kinematic analyses of brittle roto translational planar and listric faults based on various rotational to translational velocities of the faulted blocks abstract research on rotational roto translational faults have been relatively less than translational faults this is despite perfect translational faults seldom occur in mega scale this work models slickenside lineation patterns on planar and listric fault planes for different ratios of rates of rotation to the uniform speed towards a specific geographic direction v of faulted blocks curves simulated for the planar fault planes are fitted with natural examples of such roto translational faults in our 10 chosen examples the v ratio ranges between 0 2 fault at san miguelito range central mexico and as high as 2 4 fault at hyogoken nambu japan knowing the v ratios from terrains can better interpret its tectonics for example if v and the total time of duration of the deformation are known from some other studies even the total amount of rotation can be estimated the far reaching implication of this study is that as several hydrocarbon reserves and terrains with landslides are related to roto translational faults this work will be a stepping stone in petroleum geosciences e g stability of hydercarbon reserve and engineering geology e g stability of slope

diurnal tides near the yermak plateau recent current measurements obtained from drifting platforms over the yermak plateau in the eastern arctic ocean confirm that the plateau is a region of greatly enhanced diurnal tidal currents modulation of the diurnal currents is clearly related to the plateau topography as has been previously proposed we show however that temporal variability due to spring neap modulation must also be considered in interpreting records from drifting platforms we review simple models of tidal current amplification in this region and find that the previous assumption of near resonant barotropic shelf waves propagating around the plateau s entire perimeter is inconsistent with the true topography instead we propose that the diurnal variability is due to topographic shelf waves at the k1 and o1 tidal frequencies that are generated at points on the plateau s perimeter where the waves group velocities are near zero observed cross slope variations in ellipticity orientation and magnitude of tidal oscillations are consistent with the presence of topographic waves generated in this manner the topographic enhancement of the diurnal tide near the yermak plateau has important consequences for the sea ice cover hydrography and general circulation of this region for example the stress divergence applied by the tidal currents at the ice base greatly exceeds the typical divergence of the surface wind stress and tides may therefore be important to local ice deformation the strong cross slope tidal currents also appear to be responsible for the production of high frequency internal wave packets which are associated with energetic diapycnal mixing in the pycnocline we also consider the possibility that tidal rectification is responsible for a mean current transporting atlantic water clockwise around the plateau

wind wave variability in hornsund fjord west spitsbergen abstract in this study the third generation spectral wave model simulating waves nearshore swan is applied to an analysis of wind wave conditions in hornsund a relatively small fjord in the southwestern part of spitsbergen svalbard archipelago the model is run on a series of three nested grids with increasing spatial resolution wave energy spectra from a large scale wavewatch iii model wind from the global forecast system and water levels from a tidal model of the arctic ocean are used as input data the modelling results are validated against observational data from four coastal locations within hornsund one in gashamna and three in isbjornhamna hansbukta i h which is the main area of interest in this study within the frequency range available in observations

the geometry of echelon fractures in rock implications from laboratory and numerical experiments abstract the traces of echelon joints veins and dikes in rock range from curving to straight theoretical analyses using boundary element numerical methods have concluded that straight open fractures imply a significant remote differential stress whereas curving traces imply a more nearly isotropic stress we present a series of laboratory experiments which investigate the two dimensional propagation paths of echelon fractures in pmma plates as a function of the applied biaxial loading and the initial geometry of a simple fracture array the experimental results support the theoretical conclusions and verify the accuracy of the numerical method at the grain scale rock does not rigorously conform to the assumptions of isotropy homogeneity and linear elasticity demanded by the numerical method nevertheless results from crack path stability theory suggest that small scale deviations of a fracture from the ideal path generally do not affect its large scale behavior fracture paths which become kinked or curved by local heterogeneities are found to self correct to a path governed by competition between the fracture tip and remote stress fields provided the remote differential stress is non zero this enhances our confidence that the numerical method can be used to produce and explain realistic fracture geometries in rock an unexpected experimental result is the non perpendicular intersection of fractures grown in the laboratory free surface boundary conditions require that the walls of an open fracture be free of shear stress the principal stresses are therefore aligned with the crack wall and we might consequently expect an approaching opening mode fracture either to intersect the free surface at a right angle or to turn away and follow an asymptotic nonintersecting path experimental and numerical modeling however shows how the near tip stresses generated by an approaching fracture dominate the local stress field and allow it to propagate along an oblique path very close to intersection with the adjacent free surface

a barotropic inverse tidal model for the arctic ocean 1 we describe high resolution 5 km grid linear dynamics and inverse models of arctic ocean barotropic tides obtained with the osu tidal inversion software otis package the 8 constituent dynamics based model uses the latest ibcao bathymetry and open boundary forcing from the recent tpxo 6 2 global barotropic tidal solution this model performs significantly better than the present benchmark arctic tidal model 14 km grid by z kowalik and a proshutinsky as judged by comparisons with 300 coastal tide gauges the greatest improvements are found in the canadian arctic archipelago nares strait and the baffin bay and labrador sea and can be explained by the higher resolution of the new model in these topographically complex regions the new arctic inverse model assimilates coastal and benthic tide gauges and topex poseidon and ers altimetry for further improvements of the 4 dominant constituents m2 s2 k1 and o1

accuracy assessment of recent ocean tide models over 20 global ocean tide models have been developed since 1994 primarily as a consequence of analysis of the precise altimetric measurements from topex poseidon and as a result of parallel developments in numerical tidal modeling and data assimilation this paper provides an accuracy assessment of 10 such tide models and discusses their benefits in many fields including geodesy oceanography and geophysics a variety of tests indicate that all these tide models agree within 2 3 cm in the deep ocean and they represent a significant improvement over the classical schwiderski 1980 model by approximately 5 cm rms as a result two tide models were selected for the reprocessing of topex poseidon geophysical data records in late 1995 current ocean tide models allow an improved observation of deep ocean surface dynamic topography using satellite altimetry other significant contributions include theft applications in an improved orbit computation for topex poseidon and other geodetic satellites to yield accurate predictions of earth rotation excitations and improved estimates of ocean loading corrections for geodetic observatories and to allow better separation of astronomical tides from phenomena with meteorological and geophysical origins the largest differences between these tide models occur in shallow waters indicating that the current models are still problematic in these areas future improvement of global tide models is anticipated with additional high quality altimeter data and with advances in numerical techniques to assimilate data into high resolution hydrodynamic models

climatological features of global multiple tropopause events 1 this study examines various climatological features related to multiple tropopause events mt events the analysis is based on the lapse rate definition of the tropopause and is performed on a radiosonde data subset taken from the integrated global radiosonde archive database the global statistics of mt events are analyzed taking into consideration both their seasonal and geographical variations our results are in moderate qualitative agreement with those of earlier studies they reinforce the analytical findings of other researchers but at the same time highlight important differences in both the number and position of the maximum occurrence of mt events we found a latitudinal band of multiple tropopause occurrence in the northern hemisphere and three centers in the southern hemisphere which coincided with identified zones of maximum cyclogenesis the climatological features of pressure temperature and vertical separation of mt events revealed the complexity of these phenomena which behave very differently according to latitude and season

parameterizing tidal dissipation over rough topography the traditional model of tidal dissipation is based on a frictional bottom boundary layer in which the work done by bottom drag is proportional to a drag coefficient and the velocity cubed however away from shallow coastal regions the tidal velocities are small and the work done by the bottom boundary layer can account for only weak levels of dissipation in the deep ocean the energy flux carried by internal waves generated over rough topography dominates the energy transfer away from barotropic flow a parameterization for the internal wave drag over rough topography is included as a dissipative mechanism in a model for the barotropic tides model results suggest that the inclusion of this dissipation mechanism improves hydro dynamical models of the ocean tide it also substantially increases the amount of modeled tidal dissipation in the deep ocean bringing dissipation levels there into agreement with recent estimates from topex poseidon altimetry data

nares strait hydrography and salinity field from a 3 year moored array 1 nares strait to the west of greenland facilitates the exchange of heat and freshwater between the arctic and atlantic oceans this study focuses on salinity temperature and density measurements from nares strait from a mooring array deployed from 2003 to 2006 innovative moorings requiring novel analysis methods measured seawater properties near 80 5 n at spacing sufficient to resolve the internal rossby deformation radius the 3 year mean geostrophic velocity has a surface intensified southward flow of 0 20 m s 1 against the western side of the strait and a secondary core flowing southward at 0 14 m s 1 in the middle of the strait data show warm salty water on the greenland side and cold fresher water on the ellesmere island side especially in the top layers there was a clear difference in hydrographic structure between times when sea ice was drifting and when it was land fast ice was drifting in late summer fall and early winter with a strong surface intensified geostrophic flow in the middle of the strait ice was land fast in late winter spring and early summer when there was a subsurface core of strong geostrophic flow adjacent to the western side of the strait salinity variations of about 2 psu in time and space reflect a variable freshwater outflow from the arctic ocean one particularly strong pulse occurred at the end of july 2005 for several days steeply sloping isohalines indicated strong geostrophic flow down the middle of the strait coinciding with an amplified ice export from the arctic due to strong southward winds

grounding line migration from 1992 to 2011 on petermann glacier north west greenland we use satellite radar interferometry to investigate changes in the location of the petermann glacier grounding line between 1992 and 2011 the grounding line location was identified in 17 quadruple difference interferograms produced from european remote sensing ers 1 2 data the most extensive time series assembled at any ice stream to date there is close agreement 20 6 cm between vertical displacement of the floating ice shelf and relative tide amplitudes simulated by the arctic ocean dynamics based tide model 5 aodtm 5 arctic tide model over the 19 a period the groundling line position varied by 470 m on average with a maximum range of 7 0 km observed on the north east margin of the ice stream although the mean range 2 8 km and variability 320 m of the grounding line position is considerably lower if the unusually variable north east sector is not considered our observations demonstrate that large isolated movements cannot be precluded thus sparse temporal records should be analysed with care the grounding line migration observed on petermann glacier is not significantly correlated with time r 2 0 22 despite reported ice shelf thinning and episodes of large iceberg calving which suggests that unlike other ice streams on the south west margin of the greenland ice sheet petermann glacier is dynamically stable

on the choice of orbits for an altimetric satellite to study ocean circulation and tides the choice of an orbit for satellite altimetric studies of the ocean s circulation and tides requires an understanding of the orbital characteristics that influence the accuracy of the satellite s measurements of sea level and the temporal and spatial distribution of the measurements three orbital parameters determine the temporal and spatial sampling characteristics of the satellite the orbital altitude the inclination of the orbit and the repetition period the eccentricity of the chosen orbit should be less than 0 001 to minimize altimeter errors caused by uncertainty in determining the time of each altimeter measurement and to maintain the rate of height variation over the oceans within the limits of the altimeter tracker the choice of the satellite s orbital altitude is constrained by the influences of atmospheric drag and errors in models of the gravity field which decrease with height and the required complexity of the altimeter e g the power and or antenna size required and the effect on satellite systems of radiation from earth s radiation belts which increase with height the choice of inclination is constrained by a desire to measure sea level over all the ocean by the requirement that the acute angle between intersections of the subsatellite track be as large as possible and by the time phasing of the repeat of the satellite s ground track as a function of inclination which determines the aliased frequencies of the measurements of the oceanic tides the choice of repetition period is constrained by tradeoffs between temporal and spatial coverage and by the aliasing of tidal constituents combining the above constraints leads to a set of orbits in a narrow range of altitude and inclination called here the topex poseidon window this window extends from 1100 to 1500 km altitude and 62 to 66 inclination for a 10 day repeat period and consists of three subwindows following lines of equal orbit plane precession there are four choices of orbits within these subwindows that overfly the planned calibration sites at bermuda and dakar these are at 64 80 and 1335 km 62 01 and 1252 km 65 84 and 1255 km and 62 69 and 1173 km these choices have a minimum separation between the aliased frequencies of the eight largest diurnal and semidiurnal tides of one cycle per 4 71 years one cycle per 4 86 years one cycle per 4 87 years and one cycle per 4 27 years respectively thus there will be less than one cycle separation over the nominal 3 years mission of these four choices the first at 64 8 and 1335 km is preferable because it is less sensitive to error in estimating the upcoming solar cycle which will be a maximum during the mission and because it is more nearly centered in terms of inclination than the other choices for other calibration sites other choices would have to be made additional work beyond the scope of this paper will also be necessary to determine if the topex poseidon mission requires a frozen orbit i e an orbit for which there are no long term variations in the eccentricity and argument of perigee of the orbit if a frozen orbit is required then the first and third choices listed above have frozen orbits with an eccentricity that is acceptable for topex poseidon

the influence of fault geometry on small strike slip fault mechanics abstract meter scale subvertical strike slip fault traces in the central californian sierra nevada exhibit geometric complexities that significantly contribute to their mechanical behavior sections of faults that opened at depth channelized fluid flow as evidenced by hydrothermal mineral infillings and alteration haloes thin sections show a variation in the style of ductile deformation of infill along the fault with greater intensities of deformation along restraining bends orthorectified photomosaics of outcrops provide model geometries and parameter constraints used in a two dimensional displacement discontinuity model incorporating a complementarity algorithm model results show that fault shape influences the distribution of opening and consequently the spatial distribution of fluid conduits geometric irregularities are present at many scales and sections of opening occur along both releasing and restraining bends model sensitivity tests focus on boundary conditions along the fault frictional properties on closed sections and fluid pressure within sections of opening the influence of the remote stress state varies along a non planar fault complicating the relationships between remote stresses frictional properties slip and opening discontinuous sections of opening along model faults are similar in spatial distribution and aperture to the epidote infill assemblages observed in the field

earthquake nucleation on rough faults earthquake nucleation is currently explained using rate and state stability analysis which successfully models the behavior of laboratory simulated faults with constant thickness gouge layers however roughness is widely observed on natural faults and its influence on earthquake nucleation is little explored here we conduct frictional sliding experiments with different roughness on granite samples at upper crustal conditions 30 200 mpa we observe a wide range of behaviors from stable sliding to stick slip depending on the combination of roughness parameters and normal stress stick slip is repeatedly observed in velocity strengthening regimes and increases in normal stress stabilize slip these features are not fully predicted by current stability analysis we derive a new instability criterion that matches our observations based on fracture energy considerations and the size of weak patches created by fault roughness

stress concentrations around voids in three dimensions the roots of failure abstract we present stress concentration factors at the edges of 3d voids in uniaxial compression variations in these stress concentration factors due to poisson s ratio of the host material void shape and void void proximity are explicitly quantified voids loaded by a vertical compressive stress are hypothesised to fail in one or two ways 1 tension crack development due to tensile stress concentrations at the void poles or 2 compressive stress concentrations at the void sides causing the void wall to fail in shear the stress concentration factors in this study are found using the numerical displacement discontinuity method equations are provided to assess the proximity of a void to the two hypothesised modes of failure for 3d voids thinned in an axis that lies parallel to the compressive stress these have increasingly high stress concentrations at their sides changes in stress concentrations due to the poisson s ratio of the matrix are minor apart from for the intermediate stress at the void sides void shape void separation and void alignment are critical factors in the concentration of stresses this suggests a significant departure from strength predictions for porous material that are based solely on scalar values of porosity

the recent increase in north atlantic wave heights the nature and causes of the recent increase in north atlantic wave heights are explored by combining a numerical hindcast with a statistical analysis the numerical hindcast incorporates a 10 yr history 1980 89 of north atlantic twice daily wind analyses to generate a monthly averaged significant wave height swh history the hindcast compares favorably with published monthly averaged swh observations the link between modelgenerated wintertime monthly swh and monthly averaged sea level pressure slp data is determined by means of a canonical correlation analysis cca within the analysis domain most of the variance in swh and slp is captured by two pairs of joint patterns the leading pair consists of a slp dipole resembling the north atlantic oscillation nao and a swh dipole in spatial quadrature relation to it using the cca results an extended statistical hindcast of monthly wave fields is generated from sea level pressure data and used to quantitatively estimate the systematic increase in wave heights since the 1960s it is shown that an increasing trend in swh at several northeast atlantic locations since 1960 or so is related to the systematic deepening of the icelandic low and intensification of the azores high over the last three decades the analysis suggests that wave height south of 408n has decreased during the same period

oscillating dense plumes abstractthe flow of dense polar shelf waters down continental slopes is a critical component of the global ocean circulation recent observations suggest that such plumes can be heavily impacted by tidal variability and many of the world s important dense water sources are located in tidally active areas tides affect the source of dense water by modulating the location of hydrographic gradients and control the subsequent plume mixing and flow path in an effort to separate these effects dense plumes are modeled here by extending a classical one dimensional plume model to two unsteady scenarios in which the plume path is fixed the first case features a pulsed release of dense water into a stagnant ambient and the model predicts that gravity waves propagate down the plume advective waves in plume density travel with the mean velocity of the current and thus have a wavelength of the product of plume velocity and the oscillation period p the second case is of a steady sourced plume flowing through

slickenline orientations as a record of fault rock rheology abstract contact of geometric asperities across rough faults causes perturbations to the shear traction resolved on a fault surface that could potentially deflect the local slip direction slickenlines which record the relative displacement of opposing sides of a fault may therefore be sensitive to fault surface geometry to investigate the relationship between fault geometry shear traction and slip we use ground based lidar to measure the orientations of slickenlines defined by centimeter amplitude corrugations on three fault surfaces slickenline rakes measured in the mean plane of each fault rarely vary by more than a few degrees deviations from the mean rake do not correlate with the fault surface topography at scales up to a few meters but a weak correlation may be present at larger scales slip directions are therefore insensitive to any shear traction perturbations from the contact of geometric asperities at small scales this observation is consistent with scale dependent deformation we show that the roughness of fault surfaces implies that short wavelength asperities fail inelastically because of flattening during fault slip a crossover to elastic deformation occurs at lengths of 10 2 to 10 0 m which defines the minimum dimension of a strength asperity that influences the displacement field the roughness at the crossover length scale corresponds to the typical thickness of fault rocks in the fault core suggesting that fault rock thickness is related to the crossover length scale the data requires that multiple processes combine to produce the fault surface geometry we reconcile the variety of processes with the consistent surface roughness scaling by noting that all of the processes are governed in different ways by the elastic limit of rock

fault slip distribution and fault roughness summary we present analysis of the spatial correlations of seismological slip maps and fault topography roughness illuminating their identical self affine exponent though the complexity of the coseismic spatial slip distribution can be intuitively associated with geometrical or stress heterogeneities along the fault surface this has never been demonstrated based on new measurements of fault surface topography and on statistical analyses of kinematic inversions of slip maps we propose a model which quantitatively characterizes the link between slip distribution and fault surface roughness our approach can be divided into two complementary steps i using a numerical computation we estimate the influence of fault roughness on the frictional strength pre stress we model a fault as a rough interface where elastic asperities are squeezed the hurst exponent h characterizing the self affinity of the frictional strength field approaches h h 1 where h is the roughness exponent of the fault surface in the direction of slip ii using a quasi static model of fault propagation which includes the effect of long range elastic interactions and spatial correlations in the frictional strength the spatial slip correlation is observed to scale as hs h 1 where hs represents the hurst exponent of the slip distribution under the assumption that the origin of the spatial fluctuations in frictional strength along faults is the elastic squeeze of fault asperities we show that self affine geometrical properties of fault surface roughness control slip correlations and that hs h given that h 0 6 for a wide range of faults various accumulated displacement host rock and slip movement we predict that hs 0 6 even if our quasi static fault model is more relevant for creeping faults the spatial slip correlations observed are consistent with those of seismological slip maps a consequence is that the self affinity property of slip roughness may be explained by fault geometry without considering dynamical effects produced during an earthquake

new fjords new coasts new landscapes the geomorphology of paraglacial coasts formed after recent glacier retreat in brepollen hornsund southern svalbard

fault slip directions in central and southern greece measured from striated and corrugated fault planes comparison with focal mechanism and geodetic data fault slip directions recorded by outcropping striated and corrugated fault planes in central and southern greece have been measured for comparison with extension directions derived from focal mechanism and global positioning system gps data for the last 100 years to test how far back in time velocity fields and deformation dynamics derived from the latter data sets can be extrapolated the fault slip data have been collected from the basin bounding faults to plio pleistocene to recent extensional basins and include data from arrays of footwall faults formed during the early stages of fault growth we show that the orientation of the inferred stress field varies along faults and earthquake ruptures so we use only slip directions from the centers of faults where dip slip motion occurs to constrain regionally significant extension directions the fault slip directions for the peloponnese and gulfs of evia and corinth are statistically different at the 99 confidence level but statistically the same as those implied by earthquake focal mechanisms for each region at the 99 confidence level they are also qualitatively similar to the principal strain axes derived from gps studies extension directions derived from fault slip data are 043 047 for the southern peloponnese 353 for the gulf of corinth and 015 014 for the gulf of evia extension on active normal faults in the two latter areas appears to grade into strike slip along the north anatolian fault through a gradual change in fault slip directions and fault strikes to reconcile the above with 5 myr 1 clockwise rotations suggested for the area we suggest that the faults considered formed during a single phase of extension the deformation and formation of the normal fault systems examined must have been sufficiently rapid and recent for rotations about vertical axes to have been unable to disperse the fault slip directions from the extension directions implied by focal mechanisms and gps data thus in central and southern greece the velocity fields derived from focal mechanism and gps data may help explain the dynamics of the deformation over longer time periods than the 100 years over which they were measured this may include the entire deformation history of the fault systems considered a time period that may exceed 1 2 myr

topography of natural and artificial fractures in granitic rocks implications for studies of rock friction and fluid migration abstract the topography of fractures and joints has a strong influence on their frictional strength and fracture permeability important aspects of the surfaces are the size distribution and density of contact spots between the surfaces which can be calculated using topographic data for a variety of tensile fracture surfaces in granite including both natural joints and man made fractures spectral and statistical properties are similar suggesting that man made fractures in granites can be acceptable substitutes for natural fractures in some experimental situations the topographic data indicate that fracture surfaces at scales from 0 1 to 200 mm are approximately fractal and statistically self affine a log log plot of power spectral density vs spatial frequency calculated from the fracture surfaces indicates a spectral slope of 2 3 0 2 yielding a fractal dimension d between 2 25 and 2 45 shear fracture surfaces are also fractal but have anisotropic roughness which develops during the fracture initiation process the amount of anisotropy that develops on the shear fracture surfaces is small in comparison to that exhibited by natural fault surfaces which include anisotropy that results from post failure wear and from surface evolution for fractures like those measured in this study simple simulations indicate that the aperture size and number density of wall to wall contacts between the surfaces change non linearly with relative shear displacement of the surfaces it is possible to make preliminary estimates of how the permeability and frictional properties of fractures and joints depend on the size distribution and character of the contact spots furthermore given that artificial fractures can be generated numerically with statistical properties similar to those of natural or man made fractures it is reasonable for systematic studies of the effects of roughness on friction and fluid flow to use computer designed surfaces to provide a range of variability that is not easily accessible in the laboratory

propagation and vertical structure of the tidal flow in nares strait the southward freshwater flux through nares strait is an important component of the arctic s freshwater budget on short time scales flow through the strait is dominated by the tides and tidal dynamics may be important for the magnitude of the freshwater flux over longer periods here we build upon our existing knowledge of the tides in the region by exploring their propagation and vertical structure using data from four bottom mounted acoustic doppler current profilers deployed in nares strait between 2003 and 2006 we observe that propagating barotropic semidiurnal tidal waves interact to create a standing wave pattern explaining the abnormally large tidal amplitudes that are observed in this region in the along strait direction semidiurnal tidal currents exhibit strong variations with depth in contrast the diurnal tides propagate northward through the strait as progressive waves and the tidal currents are broadly depth invariant proximity of nares strait to the semidiurnal critical latitude and the topographical restriction imposed by the steep side wall of ellesmere island are primary drivers behind the observed vertical variability in the upper part of the water column baroclinic activity increases the tidal current amplitude by up to 25 in the across strait direction a two layer structure exists in both the diurnal and semidiurnal tidal flow with a phase lag of approximately a quarter of a tidal cycle across the strait for the semidiurnal tide our results suggest that strong vertical motion exists against the side walls of nares strait as the across strait flow interacts with the steeply sloping bathymetry

constraints from fault roughness on the scale dependent strength of rocks principal slip surfaces in faults have measurable roughness generated during slip the roughness both records previous events and poses the boundary conditions for future rupture digital high precision roughness data are now available at the field scale tens of centimeters to tens of meters for at least 22 faults and at the laboratory scale millimeters to tens of centimeters for a subset of these we quantify the slip surface roughness by measuring the aspect ratio which is the average asperity height divided by the profile length higher aspect ratios indicate rougher surfaces from the field studies two major trends have emerged 1 fault surface roughness lies in a restricted range with aspect ratios in the slip parallel direction of 0 07 0 5 for profiles of 1 m length and 2 fault surfaces are rougher at small scales than large ones these features can both be interpreted as fingerprints of scale dependent strength which sets a limit to the aspect ratio of the surface the measurements imply that shear strength scales with the observation scale l as l 0 4 the new understanding of the physical controls on roughness allows generalization of the extant measurements of a wide array of faults

wind wave variability in a shallow tidal sea spectral modelling combined with neural network methods in this paper the wind wave variability in the tidal basins of the german wadden sea is modelled with combined numerical and neural network nn methods first the wave propagation and transformation in the study area are modelled with the state of the art third generation spectral wave model swan the ability of swan to accurately reproduce the phenomena of interest in nonstationary conditions governed by highly variable winds water levels and currents is shown by comparisons of the modelled and measured mean wave parameters at four stations the principal component analysis of the swan results is then used to reveal the dominating spatial patterns in the data and to reduce their dimensionality thus enabling an efficient and relatively straightforward nn modelling of mean wave parameters in the whole study area it is shown that the data produced with the approach developed in this work have statistical properties discrete probability distributions of the mean wave parameters etc very close to the properties of the data obtained with swan thus proving that this approach can be used as a reliable tool for wind wave simulation in coastal areas complementary to often computationally demanding spectral wave models

a new tide model for the antarctic ice shelves and seas we describe a new tide model for the seas surrounding antarctica including the ocean cavities under the floating ice shelves the model uses data assimilation to improve its fit to available data typical peak to peak tide ranges on ice shelves are 1 2 m but can exceed 3 m for the filchner ronne and larsen ice shelves in the weddell sea spring tidal ranges are about twice these values model performance is judged relative to the 5 10 cm accuracy that is needed to fully utilize ice shelf height data that will be collected with the geoscience laser altimeter system scheduled to be launched on the ice cloud and land elevation satellite in late 2002 the model does not yet achieve this level of accuracy except very near the few high quality tidal records that have been assimilated into the model some improvement in predictive skill is expected from increased sophistication of model physics but we also require better definition of ice shelf grounding lines and more accurate water column thickness data in shelf seas and under the ice shelves long duration tide measurements bottom pressure gauge or gps in critical data sparse areas particularly near and on the filchner ronne and ross ice shelves and pine island bay are required to improve the performance of the data assimilation model

critical fluid injection volumes for uncontrolled fracture ascent hydro fracturing is a routine industrial technique whose safety depends on fractures remaining confined within the target rock volume both observations and theoretical models show that if the fluid volume is larger than a critical value pockets of fluid can propagate large distances in the earths crust in a self sustained uncontrolled manner existing models for such critical volumes are unsatisfactory most are two dimensional and depend on poorly constrained parameters typically the fracture length here we derive both analytically and numerically in three dimensions scale independent critical volumes as a function of only rock and fluid properties we apply our model to gas water and magma injections in laboratory industrial and natural settings showing that our critical volumes are consistent with observations and can be used as conservative estimates we discuss competing mechanisms promoting fracture arrest whose quantitative study could help to assess more comprehensively the safety of hydro fracturing operations

slip heterogeneity on a corrugated fault abstract slip heterogeneity reflects the fundamental physics of earthquake rupture and has been attributed to strong fault patches termed asperities or barriers we propose that variations in fault surface orientation due to slip parallel corrugations may act as geometric asperities and barriers generating variations in incremental i e due to a single earthquake slip across a fault surface we evaluate this hypothesis using observations from the arkitsa normal fault exposure in central greece a scan of the arkitsa fault surface with 1 m spatial resolution and mm scale precision reveals corrugations made up of 1 5 m wide synforms antiforms and nearly planar fault sections with long axes that extend in the slip direction across the entire exposed surface the surface is thus more than an order of magnitude smoother in the direction of slip than in the perpendicular direction slip perpendicular profiles exhibit nearly self similar scaling across the range of observed wavelengths 2 50 m whereas slip parallel profiles are significantly smoother at shorter wavelengths

circulation of winter water on the chukchi shelf in early summer abstract using a variety of data sources we investigate the properties and pathways of pacific origin winter water as it spreads across the eastern chukchi shelf in early summer the focus is on the time period june july 2011 during which an extensive shipboard hydrographic velocity survey was undertaken as part of the impacts of climate on ecosystem and chemistry of the arctic pacific environment icescape program a revised circulation scheme is constructed revealing that the transport pathways on the chukchi shelf are more complex than previously thought notably the well known branch progressing northward from the central channel bifurcates as it reaches hanna shoal flowing around both sides of the shoal and dividing into smaller filaments that continue towards barrow canyon mass is conserved in the circulation scheme with approximately 1 sverdrup flowing poleward across the chukchi shelf within these pathways then exiting barrow canyon the salinity of the winter water varied on the shelf in 2011 with saltier water found in the upstream portion of what is defined as the central pathway using sea ice concentration data and atmospheric reanalysis fields we argue that salinization of the winter water in the central pathway occurred via brine rejection as the parcels progressed north and passed through the cape lisburne polynya this demonstrates that winter water pervading the interior shelf can be transformed by convective overturning north of bering strait presumably stirring up nutrients from the sediments and thereby influencing primary productivity in the region of hanna shoal

observations of tidally induced currents over the continental slope of the laptev sea arctic ocean abstracttwo year long 2004 05 and 2005 06 records of currents from two moorings deployed at the continental slope of the laptev sea 78 26 n 125 40 e are used in order to define the properties of tidal currents in the upper 200 m ocean layer harmonic and spectral analyses of currents showed that the semidiurnal tidal constituent s2 dominates over the semidiurnal m2 and diurnal constituents this dominance of the s2 constituent in the tidal currents is due to resonant interaction of the superinertial wave with sloping bottom topography in contrast to the tidal currents sea level changes are dominated by the m2 constituent as seen from a tidal model by l padman and s erofeeva using assimilation of observational data strong anticorrelation 0 73 0 05 was found between the upper 50 m s2 current amplitudes and local sea ice concentration with fourfold from 2 0 to 8 5 cm s 1 amplification of tidal currents under ice free conditions this is probably due to a change of local resonance condit

turbulent kinetic energy dissipation in barrow canyon pacificwaterflowsacross theshallowchukchisea beforereachingthe arctic ocean where it isa sourceof heat freshwater nutrients and carbon a substantial portion of pacific water is routed through barrow canyon located in the northeast corner of the chukchi barrow canyon is a region of complex geometry and forcing where a variety of water masses have been observed to coexist these factors contribute to a dynamic physical environment with the potential for significant water mass transformation the measurements of turbulent kinetic energy dissipation presented here indicate diapycnal mixing is important in the upper canyon elevated dissipation rates were observed near the pycnocline effectively mixing winter and summer water masses as well as within the bottom boundary layer the slopes of shear stratification layers combined with analysis of rotary spectra suggest that near inertial wave activity may be important in modulating dissipation near the bottom because the canyon is known to be a hotspot of productivity with an active benthic community mixing may be an important factor in maintenance of the biological environment

mooring based observations of double diffusive staircases over the laptev sea slope abstracta yearlong time series from mooring based high resolution profiles of water temperature and salinity from the laptev sea slope 2003 04 2686 m depth 78 26 n 125 37 e shows six remarkably persistent staircase layers in the depth range of 140 350 m encompassing the upper atlantic water aw and lower halocline despite frequent displacement of isopycnal surfaces by internal waves and eddies and two strong aw warming pulses that passed through the mooring location in february and late august 2004 the layers preserved their properties using laboratory derived flux laws for diffusive convection the authors estimate the time averaged diapycnal heat fluxes across the four shallower layers overlying the aw core to be 8 w m 2 temporal variability of these fluxes is strong with standard deviations of 3 7 w m 2 these fluxes provide a means for effective transfer of aw heat upward over more than a 100 m depth range toward the upper halocline these findings suggest that double diffusion is an imp

integrating 3 d seismic data field analogs and mechanical models in the analysis of segmented normal faults in the wytch farm oil field southern england united kingdom we propose a methodology for the analysis of normal fault geometries in three dimensional 3 d seismic data sets to provide insights into the evolution of segmented normal fault systems and to improve recovery efforts in fault controlled oil fields limited seismic resolution can obscure subtle fault characteristics such as segmentation and gaps in fault continuity that are significant for oil migration and thus accurate reservoir characterization detailed seismic data analyses that incorporate principles of normal fault mechanics however can reveal evidence of fault segmentation we integrate seismic attribute analyses outcrop analog observations and numerical models of fault slip and displacement fields to augment the use of 3 d seismic data for fault interpretation we applied these techniques to the wytch farm oil field in southern england resulting in the recognition of significant lateral and to a lesser extent vertical segmentation of reservoir scale faults slip maxima on fault surfaces indicate two unambiguous segment nucleation depths controlled by the lithological heterogeneity of the faulted section faults initiated preferentially in brittle sandstone and limestone units subsequent growth and linkage of segments predominantly in the lateral direction resulted in composite fault surfaces that have long lateral dimensions and multiple slip maxima reservoir compartmentalization is greatest at the level of prevalent segment linkages which corresponds at wytch farm with the predominant hydrocarbon producing unit the sherwood sandstone at relatively shallower depths fault segments are younger and less evolved resulting in a greater degree of segmentation with intact relay zones

inferring paleostresses from natural fracture patterns a new method we introduce a method to infer the remote differential stress magnitude from the curvature of overlapping echelon fracture traces the curving paths of overlapping echelon cracks imply the predominance of local crack induced stresses over remote stresses during propagation nearly straight crack paths imply the controlling influence of a remote compressive crack parallel differential stress this method is used to interpret complex joint patterns mapped in sedimentary rock it is also applied to the problem of fracture pattern generation using computer models

tidal data inversion interpolation and inference initial efforts in applying inverse methods to studies of ocean tides have focused on making the best use of a small number of observations to map tidal fields in a large area as such inversion can be viewed as an objective analysis scheme which uses a dynamically appropriate spatial covariance derived from the shallow water equations to interpolate and smooth a sparse data set data from recent altimetry missions are not sparsely distributed relative to tidal wavelengths in the open ocean apparently reducing the need for complicated dynamically based interpolation schemes altimetric data sets are also quite large making application of rigorous inversion methods to global tidal modeling a challenging computational problem we describe here a new iterative solution scheme which allows us for the first time to fit the full set of topex poseidon cross over differences the resulting solution tpxo 3 fits validation tide gauges significantly better than previous inverse solutions tpxo 3 also reduces residual cross over variances relative to other recent inverse and empirical solutions particularly in shallow water where improvements are dramatic with the new solution approach very significant improvements in global tidal models should be possible in shallow areas and in the vicinity of complex bathymetry where high accuracy tidal modeling remains a challenging problem with the recent improvements in the definition of tidal elevations in the open ocean it should now also be possible to resolve some long unanswered questions about tidal energetics and dynamics inverse methods provide a natural framework for addressing these issues and making inferences about tidal dynamics in particular by bringing data and dynamics together in a single solution we can rigorously test the consistency of the two we present results of global and local inversions which suggest that over elongated bathymetric features oriented perpendicular to tidal flows energy dissipation in the open ocean is significantly enhanced presumably due to conversion of barotropic tidal motions into baroclinic modes for the m2 tide our preliminary results suggest that perhaps as much as 0 5 tw of energy is dissipated in this manner however due to the simplified linear dynamics and limited spatial resolution used for our inversion there are significant uncertainties associated with these results a more careful application of inverse methods to make more rigorous inferences about tidal energetics including use of more reasonable prior dynamics and the highest possible spatial resolution should allow for closure of the tidal energy budget within the next few years

enhanced diapycnal mixing due to near inertial internal waves propagating through an anticyclonic eddy in the ice free chukchi plateau abstractthe arctic ocean is known to be quiescent in terms of turbulent kinetic energy tke associated with internal waves to investigate the current state of tke in the seasonally ice free chukchi plateau arctic ocean this study performed a 3 week fixed point observation fpo using repeated microstructure hydrographic and current measurements in september 2014 during the fpo program the microstructure observation detected noticeable peaks of tke dissipation rate e during the transect of an anticyclonic eddy moving across the fpo station particularly e had a significant elevation in the lower halocline layer near the critical level reaching the order of 10 8 w kg 1 the adcp measured current displayed energetic near inertial internal waves niws propagating via the stratification at the top and bottom of the anticyclone according to spectral analyses of horizontal velocity the waves had almost downward energy propagation and its current amplitude reached 10 cm s 1 the wkb scaling inco

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

interannual changes of the floating ice shelf of petermann gletscher north greenland from 2000 to 2012 petermann gletscher northwest greenland drains 4 of the greenland ice sheet into nares strait its floating ice shelf retreated from 81 to 48 km in length during two large calving events in 2010 and 2012 we document changes in the three dimensional ice shelf structure from 2000 to 2012 using repeated tracks of airborne laser altimetry and ice radio echo sounding icesat laser altimetry and modis visible imagery the recent ice shelf velocity measured by tracking surface features between flights in 2010 and 2011 is 1 25 km a 1 15 30 faster than estimates made before 2010 the steady state along flow ice divergence represents 6 3 gt a 1 mass loss through basal melting 5 gt a 1 and surface melting and sublimation 1 0 gt a 1 airborne laser altimeter data reveal thinning both along a thin central channel and on the thicker ambient ice shelf from 2007 to 2010 the ice shelf thinned by 5 m a 1 which represents a non steady mass loss of 4 1 gt a 1 we suggest that thinning in the basal channels structurally weakened the ice shelf and may have played a role in the recent calving events

slip on wavy frictional faults is the 3rd dimension a sticking point abstract the formulation for the 3d triangular displacement discontinuity boundary element method with frictional constraints is described in detail its accuracy in comparison to analytical solutions is then quantified we show how this can be used to approximate stress intensity factors at the crack tips using this method we go on to quantify how slip is reduced on fault surfaces with topography where the asperities are approximated as a sinusoidal waveform i e corrugations we use stress boundary conditions compressive orientated such that frictional contacts shear we show that slip reductions relative to planar faults for 2d line and 3d penny shaped crack models are comparable within 10 when slip is perpendicular to the corrugations using the 3d model we then show how slip is reduced more when corrugation wavelengths are doubled compared to the reduction due to corrugation misalignment with the slip direction when slip is parallel with the corrugation alignment we show that reducing the out of plane stress from the normal traction acting on the fault when planar to that resolved on a perpendicular plane has the same effect as halving the length of the corrugation waveform in terms of slip reduction for a given amplitude

oblique slip and the geometry of normal fault linkage mechanics and a case study from the basin and range in oregon abstract map patterns of normal fault linkages near summer lake oregon show a systematic relationship between echelon step sense oblique slip sense and the position of linking faults where the step sense is the same as the sense of oblique slip e g left step and left oblique slip the faults are linked in the lower part of their relay ramp where the step sense and slip sense are opposite e g left step and right oblique slip the faults are linked in the upper part of the ramp a boundary element code is used to calculate the stress field around echelon normal faults during oblique slip and the model results reveal a relationship similar to the field observations if step sense and oblique slip sense are the same there is a greater potential for deformation ahead of the tip of the front fault and in the lower part of the ramp if step sense and oblique slip sense are opposite there is a greater potential for deformation ahead of the tip of the rear fault and in the upper part of the ramp the field model comparison confirms that oblique slip modifies the mechanical interaction among fault segments and thus influences fault growth and the geometry of fault linkage

mechanics slip behavior and seismic potential of corrugated dip slip faults 1 to better understand the mechanics and seismic potential of nonplanar fault surfaces we present results from a suite of numerical models of faults with sinusoidal corrugations in the downdip direction systematic variations in corrugation wavelength amplitude and loading angle are introduced to determine the effects on slip behavior and seismic moment release we find that corrugated faults in general slip less than planar faults changes in slip behavior are nearly scale independent and are dominantly controlled by the amplitude wavelength of corrugations model results suggest that obliquely loaded corrugated faults accumulate less strike slip than a planar fault with the same tip line dimensions and average orientation this result implies that slip direction is not a reliable indicator of regional stress direction and may at least partially explain repeated nearly pure dip slip coseismic events at oblique plate boundaries though the scalar seismic moment release is always less for corrugated fault surfaces due to a greater reduction in slip compared to increased surface area for geologically reasonable corrugation geometries changes in total scalar moment release are not significantly different than planar faults techniques that utilize highly simplified fault geometries may therefore accurately reproduce scalar moment release but will nonetheless incorrectly predict coseismic slip magnitudes and distributions as well as regional stress orientations

the long term coupling between column ozone and tropopause properties abstract the observational data of the vertical temperature distribution and column ozone obtained from 10 main stations in the northern hemisphere are analyzed in order to explore the tropopause variations in conjunction with the dynamical variability in column ozone from the analysis presented it is evident that the summer distribution of the frequency of occurrence of the tropopause over greece apart from its main maximum around 12 km is also characterized by a secondary one around 16 km it is proposed that this elevated maximum possibly originates from the height variation of the tropopause from 12 to 16 km depending on whether the athens station is located below the cyclonic shear side or below the anticyclonic shear side of the subtropical jet stream it is also suggested that the transport in the upper troposphere and lower stratosphere that originated in the equatorial region forces the appearance of the multiple tropopauses above greece furthermore the observational analysis of the ver

extreme wave activity during 2013 2014 winter and morphological impacts along the atlantic coast of europe studies of coastal vulnerability due to climate change tend to focus on the consequences of sea level rise rather than the complex coastal responses resulting from changes to the extreme wave climate here we investigate the 2013 2014 winter wave conditions that severely impacted the atlantic coast of europe and demonstrate that this winter was the most energetic along most of the atlantic coast of europe since at least 1948 along exposed open coast sites extensive beach and dune erosion occurred due to offshore sediment transport more sheltered sites experienced less erosion and one of the sites even experienced accretion due to beach rotation induced by alongshore sediment transport storm wave conditions such as were encountered during the 2013 2014 winter have the potential to dramatically change the equilibrium state beach gradient coastal alignment and nearshore bar position of beaches along the atlantic coast of europe

characteristics of the subtropical tropopause region based on long term highly resolved sonde records over tenerife 1 this study examines the structure of the subtropical tropopause region over tenerife the canary islands spain 28 n 16 w based on a 20 year 1992 2011 ozonesonde data and european center for medium range weather forecasts era interim potential vorticity pv and zonal wind speed reanalysis high resolution vertical profiles allowed a detailed description of the subtropical tropopause break and the associated subtropical jet stream stj where models fail to properly simulate the upper troposphere lower stratosphere utls the subtropical utls is revealed as a complex atmospheric region with a thickness 8 km which is examined through the analysis and evaluation of four different tropopause definitions thermal tt cold point ozone ot and dynamical dt tropopauses a novel method to determine the dt based on the vertical gradient of lait s modified pv is presented and the concept of a second dt has been introduced for the first time monthly climatologies of tropopause height and potential temperature are calculated for double and single tropopause events the 14 3 km height level is used to differentiate between tropical and extratropical utls regimes intimately linked to the position of the stj there is fairly good consistency between all the defined tropopauses under the double tropopause scheme except in spring when the ot is observed at lower levels due to frequent baroclinic instabilities in the upper troposphere as concerns to single tropopause events the same pattern is found from april to june reflecting the influence of analogous processes during these months in winter altitude differences between ot dt and tt resulted from poleward stj excursions forced by blocking systems over the north atlantic analysis of the tropopause inversion layer showed distinctive features for tropical and midlatitude tropopauses

the yermak pass branch a major pathway for the atlantic water north of svalbard an upward looking acoustic doppler current profiler deployed from july 2007 to september 2008 in the yermak pass north of svalbard gathered velocity data from 570 m up to 90 m at a location covered by sea ice 10 months out of 12 barotropic diurnal and semi diurnal tides are the dominant signals in the velocity more than 70 of the velocity variance in winter baroclinic eddies at periods between 5 and 15 days and pulses of one to two month periodicity are observed in the atlantic water layer and are associated with a shoaling of the pycnocline mercator ocean global operational model with daily and 1 12 degree spatial resolution is shown to have skills in representing low frequency velocity variations 1 month in the west spitsbergen current and in the yermak pass model outputs suggest that the yermak pass branch has had a robust winter pattern over the last 10 years carrying on average 31 of the atlantic water volume transport of the west spitsbergen current 36 in autumn winter however those figures have to be considered with caution as the model neither simulates tides nor fully resolves eddies and ignores residual mean currents that could be significant

high frequency ice motion and divergence in the weddell sea we describe the spatial variability of high frequency ice velocity in the weddell sea using satellite tracked ice mounted buoys ice motion is analyzed separately for diurnal 1 36 1 18 cph and semidiurnal 1 18 1 6 cph bands ice motion in both bands is caused by a combination of ocean tidal currents and wind stress monthly mean diurnal band ice speeds over the deep basin range from 2 to 4 cm s 1 depending on wind stress variance and ice concentration cice higher speeds 10 cm s 1 are found in the semidiurnal band in regions of low cice notably the northern weddell sea where the ice velocity is dominated by the inertial response to wind stress variations monthly mean tidal band ice speeds over the continental slope and shelves often exceed 10 cm s 1 we use comparisons between buoy velocities moored current meter data and an ocean tidal model to demonstrate that ice motion is frequently a good indicator of ocean tidal currents in strongly tidal regions the standard deviation of the divergence of ocean tidal currents estimated from an ocean only tidal model is small 0 1 10 6 s 1 over most of the weddell sea but has values of 1 5 10 6 s 1 along the ronne ice front and the continental shelf break high frequency ice divergence is dominated by ice response to wind stress rather than by tides except along the shelf break and ice fronts in these tidally dominated regions the periodic divergence maintains a mean lead open water area of 2 5 this increased lead fraction implies an increase in area averaged winter ocean to atmosphere heat exchange rate of 4 10 w m 2 and an increase in salt flux into the upper ocean as new ice forms in the leads

rough faults distributed weakening and off fault deformation 1 we report systematic spatial variations in fault rocks along nonplanar strike slip faults cross cutting the lake edison granodiorite sierra nevada california sierran wavy fault and lobbia outcrops of the adamello batholith in the italian alps lobbia wavy fault in the case of the sierran fault pseudotachylyte formed at contractional fault bends where it is found as thin 1 2 mm fault parallel veins epidote and chlorite developed in the same seismic context as the pseudotachylyte and are especially abundant in extensional fault bends we argue that the presence of fluids as illustrated by this example does not necessarily preclude the development of frictional melt in the case of the lobbia fault pseudotachylyte thickness varies along the length of the fault but the pseudotachylyte veins thicken and pool in extensional bends we conduct a quantitative analysis of fault roughness microcrack distribution stress and friction along the lobbia fault numerical modeling results show that opening in extensional bends and localized thermal weakening in contractional bends counteract resistance encountered by fault waviness resulting in an overall weaker fault than suggested by the corresponding static friction coefficient the models also predict static stress redistribution around bends in the faults which is consistent with distribution of microcracks indicating significant elastic and inelastic strain energy is dissipated into the wall rocks due to nonplanar fault geometry together these observations suggest that damage and energy dissipation occurs along the entire nonplanar fault during slip rather than being confined to the region close to the dynamically propagating crack tip

topographic enhancement of tidal motion in the western barents sea a high resolution numerical lattice is used to study a topographically trapped motion around islands and shallow banks of the western barents sea caused both by the semidiurnal and diurnal tidal waves observations and model computations in the vicinity of bear island show well developed trapped motion with distinctive tidal oscillatory motion numerical investigations demonstrate that one source of the trapped motion is tidal current rectification over shallow topography tidal motion supports residual currents of the order of 8 cm s 1 around bear island and shallow spitsbergenbanken the structures of enhanced tidal currents for the semidiurnal components are generated in the shallow areas due to topographic amplification in the diurnal band of oscillations the maximum current is associated with the shelf wave occurrence residual currents due to diurnal tides occur at both the shallow areas and the shelf slope in regions of maximum topographic gradients surface manifestation of the diurnal current enhancement is the local maximum of tidal amplitude at the shelf break of the order of 5 to 10 cm tidal current enhancement and tidally generated residual currents in the bear island and spitsbergenbanken regions cause an increased generation of ice leads ridges and trapped motion of the ice floes

nonplanar faults mechanics of slip and off fault damage stress interactions and sliding characteristics of faults with random fractal waviness in a purely elastic medium differ both qualitatively and quantitatively from those of faults with planar surfaces with nonplanar fault models solutions for slip diverge as resolution of the fractal features increases and the scaling of fault slip with fault rupture dimension becomes nonlinear we show that the nonlinear scaling of slip and divergence of solutions arise because stresses from geometric interactions at irregularities along nonplanar faults grow with increasing slip and produce backstresses that progressively impede slip however in real materials with finite strength yielding will halt the growth of the interaction stresses which will profoundly affect slip of nonplanar faults we infer that in the brittle seismogenic portion of the earth s crust off fault yielding occurs on pervasive secondary faults predicted rates of stress relaxation with distance from major faults with random fractal roughness follow a power law relationship that is consistent with reported clustering of background seismicity up to 15 kilometers from faults