thrust fault growth and segment linkage in the active ostler fault zone new zealand abstract thrust faulting is a fundamental mode of crustal deformation yet many of the key geometrical attributes of thrust faults and the controls on fault rupture growth and linkage remain poorly resolved numerous surface rupturing thrust faults cut through upper quaternary glacial outwash terraces within the ostler fault zone an active thrust system in the southern alps new zealand we use these deformed marker surfaces to define the three dimensional deformation field associated with their surface expression and to map displacement and length on 40 fault segments displacement transfer across two fault segment arrays occurs in distinctly different styles in one displacement is transferred between en echelon fault segments to produce a smooth linear displacement gradient in the other large scale folding and a population of small faults transfer displacement between two non overlapping fault segments with a residual displacement minimum within the transfer zone size distribution of fault segment length and maximum displacement follow a power law scaling relationship maximum displacement d max scales linearly with and represents 1 of segment trace length l d max l data from the segments of the ostler fault zone display similar scaling to a global fault dataset this similarity is surprising given that the observed displacements along the ostler fault represent only 20 ky of slip on fault segments that are likely to be many times older

the importance of small scale faulting in regional extension a recurring observation in many studies of extensional basins has been that the amount of extension visible on normal faults for example on seismic reflection profiles is significantly less than the amount of extension indicated by crustal thickness and thermal subsidence1 5 one mechanism suggested to account for this discrepancy is small scale faulting with offsets too small to be resolved seismically6 7 but earthquake studies8 10 indicate that small faults are responsible for only a small fraction of the total seismic moment in an active area scholz and cowie11 have recently attempted to extend this approach to the total strain at the end of a finite deformation interval by combining scaling laws describing the distributions of fault lengths and displacements here we present fault displacement data that directly conflict with scholz and cowie s conclusions and imply that up to 40 of the extension may be missed by summing fault offsets on basin profiles the fault population at the end of a long deformation interval may differ substantially from that responsible for the earthquake population at any one time

multiscaling of shear zones and the evolution of the brittle to viscous transition in continental crust 1 a new method is introduced for quantifying the scale and the intensity of strain localization from maps of natural shear zones the method employs autocorrelation functions to determine local areal scales of geometric homogeneity these homogenization scales are used to calculate scale dependent localization fractions of deformed rock the strain localization intensity is quantified from measurements of mean relative to maximum shear strain this approach is used to analyze shear zones on different scales from an exposure cap de creus spain of the fossil brittle to viscous transition bvt changes in the scaling characteristics of shear zones are interpreted to reflect a time sequence of localization during the evolution of the continental bvt we show that shear zone scaling is related to inherited anisotropies older schistosity lithological layering pegmatite bodies and to the predominant mode of deformation brittle viscous the length to width ratio of shear zones increases with their length up to the meter scale and decreases for larger length scales as they evolve from isolated shear fractures to interconnected mylonitic shear zones variations in strain localization intensity calculated along a single shear zone indicate that such shear zones weakened from their brittle tips to their mylonitic centers thus driving their propagation and growth to larger scales our results imply that the bvt evolves by network widening a process whereby strain localizes on progressively larger scales until a dense network of weak mylonitic layers tens to hundreds of meters wide and hundreds to thousands of meters long forms subparallel to the regional shearing plane

multiscale fracture network characterization and impact on flow a case study on the latemar carbonate platform a fracture network arrangement is quantified across an isolated carbonate platform from outcrop and aerial imagery to address its impact on fluid flow the network is described in terms of fracture density orientation and length distribution parameters of particular interest is the role of fracture cross connections and abutments on the effective permeability hence the flow simulations explicitly account for network topology by adopting discrete fracture and matrix description the interior of the latemar carbonate platform dolomites italy is taken as outcrop analogue for subsurface reservoirs of isolated carbonate build ups that exhibit a fracture dominated permeability new is our dual strategy to describe the fracture network both as deterministic and stochastic based inputs for flow simulations the fracture geometries are captured explicitly and form a multiscale data set by integration of interpretations from outcrops airborne imagery and lidar the deterministic network descriptions form the basis for descriptive rules that are diagnostic of the complex natural fracture arrangement the fracture networks exhibit a variable degree of multitier hierarchies with smaller sized fractures abutting against larger fractures under both right and oblique angles the influence of network topology on connectivity is quantified using discrete fracture single phase fluid flow simulations the simulation results show that the effective permeability for the fracture and matrix ensemble can be 50 to 400 times higher than the matrix permeability of 1 0 10 14 m2 the permeability enhancement is strongly controlled by the connectivity of the fracture network therefore the degree of intersecting and abutting fractures should be captured from outcrops with accuracy to be of value as analogue

influence of landscape coverage on measuring spatial and length properties of rock fracture networks insights from numerical simulation natural fractures are ubiquitous in the earth s crust and often deeply buried in the subsurface due to the difficulty in accessing to their three dimensional structures the study of fracture network geometry is usually achieved by sampling two dimensional 2d exposures at the earth s surface through outcrop mapping or aerial photograph techniques however the measurement results can be considerably affected by the coverage of forests and other plant species over the exposed fracture patterns we quantitatively study such effects using numerical simulation we consider the scenario of nominally isotropic natural fracture systems and represent them using 2d discrete fracture network models governed by fractal and length scaling parameters the groundcover is modelled as random patches superimposing onto the 2d fracture patterns the effects of localisation and total coverage of landscape patches are further investigated the fractal dimension and length exponent of the covered fracture networks are measured and compared with those of the original non covered patterns the results show that the measured length exponent increases with the reduced localisation and increased coverage of landscape patches which is more evident for networks dominated by very large fractures i e small underlying length exponent however the landscape coverage seems to have a minor impact on the fractal dimension measurement the research findings of this paper have important implications for field survey and statistical analysis of geological systems

populations of faults and fault displacements and their effects on estimates of fault related regional extension abstract measured populations of fault displacements derived from regional seismic oilfield seismic coalmine plans and outcrop data show a power law distribution with exponents s of 0 45 to 0 95 for singleline samples across an array of faults the more negative values indicate relatively larger numbers of smaller faults an expression for a population of active faults derived from the gutenberg richter magnitude frequency relation for earthquakes is log n a b d log d where d maximum displacement of a fault n number of faults of maximum displacement d or greater and b d 1 0 and has the same value as b for the corresponding earthquake population populations of dead faults existing at the end of a tectonic episode have been numerically derived using a fault growth model and satisfy the relation log n a e log d where e has a value between 1 6 and 2 0 numerically derived populations of fault displacements in a dead fault population have slopes of s where s e 1 the contribution of an individual fault to the regional strain varies with the lifetime seismic moment of the fault and is proportional to d 2 estimation of fault related extension by summing heaves on faults of a limited size range is valid only if the measured size range of faults accommodates most of the extension correction can be made if the s value of the fault displacement population is known

evolution of a fault surface from 3d attribute analysis and displacement measurements abstract a large fault surface evolves by growth and coalescence of numerous segments through time which results in strong undulations of the principal fault surface we interpreted a strongly segmented 13 km long fault using 3d seismic data and studied the morphology in terms of fault linkage using curvature azimuth and dip attributes displacement profiles of two horizons were measured to analyse the different displacement relations and to quantify their variation and dependence on fault morphology we identified four orders of fault segments over a scale range from a few hundred metres to several kilometres which evolved during fault growth the strong changes in orientation of the several segments might result in a heterogeneous small scale fracture distribution and different fault drag geometries displacement measurements on the undulated fault surface indicate a strong variation between real vertical and horizontal displacement values however the commonly used throw values lead to a smoothing of the real displacement curves and to an underrepresentation of their values and therefore cannot show a triangular shape that is typically identified from ruptures fault surfaces of earthquake processes therefore for any kind of fault analysis care should be taken when using throw as approximation for the real displacement

development and scaling relationships of a stylolite population abstract the frequencies amplitudes and insoluble residue thicknesses of 4639 stylolites have been measured from 674 3 m of core from four vertical wells in the khuff formation a permo triassic carbonate reservoir offshore abu dhabi although there are similar numbers of stylolites per metre of core in dolomites and limestones the stylolites in the limestones have approximately double the cumulative amplitudes and insoluble residue thicknesses than the stylolites in dolomites this indicates that stylolites in the limestones have grown at approximately twice the speed or for twice as long as the stylolites in the dolomites stylolite amplitudes in dolomites and limestones together appear to obey a power law scaling relationship over about one order of magnitude 20 150 mm stylolite amplitudes in dolomites however have a higher power law exponent than those in the limestones and appear to obey a power law down to 10 mm this indicates that stylolites in the limestones have merged more than the stylolites in the dolomites the amount of pressure solution and possibly the scaling of a population of stylolites may also be controlled by location within the fold with less pressure solution in the hinge region into which hydrocarbons migrated earlier than in the limbs

scaling of transfer zones in the british isles widths of transfer zones between stepping normal faults obey power law scaling relationships probably from widths of millimetres to tens or hundreds of kilometres relay ramp widths in the mesozoic sedimentary rocks of the somerset coast obey a power law up to 50 m above which there is a censoring effect caused by the width of the wave cut platform a structural map of the british isles indicates that transfer zones obey a power law up to widths of at least 250 km this indicates that normal faults can interact over tens or hundreds of kilometres especially where transfer zones occur between stepping half grabens interaction is therefore another aspect of faulting that obeys fractal behaviour

scaling of fault displacements from the badajoz cordoba shear zone sw spain faulting occurs over a large range of scale parts of which are sampled by various techniques e g microscopy outcrop measurement mapping seismic reflection and other forms of remote sensing use of a single technique to measure displacement or strain will not sample faults at all scales and hence will give a biased estimate in order to assess this bias a knowledge of the distribution over all scales is needed many samples of fault displacement appear to follow a power law distribution with departures which can be attributed to sampling effects the number of faults with a displacement u is given by n u cu d the power law distribution of displacement is consistent with similar distributions of other fault parameters and earthquake magnitudes when sampling along a line e g a bedding trace on a map or section a self similar fault population would have d 1 whereas self affine geometries yield d 1 displacement and extension are dominated by small faults when d 1 and by large faults when d 1 when sampling over areas or volumes these critical values are 2 and 3 respectively a set of strike slip faults from the badajoz cordoba shear zone spain were sampled at two different scales using 1 50000 maps and outcrop measurements displacement ranges over 6 orders of magnitude these and other fault populations typically have d ranging from 0 6 to 1 5 the power law relationship may be integrated to yield estimates of the displacement or extension for faults which lie beyond the resolution of the sampling system for example a knowledge of d allows the extension measured on a map or seismic section to be corrected for faults whose displacement is below the resolution of the survey based on an overall estimate of d 0 9 for the badajoz cordoba data only some 40 of the extension would be recorded by map scale faults a corrected extension of 41 along the shear zone is estimated which if typical for the entire 300 km zone represents some 87 km of along strike extension thus work suggests that significant displacement occurs on faults which are too small to be interpreted from conventional seismic profiles and geological maps

amount of extension on small faults an example from the viking graben extension estimates based on palinspastic restoration of only the largest faults in a deformed terrane may be significantly deficient due to neglect of small faults i e unsampled faults most of which have smaller displacements than do sampled faults small faults individually account for little extension but there may be large numbers of them the cumulative extension on small faults can be calculated from the fractal size distributions of fault displacements independent extension estimates support the inference from fault population statistics that small faults account for significant amounts of extension for example restorations of mesozoic faults interpreted from seismic reflection profiles across the viking graben in the north sea yield extension estimates that are only 40 75 of independent estimates the fractal size distribution of fault displacements in the viking graben is consistent with the hypothesis that the remaining 25 60 of extension resulted from displacements on small faults

spatial arrangement and size distribution of normal faults buckskin detachment upper plate western arizona abstract fault arrays typically include a wide range of fault sizes and those faults may be randomly located clustered together or regularly or periodically located in a rock volume here we investigate size distribution and spatial arrangement of normal faults using rigorous size scaling methods and normalized correlation count ncc outcrop data from miocene sedimentary rocks in the immediate upper plate of the regional buckskin detachment low angle normal fault have differing patterns of spatial arrangement as a function of displacement offset using lower size thresholds of 1 0 1 0 01 and 0 001 m displacements range over 5 orders of magnitude and have power law frequency distributions spanning four orders of magnitude from less than 0 001 m to more than 100 m with exponents of 0 6 and 0 9 the largest faults with 1 m displacement have a shallower size distribution slope and regular spacing of about 20 m in contrast smaller faults have steep size distribution slopes and irregular spacing with ncc plateau patterns indicating imposed clustering cluster widths are 15 m for the 0 1 m threshold 14 m for 0 01 m and 1 m for 0 001 m displacement threshold faults results demonstrate normalized correlation count effectively characterizes the spatial arrangement patterns of these faults our example from a high strain fault pattern above a detachment is compatible with size and spatial organization that was influenced primarily by boundary conditions such as fault shape mechanical unit thickness and internal stratigraphy on a range of scales rather than purely by interaction among faults during their propagation

changes in fault displacement populations correlated to linkage between faults in carboniferous strata exposed at the western margin of the southern appalachian u s a fold thrust belt mesoscopic faults accommodated strains as the cumberland plateau thrust sheet moved 1 km wnw on a sub horizontal detachment these faults are confined to a layer 75 m thick above the detachment in the upper part of this 75 m thick layer a laterally persistent coal seam separates two stratigraphic units subjected to different amounts of sub horizontal elongation distinct sets of mesoscopic faults that cut bedding at high angles and have normal offsets accommodate the strains in each unit below the coal seam a sample line 500 m long intersects 504 faults a plot of log n size rank vs log d dip separation in mm for these faults is linear suggesting that a scaling law n ad c holds for this population least squares regression gives c 0 8 and log10 a 3 1 above the coal seam a sample line 250 m long intersects 745 faults a plot of log n vs log d for these faults has two distinct linear trends faults with separations 1 25 m yield a scaling law n ad c with c 0 5 and log10 a 2 9 seventeen faults with separations d 1 25 m define a second linear segment n a d c with c 1 8 and log10 a 6 9 the break in slope at d 1 25 m corresponds to faults with heights of 30 m roughly equal to the thickness of the faulted strata faults here with d 1 25 m and d 1 25 m which exhibit different scaling characteristics are respectively analogous to faults within and those that extend across the brittle crust in regional studies comparing the two displacement populations described here small offset faults make a proportionally smaller contribution to the total strain in the larger strain setting this pattern which is observed elsewhere suggests that fault systems within individual layers exhibit different scaling characteristics at different stages in their history this contribution argues that fault linkage is the key to such changes in fault scaling behavior it is a mesoscopic to macroscopic structural change that alters the subsequent development of faults fault linkage like fault size or sampling dimension should be considered in examinations of fault scaling laws

quantification of fracture networks in non layered massive rock using synthetic and natural data sets abstract two quantitative measures correlation dimension and maximum lyapunov exponent are investigated for quantifying fracture spacing in massive non layered rock the correlation dimension a measure of fractal dimension characterizes some aspects of fracture distribution relative to other fractal methods used in structural geology the correlation dimension provides a more rigorous mathematical calculation of the fractal dimension and is particularly robust in cases where data is limited the maximum lyapunov exponent calculation also provides quantification of observed distributions of fracture spacing emphasizing variations in adjacent spacing measurements the two methods are tested on two different synthetic data sets to elucidate their usefulness in distinguishing between different distributions and their sensitivity to population size average fracture spacing and standard deviation both methods provide accurate results for small population sizes and for a range of average fracture spacings these methods are then used together to quantify two different fracture sets in the granitoids of the sierra nevada batholith the results indicate that the different fracture sets inferred to form from different tectonic processes have distinctive and quantifiable differences in patterns of fracture spacing

measurement and characterisation of spatial distributions of fractures abstract a variety of line sample 1 d and map 2 d datasets of faults and joints has been used to investigate the spatial distributions of fractures and to test techniques of fractal analysis the natural fracture datasets have been supplemented by synthetic datasets with known characteristics the fault datasets investigated range in scale from regional to outcrop and the joint datasets are derived from outcrop 1 d datasets were analysed by the spacing population interval counting and fracture number interval counting techniques 2 d datasets were analysed by box counting and fracture number box counting techniques results indicate that fracture spacing can be characterised in line samples using either the 1 d interval counting technique or more simply by measuring the spacing population as the cumulative frequency distribution of spaces between adjacent fractures tectonic faults frequently show a power law spacing population indicating fractal dimensions of between 0 4 and 1 0 but except for outcrop data truncation effects degrade the analysis unrefined joint datasets commonly show negative exponential or lognormal spacing cumulative frequency distributions however single orientation joint sets are characterised by a regular spacing and are therefore non fractal for both fault and joint map data box counting techniques do not yield the power law relationship between box size and the number of boxes that is expected of fractal geometries it is concluded that 2 d box counting techniques are too insensitive to characterise the many different parameters of a fracture array the fracture density technique appears not to discriminate between very different fracture patterns and therefore does not provide useful results a fracture pattern incorporates several attributes e g size distribution orientation linkage density roughness each of which may scale independently and each of which may be fractal with its own fractal dimension full characterisation of fracture patterns will therefore require independent analysis of each of these attributes

evolution of deep water rifted margins testing depth dependent extensional models 1 a general understanding of rifted margins which form by thinning of the continental lithosphere exists nevertheless the exact form of thinning is unclear this debate has been stimulated by acquisition of dense seismic wide angle and deep reflection surveys from atlantic ocean margins a central issue concerns the way in which thinning changes with depth we have tackled this issue by developing a generalized inverse model this model attempts to fit subsidence and crustal thinning observations by varying strain rate as a function of time and space depth dependent thinning is permitted but we do not prescribe its existence or form here the algorithm is applied to six margins including two of the most contentious conjugate margins newfoundland iberia and brazil angola calculated strain rate histories predict thinning estimates which broadly match estimates inferred from normal faulting the eastern indian and beaufort sea margins formed by largely uniform lithospheric thinning in contrast the newfoundland iberian conjugate margins formed by a pattern of strongly depth dependent strain rate to account for the paucity of syn rift decompression melting of the underlying asthenosphere the lithospheric mantle close to oceanic continent transition must thin more slowly than the overlying crust this form of depth dependency is not common for example the brazil angolan conjugate margin could have formed by uniform lithospheric thinning provided thick layers of salt were deposited in a preexisting 400 m deep topographic depression depth dependent thinning is not required to account for rapid subsidence of presalt strata

fractal analysis of a quaternary fault array in the central apennines italy abstract the monte vettore fault array in the central apennines fold and thrust belt is part of a major quaternary fault system displaying the main features of a regional negative flower structure associated with a roughly n s trending left lateral strike slip fault zone fractal analysis of the fault trace pattern of the area has shown that the box counting curve derived for the monte vettore array is defined by two straight line segments each showing a characteristic slope value the first segment which refers to a spatial distribution extending over about one order of magnitude is characterized by a fractal dimension of about 1 6 whereas the second one fits a euclidean i e a non fractal distribution the box counting analysis emphasizes that faults with variable sizes exhibit different scaling relations hence suggesting that fault linkage played a major role in the development and evolution of the monte vettore fault array the split point between the two segments falls at a value of log l s corresponding to a box size of 635 m hence suggesting that self similarity among faults within the array breaks down below this value fractal analysis of the monte vettore array also provides statistically based segmentation criteria for analysing a young immature fault structure capable of generating medium size earthquakes in a continental geotectonic setting

pliocene paleoenvironment and antarctic ice sheet behavior evidence from wright valley investigations in wright valley adjacent to the transantarctic mountains in east antarctica shed light on the question of whether high latitude pliocene climate was warm enough to cause widespread deglaciation of the east antarctic craton with a concurrent magellanic moorland like environment if pliocene age diatoms presently in glaciogenic deposits high in the transantarctic mountains had come from seaways on the east antarctic craton an expanding late pliocene ice sheet must have first eroded them from marine sediments and then deposited the diatoms at their present high altitude locations this hypothetical expanding glacier would have had to have come through wright valley glacial drift sediments from the central wright valley were mapped sampled analyzed and 40ar 39ar whole rock dated our evidence indicates that an east antarctic outlet glacier has not expanded through wright valley and hence cannot have overridden the dry valleys sector of the transantarctic mountains any time in the pa

fractal models for ore reserve estimation abstract traditional geometric and geostatistic methods for reserve estimation in a single deposit are difficult to use with skewed distribution mineralization variables including grade orebody thickness and grade thickness a common characteristic of most deposits and require complex data processing it has been shown that the skewed mineralization variables can be described by the number size model in a fractal domain based on the number size model assuming that orebody thickness and grade thickness are continuous variables the fractal model for reserve estimation fmre in a single deposit can be established in the fmre ore tonnage can be estimated given the orebody area and the fractal parameters of orebody thickness distribution and metal tonnage can be estimated based on the orebody area and the fractal parameters of grade thickness distribution the reserve estimated by the fmre can denote actual ore tonnage and metal tonnage that can be mined out of the deposit the frme was applied to the dayingezhuang gold deposit in the jiaodong gold province in china the gold reserves via the fmre and the traditional geometric block method are similar with relative errors of 3 11 in ore tonnage and 0 29 in metal tonnage compared to traditional reserve estimation the fmre is much easier in calculation process and is more reasonable in dealing with the skewed distribution however this new method fails to calculate local reserve which can be derived via any of the traditional estimation methods

geometry and dynamics of an east antarctic ice sheet outlet glacier under past and present climates 1 the behavior of east antarctic ice sheet eais outlet glaciers both at present and during the recent geological past is of considerable interest both from the point of view of understanding the mechanics of contemporary glacier dynamics and also with regard to epoch scale ice sheet stability during plio pleistocene climate transitions here we use a glacier flowline model that incorporates the effects of longitudinal stresses to numerically simulate ferrar glacier first under present day environmental conditions and subsequently under both colder and warmer climate regimes representing the last glacial maximum lgm and mid pliocene peak warmth respectively using airborne radar profiles insar derived surface velocities ice core and geological data for empirical constraint we present a diagnostic simulation that uses an iterative method to closely reproduce observed dynamics our model suggests that the glacier is largely cold based under present conditions flows predominantly by way of internal deformation and cascades over bedrock ridges due to the combined action of changes in cross sectional valley geometry local steepening of the glacier surface and the non local effects of longitudinal coupling time dependent evolutionary simulation of a lower profile glacier under a colder drier lgm climate predicts flow velocities lower than present with minimal bedrock erosion or basal till flux conversely the warmer than present mid pliocene climate produces a more dynamic glacier that is warm based and sliding along much of its bed we propose that eais outlet glaciers such as the ferrar respond dynamically along their length in response to changing environmental forcings with most significant changes taking place in their lower reaches adjustment to perturbations in upper catchments is more muted

multi scale fracture network characterisation on carbonate platforms abstract characterisation of fracture networks at different scales is challenging and important to many fields of geoscience especially when access to multiple resolution datasets is limited here we develop an integrated analysis of fracture networks on carbonate platforms using three scales of observation small outcrop intermediate airborne lidar and large 3d seismic statistical analyses and ternary diagrams of geometrical and topological data from cariatiz south east spain and pernambuco east brazil are used to understand the relationships and distribution of fracture networks between multi scale datasets a variety of fracture types at each scale of observation reveal how complex fracture networks are on carbonate platforms our results demonstrate that fracture network properties behave differently depending on the fracture size and that transitional scale gaps between datasets constrain fracture characterisation airborne lidar maps show that intermediate sized fractures appear to have a better controlled orientation and a lower connectivity than smaller fractures from the same area in cariatiz fracture branch length distributions fit a negative exponential or log normal distribution for massive non stratabound units this work is important as it demonstrates that the use of outcrop data is a good approach to understand fracture complexity of carbonate platforms understanding sub seismic fracture networks is therefore critical in quantifying fluid flow and permeability in carbonate reservoirs

predicting reservoir scale faults with area balance application to growth stratigraphy a reservoir that appears to lack faults at one scale of resolution or at one sampling density may nevertheless contain faults that are below the resolution of the observations the area depth relationship from a balanced cross section is shown to contain the necessary information for predicting the sub resolution fault heave existing area depth theory is extended to include growth units allowing structural length and thickness changes to be separated from the depositional changes the technique is validated with a numerical model of a growth full graben and a sand box model of a half graben then field tested in the gilbertown graben a growth structure within the regional peripheral fault trend along the northern margin of the gulf of mexico a cross section developed from wells alone is used to infer the abundance of sub resolution faults by the area balance technique a small but significant amount of sub resolution extension is predicted and then confirmed with a highresolution seismic line q 2003 elsevier science ltd all rights reserved

taking into account the complexity of natural fracture systems in reservoir single phase flow modelling abstract in order to develop a methodology for reservoir flow modelling that takes into account the complexity of natural fracture systems high quality fracture datasets were collected at different scales in a well exposed clastic formation at tayma saudi arabia and used to design a multiscale fracture model incorporating both large scale faults and medium to small scale fractures joints for numerical simulation flow modelling was then conducted taking into account three scales of permeability to represent the matrix joints and faults actually the most severe situation was considered where the permeability of the joints dominates strongly the one of the matrix the results obtained with this model show that on a local scale the maximum directional flow is always horizontal along the direction of a systematic joint set in this case nw se vertical flow is only possible where joints j and bedding planes b have conductivity ratios c j c b between 0 1 and 10 the flow properties of the model were then upscaled to simulate the entire reservoir through combining the flow properties of the jointed matrix represented by an equivalent permeability tensor with those of the large scale fault system which was modelled explicitly in a dual permeability system simulation of a pumping well to illustrate the hydraulic response of the multiscale fracture system according to different permeability ratios between the faults and the jointed rock matrix i e k f k m showed that the influence of the fault system begins to be visible at a permeability ratio of 100 at a ratio of 10 000 the hydraulic potential field is controlled completely by the fault system the fault planes becoming isopotential lines of the hydraulic field this multiscale fracture flow simulation procedure which combines the hydraulic effects of small to medium scale fractures and large scale faults could be very helpful in predicting flow responses in dual permeability reservoirs

fault size distributions are they really power law abstract power law fault size throw distributions spanning ca seven orders of magnitude are analysed using sample lines from seismic coal mine plan and outcrop data sets outcrop data sets generally have lower power law exponent values than seismic data sets consistent with a general decrease in exponent value with decrease in fault size if such a relationship does exist then probably it cannot be accounted for by sampling bias alone we suggest that either i fault size populations are not power law over a large scale range or ii they are power law but at smaller scales show a greater range of exponent values due to spatial clustering

strain and scaling of faults in the chalk at flamborough head u k analysis has been made of the orientations displacements and spacings of 1340 extensional faults with displacements of up to 6 m along an almost completely exposed 6 km length of cliff this data set has been used to study how fault populations account for strain in a region and to study relationships between different scales of fault strains have been estimated the maximum and intermediate extensions are sub horizontal with approximately equal extension e 0 01 in all horizontal directions it can be inferred that the minimum extension maximum compression was sub vertical but that the wide variety of fault orientations and cross cutting relationships resulted from variable horizontal extensions some faults have oblique slip slickenside lineations which imply a period of later dominantly nnw sse extension which possibly developed as the exposure scale faults linked up e w striking larger scale normal faults effectively forming a single wide fault zone graphs of displacement per unit distance are used to illustrate variations in displacement the scaling of fault displacement appears to follow a power law relationship the differences in orientation between the small scale and large scale faults precludes a simple estimation of the total strain over all scales

strain localisation and population changes during fault system growth within the inner moray firth northern north sea abstract the evolution of fault populations is established for an area within the late jurassic inner moray firth sub basin of the north sea sedimentation rates outstripped fault displacement rates resulting in the blanketing of fault scarps and the preservation of fault displacement histories displacement backstripping is used to establish the growth history of the fault system fault system evolution is characterised by early generation of the main fault pattern and progressive localisation of strain onto larger faults this localisation is accompanied by the death of smaller faults and an associated change in the active fault population from power law to scale bound fault length populations evolve from a power law frequency distribution containing all faults to a power law distribution with a marked non power law tail containing the largest faults this change in population character is synchronous with the development of a fully connected fault system extending across the mapped area and the accommodation of displacements almost exclusively on the largest faults strain localisation onto fewer and better connected faults represents the most efficient means of accommodating fault related deformation and is considered to be a fundamental characteristic of the spatio temporal evolution of fault systems progressive strain localisation requires complementary changes in the characteristics of associated earthquake populations

scaling systematics of fault sizes on a large scale range fault map abstract a large scale high quality fault map was produced for an intensively mined area of the u k south yorkshire coalfield this database has been used to investigate both the scaling properties of fault systems and the robustness of techniques for the prediction of sub resolution faulting the mapped area is 87 km 2 and contains 2257 individual fault traces with on average one throw reading available for every 82 m of fault trace recorded throw values range from 10 cm to 180 m and fault trace lengths from 10 m to 12 km two sets of normal faults nw and ne striking are present together with local wnw striking dextral strike slip zones size populations are power law over at least 2 5 orders of magnitude and the exponents of the throw maximum throw and fault trace length population curves are interrelated and taking into account the effects of resolution on trace length populations are internally consistent derivatives of the primary map reproduce resolutions typical of offshore seismics and illustrate the limitations of seismic data power law fault size distributions provide a basis for sub seismic fault prediction for this data set a fault throw resolution of better than 10 m would be required to provide an accurate prediction of the throw population down to ca 0 6m

contrasts in regional seismic wave propagation to station wmq in central asia summary the varying character of regional seismic phase propagation in central asia is well illustrated by the character of the seismograms at the urumqi station wmq in xinjiang china three different classes of behaviour are seen for propagation across the relatively stable platforms to the north along the tien shan chain and across the tarim basin from tibet these paths demonstrate the influences of the variation in crustal structure on the regional phases particularly the tibetan plateau and its north and south boundaries but also the influence of the pamirs on propagation along the tien shan as an interference phase lg is sensitive to changes in crustal structure and can be used to study crustal heterogeneity lg can propagate along the tien shan chain trapped by the gradients in structure on either side but with a progressive loss in amplitude and frequency however once the northern boundary of tibet is crossed the high frequencies in the lg train are lost and there is little recognizable arrival the amplitude ratios of the different crustal phases pn sn and lg can be used to characterize the behaviour and the different classes of propagation can be further separated when account is made of the frequency content in the lg window the influence of the transitions in crustal structure at the northern edge of the tibetan plateau on propagation to wmq is investigated using numerical modelling with the pseudospectral method for models of crustal variations this demonstrates how the crustal pinch at the northern boundary operates to modify the fairly efficient propagation inside tibet with substantial transfer of energy into the mantle

soil formation in wright valley antarctica since the late neogene abstract we investigated over 180 soil profiles on 15 drift units ranging from recent to pliocene or older in age in wright valley antarctica the drifts originate from 1 post valley cutting by an advance of the east antarctic ice sheet 2 advances of the wright lower glacier from grounding of ice in the ross embayment and 3 advance of alpine glaciers along the south valley wall holocene and lgm soils lack staining from oxidation of iron bearing minerals and visible salts contain ice or ice cemented permafrost in the upper 0 5 m and are classified as glacic or typic haploturbels other soils of late quaternary age are stained to 2 in the upper 70 cm of profile and are classified as typic haploturbels soils of mid late quaternary age are stained to 20 cm have ice cemented permafrost at depths in excess of 1 m and stage 2 salts flecks and patches covering 2 and are classified as typic anhyorthels soils of early quaternary to late pliocene age are oxidized to depths 30 cm have stage 3 salts flecks and patches covering 20 of the profile face contain 4000 4200 mg salts cm 2 and are classified as salic anhyorthels soils of pliocene age are deeply oxidized 50 cm have stage 5 6 salts strongly cemented or indurated salt pans contain 5000 7000 mg salts cm 2 and are classified as petrosalic anhyorthels soils of early pliocene or older age do not show the degree of development of younger soils because they are derived from peleus till which contains highly erosive fine sandy quartz rich rock our data question the notion of high level antarctic lakes occupying most of the valley during the lgm and early holocene

fractal analysis of fractures in rocks the cantor s dust method abstract the cantor s dust method of fractal analysis has been used to describe the regularity of fracture patterns in geological materials seen on a two dimensional surface this linear method of analysis is well adapted to a determination of two dimensional phenomena the determination of the fractal dimension d indicates that it varies regularly as a function of the orientation of the analysis direction this is taken to indicate that there is a relation unexplained as yet between the regularity of the fracture pattern and the forces which produced it the use of the cantor s dust method on naturally fractured materials ranging in dimension from 3 mm to 45 m in maximum dimension indicates the fractal nature of the fractures found in natural materials the analysis method can also be used to identify local variations in the stress field which caused failure such as the fractures in a feldspar compared to those in the host granite etc the method appears to be a sensitive descriptive measure of the failure patterns in rocks

simulation and characterization of fracture patterns in glaciers during drainage of subglacial lakes the surface of the glacier subsides and fractures generating a homogeneous circular fracture pattern on the rim of the resulting depression we have analyzed several fracture patterns around the skafta cauldron on iceland a regular fracture spacing was observed on the cauldron rim indicating that the region was subjected to a uniform strain in this region standard image analysis techniques were applied to find the lengths l and open areas a of the fractures we demonstrate that an understanding of sampling biases allows a scaling relation l a to be established and the exponent to be determined this relation provides a quantitative characterization of interactions between fractures in the population the value of is higher for that observed for laboratory experiments on clay but the uncertainties do not rule out a universal behavior which applies to ice rock and all other solids the size distribution of fractures did not display a similarly simple crossover behavior and a power law scaling relation could not be established without a better understanding of the crossovers for large fractures we introduce a simple simulation model that reproduces the most important visual and statistical properties of the glacier fracture pattern the direct comparison validates the use of the model to simulate geological fracturing processes

fault scaling laws and the temporal evolution of fault systems abstract through an analysis of the temporal evolution of duplex fault systems this contribution shows that it is unlikely that all faults in a deformed area will conform to a single frequency size scaling relationship the development of a duplex leads to different size frequency relationships for the faults that compose the duplex and those confined to individual horses the faults that compose the duplex define segments with relatively steep stopes on a log n number of faults i e frequency vs log d displacement magnitude i e size plot faults within individual horses define segments with relatively shallow slopes on a log n vs log d plot the distinction between these two types of faults in a duplex is akin to the distinction between large active faults which cut the entire seismogenic layer and small active faults which do not extend across the seismogenic layer if as is often the case the faults that compose a duplex do not extend across the seismogenic layer the stepped nature of the resulting log n vs log d plot may make it particularly difficult to assess the contribution of these small faults to regional deformation since duplex geometries result in part from anisotropies present in deforming rocks the anisotropy present in nearly all crustal rocks will affect the size frequency relationship observed for systems of faults different parts of a deforming rock mass are likely to have different initial anisotropies combining data on fault systems from markedly different portions of a deforming region may then obscure the unique characteristics of the size frequency relationship in either area and may lead to inaccurate assessments of the relative contributions of small and large faults to regional fault accommodated strains