ichnology of fair weather and storm deposits in an upper cretaceous estuary eutaw formation western georgia usa abstract exposures of the eutaw formation in western georgia eastern gulf coastal plain usa were examined to evaluate the ichnologic signature of fair weather and storm related strata deposited within the central bay of a late cretaceous estuary ichnofabrics of fair weather sandy muds and muddy sands compare favorably with those of previously well documented estuarine facies of the cretaceous western interior foreland basin trace fossil assemblages vary with sediment texture reflecting proximity to sources and frequency of deposition of sands but they generally are dominated by simple structures attributed to activities of trophic generalists terebellina teichichnus and planolites although this likely reflects environmental stress associated with estuarine dynamics the degree to which salinity fluctuations governed trace fossil assemblages cannot be confidently assessed trace fossil assemblages in estuarine storm sands also are variable distal central bay tempestites include fair weather ichnofossil suites however commonly in proximal parts of the central bay rapid event related accumulation of suspended clays immediately followed sand emplacement and thereby precluded burrowing of sands by subsequently established fair weather organisms by virtue of proximity to fluvial point sources and or salinity gradients this phenomenon may be unique to and diagnostic of certain estuarine settings ophiomorpha is nearly ubiquitous in storm sands normally attributed to post storm colonization by opportunistic organisms these burrow systems instead may represent the work of storm transported crustaceans

a coupled flow stress damage model for groundwater outbursts from an underlying aquifer into mining excavations abstract uncontrolled groundwater outbursts from underlying limestone aquifers into mining excavations present a significant safety challenge for underground coal mining in china although these mining hazards have been known for decades the mechanism for groundwater outbursts remains elusive a fully coupled flow stress damage model is presented to simulate the progressive development of fractures and the associated groundwater flow under incremental loading conditions resulting from mining processes the model is based on classical theories of porous media flow and damage mechanics and importantly links changes in permeability with the accumulation of damage in following the complete stress strain process this coupled flow stress damage model is applied to examine the influence of mining advance on the initiation extension and evolution of an outburst conduit as it develops adjacent to the mine panel fractures are shown to initiate both from the wings of the excavation in shear and from the center of the floor span in extension the growth of the extensile fractures is stunted by the presence of a high stress abutment but the wing fractures extend with one fracture becoming dominant as the dominant fracture develops into the underlying over pressured zone water pressures transmitted along the now open conduit reduce effective stresses and develop rapid heave displacements within the floor the result is a groundwater outburst the modeling is tuned to the results of laboratory experiments and follows the evolution of a viable outburst path observations corroborate with field measurements of permeability pre and post mining and are strong indicators of the veracity of the approach

simulation analysis of water resource damage feature and development degree of mining induced fracture at ecologically fragile mining area mining induced water damage has become one of wide concerned issues in contemporary society knowing the main causes to water resource damage especially the superficial aquifer damage as well as the damage mode is the basis for realizing water conservation in this paper the mining height and position of aquifuge are regarded as the main influencing factors in analyzing the change of aquifer taking the geological conditions of yili no 4 coal mine as an example a total of 18 numerical analysis models with different mining heights 3 5 8 10 15 20 m and different positions of aquifuge upper middle and bottom as changing conditions were established using universal distinct element code discrete element simulation software the variation characteristics of water resources in aquifers after disturbance were studied the variation of water pressure with mining height and position of aquifuge was analyzed the variation of water pressure in aquifer was proposed as a novel criterion for distinguishing the development degree of mining induced fracture the criterion for determining the failure of aquifer was established based on the ratio of water pressure change and mining height p h which is a pioneering research on the relationship between mining induced fracture and aquifer failure this study provides a reference for evaluating the development degree of mining induced fracture and provides theoretical basis for analyzing the coupling relationship between mining and water resource change in aquifer and for water conservation at ecologically fragile mining area

stress measurements in soft rocks the objective of this paper is to demonstrate that accurate and reliable in situ stress measurements can be performed in soft rocks a quick overview of the mechanical behaviour of soft rocks is presented after reviewing stress measurement techniques that have been used in soft rocks the modified doorstopper technique is presented and the advantages it has over other techniques in soft rocks are underlined results from laboratory simulations in controlled conditions show that the technique is reliable and accurate it is then shown through field applications in a potash mine in brazil in an underwater tunnel in shales in canada and in an exploratory drift in molassic rocks of the french alps how the technique yields results that can sometimes be confirmed by field observations

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

permeability variations within mining induced fractured rock mass and its influence on groundwater inrush this paper is concerned with the evaluation of permeability of fractured rock mass due to the cover stress re establishment which is a major factor in controlling water and gas flow rate induced by mining operations in fractured rock the case study considered in this paper is based on the results of observations of groundwater inrush and a decrease in water inflow from the fractured roof strata due to mining advancing in the taiping coalmine shandong province china a conceptual model of an effective porous media was used to assess the permeability distribution in the fractured zone induced by coal mining the cover stress re establishment in gob fractured rock mass was evaluated using an empirical formula based on the surface subsidence a simplified conceptual model of the fractured zone was used to evaluate the deformation of fractured zone along with the evaluation of changes in the rock permeability above the gob due to the cover stress re establishment these data were then used to calculate the water inflow rate into the panel predicted water inflow rates have been found to be in good agreement with those from monitoring data this study improved the understanding of the mechanisms of the post mining cover stress re establishment on permeability change of the overburden fracture rock strata these results can then be applied for numerical simulations of the process of overburden failure and consequent groundwater inrush due to coal mining

field trials of aquifer protection in longwall mining of shallow coal seams in china the large scale mining of shallow coal seams has a significant impact on the overlying aquifers and surface ecological environment to protect the aquifers and maximize the coal resource recovery field trials were undertaken during the operation of the lw32201 in bulianta coal mine shendong china with a severely weathered rock swr layer and two key strata ks in the overlying strata aquifer protection in longwall mining aplm relies mainly on the rapid advance in some localized zones special measures should be taken to achieve the aplm including lowering mining height backfill and slurry injection to further understand the mechanism and applicable conditions of the aplm and validate the effectiveness of the aplm variation of the water table in the aquifer was observed as the longwall face passed through the zone this paper also discusses the mechanism and basic requirements of the aplm and the relationship between the fall of the water table and the surface subsidence the results of the field trials indicated that aplm in shallow coal seams could be successful under suitable conditions

faulting associated with historical and recent earthquakes in the eastern mediterranean region summary this paper summarizes evidence for surface faulting in historical and recent earthquakes in the eastern mediterranean region and in the middle east such information is particularly important for studies of active tectonics and for palaeoseismology we have found 78 cases of faulting pre 1900 and 72 post 1900 some of which show that faults that have apparently been inactive this century had already ruptured before 1900 for some cases faulting could not have been predicted from 20th century activity and in others it could have been expected but has not been observed during the instrumental period the data are suycient to allow the derivation of relationships between magnitude and rupture length

tectonic evolution of the marmara sea and its surroundings abstract the basins in the marmara sea are the products of a superimposed evolutionary history defined by two different aged fault systems the early miocene early pliocene thrace eskisehir fault zone and its branches and the late pliocene recent north anatolian fault and its branches the thrace eskisehir fault and its westward branching secondary fault systems define the early neotectonic signature in the region the late neotectonic period started at the end of the early pliocene when the north anatolian fault divided the thrace eskisehir fault into four parts during the late neotectonic period the north anatolian fault extended westward as a number of splays by joining with the ganos bandirma behramkale and manyas edremit fault zones the branches of the north anatolian fault zone nafz caused the evolution of a number of basins which differ in character depending on the trend and past characteristics of the older branches that became connected since the northern branch of the north anatolian fault is connected to the n80 e trending ganos fault zone gfz in the west a single buried fault has developed in the marmara sea causing the well known troughs and ridges superimposed onto the negative flower structure formed by the gfz in the early neotectonic period the middle strand which extends from iznik lake to bandirma is oriented east west up to the n60 e trending bandirma behramkale fault zone then turns southward in the vicinity of bandirma forming a region dominated by compressional tectonics this bending caused n30 e trending tension in addition to the strike slip motion between the eastern part of gemlik bay and bandirma bay the southern branch of the nafz on the other hand produced three pull apart basins with different characteristics along the yenisehir bursa and manyas segments the southern branch of the nafz connected to the manyas edremit fault zone which is oriented n45 e to the south of manyas and the associated bending and rotation caused a n15 e trending extension in addition to the strike slip regime between manyas and uluabat the branches of north anatolian fault cut through the thrace eskisehir fault at three places the east marmara sea region in gemlik bay and to the east of bursa giving lateral offsets of 58 59 7 8 and 10 11 km respectively the cumulative motion is 75 78 km corresponding to the total lateral offset of the north anatolian fault in the region the correlation of these offsets with global positioning system slip vectors and with stratigraphic results implies that the north anatolian fault reached into the marmara sea region about 3 5 million yr ago tectonic processes forming the marmara sea and its environs were initiated by the thrace eskisehir fault and its splays have been most recently controlled by the north anatolian fault and its splays during the last 3 5 million yr

mining induced strata stress changes fractures and gas flow dynamics in multi seam longwall mining abstract this paper presents key findings from a recent comprehensive study of longwall mining induced strata movement stress changes fractures and gas flow dynamics in a deep underground coal mine in anhui china the study includes field monitoring of overburden displacement stress and water pressure changes at the longwall panel 1115 1 of the guqiao mine in addition 3d modelling of strata behaviour at the longwall panel using a 3d finite element code and goaf gas flow simulations with a cfd code are carried out this research has resulted in many new insights into the complex dynamic interaction between mining induced strata stress changes fractures and gas flow patterns based on the findings from the field monitoring and numerical modelling a three dimensional annular shaped overlying zone along the perimeter of the longwall panel is identified for optimal methane drainage during mining a practical method that helps define the geometry and boundary of this zone is proposed this study provides a new methodology and a set of engineering principles for the design of optimal co extraction of coal and methane

delineation of large localized damage structures forming ahead of an active mining front by using advanced acoustic emission mapping techniques abstract we applied advanced mapping techniques to 291 230 acoustic emission ae events as small as around m 4 that were recorded over 50 days by an ultra high resolution network close to the active front of a tabular mining stope being advanced northward at 1 km depth in the cooke 4 gold mine in south africa we first applied joint hypocenter determination jhd to improve absolute locations and then applied the double difference relative location algorithm to the jhd output these steps resolved the seemingly continuous dense cloud of aes that extend about 20 m ahead of the stope front into several discrete steeply dipping tabular clusters a few meters thick and 10 30 m in dip extent separated by quiet intervals a few meters thick the clusters have a strike parallel to the stope face and a dip of about 65 resembling commonly observed large shear fractures along the plane of maximum shear ortlepp shears in general the activity of the clusters changed in similar ways as the stope face advanced but each cluster remained stationary and the gaps between clusters were impressively quiet this study demonstrates that high resolution ae mapping can delineate the formation of large structures of localized damage in the highly stressed intact rock mass ahead of the stope face a process that may culminate in hazardous seismic events

upper cretaceous depositional sequences in the alabama gulf coastal plain their characteristics origin and constituent clastic aquifers abstract in central and eastern alabama there are 13 upper cretaceous late santonian to latest maastrichtian 85 to 67 ma depositional sequences in the outcrop and shallow subsurface stratigraphic section each depositional sequence is composed of paralic and shelfal facies associations within their transgressive and highstand systems tracts within each depositional sequence the gross depositional strike mode and specific position of shoreline trend are both directly related to second and third order changes of sea level respectively depositional sequence paleogeography and the sedimentary facies relations within depositional sequences and their constituent systems tracts both transgressive and highstand dictate the distribution of coarse clastic paralic aquifer facies that have s gnificant primary permeabilities the coarse clastic facies specifically barrier island and lower shoreface facies are significant local confined clastic aquifers that taken together constitute significant regional aquifer systems all depositional sequences and the facies tracts within them have locally and regionally correlative bounding surfaces of hydrogeologic significance

the sea of marmara a plate boundary sea in an escape tectonic regime abstract the sea of marmara is dissected by two major fault systems the first consists of two east west striking transtensional boundary faults and a number of secondary faults subparallel to them the second is made up of ne sw trending subvertical strike slips and their conjugates oriented nw se that offset the first system these fault systems segment the deep marmara sea into 5 blocks that are either rhomboidal lazy z or wedge shaped three of these blocks may be interpreted as pull apart basins characterized by transtension while the other two sill areas which separate the basins are transpressional push up structures the blocks are subjected to rapid episodic subsidence but they also undergo pervasive vertical motions and possible rotations relative to one another the sedimentary column above the acoustic basement mapped within the sea of marmara can be divided into 3 seismic units a folded and truncated pre transform unit and two syn transform units the lower thick syn transform unit exhibits 3 distinct seismic facies a well stratified basin fill facies cut by subvertical growth faults a push up facies with a contorted or chaotic internal configuration and a slump facies the observed neotectonic and sedimentary regimes result from compressional movement between eurasia and africa which has led to major dextral transform movements along the north anatolian fault zone escape tectonics and from the fact that this fault zone splinters into two overlapping right stepping oblique master faults at the eastern and western border of the sea of marmara respectively

hotspot origin of the mississippi embayment and its possible impact on contemporary seismicity abstract previous authors have related the late cretaceous early tertiary subsidence of the mississippi embayment to the opening of the gulf of mexico but the gulf opened earlier in triassic jurassic time we offer an alternative hypothesis that development of the embayment was coeval with the passage of the mississippi valley graben system over the bermuda hotspot about 90 ma several lines of evidence of significant uplift of the embayment axis accompanying mid cretaceous magmatism and prior to late cretaceous subsidence support this proposal first reactivation of the pascola arch in the northern embayment is recorded by flanking deposits of basal upper cretaceous gravel second beneath a regional mid cretaceous unconformity subcrops of jurassic and early cretaceous strata define a pronounced southwest plunging arch in the southern embayment this arch is collinear with an arch revealed in paleozoic rocks after restoration to mid cretaceous structural geometries third a deep weathering profile on mid cretaceous alkalic plutons along the western embayment margin is nonconformably overlain by paleocene sediments and rapid mid cretaceous cooling of these intrusions has been interpreted from apatite fission tracks moreover exploratory holes along the embayment axis encountered similar weathered alkalic intrusions nonconformably overlain by basal upper cretaceous strata fourth there was an anomalous influx of clastic sediment into the northern gulf of mexico during mid cretaceous time and subsequent clastic facies patterns suggest the mississippi river drainage began to enter the gulf in the late cretaceous passage of the mississippi valley graben over the bermuda hotspot during elevated hotspot activity of cretaceous time may have significantly weakened the previously rifted lithosphere rifted continental margin at charleston south carolina also passed over this hotspot in latest cretaceous time similarly the st lawrence rift system passed over the great meteor hotspot during the cretaceous it is important to note that these rift systems are the principal loci of strong seismicity in eastern north america and thus weakening by increased cretaceous hotspot activity may be an important common factor for these seismic rift zones

structural relationship between the sea of marmara basin and the north anatolian fault zone the north anatolian fault naf zone is 1500 km long extending almost up to the greek mainland in the west it is a seismically active right lateral strike slip fault that accommodates the relative motion between the turkish block and black sea plate the sea of marmara lies along the western part of the naf and shows evidence of subsidence in this area pure strike slip motion of the fault zone changes into extensional strike slip movement that is responsible for the creation of the sea of marmara and the north aegean basins the northern half of the sea of marmara is interpreted as a large pull apart basin this basin is subdivided into three smaller basins separated by strike slip fault segments of uplifted blocks ne sw basinal areas are covered by horizontally layered sedimentary sequences uplifted blocks have undergone compressional stress all the blocks are subsiding and are undergoing vertical motions and rotations relative to one another the uplifted blocks exhibit positive bouguer gravity anomalies according to gravity interpretation there is relative crustal thinning under the sea of marmara the northern side of the sea of marmara is marked by a distinctive deep rooted magnetic anomaly which is dissected and shifted southward by strike slip faulting the southern shelf areas of the sea of marmara are dominated by short wavelength magnetic anomalies of shallow origin

shallow marine impact origin of the wetumpka structure alabama usa the wetumpka structure an arcuate 7 6 km diameter rimmed feature of the inner coastal plain alabama is a late cretaceous shallow marine impact crater in this paper we show unequivocal evidence of wetumpka s impact origin within and about this structure pre existing upper cretaceous stratigraphy was resedimented and or deformed thus creating distinctive intra structure and extra structure terrains these terrains are located respectively within wetumpka s crystalline rim terrain and adjacent to the structure on the southern side core drilling near the structure s geographic center revealed that wetumpka s basin filling sequence has two distinctive units suggestive of a two stage filling process consisting of 1 fall back plus resurge followed by 2 a later secondary seawater resurge event wetumpka s lower subsurface unit includes polymict impact breccias which contain quartz grains displaying shock characteristic multiple sets of planar deformation features selected subsurface samples of this breccia also contain elevated ir co ni and cr concentrations indicative of a minor extraterrestrial component 9 2002 elsevier science b v all rights reserved

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

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

tectonic elements controlling the evolution of the gulf of saros northeastern aegean sea turkey abstract tectonic elements controlling the evolution of the gulf of saros have been studied based upon the high resolution shallow seismic data integrated with the geological field observations evolution of the gulf of saros started in the middle to late miocene due to the nw se compression caused by the counterclockwise movement of the thrace and biga peninsulas along the thrace fault zone hence the north anatolian fault zone is not an active structural element responsible for the starting of the evolution of the gulf of saros the compression caused by the rotational movement was compensated by tectonic escape along the pre existing ganos fault system two most significant controllers of this deformation are the sinistral ganos fault and the dextral northern saros fault zone both extending along the gulf of saros the most important evidences of this movement are the left and right oriented shear deformations which are correlated with structural elements observed on the land and on the high resolution shallow seismic records at the sea another important line of evidence supporting the evolution of this deformation is that the transgression started in the early late miocene and turned as a result of regional uplift into a regression on the gelibolu peninsula during the turolian and in the north of the saros trough during the early pliocene the deformation on the gelibolu peninsula continued effectively until the pleistocene taking into account the fact that this deformation affected the late pleistocene units of the marmara formation the graben formation of the gulf of saros is interpreted as a recent event however at least a small amount of compression on the gelibolu peninsula is observed it is also evident that compression ceased at the northern shelf area of the gulf of saros

frequency magnitude distribution of 3 7 mw 1 mining induced earthquakes around a mining front and b value invariance with post blast time we investigated frequency magnitude distribution fmd of acoustic emissions ae occurring near an active mining front in a south african gold mine using a catalog developed from an ae network which is capable of detecting aes down to m w 5 when records of blasts were removed fmds of aes obeyed a gutenberg richter law with similar b values not depending on post blasting time from the initial 1 min interval through more than 30 h this result denies a suggestion in a previous study richardson and jordan bull seismol soc am 92 1766 1782 2002 that new fractures generated by blasting disturb the size distribution of background events which they interpreted as slip events on existing weak planes our ae catalog showed that the gr law with b 1 2 was valid between m w 3 7 and 0 for aes around the mining front further using the mine s seismic catalog which covers a longer time period of the same area we could extend the validity range of the gr law with the same b value up to m w 1

height of the mining induced fractured zone above a coal face abstract the development height of a gas conducting fracture zone gfz in the gob overlying strata is crucial to the gas drainage and safe production of a coal mine in order to address the issues of excessive gas concentration and uncertain gfz height in no 7435 face overlying strata of kongzhuang coal mine china the caving characteristics of overlying strata were explored using both physical experiments on similar materials and numerical simulations of particle flow code pfc software and verified each other the relationship of cracks development to porosity changing characteristics was introduced to quantitatively determine the height of the local gfz the quantified gfz heights were compared with those measured using the in situ drilling flow method the results showed that 1 pfc software could accurately simulate the overlying strata caving behaviors thus saving manpower materials and financial resources needed for related physical experiments and 2 the temporospatial distribution characteristics of porosity could be used to forecast gfz height and are of significant importance for determination of gfz overall the conclusions are of engineering significance for accurate arrangement of boreholes for gas drainage and reduction of mine gas disasters

kinematics and evolution of the northern branch of the north anatolian fault ganos fault between the sea of marmara and the gulf of saros abstract the wsw ene trending ganos fault is a dextral strike slip fault running parallel to and southwest of the west marmara trough and south of the saros trough dextral structures started evolving in the early miocene and at this time the ganos fault system developed from a part of the thrace eskisehir fault system beginning in the late pliocene 3 5 ma the north anatolian transform fault propagated into the marmara region and captured the ganos fault subsequently this fault has accommodated the westward movement of the anatolian block because of the curvature of the microplate boundary in this area the ganos fault system has tended to rotate counterclockwise farther west in the gulf of saros the strike slip motion was accommodated by a new fault on the northern margin of the gulf rather than along the northern coast of the gelibolu peninsula as previously thought this interpretation differs from previous assessments of the position of the northern strand of the north anatolian fault marmara segment in the marmara sea and in the gulf of saros the role of the ganos fault proposed in this paper is considerably different from that proposed by earlier studies while the revised orientation of the north anatolian fault on land is about 7 different than specified by previous authors at sea it is different by 32 counterclockwise and 23 clockwise in the west marmara and saros submarine depressions respectively the revised position of the ganos fault in the marmara sea derived from shallow and conventional seismic reflection data calls into question the validity of evolutionary models previously used in kinematic and stress failure analyses in particular it is not possible to regard the marmara sea as a pull apart basin and the gulf of saros as a transtensional half graben furthermore palinspastic maps taking into account the revised position of the ganos fault and gps slip vectors support the idea that a dextral master fault is present to the north of the saros trough with a sinistral oblique fault dominated by normal offset gelibolu fault to its south the gelibolu fault is reactivated in a limited region

active faults and evolving strike slip basins in the marmara sea northwest turkey a multichannel seismic reflection study abstract the north anatolian fault is a 1200 km long transform fault forming the boundary between the anatolian and eurasian plates near its western end it strikes through the marmara sea and is responsible for the creation of three deep marine depressions the north anatolian fault system and the linked basins in the eastern marmara sea were studied using newly acquired multi channel seismic reflection data in the marmara sea the north anatolian fault consists of a main strand and a few subsidiary branches the main strand is made up of the ganos 15 km long central marmara 105 km and north boundary 45 km fault segments the north boundary fault joins in the east to the izmit segment which was ruptured during the m s 7 4 earthquake on 17 8 1999 the north boundary fault is highly oblique to the regional displacement vector which results in the generation of a symmetrical fault wedge basin this cinarcik basin is a wedge shaped deep marine depression south of istanbul it is about 50 km long up to 20 km wide and 1250 m deep and is filled with pliocene to quaternary sediments over 3 km thick the north boundary fault joins in the west to the transpressional central marmara fault around the restraining segment boundary the syntransform sediments are being deformed into a large anticlinorium the cinarcik basin started to form when the westward propagating north anatolian fault intersected a northwest trending pre existing fault zone during the pliocene and bifurcated into nw and sw trending segments forming a transform transform transform type triple junction dextral strike slip movement along the arms of the triple junction led to the development of the cinarcik basin the present fault geometry in the marmara region was achieved later during the mid pliocene following the termination of the triple junction geometry south of the main north anatolian fault system there is a second active strike slip fault in the marmara sea made up of several segments a highly asymmetrical fault bend basin comprising pliocene quaternary sediments over 2 5 km thick is forming along a releasing fault segment of this south boundary fault system

the kazova basin an active negative flower structure on the almus fault zone a splay fault system of the north anatolian fault zone turkey abstract the kazova basin is located within the almus fault zone afz a splay fault system of the north anatolian fault zone in the central pontides turkey it is a 0 7 10 km wide 60 km long wedge shaped right lateral strike slip depression bounded by the mercimekda i camdere fault set in the north and the tokat fault set in the south the kazova basin is superimposed on pre pliocene basement rocks while its basin fill comprises the pliocene to lower quaternary kizkayasi and cerci formations and quaternary alluvials the mercimekda i camdere and tokat fault sets of the afz the basin margin faults of the kazova basin have a considerable amount of normal separation and show a divergent character here the kazova basin is interpreted as an active negative flower structure where the combination of normal movement extension along the different segments of the afz and the oblique extension between its branching splays resulted from a natural response to the anticlockwise rotation along the afz are suggested basin forming mechanism this kind of basin is first from turkey although different types of strike slip basins such as fault wedge pull aparts composite pull aparts are widely represented and well known

development of asymmetric basins along continental transform faults abstract many basins associated with wrench or transform faults are asymmetrical both longitudinally and laterally the sense of basin asymmetry changes along the strike of transform faults geophysical data from the dead sea rift and other transforms indicate that wrench induced asymmetric basins are bounded on only one side by a transform fault this implies that during the evolution of such basins maximum compression was parallel to the transform the direction of extension can change during the geologic evolution of a basin a possible explanation of this observation takes the strength of the fault into into consideration in the case of a weak fault in a strong crust the horizontal principal stresses would probably rotate to orientations parallel and perpendicular to the fault thus minimizing the shear stress on the main fault basins formed by regional extension such as in the east african rift system sometimes show similar features recent studies have shown that these basins often undergo oblique extension this suggests that the asymmetry in these basins may result from simultaneous strike slip motion and fault normal extension similar to the way asymmetry is produced in large transform basins periods of oblique extension can alternate with periods of orthogonal extension the asymmetry formed during periods of oblique extension is often preserved in the stratigraphic record

numerical simulation and experimental study on floor failure mechanism of typical working face in thick coal seam in chenghe mining area of weibei china the hydrogeological conditions of weibei coalfield in china are complex the main mining no 5 coal seam is seriously threatened by ordovician limestone karst water disaster at the bottom of coal measures chenghe no 2 mine is a typical example with the increase of mining depth confined water pressure increases year by year to find out the law of floor deformation and failure caused by no 5 coal seam mining in chenghe no 2 coal mine this paper takes 24 508 working face of chenghe no 2 coal mine as engineering geological background and carries out research by numerical simulation and field test methods the stress field displacement field distribution law and plastic zone evolution characteristics of no 5 coal seam roof and floor varying with the advancing degree of mining face are obtained by simulation calculation the progressive failure process of the whole floor stratum is reproduced dynamically and the development height of the water conducting fracture zone of overburden is given the maximum failure depth of the floor occurs at the mining distance of about 1 5 times the mining width at which time the saddle shape supporting pressure arch reaches its maximum at the same time the multi point separated layer displacement meter is used to carry out field measurements the results show that the maximum failure depth of floor occurs in the goaf and the maximum range of the relative displacement of the floor is 8 0 8 5 m which is close to 6 1 m from the coal mining surface consistent with the results of the numerical simulation comprehensive analysis shows that the maximum failure depth of coal seam floor in chenghe no 2 coal mine is 8 3 m the conclusion provides a favorable basis for the rational formulation of water disaster control countermeasures it provides reference and experience for mining under safe water pressure of aquifuge for prevention and cure water of similar working face in chenghe mining area in the future

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