ground motion attenuation relationships for cascadia subduction zone megathrust earthquakes based on a stochastic finite fault model the number of strong ground motion recordings available for regression analysis in developing empirical attenuation relationships has rapidly grown in the last 10 years however the dearth of strong motion data from the cascadia subduc tion zone has limited this development of relationships for the cascadia subduction zone megathrust which can be used in the calculation of design spectra for engi neered structures a stochastic finite fault ground motion model has been used to simulate ground motions for moment magnitude m 8 0 8 5 and 9 0 megathrust earthquakes along the cascadia subduction zone for both rock and soil site condi tions the stochastic finite fault model was validated against the 1985 m 8 0 mi choacan mexico and the 1985 m 8 0 valpariso chile earthquakes these two subduction zone megathrust earthquakes were recorded at several rock sites located near the fault rupture for the cascadia megathrust earthquakes three different rup ture geometries were used to model the m 8 0 8 5 and 9 0 events the geometries only differ in their respective fault lengths a fault dip of 9 to the east with a rupture width of 90 km was selected to represent average properties of the cascadia sub duction zone geometry a regional crustal damping and velocity model was used with the stochastic finite fault model simulations ground motions were computed for 16 site locations the parametric uncertainties associated with the variation in source path and site effects were included in the development of the ground motions a functional form was fit to the ground motion model simulations to develop region specific attenuation relationships for the cascadia megathrust rupture zone for both rock and soil site conditions the total uncertainty was based on a combination of the modeling and parametric uncertainties sigmas these newly developed atten uation relationships for cascadia subduction zone megathrust earthquakes can be used in both the probabilistic and deterministic seismic hazard studies for engineer ing design for the pacific northwest

two dimensional strain determination by the inverse surfor wheel abstract a simple method of two dimensional strain determination from the preferred orientation of deformed lines is presented it is based on the change of probability of intersecting lines on a given traverse as a function of traverse orientation the method can be applied to real lines such as grain boundary outlines or to virtual lines such as the tie lines between centre points of neighbouring grains in this manner estimates for the strain of surfaces i e of the particles enclosed by the surfaces and of bulk strain can be obtained

the spatial distribution of grains and crystals in rocks characterisation and analysis of the spatial distribution pattern sdp of grains or crystals in rocks is potentially a powerful technique which can be used to constrain the processes which operate in the formation of rocks a method to quantify the sdp of grains in thin section is presented the distance betwen the centre of a grain and the centre of its nearest neighbour is calculated for all the grains in the sample area to produce a distribution of distances that characterises the spatial pattern of grains in the rock this distribution is then normalised to a random distribution of points with the same population density to give a descriptive value r values of r for rock samples are plotted against porosity modal abundance of other phases in igneous and metamorphic rocks to characterise the sdp the sdp of randomly packed distributions of equal size spheres varies systematically with porosity producing a line on a porosity versus r plot termed the random sphere distribution line rsdl rocks which plot above the rsdl have an ordered sdp and those that plot below a clustered sdp the effects of variation in grain packing order grain sorting compaction and random crystallisation overgrowth on determined r values were investigated using a combination of 3 d sphere models and 2 d texture models the maximum possible value of r is 2 148 corresponding to a perfect section through hexagonal cubic close packing of grains the minimum value of r is dependent on the proportion of grains in the sample volume and may be as low as 1 2 for a sample volume with 30 grains which are clustered variations in size sorting can cause r to vary by approximately 0 25 mechanical compaction of a loose framework of grains results in a higher packing order and an increase in r continued compaction creates a fabric in the texture and r decreases as cluster patterns are developed perpendicular to the principal stress the overgrowth of grains in a touching framework alters the location of the geometric grain centre as the crystal shape changes leading to an increase in r as porosity decreases results reveal that grain sorting compaction and grain overgrowth produce different r versus porosity relationships which can be identified in and therefore used to constrain the relative importance of these processes in rock samples

fabric analysis by orientation distribution functions abstract crystalline materials natural or artificial may consist of several phases minerals the crystal structures and relative amounts of which will generally be known in order to fully characterize such a material also the form and spatial distribution of the phases the grain structure and lattice defects and their distribution must be specified by appropriate distribution functions among these the orientation distribution function texture fabric structure plays an important role it can be deduced from experimental pole figures by series expansion methods in textured materials two different symmetries can be distinguished the crystal symmetry and the statistical sample symmetry special consideration must be given to the inversion centre as an element of either of these symmetries and in friedels law a complete description of all possible sample symmetries can be given in terms of black white symmetry groups the determination of the odd part of the texture function is strongly related to these groups and the various kinds of the inversion centre each combination of a certain crystal symmetry group with a certain sample symmetry group induces a certain space group in the orientation space the proper consideration of which minimizes the required amount of numerical calculations the texture function odf is the most important factor in the relation between anisotropic properties of single crystals and the polycrystalline material changes of the odf can be used as a sensitive indicator for solid state processes having occurred in the material

fabric analysis using the intercept method abstract the intercept method is a convenient yet powerful method for the numerical analysis of fabrics for geological applications it can be used when a set of objects e g pores grains or aggregates of a specific mineral lineaments etc with unique characteristics can be identified in an image the intercept method analyses boundaries of objects as a population of lines how intercepts are definined is therefore important in order to establish the significance of the intercept counts when the method is applied to digital images the subdivision of the information into square pixels must also be considered we apply a linear filter which minimizes the effects of grid anisotropy on the counting of intercepts analysis of the resulting rose of intercept counts by a fourier series considerably facilitates the interpretation of the data a rose of directions can readily be derived for the phase boundaries if a population of objects can be assumed to have started with an originally isotropic orientation and to have been deformed passively the fourier components of the rose of intercepts also give the sectional strain the fourier components also permit an objective test of the validity of describing a fabric as resulting from a homogeneous strain on an initially isotropic section two computer programs for the counting and analysis of intercepts on digital images are presented and applied in four examples which illustrate the usefulness of the intercept method for magmatic fabric measurement strain analysis and lineament analysis we also illustrate the importance of fourier series decomposition of rose of intercept counts for fabric interpretations intercept results are also shown to be compatible with those derived by other methods eigenvector surfor inertia tensor autocorrelation methods

quantification of the spatial distribution of mineral phases and grains in rock using a 2 d multiple area density map technique abstract the most widely used method for quantitative analyses of the spatial distribution of grains in a rock body is the nearest neighbor method a position based method which recognizes the grain center as the position of the grain without consideration of grain size or shape however the spatial distribution of grains is influenced by their size and shape as well as their position here we propose a multiple area density map madm method to quantify the spatial distribution of phases or grains the method is based on image analysis and simultaneously considers the position size shape and proportion of grains the madm constructed by overlaying density maps of grain areas with a set of template size produces a normalized standard deviation nsd value of phase area density which represents the degree to which it is spatially clustered the nsd value is used to quantify the distribution of the phase without considering individual grains to identify the spatial distribution of individual grains the method employs the clustering index ci which is calculated from the ratio of nsd to the reciprocal of the number of grains in a log log plot

granite emplacement in an extensional setting an ams study of the magmatic structures of monte capanne elba italy abstract monte capanne elba is an excellent example of a granite pluton 42 km 2 emplaced 6 m y ago in a well known extensional environment that of the tyrrhenian sea its internal fabric has been studied using the magnitude of magnetic susceptibility and anisotropy measurements at 74 regularly distributed stations susceptibility magnitudes reveal a normal and asymmetrical petrographical zoning in the pluton the magnetic lineations are remarkably well organized mostly of nw se azimuth with slight plunges and always normal to the walls of the late aplitic dykes these lineations are also parallel to the stretching lineations of the immediate country rocks of the pluton in the western and probably deepest part of the pluton a ne sw trending magnetic magmatic lineation is also imprinted the following scenario is proposed for the emplacement of monte capanne during the opening of the tyrrhenian sea an approximately e w trending sinistral transform fault is taken as being responsible for the creation of a pull apart void that permitted upwelling of the magma orientations of the magmatic structures at depth are parallel to the elongation of the feeding zone of this void i e ne sw the very top part of the pluton was sheared parallel to the granite country rock interface i e nw se parallel to the local stretching of the tyrrhenian sea at the time of emplacement

strain and fabric analyses based on porphyroclast interaction abstract two dimensional computer models of the interaction of elliptical clasts in a variety of kinematic conditions are used to study how clast imbrication and shape fabric development relate to strain and strain history the models provide templates for a known clast density and clast ellipticity that correlate clast imbrication angle of collision and clast shape fabric to strain and kinematics of deformed rocks modeling also shows that the mode of clast interaction plays a significant role in the accumulation of imbricated clasts and the development of shape fabric upon collision between clasts the trains formed can remain fixed or rotate if they rotate imbricated clasts can become independent when they are no longer forced together by the flow based upon the mode of clast and train rotation using the march rotation of passive lines and the jeffery rotation of rigid particles as end members three models are defined in an attempt to simulate the conditions of clast interaction under varying conditions the march fixed train march rotating train and jeffery rotating train models simulate solid state intermediate and magmatic conditions respectively modeling shows that the two march models produce similar results but the jeffery model of train rotation always produces a lower proportion of imbricated clasts and a much weaker shape fabric application of the modeling to the study of a syntectonic granite in the sierra nevada suggests that deformation was dominated by simple shear some k feldspar imbrication and fabric development took place initially in the magmatic stage and culminated in the solid state to produce a large proportion of imbricated k feldspar porphyroclasts which define a strong shape fabric this type of analysis provides a rationale to determine syn vs post emplacement deformation in the granite

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

three dimensional quantitative textural analysis of metamorphic rocks using high resolution computed x ray tomography part i methods and techniques macroscopic textures resulting from different atomic scale mechanisms for metamorphic crystallization display different degrees of order clustering intergrowth and relative isolation of porphyroblasts data on the sizes and locations of thousands of crystals in a three dimensional volume are required to identify reliably the mechanisms governing nucleation and growth of porphyroblasts from these textural features these data can now be acquired by means of high resolution computed x ray tomography numerical models that simulate porphyroblast formation governed by either interface controlled or diffusion controlled reaction mechanisms indicate that quantitative textural analysis can discriminate between these possibilities these numerical models also allow a comparison between textures predicted for different crystallization mechanisms and textures measured in natural samples from which inferences can be drawn concerning the relative importance of these mechanisms in nature an independent test of the validity of such inferences is possible for porphyroblasts such as garnet that may preserve prograde growth zoning and allow the examination of normalized radius rate relations

automatic reconstruction of fault networks from seismicity catalogs three dimensional optimal anisotropic dynamic clustering 1 we propose a new pattern recognition method that is able to reconstruct the three dimensional structure of the active part of a fault network using the spatial location of earthquakes the method is a generalization of the so called dynamic clustering or k means method that partitions a set of data points into clusters using a global minimization criterion of the variance of the hypocenters locations about their center of mass the new method improves on the original k means method by taking into account the full spatial covariance tensor of each cluster in order to partition the data set into fault like anisotropic clusters given a catalog of seismic events the output is the optimal set of plane segments that fits the spatial structure of the data each plane segment is fully characterized by its location size and orientation the main tunable parameter is the accuracy of the earthquake locations which fixes the resolution i e the residual variance of the fit the resolution determines the number of fault segments needed to describe the earthquake catalog the better the resolution the finer the structure of the reconstructed fault segments the algorithm successfully reconstructs the fault segments of synthetic earthquake catalogs applied to the real catalog constituted of a subset of the aftershock sequence of the 28 june 1992 landers earthquake in southern california the reconstructed plane segments fully agree with faults already known on geological maps or with blind faults that appear quite obvious in longer term catalogs future improvements of the method are discussed as well as its potential use in the multiscale study of the inner structure of fault zones

quantitative texture analysis of naturally deformed anhydrite by neutron diffraction texture goniometry abstract the crystallographic texture of coarse grained 1 mm foliated anhydrite from an evaporite diapir in the canadian arctic islands was analysed by neutron diffraction texture goniometry the orientation distribution function odf which quantatively defines the texture was calculated from eight pole figures the odf was used to calculate the pole figures for slip systems and twin planes a strong concentration of 020 was found parallel to the lineation x with 002 forming a girdle normal to the lineation with a strong maximum near the foliation normal z the maxima are slightly asymmetric with respect to the structural framework x y z which is typical of non coaxial deformation the orientation of 020 and 002 are consistent with 010 001 glide in a non coaxial flow regime the axial symmetry about the lineation x of the pole figures and the tubular structure of the odf are thought to have been caused by an important component of extension parallel to x the calculated 100 pole figure has a submaximum parallel to z presumably a direction of high compressive stress the 101 maxima at about 45 to z are then indicative of twinning on 101 approximately 30 of the odf is in a twinned orientation 100 subparallel to z and it is suggested that twinning contributed to the axial symmetry of the fabric few grains show undulary extinction their boundaries are generally straight and rarely serrated this points to extensive migration recrystallization and associated twin gliding at 300 c previous studies seem to have underestimated the contribution of twinning to texture development which is dominated by 010 001 slip

shear criteria in granite and migmatite deformed in the magmatic and solid states microstructural criteria for the determination of the sense of shear in rocks homogeneously deformed in the partially melted state are similar to those which apply to solid state deformation sense of shear determination is either direct deduced from the sense of rotation of markers or indirect involving the obliquity between the shear and foliation planes or between the successive foliations imprinted at different stages of progressive deformation this study is a by product of the detailed structural and microstructural investigation of a high grade metamorphic rock pile variscan vosges massif france which underwent subhorizontal shearing during partial melting and further solidification depending on the rock chemistry on the position in the pile and the relative timing of progressive deformation layered migmatites and homogeneous granites were variously deformed in the partially melted and solid states the sense of shear obtained from these rock types using the criteria presented here consistently gives a top to sw direction

magnitudes of large shallow earthquakes from 1904 to 1980 abstract in order to obtain a uniform magnitude catalogue surface wave magnitudes ms and broad band body wave magnitudes mb have been determined for large shallow earthquakes from 1904 to 1980 in making the catalogue homogeneous the author consistently adheres to the original definitions of ms and mb given by gutenberg 1945 and gutenberg and richter 1956 the determinations of ms and mb are all based on the amplitude and period data listed in gutenberg and richter s unpublished notes bulletins from stations worldwide and other basic information mb is measured on broad band instruments in periods of 8 s consistency of the magnitude determinations from these different sources is carefully checked in detail more than 900 shallow shocks of magnitude 7 and over are catalogued the meaning of the magnitude scales in various catalogues is examined in terms of ms and mb most of the magnitudes listed by gutenberg and richter 1954 in their seismicity of the earth are basically ms for large shocks shallower than 40 km but are basically mb for large shocks at depths of 40 60 km the surface wave magnitudes given by earthquake data reports are higher than ms by 0 2 unit whether the combined horizontal amplitude or the vertical amplitude is used mb and the currently used 1 s body wave magnitude are measured at different periods and should not be directly compared

analysis of spatial order in sandstones ii grain clusters packing flaws and the small scale structure of sandstones abstract sandstone microstructure at scales of 5 5000 m is a domainal structure consisting of juxtaposed clusters of efficiently packed grains bounded by packing flaws the flaws represent zones of loose packing arising from grain to grain mismatches between well packed clusters flaws tend to propagate throughout the sediment and are marked in thin section by zones of oversized pores known to be associated with enhanced fluid flow using a two dimensional fourier transform it is possible to identify these flawed zones and examine not only their spatial distribution but also the relative contribution of close packed and flawed porosity to the pore network as a whole flaws represent zones of disorder formed through a variety of depositional and postdepositional processes two flaw producing mechanisms have been recognized in random aggregates of spheres created in a laboratory the first arises from grain to grain mismatches at the boundaries of concurrently growing grain clusters the second type is associated with the growth of well packed clusters over a preexisting cohesive substrate in the laboratory this is represented by the walls of the container holding the aggregate the distribution of loose packed and well packed grain domains in natural sands is governed by depositional environment the size and shape of the constituent grains define the fundamental spatial frequency of porosity but factors such as grain orientation and size sorti g affect the orientation of clusters and flaws as well as the scale at which they exist for example flaws in poorly sorted sands arise from the misfit of the finer size classes in a grain matrix controlled by the larger grains the flaws generated by this misfit propagate throughout the fine grained sections of the sediment with a spatial period characteristic of the coarser size classes grain clusters and flaws can be recognized as major textural elements in all sands and sandstones even those with macroporosity as low as 5 not only is the depositional signal preserved as porosity decreases its existence affords the opportunity to closely examine the effects of diagenesis upon the pore network as porosity decreases the relative proportion of flawed porosity increases by the time total porosity has been reduced to 5 flawed porosity has increased to the point that it constitutes 80 of the remainder the increase in relative proportion of loose packed porosity is due to preferential cementation within well packed clusters as well us an increase in loose packed porosity due to dissolution of unstable mineral grains in all the diagenetically altered sandston s examined the only grain molds or partially dissolved grains present were found to be located either within or immediately adjacent to packing flaws

scale dependence of textural alignment in shales quantified using electron microscopy abstract textural alignment is the primary cause of anisotropy associated with the permeability and mechanical and acoustic properties of rocks although particle alignment in shales is known to be influenced by burial depth mineralogical composition and diagenetic history understanding how these influence image based measures of compaction at the micrometer to nanometer scale is not well understood here we use a novel method which combines scanning electron microscopy and image analysis algorithms to quantify clay alignment in sedimentary rocks for a given field of view the alignment intensity in shales from the podhale basin in poland is positively correlated with clay content based on image analysis however our analysis also shows that the intensity is strongly dependent on the spatial scale of imaging as magnification increases and the field of view in the sem images decreases the alignment intensity drops therefore in images with small fields of view clay alignment is determined by the presence of localized equant silicate mineral grains which effectively hinder the alignment process at the micrometer scale by contrast in images with larger fields of view alignment intensity is determined by the overall compaction state we also show that when the field of view is constant alignment intensity decreases with pixel density and we suggest a range of operating parameters required for obtaining optimum values for alignment intensity from sem images of shales

a ridgelet transform method for constraining tectonic models via abyssal hill morphology abyssal hill shape and orientation are related to the direction and spreading rate of paleo spreading centers therefore analyzing abyssal hill shape and trend is useful for constraining tectonic models of regions devoid of magnetic reversal anomalies detecting systematic changes of abyssal hill shapes or trends due to changes in spreading rate or direction is not straightforward which makes it difficult to determine appropriate regions over which to average abyssal hill parameters often however detecting these systematic changes where they occur and the scale over which they occur is of primary importance for tectonic reconstructions we present a new method of abyssal hill analysis that is based on the ridgelet transform a relative of the two dimensional wavelet transform our method is capable of locally estimating the width azimuth and root mean square rms amplitude of abyssal hill fabric and highlights changes in these parameters across a survey area making it possible to identify regions created with a constant spreading rate and direction we use three multibeam swaths one crossing the osbourn trough in the southwest pacific basin one crossing the east pacific rise and one crossing the mid atlantic ridge to demonstrate the utility and performance of our method

deformation around rigid particles the influence of slip at the particle matrix interface abstract theoretical and previous experimental studies of rigid particle structures have only considered the behaviour of rigid particles for which the interface between particle and matrix is coherent in natural rocks the boundary behaviour may cover the whole range from free slip to complete coherence examples where slip may be promoted include crack seal deformation during the development of pressure shadows core mantle structures where the mantle is composed of much weaker fine recrystallized material and crystallizing magmas or partially molten rocks where grain boundaries are lubricated by the melt phase analogue scale model experiments have been performed under pure shear and simple shear conditions to compare the particle rotation and the flow in the matrix for both slipping and non slipping particle matrix interfaces when slip does occur particles rotate faster in pure shear and slower in simple shear than for non slip leading to the more rapid development of a shape preferred orientation the preferred orientation tends to be bimodal in simple shear flow the flow and finite strain patterns in the matrix are also strongly influenced by slip at the interface and porphyroclast systems can develop geometries with ambiguous or contradictory shear senses dependent on the original particle orientation in multi particle experiments slip on the interfaces enhances strong strain localization in non linear viscous material to produce patterns very similar to natural s c fabrics

two and three dimensional shape fabric analysis by the intercept method in grey levels the count intercept is a robust method for the numerical analysis of fabrics launeau and robin 1996 it counts the number of intersections between a set of parallel scan lines and a mineral phase which must be identified on a digital image however the method is only sensitive to boundaries and therefore supposes the user has some knowledge about their significance the aim of this paper is to show that a proper grey level detection of boundaries along scan lines is sufficient to calculate the two dimensional anisotropy of grain or crystal distributions without any particular image processing populations of grains and crystals usually display elliptical anisotropies in rocks when confirmed by the intercept analysis a combination of a minimum of 3 mean length intercept roses taken on 3 more or less perpendicular sections allows the calculation of 3 dimensional ellipsoids and the determination of their standard deviation with direction and intensity in 3 dimensions as well the feasibility of this quick method is attested by numerous examples on theoretical objects deformed by active and passive deformation on bse images of synthetic magma flow on drawing or direct analysis of thin section pictures of sandstones and on digital images of granites directly taken and measured in the field

first investigation of quartz and calcite shape fabrics in strained shales by means of x ray tomography abstract we document the evolution of the 3d fabric of shale along a km long strain gradient in the jaca basin southern pyrenees spain with respect to the distance from a thrust samples were collected in the cleavage free domain at the onset of the pencil cleavage domain within the pencil cleavage domain and within the slaty cleavage domain by combining high resolution x ray computed tomography xct and energy dispersive x ray spectroscopy eds the morphology and the shape preferred orientation spo of thousands of quartz grains calcite grains and pores was studied in the least deformed samples quartz and calcite display mean foliation parallel to bedding with comparable dispersion in the pencil cleavage domain quartz foliation still follows the bedding while calcite foliation is mostly governed by cleavage in the slaty cleavage domain calcite shows a much better organization with foliation parallel to cleavage mimicking closely the pore fabric by contrast the quartz shape fabric is much less defined scattered between bedding and cleavage planes this suggests that quartz grain act as rigid marker in the ductile matrix while calcite grain orientation is governed by dissolution precipitation processes

evaluating the stratigraphic response to eustasy from oligocene strata in new jersey previously published oligocene eustatic records are compared with observed stratigraphic architecture at the new jersey continental margin in order to evaluate the stratigraphic response to eustatic change lower to mid oligocene sequence boundaries 33 8 28 0 ma are associated with relatively long hiatuses 0 3 0 6 m y in which sedimentation in many places terminated during eustatic falls and resumed early during eustatic rises upper oligocene sequence boundaries are associated with relatively short hiatuses 0 3 m y and provide the best constraints on phase relations between sea level forcing and margin response the interval represented by each upper oligocene sequence varies in dip profile at updip locations landward of the clinoform rollover in the underlying sequence boundary sedimentation commenced after the eustatic low and terminated before the eustatic high with partial erosion of any younger record at downdip locations sedimentation within each sequence was progressively delayed in a seaward direction beginning during the eustatic rise and terminating near the eustatic low combining data from all available boreholes ages of sequence boundaries correlative surfaces correspond closely with the timing of eustatic lows and ages of condensed sections intervals of sediment starvation correspond with eustatic highs

transferable wavelet method for grain size distribution from images of sediment surfaces and thin sections and other natural granular patterns in images of sedimentary or granular material or simulations of binary two phase granular media in which the individual grains are resolved the complete size distribution of apparent grain axes is well approximated by the global power spectral density function derived using a morlet wavelet this approach overcomes many limitations of previous automated methods for estimating the grain size distribution from images all of which rely on either identification and segmentation of individual grains calibration and or relatively large sample sizes the new method presented here is tested using i various types of simulations of two phase media with a size distribution with and without preferred orientation ii 300 sample images drawn from 46 populations of sands and gravels from around the world displaying a wide variability in origin biogenic and mineralogical size surface texture and shape iii petrographic thin section samples from nine populations of sedimentary rock iv high resolution scans of marine sediment cores and v non sedimentary natural granular patterns including sea ice and patterned ground the grain size distribution obtained is equivalent to the distribution of apparent intermediate grain diameters grid by number style for images containing sufficient well resolved grains root mean square errors are within tens of percent for percentiles across the entire grain size distribution as such this method is the first of its type which is completely transferable unmodified without calibration for both consolidated and unconsolidated sediment isotropic and anisotropic two phase media and even non sedimentary granular patterns the success of the wavelet approach is due in part to it quantifying both spectral and spatial information from the sediment image simultaneously something which no previously developed technique is able to do

an illustration of the advantages of a complete texture analysis described by the orientation distribution function odf using quartz pole figure data abstract the preferred orientation of eight crystal directions of quartz was measured with an x ray texture goniometer for selected quartz bearing tectonites with a clear pattern of c axis preferred orientation the advantages of data analysis by means of calculations of the orientation distribution function and other forms of data presentation derived from the odf are demonstrated

the autocorrelation function an image processing tool for fabric analysis abstract the use of the autocorrelation function acf is proposed as a method for fabric and or strain analysis its chief purpose is to extend fabric analysis to fine grained materials such as clays micrites etc or to materials where the determination of individual grain shapes is tedious or impossible the main advantage of the method is that no segmentation of the image prior to analysis is necessary in other words any bias associated with identifying grain boundaries and the like is avoided in as much as the recognition of grains or grain boundaries is a matter of scale the acf can be used without loss of generality whenever the grain size is small in comparison with the size of the analysed area the method is computer based it requires a scanner for the digitization of the images and sufficient storage space and computing power for digital image processing the method uses half tone images as input these can be obtained from thin sections acetate peels polished surfaces photographic negatives or positives etc the acf is a two dimensional function that is related to the average shape that occurs in the fabric it is scaled with respect to the original image and allows simultaneous analysis of small and large features the acf enables a a quantitative description of the fabric in general terms b an efficient grain size determination and c if strain is a valid interpretation of the fabric the derivation of the finite strains in the plane of observation in the first part of the paper the acf method is introduced by way of a few numerically generated fabrics and compared to other methods of fabric and strain analysis in the second part an application to three samples of experimentally deformed solnhofen limestone is demonstrated

three dimensional dislocation model for great earthquakes of the cascadia subduction zone there have been no historical cascadia great subduction thrust earthquakes but there is good recent evidence that very large earthquakes have occurred in the past and that strain is building up toward a future great event geodetic measurements in the coastal region from northern california to southern british columbia show vertical and horizontal deformation as expected for the strain accumulation of a locked thrust fault the segment of the subduction thrust that is locked and may rupture in future great events has previously been estimated through two dimensional 2 d elastic dislocation modeling of interseismic deformation geodetic data in this study a general 3 d dislocation model for thrust faults has been developed that accommodates curved fault geometry and nonuniform interseismic locking or coseismic rupture the model is based on die surface deformation due to shear faulting in an elastic half space the 3 d model of the cascadia subduction zone calculates the surface deformation for a locked zone or a rupture zone of variable width along the margin the bend in the margin trend and subducting slab end effects are included there is a downdip transition zone between interseismic completely locked and free slip portions of the fault or between coseismic full rupture and no displacement an initial 3 d model based upon 2 d dislocation models and upon thermal constraints was adjusted to optimize the fit of the predicted interseismic surface deformation to current deformation geodetic data the best fit model has the thrust locked along the whole margin with an average locked zone width of 60 km and a transition zone width of 60 km the two zones lie mainly offshore beneath the continental shelf and slope the locked and transition zone widths vary smoothly along the margin being greater off northern washington where the thrust dip is shallow and narrower off central oregon assuming that the locked plus transition zones approximate the maximum coseismic rupture area these widths permit amw 9 earthquake

the normalised optimised anisotropic wavelet coefficient noawc method an image processing tool for multi scale analysis of rock fabric the 2d anisotropic wavelet transform 2dawt is an image analysis tool which is able to decipher signals where information obtained from different scales are intermixed extended from the optimised anisotropic wavelet coefficient method oawc of ouillon et al 1995 we present a method which discriminates the objects and groups of objects depending on their area shape ratio orientation and position illustrated in a synthetic example we show that this method allows one to distinguish between different sub populations of objects within a single phase and quantify the anisotropies of shape orientation and spatial distribution at different scales objects clusters of objects alignments of objects or clusters applied to a natural rock sample sidobre granite montagne noire france the 2dawt has permitted us to detect and accurately characterise the different levels of mineral organisation and thus to contribute to the understanding of the physical processes such as crystallisation fluid migration deformation etc responsible for such organisations

complements to magnitudes of large shallow earthquakes from 1904 to 1980 abstract in the previous paper magnitudes of large earthquakes of the world were determined on a very uniform basis and catalogued in order to arrive at a more homogeneous catalogue for a study of global seismicity some complements are presented the major complements are as follows 1 the m s values for the period 1904 1909 in the previous paper were overestimated in the extreme case by 0 5 magnitude units 2 the m b values for the period 1904 1908 in the previous paper were also overestimated 3 the magnitudes of deep and intermediate shocks which are listed in seismicity of the earth by gutenberg and richter are found to be approximated by m b m b 7 4 4 the catalogues of m b for shallow intermediate and deep shocks are continued for the period up to 1980

a new statistical description of the spatial distribution of minerals in rocks we propose a new method to describe quantitatively rock textures with a special emphasis on the spatial distributions of minerals the method employs a statistical approach and examines probabilities for particular mineral pairs to occur for variable interpoint distances the probability is measured by counting the number of point pairs on digitized images of rock textures that are obtained with a computer aided digital image processor several problems in obtaining textural images and processing the data that were encountered in the actual procedures are reviewed the method is applied to two rock samples granite and contact metamorphic hornfels the method is useful in examining the extent of homogeneity and randomness of mineral distributions and spatial correlations among minerals of different kinds

submagmatic microfractures in granites microstructures in hercynian granite plutons of the pyrenees indicate fracturing of plagioclase crystals in the presence of melt this is represented mainly by quartz and or feldspar that fills fractures electron microprobe analyses demonstrate that in compositional agreement with the rims of the zoned plagioclase the feldspar infillings are more sodic with decreasing melt fraction fracturing resulted from concentration of stress at contacts between grains while the granite was submagmatic i e when the melt was below the critical fraction for magmatic flow material compositionally far from eutectic is petrologically the best candictate to develop submagmatic fractures because during cooling the volume fraction of melt remains low for a large temperature range a strong tendency for microfractures to be oblique to flow foliation may constitute a new criterion for shear sense in magmas

three dimensional quantitative textural analysis of metamorphic rocks using high resolution computed x ray tomography part ii application to natural samples three dimensional quantitative textural analysis coupled with numerical modelling has been used to assess the dominant mechanisms governing crystallization of garnet porphyroblasts in rocks from diverse regional metamorphic environments in every case spatial dispositions crystal size distributions and compositional zoning patterns of porphyroblasts indicate the dominance of diffusion controlled nucleation and growth mechanisms nine samples from three geological areas were studied a suite of semi pelitic rocks from the picuris mountains new mexico usa a suite of mafic samples from the llano uplift texas usa and a kyanite schist from mica dam british columbia canada the semi pelitic suite exhibits post deformational garnet growth whereas garnet in the mafic suite and in the kyanite schist grew synkinematically in rocks displaying weak and strong penetrative fabrics respectively for each sample the centres and radii of thousands of garnet crystals were located and measured in three dimensions using images produced by high resolution computed x ray tomography statistical measures of the degree of ordering and clustering of nucleation sites and estimates of crystal isolation for each porphyroblast were then computed from the measured spatial dispositions these measures can be reproduced in simple numerical models only by diffusion controlled nucleation and growth mechanisms normalized radius rate relations computed from compositional zoning patterns in the garnets require thermally accelerated diffusion controlled growth providing independent confirmation of the conclusions based on textural analysis the unexpected similarity of results from all samples indicates that diffusion controlled nucleation and growth mechanisms may govern porphyroblast crystallization in many metamorphic regimes

magnetic pore fabric analysis verification through image autocorrelation the pore fabric of sandstones is studied by impregnating porous samples with a magnetic suspension ferrofluid and subsequently measuring their anisotropy of magnetic susceptibility ams similar to the use of natural ams for estimation of grain fabric we determine average orientation and shape anisotropy of pore bodies in three dimensions this new approach overcomes restrictions of previous methods of pore structure characterization the interpretation of ams in terms of pore fabric anisotropy is tested by comparison with pore shape observed in thin section an image analytical technique is used to derive statistically the elongation direction of digitized pore cross sections by computing the two dimensional autocorrelation function we obtain section ellipses reflecting average pore shape and orientation combination of ellipses of three mutually perpendicular images leads to fabric ellipsoids comparable to ams comparison of the two anisotropies shows a close correspondence between the principal axis directions of ams and fabric ellipsoids owing to the bedded nature of the samples the ellipsoids are of oblate shape with minimum axes perpendicular to bedding however even small anisotropies within the bedding plane can be detected successfully axial ratios of ams and fabric ellipsoids correlate closely if rock sample ams is corrected for pore directional scattering the method represents a powerful tool to analyze pore fabric of sedimentary rocks and to study its effects on petrophysical properties

time and size of a giant earthquake in cascadia inferred from japanese tsunami records of january 1700 geological evidence shows that great earthquakes have occurred in the recent prehistoric past in the cascadia subduction zone off the pacific coast of north america the most recent event or series of events is dated at about 300 years ago1 4 but the precise date and magnitude have not been determined geological investigations have not been able to distinguish a single giant earthquake from a series of great earthquakes occurring over a timespan of a decade or two4 although this information is important for the assessment of future hazard5 we have found several tsunami records in japan from ad 1700 with no indication of a local cause historical earthquake records and palaeoseismic evidence indicate the absence of a large earthquake in 1700 in south america alaska or kamchatka leaving cascadia as the most likely source of this tsunami the estimated time of the earthquake is the evening about 21 00 local time of 26 january 1700 the magnitude is estimated as 9 from the tsunami heights in which case the earthquake ruptured the entire length of the cascadia subduction zone2 these estimates are consistent with native american legends that an earthquake occurred on a winter night6

wavelet transform a future of rock fabric analysis abstract although twenty years ago fabric was defined as the complete spatial and geometrical configuration of all those components that make up a deformed rock fabric was mainly synonymous with lattice preferred orientation very little attention has been paid to the multi scale geometrical and spatial relationships of the rock components fabric quantification in terms of size shape orientation and location at all scales is now performed in two dimensions using anisotropic wavelets as a first example the wavelets are applied to the famous colour plate of sander and the results compared to his axial distribution analysis applied to the k feldspars of a rock section from the sidobre granite pluton montagne noire france the wavelet analysis shows i alignment of grains resulting from mechanical interactions between grains and shows that shearing occurred within the crystalline frame ii preferred grain orientation the classical grain shape fabric parallel to the overall mineral lineation and iii small tensional domains elongate perpendicular to the lineation infilled by the residual melt just before total crystallisation attesting to the stretching nature of the mineral lineation the future of rock fabric analysis will come from new steps in understanding the processes acting during fabric development along with a further development of wavelet analysis using high resolution three dimensional fabric data

effect of mechanical interactions on the development of shape preferred orientations a two dimensional experimental approach abstract modifications in the development of preferred orientations of rigid particles due to mechanical interactions between particles are studied experimentally in two dimensions experiments in both pure shear and simple shear were performed and the results analysed using an easy and fast new automatic method for increased concentration of rigid particles the rotation of individual particles may be slowed down or even stopped due to collisions or disturbance of the flow in the matrix caused by neighbours in coaxial flow the fabric intensity is consequently reduced in simple shear flow the fabric evolution is no longer cyclic the intensity is on average weaker and the fabric axis rotates asymptotically toward the shear plane in the case of preferred orientations of particles having a low aspect ratio 2 5 the fabric rotates through the shear plane then undergoes a reverse rotation and rotates toward the shear plane again in the light of these experimental results we emphasize that quantification of finite strain based on such fabrics may lead to significant underestimates and calculated values should be taken as minimum estimates the kinematic significance of concentrated rigid particle preferred orientations in rocks is modified by interactions between particles techniques for qualitative or quantitative kinematic analysis may become unreliable for simple shear flows the concentrated population fabrics show an angular behaviour close to that of passive markers they tend to align parallel to the shear plane in simple shear flow