horizontal wave number spectra of density and temperature perturbations in the mesosphere measured during the 4 august flight of anlc 93 on 4 august 1993 during anlc 93 the ncar electra completed a round trip flight west from edmonton alberta to the pacific ocean the university of illinois na lidar and utah state michelson interferometer observations were used to study the vertical wave number m and zonal wave number k spectra of relative atmospheric density na abundance oh emission intensity and rotational temperature perturbations the spectral indices of the m and k spectra inferred from the lidar data are smaller than those reported by hosteller and gardner 1994 over the mid pacific but similar to those reported by kwon et al 1990 over the rocky mountains and great plains these differences may be a consequence of different gravity wave source characteristics over the rocky mountains compared to the equatorial mid pacific region where convection is strong and orographic forcing is absent the na abundance spectrum closely follows a power law over the range from k 2 1000 km to 2 3 km this observation contradicts simple gravity wave theory which predicts that the abundance spectrum should fall rapidly to zero at wave numbers larger than 2 25 km

gravity wave propagation and dissipation from the stratosphere to the lower thermosphere 1 one night 28 october 2003 temperature and horizontal wind measurements by a resonance sodium na wind temperature lidar at maui 20 7 n 156 3 w and temperature measurement by a rayleigh lidar at mauna loa observatory mlo 19 5 n 155 6 w hawaii were used to study gravity wave gw propagation from the lower stratosphere to the lower thermosphere a dominant wave mode was identified from 35 to 103 km the wave was partially dissipated and propagating upward with a scale height of temperature amplitude at 14 km a damping layer was present around the stratopause where the wave amplitude was small which also corresponded to a low static stability layer the vertical wavelengths were larger in the mesosphere 12 13 km than in the stratosphere 6 7 km consistent with the decreasing static stability with altitude hodograph analysis of the na lidar wind data showed that the wave was propagating northward and the horizontal wavelength was 2140 km and intrinsic period was 15 h in the region 84 103 km the apparent period was 6 h and consistent with doppler shift of the background wind it is suggested that the convective zone over the equator to the south of hawaii provided a constant gw source that is responsible for the observed gw throughout the night

estimation of fracture height using microseismicity associated with hydraulic fracturing the ratio of horizontal to vertical h v particle velocity in background microseismic radiation associated with hydraulic fracturing is substantially higher in the dilatant low velocity fractured zone than it is outside this provides a useful diagnostic for determining the height of the fractured zone numerical synthesis of guided wave phenomena within the low velocity fractured zone accounts for much of the observed behavior but measured h v patterns are not totally consistent with either pure tensile or pure shear sources a composite model containing both tensile compressional sources and asperity shear failures appears to satisfy the main observations better than either source type does alone this composite is consistent with current models of earthquake aftershock sequences which also have different mechanisms at the edges and in the interior of a fracture zone tensile and shear respectively the h v phenomenon is consistent with a predominance of energy with shear wave polarization traveli

age and significance of sequence boundaries on jurassic and early cretaceous rifted continental margins the age and significance of sequence boundaries on jurassic to early cretaceous rifted continental margins in three ocean basins have been documented the margins are the santos basin in the south atlantic the grand banks in the north atlantic and the beaufort sea in the arctic ocean large industry data bases were used for the interpretation of each area megasequence boundaries separate the major phases of basin evolution for example syn rift and post rift boundaries developed with an average periodicity of 49 m y sequence boundaries define the component parts of each megasequence and developed with a modal periodicity of 10 15 m y out of 27 total boundary ages most 16 are developed on just one margin only two possible age ranges overlap on all three margins ighty percent of the megasequence boundaries and 50 of the sequence boundaries show a direct causal connection with coeval faulting and or folding the rest of the boundaries appear as unstructured surfaces separating transgressive and or regressive sedimentary wedges and are interpreted to result from changes in the rate of basin subsidence sediment input and long term eustatic sea level these data do not support theories advocating synchronous worldwide boundary development resulting from periodic short term falls in global eustatic sea level only in like basins of the same age with identical subsidence and sediment input rates are boundaries likely to develop synchronously hence the concept of global synchroneity of sequence boundary development may well be an illusion creat d by the similarity in age of the majority of basins studied as a result of this study it seems wise discard the global approach to basin analysis

musings over sedimentary basin evolution field geologists and explorationists are of necessity immersed in numerous very detailed surface and subsurface observations they are often perplexed by the choice of relatively simple geophysical models that so elegantly explain the origin and evolution of sedimentary basins geophysicists on the other hand search for a simple theme to explain the origin of sedimentary basins and much like managers are often impatient with lengthy detailed geological discourse that often uses fancy jargon to hide the very real difficulty that geologists have in separating important evidence from mere encyclopaedic description the following musings address the quality and limitations of geologic and geophysical evidence that may be used to evaluate the relative roles of stress thermal effects and gravity loading which have been so lucidly summarized by m h p bott in the preceding summary the fine papers presented during this meeting of course have led to significant modifications of some of my earlier thoughts because these have been previously published elsewhere bally snelson 1980 bally 1980 they are summarized here only for the convenience of the reader

dual simulations of fluid flow and seismic wave propagation in a fractured network effects of pore pressure on seismic signature summary fluid flow in the earth s crust plays an important role in a number of geological processes in relatively tight rock formations such flow is usually controlled by open macrofractures with significant implications for ground water flow and hydrocarbon reservoir management the movement of fluids in the fractured media will result in changes in the pore pressure and consequently will cause changes to the effective stress traction and elastic properties the main purpose of this study is to numerically examine the effect of pore pressure changes on seismic wave propagation i e the effects of pore pressures on amplitude arrival time frequency content this is achieved by using dual simulations of fluid flow and seismic propagation in a common 2 d fracture network note that the dual simulations are performed separately as the coupled simulations of fluid flow and seismic wave propagations in such fracture network is not possible because the timescales of fluid flow and wave propagation are considerably different typically fluid flows in hours whereas wave propagation in seconds the flow simulation updates the pore pressure at consecutive time steps and thus the elastic properties of the rock for the seismic modelling in other words during each time step of the flow simulations we compute the elastic response corresponding to the pore pressure distribution the relationship between pore pressure and fractures is linked via an empirical relationship given by schoenberg and the elastic response of fractures is computed using the equivalent medium theory described by hudson and liu therefore we can evaluate the possibility of inferring the changes of fluid properties directly from seismic data our results indicate that p waves are not as sensitive to pore pressure changes as s and coda or scattered waves the increase in pore pressure causes a shift of the energy towards lower frequencies as shown from the spectrum as a result of scattering attenuation another important observation is that the fluid effects on the wavefield vary significantly with the source receiver direction that is the azimuth relative to the fracture orientation these results have significant implications for the characterization of naturally fractured reservoirs using seismic methods and may impact on experimental design to infer such attributes in a real reservoir situation particularly in acquiring time lapse seismic data

radiation from point sources in general anisotropic media summary a procedure to evaluate the geometrical properties of the slowness surface for arbitrary anisotropic media is presented this allows us to use results for computing the displacement field from point sources in general anisotropic media utilizing the gaussian curvature of the slowness surface of the considered waves since the formulae used are based on high frequency asymptotics the procedure gives reliable results as long as no parabolic points of the slowness surface are encountered radiation patterns of point sources for models representing rocks in the crust and upper mantle are presented and discussed the radiation from point sources in anisotropic models is compared with the radiation from point sources in average isotropic models to emphasize the differences anisotropy is either caused by aligned cracks crustal rocks or by aligned olivine crystals upper mantle rocks considering models of aligned cracks differing only in the physical parameters of the crack material water or gas significantly different radiation patterns are obtained models with wet cracks exhibit focusing of quasi s wave energy for some directions whereas this effect is not observed for the corresponding model with dry cracks the quasi s wave radiation pattern from explosions are multilobed and the wet crack models exhibit more lobes than the dry crack models the radiation of single forces in olivine shows strong energy focusing wave tuning of quasi s waves however for realistic compositions of upper mantle rocks with some 10 per cent of preferentially orientated olivine this wave tuning is less pronounced

contrasting styles of late jurassic syn rift turbidite sedimentation a comparative study of the magnus and oseberg areas northern north sea abstract contrasting types of sediment gravity flow and hemipelagite deposition are recorded by the late jurassic syn rift successions in the magnus and oseberg areas in the northern north sea in both areas the late jurassic rift interval was characterized by recurrent tectonic phases during the late oxfordian to early volgian the penguin halfgraben in the magnus area received a significant amount of coarse clastics and can be regarded as an example of a well fed deeper marine riftbasin periods with high rates of extensional faulting are characterized by isolated sediment gravity flow lobes which stack in an uneven albeit downdip shifting or backstepping manner the stratigraphic motif of these intervals is overall mud prone with coarse clastics represented by thick conglomerate sandstone mudstone aprons along the basin bounding masterfaults in contrast periods with low rates of extensional faulting are characterized by basinwide sheet like parallel layered sediment gravity flow packages which infill the riftbasin in a progradational manner from the middle volgian the penguin halfgraben became sediment starved and shows a similar development to the oseberg area in the oseberg area the late jurassic syn rift succession provides a typical example of a sediment starved deeper marine riftbasin sediment gravity flow deposition in this area is limited to periods of high rates of extensional faulting these coarser clastic depositional episodes mimic their counterparts in the penguin halfgraben being characterized by mud prone strata with localized isolated sediment gravity flow lobes and footwall derived clastic wedges along the basin bounding masterfaults in contrast to the well fed basins the intervening stages of tectonic quiescence in the sediment starved basins are characterized by basinwide blanketing of clay commonly of high source rock potential in both basins the rotational tilt packages can be subdivided into an early a climax and a late syn rotational interval based on the architecture of their contained facies tracts these depositional episodes reflect the temporal evolution of the riftbasins catchment areas and their linked depositional systems it is mainly the nature and amount of sediment supply during the following tectonic quiescence or post rift stages that determine whether the riftbasin remained sediment starved or became infilled simplified sequence stratigraphic models are of limited use in the analyses and lithology prediction of riftbasin infills as individual halfgrabens often have their own specific infill history and hence characteristic syn rift stratigraphic signature the main controls on the variability of these deeper marine syn rift sediment gravity flow hemipelagite packages are the style and rate of extensional faulting sediment supply the source area s sediment yield potential and calibre and the halfgraben configuration and location with respect to the main hinterland areas

airborne sodium lidar observations of horizontal and vertical wave number spectra of mesopause density and wind perturbations we present kinetic energy horizontal and vertical wave number spectra of wind and density perturbations at mid latitudes for the altitude range from approximately 80 to 100 km the spectra are inferred from na density profiles collected with an airborne lidar during two flights conducted in november 1986 the two flights included one round trip from denver colorado to springfield illinois and another round trip from denver to the pacific coast the horizontal wave number spectra exhibited an approximately kh 1 2 dependence at horizontal scales from 70 to 700 km while the vertical wave number spectra exhibited an approximately kz 2 7 dependence at vertical scales from 2 to 10 km these spectra are compared with spectra obtained from ground based lidar radar shuttle re entry and global atmospheric sampling program observations the rms horizontal wind velocity inferred from the airborne na lidar data increased with time and with longitude from the pacific coast to the great plains the inferred mean rms horizontal wind velocity was 32 m s 1 and the mean horizontal velocity variance was about 1100 m2 s 2 this horizontal velocity variance is comparable to horizontal velocity variances inferred from radar observations but larger than horizontal velocity variances inferred from shuttle re entry observations during the round trip flight from denver colorado to springfield illinois two quasi monochromatic waves were observed the longer wavelength wave had an intrinsic zonal wavelength of 772 km intrinsic zonal phase velocity of 35 m s 1 westward and intrinsic period of 6 1 hours this wave appears to be propagating almost due west the shorter wavelength wave had an intrinsic zonal wavelength of 263 km zonal phase velocity of 43 m s 1 westward and period of 1 7 hours

gravity wave and equatorial wave morphology of the stratosphere derived from long term rocket soundings fluctuations in vertical profiles of atmospheric temperature and horizontal wind in the 20 60 km altitude range have been isolated from meteorological rocket measurements during 1977 87 at 15 widely separated sites the seasonal geographical and vertical variability of the variance of horizontal velocities u 2 2 and relative temperature perturbations t 2 were studied the bulk of the variance of both quantities in the 2 10 km and 2 20 km vertical wavelength bands was associated with gravity wave motions although in depth study of the wave polarization shows that planetary scale equatorial wave modes contribute to the variance at equatorial sites annual mean variances varied widely among the 15 stations suggesting appreciable geographical variability in stratospheric wave activity

wave velocities and attenuation of shaley sandstones as a function of pore pressure and partial saturation we obtain the wave velocities and quality factors of clay bearing sandstones as a function of pore pressure frequency and partial saturation the model is based on a biot type three phase theory that considers the coexistence of two solids sand grains and clay particles and a fluid mixture additional attenuation is described with the constant q model and viscodynamic functions to model the high frequency behaviour we apply a uniform gas fluid mixing law that satisfies the wood and voigt averages at low and high frequencies respectively pressure effects are accounted for by using an effective stress law by fitting a permeability model of the kozeny carman type to core data the model is able to predict wave velocity and attenuation from seismic to ultrasonic frequencies including the effects of partial saturation testing of the model with laboratory data shows good agreement between predictions and measurements

mesoscale spectral analysis of in situ horizontal and vertical wind measurements at 6 km as part of the aloha anlc 93 campaign to investigate atmospheric dynamics in situ wind measurements collected at 6 km with the gust probe sensor attached to the national center for atmospheric research electra aircraft were analyzed for 16 flight segments between 61 n and 14 s and between 92 w and 170 w over land and water horizontal wavenumber spectra for the vertical wind and both zonal and meridional horizontal wind components were calculated the zonal and meridional wavenumber spectra exhibited a decrease in the spectral slope from 1 98 0 02 for wavelengths between 2 km and 100 km to 3 18 0 06 for the longer wavelengths between 100 km and 330 km the wavenumber spectrum for the vertical wind component showed a 2 power law dependence for wavelengths in excess of 5 km and a generally flat shape at shorter wavelengths an increase in power at the wavelength of 10 km was detected for the meridional wavenumber spectrum these results were compared with predictions from two spectral models and with spectral results from other observations

quantitative determination of hydraulic properties of fractured rock using seismic techniques there have been significant advances over the last ten years in the use of the seismic anisotropy concept to characterize subsurface fracture systems measurements of seismic anisotropy are now used to deduce quantitative information about the fracture orientation and the spatial distribution of fracture intensity analysis of the data is based upon various equivalent medium theories that describe the elastic response of a rock containing cracks or fractures in the long wavelength limit conventional models assume scale frequency independence and hence cannot distinguish between micro cracks and macrofractures the latter however control the fluid flow in many oil gas reservoirs as the fracture size and spacing hence fracture storability are essential parameters for reservoir engineers recently a new equivalent medium theory for modelling of wave propagation in media with multi scale fractures has been presented the model predicts velocity dispersion and attenuation due to a squirt flow mechanism at two different scales the grain scale micro cracks and equant matrix porosity and formation scale fractures application of this model to field data shows that fracture density and fracture size can be inverted successfully from the frequency dependence of the time delay between split shear waves the derived fracture length matches independent observations from borehole data this paper presents the results of the latest development in the seismic characterization of natural fractures with an emphasis on the quantitative determination of fracture sizes

strike slip duplexes abstract strike slip fault systems often contain zones of steep imbricate faults geometrically similar to imbricate fans and duplexes in dip slip thrust and normal fault systems they are evident in map view rather than in vertical sections examples of duplexes are cited from both active and ancient systems and from theoretical and physical models duplexes may form at bends on strike slip faults by a process kinematically analogous to the sequential imbrication of ramps on dip slip faults however some may form and many may initiate as non sequential riedel fractures at fault offsets or on straight fault segments this process is more marked than in dip slip systems where primary anisotropy such as bedding exerts more control on fault geometry strike slip duplexes may be shunted along the fault system parallel to the regional slip vector however duplexes or individual horses will usually also move up or down perpendicular to the slip vector because of the unconstrained upper surface to the fault system these factors mean that no section through a strike slip system should be expected to area balance the faults of strike slip duplexes and imbricate fans may root in kinematically necessary low dip faults or may converge downwards and appear in vertical sections as flower structures

plate tectonics and the evolution of the british isles this paper is an essay on the rationalism and difficulties of the geological corollaries of plate tectonics with illustrations particularly from the geological history of the british isles there is special emphasis on the mechanics of continental lithosphere in extension when basins are formed and in convergence whereby continental lithosphere thinned in extension is shortened and restacked to form orogenic belts an upper lithosphere stress concentrating elastic lid suffers extremely complex inhomogeneous deformations above a simpler viscoelastic lower lithosphere whose deformation drives strain and displacement in the elastic lid the very nature of plate tectonics as relative motion among a multi plate mosaic of plates provides a rational semi quantitative framework for large scale geological complexity in space and time the caledonian and hercynian history of the british isles may be explained semi quantitatively in terms of plate boundary evolution but it is not possible to define unequivocal solutions the rationalism of plate tectonics is exhibited on a smaller more direct field scale by many of the complexities of ophiolite complexes such as ballantrae scotland that can be explained as the effects of the evolution of ridge ridge transforms and by diachronous deformation and sedimentation in subduction accretion prisms such as the southern uplands deformational and sedimentary patterns in nw europe from triassic times to the present day resulted from a complex interaction of extensional events related to diachronous atlantic opening and compressional events related to sequential alpine shortening phases those widespread events are typical of intracontinental plate boundary systems and create great difficulties for the geologist wishing to decipher relative plate motion from geological sequences because huge areas much larger than the british isles must be analysed and synthesized before much sense can be extracted further difficulties arise from the palinspastic and preservation problems of convergent boundaries orogenic shortening telescopes and partially subducts facies belts most orogenic belts were assembled as a collage of displaced and rotated terrain elements that were subsequently flattened elongated and straightened to an apparent but deceiving simplicity therefore while plate tectonics provides a rational geological framework against which for example british basin evolution can be tested and explained we cannot yet use the geological effects of plate boundary evolution to reconstruct relative plate motion quantitatively

seismic velocities of fractured carbonate rocks southern apennines italy summary a study of the effect of fractures on seismic velocities has been carried out through a comparative study in the field and the laboratory p and s wave velocities were obtained from surface and borehole seismic measurements and in the laboratory ultrasonic velocities were measured on intact and artificially fractured specimens of carbonate rocks from the miranda area southern apennine chain italy calcareous and calcareous chert sequences are present in the area with a discontinuity spacing from very close to very wide essentially dry rocks have been tested a correspondence was found between visible rock fracturing and compressional wave velocities from surface seismic measurements the downhole velocities were lower than the corresponding ultrasonic velocities on core specimens and increased with depth specimens were then cut to simulate field discontinuities and loaded to study the influence of vertical pressure on the seismic velocities laboratory and field velocities were finally compared as functions of vertical pressure it turns out that fractures reduce and vertical pressure increases velocities since the rock quality designation rqd indices were generally very low the increasing seismic velocities with depths in poor quality rocks can be explained in terms of better contact between fracture surfaces

seismic velocities in fractured rocks an experimental verification of hudson s theory flow of fluids in many hydrocarbon reservoirs aquifers is enhanced by the presence of cracks and fractures these cracks could be detected by their effects on propagation of compressional and shear waves through the reservoir several theories including hudson s claim to predict the seismic effects of cracks although hudson s theory has already been used to calculate crack densities from seismic survey s the predictions of the theory have not yet been tested experimentally on rocks containing a known crack distribution this paper describes an experimental verification of the theory the rock used carrara marble was chosen for its uniformity and low porosity so that the effect of cracks would not be obscured by other influences cracks were induced by loading of laboratory specimens velocities of compressional and shear waves were measured by ultrasound at 0 85 mhz in dry and water saturated specimens at high and low effective pressures the cracks were then counted in polished sections of the specimens in dry specimens with both dry and saturated cracks hudson s theory overpredicted observed crack densities by a constant amount that is attributed to the observed value being systematically underestimated the theory made poor predictions for fully saturated specimens shear wave splitting caused by anisotropy duemore to both crystal and crack alignment was observed cracks were seen to follow grain boundaries rather than the direction of maximum compression due to loading the results demonstrate that hudson s theory may be used in some cases to determine crack and fracture densities from compressional and shear wave velocity data less

depositional systems and sequence stratigraphy of mesozoic lacustrine rift basins in ne china a case study of the wulan hua sag in the southern erlian basin abstract the deltaic and lacustrine sediments respectively in the syn and post rift stages are recorded during the cretaceous at the wulan hua sag erlian basin inner mongolia in this study the mesozoic depositional system and sequence stratigraphic framework are recognized in the wulan hua sag using core well log and seismic data five sedimentary facies have been identified including fan delta braided delta shallow lacustrine deep lacustrine and sublacustrine fan during cretaceous at the wulan hua sag one first order sequence msq1 three second order sequences ssq1 ssq2 and ssq3 and five third order sequences sq1 sq2 sq3 sq4 and sq5 are classified by subaerial unconformities along the basin margins and correlative conformities in the central part of the basin during the depositional period of sq1 sq2 and sq3 the depocenter controlled by lake level fluctuations migrated from southern to northern part companying with multiple to single provenance supplies the characteristics of sedimentary facies and sequence stratigraphy in the wulan hua sag are commonly controlled by faults provenance and depocenters the development of the third order sequences is dominated by tectonism and sediment supplies as well as lake level changes driven by climate the favorable targets for hydrocarbon located in the lowstand system tract of sq1 sq2 and sq3 at the southern parts of the wulan hua sag

reflection transmission coefficients and azimuthal anisotropy in marine seismic studies summary introduce two methods for inferring the direction of vertical fractures from marine seismic data first we derive the necessary reflection and transmission coefficients for an interface between a liquid and an azimuthally anisotropic solid next we show that multicomponent ocean bottom seismometer data from surface airgun sources along two perpendicular shot lines can be rotated into the principal directions of azimuthal anisotropy to determine the orientation of vertical fractures finally we show that p wave amplitude versus offset avo depends on the orientation of the shot line with respect to the vertical fractures thus p wave avo can also be used to determine fracture orientation

seismic characterization of vertical fractures described as general linear slip interfaces fluid flow in many hydrocarbon reservoirs is controlled by aligned fractures which make the medium anisotropic on the scale of seismic wavelength applying the linear slip theory we investigate seismic signatures of the effective medium produced by a single set of general vertical fractures embedded in a purely isotropic host rock the generality of our fracture model means the allowance for coupling between the normal to the fracture plane stress and the tangential jump in displacement and vice versa despite its low triclinic symmetry the medium is described by just nine independent effective parameters and possesses several distinct features which help to identify the physical model and estimate the fracture compliances and background velocities for example the polarization vector of the vertically propagating fast shear wave s1 and the semi major axis of the s1 wave normal moveout nmo ellipse from a horizontal reflector always point in the direction of the fracture strike moreover for the s1 wave both the vertical velocity and the nmo velocity along the fractures are equal to the shear wave velocity in the host rock analysis of seismic signatures in the limit of small fracture weaknesses allows us to select the input data needed for unambiguous fracture characterization the fracture and background parameters can be estimated using the nmo ellipses from horizontal reflectors and vertical velocities of p waves and two split s waves combined with a portion of the p wave slowness surface reconstructed from multi azimuth walkaway vertical seismic profiling vsp data the stability of the parameter estimation procedure is verified by performing non linear inversion based on the exact equations

observations of high frequency temporal gravity wave spectra in the middle upper stratosphere there is a paucity of high frequency temporal gravity wave spectra in the middle upper stratosphere 30 40 km as most instruments that are capable of accessing this region do not have the capability to make measurements for any extended period of time the spectral analysis of density fluctuations obtained with the purple crow rayleigh scatter lidar has shown that middle upper stratospheric temporal spectra follow the expected 1 5 to 2 0 power law relationship for frequencies less than 1 10 3 s 1 at frequencies greater than 1 10 3 s 1 the shape of the temporal spectrum is much more variable with strong quasi monochromatic features appearing intermittently on certain nights these higher frequency features have been attributed to nonlinear wave interactions and suggest that estimates of gravity wave activity in the middle upper stratosphere may be larger and much more variable than previously assumed this variability also suggests that middle upper stratospheric energy dissipation and eddy diffusion values may be much larger and more variable than previously assumed current parameterizations of subgrid dynamical processes in general circulation models that resolve this region may need to be reexamined in this light

mesospheric winds from lidar observations of atmospheric sodium laser radar observations of the atmospheric sodium layer made by various groups of workers during the past decade have shown that the layer exhibits considerable time varying structure in this paper we describe horizontally spaced measurements of this structure and use the results of these observations to derive horizontal velocities in the height range 82 to 99 km the measurements were made with a steerable lidar operating at a fixed zenith angle of 20 9 and pointed at each of three azimuths in turn the complete sequence taking 5 min the azimuths were chosen such that the intersections of the lidar beam with the sodium layer formed a triangle with approximately 60 km sides we present here the analysis of a 10 hour data run taken on the night of july 21 1979 after low pass filtering to remove rapid uncorrelated fluctuations a cross correlation analysis was carried out for each of the height intervals in the range 82 to 99 km the velocities calculated from the derived time shifts were found to vary with height in an oscillatory manner with amplitude increasing with height the east west component showed a vertical wavelength of approximately 10 km the north south component a wavelength of 5 km and the magnitude of the velocity varied between 6 and 146 m s 1

simulation of lidar measurements of gravity waves in the mesosphere lidar measurements of mesospheric gravity wave characteristics are simulated using a simple numerical model simple theory is used to superimpose gravity wave fluctuations upon typical background densities and sodium abundances in the height range 80 100 km which we then assume are perfectly observed by a rayleigh and na lidar respectively these lidar data are then analyzed for their gravity wave content using the standard reduction and analysis methods which are routinely applied to these data sets our goal is to assess whether this analysis of lidar data faithfully recovers the underlying wave field in both quasi monochromatic and spectral wave studies the height range over which na number density can be measured and the shape of the background na profile impose a limit on the gravity wave information which can be extracted from na lidar data the limitations due to background layer shape do not exist for rayleigh lidar measurements the simulations reveal that quasi monochromatic gravity waves with vertical wavelengths larger than approximately 10 km may not be reliably retrieved from na lidar data it is also shown that there are limitations on the accurate extraction of spectral parameters from na lidar data due to the limited vertical extent of the mesospheric na layer

continuity conditions for a fault consisting of obliquely aligned cracks summary expressions exist for the continuity conditions that apply to a plane fault that is modelled as a distribution of circular cracks lying in the plane of the fault these are conditions that apply when the wavelength of the incident wave is large compared with crack size and spacing and they are approximate for a small number density of the cracks in form they are identical to the fault slip conditions of murty schoenberg and pyrak nolte myer cook in which the traction is proportional to the displacement discontinuity across the fault it is possible to envisage a fault consisting of obliquely aligned cracks whose centres lie in the median plane of the fault but whose normals are not necessarily perpendicular to the fault we have found the interface conditions for this model to be more complex than those for the fault slip model and involve elements of the stress tensor other than the tractions on the plane of the fault the continuity conditions are compared with those for a thin anisotropic layer and it is found that there is no equivalent material layer representation unless the cracks are parallel to the plane

estimation of fracture parameters from reflection seismic data part iii fractured models with monoclinic symmetry existing geophysical and geological data indicate that orthorhombic media with a horizontal symmetry plane should be rather common for naturally fractured reservoirs here we consider two orthorhombic models one that contains parallel vertical fractures embedded in a transversely isotropic background with a vertical symmetry axis vti medium and the other formed by two orthogonal sets of rotationally invariant vertical fractures in a purely isotropic host rock using the linear slip theory we obtain simple analytic expressions for the anisotropic coefficients of effective orthorhombic media under the assumptions of weak anisotropy of the background medium for the first model and small compliances of the fractures all effective anisotropic parameters reduce to the sum of the background values and the parameters associated with each fracture set for the model with a single fracture system this result allows us to eliminate the influence of the vti background by evaluating the differences between t

rayleigh lidar measurements of the temporal frequency and vertical wavenumber spectra in the mesosphere over the rocky mountain region temporal and spatial spectral analysis techniques were applied to lidar data collected over a period of 18 months above the rocky mountain region at an altitude range from 45 to 70 km by a rayleigh lidar system located in logan utah 41 7 n 111 8 w examination of the averaged temporal frequency f and vertical wavenumber f m spectra showed spectral slope values of 1 49 0 03 and 2 3 0 1 respectively the observed slope for the overall averaged f m spectrum is considerably more positive than the value of 3 predicted by the linear instability theory but close to the value of 2 that is predicted by the scale independent diffusive filtering theory using the measured f slope parameter however examination of the monthly averaged f m spectra for the transition from winter to summer showed the spectra became flatter suggesting that doppler shift effects caused by the seasonal change in the magnitude and direction of the background wind field are significant the characteristic vertical wavelength was found to be 12 km for the altitude region of 45 70 km comparison of this value with the characteristic wavelengths from other lidar observations at lower and higher altitude ranges showed an overall increase of with height the observed enhancement of the f m spectral magnitude in winter is believed to be caused in part by the low frequency wave activity observed in the temperature profiles

using high resolution stratigraphy to date fold and thrust activity examples from the neogene of south central sicily the integration of structural and stratigraphic data is fundamental for determining rates of deformation in the uppermost continental crust the high temporal resolution provided by neogene marine sediments is used here to examine deformation rates in part of a thrust belt chosen from the maghrebian orogen of sicily conventional biozonal stratigraphy calibrated against the geomagnetic polarity time scale shows that individual thrust fold structures grew steadily over many millions of years structures across the thrust belt were active at the same time and accommodated bulk shortening rates of c 0 5 mm a 1 in contrast the basal detachment operated about ten times faster these results are in broad agreement with some theoretical models for orogenic wedge kinematics shore line carbonate successions calibrated with precession cycles of sea level change provide a very high resolution temporal scale with which to chart tilt rates on fold limbs 1 27 6 ka 0 036 ka 1 these show that fold amplification was continuous although the rates may have varied with time incremental tilting of limbs during fold amplification is not predicted by popular models of fault bend and 9fault propagation9 folding geometric modelling suggests that folding occurred by limb rotation with minor hinge migration during buckling above buried thrusts thus stratigraphic data may be used to examine the kinematic evolution of thrust fold systems along regional cross sections and of local structures however the types of structural models that can be tested using estimates of deformation rates depend upon the chrono stratigraphic resolution available for the syn tectonic sediments

improved middle atmosphere climate and forecasts in the ecmwf model through a nonorographic gravity wave drag parameterization abstract in model cycle 35r3 cy35r3 of the ecmwf integrated forecast system ifs the momentum deposition from small scale nonorographic gravity waves is parameterized by the scinocca scheme which uses hydrostatic nonrotational wave dynamics to describe the vertical evolution of a broad constant and isotropic spectrum of gravity waves emanating from the troposphere the cy35r3 middle atmosphere climate shows the following i an improved representation of the zonal mean circulation and temperature structure ii a realistic parameterized gravity wave drag iii a reasonable stationary planetary wave structure and stationary wave driving in july and an underestimate of the generation of stationary wave activity in the troposphere and stationary wave driving in january iv an improved representation of the tropical variability of the stratospheric circulation although the westerly phase of the semiannual oscillation is missing and v a realistic horizontal distribution of momentum flux in the

rayleigh lidar observations of mesosphere temperature structure ground based observations of atmospheric density profiles to 92 km were obtained for four successive seasons between summer 1989 and spring 1990 these results were obtained with a powerful rayleigh lidar facility located at wright patterson air force base dayton ohio this instrument combined a 14 w xef laser transmitter with a 2 54 m receiver mirror to observe returns from altitudes between 40 and 95 km analysis of the scale height dependence of the density profiles produced temperatures with a measurement error of about 5 k 2 5 at 90 km when the lidar data was averaged for 20 min and smoothed in height over 2 7 km examination of these profiles for the total of 18 nights showed that there often existed in the mesophere a layer of enhanced temperatures when compared with the u s standard profile the layer centroid height was about 85 km for summer and 70 to 75 km for winter data obtained for the equinoctial periods showed the amplitude of these layers to be weak the winter temperature profiles showed evidence forlong period waves passing through the region of the thermal anomaly while the equinox profiles revealed more sporadic wave activity with shorter vertical wavelengths both the winter and summer temperature data displayed regions where the observed lapse rate approached the adiabatic lapse rate in the summer the wave activity near the inversion layer was weak

rayleigh lidar observations of quasi sinusoidal waves in the tropical middle atmosphere 1 rayleigh lidar observations of temperature for 2 7 hours on 38 nights during the period of 18 january 5 march 1999 and for 3 hours on 29 nights during 29 february 2 april 2000 in the altitude region of 27 60 km over gadanki 13 5 n 85 e clearly show the dominance of the quasi sinusoidal waves of periods in the range of 6 13 hours in temperature in the tropical middle atmosphere during 1999 the vertical wavelength of these waves ranges from 7 1 to 17 km with a mean value of 12 0 2 4 km while during 2000 it ranges from 5 5 to 17 km with a mean value of 11 4 3 5 km the wave periods estimated from the observations during 1999 are generally greater than the observation period on each night and are estimated to be in the range of 6 5 13 1 hours with an average period of 9 7 1 8 hours which is significantly smaller than the inertial period of 53 hours the amplitudes of these waves are in the range of 1 to 8 k such sinusoidal wave modes are clearly discernible in the temperature profiles for 50 nights of observation another striking feature is that the quasi sinusoidal structure is clearly observed in the equivalent day analysis also indicating only small day to day variability in phase a property that is characteristic of atmospheric tides

simultaneous na lidar and hf radar observations of vertical velocities in the mesosphere above urbana illinois the first simultaneous na lidar and medium frequency 2 66 mhz doppler radar observations of vertical winds in the mesosphere 79 5 100 km above urbana illinois are reported the lidar and radar systems were operated simultaneously for a 24 h period during january 1989 the lidar measured na density profiles and the radar measured the vertical component of velocity the na density data was used to derive the vertical velocity using the continuity equation this data set provides a unique opportunity to check the consistency of parameters measured by the two very different experimental techniques excellent agreement is found between the radar velocities and the velocities inferred from the na density on the bottomside of the na layer significant differences are found between the velocities obtained with the two techniques on the top side of the na layer possible reasons for this discrepancy are discussed

gravity wave structure between 60 and 90 km inferred from space shuttle reentry data abstract density fluctuations obtained along seven space shuttle reentry tracks are used in this paper to examine the horizontal structure and the vertical distribution of density variance in the mesosphere and lower thermosphere the tracks lie primarily over open ocean at middle and low latitudes and represent the only measurements of horizontal atmospheric structure at these heights available to date the density fluctuations are interpreted in terms of gravity wave motions and reveal significant density and velocity variance at horizontal scales ranging from 10 to 1000 km fluctuation amplitudes are used to infer corresponding velocity perturbations and characteristic vertical scales and frequencies of the wave spectrum results suggest that the mean velocity variance is smaller over the pacific ocean than observed over major land masses and that the variance increases with height in a manner consistent with that expected in the presence of wave saturation processes

a climatology of gravity wave motions in the mesopause region at adelaide australia abstract a statistical study of gravity wave motions in the mesosphere and lower thermosphere measured with a mf partial reflection radar located at buckland park new adelaide 35 s 138 e in the period november 1933 to december 1984 is presented the analyses am confined to waves with ground based periods between 1 and 24 h time height cross sections show that the mean square amplitudes u 2 and v 2 of the zonal and meridional perturbation velocities respectively vary in a predominantly semiannual manner such that the minima in wave activity coincide with the reversals in the zonal circulation in the middle atmosphere in most instances v 2 is greater than u 2 which together with the small but nonzero u v fluxes shows that the gravity wave field is partially polarized a technique similar to that used to analyse partially polarized electromagnetic waves suggests that on a seasonal basis the wave field is polarized by about 10 to 20 but for shorter periods the degree of polarization may be signi

noctilucent clouds and wave dynamics observations at sondrestrom greenland rayleigh lidar measurements of the arctic summer stratosphere and mesosphere have been conducted routinely since 1994 at the sondrestrom atmospheric research facility near kangerlussuaq greenland 67 0n 50 9w between 1994 and 1996 seventeen separate events of noctilucent clouds nlcs as well as corresponding stratospheric wave structure have been observed we present in this study two main results 1 the occurrence of persistent quasi monochromatic wave structure in the stratosphere having observed vertical wavelengths of 8 to 12 km and observed temporal periods of approximately 2 3 hours and 2 evidence that the strength of such lower altitude waves may be associated with the overall strength of the observed nlc volume backscatter coefficient

correlative radar and airborne sodium lidar observations of the vertical and horizontal structure of gravity waves near the mesopause in november 1986 joint radar and na lidar observations were conducted in colorado to study mesopause dynamics the radar observations were conducted at platteville colorado with a stratosphere troposphere st radar in a meteor echo detection mode the na lidar observations included ground based observations at broomfield and denver colorado and airbome observations during three flights over the great plains rocky mountains and pacific coast both radar and lidar identified a 6 hour wave that was remarkably coherent during the november campaign the vertical wavelength of the 6 hour wave estimated from the radar data was 8 to 9 km the amplitude of the zonal wind component was 10 m s 1 and the amplitude of the meridional wind component was 4 m s 1 the vertical wavelength estimated from the ground based and airborne lidar data was 7 3 km and the amplitude of the scalar horizontal wind ranged from 13 to 16 m s 1 the zonal wavelength of this wave was approximately 772 km and the intrinsic zonal phase velocity was 35 m s 1 westward the 6 hour wave was dominant in the height range of 80 90 km which corresponds to the bottomside of the na layer an additional 2 hour wave was observed with the na lidar during both the ground based and airborne observations the vertical wavelength of this wave was about 12 km and the zonal wavelength was 260 km the intrinsic zonal phase velocity was 43 m s 1 westward this 2 hour wave was also present only on the bottomside of the na layer

intraplate stresses a new tectonic mechanism for fluctuations of relative sea level stress variations in the lithosphere of a few hundred bars can explain the major part of the seismostratigraphic record at passive margins and intracratonic basins however to induce apparent sea level fluctuations with magnitudes greater than 50 m changes in stress level of more than 1 kbar are required these must be related to major reorganizations at convergent plate boundaries fragmentation of plates or collision processes specific rapid falls in the vail et al curves can be associated quantitatively with particular plate tectonic reorganizations of lithospheric stress fields the seismostratigraphic record may provide a new source of information on paleo stress fields to be correlated with results of independent numerical modeling of intraplate stresses

spatial and temporal evolution of rifting and continental breakup in the eastern black sea basin revealed by long offset seismic reflection data the age and distribution of the syn rift and early post rift infill records the spatial and temporal distribution of extension and breakup processes in a rift basin the eastern black sea basin ebsb is thought to have formed by back arc extension during cretaceous to early cenozoic time however a lack of direct constraints on its deep stratigraphy leaves uncertainties over the time duration and location for rifting and breakup processes in the basin here we use the enhanced imaging provided by 2d long offset seismic reflection profiles to analyze the deep structural and stratigraphic elements of the ebsb based on these elements we infer the presence of two distinct late cretaceous syn rift units recording initial extension rift stage 1 over the continental highs shatsky ridge and the mid black sea high followed by strain localization along the major basin bounding faults and rift migration towards the basin axis rift stage 2 overlying these units palaeocene eocene and oligocene units show a syn kinematic character in the nw with evidence for ongoing extension until oligocene time towards the se these sequences are instead post kinematic directly overlaying a basement emplaced during breakup we interpret the palaeocene oligocene units to record the time spanning from the initiation of breakup late cretaceous palaeocene in the se to the end of extension oligocene in the nw the first ubiquitously post rift infill is the lower miocene maykop formation our results highlight the along strike temporal variability of extension and breakup processes in the ebsb

fluid dependent shear wave splitting in fractured media azimuthal anisotropy in rocks can result from the presence of one or more sets of partially aligned fractures with orientations determined by the stress history of the rock a shear wave propagating in an azimuthally anisotropic medium splits into two components with different polarizations if the source polarization is not aligned with the principal axes of the medium for vertical propagation of shear waves in a horizontally layered medium containing vertical fractures the shear wave splitting depends on the shear compliance of the fractures but is independent of their normal compliance if the fractures are not perfectly vertical the shear wave splitting also depends on the normal compliance of the fractures the normal compliance of a fluid filled fracture decreases with increasing fluid bulk modulus for dipping fractures this results in a decrease in shear wave splitting and an increase in shear wave velocity with increasing fluid bulk modulus the sensitivity of the shear wave splitting to fluid bulk modulus depends on the interconnectivity of the fracture network the permeability of the background medium and on whether the fracture is fully or partially saturated

seismic properties of rocks with distributions of small cracks summary hudson s theory of multiple scattering for the dynamic properties of cracked rock is applied to media containing cracks of varying orientation radius and aspect ratio angular variation of velocity and attenuation due to parallel and nearly parallel cracks and cracks with normals at a fixed angle to a given axis are presented anisotropy gradually decreases as the distribution of orientations is widened from exactly parallel to random increasing the aspect ratio of thin saturated cracks generally causes the elastic properties to approach those due to dry gas filled cracks for fluid filled cracks the line singularity where the birefringent shear waves have equal velocity moves closer to the symmetry axis as either the distribution of orientations is widened or the aspect ratio is increased calculated attenuations due to rayleigh scattering and viscous dissipation in crack filling fluids are many orders of magnitude less than reported attenuations in the earth viscous dissipation varies linearly with frequency and aspect ratio of thin fluid filled cracks a power law distribution of crack radii intended to represent that found in the earth s crust has no effect on the angular variations of seismic velocities or viscous attenuation but scattering attenuation is sensitive to the power law exponent lognormal distributions of aspect ratio also corresponding to observations in real rock affect velocity as well as attenuation velocities derived from the theory are compared with those measured in laboratory specimens with known geometries of cracks

t matrix approach to shale acoustics summary the t matrix approach of quantum scattering theory is used here to place many long wavelength equivalent medium approximations for porous composites polycrystals and cracked media on a common footing and to indicate their limitations but also to derive some new results based on two point statistics in this way we have obtained an insight into the difficult problem of elastic inclusions at finite concentrations which is of foremost relevance when estimating the effective material parameters of porous cracked shales involving stacks of more or less horizontally aligned clay platelets mixed together with more rounded silt minerals and with fluid filling the spaces a rather involved perturbative analysis of the effects of interactions between or structural correlations among the various inclusions minerals and cavities making up a real shale of hexagonal symmetry was performed in an attempt to obtain a better match between theoretical predictions based on a combination of coherent and optical potential approximations and experimental results recovered from ultrasonic wave speeds for the effective elastic stiffness tensor for the particular data set considered in this study the t matrix approach was able to match the data better than the approach of hornby et al but the match was not completely satisfactory further progress in theoretical shale modelling may come from a better knowledge of the elastic properties of pure clay minerals a more detailed knowledge of the microstructure of shales the incorporation of constraints obtained from comparisons between theoretical predictions and experimental results as well as a continuing development of the t matrix approach numerical results also for the effect of bedding parallel microcracks on the elasticity of such a real shale have value in illustrating the importance of taking into account the effects of spatial distribution when trying to deal with non dilute mixtures of highly contrasting material properties

a conceptual model for the preservation of thick transgressive shoreline successions examples from the forearc nanaimo basin british columbia canada abstract sequence stratigraphic models derived from passive margins and foreland basins characterize transgressive shorelines excluding incised valleys as recording periods of sediment starvation and are commonly represented as thin 10 m are more likely to be developed in active tectonic settings e g forearc and rift basins which generally experience high sedimentation rates and relatively rapid changes in base level settings with high sedimentation rates and moderate base level rise lead to progradational trends despite overall transgression of the shoreline in settings where changes in eustatic sea level mainly control the resulting stratigraphic architecture e g passive margins thin transgressive successions 1 10 m are more likely to be produced finally in settings defined by relatively slow base level change e g foreland basins the resultant transgressive succession typically comprises a lag 1 m overlain by offshore mudstones this conceptual model highlights the importance of the interplay between sedimentation rates and base level rise and is intended as a guide for the predictive modeling of sedimentary basins

seismic wave propagation through material containing partially saturated cracks summary expressions for the wave speeds and attenuation of elastic waves through material containing aligned cracks are available in an approximation valid up to second order in the number density of cracks and for wavelengths that are long compared with the size of the cracks conditions within the crack may vary from dry stress free to fluid or solid filled the situation where cracks are partially filled with liquid and part with gas is very different from either extreme of dry or liquid filled cracks since the liquid is forced to flow laterally within a crack at the expense of the more compressible gas by tensions or compressions imposed normal to the plane of the crack expressions are derived here which enable the range of internal crack conditions to be extended to the case of partial saturation in the formulae for the propagation characteristics of waves of long wavelength through material containing such cracks

lidar temperature measurements of gravity waves over kuhlungsborn 54 n from 1 to 105 km a winter summer comparison 1 since august 2002 temperature measurements from 1 to 105 km are performed at the leibniz institute of atmospheric physics in kuhlungsborn 54 n with a combination of different lidars results from 14 nights in winter and 31 in summer are presented nightly mean profiles and fluctuations with a temporal and vertical resolution of 15 min and 1 km respectively are derived in both seasons wave energy propagates upward phase propagates downward with vertical phase speeds of 0 25 to 1 9 m s phase speeds are generally larger in the mesosphere compared to the stratosphere because of decreasing static stability wave periods are found in the entire range of 1 8 hours given by experimental constraints with no preference for particular periods the observed vertical wavelengths cover the entire instrumental range of 5 50 km but the majority lies below 22 km in both seasons in single nights a few waves up to three dominate the wave spectrum and represent 45 65 of the entire variability wave amplitudes generally increase with altitude with a scale height of 18 22 km i e less than expected 14 km for propagation conserving momentum flux density the gravity wave energy loss changes with altitude and is different in both seasons local fluctuation minima nodes are often observed frequently colocated with convective instabilities temperature fluctuations are generally smaller in summer compared to winter maximum values are 10 and 25 k respectively applying gravity wave polarization relations to the mean winter and summer lidar temperature profiles the difference of fluctuations is basically determined by the background conditions especially at 60 80 km

a coordinated study of 1 h mesoscale gravity waves propagating from logan to boulder with crrl na doppler lidars and temperature mapper we present the first coordinated study using two lidars at two separate locations to characterize a 1 h mesoscale gravity wave event in the mesopause region the simultaneous observations were made with the student training and atmospheric research star na doppler lidar at boulder co and the utah state university na doppler lidar and temperature mapper at logan ut on 27 november 2013 the high precision possessed by the star lidar enabled these waves to be detected in vertical wind the mean wave amplitudes are 0 44 m s in vertical wind and 1 in relative temperature at altitudes of 82 107 km those in the zonal and meridional winds are 6 1 and 5 2 m s averaged from 84 to 99 km the horizontal and vertical wavelengths inferred from the mapper and lidars are 219 4 and 16 0 0 3 km respectively the intrinsic period is 1 3 h for the airglow layer doppler shifted by a mean wind of 17 m s the wave packet propagates from logan to boulder with an azimuth angle of 135 clockwise from north and an elevation angle of 3 from the horizon the observed phase difference between the two locations can be explained by the traveling time of the 1 h wave from logan to boulder which is about 2 4 h the wave polarization relations are examined through the simultaneous quantifications of the three wind components and temperature this study has developed a systematic methodology for fully characterizing mesoscale gravity waves inspecting their intrinsic properties and validating the derivation of horizontal wave structures by applying multiple instruments from coordinated stations

lidar observations of mesospheric fe and sporadic fe layers at urbana illinois lidar measurements of mesospheric fe were conducted at urbana il 40 degree n 88 degree w during 4 nights in late october 1989 the average fe abundances layer centroid heights and rms widths varied between 1 0 2 0 times 10 sup 10 cm sup minus 2 89 0 90 5 km and 3 2 4 1 km respectively the peak densities of the layer near 90 km varied between 15 25 times 10 sup 3 cm sup minus 3 considerable gravity wave and tidal activity was observed in the fe profiles on 3 nights the formation and dissipation of 3 large sporadic fe fe sub s layers was observed these are the first observations of this phenomenon the 2 largest fe sub s layers formed at 102 4 km and 91 4 km over a period of about 20 min and their widths were approximately 2 3 km fwhm the peak densities of the fe sub s layers were as high as 31 times 10 sup 3 cm sup minus 3 and the abundances were as high as 5 8 times 10 sup 9 cm sup minus 2 the observations are compared with previous measurements of mesospheric fe and with recent observations of sporadic na na sub s layers

tectonic evolution of the north sea basin crustal stretching and subsidence summary the lithospheric stretching model for the formation of sedimentary basins was tested in the central north sea by a combined study of crustal thinning and basement subsidence patterns a profile of crustal structure was obtained by shooting a long range seismic experiment across the central graben the main axis of subsidence a seabed array of 12 seismometers in the graben was used to record shots fired in a line 530 km long across the basin the data collected during the experiment were interpreted by modelling synthetic seismograms from a laterally varying structure and the final model showed substantial crustal thinning beneath the graben subsidence data from 19 exploration wells were analysed to obtain subsidence patterns in the central north sea since jurassic times changes in water depth were quantified using foraminiferal assemblages where possible and observed basement subsidence paths were corrected for sediment loading compaction and changes in water depth through time the seismic model is shown to be compatible with the observed gravity field and the small size of observed gravity anomalies is used to argue that the basin is in local isostatic equilibrium both crustal thinning and basement subsidence studies indicate about 70 km of stretching across the central graben during the mid jurassic to early cretaceous extensional event this extension appears to have occurred over crust already slightly thinned beneath the graben and the seismic data suggest that total extension since the early permian may have been more than 100km the data presented here may all be explained using a simple model of uniform extension of the lithosphere

relative sea level changes in baltoscandia in the cumbrian and early ordovician the predominance of tectonic factors and the absence of large scale eustatic fluctuations abstract fluctuations in sea depth within a magnitude 20 100 m and a duration of 1 10 m y are often explained by rapid eustatic changes so called third order eustatic events considerable influence of regional tectonics on relative sea level changes has been demonstrated by many authors but because of uncertainties in the timing of short events in widely separated regions the problem of separating tectonic and eustatic factors still remains unsolved in this paper a new and simple approach is used to reveal the presence or absence of eustatic events we consider the st petersburg area and north estonia in the north eastern region of the east baltic from the late early cambrian until the middle of the tremadoc early ordovician deposition was extremely slow and the sea bed remained for a long time in a well defined peritidal zone in a water depth 10 m under such environmental conditions a sea level rise of 10 m would result in marked changes in the character of faunas and sedimentation in the time interval considered here significant sea deepening in the north eastern baltic region occurred only twice and its magnitude did not exceed 10 20 m a fall of sea level by 10 m would result in complete regression in the peritidal zone this situation also occurred in region however the preservation of a sequence of unconsolidated sands which is only a few tens of metres thick and includes all the main stratigraphic subdivisions on a regional scale indicates that the crustal surface reached a very low altitude 10 20 m above sea level these data show that in the late late cambrian to the middle of the tremadoc over a period of 40 m y long eustatic sea level changes did not exceed 10 20 m this limits the magnitude of several third order cycles eustatic events with duration of a few million years which have been proposed previously for the epoch of the transition from the cambrian to the ordovician in the late early cambrian to the late cambrian transgressions and regressions with a magnitude of 50 150 m took place in southern sweden and lithuania since these phenomena occurred when there were no comparable eustatic sea level changes they must be associated with regional tectonic movements some were rapid and could be easily misinterpreted as indications of third order eustatic changes it is probable that some of the other eustatic events that have been proposed for the phanerozoic were actually not of eustatic but of tectonic origin such rapid tectonic movements with magnitude of 50 100 m in cratonic areas can be caused by changes in the forces in the lithospheric layer with a laterally variable thickness and by phase transitions in the mafic lower crust depending on the spatial distribution of vertical crustal movements both these mechanisms could have been operating in the east baltic and southern sweden in the cambrian

deep seismic images and the tectonic framework of early rifting in the otway basin australian southern margin abstract the otway basin is one of a number of basins formed along australia s southern continental margin during the late jurassic early cretaceous rifting of australia from antarctica it lies on a transitional area of extended lithosphere between the margin to the west where continental separation took place close to the australian craton and the region to the east where separation failed to develop through bass strait but instead switched to the south of tasmania seven agso regional deep seismic profiles recorded during 1992 across onshore parts of the basin provide images of synrift basin bounding faults that dip predominantly towards the continent basin sequences in half graben rift segments at two way times greater than 4 s and mid crustal detachments with ramp and flat geometry at mid crustal levels when combined with industry seismic data trend variations on faults indicate that extensional strain direction varied along the rift system probably locally controlled by pre existing palaeozoic geology but consistent with general north south lithospheric extension basement highs between some of the rift segments are interpreted as accommodation or transfer zones multiple basin bounding faults in some places mirror features within basement and may indicate a component of local strike slip during early rifting the syn rift segments form part of the first stage early cretaceous failed rift system in the otway bass strait region crustal thickness is interpreted to be 31 km 10 3 10 5 s twt near the northern basin margin thinning to about 25 km 9 s twt 40 reduction in thickness of palaeozoic crust seaward of the tartwaup fault zone this fault zone and the timboon fault system farther east are interpreted to be headwall faults landward limit of a late cretaceous second stage rifting system along a lower plate margin which ultimately separated australia from antarctica

seismic anisotropy in granite at the underground research laboratory manitoba the shear wave experiment at atomic energy of canada limited s underground research laboratory was probably the first controlled source shear wave survey in a mine environment taking place in conjunction with the excavation of the mine by test tunnel at 420 m depth the shear wave experiment was designed to measure the in situ anisotropy of the rockmass and to use shear waves to observe excavation effects using the greatest variety of raypath directions of any in situ shear wave survey to date inversion of the shear wave polarizations shows that the anisotropy of the in situ rockmass is consistent with hexagonal symmetry with an approximate fabric orientation of strike 023 degree and dip 35 degree the in situ anisotropy is probably due to microcracks with orientations governed by the in situ stress field and to mineral alignment within the weak gneissic layering however there is no unique interpretation as to the cause of the in situ anisotropy as the fabric orientation agrees approximately with both the orientation expected from extensive dilatancy anisotropy and that of the gneissic layering eight raypaths with shear waves propagating wholly or almost wholly through granodiorite rather than granite do not show the expected shear wave splitting and indicate a lower in situ anisotropy which maymore be due to the finer grain size and or the absence of gneissic layering within the granodiorite these results suggest that shear waves may be used to determine crack and mineral orientations and for remote monitoring of a rockmass this has potential applications in mining and waste monitoring less

mean and gravity wave structures and variability in the mars upper atmosphere inferred from mars global surveyor and mars odyssey aerobraking densities 1 we have used density measurements obtained during aerobraking ab on mars global surveyor and mars odyssey to examine mean densities and the characteristics and variability of gravity waves gws in the upper atmosphere of mars mean densities exhibit variability with latitude and season and in response to variable forcing and filtering from below these data also reveal significant variability of gws both spatially and temporally in general gw amplitudes increase while apparent horizontal scales remain the same with increasing altitude the dominant spatial scales at the lower ab altitudes are typically 20 200 km and density fluctuations vary from 5 to 50 though even larger values are occasionally observed gw amplitudes also vary significantly with season being generally larger in winter and at middle and high latitudes and apparently reflecting mean source and filtering conditions amplitudes also appear to vary with longitude and time and may provide clues to variability of and interactions with larger scale motions

equivalent medium representation of fractured rock a similarity may be found between various approaches for determining the effects of parallel fractures or aligned cracks on seismic wave propagation at wavelengths that are long compared with the scale length of the cracks fractures can be modeled using an empirical linear slip condition however natural fracture surfaces can also be simulated directly as planar distributions of small isolated areas of slip cracks model 1 or conversely as planar distributions of imperfect interfacial contacts model 2 an alternative is plane surfaces separated by thin continuous layers of viscous fluid or a soft material model 3 we present analytic expressions for the fracture compliances for these three models and using these analytic results compute the effective compliances and stiffnesses of the fractured material as a result it is possible to relate the measured compliances or stiffnesses directly to the statistics of the microstructural details of a fracture given appropriate a priori information on the fracture surfaces the results for model 1 are equivalent to a volume distribution of cracks as studied by hudson 1980 1981 for small crack density the results for model 2 are basically the same as those given by white 1983 for a packing of spheres and finally the results for model 3 are in agreement with those given by backus 1962 for combinations of two constituent layers these results can be extended to the case of nonaligned fractures and to allow for fluid flow between cracks and into a porous matrix rock finally it is shown that the ratio of the normal to shear fracture compliance is a good indicator of the properties of the fracture infill

crack distributions which account for a given seismic anisotropy summary the effect of microfractures or small scale inclusions within earth structures may be measured seismically wavespeeds as a function of wave normal direction lead to effective or mean elastic parameters and the difference between these and the values for unfractured material is related to parameters for the size distribution and internal conditions of the cracks or inclusions thus it appears that measurement of the seismic wavespeeds for a sequence of different propagation directions can lead to information about fractures or inclusions within the rock even though the scale size of this microstructure may be very small compared with a wavelength however the crack parameters are continuous functions of orientation and the elastic parameters for the material provide values for only 21 independent quantities this is enough to describe the crack distribution in terms of spherical surface harmonics up to fourth order only the relationship between the effective elastic parameters and t he crack distribution is accurate to second order in the number density which limits the applications to materials where the contribution of microfractures is less than 10 per cent the relationships referred to above show that inherent material anisotropy is equivalent to a distribution of hypothetical cracks embedded in an isotropic material it then follows that the effect of microfractures in an anisotropic solid may be calculated by imposing both systems of cracks real and hypothetical on an isotropic matrix for which solutions are known

mesosphere inversion layers and stratosphere temperature enhancements 1 it has been known for at least 30 years that vertically narrow thermal layers form within the middle atmosphere two types of temperature enhancements the low latitude to midlatitude mesosphere inversion layer mil and the high latitude winter stratosphere temperature enhancement ste have both received much attention within the atmospheric science community because of their unexplained formation mechanisms and potential impacts on the middle atmosphere global circulation numerous experimental numerical and theoretical studies have attempted to explain certain aspects of these respective thermal layers but no one theory consistently and satisfactorily describes all the features observed we present a review of the literature and explicitly propose a classification scheme based on the different formation mechanisms suspected to cause these events for the mil we demonstrate that there are two subtypes the first one is tidally driven and tends to occur above 85 km this mil originates from large amplitude tidal waves propagating into the mesosphere and their subsequent nonlinear interactions with gravity waves which can often create the appearance of a double mil separated by approximately one vertical tidal wavelength 25 km the other subtype of mil is formed by a climatological planetary wave dissipation mechanism that occurs at a zero wind line the dissipation of the planetary wave tends to generate a mesoscale 1000 km inversion layer in the range of 65 80 km these two formation mechanisms explain a host of observed characteristics including the reason behind the downward progression of some mils and not others the different climatological nature of the two forms of mil events and the relative scarcity of mil observations at high latitudes the ste is believed to be generated by an altogether different process namely the nonlinear interaction between the polar vortex and planetary waves aleutian high the induced temperatures typically peak around 40 km and often exceed 300 k generating what appears to be a low hot stratopause when vertical temperature profiles are combined with synoptic analyses one observes that the ste is the consequence of high latitude vortex interactions creating a baroclinic atmosphere i e a downward adiabatic compression induced by an ageostropic flow we summarize the details of the relationship between this feature and sudden stratospheric warmings as well as the potential for in situ gravity wave generation we close with a review of currently unexplained mil ste features and offer new directions for future middle atmosphere thermal layer research

rayleigh lidar observations of gravity wave activity in the upper stratosphere at urbana illinois abstract during 13 nights of rayleigh lidar measurements at urbana illinois in 1984 86 thirty six quasi monochromatic gravity waves were observed in the 35 50 km altitude region of the stratosphere the characteristics of the waves are compared with other lidar and radar measurements of gravity waves and with theoretical models of wave saturation and dissipation phenomena the measured vertical wavelengths 2 ranged from 2 to 11 5 km and the measured vertical phase velocities cz ranged from 10 to 85 cm s 1 the vertical wavelengths and vertical phase velocities were used to infer observed wave periods tob which ranged from 100 to 1000 min and horizontal wavelengths x which ranged firm 70 to 2000 km there may be errors in the inferred values of the horizontal wavelengths because they were calculated by assuming that the observed period inferred the intrinsic period dominant wave activity was found at vertical wavelengths between 2 4 km and 7 10 km no significant seasonal variations were evide

atmospheric tide 2 the solar and lunar semidiurnal components solar and lunar semidiurnal wind and temperature oscillations from the surface to 400 km are simulated for average solar activity conditions utilizing the numerical tidal model described in part 1 hough mode decomposition of the solstitial solar semidiurnal tide excited by h2o and o3 insolation absorption below 80 km indicates that it is characterized by a predominance of 2 2 below 60 km about equal contributions of 2 2 2 3 and 2 4 between 70 and 90 km mostly 2 4 with some 2 5 and 2 2 between 90 and 120 km and a predominance of 2 2 above 140 km with secondary contributions from 2 3 and 2 5 the solstitial lunar semidiurnal tide is characterized by a predominance of 2 2 below 70 km 2 4 with secondary contributions from 2 2 2 3 and 2 5 between 80 and 110 km and by 2 2 with a fairly strong secondary contribution from 2 3 above 120 km similar descriptions for both the solar and lunar oscillations apply at equinox except that the asymmetric 2 3 and 2 5 modes are absent relative to the solar component lunar temperature and wind amplitudes are sufficiently large 20 in the lower and upper thermosphere to account for some of the observed variability previously attributed to the solar tide amplitudes of the 2 4 and 2 5 modes above 100 km are significantly affected by mesospheric eddy diffusion coefficients in excess of 2 106 cm s 1 the total solar semidiurnal exospheric temperature oscillation for average solar conditions ranges from 10 20 k poleward of 40 n to 40 60 k equatorward of 30 n and has its origin in three sources of excitation all of comparable importance 1 euv solar radiation absorption in the lower thermosphere 100 200 km 2 in situ momentum coupling due to the interaction of diurnal winds and diurnally varying ion drag and 3 tides propagating upwards from below 100 km in addition the calculations are compared with rocket meteor radar partial reflection thomson scatter and satellite data to evaluate the consistency of the model with observations

the gravity wave response above deep convection in a squall line simulation abstract high frequency gravity waves generated by convective storms likely play an important role in the general circulation of the middle atmosphere yet little is known about waves from this source this work utilizes a fully compressible nonlinear numerical two dimensional simulation of a midlatitude squall line to study vertically propagating waves generated by deep convection the model includes a deep stratosphere layer with high enough resolution to characterize the wave motions at these altitudes a spectral analysis of the stratospheric waves provides an understanding of the necessary characteristics of the spectrum for future studies of their effects on the middle atmosphere in realistic mean wind scenarios the wave spectrum also displays specific characteristics that point to low physical mechanisms within the storm responsible for their forcing understanding these forcing mechanisms and the properties of the storm and atmosphere that control them are crucial first steps toward developing

an inversion scheme to model subsurface fracture systems using shear wave splitting polarization and delay time observations simultaneously summary shear wave splitting polarization p and delay time t observations are used to invert for fracture orientation and intensity of fracturing simultaneously by addressing the different levels of uncertainty involved in measurements of these two parameters as well as their dissimilar relationships to fracture configuration we have developed an inversion algorithm which reduces the primary double response inversion to two connected single response ones we show that its inherent non linearity complicates this problem which therefore requires a more sophisticated attack than conventional inversion schemes it will be shown that the construction of residue function contours in the model plane and the generation of surrogate data by simulation process are essential to this approach we illustrate the capabilities of this technique by inverting shear wave splitting data from the geysers geothermal reservoir in california in principle the method should be useful for characterizing fractured reservoirs whether geothermal or hydrocarbon

simultaneous lidar measurements of the sodium layer at the air force geophysics laboratory and the university of illinois simultaneous lidar measurements of the mesospheric sodium layer were made at the air force geophysics laboratory afgl and university of illinois at urbana champaign uiuc on the nights of august 28 october 9 and october 16 1985 on these nights the layer centroid height was 1 to 3 km lower at afgl in october the altitude of the layer bottomside was near 80 km at afgl compared to 85 km at uiuc gravity wave activity was present in the layer at both sites on all 3 nights in october the wave amplitudes were significantly larger at afgl the sodium profiles were compared with similar measurements obtained at the goddard space flight center in october 1981 and at the white sands missile range in october 1984 the data from all four sites indicate that there is a significant longitudinal variation in the layer structure between 70 w and 90 w it is suggested that these structural differences may be due to dynamics the most promising mechanism capable of producing the large 1 to 3 km differences in the layer centroid heights between uiuc and afgl is a small difference in the mean vertical wind velocity because the typical residence time for a sodium atom in the layer is approximately 5 8 days a 0 4 cm s 1 difference in the mean vertical wind velocities at the two sites is capable of inducing a 2 km difference in the centroid height of the sodium layer

dynamics of the equatorial mesosphere first results with a new generation partial reflection radar the first observations of mesospheric winds made between january august 1990 with an mf partial reflection radar located on christmas island 2 n 157 w in the central pacific are described the mean zonal winds are in general westward but show clear evidence for a wave driven circulation power spectral studies indicate that waves are present over a wide range of periods ultra fast kelvin waves are especially evident in january march with peak amplitudes 20 ms 1 and intrinsic phase speeds of 150 ms 1 indicated the kelvin waves are estimated to contribute an eastward acceleration of up to 10 ms 1 day 1 gravity wave amplitudes are also found to be almost as large as those observed at mid latitude sites which suggests that convection is a major source of gravity wave activity

unfolding impacts of freaky tectonics on sedimentary sequences along passive margins pioneer findings from western indian continental margin offshore indus basin abstract the western passive continental margin of the indian plate wcmi serves as an elegant laboratory for understanding the syn sedimentary rift drift tectonics preserving a variety of episodic structural deformations and complex sedimentary infill here we present a multidisciplinary study on offshore indus basin oib that is less investigated compared to adjacent marginal basins along wcmi reflection seismic gravity borehole and biostratigraphic data have been used to reconstruct the tectono sedimentary history of the meso cenozoic succession in oib seismic based dynamic stratigraphy helped in mapping seven different depositional sequences grounded on morpho tectonic considerations the seismic expression of these sequences provided an idea of the depositional styles with different tectonic episodes since rifting in jurassic to basin inversion in miocene continued to present time the oib initially filled from the north with the sediments rapidly prograding southwards in general the basin deepens in the central and northwestern part where the formations achieve maximum depths the analysis of 3d structural models revealed that the region experienced poly phase deformation from the late cretaceous to recent times that include steeply dipping normal faults horst and graben half graben half graben with growth faulting flower structures anticline syncline and uplift with an angular unconformity the most remarkable tectonic activity happened at the early miocene and resulted in the reactivation of extensional faults into strike slip faults giving rise to a spectacular structural inversion due to transform movement between indian and arabian plates that continues to present day the most predominant faults are oriented in s20 50 e with azimuth as 120 160 and the maximum dip angles are 80 in the southwest flank of the basin the main fault trend is s20 e n20 w and dip angles ranging between 40 and 80 and above a thick crust and the ocean continent transition oct is imaged with massive felsic mafic and ultramafic intrusions by the help of forward gravity modeling an initial onset of syn rift tectonic subsidence between 90 and 68 ma with a post rift general increase between 68 and 54 ma is comprehended while two uplift events at 40 ma and 18 ma are documented through backstripping analysis it is inferred that the region is rapidly under complex structural inversion with growing folding faulting and flowering structures this study could help in explaining the unanswered reasons of structural complexities depositional styles and basin inversion along worldwide passive margins

sequence stratigraphy sedimentary systems and petroleum plays in a low accommodation basin middle to upper members of the lower jurassic sangonghe formation central junggar basin northwestern china abstract the lower jurassic junggar basin is a low accommodation basin in northwestern china because of low subsidence rates and a warm wet climate deposits of the central subbasin of the junggar basin formed from fluvial deltaic shallow lake facies sequence stratigraphy and sedimentary systems of the lower jurassic members of the sangonghe formation j1s were evaluated by observing cores interpreting wireline logs and examining seismic profiles two third order sequences were recognized in the strata the distribution of the sedimentary systems in the systems tracts shows that tectonic movement paleorelief paleoclimate and changes in lake level controlled the architecture of individual sequences during the development of the lowstand systems tract lst the intense structural movement of the basin resulted in a significant fall in the water level in the lake accompanied by rapid accommodation decrease braided rivers and their deltaic systems were also developed in the central junggar basin sediments carried by braided rivers were deposited on upward slopes of the paleorelief and braid delta fronts were deposited on downward slopes during the transgressive systems tract tst the tectonic movement of the basin was quiescent and the climate was warm and humid lake levels rose and accommodation increased quickly shoal lines moved landward and shore to shallow lake deposits sublacustrine fans and deep lake facies were deposited in shallow to deep lake environments during the highstand systems tract hst the accommodation no longer increased but sediment supply continued far exceeding accommodation hst deposits slowly formed in shallow lake to meandering river delta front environments relatively low rates of structural subsidence and low accommodation resulted in coarse grained successions that were fining upward deposits were controlled by structural movement and paleorelief within the lst to tst deposits in the central subbasin fine to medium grained coarsening upward successions developed during the hst the sand bodies of braid delta fronts on the downward slopes of the paleorelief in the lst and the sublacustrine fans in the tst became reservoirs for hydrocarbon accumulation petroleum plays have only been found in the sangonghe formation j1s located on structural ridges that consist of sand bodies comprising these sequences favorable conditions for petroleum plays in hst1 lst2 occur where the sand bodies have been fractured by faults and sealed by denudation and pinch out lines then overlain by deep lake mudstone in tst2 the favorable condition of the sand bodies within tst2 occurs where isolated sand bodies have been fractured by faults

daytime lidar measurements of tidal winds in the mesospheric sodium layer at urbana illinois the first daytime lidar observations of the mesospheric na layer at urbana illinois 40 degrees n 88 degrees w were made in january and march 1986 the data show strong 12 hour oscillations of the na density and layer centroid height which appear to be caused by the semidiurnal tide the peak to peak variations in column abundance and centroid height were of the order of 100 and 3 km respectively the vertical wind velocities were inferred from the temporal variations of the density gradients on the layer topside the inferred wind amplitudes and vertical wavelengths for the semidiurnal tide were approximately 30 cm s sup minus 1 and approximately 50 km respectively the maximum upward vertical velocity occurs at about 1 100 lst and 2 300 lst

reply to comments on crustal anisotropy from local observations of shear wave splitting in west bohemia czech republic by g h r bokelmann and j kawahara can the hudson crack model describe behavior of real cracks

seismic wave propagation in cracked porous media summary the movement of interstitial fluids within a cracked solid can have a significant effect on the properties of seismic waves of long wavelength propagating through the solid we consider three distinct mechanisms of wave induced fluid flow flow through connections between cracks in an otherwise non porous material fluid movement within partially saturated cracks and diffusion from the cracks into a porous matrix material in each case the cracks may be aligned or randomly oriented leading respectively to anisotropic or isotropic wave speeds and attenuation factors in general seismic velocities exhibit behaviour that is intermediate between that of empty cracks and that of isolated liquid filled cracks if fluid flow is significant in the range of frequencies for which considerable fluid flow occurs there is high attenuation and dispersion of seismic waves fluid flow may be on either a wavelength scale or a local scale depending on the model and whether the cracks are aligned or randomly oriented resulting in completely different effects on seismic wave propagation a numerical analysis shows that all models can have an effect over the exploration seismic frequency range

density variability at scales typical of gravity waves observed in mars thermosphere by the mgs accelerometer 1 examination of the small scale density perturbations in mars thermosphere inferred from mars global surveyor mgs accelerometer data reveals wave like structures consistent with gravity waves the structures are interpreted to be horizontal with dominant wavelengths of 100 300 km observed along the orbital path density perturbations are significantly stronger in winter versus spring summer suggesting that the zonal mean winds play a major role in filtering these waves there is also evidence of possible modulation by the mean winds due to local time differences no correlation is found with the underlying topography a source region on earth for gravity waves in fact density perturbations in the northern hemisphere are observed to be greater than those in the southern hemisphere which has a higher orographic variance over the martian tropics an observed source region for gravity waves density perturbations are again not elevated leaving questions on how gravity waves observed in the lower atmosphere are related to those observed in the thermosphere

an upper e region quarterdiurnal tide at arecibo studies of the time height trajectories of ionosphere e region layers at arecibo have revealed not only the usual diurnal sporadic e and semidiurnal intermediate layer structures but also that on occasion extra layers form and descend through the e region in particular during january 1981 four layers per day were observed to descend through the upper e region this four per day layer system was remarkably coherent over the 3 days of observation and suggests the existence of a 6 hour period or quarterdiurnal tidal wind system in the upper e region numerical simulations of ion trajectories in a realistic model atmosphere with diurnal semidiurnal and quarterdiurnal tidal wind systems of appropriate amplitude and phase structures confirm that the presence of a quarterdiurnal tide is sufficient to explain the observations

statistics of gravity waves seen in o2 nightglow over bear lake observatory fluctuations in the o2 nightglow column emission rate and rotational temperature were measured over bear lake observatory on 63 nights 11 of them nearly coinciding with a mesosphere lower thermosphere coupling study mltcs campaign on january 20 30 1993 the instrument allows for simultaneous measurement at 12 points in the sky every 2 4 min from these the frequency the horizontal wavelength and the propagation direction can be measured directly and from these the horizontal phase velocity and the vertical wavelength can be derived frequency spectra are shown to have slopes near to the widely accepted 5 3 law correction to intrinsic frequency was made by using the simultaneously acquired winds from the satellite borne wind imaging interferometer windii the relation between frequency and horizontal wavenumber was scattered rather than clearly linear and there was no obvious boundary suggesting severe mesospheric filtering when the vertical wavenumber was plotted against the horizontal zonal phase speeds were favored during the january period but on average the waves were isotropic at speeds above 30 m s absorption of westward traveling waves at speeds less than 30 m s was evident

the transition from passive to active margin tectonics a case study from the zone of samedan eastern switzerland the zone of samedan is part of a fossil early mesozoic rift system originally situated in the distal lower austro alpine domain of the adriatic passive continental margin an early mesozoic configuration of asymmetrical rift basins bounded by relative structural highs compartmentalized late cretaceous active margin tectonics jurassic half grabens were folded into arcuate synclines whereas relative structural highs engendered thin imbricated thrust sheets west directed thrusting and folding initiated at the surface and continued to depths favoring mylonitization under lower greenschist facies conditions at this time liguria piemontese ophiolites were accreted to lower austro alpine units directly underlying the zone of samedan late cretaceous orogenic collapse of the adriatic active margin involved the reactivation of west directed thrusts as low angle top to the east normal faults these faults accommodated extensional uplift of liguria piemontese ophiolites and lower austro alpine units beneath and within the zone of samedan during paleogene collision some late cretaceous faults in the zone of samedan were reactivated under lower anchizonal conditions as north directed thrusts the latter stages of this early tertiary thickening were transitional to brittle high angle normal faulting associated with top to the east extension and spreading above the warm uplifting lepontine dome

sequence stratigraphy and importance of syndepositional structural slope break for architecture of paleogene syn rift lacustrine strata bohai bay basin e china abstract sequence stratigraphy and syndepositional structural slope break zones define the architecture of the paleogene syn rift lacustrine succession in eastern china s bohai bay basin jiyang huanghua and liaohe subbasins are of particular interest and were our primary research objectives interpretation of 3d seismic data well logs and cores reveals one first order sequence 4 second order sequences and ten to thirteen third order sequences were identified on the basis of the tectonic evolution lithologic assemblage and unconformities in the subbasins of bohai bay basin three types of syndepositional paleo structure styles are recognized in this basin they are identified as fault controlled slope break zone flexure controlled slope break zone and gentle slope the three active structural styles affect the sequence stratigraphy distinct third order sequences within second order sequences have variable systems tract architecture due to structuring effects during tectonic episodes second order sequences 1 and 2 were formed during rifting episodes 1 and 2 the development of the third order sequences within these 2 second order sequences was controlled by the active nw and ne oriented fault controlled slope break zones second order sequence 3 formed during rifting episode 3 the most intense extensional faulting of the basin two types of distinctive lacustrine depositional sequence were formed during rifting episode 3 one was developed in an active fault controlled slope break zone the other in an active flexure controlled slope break zone second order sequence 4 was formed during the fourth episode of rifting syndepositional fault and flexure controlled slope break zones developed in the subsidence center shore to offshore areas of the basin and controlled the architecture of third order sequences in a way similar to that in second order sequence 3 sequences in the gentle slope and syndepositional flexure controlled slope break zones were developed in subaerial region distribution of lowstand sandbodies was controlled primarily by active structuring on the slope break zones and these sandbodies were deposited downdip of the slope break zones sand bodies within lowstand systems tracts have good reservoir quality and are usually sealed by the shale sediments of the subsequent transgressive systems tract they are favorable plays for stratigraphic trap exploration

tectonics and seismic sequence stratigraphy an introduction the application of sequence stratigraphic models to seismic data is restricted by the vertical and spatial resolution of the data the fundamental stratigraphic unit of the sequence stratigraphic technique is the seismically distinguished sequence although the concept of tectonically related mega sequences is useful basin stratigraphy is controlled to varying degrees by eustatic sea level change or base level in lakes subsidence uplift and sediment supply three main basin types rift wrench and thrust related basins have distinctive gross stratigraphic architectures localized tectonically controlled subsidence and uplift has a significant control on three dimensional stratigraphic patterns stratigraphy is the partial record of basin evolution resulting from the interaction of a number of factors such as regional and local subsidence uplift sediment supply eustacy and climatic change fig 1 basins that have a marine connection will show significant stratigraphic variations especially in coastal deposits that result from eustatic sea level fluctuations other key factors will include the availability of sediment and the role of tectonically induced subsidence and uplift alternatively land locked or intermontane basins whose fluvial systems drain ultimately into a lake will preserve a stratigraphy dominated by local relative uplift and subsidence local tectonics by climatic controls and the rate of sediment supply tectonic activity is an important factor in controlling stratigraphy in the majority of sedimentary basins tectonism generates accommodation space in basins it alters base levels and it controls source areas when mountain ranges are generated tectonics may even influence local climatic patterns it is difficult to separate the relative importance of tectonics versus other factors in controlling stratigraphic architecture in basins in this introduction basins formed on continental lithosphere and their associated stratigraphies will be considered

sprites as evidence of vertical gravity wave structures above mesoscale thunderstorms large area multicell thunderstorms lead to the formation of vertically oriented cylindrical structures of gravity waves at mesospheric altitudes closely resembling those observed in optical emissions associated with transient luminous glows called sprites

airborne sodium lidar measurements of gravity wave intrinsic parameters we describe a data analysis technique for determining gravity wave intrinsic parameters including wave propagation direction the technique involves measuring the altitude variations of the wave induced density perturbations of the atmospheric na layer this technique can be used with airborne lidars multiple ground based lidars and steerable lidars in this paper the technique is applied to airborne na lidar data obtained during a roundtrip flight from denver colorado to the pacific coast in november 1986 during the flight strong wave perturbations were observed in the na layer near the pacific coast over a horizontal distance of nearly 700 km the intrinsic horizontal wavelength of this wave was estimated to be about 85 km and the vertical wavelength was 4 1 km the intrinsic period was about 102 min and the propagation direction was almost due south

overall properties of heterogeneous material summary small scale heterogeneity in crustal structure can be very complex and difficult to describe in detail and yet at the same time can be very important for the description of for instance tectonic stress and porosity statistical properties of such heterogeneity can be derived from the properties of waves of relatively large wavelength as they propagate through the crust the differences between measured wavelengths and attenuation coefficients and those of compact rock and the variations of these quantities in space and time provide in principle a means of determining quantities like the density and orientations of microfractures and the nature of crack infill material the theoretical basis for inferences of this kind is the concept of the effective or equivalent material based on an averaging process taken over the microstructure a number of methods have been used to calculate the properties of the effective medium several of which are described here

observations of a 12 h wave in the mesopause region at the south pole in december 1989 a na lidar was installed at the amundsen scott south pole station and was used to measure aerosol stratospheric temperature and mesospheric na profiles through october 1990 the mesospheric na data are used to characterize the gravity wave field in the mesopause region these first lidar observations of na layer dynamics at the south pole show strong wave activity during the antarctic winter data for 25 june and 19 august 1990 ut are presented here the total wave induced variances in atmospheric density are respectively 29 and 35 2 the na layer centroid height is very low during both observation periods on 25 june a strong 12 h oscillation is observed in the bottomside of the na layer which extends to altitudes as low as 74 km the vertical displacement and temperature amplitudes associated with the 12 h oscillation are respectively 1 9 km and 19 k the characteristics of the 12 h wave are similar to the pseudotide observed at svalbard by walterscheid et al 1986

spectra of gravity wave density and wind perturbations observed during arctic noctilucent cloud anlc 93 campaign over the canadian prairies synergistic airborne na lidar and mf radar observations the airborne na lidar and the saskatoon and canadian network for space research cnsr medium frequency mf radars were used to measure the spectra of gravity wave density and wind perturbations during the arctic noctilucent cloud anlc 93 campaign the national center for atmospheric research electra flight between sylvan lake saskatoon and great falls occurred on august 12 1993 this provided vertical and horizontal wave number spectra for relative atmospheric density fluctuations along the flight legs slopes are 2 5 0 1 and 1 3 0 1 respectively for the vertical and one dimensional horizontal wave number spectra the radars provided temporal frequency and vertical wave number spectra for the flight mission day and duration july 15 to august 15 of the campaign so that the fluxes on august 12 could be related to typical summer values the slopes of frequency spectra are typically 2 1 1 6 hours and 1 0 10 100 min gravity wave gw parameters from the two observation systems are compared on august 12 including horizontal anisotropies and dominant horizontal and vertical scale sizes in particular several new analyses are developed to illustrate the synergy that is possible between such systems the radar winds data using variance ovals and a new correlation vector technique provide evidence for gw propagation into the ne quadrant this anisotropy of gw propagation is also shown to be evident in the lidar data an innovative analysis is applied to the saskatoon mf radar using doppler and angle of arrival data and used to characterize a unique gw event which is also observed spatially by the lidar when close to saskatoon

observations of horizontal and vertical wave number spectra of gravity wave motions in the stratosphere and mesosphere over the mid pacific we present vertical and horizontal wave number spectra of density perturbations in the upper stratosphere 25 40 km and the upper mesosphere 80 105 km inferred from 45 hours of airborne na rayleigh lidar observations in the vicinity of hawaii the mean density variance is 0 92 2 for the upper stratosphere and 6 1 2 and for the upper mesosphere the mean vertical shear variance and richardson s number for the upper mesosphere are 6 1 km 2 and 0 69 respectively the observed vertical wave number m and horizontal wave number k spectra exhibit power law dependencies the mean slopes of the vertical wave number spectra are 2 5 for the upper stratosphere and 3 1 for the upper mesosphere the mean slope of the horizontal wave number spectra is 1 9 for the upper mesosphere the mean characteristic vertical and horizontal wavelengths inferred from the spectra are 13 4 and 5810 km respectively in all cases the magnitudes of the upper stratosphere m spectra are more than an order of magnitude smaller than those of the upper mesosphere at all observable scales in the stratosphere the m spectra exhibit significant energy at low wave numbers that are less than the values expected for the characteristic wave numbers this suggests the presence of gravity wave sources capable of generating significant energy at long vertical scales the source is believed to be geostrophic adjustment of the jet stream a large amplitude highly coherent quasi monochromatic short horizontal scale h 16 km oscillation in the na layer was observed on the march 22 flight the oscillation resembled short horizontal scale structures often observed in oh airglow images and was found to be consistent with a gravity wave interpretation