earth stress and reservoir quality evaluation in high and steep structure the lower cretaceous in the kuqa depression tarim basin china abstract knowledge of the state of the in situ stress field provides important insights into the petroleum engineering and geology the in situ stress orientation and magnitudes in the high and steep structure of lower cretaceous bashijiqike formation in kuqa depression were analyzed based on well log calculations and the impacts of in situ stress field on reservoir quality macroscopic reservoir properties and microscopic pore structure as well as fracture aperture were investigated the maximum horizontal stress shmax orientation was determined as nearly north south according to the image log derived drilling induced fractures and borehole breakouts the vertical stress sv shmax and minimum horizontal stress shmin magnitudes were calculated via well logs the result reveals a dominant strike slip stress regime shmax sv shmin in the bashijiqike formation in the kuqa depression the sv at the depth ranging from 5000 to 7100 m is 150 180 mpa and horizontal stresses shmax and shmin vary significantly from 130 to 210 mpa the horizontal stress difference is in the range from 40 to 70 mpa and fluid overpressures are commonly encountered the effective stress e has a positive relationship with the when the is less than 50 mpa intergranular pores can be preserved in layers with low values the microscopic pore structure will be complex and macroscopic reservoir quality will be poor with the increasing values in addition fractures are mainly corresponding with the layers where the value is low and the fracture aperture and porosity decreased significantly with the effective stress e by determining the magnitude and orientation of in situ stresses around the wellbore insights can be provided into the wellbore instability optimum drilling trajectories and reservoir quality evaluation

compressive and tensile failure of inclined well bores and determination of in situ stress and rock strength in this paper we investigate the occurrence of compressive and tensile failures of arbitrarily inclined well bores under a wide variety of stress conditions the principal assumptions in this analysis are that the rock is isotropic and that it deforms elastically to the point of failure as has been shown by previous investigators for a given stress state and well bore orientation it is straightforward to predict the orientation of the failures around the well bore as well as whether failure is likely to occur depending on such parameters as rock strength and borehole fluid pressure however as the stress state is almost never known in situ we demonstrate how observations of compressive and tensile wall failures in inclined holes can be used to constrain in situ stress orientations and magnitudes if there are independent data on the magnitude of the least principal stress from either leak off or microfrac tests and on the formation pore pressure we further demonstrate how once the stress state is determined it is possible to assess both an upper bound on the effective in situ rock strength and the degree to which increasing the borehole fluid pressure or mud weight can reduce the likelihood of borehole failure through application of this methodology to an inclined well bore in an area of complex faulting in the gulf of mexico we illustrate how it is possible to utilize observations of borehole failures to determine the magnitude and orientation of the stress tensor in areas such as offshore sedimentary basins where drilling inclined well bores is quite common

historical environmental pollution trend and ecological risk assessment of trace metals in marine sediments off adyar estuary bay of bengal india geochemical mineralogical and textural analyses were carried out in core sediments off adyar estuary bay of bengal india to record the contamination trend from urban and industrial activities during the historical past quartz feldspar kaolinite chlorite and illite were the main lithogenic and clay minerals carbonate was the predominant biogenic mineral trace metals fe al cu cr ni pb and zn indicate more enrichment in the surface sediment layers due to recent anthropogenic activities the mean anthropogenic factor af values for trace metals in core sediments decreased in the following order cr ni zn cu pb the pollution load index pli values in adyar core sediments ranged from 1 to 1 25 with an average of 1 07 based on af pli and sediment quality guidelines values for trace metals significant metal enrichment and ecological risk were obtained in upper most sediment layer multivariate statistical methods such as correlation matrix principal component analysis and cluster analysis were carried out to find the relationships among the texture size metals and minerals the pollution of adyar estuarine sediments was started in the 1960s responding to the rapid economic development in chennai coastal and adyar estuarine region in the last five decades despite these high concentrations in the upper layer development and expansion of industries are still continuing the stricter regulations for the discharge and remediation of sediments are urgent for the conservation of environments and human health

global crustal stress pattern based on the world stress map database release 2008 the world stress map wsm project is a global compilation of information on the contemporary crustal stress field from a wide range of stress indicators the wsm database release 2008 contains 21 750 stress data records that are quality ranked using an updated and refined quality ranking scheme almost 17 000 of these data records have a c quality and are considered to record the orientation of maximum horizontal compressional stress sh to within 25 as this is almost a triplication of data records compared with the first wsm database release in 1992 we reinvestigate the spatial wave length of the stress patterns with a statistical analysis on a global 0 5 grid the resulting smoothed global stress map displays both the mean sh orientation that follows from the maximum smoothing radius for which the standard deviation is b25 and a countour map that displays the wave length of the stress pattern this smoothed global map confirms that long wave length stress patterns n2000 km exist for example in north america and ne asia these have been used in earlier analyses to conclude that the global stress pattern is primarily controlled by plate boundary forces that are transmitted into the intraplate region however our analysis reveals that rather short wave length of the stress pattern b200 km are quite frequent too particularly in western europe alaska and the aleutians the southern rocky mountains basin and range province scandinavia caucasus most of the himalayas and indonesia this implies that local stress sources such as density contrasts and active fault systems in some areas have high impact in comparison to plate boundary forces and control the regional stress pattern

present day stress orientations adjacent to active strike slip faults california and sumatra present day stress directions interpreted from well bore breakouts adjacent to two crastal scale active strike slip faults the san andreas fault in california and the great sumatran fault in sumatra indicate that the maximum horizontal stress direction sh is oriented at a high angle 70 90 to both faults the regionally defined stress fields spanning these faults show that adjacent young or actively growing folds have formed orthogonal to sh and are therefore in the thrust fault orientation these observations indicate a decoupling of the strike slip and compressional components of the deformation within these broadly transpressive zones borehole breakouts in 118 wells in western california indicate a regionally consistent stress pattern with sh generally oriented ne sw nearly perpendicular 80 90 to the strike of the san andreas fault the orientation of sh nearly perpendicular to the san andreas fault implies low shear stress on the fault and is consistent with geological interpretations of the coast and transverse ranges indicating active compressional deformation fault plane solutions for recent dip slip style earthquakes principal stress directions determined from inversion of earthquake focal mechanisms and induced hydraulic fracture orientations a stress trajectory map for western california is computed using an iterative statistical algorithm in which observed directional data such as breakout directions are used to obtain a model regional stress field analysis of well bore breakouts in 25 wells within the central and southern oil districts of sumatra indicates that the regionally defined sh adjacent to the active great sumatran strike slip fault is oriented at a high angle 70 80 to the fault this orientation of sh is consistent regionally with geologic stress indicators and focal mechanisms of dip slip earthquakes preliminary analysis of the stress field in the vicinity of the philippine and alpine faults suggests sh is also oriented at a high angle to these active strike slip faults similarly the minimum horizontal stress sh is oriented at a high angle to the the kane and dead sea transforms the observation of sh and sh in the vicinity of active strike slip faults being oriented nearly perpendicular and parallel to the faults suggests that large crustal scale strike slip faults may in general be inherently weak surfaces

a preliminary study of the present day in situ stress state in the ahe tight gas reservoir dibei gasfield kuqa depression abstract knowledge of the present day in situ stress state has significant applications in the exploration and development of tight gas reservoirs the ahe formation is an important tight gas reservoir in the dibei gasfield of kuqa depression however prior to this study little attention has been paid to the present day in situ stress field within the formation in the present study the in situ stress orientation and magnitudes were investigated based on well log calculations and geomechanical modeling the horizontal maximum principal stress shmax orientation was determined from interpretations of drilling induced tensile fractures ditfs and borehole breakouts in imaging logs which showed variations between nnw sse trending and nne ssw trending in the dibei gasfield the in situ stress magnitudes were calculated in four wells based on well logs the results indicated a normal faulting stress regime within the ahe tight gas reservoir numerical simulation of the present day in situ stresses showed that the magnitudes of vertical stress sv shmax and horizontal minimum principal stress shmin were 105 5 mpa 191 0 mpa 88 9 mpa 142 9 mpa and 79 1 mpa 127 7 mpa within the ahe formation respectively in addition considering the present day in situ stress state in the ahe formation of dibei gasfield natural fractures in directions parallel sub parallel to the shmax orientation with high fracture angles showed great contributions to subsurface fluid flow borehole instability may become a potentially significant problem when drilling vertical wells and horizontal wells deviated toward the shmax orientation in the ahe tight gas reservoir of dibei gasfield

evidence for pre folding vein development in the oligo miocene asmari formation in the central zagros fold belt iran in order to understand the interplay between vein development and folding in the carbonates of the oligo miocene asmari formation one of the main hydrocarbon reservoir rocks in iran several anticlines have been investigated in the central part of the zagros folded belt combining observations of relative chronology between veins based on calcite filling phases and crosscutting abutting relationships as well as aerial satellite image interpretation on several anticlines allowed proposing a tectonic model highlighting the widespread development of veins and other extensional micro meso structures in the central zagros folded belt our data suggest that most of the veins affecting the asmari formation predated the main miocene pliocene folding episode an early regional vein set striking n50 marked the onset of collisional stress build up in the region then n150 and n20 trending vein sets were initiated in response to local extension caused by large scale flexure drape folds above n s and n140 basement faults reactivated under the regional ne compression at the onset and during miocene pliocene folding of the sedimentary cover the early formed veins were reactivated reopened and or sheared while duplexes low angle reverse faults and thrusts formed beyond regional implications this study puts emphasis on the need of carefully considering regional local vein development predating folding as well as influence of underlying basement faults in models of folded fractured reservoirs in fold thrust belts

subsurface fractures in situ stress and permeability variations in the walloon coal measures eastern surat basin queensland australia abstract in situ stress pattern and subsurface fractures control the production of coal seam gas csg reservoirs and hence comprehensive analyses are required for better development of these reservoirs the surat basin is a prolific csg province with major economic impacts in eastern australia recent studies have reported significant stress variations in this basin due to local geological structures however a systematic analysis of localised stress perturbations within the basin and their impacts on reservoir permeability have not been presented thus far in the published literature in this paper we combine different sets of data including conventional log data wellbore image logs 2d seismic lines and interpreted permeability from well test data in order to characterise the role of geological structures in the subsurface fluid flow of the walloon coal measures in eastern surat basin analysis of 7 3 km of borehole image log across 33 vertical wells revealed a regional ene wsw orientation of the maximum horizontal stress shmax in the study area however there are massive variability in the shmax orientation spatially and with depth analysis of 2d seismic lines highlight the role of geological structures in stress perturbation and the interpretation of natural fractures using image logs show that most of the open fractures are oriented sub parallel to the acute angle of local shmax orientation interpreted well test data in the study wells demonstrates that most of the high permeability data points are located where in situ stress rotation is observed this indicates the influence of local shmax orientation responding to geological structures on the subsurface fluid flow in the eastern part of the surat basin

understanding tectonic stress in the oil patch the world stress map project knowledge of the present day tectonic stress is essential for numerous applications in petroleum exploration and production and in civil and mining engineering such as improving the stability of boreholes and tunnels and enhancing petroleum production through natural or induced fractures the world stress map wsm project is a collaborative project between academia industry and government that is building a comprehensive global database of present day stress information to better understand the state and sources of contemporary tectonic stress in the lithosphere figure 1

present day stress field of southeast asia article i nfo it is now well established that ridge push forces provide a major control on the plate scale stress field in most of the earth s tectonic plates however the sunda plate that comprises much of southeast asia is one of only two plates not bounded by a major spreading centre and thus provides an opportunity to evaluate other forces that control the intraplate stress field the cenozoic tectonic evolution of the sunda plate is usually considered to be controlled by escape tectonics associated with india eurasia collision however the sunda plate is bounded by a poorly understood and complex range of convergent and strike slip zones and little is known about the effect of these other plate boundaries on the intraplate stress field in the region we compile the first extensive stress dataset for southeast asia containing 275 a d quality 177 a c horizontal stress orientations consisting of 72 stress indicators from earthquakes located mostly on the periphery of the plate 202 stress indicators from breakouts and drilling induced fractures and one hydraulic fracture test within 14 provinces in the plate interior this data reveals that a variable stress pattern exists throughout southeast asia that is largely inconsistent with the sunda plate s approximately ese absolute motion direction the present day maximum horizontal stress in thailand vietnam and the malay basin is predominately north south consistent with the radiating stress patterns arising from the eastern himalayan syntaxis however the present day maximum horizontal stress is primarily oriented nw se in borneo a direction that may reflect plate boundary forces or topographic stresses exerted by the central borneo highlands furthermore the south and central sumatra basins exhibit a ne sw maximum horizontal stress direction that is perpendicular to the indo australian subduction front hence the plate scale stress field in southeast asia appears to be controlled by a combination of himalayan orogeny related deformation forces related to subduction primarily trench suction and collision and intraplate sources of stress such as topography and basin geometry

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

are open fractures necessarily aligned with maximum horizontal stress abstract fluid flow in fractured rock is an increasingly central issue in recovering water and hydrocarbon supplies and geothermal energy in predicting flow of pollutants underground in engineering structures and in understanding large scale crustal behaviour conventional wisdom assumes that fluids prefer to flow along fractures oriented parallel or nearly parallel to modern day maximum horizontal compressive stress or s hmax the reasoning is that these fractures have the lowest normal stresses across them and therefore provide the least resistance to flow for example this view governs how geophysicists design and interpret seismic experiments to probe fracture fluid pathways in the deep subsurface contrary to these widely held views here we use core stress measurement and fluid flow data to show that s hmax does not necessarily coincide with the direction of open natural fractures in the subsurface 3 km depth consequently in situ stress direction cannot be considered to predict or control the direction of maximum permeability in rock where effective stress is compressive and fractures are expected to be closed chemical alteration dictates location of open conduits either preserving or destroying fracture flow pathways no matter their orientation

relationships among in situ stress fractures and faults and fluid flow monterey formation santa maria basin california we used borehole televiewer bhtv data from four wells within the onshore and offshore santa maria basin california to investigate the relationships among fracture distribution orientation and variation with depth and in situ stress our analysis of stress induced well bore breakouts shows a uniform northeast maximum horizontal stress sh max orientation in each well this direction is consistent with the sh max direction determined from well bore breakouts in other wells in this region the northwest trend of active fold axes and kinematic inversion of nearby earthquake focal plane mechanisms in contrast to the uniformity of the stress field fracture orientation dip and frequency vary considerably from well to well and within each well with depth fractures can be divided into distinct subsets on the basis of fracture frequency and orientation which correlate with changes of lithology and physical properties although factors such as tectonic history diagenesis and structural variations obviously have influenced fracture distribution integration of the in situ stress and fracture data sets indicates that many of the fractures faults and bedding planes are active small scale strike slip and reverse faults in the current northeast trending transpressive stress field in fact we observed local breakout rotations in the wells providing kinematic evidence for recent shear motion along fracture copyright 1997 the american association of petroleum geologists all rights reserved 1manuscript received april 15 1996 revised manuscript received december 27 1996 final acceptance july 15 1997 2department of geophysics stanford university stanford california 94305 2215 we wish to thank tom zalan of the chevron u s a production company for providing the offshore well data unocal corporation for providing the data on the onshore well and marcia mclaren from pacific gas and electric company for providing the earthquake focal mechanisms used in the stress inversion analysis the data used as background seismicity in figure 1 were extracted from the world wide web of the southern california seismic network scsn catalog operated jointly by the seismological laboratory at caltech and the u s geological survey both in pasadena california we appreciate the comments and helpful discussions from daniel moos steve graham and lev vernik

plate boundary forces are not enough second and third order stress patterns highlighted in the world stress map database 1 the world stress map project compiles a global database of contemporary tectonic stress information of the earth s crust early releases of the world stress map project demonstrated the existence of first order plate scale stress fields controlled by plate boundary forces and second order regional stress fields controlled by major intraplate stress sources such as mountain belts and zones of widespread glacial rebound the 2005 release of the world stress map project database provides for some areas high data density that enables us to investigate third order local stress field variations and the forces controlling them such as active faults local inclusions detachment horizons and density contrasts these forces act as major controls on the stress field orientations when the magnitudes of the horizontal stresses are close to isotropic we present and discuss examples for venezuela australia romania brunei western europe and southern italy where a substantial increase of data records demonstrates some of the additional factors controlling regional and local stress patterns

a baseline study of trace metals in a coral reef sedimentary environment lakshadweep archipelago surficial and core samples collected from the sedimentary microenvironments of lakshadweep archipelago were analysed for their trace metal contents the synoptical relations in spatial distributions with respect to environmental conditions such as ph organic carbon and sediment texture were inter correlated some of the metals exhibited good correlations with fe mn which reflect their similarity in distribution rather than anthropogenic enrichment inter relating the variations in metal ph relationships with metal organic carbon in general those which exhibited positive correlations with ph displayed negative interactions with organic carbon content and vice versa comparatively higher values of fe in the mangrove area of one of the islands highlight the possibility of precipitation of fe as iron sulphides which are common in mangrove ecosystem based on the contamination factors for pb zn and cd as well as the geo accumulation index of cd it can be generalised that some of the islands remain polluted with respect to these elements an evaluation based on pollution load index shows that none of the islands surveyed for this study posed a serious threat in trace metal pollution bray curtis similarity index was computed to find out the similarity among metals islands using non transformed data of metal concentrations group linkage clustering technique was used for drawing dendrograms to show the similarity among them

tectonics of the zagros orogenic belt of iran new data and interpretations abstract the zagros orogenic belt of iran is the result of the opening and closure of the neo tethys oceanic realm and consists from northeast to southwest of three parallel tectonic subdivisions 1 1 the urumieh dokhtar magmatic assemblage 2 2 the sanandaj sirjan zone and 3 3 the zagros simply folded belt recent detailed and reconnaissance mapping and stratigraphie structural analyses in various parts of the belt indicate that the tectonics of the sanandaj sirjan zone is dominated by either large scale composite duplex structures or low and high angle ne dipping imbricate systems these thrust systems have transported numerous horses and sheets nappes of metamorphosed and non metamorphosed phanerozoic rocks for tens or possibly hundreds of kilometers stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the late cretaceous and has continued episodically since that time shear sense indicators in various parts of the zone reveal a ne sw direction of transport thrust systems generated in each episode are superimposed upon the previous structures cutting across and displacing them and producing complicated stacks of thrust sheets southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10 15 km in the thickness of the continental crust in the southwestern part of this zone the so called z main zagros thrust which has been traditionally considered as the boundary between the sanandaj sirjan zone and the zagros simply folded belt is by no means a single high angle reverse fault nor is it a narrow zone of crushed rocks but a series of low angle thrusts locally cut by normal faults these thrusts are indistinguishable from those mapped in the sanandaj sirjan zone and are geometrically part of the sanandaj sirjan zone structures there is no single thrust among them that can be singled out and referred to as the main one the boundary of the sanandaj sirjan zone with the urumieh dokhtar magmatic assemblage to the northeast is characterized by a series of structural depressions formed by compression rock sequences including ophiolite complexes exposed along this boundary are strongly dismembered sheared and mylonitized shearing planes and foliations are either subvertical or dipping at high angles to the northeast this zone is suggested to be the suture between the afro arabian and the iranian plates overall the intensity of deformation increases northeastward from the persian gulf mesopotamian basin where strata are undeformed and horizontal through the zagros simply folded belt which is characterized by en echelon doubly plunging flexural slip folds gentle to open in the southwest and close to locally sw overturned in the northeast the intensity of deformation continues to increase further northeastward through the sanandaj sirjan zone where thrust faulting is dominant this pattern suggests that the deformational front has migrated through time from the northeastern part of the sanandaj sirjan zone i e the suture zone to its present position in the central portion of the persian gulf mesopotamian foreland basin

a review on the applications of image logs in structural analysis and sedimentary characterization abstract image logs provide important information on lithology sedimentary textures paleoflow directions fractures and in situ stress analysis lacking of criteria used for establishing the image log facies limits the applications of image logs in sedimentary reservoir interpretation this paper provides a thoroughgoing review focusing on the recent applications of borehole image logs for sedimentological and structural description and interpretation and aims to establish image log facies which can provide guidelines in sedimentary reservoir interpretation this paper firstly summarizes the principles and basic characteristics of various imaging logging tools and then briefly introduces the pre processing workflow of the image log data then the generated images are used for depth and orientation shifts of cores by calibrating individual sedimentary and structural features descriptive and concise image log facies are established based on combinations of image textures including dip type dip pattern and color scheme and the characteristics as well as physical criteria for each individual image facies are summarized the established image log facies are then interpreted in terms of structural and sedimentological features such as lithology sedimentary structures vugs fractures and faults the image log facies and its stacking patterns are then used to interpret the lithofacies associations by calibrating with cores and conventional logs natural fractures and induced fractures are recognized by image logs and the principles of breakouts and drilling induced fractures for in situ stress analysis are reviewed then the applications of image logs in investigation of fracture attitudes and states as well as in computation of fracture parameters are summarized the procedures to evaluate fracture effectiveness through image logs are discussed at last the application of image logs for structural dip analysis is reviewed and image logs are used for recognizing faults fracture sets and attitudes of stratum through the dip patterns the basic procedures for paleocurrent reconstruction which includes dip picking of cross beddings structural dip determination and structural dip removal are reviewed then the paleocurrent directions of the lower cretaceous bashijiqike formation in the kuqa depression were reconstructed which could help further understanding of the depositional systems this review will help extend the utility of image logs in interpreting small to large scale sedimentary and structural features and bridges the gaps between well log analysis and sedimentary and structural interpretation

spatio temporal dynamics of heavy metals in sediments of the river estuarine system mahanadi basin india dynamics of heavy metals in the surface sediments of mahanadi river estuarine system were studied for three different seasons this study demonstrates that the relative abundance of these metals follows in the order of fe mn zn pb cr ni co cu cd the spatial pattern of heavy metals supported by enrichment ratio data suggests their anthropogenic sources possibly from various industrial wastes and municipal wastes as well as agricultural runoff the metal concentrations in estuarine sediments are relatively higher than in the river due to adsorption accumulation of metals on sediments during saline mixing while there is a decreasing trend of heavy metal concentrations towards the marine side the temporal variations for metals such as fe mn zn ni and pb exhibit higher values during monsoon season which are related to agricultural runoff higher elemental concentrations are observed during pre monsoon season for these above metals except ni at the polluted stations and for metals such as cr co and cd at all sites which demonstrate the intensity of anthropogenic contribution r mode factor analysis reveals that fe mn oxy hydroxide organic matter caco3 and textural variables factors are the major controlling geochemical factors for the enrichment of heavy metals in river estuarine sediment and their seasonal variations though their intensities were different for different seasons the relationships among the stations are highlighted by cluster analysis represented in dendrograms to categorize different contributing sites for the enrichment of heavy metals in the river estuarine system

in situ stress orientations in the xiagou tight oil reservoir of qingxi oilfield jiuxi basin northwestern china abstract knowledge of the present day in situ stress orientation is important for borehole stability fluid flow in fractured reservoirs and hydraulic fracture stimulation etc the qingxi oilfield of jiuxi basin northwestern china is an old oilfield however within which there were no systematic investigations into the present day in situ stress orientation prior this study in the present study the orientation of horizontal maximum stress shmax in the qingxi oilfield was interpreted and analyzed based on 149 borehole breakouts bos and 131 drilling induced fractures difs from electrical borehole imaging logs in 23 wells our interpretations revealed a prevailing ne sw trending 14 94 n 52 74 n shmax orientation in the xiagou tight oil reservoir of qingxi oilfield however the shmax orientation indicated various tendencies both laterally and with burial depth within single wells which were influenced by well developed faults natural fractures and bedding planes the presence of these structures caused great contrasts of rock mechanical properties influencing stress orientation variations in addition the effects of present day in situ stress orientation on natural fractures hydraulic fracture stimulation and borehole stability were discussed in the qingxi oilfield ne sw trending natural fractures indicated favorable contributions to subsurface fluid flow hydraulic fractures would propagate vertically following ne sw trending wells were more likely to experience borehole instability issues if they were deviated towards ne sw trending the results can provide geological references for subsequent tight oil production in the qingxi oilfield of jiuxi basin

geochemical and geo statistical assessment of heavy metal concentration in the sediments of different coastal ecosystems of andaman islands india spatial distribution of metal concentrations in the surface sediment samples collected from 16 marine locations covering different coastal ecosystems such as mangroves seagrasses dead coral and sandy beaches of the andaman islands india was studied ph ec sediment grain size and heavy metal al cd co cr cu fe mg mn ni pb and zn concentrations were determined and contamination factor cf and geo accumulation index igeo were calculated to understand the pollution status of the study area based on the background values cf of different heavy metals has revealed that different metals have different levels of accumulation viz al 0 01 0 22 mg 0 38 1 85 fe 0 06 0 74 mn 0 04 1 18 cu 0 18 2 93 cr 0 52 12 6 zn 0 3 1 39 ni 0 06 0 89 pb bdl 0 74 co 0 1 0 35 and cd 2 3 12 9 in general the metal concentration was less in these ecosystems when compared to similar ecosystems of mainland of india concentration of some metals like cr and cd was comparatively higher than the background values which is an important issue of concern to the coastal managers of the region spatial data on heavy metals collected now would help the coastal zone managers to identify the vulnerable sites and take remedial actions

a reassessment of the stress and natural fracture orientations from analysis of image logs in the chinese continental scientific drilling program borehole at donghai county jiangsu province china abstract the chinese continental scientific drilling ccsd project has drilled a 5100 m deep research borehole in the sulu ultra high pressure uhp metamorphic belt eastern china the uhp metamorphic belt is thought to be a product of continent continent collision and has consequently experienced very intensive structural deformation based on a more complete well log data set of ccsd borehole we can have a more detailed and reliable study on the structure features of borehole wall and other rock physical properties than a previous study published in 2009 abundant data related to borehole breakouts bos drilling induced tensile fractures ditfs and natural fractures were collected from the image logs the bo and ditf data indicate that the average direction of the maximum horizontal principal stress sh of the ccsd borehole site is about 79 2 which is consistent with the convergent direction e w of the pacific sea plate with respect to the eurasian plate analysis of ditfs indicated that in the case of the ccsd borehole axial drilling induced tensile fractures aditfs occur occasionally in the upper section 0 2300 m of the borehole with low dipping angle 0 10 while transverse drilling induced tensile fractures tditfs occur significantly in the lower section 3800 5000 m with high dipping angle 10 30 the natural fracture distribution at depth in the metamorphic rocks of the ccsd borehole indicates that 1 the failure strength of rocks and borehole depth are two factors that affects natural fracture frequency 2 most of the dip azimuth of natural fractures is consistent with the dip azimuth of foliations observed in the core 3 the development of most of the natural fractures probably was dominated by the development of foliations and both the natural fractures and foliations developed in response to the subduction and exhumation of the sulu terrene

structures of the zagros fold thrust belt in iran the zagros fold thrust belt in iran forms the external part of the zagros active orogenic wedge it includes a sequence of heterogeneous latest neoproterozoic phanerozoic sedimentary cover strata 7 to 12 km thick and composed of alternating incompetent and competent layers overlying precambrian crystalline basement with a complex pre zagros structural fabric balancing structures of the cover statigraphic units in the zagros fold thrust belt requires in sequence and out of sequence involvement of the precambrian basement in the deformation six detailed balanced and retrodeformable cross sections which are constructed based on geological and geophysical data across various sectors of the belt show fault bend and fault propagation folds interpreted to have formed by slip on their subjacent thrusts out of sequence basement rooted thrusts as the interpretations in the constructed cross sections suggest have breached the cover basement interface and using incompetent cover strata for propagation cut across the cover structures and have created associated new folds superimposed upon the pre existing structures this style of deformation which has resulted in structural complexity of the belt characterizes a 200 to 300 km wide zone of distributed partly synchronous deformation with along strike and across strike variations it also implies that the zagros fold thrust belt as the external part of the orogenic wedge is still in its subcritical condition with internal deformation to achieve a critical taper in creating structural complexity in addition to out of sequence thrusting mechanically weak layers evaporites and mudstones of the cover strata have played a significant role by providing several detachment horizons shortening estimates across the belt are variable based on the constructed cross sections and their restorations minimum shortening estimates range from 16 percent to 30 percent in different sectors of the belt

identifying fracture orientation in a mature carbonate platform reservoir the permian guadalupian san andres reservoir at keystone field winkler county texas is divided into three major stratigraphic units and twelve flow units on the basis of an analysis of multiple shoaling upward cycles of shallow water marine to tidal flat carbonate facies these rocks are now thoroughly dolomitized and cemented with anhydrite and gypsum the distribution of original oil in place was mapped both laterally and vertically most of the resource is in the upper five flow units and the original oil in place map of these upper flow units indicates that the highest concentration of hydrocarbons is in the center of the study area porosities in this reservoir are nearly 10 and permeabilities are generally less than 1 md despite these low matrix permeabilities recently drilled wells initially produced at rates as high as 120 bbl of oil per day although these rates declined an average of 75 in the first 6 months primary recovery from this reservoir is only 8 of original oil in place subvertical fractures in this reservoir are visible in cores and on a microimage log early floodwater breakthrough occurred without increased oil production in a pilot waterflood these production characteristics combined with direct observations of fractures indicate that productivity is dependent on fracture permeability horizontal boreholes perpendicular to the strike of effective fractures and within the part of the reservoir that contains highest remaining oil will maximize primary recovery borehole breakouts and regional stress measurements suggest that the direction of principal horizontal compressive stress is northeast southwest and natural fractures that strike in this direction are most likely to be open and capable of transmitting fluids

an alternative interpretation for slip vector residuals of subduction interface earthquakes a case study in the westernmost ryukyu slab abstract slip partitioning along oblique subduction zones has conventionally been examined by slip vector residuals determined from interface earthquakes it is measured through contrasting the slip vector with respect to the local plate convergence direction defined on the surface of the earth by the euler vector interpretation of regional plate kinematics based on slip vector residuals thus defined may be misleading besides the apparent discrepancy attributable to the surface projection of vectors on an obliquely plunging surface a more fundamental problem is the construction of the reference subduction flow field for the subducted slab based upon the known plate convergence it can be shown that for complicated slab geometry the conventional practice of intuitively rotating the euler kinematics onto the subducted slab leads to unrealistic intraplate deformation that invalidates the mechanical integrity of the oceanic lithosphere alternatively we propose to calculate the velocity field for the specific slab geometry based on the rationale that the subduction flow field should be the one that endures the least amount of intraplate deformation the calculated flow field for the westernmost ryukyu slab that is in transition to the philippine sea plate psp eurasian plate ep collision near taiwan reveals quite distinct subduction flow field the particle paths associated with the calculated flow field are in better accordance with the observed slip vectors while the corresponding strain rate field is consistent with the previously reported lateral compression seismogenic zone furthermore it is speculated that the plate kinematics of the northwestern corner of psp that is impinging the vicinity of the collision might have also undergone significant readjustment to accommodate the potential intraplate deformation it is noted that the westernmost subducted ryukyu slab and the northwestern corner of psp belong to a mechanically coherent tectonic unit the 3d geometric constraints set up by the subducted slab and the unfriendly kinematic constraints imposed by the collision boundary both play important roles in configuring the intraplate deformation within psp manifestation in the local kinematics might indicate deviation from the general psp ep convergence and is thus of crucial importance to tectonic interpretations of geophysical observations in this area

fracture analysis and determination of in situ stress direction from resistivity and acoustic image logs and core data in the wenchuan earthquake fault scientific drilling borehole 2 50 1370 m abstract after the wenchuan earthquake on may 12th 2008 the wenchuan earthquake fault scientific drilling project wfsd was initiated in order to investigate the structure of the fault zones and the mechanism of the earthquake the wfsd contains four boreholes wfsd 1 wfsd 2 wfsd 3 and wfsd 4 lying at the maximum displacement locations along the yingxiu beichuan fault zone and the guanxian anxian fault zone and wfsd 2 is the second borehole and is still being drilled core samples resistivity and acoustic image logging data were acquired from 50 to 1370 m the natural fractures borehole breakouts drilling induced fractures and drilling enhanced natural fractures were identified from the cores and the image logs and were statistically analyzed the strikes of the natural fractures systematically vary and can be sorted into four groups according to depth 1 above 637 m mainly striking ene wsw 2 in the interval of 637 932 6 m striking nne ssw 3 in the interval of 932 6 1200 m directed ene wsw then to wnw ese while striking ne sw from 1030 m to 1150 m 4 from 1200 m to 1370 m maintaining a strike of wnw ese the natural fractures from 50 m to 637 m seem to be reverse faults which strike approximately parallelly to the main fault two sets of conjugate fractures around 1002 4 m indicating subvertical maximum principal paleo stress direction may be a subordinate structure of the main fault caused by a local stress field and it reveals the complex stress field of yingxiu beichuan fault zone when the fractures formed a total of 12 bos 2 sets of difs and one set of defs with an overall length of 30 4 m were interpreted from 960 m to 1370 m in wfsd 2 the average shmax orientation interpreted for wfsd 2 960 1370 m is 120 7 300 7 n i e wnw ese with the standard deviation of 9 2 and it is consistent with the stress status of yingxiu beichuan fault zone which is one of the main fault zones in the 2008 wenchuan earthquake

subsurface fracture analysis and determination of in situ stress direction using fmi logs an example from the santonian carbonates ilam formation in the abadan plain iran abstract the relationship between the present day stress field and natural fractures can have significant implications for subsurface fluid flow in particular fractures that are aligned in orientations favourable for reactivation by either shear or tensile failure in the in situ stress field often exhibit higher hydraulic conductivities the ilam formation of southwestern iran is an important hydrocarbon reservoir containing numerous natural fractures however little is known about the state of stress in this region or any of iran s petroleum provinces we conducted analysis of the present day maximum horizontal stress orientation and the density orientation and hydraulic conductivity of natural fractures in the ilam carbonates using high resolution formation micro imager resistivity logs in two wells a total of 51 breakouts with an overall length of 215 m were observed in the two wells indicating a maximum horizontal stress orientation of 68 n 7 6 in well a and 58 n 6 3 in well b furthermore the wellbore derived stress orientations determined herein are consistent with those inferred from nearby earthquake focal mechanism solutions indicating that stresses in the sedimentary cover are linked to the resistance forces generated by arabia eurasia collision furthermore the correlation between stress orientations estimated from earthquake focal mechanism solutions and breakouts indicates that focal mechanism solution data which is often considered to be unreliable for stress field analysis near transform margins may provide reliable information on the stress orientation near continental collision zones the image log data also reveals three sets of open and presumably hydraulically conductive fractures with strikes of i 160 170 n ii 110 140 n and iii 070 080 n fracture set iii is consistent with being formed and open in the present day stress field however fracture sets i and ii strike at a high angle to the present day maximum horizontal stress and are interpreted herein to be the result of either pre or syn folding related forces the observation that different sets of open fractures in the field can be either sensitive or insensitive to the present day stress is critical for improving hydrocarbon recovery

the in situ stress field of the perth basin australia a total of 17 wells in the perth basin were interpreted to have 114 breakouts covering a combined length of 3 2 km and a mean hmax orientation of 108 n the inferred mean orientation of hmax in the perth basin is broadly consistent with that in the adjacent basement yilgarn block the new data confirm that hmax orientation in the region is consistent with other stress indicators different depths and different geological provinces the new data also confirm that the orientation of hmax does not parallel the nne direction of absolute plate velocity anomalous north south hmax orientations identified in a number of wells in the perth basin can be attributed to local structural effects

experimental validation of fracture aperture determination from borehole electric microresistivity measurements we studied the electric response of fractures with laboratory experiments and numerical simulations for a full bore formation microimaging tool the laboratory setup was designed and built to perform controlled experiments with accurate measurements of all principal properties involved for electric borehole imaging these properties are formation resistivity mud resistivity fracture aperture pad position and button current the experiments were conducted on two types of limestone for fracture apertures ranging from 0 1 to 0 9 mm and mud formation resistivity contrasts varying from 1 100 to 1 10 000 a numerical model was used to reproduce the laboratory configuration and to validate the results the model proved to be an effective tool to optimize the experimental setup and it was also used to study the effect of standoff up to 5 mm on the measured integrated additional current linear relationships between the fracture aperture and measured integrated current were found to be valid for the laboratory experiment and the corresponding numerical simulation the measured integrated current could therefore be used to determine the fracture aperture if the other parameters are known two coefficients in the relationship were found to differ from those previously found using numerical simulations for the actual borehole situation these differences are attributed to tool and scale dependent factors

metals background and enrichment in the chiloe interior sea sediments chile is there any segregation between fjords channels and sounds abstract the range and spatial distribution of metal concentrations in the chiloe interior sea were investigated from 37 surface sediment samples collected during the cimar 10 fiordos cruise grain size distribution total organic carbon and nitrogen 13c major al fe and biogenic opal and trace cd co cu ni pb and zn elements were determined metal background concentrations of each metal in sediment were defined from linear regression equations of metal versus al as baseline information for future research on the status of sediment contamination in the northern patagonian marine area metal levels in chiloe sediments were of the same order of magnitude as uncontaminated sediments around the world and contamination can be considered negligible moderate normalized enrichment factors lower than 3 in this southern pacific region the chiloe interior sea can be segregated into two zones on the basis of metal content by applying a principal component analysis the first pertains to inner fjords and it has terrestrial origin associated to co cu pb zn and the second zone features channels and gulfs of a predominantly marine source cd cu nevertheless only one background equation is needed to predict metal concentrations in the natural sediment of the chiloe interior sea

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

paleotectonic stress field modeling and prediction of natural fractures in the lower silurian longmaxi shale reservoirs nanchuan region south china abstract natural fractures serve as significant storage spaces for hydrocarbons and are favorable for fluid flow in shale gas reservoirs therefore predicting the intensity and distribution of natural fractures within reservoirs are of extreme significance for shale gas exploration and development natural fractures in the nanchuan region are generally in high dip angles and the dominant fracture strikes are in the ne sw and nw se directions most natural fractures within the longmaxi formation are formed in the late yanshanian period therefore in this study the late yanshanian paleotectonic stress field was numerically investigated the comprehensive rupture rate crr was defined and calculated as an indicator to quantitatively predict the intensity and distribution of natural fractures within the longmaxi formation the results indicated that regions with well developed fractures were mainly located in around fault zones and fold zones among fault fold orientations change and at fault tips the intensity and distribution of natural fractures in the longmaxi formation of nanchuan region were influenced by many factors including tectonic activities mineral compositions etc the present study provides preliminary insights into natural fractures within the longmaxi formation of nanchuan region south china which can guide and support shale gas exploration and development

fracture detection in oil based drilling mud using a combination of borehole image and sonic logs abstract the deeply buried 5 5 7 1 km lower cretaceous bashijiqike sandstones are important fractured reservoirs in the kuqa depression in these high temperature high pressure drilling environments oil based muds are used to limit drilling risks and improve efficiency making facture detection using resistivity based image logs difficult the maximum horizontal stress sh max trends close to north south 0 10 based on orientations of the drilling induced fractures and borehole breakouts core descriptions thin sections and image logs used to describe the fractures in the bashijiqike sandstone reservoirs show that opening mode natural fractures are common and the fractures range from fully open to sealed by calcite and clay minerals the open fractures are dominantly steeply dipping or vertical and primarily strike north south locally horizontal fractures or fractures with low angle dip are detected we compare fracture visibility on image logs acquired in the same ks 2 2 12 key well in oil based mud and water based mud fmi hd logs successfully detect large 0 1 mm aperture vertical fractures in oil based mud better than obmi image logs and the two imaging tools have a similar ability in detecting the high dip angle fractures since the ubi tool is not affected by oil based muds most of the fractures can be picked out on ubi images minor negative deviations of bulk density could be observed in fractured zones and the presence of fractures obviously causes an increase in sonic transit time full waveforms from dsi tools combined with electrical image logs detect fractured zones both the velocity and amplitude of the sonic waves are sensitive to fractures and the fractured zones could be identified according to the attenuation of stoneley waves the combination of cores image logs and full wave sonic logs offers comprehensive detection of fractures in oil based mud environments

sources and timing of trace metal contamination to sediments in remote sealochs n w scotland sediment cores from a transect of sealochs etive sunart nevis duich broom and torridon in n w scotland were analysed for the trace metals lead copper and zinc in addition sediment cores from the clyde sea basin loch fyne the gareloch clyde dumpsite and from the irish and celtic seas were analysed as possible source areas for contaminated particles the sediment cores were dated using excess 210pb and 137cs and al normalisation was used to correct for sediment compositional effects all cores showed increased concentrations of all trace metals and m al towards the surface with a maximum of 280 500 above background being observed in loch etive only cores from duich and torridon zn al and pb al and etive zn al did not continue to show an increase in trace metals to the uppermost samples the burden of atmospherically derived trace metals accumulated over the past 100 years was compared with similar published burdens from a series of freshwater lochs adjacent to the sealochs plots of excess 210pb used to correct for sediment focusing against atmospherically derived pb showed a series of linear relationships of systematically decreasing gradient towards the north west away from potential urban sources of lead it was calculated that 49 15 77 of the pb but only 3 1 4 of the zn and 2 0 3 of the cu reached the sealochs from atmospheric sources the remaining trace metals deposited in the sealochs came from marine particles using trace metal ratios as an indicator of pollutant provenance it was shown that the trace metals came predominantly from the irish sea there was no evidence of trace metals derived from the firth of clyde basin it was concluded that trace metal contamination from the clyde and the surrounding industrialised urban area was mainly deposited in the estuary and the clyde sea basin with its adjoining sealochs such as the gareloch and loch fyne

the effect of magmatic intrusions on coalbed methane reservoir characteristics a case study from the hoskissons coalbed gunnedah basin australia magmatic intrusions can deteriorate coalbed methane reservoir quality by precipitating minerals in natural fracture and cleat system to date the effect of magmatic intrusions on coal rank and maturity has been studied extensively however their impact on fluid flow capacity and gas content is poorly investigated this study evaluates the impact of magmatic intrusions on reservoir characteristics of the hoskissons coal interval in the gunnedah basin eastern australia where numerous coal intrusion associations exist drill stem test dst borehole image logs and core data are used to determine fluid flow characteristics gas content and quality in 14 wells across the gunnedah basin the integration of borehole image logs and dst data analysis enables us to determine the existence openness and hydraulic conductivity of natural fracture and cleat systems in the hoskissons coal interval in addition available desorption canister data gas composition data and conventional well logs are interpreted to investigate probable thermal effect on gas content our analyses of different datasets reveal that the thickness of intrusions and their positions with respect to the hoskissons coal interval are variable in the studied wells permeability varies from 1091 md down to zero owing to heterogeneous fracture and cleat systems interpreted natural fracture cleat systems are well correlated with measured permeability from dst data analysis this highlights the role of open natural fractures cleats in fluid flow characteristics of the hoskissons coal interval results indicate that the mineralizing effect of hydro thermal fluids derived either from magmatic intrusions or coal itself is not a controlling factor in fluid flow capacity of the hoskissons coal interval in the studied wells this is described by either the distance between coal section and major intrusions in some wells or perhaps emplacement of intrusive bodies prior to development of cleat and natural fracture networks the destructive impact of intrusions on permeability is observed in one of the studied wells in which in situ stress perturbation is large due to presence of magmatic intrusions in sedimentary rocks variable in situ stress orientation can decrease fracture connectivity and consequently fluid flow properties are affected gas content largely varies in heat affected coal intervals this signature is the result of thermal effect fading with distance and is more pronounced when intrusions are in close proximity to coal intervals gas composition is variable in the studied wells gas composition data indicate that high quality desorbed gas with methane concentration higher than 90 could be found even in coal intervals which are heavily intruded c 2016 elsevier b v all rights reserved

contemporary tectonic stress pattern of the taranaki basin new zealand the present day stress state is a key parameter in numerous geoscientific research fields including geodynamics seismic hazard assessment and geomechanics of georeservoirs the taranaki basin of new zealand is located on the australian plate and forms the western boundary of tectonic deformation due to pacific plate subduction along the hikurangi margin this paper presents the first comprehensive wellbore derived basin scale in situ stress analysis in new zealand we analyze borehole image and oriented caliper data from 129 petroleum wells in the taranaki basin to interpret the shape of boreholes and determine the orientation of maximum horizontal stress s hmax we combine these data 151 s hmax data records with 40 stress data records derived from individual earthquake focal mechanism solutions 6 from stress inversions of focal mechanisms and 1 data record using the average of several focal mechanism solutions the resulting data set has 198 data records for the taranaki basin and suggests a regional s hmax orientation of n068 degrees e 22 degrees which is in agreement with nw se extension suggested by geological data furthermore this ene wsw average s hmax orientation is subparallel to the subduction trench and strike of the subducting slab n50 degrees e beneath the central western north island hence we suggest that the slab geometry and the associated forces due to slab rollback are the key control of crustal stress in the taranaki basin in addition we find stress perturbations with depth in the vicinity of faults in some of the studied wells which highlight the impact of local stress sources on the present day stress rotation

evaluation of trace metal enrichments from the 26 december 2004 tsunami sediments along the southeast coast of india the tsunami sediments deposited after the december 2004 tsunami were sampled immediately in the coastal environment of tamil nadu state on the southeast coast of india fifty four sediment samples were collected and 14 representative samples were selected to identify the level of metal contamination in tsunami sediments the results indicate that the sediments are mainly of fine to medium grained sand and contain significantly high contents of dissolved salts in sediments na k ca 2 mg 2 cl in water soluble fraction due to seawater deposition and evaporation correlation of acid leachable trace metals cr cu ni co pb zn indicate that fe mn oxyhydroxides might play an important role in controlling their association between them enrichment of trace metals is observed in all the locations with reference to the background samples high values of trace metals in the southern part of the study area are due to the large scale industries along the coast and they are probably anthropogenic in nature and of marine origin which could cause serious environmental problems

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

revel a model for recent plate velocities from space geodesy 1 we present a new global model for recent plate velocities revel describing the relative velocities of 19 plates and continental blocks the model is derived from publicly available space geodetic primarily gps data for the period 1993 2000 we include an independent and rigorous estimate for gps velocity uncertainties to assess plate rigidity and propagate these uncertainties to the velocity estimates the velocity fields for north america eurasia and antarctica clearly show the effects of glacial isostatic adjustment and australia appears to depart from rigid plate behavior in a manner consistent with the mapped intraplate stress field two thirds of tested plate pairs agree with the nuvel 1a geologic 3 myr average velocities within uncertainties three plate pairs caribbean north america caribbean south america and north america pacific exhibit significant differences between the geodetic and geologic model that may reflect systematic errors in nuvel 1a due to the use of seafloor magnetic rate data that do not reflect the full plate rate because of tectonic complexities most other differences probably reflect real velocity changes over the last few million years several plate pairs arabia eurasia arabia nubia eurasia india move more slowly than the 3 myr nuvel 1a average perhaps reflecting long term deceleration associated with continental collision several other plate pairs including nazca pacific nazca south america and nubia south america are experiencing slowing that began 25 ma the beginning of the current phase of andean crustal shortening

distribution and assessment of sediment toxicity in tamaki estuary auckland new zealand heavy metal levels in surface sediments from tamaki estuary demonstrate significant up estuary increases in cu pb zn cd and mud concentrations increased metal levels towards the head of the estuary are linked to local catchment sources reflecting the historical development industrialisation and urbanisation of catchment areas surrounding the upper estuary the relatively narrow constriction in the middle estuary panmure area makes it susceptible to accumulation of upper estuary pollutants since the constriction reduces circulation and extends the time required for fine waterborne sediments in the upper estuary to exchange with fresh coastal water as a result fine fraction sediments trapped in the upper estuary facilitate capture and retention of pollutants at the head of the estuary the increase in sandy mud poor sediments towards the mouth of the estuary is associated with generally low metal concentrations the estuary s geomorphic shape with a mid estuary constriction sediment texture and mineralogy and catchment history are significant factors in understanding the overall spatial distribution of contaminants in the estuary bulk concentration values for cu pb zn and cd in all the studied surface samples occur below anzecc isqg h toxicity values cd and cu concentrations are also below the isqg l toxicity levels for these elements however pb and zn concentrations do exceed the isqg l values in some of the surface bulk samples in the upper estuary proximal to long established sources of catchment pollution