experiments on non channelized turbidity currents and their deposits abstract large scale experiments on non channelized turbidity currents show that a wide flow opening angle forms and a rapid dilution of the current with distance takes place the thickness of the deposit decreases radially away from the source resulting in tongue shaped isopachs the mean grain diameter also decreases with distance while the sorting improves with increasing distance the following succession of bedforms was observed non deposition parallel lamination ripples parallel lamination this corresponds to the b c and d division of the bouma sequence for turbidites the experiments are in good agreement with the models presented by bouma mutti and ricci lucchi and walker for classical turbidites in the depositional lobes of submarine fans

effect of mechanical interaction on the development of strike slip faults with echelon patterns abstract the overlapping geometry of echelon strike slip faults is well known we have quantified this observation by measuring the amount of overlap and separation and plotting them against each other for over 120 examples although there is large scatter the data show a linear trend suggesting that the overlap increases proportionally with separation up to a limiting value we have analyzed this conspicuous relationship in terms of fault interaction by using a numerical model based on displacement discontinuity the results show that fault interaction is in fact an important factor in contributing to the overlapping geometry of echelon strike slip faults

shear fracture patterns and connectivity at geometric complexities along strike slip faults shear fracture patterns and connectivity at geometric complexities such as echelon fault steps and fault bends along strike slip faults are investigated by simulating shear fracture propagation paths using a displacement discontinuity boundary element method together with a maximum distortional strain energy density criterion it is shown that shear fracture patterns and connectivity depend on the specific geometric configurations the applied stress orientations and the coefficient of friction for a given initial configuration of the major faults the subsequent patterns of the associated shear fractures and their linkage can be predicted if the remote state of stress and the coefficient of friction are known the analyses of fault geometries commonly encountered in nature have important implications for evaluating the effect of faults on fluid flow and earthquake hazards associated with the geometric complexities along strike slip faults in the upper crust

formation of compound strike slip fault zones mount abbot quadrangle california abstract numerous strike slip fault zones in granitic rocks of the mount abbot quadrangle california developed from steeply dipping subparallel joints these joints generally were less than 50 m long and were spaced several centimeters to several meters apart some joints subsequently slipped and became small faults simple fault zones formed as oblique dilatant fractures splay fractures linked non coplanar faults side to side and end to end these simple fault zones are as much as 1 km long and accommodated displacements as great as 10 m compound fault zones formed as splay fractures linked small faults and simple fault zones they are as much as several kilometers long and accommodated displacements as great as 100 m these zones are distinctly different from riedel shear zones and the mechanics of their formation are unlikely to be described well by mohr coulomb mechanisms simple and compound fault zones are composed of non coplanar segments that join at steps or bends splay fracture length determines step widths the longest splay fractures occur along the longest fault zones allowing step widths to increase as the length and displacement across the zones increase these findings are consistent with the structure of some active seismogenic faults and they provide a mechanically consistent field based conceptual model for fault zones that grow in basement rocks from a preexisting set of joints

mesoscale strike slip faults and damage zones at marsalforn gozo island malta well exposed strike slip faults in limestones in the north western part of gozo show damage zones that can be grouped into three categories based on their location along faults tip damage linking damage and distributed damage the predominant fracture types within damage zones include extension fractures and secondary faults tip damage zones usually show wedge shaped patterns formed by antithetic faults and extension fractures commonly accompanied by block rotation several fractures are combined at linking damage zones typically with the concentration of a high intensity of fractures structures in distributed damage zones are typically similar to the classical riedel shear pattern evolutionary and 3d models are proposed in terms of the geometries of damage zones for small displacement strike slip fault zones different evolutionary routes depend on fault tip modes and locations

simulating brittle fault growth from linkage of preexisting structures many researchers have proposed conceptual models of fault development that are based on the linkage of preexisting structures such as isolated faults joints or veins to date such models largely use theoretical mechanics to explain the detailed damage zone geometries observed in linkage structures in this paper we present the first numerical simulations of the temporal and spatial development of geometrically complex fault linkage structures using the finite element model for fault damage zone evolution mopedz simulations show spatial and temporal fault zone evolution for a range of preexisting joint or fault geometries and stress conditions simulations show that linkage geometries are governed by three key factors the stress ratio the original joint geometry such as contractional or dilational configurations and the orientation of the principal stress simulated linkage structures display close correspondence to field observations of fault zone geometry with all secondary and tertiary damage features being reproduced the research also demonstrates that given information on the regional stress conditions numerical modeling can be used to predict fault zone geometries and hence identify the most and least likely structures for promoting fluid flow

formation of listric normal faults by extensional duplexing a case study from the active langshan piedmont fault nw china abstract the development of normal faults is controlled by many factors among which mechanical layers or pre existing fabrics play an important role in the growth of normal faults it is widely accepted that normal faults are rarely continuous surfaces but are zones composed of fault segments heterogeneously distributed fault rocks of various compositions slip bands blocks and other deformation elements listric normal faults particularly those developed in metamorphic crystalline rocks or preexisting fabric developed basements may be composed of subparallel faults in cross sections linked by extensional duplex structures here we choose a listric rift bounding fault rooted in foliation developed basements the langshan normal fault in the northwest corner of the ordos block to conduct an outcrop analysis of fault geometry and linkage behavior from cross sectional views the langshan normal fault zone is composed of mixed regions of high and low angle segments linked by duplex structures at various scales mylonitic foliations play a significant role in the formation of fault segments and the evolution of the listric fault zones lines of evidence show that small en echelon faults initiated from preexisting foliations local stress perturbation between overstepping faults results in the formation of duplex structures and displays a high fracture density which serve to the coalesce of fault segments consequently the progressive localization of strain onto a large listric fault is achieved by progressive development of extensional duplexing among fault segments in cross sections these extensional duplexes imply a scale invariant property based on which we can extrapolate this pattern occurs on larger scales and is verified by seismic data the case of langshan piedmont fault demonstrates the possibility of a listric fault being formed by subparallel planner faults and highlights the effects of preexisting fabrics on the evolution of listric faults especially in basement fabrics developed regions along the fault

experiments on self channelized subaqueous fans emplaced by turbidity currents and dilute mudflows the passage of turbidity currents over submarine fans often results in intense channelization the channels are typically bounded by levees and they vary from mildly to strongly meandering the process of self channelization remains however somewhat obscure preliminary experiments reported here demonstrate for the first time that self channelization of subaqueous fans by turbidity currents can be reproduced at laboratory scale the same experiments also illustrate self channelization by dilute mudflows the resulting weakly sinuous channels can be predominantly depositional predominantly erosional or some combination of the two the channels can elongate to the length of the entire reach available for their formation they can show both gradual shift and avulsion a necessary condition for the formation of intricate channelization in the laboratory experiments appears to be a turbidity current that is insufficient to cover the entire area of the fan at any given time loose field analogs to the experimental channelized fans i e analogs that are imprecise but contain many similarities can often be found at the distal end of submarine fans two possible examples are cited one from the pochnoi system bering sea and one from the gulf of cadiz

seventeenth canadian geotechnical colloquium the effect of cohesion loss and stress path on brittle rock strength stress strain curves for brittle rocks show three characteristic stress levels crack initiation long term strength and peak strength damage controlled testing at low confining stresses has shown that the long term and peak strengths are sensitive to the amount of induced damage i e the greater the amount of damage the lower the long term and peak strengths these tests also showed that the brittle failure process is characterized by a loss of cohesion as friction is mobilized excavation of a circular test tunnel in massive brittle rock resulted in failure around the tunnel the back calculated strength for the failed rock around the tunnel is approximately one half of that measured in laboratory tests crack induced damage of lac du bonnet granite both in the laboratory and in situ begins when the load exceeds approximately one third of the unconfined compressive strength however the stress level associated with failure is a function of loading path in the laboratory where the loading path monotonically increases the ultimate strength of an unconfined sample is 225 mpa numerical studies suggest that in situ the loading path around the tunnel is more complex involving stress increase and decrease and stress rotation for this loading path failure initiates at a stress between 100 and 120 mpa conventional frictional failure criteria did not adequately predict the extent of brittle failure measured around the circular tunnel the results from the damage controlled laboratory tests and the microseismic monitoring carried out during tunnel construction indicate a constant deviatoric stress criterion is a reliable indicator for predicting the onset of damage this criterion was also found to give a reasonable prediction for the maximum depth of failure around the test tunnel the fundamental assumption in the constant deviatoric stress criterion is that at low confining stresses such as those which occur around underground openings the brittle failure process is dominated by cohesion loss

noninvasive methods for hydraulic characterization of density currents with application to submarine fan experiments abstractlaboratory experiments are a convenient way to study morphodynamic processes associated with subaqueous fans however the flows driving such systems can be difficult to hydraulically characterize due to the shallowness of the flows the spatial and temporal dynamics of the autogenic channels and the mixing at the interface of the ambient fluid and density current the objective of this study is to develop a set of methods to quantify hydraulic variables in laterally unconstrained and morphologically active density currents herein a methodology is presented capable of characterizing a density current flow field with direct application to submarine fan experiments this is done with a combination of 1 particle tracking velocimetry ptv analysis of tracers within the density current 2 flow width measurements from overhead images and 3 solution of the mass and volume conservation equations in one dimension to obtain layer averaged velocity depth and fractional excess density

energy budget and propagation of faults via shearing and opening using work optimization we present numerical models of faults propagating by work optimization in a homogeneous medium these simulations allow quantification and comparison of the energy budgets of fault growth by shear versus tensile failure the energy consumed by growth of a fault wgrow propagating by in line shearing is 76 of the total energy associated with that growth while 24 is spent on frictional work during propagation wgrow for a fault propagating into intact rock by tensile failure at an angle to the parent fault consumes 60 of the work budget while only 6 is consumed by frictional work associated with propagation following the conservation of energy this leaves 34 of the energy budget available for other activities and suggests that out of plane propagation of faults in earth s crust may release energy for other processes such as permanent damage zone formation or rupture acceleration comparison of these estimates of wgrow with estimates of the critical energy release rate and earthquake fracture energy at several scales underscores their theoretical similarities and their dependence on stress drop

seismicity relocation and fault structure near the leech river fault zone southern vancouver island relatively low rates of seismicity and fault loading have made it challenging to correlate microseismicity to mapped surface faults on the forearc of southern vancouver island here we use precise relocations of microsciesmicity integrated with existing geologic data to present the first identification of subsurface seismogenic structures associated with the leech river fault zone lrfz on southern vancouver island we used the hypodd double difference relocation method to relocate 1253 earthquakes reported by the canadian national seismograph network cnsn catalog from 1992 to 2015 our results reveal an 8 10 km wide nne dipping zone of seismicity representing a subsurface structure along the eastern 30 km of the terrestrial lrfz and extending 20 km farther eastward offshore where the fault bifurcates beneath the juan de fuca strait using a clustering analysis we identify secondary structures within the nne dipping fault zone many of which are sub vertical and exhibit right lateral strike slip focal mechanisms we suggest that the arrangement of these near vertical dextral secondary structures within a more general ne dipping fault zone located 10 15 km beneath the leech river fault lrf as imaged by lithoprobe may be a consequence of the reactivation of this fault system as a right lateral structure in crust with a pre existing nne dipping structural fabric our results provide the first confirmation of active terrestrial crustal faults on vancouver island using a relocation method we suggest that slowly slipping active crustal faults especially in regions with pre existing foliations may result in microseismicity along fracture arrays rather than along single planar structures

numerical simulation of progressive rock failure and associated seismicity in this paper a numerical approach to modeling progressive failure leading to collapse in rock and associated seismicity is reported in the first part a newly developed numerical code rfpaz rock failure process analysis is introduced the program allows modeling of the observed evolution of damage and associated seismic events due to progressive failure leading to collapse in brittle rock there are three features distinguishing the approach from conventional numerical methods such as fem 1 by introducing heterogeneity of rock parameters into the model rfpaz can simulate non linear behavior in rock using a linear method 2 by introducing elastic modulus reduction for failed elements rfpa2d can process discontinuum mechanics problems by a continuum mechanics method and 3 by recording the event rate of failed elements the seismicities associated with the progressive failure in rock can be simulated in the second part of the paper the applications of rfpa2d in simulating geological process and in solving mining design problems are illustrated numerical simulation of a fault initiation process indicates that some of the important phenomena such as coalescence of microfracture the nucleation and growth of crack clusters fault initiation and development elastic rebound dilatation uplift and seismic behavior etc can be simulated with this numerical code the simulation of progressive failure leading to collapse in underground openings demonstrates the capacity of this code in solving mining design problems

hydraulics of shallow and stratified mixing channel the properties of buoyant and dense discharges in a horizontal mixing channel are evaluated analytically and experimentally the mixing channel is shallow of specified length and roughness and connected to a reservoir or stream the flow in the channel consists of a mixing zone and a gradually varied counterflow mixing modes associated with four possible interactions are described a hydraulic theory is formulated and used to develop synthesized dilution curves experiments conducted in a laboratory flume confirmed the existence of four mixing modes and dilution measurements are consistent with predicted trends in practice the theory would be useful in the design and operation of such a facility

the kinematics of turbulent suspension currents turbidity currents on inclined boundaries abstract turbulent suspension currents are investigated theoretically and experimentally for a wide density range of suspended particles it was found that suspension currents approach an equilibrium state normal state with a balance between gravity entrainment of ambient water bottom friction and the sedimentation of suspended particles for given boundary conditions the equilibrium state can be described by only four characteristic and easily measurable parameters such as a velocity a length or time scale a scale for the buoyancy and one for the buoyancy loss due to sedimentation an important dimensionless product is the sedimentation number which is proportional to the rate at which the buoyancy is lost and which remains approximately constant during an experiment other dimensionless products such as the richardson number are therefore also spatially invariant a large sedimentation number decreases the richardson number and the latter is always smaller for suspension currents which loose sediment than for density currents without buoyancy loss in the case of the geologically important suspension clouds currents fed by an instantaneous source e g a slump experimental and field data suggest an invariant number g sed u 2 which contains the thickness of the deposit the densimetric gravitational acceleration acting on the bulk of the deposit g sed and the front velocity of the current u the magnitude of the invariant number is about 0 3

role of grain size in phyllonitisation insights from mineralogy microstructures strain analyses and numerical modeling abstract brittle y and p planes exist in an exposure of greywacke in the garhwal lesser himalaya india although y planes are well developed throughout the p planes are prominent only in some parts domain a and not elsewhere domain b to investigate why the p planes developed selectively the following studies were undertaken 1 clay separated xrd analyses clinochlore and illite are present in both the domains 2 strain analyses by rf method it deduces strain magnitudes of 1 8 for the ductile deformed quartz grains from both the domains a and b 3 grain size analyses of quartz clasts domain a is mostly composed of finer grains area up to 40 000 m2 whereas domain b consists of a population of coarser grains area 45 000 m2 a 2d finite element modeling of linear elastic material was performed using comsol software to investigate the control of grain size variation on the generation brittle shear planes the results of numerical modeling corroborate the known fact that an increase in grain size reduces the elastic strain energy density a broader grain size distribution increases the effects of diffusion creep and resists the onset of dislocation creep thus rocks with coarser grain population domain b tend to resist the generation of shear fractures unlike their fine grained counterpart domain a

distant off fault damage and gold mineralization the impact of rock heterogeneity field observations have established that fault related damage can occur at locations far from the principal slip surface which are well outside the fractured region currently predicted by models of fault damage we use a finite element model to simulate fracture initiation due to fault linkage and show how variations in rock properties allow off fault damage to develop at surprisingly large distances away from the main fault off fault damage continues to grow even after two adjacent closely spaced fault segments have interacted and linked we demonstrate that this process was important for the formation of fracture hosted gold deposits in the mount pleasant goldfield western australia the strength of lithological contacts also has a significant impact on off fault damage location and intensity our approach may go some way to explaining the non intuitive distribution of mineralization in certain mineral systems as well as being applicable to predict subsurface fracturing and fluid flow in hydrothermal geothermal reservoirs

experimental alluvial fan evolution channel dynamics slope controls and shoreline growth 1 river deltas and alluvial fans have channelization and deposition dynamics that are not entirely understood but which dictate the evolution of landscapes of great social economic and ecologic value our lack of a process based understanding of fan dynamics hampers our ability to construct accurate prediction and hazard models leaving these regions vulnerable here we describe the growth of a series of experimental alluvial fans composed of a noncohesive grain mixture bimodal in size and density we impose conditions that simulate a gravel sand fan prograding into a static basin with constant water and sediment influx and the resulting fans display realistic channelization and avulsion dynamics we find that we can describe the dynamics of our fans in terms of a few processes 1 an avulsion sequence with a timescale dictated by mass conservation between incoming flux and deposit volume 2 a tendency for flow to reoccupy former channel paths and 3 bistable slopes corresponding to separate entrainment and deposition conditions for grains several important observations related to these processes are an avulsion timescale that increases with time and decreases with sediment feed rate fan lobes that grow in a self similar quasi radial pattern and channel geometry that is adjusted to the threshold entrainment stress we propose that the formation of well defined channels in noncohesive fans is a transient phenomenon resulting from incision following avulsion and can be directly described with dual transport thresholds we present a fairly complete process based description of the mechanics of avulsion and its resulting timescale on our fans because the relevant dynamics depend only on threshold transport conditions and conservation of mass we show how results may be directly applied to field scale systems

lagrangian observations of the along slope path of the california undercurrent abstract the flow of the california undercurrent cuc along the continental slope and its interaction with deeper offshore waters is studied using trajectories of 53 isobaric rafos the floats were launched off central california and data collected between 1993 and 2009 the mean pressure for the float measurements was 382 dbar the trajectories were broken into 126 segments of continuous alongshore drift over the continental slope poleward drift occurred 88 of the time the mean length of the poleward equatorward drift segments was 262 km 98 km and the exit time for these distances was 32 3 2 3 days 16 1 2 2 days five poleward drift segments exceeded 500 km in length the longest segment stretched from central california to central oregon a distance of 966 km locations where floats left or joined the along slope flow occurred at most latitudes between 35 5 n to 42 5 n here the mean rate at which floats left joined along slope drift was 5 3 3 5 per 50 km of coastline each year locations favored for leaving the undercurrent included the northern edge of the gulf of the farallones 37 5 n and between cape mendocino and cape blanco 41 5 42 n a location favored for joining the undercurrent was the northern edge of the santa lucia bank 35 5 n no floats were observed to join the alongshore flow immediately north of cape mendocino 40 5 41 n longer 290 day float missions often included offshore excursions into the northeastern pacific ocean thirty one westward excursions of the undercurrent were observed with a mean duration of 88 days and a mean offshore distance of 199 km the character of the excursions varied but included offshore and onshore transport in jets cyclonic and anticyclonic eddies and interaction with cold filaments the longest excursion lasted 587 days and extended 1007 km to the west

the contact uranium prospect kiggavik project nunavut canada tectonic history structural constraints and timing of mineralization uranium mineralization in the kiggavik area on the eastern border of the thelon basin nunavut canada hosts significant uranium resources within the basement and its understanding is critical to comprehending the genesis of unconformity related deposits structural controls and therefore exploration of these types of deposits in this prospective district this article deciphers the complex multiphase fracture network associated with uranium mineralization of the most recently discovered basement hosted prospect in the kiggavik area named contact the contact prospect is located along the andrew lake fault alf a major ne sw fault corridor in the area this study combines field work drillcore logging sampling and macro to micro petro structural analyses key results from this study highlight that the ne trending alf along with the ene trending thelon tf and judge sissons jsf faults formed early during intracratonic rifting and deposition of the baker lake and wharton groups ca 1850 1750 ma in response to the thelon and trans hudsonian orogeny the alf was affected by a strong silicification brecciation event that likely developed at ca 1750 ma and partitioned later deformation and fluid circulation in the contact prospect the alf was reactivated multiple times and mineralized in three stages with distinctive secondary fracture patterns alteration and mineralization types ten fracture stages have been identified at the contact prospect f1 to f10 the first stage of mineralization coeval with f5 is related to fluids of unconstrained origin that circulated through e w faults in the area that locally reactivated quartz veins of the brecciation event at the intersection with the alf mineralization at this stage is polymetallic and associated with weak clay alteration the second stage of uranium mineralization occurred coeval with transtensional reactivation of the ne sw trending alf f6c and in relation to circulation of oxidizing basinal brines within the fault zone mineralization at this stage is monometallic and associated with illite and sudoite alteration later reactivation of the inherited fracture network f8 led to strong illitization and bleaching of the host rock with local reworking of the ore body finally reactivation of the fracture network during f9 and 10 lead to circulation of meteoric fluids that remobilized mineralization in a third stage of uranium re concentration along redox fronts with strong illitization and bleaching of the host rock unlike the classic unconformity related uranium deposits in the athabasca basin where clay alteration halos occur around the ore bodies related to mineralizing processes in the contact prospect the strongest clay alteration event f8 postdates both main stages of mineralization along with uranium remobilization the basement hosted contact prospect is likely a relict of what was once a larger deposit

experiments on hydraulic jumps in turbidity currents near a canyon fan transition the point at which a submarine canyon debouches on its associated abyssal fan is generally characterized by a drop in channel slope turbidity currents of the kind responsible for the genesis of the canyon and fan should display an internal hydraulic jump near the slope transition no direct field observations of any such jump appear however to have been made experiments on the nature of the jump and the resulting sedimentary deposits indicate that the thickness of the deposits just downstream of the jump tends to increase as the ratio of bed shear velocity immediately behind the jump to particle fall velocity decreases

hydraulic jumps in sediment driven bottom currents laboratory experiments were conducted to observe the behavior of turbidity currents in the vicinity of a slope transition both sediment laden and saline hydraulic jumps were produced the vertical structure of the currents was found to depend on flow regime the saline and turbid hydraulic jumps showed similar characteristics the amount of water entrained by the flows through a jump was small the change in flow regime caused a marked reduction of the bed shear stress downstream of the jump in nature a turbidity current experiencing a hydraulic jump will drop most of its bedload immediately downstream from the jump while the suspended load will respond more gradually to the change in flow regime and will deposit sediment over a distance far exceeding 1 000 times the jump height

feature based image processing methods applied to bathymetric measurements from airborne remote sensing in fluvial environments bathymetric maps produced from remotely sensed imagery are increasingly common however when this method is applied to fluvial environments changing scenes and illumination variations severely hinder the application of well established empirical calibration methods used to obtain predictive depth colour relationships in this paper illumination variations are corrected with feature based image processing which is used to identify areas in an image with a near zero water depth this information can then be included in the depth colour calibration process which results in an improved prediction quality the end product is an automated bathymetric mapping method capable of a 4 m2 spatial resolution with a precision of 15 cm which allows for a more widespread application of bathymetric mapping copyright 2006 john wiley sons ltd

simulating brittle fault evolution from networks of pre existing joints within crystalline rock many faults grow by linkage of smaller structures and damage zones around faults may arise as a result of this linkage process in this paper we present the first numerical simulations of the temporal and spatial evolution of fault linkage structures from more than 20 pre existing joints the initial positions of which are based on field observation we show how the constantly evolving geometry and local stress field within this network of joints contribute to the fracture pattern markedly different fault zone trace geometries are predicted when the joints are at different angles to the maximum compressive far field stress ranging from evolving smooth linear structures to complex stepped fault zone trace geometries we show that evolution of the complex fault zone geometry is governed by 1 the strong local variations in the stress field due to complex interactions between neighbouring joints and 2 the orientation of the initial joint pattern with respect to the far field stress

autocyclic behaviour of fan deltas an analogue experimental study fan deltas are excellent recorders of fan building processes because of their high sedimentation rate particularly in tectonically active settings although previous research focuses mainly on allogenic controls there is clear evidence for autogenically produced storage and release of sediment by flume and numerical modelling that demands further definition of characteristics and significance of autogenically forced facies and stratigraphy analogue experiments were performed on fan deltas with constant extrinsic variables discharge sediment supply sea level and basin relief to demonstrate that fan delta evolution consists of prominent cyclic alternations of channellized flow and sheet flow the channellized flow is initiated by slope induced scouring and subsequent headward erosion to form a channel that connected with the valley while the removed sediment is deposited in a rapidly prograding delta lobe the resulting decrease in channel gradient causes a reduction in flow strength mouth bar formation flow bifurcation and progressive backfilling of the channel in the final stage of channel filling sheet flow coexists for a while with channellized flow semi confined flow although in cycle 1 this phase of semi confined flow was absent subsequent autocyclic incisions are very similar in morphology and gradient however they erode deeper into the delta plain and as a result take more time to backfill the duration of the semi confined flow increases with each subsequent cycle during the period of sheet flow the delta plain aggrades up to the critical gradient required for the initiation of autocyclic incision this critical gradient is dependent on the sediment transport capacity defined by the input conditions these autogenic cycles of erosion and aggradation confirm earlier findings that storage and release of sediment and associated slope variation play an important role in fan delta evolution the erosional surfaces produced by the autocyclic incisions are well preserved by the backfilling process in the deposits of the fan deltas these erosional surfaces can easily be misinterpreted as climate sea level or tectonically produced bounding surfaces

field evidences for the role of static friction on fracture orientation in extensional relays along strike slip faults comparison with photoelasticity and 3 d numerical modeling fault friction is a parameter that is difficult to assess along fault zones since its determination depends on the knowledge of any factor controlling the state of stress around faults in brittle homogeneous rocks a limited number of these factors such as the shape of the fault surface the vicinity of fault tips or the remote stress ratio are crucial to constrain for this determination in this paper we propose to analyse a field example in which all these properties are met and where the nature of the slipped structure suggest differences in static friction we compare the orientations of branching fractures at strike slip relay zones between en echelon stylolites and en echelon joints both reactivated in shear the field data are compared with both photoelastic and 3 d numerical models that consider the remote stress conditions and the role of the geometry of the strike slip segments based on field observations these analyses quantitatively demonstrate the significant role of fault friction on the local stress field orientation and subsequent fracture formation this work points out that estimations of fault friction based on analyses of fracture patterns or in situ stresses must be accompanied with a thorough investigation of the 3 d fault shape its segmentation and the remote stress state

influence of normal fault growth and linkage on the evolution of a rift basin a case from the gaoyou depression of the subei basin eastern china abstract it is widely acknowledged that the growth and linkage of a boundary fault affects the evolution of the accompanying sedimentary basin and exerts a strong influence on its sedimentary characteristics in this study we attempt to discuss the evolution of a boundary fault and rift basin by using seismic interpretation incremental fault throw and growth rate distance g d profile which are more suitable parameters than the expansion index in rift basins where footwall strata are missing because of erosion or a depositional hiatus therefore the gaoyou depression is taken as an example the gaoyou depression is the largest hydrocarbon bearing depression in the subei basin which is a representative rift basin in eastern china the depression is bounded to the south by the jiangdu wubao fault zone which includes the zhen 1 wu 1 zhen 2 and wu 2 faults using high resolution three dimensional seismic data the zhen 1 wu 1 fault can be subdivided into four segments based on its g d profile the shaobo fanchuan liuwushe and liulu segments growth rates indicate that the zhen 1 wu 1 fault and the zhen 2 and wu 2 faults developed successively from the late cretaceous to the miocene during rifting of the gaoyou depression and that development of the zhen 2 and wu 2 faults was controlled by the zhen 1 wu 1 fault the four segments of the zhen 1 wu 1 fault were linked with each other by the time the zhen 2 and wu 2 faults formed in the late paleocene an evolution model of the gaoyou depression is set up in this study integrating the fault activity with previous sedimentological studies we suggest that the evolution of the gaoyou depression was controlled by the jiangdu wubao fault zone rather than by a single fault successive slip of the zhen 1 wu 1 fault and the zhen 2 and wu 2 faults caused subsidence and migration of the depocenters this study presents a case investigation of the effects of boundary faults on rift basins in eastern china

autogenic incision backfilling cycles and lobe formation during the growth of alluvial fans with supercritical distributaries autogenic cycles of channelization terminal deposit formation channel backfilling and channel abandonment have been observed in the formation of fans and deltas in subcritical flow these terminal deposits are characterized as mouth bars that lead to flow bifurcation backwater and eventual channel backfilling similar although less well characterized cycles also take place on supercritical subaerial and submarine fans this study investigates the hydraulics and morphodynamics of autogenic incision and backfilling cycles associated with supercritical distributive channel flow in alluvial fans the research questions of the study are i how are supercritical autogenic cycles on alluvial fans different from the subcritical cycles ii what are the hydraulic and sediment transport characteristics at the various stages of autogenic feedback cycles and iii what role do the cycles play in the overall fan evolution these questions are investigated in the laboratory and emphasis is placed on measuring the hydraulic and topographic evolution of the systems during the cycles the cycles arise quasi periodically under constant water and sediment discharge periods of sheet like flow are competent to move sediment but not competent enough to carry the full imposed load the net result is preferential deposition near the inlet resulting in fan steepening and an increase in flow competency with time at a sediment supply to capacity ratio of the sheet like flow is unstable to small erosional events near the inlet resulting in the collapse of the distributed flow to a strong channelized state during channelization a graded supercritical fr 1 channel develops and transports eroded and fed sediment up to and through the fan front extending the fan initiating a lobe shaped deposit and reducing the local slope the slopes defined by a sheet like flow with and channelized flow with set the maximum and minimum slopes on the fan respectively once formed graded channels act as bypass conduits linking the inlet with the terminal deposit on average deposits are up to six channel depths in thickness and have volumes approximately five times that of the excavated channel the main distinctive characteristics of the supercritical cycles relate to how the flow interacts with the terminal deposit at the channel to deposit transition the flow undergoes a weak hydraulic jump resulting in rapid sedimentation dechannelization and lateral expansion of the flow and deposition of any remaining sediment on top of the channel fill and floodplain this process often caps the channel as the deposit propagates up channel erasing memory of the excavated channel

tan lu fault system and its significance in oil accumulation in the central liaodong bay subbasin bohai bay basin china the tan lu fault system in the central liaodong bay subbasin bohai bay basin has complex structural characteristics and its tectonism during the cenozoic is an important factor in oil accumulation three dimensional seismic data were used to document the structural features and evolution of the system variations in source rock occurrence oil catchment area and faulting intensity were comprehensively evaluated to discuss the heterogeneity of oil occurrence along the system detailed analysis of the seismic data indicates a right lateral slip for the tan lu fault system transpression and transtension occur on two branches of the tan lu fault with different orientations indicating a likely slip azimuth that is between the two orientations i e 30 35 the strike slip began at the middle stage of deposition of the shahejie formation and reached its climax during deposition of the first and second members of the dongying formation to date the slip is still continuing in the transpressional system the lower strata on opposite sides of the strike slip fault were shortened and folded whereby the upper strata were stretched and normal faulted as a result a negative flower structure developed immediately above a positive flower structure strain distribution in this system is similar to that in a classic fold moderate tectonic deformation could enlarge the oil catchment area benefiting oil accumulation weak or intense deformation is unfavorable for commercial oil accumulation because of a small oil catchment area and poor oil preservation respectively

continuity of the poleward undercurrent along the eastern boundary of the mid latitude north pacific abstract several recent data sets improve our view of the poleward undercurrent of the california current system as part of a triennial national marine fisheries service nmfs survey of pacific whiting a series of 105 shipboard acoustic doppler current profiler adcp velocity sections across the shelf break from 33 to 51 n at about 18 km meridional spacing were collected from july to august 1995 significant 0 05 m s 1 subsurface poleward flow occurred in 91 of the sections a mean cross shelf section using the entire data set has statistical significance revealing an undercurrent core 0 1 m s 1 from 200 275 m depth 20 25 km off the shelf break the mean poleward volume transport in a 125 325 m layer is 0 8 0 2 10 6 m 3 s 1 we focus particular attention on the cape blanco to cape mendocino region and the nmfs results are compared with shipboard adcp three weeks later from a study of coastal upwelling processes near cape blanco adcp streamfunction maps are derived and strongly suggest that one portion of flow is continuous over the 440 km meridional extent of the analysis region other portions of the flow show evidence of offshore turning separation and the formation of anti cyclonic eddies we also note that isopycnic potential vorticity from alongslope ctd stations during the nmfs survey appears to be a tracer for the poleward flow