a compositional classification scheme for meteoritic chondrules a taxonomic scheme is proposed for the main component of the primitive chondrite meteorites the chondrules the scheme provides insight into the variety of chondrules originally produced in the primordial solar nebula and the effects on them of secondary processes on meteorite parent bodies it may also contribute to understanding the origin of compositional diversity in the chondrites

chondrules in h3 chondrites textures compositions and origins major and minor element bulk compositions of 90 individual chondrules and 16 compound chondrule sets in unequilibrated type 3 h group chondrites were determined in polished thin sections by broad beam electron probe analysis and the chondrules were classified petrographically into six textural types barred olivine porphyritic olivine porphyritic pyroxene barred pyroxene radiating pyroxene fine grained although analyses of individual chondrules scatter widely the mean composition of each textural type except barred pyroxene is rather distinct as verified by discriminant function analysis al2o3 tio2 and na3o are correlated in chondrules but al2o3 and cao do not correlate compound chondrule sets were found to consist almost entirely of chondrules or partial chondrules of similar texture and composition the data suggest that composition played a conspicuous role in producing the observed textures of chondrules though other factors such as cooling rates and degrees of supercooling prior to nucleation were also important if compound chondrules formed and joined when they were still molten or plastic then the data suggest that chondrules of each textural type could have formed together in space or time the correlation of al2o3 and tio2 with na2o and not with cao appears to rule out formation of chondrules by direct equilibrium condensation from the nebula we conclude that the most reasonable model for formation of the majority of chondrules is that they originated from mixtures of differing fractions of high intermediate and low temperature nebular condensates that underwent melting in space a small percentage of chondrules might have formed by impacts in meteorite parent body regoliths

crustal structure and earthquake focal depths beneath northeastern india and southern tibet summary we use broad band teleseismic data recorded at eight sites along a north south profile from karimganj 24 84 n 92 34 e south of the eastern shillong plateau to bomdilla 27 27 n 92 41 e in the eastern lesser himalaya to determine the seismic characteristics of the crust in northeastern india we also analyse data from the chinese digital seismic network station at lhasa and indepthii stations located on the southern tibetan plateau north of our profile to extend the seismic images of the crust further northwards although the northeastern indian stations and the tibetan stations do not lie along a linear profile across the himalaya the wellrecognized uniformity of the himalaya along strike make this comparison of the two profiles meaningful receiver functions calculated from these data show that the crust is thinnest 35 38 km beneath the shillong plateau receiver functions at cherrapunji on the southern edge of the shillong plateau have a strong azimuthal dependence those from northern backazimuth events show that the moho beneath the southernmost shillong plateau is at a depth of 38 km while receiver functions from southern backazimuth events indicate that the moho beneath the northernmost bengal basin is at a depth of 44 km receiver functions from sites on the brahmaputra valley demonstrate that the moho is deeper by 5 7 km than below the shillong plateau a result which agrees with the hypothesis that the shillong plateau is supported by shearing stress on two steep faults that cut through the crust further north of the eastern himalayan foredeep the moho dips gently northwards reaching a depth of 48 km beneath bomdilla in the lesser himalaya and 88 km below lhasa in tibet using the crustal velocity models obtained from receiver function inversions we redetermined focal depths of wellrecorded earthquakes across this part of the indo tibetan collision zone and find all of these to occur within the crust hence we find no evidence for bimodal depth distribution of earthquakes beneath this region of northeastern india

mechano chemical interactions in sedimentary rocks in the context of co2 storage weak acid weak effects abstract due to the corrosive nature of dissolved co2 the potential short or long term alteration of rock properties represents a major issue in several sites where natural co2 circulation is observed as well as in reservoirs targeted for storage of anthropogenic co2 to date this has been primarily studied from a transport chemical perspective with laboratory evidence of microstructural modifications together with the consequences for flow properties compared to the transport chemical aspects the mechanical chemical aspects have been less investigated though it is to be expected that mechanical properties e g elastic properties failure parameters and time dependent mechanical behaviour could potentially be affected in a similar manner to hydraulic parameters yet since co2 is a weak acid the ph drop is expected to be moderate with a likely lower limit close to 4 0 the buffering of ph by calcite minerals present in most reservoirs targeted for storage may further limit the ph drop as well as confining it to a localized rock volume around the injection well this leads to the question of the magnitude and time spatial scales of chemically mediated mechanical processes during co2 sequestration the authors propose to address this issue by reviewing recent laboratory based studies restricted to sedimentary rocks namely reservoir rocks carbonate or sandstone intact or fractured caprocks and fault rocks key findings include the following 1 the short term impact on the elastic and inelastic behaviour of intact caprocks remains limited 2 shear strength weakening is likely to be respectively low and low to moderate for shale clay rich and anhydrite rich faults but without modifying slip stability in either case 3 the largest impact is located within carbonate reservoirs but with a broad range of reported responses depending on hydrodynamic conditions closed or open and on dissolution regime uniform or channelling and 4 creep experiments confirm that co2 induced dissolution may enhance long term compaction of carbonate reservoirs but the magnitude of acceleration varying from non significant to 50 times depends to a large extent on site specific conditions grain size ph temperature effective stress state etc which renders any direct extrapolation from laboratory to reservoir scale difficult finally some directions for future research studies are discussed

refractory precursor components of semarkona chondrules and the fractionation of refractory elements among chondrites abstract chondrules from the semarkona ll3 0 chondrite show refractory and common lithophile fractionation trends similar to those observed among the chondrite groups it appears that chondrules are mixtures of a small number of pre existing solid components and we infer that chondrule precursor materials were related to the nebular components involved in the lithophile element fractionations recognized in ordinary chondrites compositional trends among the chondrules can be used to deduce the compositions of these components we use instrumental neutron activation analysis to measure many 20 of the lithophile elements in 30 chondrules the amounts of oxidized iron were calculated from other compositional parameters concentrations of si were estimated using mass balance considerations the data were corrected for the diluting effects of non lithophile constituents plots of lithophile elements versus a reference refractory element such as al show that there were two major chondrule silicate precursor components a refractory olivine rich feo free one and a non refractory sio 2 feo rich one the refractory component probably forms from olivine enriched condensates formed above the condensation temperature of enstatite the non refractory component must have formed from fine grained materials that were able to equilibrate down to lower nebular temperatures chondrite matrix may have had an origin similar to that of the non refractory material and constitutes a third lithophile bearing component that took part in chondrite fractionation processes the low abundance of refractories and mg in ordinary and enstatite chondrites was produced by the loss of materials having a higher refractory element mg ratio than that in the refractory component of chondrules

analysis of asymmetric multipathing with a generalization of the double beam method abstract an array method integrating source and receiver array beamforming is presented the method is a generalization of previous work kruger et al 1993 to independent variation of slowness and azimuth in both the source and the receiver array compared to the analysis capabilities of a single array the resolution is enhanced and asymmetric scattering configurations and multipathing can be studied the generalized double beam method dbm is applied to a data set consisting of nuclear explosions detonated in eastern kazakhstan and recorded at the yellowknife array in northern canada the multipathing found for pcp and pdp is interpreted in terms of lateral inhomogeneity in the lowermost mantle below severnaya zemlya indications for rayleigh to p wave scattering observed for the shagan river and degelen subsites of the former main test site of the ussr in eastern kazakhstan can be related to the structure in the vicinity of the two subsites

chemical and physical studies of type 3 chondrites ix thermoluminescence and hydrothermal annealing experiments and their relationship to metamorphism and aqueous alteration in type 3 3 ordinary chondrites samples of four type 3 chondrites have been annealed at 400 850 c and 0 77 1 kbar for 10 500 h in the presence of various amounts of water 0 10 wt and sodium disilicate 0 2 molal and their thermoluminescence properties measured after annealing for 20 h at temperatures 600 c the tl sensitivity of the samples increased by factors of up to 40 after annealing at 800 c when both high and low forms were present originally the low form was destroyed preferentially we suggest that these data are consistent with the tl metamorphism trends observed in type 3 2 chondrites being due to the formation of feldspar with structural details being dependent on formation temperature by the devitrification of chondrule glass during metamorphism for types 3 2 the tl data are equally consistent with these types experiencing lower levels of metamorphism than the higher types or with type 3 0 being produced from higher types by aqueous alteration the presence of water with non terrestrial d h ratios and petrographic evidence for aqueous alteration in semarkona lead us to favour the aqueous alteration hypothesis

double beam analysis of anomalies in the core mantle boundary region seismic p waves from nuclear explosions at the kazakhstan test site in eastern kazakhstan kts observed at the yellowknife array yka canada are used to analyze the structure at the base of the mantle under severnaya zemlya arctic sea 18 events at the degelen subsite and 9 events at the shagan river subsite of kts are studied the simple waveforms and well controlled source parameters of nuclear explosions allow the use of the events as source arrays in addition to the usual receiver array configuration a new method double beamforming integrating both concepts is presented this method increases the resolution considerably for the degelen yka path one anomalous arrival 1 9 s before pcp slowness between p and pcp slowness is observed smaller anomalous arrivals are found 6 5 s degelen yka and 8 1 s before pcp shagan river yka these anomalous phases cannot be explained with standard earth models they are produced by reflections from an inhomogeneity in the lowermost mantle at 82 3n 107 5e under the area north of severnaya zemlya the strong variations between the wavefields for the two source receiver combinations indicate a heterogeneous structure in the lower mantle the anomaly found here is located close to an anomaly in the lowermost mantle beneath the nansen basin

analysis of historical seismograms root mean square lg magnitudes yields and depths of explosions at the semipalatinsk test range summary magnitudes mb lg based on rms amplitudes of lg waves recorded at nine internal soviet stations for 83 underground nuclear explosions at the semipalatinsk test range were analysed network magnitudes based on a combination of station magnitudes were formed as weighted averages over the station magnitudes after adjusting for variations among station magnitudes in scaling with source strength combining the station magnitudes into network magnitudes although the number of stations was small less than six appeared to reduce scatter in magnitude yield relations the correlation between network mb lg and announced explosion yields was very high and mb lg closely approximated simple proportionality with the logarithm of yield throughout the yield interval 2 165 kt the error of misfit was about 0 04 magnitude units excluding data for the explosion of 1972 august 16 8 kt at 139m the yield of which appeared high compared to mb lg the close correlation between network mb lg and explosion yield together with the fact that several of the explosions were not at scaled depths indicates that mb lg may not be critically dependent on depth of burial at least for depth ranges within a factor of two

sedimentary heterogeneity and petrophysical characterization of barremian tsunami and barrier island inlet deposits the aliaga outcrop as a reservoir analogue galve sub basin eastern spain abstract the present study examined two sandstone deposits in the aliaga outcrop as a reservoir analogue over a distance of 200 m long and attempted to establish a correlation between sand facies and the petrophysical properties of the sandstones in order to investigate the reservoir heterogeneity the aliaga reservoir analogue represents the upper part of camarillas fm deposited during the barremian synrift phase of the galve sub basin iberian basin spain it is characterized by a transitional sedimentary interval from sandy dominant deposits to carbonate dominant deposits which were deposited under the same palaeoenvironmental conditions in relation to systems of back barrier sedimentation the description of the aliaga outcrop provided here consists of lithological descriptions of two sandstone deposits a tsunami and a barrier island inlet at both mesoscopic decimetres to tens of metres and microscopic scales millimetres to centimetres both deposits recognized at the basin scale were described in terms of sand grain size sand sorting and cementation further cores were drilled along outcrop to collect samples for porosity and permeability measurements both sandstone reservoirs are the result of different sedimentary processes that determined facies characteristics as the different petrophysical properties observed in these deposits consequently the sedimentary process controls the heterogeneity of the sandstones facies and thus the sand heterogeneity controls the distribution of the petrophysical properties the classification of sand facies in terms of sand sorting seems to be more appropriate for describing sand heterogeneity accordingly petrophysical parameters in both deposits were also influenced by sand sorting the sand facies and petrophysics heterogeneity of the described deposits can be hierarchically ordered first order heterogeneity is related to the basin scale second order heterogeneity is related to genesis and the conditions of sediment deposition and third order heterogeneity is related to synsedimentary faults and or post sedimentation events

linking outcrop analogue with flow simulation to reduce uncertainty in sub surface carbon capture and storage an example from the sherwood sandstone group of the wessex basin uk modelling the behaviour of carbon dioxide co2 injected into sub surface reservoirs as part of carbon capture and storage ccs strategies is often performed using models that incorporate very limited geological detail particularly at the subseismic metre to decametre scale those modelling studies that incorporate varying degrees of geological realism show the inherent risks and uncertainties that can result from neglecting heterogeneity and reservoir caprock topography along the migration path of an injected co2 plume a key problem is that detailed geological data are often not available for the relatively deep saline aquifers that are an important target for ccs deep saline aquifers fall between the relatively data rich environments of shallow freshwater aquifers and hydrocarbon reservoirs and it is in these settings that outcrop analogues may play an important part in reducing the risks and uncertainties associated with ccs this study uses an example from the sherwood sandstone group otter sandstone formation of the wessex basin to show how an outcrop study can impart a much greater understanding of heterogeneity in critical reservoir caprock zones here the transition from the sherwood sandstone group fluvial sandstone reservoir to the mercia mudstone group playa lacustrine mudstone seal is not simple but includes a major change in fluvial style that introduces considerable heterogeneity at the top of the reservoir the study shows how laser scanned outcrop can be used to rapidly construct static geological models that are taken through to flow simulations in combination the use of appropriate outcrop analogues and flow modelling can reduce the risks and uncertainties associated with ccs

crustal shear velocity structure of the south indian shield 1 the south indian shield is a collage of precambrian terrains gathered around and in part derived from the archean age dharwar craton we operated seven broadband seismographs on the shield along a n s corridor from nanded nnd to bangalore bgl and used data from these to determine the seismic characteristics of this part of the shield surface wave dispersion and receiver function data from these sites and the geoscope station at hyderabad hyb give the shear wave velocity structure of the crust along this 600 km long transect inversion of rayleigh wave phase velocity measured along the profile shows that the crust has an average thickness of 35 km and consists of a 3 66 km s 1 12 km thick layer overlying a 3 81 km s 1 23 km thick lower crust at all sites the receiver functions are extremely simple indicating that the crust beneath each site is also simple with no significant intracrustal discontinuities joint inversion of the receiver function and surface wave phase velocity data shows the seismic characteristics of this part of the dharwar crust to be remarkably uniform throughout and that it varies within fairly narrow bounds crustal thickness 35 2 km average shear wave speed 3 79 0 09 km s 1 and vp vs ratio 1 746 0 014 there is no evidence for a high velocity basal layer in the receiver function crustal images of the central dharwar craton suggesting that there is no seismically distinct layer of mafic cumulates overlying the moho and implying that the base of the dharwar crust has remained fairly refractory since its cratonization index terms 7203 seismology body wave propagation 7205 seismology continental crust 1242 7255 seismology surface waves and free oscillations keywords continental crust archean crust receiver function indian shield

geologic factors controlling co2 storage capacity and permanence case studies based on experience with heterogeneity in oil and gas reservoirs applied to co2 storage a variety of structural and stratigraphic factors control geological heterogeneity inferred to influence both sequestration capacity and effectiveness as well as seal capacity structural heterogeneity factors include faults folds and fracture intensity stratigraphic heterogeneity is primarily controlled by the geometry of depositional facies and sandbody continuity which controls permeability structure the permeability structure in turn has implications for co2 injectivity and near term migration pathways whereas the long term sequestration capacity can be inferred from the production history examples of gulf coast oil and gas reservoirs with differing styles of stratigraphic heterogeneity demonstrate the impact of facies variability on fluid flow and co2 sequestration potential beach and barrier island deposits in west ranch field in southeast texas are homogeneous and continuous in contrast seeligson and stratton fields in south texas examples of major heterogeneity in fluvial systems are composed of discontinuous channel fill sandstones confined to narrow sinuous belts these heterogeneous deposits contain limited compartments for potential co2 storage although co2 sequestration effectiveness may be enhanced by the high number of intraformational shale beds these field examples demonstrate that areas for co2 storage can be optimized by assessing sites for enhanced oil and gas recovery in mature hydrocarbon provinces

thermoluminescence and compositional zoning in the mesostasis of a semarkona group a1 chondrule and new insights into the chondrule forming process a large group a1 porphyritic olivine chondrule in the semarkona ll3 0 chondrite with induced thermoluminescence tl and compositional zoning in its mesostasis has been discovered the chondrule has ca rich and fe poor olivine cao 0 36 0 40 wt fa0 3 0 5 and its mesostasis is highly anorthite normative 52 5 wt the chondrule shows an intense induced tl peak at 300 c with a half width of 180 c the induced tl in the 40 440 c range increases monotonically by a factor of 6 from center to rim while sio2 na2o and mno increase by factors of 1 1 3 6 and 6 respectively the spectrum of the induced tl over the 200 350 c range i e a dominant peak at 570 nm with a half width of about 100 nm and the mn tl correlation suggest mn activated plagioclase is an important constituent of the refractory mesostases in group a1 chondrules the zoning may reflect fractional crystallization soret diffusion transport of volatiles into the chondrule by aqueous alteration a zoned precursor reduction of precursor dust aggregate or recondensation of volatiles lost during chondrule formation the first four possibilities seem unlikely explanations for the zoning of the mesostasis but both reduction of precursor dust aggregate and recondensation of volatiles seem to have played significant roles to the formation of the zoning reducing conditions at high temperatures are suggested to have prevailed during the formation of group a1 chondrules

investigation of geomechanical responses of reservoirs induced by carbon dioxide storage assessment of the suitability of potential sub surface storage sites for co2 storage cuts across several issues a dominant part being the sustainability in terms of the retention capacity of prospective reservoirs questions often raised but not properly investigated border on the stability of underground reservoirs during the injection process and the protracted effect after injection is fully completed a review of studies on co2 sequestration reveals several uncovered areas with one significant aspect being the geo mechanical effect of co2 injection and storage within the underground formation a computational framework has been built as part of a series of ongoing investigations to ascertain the susceptibility of underground formations during and after co2 is introduced this is made possible by adopting a discrete element modelling methodology as a first step in the sequence of a designed procedure by applying this technique the formation materials are idealised as an assembly of discrete particles interacting in a manner which allows for specific descriptions of the morphology and fracturing events computational tests conducted on several types of models representative of reservoir formations reveal reservoir geo mechanical responses highly dependent on factors such as material property of rocks pressure build up and injection pressure an example of this is observed in the mode of fracturing events which is significantly influenced by the rate of fluid injection the outcome of this study forms a strong basis towards a better understanding of the behaviour of reservoir formations subjected to co2 injection and storage in addition information from these studies could serve as a reference for enhanced oil recovery processes and enhanced coal bed methane productions

regional seismic event location with a sparse network application to eastern kazakhstan ussr three component data from a sparse three station seismic network in eastern kazakhstan surrounding the soviet nuclear test site have been analyzed to determine location estimates for regional events recorded by two or three stations included among these events are the september 1987 chemical explosions whose locations are known locations are calculated using arrival times of p and s phases and arrival azimuths from first p location uncertainties are estimated using a combination of a priori and a posteriori data uncertainties a layered p wave velocity model adapted from soviet deep seismic sounding surveys is employed for calculating travel times and two s models are tried location results for the chemical explosions are excellent even if only two stations are used absolute location errors are less than 10 km and estimated 90 confidence uncertainties are only a few kilometers the data are also adequate to determine correctly their depth i e focus at the surface the other regional events include numerous suspected mine blasts and two earthquakes from the tien shan the calculated locations of the latter events agree well with a teleseismic location for one of them falling within a belt of regular seismic activity nearly all of the presumed blasts can be associated with mapped mines and we have been able to identify the source areas for two sets of blasts in high resolution satellite images before and after photographs allow us to identify specific active mines our location estimates agree quite well with the observed active mines

co2 induced geochemical reactions in heterogeneous sandstone and potential conditions causing the tight cementation abstract the contribution of tight gas stored in sandstone reservoirs to hydrocarbon production has been increasing however the formation mechanisms of these tight sandstone reservoirs remain unclear and the conditions leading to them are not well understood it is generally thought that early co2 emission may have caused the sandstones of the permian shihezi formation in the ordos basin china to become tight in this study we quantitatively investigate the effects of co2 intrusion on reservoir evolution choosing three factors thought to dominate this process i e detrital mineral assemblage formation water and intruded co2 volume for sensitivity analyses we constructed eight two dimensional models to investigate co2 water rock reactions and reservoir porosity changes under various conditions subsequent to determination of the potential conditions leading to the formation of tight reservoirs we then constructed a three dimensional model applying given heterogeneities in porosity permeability k and mineral assemblages to evaluate porosity distribution results show that the processes underlying the formation of tight reservoirs are controlled by various factors rather than any single one reservoirs containing ca rich minerals i e calcite and anorthite and ca2 rich formation water are apt to become tight as a result of co2 intrusion because of large scale carbonate precipitation in addition under primary geological and geochemically heterogeneous conditions co2 water rock reactions vary spatially which further enhances reservoir heterogeneities although minerals are heterogeneously distributed they exhibit some similar characteristics as their common ions link them results show that it is possible to predict both high quality and tight reservoirs in the study area favorable reservoirs are found in regions with initially high high k and high feldspar mineral contents while regions that are characterized by low and k as well as ca2 rich formation water and a high content of ca rich minerals tend to become tight after co2 intrusion

facies and petrophysical modelling of a thick lower cretaceous tsunami deposit in e spain up scaling from sample to outcrop scales abstract the tsunami deposit up to 3 m thick of the cretaceous camarillas formation in the galve sub basin eastern spain is characterized by a large lateral extent 35 km 2 and facies uniformity consisting in fine to coarse subarkosic arkosic sandstones at the scale of outcrop observation different lithofacies were distinguished and related to sedimentation processes sand facies distribution conditioned the facies heterogeneity at both mesoscopic or outcrop scales 10 1 10 1 m scale and sample scale 10 3 10 2 m the sample features were up scaled to that of a facies model using probability functions and variograms as well as to outcrop scale data geometry and size of facies distribution and it showed a good correlation with the facies distribution at the outcrop porosity is strongly correlated to permeability and the pairs of porosity and permeability values fall into the global hydraulic element ghes 5 so that they can be up scaled into reservoir models in terms of hydraulic properties from data analysis no apparent link between sand sorting and porosity and permeability values was observed the petrophysical models which were independent of facies models were up scaled taking into account the porosity and permeability values from sample data and the statistical analysis of their distribution along the outcrop the permeability model was carried out as a function of porosity by applying a linear relation which simplified the modelling process and discarded permeability uncertainties linked to facies distribution in the deposit in spite of different source data the petrophysical models show a distribution of lower and higher values that resembles the facies model consequently our modelling results clearly suggest the link of facies type and their grain size distributions with the petrophysical properties into the deposit consistency between facies and petrophysical models and outcrop scale observations make it possible to extrapolate to other deposits related to similar sedimentary processes

regional seismic recordings of the soviet nuclear explosion of the joint verification experiment during august and september 1988 the united states and the soviet union conducted a joint verification experiment in which each country was permitted to observe a nuclear explosion at the other country s test site using hydrodynamic means we have seismically recorded the soviet explosion at four stations at regional distances 750km and here report those observations the peak to peak particle motion in the p wave varied from 7 54 10 1 cm sec at 160 km to 1 02 10 2 cm sec at 740 km the average mb lg was 5 97 corresponding to a yield of 118 kt based on the nts mb lg yield relation of patton 1988 the average pn corner frequency of the soviet explosion was 4 hz with evidence of a second corner at about 0 7 hz both of these corners could be affected by spall near regional seismograms of the soviet jve explosion show a large arrival within the lg phase on the transverse component at all four sites this may correspond to tectonic release accompanying the explosion or to the effects of anisotropy on seismic wave propagation

fluvial architecture and reservoir compartmentalization in the oligocene middle frio formation south texas abstract seeligson stratton and agua dulce fields south texas are being studied as part of a gas research institute department of energy state of texas cosponsored program designed to develop and test methodologies and technologies for gas reserve growth in conventional reservoirs in mature gas fields over the last five decades each field has produced approximately 2 tcf of gas from middle frio reservoirs alone recent drilling old well workover results and reservoir pressure data however point to the possibility of additional reserves within these fields the middle frio oligocene is composed of sand rich channel fill and splay deposits interstratified with floodplain mudstones all forming part of the gueydan fluvial system channel fill deposits are 30 ft 9 m thick and 2 500 ft 76 m wide splay deposits are as much as 20 ft 6 m thick proximal to channels and extend as much as 2 mi 3 km from channels channel fill and associated splay sandstones are reservoir facies porosity 20 percent permeability 10 s to 100 s md floodplain mudstones and levee sandy mudstones impede or obstruct flow and separate individual reservoirs and compartments both vertically and laterally deposition on an aggrading coastal plain resulted in a continuum of fluvial architectural styles that has important implications for reservoir compartmentalization relatively slow aggradation resulted in laterally stacked channel systems whereas more rapid aggradation resulted in vertically stacked channel systems in seeligson field laterally stacked architecture alternates with vertically stacked architecture through the 2 000 ft 610 m thick middle frio section in stratton and agua dulce fields the same general alternation in architectural modes exists through the 2 500 ft 763 m thick middle frio section in stratton and agua dulce however the reservoir zones composed of laterally stacked architecture are not laterally continuous instead the laterally stacked architecture locally changes into a vertically stacked architecture because laterally stacked sandstone bodies lead to separate but potentially leaky reservoir compartments and vertically stacked sandstone bodies favor more isolated reservoir compartments a high potential for reserve growth through the identification of untapped poorly drained and bypassed gas reservoir compartments exists in each of these fields differences in reservoir architecture also must be taken into account as part of exploitation strategies

chemical and physical studies of type 3 chondrites i metamorphism related studies of antarctic and other type 3 ordinary chondrites abstract thermoluminescence sensitivity measurements have been made on 18 unequilibrated ordinary chondrites 12 finds from antarctica 5 non antarctic finds and 1 fall the tl sensitivities of these meteorites normalized to dhajala range from 0 034 st mary s county to 2 3 allan hills a78084 and based primarily on these data petrologic type assignments range from 3 3 st mary s county to 3 9 allan hills a78084 although the very low levels of metamorphism experienced by types 3 0 to 3 4 evidently cause large changes in tl sensitivity the new data demonstrate that they are unable to cause any appreciable homogenization of silicate compositions we have therefore slightly revised the silicate heterogeneity ranges corresponding to the lower petrologic types we have discovered that the temperature of maximum tl emission and the broadness of the major tl peak vary systematically with tl sensitivity as tl increases these parameters first decrease and then increase several mechanisms which could account partially or completely for the relationship between tl sensitivity and metamorphism are discussed those which involve the formation of feldspar the tl phosphor in equilibrated meteorites seem to be consistent with the trends in peak temperature and peak width since experiments on terrestrial albite show that the tl peak broadens and moves to higher temperatures as the stable form changes from the low ordered state to the high disordered state the post metamorphism equilibration temperature of type 3 5 meteorites would then correspond to the transformation temperature for the high to low form of meteorite feldspar other factors which may be involved are obscuration of the tl by carbonaceous material changes in the composition of the phosphor and changes in the identity of the phosphor

influence of pore fluid salt content on compaction creep of calcite aggregates in the presence of supercritical co2 abstract we have performed uniaxial compaction experiments on simulated porous carbonate rocks crushed and sieved carrara marble using pore fluids of varying salinity saturated with co2 in order to investigate the long term chemically coupled effects of co2 on creep of such rock materials experiments were performed at reservoir conditions equivalent to 3 km depth which is up to 30 mpa effective pressure and a temperature of 80 c on samples with mean grain sizes of 28 37 50 and 106 m the tests were carried out using saline pore fluid solutions containing 0 0 6 1 2 and 3 m nacl or 0 1 and 2 m mgcl2 with and without supercritical co2 at a pressure of 10 mpa addition of either salt nacl or mgcl2 to the pore fluid in samples compacted with co2 caused a reduction in compaction creep rate at low salt concentrations 0 6 1 m as salt concentration was increased to values of 2 3 m creep rates increased to approach or exceed values obtained in salt free experiments by comparison of our data on the compaction creep of carbonate aggregates in the presence of added salts and supercritical co2 with microphysical models and previous work on fluid enhanced deformation mechanisms we suggest that the effect of increasing salt concentration in samples tested with supercritical co2 is the net result of progressive inhibition of pressure solution and enhancement of the role of subcritical crack growth the present results imply that storage of co2 in highly porous carbonate formations increases creep rates by up to ten times depending on the salt concentration however it remains difficult to quantify the rate of compaction creep of specific carbonate reservoirs in the context of co2 storage as compaction behaviour is strongly influenced by porosity and other microstructural and compositional factors as well as by salinity

the matrices of unequilibrated ordinary chondrites implications for the origin and history of chondrites abstract the matrices of sixteen unequilibrated ordinary chondrites all witnessed falls were studied microscopically in transmitted and reflected light and analyzed by electron microprobe selected specimens were also studied by scanning electron microscopy these studies indicate that the fine grained opaque silicate matrix of type 3 unequilibrated chondrites is compositionally mineralogically and texturally distinct from the chondrules and chondrule fragments and may be the low temperature condensate proposed by larimer and anders 1967 1970 examination of the matrices of unequilibrated chondrites also shows that each meteorite has been metamorphosed with the alteration ranging in intensity from quite mild where the matrix has been only slightly altered to a more severe metamorphism that has completely recrystallized the opaque matrix most of the metamorphic changes in the matrix occurred without significant effects on the compositions or textures of the chondrules the metamorphic alteration probably resulted from a combination of processes including thermal metamorphism and the passage of shock waves the present appearance of each unequilibrated chondrite is a result of the particular temperature and pressure conditions under which it and its components formed plus the subsequent metamorphic alteration it experienced

a geological database for parameterization in numerical modeling of subsurface storage in northern germany underground land use can play a significant role in future concepts of energy and gas storage and requires an improved understanding of the parameters of potential storage formations saline aquifers for instance of porosity and permeability and also of mineralogical and gas compositions this study aims at providing data examples and calculating vertical spatial variations through variogram analyses of important north german geological reservoirs from dogger rhaetian middle buntsandstein and rotliegend sub groups and formations focusing on the western part of the north german basin vertical correlation lengths of porosity and permeability data range between 0 and 30 m while most results are calculated at approximately 2 4 m and do not show relevant differences among the evaluated formations in the majority of the regarded formations the kozeny carman relationship between porosity and permeability is supported as long as low porosity and permeability values are excluded from the evaluation mineral percentages varied significantly among the evaluated sediments besides quartz ankerite is the main compound in the dogger group while feldspars and clay minerals were more frequent in the rhaetian middle buntsandstein and rotliegend sediments methane was the main gas compound in the reservoirs followed by nitrogen ethane and carbon dioxide this study serves as preparatory work to allow for the parameterization of geological models and a subsequent simulation of fluid transport to evaluate long term safety and impacts of geothermal and gas storage projects

isochronous fluvial systems in miocene deposits of northern pakistan a palacomagnetic isochron dated at about 8 1 myr bp and detailed lithostratigraph of a 40 m interval exposed along strike for 40 km establish the depositional patterns of two contemporaneous interfingering fluvial systems in the upper part of the meddle siwalik sequence the two systems referred to as the buff and blue grey differ in unit shape lithofacies bedding sequence palaeocurrent direction and sand composition interfingering occurs along the south west north east strike of the outcrops with the palaeodrainage directions of the two systems generally perpendicular to this line the axis of the blue grey system which deposited widespread sheet sands and silts lay toward the south west end of the study area the more complex axis of the buff system which deposited shoe string sand bodies and lage volumes of silt and clay lay toward the north east the source area for both systems was the rising himalyan belt to the north and noth east of the study area at maximum extent the blue grey system occupied a channel belt at least 25 km wide channel belt widths and depths for the buff system are 1 3 km and 3 7 m respectively current directions averge 94 for blue grey sands and 136 for buff sands blur grey sands contain 20 more rock fragments and are otherwise less mature than buff sands the buff system shows a verticla pattern of avulsion palaeosol formation and floodplain aggradation which we attribute to autocyclic processes of parallel rivers the blue grey system shows phases of erosion accompaniced laterally by plaeosol formation folowed by valley fill and overfowing of interfluve surfaces theis pattern may be caused by allocyclic presses affecting the source area we interpret the blue grey system as a major drainage from the interior himalayas perhaps the ancestral indus and the buff system as a complex of smaller drinages along the mountain front which were probably ributaries to the bluegrey syste vertebrate fossils including hominoid primates from the area are almost exclusively associated with lithofacies of the buff system and this probably refects both taphonomic and palaeoecological differences between the two systems

determination of seismic energy from lg waves seismic energy is a physical concept related to broadband information on the source radiation this is different from seismic moment which is related to low frequency information improved estimates of seismic moment and radiated energy can improve the scientific framework for interpreting observed seismicity in terms of physical source processes this study evaluates the utility of regional lg waves the dominant feature of seismograms for regional earthquakes for the estimation of radiated seismic energy the rms lg which is defined as the root mean square of lg wave ground velocity within a certain group velocity range is proportional to the square root of lg wave radiated energy flux we find that rms lg is a good quantity for estimating the energy release of earthquakes because a large fraction of the total seismic energy is radiated as lg waves we scale the network averaged rms lg value to a reference distance of 100 km for a set of 52 earthquakes in the northeastern united states using an empirically derived relation between rms lg and epicentral distance we apply the source parameters estimated for these earthquakes to boatwright s deceleration source model and calculate the total seismic energy expected to have been radiated by each event assuming it can be modeled by this source we then obtain for earthquakes in the northeastern united states the scaling of the total radiated seismic energy of earthquakes with network averaged rms lg values from synthetic seismograms it is found that different velocity structures have an effect on the efficiency of lg wave radiation using measurements of rms lg made from synthetics we find that the vertical strike slip source tends to radiate less lg wave energy than other source mechanisms manuscript received 4 february 1998

chemical and physical studies of type 3 chondrites iii chondrules from the dhajala h3 8 chondrite abstract fifty eight chondrules were separated from the dhajala h3 8 chondrite and their thermoluminescence properties were measured chips from 30 of the chondrules were examined petrographically and with electron microprobe techniques the bulk compositions of 30 chondrules were determined by the fused bead technique porphyritic chondrules especially 5 which have particularly high contents of mesostasis tend to have higher tl mass normalized than non porphyritic chondrules significant correlations between log tl and the bulk cao al 2 o 3 and mno content of the chondrules and between log tl and the cao al 2 o 3 sio 2 and normative anorthite content of the chondrule glass indicate an association between tl and the abundance and composition of mesostasis unequilibrated chondrules i e those whose olivine is compositionally heterogeneous and high in ca have low tl whereas equilibrated chondrules have a wide range of tl depending on their chemical and petrographic properties we suggest that the tl level in a given chondrule is governed by its bulk composition which largely determined the abundance and composition of constituent glass and by metamorphism which devitrfied the glass in those chondrules with high ca glass to produce the tl phosphor we also suggest that one reason why certain chondrules in type 3 ordinary chondrites are unequilibrated while others are equilibrated is that the mesostasis of the unequilibrated chondrules resisted the devitrification this devitrification is necessary for the diffusive communication between chondrule grains and matrix that enables equilibration

crevasse splay processes and deposits in an ancient distributive fluvial system the lower beaufort group south africa abstract up to 12 of the mud prone ephemeral distributive fluvial system stratigraphy in the permo triassic lower beaufort group south africa comprises tabular fine grained sandstone to coarse grained siltstone bodies which are interpreted as proximal to distal crevasse splay deposits crevasse splay sandstones predominantly exhibit ripple to climbing ripple cross lamination with some structureless and planar laminated beds a hierarchical architectural scheme is adopted in which 1 m thick crevasse splay elements extend for tens to several hundreds of meters laterally and stack with other splay elements to form crevasse splay sets up to 4 m thick and several kilometers in width and length paleosols and nodular horizons developed during periods or in areas of reduced overbank flooding are used to subdivide the stratigraphy separating crevasse splay sets deposits from crevasse splays differ from frontal splays as their proximal deposits are much thinner and narrower with paleocurrents oblique to the main paleochannel in order for crevasse splay sets to develop the parent channel belt and the location where crevasse splays form must stay relatively fixed during a period of multiple flood events beaufort group splays have similar geometries to those of contemporary perennial rivers but exhibit more lateral variability in facies which is interpreted to be the result of more extreme fluctuations in discharge regime sharp based crevasse splay packages are associated with channel avulsion but most are characterized by a gradual coarsening upward interpreted to represent progradation the dominance of progradational splays beneath channel belt deposits may be more characteristic of progradational stratigraphy in a distributive fluvial system rather than dominated by avulsion processes in a trunk river system this stratigraphic motif may therefore be an additional criterion for recognition of distributive fluvial systems in the ancient record

co2 source sink matching in the lower 48 united states with examples from the texas gulf coast and permian basin documenting geographic distribution and spatial linkages between co2 sources and potential sinks in areas with significant levels of co2 emissions is important when considering carbon management strategies such as geologic sequestration or enhanced oil recovery eor for example the us gulf coast overlies a thick succession 6 000 m 20 000 ft of highly porous and permeable sandstone formations separated by thick regionally extensive shale aquitards the gulf coast and permian basin also have a large potential for eor in which co2 injected into suitable oil reservoirs could be followed by long term storage of co2 in nonproductive formations below reservoir intervals for example 6 billion barrels bbbl of oil from 182 large reservoirs is technically recoverable in the permian basin as a result of miscible co2 flooding the gulf coast also contains an additional 4 5 bbbl of oil that could be produced by using miscible co2 although the co2 pipeline infrastructure is well developed in the permian basin east texas and the texas gulf coast may have a greater long term potential for deep permanent storage of co2 because of thick brine bearing formations near both major subsurface and point sources of co2

crustal structure in eastern kazakh u s s r from teleseismic receiver functions broadband receiver functions determined from teleseismic p waveforms recorded at two seismic stations in eastern kazakh u s s r are inverted for the vertical velocity structure beneath the stations the detailed broadband receiver functions are obtained by stacking source equalized radial components of teleseismic p waveforms a time domain inversion of the radial receiver function is used to determine the structure assuming a crustal model parameterized by flat lying homogeneous layers the general features of the inversion results are a complex shallow crust velocities less than 6 km s in the upper crust a high velocity 6 9 7 5 km s lower crust and a moho that varies between 47 and 57 km depth these results compare favorably with a composite velocity model from deep seismic sounding data but show lower velocities in the upper crust and higher velocities in the lower crust the results indicate that the crust in this region is relatively uniform however the nature and depth of the moho changes significantly across the region the receiver function inversion structure for the kazakh sites is similar to a published receiver function structure for a site on the canadian shield

reservoir facies architecture in a micro tidal barrier system frio formation texas gulf coast abstract barrier bar sand bodies are a complex mosaic of barrier core shoreface inlet fill tidal delta and back barrier facies in addition sandbody stratigraphy and internal depositional architecture are determined by the progradational aggradational or transgressive origin of the barrier complex the frio barrier strandplain system of the middle texas gulf coast has produced more than 3 billion bbl of oil examination of the greta glasscock and 41 a sands in west ranch field illustrates the variability of barrier reservoirs each reservoir is a mosaic of variably interconnected compartments having sheet tab pod or channel geometries conventional facies analysis isolith and log pattern mapping and limited core examination combined with semiquantitative delineation of hydrocarbon saturation distribution using resistivity logs defined the facies components of each reservoir the 41 a sand consists of juxtaposed progradational barrier core inlet fill and flood tidal delta units the glasscock sand is largely a transgressive barrier flat and washoverfan deposit the greta sand is a complex of aggradational barrier core and inlet fill facies productive attributes of each reservoir are influenced by its facies architecture and attendant relative permeabilities natural water drive is ineffective in the volumetrically restricted transgressive glasscock reservoir permeability distribution in the 41 a reservoir is facies defined erratic injection response irregular oil water contact advance and variable water oil ratios observed during the productive history of individual reservoirs document localized facies effects on fluid flow spatial variation of the gas oil ratio may also reflect facies distribution end of article last page 478

the validity of generic trends on multiple scales in rock physical and rock mechanical properties of the whitby mudstone united kingdom abstract finding generic trends in mechanical and physical rock properties will help to make predictions of the rock mechanical behaviour of shales understanding the rock mechanical behaviour of shales is important for the successful development of unconventional hydrocarbon reservoirs this paper presents the effect of heterogeneities in mineralogy and petrophysical properties on the validity of generic trends on multiple scales in rock mechanical and rock physical properties of the whitby mudstone rock mechanical laboratory experiments have been performed on whitby mudstone samples from multiple outcrops within five kilometres laterally in order to investigate the heterogeneity and possible trends on an outcrop scale unconfined compression tests and acoustic measurements have been conducted to obtain the rock mechanical properties including rock strength young s modulus poisson s ratio and velocity anisotropy the rock physical properties including mineralogy porosity and matrix density were measured using x ray fluorescence and helium pycnometry various methodologies have been applied to the resultant data in order to derive different brittleness indices significant heterogeneity in rock mechanical and rock physical properties is present on an outcrop scale there is no obvious correlation between mineral content and rock mechanical properties on an outcrop scale in the whitby mudstone comparison with shales from different basins show however correlations between composition and elastic properties the presence of significant heterogeneities on an outcrop scale and between shales from different basins make it difficult to find generic trends in rock physical and rock mechanical properties

palaeosols as indicators of geomorphic stability in two old red sandstone alluvial suites south wales palaeosols fossil soils are abundant in the alluvial late silurian early devonian moor cliffs formation and rat island mudstone freshwater west formation of south dyfed south wales the palaeosols occur in thick mudstones deposited on floodplains under a seasonal semi arid climate and represent vertisol type soils simple single profiles are rare and most of the mudstone intervals exhibit complex overprinted profiles however a major difference exists between the palaeo vertisols in each of the two units studied the moor cliffs formation contains thick floodplain intervals with evidence of frequent erosion and reactivation of earlier soil horizons the associated coarser channel deposits mainly represent ephemeral streams the alluvial system was unstable flashy and prone to extensive stripping of stored floodplain sediment arroyos unstable ephemeral stream channels probably developed during this interval evidence for any marine influence on soil development is missing and previous speculations that the formation may represent deposition in an upper intertidal or supratidal system are not supported the rat island mudstone represents a complete contrast in that there was little or no stripping of floodplain sediments the channel deposits are typically of the fining upwards type representing more stable low sinuosity channels and with ephemeral stream floods by integrating the palaeosols a more detailed picture of the geomorphic history of these units can be formulated comparison with contemporary drainage basins indicates that a change in climate was a possible cause for the differences between the two units less frequent and more severe storms occurring during the deposition of the rat island mudstone

facies heterogeneity pay continuity and infill potential in barrier island fluvial and submarine fan reservoirs examples from the texas gulf coast and midland basin three reservoirs representing different depositional environments barrier island west ranch field south central texas fluvial la gloria field south texas and submarine fan spraberry trend midland basin illustrate variations in reservoir continuity pay continuity methods based on facies geometry and variations in permeability and thickness between wells can quantify reservoir heterogeneity in each of these examples although barrier island reservoirs are relatively homogeneous west ranch field contains wide 1000 5000 ft or 300 1500 m dip parallel belts of lenticular inlet fill facies that disrupt reservoir continuity in the main barrier core facies other reservoir compartments in west ranch field are in flood tidal delta deposits partly encased in lagoonal mudstones updip of the barrier core fluvial reservoirs have a higher degree of internal complexity than barrier island reservoirs in la gloria field reservoirs exhibit significant heterogeneity in the form of numerous sandstone stringers bounded vertically and laterally by thin mudstone layers successful infill wells in la gloria field contact partly drained reservoir compartments in splay deposits that pinch out laterally into flood plain mudstones recompletions in vertically isolated sandstone stringers in la gloria field contact other reservoir compartments submarine fan deposits are extremely heterogeneous and may have the greatest potential for infill drilling to tap isolated compartmentsmore in clastic reservoirs the spraberry trend contains thin discontinuous reservoir sandstones deposited in complex mid fan channels although facies relationships in spraberry reservoirs are similar to those in fluvial reservoirs in la gloria field individual pay stringers are thinner and more completely encased in low permeability mudstone facies less

geologic and infrastructure factors for delineating areas for clean coal examples in texas usa texas has a wide variety of areas that can be targeted for new clean coal facilities these areas are delineated by mapping spatial linkages between coal and lignite bearing formations groundwater and surface water resources and co2 sinks in brine formations for long term co2 storage or in mature oil fields with potential for enhanced oil recovery eor however a variety of infrastructure factors make it feasible to also target numerous areas outside coal and lignite basins in texas these infrastructure factors include pipelines for delivery of co2 to subsurface sinks and delivery of coal produced hydrogen to refineries ease of connection to existing transmission lines distribution of nonattainment areas where new clean coal facilities could be constructed and be compliant with strict air quality standards and railroads that can transport coal and other feedstock to new clean coal facilities primary regions in texas where favorably co located co2 source sink factors related to coal and lignite trends include the gulf coast the eastern shelf of the permian basin and the fort worth basin however areas outside coal and lignite basins particularly the permian basin where a new clean coal facility is being planned also have clean coal potential because of existing co2 pipelines and proximity to eor fields that can economically sustain new clean coal facilities

chemical and physical studies of type 3 chondrites 2 thermoluminescence of sixteen type 3 ordinary chondrites and relationships with oxygen isotopes thermoluminescence tl sensitivity values for sixteen type 3 ordinary chondrites fourteen of them from antarctica have been measured the values obtained normalized to the tl sensitivity of the dhajala meteorite range from 1 6 allan hills a77216 to 0 010 allan hills a77176 and include two reckling peak a80207 and allan hills a77176 that are particularly low they fill a hiatus in the tl distribution that previously existed between st mary s county and bishunpur the latter being a meteorite with one of the lowest tl sensitivities known the histogram of tl sensitivity values now shows a single distribution with higher values preferred it resembles the histogram for l chondrites occupying the petrologic types 3 4 5 and 6 there is a tendency for the tl sensitivity of meteorites to decrease as 18o increases equilibrated meteorites have tl sensitivities of 5 50 and 18o 4 5 to 5 0 while the most primitive meteorites with tl 0 01 have 18o 5 7 to 6 2 meteorites with intermediate tl have intermediate 18o theoretically it is possible that the range of 18o values observed may reflect progressive loss of o in the form of co at very low temperatures but very restrictive physical conditions and a complex history seem to be required

the thermoluminescence sensitivity metamorphism relationship in ordinary chondrites experimental data on the mechanism and implications for terrestrial systems hydrothermal annealing experiments have been performed on samples of the sharps meteorite in order to investigate the mechanism responsible for the metamorphism related 105 fold range in the thermoluminescence tl sensitivity in ordinary chondrites duplicate 50 mg samples of meteorite were annealed under the following conditions a 168 h at 785 c and 1 kbar b the same time temperature and pressure but with 2 wt water c 174 h at 855 c and 0 77 kbar with 2 wt water and 2 molal sodium disilicate nadisi d the same time temperature and pressure as the preceding samples but with 10 wt h2o and 2 molal nadisi samples annealed under the first three sets of conditions showed little or no change in their tl sensitivities however the samples annealed with 10 wt water and 2 molal nadisi showed a 3 to 10 fold increase in tl sensitivity and the temperature of the tl peak was suggestive of feldspar in the high temperature form we suggest that these data are consistent with the tl sensitivity metamorphism relationship in ordinary chondrites being due to the formation of the tl phosphor feldspar by the crystallization of chondrule glass

thermoluminescence of meteorites and their orbits the thermoluminescence tl levels of 45 ordinary chondrites were measured to obtain information about the meteorite orbits the low temperature tl reaches equilibrium while the meteorite is in space and reflects the temperature of the meteorite at perihelion samples of pribram lost city and innisfree whose orbits are accurately known were used as control samples the tl levels in 40 out ot 42 meteorites are similar to the three control samples indicating that the vast majority of ordinary chondrites that survive atmospheric entry have perihelia similar to three known orbits i e in the range 0 8 1 au the effects of albedo and rotation are also considered a simple model indicates that temperature gradients of 1 2 k cm are possible in slowly rotating meteoroids and such a temperature gradient is consistent with the unusually large tl gradient measured in the farmville meteorite since slow rotation rates are improbable other possibilities are examined but no satisfactory explanation has been found the tl level measured in the malakal meteorite is two orders of magnitude lower than control samples and is best explained by thermal draining due to solar heating in an orbit with a small perihelion distance the perihelion is estimated to be 0 5 0 6au

tectonic release from the soviet joint verification experiment the regional broadband seismic recordings of the soviet joint verification experiment underground nuclear explosion show evidence of tectonic release in the form of love waves at long periods and high frequency s sub m s phases on the transverse components the authors present the results of some simple forward modeling of this data in order to quantify both the moment and mechanism of the tectonic release using 10 20 second love wave amplitude and phase data they estimate the tectonic release moments to be 3 5 times 10 sup 15 n m for a north striking right lateral strike slip fault and 7 0 times 10 sup 15 n m for a northwest striking reverse fault using the results of these end member tectonic models the rayleigh waves can be satisfied with explosion moments of 1 7 times 10 sup 16 n m f 0 31 and 2 4 times 10 sup 16 n m f 0 44 respectively to resolve the ambiguity in tectonic mechanism the authors used the reflectivity method to generate synthetics and compare the relative amplitudes of the sh and sv parts of the s sub m s phase while the results favor the strike slip mechanism of tectonic release application of source inversion techniques to this data and other regional data will be needed to evaluate more realistic tectonic releasemore models involving for example oblique fault slip and dip less

site characterization for co 2 geologic storage and vice versa the frio brine pilot texas usa as a case study careful site characterization is critical for successful geologic storage of carbon dioxide co2 because of the many physical and chemical processes impacting co2 movement and containment under field conditions traditional site characterization techniques such as geological mapping geophysical imaging well logging core analyses and hydraulic well testing provide the basis for judging whether or not a site is suitable for co2 storage however only through the injection and monitoring of co2 itself can the coupling between buoyancy flow geologic heterogeneity and history dependent multi phase flow effects be observed and quantified co2 injection and monitoring can therefore provide a valuable addition to the site characterization process additionally careful monitoring and verification of co2 plume development during the early stages of commercial operation should be performed to assess storage potential and demonstrate permanence the frio brine pilot a research project located in dayton texas usa is used as a case study to illustrate the concept of an iterative sequence in which traditional site characterization is used to prepare for co2 injection and then co2 injection itself is used to further site characterization efforts constrain geologic storage potential and validate understanding of geochemical and hydrological processes at the frio brine pilot in addition to traditional site characterization techniques co2 movement in the subsurface is monitored by sampling fluid at an observation well running co2 saturation sensitive well logs periodically in both injection and observation wells imaging with crosswell seismic in the plane between the injection and observation wells and obtaining vertical seismic profiles to monitor the co2 plume as it migrates beyond the immediate vicinity of the wells numerical modeling plays a central role in integrating geological geophysical and hydrological field observations

mapping moho depth variations in central italy from psmoho p delay times evidence of an e w transition in the adriatic moho at 42 n latitude 1 along the italian peninsula adjoin two crustal domains peri tyrrhenian and adriatic whose boundary is not univocal in central italy in this area we attempt to map the extent of the moho in the two terrains from variations of the travel time difference between the direct p wave and the p to s wave converted at the crust mantle boundary called psmoho we use teleseismic receiver functions computed at 38 broad band stations in this and previous studies and assigned each of the recording sites to the adriatic or peri tyrrhenian terrains based on station location geologic and geophysical data and interpretation and consistency of delays with the regional moho trend the results of the present study show that the psmoho arrival time varies from 2 3 to 4 1 s in the peri tyrrhenian domain and from 3 7 to 5 5 s in the adriatic domain as expected the lowest time difference is observed along the tyrrhenian coastline and the largest values are observed in the axial zone of the apennine chain a key new result of this study is a sharp e w boundary in the adriatic domain that separates a deeper moho north of about 42 n latitude from a shallower moho to the south this feature is constrained for a length of about 40 km by the observations available in this study the e w boundary requires a revision of prior mapping of the moho in central italy and supports previous hypotheses of lithosphere segmentation

efficient calculation of differential seismograms for lithospheric receiver functions summary a new technique for computing differential seismograms for crustal and upper mantle response to a teleseismic wave receiver functions is developed using the matrix formalism of kennett the work was motivated by the difficulty of modelling teleseismic sv waves and has also proven useful for modelling teleseismic p waves this efficient method for calculating differential seismograms is based on three separate methods for computing synthetic seismograms two of the synthetic seismogram methods save intermediate results then the remaining synthetic seismogram algorithm uses the stored results in an efficient calculation of a new synthetic seismogram for a perturbed velocity model these developments have led to a faster for a 30 layer model a 90 per cent reduction in computation time and more accurate linearized inversion scheme for the determination of velocity models using teleseismic waves

anatomy of regional phases and source characterization of the soviet joint verification experiment underground nuclear explosion broadband data from the nrdc deployment of stations in kazakhstan at karkaralinsk kkl and bayanual bay are subjected to detailed waveform modeling to understand the nature of regional wave propagation and to determine the nature of the explosion time function and sources of low and high frequency tectonic release minor modification of a crustal model inferred from dss studies in the region is very effective in explaining the arrival times amplitudes and waveshapes of the pn and pmp arrivals at both stations the sh wave data are remarkable however for showing a large high frequency arrival after the expected and observed arrival of sms from the explosion source these secondary s arrivals imply a secondary source 1 to a few kilometers to the south of the shot point shear waves from this source dominate the seismic data at high frequency but are minor at low frequency where shear waves and surface waves from the inferred relaxation of the explosion cavity dominate the wave field the secondary s wave source is inferred to represent explosion driven faulting with no net moment significant overshoot in the rdp is required to match the p wave data it is found that von seggern blandford and haskell source functions are incapable of producing the observed overshoot however the mueller murphy source model is very effective in matching the clear overshoot effects seen in the p waves spall effects are also considered but appear to be minor and serve to require even more overshoot in the rdp the excitation and dispersion of rayleigh waves in the period band of 1 to 10 sec is seen to be a sensitive but nonunique function of both vs and vp in the upper crustal layer high poisson ratios in this layer are needed to explain the rayleigh waveform

depositional patterns following the 1870s avulsion of the saskatchewan river cumberland marshes saskatchewan canada abstract the avulsion of the saskatchewan river cumberland marshes east central saskatchewan canada has resulted in new floodplain deposition over an area of more than 500 km2 since beginning in the 1870s the avulsion deposits are predominantly fine grained and could be otherwise classifiable as overbank sediments in alluvial floodplains presumed to be supplied by intermittent flooding of dominant master channels the north angling and cadotte channels are older pre existing channels that were intercepted and appropriated by the expanding avulsion following annexation of the north angling channel stable cohesive banks inhibited channel enlargement and crevassing forcing the increasing discharges to be accommodated by overbank flow and in the process enhancing new levee aggradation these levee deposits coarsen upward and thin downstream as a result of greater competence and higher proximal deposition rates brought on by the larger flows in contrast the cadotte channel responded to increasing discharges by levee breaching giving rise to splay progradation and floodbasin filling the cadotte splay complex formed from the avulsively annexed cadotte channel represents a small but typical area of the avulsion belt facies characteristics and interrelationships examined from auger borings and vibracores are presented to illustrate patterns of deposition and floodplain development avulsive flooding initially raised local water surface elevations deepening small existing lakes and creating new shallow 1 2 m deep lakes on the floodplain surface deposition began when levees of the cadotte channel were breached allowing water and coarser sediment to spread as sheet like flows while finer sediment was carried and deposited farther into the basin later as the proximal splay sheets coalesced and grew basinward flows became channelized and progradation of mouth bars into marshes and shallow lakes together with deposition of interchannel fines became dominant forming coarsening upward sequences further floodplain aggradation developed by overbank flooding when splay channels became stabilized and bordered by levees gradual abandonment was accompanied by deposition of organic rich fine grained sediment on top of the progradational sequences throughout the avulsion the north angling channel has stood as an older alluvial ridge separating two broad areas of avulsive deposition its recent levee deposits now grade basinward into these new floodplain sediments composed of thicker heterogeneous predominantly upward coarsening and rapidly deposited facies of the avulsion

the receiver structure beneath mina nevada abstract receiver functions obtained from broadband teleseismic p waveforms recorded at seismic station mnv near mina nevada are inverted for the vertical shear wave velocity structure southeast of the station the time domain inversion procedure for vertically heterogeneous and laterally homogeneous one dimensional models includes smoothness constraints to minimize model roughness and a pseudo monte carlo approach to investigate the nonuniqueness of the solution models we also report on the potential effects of scattering on a receiver function inversion for a one dimensional velocity structure mnv receiver functions sample the walker belt crust and upper mantle beneath the soda spring valley and pilot mountains to the east and the garfield hills and excelsior mountains to the west of the station the preferred southeast solution models show a smooth positive gradient in the mid and lower crust with the top of the crust mantle boundary at 34 to 36 km depth reaching an upper mantle p velocity of 7 8 to 7 9 km sec 1 between 38 and 40 km these results suggest that the crust beneath mnv may be representative of a transition zone between typical basin and range province crust to the east and a thicker sierran block to the west of the station

seismic velocity structure and event relocation in kazakhstan from secondary p phases abstract three component seismic data from a set of presumed explosions recorded by stations at bayanaul and karkaralinsk in kazakhstan were analyzed in order to model the crustal structure of the region and to examine the use of the arrival times of secondary p phases primarily pmp in regional event location polarization analysis aided in the identification of the secondary phases low pass filtered data 4 hz corner from the first 5 to 10 sec of 13 presumed explosions were modeled with the reflectivity method the two chemical explosions in 1987 provided a check on accuracy as their locations and origin times are accurately known a good fit to the arrival times and amplitudes in the first 5 sec of the p wave pn pg and pmp was obtained in the epicentral distance range of 100 to 300 km beyond 300 km the simple layered model was not adequate to model the pmp arrival the crustal p wave velocity model we derived has an upper crustal velocity increasing fairly rapidly from 4 5 km sec near the surface to 6 5 km sec at 15 km depth then increasing more slowly to 7 05 km sec at 50 km depth the observed difference in the arrival times of the phases pg pmp and pn in the range between 100 and 250 km distance required a relatively sharp transition at the crust mantle boundary the model is generally similar to previous estimates of p velocity structure in the region though with a gentler gradient in the upper crust and a steeper gradient in the lower crust we used the derived crustal model and the primary and secondary p wave arrival times to relocate events in the kazakhstan region inclusion of the phase pmp substantially decreases the focal depth uncertainty for many of the events all but one of the events analyzed are concluded to be surface explosions the identity of the remaining event is uncertain

hypocenter constraint with regional seismic data a theoretical analysis for the natural resources defense council network in kazakhstan ussr source depth and epicenter determination remains a simple but key method for discrimination between earthquakes and nuclear explosions at near regional distances a variety of secondary body wave arrivals can be observed that may be useful for constraining source depth and epicenter in this paper we study the source location problem using regional arrival time and arrival azimuth data from a sparse seismic network a theoretical analysis of the source location inverse problem provides estimates of the stability and uncertainty of the solution for a particular suite of data as a function of epicenter and depth as well as evaluating the importance of each datum to the solution an empirical analysis with actual data complements the theoretical analysis our approach is applied to the three station natural resources defense council soviet academy of sciences network in kazakhstan the theoretical analysis indicates that reasonable constraint on depth and epicenter is possible whenever three distinct phases p pn pg pzp and pmp or equivalent s phases are observed at two or three stations our theoretical analysis for two station locations shows that the epicenter constraints are extremely poor for sources along the line passing through the two observing stations the use of arrival azimuth in two station locations results in improvement in epicenter constraint for events occurring in the vicinity of the line connecting the two stations but there is no significant improvement elsewhere an empirical analysis of data from two of the september 1987 chemical explosions and data from an explosion in an active mining area supports the theoretical analysis showing that two station locations both epicenter and depth are quite reliable furthermore the theoretical analysis also indicates that even with data from a single observing station satisfactory results are obtained if three or more phases plus arrival azimuth are available

emission spectra of meteorites during thermoluminescence abstract the emission spectra of four ordinary chondrite meteorites of petrological type 5 have been recorded during thermoluminescence spectra from all four samples are similar a very broad emission structure peaked near 470 nm and extending from 300 to at least 700 nm is found for the glow peaks from 150 to 250 c the higher temperature peak 300 500 c exhibits a different character with a narrow emission band near 400 nm a tentative model for a luminescence site is offered the broad similarity between the four samples is particularly interesting as the samples include chondrites of different shock history the importance of the changes in glow curve spectra with temperature are noted for kinetic analyses of conventional glow curves

defining the 3d geometry of thin shale units in the sleipner reservoir using seismic attributes acknowledgments the seismic interpretation and image processing was carried out in the seislab facility at the university of aberdeen sponsored by bg bp and chevron seismic imaging analysis was performed using geoteric ffa and analysis of seismic amplitudes was performed in petrel 2015 schlumberger we would like to thank the nddc rg11766 10 for funding this research and statoil for the release of the sleipner field seismic dataset utilized in this research paper and also anne kari furre and her colleagues for their assistance we also thank the editor alejandro escalona and the two anonymous reviewers for their constructive and in depth comments that improved the paper

chondrules and other components in c o and e chondrites similarities in their properties and origins we describe three types of chondrules that are common to h3 ll3 cm2 co3 and cv3 chondrites low and high feo porphyritic olivine chondrules contain olivine with fa0 3 8 and fa5 50 respectively and can easily be distinguished petrographically poikilitic pyroxene chondrules have 1 20 vol olivine fa0 2 8 enclosed by low ca pyroxene fs0 5 7 and also occur in e chondrites these three types formed in separate nebular regions which had dimensions and spacings such that a few percent of the chondrules that collided to form compound chondrules were of different types sorting of chondrule precursor material and mixing of chondrule types probably account for most variations in bulk and mineral chemistry among chondrite groups metallic fe ni grains containing 0 1 1 cr si and p are present in low feo olivine chondrules from all type 2 and least metamorphosed type 3 chondrites metal compositions reflect reduction during chondrule formation in the nebula not nebular condensation opaque matrices in type 3 ordinary and carbonaceous chondrites are somewhat similar in composition and mineralogy and probably have related origins we conclude that chondrules in all known chondrite groups share similar nebular origins

matrices of type 3 ordinary chondrites primitive nebular records petrologic studies were made on the fine grained matrices of type 3 ordinary chondrites of the lowest petrologic subtype the matrix minerals in order of abundance are olivine fo99 to fo9 enstatite or bronzite augite or subcalcic augite albite fe ni metal troilite magnetite spinel mgal2o4 chromite and calcite fe and mg rich fluffy particles and albite like particles are also major constituents the chemical compositions of olivine and pyroxenes vary within and among the chondrites and are in gross disequilibrium showing that the matrix materials were hardly heated after their formation textural relationships indicate that magnesian olivine was formed after ca pyroxene followed by intermediate to iron rich olivine intermediate olivine was formed from enstatite and metallic iron under relatively oxidizing conditions the observations indicate that matrices of chondrites are neither the fragments of chondrules nor the precursors of chondrules they were mostly the products of condensation and reaction among solids and or between solids and the ambient gas mostly at low temperatures and thus they contain records of primitive processes in the nebula in order to explain the presence of olivines more iron rich than fo50 the presence of free sio2 or a high activity of sio2 in the gas is necessary which was not shown in previous thermochemical calculations mineral assemblages of matrix minerals of chondrites of different chemical groups differ systematically according to oxidation state of the parental meteorites indicating that they were formed at different oxygen fugacities the rims of chondrules and surrounding matrix materials must have accreted onto chondrules during turbulent movements of the nebula

precise relative location of 25 ton chemical explosions at balapan using ims stations wetest how well low magnitude m blg 1 8 to 2 6 25 ton chemical explosions at balapan kazakhstan can be located using ims stations and standard earth models relying on precisely determined relative arrival times of nearly similar regional and teleseismic waveforms three 1997 balapan explosions were recorded by a number of currently reporting and surrogate ims stations three regional stations and two teleseismic arrays yielded consistent waveforms appropriate for relative picking master event locations based on the ak135 model and ground truth information from the first shallowest and best recorded explosion fell under 1 km from known locations for depths constrained to that of the master event the resulting 90 confidence ellipses covered 12 13 km2and contained the true locations however results for depth constrained to true depth were slightly less satisfactory from predictions based on ground truth we found a pgcoda phase at makanchi kazakhstan to be misidentified and poorly modeled after accounting for this 90 ellipses shrank to 2 3 km2and true depth mislocation vectors became more consistent with confidence ellipse orientations these results suggest that a high level of precision could be provided by a tripartite array of calibration shots in cases where models are poorly known we hope that the successful relocation of these small balapan shots will support the role of calibration explosions in verification monitoring and special event studies including on site inspection

detection of seismic bedrock using radial receiver function the receiver function rf method has been widely applied to estimate velocity structures of earth s crust and mantle using teleseismic data in this study we perform a rf iterative deconvolution method to detect the depth variations of seismic bedrock in the taipei basin and chiayi area we use strong motion data recorded by five and seven stations in the taipei basin and chiayi area respectively the ps p times appear at about 0 235 0 93 s for the taipei basin and 1 015 1 685 s for the chiayi area the time differences imply gradually increases of the bedrock depth from southeast to northwest in the taipei basin and from east to west in the chiayi area our results show that the method can efficiently detect depth variations of seismic bedrock which are consistent with those from other geophysical observations as well

effective models for co2 migration in geological systems with varying topography 1 geological co2 sequestration relies on a competent sealing layer or caprock that bounds the formation top and prevents vertical migration of co2 and brine modeling studies have shown that caprock topography or roughness can significantly decrease updip migration speed of co2 and increase structural trapping caprock roughness can be characterized at different spatial scales for instance regional scale features such as domes traps and spill points can be detected in seismic surveys and have been shown to affect large scale migration patterns however structural and topographical variability known as rugosity exists below seismic detection limits but can be measured at the scale of centimeters and meters using lidar scanning of formation outcrops little is known about the actual impact of structural rugosity on co2 plume migration practically speaking given the large scales required to model commercial scale co2 storage projects and the limitations on computational power only seismic scale caprock topography can be resolved using standard discretization techniques therefore caprock variability that exists below the model resolution scale is defined as subscale and must be handled by upscaling in this paper we derive effective equations for co2 migration that include the impact of fine scale variability in caprock topography using static equilibrium upscaling an approach that is adapted for the vertical equilibrium modeling framework the effective equations give estimates of the impact of rugosity on co2 plume migration and trapping in large scale systems

retention of sodium during chondrule melting abstract type i chondrules in unequilibrated ordinary and carbonaceous chondrites tend to be enriched in refractory elements and depleted in volatiles relative to bulk ci type ii chondrules show chondritic concentrations of major and minor lithophile elements with na in particular at or slightly above the appropriate bulk rock values element ratio diagrams for chondrule bulk compositions show that type ii chondrules plot on a mixing line between forsterite and a na phase with na al 1 1 whereas type i compositions can be explained by mixing forsterite with melilite or cai or other refractory component with little na calcium in type ii chondrules must have been added as an al free phase such as diopside if their bulk compositions are manipulated subtracting ca as diopside and fe mg as olivine the residue is 90 albite and 10 silica which would be in pyroxene albite was incorporated into the precursors of type ii chondrules which clearly have not been depleted in na although their initial temperatures overlap with those of type i there is no negative correlation between type i liquidus temperatures 1450 1900 c and na al ratios and hence no indication of na loss from the melt if type i precursors contained albite the most aluminous chondrules would have suffered the most extreme na loss but these have the lowest liquidus temperatures their precursors were na depleted whereas those of type ii were na enriched as a function of the abundance of albite the simplest way to obtain the bulk compositions of chondrules is to assemble condensates into precursors at different temperatures and concentration of solids in the nebula or exceptionally rapid heating is required to preserve na in chondrules after melting substantial exchange of na occurred between chondrules and chondrite matrix during parent body metamorphism to petrologic type 3 6

seismic evidence for an ancient rift beneath the cumberland plateau tennessee a detailed analysis of broadband teleseismic p waveforms broadband receiver functions developed from teleseismic p waveforms recorded on the midperiod passband of regional seismic test network station rscp are inverted for vertical velocity structure beneath the cumberland plateau tennessee the detailed broadband receiver functions are obtained by stacking source equalizd horizontal components of teleseismic p waveforms the resulting receiver functions are most sensitive to the shear velocity structure near the station a time domain inversion routine utilizes the radial receiver function to determine this structure assuming a crustal model parameterized by many thin flat lying homogeneous layers lateral changes in structure are identified by examining azimuthal variations in the vertical structure the results reveal significant rapid lateral changes in the midcrustal structure beneath the station that are interpreted in relation to the origin of the east continent gravity high located northeast of rscp the results from events arriving from the northeast show a high velocity midcrustal layer not present in results from the southeast azimuth this velocity structure can be shown to support the idea that this feature is part of a keweenawan rift system another interesting feature of the derived velocity models is the indication that the crust mantle boundary beneath the cumberland plateau is a thick probably laminated transition zonemore between the depths of 40 and 55 km a result consistent with interpretations of early refraction work in the area less

influence of small scale fluvial architecture on co 2 trapping processes in deep brine reservoirs a number of important candidate co2 reservoirs exhibit sedimentary architecture reflecting fluvial deposition recent studies have led to new conceptual and quantitative models for sedimentary architecture in fluvial deposits over a range of scales that are relevant to co2 injection and storage we used a geocellular modeling approach to represent this multiscaled and hierarchical sedimentary architecture with this model we investigated the dynamics of co2 plumes during and after injection in such reservoirs the physical mechanism of co2 trapping by capillary trapping incorporates a number of related processes i e residual trapping trapping due to hysteresis of the relative permeability and trapping due to hysteresis of the capillary pressure additionally co2 may be trapped due to differences in capillary entry pressure for different textural sedimentary facies e g coarser grained versus finer grained cross sets the amount of co2 trapped by these processes depends upon a complex system of nonlinear and hysteretic characteristic relationships including how relative permeability and capillary pressure vary with brine and co2 saturation the results strongly suggest that representing small scale features decimeter to meter including their organization within a hierarchy of larger scale features and representing their differences in characteristic relationships can all be critical to understanding trapping processes in some important candidate co2 reservoirs

the excitation of lg waves by explosions a finite difference investigation several mechanisms have been proposed to explain the excitation of the regional lg phase by explosions we examine some of these mechanisms with finite difference simulations an energy flux technique is used to analyze the synthetic signals the method is adapted from conventional array analysis techniques and gives a clear characterization of wave field intensity wave slow ness and propagation direction the vector energy flux in the model is studied instead of the scalar distribution of energy in the space time domain the cal culations show that for an explosive source in a high p wave velocity crust p wave energy cannot be effectively trapped in the crust and the nongeomet rical phase s may be the primary contributor to thelg phase for an explosive source buried in a low velocity upper crust i e where the p wave velocity is lower than the upper mantle s wave velocity part of the ps wave can be trapped in the crustal wave guide to form the lg phase the relative lg excitation de pends on the ratio between the p wave velocity in the source region and the s wave velocity in the uppermost mantle scattering effects can transfer p wave or surface wave energy into lg but the efficiency strongly depends on both the wave frequency and the characteristic size of the scatterers any source process that directly excites s waves is more efficient for generating lg than the afore mentioned mechanisms spall directly generates s wave energy and conse quently is an efficient source for lg for actual explosions all of these factors may simultaneously contribute to lg excitation determining their relative im portance and interactions requires additional observations

paleosols in the upper guantao formation miocene of the gudong oil field and their application to the correlation of fluvial deposits the main pay zone of the upper guantao formation of the gudong oil field north china basin is a 300 m thick fluvial sequence due to lack of bio and lithostratigraphic markers correlation of the main pay zone has been difficult especially in the beginning of the oil field development however paleosols are well developed in this fluvial sequence core investigation indicates that the paleosols can be identified by a set of characteristics including color of sediment original plant roots caliche nodules sedimentary structures distribution of facies and mineral composition log responses of paleosols include lower gamma ray activity and higher sonic dgrt value relative to non paleosol sediments an analysis of the evolution of paleosols and controlling geological factors illustrates that paleosols present time stratigraphic markers and can be used to solve correlation problems a stratigraphic framework in which the upper guantao formation was divided into three paleosol sets and two non paleosol sets was built using paleosols as correlation markers the results prove that the paleosol method of correlation is viable and very helpful for geological study of similar oil fields in the early evaluation and development design phase

the thermoluminescence carrier in the dhajala chondrite the thermoluminescence tl sensitivities of 58 chondrules separated from the dhajala h3 8 chondrite have been measured in order to investigate the cause of the 105 fold variation in the tl sensitivity of ordinary chondrites the tl sensitivities of the individual chondrites range over nearly two orders of magnitude from 0 002 to 0 12 where 4 mg of bulk dhajala powder 1 with no correlation with chondrule mass cross sectional area or diameter some chondrules have tl per unit mass ten times that of bulk dhajala powder and mass tl balance arguments suggest that these chondrules are a major tl carrier the composition of 15 chondrules was also determined and it was found that high tl chondrules tend to have ca contents at the upper end of the range observed these observations are consistent with the tl sensitivity variation in ordinary chondrites which is related to metamorphism being caused by the devitrification of glass to produce feldspar and with feldspar being the dominant tl phosphor in dhajala that chondrules are an important tl carrier would also be consistent with primary feldspar as the tl phosphor but petrologic observations probably make this appear unlikely

geology of the chinese nuclear test site near lop nor xinjiang uygur autonomous region china abstract the chinese underground nuclear test site in the kuruktag and kyzyltag mountains of the xinjiang uygur autonomous region of northwest china is the location of sixteen underground tests that occurred between 1969 and 1992 the largest test to date conducted on 21 may 1992 had a reported yield of about one megaton geophysical properties of the rocks and a large scale geologic map of part of the test area were published by the chinese in 1986 and 1987 and are the first site specific data available for this test site in areas of low relief underground nuclear testing has occurred below the water table in shafts drilled vertically into dense low porosity paleozoic granitic and metasedimentary rocks additional testing in areas of more rugged terrain has occurred in horizontal tunnels probably abovethe water table at least one of these tunnels was driven into granite the upper 50 m of the rock in the area of the vertical tests is weathered and fractured these conditions have been shown to influence the magnitude of the disturbance of the land surface after a nuclear explosion these descriptions suggest hard rock coupling at depth and a closer resemblance to the former soviet test site in eastern kazakhstan than to the u s test site in nevada

comparison of crustal velocity profiles determined by seismic refraction and teleseismic methods recently two diverse seismic techniques were applied independently to the study of the crustal structure of the cumberland plateau eastern tennessee one involved a reinterpretation of a refraction experiment performed in 1965 by the u s geological survey consisting of two 400 km long reversed refraction lines the other entailed the inversion of broadband teleseismic p waveforms recorded at a single three component broadband station rscp located at the intersection of the two refraction profiles a comparison of the two sets of velocity profiles revealed many similarities and some significant differences both sets of velocity models consist of three major crustal layers 1 an upper crust vp 6 1 6 4 km s down to about 17 km 2 a mid crust vp 6 7 6 9 km s between 17 and 40 km depth 3 a lower crust vp 7 2 7 4 km s from 40 to 51 km depth the refraction models have linear transition zones up to 11 km thick at the base of each layer whereas the teleseismic models have more irregular transition zones at the base of the mid and lower crust the differences in the results of these studies are attributed to the differing frequency bandwidths of the data sets the predominant sensitivity of the teleseismic data to shear velocities compared to compressional velocities for the refraction data and the different analysis procedures involved in each method nevertheless the similarities indicate that the teleseismic waveform method with broadband data is capable of retreiving comparable crustal information as the cumberland plateau refraction survey in addition it provides the kind of complementary information required to constrain the composition of the continental lower crust and uppermost mantle

the influence of water and supercritical co2 on the failure behavior of chalk abstract reduction of compressive strength by injection of water into chalk is a well known mechanism responsible for increased compaction in chalk reservoirs this raises the question of whether such effects might be enhanced in the context of long term storage of co 2 or of co 2 injection for enhanced oil and gas recovery eor egr purposes therefore data regarding the effect of supercritical co 2 on the mechanical behavior of chalk are needed the effect of supercritical co 2 on the short term failure behavior of wet chalk was accordingly investigated by means of conventional triaxial deformation experiments performed on maastrichtian chalk cores under dry conditions in the presence of saturated chalk solution and using co 2 saturated solution at temperatures simulating reservoir conditions 20 80 c and effective confining pressures up to 7 mpa increasing temperature from 20 to 80 c did not show any significant effects on the strength of the dry samples addition of aqueous solution to the samples led to drastic weakening of the chalk the effect being more pronounced at high effective confining pressures peff 3 mpa addition of 10 mpa supercritical co 2 to wet samples did not produce any significant additional effect in comparison with the wet samples all samples showed a yield strength envelope characterized by shear failure at low effective mean stresses giving way to a compaction cap at high mean stresses the weakening effect of aqueous solution was explained in terms of a reduction in frictional resistance of the material due to water enhanced grain contact cracking and perhaps pressure solution with a possible contribution by disjoining pressure effects caused by water adsorption while co 2 does not seem to reduce short term failure strength of wet chalk processes such as intergranular pressure solution have to be considered for assessing mechanical stability of chalk in the context of long term co 2 storage or eor egr operations