electrokinetic experimental study on saturated rock samples zeta potential and surface conductance summary it is important to know the electrokinetic properties of crustal rocks for interpreting the conductivity mechanisms and seismoelectric phenomena during earthquakes and seismoelectric well logging in this study electrokinetic experiments are conducted using a special coreholder by employing an ac lock in technique a series of experiments are conducted on 10 sandstone samples to measure the streaming potentials and streaming currents and the experiments on each sample are done at six different salinities the streaming potential coefficient and streaming current coefficient are calculated from the measured streaming potentials and streaming currents the experimental results show that streaming potential coefficient and streaming current coefficient decrease as the salinity increases the dependence of these two coefficients on permeability and pore radius are analysed and compared with previous works at low salinities the streaming potential coefficient and streaming current coefficient increase with the increasing permeability and pore radius at high salinities the streaming potential coefficient streaming current coefficient almost share a same value for 10 different samples this conclusion indicates that the differences of rock parameters can only be well recognized at lower salinities and the electrokinetic signals are invalid at high salinities which offers a restrictive condition for using the amplitude of electrokinetic signals to estimate rock parameters the zeta potential have also been estimated through combined measurements of streaming potential and streaming current the surface conductivity and its contribution to electrokinetic effects are determined from a comparison of zeta potentials by two different methods and then the validation of the helmholz smoluchowski equation for a capillary tube is tested in rocks we also compare our date with theoretical and experimental works and set up an expression about the relationship between zeta potential and salinity which fits the experimental data well

teleseismic pn arrivals influence of mantle velocity gradient and crustal scattering teleseismic p n phases with a long high amplitude coda are observed to offsets 3000 km along the peaceful nuclear explosion seismic profiles quartz and ruby for the high frequency 5 hz part of the quartz data which is shown here coda lengths of more than 10 s can be visually observed in the seismic sections we interpret the teleseismic p n arrivals as multiple sub moho refractions whispering gallery phases which travel over large distances due to a positive upper mantle velocity gradient the coda of these arrivals is explained by lower crustal scattering of the whispering gallery phases from the mantle the modelling is based on calculation of reflectivity and 2 d visco elastic finite difference synthetic seismograms our models are in agreement with other deep seismic data from continental areas which typically show a reflective lower crust and an almost transparent uppermost mantle the lower crustal heterogeneity is described by von karman distribution with a standard deviation of 0 5 km s 1 for the p wave velocity and correlation lengths of 2 4 km horizontally and 0 6 km vertically the positive vertical upper mantle velocity gradient of 0 004 km s 1 km 1 which is characteristic for profile quartz forms a waveguide which gives rise to the teleseismic p n it is not necessary to include upper mantle heterogeneity in order to explain the characteristics of this arrival

the effect of a percolation threshold in the kozeny carman relation one of the most important properties of reservoir rocks and perhaps the most difficult to predict is permeability laboratory studies have shown that permeability depends on a long list of parameters porosity pore size and shape clay content stress pore pressure fluid type saturation a nearly overwhelming complexity in spite of this the essential behavior can often be expressed successfully using the remarkably simple kozeny carman kozeny 1927 carman 1937 1956 bear 1972 scheidegger 1974 relation b 3s2 where is the permeability is the porosity s is the specific surface area pore surface area per volume of rock and b is a geometric factor

building a 3d model of lithological contacts and near mine structures in the kevitsa mining and exploration site northern finland constraints from 2d and 3d reflection seismic data the kevitsa mafic ultramafic intrusion in northern finland hosts a large disseminated nickel copper sulphide ore body the kevitsa intrusion is an active mining and exploration site for which we

underestimation of scale lengths in stochastic fields and their seismic response a quantification exercise summary the possibility that parts of the earth s continental lower crust can be described with stochastic geological models has been suggested for some time recent studies of deeper well logs also indicate a possible stochastic structure at mid crustal levels this motivates a closer examination of the relation between the statistics of reflection wavefields and that of the lower crust such a relation can put important constraints on possible lower crustal models this study follows up earlier efforts to quantify the statistics of both stochastic lower crustal models and the reflected wavefield since modelling of the seismic response of stochastic von karman fields implies the usage of the impedance contrast field of the latter we wish to compare the second order statistics of both types of fields velocity and impedance this study concludes that the vertical derivative operator on a von karman velocity field implicitly present in the impedance contrast field alters the second order horizontal von karman statistics of the velocity fields in a profound way wavefield effects undoubtedly present in observed seismic data which have earlier been proposed as possible causes for the aforementioned change seem to play a secondary role the vertical derivative operation inherent in the impedance contrast field reduces the estimated horizontal scale length and hurst number by a factor of 2 22 and 1 3 respectively original vertical scale length and hurst number of the velocity fields have a quasi linear influence on this underestimation horizontal scale lengths and hurst numbers were also estimated from the seismic response primary reflectivity section of the von karman fields the values obtained are close to those obtained from the causative impedance contrast fields and are similarly underestimated this suggests a dominant role for the vertical derivative operator in the underestimation of horizontal scale length and hurst number this attempt to quantify the relation between the horizontal spatial statistics of von karman fields and the estimates derived from their seismic response may be useful in upscaling the latter

mapping correlation lengths of lower crustal heterogeneities together with their maximum likelihood uncertainties abstract a novel statistical technique has been applied to the ag 48 seismic line from the lithoprobe dataset passing through the abitibi grenville province canada the method maps lateral stochastic parameters representing von karman heterogeneity distributions in the crust estimated from migrated deep reflection data together with these parameters viz lateral correlation length and power law exponent we also compute their associated maximum likelihood uncertainties combining normalised measurements of lateral correlation and their uncertainties objective profiles of crustal fabric can be made these profiles indicate significant spatial variations in macro scale petrofabric correlation length which carries useful information about structural scale lengths of heterogeneous bodies is an especially robust parameter with moderate associated uncertainties although the general outline of the profiles conforms to the earlier tectonic interpretations based on line drawings new features are visible too the macro scale petrofabric is seen to vary significantly within the tectonic terrains identified earlier in depth as well as laterally a consequence of this additional delineation is that we can explain an existing part of the ag 48 line equally well in terms of collisional deformation and in terms of the effects of a major shear zone projected onto a parallel segment of the line

estimation of vertical stochastic scale parameters in the earth s crystalline crust from seismic reflection data 1 its been shown that the statistical properties of a reflected seismic wavefield can be related to the statistical properties of the crust in this paper we report on a method to invert a reflected seismic wavefield for vertical stochastic parameters the method is founded on a deconvolution thresholding and numerical integration procedure to estimate the earth s bi modal velocity perturbation we then fit a von karman autocorrelation function to the autocorrelation of the estimated velocity perturbation and record the von karman parameters which result in the minimum misfit tests show that our scheme is successful at recovering the vertical characteristic length in synthetic seismic reflection data

statistical measures of crustal heterogeneity from reflection seismic data the role of seismic bandwidth in recent years there has been a growing realization that geological media vary over a broad scale range as such heterogeneity cannot be described in a deterministic way a parallel growth in stochastic analyses of geological geophysical data has emerged the stochastic description of these media is usually through some form of correlation function of which the von karman is the most widely employed using this form media can be described in terms of a characteristic scale size or correlation length l and a coloured scaling regime with scaling described by h the hurst exponent beyond the correlation length the material follows a white noise spectrum where material average properties dominate below the correlation length local heterogeneity dominates hence the correlation length is a fundamental parameter in a range of geodynamical problems in situ information about stochastic properties of deep crustal rocks can be obtained from the statistical analysis of reflection seismic data typical correlation distances within the crust are found to be several hundred metres here we show that correlation distances derived from reflection seismic data are strongly influenced by the spectral content of the source in particular we conclude that there is no reliable evidence for hundred metre scale correlation lengths for crustal heterogeneity

data mining of petrophysical and lithogeochemical borehole data to elucidate the origin of seismic reflectivity within the kevitsa ni cu pge bearing intrusion northern finland the kevitsa mafic ultramafic intrusion located within the central lapland greenstone belt in northern finland hosts a large disseminated ni cu pge sulphide deposit a three dimensional seismic r

laboratory studies of electrical potential during rock failure we have investigated electrical potential and acoustic emissions signals associated with rock deformation five rock types were studied clashach bentheim and darley dale sandstones all quartz rich and a seljadur basalt and portland limestone both quartz free both air dry and the rocks were tested in distilled water shallow crustal conditions were simulated in a triaxial rock deformation cell with a confining pressure simulating depth of 40 mpa pore pressures ranging 5 35 mpa and strain rates 10 7 10 4 s 1 precursory electric potential signals prior to failure were observed in both saturated and dry samples of the quartz rich sandstones but only observed in the water saturated quartz free rocks co seismic electrical signals were obtained in all tests providing strong evidence that two of the main sources for precursory and co seismic signals are the piezoelectric and electrokinetic phenomena lowering the strain rate resulted in an increase in the number of acoustic emissions the pore volume changes during compaction and dilatancy remained approximately constant for all strain rates streaming potential generated by fluid flow across the sample was also measured at different stages of deformation the potential signals increased with the pore pressure gradient c 2005 elsevier ltd all rights reserved

stochastic characterization and seismic response of upper and middle crustal rocks based on the lewisian gneiss complex scotland summary we have developed statistical models of upper and middle crustal seismic velocity heterogeneity based on geologic maps and petrophysical data from the lewisian gneiss complex scotland the level of heterogeneity we have measured is relevant to seismic exploration of the crystalline crust using conventional reflection and refraction techniques we digitized two 1 10560 geologic maps of laxfordian archean age lewisian rocks on a 26 8m grid both maps are believed to be representative of the upper and middle crust in north western scotland and both are believed to provide cross sectional views of parts of the crust the digital maps were characterized by the statistics of their lithologic populations and by their 2 d spatial autocorrelation functions different lithologies were assigned seismic velocities appropriate for the mid crust using petrophysical data three lithologies are dominant silicic gneisses vp 6 2 km s 1 mafic amphibolites vp 6 75 kms 1 and intermediate composition schists vp 6 5kms 1 both maps have self affine spatial fabrics the first map covers the core of a syncline its autocorrelation function defines a medium with a fractal dimension of 2 78 a horizontal characteristic length of about 244m and a vertical correlation of about 133m aspect ratio is 2 1 it has an essentially trimodal velocity lithology population consisting of 37 per cent silicicgneiss 43 per cent mafic amphibolites and 20 per cent schists this map is representative of 30 40 per cent of laxfordian rocks the second map is a plan view which can be rotated 90 about an axis perpendicular to strike to give a cross section this map is characterized by a fractal dimension of 2 55 with a horizontal correlation length of about 111m and a vertical correlation of about 38m aspect ratio 3 1 it has a nearly bimodal population consisting of 77 per cent silicic gneisses and 22 per cent mafic amphibotites it is representative of 60 70 per cent of laxfordian rocks lastly we examine the seismic response of an upper to middle crust based on our statistical models using acoustic and elastic 2 d finite difference synthetic seismograms short offset shot records demonstrate that a lewisian upper crust produces scattered waves which significantly disrupt signals reflecting from deeper levels measurements of transmission scattering q and coda decay rates confirm that seismic scattering in lewisian type crust is strong the migrated cmp response of a lewisian crustal model shows the characteristic salt and pepper pattern often observed in the upper crust and described incorrectly as transparent we suggest that translucent is a more appropriate descriptor

seismic reflection profiling of the pyhasalmi vhms deposit a complementary approach to the deep base metal exploration in finland abstractin the pyhasalmi case study the seismic data is used in direct targeting of shallowly dipping mineralized zones in a massive sulfide ore system that was deformed in complex fold interference structures under high grade metamorphic conditions the pyhasalmi volcanic hosted massive sulfide vhms deposit 50 mt is located in a proterozoic volcanic belt in central finland acoustic impedance of pyhasalmi ore 32 106 kg m2 s is distinct from the host rocks 16 19 106 kg m2s enabling its detection with seismic reflection methods drill hole logging further indicates that the seismic imaging of a contact zone between mafic and felsic volcanic rocks possibly hosting additional mineralizations is plausible six seismic profiles showed discontinuous reflectors and complicated reflectivity patterns due to the complex geology the most prominent reflective package at 1 2 km depth was produced by shallowly dipping contacts between interlayered felsic and mafic volcanic rocks the topmost of these b

seismic wave gradiometry using the wavelet transform application to the analysis of complex surface waves recorded at the glendora array sullivan indiana usa abstract this article describes a new development in seismic wave gradiometry the work follows previous work on time domain wave gradiometry but proposes applying a wavelet transform to the data prior to wave gradiometric analysis the result is a more complete picture of wave attributes which vary in time as well as frequency in this article the new data analysis approach is used to analyze two underwater shots that were recorded by a portion of the glendora array the glendora site is a former surface coal mine that has subsequently been filled by mine tailings and as such forms an artificial sedimentary basin in which the geometry is well known the array used for the analysis was located in a corner formed by the intersection of two vertically oriented boundaries between mine tailings and the surrounding bedrock the analysis of the data revealed the presence of typical body waves and surface waves in addition to several phases that are interpreted to be 1 reflections of surface waves off of the vertical tailings bedrock boundaries 2 surface waves generated by the interaction of direct arrival waterborne acoustic waves with the water tailing interface the lake shore and 3 the interaction of other waterborne acoustic waves in glendora lake with other water tailing interfaces the surface waves are highly time dependent and frequency dependent and highlight the extreme complexity of surface wave propagation in geologically complex areas

origin of ultra nickeliferous olivine in the kevitsa ni cu pge mineralized intrusion northern finland the 2 058 4 ma mafic ultramafic kevitsa intrusion is located in the central lapland greenstone belt northern finland it is hosted by a paleoproterozoic volcano sedimentary sequence that contains komatiitic volcanic rocks and sulfide and graphite rich black schists economic ni cu pge sulfide mineralization occurs in the middle part of the ultramafic lower unit of the intrusion two main types of ore are distinguished normal and ni pge ores the normal ore is characterized by 2 to 6 vol disseminated sulfides and average ni and cu grades of 0 3 and 0 42 wt respectively ni cu 1 the ni pge ore has broadly similar sulfide contents but a higher ni grade and lower cu grade as a result the ni cu ratio reaches 15 much higher than in the normal ore the ni pge ores occur as irregular discontinuous lense like bodies in the ultramafic rocks notably the olivines in the ni pge ore contain extremely high ni contents of up to 14 000 ppm which is significantly higher than the ni content of olivine in other mafic ultramafic igneous rocks globally up to 5 000 ppm and in harmony with the associated ni rich sulfide assemblage containing pentlandite millerite and pyrite microprobe mapping of olivine from the ni pge ore suggests relatively low and homogeneous s contents and homogeneous distribution of ni mg fe which is inconsistent with the presence of sulfide inclusions in the olivine grains or diffusion of ni from interstitial sulfides into the olivine grains we therefore conclude that ni substitutes for mg in the olivine lattice the clinopyroxenes from the ni pge ore also have unusually high ni concentrations reaching 1 500 ppm and show a positive correlation with the nickel content of the associated olivine the nicpx niolivine is 0 1 to 0 2 corresponding to high t partitioning of ni between clinopyroxene and olivine k d of 20 can account for the partitioning of nickel between olivine and the sulfide phase consistent with magmatic equilibration these data suggest that the olivine clinopyroxene and sulfides all crystallized from a basaltic magma with an unexceptionally high ni content ranging from 300 to 1 100 ppm the ni pge ores are spatially associated with ultramafic xenoliths olivine in these ultramafic xenoliths have relatively high fo contents up to 90 mol and high ni contents up to 5 200 ppm suggesting that the xenoliths formed from a komatiitic parental magma it is proposed that assimilation by the kevitsa magma of massive or semi massive sulfides associated with komatiitic rocks elevated the ni content of the magma and resulted in the formation of ni pge ores and related extremely ni rich olivines

seismic methods for deep mineral exploration mature technologies adapted to new targets nonseismic methods such as electromagnetic induced polarization and potential field surveying techniques have been the geophysical backbone of mineral exploration for decades these methods exploit anomalous physical properties of ore deposits e g enhanced conductivity chargeability or magnetization to locate potential targets for drilling although well suited to many shallow 500 m exploration problems the underlying physical principles of these methods impose inescapable limitations on their sensitivity and resolving power at depth recent declines in base metal reserves caused by the depletion of known shallow deposits and declining rates of discovery for new deposits underscore the need for geophysical exploration methods that can locate economically viable deposits at depths of up to several km seismic methods offer one possible solution the need to develop efficient and robust seismic imaging techniques for mineral exploration has long been recognized in the 1980s two key case histories established the potential of seismics as a mapping tool in the hardrock environment green and mair 1983 presented seismic images of complex fracture systems at a radioactive waste disposal site in the canadian shield subsequently pretorius et al 1989 demonstrated the usefulness of an integrated seismic and petrophysical approach to image key geologic structures for mineral exploration in witwatersrand basin south africa these initial studies served as catalysts for a number of largely independent research efforts over the following decade in north america southern africa scandinavia and australia aimed at developing useful and cost effective seismic technology for deep mineral exploration and mine planning a number of fundamental aspects of seismic exploration for minerals including the acoustic properties of ores and the scattering characteristics of orebodies were poorly known until recently moreover significant advances have been made in seismic imaging technology for mineral exploration from downhole seismic techniques to large scale 3d surveys over known deposits this article reviews some advances in applying seismic

a review of reflection seismic investigations in three major metallogenic regions the kevitsa ni cu pge district finland witwatersrand goldfields south africa and the bathurst mining camp canada abstract effective exploration for mineral deposits depends on a sound understanding of the processes and geological structures that contributed to their formation the reflection seismic method has proven to be a powerful tool that provides a high resolution image of the subsurface and information about structural and lithological relationships that control mineral deposits the method has also become an attractive geophysical tool for deep exploration and mine planning in this paper we review the use of reflection seismic methods to obtain a better understanding of the architecture and ore forming processes of three diverse mineral regions the kevitsa ni cu pge district in finland the goldfields of the witwatersrand basin south africa and the bathurst mining camp canada seismic data both 2d and 3d from the kevitsa deposit clearly image the 3d geometry of the ore bearing intrusion and provide information about its relationship to the host rock units and nearby intrusions within a larger tectonic framework 3d seismic data from the witwatersrand basin not only provide clear images of major structures including a distinct reflection that acts as a marker horizon for the gold bearing reef but also provide information that may be useful in resolving a long standing controversy regarding the origin of the gold in the basin for example it might be possible to show that dykes formed impermeable barriers thereby falsifying the epigenetic hydrothermal models 2d and 3d seismic data from the brunswick no 6 area in the bathurst mining camp suggest that the brunswick horizon which contains the bulk of the massive sulfide and associated iron deposits occurs within a reflective package that extends down to at least 6 7 km depth

crustal structure and contact relationship revealed from deep seismic sounding data in south china abstract a 400 km long wide angle seismic profile in the south china crosses three tectonic domains southeast continental margin of yangtze block northwest continental margin of cathaysia block and south china suture zone separating these two blocks the crustal velocity model constructed from traveltime fitting shows that the crust thickness thins from the northwest to the southeast along the profile it also reveals the crustal contact relationship between the yangtze and cathaysia blocks where the wuchuan sihui fault is the boundary between them combining this profile with two more profiles in the continental south china and three profiles in the northern margin of south china sea constructs a continent ocean transition section this cross section reveals that the moho depth shallows gradually along the cross section from the yangtze block to the cathaysia block and the northern margin of south china sea but shallows abruptly in the continent ocean transition to the south china sea

estimation of crustal stochastic parameters from seismic exploration data stochastic models for the crystalline crust produce synthetic seismograms that compare well with recorded data for a variety of crustal ages and tectonic environments in this paper we explore the parameter space describing such stochastic models as a basis for formulating the inverse problem that is we wish to estimate the parameters which define a stochastic model from the recorded backscattered wave field we base the estimation on approximate relations between the primary reflectivity series which is the ideal wave field response of a medium and various seismic gathers a two dimensional lateral correlation method is used to investigate the sensitivity of synthetic wave fields to horizontal characteristic length a derived empirical relationship relates the scale length to the half width of the correlation coefficient a horizontal wavenumber time domain spectral analysis successfully estimates the horizontal characteristic length ax and the fractal dimension d of the stochastic medium from which the wave field was backscattered we employ a monte carlo based optimization scheme to fit the observed spectral values to a one dimensional von karman function and simultaneously estimate values for ax and the hurst number the method yields consistent results when tested on synthetic data application of this technique to data sorted into different domains shows that zero offset sections yield the best estimate we also present results of our estimates using this method on a program for array seismic studies of the continental lithosphere passcal dynamite source shot gather and a vibroseis source consortium for continental reflection profiling cocorp data set recorded in the basin and range province

conservation of lateral stochastic structure of a medium in its simulated seismic response 1 mapping correlation lengths of continental lower crustal heterogeneity directly from deep reflection data can be a valuable additional interpretation tool for deep seismic imaging in this feasibility study we investigate the conservation of lateral correlation length and power law structure in the seismic response of lower crustal stochastic lithology the conservation of von karman power law heterogeneity in backscattered wavefields is evaluated in a range of challenging seismic scenarios we pay special attention to the limitations of this conservation due to the effect of spatial band limitation caused by limited seismic recording aperture and to the effect of complex seismic scattering conditions the comparison of average lateral correlations in von karman media and their modeled reflection responses reveals two important facts spatial band limitation by limited seismic illumination severely affects the estimated power law exponent the hurst number of the von karman heterogeneity distribution but the estimated correlation length is unaffected and scales linearly with the original value the original type of lateral power law distribution is conserved under nearly all seismic scattering conditions investigated albeit with an underestimated correlation length and overestimated hurst number our results can be quantitatively explained which allows for stable estimations of correlation length under various seismic scattering scenarios this study confirms the potential of utilizing estimates of lateral von karman structure to characterize the middle and lower crust from deep seismic reflection data

heterogeneity and seismic scattering in exploration environments abstract seismic scattering and the corresponding reduction in signal to noise ratio is a severe limitation to seismic exploration in crystalline environments in this paper we summarize recent elastic numerical modeling of scattering regimes and discuss the implications for seismic exploration in shallow hardrock environments the resulting synthetic seismograms range from relatively transparent to highly reflective depending on the ratio of seismic wavelength to heterogeneity scale length we note that the archean canadian shield is characterized by large scale lengths typical for crystalline environments which translates to moderately reflective seismic sections exhibiting scattering features that are coherent over large distances in contrast the highly fractured footwall of the sudbury impact structure in the canadian shield translates to a medium with small to moderate scale lengths resulting in seismic sections that can in places be highly reflective or relatively transparent from the perspective of mineral exploration in sudbury we find that the possible detection of massive sulfide targets is dependent not only on the shape and size of the deposit but on the scattering nature of the background as well with information about the petrophysical properties and the distribution of heterogeneity within an exploration area acquisition parameters such as source frequencies and minimum receiver spacing can be adjusted in order to survey within the scattering regime that will produce the least amount of noise

delineating tectonic units beneath the donbas fold belt using scale lengths estimated from dobre 2000 2001 deep reflection data 1 a novel statistical analysis which augments conventional interpretation of deep seismic reflection refraction data is applied to the dobre 2000 2001 reflection profile the goal is to improve delineation of the lithosphere in terms of lithotectonic units and to compare these to existing interpretations after a successful validation of the method using synthetic data stochastic parameters estimated from windowed average lateral autocorrelations in the dobre data are compiled in a two dimensional profile of von karman type causative reflectivity these estimates in terms of lateral correlation lengths and power law exponents are accompanied by associated uncertainties given its low uncertainties the lateral correlation length ax turns out to be a robust delineator the profile of ax reveals systematic spatial variations in the lithospheric fabric below the donbas fold belt as in earlier interpretations based upon conventional processing of reflection refraction data both the sedimentary basin and moho discontinuity stand out clearly as well as a region indicating massive vertical intrusion in the crust from upper mantle sills and ultramafic underplating of the lower crust notable differences with conventional interpretations include the number and extent of supra moho rift pillow structures the lack of imaging a crust cutting dislocation feature and a laterally disturbed uppermost mantle von karman lateral correlation length provides new independent information at a scale between velocity models from wide angle reflection refraction data and line drawings from near vertical reflections and provides new insights and understanding of lithospheric evolution

stochastic modeling of the reflective lower crust petrophysical and geological evidence from the ivera zone northern italy crustal scale seismic wave equation modeling demonstrates that wavelength scale velocity fluctuations can dominate the seismic response over a wide range of offsets and that a wide range of velocity distributions qualitatively can explain deep seismic data this range can be narrowed by studying the detailed petrophysical and structural properties of middle and lower crustal exposures the ivrea zone in the southern alps is a well studied sliver of extended lower continental crust brought into its present upright position as a result of late alpine lithospheric shortening the high degree of structural and petrophysical complexity and in particular the limited exposure of the ivrea zone favor a statistical rather than deterministic approach to develop a two dimensional crustal scale seismic model for this purpose we digitized two 1 25 000 geological maps from the central ivrea zone on a 60 m grid we find that the ivrea zone is characterized by a bimodal velocity distribution and a band limited self affine structure having a fractal dimension of 2 7 a characteristic horizontal scale of 500 to 1000 m and an aspect ratio around 4 0 assuming statistical stationarity a realization of this stochastic model was used to develop synthetic seismograms typical of ivrea type lower continental crust our results indicate that 1 ivrea type lower crust can explain qualitatively commonly observed lower crustal reflectivity 2 relatively minor changes in bulk composition and or metamorphic grade may lead to dramatic changes in reflectivity which cannot be explained by current generic models on the origin of lower crustal reflections and 3 travel time interpretation of the synthetic wide angle data may lead to erroneous large scale velocity structures

statistical approaches to interpretation of seismic reflection data abstract statistical approaches offer a potentially powerful tool for interpretation of the complex seismic reflection patterns typically recorded from the crystalline crust these methods focus on characterization of the complexity scaling characteristics and spatial variability of the wave field with the ultimate aim of recovering information on the geometric variation of the geology in this paper we examine the potential and limitations of statistical approaches focusing on the issues of quality of the statistical estimator how noise and migration affect spatial statistics and the potential for both qualitative and quantitative approaches to statistics based interpretation the limited spatial bandwidth of typical seismic data presently inhibits complete quantitative recovery of the spatial properties of the geology migration which should increase the spatial bandwidth has to date not proven particularly effective on complex wave fields mapping of relative variation in the spatial properties of the wave field reveals subtle differences that are directly associated with the geometric character of the geology such mapping allows identification and mapping of variations in the geologic fabric at scales significantly larger than the seismic wavelength and objective access to scaling information that has previously been unavailable

permeability models of porous media characteristic length scales scaling constants and time dependent electrokinetic coupling fluidpermeabilityisoneofthemostimportantcharacteristics of a hydrocarbon reservoir and is described by a number of empirical and theoretical models we have taken four of the most importantmodels eachofwhichisderivedfromadifferentphysicalapproach andhaverewrittentheminagenericformthatimplies a characteristic scale length and scaling constant for each model the four models have been compared theoretically and using experimental data from 22 bead packs and 188 rock cores from a sand shale sequence in the u k sector of the north sea thekozeny carmanmodeldidnotperformwellbecauseittakes no account of the connectedness of the pore network and should no longer be used the other three models schwartz sen and johnsonssj katzandthompsonkt andtherevil glover pezard andzamorargpzallperformedwellwhenusedwith their respective length scales and scaling constants surprisingly we found that the ssj and kt models are extremely similar such that their characteristic scale lengths and scaling constants arealmostidenticaleventhoughtheyarederivedusingextremely different approaches the ssj model by weighting the kozeny carman model using the local electrical field and the kt model by using entry radii from fluid imbibition measurements theexperimentallydeterminedscalingconstantsforeach model were found to be cssjckt8 3crgpz 3 use of these models with ac electrokinetic theory has also allowed us to showthatthesescalingconstantsarealsorelatedtotheavaluein the rgpz model and the m value in time dependent electrokinetictheoryandthentoderivearelationshipbetweentheelectrokinetic transition frequency and the rgpz scale length which we have validated using experimental data the practical implication of this work for permeability prediction is that the kt model should be used when fluid imbibition data are available whereasthergpzmodelshouldbeusedwhenelectricaldataare available

stochastic modeling of seafloor morphology inversion of sea beam data for second order statistics at scale lengths less than 100 km or so statistical descriptions of seafloor morphology can be usefully employed to characterize ridge crest processes off ridge tectonics and vulcanism sedimentation and postdepositional transport we seek to develop methods for the estimation of seafloor statistics that take into account the finite precision resolution and sampling obtained by actual echo sounding systems in this initial paper we restrict our attention to the problem of recovering second order statistics from data sets collected by multibeam devices such as sea beam the seafloor is modeled as a stationary zero mean gaussian random field completely specified by its two point covariance function we introduce an anisotropic two point covariance function that has five free parameters describing the amplitude orientation characteristic wave numbers and hausdorff fractal dimension of seafloor topography we formulate the general forward problem relating this model to the statistics of an ideal multibeam echo sounder in particular the along track autocovariance functions of individual beams and the cross covariance functions between beams of arbitrary separation using these second moments as data functionals we then pose the inverse problem of estimating the seafloor parameters from realistic noisy data sets with finite sampling and beamwidth and we solve this inverse problem by an iterative linearized least squares method the inversion method is applied to sea beam transit data from both the pacific and atlantic oceans sea beam system noise stands out as a sharp spike on the along track autocovariance function and can be modeled as a white noise process whose amplitude generally increases with beam angle the five parameters in our second order model can be estimated from the inversion of data sets comprising 100 200 km of track length in general the cross track wave number is the most poorly determined although uncertainties in the assumed sea beam response may bias the values of the fractal dimension using the assumed beamwidth the measured noise values and the seafloor parameters recovered from the inversion we generate sea beam synthetics whose statistical character can be directly compared with raw sea beam data for most of the track segments we have processed thus far the synthetics are similar to the data in the case of one atlantic profile however the comparison clearly indicates the necessity of incorporating higher order statistics the space domain procedures described in this paper can be extended for this purpose

estimation of the lateral correlation structure of subsurface water content from surface based ground penetrating radar reflection images 1 over the past decade significant interest has been expressed in relating the spatial statistics of surface based reflection ground penetrating radar gpr data to those of the imaged subsurface volume a primary motivation for this work is that changes in the radar wave velocity which largely control the character of the observed data are expected to be related to corresponding changes in subsurface water content although previous work has indeed indicated that the spatial statistics of gpr images are linked to those of the water content distribution of the probed region a viable method for quantitatively analyzing the gpr data and solving the corresponding inverse problem has not yet been presented here we address this issue by first deriving a relationship between the 2 d autocorrelation of a water content distribution and that of the corresponding gpr reflection image we then show how a bayesian inversion strategy based on markov chain monte carlo sampling can be used to estimate the posterior distribution of subsurface correlation model parameters that are consistent with the gpr data our results indicate that if the underlying assumptions are valid and we possess adequate prior knowledge regarding the water content distribution in particular its vertical variability this methodology allows not only for the reliable recovery of lateral correlation model parameters but also for estimates of parameter uncertainties in the case where prior knowledge regarding the vertical variability of water content is not available the results show that the methodology still reliably recovers the aspect ratio of the heterogeneity

seismic methods in mineral exploration and mine planning a general overview of past and present case histories and a look into the future abstractdue to high metal prices and increased difficulties in finding shallower deposits the exploration for and exploitation of mineral resources is expected to move to greater depths consequently seismic methods will become a more important tool to help unravel structures hosting mineral deposits at great depth for mine planning and exploration these methods also can be used with varying degrees of success to directly target mineral deposits at depth we review important contributions that have been made in developing these techniques for the mining industry with focus on four main regions australia europe canada and south africa a wide range of case studies are covered including some that are published in the special issue accompanying this article from surface to borehole seismic methods as well as petrophysical data and seismic modeling of mineral deposits at present high resolution 2d surveys mostly are performed in mining areas but there is a general increasing trend in the use of 3

shear velocity and vp vs ratio structure of the crust beneath the southern margin of south china continent abstract we here present the results of the inverse modeling of crustal s phases recorded from a 400 km long seismic profile with azimuth nearly n30w from lianxian near hunan province to gangkou island near guangzhou city guangdong province in the southern margin of south china continent the finding in this case is that many shot gathers provided by this wide angle seismic experiment show relatively strong reflected and refracted s phases in particular some crustal refractions sg waves and moho reflections sms waves or simply sm waves the p wave velocity structure of the crust and uppermost mantle was already obtained through the interpretation of vertical component shot gathers now with constraints introduced by the p wave velocity architecture and after picking up s wave traveltime data on the seismograms we have obtained the s velocity model of the crust by adjusting these traveltimes but keeping the geometry of the crustal reflectors our results demonstrate 1 the average crustal s velocity is about 3 64 km s to the northwest of the wuchuan sihui fault and 3 62 km s to the southeast of this fault 2 relatively constant s velocity of about 3 42 km s for the upper crust 3 55 km s for the middle crust and laterally varying shear velocity around 3 82 km s for the lower crust 3 correspondingly vp vs ratio is 1 73 for the upper crust 1 71 for the middle crust and 1 74 for the lower crust both shear velocities and vp vs ratio correlate well with the major active faults that break the study area and show significant changes especially in the upper crust high poisson s ratio 1 8 is observed at shallow depth beneath the minzhong depression to the southeast of the wuchuan sihui fault and the huiyuan depression in the southern margin of south china continent in contrast a very low vp vs ratio 1 68 is observed between 8 and 14 km depth beneath huiyuan at deeper depth a high vp vs ratio 1 76 is observed in the lower crust beneath the minzhong depression

geostatistical inversion of seismic and ground penetrating radar reflection images what can we actually resolve 1 estimation of the spatial statistics of subsurface velocity heterogeneity from surface based geophysical reflection survey data is a problem of significant interest in seismic and ground penetrating radar gpr research a method to effectively address this problem has been recently presented but our knowledge regarding the resolution of the estimated parameters is still inadequate here we examine this issue using an analytical approach that is based on the realistic assumption that the subsurface velocity structure can be characterized as a band limited scale invariant medium our work importantly confirms recent numerical findings that the inversion of seismic or gpr reflection data for the geostatistical properties of the probed subsurface region is sensitive to the aspect ratio of the velocity heterogeneity and to the decay of its power spectrum but not to the individual values of the horizontal and vertical correlation lengths

introduction to special issue on hard rock seismic imaging the exploration of non hydrocarbon resources is receiving increased attention worldwide particularly in terms of renewables e g geothermal energy or minerals both resources are often bound to hard rock environments which normally exhibit a strong degree of heterogeneity including faults and fractures on all scales land seismic surveys for characterizing geothermal reservoirs and mineral deposits are therefore facing the challenge of adapting the methods and tools developed for stratified sedimentary environments to strongly scattering crystalline rocks this comprises not only the pre processing of seismic data but also the imaging steps and furthermore the description and quantification of the resulting images this special issue of geophysical prospecting contains 16 papers resulting from a workshop titled hard rock seismic imaging during the 76th eage conference exhibition 2014 in amsterdam the objective of the workshop was to address all parts of the workflow from modelling and data acquisition design over data processing and imaging to interpretation general concepts and case studies were presented and the workshop attracted a large number of participants from both industry and academia from all over the world a brief introduction to the papers included in this special issue follows divided into the two main categories of the workshop mineral exploration and geothermal prospecting interested readers are also encouraged to check the two earlier special volumes on similar topics by eaton et al 2003 and the references therein and malehmir et al 2012 and the references therein

permeability prediction from micp and nmr data using an electrokinetic approach theaccuratemodelingofoil gas andwaterreservoirsdependsfundamentallyuponaccesstoreliablerockpermeabilitiesthatcannotbeobtaineddirectlyfromdownholelogs instead a range of empirical models are usually employed we propose a new model that has been derived analytically from electrokinetic theory and is equally valid for all lithologies the predictions of the new model and four other common models kozeny carman berg swanson and van baaren have been compared using measurements carried out on fusedandunfusedglassbeadpacksaswellason91rocksamples representing 11 lithologies and three coring directions the new model provides the best predictions for the glass beadpacksaswellforallthelithologies thecruxofthenew modelistohaveagoodknowledgeoftherelevantmeangrain diameter forexample frommicpdata hence wehavealso predictedthepermeabilitiesof21northseawellcoresusing all five models and five different measures of relevant grain size these data show that the best predictions are provided by the use of the new model with the geometric mean grain size wehavealsoappliedthenewmodeltothepredictionof permeability from nmr data of a 500 m thick sand shale succession in the north sea by inverting the t2 spectrum to provide a value for the geometric mean grain size the new model shows a good match to all 348 core measurements fromthesuccession performingbetterthanthesdr timurcoates hscm andkozeny carmanpredictions

a stochastic view of lower crustal fabric based on evidence from the ivrea zone despite its complicated history the ivrea zone is considered to be a representative surface exposure of extended continental crust we have digitized two standard 1 25 000 geological maps from this area and evaluated their structural statistics because of the subvertical orientation of the ivrea zone these maps can be considered as small scale cross sections through the lower continental crust the autocorrelation functions of the digitized lithologies measured from these maps show a clear self similar or fractal rather than a gaussian or deterministic trend we found that an anisotropic von karman correlation function with an aspect ratio around 4 and a hurst number of 0 3 corresponding to a fractal dimension of 2 7 matches the observed data our results represent an explicit confirmation of previous indirect evidence for the fractal nature of lithospheric heterogeneities and provide the means to construct realistic crustal scale seismic models of ivrea type lower continental crust

what is the cementation exponent a new interpretation in 2003 182 billion barrels of oil reserves worth about us 4 5 trillion were discovered worldwide johnson et al 2004 moreover between 1950 and 2002 the total volume of reserves discovered has run to more than 1500 billion barrels for oil and 7 5 trillion cubic feet for gas bentley 2002 more than half of these resources have already been produced and have driven the global economy for the last 50 years

permeability prediction in tight carbonate rocks using capillary pressure measurements abstract the prediction of permeability in tight carbonate reservoirs presents ever more of a challenge in the hydrocarbon industry today it is the aim of this paper to ascertain which models have the capacity to predict permeability reliably in tight carbonates and to develop a new one if required this paper presents i the results of laboratory klinkenberg corrected pulse decay measurements of carbonates with permeabilities in the range 65 nd to 0 7 md ii use of the data to assess the performance of 16 permeability prediction models iii the development of an improved prediction model for tight carbonate rocks and iv its validation using an independent data set initial measurements including porosity permeability and mercury injection capillary pressure measurements micp were carried out on a suite of samples of kometan limestone from the kurdistan region of iraq the prediction performance of sixteen different percolation type and poiseuille type permeability prediction models were analysed with the measured data analysis of the eight best models is included in this paper and the analysis of the remainder is provided in supplementary material some of the models were developed especially for tight gas sands while many were not critically none were developed for tight gas carbonates predictably then the best prediction was obtained from the generic model and the rgpz models r 2 0 923 0 920 and 0 915 respectively with other models performing extremely badly in an attempt to provide a better model for use with tight carbonates we have developed a new model based on the rgpz theoretical model by adding an empirical scaling parameter to account for the relationship between grain size and pore throat size in carbonates the generic model the new rgpz carbonate model and the two original rgpz models have been tested against independent data from a suite of 42 samples of tight solnhofen carbonates all four models performed very creditably with the generic and the new rgpz carbonate models performing well r 2 0 840 and 0 799 respectively it is clear from this study that the blind application of conventional permeability prediction techniques to carbonates and particularly to tight carbonates will lead to gross errors and that the development of new methods that are specific to tight carbonates is unavoidable

3d reflection seismic imaging for open pit mine planning and deep exploration in the kevitsa ni cu pge deposit northern finland a 3d reflection seismic survey was conducted over an area of about 9 km 2 at the kevitsa ni cu pge platinum group elements orebody northern finland where open pit mining started in mid 2012 t