convectively forced internal gravity waves results from two dimensional numerical experiments two dimensional numerical simulations were performed to investigate the nature of tropospheric internal gravity waves of the type which are observed to occur above active thermal convection over an unstable boundary layer these gravity waves are believed to be excited by a combination of pure thermal forcing and by the boundary layer eddies and cumulus clouds acting as obstacles to the flow in the presence of mean environmental wind shear large amplitude internal gravity waves were obtained in the simulations with amplitudes and horizontal scales similar to the 12 june 1984 aircraft observations over western nebraska this was a day with strong wind shear in the lowest 3 km above the ground and with scattered cumulus clouds topping the boundary layer the simulations show that there is significant difference between the early time solutions as might be predicted by linear theory and late time solutions for the boundary layer eddy structure a layer interaction occurs in which gravity waves of the stable layer are excited by the boundary layer convection there is evidence to suggest that this layer interaction occurs both with and without shear but that it is stronger in the presence of low level shear results indicate that shear or the obstacle effect is a more efficient generator of gravity waves than is the pure thermal forcing the simulations show that the gravity waves initially forced by the boundary layer eddies lead to a feedback mechanism that acts to organize the boundary layer eddies and the cumulus convection the solutions suggest that the character of fair weather convection moist or dry is a non local problem involving at times the full depth of the troposphere the clouds produced in the simulations have very little influence on the wave field or boundary layer eddy structure as they are relatively small cumuli on the other hand the clouds are strongly influenced by the interactions between the wave and eddy fields upshear growth of cumulus clouds similar to that which is frequently observed in nature is reproduced in the simulations the development of feeder feeder is used here in a dynamical sense only clouds on typically the upshear side of the cloud is found to be a result of the interaction between the gravity wave field and the dry and moist convection the relative phase velocity between the gravity waves and the cloud plays a crucial role in determining the character of the cumulus cloud growth in the present simulations these simulations suggest that the dynamics both internal and external to the boundary of a cumulus cloud is a complicated mix between wave dynamics and the usually considered convection dynamics a brief discussion of the implications of the present results to cloud boundary baroclinic instability dynamics is also presented

diurnal shear instability the descent of the surface shear layer and the deep cycle of equatorial turbulence a new theory of shear instability in a turbulent environment is applied to eight days of velocity and density profiles from the upper equatorial pacific this period featured a regular diurnal cycle of surface forcing together with a clear response in upper ocean mixing during the day a layer of stable stratification and shear forms at the surface during late afternoon and evening this stratified shear layer descends leaving the nocturnal mixing layer above it using high resolution current measurements the detailed structure of the descending shear layer is seen for the first time linear stability analysis is conducted using a new method that accountsfortheeffectsofpreexistingturbulenceoninstabilitygrowth shearinstabilityfollowsadiurnalcycle linked to the afternoon descent of the surface shear layer this cycle is revealed only when the effect of turbulence is accounted for in the stability analysis the cycle of instability leads the diurnal mixing cycle typically by 2 3h consistent with the time needed for instabilities to grow and break late at night the resulting turbulence suppresses further instabilities lending an asymmetry to the mixing cycle that has not been noticed in previous measurements deep cycle mixing is triggered by instabilities formed as the descending shear layer merges with the marginally unstable shear of the equatorial undercurrent in the morning turbulence decays and the upper ocean restratifies wind accelerates the near surface flow to form a new unstable shear layer and the cycle begins again

modulation of equatorial turbulence by a tropical instability wave 1 strong modulation of turbulent mixing by a westward propagating tropical instability wave tiw was observed in the stratified shear layer between the equatorial undercurrent euc and the surface mixed layer during october and november 2008 at 0 n 140 w the unique deep diurnal cycle mixing in the stratified layer beneath the equatorial cold tongue was observed where nighttime turbulent mixing was a factor of 10 greater than during daytime the turbulent kinetic energy dissipation rate e was 10 6 w kg 1 and the turbulent heat flux was 500 w m 2 at least 5 10 times greater than observed previously in the central equatorial pacific turbulence mixing varied significantly during the four distinct phases of the meridional flow associated with the tiw observations during the northward to southward transition recorded the largest values of reduced shear squared the thickest nighttime surface mixed layer the deepest penetration of the deep cycle turbulence and the largest turbulent heat flux and largest integrated e in the deep cycle layer dcl during steady southward flow the depth of the bases of the nighttime surface mixed layer and of the dcl were the shallowest a 50 m thick layer of strong turbulence was observed immediately above the euc core during the northward to southward and steady southward phases here the average e exceeded 10 6 w kg 1 the eddy diffusivity exceeded 10 3 m2 s 1 and the turbulent heat flux was 500 w m 2 to parameterize mixing in the central equatorial pacific accurately numerical models must simulate the enhancement of mixing associated with tiws and also the variability of mixing in different tiw phases

centroid moment tensor solutions for july september 1998 abstract centroid moment tensor solutions are presented for 214 earthquakes that occurred during the third quarter of 1998 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging plenum new york 19 785 797 a new model of anelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of anelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms

sources of tsunami and tsunamigenic earthquakes in subduction zones we classified tsunamigenic earthquakes in subduction zones into three types earth quakes at the plate interface typical interplate events earthquakes at the outer rise within the subducting slab or overlying crust intraplate events and tsunami earthquakes that generate considerably larger tsunamis than expected from seismic waves the depth range of a typical interplate earthquake source is 10 40km controlled by temperature and other geological parameters the slip distribution varies both with depth and along strike recent examples show very different temporal change of slip distribution in the aleutians and the japan trench the tsunamigenic coseismic slip of the 1957 aleutian earthquake was concentrated on an asperity located in the western half of an aftershock zone 1200km long this asperity ruptured again in the 1986 andreanof islands and 1996 delarof islands earthquakes by contrast the source of the 1994 sanriku oki earthquake corresponds to the low slip region of the previous interplate event the 1968 tokachi oki earthquake tsunamis from intraplate earthquakes within the subducting slab can be at least as large as those from interplate earthquakes tsunami hazard assessments must include such events similarity in macroseismic data from two southern kuril earthquakes illustrates difficulty in distinguishing interplate and slab events on the basis of historical data such as felt reports and tsunami heights most moment release of tsunami earthquakes occurs in a narrow region near the trench and the concentrated slip is responsible for the large tsunami numerical modeling of the 1996 peru earthquake confirms this model which has been proposed for other tsunami earthquakes including 1896 sanriku 1946 aleutian and 1992 nicaragua

numerical modelling of tsunami generation and propagation from submarine slumps the 1998 papua new guinea event summary deep and large submarine slumps may generate tsunamis as disastrous as tsunamis of tectonic origin such a landslide is likely to be the origin of the 1998 july 17 tsunami of papua new guinea the deadliest tsunami in the last 50 years water waves devastated a 20 km stretch of coastline wiping out three villages and killing more than 2200 people a numerical model has been developed to study the efficiency of deep slumps in producing tsunamis and has been applied to the papua new guinea event the landslide is treated as the flow of a homogeneous gravity driven continuum governed by a rheological law water waves are generated by sea bottom displacements induced by the landslide the shallow water approximation is adopted for both the landslide and the associated water waves the resulting differential equations are solved by a finite difference method based on shock capturing the shallow water hypothesis is tested by comparison with a model solving navier stokes equations for a mixture of water and sediments sensitivity tests carried out for a 2 d simplified geometry show that the water surface profile depends strongly on the constitutive law of the landslide the 1998 event is simulated numerically by the shallow water model testing different friction laws the observed inundation height distribution is well reproduced by the model for a volume of 4 km3 with its top located at a water depth of 550 m and sliding with a coulomb type friction law over a distance of 5 km

on the formation of a subsurface weakly sheared laminar layer and an upper thermocline strongly sheared turbulent layer in the eastern equatorial pacific interplays of multiple time scale equatorial waves

downward propagating internal waves generated at the base of the surface layer of a stratified fluid downward propagating internal waves are observed in laboratory experiments they appear to be generated by the obstacle effect beneath a turbulent surface layer in a surface stress driven stratified flow experiment in a rectangular cavity the obstacles are the perturbations at the base of the surface layer and the shear is created by a combination of an internal seiche and the circulation in the upper layer the proportion of energy lost from the surface layer is comparable to increases in potential energy due to vertical entrainment consequently if conditions are favourable a reduction in vertical entrainment may occur

internal waves and mixing in the upper equatorial pacific ocean microstructure measurements in the equatorial pacific at 140 w in late 1984 show a pronounced diurnal variation in both high frequency internal wave energy and kinetic energy dissipation rate observations indicated that after sunset internal waves presumably generated by convective overturns in the mixed layer propagate downward and increase turbulence levels in the pycnocline it is proposed that large mixed layer eddies in the south equatorial current interact with the large shear caused by the equatorial undercurrent to generate a westward going anisotropic wave field the momentum transport in the radiated wave field results in a drag force on the equatorial mean flow field the observed mean wind stress at 140 w during tropic heat i which is twice as large as the annual mean wind is closer to the estimated radiation stress 10 4 m2 s 2 at the base of the mixed layer 30 m than to the estimated turbulent stress 10 5 m2 s 2 a wave dissipation model based on the observed turbulent kinetic energy dissipation rate is introduced in order to estimate the wave momentum flux divergence in the stratified region above the undercurrent core the model predicts that most of the downward wave momentum flux penetrates through the undercurrent core it is hypothesized that when the wind stress is strong the equatorial pacific ocean responds by generating a westward traveling internal wave field which transports much of the surface wind stress below the actively mixing surface layer

fine scale variability at 140 w in the equatorial pacific in november december 1984 we carried out an intensive 12 day upper ocean sampling program on the equator at 140 w as part of the tropic heat experiment from our observations we constructed hourly averaged profiles of temperature salinity t turbulent kinetic energy dissipation rate and horizontal velocity these data were used to examine the correspondence between hydrographic and velocity fields and to compare the measured turbulent dissipations with the calculated richardson numbers we found that the core of the equatorial undercurrent tracked a density surface t 25 25 on times as short as 1 hour the variability in both hydrographic and velocity fields was greatest at the semidiurnal frequency the supertidal energy was not significantly different from the garrett munk mid latitude level once latitudinal scaling was removed from the garrett munk model parameters horizontal velocity spectra were found to be contaminated by displacement of the background shear turbulent dissipation was dominated by a diurnal cycle with high values of dissipation occurring at night above the undercurrent core shear and buoyancy frequency calculated over 12 m vertical scales were observed to track each other above the core and were dominated by a diurnal period above 40 m and by a semidiurnal period below 40 m when shear and buoyancy frequency were combined to form a richardson number neither diurnal nor semidiurnal cycles were present above the undercurrent core the richardson numbers were uniformly small 0 3 to 0 6

internal gravity waves in the upper eastern equatorial pacific observations and numerical solutions on the basis of data from a towed thermistor chain collected near 140 w on the equator during april 1987 the zonal wavenumber and vertical structure of internal gravity waves were observed to vary significantly between wave events our hypothesis is that this variability is due to changes in the vertical structure of mean horizontal velocity and density assuming that the observed waves were the fastest growing modes for shear instability we solve the taylor goldstein equation using different analytical basic states including a zonal and meridional flow to simulate the different conditions during 4 nights of intense internal wave activity we find that while the observed waves are of finite amplitude linear shear instability is sufficient to explain the wavelength and vertical structure of vertical displacement for most of the waves the fastest growing unstable mode one solutions have e folding growth times of less than 10 min these solutions show wave phase speeds and vertical structures to be highly dependent upon the velocity structure of the uppermost 40 m near the base of the mixed layer at a flow inflection point the kinetic energy of the mean flow is extracted for wave growth wave vertical displacement is maximum near this inflection point zonal phase speeds range from 0 8 to 0 1 m s the propagation direction of waves with growth rates of 75 of the maximum growth rate can range from about 45 north to 45 south of the zonal direction the vertical wave induced reynolds stress divergence could explain a discrepancy in zonal momentum budgets of the upper 90 m of this region estimates of this stress divergence show that only about 100 days of intense internal wave activity is needed per year for these internal waves to explain estimated residuals of the mean zonal momentum budgets of this region at 50 to 100 m depth

diagnostic model of the three dimensional circulation in the upper equatorial pacific ocean abstract to investigate the processes that maintain the large scale annual average thermal structure of the equatorial pacific the three dimensional ocean circulation for a large area is determined from a diagnostic model applied to repeated meridional hydrographic sections along 150 w and 11o w from 5 n to 5 s geostrophic balances are used to determine velocity profiles from 0 to 500 db across the boundaries of the region zonal velocities across 150 w and 110 w at approximately 1 lattitude intervals from 5 n to 5 s and meridional velocities across 5 n and 5 s averaged over the zonal distance between 150 w and 110 w poleward wind driven flows across 5 n and 5 s based on climatological zonal wind stress are added to the geostrophic velocities in the mixed layers to achieve overall mass conservation the reference dynamic height field at 500 db is adjusted at four of the 21 stations by about 1 dyn cm horizontal nondivergence is used to determine meridional velocities between 0 75 and 5 latitudes

variations in fluvial style in the westwater canyon member morrison formation jurassic san juan basin colorado plateau abstract techniques of architectural element analysis and lateral profiling have been applied to the fluvial westwater canyon member of the morrison formation jurassic in southern san juan basin on a large scale the sandstone body architecture consists mainly of a series of tabular sandstone sheets 5 15 m thick and hundreds of meters wide separated by thin fine grained units internally these sheets contain lateral accretion surfaces and are cut by channels 10 20 m deep and at least 250 m wide on a more detailed scale interpretations made from large scale photomosaics show a complex of architectural elements and bounding surfaces typical indicators of moderate to high sinuosity channels lateral accretion deposits coexist in the same outcrop with downstream accreted macroform deposits that are typical of sand flats of low sinuosity multiple channel rivers broad deep channels with gently to steeply dipping margins were mapped in several of the outcrops by carefully tracing major bounding surfaces locally thick accumulations of plane laminated and low angle cross laminated sandstone lithofacies suggest rapid flow probably transitional to upper flow regime conditions such a depositional style is most typical of ephemeral rivers or those periodically undergoing major seasonal or more erratic stage fluctuations an interpretation consistent with independent mineralogical evidence of aridity fining upward sequences are rare in the project area contrary to the descriptions of campbell 1976 the humid alluvial fan model of galloway 1978 cannot be substantiated and similarly the architectural model of campbell 1976 requires major revision comparisons with the depositional architecture of the large indian rivers such as the ganges and brahmaputra still seem reasonable as originally proposed by campbell 1976 although there is now convincing evidence for aridity and for major stage fluctuations which differs both from those modern rivers and campbell s interpretation

regional paleoclimatic and stratigraphic implications of paleosols and fluvial overbank architecture in the morrison formation upper jurassic western interior usa abstract paleosols in the morrison formation upper jurassic from the western interior and colorado plateau regions occur in fluvial overbank and marginal lacustrine depositional facies associated with aggradational settings and at sequence bounding unconformities that mark divisions between major aggradational and degradational successions pedogenic features within these horizons preserve important contextual information about the local and regional paleoclimate and paleoenvironment in which the soils formed floodplain and lake margin paleosols show evidence that most of the morrison basin was characterized by a semi arid to tropical wet dry paleoclimate with fluctuating groundwater conditions a low precipitation to evaporation ratio and weak to moderately seasonal precipitation paleosol ichnofauna show evidence of a diverse and opportunistic flora and fauna that exploited changing conditions and existing nutrient and moisture regimes changes in paleosol type and degree of development over the basin indicate the overall regional paleoclimate was drier in the western and southern portions of the basin vertical trends indicate paleoclimatic conditions over the basin became steadily more humid through time laterally continuous well developed deeply weathered paleosols formed during times of little or no deposition and mark regional unconformities the paleosols at these sequence bounding unconformities serve as useful regional stratigraphic markers to trace genetic packages across the morrison depositional basin and to determine regional accommodation trends

gps measurements of crustal deformation within the pacific australia plate boundary zone in irian jaya indonesia abstract global positioning system gps measurements made in 1991 1992 and 1993 provide preliminary estimates of slip distribution between the australian and pacific plates in irian jaya indonesia we interpret the gps results with constraints from earthquake mechanisms and slip vectors recent marine surveys and geology three gps sites in southeastern irian jaya show motions that are within 10 mm yr of the expected motion of australia a coast to coast n s baseline along 140 5 e crosses all known onland regions of active deformation but reveals no more than 15 mm yr of shortening and 20 mm yr of left lateral shear in the 27 month period the remaining 40 mm yr of expected convergence between the pacific and australian plates probably occurs at the new guinea trough gps sites on the island of biak at 136 e and at sorong near the western tip of bird s head at 131 e both move 90 100 mm yr in a wsw direction relative to irian jaya but less than 15 mm yr relative to each other these sites are on either side of the sorong fault and demonstrate that it is not presently the major boundary between the australian and pacific plates instead the plate boundary is now south of the sorong and biak sites earthquakes suggest possible structures that accomodate motion between bird s head and australia but the relative importance of them remains uncertain

reconnaissance of upper jurassic morrison formation ichnofossils rocky mountain region usa paleoenvironmental stratigraphic and paleoclimatic significance of terrestrial and freshwater ichnocoenoses seventy five types of ichnofossils documented during a four year reconnaissance study in the upper jurassic morrison formation demonstrate that highly diverse and abundant plants invertebrates and vertebrates occur throughout most of the morrison or equivalent strata invertebrate ichnofossils preserving the most environmentally and climatically sensitive in situ behavior of morrison organisms are in nearly all outcrops terrestrial ichnofossils record biotic processes in soil formation indicating soil moisture and water table levels freshwater ichnofossils preserve evidence of water depth salinity and seasonality of water bodies ichnofossils categorized as epiterraphilic terraphilic hygrophilic and hydrophilic new terms reflect the moisture regime where they were constructed the ichnofossils are vertically zoned with respect to physical chemical and biological factors in the environment that controlled their distribution and abundance and are expressed as surficial shallow intermediate and deep the sedimentologic stratigraphic and geographic distribution of morrison ichnofossils reflects the environmental and climatic variations across the basin through time marginal marine tidal to brackish water ichnofossils are mainly restricted to the windy hill member very large to small termite nests dominate the salt wash member similar size ranges of ant nests dominate the brushy basin member soil bee nests dominate in the salt wash decreasing in abundance through the brushy basin deeper and larger insect nests indicate more seasonal distribution of precipitation and rainfall shallower and smaller insect nests indicate either dry or wet substrate conditions depending on the nest architecture and paleopedogenic and sedimentologic character of the substrate trace fossil indicators of flowing or standing water conditions are dominant in the tidwell member and in fluvial sandstones of the salt wash and brushy basin members large communities of perennial freshwater bivalve traces are abundant in the tidwell and brushy basin members but to a lesser extent in the salt wash member shallow crayfish burrows indicating a water table level close to the surface 1 m are restricted to channel bank and proximal alluvial deposits in the salt wash recapture and brushy basin members sauropod theropod pterosaur and other vertebrate tracks occur throughout the morrison formation associated with alluvial lacustrine and transitional marine shoreline deposits ichnofossils and co occurring paleosols in the morrison reflect the local and regional paleohydrologic settings which record the annual soil moisture budget and were largely controlled by the climate in the basin contributions to near surface biologic systems by groundwater from distant sources were minor except where the water table perennially seasonally or ephemerally intersected the ground surface the jurassic morrison formation in the southern portion of the basin experienced a mosaic of seasonal climates that varied from a drier tidwell windy hill deposition to a wetter lower and middle salt wash deposition and slightly drier upper salt wash deposition tropical wet dry climate returning to a wetter tropical wet dry climate near the end of morrison deposition brushy basin deposition the northern part of the basin experienced similar trends across a mosaic of mediterranean climate types the range and mosaic pattern of wet dry morrison climates is analogous to the range of climates and their seasonal variability that dominates the african savanna today

the role of the turbulent stress divergence in the equatorial pacific zonal momentum balance from a comprehensive set of upper ocean measurements made during a moderate e1 nifio in boreal spring 1987 we reassess the role of turbulence in transporting momentum vertically at the equator an examination of the terms in the vertically integrated zonal momentum equations indicates that on short time scales the zonal pressure gradient is not balanced by the surface wind stress despite an apparent balance of these terms on longer seasonal time scales the vertical redistribution of zonal momentum is complex the strength of the wind determines both the magnitude and likely the mechanisms of momentum transport between the surface and the core of the undercurrent during low wind

case of the phantom foredeep early cretaceous in west central utah a reconstruction of the structure in west central utah shows that a major foredeep with sedimentary deposits possibly as thick as 6 km now eroded probably existed at the present site of the sevier desert during early cretaceous time and conceivably during late jurassic time concurrent emplacement and erosion of the canyon range thrust sheet provided the load and sediment much like the willard paris thrust sheet did for the better documented early cretaceous foredeep in northern utah and eastern idaho the onset of major thrusting in western utah may have been as early as callovian or as late as albian a 50 m y time span

lower eocene alluvial paleosols pedogenic development stratigraphic relationships and paleosol landscape associations abstract two kinds of cumulative floodplain paleosols red and grey paleosols formed on overbank deposits of the willwood formation in the sand coulee area of the bighorn basin wyoming although both kinds experienced down profile iron movement due to seasonal saturation of a clay rich a horizon the red paleosols were better drained and their b horizons were rubified various redoximorphic features indicate that the grey paleosols were poorly drained the red paleosols show progressive increases in the degree of profile development away from an associated channel sandstone a paleosol landscape relationship termed pedofacies by bown and kraus 1987 although the grey paleosols show relatively systematic changes in hydromorphy consistent pedofacies changes were not recognized furthermore no lateral relationship between the red and grey paleosols was observed these features suggest that because of the retarding effects of poor drainage on soil weathering poorly drained soils are not amenable to pedofacies modelling and that the landscape associations of well drained and poorly drained soils may be difficult to document without unusually extensive exposures results of this study also show that the pedofacies model is limited by sediment accumulation rates and the kind of fine grained facies on which paleosols developed although readily observable in sand coulee pedofacies are difficult to recognize in the elk creek area where accumulation rates were approximately half as rapid as in sand coulee the attainment of steady state conditions is believed to have obscured pedofacies in the elk creek area finally pedofacies are only developed on true overbank deposits which in the willwood formation and probably many other ancient alluvial sequences make up only a fraction of the fine grained deposits only immature soils formed on the remainder of the fine grained facies because they were deposited very rapidly as a result of channel avulsion

wind driven ageostrophic transport in the north equatorial countercurrent of the eastern pacific at 95 w abstract observations of horizontal velocity from two shipboard acoustic doppler current profilers adcps as well as wind temperature and salinity observations from a cruise during june july 2001 are used to compute a simplified mean meridional momentum balance of the north equatorial countercurrent necc at 95 w the terms that are retained in the momentum balance and derived using the measurements are the coriolis and pressure gradient forces and the vertical divergence of the turbulent stress all terms were vertically integrated over the surface turbulent layer the k profile parameterization kpp prescribed richardson number ri is used to determine the depth of the turbulent boundary layer h at which the turbulent stress and its gradient vanish at the time of the cruise surface drifters and altimeter data show the flow structure of the necc was complicated by the presence of tropical instability waves to the south and a strong costa rica dome to the north nonetheless a consistent simpl

isotopic evidence for eolian recycling of pedogenic carbonate and variations in carbonate dust sources throughout the southwest united states using isotopic ratios of sr c and o we trace calcium carbonate through surface systems across a wide region of semi arid terrain in arizona southwestern usa in order to evaluate the contribution of cations from silicate weathering to soil carbonate we present 87sr 86sr ratios of soil carbonate parent rock dry river course silts floodplain playa dust and rain samples as well as 18o and 13c values of selected samples results show that both parent rock and dust are important sources of cations for soil carbonate in this inland setting where bedrock is dominated by silicate lithologies dust in southeast arizona has higher 87sr 86sr ratios 0 7100 0 7123 than phanerozoic sea water 0 7070 0 7096 these high ratios derive ultimately from silicate rocks our 18o and 13c data show clearly that the dominant source of carbonate dust is eroded older soil carbonate not bedrock limestone because dust contributes significantly to newly forming soil carbonate some products of silicate weathering may reside in soil carbonate two or more times before being removed from the region and this recycling retards the rate at which the products of silicate weathering enter the sedimentary system comparison of the 87sr 86sr ratios of carbonate dust from southeast arizona with those from surrounding regions shows that dust 87sr 86sr ratios and by inference carbonate dust sources vary on a scale of 200 300 km in the southwest united states

classification of paleosols despite increased interest in paleosols during the past decade no satisfactory classification is in current use presented here is a largely descriptive classification system that utilizes those pedogenic features that have the highest preservation potential in the rock record emphasized in the classification are morphological and mineralogical features that are easily recognizable in the field and through the petrographic microscope the classification is based on evaluation of the relative prominence in a paleosol of six pedogenic features or processes organic matter content horizonation redox conditions in situ mineral alteration illuviation of insoluble minerals compounds and accumulation of soluble minerals the most prominent of these six features processes provides the key to classifying a paleosol into one of nine orders four of the order names are borrowed from soil taxonomy histosol spodosol oxisol vertisol whereas the other five order names are presented here for the first time calcisol gypsisol gleysol argillisol protosol the orders may be preceded by one or more subordinate modifiers that describe other important features of the paleosol the classification is relatively easy to apply to the rock record and should enhance communication and aid in the standardization of terminology

a linear stratified ocean model of the equatorial undercurrent a linear stratified ocean model is used to study the wind driven response of the equatorial ocean the model is an extension of the lighthill 1969 model that allows the diffusion of heat and momentum into the deeper ocean and so can develop non trivial steady solutions to retain the ability to expand solutions into sums of vertical normal modes mixing coefficients must be inversely proportional to the square of the back ground vaisala frequency the model is also similar to the earlier homogeneous ocean model of stommel i960 he extended ekman dynamics to the equator by allowing his model to generate a barotropic pressure field the present model differs in that the presence of stratification allows the generation of a baroclinic pressure field as well the most important result of this paper is that linear theory can produce a realistic equatorial current structure the model undercurrent has a reasonable width and depth scale there is westward flow both above and below the undercurrent the meridional circulation conforms to the classical picture suggested by cromwell 1953 unlike the stommel solution the response here is less sensitive to variations of parameters ocean boundaries are not necessary for the existence of the undercurrent but are necessary for the existence of the deeper equatorial intermediate current the radiation of equatorially trapped rossby and kelvin waves is essential to the development of a realistic undercurrent because the system supports the existence of these waves low order vertical modes can very nearly adjust to sverdrup balance defined below which in a bounded ocean and for winds without curl is a state of rest as a result higher order vertical modes are much more visible in the total solution this property accounts for the surface trapping and narrow width scale of the equatorial currents the high order modes tend to be in yoshida balance defined below and generate the characteristic meridional circulation pattern associated with equatorial ekman pumping

teleseismic estimates of radiated seismic energy the e m 0 discriminant for tsunami earthquakes we adapt the formalism of boatwright and choy for the computation of radiated seismic energy from broadband records at teleseismic distances to the real time situation when neither the depth nor the focal geometry of the source is known accurately the analysis of a large data set of more than 500 records from 52 large recent earthquakes shows that this procedure yields values of the estimated energy ee in good agreement with values computed from available source parameters for example as published by the national earthquake information center neic the average logarithmic residual being only 0 26 units we analyze the energy to moment ratio by defining log10 ee m0 for regular earthquakes this parameter agrees well with values expected from theoretical models and from the worldwide neic catalogue there is a one to one correspondence between values of that are deficient by one full unit or more and the so called tsunami earthquakes previously identified in the literature as having exceedingly slow sources and believed due to the presence of sedimentary structures in the fault zone our formalism can be applied to single station measurements and its coupling to automated real time measurements of the seismic moment using the mantle magnitude mm should significantly improve real time tsunami warning

internal waves in the upper ocean abstract previous work has shown that the deep ocean internal wave field has little variability and can be described by a stationary spectrum this analysis of upper ocean internal wave data supports the hypothesis that the variable upper ocean within the upper 200 m internal wave field can be represented as fluctuations superimposed on the base state stationary spectrum such as that given by the model of garrett and munk that is we hypothesize that the variability is present in addition to the stationary background rather than instead the parameters of the garrett munk model are particularized by a best fit to the deep ocean iwex data the model is then directly compared to upper ocean internal wave data from cape cod flip gate st croix and the nrl towed chain these data properly interpreted line sensor data and the existence of a dynamic saturation mechanism are all consistent with the hypothesis

application of analytical modeling to the far field investigation of tsunami and oceanic rayleigh waves from the 1998 papua new guinea earthquake we analyze far field rayleigh and tsunami waves generated by the 1998 papua new guinea png earthquake using the normal mode theory and thomson haskell matrix formalism we calculate synthetic mareograms of oceanic surface waves excited by finite dimensional line source and propagated in a flat multilayered oceanic structure assuming that the source of destructive sea waves was the main shock of the png event and based on the expression for seismic wave displacement in the far field zone we compute the energy of the seismic and tsunami waves and the e z e ts ratio the results of our modeling are generally consistent with those obtained empirically for events with magnitude 7 also treating the results of a submarine slide as a single solitary wave and using the theoretical arguments of striem and miloh 1976 we estimate the energy of the tsunami induced by a landslide the difference between the energy of the seismic tsunami and of the aseismic one is about one order of magnitude the results of our theoretical modeling show that surface sea waves in the far field zone account well for seismic origin although additional tsunami energy from a landslide source could be required to explain the local massive tsunami in the sissano lagoon

zonal momentum balance at the equator abstract the conventional view of equatorial dynamics requires that the zonal equatorial wind stress be balanced in the mean by the vertical integral of large scale terms such as the zonal pressure gradient mesoscale eddy flux and mean advection over the upper few hundred meters it is usually presumed that the surface wind stress is communicated to the interior by turbulent processes turbulent kinetic energy dissipation rates measured at 140 w during the tropic heat i experiment and a production rate dissipation rate balance argument have been used to calculate the zonal turbulent stress at 30 to 90 m depth the calculated turbulent stress at 30 m depth amounts to only 20 of the wind stress and decreases exponentially with depth below 30 m typical large scale estimates of the zonal pressure gradient mesoscale eddy flux and advection have a depth scale larger than the turbulent stress and are inconsistent with the vertical divergence of the stress as estimated from the dissipation rate measu

moment tensor inversion for offshore earthquakes east of taiwan and their implications to regional collision reliable determination of source parameters for offshore earthquakes east of taiwan with mb 5 5 was a difficult task because of the poor azimuthal coverage by local network and the lack of signals at teleseismic distances we take advantage of the recently established broadband array in taiwan for seismology bats to invert seismic moment tensors for 7 such events occurred in 1996 to cope with different patterns of background noise and unknown structural details we utilize variable frequency bands in the inversion and adapt a two step procedure to select best velocity models for individual epicenter station paths our results are consistent with the overall patterns of regional collision and indicate that the resulting compressive stress has caused significant intraplate deformation within the philippine sea plate simulation of the region s geological evolution and orogenic processes should take this factor into account and allow the philippine sea plate to deform internally

fining upward cycles in the sandy braided river deposits of the westwater canyon member upper jurassic morrison formation new mexico abstract vertical and lateral profiles demonstrate that fining upward cycles are present in the sandy braided fluvial units of the westwater canyon member an upper jurassic morrison formation sheet sandstone in northwestern new mexico the technique of bounding surface classification successfully delineates these cycles on three scales of sedimentary influence namely the macroform scale cycle the channel scale cycle and the sheet scale cycle autocyclic macroform scale cycles are generally 1 6 m in thickness and bounded above and below by 3rd or higher order surfaces one of which must be of 3rd or 4th order channel scale cycles deposits infilling large scale scours and possibly individual channels are 1 10 m in thickness bounded above and below by laterally inextensive 5th or 6th order surfaces sheet scale cycles in contrast are 4 16 m in thickness the products of autocyclic channel avulsion processes bounded both above and below by laterally extensive planar 5th or 6th order surfaces a proposal by previous workers that lithofacies cyclicity also exists in the westwater canyon member is examined and rejected following field work and markov chain analysis further theoretical discussion of markov chain analysis points out several problems with the identification of cycles including the need for proper definition of the bounding surfaces that mark lithofacies transitions

source mechanism of the magnitude 7 2 grand banks earthquake of november 1929 double couple or submarine landslide we have examined p s and surface waves derived from seismograms that we collected for the 1929 grand banks canada earthquake this event is noteworthy for the sediment slide and turbidity current that broke the trans atlantic cables and for its destructive tsunami both the surface wave magnitude m s and the body wave magnitude m b calculated from these seismograms are 7 2 fault mechanisms previously suggested for this event include a nw se striking strike slip mechanism and an approximately e w striking thrust mechanism in addition because of the presence of an extensive area of slump and turbidity current there exists the possibility that sediment slumping could also be a primary causative factor of this event we tested these fault models and a horizontal single force oriented n5 w model representing a sediment slide against our data among these models only the single force model is consistent with the p s and surface wave data our data however do not preclude fault models which were not tested from the spectral data of love waves at a 50 sec period we estimated the magnitude of the single force to be about 1 4 10 20 dynes from this value we estimated the total volume of sedimentary slumping to be about 5 5 10 11 m 3 which is approximately 5 times larger than a recent estimate of volume from in situ measurements the difference in estimates of overall volume is likely due to a combination of the inherent difficulty in estimating accurately the displaced sediments from in situ measurements and of inadequacy of the seismic model or perhaps because not only the slump but also a tectonic earthquake could have been the cause of this event and contributed significantly to the waveforms studied

the coupling of a submarine slide and the surface waves which it generates underwater landslides are a common source of small scale tsunamis in coastal areas they have been the object of only a few theoretical and experimental studies a numerical model is developed to study the coupling of a submarine landslide and the surface waves which it generates a formulation of the dynamics of the problem is presented where the landslide is treated as the laminar flow of an incompressible viscous fluid and the water motion is assumed irrotational long wave approximation is adopted for both water waves and the mudslide the resulting differential equations are solved by a finite difference method we present the numerical results which contrast the behavior of the mud flow under a fixed surface in the presence of one way coupling bottom deformations affect the free surface and with full coupling surface pressure gradients react on the mud flow it is found that three main waves are generated by a landslide starting from rest on a gentle uniform slope the first wave is a crest which propagates away from the mudslide site into deeper water this crest is followed by a trough in the form of a forced wave which propagates with the speed of the mudslide front the third wave is a relatively small trough which propagates shoreward two major parameters dominate the interaction between the slide and the waves it produces the density of sliding material and the depth of water at the mudslide site the two way interactions are significant for the cases of a smaller mud density and shallower waters for the cases of larger mud density and shallower waters the two way interactions are small but the waves generated are very large for larger initiation depth of the mudslide the interactions are weak and the waves generated are small we also examined the possibility of a resonance between the slide and the waves our numerical results indicate that a resonance is not expected in many practical cases

seismic yield determination of soviet underground nuclear explosions at the shagan river test site summary a study of p and lg based source size estimators has been conducted for 101 presumed underground nuclear explosions at the shagan river test site near semipalatinsk ussr a systematic variation in the relative patterns across the test site has been observed when comparing the p wave estimators world wide mb and ulm and the lg based observations rms lg determined from norsar and grafenberg array recordings these variations correlate well with geological features determined from satellite imagery and suggest in particular that the northeast and southwest portions of the test site divided by the chinrau fault are characterized by distinct geophysical properties a difference in m p mlg bias of as much as 0 15 magnitude units exists between these two subareas available data indicate that the mlg observations are very consistent with published yields and suggest that the magnitude yield relationship for p wave based estimators can be significantly improved by introducing regional bias corrections we have determined such corrections for three subareas of the test site and used the corrected mh and ym observations in combination with the lg data in a weighted averaging scheme to arrive at yield estimates for all events in the database for the explosion of 1988 september 14 we obtain yield estimates from the three estimators ranging from 106 to 118 kt which is consistent with the independently derived estimates of 115 122 kt quoted by sykes ekstrom 1989 a further assessment of the validity of our results would require access to independently measured yields of additional explosions

the effect of bathymetry on tsunami characteristics at sisano lagoon papua new guinea the 1998 papua new guinea tsunami was greater than expected from its earthquake magnitude the area of significant impact was small approximately a 30 km stretch near the mouth of sissano lagoon papua new guinea to explain the localized nature of the event a submarine landslide has been conjectured to be responsible our study indicates that offshore bathymetry is critical to predicting tsunami coastal behavior model runs with newly obtained bathymetric data indicate that an earthquake fault source combined with the existing seafloor geometry may also explain the concentrated tsunami although the definitive cause of the papua new guinea tsunami remains uncertain local bathymetry had a notable effect on the wave behavior

analytical model for gravity and rayleigh wave investigation in the layered ocean earth structure in terms of the linear theory of elasticity we analyze the gravity and rayleigh wave excitation and propagation process in a three layered ocean earth model which includes a superficial liquid layer and two layers of sediments soft and hard to compute the oceanic surface wave dispersion function the thomson haskell matrix method is used the solution is obtained by applying the normal mode formalism to the flat homogeneous layered ocean earth structure based on this theory the spectra of the excitation functions are investigated in detail for 45 thrust dip slip and strike slip point sources in the half space a numerical experiment reveals that the rigidity of the rock exerts a strong influence on both gravity and rayleigh waves in the case of rayleigh waves a layered structure of the bottom strongly affects the propagation process the main focus of the present study is to model tsunami and tsunamigenic events it is well known from observations that earthquakes that generate abnormally large tsunamis are mostly thrust events characterized by long source duration 2 4 times longer than typical earthquakes of similar moment and shallow source depth and are located near the trench axis meanwhile typical tsunamigenic earthquakes are generally dip slip and thrust events with depths between 15 and 50 km on this basis and using the distributed model of seismic source the influence of source mechanism location and source duration on the tsunami wave amplitude are investigated here the results of our model computations of the seismic sea waves from tsunami and tsunamigenic earthquake are in good agreement with real observation data

downward lee wave radiation from tropical instability waves in the central equatorial pacific ocean a possible energy pathway to turbulent mixing turbulent mixing in the equatorial pacific ocean is an important process that controls diapycnal heat transport and hence affects the air sea interactions and global climate it is recently shown that in the eastern equatorial pacific strong mixing is induced in the thermocline by enhanced vertical shear associated with tropical instability waves tiws which propagate westward along the equator at a speed of 0 5 m s 1 with a wavelength of 1000 km in this study using a high resolution ocean general circulation model we show that the tiws can play an important role in inducing turbulent mixing in the thermocline also in the central equatorial pacific although the thermocline is too deep to be directly affected by the vertical shear of the tiws the front of the tiw is clearly manifested as a narrow strip of strong convergence of horizontal surface flow from which area downward and westward propagating internal waves are intermittently emanated these internal waves can be interpreted as lee waves generated by the surface flow convergence zone which acts like an inverted obstacle moving along the stratified ocean surface by inducing downward flow the associated downward energy flux below the surface mixed layer increases as the tiw structure becomes deeper toward the central equatorial pacific so that the energy pathway to turbulent mixing in the thermocline can be created the downward energy flux integrated over the entire equatorial pacific and averaged during january 2011 amounts to 8 1 gw occupying a significant fraction of the energy input to the tiws

regional paleohydrologic and paleoclimatic settings of wetland lacustrine depositional systems in the morrison formation upper jurassic western interior usa abstract during deposition of the upper jurassic morrison formation water that originated as precipitation in uplands to the west of the western interior depositional basin infiltrated regional aquifers that underlay the basin this regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland lacustrine successions a freshwater carbonate wetland lacustrine succession formed in the distal reaches of the basin where regional groundwater discharged into the denver julesburg basin which was a smaller structural basin within the more extensive western interior depositional basin an alkaline saline wetland lacustrine complex lake t oo dichi formed farther upstream where shallower aquifers discharged into the san juan paradox basin which was another small structural basin in the western interior depositional basin these were both wetlands in the sense that groundwater was the major source of water input from surface and meteoric water was limited in both basins lacustrine conditions developed during episodes of increased input of surface water inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology the distal carbonate wetland lacustrine deposits are well developed in the morrison formation of east central colorado occupying a stratigraphic interval that is equivalent to the lower morrison but extends into the upper morrison formation sedimentologic paleontologic and isotopic evidence indicate that regional groundwater discharge maintained shallow hydrologically open well oxygenated perennial carbonate wetlands and lakes despite the semi arid climate wetland deposits include charophyte rich wackestone and green mudstone lacustrine episodes in which surface water input was significant were times of carbonate and siliciclastic deposition in scarce deltaic and shoreline deposits marginal lacustrine deposits include ooid and skeletal packstone grainstone siltstone and sandstone distal lacustrine units are skeletal mudstone wackestone microbialites and laminated siliciclastic mudstone differentiation between wetlands and distal lacustrine units is not always possible palustrine features magadi type chert mtc and evaporites record episodes of increased aridity and exposure farther upstream during deposition of the upper part of the brushy basin member the ancestral uncompahgre uplift imposed a barrier to shallow eastward flowing groundwater that discharged into the san juan paradox basin on the upstream side of the uplift this created the closed hydrologic setting necessary for development of an alkaline saline wetland lacustrine complex lake t oo dichi silicic volcanic ash delivered by prevailing winds from calderas west and southwest of the basin contributed to the pore water evolution in the sediments a distinctive lateral hydrogeochemical gradient reflecting increasing salinity and alkalinity in the pore waters altered the ash to a variety of authigenic minerals that define concentric zones within the basin the basinward progression of diagenetic mineral zones is smectite clinoptilolite analcime potassium feldspar albite the groundwater fed wetlands were shallow and frequently evaporated to dryness scarce laminated gray mudstone beds record distinct episodes of freshwater lacustrine deposition that resulted from intermittent streams that carried detritus well out into the basin

a single force model for the 1975 kalapana hawaii earthquake a single force mechanism is investigated as the source of long period seismic radiation from the 1975 kalapana hawaii earthquake m s 7 1 the observed love wave radiation pattern determined from the spectra of world wide standard seismograph network and high gain long period records at 100 s is two lobed with azimuth consistent with a near horizontal single force acting opposite strike 330 to the observed displacement direction of the earthquake this pattern is inconsistent with the expected double couple pattern assuming a form of the force time history of a one cycle sinusoid the total duration of the event estimated from rayleigh waves at two international deployment of accelerometers stations is approximately 180 s the peak amplitude f o of the time function is 1 10 15 n from amplitudes of love and rayleigh waves the interpretation is that the bulk of the seismic radiation was produced by large scale slumping of a large area of the south flank of kilauea volcano the single force is a crude representation of the effect on the earth of the motion of a partially decoupled large slide mass using the mass estimated from the tsunami generation area 10 15 10 16 kg the peak acceleration of the slide block 0 1 1 m s 2 inferred from the seismic force is comparable with the acceleration due to gravity on a gently inclined plane the slump model for the kalapana earthquake is also more qualitatively consistent with the large horizontal deformation 8 m on land and tsunami associated with the earthquake which are difficult to explain with the conventional double couple source model the single force source has been used previously to model the long period seismic waves from the landslide accompanying the eruption of mount st helens volcano and may explain other anomalous seismic events as being due to massive slumping of sediments or unconsolidated material and not to elastic dislocation

analysis of the far field tsunamis generated by the 1998 papua new guinea earthquake the tsunami generated by the 1998 papua new guinea earthquake was observed at several tide gauges and ocean bottom pressure gauges in japan the fault model of the 1998 papua new guinea earthquake was estimated using those tsunami waveforms observed in japan and coseismic subsidence observed along the coast of papua new guinea near the source region the numerical simulation of the tsunami using the linear boussinesq equation was carried out the tsunami waveforms in japan are explained by the fault model which is consistent with the harvard cmt solution including the seismic moment of 3 7 1019 nm the additional tsunami source such as a sediment slump is not needed to explain the observed tsunami in japan the mechanism of the earthquake was likely to be a steeply dipping reverse fault the 1998 papua new guinea earthquake was likely to occur within a small accretionary prism near the new guinea trench

estimation of current plate motions in papua new guinea from global positioning system observations plate tectonic motions have been estimated in papua new guinea from a 20 station network of global positioning system sites that has been observed over five campaigns from 1990 to 1996 the present velocities of the sites are consistent with geological models in which the south bismarck woodlark and solomon sea plates form the principal tectonic elements between the pacific and australian plates in this region active spreading is observed on the woodlark basin spreading centre but at a rate that is about half the rate determined from magnetic reversals the other major motions observed are subduction on the new britain trench seafloor spreading across the bismarck sea seismic lineation convergence across the ramu markham fault and left lateral strike slip across the papuan peninsula these motions are consistent with a 8 2 myr 1 clockwise rotation of the south bismarck plate about a pole in the huon gulf and a rotation of the woodlark plate away from the australian plate second order deformation may also be occurring in particular manus island and northern new ireland may be moving northward relative to the pacific plate at 5 8 mm yr 1 significant at the 95 but not at the 99 confidence level which may suggest the existence of a north bismarck plate

convection waves observations of gravity wave systems over convectively active boundary layers widespread gravity wave systems have been found to exist over convectively active boundary layers cbls in the presence of vertical wind shear in contrast to mountain waves these convection waves occur over flat terrain and are ubiquitous over fields of shallow fair weather cumuli or clear air thermals they extend vertically to at least 9km a m s l probably to the tropopause first discovered by glider pilots as thermal waves they have now been systematically investigated by research aircraft during the ncar convection wave project which also incorporates an effort in numerical simulation the flight results are reported in this paper while the numerical simulations are described in a companion paper typical wavelengths of convection waves were found to range from 5 to 15 km average 9 km and typical vertical motion amplitudes from 1 to 3 m s 1 in all cases vertical wind shear exceeded 3 10 3s 1 under these conditions cloud tops were measured to move with relative velocities of 8 to 10 m s 1 against their environment hence they present an obstacle to the surrounding airflow the analogy to mountainous obstacles launching gravity waves into the atmosphere is suggestive and borne out by the aforementioned numerical simulations which describe this process step by step the interaction between the cbl and the overlying stable layers is studied by spectral and cross spectral analysis of aircraft data including coherence and phase relations between wave motions and cloud population underneath consideration is given to other potential sources of the observed gravity waves at this stage the conclusions of our pilot study may be considered tentative some implications for further research are also discussed

paleoclimate and the global distribution of paleosols a theoretical model is developed for the relationship between paleoclimate and paleosols for the time interval following the widespread appearance of vascular land plants the model defines four paleoclimatic zones 1 a wet equatorial zone primarily characterized by oxisols and secondarily by argillisols and histosols 2 a subtropical dry zone containing calcisols and less commonly gypsisols and vertisols 3 a moist mid latitude zone with argillisols spodosols gleysols and histosols and 4 a polar zone featuring protosols and gleysols the model is general in nature and its application to the geologic past will be affected by variability through time in paleogeography and paleoclimatic parameters

response of the internal wave field to remote wind forcing by tropical cyclones abstractin the tropical north atlantic mean winds introduce relatively little energy into the internal wave field but hurricanes act as very energetic sources for near inertial waves in addition to the eventlike passage of such tropical cyclones changes in the wind speed north of the trade wind system induce a seasonal cycle in surface swell with potential implications for the high frequency part of the internal wave field using a 5 yr mooring time series in the interior of the tropical north atlantic at 16 n the temporal variability of internal wave energy south of the main hurricane track in different frequency bands is studied and the magnitude of its variability along with possible energy transfer mechanisms is analyzed the results show that changes in near inertial energy are dominated by the passage of internal waves generated by hurricanes centered several hundred kilometers north of the mooring the major role of hurricanes in the generation of near inertial waves is also seen in an ext

seasonality of deep cycle turbulence in the eastern equatorial pacific abstractthe seasonal cycles of the various oceanic and atmospheric factors influencing the deep cycle of turbulence in the eastern pacific cold tongue are explored moored observations at 140 w have shown seasonal variability in the stratification velocity shear and turbulence above the pacific equatorial undercurrent euc in boreal spring the thermocline and euc shoal and turbulence decreases marginal instability clustering of the local gradient richardson number around the critical value of 1 4 evident throughout the rest of the year has not been detected during spring while the daily averaged turbulent energy dissipation in the euc is weakest during the spring it is not clear whether the diurnal fluctuations that define the deep cycle cease large eddy simulations are performed using climatological initial and boundary conditions representative of january april july and october deep cycle turbulence is evident in all cases the mechanism remains the same and the maximum turbulence leve