temporal spatial distribution of thin moist layers in the midtroposphere over the tropical eastern pacific abstract the temporal spatial distribution of thin moist layers in the midtroposphere over the tropical eastern pacific is studied by data analyses of radiosonde soundings and downscaling numerical experiments with a regional model radiosonde soundings at san cristobal galapagos show frequent existence of thin moist layers between 2 and 10 km in altitude with a local minimum at 7 8 km the downscaling experiments with global objective analyses are completed for 2005 06 september and december of 1999 2004 and march of 2000 04 the vertical distribution of thin moist layers has three local maxima at 5 10 and 16 km where bimodality of the frequency distribution of water vapor is evident between 4 and 7 km an annual variation is dominant in the occurrence ratio of thin moist layers which tend to appear in nonconvective regions in boreal winter the layers appear to the north of the intertropical convergence zone itcz whereas in boreal summer the layers appear in the equator side of the itcz i

numerical upscaling in 2 d heterogeneous poroelastic rocks anisotropic attenuation and dispersion of seismic waves the presence of stiffness contrasts at scales larger than the typical pore sizes but smaller than the predominant seismic wavelengths can produce seismic attenuation and velocity dispersion in fluid saturated porous rocks this energy dissipation mechanism is caused by wave induced fluid pressure diffusion among the different components of the probed geological formations in many cases heterogeneities have elongated shapes and preferential orientations which implies that the overall response of the medium is anisotropic in this work we propose a numerical upscaling procedure that permits to quantify seismic attenuation and phase velocity considering fluid pressure diffusion effects as well as generic anisotropy at the sample s scale the methodology is based on a set of three relaxation tests performed on a 2d synthetic rock sample representative of the medium of interest it provides a complex valued frequency dependent equivalent stiffness matrix through a least squares procedure we also derive an approach for computing various poroelastic fields associated with the considered sample in response to the propagation of a seismic wave with arbitrary incidence angle using this approach we provide an energy based estimation of seismic attenuation a comprehensive numerical analysis indicates that the methodology is suitable for handling complex media and different levels of overall anisotropy comparisons with the energy based estimations demonstrate that the dynamic equivalent viscoelastic medium assumption made by the numerical upscaling procedure is reasonable even in presence of high levels of overall anisotropy this work also highlights the usefulness of poroelastic fields for the physical interpretation of seismic wave phenomena in strongly heterogeneous and complex media

validation of models and empirical equations to estimate deformations in jointed rock through the monitoring of a 40 storey tower foundation abstract there is a pressing need in rock mechanics for the calculation of deformations and stresses of structures in rock with this aim the rock mass modulus must be estimated and a model chosen to perform the calculations monitoring the foundation of twin towers in tenerife island has allowed validating both the rock mass modulus estimated from empirical equations and the model in this paper only the second tower tower n with a structural height of 137 4 m above foundation has been studied because the first tower had been previously presented by justo et al int j rock mech min sci 2006 43 267 81 the foundations of both towers are supported by jointed vesicular and weathered basalt and scoria the parameters have been deduced from the simple empirical equations proposed by several authors as a function of geological strength index gsi or rock mass rating rmr three dimensional elastic and advanced elasto plastic finite element fe programs have permitted calculation of the displacements of tower n the stresses in the slab and the factor of safety fos of the excavation the installation of rod extensometers at different depths below the slab has permitted comparison between measured and calculated displacements good fit has been obtained in this type of rock these results increase our confidence in the use of classification schemes to estimate the deformations in jointed rock in construction processes that involve unloading reloading it is important to use a material model that considers these processes the use of advanced elasto plastic methods increases the calculated settlements even if there are no failure points as the pre consolidation stress and the mobilized angle reached during the excavation phase are exceeded at many points during the loading phase tension cut off points also increase deformations with respect to linear elastic behaviour the hardening soil model improves fit between measured and calculated settlements as well

water saturation effects on p wave anisotropy in synthetic sandstone with aligned fractures the seismic properties of rocks are known to be sensitive to partial liquid or gas saturation and to aligned fractures p wave anisotropy is widely used for fracture characterization and is known to be sensitive to the saturating fluid however studies combining the effect of multiphase saturation and aligned fractures are limited even though such conditions are common in the subsurface an understanding of the effects of partial liquid or gas saturation on p wave anisotropy could help improve seismic characterization of fractured gas bearing reservoirs using octagonal shaped synthetic sandstone samples one containing aligned penny shaped fractures and the other without fractures we examined the influence of water saturation on p wave anisotropy in fractured rocks in the fractured rock the saturation related stiffening effect at higher water saturation values is larger in the direction across the fractures than along the fractures consequently the anisotropy parameter decreases as a result of this fluid stiffening effect these effects are frequency dependent as a result of wave induced fluid flow mechanisms our observations can be explained by combining a frequency dependent fractured rock model and a frequency dependent partial saturation model

predicting the deformation moduli of rock masses abstract predictive empirical models for the mechanical properties of rock masses have been used in rock engineering because direct measurement of the properties is difficult due to the presence of discontinuities such empirical models are open to improvement because they are based on collected data the purposes of the present study are to assess the existing empirical equations and to develop a new empirical approach for this reason in the first stage of the study the prediction performance of the existing models proposed for predicting the deformation modulus of rock masses were evaluated statistically by using a database including 115 data values obtained from in situ plate loading and dilatometer tests a new empirical approach with higher prediction capacity than the existing empirical models was developed in the subsequent stage of the study the new empirical model considers the modulus ratio of intact rock e i ucs rock quality designation rqd and weathering degree wd although data obtained from very weak and weak rock masses were included in the development of the new empirical equation the type of rocks employed in the study were limited therefore a crosscheck between the new empirical equation and previous empirical approaches should be performed in the design stage

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

quantitative estimate of fracture density variations in the nordegg with azimuthal avo and curvature a case study we investigated the accuracy of surface seismic attributes in predicting fracture density variations within the nordegg formation in west central alberta we know from core drill samples well log and drilling data that the nordegg zone is fractured to some degree these fractures are of interest because the reservoir has very low permeability and therefore natural fractures may materially affect well performance 3d surface seismic techniques such as amplitude variation with azimuth or azimuthal avo avaz variation of velocity with azimuth vvaz curvature and coherence techniques are all tools that have been used to predict fractures in a qualitative fashion in this study we wanted to understand how well these attributes predicted the reservoir quality in a quantitative fashion previous quantitative studies have used image log orientation data or estimated ultimate recoveries eur in vertical wells as validation data the conclusiveness of these studies has been subject to several problems f

method for estimating the deformability of heavily jointed rock masses determination of the deformability of jointed rock masses is an important and challenging task in rock mechanics and rock engineering in this paper simple expressions are derived for estimating the equivalent isotropic deformation properties of heavily jointed rock masses using the methodology of equivalent continuum approach the derived expressions are compared with two analytical relations in the literature and the field test data relating rock quality designation rqd and deformation modulus ratio em er where em and er are the deformation modulus of the rock mass and the intact rock respectively the derived expressions are in reasonable agreement with the existing analytical relations in the literature and satisfactorily predict the range of the field rqd versus modulus ratio em er data finally two examples are presented to demonstrate the application of the derived expressions by applying them to estimate the deformation modulus of jointed rock mass at two sites the results of the paper

in situ measurements of rock mass deformability using fiber bragg grating strain gauges abstract in order to examine how the mechanical properties of a rock mass vary from the centimeter to meter scale we performed two field point loading tests 89 kn and 890 kn to determine the in situ modulus of deformation of a rock mass the experimental setup is analogous to plate jacking type tests but instead using a point load the experiments were done in the poorman formation on the 4100 level 1250 m underground of the sanford underground research facility surf at the site of the former homestake gold mine in lead sd for comparison with in situ values we also conducted laboratory mechanical tests and used two geotechnical classification systems to evaluate rock stiffness the in situ modulus of deformation increases with depth into the rock mass this increase in stiffness is a result of the differences in mechanical properties due to the effect of excavation of the underground space near the surface 0 1 2 m depth the rock is softest due to induced fractures and damage from blasting beyond this damaged zone is the stress relief zone 1 2 1 5 m depth where open joint sets affect rock stiffness and beyond that lies the undisturbed zone 1 5 m depth where the rock is the stiffest if done properly in situ measurements of rock stiffness are a valuable tool to fully characterize the gradient in stiffness of a rock mass which laboratory tests or geotechnical classification systems do not fully capture

frequency dependent anisotropy due to meso scale fractures in the presence of equant porosity fractured rock is often modelled under the assumption of perfect fluid pressure equalization between the fractures and equant porosity this is consistent with laboratory estimates of the characteristic squirt flow frequency however these laboratory measurements are carried out on rock samples which do not contain large fractures we consider coupled fluid motion on two scales the grain scale which controls behaviour in laboratory experiments and the fracture scale our approach reproduces generally accepted results in the low and high frequency limits even under the assumption of a high squirt flow frequency we find that frequency dependent anisotropy can occur in the seismic frequency band when larger fractures are present shear wave splitting becomes dependent on frequency with the size of the fractures playing a controlling role in the relationship strong anisotropic attenuation can occur in the seismic frequency band the magnitude of the frequency dependence is influenced strongly by the extent of equant porosity with these results it becomes possible in principle to distinguish between fracture and microcrack induced anisotropy or more ambitiously to measure a characteristic fracture length from seismic data

an example of estimating rock mass deformation around an underground opening using numerical modeling abstract in rock engineering rock strength is regarded as an important rock mass parameter and it is widely estimated using the uniaxial compressive strength ucs test a ucs test in laboratory requires sampling and preparation of core samples which necessitates time consuming and expensive studies furthermore preparation of cores is almost impossible for a weak rock material taken from foliated laminated or thinly bedded rock masses of low rock quality designation rqd values 0 20 in this case determination of ucs by laboratory test may be impossible in compliance with isrm or astm standards to overcome this difficulty indirect tests such as point load index pli schmidt hammer sh rebound number tests are often employed to predict the ucs however indirect tests are likely to yield ucs values with large standard deviations depending on the geological origin of the rock mass the block punch index bpi has recently been developed to overcome the drawbacks of ucs and indirect tests and to minimize the errors arisen from the structural deficiencies and large standard deviations in this study determination of rock mass behavior in laminated foliated bornova melange yellowish brown flysch and grayish black flysch and well jointed yamanlar volcanics altindag formation where the second phase of the izmir metro tunnels was excavated is aimed the bpi ratings were directly used in rmr calculations and indirectly used to estimate the ucs values of rock materials then the obtained results were input into numerical models along with the rock mass strength ucs rm and deformation modulus of rock mass e rm the results obtained from the numerical models agreed with that obtained results from inner tunnel convergence and ground settlement measurements

the interaction of clouds and dry air in the eastern tropical pacific cloud radar observations of eastern pacific intertropical convergence zone cloud vertical structure are interpreted in light of soundings 100 km scale divergence profiles calculated from precipitation radar doppler velocities and surface rain gauge data from a ship at 10 n 95 w during the 2001 east pacific investigation of climate epic experiment the transition from convective to stratiform rain is clear in all four datasets indicating a coherence from local to 100 km scale a novel finding is dry air intrusions at altitudes of 6 8 km often undercutting upper level ice clouds two distinct dry air source regions are identified one is a relatively dry area overlying the cooler waters of the costa rica oceanic thermocline dome centered approximately 400 km east northeast of the ship site the other is the even drier nearequatorial subsidence zone south of 6 7 n the former source is somewhat peculiar to this specific ship location so that the ship sample is not entirely representative of the region the 20 25 september period is studied in detail as it depicts two influences of the dry air on cloud vertical structure one is the modulation of small scale surface based convection evident as a weakening and narrowing of cloud radar reflectivity features the other springs from intense sublimation cooling as differential advection brought snowing anvil clouds over the dry layers during one half day period of strong sublimation the cooling rate is inferred to be several tens of degrees per day over a 100 hpa layer based on a heat budget estimate at 100 km scale involving the horizontal wind divergence data this is consistent with fluxing ice water contents of 0 05 0 10 g m 3 derived from the cloud radar reflectivities the temperature profile shows the dynamically expected response to this cooling a positive negative positive temperature anomaly pattern centered on the sublimating layer a buoyancy sorting diagnostic model of convection indicates that these upper troposphere temperature anomalies can cause premature detrainment of updrafts into the lower part of the cloudy layer a feedback that may actively maintain these long lasting dense anvils middle troposphere southerly dry air inflow is also evident in large scale analysis given the proximity of the dry equatorial subsidence zone to the eastern tropical pacific the differential advection of dry and cloudy air the ensuing sublimation and its dynamical aftereffects may play a role in establishing the region s climate although the extent of their significance needs to be further established

water saturation effects on elastic wave attenuation in porous rocks with aligned fractures summary elastic wave attenuation anisotropy in porous rocks with aligned fractures is of interest to seismic remote sensing of the earth s structure and to hydrocarbon reservoir characterization in particular we investigated the effect of partial water saturation on attenuation in fractured rocks in the laboratory by conducting ultrasonic pulse echo measurements on synthetic silicacemented sandstones with aligned penny shaped voids fracture density of 0 0298 0 0077 chosen to simulate the effect of natural fractures in the earth according to theoretical models our results show for the first time contrasting variations in the attenuation q 1 o fp and s

characteristics of mid level clouds over west africa mid level clouds located between 2 and 9 km height are ubiquitous in the tropical belt however few studies have documented their characteristics and tried to identify the associated thermodynamic properties particularly in west africa this region is characterized by a strong seasonality with precipitation occurring in the sahel from june to september monsoon season this period also coincides with the annual maximum of the cloud cover here we document the macro and microphysical properties of mid level clouds the environment in which such clouds occur as well as their radiative properties across west africa to do so we combined high resolution observations from two ground based sites including lidar and cloud radar in contrasted environments one in the sahel niamey amma campaign 2006 and the other in the sahara bordj badji mokhtar fennec campaign june 2011 along with the merged cloudsat calipso satellite products the results show that mid level clouds are found throughout the year with a predominance around the monsoon season early in the morning they also are preferentially observed in the southern and western parts of west africa they are usually thin most of them are less than 1000 m deep and as observed in niamey mainly composed of liquid water a clustering method applied to niamey data allows us to distinguish three different types of cloud one with low bases one with high bases and another with large thicknesses the two first cloud families are capped by an inversion the last family is associated with a large vertical moisture transport and likely has the highest radiative effect at the earth s surface among the three cloud types

upper tropospheric inversion and easterly jet in the tropics 1 shipboard radiosonde measurements revealed a persistent temperature inversion layer with a thickness of 200 m at 12 13 km in a nonconvective region over the tropical eastern pacific along 2 n in september 1999 simultaneous relative humidity measurements indicated that the thin inversion layer was located at the top of a very wet layer with a thickness of 3 4 km which was found to originate from the intertropical convergence zone itcz to the north radiative transfer calculations suggested that this upper tropospheric inversion uti was produced and maintained by strong longwave cooling in this wet layer a strong easterly jet stream was also observed at 12 13 km centered around 4 5 n this easterly jet was in the thermal wind balance with meridional temperature gradients produced by the cloud and radiative processes in the itcz and the wet outflow furthermore the jet in turn acted to spread inversions further downstream through the transport of radiatively active water vapor this feedback mechanism may explain the omnipresence of temperature inversions and layering structures in trace gases in the tropical troposphere examination of high resolution radiosonde data at other sites in the tropical pacific indicates that similar utis often appear around 12 15 km the uti around 12 15 km may thus be characterized as one of the climatological inversions in the tropical troposphere forming the lower boundary of the so called tropical tropopause layer where the tropospheric air is processed photochemically and microphysically before entering the stratosphere

using avo for fracture detection analytic basis and practical solutions tight low porosity reservoirs can produce significant amounts of hydrocarbons if fracture networks provide the necessary permeability characterization of naturally fractured reservoirs using surface seismic data is an important exploration problem that has attracted much attention in the literature tle for example had an entire issue august 1996 on this subject while the data and modeling in existing publications demonstrate that fracturing causes significant azimuthal variation in recorded seismic signatures the problem is how to infer fracture parameters from these data

spatial variability of atmospheric boundary layer structure over the eastern equatorial pacific abstract variations in the atmospheric boundary layer structure over the eastern equatorial pacific are analyzed using 916 soundings collected during the first global atmospheric research program global experiment unstable boundary layer structures are observed much more frequently in soundings north of the ocean front located near 2 5 n in the eastern equatorial pacific than in soundings south of the front an objective criterion is applied to identify the presence of the transition layer a weak stable layer near cloud base in the soundings the transition is observed in about 45 of the soundings in both the unstable and the inversion categories a comparison of soundings over the cold tongue with those over the itcz indicates that differences in static stability between these regions are limited to the layer from the surface to about 850 mb which is the mean height of the inversions capping the cloud layer over the cold tongue the cold tongue soundings on average are found to be drier from the sur

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

poisson s ratio values for rocks abstract compared to other basic mechanical properties of rocks poisson s ratio is an elastic constant of which the significance is generally underrated yet in rock mechanics there is a considerable number of diverse areas which require a prior knowledge or estimation of the value of poisson s ratio this paper examines the values and applications of poisson s ratio in rock mechanics following an historical account of the initial controversy whether it was a material constant or not the effects of poisson s ratio in the elastic deformation of materials intact rocks and rock masses are briefly reviewed also the reported values of poisson s ratio for some elements materials and minerals are compiled while typical ranges of values are presented for some rocks and granular soils finally poisson s ratio classifications are recommended for isotropic intact rocks

potential vorticity generation by west african squall lines abstractthe west african summer monsoon features multiple complex interactions between african easterly waves aews moist convection variable land surface properties dust aerosols and the diu

rock anelasticity due to patchy saturation and fabric heterogeneity a double double porosity model of wave propagation heterogeneity of rock s fabric can induce heterogeneous distribution of immiscible fluids in natural reservoirs since the lithological variations mainly permeability may affect fluid migration in geological time scales resulting in patchy saturation of fluids therefore fabric and saturation inhomogeneities both affect wave propagation to model the wave effects attenuation and velocity dispersion we introduce a double double porosity model where pores saturated with two different fluids overlap with pores having dissimilar compressibilities the governing equations are derived by using hamilton s principle based on the potential energy kinetic energy and dissipation functions and the stiffness coefficients are determined by gedanken experiments yielding one fast p wave and four slow biot waves three examples are given namely muddy siltstones clean dolomites and tight sandstones where fabric heterogeneities at three different spatial scales are analyzed in comparison with experimental data in muddy siltstones where intrapore clay and intergranular pores constitute a submicroscopic double porosity structure wave anelasticity mainly occurs in the frequency range 104 107 hz while in pure dolomites with microscopic heterogeneity of grain contacts and tight sandstones with mesoscopic heterogeneity of less consolidated sands it occurs at 103 107 hz and 101 103 hz seismic band respectively the predicted maximum quality factor of the fast compressional wave for the sandstone is the lowest approximately 8 and that of the dolomite is the highest the results of the diffusive slow waves are affected by the strong friction effects between solids and fluids the model describes wave propagation in patchy saturated rocks with fabric heterogeneity at different scales and the relevant theoretical predictions agree well with the experimental data in fully and partially saturated rocks

determination of deformation modulus in a weak rock mass by using menard pressuremeter abstract the deformation modulus of heavily jointed andesitic rock mass was investigated by using 41 menard pressuremeter test results and geotechnical information obtained from seven geotechnical boreholes the geotechnical borehole logs and laboratory test results provided by a mining company were used for the assessment of rock mass characterization the log and the test results were taken into account in the rock mass classification work the well known empirical equations were employed to predict the deformation modulus of the rock mass the predictions and the pressuremeter test results were compared and their performance indicators were presented non linear multiple regression methods were used for predictive modelling of the deformation modulus of the rock mass by considering the available data rock quality designation rqd discontinuity condition rating dc of the rock mass rating rmr system and uniaxial compressive strength of the intact rock ci were taken into consideration as input parameters in four new prediction equations to be used for determination of deformation modulus one more equation was proposed by the addition of the depth as a predictive parameter the influence of the depth and vertical to horizontal stress ratio k on the deformation modulus was preliminarily examined by using finite element modelling initially the rock mass was assumed to be an isotropic elastic brittle plastic medium later on the rock mass was modelled as a discontinuum by imposing a discrete fracture network dfn keeping all of the mechanical properties constant different depth and k parameters were applied to the pressuremeter models no influence of the depth and k on the deformation modulus was observed for the isotropic medium while the depth contributed to an increase in the modulus in the anisotropic discontinuum analysis the numerical modelling findings constituted a basis for the inclusion of the depth parameter into the new predictions

time lapse seismic reservoir monitoring time lapse seismic reservoir monitoring has advanced rapidly over the past decade there are currently about 75 active projects worldwide and more than 100 cumulative projects in the past decade or so the present total annual expenditures on 4 d seismic projects are on the order of 50 100 million us this currently represents a much smaller market than 3 d seismic but the use of 4 d seismic has grown exponentially over the past decade and is expected to continue to do so

numerical upscaling of frequency dependent p and s wave moduli in fractured porous media relating seismic attributes to the characteristics of mesoscopic fractures is inherently challenging yet these heterogeneities tend to dominate the mechanical and hydraulic properties of the medium analytical approaches linking the effects of material properties on seismic attributes such as attenuation and velocity dispersion tend to be limited to simple geometries low fracture densities and or non interacting fractures furthermore the influence of fluid flow within interconnected fractures on p wave and s wave attenuation is difficult to accommodate in analytical models one way to overcome these limitations is through numerical upscaling in this paper we apply a numerical upscaling approach based on the theory of quasi static poroelasticity to fluid saturated porous media containing randomly distributed horizontal and vertical fractures the inferred frequency dependent elastic moduli represent the effective behaviour of the underlying fractured medium if the considered sub volume has at least the size of a representative elementary volume we adapt a combined statistical and numerical approach originally proposed for elastic composites to explore wether the overall statistical properties of simple fracture networks can be captured by computationally feasible representative elementary volume sizes our results indicate that for the considered scenarios this is indeed possible and thus represent an important first step towards the estimation of frequency dependent effective moduli of realistic fracture networks

seismoacoustic signatures of fracture connectivity wave induced fluid flow wiff between fractures and the embedding matrix as well as within connected fractures tends to produce significant seismic attenuation and velocity dispersion while wiff between fractures and matrix is well understood the corresponding effects related to fracture connectivity and the characteristics of the energy dissipation due to flow within fractures are largely unexplored in this work we use oscillatory relaxation simulations based on the quasi static poroelastic equations to study these phenomena we first consider synthetic rock samples containing connected and unconnected fractures and compute the corresponding attenuation and phase velocity we also determine the relative fluid displacement and pressure fields in order to gain insight into the physical processes involved in the two manifestations of wiff in fractured media to quantify the contributions of the two wiff mechanisms to the total seismic attenuation we compute the spatial distribution of the local energy dissipation finally we perform an exhaustive sensitivity analysis to study the role played by different characteristics of fracture networks on the seismic signatures we show that in the presence of connected fractures both p wave attenuation and phase velocity are sensitive to some key characteristics of the probed medium notably to the lengths permeabilities and intersection angles of the fractures as well as to the overall degree of connectivity of the fracture network this in turn indicates that a deeper understanding of these two manifestations of wiff in fractured media may eventually allow for the extraction of some of these properties from seismic data

determination of geomechanical properties and collapse potential of a caliche by in situ and laboratory tests working in complex grounds have always been difficult for engineering geologists because of the heterogenous nature of such geo materials which results in different behaviors under stresses the caliches outcropping in the adana basin and its close vicinity are selected as the study material because of their highly complex nature and also understanding their mechanical behaviour and collapse potential is too difficult although their aerial extent is large in the region for this reason investigation of the collapse potential and mechanical behaviour of the caliches by applying new approaches besides the conventional in situ and laboratory tests is the purpose of the study the study includes five main stages such as measurements of caliche profiles in situ tests plate loading sampling shooting photographs for photoanalyses and laboratory studies four different levels such as hard pan silty sandy layer gravelly blocky layer and clayey level are described for the caliches employed the hard pan level is a weak rock with an average uniaxial compressive strength of 11 89 mpa while the others have typical soil characteristics a series of plate loading tests are applied on the blocky gravelly level of the caliche to determine the modulus of elasticity the modulus of elasticity and the allowable bearing capacity are determined between 28 6 65 3 and 1 5 2 0 mpa respectively to determine the grain size distribution curve in addition to sieve analyses a photoanalysis technique is also applied and a combination procedure between the results from both sieve analyses and photoanalyses is introduced and the grain size curves for the blocky gravelly level of the caliche are obtained according to the results of collapse potential index tests performed on the samples collected from 20 locations of the study area the soft pan level of the caliche has slight to moderate degree of collapse indices in the final stage various simple and statistically meaningful empirical equations are proposed for the indirect determination of the collapse index by employing simple paramateres

indirect determination of the modulus of deformation of rock masses based on the gsi system today as a result of the increase in the number of large tunnel constructions and underground excavations required for civil engineering and waste disposal and the operation of deep open pit mines determination of rock mass properties has become one of the most important stages in design and construction for rock engineering when rocks and rock masses are classified for geotechnical purposes this needs to be on the basis of strength or static modulus of deformation to give an indication of their stability or deformational response in addition the strength and modulus of deformation are the necessary input parameters of the rock masses to be utilized by numerical methods the modulus of elasticity of the rock material is undoubtly the geomechanical parameter that best represents the mechanical behaviour of rock material a similar conclusion can also be made for rock masses however the modulus of deformation of rock masses should be determined in situ by carrying out special tests which normally implies considerable costs and operational difficulties because of such difficulties the determination of the modulus of deformation of the rock masses continues to attract the attention of rock engineers and engineering geologists given the importance of having the value of the modulus of deformation available and at the same time the operational and economical difficulties mentioned above many researchers mentioned below were led to consider several cost effective and not too time consuming indirect procedures that can provide information on the modulus of deformation these attempts

predictive model for uniaxial compressive strength for grade iii granitic rocks from macao abstract determination of the uniaxial compressive strength ucs of rocks is an important task for rock and geotechnical engineering applications direct measurement is expensive time consuming and even infeasible in some circumstances due to the difficulty in obtaining core samples therefore empirical models are particularly favorable to engineers especially in the preliminary design stage however there is a lack of predictive ucs model for granite of weathering grade iii but it is well recognized to be crucial to the design of pile foundations on granitic bedrocks in this study a reliable predictive model will be developed under the bayesian framework an extensive experimental program was performed in this study to construct a comprehensive database of the measurements of uniaxial compressive strength point load index schmidt rebound hammer value p wave velocity effective porosity specific gravity and dry density it has been proven that the proposed model possesses satisfactory predictive performance

a comparative study of the determination of rock mass deformation modulus by using different empirical approaches abstract the increase in rock engineering projects over the last decade has made an increase in the importance of the determination of the rock mass parameters although properties of rock material are usually determined at laboratory it can also be determined by special in situ tests these in situ tests are both expensive and time consuming therefore empirical equations are developed to estimate rock mass properties by several researchers in numerical modelling rock mass properties are important furthermore controlling the results of models making back analysis and taking the feedback are very important comparison of different empirical equations of deformation modulus of rock mass suggested by different researchers by using field displacement measurements and numerical modelling results is aimed in this study

seismic modeling and analysis of a prototype heated nuclear waste storage tunnel yucca mountain nevada wehavedevelopedseismicvelocitymodelsfortheheated rock surrounding a tunnel in yucca mountain tuff and compared the results with field data obtained at theyucca mountain drift scale test dst facility from 1998 to 2002 during that time the tunnel was heated to replicate the effects of long term storage of decaying nuclear waste and to study the effects of extreme temperatures on the surrounding rock and groundwater flow our velocity models are based on borehole temperature data thermal models and laboratory measurements on granite comparisons between field and synthetic seismograms show that superheating the rock around the tunnel causes thermally induced variations in p and s wave arrival time separation barring out of plane reflections 2d spectral element waveform modeling in the source planeconsistentlyreplicatesseismicreceiverwaveformsand classicbehaviorofpulsesreflectedfromcylinders ourmodels constrain the in situ v 1 dv dt velocity temperature derivative of the tuff to be approximately 0 5 per 100 c this velocity change is consistent with thermally induced wavespeedchangesindryrocksamplesandislowerthanexpected for water to steam conversion in saturated rock we infer that velocity changes are controlled by thermal expansion and fracturing additionally we have developed an improved method for monitoring tunnel conditions that uses waves diffracted around the tunnel in the region of changing velocity

scale interactions involved in the initiation structure and evolution of the 15 december 1992 mcs observed during toga coare part i synoptic scale processes this paper the first of a series examines the synoptic scale mechanisms involved in the initiation structure and evolution of a mesoscale convective system observed during toga coare this study relies upon the use of the japanese geosynchronous meteorological satellite 4 imagery and ecmwf model outputs from which diagnostic parameters are derived and interpreted this mesoscale convective system consists initially of two groups of convective entities that progressively move toward each other and merge it is shown that the synoptic scale flow creates a favorable environment for the formation of this large convective system through the production of convective available potential energy cape by horizontal advection and the enhancement of low level convergence in the region where the convective system formed moreover the general evolution of the system is found to be governed by the synoptic scale circulation and more precisely by the temporal evolution of cape and low level convergence the mechanisms leading to the initiation and general evolution of the system are examined the easterly equatorial jet at 500 hpa triggered positive potential vorticity areas that propagated westward and generated an anticyclonic circulation this anticyclonic circulation was enhanced during the development phase of the convective system through vortex stretching and tilting which accelerated the low level westerlies corresponding to the southern branch of this circulation and enhanced the low level convergence associated with the studied convective system in a companion paper the mesoscale and convective scale processes involved in the internal organization of this mesoscale convective system are examined using the airborne doppler radar dataset collected within the system from 1700 to 2100 utc the downscale interactions i e from synoptic scale to mesoscale and convective scale are scrutinized using both the synoptic scale context described in this paper and the mesoscale and convective scale characteristics derived from the airborne radar observations

climatological description of seasonal variations in lower tropospheric temperature inversion layers over the indochina peninsula abstract in this study operational rawinsonde data are used to investigate climatological features of seasonal variations in static stability in order to understand the behavior of temperature inversion layers that is extremely stable layers in the lower troposphere over the indochina peninsula region at the southeastern edge of the asian continent static stability was evaluated from the vertical gradient in potential temperature z stable z 10 k km 1 and unstable z 1 k km 1 layers frequently appear over the indochina peninsula region during boreal winter temporal and vertical variations in stability during the boreal winter can be categorized into three characteristic types type i the mean height of stable layers increases from 2 to 5 km from the dry to the rainy season over inland areas of the indochina peninsula and southern china type ii similar to type i with the additional occurrence of stable layers at a height of 1 km mainly over coastal areas of the indochina pen

tropical inversions near the 0 c level abstract soundings taken from the tropical western pacific warm pool region during toga coare reveal the common occurrence of temperature and moisture perturbations near the 0 c level the perturbations frequently are characterized by shallow layers of increased stability or occasionally temperature inversions and reversals or inflections in the vertical profile of specific humidity similar temperature and moisture inversions have been observed elsewhere in the tropics and midlatitudes but have not received much attention isothermal layers are known to exist just below the melting level in stratiform rain regions however not all stable layers observed over the warm pool are confined to precipitation systems the perturbation in the specific humidity profile accounts for the often observed double peak structure in the apparent moisture sink q2 in tie tropics stratification of the data based on relative humidity criteria indicates that the stable layers near the 0 c level generally fall into two main

the foundation of a 40 storey tower in jointed basalt abstract a 132 70 m high tower above foundation has been successfully completed at tenerife island the foundation of the tower a 2 m thick reinforced concrete slab is supported by jointed vesicular and weathered basalt and scoria a three dimensional elastic finite element program has permitted to calculate the displacements of the tower and the stresses in the slab the installation of rod extensometers at different depths below the slab and clinometers at the lower basement has provided comparison between measured and calculated displacements and the estimation of in situ deformation moduli a first stage prediction before construction has allowed establishment of an upper limit based upon pressuremeter modulus and a lower limit based upon bieniawski s equation the geomechanics classification in rock engineering applications in proceedings of the fourth cong isrm congress montreux vol 2 1979 p 41 48 of the settlements of the tower slab the geometric mean of these values comes close to the measured settlement the moduli deduced from the simple empirical equation proposed by gokceoglu et al predicting the deformation modulus of rock masses a comparative study int j rock mech min sci 2003 40 701 10 and hoek and brown practical estimates of rock mass strength int j rock mech min sci 1997 40 701 10 as a function of gsi provide a good fit with the measured settlements in this type of rock a good correlation is also obtained with the empirical equation presented by verman et al effect of tunnel depth on modulus of deformation of rock mass rock mech rock eng 1997 30 3 121 7 that incorporates the influence of the confining stress in the deformation modulus

the vertical cloud structure of the west african monsoon a 4 year climatology using cloudsat and calipso the west african summer monsoon wam is an important driver of the global climate and locally provides most of the annual rainfall a solid climatological knowledge of the complex vertical cloud structure is invaluable to forecasters and modelers to improve the understanding of the wam in this paper 4 years of data from the cloudsat profiling radar and calipso are used to create a composite zonal mean vertical cloud and precipitation structure for the wam for the first time the near coincident vertical radar and lidar profiles allow for the identification of individual cloud types from optically thin cirrus and shallow cumulus to congestus and deep convection a clear diurnal signal in zonal mean cloud structure is observed for the wam with deep convective activity enhanced at night producing extensive anvil and cirrus while daytime observations show more shallow cloud and congestus a layer of altocumulus is frequently observed over the sahara at night and day extending southward to the coastline and the majority of this cloud is shown to contain supercooled liquid in the top the occurrence of deep convective systems and congestus in relation to the position of the african easterly jet is studied but only the daytime cumulonimbus distribution indicates some influence of the jet position

sea surface salinity measurements in the historical database 1 we have examined historical distributions of sea surface salinity sss observations in a data set consisting of a combination of the world ocean database 1998 wod98 and a thermosalinograph and bucket salinity database collected from volunteer observing ships it is well known that sss in much of the world s ocean is measured infrequently or not at all we find that 27 of one degree squares in the world ocean open and coastal excluding the arctic ocean had no observations of sss in the historical database and 70 had 10 or fewer systematic sampling of sss more than 10 000 observations per year globally did not start until after 1960 most sss observations in the wod98 are concentrated in the north sea and coast of northern europe the east and west coasts of north america and around japan about 28 of sss measurements are in coastal waters we plotted frequency histograms of sss for some selected well sampled one degree squares in the north atlantic and tropical pacific we found most frequency histograms to be non gaussian the main departure from normal distribution is due to anomalous low salinity measurements creating a negative skewness this conclusion is verified as a global phenomenon by examining statistics of mean median sss difference within one degree squares this quantity is found to be predominantly negative over the global ocean these anomalous low salinity values may be due to rainfall events but there are other plausible physical mechanisms like frontal movement and eddy activity there were also areas where the distributions were bimodal due to the presence of meandering fronts with little cross frontal mixing examples are shown where the non gaussian nature of the distributions in the areas examined is both a short term and a long term phenomenon that is the distributions are skewed on a nearly instantaneous 1 month basis and averaged over long time periods 1 years this has important implications for climatologies because the differences between mean and modal sss for the analyzed one degree squares is of order 0 1 furthermore the implication for validation studies for remote sensing missions is that the studies must make enough measurements of sss to determine the extent to which the probability density is not gaussian

modeling deformation modulus of a stratified sedimentary rock mass using neural network fuzzy inference and genetic programming abstract this paper investigates a series of experimental results and numerical simulations employed to estimate the deformation modulus of a stratified rock mass the deformation modulus of rock mass has a significant importance for some applications in engineering geology and geotechnical projects including foundation slope and tunnel designs deformation modulus of a rock mass can be determined using large scale in situ tests this large scale sophisticated in situ testing equipments are sometimes difficult to install plus time consuming to be employed in the field therefore this study aims to estimate indirectly the deformation modulus values via empirical methods such as the neural network neuro fuzzy and genetic programming approaches a series of analyses have been developed for correlating various relationships between the deformation modulus of rock mass rock mass rating rock quality designation uniaxial compressive strength and elasticity modulus of intact rock parameters the performance capacities of proposed models are assessed and found as quite satisfactory at the completion of a comparative study on the accuracy of models in the results it is seen that overall genetic programming models yielded more precise results than neural network and neuro fuzzy models

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

estimating the deformation modulus of rock masses a comparative study although the modulus of deformation of rock masses has crucial importance for geotechnical projects such as tunnels and dams the determination of this parameter by in situ tests requires considerable costs and involves difficult operational processes for this reason empirical equations for the indirect estimation of the modulus of deformation are an interesting issue for rock engineers and engineering geologists this study includes assessment of the prediction performances of some existing empirical equations using in situ plate loading test data and rock mass properties producing an empirical equation depending on the new data construction of a fuzzy inference system for the estimation of modulus of deformation and making a comparison between results obtained from the empirical equations and fuzzy inference system a series of calculations and statistical analyses were undertaken it is concluded that the performance of the empirical equations and fuzzy inference system obtained in this study is satisfactory however the prediction models developed in this study are limited by the number of the data used and the rock types employed for these reasons a cross check should be performed before using these prediction models for design purposes

numerical analysis of wave induced fluid flow effects on seismic data application to monitoring of co2 storage at the sleipner field 1 in this work we analyze how patchy distributions of co2 and brine within sand reservoirs may lead to significant attenuation and velocity dispersion effects which in turn may have a profound impact on surface seismic data the ultimate goal of this paper is to contribute to the understanding of these processes within the framework of the seismic monitoring of co2 sequestration a key strategy to mitigate global warming we first carry out a monte carlo analysis to study the statistical behavior of attenuation and velocity dispersion of compressional waves traveling through rocks with properties similar to those at the utsira sand sleipner field containing quasi fractal patchy distributions of co2 and brine these results show that the mean patch size and co2 saturation play key roles in the observed wave induced fluid flow effects the latter can be remarkably important when co2 concentrations are low and mean patch sizes are relatively large to analyze these effects on the corresponding surface seismic data we perform numerical simulations of wave propagation considering reservoir models and co2 accumulation patterns similar to the co2 injection site in the sleipner field these numerical experiments suggest that wave induced fluid flow effects may produce changes in the reservoir s seismic response modifying significantly the main seismic attributes usually employed in the characterization of these environments consequently the determination of the nature of the fluid distributions as well as the proper modeling of the seismic data constitute important aspects that should not be ignored in the seismic monitoring of co2 sequestration problems

do seismic waves sense fracture connectivity 1 a defining characteristic of fractured rocks is their very high level of seismic attenuation which so far has been assumed to be mainly due to wave induced fluid flow wiff between the fractures and the pore space of the embedding matrix using oscillatory compressibility simulations based on the quasi static poroelastic equations we show that another important and as of yet undocumented manifestation of wiff is at play in the presence of fracture connectivity this additional energy loss is predominantly due to fluid flow within the connected fractures and is sensitive to their lengths permeabilities and intersection angles correspondingly it contains key information on the governing hydraulic properties of fractured rock masses and hence should be accounted for whenever realistic seismic models of such media are needed

the interaction of moist convection and mid level dry air in the advance of the onset of the indian monsoon the advance of the onset of the indian monsoon is here explained in terms of a balance between the low level monsoon flow and an over running intrusion of mid tropospheric dry air the monsoon advances over a period of about 6 weeks from the south of the country to the northwest given that the low level monsoon winds are westerly or southwesterly and the midlevel winds northwesterly the monsoon onset propagates upwind relative to midlevel flow and perpendicular to the low level flow and is not directly caused by moisture flux toward the northwest lacking a conceptual model for the advance means that it has been hard to understand and correct known biases in weather and climate prediction models the mid level northwesterlies form a wedge of dry air that is deep in the far northwest of india and over runs the monsoon flow the dry layer is moistened from below by shallow cumulus and congestus clouds so that the profile becomes much closer to moist adiabatic and the dry layer is much shallower in the vertical toward the southeast of india the profiles associated with this dry air show how the most favourable environment for deep convection occurs in the south and onset occurs here first as the onset advances across india the advection of moisture from the arabian sea becomes stronger and the mid level dry air is increasingly moistened from below this increased moistening makes the wedge of dry air shallower throughout its horizontal extent and forces the northern limit of moist convection to move toward the northwest wetting of the land surface by rainfall will further reinforce the north westward progression by sustaining the supply of boundary layer moisture and shallow cumulus the local advance of the monsoon onset is coincident with weakening of the mid level northwesterlies and therefore weakened mid level dry advection

modeling the effect of multiple sets of mesoscale fractures in porous rock on frequency dependent anisotropy this study models the seismic response of porous rock containing two fracture sets with different orientations sizes and connectivities modeling demonstrates frequency dependent anisotropy controlled by two characteristic frequencies that are defined by fluid mobility and the length scales of the fractures fracture related dispersion and attenuation typically occur over a wider frequency band than is seen in the case of a single fracture set when one set of fractures is modeled as being sealed the azimuthal variation of velocity and attenuation can be different with the azimuth of minimum attenuation coinciding with the strike direction of the open fracture set the results should support attempts to differentiate between open and closed fractures on the basis of seismic measurements

an empirical method for determining the mechanical properties of jointed rock mass using drilling energy abstract characterization of jointed rock masses and evaluation of their mechanical properties are challenging tasks in rock engineering this paper presents an experimental investigation of the response characteristics of drilling energy to the discontinuity of rock mass using a drilling method the linear relationship between the drilling energy and discontinuity frequency is revealed which only depends on the rock type and is independent of calculation units a new empirical method for determining the rock quality designation rqd versus the variation of drilling energy is proposed based on the discontinuity frequency comparison between the prediction and in situ investigation results demonstrates that the rqd can be estimated from this empirical method the em er modulus ratio and cm c strength ratio versus rqd relations are modified for the determination of rock mass strength and deformation modulus in order to consider the continuous variation of em er and cm c with the model parameter which is related to the drilling energy and modulus of elasticity of intact rock and the variation of drilling energy for rock mass the results show that the modified em er cm c versus rqd relations can give proper values compared with the field test results as well as compared with the various proposed relations from rmr q and gsi the modified relations can provide a practical fast and easy to use method for the estimated rock mass strength and deformation modulus but they are only a first approximation

on attenuation of seismic waves associated with flow in fractures heterogeneity of porous media induces a number of fluid flow mechanisms causing attenuation of seismic waves attenuation induced by squirt type mechanisms has previously been analyzed for aspect ratios smaller or equal to 10 3 using a hybrid dimensional modeling approach particularly apt for large aspect ratio conduits we numerically simulated deformation induced fluid flow along two intersecting fractures to investigate the physics of attenuation related to the interaction of fracture induced fluid flow and to leak off attenuation related to fracture flow increases in magnitude with increasing geometrical aspect ratio of the fracture the inherent time scales of both flow mechanisms do not influence each other but the faster process is associated with stronger attenuation than the slower process models relying on simple diffusion equations have rather limited potential for approximation of pressure transients