject to small variations due to non-stationarity of the perturbing factors. The model is verified and compared with predictions over a long time interval published by the International Earth Rotation and Reference Systems Service (IERS).     

An Integrated Numerical Modelling–Discrete Fracture Network Approach Applied to the Characterisation of Rock Mass Strength of Naturally Fractured Pillars

Naturally fractured mine pillars provide an excellent example of the importance of accurately determining rock mass strength. Failure in slender pillars is predominantly controlled by naturally occurring discontinuities, their influence diminishing with increasing pillar width, with wider pillars failing through a combination of brittle and shearing processes. To accurately simulate this behaviour by numerical modelling, the current analysis incorporates a more realistic representation of the mechanical behaviour of discrete fracture systems. This involves realistic simulation and representation of fracture networks, either as individual entities or as a collective system of fracture sets, or a combination of both. By using an integrated finite element/discrete element–discrete fracture network approach it is possible to study the failure of rock masses in tension and compression, along both existing pre-existing fractures and through intact rock bridges, and incorporating complex kinematic mechanisms. The proposed modelling approach fully captures the anisotropic and inhomogeneous effects of natural jointing and is considered to be more realistic than methods relying solely on continuum or discontinuum representation. The paper concludes with a discussion on the development of synthetic rock mass properties, with the intention of providing a more robust link between rock mass strength and rock mass classification systems.     

Analysis of Remote Sensing Images of Ground Ruptures Resulting from the Kunlun Mountain Pass Earthquake in 2001

1 IntroductionOn November 14, 2001, a large earthquake of M-8.1(magnitude of 8.1) occurred to the west of the KunlunMountain Pass which bounds Xinjiang Uygur AutonomousRegion and Qinghai Province. The Chinese seismicnetwork measured the epicenter of this event to be locatedat 36.2°N, 90.9°E, 350 km away from Golmud City ofQinghai and 400 km from Ruoqiang County of Xinjiang.This is the largest earthquake in the Chinese mainland sincethe M-8.0 earthquake occurring in Damxung of Tibet…     

Terrestrial Photogrammetry and Numerical Modelling for the Stability Analysis of Rock Slopes in High Mountain Areas: Aiguilles Marbrées case

Several high-altitude slope instability phenomena, involving rock blocks of different volumes, have been observed in recent years. The increase in these phenomena could be correlated to climatic variations and to a general increase in temperature that has induced both ice melting with consequent water seepage and glacial lowering, with a consequent loss of support of the rock face. The degradation of the high-altitude thermal layer, which is known as “permafrost”, can determine the formation of highly fractured rock slopes where instabilities can concentrate. The present research has developed a methodology to improve the understanding and assessment of rock slope stability conditions in high mountain environments where access is difficult. The observed instabilities are controlled by the presence of discontinuities that can determine block detachments. Consequently, a detailed survey of the rock faces is necessary, both in terms of topography and geological structure, and in order to locate the discontinuities on the slope to obtain a better geometric reconstruction and subsequent stability analysis of the blocky rock mass. Photogrammetric surveys performed at different times allow the geostructure of the rock mass to be determined and the rock block volumes and detachment mechanisms to be estimated, in order to assess the stability conditions and potential triggering mechanisms. Photogrammetric surveys facilitate both the characterisation of the rock mass and the monitoring of slope instabilities over time. The methodology has been applied in a case study pertaining to the North Face of Aiguilles Marbrées in the Mont Blanc massif, which suffers from frequent instability phenomena. A slope failure that occurred in 2007 has been back-analysed using both the limit equilibrium method (LEM) and 3D distinct element modelling (DEM). The method has been supported and validated with traditional in situ surveys and measurements of the discontinuity orientation and other rock mass features.     

The palynology and geology of the Lower Cretaceous (Aptian–Albian) of Munday’s Hill Quarry,Bedfordshire, UK

Early Cretaceous sediments of Aptian–Albian age outcrop at Munday’s Hill Quarry, Bedfordshire, England. Previous papers describing the section have resulted in different terminologies being applied. The Lower Cretaceous in Bedfordshire is represented by sediments belonging to the Lower Greensand Group and the Gault Clay Formation. Within the Lower Greensand Group in the study area the Woburn Sands Formation, are of Aptian–Albian age. Selected samples have been analysed for palynology. The analysis reveals diverse palynomorph assemblages, including well-preserved dinoflagellate cysts and sporomorphs. Comparison of the assemblages with published records indicates that the lower samples are of Late Aptian age. Forms recorded include common Kiokansium unituberculatum, Cerbia tabulata, Aptea polymorpha and Cyclonephelium inconspicuum. An Early Albian age is indicated for the uppermost sample.     

A GIS and Remote Sensing-based Analysis of Land Use Change Using the Asymmetric Relation Analysis Method: A Case Study from the City of Hangzhou,China

Urbanization has been an important component of land use and land cover change. Quantifying land use patterns and their changes is essential for monitoring and assessing the impact of urbanization. Data on existing and changing land use provide crucial clues for future development. Combining the application of remote sensing with geographic information systems (GIS) data, this study accomplishes (i) the creation of time-series land use maps in the core urban area of the city of Hangzhou, China; (ii) the examination of the land use cross-tabulation matrix to assess the transitions between land use types; and (iii) the introduction of a new asymmetric relation analysis method to explore the dependency relationship of different times in land use. The investigation was based on a 12-year time series dataset (1990–2002), compiled from fine-resolution satellite imagery and GIS-based maps. The results of the study showed that, first, there are strong associations between different stages (1990, 1996, and 2002) in land use development, and, secondly, the dependency between land use states was asymmetric in both stages of development. In addition, urbanization in Hangzhou has resulted in notable increases in the surface area of urban land and sharp decreases in the surface area of cropland.     

New haramiyidan and reptile fossils from a Rhaetian bedded sequence close to the famous ‘Microlestes’ Quarry of Holwell,UK

We describe here new Late Triassic haramiyidan mammaliaform and reptile fossils from near the classic ‘Microlestes’ Quarry’ at Holwell, Somerset, U.K., where Charles Moore discovered a huge collection of microvertebrates in the 1850s. Moore’s discoveries included the haramiyid Thomasia (formerly ‘Microlestes’ and Microcleptes) for which he achieved worldwide fame. Subsequently, despite much fossicking by researchers at Holwell, few new identifiable specimens of mammaliamorphs and lepidosaurs have been recorded and these were by Kühne in 1939. The new finds described here from a bedded sequence, not from a fissure, add significantly to our knowledge of the Holwell tetrapods and to the Rhaetian terrestrial faunas of the SW U.K. Our discovery of haramiyidan teeth includes a previously unknown type of Theroteinus, a genus not previously recorded from outside of the St-Nicholas-de-Port locality in France. An archosaur tooth, possibly from a phytosaur, is also recorded. The new lepidosaur specimens add significant detail to the recently described ‘basal’ rhynchocephalian Penegephyrosaurus curtiscoppi as well as demonstrating that the global diversity of Lepidosauria in the Late Triassic remains incompletely known.     

The shark-beds of the Eyam Limestone Formation (Lower Carboniferous,Viséan) of Steeplehouse Quarry,Wirksworth, Derbyshire,UK

The Eyam Limestone Formation of Steeplehouse Quarry, Wirksworth, Derbyshire, UK yields a diverse assemblage of Lower Carboniferous vertebrate remains. The assemblage is dominated by dermal denticles of the enigmatic selachian Petrodus patelliformis M’Coy, 1848, but also contains teeth of petalodonts, hybodonts and neoselachians. Actinopterygian remains also occur. The assemblage has yielded the earliest Neoselachian, Cooleyella fordi (Duffin and Ward, 1983) and the earliest British lonchidiid, Reesodus wirksworthensis (Duffin 1985). The first occurrence of the enigmatic spiny shark Acanthorhachis (Listracanthidae) is reported from the Viséan, extending its range back some 10 million years. Associated invertebrate remains and sedimentological data indicates a thriving fore-reef environment, deposited in a low energy off-reef setting. The vertebrate remains are well preserved with little abrasion, indicating short transport distances. Conodont elements indicating a late Brigantian age (Early Carboniferous, Viséan) have unusual and extensive euhedral apatite overgrowths.     

Remote Sensing Study of Gold Biogeochemical Effects in the Western Guangdong-Hainan Region——A Case Study of the Hetai Gold Deposit

The vegetation has been poisoned by gold in the western Guangdong-Hainan region. The gold content ofthe leaves there is as high as 10-1961 times the abundance, the chlorophyll content is 10%-30% lower thanthat of the vegetation in metamorphic terrains and 10%-20% higher than that in granite terrains, and thecarotenoid content is 10%-44% lower than the background value. The water content of leaves is 10% to 20%lower than the background value. The cells of leaves are deformed and broken. The leaf surface shows colourspots and becomes yellow or dark green. The spectral reflectance of the leaf surface is 5%-30% higher than thebackground value: the spectral shape has shifted 5-15 nm to the short wavelength. The gray scales of eanopyon images of Landsat TM and airborne imaging scanner (AIS) are 10%-100% higher than the backgroundvalues. On Landsat TM and AIS false colour images, plants poisoned by gold display a yellow color, whichdisinguishes them from background plants. According to the spectral and image features of goldbiogeochemical effects, the author has constructed a gold information system and expert prediction system,and thus two gold target areas and two gold prospect areas have been identified rapidly, economically andaccurately in the western Guangdong-Hainan region which is extensively covered by vegetation.     

A New Approach to ID-TIMS U–Pb Dating of Cassiterite by the Example of the Pitkäranta Tin Deposit

Doklady Earth Sciences - A new technique for the complete dissolution of cassiterite, which makes it possible to determine the age of this mineral by U–Pb isotope dilution (ID-TIMS), has been...     

Using Remote Sensing Data to Delineate the Lineaments for Hydrothermal Mineral Prediction in Heqing Area, Northwest Yunnan Province, China

Lineament extraction and analysis is one of the routine work in mapping medium and large areas using remote sensing data, most of which are satellite images. Landsat Enhanced Thematic Mapper （ETM） of 945×1 232 pixels subscene acquired on 21 March 2000 covering the northwestern part of Yunnan Province has been digitally processed using ER Mapper software. This article aims to produce lineament density map that predicts favorable zones for hydrothermal mineral occurrences and quantify spatial associations between the known hydrothermal mineral deposits. In the process of lineament extraction a number of image processing techniques were applied. The extracted lineaments were imported into MapGIS software and a suitable grid of 100 m×100 m was chosen. The Kriging method was used to create the lineament density map of the area. The results show that remote sensing data could be useful to extract the lineaments in the area. These lineaments are closely correlated with the faults obtained through other geological investigation methods. On comparing with field data the lineament-density map identifies two important high prospective zones, where large-scale deposits are already existing. In addition the map highlights unrecognized target areas that require follow up investigation.     

A Comprehensive Study of Buried Structures in the Beijing Plain Using Multi-Temporal Remote Sensing Data Processing And Multiple Information Sources

Proceeding from gaining a knowledge of the structural settings in this area, the authors applied remotesensing techniques and selected multi-temporal image processing to extract information of buried structures inthe Beijing plain area. Good results have been achieved. Through an integrated analysis of remote-sensing, geo-logical, seismic and aeromagnetic data, it is pointed out that there exist two sets of buried fractures of differingtrends and orders-the northeast set and the northwest set. forming a rhombic framework in the images. Thetwo sets of fractures have still been active since the Quaternary. which is of practical signifcance for geologicalstudy, earthquake prevention and planning of urban construction in the area. The results demonstrate that theselection of multi-temporal processing of remote sensing images and the integrated analytic method are impor-tant in the study of buried structures.     

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in order to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding.     

3D Numerical model of the Obama hydrothermal–geothermal system,Southwestern Japan

The Obama geothermal field is one of the most interesting geothermal areas in Kyushu Island, Southwestern Japan, because of its large number of high-temperature springs. A 3D numerical simulation study using the simulator TOUGH2 (module EOS3) was carried out to obtain a comprehensive hydrothermal model of the field. From previous geochemical studies, two main fluid sources were suggested for the Obama geothermal system: cold (sea, surface, and ground) water and deep geothermal fluids. We propose two heat sources, a lateral one at the eastern boundary of the system, near the West Unzen High Temperature Body located west of the Unzen fumarolic field, and a second one beneath the Obama geothermal field. The first source contributes the system by 150°C fluids. The second source contributes by 100°C fluids. Our model indicates that the first source has a temperature of 150°C, which agrees with the results from previous geochemical studies. The low enthalpy of the second source could be explained by the mixing of geothermal fluids with seawater, as the area is near the seashore and is highly faulted. The model that was developed can explain many of the subsurface processes active in the Obama geothermal field.     

Analysis of Meteorological and Terrain Features Leading to the Izmir Flash Flood, 3–4 November 1995

Flash floods associated with heavy precipitation has become a hazardous phenomenon along the Mediterranean coasts of Turkey in recent years. During 3 and 4 November 1995 heavy and intense rainstorm activity over the Aegean coast led to flash flooding in the city of zmir. Damage exceeded $50 million and 61 people died as a result of the flood. The Karyaka district suffered the most severe damage. This study presents an analysis of the meteorological settings that led to the development of these intense storms and describes the role of the terrain features involved in the zmir flood.The important mesoscale features which initiated the severe weather outbreak included pronounced low-level advection, positive vorticity and strong upper level divergence. A surface low centered over the Aegean Sea enhanced the advection of warm and moist unstable air masses coming from the southwest over the Mediterranean Sea along a southwesterly low level jet (LLJ). A squall line oriented NE-SW over the Aegean Sea also contributed to the storm development, and intensity of the storms was further enhanced by the orographic effect. The presence of a frontal system, the stability indices associated with the event, and other meteorological features are all reminiscent of the synoptic type flash floods identified by Maddox. While the pressure and moisture patterns were favorable for severe storm activity, nonmeteorological factors including the topography, geomporphology, and and land-use contributed to the flooding to a great extent. Settling in the flood-prone zone, insufficient floodwater structures, and the lack of channel improvements in the creeks enhanced flood damage to the city. Many of the deaths occurred in the settlements located in the flood-prone zone of the Ilca and Dallk creeks.     

A Before–After–Control–Impact Analysis of the Effects of a Mississippi River Freshwater Diversion on Estuarine Nekton in Louisiana, USA

Since 1991, the Caernarvon Freshwater Diversion has been reintroducing Mississippi River water into a previously hydrologically isolated estuary in an effort to restore wetlands. To determine the effect of freshwater inflow on estuarine nekton community structure, a Before?CAfter?CControl?CImpact study design was applied. As a result of the opening, salinities in the impact area decreased, and the nekton community structure in the estuary changed significantly. Species of economical or ecological importance either increased in biomass or exhibited no response to the opening of the diversion. Higher abundances of small fish were observed in the area receiving freshwater flow, which is an indication that the area serves as a refuge from large marine predators. Because a salinity gradient was established, as opposed to a uniform but lower salinity regime, aquatic habitat was available to nekton species from a wide spectrum of salinity tolerances.     

Micromechanical Modelling of the Complete Stress–Strain Relationship for Crack Weakened Rock Subjected to Compressive Loading

Summary  A micromechanics-based model, able to quantify the effect of various parameters on the complete stress–strain relationship, is described. The closed-form explicit expression for the complete stress–strain relationship of a rock material containing an echelon cracks arrangement subjected to compressive loading is obtained. The complete stress–strain relationship including the stages of linear elasticity, non-linear hardening and strain softening is established. The results show that the complete stress–strain relationship and the strength of rock with echelon cracks depend on the crack interface friction coefficient, the sliding crack spacing, the perpendicular distance between the two adjacent rows, the fracture toughness of rock material and orientation of the cracks. The present model is used to evaluate the complete stress–strain relationship and strength for crack-weakened rock at the underground cavern complex of the Ertan Hydroelectric Project. The predicted strength is in agreement with that obtained by the Hoek–Brown criterion. The numerical results obtained with the complete stress–strain relationship seem to be in good agreement with the measured values. Author’s address: Xiao-Ping Zhou, School of Civil Engineering, Chongqing University, 443002 Chongqing, P.R. China     

Application of Numerical Modeling for Groundwater Flow System Analysis in the Akaki Catchment,Central Ethiopia

A three dimensional steady-state finite difference groundwater flow model is used to quantify the groundwater fluxes and analyze the subsurface hydrodynamics in the Akaki catchment by giving particular emphasis to the well field that supplies water to the city of Addis Ababa. The area is characterized by Tertiary volcanics covered with thick residual and alluvial soils. The model is calibrated using head observations from 131 wells. The simulation is made in a two layer unconfined aquifer with spatially variable recharge and hydraulic conductivities under well-defined boundary conditions. The calibrated model is used to forecast groundwater flow pattern, the interaction of groundwater and surface water, and the effect of pumping on the well field under different scenarios. The result indicates that the groundwater flows regionally to the south converging to the major well field. Reservoirs and rivers play an important role in recharging the aquifer. Simulations made under different pumping rate indicate that an increase in pumping rate results in substantial regional groundwater level decline, which will lead to the drying of springs and shallow hand dug wells. Also, it has implications of reversal of flow from contaminated rivers into productive aquifers close to main river courses. The scenario analysis shows that the groundwater potential is not enough to sustain the ever-growing water demand of the city of Addis Ababa. The sensitivity and scenario analysis provided important information on the data gaps and the specific sites to be selected for monitoring, and may be of great help for transient model development. This study has laid the foundation for developing detailed predictive groundwater model, which can be readily used for groundwater management practices.