influence of structure on the behavior of a saturated clayey loess an intensive experimental investigation by means of triaxial and oedometer tests was performed on a clayey loess that was retrieved from two depths at a location on the southern chinese loess plate

fractal reconstruction of sea floor topography sea floor bathymetric profiles exhibit features at many different scales of length this suggests that they could be described as fractals an algorithm interpolating a fractal line between points has been used to reconstruct bathymetric profiles from a few data points in general this fractal line has the same fourier amplitude spectrum as real bathymetry and if the parameters of the interpolation are suitably chosen it has a very similar appearance the success of this fractal reconstruction algorithm for the sea floor raises the possibility that it could be used to extrapolate from data collected at one scale the properties of the sea floor at finer scales and that similar techniques could be used to interpolate a surface between bathymetric profiles the fractal character is a sign that the processes that shape the sea floor are scale invariant and suggests that the renormalization group technique could be used to model these processes

lithospheric flexure at fracture zones bathymetric profiles across six major fracture zones fz s in the north pacific are used to demonstrate the absence of vertical slip on the fossil fault planes the scarp heights on these fz s are constant with age and equal to the initial vertical offsets at the ridge transform fault fz intersections because of the frozen in scarp and the differential subsidence of lithosphere far from the fz the lithosphere bends in the vicinity of the fz this flexure results in a characteristic ridge trough topographic fz signature the flexural amplitude which is the difference between the scarp height and the overall change in depth across the fz increases with age good fits to the bathymetric profiles across the mendocino and pioneer fz s are obtained by modelling the topography as the flexure of a thin elastic plate with an age dependent effective elastic thickness results of the modelling indicate that the base of the elastic lithosphere is approximately defined by the 450 c isotherm maximum bending stresses at fz s are on the order of 100 mpa substantially less than the stresses encountered at subduction zones because the mendocino and pioneer fz s are separated by less than a flexural wavelength they are elastically coupled

interrelationships between topography quaternary vertical displacement active faults and short term horizontal crustal strain in honshu japan regional and local characteristics of active fault patterns and elevation variation throughout honshu japan are characterized in terms of their fractal dimensions this allows variation in these complex variables to be compared directly to the scalar properties of net quaternary vertical displacement elevation and 10 and 110 year horizontal strains the comparisons reveal that throughout honshu as a whole there is significant correlation r 0 75 between quaternary vertical displacement elevation and its fractal properties there is poor correlation however of elevation and its fractal properties to horizontal crustal strain and also between quaternary vertical displacement and horizontal crustal strain a slight negative correlation is observed between the fractal properties of the active fault system and horizontal crustal strain measured over 10 and 110 year time periods 0 43 and 0 26 respectively the correlation between the 10 year 1985 1994 and 110 year 1883 1994 area strains 0 48 reveals the occurrence of considerable change in the distribution of regional strain over these short time frames local computations of the correlation between data sets made for overlapping 160 km length windows of data spaced every 20 km along analysis lines reveal internal fluctuations in the correlation between variables the local correlation between quaternary vertical displacement and elevation is highest through central japan and the kinki triangle there is weak negative correlation between area strain and fractal dimensions of the active fault network the local correlation between the fractal dimensions of active faults and horizontal area strain over the recent 10 year time period averages about 0 6 through central japan in an area that extends across the kinki triangle through the northern part of central honshu and northeast across the itoigawa shizuoka tectonic line in general regions of greatest complexity in the active fault network are associated with persistent negative area or compressional strain sparsely faulted areas in general coincide with areas of positive or roughly zero area strain the presence of negative correlation through central japan and the kinki triangle area in the recent 10 year period results from a decrease of area strain within an increasingly complex active fault system that reaches maximum negative values concentrated in the kinki triangle during the 1985 1994 time period

stratigraphic relationships within martian polar cap deposits abstract deposits of layered ice and dust accumulate on the smooth and banded terrains of the north and south polar cap deposits while erosion of equator facing slopes of layered terrain expose these layers banded terrain occurs at exposures of irregular layers resulting from slight erosion of the feather edges of layers deposited on pole facing trough walls these deposits unconformably overlap onto adjacent layered terrain stripping of layers occurs in areas of strong multidirectional wind forming striped terrain local wind scour has also produced steep scarps with crescentic planform often associated with dune fields positioned immediately downwind unconformities are common within layered deposits in areas of complex topography at the north pole these indicate that episodes of deposition of 5 10 layers alternate with slight erosion of pole facing trough walls troughs that strike north south alternate between erosional widening and deepening and depositional infilling creating multiple unconformities troughs near the equatorward limit of polar deposits increase in relief by deposition on adjacent smooth terrain and locally by erosional deepening troughs may migrate poleward replacing the relief increase by depositional infilling when they near the poles

a method of reconstituting an aragonite soil using a synthetic flocculant calcareous soils exist in many different forms each possessing unique characteristics this paper deals with a 100 m deep calcareous soil deposit consisting of over 60 aragonite an orthorhombic shaped crystalline form of calcium carbonate undisturbed push tube samples of the soil show void ratios generally greater than about 1 7 even to depths of 100 m when the samples are reconstituted by sedimentation and reconsolidation the highest void ratio that can be achieved is about 1 3 at equivalent effective stress levels a technique for achieving higher void ratios is described this involves sedimenting the soil in water containing a synthetic flocculant dash magnafloc mg 919 from allied colloids australia pty ltd the resulting samples have void ratios equivalent to those of the undisturbed samples at corresponding effective stress levels however additional curing of the samples using heat treatment was found to be necessary to achieve the same monotonic and cyclic shear behaviour as that o

the role of sublimation for the formation of the northern ice cap results from the mars orbiter laser altimeter abstract the evolutionary history of the martian ice caps is practically unknown and the caps are key to understanding the climatic history of mars sublimation and ice flow are two hypotheses that have recently been suggested to explain the observed form of the northern ice cap here we present a sublimation model and compare the shape of the cap obtained from this model with mars orbiter laser altimeter mola observations of the north polar region this model can reproduce the shape of the cap and individual troughs sublimation is an important process as are flow and wind erosion we were able to constrain the time scales of sublimation only to about two orders of magnitude 1 100 million years this estimate depends on many unknown parameters such as friction velocity and wind speed over the ice caps these can be determined only by direct measurement over the surface

variability of mars north polar water ice cap i analysis of mariner 9 and viking orbiter imaging data abstract previous studies interpreted differences in ice coverage between mariner 9 and viking orbiter observations of mars north residual polar cap as evidence of interannual variability of ice deposition on the cap however these investigators did not consider the possibility that there could be significant changes in the ice coverage within the northern residual cap over the course of the summer season our more comprehensive analysis of mariner 9 and viking orbiter imaging data shows that the appearance of the residual cap does not show large scale variance on an interannual basis rather we find evidence that regions that were dark at the beginning of summer look bright by the end of summer and that this seasonal variation of the cap repeats from year to year our results suggest that this brightening was due to the deposition of newly formed water ice on the surface we find that newly formed ice deposits in the summer season have the same red to violet band image ratios as permanently bright deposits within the residual cap we believe the newly formed ice accumulates in a continuous layer to constrain the minimum amount of deposited ice we used observed albedo data in conjunction with calculations using mie theory for single scattering and a delta eddington approximation of radiative transfer for multiple scattering the brightening could have been produced by a minimum of 1 a 35 m thick layer of 50 m sized ice particles with 10 dust or 2 a 14 m thick layer of 10 m sized ice particles with 50 dust

modelling rough interfaces on seismic reflection profiles the application of fractal concepts the distortion of reflection continuity and amplitude by overburden structure in seismic reflection images of the sub surface is easily recognised and modelled when the wavelength of the shallower structure is relatively large the effects of shorter wavelength structure although giving rise to little reflective response itself cause significant distortion of the propagating wavefield particularly when a moderate or strong acoustic impedance contrast is present in the shallow sub surface here we show how short as well as long spatial wavelengths of horizon roughness affect deeper reflection continuity and develop a new method using fractal interpolation techniques to predict the total roughness of sub surface horizons from information contained in seismic reflection sections fractally complete depth velocity models are used in forward models using the finite difference technique to produce synthetic seismic profiles the technique is illustrated with data from the edoras bank area of the rockall plateau ne atlantic where apparently discontinuous reflectors underlying basalt flows are shown to be from continuous sedimentary horizons distorted by overlying rough horizons

a kinematic hardening constitutive model for natural clays with loss of structure a rate independent constitutive model for natural clays is presented formulated within the framework of kinematic hardening with elements of bounding surface plasticity the modelling framework is intended to include effects of damage to structure caused by irrecoverable plastic strains caused by sampling laboratory testing or geotechnical loading the incorporation of a structure measure allows the size of the bounding surface to decay with plastic deformations this model can be seen as a logical extension from the cam clay model the steady fall of stiffness with strain towards the cam clay value is controlled by a particular interpolation function this ensures a smooth degree of approach between a kinematically hardening bubble which is the boundary of the elastic region and the bounding surface during their relative translation with stress history the model describes the essential phenomena of pre failure behaviour of natural clays stiffness variation with strain volumetric change accompanyi

northern east pacific rise magnetic anomaly and bathymetric framework the oceanic crust in the eastern pacific between 7on and 30on and east of 127ow contains a fairly complete history of the spreading centers associated with the east pacific rise since 25 m y b p late oligocene in this paper we have summarized the seafloor spreading magnetic anomaly data and the bathymetric data that reflect the record of this tectonic history the well defined magnetic lineations north of the clarion fracture zone in the mouth of the gulf of california and on the east flank of the east pacific rise epr are carefully examined and used to provide a guide for interpreting the spreading pattern between the clarion and clipperton fracture zones southward of the rivera fracture zone over the mathematician ridge and over the entire epr east of the mathematician ridge between the rivera and siqueiros fracture zones the bathymetric data provide a trace of the fracture zone pattern in each of the above mentioned areas the fracture zone bathymetry and the seafloor spreading magnetic lineations on the epr south of the rivera fracture zone have a distinctive fanning pattern caused by close poles of rotation and plate boundary reorganizations all these data provide a good record of the plate reorganizations in the middle miocene at magnetic anomaly 5a time 12 5 to 11 m y b p in the late miocene at magnetic anomaly 3 4 time 6 5 m y b p and in the pliocene at magnetic anomaly 2 3 time 3 5 m y b p several abandoned spreading centers including the mathematician ridge were left behind as a result of these reorganizations the mathematician ridge is shown to be a set of ridges and trough whose origin is related to the tectonic activity associated with each of the above mentioned reorganizations since anomaly 5a

perennial water ice identified in the south polar cap of mars the inventory of water and carbon dioxide reservoirs on mars are important clues for understanding the geological climatic and potentially exobiological evolution of the planet1 from the early mapping observation of the permanent ice caps on the martian poles2 3 the northern cap was believed to be mainly composed of water ice whereas the southern cap was thought to be constituted of carbon dioxide ice however recent missions nasa missions mars global surveyor and odyssey have revealed surface structures4 altimetry profiles5 underlying buried hydrogen6 and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide7 here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes at a resolution of 2 km during the local summer when the extent of the polar ice is at its minimum we observe that this south polar cap contains perennial water ice in extended areas as a small admixture to carbon dioxide in the bright regions associated with dust without carbon dioxide at the edges of this bright cap and unexpectedly in large areas tens of kilometres away from the bright cap

introduction to the seafloor mapping section the widespread use of echo sounders on oceanographic research vessels in the years following world war ii revolutionized marine geology by providing a technique for routinely measuring the depth of the seafloor along a ship s track within two decades precision depth recorders pdrs had been used to identify the major morphotectonic features in the ocean basins and compilations of depths measured on thousands of cruise tracks yielded the first reliable global maps of seafloor topography e g heezen and tharp 1960 1968 chase et al 1971 the existence of these maps played an important role in the development and acceptance of the ideas of seafloor spreading and plate tectonics in the mid and late 1960s during the past decade the emphasis in marine geology has shifted away from the reconnaissance geographical surveys of the 1950s and 1960s toward much more detailed studies aimed at investigating the important volcanic tectonic and sedimentological processes operating in the ocean basins with this change has come the need for much higher resolution bathymetry maps and new techniques for rapidly surveying large areas of the seafloor the result has been the development of a suite of new seafloor mapping tools with names like deep tow sea beam sea marc i and ii gloria and seasat these new tools have provided some remarkable new images of the seafloor and promise to revolutionize our understanding of geological processes in the ocean basins in much the same way that the introduction of the precision depth recorder did 40 years ago

quantitative methods for analyzing the roughness of the seafloor the bathymetry of the world ocean has been mapped using a variety of acoustic sounding instruments and traditional contouring methods prior to this study relatively few quantitative studies have been focused on the detailed morphology of the seafloor the work of most investigators has generally dealt with the analysis of seafloor relief without regard to spatial frequency or concern for obvious morphologic anisotropies a brief review of previous work is presented and is accompanied by an identification of the specific applications and limitations of those approaches the availability of more precise digital sounding data coupled with the development of higher resolution sonar mapping instruments e g deeptow seamarc now make it possible to investigate quantitatively many important aspects of seafloor relief and the geological processes responsible for its formation typical bathymetric contour maps represent a low frequency deterministic model of the seafloor to describe the higher frequency variability or roughness of the seafloor requires the development of an appropriate statistical method for generating a valid stochastic model new methods are developed herein which allow valid statistical models of the variability of oceanic depths to be derived from existing digital bathymetric soundings the smooth contoured surface often preserved as a geographic grid of depths when supplemented by such a roughness model can provide an essentially complete statistical description of the relief statistical models of seafloor roughness are also valuable tools for predicting acoustic scattering and bottom loss and in addition contain a wealth of information for more comprehensive interpretations of deep sea relief forming geological processes to allow the variability of depths to be described as a function of scale spatial frequency the amplitude spectrum is employed as the fundamental statistic underlying the model since the validity of the amplitude spectrum depends upon the assumption of a statistically stationary sample space a computer algorithm operating in the spatial domain was developed which delineates geographic provinces of limited statistical heterogeneity within each of these provinces a spectral model is derived by fitting the amplitude estimates with one or two two parameter power law functions using specialized regression techniques the distribution of resultant model parameters is examined for a large test area adjacent to the coast of oregon 42 45 n 130 124 w which includes several contrasting geologic environments the distribution of roughness corresponds generally with the various physiographic provinces observed in the region within some provinces additional complexities are apparent in the roughness model which cannot be inferred by simply studying the bathymetry these patterns are related to a variety of geological processes operating in the region such as the convergence of the continental margin and the presence of a propagating rift on the northern gorda rise in contrast a very large area of the continental margin off the east coast of the united states was found to have in common a single distinct amplitude spectrum this amplitude spectrum is almost identical to that found from the tufts abyssal plain region off the west coast of the united states spectra from both of these areas can be clearly separated into two straight line segments of different slope the two segments of these spectra are interpreted as reflecting two dominant relief forming processes the higher frequency band representing a sedimentary regime and the lower frequency band representing an underlying tectonic volcanogenic regime in many cases the calculated roughness statistics are not constant for data collected along different ship track directions this is due to the anisotropic nature of the seafloor relief a simple model is developed which describes the roughness statistics as a function of azimuth the parameters of this model quantify the anistropy of the seafloor allowing insight into the directionality of the corresponding relief forming processes and the physical meaning of the derived model statistical parameters finally the model is used to successfully predict the roughness of a surface at scales much smaller than those resolvable by surface sonar systems the model regression line derived from a hull mounted sonar is compared to data from deep towed sonars and bottom photographs the amplitude of roughness is predicted to within half an order of magnitude over five decades of spatial frequency and this prediction capability can probably be improved even further the stochastic models presented also demonstrate the potential for closely approximating the full two dimensional nature of some areas of the seafloor with only four statistical parameters these parameters can be estimated from random ship track data given a sufficient number of tracks and range of headings

on the behaviour of deep ocean sediments the behaviour of deep ocean sediments from the north atlantic abyssal plains is examined within the context of a recognised framework the sensitivity framework which was developed by cotecchia chandler for structured terrestrial clays the deep ocean sediments have very high sensitivities of the order of those of quick clays but in volumetric compression their destructuration occurs at more moderate rates similar to those usually found in terrestrial clays of medium sensitivities the deep sea sediments were retrieved using different types of sampler which influenced greatly the strength and stiffness of the different samples in particular in the lower quality samples the greater disturbance caused by sampling is responsible for changing their behaviour from brittle to ductile during shearing after compression to stresses post gross yield giving them an apparent insensitivity to shear strains results from numerical analyses using a constitutive model that was developed for structured terrestri

uncertainty estimation for databased bathymetry using a bayesian network approach 1 a bayesian network approach has been developed to estimate uncertainties for gridded bathymetry models that store grids of large regional or worldwide bathymetry a previous technique to estimate uncertainty for historical data uses monte carlo simulations to estimate uncertainty using soundings data but it is infeasible to implement for gridded bathymetry models the bayesian network is designed to estimate uncertainty using gridded bathymetry and a distribution of navigation uncertainties for the survey data used to create the grid as inputs this paper discusses how the monte carlo technique is used to train the network and how to implement it to estimate gridded uncertainty a demonstration of this approach is presented that uses the data from the original paper for the monte carlo technique both monte carlo and bayesian network estimators provide higher uncertainty with bottom slope the bayesian network estimate is generally greater than the monte carlo approach which is by design for navigation safety but is within an order of magnitude agreement

how do spiral troughs form on mars a three dimensional model for the coupled evolution of ice surface temperature and elevation in the martian polar ice caps is presented the model includes 1 1 enhanced heat absorption on steep dust exposed scarps 2 2 accumulation and ablation and 3 3 lateral conduction of heat within the ice cap the model equations are similar to classic equations for excitable media including nerve fibers and chemical oscillators in two dimensions a small zone of initial melting in the model develops into a train of poleward migrating troughs with widths similar to those observed on mars starting from random initial conditions the three dimensional model reproduces spiral waves very similar to those in the north polar ice cap including secondary features such as gull wing shaped troughs bifurcations and terminations these results suggest that eolian processes and ice flow may not control trough morphology 1 disp formula 1 2 disp formula 2 3 disp formula 3

a statistical correlation between ridge crest offsets and spreading rate ridge crest offsets follow the statistical distribution n a exp b ln l lo where n is the cumulative number of ridge crest offsets with lengths greater than l lo is the cutoff length and a and b are constants we measured a and b for the slow spreading mid atlantic ridge the intermediate spreading juan de fuca ridge and the fast spreading east pacific rise the predicted mean distances between offsets greater than 4 km long are 30 32 and 74 km on the slow intermediate and fast spreading ridge crests these distances are in agreement with observations of other workers and calculations of modal ridge lengths

thermomechanical evolution of oceanic fracture zones a fracture zone fz model is constructed from existing models of the thermal and mechanical evolution of the oceanic lithosphere as the lithosphere cools by conduction thermal and mechanical boundary layers develop and increase in thickness as age 1 2 surface expressions of this development such as topography and deflection of the vertical i e gravity field are most apparent along major fz s because of the sharp age contrast a simple model including the effects of lateral heat transport but with no elastic layer predicts that variations in seafloor depth and deflection of the vertical will become increasingly smooth and ultimately disappear as the fz ages observations however show that both the fz topography and the deflection of the vertical remain sharp as the fz evolves these two observations as well as the observed asymmetry in deflection of the vertical profiles across the udintsev romanche and mendocino fz s are explained by including a continuous elastic layer in the model the asymmetry in deflection of the vertical is a consequence of elastic thickness variations across the fz modeling also shows that the evolution of the fz topography is extremely sensitive to the initial thermal structure near the ridge transform intersection model geoid steps and their development with age are used to access techniques for measuring geoid offsets across fz s reasonable step estimation techniques will underestimate the overall step amplitude by up to 50 this implies that abnormally thin thermal boundary layers derived from studies of geoid height versus age are not required by the data

seafloor topography a record of a chaotic dynamical system we suggest that limits on the number of independent variables that play a role in controlling the shape of the seafloor can be obtained directly from bathymetry data to obtain this information seafloor topography is considered as a product of a larger system that produces the oceanic lithosphere we hypothesize that this dynamical system is chaotic and use bathymetric depth values to search for evidence of a strange attractor the dimension of which approximates the number of degrees of freedom in the system an analysis of sea beam multibeam data collected along a flow line of seafloor spreading in the northeast pacific ocean indicates that the dynamical system that forms the topography on the length scale of 100 s of meters has an underlying structure indicative of a high order attractor

the general and congruent effects of structure in natural soils and weak rocks the engineering properties of naturally occurring sedimentary and residual deposits which are usually treated in geotechnical engineering as soils are reviewed and it is shown that usually they have characteristics due to bonded structure which are similar to those of porous weak rock while this structure can arise from many causes its effects follow a simple general pattern that involves stiff behaviour followed by yield this yield can be described in a similar way to that occurring due to overconsolidation although it is a separate phenomenon the effects of structure are as important in determining engineering behaviour as are the effects of initial porosity and stress history which are the basic concepts of soil mechanics as it can be described in a general way it is concluded that structure and its effects should be treated as a further basic concept of equal importance l article passe en revue les proprietes des depots sedimentaires et residuels naturels qui sont nor malement traites comm

a renormalization group approach to the stick slip behavior of faults we treat a fault as an array of asperities with a prescribed statistical distribution of strengths when an asperity fails the stress on the failed asperity is transferred to one or more adjacent asperities for a linear array the stress is transferred to a single adjacent asperity and for a two dimensional array to three adjacent asperities using a renormalization group rg method we investigate the properties of a scale invariant hierarchical model for the stochastic growth of fault breaks through induced failure by stress transfer an extrapolation to arbitrarily large scales shows the existence of a critical applied stress at which the solutions bifurcate at stresses less than the critical stress virtually no asperities fail on a large scale and the fault is locked above the critical stress asperity failure cascades away from the nucleus of failure we interpret this catastrophic failure as an earthquake and it corresponds to the transition from stick to slip behavior on the fault thus the stick slip behavior of most faults can be attributed to the distribution of asperities on the fault we propose our stochastic mechanism as an alternative to the traditional hypotheses for the stick slip behavior of faults a major advantage of our approach is the inclusion of scale invariance thus the observed frequency magnitude relation for seismicity is a natural consequence of our basic hypothesis

patterning instability on the mars polar ice caps 1 we present a mathematical theory to study the origin of large scale spiral troughs on the mars residual polar caps starting with the hypothesis that atmospheric circulation governs the planform of the troughs via an instability that operates in the flow direction of surface winds this concept can explain why the troughs spiral at each pole in an opposite sense to that expected for coriolis deflected winds the instability arises from interactions on water ice assumed to contain dust and depends on how the exchange of atmospheric dust and moisture h2o with the polar cap surface controls its albedo and mass and energy balance our model predicts spatial patterns to form when moisture is carried by wind over the surface owing to unstable coupling between the albedo and the h2o vapor pressure the resulting albedo pattern causes an alternating accumulation ablation mass balance so that an undulating topography develops which resembles the dark troughs and their adjacent bright smooth terrains on the polar caps because the albedo patterning process is fast whereas topographic evolution is slow we suggest that an ancient imprint in the surface albedo preconditions today s trough morphology

geologic history of the polar regions of mars based on mars global surveyor data ii amazonian period based on mars orbiter laser altimeter mola and mars orbiter camera moc observations of amazonian polar layered deposits pld morphology composition and thickness we conclude that the plds are composed of porous unconsolidated layers that have not experienced significant basal melting or other glacial type processes morphologic features and associations within the pld chasmata including preserved craters and sinuous ridges indicate that the dominant process of chasmata formation is wind scouring our detailed analysis of south polar spiral trough topography in conjunction with the identification of similar layered stratigraphy within north polar spiral troughs suggests that trough migration due to preferential ablation of sun facing slopes cannot be demonstrated within the layered sequences we have not identified widespread unconformities discontinuities or pinch outs that would indicate an accublation origin of the plds we therefore postulate that the well defined plds at both poles eventually reached and maintained their present form following deposition without extensive deformation or redeposition large cuspate ridges in the ultimi lobe of planum australe appear to be layered and may be unusual erosional remnants of a once thicker pld in this area beneath the north polar layered deposits in planum boreum we have identified a platform of older highly degraded polar deposits as much as a kilometer thick that may have once covered an area larger than planum boreum

space time correlations of seismotectonic parameters examples from japan and from turkey preceding the izmit earthquake analysis of the correlation between fractal attributes of complex seis motectonic variables may offer insights into seismic hazard assessment the guten berg richter moment magnitude and moment source area relations yield a direct fractal relationship among the gutenberg richter b value occurrence rate and the characteristic linear dimension of the fault plane square root of fault surface area in contrast temporal variation in the correlation dimension of epicenters dc i s found in several studies to correlate negatively with the b value in different regions of the world spatial variations between the b value and dc also tend to oppose each other in japan negative correlations are also observed in the regional scale com parisons of the capacity dimension do of active fault systems and the b value however at local scales the relationship yields both positive and negative correla tion the occurrence of positive or negative correlation appears to be controlled by different modes of failure within the active fault complex spatial variations between the b value and dc along the northern anatolian fault zone nafz suggest that on average from 1900 to 1992 earthquake magnitudes were higher and epicenters more scattered within the central nafz than in its eastern and western segments temporal analysis reveals that the relationship between the b value and dc are nonstationary temporal correlations are generally negative a period of positive correlation is observed between 1976 and 1988 during the last 3 yr of this period 1985 1988 both the b value and d c rose significantly suggesting that stress release occurs through increased levels of low magnitude and increasingly scattered seismicity this dispersed pattern of seismicity in combination with higher slip rates in the central nafz may be one that did not adequately relieve stress along the main fault zone this change in behavior and the tendency during the last century for the seismicity to migrate westward along the nafz may point to an increased risk of larger magnitude events such as the i zmit earthquake

topography and stratigraphy of martian polar layered deposits abstract topography and stratigraphy of young sediments in the martian north polar region are being studied from high resolution viking orbiter images to test and constrain theories of terrain evolution driven by cyclical climate change several steepened slopes upon which layers are exposed in section were found to have local relief of 200 to 800 m and slopes ranging from 1 to 8 first attempts to calculate average layer thicknesses from portions of sections yielded results ranging from 14 to 46 m linearly correlated with slope in some cases under the assumption of short range lateral continuity a greater number of layers was inferred to be present than was actually resolved on a particular section when apparent layer thickness are revised accordingly the correlation with slope is destroyed we conclude that images of the shallowest sloping sections of layered deposits should yield the most stratigraphic information and layers thinner than 14 m may occur indeed they may even be common or typical because of the sensitivity of summer frost distribution to local slope and other properties of exposed strata interseasonal comparisons of images promise to enhance the capability to detect layers and differentiate them by material properties

the accommodation of large strains in the upper lithosphere of the earth and other solids by self similar fault systems the geometrical origin of b value plate tectonics has provided a method of visualizing the geometry of the deformation of the earth s lithosphere on a large scale the description is so concise that for many purposes it provides an explanation of geological processes that overshadows the need to understand the driving processes the mechanics of the zones between the plates are less well understood particularly in continental regions where large areas are subject to deformation both continuous and discontinuous models have been tried but both have obvious drawbacks

summer evolution of the north polar cap of mars as observed by omega mars express the observatoire pour la mineralogie l eau les glaces et l activite omega visible infrared imaging spectrometer extensively observed regions of mars with latitudes above 70 n in late 2004 heliocentric longitude from ls 93 to ls 127 the extent of water ice at the surface and the size of ice grains were monitored as a function of time bright small grained frost which initially covered a large fraction of the polar cap waned in favor of large grained ice in outlying regions dominated by large grained ice the albedo increased over the period evaluating the dust content was model dependent however contamination of ice by dust was low

fractal interrelationships between topography and structure fractal interrelationships between topography and structure are investigated in two areas of the north american central appalachian mountains one in the intensely deformed valley and ridge province and the other in the relatively undeformed foreland area of the appalachian plateau province in the valley and ridge province the fractal dimensions of topographic and structural relief vary systematically along the strike of major folds following a second order polynominal trend cross correlation of the fractal dimensions of topography to structure indicates that there is a significant positive correlation between the two fractal analysis of topography in the relatively undeformed foreland area of the appalachian plateau revealed no significant variation in the fractal characteristics of topography across the study area consistent with the lack of near surface structure however fractal analysis of deeper structures beneath the plateau area undertaken using reflection seismic data revealed step wise increases in fractal dimension from the deeply buried precambrian basement to the near surface these vertical changes in fractal dimension can be related to the tectonic history of the area taken together these studies indicate that fractal analysis provides a means to quantify and compare the influence of near surface structure on topographic development and lateral and vertical structural variability fractal analysis provides a means to characterize the systematic changes in the complex patterns formed by topography and structure and the interrelationships between them similarity in their fractal characteristics implies similarity in the relative amplitude and abundance of different wavelength features in the topographic or structural profile 1998 john wiley sons ltd

disturbance of the bothkennar clay prior to laboratory testing interpretation of laboratory tests in the characterization study of the bothkennar clay required an assessment to be made of the effects of disturbance prior to testing disturbance is shown to have occurred as a result of tube sampling sample transport and specimen preparation the effects of disturbance in the clay are to reduce the mean effective stress in the sample and shrink the initial bounding surface the consequences of these changes are illustrated for the case of unconsoli dated undrained triaxial tests undrained triaxial compression and extension tests after reconsolidation to in situ stress and oedometer tests reduction in peak strength stiffness yield stress and post yield compressibility are shown to be a consequence of disturbance the evaluation of sample quality on the basis of strains during reconsolidation is examined l interpretation des essais de laboratoire dans l etude de caracterisation de l argile de bothkennar necessita l evaluation des effets du remaniement avant essai