coastal gravel barrier hydrology observations from a prototype scale laboratory experiment bardex abstract a prototype scale laboratory study bardex barrier dynamics experiment was conducted within the 250 m long and 7 m deep delta wave flume the netherlands a 4 m high and 50 m long gravel barrier d50 11 mm was constructed within the central region of the flume enabling a back barrier lagoon to be located at its landward side by the installation of a multi stage pump system the water levels at the sea and lagoon sides of the barrier could be manipulated independently a series of experiments were undertaken to examine the groundwater fluctuations and flow within the barrier system subject to varying lagoon levels and wave conditions in accordance with previous sand experiments the wave induced watertable over height at the beachface was confirmed to be independent of sediment characteristics varying back barrier lagoon levels were observed to have significant effect on both the maximum watertable over height within the barrier and shoreline set up vertical position of the point of intersection between mean water surface through the swash zone and beachface as well as the direction and magnitude of though barrier groundwater flux the effective hydraulic conductivity of the d50 11 mm gravel barrier was determined to be k 0 16 m s 1 at higher reynolds numbers re 40 associated with local watertable gradients exceeding 0 025 and resulting turbulent losses the transition from laminar to turbulent through barrier flow was indicated by a reduction in local k however for the parameter range encountered this effect was modest only

modelling gravel barrier profile response to combined waves and tides using xbeach laboratory and field results abstract xbeach a process based numerical model capable of computing nearshore circulation and morphodynamics including overwash and breaching has been used in 1d mode to simulate erosion occurring on a gravel barrier beach d50 11 mm subjected to wave and tidal forcing during selected tests undertaken during the bardex experiments the model demonstrated good quantitative skill brier skill score bss typically 0 65 with respect to beach face erosion offshore accretion and morphological impacts of washover xbeach was also used to model storm impacts on a steep average tan 0 12 4 5 km long and 100 m 140 m wide macrotidal gravel barrier d50 2 mm to 10 mm located in sw england although the development of a storm berm was not reproduced well erosion was predicted with sufficient skill bss 0 60 to meet practical engineering requirements concerned with predicting storm impacts and threshold wave and water level conditions for gravel barrier overwashing

scaling and connectivity of joint systems in sandstones from western norway abstract the scaling properties of a joint system in devonian sandstones in western norway have been investigated using seven maps covering areas from 18 to 720 m across which were generated by mapping in the field and from low level aerial photography taken from different heights each map represent a scale window on the fracture population bounded by resolution at small scales and the sample size at large scales a power law relationship between fracture trace length and critical observation height maximum height at which a trace can be identified is derived and used to create a statistical model for the resolution effects the model indicates that a continuous smooth curve without a straight line segment on a log log cumulative frequency distribution plot does not necessarily rule out a power law as the underlying population distribution together the maps indicate a powerlaw trace length distribution with an exponent of 2 1 this power law may be valid over four or more orders of magnitude with natural lower cut off of around 1 m the exponent is significantly different from 2 0 strictly selfsimilar case and is reflected in a decrease in the abundance of fractures with length comparable to map size as map scale decreases the fracture trace length distribution results in a decrease in apparent connectivity with decreasing scale high resolution large scale maps are well connected while the lowest resolution map smallest scale is unconnected fractures in the smallest scale map are however connected by small fractures below the limit of resolution represented by the largest scale map the variation in apparent connectivity with scale has implications for fluid flow when fractures are open to fluid flow the scaling properties of apparent connectivity imply that beyond a certain scale the size of fracture controlling flow will be scale independent in this fracture system this appears to occur in sample areas of around 300 m across

some consequences of a proposed fractal nature of continental faulting a key question in the study of continental deformation concerns the preservation of undeformed regions sometimes quite large in the midst of otherwise penetrative deformation some authors1 have interpreted such regions as being relatively strong but we argue here that the existence of large undeformed regions might instead arise naturally from a fractal style of continental faulting a scaling analysis derived from laboratory simulations of the india asia collision2 5 yields a predicted distribution of undeformed regions which can be tested in the field we also show that if continental faulting is fractal in nature this will limit the validity of homogenization approaches to the modelling of continental deformation in which the rheology of the lithosphere is assumed to be homogeneous at scales larger than a threshold value

the influence of beach porosity on wave uprush and backwash abstract packwood a r 1983 the influence of beach porosity on wave uprush and backwash coastal eng 7 29 40 a numerical model is described to calculate the influence of a porous bed on the run up of a bore on a gently sloping sandy beach it is shown that fine medium grade sands have very little effect in the run up phase significant differences between impermeable and porous bed solutions are found in the backwash which might explain certain sand erosion and deposition phenomena

a statistical scaling model for fracture network geometry with validation on a multiscale mapping of a joint network hornelen basin norway 1 fracture patterns are characterized by a complex geometry which involves a large length distribution and nonhomogeneous density distributions here we address the issue of the modeling of this complex geometry over scales through a first order model providing the characterization of the number of fractures of a given length and at a given scale we propose that the simplest model is a power law in both space and fracture length with three main parameters the exponent a of a power law length distribution the fractal dimension d which fixes the scale dependence of the number of fractures and the fracture density we verify the applicability of this model on seven fracture patterns mapped from the metric scale up to almost the kilometric scale in the hornelen basin the model efficiently describes fracture network properties at all scales with a single set of parameters for the hornelen fracture networks we found a simple relationship between basic exponents a d 1 implying that the fracture network is self similar through this analysis we present different methodological developments for deriving the basic exponents a and d and for verifying the consistency of the model overall the main methodological development is about the normalization of the measurements made from different scales of observation finally we discuss both the limitations and the uses of such a model for analyzing the hydraulic and mechanical properties of fracture networks

non hydrostatic modeling of surf zone wave dynamics abstract non hydrostatic models such as surface waves till shore swash resolve many of the relevant physics in coastal wave propagation such as dispersion shoaling refraction dissipation and nonlinearity however for efficiency they assume a single valued surface and therefore do not resolve some aspects of breaking waves such as wave overturning turbulence generation and air entrainment to study the ability of such models to represent nonlinear wave dynamics and statistics in a dissipative surf zone we compare simulations with swash to flume observations of random unidirectional waves incident on a 1 30 planar beach the experimental data includes a wide variation in the incident wave fields so that model performance can be studied over a large range of wave conditions our results show that without specific calibration the model accurately predicts second order bulk parameters such as wave height and period the details of the spectral evolution and higher order statistics such as skewness and asymmetry of the waves monte carlo simulations show that the model can capture the principal features of the wave probability density function in the surf zone and that the spectral distribution of dissipation in swash is proportional to the frequency squared which is consistent with observations reported by earlier studies these results show that relatively efficient non hydrostatic models such as swash can be successfully used to parametrize surf zone wave processes

swash an operational public domain code for simulating wave fields and rapidly varied flows in coastal waters abstract a computational procedure has been developed for simulating non hydrostatic free surface rotational flows in one and two horizontal dimensions its implementation in the publicly available swash an acronym of simulating waves till shore is intended to be used for predicting transformation of surface waves and rapidly varied shallow water flows in coastal waters this open source code http swash sourceforge net has been developed based on the work of stelling and zijlema 2003 stelling and duinmeijer 2003 zijlema and stelling 2005 zijlema and stelling 2008 the governing equations are the nonlinear shallow water equations including non hydrostatic pressure and provide a general basis for describing complex changes to rapidly varied flows typically found in coastal flooding resulting from e g dike breaks and tsunamis and wave transformation in both surf and swash zones due to nonlinear wave wave interactions interaction of waves with currents and wave breaking as well as runup at the shoreline the present paper provides a complete description of the numerical algorithms currently used in the code the code is benchmarked using some analytical problems moreover the numerical results are validated with various cases of laboratory data with the principal aim to convey the capabilities of the swash code in particular emphasis is put on an analysis of model performance and associated physical implications serial and parallel performance scalings are also presented

the connectivity of two dimensional networks of spatially correlated fractures 1 continuum percolation thresholds for fracture systems are based on models with random fracture locations resulting in uniformly clustered systems in which all connections are fracture intersections fractures in natural systems can be either clustered or anticlustered and a significant portion of the connectivity is achieved through fracture abutments or splays analytical and numerical methods are combined to define critical properties of isotropic networks of constant length lines as a function of fracture clustering and of the ratio of abutments to intersections a second suite of numerical results indicates that the influence of these parameters varies as a function of the fracture length distribution a preliminary predictor of critical density of anisotropic nonrandom systems with lognormal length distributions is derived and applied to a suite of natural fracture systems predicted connectivities are closer to the observed connectivities when the predictor is used than when connectivity is estimated from the random threshold

two dimensional time dependent hurricane overwash and erosion modeling at santa rosa island abstract a 2dh numerical model which is capable of computing nearshore circulation and morphodynamics including dune erosion breaching and overwash is used to simulate overwash caused by hurricane ivan 2004 on a barrier island the model is forced using parametric wave and surge time series based on field data and large scale numerical model results the model predicted beach face and dune erosion reasonably well as well as the development of washover fans furthermore the model demonstrated considerable quantitative skill upwards of 66 of variance explained maximum bias 0 21 m in hindcasting the post storm shape and elevation of the subaerial barrier island when a sheet flow sediment transport limiter was applied the prediction skill ranged between 0 66 and 0 77 in a series of sensitivity tests in which several hydraulic forcing parameters were varied the sensitivity studies showed that the variations in the incident wave height and wave period affected the entire simulated island morphology while variations in the surge level gradient between the ocean and back barrier bay affected the amount of deposition on the back barrier and in the back barrier bay the model sensitivity to the sheet flow sediment transport limiter which served as a proxy for unknown factors controlling the resistance to erosion was significantly greater than the sensitivity to the hydraulic forcing parameters if no limiter was applied the simulated morphological response of the barrier island was an order of magnitude greater than the measured morphological response

theoretical correlations between the elastic and electrical properties in layered porous rocks with cracks of varying orientations abstract cracks that are widely existing in geological formations play an important role in affecting the elastic and electrical rock properties which are remotely measured for detecting and characterizing cracked rocks joint interpretation of the complementary elastic and electrical data is expected to give a better assessment of the cracks however the correlations between the elastic and electrical rock properties which are the key to the successful joint interpretation remain poorly understood in layered porous rocks with cracks of varying orientations we reviewed and summarized the most recent advances in the theoretical models for the elastic and electrical properties of layered porous rocks with inclined and rotated cracks as well as with randomly orienting cracks the limitations of the models were identified by comparing the modeling results with available experimental data and we applied the models within their validity range to obtaining theoretically the correlations between the elastic and electrical properties in layered porous rocks with cracks of the above mentioned orientations in the horizontal and vertical directions respectively we showed that the elastic and electrical properties are systematically correlated with cracks of varying crack densities and aspect ratios different cracks orientations affect the correlations in varying ways the results not only illustrate the link between the elastic and electrical properties in cracked rocks but also have important practical applications when the seismic and electromagnetic exploration data are jointly interpreted to gain better knowledge about the subsurface earth although future work is required to extend the models to more realistic cracked formations and to experimentally test the validity of the models and the theoretically obtained joint correlations

hydrothermal fluids assisted crustal scale strike slip on the argentat fault zone abstract the role of hydrothermal fluids in assisting the activity of strike slip faults is investigated using a range of new geological geophysical and geochemical data obtained on the argentat fault massif central france this fault zone 180 km long and 6 to 8 km width has experienced coeval intense channeling of hydrothermal fluids and brittle deformation during a short time span 300 295 ma according to seismic data the fault core is a 4 km wide vertical zone of high fracture density that rooted in the middle crust 13 km and that involved fluids in its deeper parts 9 13 km depth if stress analyses in the fault core and strain analyses in the damage zone both support a left lateral movement along the fault zone it is inferred that hydrothermal fluids have strongly influenced fault development and the resulting fault has influenced fluid flow fluid pressure made easier fracturing and faulting in zones of competent rocks units and along rheological boundaries repeated cycles of increase of fault fracture permeability then overpressure of hydrothermal fluids at fault extremity favored strong and fast development of the crustal scale strike slip fault the high permeability obtained along the fault zone permitted a decrease of coupling across the weak fault core connections between shallower and lower crustal fluids reservoirs precipitate the decrease of fault activity by quartz precipitation and sulfides deposition the zones of intense hydrothermal alteration at shallows crustal levels and the zones of fluid overpressure at the base of the upper crust both controlled the final geometry of the crustal scale fault zone

the role of swash infiltration in determining the beachface gradient a numerical study on sand and gravel beaches the increase of the gradient of the beachface with increasing sediment size has been attributed to swash infiltration the present study uses a process based numerical model to examine in detail the role of swash infiltration in determining the beachface gradient it is found that swash infiltration increases the onshore asymmetry in the swash flow thereby enhancing onshore sediment transport and resulting in relatively steep beachface gradients however the accretionary effects of swash infiltration are only evident when the rate of infiltration is sufficiently large i e when the total infiltration volume over a wave cycle exceeds c 2 of the uprush volume this threshold is attained when the hydraulic conductivity exceeds 1 cm s which is approximately equivalent to a grain size coarser than 1 5 mm this finding suggests that the correlation between beachface gradient and sediment size observed on sandy beaches is not due to enhanced swash asymmetry caused by swash infiltration for gravel beaches however swash infiltration is likely to be the dominant factor in controlling the beachface gradient with increased hydraulic conductivity i e sediment size resulting in steeper beachface gradients c 2001 elsevier science b v all rights reserved

generation of spatially correlated fracture models for seismic simulations summary the critical geometrical parameters that quantify the spatial distribution of natural fractures are the orientation length and position of fractures knowledge of their spatial distribution is important as they control the movement of subsurface fluids and also influence seismic waves propagating in the subsurface however generating realistic models of all of these geometrical parameters to use in forward seismic modelling or inversion applications can become very difficult especially when constraints are available only at a few sparse well locations hence this provides strong motivation for applying seismic data to estimate these quantities in field settings and reliable seismic modelling provides important constraints for interpretation and inversion the discrete fracture network dfn approach has been used frequently to generate models with stochastic distributions of fractures based on sparse well and seismic data however most of these studies lack any constraint from physical models of the behaviour of fractured media in this paper we implement and extend an alternative modelling technique to generate several realizations of a fracture model beginning with theoretical results for the strain energy of a fractured material and propose ways to better incorporate geological field observations the method utilizes an elastic energy function that sums the interactions of all pairs of fractures present in the model the energy for each pair depends on the distance between the two fractures their orientations lengths and some material properties this energy function also serves as an objective function for a simulated annealing sa algorithm used to obtain multiple realizations of correlated fracture networks we improve earlier versions of this technique by incorporating periodic boundary conditions including criteria to limit the maximum range of pair wise calculations and suggesting methods to constrain models to match field data assuming that the host rock is isotropic and homogeneous this method produces orthogonal sets of fractures a pattern that is commonly observed during basin formation or subsidence this shows how the method can be utilized to provide constraints with a physical basis to facilitate the development of fracture models we also outline how the fracture model can be converted into an anisotropic seismic velocity model to compute synthetic seismograms for reservoir characterization applications

modelling storm hydrodynamics on gravel beaches with xbeach g abstract in this paper we present a process based numerical model for the prediction of storm hydrodynamics and hydrology on gravel beaches the model comprises an extension of an existing open source storm impact model for sandy coasts xbeach through the application of 1 a non hydrostatic pressure correction term that allows wave by wave modelling of the surface elevation and depth averaged flow and 2 a groundwater model that allows infiltration and exfiltration through the permeable gravel bed to be simulated and is referred to as xbeach g although the model contains validated sediment transport relations for sandy environments transport relations for gravel in the model are currently under development and unvalidated consequently all simulations in this paper are carried out without morphodynamic feedback modelled hydrodynamics are validated using data collected during a large scale physical model experiment and detailed in situ field data collected at loe bar cornwall uk as well as remote sensed data collected at four gravel beach locations along the uk coast during the 2012 2013 storm season validation results show that the model has good skill in predicting wave transformation overall sci 0 14 0 21 run up levels sci

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

modelling gravel beach dynamics with xbeach abstract numerical cross shore profile evolution models have been good at predicting beach erosion during storm conditions but have difficulty in predicting the accretion of the beach during calm periods this paper describes the progress made in modifying and applying the public domain xbeach code to the prediction and explanation of the observed behaviour of coarse grained beaches in the laboratory and the field under accretive conditions the paper outlines in details the changes made to the original code version 12 including the introduction of a new morphological module based upon soulsby s sediment transport equation for waves and currents and the incorporation of packwood s infiltration approach in the unsaturated area of the swash region the competence of this modified model during calm conditions for describing the steepening of the profile and the growth of the beach berm is demonstrated preliminary results on the behaviour of the beach subject to both waves and tides are presented good agreement is found between the model simulations and large scale laboratory measurements as well as field observations from a composite beach in the uk the reasons for the model s capabilities are discussed

from field data to fracture network modeling an example incorporating spatial structure this paper describes a technique for processing field data for a fracture network model which accounts for the observed spatial variability this has been done by generating a network subregion by subregion where the properties of each subregion are predicted through geostatistics once the geometry of a particular realization is specified flow through the network is studied we develop the method for a two dimensional analysis based on data from fanay augeres a uranium mine in france we plan to extend the analysis to three dimensions and compare the results with in situ test results in particular we have focused on the data collected in a long section of a drift where fractures have been mapped and steady state permeability tests have been performed in 10 boreholes in order to generate fractures in a statistically heterogeneous region we first divided the region into statistically homogeneous subregions in each subregion and for each fracture set we must specify the areal fracture density and the orientation length and aperture distributions we divided the fractures into five sets based on tectonic history and observed that for each set fractures spaced close together tended to have similar orientations this was built into the simulation an estimate of the aperture distribution for each set was made by assuming that the hydraulic apertures of the fractures intersecting a well test zone were proportional to the fracture opening observed in the core data input to the geostatistical analysis for each set consisted of 16 values of mean length and density of fractures in each 5 m by 2 m section of the drift wall the results of the simulation are tables of values for mean length and fracture density for each of the five sets the value of density simulated for each subregion was used directly to determine the number of fractures to be generated of that set in the subregion the value of mean length was used as the mean of the length distribution in the subregion the local coefficient of variation for length was the same in every subregion using the data described above we generated a 100 m by 100 m fracture network in a series of 100 statistically homogeneous subregions the fractured region generated has a total of 65 740 fractures a 70 m by 70 m region was isolated for directional permeability testing results show that the system is barely connected about 0 1 of the fractures essentially control permeability in the language of percolation theory this mesh is close to the critical density for which infinite clusters of fractures are found problems remaining include that 1 the analysis should be extended to three dimensions 2 the geostatistical simulation and network simulation should be combined rather than used as two separate operations and 3 the nature of flow through single fractures at fanay augeres should be investigated

scaling of fracture connectivity in geological formations a new method to quantify fracture network connectivity is developed and applied to analyze two classical examples of fault and joint networks in natural geological formations the connectivity measure accounts for the scaling properties of fracture networks which are controlled by the power law length distribution exponent a the fractal dimension d and the fracture density the connectivity behavior of fracture patterns depends on the scale of measurement for a d 1 analysis of the san andreas fault system shows that a d 1 and that the connectivity threshold is reached only at a critical length scale in contrast for a typical sandstone joint pattern a d 1 which is on the cusp where the connectivity threshold is highly sensitive to the minimum fracture length in the system

role of fluids in faulting inferred from stress field signatures the stress orientation signature of weak faults containing high pressure fluids has been observed for segments of the san andreas fault system in southern california the inferred lithostatic fluid pressures extend into the surrounding relatively intact rock in a zone scaling with the width of the interseismic strain accumulation repeated strain related fracturing and crack sealing may have created low permeability barriers that seal fluids into the network of currently active fractures

seismoacoustic signatures of fracture connectivity wave induced fluid flow wiff between fractures and the embedding matrix as well as within connected fractures tends to produce significant seismic attenuation and velocity dispersion while wiff between fractures and matrix is well understood the corresponding effects related to fracture connectivity and the characteristics of the energy dissipation due to flow within fractures are largely unexplored in this work we use oscillatory relaxation simulations based on the quasi static poroelastic equations to study these phenomena we first consider synthetic rock samples containing connected and unconnected fractures and compute the corresponding attenuation and phase velocity we also determine the relative fluid displacement and pressure fields in order to gain insight into the physical processes involved in the two manifestations of wiff in fractured media to quantify the contributions of the two wiff mechanisms to the total seismic attenuation we compute the spatial distribution of the local energy dissipation finally we perform an exhaustive sensitivity analysis to study the role played by different characteristics of fracture networks on the seismic signatures we show that in the presence of connected fractures both p wave attenuation and phase velocity are sensitive to some key characteristics of the probed medium notably to the lengths permeabilities and intersection angles of the fractures as well as to the overall degree of connectivity of the fracture network this in turn indicates that a deeper understanding of these two manifestations of wiff in fractured media may eventually allow for the extraction of some of these properties from seismic data

concepts in gravel beach dynamics abstract the dominant processes in gravel beach dynamics are reviewed highlighting some common themes which unify the various components of the gravel beach system the repercussions of which impart on how gravel beach dynamics might be understood conceptually in particular gravel beach dynamics are thought to be highly dependent on the temporal and spatial variation in grain size and the continual adjustments made by an active beach step both of which act not only as the expression of changing morphodynamic conditions but also as a controlling influence morphodynamics the notion that the exchanges on beaches between the hydrodynamics sediment transport and morphological change takes the form of reciprocal relationships which are mediated through feedback mechanisms in such a way that they cannot be thought of or studied independently is not a new one yet it appears that for the gravel beach morphodynamics must be re defined to describe conditions where variations in sediment size are thought to deserve parity rather than as merely a sequent entity or boundary condition morpho sedimentary dynamics is a phrase coined to intuit such cause and effect detailing the co evolution of morphology hydro hydraulics and sediment properties whilst acknowledging causative pluralism feedbacks and multiplier effects this is the recommended conceptual framework within which to crystallise thought and organise further research for the gravel beach essentially it increases the minimum number of parameters needed to describe the state of the gravel beach as a physical system therefore it is advised that simplicity will be most expedient in our future modelling efforts if complexity is to be adequately encapsulated

seismic evidence for a lower crustal detachment beneath san francisco bay california results from the san francisco bay area seismic imaging experiment basix reveal the presence of a prominent lower crustal reflector at a depth of 15 kilometers beneath san francisco and san pablo bays velocity analyses indicate that this reflector marks the base of franciscan assemblage rocks and the top of a mafic lower crust because this compositional contrast would imply a strong rheological contrast this interface may correspond to a lower crustal detachment surface if so it may represent a subhorizontal segment of the north america and pacific plate boundary proposed by earlier thermo mechanical and geological models

on the cross shore profile change of gravel beaches abstract this paper investigates cross shore profile changes of gravel beaches with particular regard to discussing the tendency for onshore transport and profile steepening in the swash zone the discussion includes observed morphological changes on a gravel beach from experimental investigations at the large wave flume gwk in hanover germany during the tests all the profile changes occurred in the swash zone resulting in erosion below the still water line swl and formation of a berm above the swl we investigate the profile evolution evaluating the transport rates from a bed load sediment transport formulation coupled with velocities calculated from a set of boussinesq equations that have been validated for its use in the surf and swash zones lynett p j wu t r and liu l f p 2002 modelling wave runup with depth integrated equations coastal engineering 46 89 107 otta a k and pedrozo acuna a 2004 swash boundary and cross shore variation of horizontal velocity on a slope in j m smith editor proceedings 29th international conference on coastal engineering world scientific lisbon portugal pp 1616 1628 we discuss the influence of bottom friction on the predicted profiles using reported friction factors from experimental studies it is shown that the use of a different friction factor within a realistic range in each phase of the swash uprush and backwash improves prediction of the beach profiles although quantitative agreement between the measured and computed profile evolutions is not satisfactory furthermore if the friction factor and the transport efficiency c of the sediment transport formulation are kept the same in the uprush and backwash accurate representation of profile evolution is not possible indeed the features of the predicted profiles are reversed however when the c parameter is set larger during the uprush than during the backwash the predicted profiles are closer to the observations differences between the predicted profiles from setting non identical c values and friction factors for the swash phase are believed to be linked to both the infiltration effects on the flow above the beachface and the more accelerated flow in the uprush

statistical mechanics and scaling of fault populations with increasing strain in the corinth rift scaling properties of fracture fault systems are studied in order to characterize the mechanical properties of rocks and to provide insight into the mechanisms that govern fault growth a comprehensive image of the fault network in the corinth rift greece obtained through numerous field studies and marine geophysical surveys allows for the first time such a study over the entire area of the rift we compile a detailed fault map of the area and analyze the scaling properties of fault trace lengths by using a statistical mechanics model derived in the framework of generalized statistical mechanics and associated maximum entropy principle by using this framework a range of asymptotic power law to exponential like distributions are derived that can well describe the observed scaling patterns of fault trace lengths in the rift systematic variations and in particular a transition from asymptotic power law to exponential like scaling are observed to be a function of increasing strain in distinct strain regimes in the rift providing quantitative evidence for such crustal processes in a single tectonic setting these results indicate the organization of the fault system as a function of brittle strain in the earth s crust and suggest there are different mechanisms for fault growth in the distinct parts of the rift in addition other factors such as fault interactions and the thickness of the brittle layer affect how the fault system evolves in time the results suggest that regional strain fault interactions and the boundary condition of the brittle layer may control fault growth and the fault network evolution in the corinth rift

do seismic waves sense fracture connectivity 1 a defining characteristic of fractured rocks is their very high level of seismic attenuation which so far has been assumed to be mainly due to wave induced fluid flow wiff between the fractures and the pore space of the embedding matrix using oscillatory compressibility simulations based on the quasi static poroelastic equations we show that another important and as of yet undocumented manifestation of wiff is at play in the presence of fracture connectivity this additional energy loss is predominantly due to fluid flow within the connected fractures and is sensitive to their lengths permeabilities and intersection angles correspondingly it contains key information on the governing hydraulic properties of fractured rock masses and hence should be accounted for whenever realistic seismic models of such media are needed

analysis of a strike slip fault network using high resolution multibeam bathymetry offshore nw devon u k abstract imaging of the sea floor offshore from hartland point north devon u k using high resolution multibeam bathymetry reveals a strike slip fault network this consists of ne trending left lateral faults and nw trending right lateral faults that cut folded and steeply dipping strata 60 faults were accurately mapped using the multibeam imagery and lateral separations of marker beds measured along fault traces these data are used to examine the spatial arrangement fault displacement and strain distribution within the network at different displacement cut offs at high displacement cut offs the fault network is dominated by a few long isolated right lateral fault segments that bound fault blocks but at lower displacement cut offs shorter left lateral and right lateral fault segments make up fault tips and infill fault blocks the majority 70 of fault trace length is taken up by small fault segments that have 10 m displacement the topology and relative connectivity of the network is analysed in terms of a system of fault branches between tips i nodes or intersections x or y nodes the relative proportions of which reflect the connectivity of the network although the kinematic behaviour of the fault network is controlled by large fault segments connectivity is very dependent on the small fault segments a comparison with a similar nearby strike slip fault network at westward ho north devon shows many similarities and indicates that fault networks are better connected with increasing strain and that the network becomes better connected when strain is localized within damage zones rather than on individual faults

quantifying vein attributes in massive mudstones triassic sw england implications for progressive evolution of opening mode fracture networks abstract attributes of gypsum vein arrays in the triassic massive mudstones of sw england were analyzed to infer the process of vein network evolution field data demonstrate that there is no clear correlation between vein orientation and thickness however sub horizontal veins have a higher average thickness than the inclined veins vein thickness distribution is best characterized by a log normal distribution the fractal dimensions d of vein networks analyzed range from 1 44 to 1 71 vein networks which contain abundant bridging veins between neighbouring sub horizontal veins to form an anastomosing pattern exhibit a higher d value the fraction of vein volume derived from image analysis ranges from 6 75 to 17 94 a positive correlation is revealed by plotting the fractal dimensions of the vein networks versus the number of vein intersection points suggesting that an anti clustering distribution of veins could contribute to more interactions and also intersections of the gypsum veins the vein attribute data presented indicate that mineralization in the massive mudstones is mainly localized to some of the largest veins as a result of mechanical interaction of neighbouring veins during vein propagation hindering the nucleation of new veins as a consequence accommodation of the bulk rock strain could be facilitated mainly by expansion of the large backbone veins which follow a positive feedback mechanism of growth this study reveals a strong link between the geometric parameters of opening mode fractures with the history of their formation propagation and intersection

a model of fracture nucleation growth and arrest and consequences for fracture density and scaling 1 in order to improve discrete fracture network dfn models which are increasingly required into groundwater and rock mechanics applications we propose a new dfn modeling based on the evolution of fracture network formation nucleation growth and arrest with simplified mechanical rules the central idea of the model relies on the mechanical role played by large fractures in stopping the growth of smaller ones the modeling framework combines in a time wise approach fracture nucleation growth and arrest it yields two main regimes below a certain critical scale the density distribution of fracture sizes is a power law with a scaling exponent directly derived from the growth law and nuclei properties above the critical scale a quasi universal self similar regime establishes with a self similar scaling the density term of the dense regime is related to the details of arrest rule and to the orientation distribution of the fractures the dfn model so defined is fully consistent with field cases former studied unlike more usual stochastic dfn models ours is based on a simplified description of fracture interactions which eventually reproduces the multiscale self similar fracture size distribution often observed and reported in the literature the model is a potential significant step forward for further applications to groundwater flow and rock mechanical issues

percolation conditions in fractured hard rocks a numerical approach using the three dimensional binary fractal fracture network 3d bffn model 1 we numerically investigate fracture connectivity and percolation conditions in fractured hard rocks using a three dimensional binary fractal fracture network 3d bffn model based on three fractal geometric parameters the fractal dimensions d2 of the spatial distribution of fractures the exponent of the power law cumulative fracture length distribution a and the maximum fracture length lmax normalized by the domain length l lmax l numerical results clarify that the percolation threshold in 3d bffn models is strongly controlled by fractal geometric parameters and is independent of any anisotropy in the orientations in addition when a 0 55 are percolated domains the zone of percolation within seismogenic fracture networks between mi and ki reveals that the networks formed from seismic swarm related seismogenic fractures over a 7 week period related to the intrusion of a dyke inferred previously from seismicity and deformation data

on attenuation of seismic waves associated with flow in fractures heterogeneity of porous media induces a number of fluid flow mechanisms causing attenuation of seismic waves attenuation induced by squirt type mechanisms has previously been analyzed for aspect ratios smaller or equal to 10 3 using a hybrid dimensional modeling approach particularly apt for large aspect ratio conduits we numerically simulated deformation induced fluid flow along two intersecting fractures to investigate the physics of attenuation related to the interaction of fracture induced fluid flow and to leak off attenuation related to fracture flow increases in magnitude with increasing geometrical aspect ratio of the fracture the inherent time scales of both flow mechanisms do not influence each other but the faster process is associated with stronger attenuation than the slower process models relying on simple diffusion equations have rather limited potential for approximation of pressure transients