on the use of combined geophysical methods to assess water content and water conductivity of near surface formations abstract we propose to deepen the interpretation of combined geophysical methods georadar seismic and electric to assess physical properties characterizing the near surface porous formations especially the influence of water velocity analysis of multioffset georadar data are used together with seismic methods to estimate lateral and vertical ground water fluctuations this enables us to identify transitions from non saturated to fully saturated porous layers with certainty furthermore the accurate knowledge of seismic velocities helps to estimate the porosity of the ground water formations finally we show how the radar technique may be useful in solving the problem of trade off between bulk resistivity which is deduced from electrical measurements and that of water ionic conductivity and water content these theoretical considerations are illustrated using various measurements conducted at the same test site our interpretation is compared with a few laboratory measurements on water and soil samples this study displays the impact of combined geophysical approaches for providing models of water and ionic transfers down to a depth of several metres

anisotropy of electrical conductivity record of initial strain at the toe of the nankai accretionary wedge an approach based on march s theory is applied to measurements of the anisotropy of electrical conductivity on samples and is used to quantify initial strain at the toe of the nankai accretionary wedge a quantitative determination of strain is possible from simple assumptions passive reorientation offlat pores forming the porous network and existence of a linear relationship between fabric tensor and electrical conductivity tensor we show that this simple model correctly accounts for the increase of anisotropy with compaction at a reference site located in the trench ocean drilling program drill site 1173 at the toe of the accretionary wedge site1174 development of anisotropy in the horizontal plane and concurrent reduction of vertical plane anisotropy are observed this can be explained by 12 horizontal ductile shortening occurring after decollement initiation but before slip on imbricate thrust faults anisotropy in the underthrust sequence is correctly described by vertical compaction consistent with decoupled stress states across the decollement at site 1174 the magnitude of ductile strain implies at least 75m slip on the decollement ductile shortening is associated with porosity loss implying partly drained conditions above the decollement

impact of water saturation on seismoelectric transfer functions a laboratory study of coseismic phenomenon s u m m a r y seismic waves propagating in a porous medium under favourable conditions generate measurable electromagnetic fields due to electrokinetic effects it has been proposed following experimental and numerical studies that these so called seismoelectromagnetic couplings depend on pore fluid properties the theoretical frame describing these phenomena are based on the original biot s theory assuming that pores are fluid filled we study here the impact of a partially saturated medium on amplitudes of those seismoelectric couplings by comparing experimental data to an effective fluid model we have built a 1 m length scale experiment designed for imbibition and drainage of an homogeneous silica sand the experimental setup includes a seismic source accelerometers electric dipoles and capacitance probes in order to monitor seismic and seismoelectric fields during water saturation apparent velocities and frequency spectra in the kilohertz range are derived from seismic and electrical measurements during experiments in varying saturation conditions amplitudes of seismic and seismoelectric waves and their ratios i e transfer functions are discussed using a spectral analysis performed by continuous wavelet transform the experiments reveal that amplitude ratios of seismic to coseismic electric signals remain rather constant as a function of the water saturation in the s w 0 2 0 9 range consistently with theoretically predicted transfer functions

sedimentology of rift climax deep water systems lower rudeis formation hammam faraun fault block suez rift egypt abstract in most marine rift basins subsidence outpaces sedimentation during rift climax times typically this results in sediment starved hangingwall depocentres dominated by deep marine mudstones with subordinate local development of coarser clastics in the immediate hangingwall derived from restricted catchments on the immediate footwall scarp to highlight the spatial variability of rift climax facies and the controls upon them we have investigated the detailed three dimensional geometry and facies relationships of the extremely well exposed miocene rift climax lower rudeis formation in the immediate hangingwall to the thal fault zone suez rift egypt detailed sedimentological analyses allows the lower rudeis formation to be divided into two contemporaneous depositional systems 1 a laterally continuous slope system comprising hangingwall restricted interpretation of individual facies facies relationships and their spatial variability indicate that deposition in the immediate hangingwall to the thal fault occurred via a range of submarine concentrated density flows surge like turbidity flows mass wasting and hemipelagic processes major controls on the spatial variability and stratigraphic architecture of the depositional systems identified reflect the influence of the steep footwall physiography accommodation and drainage evolution associated with the growth of the thal fault the under filled nature of the hangingwall depocentre combined with the steep footwall gradient result in a steep fault controlled basin margin characterised by either slope bypass or erosion with limited coastal plain or shelf area sediment supply to the slope apron deposits is controlled in part by the evolution and size of small footwall drainage catchments in contrast the localized submarine fan is interpreted to have been fed by a larger antecedent drainage network the structural style of the immediate footwall is also believed to exert a control on facies development and stratigraphic evolution in particular fault scarp degradation is enhanced by fault propagation folding which creates basinward dipping bedding planes in the pre rift footwall strata that large pre rift blocks slide on

introduction to aloha 90 the airborne lidar and observations of the hawaiian airglow campaign the middle atmosphere is a region of complex photochemical and dynamic interactions stretching from roughly 30 to 100 km altitude this is the transition region between the stratosphere and thermosphere and is perhaps the least understood region of the earth s atmosphere a variety of interesting and important structures are found in this region including the ozone layer noctilucent clouds the airglow layers the meteoric metal layers and the recently discovered sporadic na and fe layer phenomena

mean winds tides and gravity waves in the upper middle atmosphere during aloha 90 wind measurements made with a partial reflection radar located on christmas island 2 n 157 w are used to describe the dynamical state of the equatorial mesopause region during aloha 90 time mean westward easterly winds prevailed at most heights and reached their maximum values of about 60 ms 1 near 85 km but the mean meridional motions were weak strong oscillations due to the 24 12 and 8 hr atmospheric tides were also observed in both wind components the inferred vertical wavelengths were large even for the diurnal tide on the nights of 22 and 25 march when airborne lidar observations were made in the vicinity of christmas island the prevailing and tidal winds combined to produce especially strong westward winds 100 ms 1 gravity wave activity was also high during march april especially for short period waves although considerable day to day variability was noted

reply to comment by a revil and n linde on streaming potential dependence on water content in fontainebleau sand revil and linde recently commented our paper concerning streaming potential sp measurements in unsaturated sand during drainage experiments this comment suggests that the approach used to infer sp coefficients was inappropriate for unsaturated conditions and therefore yielded wrong conclusions and unphysical results regarding the behaviour of the relative sp coefficient this reply argues that even if in allegre et al we neglected some secondary electrokinetic sources the resulting conclusions are still representative of the behaviour of the true sp coefficient and that the remarks of revil linde arose from a misunderstanding of the drainage experiment conditions we also find support for our results from a comparison between our observations and previous experimental studies

radar reflections and water content estimation of aeolian sand dune many ground penetrating radar gpr profiles acquired on the dry aeolian environment have shown a strong reflectivity inside the present day dunes changes in water content are believed to be the origin of this reflectivity in this paper we try to model the radar reflections coming from the bottom of a dry aeolian dune by using the 1d wavelet modeling method the principle of this method is to calculate the effects of the propagation absorption dispersion and geometrical spreading and reflection on a reference wavelet for different values of various parameters and the best fit between the observed and calculated data leads to the optimum set of parameters by combining the wavelet modeling method with a semi empirical mixing formula for the bulk permittivity of moist sandy soils we estimate the water content and explain the importance of this latter parameter on reflection coefficient and on wavelet modeling

detection of fluid flow variations at the nankai trough by electric and magnetic measurements in boreholes or at the seafloor detection of changes in the flow rate of expelled fluids in accretionary prisms by monitoring of electric and magnetic fields is discussed a numerical model of the electric and magnetic fields associated with fluid flow variations at the nankai trough is presented which gives a numerical solution of the coupled system of electric convection currents and conduction currents that directly determines the magnetic anomaly itself measurements in a borehole located between two vents are shown to be well adapted to detection of fluid flow variations using the vertical gradient of the electric potential and the horizontal magnetic field the vertical electric field is about 10 mv km up to 500 m depth where there is a lithologic reflector and about 50 mv km below this reflector the horizontal gradient of the magnetic field is 2 nt km at the seafloor modelization with a lower fault conductivity and a larger decollement thickness has also been modeled the vertical gradient of the horizontal magnetic field is 5 to 15 nt km a variation of 3 mv and 1 5 to 3 nt at 600 m depth in a borehole could reveal a fluid flow rate variation of 20 which is a reasonable fluid flow change based on some observations at short scale time since a 1 5 to 3 nt anomaly seems easier to detect than a 3 mv anomaly it is likely that the variation of the magnetic field would more sensitively reveal fluid flow variations when monitoring the magnetic field at the seafloor a change of 0 4 nt km in the horizontal gradient could reveal a fluid flow rate variation of 20

electromagnetic to seismic conversion a new direct hydrocarbon indicator we present novel methods that directly detect hydrocarbons based on conversions between electromagnetic and seismic energy we first introduce the subject and then discuss the experimental methods in three field tests next we present the results of the tests and then end with a few model results and thoughts about future applications

curvelet based seismoelectric data processing seismoelectromagnetic conversions are induced through electrokinetic phenomena occurring when passing seismic waves induce relative fluid to solid displacements information on porous material properties provided by the type i coseismic electric field accompanying surface and body waves is limited to the vicinity of the electrical receivers as opposed to the type ii electromagnetic interface response ir which can help detect porous contrasts and or fluid changes within the subsurface at depth for general field geometries the problem is that type ii disturbances exhibit lower amplitudes than type i fields and are difficult to access directly hence separating both types of waves is a critical step when processing seismoelectric data synthetic seismograms and electrograms generated with a full waveform seismoelectric forward modelling code written by garambois dietrich enabled us to study the behaviour of the ir s characteristic dipolar amplitude pattern recovered through filtering the definitive version is available at www blackwell synergy com to better preserve the ir amplitudes we have developed a new filtering strategy based on the fast discrete curvelet transform seismic or seismoelectric wave fronts can be optimall described using this multiscale decomposition over multidirectional anisotropic needle shape structures we have built a mask in the curvelet domain zeroing out seismoelectric samples corresponding to non zero samples from the accelerogram thus taking advantage of the relationship between seismic and seismoelectric waves for type i fields this mask consists of a threshold function combined with a gaussian distribution promoting horizontal i e zero slowness directions when applied to synthetic data this filter enabled to successfully extract the ir although less altering its dipolar radiation pattern than the conventional dip based techniques this strategy was successfully applied to a seismoelectric data set acquired in sedimentary deposits and permitted to isolate an ir generated at the water table

on the difficulty of detecting streaming potentials generated at depth in order to investigate how a streaming potential coefficient measured in the laboratory at a typical scale of 10 cm can be incorporated into a field model with a typical scale of 1 to 10 km we measured the electric field induced by water flows forced at 150 m depth through a 10 m wide granite fractured zone the water flows were obtained by pumping cyclically 10 m of water from a borehole that cut the fractured zone at depth and contemporaneously reinjecting it into another borehole located 50 m away after one day a steady state fluid flow regime was reached with pumping cycles lasting 45 minutes indicating a hydraulic conductivity of 10 5 m s 1 and a specific storage coefficient of 3 25 10 6 m 1 the expected self potential at the surface was an anomaly with two maxima of opposite sign and 2 v amplitude each both located 160 m away from the middle of the borehole heads the signal being divided by two 500 m away from the middle of the borehole heads in agreement with wurmstich and morgan 1994 instead we observed an electrical signal of 8 mv midway between the borehole heads and smaller than 5 mv 33 m away from the borehole heads the discrepancy observed between the data and the model can be explained by fluid flow leakages that occurred close to the water table head represented about 20 of the total water flow and activated smaller but closer electric sources this experiment thus illustrates the practical difficulty of detecting streaming potentials generated at depth it shows in particular that in fractured zones and hence in the vicinity of a major active fault small water flows located distantly from an energetic targeted source but close to some of the electrodes of the network can sometimes drastically distort the shape of the expected anomaly models of possible electrical earthquake precursors therefore turn out to be more speculative than expected

mean winds and waves in the troposphere during aloha 90 measurements of the tropospheric horizontal wind field at christmas island during the aloha 90 campaign are presented in this paper a diurnal cycle is observed on several days but is not consistent from day to day significant variance associated with the high frequency wave motions occurred between march 22 and 26 1990 this large wave activity in the troposphere is consistent with mesospheric wave activity during the same time interval

shear wave reflection seismics as a valuable tool for near surface urban applications subsurface investigations in urban areas have to take sealed surfaces and densely built and populated areas into account the shear wave reflection seismic system developed at the leibniz institute for applied geophysics liag provides a solution for this acquisition technology problem using horizontally polarized shear waves sh waves and noninvasive source and receiver designs

estimating aquifer hydraulic properties from the inversion of surface streaming potential sp anomalies 1 electrokinetic effects of water flow during pumping tests have been shown to generate surface streaming potential sp anomalies of several tens of mv that are well correlated with the geometry of the water table it follows that sp measurements can be used to estimate aquifer hydraulic properties we have developed an inversion scheme for surface sp data generated by flow pumping and found that we are able to estimate the hydraulic conductivity and the depth and the thickness of the aquifer we applied our inversion scheme to the data from bogoslovsky and ogilvy 1973 and found a hydraulic conductivity of 10 5 m s 1 an aquifer thickness of roughly 28 m and an electrokinetic coupling coefficient of 1 mv m 1 these values are in the range of what is expected for this kind of environment

influence of the mineralogical composition on the self potential response to advection of kcl concentration fronts through sand 1 we measured the self potential sp response to advective transport of kcl concentration fronts through two laboratory scale sand bodies with different mineralogical composition in pure quartz sand the amplitude and polarity of the sp signals agreed with a previously published model in sand containing 3 potassic feldspars and 1 micas and clays the shape of the sp response differed significantly the amplitude was much larger than the model prediction and a change in polarity occurred after the passage of the front furthermore the kcl concentration in the effluent was strongly reduced we suggest that the minor mineral phases reacted with the k ions trapping them during the front passage and releasing them later even though the reactions involved are not fully identified to date this study demonstrates that even small amounts of chemically active mineral phases such as micas or clays can significantly influence the sp signals

fluid flow monitoring in oil fields using downhole measurements of electrokinetic potential downhole measurements of electrokinetic potential are a promising new technology for hydrocarbon reservoir monitoring usinga3dfinite elementmodelcombiningbothmultiphase flow and electrokinetic components we investigated the behavior of electrokinetic streaming potential during oil production in a range of reservoir environments we found that streamingpotential signals originate at fluid fronts and at geologic boundaries where fluid saturation changes as water encroaches on an oil production well the streaming potential signal associated with the water front encompasses the well even when the front is up to 100 m away so the potential measured at the well starts to change significantly relative to a distant reference electrode variations in the geometry of the encroaching water front can be characterized using an array of electrodes positioned along the well but a good understanding of the local reservoir geology is required to identify signals caused by the front the streaming potential measured at a well is maximized in low permeability reservoirsproducedatahighrateandinthickreservoirswithlow shale content however considerable uncertainties remain particularly relating to the nature of electrokinetic coupling at high salinity and during multiphase flow our results suggest that the streaming potential at low salinity 10 3 10 4 mol l is large 100 1000 mv but might become too small to resolve 0 1 mv at high salinity 0 5 2 mol l depending on how the available data for the electrokinetic coupling at low salinity are extrapolated into the high salinity domain more work remains to determine the behavior of electrokinetic coupling andthereforetheutilityofthistechniqueathighsalinity

characterization of electrical daily variations induced by capillary flow in the non saturated zone electrical daily variations without an associated magnetic field were observed for a period of six weeks on independent parallel dipoles during the one year electrode inter comparison experiment that took place in garchy france from april 1995 to april 1996 these daily variations appeared suddenly during summer when the soil was dry on the surface their amplitude ranged from 0 1 to 1 5 mv for 50 m long dipoles and characteristic relative phases the amplitude of the variations was found to be related to soil temperature these daily variations are accounted for in a model where streaming potentials are produced by coherent capillary flow in the non saturated zone such daily variations are important to control in long period magnetotelluric sounding and may be of practical use for agricultural applications as their amplitude strongly depends on time varying soil conditions they may also lead to erroneous interpretations as earthquake precursors

dependence of seismoelectric amplitudes on water content summary the expectation behind seismoelectric field measurements is to achieve a combination of the sensitivity of electrical properties to water content and permeability and the high spatial resolution of seismic surveys a better understanding of the physical processes and a reliable quantification of the conversion between seismic energy and electric energy are necessary and need to take into account the effect of water content especially for shallow subsurface investigations we performed a field survey to quantify the seismoelectric signals as the water content changed we measured seismoelectric signals induced by seismic wave propagation by repeating the observations on the same two profiles during several months the electrical resistivity was monitored to take into account the water content variations weshowthatthehorizontalcomponentoftheseismoelectricfield normalizedwithrespectto the horizontal component of the seismic acceleration is inversely proportional to the electrical resistivity 0 42 0 25 assuming that the observed resistivity changes depend only on the water content this result implies that the electrokinetic coefficient should increase with increasing water saturation taking into account the water saturation and combining our results with the archie law for the resistivity in non saturated conditions the normalized seismoelectric field is a power law of the effective saturation with the exponent 0 42 0 25 n where n is archie s saturation exponent

the signature of shear wave splitting theory and observations on heavy oil data the use of shear wave splitting analysis as a tool for fracture analysis is well established in this article we discuss the analysis of shear wave splitting in a relatively new context shallow heavy oil plays where we believe stress is the dominant cause of the shear wave splitting rather than macroscale fracturing there is clear laboratory evidence in the literature for shear wave splitting caused by differential stress which we believe supports this viewpoint we are particularly interested in the use of shear wave splitting technology for monitoring reservoir stress changes which correlate with thermal production for heavy oil reservoirs this article also takes a fresh look at some well established characteristics of split shear waves as they appear in wide azimuth multicomponent data and in particular the relative merits of the radial and transverse amplitude signatures we describe a recently developed method which combines both radial and transverse analysis to improve the effective azimutha

implementation of magnetic gravity and resistivity data in identifying groundwater occurrences in el qaa plain area southern sinai egypt abstract el qaa plain is one of the areas that have been proved to be promising as to its soil and groundwater resources in the southwestern part of sinai this study was carried out to study the lateral and vertical variations in the subsurface lithologic properties in el qaa plain area and delineating the subsurface structure that affecting el qaa plain depression gravity magnetic data fifty one 51 vertical electrical sounding ves s and digital elevation model dem map were used two dimensional density modeling analytical signal tilt derivatives euler deconvolution techniques and interpretation of the resistivity data were applied on potential data this study concluded that el qaa plain is a ne sw depression confined by two normal faults and subdivided into five sedimentary units rock fragments and boulders derived to the plain from the surrounding highlands are the main components of the first surface unit that characterized by high resistivity values this layer is overly another unit composed of gravelly sand with thickness ranging between 10 and 140 m the third unit is composed mainly of sand with intercalations of clay with thickness ranging from 2 to 152 m a reefal limestone unit is a fourth unit interpreted from this study the fifth unit is composed of clay the water bearing formations in el qaa plain area are located principally in the second and the third layers finally the depth to the basement surface ranges from 400 m to more than 1 5 km below sea level also there are many minor structural trends interpreted from this study and affecting the el qaa plain are striking in n s e w and ne sw directions

evidence of the theoretically predicted seismo magnetic conversion summary seismo electromagnetic phenomena in porous media arise from seismic wave induced fluid motion in the pore space which perturbs the equilibrium of the electric double layer this paper describes with details the original experimental apparatus built within the ultra shielded chamber of the low noise underground laboratory of rustrel france we measured seismo magnetic conversions in moist sand using two induction magnetometers and a pneumatic seismic source to generate the seismic wave propagation we ensured to avoid the magnetometer vibrations which could induce strong disturbances from induction origin interpretation of the data is improved by an analytical description of phase velocities for fast pf and slow ps longitudinal modes transverse mode s as well as the extensional mode due to the cylindrical geometry of the sample the purpose of this paper is to provide elements to measure correctly coseismic seismomagnetic fields and to specify their amplitude the seismic arrivals recorded in the sample showing a 1200 1300 m s 1 velocity have been associated to p and extensional waves the measured seismo magnetic arrivals show a velocity of about 800 m s 1 close to the calculated phase velocity of s waves therefore we show that the seismo magnetic field is associated to the transverse part of the propagation as theoretically predicted by pride 1994 but never measured up to now moreover the combined experimental and analytical approaches lead us to the conclusion that the measured seismo magnetic field is probably about 0 035 nt for a 1 m s 2 seismic source acceleration 0 1 g

2 5 d gravity magnetic model studies in sahl el qaa area southwestern sinai egypt the 2 5 d gravity magnetic models of the upper crustal structures of sahl el qaa area southwestern sinai were constructed along seven profiles focusing on the uppermost crustal layers to a depth of 4 5 km in addition separation filtering process spectral analysis and trend analysis were used to investigate the bouguer and total intensity aeromagnetic field maps qualitatively and quantitatively the study showed that the regional structures consist of tilted blocks in the form of a major nw synclinal feature with an axis dipping northward this feature is dissected by the ne trending cross faults forming horsts grabens and step fault structures the tilted blocks are controlled by a major normal fault system and are greatly modified in the dip regime from north to south they show a regional nw dip regime in northern and southern parts where the depth to the basement reaches about 2 3 km in the down dip in the central portion the basin is dipping steeply to the east with maximum depths attaining about 4 5 km

laboratory monitoring of p waves in partially saturated sand energy dissipation is observed on seismic data when a wave propagates through a porous medium involving different frequency regimes depending on the nature of rock and fluid types we focus here on the role of partial fluid saturation in unconsolidated porous media looking in particular at p wave phase velocity and attenuation the study consists in running an experiment in a sand filled tank partially saturated with water seismic propagation in the tank is generated in the khz range by hitting a steel ball on a granite plate seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation several imbibition drainage cycles were performed between the water and gas residual saturations a continuous wavelet transform applied on seismic records allowed us to extract the direct p wave at each receiver we observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage phase velocities and inverse quality factors are then jointly inverted to get a final poro visco elastic model of the partially saturated sand that satisfactorily reproduces the data the model formulation consists in generalizing the biot theory to effective properties of the fluid and medium permeability and bulk modulus in order to properly explain the phase velocity variation as a function of the saturation the strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding adding to biot s losses this study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct p waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media

the amplitude and phase response of a seismic vibrator the amplitude and phase response of a simple model is compared with the performance of a real vibrator working in the field the field results show a characteristic phase response which confirms that the real drive force applied to the baseplate and its load impedance is faithfully represented by the acceleration of the reaction mass it follows that all the parameters necessary to calculate the load impedance and the true power dissipated in the earth can be measured at the output of the vibrator it also follows that the current method of baseplate phase compensation should be reconsidered

influence of water pressure dynamics and fluid flow on the streaming potential response for unsaturated conditions streaming potentials are produced by electrokinetic effects in relation to fluid flow and are used for geophysical prospecting the aim of this study is to model streaming potential measurements for unsaturated conditions using an empirical approach a conceptual model is applied to streaming potential measurements obtained from two drainage experiments in sand the streaming potential data presented here show a non monotonous behaviour with increasing water saturation following a pattern that cannot be predicted by existing models a model involving quasi static and dynamic components is proposed to reproduce the streaming potential measurements the dynamic component is based on the first time derivative of the driving pore pressure the influence of this component is investigated with respect to fluid velocity which is very different between the two experiments the results demonstrate that the dynamic component is predominant at the onset of drainage in experiments with the slowest water flow on the other hand its influence appears to vanish with increasing drainage velocity our results suggest that fluid flow and water distribution at the pore scale have an important influence on the streaming potential response for unsaturated conditions we propose to explain this specific streaming potential response in terms of the behaviour of both rock water interface and water air interfaces created during desaturation processes the water air interfaces are negatively charged as also observed in the case of water rock interfaces both the surface area and the flow velocity across these interfaces are thought to contribute to the non monotonous behaviour of the streaming potential coefficient as well as the variations in its amplitude the non monotonous behaviour of air water interfaces created during the flow was highlighted as it was measured and modelled by studies published in the literature the streaming potential coefficient can increase to about 10 to 40 when water saturation decreases such an increase is possible if the amount of water air interfaces is increased in sufficient amount which can be the case

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