intrinsic and scattering seismic wave attenuation in the central apennines italy abstract recently an earthquake sequence formed by a series of subsequences characterized by large earthquakes three events m 6 0 and five events m 5 0 occurred in the central apennines in 6 7 months during 2016 2017 several studies interpreted this cascading type of earthquake occurrence as associated with fluid movements through an interconnected network of cracks around the active faults that triggered the subsequences in different time and location in the present study we aim to verify if the presence of fluids is confirmed by the pattern of seismic wave attenuation to do so we separately estimate the space averaged parameters intrinsic qi 1 and scattering qs 1 proportional to the correspondent attenuation parameters by applying a modified multiple lapse time window analysis mltwa in order to establish reference background values for the study region mltwa measures the decay of s wave energy with distance and lapse time and fit it to the energy transport equation solution for scattering yielding the seismic albedo b0 qs 1 qt 1 and the extinction length le qt 1 parameters as a function of frequency the knowledge of the separated attenuation parameters allows determining which process of seismic energy dissipation dominates in the region in the present study b0 results to be around0 6 at 1 5 hz and decreases with increasing frequency down to 0 2 indicating that the attenuation of the seismic energy carried by s wave is controlled by intrinsic dissipation rather than by scattering moreover the intrinsic attenuation is frequency dependent f 0 9 for the uniform model and f 0 4 for the crust moho model this behavior well matches with the presence of fluids in the faults and fracture zones in the central apennines in agreement with results from other independent studies in the region finally a comparison among the attenuation parameters estimated for this area and those measured in several areas of italy and other parts of the world is presented together with a discussion on the comparison between the present mltwa attenuation estimates and homologous results obtained for the same area with different approaches

a model for slow motion of natural slopes a new model for describing the slow movement of natural slopes is proposed the geological material in the slope is modeled with a nonhomogeneous bingham constitutive equation this model describes the effect of gravitational consolidation on the material response and allows for a variation of density and yield stress with depth a criterion for shear flow initiation is formulated and the ensuing motion is described velocity profiles for several slip conditions at the interface with the bedrock are given the model is used to predict the observed field behavior of a natural slope villarbeney switzerland key words natural slope incipient shear flow nonhomogeneous bingham law creep flow gravitational consolidation

granitic dimensional stones in uruguay evaluation and assessment of potential resources in uruguay commercial granite varieties comprise mafic rocks granitoids and syenitoids there is a long tradition in uruguay as well as worldwide of using dimensional stones in architecture and art specially granitic ones some of the present applications of these dimensional stones are as facade cladding countertops and outdoor and indoor floor slabs the color spectrum of the uruguayan granitic dimensional stones varies from black to light gray covering a wide variety of red and pink and minor greenish gray the decor of these granitic dimensional stones is mainly determined by their fabric fundamentally the grain size and the color distribution between the different minerals that compose the rocks in the present research the most important commercial granites were sampled to analyze their petrography and petrophysical properties a detailed structural analysis has been performed in several deposits as well as the application of the software 3d block expert for modeling the possible raw block size distribution other factors controlling the mining viability of the deposits were also studied e g homogeneity heterogeneity of color and decor and the possible reserves were calculated

seismic attenuation and velocity dispersion in heterogeneous partially saturated porous rocks summary using a numerical approach we explore wave induced fluid flow effects in partially saturated porous rocks in which the gas water saturation patterns are governed by mesoscopic heterogeneities associated with the dry frame properties the link between the dry frame properties and the gas saturation is defined by the assumption of capillary pressure equilibrium which in the presence of heterogeneity implies that neighbouring regions can exhibit different levels of saturation to determine the equivalent attenuation and phase velocity of the synthetic rock samples considered in this study we apply a numerical upscaling procedure which permits to take into account mesoscopic heterogeneities associated with the dry frame properties as well as spatially continuous variations of the pore fluid properties the multiscale nature of the fluid saturation is taken into account by locally computing the physical properties of an effective fluid which are then used for the larger scale simulations we consider two sets of numerical experiments to analyse such effects in heterogeneous partially saturated porous media where the saturation field is determined by variations in porosity and clay content respectively in both cases we also evaluate the seismic responses of corresponding binary patchy type saturation patterns our results indicate that significant attenuation and modest velocity dispersion effects take place in this kind of media for both binary patchy type and spatially continuous gas saturation patterns and in particular in the presence of relatively small amounts of gas the numerical experiments also show that the nature of the gas distribution patterns is a critical parameter controlling the seismic responses of these environments since attenuation and velocity dispersion effects are much more significant and occur over a broader saturation range for binary patchy type gas water distributions this analysis therefore suggests that the physical mechanisms governing partial saturation should be accounted for when analysing seismic data in a poroelastic framework in this context heterogeneities associated with the dry frame properties which do not play important roles in wave induced fluid flow processes per se should be taken into account since they may determine the kind of gas distribution pattern taking place in the porous rock

origin of gassmann s equations gassmann s relations are receiving more attention as seismic data are increasingly used for reservoir monitoring correct interpretation of underground fluid migration from seismic data requires a quantitative understanding of the relationships among the velocity data and fluid properties in the form of fluid substitution formulas and these formulas are very commonly based on gassmann s equations nevertheless confusion persists about the basic assumptions and the derivation of gassmann s 1951 well known equation in poroelasticity relating dry or drained bulk elastic constants to those for fluid saturated and undrained conditions it is frequently stated for example but quite incorrect to say that gassmann assumes the shear modulus is constant i e mechanically independent of the presence of the saturating fluid this note clarifies the situation by presenting an unusually brief derivation of gassmann s relations that emphasizes the true origin of the constant shear modulus result while also cla

influence of fracture system on the exploitation of building stones the case of the mondim de basto granite north portugal the most negative aspects in the exploitation of weathered granites as ornamental stones tend to be heterogenic coloration and fracturing therefore an accurate study is needed for a comprehensive evaluation of the granite resources during an exploration campaign this paper presents the results of the fracturing evaluation of a region located in north of portugal where the mondim de basto granite a stone with a high weathering degree is exploited the regional fracturing was evaluated from lineaments in aerial photos and then compared with local jointing in quarries the jointing in each quarry is characterized according to the strike and dip joint spacing and volumetric joint count two indices were proposed to facilitate the jointing comparison among quarries the joint space length ljs and joint set spacing sjs ljs is based on the sum of all the spacing values obtained perpendicularly to the strike direction sjs is computed based on the overall mean median spacing and on the number of joint sets observed in each quarry the most important joint sets in the subdivision of the rock mass were found not to be in accordance with the regional fracturing patterns highlighting the necessity of studying the fracturing at all scales

zur geometrie einiger flusse im mittleren buntsandstein trias der hohere mittlere buntsandstein am ostrand des rheinischen schiefergebirges im raum marburg lahn zeigt eine folge fluviatiler sedimente in die grosere temporare aufschlusse einblick gewahren einige querschnitte durch flusrinnen und die dazugehorenden zyklischen sedimente deuten auf eine entwicklung von flachen sandreichen verwilderten flussen der hardegsen folge zu weniger verflochtenen eher solitaren wasserlaufen der solling folge mit machtigeren hochwassersedimenten hin die entwicklung ist hier im randbereich kontinuierlich und weicht etwa durch das fehlen der h diskordanz von anderen gebieten des buntsandsteinbeckens ab

seismic attenuation in partially saturated rocks recent advances and future directions the large amount of data collected with the broadband attenuation vessel bbav and other laboratory devices and analyzed in the last five years sheds light on the physics of wave induced fluid flow in berea sandstone however the knowledge is insufficient to fully exploit the physics of seismic wave attenuation in partially saturated rocks in particular some technical challenges have limited the depth of research soon these challenges will be overcome by the use of fluid pressure sensors capable of measuring wave induced fluid pressure in the seismic bandwidth when the sample is under high confining pressures in addition a new subresonance apparatus paired with a micro ct system will be used to further investigate the influence of fluid distribution and microstructural features on attenuation

equivalent viscoelastic solids for heterogeneous fluid saturated porous rocks differenttheoreticalandlaboratorystudiesonthepropagation ofelasticwavesinrealrockshaveshownthatthepresenceofheterogeneities larger than the pore size but smaller than the predominant wavelengths mesoscopic scale heterogeneities may producesignificantattenuationandvelocitydispersioneffectson seismic waves such phenomena are known as mesoscopic effects and are caused by equilibration of wave induced fluid pressure gradients we propose a numerical upscaling procedure to obtain equivalent viscoelastic solids for heterogeneous fluidsaturated rocks it consists in simulating oscillatory compressibility and shear tests in the space frequency domain which enable us to obtain the equivalent complex undrained plane wave and shear moduli of the rock sample we assume that the behavior of the porous media obeys biot s equations and use a finiteelementproceduretoapproximatethesolutionsoftheassociated boundary value problems also because at mesoscopic scales rock parameter distributions are generally uncertain and of stochastic nature we propose applying the compressibility and sheartestsinamontecarlofashion thisfacilitatesthedefinition of average equivalent viscoelastic media by computing the moments of the equivalent phase velocities and inverse quality factors over a set of realizations of stochastic rock parameters described by a given spectral density distribution we analyzed the sensitivity of the mesoscopic effects to different kinds of heterogeneities in the rock and fluid properties using numerical examples also theapplicationofthemontecarloprocedureallowed us to determine the statistical properties of phase velocities and inverse quality factors for the particular case of quasi fractal heterogeneities

the architecture of a sandy braided meandering river system an example from the lower triassic soiling formation m buntsandstein in w germany the dominantly sandy fluvial deposits of the soiling formation in the hessian depression in w germany are excellently exposed in abandoned sandstone quarries n of kassel near bad karlshafen und stadtoldendorf detailed mapping of the quarry walls indicates the presence of five architectural elements 1 lateral accretion deposits 2 minor cross cutting channel fills 3 major broad channel deposits 4 laminated sand sheets and 5 muddy deposits the vertical and lateral relationships of these elements suggest deposition in a braided meandering river system sinuous parts of the river channels were dominated by point bar deposition at river high stage element 1 whereas low stage flow was characterized by a braided stream pattern element 2 less sinuous parts of the river channels were characterized by moderate braiding indices element 3 proximal overbank areas were dominated by sandy sheet flows element 4 whereas distal overbank areas received muddy sediments element 5

black dimensional stones geology technical properties and deposit characterization of the dolerites from uruguay dimensional stones with a black color occupy a prominent place on the international market uruguayan dolerite dikes of andesitic and andesitic basaltic compo sition are mined for commercial blocks of black dimen sional stones a total of 16 dikes of both compositions were studied and samples collected for geochemical and petro graphical analysis color measurements were performed on different black dimensional stones in order to compare them with the uruguayan dolerites samples of the two commercial varieties absolute black and moderate black were obtained for petrophysical analysis e g density porosity uniaxial compressive strength tensile strength etc detailed structural analyses were performed in sev eral quarries geochemistry and petrography determines the intensity of the black color the uruguayan dolerite absolute black is the darkest black dimensional stone analyzed in this study the petrophysical properties of uruguayan dolerites make them one of the highest quality black dimensional stones structural analyses show that five joint sets have been recognized two sub vertical joints one horizontal and two diagonal these joint sets are one of the most important factors that control the deposits since they control the block size distribution and the amount of waste material

seismic attenuation due to wave induced flow analytical expressions for three p wave attenuation mechanisms in sedimentary rocks are given a unified theoretical framework two of the models concern wave induced flow due to heterogeneity in the elastic moduli at mesoscopic scales scales greater than grain sizes but smaller than wavelengths in the first model the heterogeneity is due to lithological variations e g mixtures of sands and clays with a single fluid saturating all the pores in the second model a single uniform lithology is saturated in mesoscopic patches by two immiscible fluids e g air and water in the third model the heterogeneity is at microscopic grain scales broken grain contacts and or micro cracks in the grains and the associated fluid response corresponds to squirt flow the model of squirt flow derived here reduces to proper limits as any of the fluid bulk modulus crack porosity and or frequency is reduced to zero it is shown that squirt flow is incapable of explaining the measured level of loss 10 sup 2 q sup 1 10 sup 1 within the seismic band of frequencies 1 to 10 sup 4 hz however either of the two mesoscopic scale models easily produce enough attenuation to explain the field data

seismic and electrical properties of sandstones at low saturations laboratory measurements of elastic wave velocities attenuation and electrical resistivity of sandstones all show distinct changes in the measured properties at very low levels of water saturation velocity decreases attenuation reaches a maximum and electrical resistivity decreases over a limited range in saturation we assume that all the water at low saturations is present in the rock as a layer of uniform thickness covering the entire internal surface area of the sample with this model we calculate the thickness of surface water that corresponds to the distinct low saturation region in all cases for both the seismic and the electrical data the thickness is equal to one to four monolayers of water this is interpreted as marking the transition in the behavior of water in a sandstone from that of a surface adsorbed phase to a bulk water phase the changes in seismic properties can be modeled by considering the effect of adding surface and bulk water to grain contacts in a similar treatment the role of contacts is shown to be a dominant factor in the electrical resistivity of sandstones at low saturations such that the addition of water to the contact area causes a dramatic decrease in the electrical resistivity

an overview of laboratory apparatuses to measure seismic attenuation in reservoir rocks intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability fluid properties and saturation however in order to use attenuation as an attribute to extract information on rock fluid properties from seismic data experimental studies on attenuation are necessary for a better understanding of physical mechanisms that are dominant at those frequencies an appropriate laboratory methodology to measure attenuation at seismic frequencies is the forced oscillation method but technical challenges kept this technique from being widely used there is a need for the standardization of devices employing this method and a comparison of existing setups is a step towards it here we summarize the apparatuses based on the forced oscillation method that were built in the last 30 years and were used to measure frequency dependent attenuation in fluid saturated and or dry reservoir rocks under small strains 10 8 10 5 we list and discuss important technical aspects to be taken into account when working with these devices or in the course of designing a new one we also present a summary of the attenuation measurements in reservoir rock samples performed with these apparatuses so far

effect of quarrying on the slope stability in banasuramala an offshoot valley of western ghats kerala india the narippara area which is nestled in the banasuramala of wayanad district witnessed initiation of landslide which was manifested in the form of curvilinear cracks running for a length of 170 m in the event of continuous rainfall these cracks may get reactivated leading to a major landslide this could affect the life and livelihood of a large number of families living downslope and could cause extensive damage to property extensive mining for building stones in this area has been a cause for much concern amongst the local population this study aims at understanding the impact of quarrying on slope stability through geotechnical geophysical and environmental impact assessment eia geotechnical analysis shows that the area is stable under dry condition but parts of the area are critical under wet and saturated conditions moreover resistivity studies revealed that the cracks that had developed extend up to the bedrock and the suspected mechanism of failure will be translational in nature eia reveal that due to quarrying and mining operations the possibility of land disturbances cannot be ruled out during the monsoon season in the present study an attempt is also made to suggest management strategies for mitigating further effects of landslides in this area

effects of partial liquid gas saturation on extensional wave attenuation in berea sandstone extensional wave attenuation measurements on berea sandstone were made during increasing imbibition and decreasing drainage brine saturations measurements on samples with both open pore and closed pore surfaces were made using the resonant bar technique the frequency dependence was examined using the forced deformation method the attenuation was found to be dependent on saturation history as well as degree of saturation and boundary flow conditions the sample with open pore surface had a larger attenuation which peaked at greater brine saturations than the sample with closed pore surface during drainage the attenuation reached a maximum at about 90 brine saturation as opposed to about 97 brine saturation during imbibition the variation of the size and number of air pockets within the rock can account for this discrepancy the magnitude of the attenuation peak value decreases substantially with decreasing frequency to the extent that no attenuation peak with saturation was apparent at seismic frequencies say below 100 hz

insolation weathering and hygric dilatation two competitive factors in stone degradation in the natural environment temperature and moisture are very important parameters in stone degradation therefore on 28 samples from different lithologies magmatic metamorphic and sedimentary rocks thermal and hygric expansion measurements were performed in order to constrain their behaviour related to environmental changes it was shown that marbles even those that are dolomitic are sensitive to temperature impacts for rocks with clay minerals the effect of temperature may be responsible for shrinking finally the amount of residual strain i e the formation of microcracks due to temperature action controls the rate of stone degradation for most sedimentary rocks no residual strain after heating was observed in contrast to most magmatic and metamorphic low porosity rocks sedimentary rocks contain swelling minerals like smectite and even phyllosilicates which are very sensitive to hygric attacks the cycles of wetting and drying i e the natural environmental effects may significantly control the deterioration velocity caused by hygric expansion

characterization and quality assessment of granitic building stone deposits a case study of two different portuguese granites abstract several factors determine building stone exploration in order to maximize the extraction processing and application of these natural materials some factors are intrinsic to stones such as their physical mechanical properties while others are related to their exploitability such as quarry reserves or fracturing density during an exploration campaign these factors are not always considered or properly weighed in terms of the negative consequences on quarry activities or rock behaviour under particular conditions in this study two well known portuguese granites are assessed to highlight the main factors these granites have different characteristics weathered and sound and are exploited in quarries with different joint densities the most relevant physical mechanical properties were evaluated and related to the specific petrophysical features of each granite the fracture patterns were identified in the quarries and then modelled in order to compute the quarry yield the weathered granite shows an important microcrack network and a general alteration of the rock forming minerals which has an important impact on its physical mechanical properties and on the resistance to environmental factors moreover the extreme differences in the degree of weathering require careful choices for the possible applications in both quarries the joint sets are similar to the regional faulting but some random joints can be found and consequently diminish the quarry yield the development of horizontal sheet joints during the exploitation process could have a great influence on the quarry productivity if they are not used do delimitate the extracted blocks the modelling of the natural fracture pattern allows us to determine the potential volume of blocks that could be exploited however the quality of the information gathered could lead to an over estimation of the quarry production this example shows the importance of the exhaustive researches during a building stone assessment campaign

a simple hydromechanical approach for simulating squirt type flow abstractthe deformations caused by an acoustic wavefield in subsurface rock can induce fluid flow within hydraulically interconnected mesoscopic fractures from one fracture into the other the viscous friction associated with this squirt type fluid flow parallel to the fracture walls results in energy dissipation and velocity dispersion we have developed a quasi static hydromechanical approach that is suitable for simulating squirt type flow in the mesoscopic scale range and microscopic squirt flow our approach couples navier stokes equation with hooke s law to describe the laminar flow of a viscous compressible fluid in conduits embedded in an elastic solid background results from the proposed method were compared with those obtained with biot s equations for a model containing interconnected mesoscopic fractures embedded in a background of very low porosity and permeability despite significant differences in the flow and dissipation spatial patterns we have observed an essentially perfect agreemen

numerical modeling and laboratory measurements of seismic attenuation in partially saturated rock to better understand the effects of fluid saturation on seismic attenuation we combined numerical modeling in poroelastic media and laboratory measurements of seismic attenuation in partially saturated berea sandstone samples although in laboratory experiments many physical mechanisms for seismic attenuation take place simultaneously with numerical modeling we separately studied the effect of a single physical mechanism wave induced fluid flow on the mesoscopic scale using the finite element method we solved biot s equations of consolidation by performing a quasistatic creep test on a 3d poroelastic model this model represents a partially saturated rock sample we obtained the stress strain relation from which we calculated frequency dependent attenuation in the laboratory we measured attenuation in extensional mode for dry and partially water saturated berea sandstone samples in the frequency range from 0 1 to 100 hz all the measurements were performed at room pressure and temperature conditions from numerical simulations we found that attenuation varies significantly with fluid distribution within the model in addition to binary distributions we used spatially continuous distributions of fluid saturation for the numerical models such continuous saturation distribution was implemented using properties of an effective single phase fluid by taking into account the matrix anelasticity we found that wave induced fluid flow on the mesoscopic scale due to a continuous distribution of fluid saturation can reproduce seismic attenuation data measured in a partially saturated sample the matrix anelasticity was the attenuation measured in the room condition dry sample

monitoring fluid substitution in rock samples from noise correlation an alternative laboratory technique to measure the elastic constants of solid samples based on the analysis of the cross correlation spectra of the vibratory response of randomly excited short solid cylinders has been recently proposed the aim of this paper is to check the ability of the technique called passive ultrasonic interferometry to monitor fluid substitution in different rock samples velocity variations due to fluid substitution are easily measured if the wave attenuation in the fluid saturated rock is not too large typically in rocks with few cracks or microfractures the experimental results are in agreement with the predictions of biot gassmann poroelastic theory the effect of substituting water with a stiffer saturating fluid such as ethylene glycol is to increase the overall bulk modulus of the rock without any substantial effect on shear modulus furthermore the experimental results compare well with those obtained independently with conventional pulse transmission technique using ultrasonic transducers however the measured pulse transmission bulk moduli are slightly larger than the corresponding measured ultrasonic interferometry moduli with the deviation increasing with increasing fluid viscosity this can be explained by dispersion due to wave induced flow of the viscous fluid since pulsetransmission experiments involve higher frequencies than ultrasonic interferometry experiments

velocity saturation relation in partially saturated rocks modelling the effect of injection rate changes the relationship between p wave velocity and fluid saturation in a porous medium is of importance for reservoir rock characterization forced imbibition experiments in the laboratory reveal rather complicated velocity saturation relations including rollover like patterns induced by injection rate changes poroelasticity theory based patchy saturation models using a constant fluid patch size are not able to describe these velocity saturation relations therefore we incorporate a saturation dependent patch size function into two models for patchy saturation this recipe allows us to model observed velocity saturation relations obtained for different and variable injection rates the results reveal an increase in patch size with fluid saturation and show a reduction in the patch size for decreasing injection rate this indicates that there can exist a distinct relation between patch size and injection rate we assess the relative importance of capillarity on velocity saturation relations and find that capillarity stiffening impairs the impact of patch size changes capillarity stiffening appears to be a plausible explanation when a decrease in the injection rate is expected to boost the importance of capillarity

optimized extraction of dimension stone blocks the profitable production of dimension stone mainly depends on the extractable block size the regularity and volume of the blocks are of critical importance and are controlled by the three dimensional pattern of the discontinuity system therefore optimization of block size has to be the aim when quarrying for natural stone this is mainly connected to the quantification of joints and fractures i e their spacing and orientation the problem of finding unfractured blocks within arbitrarily oriented and distributed planes can be solved effectively by a numerical algorithm the main effects of joint orientations on block sizes and shapes will be presented in this article quantification of unfractured blocks with the aim of optimization is illustrated by detailed studies on several quarries the algorithm used in this study can be applied as a powerful tool in the planning of a quarry and the future exploitation of dimension stone application of the described approach is demonstrated on practical examples of quarrying natural stones namely sandstone granite rhyolite etc block quarrying can be optimized by using the new 3d blockexpert approach the quantification of unfractured rock masses is also shown to contribute to a more ecological protection and the sustainable use of natural resources

surface temperature differences between minerals in crystalline rocks implications for granular disaggregation of granites through thermal fatigue thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation however there have been no definitive demonstrations of the efficacy of this weathering mechanism different surface temperatures between minerals should magnify thermal expansion differences and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure this work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation the influence of colour as a surrogate for albedo and crystal size as a function of thermal mass are specifically identified because of their ease of quantification four rock types with a range of these properties were examined and subjected to repeated short term temperature cycles by radiative heating and cooling under laboratory conditions results show that while albedo is the main control for overall and individual maximum temperatures crystal size is the main factor controlling higher temperature differences between minerals thus stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences

effect of anelastic patchy saturated sand layers on the reflection and transmission responses of a periodically layered medium based on analytic relations we compute the reflection and transmission responses of a periodically layered medium with a stack of elastic shales and partially saturated sands the sand layers are considered anelastic using patchy saturation theory or elastic with effective velocity using the patchy saturation theory we introduce a velocity dispersion due to mesoscale attenuation in the sand layer this intrinsic anelasticity is creating frequency dependence which is added to the one coming from the layering macroscale we choose several configurations of the periodically layered medium to enhance more or less the effect of anelasticity the worst case to see the effect of intrinsic anelasticity is obtained with low dispersion in the sand layer strong contrast between shales and sands and a low value of the net togross ratio sand proportion divided by the sand shale proportion whereas the best case is constituted by high dispersion weak contrast and high net to gross ratio we then compare the results to show which dispersion effect is dominating in reflection and transmission responses in frequency domain the influence of the intrinsic anelasticity is not negligible compared with the layering effect even if the main resonance patterns are the same the resonance peaks for anelastic cases are shifted towards high frequencies and have a slightly lower amplitude than for elastic cases these observations are more emphasized when we combine all effects and when the net to gross ratio increases whereas the differences between anelastic and elastic results are less affected by the level of intrinsic dispersion and by the contrast between the layers in the time domain the amplitude of the responses is significantly lower when we consider intrinsic anelastic layers even if the phase response has the same features for elastic and anelastic cases the anelastic model responses are clearly more attenuated than the elastic ones we conclude that the frequency dependence due to the layering is not always dominating the responses the frequency dependence coming from intrinsic visco elastic phenomena affects the amplitude of the responses in the frequency and time domains considering intrinsic attenuation and velocity dispersion of some layers should be analyzed while looking at seismic and log data in thin layered reservoirs

the bowing potential of granitic rocks rock fabrics thermal properties and residual strain the bowing of natural stone panels is especially known for marble slabs the bowing of granite is mainly known from tombstones in subtropical humid climate field inspections in combination with laboratory investigations with respect to the thermal expansion and the bowing potential was performed on two different granitoids cezlak granodiorite and flossenburg granite which differ in the composition and rock fabrics in addition to describe and explain the effect of bowing of granitoid facade panels neutron time of flight diffraction was applied to determine residual macro and microstrain the measurements were combined with investigations of the crystallographic preferred orientation of quartz and biotite both samples show a significant bowing as a function of panel thickness and destination temperature in comparison to marbles the effect of bowing is more pronounced in granitoids at temperatures of 120 c the bowing as well as the thermal expansion of the cezlak sample is also anisotropic with respect to the rock fabrics a quantitative estimate was performed based on the observed textures the effect of the locked in stresses may also have a control on the bowing together with the thermal stresses related to the different volume expansion of the rock forming minerals

hematite in porous red clouded feldspars evidence of large scale crustal fluid rock interaction abstract transmission electron microscopy shows that red clouded alkali feldspars from granitic rocks contain numerous open pores up to several hundred nanometres in cross section and that almost every pore contains rosettes or needles of crystalline hematite in the samples described here the hematite forms at the reaction interfaces at which plagioclase feldspar is replaced by alkali feldspar these observations together with the fact that the origin of the porosity can be explained by the mechanism of sub solidus mineral fluid replacement processes indicate that hematite is a direct product of fluid rock interaction and is not a solid state exsolution product from the feldspar

pore fluid effects on s wave attenuation caused by wave induced fluid flow we studied seismic attenuation of p and s waves caused by the physical mechanism of wave induced fluid flow at the mesoscopic scale stress relaxation experiments were numerically simulated by solving biot s equations for consolidation of 2d poroelastic media with finite element modeling the experiments yielded time dependent stress strain relations that were used to calculate the complex moduli from which frequency dependent attenuation was determined our model consisted of periodically distributed circular or elliptical heterogeneities with much lower porosityandpermeabilitythan thebackgroundmedia which contained 80 of the total pore space of the media this model can represent a hydrocarbon reservoir where the porous background is fully saturated with oil or gas and the low porosity regions are always saturated with water three different saturation scenarios were considered oil saturated 80 oil 20 water gas saturated 80 gas 20 water and fully water saturated media varying the dry bulk and shear moduli in the background and in the heterogeneities a consistent tendency was observed in the relative behavior of the s wave attenuation among the different saturation scenarios first in the gas saturated media the s wave attenuation was very low and much lower than in the oil saturated or in the fully water saturated media second at low frequencies the s wave attenuation was significantly higher in the oil saturated media than in the fully water saturated media the p wave attenuation exhibited a more variable relative behavior among the different saturation degrees based on the mechanism of wave induced fluid flow and on our numerical results we suggest that s wave attenuation could be used as an indicator of fluid content in a reservoir additionally we observed that impermeable barriers in the background can cause a significant increasein s waveattenuation thissuggests that s wave attenuation could also be an indicator of permeability changes in a reservoir due to for example fracturing operations

depositional environment and diagenesis as controlling factors for petro physical properties and weathering resistance of siliciclastic dimension stones integrative case study on the wesersandstein northern germany middle buntsandstein

statistical approach of the influence of petrography in mechanical properties and durability of granitic stones the influence of petrographic features on the strength of granitic stones is a wide studied topic which finds different correlations depending on the research and the granite type the aim of this article was to provide an accurate statistical analysis in which the amount of analysed data did not imply any doubt about the representativity of the samples and the accuracy of the results the focused principal component analysis was used because it allows to explain a determinate property in relation to several variables in addition the expression of the results was done as a simple and graphical representation that allowed to interpret the results in a global way data of texture mineralogy and strength of 12 granites were obtained in this study and were completed by those of more than 100 granites obtained from the literature the durability of the twelve granite characterized was also assessed a thermal fatigue test was carried out in 5 5 5 cm cubes revealing that the thermal expansion experimented by the different minerals was enough to produce variations in the crack network even if temperature was lower than the microfissuration threshold

differences in the quality of polishing between sound and weathered granites aesthetic characteristics are important when rocks are used as construction materials among all the surface finishes available the polished finish is the one which best enhances the rock attractiveness colour c roughness r and gloss g are surface properties usually used to assess the rock polishing in this research the crg properties were assessed in polished samples of three ornamental granites with different textures and physical mechanical properties one weathered and two sound c was evaluated in cie l a b and cie l c abhab systems r with ra and rz parameters and g using the 20 60 and 85 geometries the weathered granite presents a noticeable colour variation especially in the b parameter while the sound ones have a more homogeneous colour sound and more textural homogeneous granites have a low surface roughness and high gloss which are uniformly distributed the weathered granite shows a higher surface roughness and lower gloss with scattered distribution the mineral contacts are the main cause of the surface irregularities the results show the interdependence between the crg properties and stress the importance of the polishing process for enhancing the aesthetic characteristics of the granites crg properties could be used for quality control in granite processing plants thus avoiding noticeable differences in the facades of buildings particularly when weathered granites are used

discontinuity modelling and rock block geometry identification to optimize production in dimension stone quarries abstract evaluating the reserves of commercial blocks in dimension stone quarries requires determining in situ block geometry furthermore to extract blocks the planes need to be cut and the intersection between the fracture network and the cutting patterns forms smaller blocks the optimization of the cutting patterns can increase quarrying efficiency resulting in less environmental damage in this paper a numerical algorithm was selected from various algorithms and was developed for in situ block identification the optimization approach was adopted to increase quarry productivity and to investigate quarrying direction on a large scale however on a small scale this approach was employed for checking the distance between the cutting planes according to the algorithms developed 3d quarryoptimizer was programmed in the matlab environment to determine the geometry of the blocks and to optimize extraction based on the quality classification of the blocks formed the algorithms developed have such advantages as the optimization approach and taking the geometry of the blocks into consideration this methodology was applied in a marble quarry and a granite quarry research conducted in the granite quarry showed that the program is a practical tool to determine the geometry of in situ blocks and their quality classification the marble quarry was studied for the optimization phase the large scale optimization indicated a maximum difference of 17 in the yield among several quarrying directions on a small scale however a 120 increase in quarry yield was achieved with the optimal interval between the cutting planes

stress associated intrinsic and scattering attenuation from laboratory ultrasonic measurements on shales seismic attenuation is sensitive to stress induced subtle changes in the physical state of rocks in this study the stress and frequency associated attenuation is quantified through ultrasonic measurements on three differently oriented cylindrical shale samples under various axial stresses as an improvement to the single scattering model the elastic monte carlo method is employed to investigate multiple scattering attenuations by incorporating the boundary reflections and wave conversions our results show that as the axial stress increases the intrinsic attenuation decreases in all directions while the scattering attenuation decreases slightly in the direction perpendicular to the bedding but increases largely and nonlinearly in other directions these discrepancies result from different attenuation mechanisms both the intrinsic and scattering attenuation are found to be largest in the direction 45 to the bedding but least in the perpendicular direction the s wave attenuation is larger and more sensitive to stress changes than p wave attenuation due to its shorter wavelength as expected from sandstone examples the scattering attenuation in shales is significantly larger and more sensitive to stress changes than the intrinsic attenuation the frequency dependence of scattering attenuation suggests that the peak frequency with the maximum scattering attenuation is independent of axial stresses but varies in different directions of an individual rock with different heterogeneity and anisotropy scales the peak frequency of s coda is smaller and its peak scattering attenuation is larger than p coda in conclusion the stress and frequency dependence of ultrasonic attenuations in shales differ largely in various directions indicating significant anisotropy and heterogeneity

a new seismic wave attenuation module to experimentally measure low frequency attenuation in extensional mode abstract a seismic wave attenuation module is developed to experimentally measure the attenuation in extensional mode qe 1 and the young s modulus of copper jacketed 60 mm long and 25 4 mm in diameter samples in a gas medium paterson rig the new module is suitable for natural rock samples and was tested under confining pressure up to 50 mpa and room temperature the module is designed to operate at a strain 10 6 for which rocks behave linearly to calculate attenuation both the applied force and the bulk shortening of the sample are measured employing linear variable differential transformers this technique allows measuring samples with a high degree of heterogeneity attenuation at low seismic frequencies 10 2 102 hz is obtained for rocks at dry and various saturation conditions we present a series of measurements on berea sandstone in a room dry condition and saturated with different fluids water and glycerine solutions with viscosities of 10 cp and 22 cp respectively at a confining pressure of 10 mpa and with a pore pressure of 1 mpa the accuracy of the attenuation data expressed as a phase shift is 0 0019 rad

laboratory measurements of seismic attenuation in sandstone strain versus fluid saturation effects abstractin the past few decades great attention has been focused on uncovering the physics of seismic wave attenuation in fluid saturated rocks however the relationship among many variables affecting attenuation is still not completely clear for instance although the role of strain in enhancing friction dissipation is relatively well known for dry rocks it remains unclear how and how much it affects attenuation in fluid saturated rocks we experimentally measured attenuation in the extensional mode in berea sandstone at strains between 7 8 10 7 and 1 9 10 5 and at frequencies in the seismic bandwidth 1 100 hz these strains were similar to those typically observed in seismic exploration 10 6 we also measured the transient fluid pressure caused when a stepwise stress was applied resulting in such strains for the studied strain range our results indicated that 1 the overall attenuation in dry berea sandstone increased linearly with strain 2 the frequency dependent component of attenuati

estimating gas saturation in a thin layer by using frequency dependent amplitude versus offset modelling various models have been proposed to link partial gas saturation to seismic attenuation and dispersion suggesting that the reflection coefficient should be frequencydependent in many cases of practical importance previous approaches to studying this phenomenon typically have been limited to single interface models here we propose a modelling technique that allows us to incorporate frequency dependent reflectivity into convolutional modelling with this modelling framework seismic data can be synthesised from well logs of velocity density porosity and water saturation this forward modelling could act as a basis for inversion schemes aimed at recovering gas saturation variations with depth we present a bayesian inversion scheme for a simple thin layer case and a particular rock physics model and show that although the method is very sensitive to prior information and constraints both gas saturation and layer thickness theoretically can be estimated in the case of interfering reflections

intergranular pressure solution in four quartzose sandstones abstract cathodoluminescence petrography and scanning electron microscopy reveal that several geologic variables significantly influenced intergranular pressure solution and quartz cementation in the bromide ordovician oklahoma upper minnelusa permian wyoming nugget jurassic utah and tuscarora silurian pennsylvania sandstones a linear relationship exists between mean grain size and intergranular pressure solution with finer grained samples having experienced more intergranular pressure solution than coarser grained ones samples that display pervasive illite grain coatings have also experienced more intergranular pressure solution than those with no or poorly developed grain coatings sorting and limited framework grain compositional variability have exerted little influence o intergranular pressure solution silica budgets indicate that in the bromide upper minnelusa and nugget sandstones more quartz has been dissolved by intergranular pressure solution than is present as cement these sandstones have exported silica during burial diagenesis in the tuscarora the amount of quartz dissolved by intergranular pressure solution is about equal to the amount of quartz cement present implying approximate mass balance however petrographic evidence suggests that most of the quartz cement in at least three of these sandstones predates most intergranular pressure solution implying that they acted as silica importers during shallow diagenesis and silica exporters during deeper diagenesis intergranular pressure solution has played varying roles in determining the ultimate porosity of these four sandstones in the nugget intergranular pressure solution was the single most important diagenetic process that influenced porosity evolution in the bromide intergranular pressure solution was slightly more important than mechanical compaction and considerably more important than cementation in the tuscarora intergranular pressure solution was slightly more important than mechanical compaction and of about equal importance to quartz cementation in the upper minnelusa intergranular pressure solution was less important than both mechanical compaction and gypsum anhydrite cementation

fluorite particles inducing butterfly aggregates of incipient microperthite in alkali feldspar from a syenite the patagonian andes southern chile alkali feldspar grains found in a syenite from the patagonian andes southern chile have bulk compositions of about or 4 0 ab 5 9 an 0 5 and consist of two parts when viewed under an optical microscope a clear part anda turbid part grain interiors are mixtures of the two parts whereas the rims are mainly turbid the microscopically clear part which is almost free of micropores is cryptoperthitic whereas the turbid part is microperthitic the microperthite is of the patch type and the turbidity is due to abundant micropores that are polygonal and generally less than 1 m in diameter the patch microperthite has been formed by coarsening of primary cryptoperthite by hydrothermal reactions an incipient stage of the microperthite formation is recorded as the segregation of the or rich feldspar with diagonal elongation and ab rich feldspar into aggregates that have a butterfly shape each butterfly aggregate of microperthite is generally less than 10 m in length the centers of the butterfly aggregates are usually occupied by round fluorite particles about 1 m in diameter which were identified by epma and tem analyses the fluorite particles may have been formed at the fluid stage the microperthite formation may have started as butterfly aggregates along the interfaces with the fluorite particles at the hydrothermal stage the butterfly aggregates have changed to patch microperthite with further coarsening the timing and process of the formation of the fluorite particles are important in relation to the evolution of feldspar microtextures and the behavior of fluorine in alkaline igneous rocks

the complex hydrothermal history of granitic rocks multiple feldspar replacement reactions under subsolidus conditions recurring subsolidus re equilibration of granitic feldspars induced by fluid infiltration events provides a record of fluid rock interactions that affect large volumes of the earth s continental crust this has a direct bearing on the interpretation of the present day granitic rock mineralogy and geochemistry we examine palaeoproterozoic grey and red stained granitoids from the simpevarp and laxemar areas in se sweden particularly focusing on consecutive feldspar replacement reactions to provide an in depth understanding of subsolidus re equilibration of granitic rocks with hydrothermal fluids the apparently most unaltered grey granitoids contain highly porous oligoclase grains that enclose crystallographically continuous microcline relicts this texture suggests that the oligoclase is already secondary and may be a replacement product of original microcline oligoclase is progressively replaced by albite an9 along polysynthetic twinning and intragranular fractures the features of this replacement are characteristic of a dissolution reprecipitation mechanism finegrained mica sericite is closely associated with the albite porosity within micron sized pores observable with scanning electron microscopy as well as in nanopores imaged with transmission electron microscopy the reddening phenomenon in the vicinity of fractures is contemporaneously related to the k feldspathization of sericite which is restricted to the altered oligoclase submicron size hematite precipitation within orthoclase pores at the replacement front results in the red coloration the complex associations between the fluid feldspar reactions indicate that the replacement reactions may be due to sequential fluid infiltration events and that the granitoids have undergone extensive subsolidus re equilibration changing the original magmatic mineralogy therefore the effects of large scale re equilibrations of granitic rocks through hydrothermal convection systems should be more closely considered

early triassic terrestrial tetrapod fauna a review abstract the permian triassic mass extinction ptme ca 252 mya was one of the most severe biotic crises of the phanerozoic eliminating 90 of marine and terrestrial species this was followed by a long period of recovery in the early and middle triassic which revolutionised the structure of both marine and terrestrial ecosystems triggering the new ecosystem structure of the mesozoic and cenozoic entire new clades emerged after the mass extinction including decapods and marine reptiles in the oceans and new tetrapods on land in both marine and terrestrial ecosystems the recovery is interpreted as stepwise and slow from a combination of continuing environmental perturbations and complex multilevel interaction between species in the new environments as ecosystems reconstructed themselves here we present a review of early triassic terrestrial tetrapod faunas geological formations and outcrops around the world and provide a semi quantitative analysis of a data set of early triassic terrestrial tetrapods we identify a marked regionalisation of early triassic terrestrial tetrapods with faunas varying in both taxonomic composition and relative abundance according to palaeolatitudinal belt we reject the alleged uniformity of faunas around pangaea suggested in the literature as a result of the hot house climate in addition we can restrict the tetrapod gap of terrestrial life in the early triassic to palaeolatitudes between 15 n and about 31 s in contrast to the earlier suggestion of total absence of tetrapod taxa between 30 n and 40 s there was fairly strong provincialism following the ptme according to cluster analysis of a taxon presence matrix entirely consistent with early triassic palaeobiogeography unexpectedly the overall pattern for early triassic terrestrial tetrapod faunas largely reflects that of the late permian suggesting that the recovery faunas in the early triassic retained some kind of imprint of tetrapod distributions according to palaeogeography and palaeoclimate despite the near total extinction of life through the ptme

modeling forced imbibition processes and the associated seismic attenuation in heterogeneous porous rocks quantifying seismic attenuation during laboratory imbibition experiments can provide useful information towards the use of seismic waves for monitoring injection and extraction of fluids in the earth s crust however a deeper understanding of the physical causes producing the observed attenuation is needed for this purpose in this work we analyze seismic attenuation due to mesoscopic wave induced fluid flow wiff produced by realistic fluid distributions representative of imbibition experiments to do so we first perform two phase flow simulations in a heterogeneous rock sample to emulate a forced imbibition experiment we then select a sub sample of the considered rock containing the resulting time dependent saturation fields and apply a numerical upscaling procedure to compute the associated seismic attenuation by exploring both saturation distributions and seismic attenuation we observe that two manifestations of wiff arise during imbibition experiments the first one is produced by the compressibility contrast associated with the saturation front whereas the second one is due to the presence of patches containing very high amounts of water that are located behind the saturation front we demonstrate that while the former process is expected to play a significant role in the case of high injection rates which are associated with viscous dominated imbibition processes the latter becomes predominant during capillary dominated processes that is for relatively low injection rates we conclude that this kind of joint numerical analysis constitutes a useful tool for improving our understanding of the physical mechanisms producing seismic attenuation during laboratory imbibition experiments

seismic attenuation in partially saturated berea sandstone submitted to a range of confining pressures using the forced oscillation method we measure the extensional mode attenuation and young s modulus of a berea sandstone sample at seismic frequencies 0 5 50 hz for varying levels of water saturation 0 100 and confining pressures 2 25 mpa attenuation is negligible for dry conditions and saturation levels 80 for saturation levels between 91 and 100 attenuation is significant and frequency dependent in the form of distinct bell shaped curves having their maxima between 1 and 20 hz increasing saturation causes an increase of the overall attenuation magnitude and a shift of its peak to lower frequencies on the other hand increasing the confining pressure causes a reduction in the attenuation magnitude and a shift of its peak to higher frequencies for saturation levels above 98 the fluid pressure increases with increasing confining pressure when the fluid pressure is high enough to ensure full water saturation of the sample attenuation becomes negligible a second series of comparable experiments reproduces these results satisfactorily based on a qualitative analysis of the data the frequency dependent attenuation meets the theoretical predictions of mesoscopic wave induced fluid flow wiff in response to a heterogeneous water distribution in the pore space so called patchy saturation these results show that mesoscopic wiff can be an important source of seismic attenuation at reservoir conditions

post collisional late neoproterozoic high ba sr granitic magmatism from the dom feliciano belt and its cratonic foreland uruguay petrography geochemistry geochronology and tectonic implications abstract post collisional granitic magmatism with high barium strontium hibasr content and shoshonitic affinity has been recently recognized both in the southern section of the dom feliciano belt of uruguay and its cratonic foreland this group of granitic rocks has a distinctive age mineralogy chemistry and field characteristics new zircon u pb la icp ms data for three of the plutons confirm their late neoproterozoic age 634 7 3 sierra de los caracoles 604 3 0 ma cortez blanco and 597 3 6 ma guayabo similar ages were published previously for the solis de mataojo granitic complex 584 13 ma as well as las flores 586 2 7 ma and sobresaliente plutons 585 2 5 ma mineral assemblages of the studied quartz monzonites granodiorites and monzogranites comprise quartz orthoclase and microcline plagioclase ab 10 30 hornblende green biotite apatite titanite and allanite they plot predominantly in the high k calc alkaline field with the exception of a few that plot in the shoshonitic field characteristically they are relatively high in na 2 o normally 4 5 in acid varieties sio 2 65 decreasing to between 3 and 4 for more basic types k 2 o normally exceeds 3 5 but can be as low as 700 ppm sr 500 ppm and light rees alongside low nb ta and heavy rees the eu anomalies are negligible to slightly positive intermediate initial 87 sr 86 sr values 0 7077 to 0 7090 and very low initial epsilon nd values 15 8 to 19 3 at 600 ma with high nd tdm 2 2 2 8 ga suggest a recycling of ancient paleoproterozoic to late archaean sources late neoproterozoic granitoids of uruguay have been emplaced within a post collisional tectonic setting controlled by major shear zones and strike slip fault zones current field and analytical data suggest that these granitoids could have been mostly generated through the partial melting of an intermediate to lower mafic continental crust and or enriched crustal sources in the presence of garnet amphibole as stable residual mineral assemblage with a possible minor mantle component

digital rock physics numerical prediction of pressure dependent ultrasonic velocities using micro ct imaging digital rock physics numerical prediction of pressure dependent ultrasonic velocities using micro ct imaging

measurements of seismic attenuation and transient fluid pressure in partially saturated berea sandstone evidence of fluid flow on the mesoscopic scale s u m m a r y a novel laboratory technique is proposed to investigate wave induced fluid flow on the mesoscopic scale as a mechanism for seismic attenuation in partially saturated rocks this technique combines measurements of seismic attenuation in the frequency range from 1 to 100 hz with measurements of transient fluid pressure as a response of a step stress applied on top of the sample we used a berea sandstone sample partially saturated with water the laboratory results suggest that wave induced fluid flow on the mesoscopic scale is dominant in partially saturated samples a 3 d numerical model representing the sample was used to verify the experimental results biot s equations of consolidation were solved with the finite element method wave induced fluid flow on the mesoscopic scale was the only attenuation mechanism accounted for in the numerical solution the numerically calculated transient fluid pressure reproduced the laboratory data moreover the numerically calculated attenuation superposed to the frequency independent matrix anelasticity reproduced the attenuation measured in the laboratory in the partially saturated sample this experimental numerical fit demonstrates that wave induced fluid flow on the mesoscopic scale and matrix anelasticity are the dominant mechanisms for seismic attenuation in partially saturated berea sandstone

quartz cementation and related sedimentary architecture of the triassic solling formation reinhardswald basin germany abstract the olenekian solling formation of the reinhardswald basin was studied with the aim to examine the dependency of the degree of silica diagenesis on the sedimentary architecture the solling formation is composed of stacked sandstone clay siltstone cycles deposited by braided i e subarkoses and meandering i e subarkosic wackes river systems the sand dominated braided rivers of the lower solling formation are characterized by channels and downstream accretion whereas mixed load meandering rivers of the upper solling formation are represented by lateral accretion and laminated sands diagenetic processes which modified the sandstone siltstone successions include compaction feldspar alteration and cementation sandy clay poor successions are highly quartz cemented i e silica importers whereas clay and mica rich successions are more compacted i e silica balanced or silica exporters three quartz cement generations with a total volume of up to 18 indicate that silica from several different sources cemented the sandy fluvial architectural elements of the lower solling formation cementation includes silica supply from internal and external to the sandstone layers which are silica from grain margin dissolution from feldspar alteration silica released from clay siltstones and silica precipitated from basinal brines this cementation history is supported by cathodoluminescence observations and fluid inclusion studies and a consistent burial history was successfully modeled by simulation of the thermal subsidence in contrast to the lower solling formation the fluvial architectural elements of the mixed load systems of the upper solling formation contain only one quartz cementation phase with a total volume up to 8 the reinhardswald basin shows a dependency of the fluvial architecture and the diagenetic features for that we define the term diagenetic architecture

bowing of dimensional granitic stones bowing is a well known phenomenon seen in marbles used as building veneers this form of rock weathering occurs as a result of external factors such as temperature humidity the system for anchoring the marble slabs or the panel dimensions under the same external conditions many factors will determine the degree of deformation including petrography thermal properties and residual locked stresses the usual way to solve the problem of bowed marble slabs is to replace them with other materials such as granites in which the deformation still exists but is less common in this study eight ornamental granites with different mineralogy grain size grain shape porosity and fabric were tested in a laboratory to assess their susceptibility to bowing three slabs of granite each cut with a different orientation were studied under different conditions of temperature 90 and 120 c and water saturation dry and wet to investigate the influence of these factors together with that of anisotropy at 90 c only the granite with the coarsest grain size and low porosity exhibited deformation under wet conditions at 120 c and wet conditions three of the granites showed evident signs of bowing again the granite with the coarsest grain size was the most deformed it was concluded that the wide grain size distribution influences microcracking more than other expected factors such as the quartz content of the rock also mineral shape preferred orientation and porosity play an important role in the bowing of the studied granites

sandstone weathering in tropical climate results of low destructive investigations at the temple of angkor wat cambodia abstract investigations at the temple of angkor wat aimed at the explanation of the major weathering processes of building sandstone as well as at the role of both intrinsic factors i e sandstone petrography and properties and extrinsic factors i e climatic and environmental influences since material sampling at the temple was limited to a few boreholes because of the high artistic rank of the building non destructive and low destructive in situ investigation methods like ultrasonic wave and drilling resistance measurements had to be applied to obtain information about the material properties of sandstone and their changes due to weathering moreover hydric swelling behaviour of the sandstone was determined on undecorated pieces of fallen blocks from the walls additional random test stable isotopic investigations of environmental influences and salts and thorough investigations of the spatial distribution of salts in the ashlars at two selected places with typical weathering patterns completed the set of data the results demonstrate that the weathering process is mainly triggered by rain dry cycles salt load found in the stone is composed of gypsum and nitrate compounds sulphur stable isotope investigations of potential sources of gypsum lead to the conclusion that soluble components of bat droppings are the major source of salts influences of environmental factors like sulphate in rainwater or so2 from the air on salt formation are unlikely gypsum may reinforce the surface deterioration due to high swelling shrinking movements of the sandstone 1 mm m during intensive wetting drying cycles

laboratory based seismic attenuation in fontainebleau sandstone evidence of squirt flow at seismic frequencies 1 100 hz we studied attenuation in the laboratory using the forced oscillation method we adopted the longitudinal mode of oscillation which yields the young s modulus and the corresponding attenuation here defined as the inverse quality factor a fontainebleau sandstone with a porosity of 8 and a permeability of 12 md was saturated with different fluids and investigated at the confining pressures of 5 10 and 15 mpa at all the measured confining pressures while attenuation was zero for the dry sample for partial and full water saturation it gradually increased from nearly zero to 0 02 with increasing frequency the sample was then fully saturated with glycerin water mixtures of varying viscosities up to that of glycerin 8 92 485 and 1414 cp at the confining pressure of 5 mpa a bell shaped attenuation curve peaking at 6 hz with a magnitude of 0 11 was observed when the sample was fully saturated with glycerin 1414 cp a decrease in viscosity of the saturating fluid shifted the attenuation curve to higher frequencies and an increase in confining pressure caused a decrease in the overall magnitude of attenuation the data obtained for glycerin were compared to a simple squirt flow model with sufficient agreement implying that squirt flow is the dominant mechanism responsible for the observed attenuation

an analytical study of seismoelectric signals produced by 1 d mesoscopic heterogeneities the presence of mesoscopic heterogeneities in fluid saturated porous rocks can produce measurable seismoelectric signals due to wave induced fluid flow between regions of differing compressibility the dependence of these signals on the petrophysical and structural characteristics of the probed rock mass remains largely unexplored in this work we derive an analytical solution to describe the seismoelectric response of a rock sample containing a horizontal layer at its center that is subjected to an oscillatory compressibility test we then adapt this general solution to compute the seismoelectric signature of a particular case related to a sample that is permeated by a horizontal fracture located at its center analyses of the general and particular solutions are performed to study the impact of different petrophysical and structural parameters on the seismoelectric response we find that the amplitude of the seismoelectric signal is directly proportional to the applied stress to the skempton coefficient contrast between the host rock and the layer and to a weighted average of the effective excess charge of the two materials our results also demonstrate that the frequency at which the maximum electrical potential amplitude prevails does not depend on the applied stress or the skempton coefficient contrast in presence of strong permeability variations this frequency is rather controlled by the permeability and thickness of the less permeable material the results of this study thus indicate that seismoelectric measurements can potentially be used to estimate key mechanical and hydraulic rock properties of mesoscopic heterogeneities such as compressibility permeability and fracture compliance

interpretation of phase reversals in seismic reflections from attenuating targets phase reversals are commonly observed during exploration seismic amplitude versus offset analysis and usually modelled with the zoeppritz equations in practice when multiple fluids are present we often deal with reflections from interfaces having a contrast in both elastic and anelastic properties in this paper we present a new phenomenological model for phase reversals in cases in which velocity dispersion and attenuation are present we demonstrate strong qualitative differences in behaviour between the elastic and anelastic cases influencing both the amplitude and phase of the reflection coefficient analysis of seismic data showing a phase reversal from a gas reservoir in the vienna basin shows a striking agreement with the modelling we conclude that the influence of fluid induced dispersion on reflection data is a significant and measurable phenomenon in cases of practical interest that recognition of the phenomena may be used as a novel fluid indicator and that frequency dependent rock physics analysis may be an important tool for both industrial geophysics and seismic monitoring of co2 storage

fluid mobility and frequency dependent seismic velocity direct measurements the influence of fluid mobility on seismic velocity dispersion is directly observed in laboratory measurements from seismic to ultrasonic frequencies a forceddeformation system is used in conjunction with pulse transmission to obtain elastic properties at seismic strain amplitude 10 7 from 5 hz to 800 khz varying fluid types and saturations document the influence of pore fluids the ratio of rock permeability to fluid viscosity defines mobility which largely controls pore fluid motion and pore pressure in a porous medium high fluid mobility permits pore pressure equilibrium either between pores or between heterogeneous regions resulting in a low frequency domain where gassmann s equations are valid in contrast low fluid mobility can produce strong dispersion even within the seismic band here the low frequency assumption fails since most rocks in the general sedimentary section have very low permeability and fluid mobility shales siltstones tight limestones etc most rocks are not in the lowfrequency domain even at seismic frequencies only those rocks with high permeability porous sands and carbonates will remain in the low frequency domain in the seismic or sonic band

geochronological constraints on the evolution of the southern dom feliciano belt uruguay abstract new u pb sensitive high resolution ion microprobe k ar and ar ar data from the southernmost dom feliciano belt allow the identification of four major events orthogneisses from the punta del este terrane indicate a magmatic episode at c 770 ma and high grade metamorphism at 641 17 ma granitoid emplacement at 627 23 ma was roughly coeval with peak metamorphism volcaniclastic rocks of the las ventanas formation dated at 573 11 ma can be correlated with the peripheral foreland basin 571 8 ma transpression and coeval high k calc alkaline magmatism is recorded in the maldonado granite dated at 564 7 ma the following events are postulated 1 magmatism at 850 750 ma related to rifting 2 metamorphism and granite emplacement at 650 600 ma 3 molasse sequences and foreland basins at c 573 ma 4 late magmatism at 580 560 ma associated with transpression the data indicate that 1 the punta del este terrane could be a portion of the coastal terrane of the kaoko belt 2 granitoid emplacement at 650 600 ma in the punta del este and nico perez terranes favours westward subduction and 3 widespread post collisional synkinematic magmatism occurred in the dom feliciano and kaoko belts between 580 and 550 ma supplementary material analytical methods and data are available at http www geolsoc org uk sup18369