late quaternary sapropel sediments in the eastern mediterranean sea faunal variations and chronology distinctive planktonic foraminiferal assemblages which characterize particular late quaternary sapropel layers in deep basin sediments from the eastern mediterranean sea have been identified using cluster analysis three distinct clusters allow for identification and intercore correlation of the nine sapropels deposited during the last 250 000 yr cluster 1 representing sapropel layers s1 and s9 exhibits low abundances of neogloboquadrina dutertrei and high abundances of globigerinoides ruber cluster 2 which groups s3 s5 and s7 contains high abundances of g ruber n dutertrei and globigerina bulloides and cluster 3 which includes samples from s4 s6 and s8 is marked by extremely abundant n dutertrei and g bulloides and rare g ruber analysis of sedimentation rates in 14 cores reveals the following approximate ages for the sapropel layers s2 52 000 yr b p s3 81 000 78 000 yr b p s4 100 000 98 000 yr b p and s5 125 000 116 000 yr b p as previously suggested sedimentation rates on the mediterranean ridge were determined to be relatively constant during the last 127 000 yr in contrast basin sedimentation rates have fluctuated markedly from lower rates during interglacial stage 5 to higher rates during the last glacial episode these glacial interglacial differences are most pronounced in the northern ionian basin because of increased terrigenous sediment deposition during glacial episodes unusually high biogenic sedimentation rates occurred in an arc south of crete during the deposition of sapropel s5 probably due to higher productivity in this region

prediction of inflow from overlying aquifers into coalmines a case study in jinggezhuang coalmine kailuan china aquifers overlying coal seams are common water sources in coalmines the unexpected inflow of water can flood mines and threatens the mine safety mine flooding caused by the overlying aquifers has occurred more frequently in recent years in china proposed in this paper is a new method that involves three basic maps and two predictions to tackle this geo hazard this new approach is based on the water abundance in the overlying aquifer and risk analysis of the roof collapse it couples groundwater flow models with rock mechanics analysis the method was successfully applied to prediction of the water intrusion from the overlying aquifer at jinggezhuang coalmine in kailuan china the areas with high risk of water intrusion were delineated visual modflow version 2 61 was used to simulate the inflows at two active working faces the developed approach can predict the total inflow for a working face and the transient inflow as the working face advances

on the relationship between isostatic elevation and the wavelengths of tectonic surface features on venus abstract regional isostatic elevation d and the widths and spacings wavelengths of tectonic features formed due to horizontal extension and compression are observed quantities on venus that are sensitive to the thermal and compositional structure of the lithosphere to investigate the relationships between these parameters and the implications for venus lithosphere structure we formulate models in which d and are functions of surface thermal gradient dt dz 0 and crustal thickness c in models that relate to dt dz 0 and c we impose a requirement that for tectonic features with multiple wavelengths of deformation to develop the growth rates of instabilities that control the dominant wavelengths must be similar in magnitude this constrains the maximum values of c and dt dz 0 that can result in multiple tectonic wavelengths on venus to be less than or equal to those determined in our previous study c 30 km and dt dz 0 25 k km m t zuber 1987 j geophys res 92 e541 e551 we also estimate the strength of venus upper crust in areas with multiple wavelengths and obtain limits that are most consistent with a compressional origin for ridge belts which are enigmatic features that have been purported to be of both extensional and compressional origin in models that relate d dt dz 0 and c we show that in areas of venus where the upper mantle is stronger than the upper crust the spacings of short wavelength 30 km features should increase with increasing d if the change in d is due to increasing c but should decrease with increasing d if the change in d is due to increasing dt dz 0 long wavelength 30 km features are not strongly correlated to variations in d due to the effect of crustal thickness on the depth distribution of lithospheric strength which influences wavelength selection in a complex manner in areas of venus where the upper mantle is weaker than the upper crust the spacings of short wavelength features should remain constant with increasing d if the change in d is due to a change in c but should decrease with increasing d if the change in d is due to increasing dt dz 0 the results demonstrate that in shallowly compensated areas of venus that contain regularly spaced tectonic features it may be possible to distinguish whether isostatic elevation differences are a consequence of variations in crustal thickness or thermal gradient we interpret the observed relationship of with d for short wavelength tectonic features in several tessera regions to reflect crustal thickness variations

in situ dynamic monitoring of stress revolution with time and space under coal seam floor during longwall mining in situ dynamic monitoring was used to obtain spatial and temporal strain and stress data in the floor strata during longwall mining at the no 1604 working face in nantun coal mine china the results reveal the presence of four stress stages distributed at four sections along the mining direction weak response stage significant increase stage dramatic decrease stage and slow restoration stage three vertical structural zones are identified under the excavation floor 1 fracture zone 2 deformation zone and 3 lightly affected zone based on detailed analysis of the collected data the relationship between the maximum vertical stress increment and depth is inversely exponential whereas the relationship between the maximum horizontal stress increment and depth is linear the monitoring results are conducive to determining the maximum depth of fracture zone under the coal seam floor and width of the significant stress increase stage which are important factors in controlling groundwater inrush in operating coal mines

assessment of groundwater inrush from underlying aquifers in tunbai coal mine shanxi province china groundwater water inrush into mines from aquifers underlying coal seams is often disastrous multiple factors control the groundwater inrush processes for coal seams 10 and 11 ten main controlling factors were determined and quantified separately the thematic map of every controlling factor was obtained with the data processing functions of gis after the data were normalized the influence weight of each factor was calculated using the ahp vulnerability index method superimposition of thematic maps with the gis results in the vulnerability zoning map for coal seams 10 and 11 the appropriate prevention and control measures against the groundwater inrush are then proposed according to the vulnerability zoning map

numerical evaluation of land subsidence induced by groundwater pumping in shanghai to predict the future behavior of land subsidence in shanghai due to pumping of groundwater a numerical model is established in the proposed model groundwater flow in three dimensional conditions and soil deformation in one dimen sional conditions are calculated the model takes into account the multi aquifer aquitard hydrogeological condition of the soft deposit of shanghai the variation of the coefficient of compressibility and coefficient of hydraulic conductivity of the soils with the consolidation process are simulated relationships among land subsidence groundwater withdrawal volume and groundwater level are analyzed comparison between the measured value and calculated value shows that the model simulates the measured value fairly well the future of land subsidence behavior due to groundwater withdrawal is predicted and discussed via consideration of the variation of the following parameters in the future 30 years net withdrawn volume of groundwater pumping layer and pumping region resume un modele numerique est propose afin de predire le comportement futur d un affaissement de sol cause par le pompage de l eau souterraine a shanghai dans le modele propose l ecoulement de l eau souterraine en trois dimensions et la deformation du sol en une dimension sont calcules le modele considere la condition hydrogeologique multi aquifere aquitard du depot mou de shanghai les variations du coefficient de compressibilite et du coefficient de conductivite hy draulique des sols lors du processus de consolidation sont simulees les relations entre l affaissement du sol le volume de retrait de l eau souterraine et le niveau phreatique sont analysees des comparaisons entre les valeurs mesurees et calculees montrent que le modele peut simuler les valeurs mesurees relativement bien le comportement futur du sol en affaissement cause par le retrait de l eau souterraine est predit et discute en considerant les variations pour les prochains 30 ans pour les parametres suivants le volume net d eau souterraine retire la couche de pompage et la region de pompage mots cles pompage de l eau souterraine affaissement du sol ecoulement de l eau souterraine en trois dimensions consoli dation en une dimension prediction traduit par la redaction

constraints on the lithospheric structure of venus from mechanical models and tectonic surface features radar images of the surface of venus show numerous structures that are interpreted as having formed due to horizontal compression and extension of the lithosphere many of these features exhibit characteristic scales widths or spacings of deformation one of 10 20 km and another of 100 300 km for a range of simple models we test the hypothesis that these length scales are controlled by dominant wavelengths arising from unstable compression or extension of the venus lithosphere results show that the existence of tectonic features that exhibit both length scales can be explained if at the time of deformation the lithosphere consisted of a crust that was relatively strong near the surface and weak at its base and an upper mantle that was stronger than or of nearly comparable strength to the upper crust the spacings of these features imply crustal thicknesses in the approximate range 5 30 km and a thermal gradient not greater than 25 k km 1 features that exhibit only the smaller scale of deformation can be explained by either a lithosphere with a thick crust that overlies a weak mantle or a lithosphere with a strong mantle but with small internal strength contrasts for a broad range of parameters the models require not only that smaller scale compressional and extensional features have similar spacings but also that the widths and spacings of larger scale compressional features be greater than those formed in extension this is consistent with observed differences in the characteristic length scales of larger scale surface features as well as the similarities in spacings of observed smaller scale features

quantitative evaluation and prediction of water inrush vulnerability from aquifers overlying coal seams in donghuantuo coal mine china the water inrush vulnerability from overlying aquifers is evaluated for a coal seam in the donghuantuo coal mine china the water inrush vulnerability is based on superposition of two zoning maps water abundance map and connectivity map the water abundance zoning map was derived from a comprehensive analysis of six types of geoscience data including 1 lithological changes of the overlying aquifer 2 geological structure 3 pumping test results 4 seepage field of water inrush event 5 geochemistry and 6 loss of drilling mud the connectivity map was constructed based on comparing the numerically calculated height of the induced fracture zone above mining areas with the thickness of formation between the coal seam and the overlying aquifer visual modflow was used to predict the mine discharges at working face 2 284 under both natural and mining conditions based on the water inrush vulnerability map and the modeling results advanced dewatering from the overlying aquifer is proposed as the main prevention and control measure against the overlying aquifer water inrush

in situ stress field inversion and its application in mining induced rock mass movement abstract based on a series of experiments in numerical simulation the model boundary conditions for in situ stress field inversion and excavation are discussed study results indicate that roller boundary conditions are reasonable for the in situ stress field inversion before excavation simulation while as a closed system changing the roller boundary conditions to fixed boundary conditions in the subsequent excavation is optimal when the dimensions of the model borders are greater enough than the zone of influence of the excavation as a case study a comparative study of the mining induced ground movement in a steeply dipping mine is carried out in two different stress fields the results show that the mining induced ground movement in the high level tectonic stress field clearly differs from that in the ideal self weight stress field because of the steep occurrence and large thickness of the ore body the mining induced ground subsidence exhibits different characteristics at different mining stages in the practical tectonic environment further studies elucidate the causes of these differences and clarify the effects of high level tectonic stresses on rock mass movement and deformation finally based on gps monitoring results on the ground surface the current ground subsidence is evaluated and its development trend is predicted

aquifer protection during longwall mining of shallow coal seams a case study in the shendong coalfield of china large scale underground mining of shallow coal seams can have significant impacts on ground surface and potentially leads to incidental damage to the overlying aquifer with subsequent environmental hazards in order to deal with the apparent conflict between water protection and high production in underground mining an aquifer protection mining technique was trialed in panel 51201 in the shangwan colliery the shendong coalfield china overburden failure water level of the unconsolidated aquifer surface cracks and ground subsidence were monitored in a series of boreholes using borescope and also by observations in a nearby water well and by surface surveys monitoring results indicate that the aquifer protection mining technique can be successfully applied by modifying a few mining parameters such as mining height or advance rate under some suitable geological conditions the critical zone in the stratigraphy appears to be the weathered bedrock located immediately below the aquifer the weathered bedrock will remain impermeable after mining as long as its thickness is greater than the mining height the development of the mining induced overburden failure is affected by the key strata but ultimately controlled by the soft aquiclude such as the weathered zone it was observed respectively that the height of the caved zone was observed to be 5 to 6 times the mining height whilst the height of the fractured zone is about 10 to 11 times the mining height

new evidence for global tectonic zones on venus venera 15 and 16 spacecraft images show clear evidence of major crustal disruptions on venus which have been interpreted to indicate crustal divergence complementary to the divergent zones are mountain belts that border the continent like high terrains the requisite transcurrent motions appear to be manifested as diffuse shear zones the rift zones form an interconnected transpolar system which ties in with previously recognized equatorial disruption zones suggesting a global tectonic network several independent lines of evidence suggest that the tectonism may be geologically young

multivariate statistical analysis of geochemical data as indicative of the hydrogeochemical evolution of groundwater in a sedimentary rock aquifer system summary the study of groundwater hydrogeochemistry of the paleozoic basses laurentides sedimentary rock aquifer system in quebec produced a large geochemical dataset groundwater samples were collected at 153 sites over a 1500 km2 study area and analyzed for major and minor ions the large number of data can lead to difficulties in the integration interpretation and representation of the results two multivariate statistical methods hierarchical cluster analysis hca and principal components analysis pca were applied to a subgroup of the dataset to evaluate their usefulness to classify the groundwater samples and to identify geochemical processes controlling groundwater geochemistry this subgroup consisted of 144 samples and 14 parameters ca2 mg2 na k hco 3 cl so 4 2 fe2 mn2 br sr2 f ba2 hs seven geochemically distinct clusters c1 c7 resulted from the hca samples from clusters c3 c4 c6 and c7 are mostly located in preferential recharge areas the majority of these samples have ca mg hco3 recharge groundwater c3 c6 c7 and na hco3 evolved groundwater c4 samples from the other three clusters c1 c2 c5 are characteristic of an aquifer system under confined conditions the majority of these samples have na hco3 evolved groundwater c1 c5 and na cl ancient groundwater that exhibits elevated concentrations in br c2 in addition to recognizing the importance of hydrogeological conditions on groundwater geochemistry the distribution of clusters also showed the importance of the geological formations on minor and trace elements such as fe2 mn2 sr2 f and ba2 the first five components of the pca account for 78 3 of the total variance in the dataset component 1 is defined by highly positive loadings in na cl and br and is related to groundwater mixing with champlain sea water and solute diffusion from the marine clay aquitard the high positive loadings in ca2 and mg2 of component 2 suggest the importance of dissolution of carbonate rocks in this aquifer system from their characteristic loadings the first two components are defined as the salinity and hardness components respectively components 3 5 are related to more local and geological effects the integration of the hca and the pca with conventional classification of groundwater types as well as with the hydrogeological and geological contexts allowed the division of the region into four main geochemical areas providing an improved regional picture of the aquifer system dynamics and hydrogeochemical evolution of groundwater the following factors were recognized as influencing the evolution of groundwater identified in every geochemical area 1 geological characteristics including sedimentary rock type and till mineralogy 2 hydrogeological characteristics represented by the level of confinement and the hydraulic gradient and 3 the geological history including the latest glaciation and the champlain sea invasion with its integrated approach this hydrogeochemical study contributes to the characterization and understanding of complex groundwater flow systems and provides an example of the long term geochemical evolution of hydrogeological systems after a major perturbation in this case seawater invasion

stable isotope 2h 18o and 87sr 86sr and hydrochemistry monitoring for groundwater hydrodynamics analysis in a karst aquifer gran sasso central italy this paper deals with chemical and isotope analyses of 21 springs which were monitored 3 times in the course of 2001 the monitoring program was focused on the groundwater of the gran sasso carbonate karst aquifer central italy typical of the mountainous mediterranean area based on the hydrogeological setting of the study area 6 groups of springs with different groundwater circulation patterns were distinguished the hydrogeochemistry of their main components provided additional information about groundwater flowpaths confirming the proposed classification the spatial distribution of their ion concentrations validated the assumptions underlying the hydrogeological conceptual model showing diverging groundwater flowpaths from the core to the boundaries of the aquifer geochemical modelling and saturation index computation elucidated water carbonate rock interaction contribution by alluvial aquifers at the karst aquifer boundaries as well as impacts of human activities the analysis of 18o 16o and 2h h values and their spatial distribution in the aquifer substantiated the hydrogeology based classification of 6 groups of springs making it possible to trace back groundwater recharge areas based on mean isotope elevations the latter were calculated by using two rain monitoring stations 87sr 86sr analyses showed seasonal changes in many springs in winter spring the changes are due to inflow of new recharge water infiltrating into younger rocks and thus increasing 87sr 86sr values in summer autumn when there is no recharge and spring discharge declines changes are due to base flow groundwater circulating in more ancient rocks with a subsequent drop in 87sr 86sr values the results of this study stress the contribution that spatio temporal isotope monitoring can give to the definition of groundwater flowpaths and hydrodynamics in fissured and karst aquifers taking into account their hydrogeological and hydrogeochemical setting

surface topography due to convection in a variable viscosity fluid application to short wavelength gravity anomalies in the central pacific ocean to examine the topography and gravity anomalies due to mantle convection we have carried out finite difference calculations of thermal convection in a fluid layer with a viscosity exponentially decreasing with temperature both surface topography and gravity anomalies are shown to be positive over regions of ascending flow and negative over regions of descending flow these results differ significantly from those of mckenzie 1977 which for similar conditions predict negative topography and gravity anomalies above rising plumes at large rayleigh number the amplitude of surface topography is found to depend on rayleigh number to the seven ninths power as predicted by boundary layer theory these results are applied to test the hypothesis that the linear small scale gravity undulations in the central pacific ocean haxby and weissel 1983 are caused by convective rolls in a layer at the base of the lithosphere for a convecting layer thickness one half the observed gravity wavelength and with plausible values of flexural rigidity and heat flux we show that convection can produce gravity anomalies of the observed magnitude with a layer viscosity comparable to that determined by post glacial rebound however a large increase of viscosity with depth is required to confine convection to a thin layer if these anomalies are actively maintained by convective stresses one possibility is that layered convection may result from compositional stratification of the mantle

tectonics of lakshmi planum venus tests for magellan the origin of lakshmi planum and its surrounding mountain belts remains an important unresolved element in the global tectonic framework of venus from the perspective of gravity signature and potential driving forces the mantle upwelling model is the simplest and its principal failure that it cannot produce radial shortening on the uplift periphery may be resolved if the lithosphere is laterally heterogeneous our preferred model consists of a hot mantle plume rising beneath a pre existing block of tessera the lithosphere is weakened at this hotter and presumably thicker crust and the outward near surface flow is attenuated at the peripheral discontinuity in lithospheric strength crustal thickening and mountain belt formation occur there we propose several criteria to test this tessera plume model together with its competitors at the higher resolution in both imaging and gravity afforded by the magellan mission

settlements around pumping wells analysis of influential factors and a simple calculation procedure abstract estimated and measured settlements caused by pumping rarely agree several reasons could explain this mismatch including the influence of layering the mechanical parameters used in the predictions or the relationship between settlements and drawdown we analyze the influence of the above issues by investigating the mechanical response of pumped elastic porous media under different conditions a radially symmetric conceptual model is considered and several hydro mechanical simulations are performed varying the boundary conditions the size of the modeled domain and the presence or not of an overlying layer the simplicity of the considered problem allows us to compare our results with existing analytical solutions to identify the role of each variable on pumping settlements and to generalize the results the most relevant results are as follows 1 settlements are proportional to drawdown only outside a circle of radius equal to 0 7 times the thickness of the pumped porous medium inside they are virtually constant which leads to two simple procedures for computing pumping settlements 2 poorly conductive layers located above or below a pumped porous medium with higher hydraulic conductivity reduce and smooth settlements 3 boundary constraints affect the local specific storage coefficient and the displacements occurred 4 the specific storage coefficient evaluated by interpreting pumping tests with the cooper and jacob method 1946 leads to overestimation of the actual young s modulus of the soil the main conclusion is that settlements are less differential than expected near pumping wells still they must always be evaluated acknowledging the nature of layering the boundary constraints and carefully selecting the mechanical parameters of the soil

the height of fractured water conducting zone in undermined rock strata the height of fractured water conducting zone is of significant importance for the safety of underground mining because of the conspicuous discrepancy of the height of fractured water conducting zone in bulianta coal mine as predicted by the traditional method with those observed in practice a systematic research has been carried out the study indicates that two aspects should be taken into account firstly the traditionally proposed empirical formula in prediction of the height of fractured zone was based on the conditions of single slice mining where the mining height was less than 3 m and the total slice mining height was limited within 15 m in such a case it would not be suitable to predict the maximum fractured zone height for the conditions where a single mining height is larger than 3 m secondly the stratum structure such as the thick and strong rock layer termed as key stratum plays an important role in controlling of the height of movement in the overburden physical model tests by making use of a similar material illustrate that if the vertical distance from the primary key stratum to the coal seam is shorter than a certain value then the developing fracture zone will extend above the key stratum into the top of bedrock resulting in a larger height of water conducting zone than is calculated by the empirical method the outcome of the work presented will be helpful in practice to prevent the overburden aquifer inrush and to avoid mine water hazard

isrm suggested methods for rock stress estimation part 3 hydraulic fracturing hf and or hydraulic testing of pre existing fractures htpf contents1 introduction 10112 summaryoftestmethods 10123 assumptionsandlimitations 10123 1 hydraulicfracturing hf 10123 2 hydraulictestsonpre existingfractures htpf 10124 apparatus 10134 1 fractureorientationdetectiondevices 10145 personnelquali cation 10146 equipmentperformance 10147 hydraulicfracturingtestprocedure 10148 hydraulic fracturedelineation 10168 1 impressionpackertechnique 10168 2 geophysicalimagingtechnique 10179 obtainingcriticalpressureparametersfromthepressure timerecords 101710 stresscalculations 101810 1 hydraulicfracturing hf 101810 2 hydraulictestsonpre existingfractures 101911 reportingofresults 1019references 1020

geological correlations with the interior density structure of venus a model has been constructed by stipulating that venusian long wavelength topography and geoid elevations are explained by the sum of density anomalies associated with mantle convection and lithospheric compensation mechanisms for convenience the latter are represented by a single airy surface because individual lithospheric components cannot be resolved at the wavelengths considered in this paper mantle convection is represented at a single depth by mass perturbations that drive viscous flow we invert spherical harmonic representations of the topography and the geoid to create global representations of the mantle convection pattern and near surface density anomalies the mantle convection pattern matches well with previous numerical simulations of mantle convection that show a pattern of isolated upwellings amidst an interconnected network of downwellings the near surface density anomalies show no particular pattern the inversion results have been compared with a global synthesis of magellan data impact crater density does not correlate with the mantle convection pattern or the near surface density anomalies large volcanic structures are associated with upwellings planitiae are associated with downwellings coronae are anticorrelated with high amplitude upwellings and downwellings and apparently are passive features associated with rifting that is related to mantle convection in a complex fashion tesserae are associated with negative lithospheric density anomalies interpreted as areas of thickened crust tesserae show no definitive relationship to the present mantle convection pattern

evaluation of the blocking effect of retaining walls on groundwater seepage in aquifers with different insertion depths abstract in the design of a deep retaining wall it is necessary to consider the blocking effect on groundwater seepage of retaining walls in aquifers in this study both laboratory tests and numerical simulation with finite element method fem were adopted to investigate the blocking effect on groundwater seepage under different insertion depths of retaining wall in aquifer laboratory tests were conducted to analyze this blocking effect in an unconfined aquifer the test results indicate that the effective insertion depth ratio j of a retaining wall in shanghai aquifer sand is about 70 a three dimensional numerical model 3d fem was conducted to analyze the laboratory test results the fem results show that fem is a reliable method to analyze the blocking effect on groundwater seepage in an aquifer based on the same aforementioned procedure a 3d fem model is established to investigate the blocking effect in the confined aquifer in shanghai deposit both laboratory test and fem results show that drawdown of groundwater level decreases with an increase of the insertion depth ratio j of retaining structures in an aquifer the optimal value of j approximately 70 is achieved for retaining wall based on the synthetic results from laboratory test fem analysis and the equation of pujades et al for either unconfined aquifers or confined aquifers of shanghai

plains tectonism on venus the deformation belts of lavinia planitia high resolution radar images from the magellan spacecraft have revealed the first details of the morphology of the lavinia planitia region of venus a number of geologic units can be distinguished including volcanic plains units with a range of ages transecting these plains over much of the lavinia region are two types of generally orthogonal features that we interpret to be compressional wrinkle ridges and extensional grooves the dominant tectonic features of lavinia are broad elevated belts of intense deformation that transect the plains with complex geometry they are many tens to a few hundred kilometers wide as much as 1000 km long and elevated hundreds of meters above the surrounding plains two classes of deformation belts are seen in the lavinia region ridge belts are composed of parallel ridges each a few hundred meters in elevation that we interpret to be folds typical fold spacings are 5 10 km fracture belts are dominated instead by intense faulting with faults in some instances paired to form narrow grabens there is also some evidence for modest amounts of horizontal shear distributed across both ridge and fracture belts crosscutting relationships among the belts show there to be a range in belt ages in western lavinia in particular many ridge and fracture belts appear to bear a relationship to the much smaller wrinkle ridges and grooves on the surrounding plains ridge morphology tends to dominate belts that lie more nearly parallel to local plains wrinkle ridges and fracture morphology tends to dominate belts that lie more nearly parallel to local plains grooves we use simple models to explore the formation of ridge and fracture belts we show that convective motions in the mantle can couple to the crust to cause horizontal stresses of a magnitude sufficient to induce the formation of deformation belts like those observed in lavinia we also use the small scale wavelengths of deformation observed within individual ridge belts to place an approximate lower limit on the venusian thermal gradient in the lavinia region at the time of deformation

hot spot evolution and the global tectonics of venus the global tectonics of venus may be dominated by plumes rising from the mantle and impinging on the lithosphere giving rise to hot spots global sea floor spreading does not take place but direct convective coupling of mantle flow fields to the lithosphere leads to regional scale deformation and may allow lithospheric transport on a limited scale a hot spot evolutionary sequence comprises i a broad domal uplift resulting from a rising mantle plume ii massive partial melting in the plume head and generation of a thickened crust or crustal plateau iii collapse of dynamic topography and iv creep spreading of the crustal plateau crust on venus is produced by gradual vertical differentiation with little recycling rather than by the rapid horizontal creation and consumption characteristic of terrestrial sea floor spreading

discrimination of water inrush source and evolution analysis of hydrochemical environment under mining in renlou coal mine anhui province china with the development of mining the hydrochemical environment has changed in the renlou coal mine anhui province china it will be of great significance to coal mine safety production by exploring the temporal and spatial evolution law of hydrochemistry of main water inrush aquifers in renlou coal mine under the effect of mining groundwater samples from three main water inrush aquifers in different periods were collected to analyze their principal components and establish the discrimination model of water inrush source the first and second principal components with eigenvalues greater than 1 were selected in which the first principal component represents sulfate dissolution and pyrite oxidation and the second principal component represents desulfurization and cation alternating adsorption the evolution law of hydrochemical environment was analyzed by combining the distribution characteristics of principal component scores with the spatial location of misjudged groundwater samples the results show that 1 quaternary aquifer is greatly affected by mining and the hydraulic connections with carboniferous limestone aquifer in the central region leads to two misjudged groundwater samples in the discriminant model 2 permian sandstone aquifer is to a certain extent affected by mining which shows a relatively closed hydrogeological environment in most areas of coal mine and an opened environment in some areas with time there are five misjudged samples in the discriminant model due to hydraulic connections with the quaternary aquifer and carboniferous aquifer in some areas 3 carboniferous limestone aquifer is controlled by typical faults and collapse columns and mining has a slight influence on it in the central area there are hydraulic connections with the quaternary aquifer and the permian sandstone aquifer due to the collapse columns which lead to four misjudged groundwater samples in the discriminant model

tectonic contraction across los angeles after removal of groundwater pumping effects after the 1987 whittier narrows and 1994 northridge earthquakes revealed that blind thrust faults represent a significant threat to metropolitan los angeles a network of 250 continuously recording global positioning system gps stations was deployed to monitor displacements associated with deep slip on both blind and surface faults here we augment this gps data with interferometric synthetic aperture radar imagery to take into account the deformation associated with groundwater pumping and strike slip faulting after removing these non tectonic signals we are left with 4 4 mm yr 1 of uniaxial contraction across the los angeles basin oriented n 36 degrees e perpendicular to the major strike slip faults in the area this indicates that the contraction is primarily accommodated on thrust faults rather than on the northeast trending strike slip faults we have found that widespread groundwater and oil pumping obscures and in some cases mimics the tectonic signals expected from the blind thrust faults in the 40 km long santa ana basin groundwater withdrawal and re injection produces 12 mm yr 1 of long term subsidence accompanied by an unprecedented seasonal oscillation of 55 mm in the vertical direction and 7 mm horizontally

stratigraphy of the western mediterranean and southern calabrian ridges eastern mediterranean abstract the present paper illustrates the stratigraphic results of a transponder navigated coring program carried out in 1978 on the southern calabrian ridge cobblestone area 4 and western mediterranean ridge cobblestone area 3 semi quantitative investigations of over 600 foraminiferal samples and 450 nannofossil slides from forty cores with a total recovery of 333 m comprise the data base of the study most of the sediments recovered are late pleistocene or holocene in age the high resolution nannofossil biostratigraphic scheme recently proposed for the quaternary coupled with sapropel stratigraphy and with tephrachronology resulted in precise correlation of the cores mid pleistocene sediments were recovered in a single core from area 4 and in one core from area 3 both located on basin walls four cores from basin walls in area 4 yielded pliocene sediments no sediments older than approximately 3 m y foraminiferal zone m pl 4 reticulofenestra pseudoumbilica nannofossil zone are exposed on the explored walls from the southern calabrian ridge early and late pliocene sediments were recovered from the walls of the deepest crater like basin explored in area 3 but only in dredges in this latter area also two peculiar lithologies were cored basically unfossiliferous but thought to be pre pliocene in age a mud breccia whose clasts yield a sparse assemblage of mid cretaceous planktonic foraminifera and a dolomitic mudstone which is attributed to the late messinian on the basis of correlation with a similar lithology cored at dsdp site 374 and substantiated by analogy in x ray controlled mineralogical composition the fairly complete record of late pleistocene and holocene sapropels recovered in the southern calabrian ridge discards the hypothesis that the southern part of the ionian sea did not undergo stagnant cycles during the ice ages another hypothesis relating the origin of cobblestone topography to olistostromes is also considered untenable on the basis of the new data the large number of cores precisely located on a previously mapped highly irregular bottom physiography disproves that large scale chaotic sedimentation occurred debris flows recorded in base of slope cores document local slope failures

origin of late glacial holocene hemipelagic sediments in the aegean sea clay mineralogy and carbonate cementation abstract four hemipelagic lithological units are identified in the late glacial to holocene sediments in the aegean sea these lithologies are silty clay and clay in texture and include a varying mixture of loose terrigenous sediments supplied from the adjacent landmass gravel to sand sized cemented carbonate clasts and nodules sand to silt sized air born volcanic debris and biogenic remains sediment dispersal during the past 14 000 years was controlled mainly by the fluvial discharge rate by sea level variations which determined the proximity of basins to river mouths and by oceanographic conditions in the aegean sea cemented carbonate clasts and nodules occur in all sediments except unit c sapropel s1 they are well to friably cemented mottled to peloidal micrite or microcrystalline inter granular cement between terrigenous and bioclastic debris and the carbonate is 10 11 mole magnesium calcite during the deposition of sapropel s1 unit c the aegean sea was strongly stratified with colder more saline water masses occupying the deep basins which prevented the development of cemented carbonate nodules and clasts aragonite as pteropods and microcrystalline aragonite is present throughout the cores and together with the cemented carbonate clasts and nodules show that shallow pore waters in the aegean sea have been saturated to supersaturated with respect to both aragonite and magnesium calcite for at least the past 14 000 years results of xrd studies show that unit c sapropel s1 is characterized by lower smectite and kaolinite and higher illite and chlorite than the other units lower smectite illite and kaolinite chlorite ratios in unit c may reflect increased supply of illite and chlorite from european lowland rivers flowing into the black sea from rivers discharging directly into the northern and eastern aegean sea and decreased supply of kaolinite which is mainly of north african origin

fundamental issues in the geology and geophysics of venus a number of important and currently unresolved issues in the global geology and geophysics of venus will be addressable with the radar imaging altimetry and gravity measurements now forthcoming from the magellan mission among these are the global volcanic flux and the rate of formation of new crust the global heat flux and its regional variations the relative importance of localized hot spots and linear centers of crustal spreading to crustal formation and tectonics and the planform of mantle convection on venus and the nature of the interactions among interior convective flow near surface deformation and magmatism

water inrush and environmental impact of shallow seam mining shallow seam mining is very common in china for enhancing coal recovery however this may cause a series of severe problems in environment and mining safety in some cases because the alluvium aquifers are directly above the shallow coal seams some typical water and sand inrush incidents resulting from shallow mining in china are analyzed based on in situ observation the mining induced strata failures are investigated the height of the fractured zone decreases as the size of the outcrop pillar or mining depth decreases the spatial distributions of the failure zones in the shallow mining have specific features compared to the deep mining these provide an advantageous condition for the shallow mining under alluvial aquifers optimal designs for outcrop pillar sizes are also given in different hydrogeological conditions for environment friendly and production safe mining at shallow depths according to in situ mining experiments in several coalfields technical measures for shallow mining are presented these primarily include the lift mining for thick seams and reduction of the thickness of extraction in the first lift short wall mining and detection of faults and other potential hazards prior to mining

numerical study on the responses of groundwater and strata to pumping and recharge in a deep confined aquifer abstract groundwater drawdown and strata settlements induced by dewatering in confined aquifers can be relieved by artificial recharge in this study numerical simulations of a field multi well pumping recharge test in a deep confined aquifer are conducted to analyze the responses of groundwater and strata to pumping and recharge a three dimensional numerical model is developed in a finite difference software which considers the fluid mechanical interaction using the biot consolidation theory the predicted groundwater drawdown and ground settlements are compared to the measured data to confirm the validation of the numerical analysis of the pumping and recharge both numerical results and measured data indicate that the effect of recharge on controlling the groundwater drawdown and strata settlements correlates with the injection rate and well arrangements since the groundwater drawdown induced by pumping can be controlled by artificial recharge soil compression can be relieved by reducing the changes of effective stress of the soils consequently strata settlement induced by pumping can be relieved by artificial recharge and ground settlements can be eliminated if an appropriate injection rate and well arrangement are being determined moreover the changes of the pore pressure and seepage force induced by pumping and recharge will also result in significant horizontal deformations in the strata near the recharge wells

prediction of water inrush risk areas in process of mining under the unconsolidated and confined aquifer a case study from the qidong coal mine in china the unconsolidated cenozoic formation is well developed in the qidong coal mine water inrushes from the bottom unconsolidated cenozoic aquifer which is the confined aquifer have happened several times during mining in the north mining area of the qidong coal mine to predict the water inrush risk areas in the south mining area of the qidong coal mine where some working faces have just begun to mine the engineering analogy method is used on basis of the fisher s discriminant model from the actual mining situation in the north mining area six main influence factors including the effective thickness the specific yield and the load transfer coefficient of the aquifer the effective thickness of the protective bedrock layer the fractal dimensional value of bedrock faults and the distance between the key hard stratum and the primary mineable coal seam are selected as discriminant indexes and their corresponding data in the north mining area of the qidong coal mine are served as training samples on this basis the fisher s discriminant model for water inrush is established and water inrush risk areas including the safety the medium risk and the risk areas of no 61 82 and 9 primary mineable coal seams in the south mining area of the qidong coal mine are predicted by the model the model s accuracy is 90 4 the scatter diagram of training samples shows obviously classified effect and the field verification indicates that the predicted type is consistent with the actual type results show that the discriminant model is well applied in the engineering analogy method and the water inrush risk areas predicted by the discriminant model contribute to the subsequent mining in the south mining area in the qidong coal mine

localization of gravity and topography constraints on the tectonics and mantle dynamics of venus summary we develop a method for spatio spectral localization of harmonic data on a sphere and use it to interpret recent high resolution global estimates of the gravity and topography of venus in the context of geodynamical models our approach applies equally to the simple spatial windowing of harmonic data and to variable length scale analyses which are analogous to a wavelet transform in the cartesian domain using the variable length scale approach we calculate the localized rms amplitudes of gravity and topography as well as the spectral admittance between the two fields as functions of position and wavelength the observed admittances over 10 per cent of the surface of venus highland plateaus and tessera regions are consistent with isostatic compensation of topography by variations in crustal thickness while admittances over the remaining 90 per cent of the surface rises plains and lowlands indicate that longwavelength topography is dominantly the result of vertical convective tractions at the base of the lithosphere the global average crustal thickness is less than 30 km but can reach values as large as 40 km beneath tesserae and highland plateaus we also note that an earth like radial viscosity structure cannot be rejected by the gravity and topography data and that without a mechanical model of the lithosphere admittance values cannot constrain the thickness of the thermal boundary layer of venus modelling the lithosphere as a thin elastic plate indicates that at the time of formation of relief in highland plateaus and tesserae the effective elastic plate thickness k was less than 20 km estimates of t at highland rises are consistently less than 30 km our inability to find regions with t 30 km is inconsistent with predictions made by a class of catastrophic resurfacing models

evaluation of fully coupled strata deformation and groundwater flow in response to longwall mining a finite element poroelastic model is presented to evaluate fully coupled strata deformation and groundwater flow resulting from underground longwall mining in variably saturated fractured geologic media through an equivalent porous elastic continuum representation the explicit coupling between the groundwater flow field and the solid skeleton deformation field is achieved by simultaneously solving the governing equations for groundwater flow and solid skeleton deformation the implicit coupling between these two fields is also accomplished by considering the effects of both unsaturated water flow and solid skeleton deformation on the hydraulic properties such as water content and hydraulic conductivity in addition to the implicit coupling caused by unsaturated water flow the other implicit coupling caused by solid skeleton deformation is also important because it may produce hydraulic heterogeneity and anisotropy in a geologic medium affecting the groundwater flow field even when the system is in a fully saturated condition a physically based constitutive model is proposed to account for the deformation strain dependencies of porosity and saturated hydraulic conductivity of the fractured media to evaluate the impacts of longwall mining and to understand their hydrogeomechanical nature the numerical model is applied to a well documented case study with satisfactory results although the numerical simulation results presented in this paper will not apply to all underground longwall mines because of differences in site specific hydrogeological and geomechanical settings the methodology described herein may find some useful applications in many longwall mining projects

characterization of underground tunnel water hydrochemical system and uses through multivariate statistical methods a case study from maddhapara granite mine dinajpur bangladesh a quality study of the drained water from maddhapara granite mine underground tunnel was undertaken to study their hydrochemical variations and suitability for various uses employing chemical analysis basic statistics correlation matrix r cluster analysis principal component factor analyses and anova as the multivariate statistical methods the results of chemical analysis of water show the modest variation in their ionic assemblage among different sampling points of the tunnel where ca hco3 type of hydrochemical facies is principally dominated the correlation matrix shows a very strong to very weak positive even negative correlation relationship suggesting the influence of different processes such as geochemical biochemical processes and multiple anthropogenic sources on controlling the hydrochemical evolution and variations of water in the mine area cluster analysis confirms that cluster 1 contains 68 75 of total samples whereas cluster 2 contains 31 25 on the whole the dominated chemical ions of first cluster groups are ca and hco3 suggesting a natural process similar to dissolution of carbonate minerals the second cluster group consisted of cl and so4 2 ions representing natural and anthropogenic hydrochemical process the results of pca fa analysis illustrate that different processes are involved in controlling the chemical composition of groundwater in the mine area the factor 1 loadings showed that ph ec tds na mg chloride and sulfate which have high loading in this factor are expected to come from carbonate dissolution to oxidation conditions one way anova describes the significance of dependent variables with respect to independent variables anova gives us the idea that ec k fetotal so 4 2 as and pb are the most important factors in controlling spatial differences in water quality in this tunnel but different results have been encountered for different independent variables which might be due to dissimilar sources of water from the qualitative analysis it is clear that water quality is not very favorable for aquatic creatures as well as for drinking purposes the water can be used for irrigation purposes without any doubt as sar and rsc analysis provides good results moreover the results of this research confirmed that the application of multivariate statistical analysis methods is apposite to inferring complex water quality data sets with its possible pollution sources at the end this research recommends 1 as water becomes more and more important water treatment plants should be built before the water being used 2 a detailed water step utilization plan should be set beforehand to guarantee tunnel water being used effectively and 3 after the water being used for agriculture elements in crops should be monitored continuously to ensure that ions and compounds that come from the tunnel water are lower than guideline values for human beings health

quantitative tests for plate tectonics on venus if plate tectonics exists on venus the rate of topographic dropoff from spreading centers should be about half that on earth due to greater rock fluid density contrast and lower temperature differential between the surface and interior using 1 1 mean elevations 21 000 km of ridge were identified on venus and 33 000 km on earth heights h at distances up to 1000 km to either side of the ridges were analyzed to make least squares determinations of the parameters ho h and n in where s is off crest distance the venus ridges have a much less well defined mode in crest heights ho than the earth ridges and a somewhat smaller exponent n on the average indicating greater concavity fixing n to the theoretical value of 0 5 plate velocities were inferred from the h s using h t from north atlantic and north pacific data on earth these velocity solutions were compared to those from plate rotations which indicate the h t is probably about 40 too high for a global mean the resulting plate creation rates on venus assuming comparable total heat generation and taking into account the density and temperature differences are 0 7 km yr or less and indicate that not more than 15 of venus s energy is delivered to the surface by plate tectonics in contrast to 2 9 km yr and 70 energy delivery on earth

relation of major volcanic center concentration on venus to global tectonic patterns global analysis of nasa magellan image data indicates that a major concentration of volcanic centers covering 40 percent of the surface of venus occurs between the beta atla and themis regiones associated with this enhanced concentration are geological characteristics commonly interpreted as rifting and mantle upwelling interconnected low plains in an annulus around this concentration are characterized by crustal shortening and infrequent volcanic centers that may represent sites of mantle return flow and net down welling together these observations suggest the existence of relatively simple largescale patterns of mantle circulation similar to those associated with concentrations of intraplate volcanism on earth

barrier effect of underground structures on aquifers abstract impervious structures below the water table modify the natural groundwater flow in aquifers they act as barriers causing heads to rise upgradient and to fall downgradient we define the barrier effect as the increase in head loss across the barrier with respect to the natural conditions prior to construction we distinguish between regional the minimum head loss observed at long distances and local the maximum head loss observed close to the structure barrier effects we use numerical and analytical methods to derive semi empirical equations to quantify the two barrier effects for semi permeable partially penetrating or fully penetrating but finite in length and barriers with a by pass in confined aquifers the resulting equations depend on the barrier geometry and on the natural head gradient in the aquifer and they are easy to apply we test their validity at two construction sites obtaining excellent agreement between the computed and observed barrier effects

interpretation of increased deformation rate in aquifer iv due to groundwater pumping in shanghai shanghai is a typical example of a region in china suffering from severe land subsidence previous investigations have shown that land subsidence is strongly related to groundwater pumping in both the temporal and spatial domains a series of field investigations shows that the deformation rate of aquifer iv aqiv has increased contributing significantly to the total subsidence in shanghai to predict the deformation behavior of aqiv in shanghai due to groundwater pumping four different models have been applied in this study i a model based on groundwater flow theory ii an elastic model based on cauchy mechanics iii a creep model incorporated into cauchy mechanics and iv a recently proposed land subsidence model by budhu based on cosserat mechanics based on a number of assumptions budhu s concept was extended to consider the time dependent behavior of groundwater potential in aquifers and the consolidation behavior of overburdened aquitards the calculated results of aqiv s deformation we

setting and tectonic evolution of some eastern mediterranean deep sea basins abstract nine discrete deep sea basins seven from the calabrian and mediterranean ridges and two from the strabo trench were explored geologically during several cruises carried out from 1978 to 1984 in the eastern mediterranean the seven basins displaying similar geological features calabrian and mediterranean ridges may be divided into three groups on the basis of their size 1 very small basins botticelli and raffaello basins whose area ranges from 1 1 to 4 3 km 2 2 small basins ares aphrodite and katia basins from 7 to 13 km 2 and 3 large basins bannock and cleft basins from 22 to 74 km 2 the two basins from the strabo trench tyro and kretheus basins whose areas range from 16 to 20 km 2 are considered separately tectonics is the most important element affecting basin formation processes progressive folding and faulting of messinian pliocene and quaternary sediments in the calabrian and mediterranean ridges allows the infiltration of water into the subbottom and dissolution of messinian evaporites so that collapse of the overlying unconsolidated plio quaternary cover creates local distensive tectonics superimposed on the regional compressive tectonic setting the size of the basins reflects different steps in this process very small basins are related to the fracturing occurring at the top of anticlines small basins originate when anticlines are faulted and large amounts of water are able to reach the evaporites and increase the intensity of leaching finally large basins are related to regional tectonic lineaments both compressive large reverse faults overthrusts and strike slip salt diapirism may be associated with some of these situations the process responsible for the tyro and kretheus basins formation is the pull apart mechanism connected with the strike slip motion occurring in that area the geometric position of subaqueously dissolved evaporites seems to influence the environment on the basin floor brines originating from the dissolution of buried evaporites are thought to disperse in the subbottom whereas brines originating from dissolution of evaporites cropping out on the basin walls can flow to the floor and cause stagnation only if the shape of the basin prevents the action of bottom currents

earthquakes as a triggering mechanism for debris flows and turbidites on the calabrian ridge abstract debris flows and turbidites have been described in piston cores bottom photographs and side looking sonar records from basin floors amid the rugged irregular topography of the calabrian ridge a sediment transport process is inferred which began with a rotational slump on the steep basin wall subsequently transformed into a debris flow and turbid cloud such events occurred approximately every 1500 years because the debris flow turbidite deposits are correlative between basins some relatively widespread mechanism such as an earthquake is required to initiate the slope failure the estimated intensity of ground shaking as a result of historical earthquakes on the nearby calabrian and hellenic arcs has been used to develop a relationship between frequency of occurrence and intensity of ground shaking extrapolation of this relation to infrequent large magnitude events shows that the 1500 yr event is small enough to be geologically plausible but large enough to cause slope failure on basin walls it is possible that the historical record fortuitously contains one of these large magnitude long repeat time events which may have caused the most recent of the observed debris flows in 1903

the geology and geomorphology of the venus surface as revealed by the radar images obtained by veneras 15 and 16 a region by region condensed description of almost all of the area that was radar photographed by veneras 15 and 16 is presented using some generalizations the diversity of terrain was reduced to a discrete set from which a geological morphological map was constructed the predominant type of terrain of the studied area is a plain that was tentatively subdivided into five morphological types ridge and band patchy rolling plain dome and butte plain smooth plain and high smooth plain stratigraphically the ridge and band plains are the oldest and the smooth plains are the youngest the stratigraphic position of the other types is yet to be determined large sections of the plains show similarities to the mare type basaltic plains of the moon mercury and mars other types of terrain are combinations of ridges and grooves in various patterns linear parallel orthogonal diagonal or chevron like and chaotic in some places the ridge and groove terrain is stratigraphically below the plain material but in other places it appears to be plain material that has been subsequently deformed near the eastern and western boundaries of ishtar terra large several hundred kilometers in diameter ring like features can be seen that are named coronae or ovoids evidence of tectonic deformation and the presence of flow like patterns support their designation as volcano tectonic features beta regio seems to be an uplifted plain showing evidence of rifting and volcanism all types of terrain are sparesely peppered with craters of obvious impact morphology their average density gives the plain an age range of 0 5 to 1 109 years the fact that many impact craters are still in the pristine state indicates a very low rate of surface reworking at least for the last 0 5 to 1 109 years no evidence for water erosion sedimentation processes has been found the tectonic activity of venus has no equivalent on the moon mercury or even mars and can be compared only with that of the earth intensive horizontal deformation previously known only on earth occurs on venus but in a characteristic venusian style

stratigraphy and sedimentation in the anoxic bannock basin eastern mediterranean abstract ten gravity and or piston cores raised from the floor and the eastern flank of the bannock basin and from nearby plateaus were investigated lithologically and biostratigraphically the bannock basin is a large rimmed depression with a vertical relief of over 600 m containing deep seated brines the brines are derived from submarine dissolution of messinian evaporites in a physiographic setting deep rimmed basin that does not permit dilution and removal by bottom currents plateau cores range in age from holocene emiliania huxleyi acme zone to middle pleistocene pseudoemiliania lacunosa zone they consist of low sedimentation rate pelagic sediments with sapropels and tephras as minor isochronous lithologies two cores on the flanks recovered pliocene pelagic sediments one of these cores displays an unconformable contact between holocene anoxic sediments and early pliocene reticulofenestra pseudoumbilica zone marls the other core is entirely pliocene consisting of a debris flow with a matrix that is referred to the discoaster tamalis subzone cores from the deeper part of the basin consist of laminated non bioturbated poorly oxygenated dark sediments rich in h 2 s and containing large gypsum crystals organic carbon content is higher than in normal eastern mediterranean pelagic sediments but lower than in true sapropels the kerogen is dominated by amorphous organic matter although the oxygen content of the bottom waters was not measured sedimentary evidence suggests that poorly oxygenated but not entirely anoxic conditions exist in the basin at the sediment water interface in particular benthic foraminifers would be much less abundant than they actually are and org c content would be higher if bottom waters were anoxic poor oxygenation started to develop in the bannock basin some 180 ka b p after the deposition of sapropel s 6 as documented in core 84 02 this long lasting period of anoxia strongly differs from the short anoxic episodes in the eastern mediterranean that were controlled by glacial interglacial changes the bannock basin anoxia is a result of brine formation causing strong density stratification with a density contrast 20 that is much higher than the density contrast derived from changes in thermohaline circulation during glacial interglacial times during these eastern mediterranean basin wide euxinic episodes the boundary between oxygenated and anoxic waters was much shallower than the 3200 m interface recorded in the bannock basin reworked and displaced foraminiferal faunas were found in the pliocene sediments recovered in the flank cores in particular the occurrence of abraded tests of the shallow water form elphidium spp of bulimina costata and of other displaced taxa does suggest that the area was subject to deposition by turbidity currents originating on the african margin and that in pliocene times no rimmed basin was in existence

styles of tectonic deformations on venus analysis of venera 15 and 16 data analysis of the radar images obtained by veneras 15 and 16 leads to the conclusion that the ridge and groove structures on the surface of venus are the result of tectonic deformation although the mechanism of such deformation cannot yet be unequivocally deduced several styles of deformation can be described areal deformation occurs where horizontal stresses have operated over large areas shear deformation appears in bands showing differential longitudinal deformation transversal stresses operating over long and relatively narrow areas have produced belt deformation circular deformation is related to a specific locus of the stresses the absence of densely cratered areas indicates that the terrains were deformed after the period of heavy bombardment the origin of the stresses could be drag of the lithosphere by asthenospheric currents or gravity induced spreading of surface material over upwellings a general conclusion is that in the surveyed area of venus neither terrestrial plate tectonics nor lunar highland type terrain exists

finite element modeling of stress distributions and problems for multi slice longwall mining in bangladesh with special reference to the barapukuria coal mine abstract this paper deals with current coal mining operations under a mega aquifer in nw bangladesh and presents a case study of underground mining in barapukuria the study uses numerical analyses to evaluate stress redistribution strata failure and water inflow enhancements that result from these coal extraction operations a total of three models a b and c are presented in this study two dimensional numerical modeling was performed to analyze the deformation and failure behavior of rock elements for two different models a and b for model a we used an elastic finite element software package considering a mohr coulomb failure criterion for model b we used boundary element method bem the first two models were applied to determine the stress patterns model a provides the tectonic stress pattern of the basin whereas model b represents the mining induced stress field the third model is a schematic model the results of model a show that tensional failure of rock elements is concentrated in the gondwana coal sequences as well as within the eastern boundary fault ebf and its surroundings failure occurs in the middle to lower part of the model and the magnitude of tensional stress in the shallow part is much greater than in the deeper part contours of max magnitudes are attributed to up bending of the overburden which would create numerous upward propagating fissures fractures the results of model b show that fracture propagation would be about 240 m upward for single slice height 3 m mining extraction from the contours of mean stress magnitudes it is observed that the high range of fracture propagation increased upward for multi slice extraction of coal it is apparent from the fracture heights that large amounts of caving would occur towards the roof due to the multi slice extraction of coal and finally would be linked with the water bearing dupi tila formation if this happened it would ultimately cause a major water inflow hazard in the mine

ridge belts evidence for regional and local scale deformation on the surface of venus we evaluate models for the formation of the ridge belt fan assemblage on venus through consideration of the orientation spatial distribution topographic expression and wavelengths of observed tectonic surface features we favor a compressional mechanism for long wavelength deformation corresponding to the spacing of ridge belts 300 400 km however short wavelength ridges and grooves 10 20 km that are contained within belts and trend parallel to them are likely to be compressional and extensional and to reflect both regional and local stress fields we hypothesize that large scale ridge spacing early stage mantle downwelling is the source of regional compression responsible for the establishment of the long wavelength of deformation

support of long wavelength loads on venus and implications for internal structure a thin shell formulation for computing stress distributions on the surfaces of one plate planets is developed the lithospheric model includes laterally varying density anomalies at two depths corresponding to undulations on a crust mantle boundary and variations in upper mantle density for a given set of model parameters values for the vertical displacement crustal thickness anomaly and mantle density anomaly required to satisfy the topographic and gravitational boundary conditions are computed along with the resulting stress field the computed stresses can then be compared to stress directions inferred from observed tectonic features this formulation is used to study loads on venus s lithosphere and it is found that most highland areas appear to have been formed in a state of isostasy or by uplift with a significant portion of their support probably derived from dynamic processes in the mantle a possible exception is ishtar terra whose circumferential mountain belts are most consistent with a radially compressive stress regime generated by flexural loading reasonable lithospheric models predict low density mantle beneath atla beta eisila thetis and tethus regiones and thick crust accompanied by higher density mantle under ishtar terra and ovda regio thus western aphrodite terra appears to be more closely related to ishtar than to the rest of the equatorial highlands these results favor a hot spot model of venus tectonics in which beta eastern aphrodite eisila and tethus are expected to be relatively young and thermally active while ovda and ishtar should be older and less active

venus limited extension and volcanism along zones of lithospheric weakness three global scale zones of possible tectonic origin are described as occurring along broad low rises within the equatorial highlands on venus lat 50 n to 50 s long 60 to 310 the two longest of these tectonic zones the aphrodite beta and themis atla zones extend for 21 000 and 14 000 km respectively several lines of evidence indicate that beta and atla regiones located at the only two intersections of the three major tectonic zones are dynamically supported volcanic terranes associated with currently active volcanism rift valleys south of aphrodite terra and between beta and phoebe regiones are characterized by 75 to 100 km widths raised rims and extensions of only a few tens of kilometers about the same magnitudes as in continental rifts on the earth horizontal extension on venus was probably restricted by an early choking off of plate motion by high crustal and upper mantle temperatures and the subsequent loss of water and an asthenosphere

gypsum precipitation from cold brines in an anoxic basin in the eastern mediterranean in 1968 hot brines from which gypsum had precipitated were discovered in the red sea in a divergent plate boundary setting with hydrothermal activity1 we now report the discovery of cold brines in an entirely different geodynamic situation a convergent plate boundary in the eastern mediterranean where the heatflow is very low2 and no hydrothermal activity occurs decimetric pure gypsum crystals precipitate from the cold brines which occupy the bottom of a rimmed anoxic basin near the southern edge of the mediterranean ridge close to the sirte abyssal plain nucleation of the crystals does not occur at the surface but from the deep brines because the salinity of the water is normal down to the depth of 3 000 m we propose the name bacino bannock for this basin after the consiglio nazionale delle ricerche r v bannock from which the bottom water brines were surveyed and sampled

horizontal stress under supercritical longwall panels abstract this study identifies the relative magnitude of horizontal stress change below a series of parallel longwall panels as a consequence of multi seam mining the investigation method yields an upper bound to the horizontal stress change by assuming that the fractured and caved overburden above the supercritical longwall panels is not able to support any lateral load finite element modelling was conducted to consider the effects of the following variables on the horizontal stress redistribution the ratio of the equivalent width of the extracted area to the overburden depth the ratio of the original horizontal to vertical in situ stress components and anisotropy in the rock mass behaviour the key findings of this research are that the maximum horizontal stress induced as a consequence of extracting multiple supercritical longwall panels will be within approximately 10 of the original in situ horizontal stress for the case of isotropic rock strata the magnitude of this horizontal stress may be larger in a stiff stratum if the overall sequence of strata consists predominantly of softer rocks anisotropy in the strata underlying the extracted longwall panels also causes an increase in the maximum horizontal stress induced into the immediate floor of the first extracted seam and an increase in the rate of dissipation of horizontal stress change with depth these findings indicate that a significant increase in horizontal stress relative to the original in situ horizontal stress should not be expected in multi seam mining situations the results from this study need to be considered in conjunction with predicted vertical stress distributions in order to accurately predict the overall stress environment likely to be encountered when conducting multi seam mining

land subsidence due to groundwater drawdown in shanghai introduction shanghai is located on the deltaic deposit of the yangtze river as illustrated in fig 1 fig 2 shows the main geological strata the total thickness of the quaternary deposit is about 300 m shanghai geology office 1976 1979 excessive pumping of the groundwater caused compression of the quaternary deposit and subsidence in shanghai although several countermeasures including recharge of the groundwater have been adopted to mitigate the rate of subsidence up to the present the recorded cumulative subsidence has been 2 3 m in the central area of shanghai this subsidence has caused a lot of social problems the immediate problem is the increase in the possibility of flooding from 1981 to 1994 rainfall flooding occurred 22 times at a rate of almost twice per year liu 2001 the possibility of tidal flooding also increased from 1956 the height of the dike along the coast line was increased four times with the crest elevation rising from 5 m to 6 8 m other problems caused by the land subsidence are damage to the sewerage system road buildings and subway tunnels etc in shanghai the monitoring of land subsidence started in 1921 the history of land subsidence in the urban area of shanghai can be divided into two periods namely a rapid subsidence period 1921 1965 and a controlled period 1965 present zhang han 2002 however there has been a tendency for the subsidence rate to increase after 1990 in this paper the mechanism of land subsidence due to excessive pumping of groundwater is discussed first then the measured field data are presented and the relationship between groundwater pumping and land subsidence is discussed

hydrochemical signatures of deep groundwater circulation in a part of the himalayan foreland basin groundwater samples were analyzed from 71 springs and wells as part of a larger study in a region of compressional tectonic regime the study site covers the peshawar basin and surroundings in the himalayan foreland of pakistan the northern portion is mountainous and the water table is discontinuous in different intermontane valleys with abundant springs with normal and anomalous temperatures and composition the southern part is divided into isolated basins with a number of drilled deep and dug shallow wells hydrochemical signatures of elevated strontium sr sio2 boron b and the geothermometric signatures all indicate a deep circulation of the emerging groundwater moreover for several of the sample sites water chemical compositions measured spring and water well temperatures and reservoir temperatures calculated for spring waters all point to origin from deep horizons within the basin remarkable proximity of all the thermal and hydrochemical anomalies to major faults suggests that the waters ascended along these faults from greater depths the area is a natural western extension of the himalayan geothermal belt described in earlier literature for the eastern and central himalayas

stress estimation in rock a brief history and review for this special issue of the journal on rock stress estimation an introduction to the subject of in situ rock stress is presented here concentrating on the history of the subject and the principles of both stress and its measurement following an historical overview of the need for rock stress information and the nature of rock engineering problems stress and stress estimation are discussed this is followed by a review of the stress measurement techniques the importance of stress estimation and associated numerical modelling is highlighted the conclusions emphasize the importance of a well conditioned stress estimation campaign by using more than one technique and supporting the campaign with a numerical model the appendix focuses on the work at the canadian underground research laboratory

geological and hydrogeological environment in shanghai with geohazards to construction and maintenance of infrastructures shanghai administrative region sar is located on the deltaic deposit of the yangtze river the bed rock under sar is generally buried in the depth of 200 m to 300 m except for several massifs where the bed rock is exposed to the ground surface the quaternary deposit in shanghai is soft sediment the variation of palaeoclimate influenced the sea level and resulted in a very complicated sedimentary environment the quaternary deposit in sar is composed of an alternated multi aquifer aquitard system maas the groundwater system is composed of one artesian aquifer and five confined aquifer layers with very high groundwater pressure head the maas was formed mainly within the warm geological era updated to 2 6 million years ago between two aquifers there is an aquitard which is composed of soft clayey soil formed mainly within the cold era the aquitards are composed of very soft clayey silt with very high compressibility and humus content the humus material was transformed into methane gas under a long term geological process with the development of economy the infrastructures were or are being constructed in the top shallow soft clayey deposit aquifer i and aquifer ii in sar the following geohazards occurred or possibly occur during the construction and maintenance of infrastructures i quicksand and piping hazards ii pumping induced hazards and recharge cutoff hazards iii long term settlement due to the seasonal fluctuation of groundwater level and iv geohazards of methane gas

turbidites and megaturbidites from the herodotus abyssal plain eastern mediterranean unrelated to seismic events abstract a transect of 9 piston and gravity cores was taken across the southeast flank of the mediterranean ridge the transect extends from the abyssal plain to a location 290 m shallower than the abyssal plain and 50 km north of the edge of the ridge each core contains two or more turbiditic layers which belong to two discrete types here called a and b type a essentially consists of black plastic clays rich in smectite with silt fraction of terrigenous nature source area is the nile cone and age is middle or late pleistocene type b turbidites are pale brown to whitish in color coarse grained carbonate rich and bioclastic in composition with shallow water fossils dominant they are poor in smectite and the silt fraction is very rich in carbonates calcite and aragonite the source area is the north african shelf south of the abyssal plain a megabed belonging to type b turbidites is correlatable from core to core with a thickness in excess of 10 m in the abyssal plain and an estimated volume of 10 km 3 its stratigraphic position in the latest pleistocene suggests that its origin is related to a sudden collapse of bioclastic sediments accumulated in a canyon head during a low sea level stand the source areas of the two discrete turbidite types belong to the essentially aseismic north african continental margin although they are presently recorded on the tectonically active mediterranean ridge no seismic events are required to account for the presence of either type of turbidite

study of multi aquifer groundwater interaction in a coal mining area in china using stable isotopes and major ion chemical data investigations have been undertaken to determine the interactions between the main aquifers in a coal mining area near the taihang mountains in china to determine the sources of water environmental isotopes 18o 2h 3h 34s and water chemistry ions ca2 mg2 na k hco3 so42 cl were used as tracers furthermore batch sampling and testing were conducted on mountain spring water and karst water in the aquifers of the taiyuan group fengfeng group and majiagou group on the seatearth of the coal mining area via field observations and laboratory experimental analysis the 18o and 2h values of the mountain spring water and karst water in the coal mining area showed a common distribution with the local meteoric water line el1 of karst water in the majiagou group but significantly deviated from the surface water evaporation line el2 in the coal mining area when combined with the distribution of karst water level values thus karst water in the coal mining area is mainly supplied by groundwater from mountainous areas furthermore the concentration of sulfate ions increased dramatically in the groundwater flow of karst water from mountain spring water to karst water in the fengfeng group and majiagou group of the coal mining area when equivalent concentrations of ca2 mg2 hco3 and so42 hco3 reached their peak the chemical type of groundwater gradually evolved from ca mg hco3 to ca mg so4 hco3 in addition significant positive correlation was found between the 34s and so42 values of the water samples indicating that gypsum is involved in groundwater lixiviation in contrast the relationships of ca na versus mg na na hco3 versus total dissolved solids tds and na versus cl revealed that tds and salinity accumulate from the mountain spring water and karst water in the taiyuan group of the coal mining area furthermore the chemical type of groundwater gradually evolved from ca mg hco3 to na hco3 as revealed by a piper trilinear diagram

evaluation of optimized depth of waterproof curtain to mitigate negative impacts during dewatering abstract dewatering using a combination of waterproof curtain and pumping wells is commonly adopted to ensure the stability of foundation pits in multi aquifer strata however dewatering is likely to result in environmental problems this paper investigates the impact on surroundings owing to the interaction between the waterproof curtain and pumping wells by numerical simulation the depth of the diaphragm wall penetrating the dewatering aquifer d and the filter length of pumping wells l are varied in the simulation the relationship between approximate hydraulic gradient i or ground settlement outside the foundation pit s with curtain depth ratio rd d over the thickness of the dewatering confined aquifer ha or filter length ratio rl l ha can be divided into three change parts namely initial gradual middle sharp and final gentle part three values of rd and rl namely effective suggested and control value are proposed rd and rl should vary between the effective and control value the suggested value of rd and rl is recommended in actual engineering by comprehensive consideration the effective suggested and control value of rd can be calculated by a linear equation according to the value of rl

global variations in the geoid topography admittance of venus global representations of geoid height and topography are used to map variations in the geoid topography ratio admittance of venus the admittance values are permissive of two mutually exclusive models for convection driven topography in the first compressive highland plateaus are expressions of present mantle downwelling broad volcanic rises are expressions of mantle upwelling and lowlands overlie regions with no substantial vertical motion in the mantle in the second compressive highland plateaus are remnants of an earlier regime of high crustal strain and most other long wavelength topographic variations arise from normal convective tractions at the base of the lithosphere

evidence for small scale mantle convection from seasat altimeter data evidence for the early development of convective instability in the thermal boundary layer associated with cooling plates has been found from gravity anomalies and residual sea surface heights derived from seasat altimeter data subtle lineated patterns trending in the direction of plate motion in the hot spot reference frame are observed over the younger portions of the fast moving pacific and indo australian plates in particular for the east central pacific ocean the seasat derived data sets reveal lineations with 1 wavelengths in the range 150 500 km perhaps increasing with plate age and 2 peak to trough amplitudes of 5 20 mgal for gravity anomalies the lineated pattern over the pacific plate which first becomes discernable over seafloor 5 to 10 m y old west of the east pacific rise is clearly oblique to the trends of the prominent pacific farallon fracture zones onset of convective instability at such early ages can be understood if young oceanic lithosphere is underlain by a layer having a viscosity of about 1018 pa s 1019 p which is about 3 orders of magnitude less than mantle viscosity inferred from postglacial rebound studies recent numerical studies of convection in fluids with a temperature and pressuredependent viscosity support an early onset time for convective instability and low viscosity zones in the upper mantle beneath young lithosphere such low viscosity zones may correspond to similarly located regions of low shear wave velocities resolved through studies of surface waves

dewatering of a deep excavation undertaken in a layered soil in order to carry out deep excavations under the water table in urban environments the safety of the work site and of the adjacent buildings is a major cause for concern one of the most common and effective methods of undertaking these excavations involves combining the cut and cover method with a dewatering system the success of a construction depends on the stability of the excavation bottom the effects produced outside the excavation by dewatering soil movements and or the state of the enclosure defects in the diaphragm walls this study proposes a realistic multidisciplinary procedure to address these issues the work emphasizes the importance of soil characterisation and underlines the need to perform a watertightness assessment test wtat before the excavation stage the procedure was applied to the excavation of a deep shaft of the high speed train hst tunnel in barcelona an earlier geological characterisation at large scale ruled out the use of deep pumping wells however a subsequent hydrogeological characterisation which involved borehole logging grain size analyses natural gamma ray and pumping tests revealed the presence of thin transmissive layers inside the low hydraulic conductivity materials the dewatering system was designed by considering different model scenarios and the safest design was selected for the excavation depths of the enclosure and of the pumping wells differed in accordance with the scenarios the impacts settlements due to pumping and the stability in each scenario were computed the state of the enclosure underwent a wtat before the start of the excavation but after constructing the enclosure to verify its low permeability the test consisted in pumping inside the enclosure and monitoring the groundwater behaviour outside the enclosure numerical interpretation of this test showed a defect in the diaphragm walls below the excavation bottom since this defect was not repaired because of its location below the bottom of the excavation the dewatering system had to be redesigned to ensure safety surface settlements which were also a source of concern were small they were computed using coupled hydro mechanical models

laboratory model tests on water inrush in foundation pit bottom numerous deep foundation pits were constructed in china in the course of urbanization water inrush is one of the most important causes of foundation pit accidents at present few images and detail courses of the water inrush have been recorded and reported the evidences for the hypothesis of water inrush calculation are not enough in this study model tests were performed to verify the water inrush course in foundation pit bottom the water inrush modes of foundation pits were analyzed for the aquitards that included clay and silty clay in shanghai china the deformation and failure characteristics of the layers under different water pressures were obtained the deformation course without water inrush was divided into three stages continuous deformation progressive deformation and equilibrium stages the deformation course with water inrush was divided into four stages continuous deformation progressive deformation shear failure and water inrush and sinking stages the course included creep deformation and micro cracks development before failure it was not an instantaneous phenomenon but a time depending one the pore water pressure was the response of aquitard to boundary water pressure which indicated the seepage in low permeable aquitard and the development of micro cracks the water inrush formula was verified and tested using the model test results the limit equilibrium method had larger safe reserves and the prestressed homogeneous continuous beam method was relatively accurately

deformational models of rifting and folding on venus tectonic features on venus with characteristic widths and or spacings can be used to place quantitative constraints on the structure of the mechanical lithosphere through geophysical modeling we develop theoretical models for both compressional buckling and extensional rifting deformation based on classical elastic plate models with characteristic spacings determined by the flexural parameter modified to account for the effects of a realistic rheology this rheology consists of a relatively weak crust overlying a more creep resistant mantle in both layers the upper portions deform by frictional yielding on preexisting faults with a yield stress that increases linearly with depth and the lower portions deform by non newtonian temperature dependent creep for extensional deformation a graben model is used in which the primary structure of the rift is formed in the strong mantle layer and secondary faulting occurs in the brittle crustal layer the introduction of a weak zone in the lower crust that acts to decouple these two layers allows the formation of rifts with the large widths and depths observed on venus the compressional folding model utilizes an elastic buckling approach in which the non elastic yielding of the upper and lower portions of the layer modifies the elastic folding wave length this approach avoids the unreasonably high stresses that are required for conventional buckling models the two scales of deformation observed in radar images 15 25 km and 100 300 km can be related to the elastic flexural properties of the crust and mantle respectively which are separated by an intermediate weak zone in the lower crust these results imply that for regions in which both scales of deformation are present the crust is 5 15 km thick and the thermal gradient is 10 15 km l in regions such as ishtar terra where only the smaller features are observed the crust may be considerably thicker the apparent structure seen in high resolution images of the beta regio rift with the major faults located at the edges of an extended linear central depression lends support to the assumption of a graben mechanism of rift formation

a gis based model of potential groundwater yield zonation for a sandstone aquifer in the juye coalfield shangdong china abstract resolving the potential groundwater yield zonation of sandstone aquifers occurring at depths of several hundred meters has been an important and challenging objective of the hydrogeological research focused on preventing flood hazards in coal mines using accessible geological exploration data we put forward a method of predicting the spatial distribution of groundwater storage potential in sandstone aquifers from permian age coal deposits in juye coalfield shangdong china a geological tectonic and lithological composition index gtlci model was created using the following parameters sandstone depth and thickness faults length density fald faults density fad fault frequency density fafd fault scale density fasd variation coefficient of the slope vcs of the coal seam intensity index of folds in horizontal direction iifoh and lithological composition index lci each of these factors was subsequently divided into 5 classes the analytic hierarchy process ahp and trapezoidal fuzzy number tfn method was applied to calculate the weight of the conditioning factor and their respective sub classes groundwater yield potential contour map which was initially constructed using the gtlci values revealed four groundwater abundance zones the map was further refined by taking into account hydrogeologic data collected during mining activities the gtlci model predictive success rate of 80 was explained by the limited number of boreholes available for validation it is considered that the gtlci model is effective at predicting zonation of groundwater yield in the sandstone aquifers from permian age coal deposits in juye coalfield china

investigations of water inrushes from aquifers under coal seams in many coal mines limestone confined aquifers underlie coal seams during coal extraction from these mines water inrushes occur frequently with disastrous consequences this paper introduces the hydrogeological conditions of the coal mines and the potential water inrush disasters from aquifers under coal seams it then presents the water inrush mechanism the main factors which control water inrushes include strata pressure mining size geologic structures and the water pressure in the underlying aquifer analysis shows that reduction of confinement due to mining is the major cause of the water conducting failure in the floor strata the depth of the failure zone is strongly dependent on the mining width this paper also presents field observation results of the water conducting failure in the floor strata and applies the finite element method coupled with stress dependent permeability to analyze hydraulic conductivity enhancement due to coal extraction finally theoretical and empirical methods to predict water inrushes are given and technical measures for improving mine design and safety for coal extraction over aquifers are presented these measures include fault and fracture grouting and mining method modification such as changing long wall to short wall mining

assessment of the impact of anthropogenic activities on the groundwater hydrology and chemistry in tarsus coastal plain mersin se turkey using fuzzy clustering multivariate statistics and gis techniques summary tarsus coastal plain tcp is an economically and ecologically important area situated in between the fertile fluvio deltaic plains of two rivers delicay and tarsus mersin se turkey where anthropogenic activities agricultural industrial and domestic are very intense twenty four water quality parameters were surveyed at 193 groundwater and 10 surface water sites during august 2008 the objective was to characterize the physico chemical properties of groundwaters in tcp assess the impact of anthropogenic activities on the groundwater hydrology and chemistry and identify the major hydrogeochemical processes occurring in the area groundwater samples were grouped into hydrochemically distinct and spatially continuous four water classes i e c1 c2 c3 and c4 using the fuzzy c means fcm clustering method where membership values were interpolated using the ordinary kriging technique principal components analysis pca was used to decipher various underlying natural and anthropogenic processes creating these distinct water classes four principal components pcs were extracted in pca which explained more than 73 of the total variance in water quality major factors responsible for the variations in chemistries of water classes are identified as 1 water rock interaction and nitrate contamination 2 salinization by seawater intrusion and evaporite dissolution 3 geogenic anthropogenic cr fe and mn and 4 anthropogenic zn pollution overexploitation of the aquifer is clearly evident especially at settlements located near the coastal zone where the water table is lowered 2 5 m below the sea level salinization is well known in the area and is attributed not only to seawater intrusion but also to dissolution of evaporitic series from the handere formation hydrochemical evidence also suggest that in the area subsurface paleo river channels and the deposits infilling the ancient lagoon area within quaternary recent alluvial deposits act as significant hydrological features where preferential groundwater flow occurs along them

the spatial distribution of coronae and related features on venus coronae are large quasi circular geologic features that are common on venus they appear to be the surface tectonic and volcanic expressions of mantle diapirs that have impinged on the underside of the venusian lithosphere we have investigated the spatial distribution of 335 coronae and related features identified in magellan radar data it is more clustered than a poisson distribution with a statistical certainty of more than 99 it is dominated by a single large cluster centered near the equator at about 245 longitude the features are preferentially found at elevation and geoid values close to the planetary mean with a paucity at both the highest and lowest levels of topography and geoid some coronae appear aligned in quasi linear chains we attribute the clustering of coronae and related features to preferential formation of these features above regions of broad scale mantle upwelling and suggest that a major mantle upwelling underlies the one large cluster we suggest that coronae are rare at the lowest elevations because these may be regions of mantle downwelling the shortage of coronae at the highest elevations may result both from obscuration by other intense tectonism there and from suppression there of their formation by an unusually thick crust corona chains may be produced by enhanced passive mantle uplift below failed or incipient rifts

magellan a new view of venus geology and geophysics within the past fifteen years the surface of venus has gone from being the least well understood of all the terrestrial planets to the most thoroughly mapped surface of any terrestrial planet including the earth this is primarily due to the magellan mission which has collected a variety of data on the surface morphology physical properties and interior density structure of venus amounting to more than 1 terabit 1012 bits of data synthetic aperture radar images have been obtained for over 95 of the surface their high resolution reveals most surface features larger than 100 200 meters across using its radar altimeter magellan has collected data on surface elevations sub meter scale roughness and radar reflectivity at a resolution of approximately 10 km further information on the physical properties of the surface was gathered by measuring the passive microwave emissivity of the surface pettengill et al 1992 two way doppler tracking of the spacecraft has yielded line of sight los gravity data and a spherical harmonic model of gravity and geoid out to degree 75 collection of high resolution gravity data has been aided by an innovative aerobraking maneuver which used venus atmosphere to brake the spacecraft and lower it from a highly elliptical orbit to a near circular orbit

response of seismic activity in mines to the stress changes due to mining induced strong seismic events the influence of the static stress transfer due to two stronger seismic events from one mine section on subsequent seismicity linked to the same section is studied the first strong tremor was provoked by destressing blasting the static stress transfer caused by this tremor had apparently a triggering effect for the occurrence of the second strong event this second event occurred in less than three weeks after the first one and on the area of simultaneous enhancement of both shear and normal components of the coulomb stress change caused by the first event it appears also that in the next few months the cumulative stress change due to both the events influenced significantly the location and rate of smaller subsequent events interestingly contrary to the results of previous analyses the negative coulomb stress changes turn out to have a major role in this respect the coseismic stress change impact even seems to prevail over the influence of time varying stress alteration caused by advancement of the mining front

characteristics of dewatering induced drawdown curve under blocking effect of retaining wall in aquifer summary for deep excavation pits that require the pumping of confined groundwater a combination of a retaining wall and dewatering with large diameter wells is usually adopted during excavation to improve safety since a retaining wall has a much lower hydraulic conductivity than the surrounding material in the aquifer blocking of seepage to prolong the seepage path of the groundwater outside of the pit is effective the retaining walls used during excavation dewatering cause hydraulic head drawdown inside the pit much faster than outside the pit thus difference in hydraulic head between inside and outside of the pit increases to investigate the mechanism of the blocking effect numerical simulation using the finite difference method fdm was conducted to analyze the effects of pumping in the pit the fdm results show that drawdown varies along the depth of the confined aquifer the influence factors of drawdown inside and outside the pit include insertion depth of retaining walls anisotropy of a confined aquifer and screen length of pumping wells in addition fdm results also show that the drawdown time curve can be divided into four stages in stage i drawdown inside the pit is very small and outside the pit it is almost zero in stage ii drawdown increases quickly with time in stage iii the drawdown curve is parallel to the cooper jacob curve on semi log axes and in stage iv the drawdown becomes constant these characteristics of the drawdown curve under the blocking effect of a retaining wall in an aquifer provide a way of estimating hydrogeological parameters according to pumping test results

an overview of rock stress measurement methods this paper presents an overview of methods that have been used to estimate the state of stress in rock masses with the emphasis on methods applicable to hard rocks and scandinavia rock stress is a difficult quantity to estimate because the rock stress measuring techniques consist of perturbing the rock measuring displacements or hydraulic parameters and converting the measured quantities into rock stresses there are two main types of method those that disturb the in situ rock conditions i e by inducing strains deformations or crack opening pressures and those that are based on observation of rock behaviour without any major influence from the measuring method the most common methods are briefly described including their application areas and limiting factors

environmental protection using dewatering technology in a deep confined aquifer beneath a shallow aquifer abstract this paper presents an innovative technology referred to as dual function well dfw which has been developed in order to reduce the construction costs of dewatering when excavation is conducted in an aquitard over a confined aquifer dfw technology is a method to lower both shallow groundwater and deep groundwater either separately or simultaneously using one well the dfw includes two or more independent screens corresponding to each aquifer and a valve is located between the screens inside a steel pipe when the valve is closed groundwater is pumped from the upper screen in the shallow aquifer when the valve is open groundwater is pumped from the screens in both the shallow and deep aquifers dfw technology is used to replace the traditional method involving two sets of wells in which the first set of wells pumps groundwater from the shallow aquifer and a second set pumps groundwater from the deep aquifer to investigate the effectiveness of dfw field pumping tests using a dfw were conducted and both groundwater head and settlement were monitored numerical simulation was adopted to simulate the results of the pumping tests comparison between the results from the dfw and from an ordinary mixing well indicates that the use of a dfw with the valve closed can reduce the pumping time from a deep aquifer and can reduce the ground settlement caused by dewatering the results indicate the dfw technology is feasible and effective

poludnista dorsa venus history and context of a deformation belt 1 rolling lowlands comprise 80 of venus s surface and thus developing a geological understating of resurfacing and tectonism is critical for our understanding of venus evolution in this paper global regional and local approaches to interpreting magellan synthetic aperture radar and altimetry radar data are used to constrain modes of lowland evolution convection processes and lithospheric structure detailed geologic mapping is combined with altimetry data test models of deformation belt evolution in venus s lowlands poludnista dorsa a complex 2000 km long deformation belt is highly segmented and broadly time transgressive long wavelength deformation is spatially independent of local short wavelength deformation within the deformation belt and temporally predates regional deformation marked by wrinkle ridges a mechanically layered lithosphere of regional extent is not required by the local geologic history local lithospheric thinning or progressive regional thickening of the mechanical layer better explains the observed sequence of events

multivariate statistical analysis of water chemistry in evaluating groundwater geochemical evolution and aquifer connectivity near a large coal mine anhui china major ion chemistry of groundwater from main aquifers near the dingi coal mine anhui china was analyzed with a suite of statistical techniques in an effort to understand aquifer connectivity and groundwater geochemical evolution fifty seven groundwater samples were analyzed from four aquifers the cenozoic top middle bottom aquifers and a permian coal strata aquifer with increasing depth of the aquifers groundwater became more mineralized showing greater hardness and salinity the dissolutions of halite and sylvite carbonate sulfate and silicate minerals were the primary processes controlling groundwater chemical compositions in the cenozoic bottom and coal strata aquifers while k na and hco3 originating from silicate mineral weathering were more enriched in the coal strata aquifer principal component analysis pca identified two principal components with the first component representing hardness variation and accounting for 57 5 of total variance and the second component 23 5 of total variance controlled primarily by salinity and sulfate reduction process the cenozoic bottom aquifer had greater hardness than other aquifers whereas the coal strata aquifer was characterized by higher salinity and larger influences of sulfate reduction cluster analysis revealed that the coal strata aquifer was largely isolated from the cenozoic aquifers with possible infiltration at discrete locations indicating that the high yield thick cenozoic aquifers may serve as a potential additional source for groundwater inrush into coal mines

facies analysis of pleistocene sediments from the bannock basin area a key to the reconstruction of its tectonic evolution abstract facies analysis was carried out on 21 selected cores from the bannock area in order to investigate the relationships between sedimentation and tectonism bannock basin is a large 3500 m uncorrected deep subcircular depression near the deformation front of the mediterranean ridge facing the sirte abyssal plain the basin is divided into several sub basins aligned along a rim syncline surrounding a central elevated area salt dome high density brines and anoxic sediments occupy the deepest part of the depressions the facies distribution is controlled by the bottom configuration in that pelagic facies typically occur on plateaus and domes debris flow deposits in base of slope settings and turbidites in basinal settings the facies distribution may therefore be used to reconstruct the evolution of the various parts of the rim syncline erosional gaps may be related to tectonism or may be features created by the passage of major turbiditic events the results of our study of the facies associations and of the rates of sediment accumulation indicate that the collapse of the eastern part of the rim syncline pre dates the collapse of the western part the western basins are deeper and larger than the eastern ones and unlike the latter are aligned at the foot of a strike slip fault with a vertical offset of at least 700 m

coldspots and hotspots global tectonics and mantle dynamics of venus magellan radar images and altimetry data and pioneer venus gravity data of major highlands and lowlands on venus are examined with the objective of relating these tectonic and volcanic landforms to convection within venus mantle two roughly circular lowlands atalanta and lavinia planitiae are bowl shaped depressions which contain compressional tectonic features and lack hotspot related features such as coronae and shield volcanoes they are identified as surface expressions of young mantle coldspots or regions of mantle downwelling highlands can be divided into two distinct groups volcanic rises and plateau shaped highlands volcanic rises are domical circular to elongate regions characterized by volcanic construction extensional tectonism large positive gravity and geoid anomalies centered on the highlands and large apparent depths of compensation volcanic rises include beta bell atla and western eistla regiones and are identified as surface expressions of large mantle hotspots or plumes plateau shaped highlands are steep sided elevated regions that range from circular alpha regio to elongate or irregular ovda regio tellus regio in shape their surfaces are dominated by complex ridged terrain rather than the shield volcanoes and flows that dominate volcanic rises most plateau shaped highlands contain compressional structures some of which commonly lie along their margins and have small gravity and geoid anomalies and small apparent depths of compensation compared to volcanic rises plateau shaped highlands which include those mentioned above and western ishtar terra thetis regio and phoebe regio are identified as surface expressions of mantle coldspots or regions of downwelling the highland coldspot features are elevated as a consequence of crustal thickening crustal thickening is absent or minor at lowland coldspots the importance of mantle downwelling in the tectonic deformation of venus suggests that its mantle like the mantle of earth is strongly heated from within the major venusian hotspots attest to the existence of large mantle plumes carrying heat upward from the planet s core

brine formation and gypsum precipitation in the bannock basin eastern mediterranean abstract sixty kilograms of gypsum crystals were collected at two dredging stations within a small anoxic hypersaline basin named the bannock basin close to the sirte abyssal plain the basin was investigated in some detail by means of ten precision positioned piston and gravity cores one nansen bottle hydrocast and three ctd stations the sediments of the basin floor are dark h 2 s rich and commonly laminated and contain centimetric crystals of gypsum the water column above the basin has normal salinity down to a depth of 3150 m below this depth the basin is filled with hypersaline brines formed from the dissolution of messinian evaporites outcropping on the steep eastern wall when the brines reach the necessary concentration in ca and in so 4 gypsum may precipitate along the steep eastern wall and within the sediments on the basin floor the very recent age of the gypsum is proved by the inclusions of quaternary planktonic fauna formainifera and pteropods and by radiometric techniques

drilling induced tensile wall fractures implications for determination of in situ stress orientation and magnitude abstract detailed investigation of failure of the borehole wall in two scientific drilling projects the german ktb kontinentales tiefbohrprogramm der bundesrepublik deutschland and the european geothermal research project at soultz sous forets france has lead to new insight in the phenomena of tensile fractures induced in the wellbore wall during drilling comparison of the orientation of the fractures with the orientation of the horizontal principal stress known from breakout and hydraulic fracturing analysis demonstrates that these fractures are reliable indicators of the orientation of the maximum horizontal principal stress s h a model for the initiation of the fractures is presented which points out the important influences of a the tectonic stress state b increased mud pressures during drilling operation and c thermal stresses induced by circulation of relatively cold drilling mud analysis of drilling induced fractures in the gpk1 borehole at soultz sous forets where the magnitude of s h is known from hydraulic fracturing experiments demonstrates the validity of this model for the initiation of the fractures further a new method is proposed to estimate the magnitude of s h from the occurrence of drilling induced fractures and knowledge of thermally induced stress and pumping pressure during drilling the method is successfully applied to both ktb boreholes an independent method to estimate the magnitude of s h based on the analytical calculation of the stress intensity factor for drilling induced fractures taking into consideration both increased mud pressure and thermal stress is also presented application of this method confirms the results derived with the analysis described above additionally the evaluation of the orientation of the fractures with respect to the wellbore axis indicates that over major depth sections of the investigated wells the vertical stress is a principal stress

a method for prevent water inrush from karst collapse column a case study from sima mine china mining induced groundwater inrush could result in serious economic losses and casualties this disaster usually depends on geological structure such as the karst collapse column kcc it could reduce the aquifuge thickness causing a great risk of water bursting in order to assess the impact of mining on the kcc we have developed a complete set of methods including three dimensional seismic exploration connectivity experiment water injection experiment in two sidewalls numerical simulation based on drucker prager d p elastoplastic damage theory this method is used to test the size type and the damage thickness of the kcc named dx1 in sima mine and the results indicate that the type of dx1 is good cementation in addition under the influence of the shear stress at the coal wall and the unloading at the goaf a significant compressive damage zone with a large damage thickness will form at the sidewall of the kcc as the roof collapses the backfill is compacted and the maximum damage thickness gradually moves to the other side of the kcc eventually an asymmetric inverted saddle shaped damage distribution is formed with a maximum compression damage depth of 32 5 m the results provide a basis for preventing water inrush from kcc