intraplate shortening and underthrusting of a large basement ridge in the eastern nankai subduction zone abstract due to the collision of the izu bonin arc with central japan the subducting philippine sea oceanic plate is affected by lithospheric shortening seaward of the eastern nankai trough in the zenisu ridge area seismic reflection and refraction profiles across the ridge show a series of low angle thrusts cutting through the entire oceanic crust they also indicate that the formation of this ridge is related to a single lithospheric thrust with 10 km throw that inserts a corner of upper mantle within the lower crust we propose that the serpentinized mantle crust transition acts as a decoupling level above which distributed shortening results in the formation of a crustal prism although the amount of deformation is much smaller than in a mountain belt such as the pyrenees a parallelism can be proposed between both systems that correspond to intraplate shortening and have in common a single mantle shear zone and overlying distributed crustal deformation the underthrusting below the eastern nankai accretionary prism of a similar and now inactive tectonic structure the paleo zenisu ridge is evidenced by the deformation pattern of the margin this ridge is probably detached on top of the subduction decollement at least where volcanoes are impinging the continental margin part of the ridge may thus be accreted to the prism backstop we show that both zenisu and paleo zenisu systems accommodate the same n s compression related to convergence partitioning process this subduction kinematics can be understood in terms of a steady state model partially constrained by the trails of volcanoes that have impinged the margin n s shortening is accommodated by the thrusts seaward of the trough and right lateral motion is prevalent along the subduction system based on these kinematics we propose that the formation of the paleo zenisu and zenisu ridges are related to the successive collisions of volcanic massifs of the izu bonin arc with the japanese arc the zenisu system is a result of the collision of the izu block since 2 ma while the paleo zenisu system was the result of the earlier collision of the tanzawa massif between 5 and 3 ma

mechanics of oblique convergence the distribution and magnitude of the strike parallel component of velocity in an obliquely converging thrust wedge or accretionary prism are determined by the geometry and mechanical properties of the wedge a mechanical analysis based on the assumption of a critical or stable geometry of the wedge for which the rate of cross strike deformation is zero leads to the following conclusions for different bulk rheologies 1 in a linear viscous wedge the strike parallel motion relative to the underthrust slab decreases exponentially away from the rear and is effectively concentrated in a shear zone with a width comparable to the thickness of the wedge at the rear the wedge also deforms by corner flow producing a circulation in the cross strike plane the strike parallel and corner flow velocities depend on the thickness and viscosity of the wedge and on the shear stresses applied to its lower and rear boundaries convergence at the wedge front is normal to strike 2 a critically tapered perfect plastic wedge moves coherently without internal deformation for low and moderate obliquities of the convergence vector the wedge moves at the same velocity as the backstop upper plate for high angles of obliquity the wedge moves laterally relative to the underthrust slab at a maximum velocity dependent on its dimensions and the stress conditions on its boundaries so that it is separated from the upper plate by a strike slip fault defining a forearc sliver no geometrical configuration exists that allows the strike parallel motion to be distributed through the wedge 3 a noncohesive coulomb wedge behaves in much the same way as a plastic wedge but the geometry and velocity depend only on its mechanical properties and the shear stresses on its boundaries and they are independent of scale

tropical extratropical interactions associated with an atlantic tropical plume and subtropical jet streak abstract tropical plumes tps are elongated bands of upper and midlevel clouds stretching from the tropics poleward and eastward into the subtropics typically accompanied by a subtropical jet stj streak and a trough on their poleward side this study uses ecmwf analyses and high resolution university of wisconsin nonhydrostatic modeling system trajectories to analyze the multiscale complex tropical extratropical interactions involved in the genesis of a pronounced tp and stj over the nh atlantic ocean in late march 2002 that was associated with extreme precipitation in arid northwest africa previous concepts for tp genesis from the literature are discussed in the light of this case study analysis of the upper level flow prior to the tp formation shows a northeastward propagation and a continuous acceleration of the stj over the atlantic ocean equatorward of a positively tilted upper level trough to the west of northwest africa both dynamic and advective processes contribute to the generation of th

the use of sequential extraction techniques for sedimentary phosphorus in eastern mediterranean sediments abstract the sedex method a sequential extraction scheme for sedimentary phosphorus phases was tested for use on eastern mediterranean sediments using two in house reference sediments in addition a 2 m nh4cl and a 0 1 m naoh extraction were tested to extract caco3 associated and iron bound p respectively these methods were then applied to samples of a sediment core from the eastern mediterranean abc26 the sum of extracted p phases of the reference sediments and core abc26 was not significantly different from total p and precision of each extraction was better then 17 1s except for detrital p and iron bound p extracted by cdb the naoh extraction dissolved only iron oxides associated with the surface of minerals while the cdb extraction dissolved a much larger fraction in core abc26 p produced in the sapropel layer s1 appeared to have diffused both upwards and downwards this p is now found as exchangeable loosely bound p and as iron oxide bound p in the adjacent oxic sediments there was evidence that p was released from caco3 p in the burn down zone which was affected by sulfide oxidation the organic c p molar ratio was 400 1 in the sapropel while it was indeterminate for the oxic layers

kinematics of the philippine sea plate in this study new instantaneous rotation vectors describing the motion of the philippine sea plate relative to surrounding plates are determined that most nearly satisfy all available geological geophysical and seismological observations along the plate margins pacific philippine and caroline pacific poles are generated from a set of trial eurasia philippine poles of rotation using published determinations of the eurasia pacific and caroline philippine poles the pacific philippine caroline pacific and eurasia philippine poles are then checked for agreement with 1 slip vectors determined from focal mechanisms of earthquakes along the ryukyu trench and the nankai trough 2 convergence at the sagami trough 3 extension in the mariana trough 4 extension behind the bonin trench 5 extension in the western sorol trough and 6 convergence at the mussau trench trial eurasia philippine poles are eliminated if predicted plate motions do not match observed plate motions the locations and rotation rates of the three best fitting poles are eurasia philippine 37 0 n 141 0 e 1 60 ma pacific philippine 3 8 n 130 4 e 1 68 ma caroline pacific 16 9 n 141 4 e 0 54 ma the plate motions predicted by these new poles are compared with the spatial distribution of earthquakes and new focal mechanism solutions in the complex region where the philippine pacific and caroline plates intersect intermediate and deep focus earthquake hypocenters along the southern mariana arc show a southward decrease in the length of the seismic zone which qualitatively agrees with the predicted convergence rate as the pole of rotation is approached and as the effect of back arc spreading in the mariana trough disappears the absence of volcanism and intermediate depth seismicity along the southernmost mariana yap and palau sections of the plate boundary is attributed to very low convergence rates a new focal mechanism solution along the trench south of guam is the first clear underthrusting solution found along the mariana trench and agrees with the convergence direction implied by the pacific philippine pole of rotation no clear underthrusting focal mechanism solutions were found along the yap and palau trenches although three high angle thrust solutions demonstrate that compression is occurring in the upper plate perpendicular to the plate boundary

fluid venting activity within the eastern nankai trough accretionary wedge a summary of the 1989 kaiko nankai results fluid flow manifestations within the outer 20 km of the eastern nankai accretionary wedge between the water depths of 4000 and 2000 m are concentrated near the outcrop of a shallow detachment fault immediately behind the frontal thrust near a depth of 3800 m and along a probable strike slip fault on the top of a 2000 m deep pop up structure 20 km inside the wedge using subbottom temperature measurements we estimate darcy upward flow velocities below clams colonies at the 3800 m site and show that one can associate a narrow range of velocities with the different types of colonies then combining a statistical survey of the distribution of colonies with the velocity estimates we compute a yearly outflow budget of 200 m 3 per metre of width of the wedge in the toe area this is forty times larger than the amount expected from steady state compactive dewatering we propose however that 80 90 of this flow is produced by shallow seawater convection because variations in sea bottom temperatures were too large we could not estimate fluid outflow budgets in the 2000 m venting area however 20 000 and 130 000 year old shells fossilized within widespread carbonate concretions indicate that fluid flow has been active in the 2000 m venting area since at least 130 000 years ago probably in a sporadic fashion chemical evidence indicates that a significant part of the fluid is coming from a depth of at least several hundred metres subbottom temperature measurements over a period of two months in the 3800 m venting site show fluctuations of 20 30 in the venting velocity below an active colony that have an apparent period of two weeks although the fluid circulation appears to be controlled by active faults at least in the shallow part of the wedge not every active fault corresponds to an aquifer in the absence of good high resolution seismic data and drill holes we cannot describe this plumbing system in any detail and are not able to show why some active faults correspond to fluid outlets and some do not

extreme fractionation of 234u238u and 230th234u in spring waters sediments and fossils at the pomme de terre valley southwestern missouri isotopic fractionation as great as 1600 exists between 234u and 238u in spring waters sediments and fossils in the pomme de terre valley southwestern missouri the activity ratios of 234u238u in five springs range from 7 2 to 16 in water which has been discharged for at least the past 30 000 years the anomalies in 234u238u ratio in deep water have potential usefulness in hydrologic investigations in southern missouri clayey units overlying the spring bog sediments of trolinger spring are enriched in 230th relative to their parent 234u by as much as 720 the results indicate that both preferential displacement via alpha recoil ejection and the preferential emplacement via recoiling and physical entrapment are significant processes that are occurring in the geologic environment

decadal oscillation of lakes and aquifers in the upper great lakes region of north america hydroclimatic implications we report a unique hydrologic time series which indicates that water levels in lakes and aquifers across the upper great lakes region of north america have been dominated by a climatically driven near decadal oscillation for at least 70 years the historical oscillation 13 years is remarkably consistent among small seepage lakes groundwater tables and the two largest laurentian great lakes despite substantial differences in hydrology hydrologic analyses indicate that the oscillation has been governed primarily by changes in the net atmospheric flux of water p e and stage dependent outflow the oscillation is hypothetically connected to large scale atmospheric circulation patterns originating in the midlatitude north pacific that support the flux of moisture into the region from the gulf of mexico recent data indicate an apparent change in the historical oscillation characterized by an 12 years downward trend beginning in 1998 record low water levels region wide may mark the onset of a new hydroclimatic regime

far upstream precursors of heavy precipitation events on the alpine south side this study examines the upper level flow pattern that foreshadows the comparatively frequent co occurrence of heavy precipitation events on the alpine south side together with potential vorticity pv streamers aloft over western europe it is hypothesized that each streamer is itself preceded by a dynamically distinctive and a thermodynamically active flow associated with the space time development and the ultimate breaking over europe of synoptic scale rossby waves the ecmwf european centre for medium range weather forecasts era 40 dataset is used to examine the nature of a streamer s coherent precursor pattern by deriving seasonal composites of refined hovmoller diagrams the upper level pattern of the pv and its gradient and mid tropospheric diabatic heating for the autumn and winter seasons the composites reveal a significant and coherent wave packet precursor signal in the pv field that can be traced back 1 week to the central and eastern pacific contemporaneously the coherent signatures in the composite pv gradient field and diabatic heating fields are conducive to triggering and or supporting the wave signal and also contribute to subsequent downstream wave breaking in spring the composite precursor pv signal appears over and propagates eastward from the atlantic basin and its limited zonal extent is attributed to the lack of a coherent pv waveguide in summer the signal appears essentially in situ in the hovmoller analysis but extends across the atlantic basin in the pv composite results an indication is also provided of the extent to which the composite characteristics are evident in two individual events and note is made of the study s implications for medium range forecasting copyright 2008 royal meteorological society

cross equatorial response to middle latitude forcing in a zonally varying basic state abstract a nonlinear model based on the shallow water equations is used to study cross equatorial propagation of forced waves in the presence of a longitudinally varying time mean basic state zonal wind field it is found that global scale planetary waves are unable to propagate past a critical latitude where the mean zonal wind speed vanishes however if the longitudinally asymmetric basic state includes a duet in which the zonal winds are westerly waves of zonal scale less than the zonal scale of the westerly duct may propagate from one hemisphere to the other even though the zonally symmetric mean zonal wind remains easterly in the equatorial region the amplitude of the response in one hemisphere to forcing in the opposite hemisphere increases strongly with the magnitude of the westerlies in the equatorial duct the existence and annual variations of a westerly duct region in the upper troposphere in the eastern pacific appear to account for some features of the low frequency variability in the no

fractionation and recycling of u and th isotopes in a semi arid endoreic depression of central syria abstract mesozoic and cenozoic carbonate rich formations including late cretaceous phosphate deposits are exposed in a structural depression which is known as the palmyra aulacogen the bottom of this depression has been occasionally filled by water bodies during quaternary humid episodes the bottom of the depression now forms a sabkha as a consequence of modern semi arid climatic conditions isotopic activity ratios and concentrations of u and th were measured in bedrock formations ground waters unsaturated soils and in quaternary lacustrine sediments cored in the sabkha in order to investigate the processes governing the fractionation and recycling of u and th within the endoreic depression the bedrock samples are close to secular equilibrium with the exception of phosphorites which show a 234 u deficit 234 u 238 u 0 83 0 04 upper soil horizons have a strong excess of 230 th 230 th 234 u 1 7 0 2 as a consequence of u removal the u loss occurs without fractionation 234 u 238 u 1 03 0 01 as it is co dissolved with the caco 3 matrix this is also shown by an inverse relationship between caco 3 vs 232 th in soils vertical profiles indicate transitional retention of u in the lower unsaturated soil horizons where deficiency in 230 th 230 th 234 u as low as 0 37 0 02 and high u concentrations up to ca 100 g t characterize secondary co precipitation of u and caco 3 which forms in response to downward decreasing pco 2 during water percolation events a rate of u removal of ca 10 4 to 10 5 a 1 from the upper soil horizons and a residence time of approximately 40 to 50 ka of soil particles in the u ablation zone were calculated using a simplified mathematical model based on the assumption that 230 th remains immobile in the soils the residence time of u corresponds to a rate of erosion of ca 1 cm for 10 3 a the activity ratios of the most recent lacustrine sediments of the sabkha upper 2 m in cores define a well correlated r 0 97 dilution curve of the form 230 th 234 u 1 91 0 03 234 u 232 th 1 0 15 0 01 this indicates that the radioisotopes inherited with the detrital fraction were diluted by an authigenic early diagenetic phase of u fixation a residence time for the diluting u ca 18 000 a can be evaluated from the asymptote value 0 15 0 01 this age corresponds to the last humid episode recorded in central syria the equivalent of the last glacial maximum at higher latitudes which was associated with lacustrine sedimentation in the basin detrital particles eroded from the surrounding soils were then characterized by 238 u 232 th and 230 th 238 u ratios lower than those observed in modern upper soil horizons i e by a longer residence time and a higher u leaching rate during their pedologic cycle

uranium series nuclides in the golden fault colorado u s a dating latest fault displacement and measuring recent uptake of radionuclides by fault zone materials abstract concentrations and isotopic ratios of u th and ra were measured in a fault zone near golden colorado where major displacement occurred between about 190 and 615 ka faulting created new surfaces for leaching and provided the pathways for u rich ground water uranium and230th the latter produced by the decay of dissolved234u are adsorbed by fault gouge hematite stained sand and brecciated sand and claystones the observed u enrichment is as much as six times baseline value and the simultaneous enrichment of230th is estimated at about ninefold relative to238u the adsorption of radionuclides chemically analogous to th such as pu iv and np and237np decay products on fault zone materials would contribute to the immobilization of high level radioactive waste in the vicinity of a repository in the event of leakage from engineered barriers into fractured rock mass

circumglobal teleconnections and wave packets associated with israeli winter precipitation this investigation performs diagnostic analyses with ncep ncar reanalysis data and israeli precipitation data to examine the dynamical processes that drive the teleconnection pattern associated with israeli winter precipitation anomalies a dipole teleconnection pattern with one centre of action over western europe and another centre of action over the eastern mediterranean em is found to be associated with the winter precipitation anomalies in israel this pattern is referred to as the southern levant sl pattern the positive negative phase of the sl pattern is found to be closely associated with enhanced reduced precipitation in israel composites of the 300 hpa stream function field show that both phases of the sl pattern are associated with eastward propagating wave packets that traverse about three quarters of the distance across the globe these wave packets which have a phase speed that is close to zero originate over the northeast pacific the east coast of north america for the positive negative sl phase and propagate eastward across the north atlantic western europe the em and southern asia until they eventually decay over the northwest pacific as these wave packets pass over western europe and the em the sl pattern is triggered and anomalies in israeli winter precipitation occur the sl pattern is found to have an e folding time scale of 4 days which is determined by the group velocity of the wave packet the time averaged spatial structure of the circumglobal wave packet closely resembles the first empirical orthogonal function of the hemispheric 300 hpa meridional wind field this suggests that the circumglobal wave packet may be a fundamental pattern of variability which is relevant for the entire northern hemisphere copyright 2008 royal meteorological society

organization of storm track anomalies by recurring low frequency circulation anomalies abstract from previous studies it is known that anomalous momentum fluxes by bandpass eddies are important in maintaining long lasting tropospheric flow anomalies evidence is presented that suggests that these anomalous fluxes do not occur at random but happen because the structure of storm track activity is modified by the presence of prominent low frequency large scale circulation anomalies this behavior is noted in an extended integration of a perpetual january simulation with a general circulation model gcm because nonlinear feedbacks between low and high frequency variability make it difficult to establish causal relationships between these two ranges of variability a model is constructed that approximates the storm track activity that would be expected to accompany a given low frequency without including the feedback of the high frequencies onto the low frequency state this model is based on the linearized primitive equations and uses a series of short integrations from random initial condi

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

diagnosing northern hemisphere jet portrayal in 17 cmip3 global climate models twenty first century projections the anthropogenic climate change impacts on the eddy jet system include an intensified midlatitude jet stream and an elevated tropopause as well as a poleward shifted jet while both responses are evident in phase 3 of the coupled model intercomparison project cmip3 ensemble mean twenty first century projections uncertainty in the poleward shift response is large enough that even the sign of the shift is not consistent among all models especially in the northern hemisphere the present analysis finds that twentyfirst century projections of the ensemble mean zonal wind change at 300 hpa predict a weakening and poleward expansion of the pacific jet and an overall expansion of the atlantic jet in contrast with the direct zonal mean climate change signal of increasing midlatitude upper level winds zonal winds are projected to decreaseinthecoreofthepacificandatlanticjets withincreasingzonalwindslocatedprimarilyinthejetexit regions and the meridional flanks of the jets uncertainties in sst changes from the twentieth century to the twenty first century between models are shown to impact modeled northern hemisphere jet stream changes

structure and evolution of baroclinic waves as inferred from regression analysis abstract the structure of transient disturbances with periods shorter than a week is documented an the basis of one point regression maps and longitude height sections derived from the national meteorological center nmc operational analyses for nine winter seasons the reference time series for the regression coefficients is highpass filtered normalized 500 mb height at a grid point in the pacific stormtrack the field variables that were regreesed on the reference time series were not filtered the regression statistics yield quantitative estimates of the amplitudes of the high frequency fluctuations in the geopotential height temperature wind ageostrophic wind vorticity divergence vertical velocity and outgoing longwave radiation fields the observed high frequency fluctuations exhibit a vertical and meridional structure suggestive of baroclinic waves evolving through the mature phase of their life cycle most of the results are in qualitative agreement with previous studies but the ageostrop

226ra and222rn contents of galapagos rift hydrothermal waters the importance of low temperature interactions with crustal rocks abstract hydrothermal waters collected by alvin from the galapagos spreading center are enriched in 222 rn by factors of 50 200 over bottom waters the 226 ra in the same samples however is enriched by less than a factor of four over bottom waters enrichments of 222 rn result primarily from recoil from rock surfaces while 226 ra enrichments are dominantly produced by high temperature alteration of cooling ridge volcanics the abundances of both nuclides exhibit positive correlations with temperature the data extrapolate to bottom water temperatures and compositions demonstrating the importance of seawater mixing different vents however have different mixing lines and vents with high 222 rn have low 226 ra we propose these patterns result from variations in the extent of low temperature crustal interaction with the hydrothermal fluids low temperature crustal waters can maintain high steady state 222 rn contents due to the recoil additions to the fluids the 226 ra however is strongly adsorbed at low temperatures resulting in low concentrations of this nuclide in low temperature crustal waters thus physical mixing of a crustal water component with hydrothermal waters or variable crustal path lengths of the hydrothermal fluids can account for the variable mixing lines and 222 rn 226 ra values of the hot springs the 222 rn 226 ra value appears to be a sensitive indicator of low temperature crustal interaction values 100 have experienced extensive crustal interaction and are indicative of diffuse hydrothermal flow values between 1 and 10 are indicative of primary hydrothermal fluids which have not experienced significant interaction with the crust values of 222 rn 226 ra between 10 3 and 10 4 are indicative of interaction of the hydrothermal fluids with sediments such values are observed in water samples from the galapagos hydrothermal mounds

helium radon and hydrothermal circulation associated with the carnmenellis radiothermal granite of southwest england the carnmenellis granite of southwest england has higher than average radioelement concentrations and a heat flow greater than 100 mw m 2 more than twice the united kingdom average measurements were made of 4he concentrations and 222rn activities in surface waters over the granite and its immediate host rocks high values greater than 48 ppb 4he 160 c min 222rn for either or both gases are interpreted as indicating discharge of groundwater from the upwelling limbs of hydrothermal convection cells 4he has a spatial distribution which agrees well with the observed variations of heat flow within the pluton but 222rn is also influenced by lithology and depth of groundwater flow although the distribution of convection cells is partly determined by the presence of nw se faults there is close similarity with theoretical models of groundwater circulation it is concluded that 4he and 222rn surveys provide a simple but effective method for mapping areas of modern hydrothermal activity

late cretaceous to early tertiary subduction history of the antarctic peninsula quantitative estimates of the rates and azimuths of phoenix plate convergence with the antarctic peninsula have been derived from plate rotation calculations for two periods in the late cretaceous and early tertiary 83 0 67 7 and 61 1 53 4 ma published marine magnetic anomaly identifications and flow lines interpreted from gravity anomaly maps were used in simple spherical geometry calculations to derive phoenix pacific stage rotations these were combined with published pacific antarctic rotation data to determine contemporaneous phoenix antarctic stage rotations the results indicate a significant change in azimuths of relative motion between the late cretaceous and early tertiary late cretaceous and perhaps earlier oblique subduction probably caused migration of fore arc slivers along the margin resulting in variations in width of the accretionary prism comparison between synthetic magnetic profiles and a 900 km long magnetic profile across ocean floor produced at the antarctic phoenix ridge during the early tertiary establishes the time of a major decrease in spreading rate and hence also in convergence rate as chron c23r 52 3 ma the associated change in subduction dynamics may have caused the dextral transtensional deformation observed in the george vi sound region and initiated uplift of blueschist facies rocks now exposed on smith island the calculated convergence history does not provide a simple explanation for the occurrence of high mg andesite lavas on alexander island which were erupted more than 20 ma before the antarctic phoenix ridge arrived at the margin the existence of these lavas implies either earlier subduction of another ridge or slab break up beneath alexander island

identification of latent faults using a radon test abstract this paper discusses the use of 222rn concentrations in water of natural springs as a geomorphological method to identify latent faults in low mid term activity areas the identification of this type of active fault may be crucial in hazard analysis structural geomorphology and in landscape evolution analysis the test used to identify these faults is based on the measuring of 222rn concentrations in water of springs linked to faults and comparison with those obtained from springs which although exactly the same lithological context are not linked with faults reference values if the difference between the measured value and the reference value is positive then an anomaly is identified and that measurement indicates a spring linked to a latent fault the test was applied and validated in springs linked to faults with a latent behaviour in cantabria northern spain these faults have shown an intermittent movement over the last 50 000 years and have contributed towards landslide processes playing a significant role in landscape evolution of the area

radium 226 and radon 222 in southern california groundwaters spatial variations and correlations as part of the radon and helium monitoring program for earthquake prediction studies in southern california concentrations of radium 226 in groundwaters have been measured along the major fault zones including the palmdale area radium was measured in order to obtain information on its spatial variation as well as baseline levels several measurements were made at selected sites to examine their temporal variations radium concentrations are used to define the portion of radium supported radon in the observed groundwater radon radium levels vary spatially by 4 orders of magnitude 0 015 to 146 dpm kg but temporally by a factor of 2 or less similar spatial and temporal variations are observed in groundwater radon 60 to 46 700 dpm kg the radon radium activity ratio ranges from 10 to 105 these values indicate that radon is in large excess over radium in groundwaters because of radon diffusion from the ambient rocks the spatial variations of radon radium and the activity ratio are probably due to different chemical and physical properties of the rocks through which groundwaters flow the dependence of groundwater radium concentrations on the water temperature and conductivity is explored it appears that radium increases in general with conductivity but not necessarily with temperature radium is probably leached more readily into the groundwater when the water is more conductive with more dissolved chemical constituents

is 222rn a suitable tracer of stream groundwater interactions a case study in central italy abstract river water infiltration into an unconfined porous aquifer 73 gravels 12 sands 15 silts and clays in the petrignano d assisi plain central italy was traced combining isotopic techniques 222 rn with hydrochemical and hydrogeologic techniques in order to characterize the system under study the 222 rn gave information about the river water residence times within the aquifer and hydrochemical data in a two component mixing model which allowed estimating the extent of mixing between surface waters and groundwater in wells at increasing distances from the river the mixing measured in the well closer to the riverbank indicated a higher contribution of river water up to 99 during the groundwater recession phase and a moderate contribution up to 64 during the recharge phase a model describing 222 rn concentrations in groundwater as the result of both parent daughter nuclide equilibrium and mixing process 222 rn mixing saturation model was used to describe observed rn concentrations and mixing index trends with the aim of evaluating water mean infiltration velocities along the transect the stream bank infiltration velocities obtained by the model ranged from 1 m day 1 during groundwater recharge periods when river water infiltration is lower to 39 m day 1 during recession phases when river water infiltration is larger

a study of uranium and thorium series isotopes in chalk groundwaters of lincolnshire u k a groundwater investigation is described in which uranium and thorium series radionuclides are applied to the study of the hydrogeologically well documented lincolnshire chalk aquifer system of north lincolnshire england the dominance of eh in controlling the uranium content of groundwaters is discussed and the 230th234u activity ratio used as an indicator of the speciation of uranium in highly reduced waters the 230th234u activity ratio approaches unity suggesting that the uranium in solution is behaving similarly to thorium in the 4 valence state in the oxidised environment the higher uranium content groundwaters exhibit lower 234u238u activity ratios a model of mixing young low 234u238u activity ratio fissure waters with old high 234u238u activity ratio pore waters is discussed but rejected it is considered that preferential dissolution of 234u in the lower rate weathering regimes produces the observed relationship between uranium content and activity ratio a method of in situ rn random release factor determination is suggested however the calculated values for rn are disproportionately high for a fissure flow system this along with evidence of a radium depleted aquifer matrix indicates that radium is being mobilised and transported from the pore water system to the fissure system and subsequently adsorbed by clay minerals lining the chalk fissures

unstable forearc stress in the eastern nankai subduction zone for the last 2 million years abstract transpressional tectonics characterizes the sw japan arc however we will show in this article that offshore seismic profiles and onshore mesoscale faults indicate that the eastern part of the forearc was subject to transtensional tectonics since ca 2 0 ma offshore normal faults imaged on the profiles run parallel to the nankai trough and started activity at 1 0 ma but transtensional tectonics commenced the onshore area earlier in order to understand the stress history in the forearc region we collected fault slip data from onshore mesoscale faults in plio pleistocene sedimentary rocks in the kakegawa area at the northeastern extension of the offshore normal faults most of the mesoscale faults are oblique normal indicating that the area was subject to transtensional tectonics the faults suggest that the compressional tectonic regime was followed by the transtensional one at 2 0 ma in agreement with regional tectonostratigraphic data which indicate that folding ceased at that time present compressional stress followed the transtensional tectonic regime sometime in the late pleistocene transtensional or extensional tectonic zone shifted from the kakegawa area to the offshore region these observations indicate that the state of stress just behind the accretionary prism of the eastern nankai subduction zone has been unstable in the last 2 million years suggesting that the forearc wedge has been at critical state in that gravitational force and basal shear traction on the wedge have been balanced but the forearc tectonics has been susceptible to small perturbations possible factors compatible with the observed stress history include the change of subduction direction of the plate at 1 0 ma and the rapid uplift of central japan thereafter

rossby wave packets on the midlatitude waveguide a review abstractrossby wave packets rwps are rossby waves for which the amplitude has a local maximum and decays to smaller values at larger distances this review focuses on upper tropospheric transient rwps along the midlatitude jet stream their central characteristic is the propagation in the zonal direction as well as the transfer of wave energy from one individual trough or ridge to its downstream neighbor a process called downstream development these rwps sometimes act as long range precursors to extreme weather and presumably have an influence on the predictability of midlatitude weather systems the paper reviews research progress in this area with an emphasis on developments during the last 15 years the current state of knowledge is summarized including a discussion of the rwp life cycle as well as rossby waveguides recent progress in the dynamical understanding of rwps has been based in part on the development of diagnostic methods these methods include algorithms to identify and track rwps

application of continuum models to deformation of the aleutian island arc continuum models were constructed to describe large scale deformation of the aleutian island arc over the past 5 m y these models consider the island arc as a continuum in the horizontal plane with the velocity boundary condition at the pacific edge stated as a fraction of pacific plate convergence transferred to the arc first a simple model of uniformly distributed strain is formulated to illustrate the mechanics of continuous deformation lineaments along the arc massif rotated about a vertical axis are matched by small element rotation calculated from the model however this model does not predict across arc variations in deformation and produces an unrealistic amount of crustal thickening after 5 m y a physically more meaningful model of deformation is the thin viscous sheet model based on averages of stress and rheology throughout the lithosphere the amount of motion transferred from the pacific plate to the arc is constrained by the rotated lineaments while the effective stress strain exponent n and the ability the lithosphere has to sustain crustal thickness contrasts the argand number are independent variables primarily bathymetry earthquake focal mechanisms and styles of faulting are used to evaluate the models the preferred model is one where the amount of motion transferred from the pacific plate is greater in an arc parallel direction than in an arc normal direction producing stresses consistent with strike slip faulting at the far western end of the arc and tensional stresses consistent with transverse normal faulting elsewhere in the arc massif this model agrees with observations of slip vectors by ekstr6m and engdahl 1989 who conclude that a portion of the arc parallel component of relative plate motion is taken up in the overriding plate this model implies that compressive stress transferred to the arc is small in comparison to along arc shear stress and that stresses conducive to strikeslip faulting are prevalent throughout the arc

circumglobal teleconnection in the northern hemisphere summer analysis of the 56 yr ncep ncar reanalysis data reveals a recurrent circumglobal teleconnection cgt pattern in the summertime midlatitude circulation of the northern hemisphere this pattern represents the second leading empirical orthogonal function of interannual variability of the uppertropospheric circulation the cgt having a zonal wavenumber 5 structure is primarily positioned within a waveguide that is associated with the westerly jet stream the spatial phases of cgt tend to lock to preferred longitudes the geographically phase locked patterns bear close similarity during june august and september but the pattern in july shows shorter wavelengths in the north pacific north america sector the cgt is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of western europe european russia india east asia and north america this implies that the cgt may be a source of climate variability and predictability in the above mentioned midlatitude regions the cgt has significant correlations with the indian summer monsoon ism and el nino southern oscillation enso however in normal ism years the cgt enso correlation disappears on the other hand in the absence of el nino or la nina the cgt ism correlation remains significant it is suggested that the ism acts as a conductor connecting the cgt and enso when the interaction between the ism and enso is active enso may influence northern china via the ism and the cgt additionally the variability of the cgt has no significant association with the arctic oscillation and the variability of the western north pacific summer monsoon the circulation of the wave train shows a barotropic structure everywhere except the cell located to the northwest of india where a baroclinic circulation structure dominates two possible scenarios are proposed the abnormal ism may excite an anomalous west central asian high and downstream rossby wave train extending to the north pacific and north america on the other hand a wave train that is excited in the jet exit region of the north atlantic may affect the westcentral asian high and thus the intensity of the ism it is hypothesized that the interaction between the global wave train and the ism heat source may be instrumental in maintaining the boreal summer cgt

experimental studies of condensation processes of silicate materials at low pressures and high temperatures i phase equilibria in the system camgsi2o6h2 in the temperature range 1200 1500 c and the pressure range ph2 10 6 to 10 9 bar phase equilibria in the system camgsi2o6h2 in the pressure and temperature ranges 10 9 to 10 6 bar and 1200 1500 c respectively have been experimentally determined the vaporous curve was determined by monitoring evaporation rate and compositional changes as a function of temperature crystalline diopside condenses from a gas phase along a vaporous curve with a positive slope of approximately 16 c log unitph2 bars from about 1360 c atph2 10 9 bar to 1388 c at 3 10 7 bar partially evaporated diopside at temperatures above its vaporous shows but systematic increase in ca mg with time and degree of evaporation there were no chemical changes with time and degree of evaporation of diopside within its own stability field at higher pressures a liquid condenses from the vapor with a slope of the liquid vapor curve of about 50 c log unitph2 bars the liquidus temperature decreases from 1388 c near the triple point to about 1350 c atph2 10 6 bar and is nearly vertical toph2 1 bar the ca mg of the liquid exceeds 1 indicating incongruent melting behavior although no additional crystalline phases were observed liquid diopside probably also evaporates incongruently provided that the phase equilibria of the diopside composition mimic those of other refractory phases condensing from the early solar nebula and that only h2 gas was present the experimental results indicate that the pressures in the nebula during condensation of crystals from vapor were significantly lower 10 4 bar alternatively if the higher pressure estimates are correct liquid silicate will condense from the vapor and vapor liquid and crystal liquid equilibria were more important during the petrogenetic processes resulting in aggregated silicate materials than suggested previously

trace element mobility in mine waters from granitic pegmatite u th ree deposits bancroft area ontario abstract small low grade granitic pegmatite u th ree deposits are found throughout the grenville geological province of eastern canada groundwater quality at historical mining properties in the bancroft area was investigated in order to better understand the mobility of trace elements that may pose health risks if there is renewed development of this class of mineral deposit groundwater samples were obtained from diamond drill holes flowing adits and flooded mine shafts uranium occurs almost entirely in the dissolved

a case study of downstream baroclinic development over the north pacific ocean part ii diagnoses of eddy energy and wave activity the sequential development of a western and then an eastern north pacific cyclone is examined in terms of eddy energy and a phase independent wave activity based on the propagation of both a contiguous wave activity center and eddy energy the development of the western cyclone appears to influence its downstream neighbor a quantitative comparison of these two diagnoses is made in terms of group velocity and only minor differences are found during much of the initial evolution it is only once the tropopause undulations lose their wavelike appearance at which point application of the group velocity concept itself becomes quite tenuous that the downstream propagation of eddy energy seems faster than that of wave activity conventional methods of tracking this wave packet are also briefly discussed

alpha emitting isotopes and chromium in a coastal california aquifer abstract the unadjusted 72 h gross alpha activities in water from two wells completed in marine and alluvial deposits in a coastal southern california aquifer 40 km north of san diego were 15 and 25 picocuries per liter pci l although activities were below the maximum contaminant level mcl of 15 pci l when adjusted for uranium activity there is concern that new wells in the area may exceed mcls or that future regulations may limit water use from the wells coupled well bore flow and depth dependent water quality data collected from the wells in 2011 with analyses for isotopes within the uranium actinium and thorium decay chains show gross alpha activity in marine deposits is associated with decay of naturally occurring 238 u and its daughter 234 u radon activities in marine deposits were as high as 2230 pci l in contrast gross alpha activities in overlying alluvium within the piedra de lumbre watershed eroded from the nearby san onofre hills were associated with decay of 232 th including its daughter 224 ra radon activities in alluvium from piedra de lumbre of 450 pci l were lower than in marine deposits chromium vi concentrations in marine deposits were less than the california mcl of 10 g l effective july 1 2014 but 53 cr compositions were near zero and within reported ranges for anthropogenic chromium alluvial deposits from the nearby las flores watershed which drains a larger area having diverse geology has low alpha activities and chromium as a result of geologic and geochemical conditions and may be more promising for future water supply development

the effects of midlatitude waves over and around the tibetan plateau on submonthly variability of the east asian summer monsoon abstract convective variability at submonthly time scales 7 25 days over the yangtze and huaihe river basins yhrbs and associated large scale atmospheric circulation during the mei yu season were examined using interpolated outgoing longwave radiation olr and ncep ncar reanalysis data for 12 yr having active submonthly convective fluctuation over the yhrbs within the period 1979 2004 correlations between convection anomalies over the yhrbs and upper level streamfunction anomalies at every grid point show two contrasting patterns one pattern exhibits high correlations along the northern to eastern peripheries of the tibetan plateau defined as the net pattern whereas the other has high correlations across the tibetan plateau defined as the at pattern composite analysis of the net pattern shows slow southward migration of convection anomalies from the northeastern periphery of the tibetan plateau to southern china in relation to southward migration of the mei yu front caused by simultaneous am

developing wave packets in the north pacific storm track developing wave packets in the western north pacific storm track are diagnosed observationally an abrupt upstream edge to baroclinic wave activity over the western north pacific facilitates comparisons between the observational results and previous theoretical predictions on the spatiotemporal evolution of an impulse disturbance results show that surface cyclogenesis events are preceded by a sharply peaked wave packet that originates poleward of the himalaya plateau and develops rapidly across the north pacific to north america composite wave packet structure is broadly consistent with linear theory for idealized models such as eady s the longitude height structure of the mature packet reveals deep growing waves with horizontal wavelengths of approximately 4000 km near the packet peak downstream from the peak amplitude decays exponentially and wavelength decreases approximately linearly to about 2500 3000 km at the leading edge meridional potential vorticity gradients are concentrated near the tropopause in contrast to linear theory the packets show an abrupt upstream edge and no evidence of upstream development as the packet travels through the along stream variations of the pacific jet stream the packet peak and leading edge group velocity vary these accelerations change the packet length and suggest that the pacific jet may act to focus the packets a sample of north atlantic storm track events reveals similar results and suggests that the atlantic storm track is often seeded by wave packets that originate over the western north pacific ocean in contrast atlantic packets refract equatorward and become trapped on the subtropical jet to the south of himalaya plateau suggesting perhaps less potential for seeding disturbances in the pacific storm track

horizontal energy propagation in a barotropic atmosphere with meridional and zonal structure abstract to investigate how the propagation of energy away from steady sources may be influenced by the horizontal structure of the time averaged flow in the troposphere solutions to a barotropic model are displayed and interpreted the model is steady and linearized about a basic state which varies in latitude and longitude emphasis is placed on cases where the longitudinal variations are gradual many of the results can be analyzed by locally applying tools developed for zonally symmetric basic states e g ray tracing and refractive indices simple background flows are constructed which have longitudinally confined critical lines reflective surfaces wave guides and regions conducive to propagation an example is given in which longitudinal derivatives of the basic state are significant the theory of ray tracing in a two dimensional wind must be employed as an interpretive tool in this case it is concluded that zonal variations tend to enhance poleward equatorward propagation in large scale tr

ground water geochemistry of 228ra 226ra and 222rn abstract 228ra 226ra and 222rn activities were determined on over 150 ground water samples collected from drilled public water supply wells throughout south carolina a wide range of aquifer lithologies were sampled including the crystalline rocks of the piedmont and sedimentary deposits of the coastal plain a significant linear relationship between log 228ra and log 226ra n 182 r 0 83 was indistinguishable between piedmont and coastal plain ground water median 228 ra 226 ra activity ratios for the piedmont 1 2 and coastal plain 1 3 ground water are close to estimated average crustal 232 th 238 u activity ratios of 1 2 to 1 5 corresponding to th u weight ratios of 3 5 to 4 5 a linear correlation was also found between log 222rn and log 226ra for piedmont n 68 r 0 62 and coastal plain n 89 r 0 64 ground water however the median 222 rn 226 ra activity ratio for piedmont ground water 6100 was much higher than for coastal plain ground water 230 higher excess 222rn activities may be due to greater retention of 226ra by the chemically active piedmont aquifers compared to the more inert sand aquifers sampled in the coastal plain the relationship between log 228ra and log 226ra was used to predict total ra 228 ra 226 ra distributions in appalachian and atlantic and gulf coastal plain ground water predictions estimate that 2 4 of appalachian and 5 3 of atlantic and gulf coastal plain ground water supplies contain total ra activities in excess of the 5 pci l limit established by the u s environmental protection agency these predictions also indicate that 40 50 of these ground water wells may be overlooked using the presently suggested screening activity of 3 0 pci l of 226ra for 228ra analysis

distribution of methane hydrate bsrs and its implication for the prism growth in the nankai trough abstract detailed mapping of a bottom simulating reflector bsr which marks the phase transition from the methane hydrate layer above the reflector to free gas below was conducted in the nankai accretionary prism off shikoku and tokai bsrs are widely distributed in the prism slope from the toe region to the forearc basin bsr positions provide us with the regional heat flow variations using pressure temperature conditions for methane hydrate stability estimated heat flows generally show constant values about 50 mw m2 shallower than the middle slope of the prism and gradually increase seaward in the lower prism slope occurrences of bsrs are regarded as accumulation of free gas beneath the base of a gas hydrate stability field bghs and or concentration of methane hydrate above the bghs these conditions can be accomplished by updip migration of methane gas because it is unlikely that such methane concentration is completed by in situ biogenic methanogenesis within sediments including low total organic carbon moreover sedimentation uplifting and sediment stacking by thrust faulting cause upward migration of the bghs and migration of methane from the dissociated hydrate to new bghs such recycling of methane gas may have actively occurred in accretionary prisms in contrast there are five regions of no bsrs the nankai trough floor prism toe slope basin steep slope and deep sea canyon the trough floor the prism toe and the slope basin are characterized by young sediments with low production of methane gas and sub horizontal strata unsuitable for migration of gases and fluids erosion at the steep slope and the canyon causes removal of hydrated sediments and downward movement of the bghs bsr distribution and thermal structure estimated from bsr positions offer information about active processes occurring in accretionary prisms

tectonic context of fluid venting at the toe of the eastern nankai accretionary prism evidence for a shallow detachment fault during the kaiko nankai diving cruise the peak of the venting activity was located near the top of the very first anticline the most prominent morphological feature between the mid slope 3870 m and the apex of the fold 3770 m is a 20 m high cliff cutting through subhorizontal massive mudstones affected by numerous joints the trend of this scarp is oblique to the fold axis and structurally controlled along two sharply defined nne sse and e w directions fresh talus and blocks found locally suggest active tectonics and recent erosion intense deformation is evident from strongly tilted strata restricted to the base of the cliff that we interpret as an upslope thrust at the scale of seabeam mapping this thrust can be followed eastward for more than 5 km along the 3820 m isobath two seismic lines recorded during one of the pre site surveys show deformation at shallow depth including small scale folding and thrusting affecting only the wedge shaped top sequence deeper layers can be traced continuously below this sequence we conclude that the boundary between the piggy back basin and the frontal fold turbidites acts as a shallow detachment fault and interpret the base of the cliff as the outcrop of the fault dense colonies ofcalyptogena clams and strongly nonlinear thermal gradients locate the major peak of fluid activity at the edge of the plateau above the main cliff scattered biological colonies as well as white bacterial mats and cemented chimneys were also found in a narrow belt along the base of the cliff fluid activity is thus closely related to the shallow detachment fault fluid being expelled both at the outcrop of the fault and above it through the overlying strata possibly using the very dense joint network

dating peat with u th disequilibrium some geochemical considerations abstract the applicability of the u th disequilibrium dating method utd for peat is investigated dating is performed by measurements of the u and th isotopes in the bulk material of the sample as well as in different fractions due to the complex geochemistry of u and th in organic matter dating peat by utd is not a simple and straightforward method it may appear from our results that the number of cases in which the method is applicable is limited because post formation contamination with th may occur however one interesting case the tenaghi phillippon core from greece seems to fulfill the requirement that little or no environmental th has entered the system after formation results obtained from this core agree well with 14 c data evidence is found for the theory that complexation of actinides with humic and fulvic acids limits the mobility of u and th the data can be explained assuming that ion exchange is the dominant process in the accumulation of u and th by peats

characterization and disequilibrium cases of radioelements in some syrian hot waters the radioactive and physical characteristics of syrian hot waters were studied the concentration of uranium its daughters and the 234u 238u activity ratios in the hot waters were measured by gamma and alpha ray spectroscopy the 234u 238u activity ratios showed that uranium in syrian hot waters are in an equilibrium state some anomalous observations of these ratios were explained by former leaching of the uranium from cretaceous phosphates by underground water also the results showed that the temperature of the studied hot waters was independent of the contained radioelements the temperature of hot waters is explained by the passing of these waters near the hot spot or by the relationship between the geological deposit of the aquifer rocks and the waters rather than the contents of the radioelements

a multifaceted climatology of atmospheric blocking and its recent linear trend abstract a dynamically based climatology is derived for northern hemisphere atmospheric blocking events blocks are viewed as large amplitude long lasting and negative potential vorticity pv anomalies located beneath the dynamical tropopause the derived climatology based on the 40 yr european centre for medium range weather forecasts ecmwf re analysis era 40 provides a concise coherent and illuminating description of the main physical characteristics of blocks and the accompanying linear trends the latitude longitude distribution of blocking frequency captures the standard bimodal geographical distribution with major peaks over the north atlantic and eastern north pacific in all four seasons the accompanying pattern for the age distribution the genesis lysis regions and the track of blocks reveals that 1 younger blocks 1 4 days are more prevalent at lower latitudes whereas significantly older blocks up to 12 days are located at higher latitudes 2 genesis is confined predominantly t

zones of origin for great lakes cyclones in north america 1899 1996 abstract the zones of origin for all cyclones that traversed the great lakes region from 1899 to 1996 are analyzed using a digital daily record of central pressure and location for individual cyclones plots of latitude of formation show that great lakes cyclones form or reform east of the rocky mountains at all latitudes between 25 and 65 n in winter about the same number of cyclones originate to the northwest as to the southwest of the great lakes region in spring the southwest zone is dominant the number of summertime cyclones is greatly reduced with the west zone of origin most active while the fall plot displays a transition between the summer and winter distributions the proportion of strong great lakes cyclones that originate in the southwest zone is greater than for all cyclones however the seasonal shifts in the latitudinal distributions of origin in the two datasets are similar an analysis of differences in frequencies by zone of origin for great lakes cyclones during months charac

asymmetry in the response of central eurasian winter temperature to amo the asymmetry in the teleconnection of the central eurasian winter surface air temperature sat with the atlantic multidecadal oscillation amo is discussed using observations and model simulations observations indicate that the winter sat over central eurasia 30 70 e 30 50 n shows significant positive anomalies during the warm amo period but weak and insignificant anomalies in the cold amo period in general the warm winters in central eurasia are associated with large scale negative sea level pressure anomalies in europe anomalous southwesterly winds at 850 hpa over europe the geopotential height anomalies at 500 hpa in the south of greenland northern europe western asia and the slant north south pattern jet stream anomalies at 200 hpa in the north and south of the caspian sea reverse patterns occur during cold winters these statistically significant features are observed in the warm phase of amo reversed circulation anomalies are observed during the cold phase of amo however these anomalies are weak and not statistically significant furthermore the asymmetry in the atmospheric response to amo is well supported by simulations with a suite of gfdl atmospheric model idealized experiments and four cmip5 models historical experiments both observations and simulations indicate that rossby waves propagating from the north atlantic eastward to eurasia emerge in the warm amo and disappear in the cold amo thus the different propagations of rossby waves induced by the different surface thermal conditions of the warm and cold amo are the potential connection between the north atlantic ocean and central eurasian climate and may explain the asymmetry

using 222rn to examine groundwater surface discharge interaction in the rio grande de manati puerto rico 222rn was used in the karst drainage basin of the rio grande de manati in puerto rico to study groundwater surface flow relationships locations of groundwater influx along two sections of the rio grande de manati were identified the 222rn measurements were used together with stream discharge data in a mass balance equation to quantify the groundwater inputs the investigation established that both of the sections of the rio manati surveyed not only gained groundwater but lost surface flow it was calculated that the river gained about 1 2m3s 1 and lost 0 5m3s 1 to the aquifer between ciales and united states geological survey gauging station 5 between united states geological survey gauging stations 6 and 7 groundwater influx and stream flow loss occurred simultaneously with groundwater inputs equalling surface discharge losses of 4m3s 1 the study successfully demonstrated the innovative application of 222rn as a geochemical tracer in examining groundwater surface flow relationships in a karst system

influence of the background state on rossby wave propagation into the great lakes region based on observations and model simulations abstractthe authors investigate the relationship between hydrology in the great lakes basin namely overlake precipitation and transient rossby waves using the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis data and historical output from phase 3 of the coupled model intercomparison project cmip3 the preferred path of observed rossby wave trains associated with overlake precipitation on lake superior depends strongly on season and appears to be related to the time mean upper level flow during summer and fall the northern hemisphere extratropical jet is relatively narrow and acts as a waveguide such that rossby wave trains traversing the great lakes region travel along the extratropical pacific and atlantic jets during other months the pacific jet is relatively broad which allows more wave activity originating in the tropics to penetrate into the midlatitudes and influence lake superior precipitation analysis is extended to cmip3 mod

radionuclide mobility in thucholitic hydrocarbons in fractured quartzite radioactive hydrocarbons thucholites fill joints and fissures in presvecokarelian quartzites around the town of vastervik southeastern sweden uranium series nuclides including stable end members and carbon isotopes have been measured in surface samples and in drill core material originating down to 60 m below the surface uranium both is adsorbed onto noncrystalline hydrocarbonaceous material and forms different mineral phases the amount of hydrocarbons and uranium rapidly decreases with depth below 60 m the accumulations were too scanty for sampling uranium series nuclides show distinct gradients the surface samples with uranium contents up to 50 wt have been enriched in uranium lead and particularly thorium in geologically recent time probably during the last glaciation along the drill cores thorium has been immobile whereas 226ra and 222rn have migrated uranium has been distinctly migratory at and close to the surface but more or less immobile below 20 m depth almost no foreign rad

u series disequilibria in early diagenetic minerals from lake magadi sediments kenya dating potential abstract at the southern end of the gregory rift valley lake magadi occupies the bottom of a relatively large drainage basin it is presently covered by a thick trona crust which overlies two silty clay units deposited during late pleistocene high lake stands these units consist of a mixture of detrital grains anorthoclase amphiboles quartz clays illite authigenic zeolites phosphates and sedimentary sodium silicates and cherts a late diagenetic calcite is occasionally observed the authigenic and or diagenetic mineralogical phases were extracted and analyzed for their uranium and thorium isotope contents all yielded highly correlated 234 u 232 th vs 238 u 232 th and 230 th 232 th vs 234 u 232 th isochrons defining two component mixing systems detrital and authigenic phases the detrital component is characterized by large excesses of 230th over 234u and by 230 th 232 th ratios carrying an imprint of the source rocks e g precambrian basement vs volcanics and indicating efficient uranium leaching processes during the previous pedologic cycle the slope of the isochrons defines the 234 u 238 u and 230 th 234 u ratios of the authigenic component i e the age of the uranium uptake episode zeolites yield an age of 10 4 0 6 ka this age is in agreement with the 14c chronology already established for the most recent high lake level episode in the basin 10 000 12 000 yr bp sodium silicates and cherts yield distinct ages of 98 5 20 and 6 3 ka respectively for the lower and upper lacustrine units these ages allow the conclusion that 1 sedimentary silicates are of late diagenetic origin and 2 that the lower lacustrine unit was deposited during a former high lake magadi level possibly during the lacustrine episode dated at 135 10 ka from uranium series measurements on littoral stromatolites finally the late diagenetic calcite which yields an age of about 5 ka indicates a significant change in the sediment interstitial water chemistry this is also shown by the occurrence of calcitic oncolites in flat deposits assigned to a mid holocene minor oscillation of lake magadi level on the basis of their 14c ages it is concluded that uranium series measurements in diagenetic minerals may give access to the age of their formation

phosphorus accumulation in marine sediments and the oceanic phosphorus cycle ideas about key factors in the oceanic mass balance of dissolved reactive phosphate have changed substantially i present an integrated overview of these here with an emphasis on evaluating the burial sinks for p and defining areas needing further research the major source of reactive p to the ocean is river input reactive p is delivered to the oceanic sediment water interface primarily in particulate organic matter p scavenged by hydrothermal iron rich oxyhydroxide particles with uptake in proportion to deep water phosphate concentrations represents a substantially smaller flux to the sediment water interface diagenetic transformations are important influences on the form of reactive p burial in marine sediments p burial occurs with organic carbon burial and as p associated with iron rich oxyhydroxide particles and coatings formation of authigenic p rich phases presumably apatite at the expense of organic p and oxide associated p is significant in open ocean marine sediments the authigenic p sink may represent a substantially larger portion of the sedimentary burial than indicated by previous estimates focused on p burial in organic rich continental margin sediments

shear partitioning in the eastern nankai trough evidence from submersible dives abstract submersible dives over the wedge of the easternmost nankai trough demonstrate the existence of a left lateral strike slip system parallel to the subduction zone this system develops as the trench turning northward toward land becomes highly oblique to the motion although shear partitioning is well known in other subduction zones the process here has the peculiarity of continuing northward into land

interpretation of temperature measurements from the kaiko nankai cruise modeling of fluid flow in clam colonies during the kaiko nankai detailed submersible survey numerous measurements of the temperature gradient inside the sediment were performed on the deepest active zone of fluid venting which is situated on the anticline related to the frontal thrust using the ifremer t naut temperature probe operated from the submersiblenautile we thus obtained the temperature structure below different types of clam colonies associated with fluid venting we used the finite element method to model the thermal structure and fluid flow pattern of these vents and to determine the velocity of upward fluid flow through the colonies on a biological basis four types of clam colonies are defined each biological type has distinctive thermal characteristics and corresponds to a particular fluid flow pattern darcian flow velocity in the most active type of colony type a is of the order of 100 m a the total amount of fluid flowing through colonies in the studied area is estimated to be 200 m3 a 1 per metre width of subduction zone most of the flow is vented through type a colonies this value is more than one order of magnitude too high to be compatible with the amount of water available from steady state compaction of sediments in the whole wedge thermal arguments suggest that downwelling of seawater occurs around type a colonies and that seawater is then mixed with upcoming fluids at a depth of 1 or 2 metres furthermore finite element modeling shows that a salinity difference of a few parts per mil between the upcoming fluids and seawater is sufficient to drive convection around the colonies as water samples from a few vents indicate that the fluid source should actually be significantly less saline than seawater we propose that the very high fluid flows measured are a consequence of the dilution of the fluid of deep origin with seawater by a factor of 5 to 10

uranium thorium series radionuclides in brines and reservoir rocks from two deep geothermal boreholes in the salton sea geothermal field southeastern california naturally occurring u and th series radionuclides have been analyzed in high temperature brines 300 c 25 wt dissolved solids and associated rocks from two deep geothermal wells located on the northeastern margin of the salton sea geothermal field ssgf these data are part of a study of the ssgf as a natural analog of possible radionuclide behavior near a nuclear waste repository constructed in salt beds and permit evaluation of some characteristics of water rock interaction in the ssgf rock brine concentration ratios rc dpm g rock dpm g brine were found to vary from near unity for isotopes of ra pb and rn to about 5 105 for 232th the high sorptivity of 232th is closely followed by that of 238u and 234u rc 5 104 suggesting that u is retained in the 4 oxidation state by the reducing conditions in the brines the relatively high solubility of 210pb and 212pb is attributed to formation of chloride complexes while the high ra solubility is attributed to chloride complexing a lack of suitable adsorption sites due to the high brine salinity and temperature and the reducing conditions that prevent mno2 and raso4 from forming the 228ra226ra ratios in the brines are approximately equal to those of their parents 232th230th in associated rocks indicating that ra equilibration in the brine rock system is achieved within the mean life of 228ra 8 3 years the 224ra228ra ratios in these brines are about 0 7 indicating that either 1 brine composition is not homogeneous and 224ra decays in fracture zones deficient in ra and th as the brine travels to the wellhead or 2 ra equilibration in the brine host rock system is not complete within the mean life of 224ra 5 2 days because the desorption of 224ra from the solid phase is impeded the 228ac228ra activity ratio in the ssgf brines studied is 0 1 and from this ratio the residence time of 228ac in the brine before sorption onto solid surfaces is estimated to be 70 minutes indicating the potential for rapid removal of reactive isotopes fom brines the brine is greatly enriched in 226ra 2 3 dpm g about 104 105 times that of its parent 230th while reservoir rocks are about 10 deficient in 226ra relative to 230th material balance calculations for 2226ra and 18o suggest that brines reside in the reservoir for 102 103 years that the ssgf formed 10 000 40 000 years b p and that porosity cannot be more than 20

radium content and the 226ra228ra activity ratio in groundwater from bedrock the relative abundance of 226ra and 228ra were determined in the groundwater from 125 drilled wells containing from 0 1 to 51 3 pci l of 226ra the determination of 228ra was carried out with a liquid scintillation counter by measuring only the weakly energetic particles emitted from 228ra thus the interference from the daughter nuclides of 226ra was avoided without specific separation of 228ac the direct measurement of 228ra made the method decisively simpler and faster in terms of the chemistry involved the concentration of 228ra was found to be independent of the amount of 226ra present in the samples the concentrations of 228ra were nearly the same over the whole range of 226ra concentrations and the average sol226ra228ra ratio sharply increased as the 226ra content of water increased the 226ra228ra ratio in the drilled wells varied from 0 3 to 26 abnormally high 226ra228ra ratios were found in areas with known uranium deposits as well as in several drilled wells at other locations the abnormally high 226ra228ra ratios present in groundwater suggest that the radioactivity anomaly is caused by uranium deposits and not by common rocks in samples with a low radioactivity level the average 226ra228ra ratio was slightly below unity corresponding to the typical u th ratio of granite the most common kind of rock in the study area the samples from the rapakivi area proved to be exceptional in that they had a low 226ra228ra ratio independent of the concentration of 226ra

state of disequilibrium between 238u 234u 226ra and 222rn in groundwater from bedrock abstract approximately one thousand drilled wells were investigated for their natural radioactivity the determinations of 238u 234u 226ra and 222rn from 310 samples showed a high state of radioactive disequilibrium between the members of the uranium series present in water the 238 u 226 ra activity ratio usually fell in the range 1 20 and the 238 u 222 rn activity ratio in the range 1 20 10 4 the highest activity ratios being from samples with an elevated uranium content the 234 u 238 u activity ratio varied between 0 76 and 4 67 the most frequent values showing a 60 excess of 234u in the samples most of the 234 u 238 u activity ratios near unity were found in samples with a high uranium content several drilled wells with anomalously high uranium contents were found in southern finland the average 226ra and 222rn contents of these wells were not exceptionally high which suggests high mobility of uranium in groundwater from the areas involved

tectonic significance of the cold seepage zones in the eastern nankai accretionary wedge an outcome of the 15 years kaiko projects abstract the tectonic significance of the cold fluid venting in the eastern nankai accretionary wedge has been elucidated based upon results of precise mapping and submersible observation executed since 1984 under the french japanese cooperative projects kaiko i ii kaiko nankai and kaiko tokai in conjunction with studies of the japan trench sagami bay and other regions the very sharp boundary of benthic communities associated with temperature anomalies indicates the occurrence of focused upflow of nutrient rich fluids through cracks in the carbonate crust existing on a near surface horizon of permeable sediment the linear alignment of venting zones is a surface expression of the shallow detachment faults methane rich fluids expelled from the conduit along a fault migrate in the overlying permeable sediment and react with circulating sea water containing sulfate to produce hydrogen sulfide and carbonate precipitate en echelon or zigzag patterns of the cracks are developed in the carbonate crust under the influence of tectonic shear stress it has been concluded that bivalve communities grow on a thin veneer of sediment above the cracks of carbonate through which fluid containing hydrogen sulfide diluted with sea water flows out on the other hand bacterial mats seem to flourish either on thin sediment overlying the fault conduit or over a thick cover of sediment without carbonate crust in the former case bivalves cannot grow because venting fluids are too dense with methane and hydrogen sulfide to maintain the oxygen rich condition of the bottom water in the western nankai trough fine grained less permeable sediment cover seems to prevent circulation of fluids whereas methane appears to be widespread in the deeper sedimentary layer there major distinctions in modes of seepage among sites are presumed to be caused by 1 the tectonic regime causing channels of upward fluid venting 2 rates and composition of venting fluids affected by mixing rates of sea water and 3 the permeability and thickness of the near bottom sediment

geometry and relative motion of the philippine sea plate and pacific plate beneath the kanto tokai district japan the recent acquisition of high density and improved seismic data by the kanto tokai k t observational network of the national research institute of earth science and disaster prevention requires the revision of conventional plate configuration models for the k t district we propose a new interpretation of the configuration and relative motion of the philippine sea phs plate pacific pac plate and eurasian eur plate on the basis of the distribution of hypocenters velocity structure and focal mechanisms in the k t district the new model for the configuration of the phs and pac slabs clearly delineates the phs slab subducting northwestward beneath the k t district from the sagami and suruga troughs and the pac slab subducting westward beneath the phs slab from the japan trench the thickness of the descending phs slab is estimated to be 30 5 km the proposed configuration of the phs slab is significantly different from those obtained by other researchers including our own previous study the new model is fully consistent with global plate motion data the new model leads to an interpretation of the tectonic processes taking place beneath the k t district for the sagami trough wing of the phs slab the northeastern portion of the slab is dipping northwestward in direct contact with the upper surface of the pac slab the southwestern portion carrying the izu peninsula has been bent upward because of its buoyancy producing the observed contorted shape for the suruga trough wing the dip direction of the phs slab gradually changes from northwestward at the eastern portion to northward at the western portion the new model also indicates the presence of offset within the phs slab between the sagami and suruga trough wings this area is characterized by a low level of seismic activity the absence of a high velocity structure and the presence of quaternary volcanoes it seems reasonable to speculate that the distribution of quaternary volcanic edifice construction is controlled by the location of the offset within the phs slab in view of this new model the tectonic processes of large earthquakes which occurred recently in the studied area are also reexamined

interplate coupling and relative plate motion in the tokai district central japan deduced from geodetic data inversion using abic summary the spatial distribution of the strength of interplate coupling between the subducting philippine sea and overlying continental plates in the tokai district central japan was investigated in detail through the inversion analysis of geodetic data using akaike s bayesian information criterion abic the geodetic data used for the analysis are annual rates of level changes 1972 1984 and horizontal length changes 1977 1988 which presumably represent average crustal movements during the interseismic period the result of the inversion analysis shows the existence of a strongly coupled region extending from 10 to 30 km in depth the total seismic moment accumulated in this area since the last event the 1854 ansei earthquake is roughly estimated to be 5 5 1027 dyne cm which corresponds to ms 7 8 the interplate coupling becomes weaker toward the shallower and deeper portions this is consistent in general tendency with a rheological model inferred from petrological viewpoints the strength of coupling also tends to decrease toward northeast over the west coast of suruga bay the direction of plate convergence inferred from the inversion analysis is oriented n30 w this is significantly different from the direction of relative plate motion between the philippine sea and eurasian plates but concordant with that between the philippine sea and north american plates

uranium geochemistry in groundwater from tertiary sediments abstract dissolved u concentrations and activity ratios ars of the u isotopes in the 238 u decay series were measured in ground and surface waters as part of an investigation to delineate the water quality in a proposed uranium mining area of northwest nebraska in oxidizing groundwaters from 67 wells completed in the tertiary sediments increasing u concentrations in the direction of groundwater flow generally were associated with a maturation of the formation water as evidenced by evolutionary trends in major ion character the increased u levels probably are associated with leaching as shown by the positive correlation between u concentrations and total dissolved solids tds r 0 83 the inverse relationships between tds and u ars r 0 73 and u levels and ars r 0 72 indicate that the decay of excess u 234 is related to maturation of the formation water and to sediment leaching along the flowpath the data are described by a model which incorporates etching decay and recoil and suggests that aquifer residence time can be estimated from the tds level the levels of soluble u in a reducing uraniferous hydrogeologic unit near crawford nebraska are affected by the proximity of the sample collection to ore in groundwater samples having similar chemistries na so 4 cl type similar ehs and collected from a close knit pattern u concentrations ranged from 0 01 to 2 037 g l 1 and ars ranged from 0 75 to 12 6 this high variability in u levels and ars is indicative of uranium ore in small areal studies where low ars almost always are associated with high u concentrations

234u 238u activity ratios of dissolved uranium in groundwaters from a jurassic limestone aquifer in england abstract uranium contents and234u 238u activity ratios have been determined for groundwaters from the lincolnshire limestone artesian aquifer in eastern england changes in the quantitative and isotopic chemistry of the dissolved uranium are explained in terms of a mixing model involving the rapidly moving fissure water and much older water stored in the pore system of this oolitic limestone the western part of the aquifer closest to recharge is dominated by oxidising groundwaters which then enter a reducing zone towards the east where there is an abrupt decrease in eh and the chlorinity of the groundwaters begins to increase uranium contents in the oxidising zone range from 0 7 to 3 4 g kg 1 and234u 238u activity ratio of this dissolved uranium is close to unity the equilibrium value the uranium content decreases abruptly when the grounwaaters enter the reducing zone averaging 0 04 g kg 1 east of the oxidation reduction barrier simultaneously with the decrease in uranium content there is an increase in234u 238u activity ratio and this ratio increases to a maximum within 7 km of the oxidation reduction barrier this increase in activity ratio is attributed to enhanced234u solution due to234th recoil from uraniferous fissure surfaces east of the oxidising zone the activity ratio of dissolved uranium in the ancient pore waters could in principle reach high values due to234th recoil from the oolith surfaces however the activity ratio actually declines further east and this can only be explained as a consequence of mixing with pore waters in which the uranium activity ratio is closer to equilibrium 234th recoil from the oolith surfaces has probably been inhibited by sealing of the uranium bearing surfaces in the process of oolith cementation

relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks north carolina usa article i nfo article history accepted 21 october 2008 naturally occurring radionuclides uranium radium and radon major dissolved constituents and trace elements were investigated in fresh groundwater in 117 wells in fractured crystalline rocks from the piedmont region north carolina usa chemical variations show a general transition between two water types 1 slightly acidic ph 5 0 6 0 oxic low total dissolved solids tds waters and 2 near neutral oxic to anoxic higher tds waters the uranium radium and radon levels in groundwater associated with granite rolesville granite are systematically higher than other rock types gneiss metasedimentary and metavolcanic rocks water chemistry plays a secondary role on radium and radon distributions as the 222 rn 226 ra activity ratio is correlated with redox sensitive solutes such as dissolved oxygen and mn

late quaternary floodplain sedimentation along the pomme de terre river southern missouri abstract new cross sections and dates from along the pomme de terre river clarify the complex local history of valley development and floodplain sedimentation the observed history begins with a series of ancient bedrock strath terraces that record past bedrock valley positions at 15 5 to more than 58 m above the modern bedrock floor each strath is capped by 1 2 m of channel gravel and sand permeated by red clay sometime previous to ca 140 000 yr b p a much lower bedrock valley only about 5 6 m above the modern level was excavated by 140 000 yr b p accumulation of red and gray mottled silty clay had commenced and had reached to 8 5 m above the modern floodplain before 48 900 900 14 c yr b p sometime between ca 49 000 and 45 000 14 c yr b p erosion caused abandonment of an oxbow meander and lowered the bedrock valley to about its present depth younger yellowish red and gray mottled silty clay alluvium then began accumulating this mid wisconsinan fill reached to 2 5 m above the modern floodplain sometime before 31 800 1340 14 c yr b p at which time another erosional phase was in progress a late wisconsinan olive clay accumulated between 27 480 1950 and ca 23 000 14 c yr b p followed by approximate stability until 13 550 400 14 c yr b p after stability an erosional episode began but by 10 200 330 14 c yr b p deposition of a distinctive brown clayey silt was underway this early holocene fill reached to about the same level as the mid wisconsinan fill by 8100 140 14 c yr b p erosion occurred between this date and 7490 170 14 c yr b p but the former floodplain level was rapidly reattained and was apparently stable until ca 5000 14 c yr b p finally erosional unconformities and 17 dates from the brown clayey silt and from younger grayish brown silty sand underlying the modern floodplain record subsequent episodes of floodplain erosion at ca 5000 2900 1500 and 350 14 c yr b p the timing of pomme de terre floodplain sedimentary regimes characterized by net aggradation erosion or stability may have been controlled by climate in particular both periods of stability appear to have been coeval to times of strongly zonal upper atmospheric circulation intensified zonal circulation would have resulted in less frequent large floods and an increased dominance by floods of small to moderate size in contrast there are no obvious parallels to be drawn between this local alluvial history and sea level or glacial outwash induced baselevel changes

234u 238u 230th 232th systematics in saline groundwaters from central missouri saline groundwaters with 4 7 to 26 total dissolved solids were sampled from springs and artesian wells in mississippian and ordovician carbonates and sandstones in central missouri u th isotopic variations provide a means of evaluating processes of water rock interaction and fluid mixing and estimating the time scales of element transport recently developed mass spectrometric techniques are used to make isotopic measurements on small volume groundwater samples 0 1 4 l with high precision e g 5 for 234 u 238 u activity ratios the groundwaters have a wide range of 238 u concentrations 50 10 12 to 200 10 12 g g 234 u 234 u activity ratios 2 15 16 0 232 th concentrations 0 10 10 12 to 33 10 12 g g and 230 th concentrations 0 91 10 17 to 26 10 17 g g unfiltered and filtered 0 4 m 0 1 m aliquots of a saline sample have the same isotopic composition and concentration of u indicating that 234 u and 238 u occur almost entirely as dissolved species the concentration of 232 th is up to seven times lower in filtered vs unfiltered aliquots indicating that 232 th is predominantly associated with particulates in the groundwaters in contrast most of the 230 th is in solution previous geochemical studies indicate that 1 the saline waters originated as meteoric recharge and evolved through halite dissolution reactions with silicates and saline dilute mixing processes during a long distance flow history and 2 interaction with limestone and dolomite aquifer rocks in central missouri has been limited a consistent relationship between u ca and 234 u 238 u activity ratio is observed in the groundwaters and provides constraints on the u ca ratios and 234 u 238 u activity ratios of end member reservoirs and on the processes of isotopic exchange in this water rock system model calculations that simulate 1 saline dilute groundwater mixing and 2 limited extents of dissolution of carbonate aquifer minerals by the groundwaters can account for the variations in u ca 234 u 238 u and 18 o 16 o in the suite of water samples the model calculations demonstrate that dissolved u isotopic compositions can be a sensitive indicator of water rock interaction which in turn limits the usefulness of 234 u 238 u disequilibria for groundwater age determinations the concentration of dissolved 230 th in the groundwaters is 1 two to three orders of magnitude below 230 th 234 u equilibrium activity levels and 2 significantly in excess of concentrations estimated for the supply of th to solution via desorption and dissolution a model involving the derivation of the excess 230 th from the in situ decay of dissolved 234 u in the groundwaters indicates the operation of an adsorption mechanism on the time scale of 10 10 3 years the results reported here may have broader application to the assessment and management of hazardous chemical species in natural environments

structure genesis and scale selection of the tropical quasi biweekly mode the quasi biweekly mode qbm and the 30 60 day mode are two major intraseasonal oscillations isos in the tropics the qbm is known to have a major influence in determining the active and break conditions of the indian monsoon during the northern summer a westward propagating equatorial rossby wave with quasi biweekly period influences the australian monsoon during the northern winter universality between the summer and winter qbm is established through analysis of daily circulation and convection data for 10 years it is shown that the mean spatial structure of the qbm in circulation and convection resembles that of a gravest meridional mode equatorial rossby wave with wavelength of about 6000 km and westward phase speed of approximately 4 5 m s 1 however the maximum zonal wind occurs at around 5 n 5 s during the northern summer winter the wave structure appears to be translated northward southward by about 5 during the northern summer winter the relationship between outgoing long wave radiation and circulation data indicates that the mode is driven unstable by coupling with moist convection similarity in temporal and spatial characteristics of the mode during the two seasons leads us to propose that the same mechanism governs the genesis and scale selection of the mode in both the seasons an acceptable mechanism for genesis and scale selection of the qbm has been lacking in the present study a mechanism for genesis and scale selection of the observed qbm is proposed a simple 2 layer model that includes a steady ekman boundary layer bl formulation incorporating effect of entrainment mixing is constructed for the convectively coupled equatorial waves without influence of the background mean flow moist feedback in the presence of frictional bl convergence drives the gravest meridional mode equatorial rossby wave unstable with observed wavelength and period but with zonal winds symmetric about the equator potential temperature perturbation associated with the rossby wave is in phase with relative vorticity perturbation at low level the bl drives moisture convergence in phase with the relative vorticity at the top of the bl release of latent heat associated with the bl convergence enhances the potential temperature leading to a positive feedback the mean flow over the indian ocean and western pacific at low levels is such that the zero ambient absolute vorticity or the dynamic equator shifts to around 5 n 5 s during summer winter and results in a shift of the unstable rossby waves towards the north south by about 5 the resulting structure of the unstable rossby mode resembles the observed structure of the biweekly mode it is shown that neither evaporation wind feedback nor vertical shear of the mean flow is crucial for the existence of the mode however these processes marginally modify the growth rate and make the structure of the unstable wave more realistic