upper mantle structure under western europe from fundamental and higher mode surface waves using the nars array summary a generalized inversion of a new data set consisting of surface wave phase velocities and sn traveltimes has resulted in a new shear velocity and density model for the west european platform wepl 2 the surface wave phase velocity data set consists of fundamental and higher mode mode 1 6 measurements from 25 to 70mhz using the network of autonomously recording stations nars array which was specifically designed for higher mode surface wave measurements the sn traveltime data set consists of isc readings for selected european events major features of wepl 2 are a high velocity lid of 80 140 km depth underlain by a pronounced low velocity zone between 160 and 220 km depth the transition zone 400 650 km depth is characterized by high shear velocities with respect to prem the density shows a positive gradient from 60 to 140 km depth followed by an approximately constant value down to 400 km depth a model for the baltic shield scsh 2 is obtained by combination of nolet s 1977 higher mode phase velocity data set for western europe including the baltic shield and the present phase velocities for the platform this shield model shows an absence of the low velocity layer and low shear velocities in the top of the transition layer with respect to wepl 2 density although less well resolved shows lower values for the shield structure between 200 and 350 km depth

genesis and microstratigraphy of calcite coralloids analysed by high resolution imaging and petrography abstract the genesis of calcite coralloid speleothems from lamalunga cave southern italy is here investigated from a purely petrographic perspective which constitutes the basis for any subsequent chemical investigation lamalunga cave coralloids formed on bones and debris on the floor of the cave they consist of elongated columnar crystals whose elongation progressively increases from the flanks to the tips of the coralloid forming a succession of lens shaped layers which may be separated by micrite or impurity rich layers organic molecules are preferentially concentrated toward the centre of convex lenses as highlighted by epifluorescence their occurrence on cave floor lens shaped morphology and concentration of impurities toward the apex of the convex lenses supports the hypothesis that their water supply was hydroaerosol generated by the fragmentation of cave drips evaporation and degassing preferentially occurred on tips enhancing the digitated morphology and trapping the organic molecules and impurities carried by the hydroaerosol between the growing crystals which became more elongated micrite layers that cap some coralloid lenses likely identify periods when decreasing in hydroaerosol resulted in stronger evaporation and higher supersaturation with respect to calcite of the parent film of fluid this interpretation of coralloid formation implies that these speleothems can be used to extract hydroclimate information

lateral variations of the upper mantle structure in eurasia from group velocities of surface waves abstract group velocities of both rayleigh and love waves in the 20 70 s period range along paths across asia and the eastern europe are used to obtain group velocity maps of the region for this purpose we developed a method for tomographic inversion on spherical surface which is practically free of a priori assumptions checker board test shows that velocity anomalies of 10 10 size can be resolved the local dispersion curves are inverted to velocity depth curves up to 160 km depth along three profiles 1 tibet the south china platform and the southern part of the japan sea 2 the west siberian platform the tienshan and the pamir 3 the east european platform and the black sea basin lateral s wave velocity variations are presented at the depths of 60 90 and 120 km a low velocity zone in asthenosphere under japan sea is extended under the south china and the north china korean platforms the upper mantle structure of the russian east european and the west siberian platforms is different a low velocity zone at 120 140 km depths is observed under the west siberian platform whereas the velocity under the russian platform increases monotonously with depth a low velocity layer appears under the black sea indicating an oceanic structure of the basin low surface wave velocities in tibet are caused not only by a thick crust but also by low s wave velocities in the upper mantle the precambrian west siberian north indian and north china korean platforms are characterized by high velocities at the depth of 120 km unlike the younger tectonic units

polarization anisotropy and fine scale structure of the eurasian upper mantle we have observed shear wave splitting with tsh tsv tsv up to 1 5 on long period records of multiply reflected s waves bottoming in the upper mantle beneath the russian and siberian platforms the dispersion of love and rayleigh waves over these paths shows discrepancies of comparable or larger magnitude with respect to smooth isotropic si structures consistent with a model of the uppermost mantle having significant apparent vertical anisotropy although the splitting and dispersion data can be fit by smooth anisotropic sa models we have investigated the apparent anisotropy associated with fine scale rough structure beneath stable eurasia we fit the data with a rough isotropic ri model having an rms shear velocity fluctuation that varies from 14 in the uppermost mantle to zero at 400 km depth these fluctuations are larger than the variation in isotropically averaged parameters expected for even a diverse assemblage of upper mantle ultrabasic rocks which we take to be evidence for some sort of intrinsic local anisotropy

the backus gilbert approach to the three dimensional structure in the upper mantle i lateral variation of surface wave phase velocity with its error and resolution summary the backus gilbert method is applied to obtain the phase velocity variations on a sphere from the measured phase velocity narrow peak kernels with radii of about 2000 km are obtained for almost everywhere on the sphere the phase velocity results are thus interpreted as an average within such regions the most trouble comes from the antipodal peak in the resolution kernel this is evaluated as contamination and is incorporated in the error estimation the total error which is a root mean square of contamination from the antipodal peak and statistical error estimated from the data covariance matrix is about 1 per cent of the phase velocity in the average earth model which is the preliminary reference earth model prem however there is about a factor of 2 variation of errors on the sphere maximum variations of phase velocity are about 3 4 per cent of the phase velocity in the average earth model and thus there still remain anomalies which exceed estimated errors the estimated errors correspond to one standard deviation under the assumptions of uncorrelated gaussian distribution for high confidence interval they show that statistically significant anomalies are scarce for the current data set generally love wave phase velocity maps show more resolved features than rayleigh wave maps and we can see in high confidence maps fast velocities in old oceans and old continents and slow velocities in tectonically active regions like the east pacific rise and various back arc regions

trajectories of thermospheric air parcels flowing over alaska reconstructed from ground based wind measurements it is widely presumed that the convective stability and enormous kinematic viscosity of earth s upper thermosphere hinders development of both horizontal and vertical wind shears and other gradients any strong local structure over scale sizes of several hundreds of kilometers that might somehow form would be expected to dissipate rapidly air flow in such an atmosphere should be relatively simple and transport effects only slowly disperse and mix air masses however our observations show that wind fields in earth s thermosphere have much more local scale structure than usually predicated by current modeling techniques at least at auroral latitudes they complicate air parcel trajectories enormously relative to typical expectations for tracing air parcels we used wind measurements of an all sky scanning doppler fabry perot interferometer and reconstructed time resolved two dimensional maps of the horizontal vector wind field to infer forward and backward air parcel trajectories over time this is the first comprehensive study to visualize the complex motions of thermospheric air parcels carried through the actual observed local scale structures in the high latitude winds results show that thermospheric air parcel transport is a very difficult observational problem because the trajectories followed are very sensitive to the detailed features of the driving wind field to reconstruct the actual motion of a given air parcel requires wind measurements everywhere along the trajectory followed with spatial resolutions of 100 km or less and temporal resolutions of a few minutes or better understanding such transport is important for example in predicting the global scale impacts of aurorally generated composition perturbations

paleokarst paleosol and rocky shore deposits at the mississippian pennsylvanian unconformity northwestern arkansas the mississippian pennsylvanian unconformity in northwestern arkansas contains pedogenically altered regolith preserved in low lying areas on paleokarst on the chesterian pitkin limestone the regolith is succeeded by transgressive rocky shore deposits of the cane hill member hale formation type morrowan pitkin cements reflect extensive meteoric phreatic diagenesis prior to karstiflcation and paleokarst features include large dissolution fragmented pitkin lithoclasts with numerous solution pipes on a low relief surface the overlying pedogenically altered regolith contains calcretized lithoclasts in clay matrix suggesting a shift from ever wet conditions to more seasonal rainfall prior to the pennsylvanian transgression that shift may represent local climatic change or short term fluctuations in mid carboniferous tropical climate the latter interpretation may support global climate models that predict warmer wetter tropics during periods of high latitude cooling basal cane hill strata consist of high energy shoreface boulder cobble conglomerate containing reworked pitkin clasts the conglomerate contains an unequivocal rockyshore community consisting of encrusting bryozoans and corals trypanites acrothoracican barnacle borings and possibly the earliest occurrence of gastrochaenolites preservation of poorly indurated paleosol beneath high energy transgressive deposits suggests very rapid transgression consistent with a glacio eustatic mechanism truncated pitkin strata were removed by karstification and subaerial erosion during the hiatus and not by erosion during transgression

neutral thermospheric dynamics observed with two scanning doppler imagers 3 horizontal wind gradients 1 this is the third and final article in a series of papers reporting on observations of the 630 0 nm thermospheric airglow emission by two spatially separated scanning doppler imagers sdi s in alaska in this article bistatic winds derived from the combined measurements of both instruments in a region of field of view overlap were used to derive local scale maps of horizontal neutral wind gradients averaged over the bistatic field of view these gradient estimates were compared with the monostatic gradient estimates routinely produced by the two sdi s the key findings to emerge from this study include 1 the bistatic gradient estimate agreed very well with monostatic estimates for the majority of the time which given the very different methods involved in each technique gives us great confidence in our ability to measure f region neutral wind gradients 2 the strongest gradient was that which describes the magnetic meridional shear of the zonal wind which is driven by momentum deposition from convecting ions 3 vortical flow was more often observed than divergent flow and both types of flow showed systematic variations with magnetic local time 4 viscous heating due to non negligible gradients was on the order of 10 11 wm 3 which while small compared to typical f region joule heating rates may be comparable to particle heating and in a time integrated sense may be an appreciable source of heating

shear wave velocity structure beneath europe the northeastern atlantic and western asia from waveform inversions including surface wave mode coupling summary waveforms of 449 seismograms have been inverted for s wave velocity structures beneath europe the northeastern atlantic and western asia down to a depth of 670 km recorded waveforms were used in the time window starting at the s wave arrival and ending after the fundamental mode rayleigh wave arrival the inversion method is based on the partitioned waveform inversion nolet 1990 with the difference that synthetic seismograms are calculated taking surface wave mode coupling into account in order to model body waves in laterally heterogeneous media more accurately the partitioning of the inversion procedure makes non linear optimization feasible even for inversions including surface wave mode coupling the non linear inversion of the waveforms resulted in linear constraints on the 3 d velocity structure in a second step these constraints were used in a linear inversion for the 3 d shear wave velocity model beneath europe the northeastern atlantic and western asia the eur sc 95 model is presented which is characterized by a wide range of length scales of the velocity structures in central europe where the ray density is highest small scale structures are recovered such as the presence of high velocities associated with the hellenic subduction zone on the edges of the inversion model where the ray density and therefore also the resolution is poorer we find larger scale features such as the relatively laterally homogeneous high velocity structure beneath the russian platform to a depth of 300 km in this paper we discuss the inversion method data processing parametrization difficulties due to the introduction of surface wave mode coupling spatial resolution of the model and structures in the eur sc 95 model

moho depth across the trans european suture zone from p and s receiver functions the mohorovicic discontinuity moho for short which marks the boundary between crust and mantle is the main first order structure within the lithosphere geodynamics and tectonic evolution determine its depth level and properties here we present a map of the moho in central europe across the teisseyre tornquist zone a region for which a number of previous studies are available our results are based on homogeneous and consistent processing of p and s receiver functions for the largest passive seismological data set in this region yet consisting of more than 40 000 receiver functions from almost 500 station besides we also provide new results for the crustal vp vs ratio for the whole area our results are in good agreement with previous more localized receiver function studies as well as with the interpretation of seismic profiles while at the same time resolving a higher level of detail than previous maps covering the area for example regarding the eifel plume region rhine graben and northern alps the close correspondence with the seismic data regarding crustal structure also increases confidence in use of the data in crustal corrections and the imaging of deeper structure for which no independent seismic information is available in addition to the pronounced stepwise transition from crustal thicknesses of 30 km in phanerozoic europe to more than 45 beneath the east european craton we can distinguish other terrane boundaries based on moho depth as well as average crustal v p v s ratio and moho phase amplitudes the terranes with distinct crustal properties span a wide range of ages from palaeoproterozoic in lithuania to cenozoic in the alps reflecting the complex tectonic history of europe crustal thickness and properties in the study area are also markedly influenced by tectonic overprinting for example the formation of the central european basin system and the european cenozoic rift system in the areas affected by cenozoic rifting and volcanism thinning of the crust corresponds to lithospheric updoming reported in recent surface wave and s receiver function studies as expected for thermally induced deformation the same correlation applies for crustal thickening not only across the trans european suture zone but also within the southern part of the bohemian massif

mapping thermospheric winds in the auroral zone a new all sky imaging fabry perot asifp spectrometer has been developed for ground based mapping of upper atmospheric wind and temperature fields in the auroral zone although several other asifp spectrometers exist for atmospheric studies rees et al 1984 sekar et al 1993 biondi et al 1995 these instruments have all operated with etalons of fixed optical gap a method potentially subject to errors in the presence of auroral intensity gradients in this instrument the etalon plate spacing is scanned periodically over one order of interference and each photon detected is assigned to a wavelength interval which is determined from both its arrival location on the detector and the etalon plate spacing prevailing at the detection time spectra accumulated this way are not distorted by spatial intensity gradients preliminary 630 nm observations were made during the winter of 1994 95 from poker flat research range alaska to illustrate some of the features we have observed in this study we present line of sight wind estimates derived for the night of december 7 1994 the background wind matches averages presented previously by sica et al 1986 and is consistent with winds driven principally by momentum deposition from ionospheric plasma convection through ion drag smaller scale curvature and divergence features are also discernable and are discussed

neutral thermospheric dynamics observed with two scanning doppler imagers 1 monostatic and bistatic winds 1 doppler shift measurements of the thermospheric 630 0 nm emission recorded by two spatially separated imaging fabry perot spectrometers in alaska have been combined to infer f region horizontal wind vectors at approximately 75 locations across their overlapping fields of view these bistatic horizontal wind estimates rely only on an assumption regarding the local vertical wind and assume a common observing volume and thus represent a more direct measurement of the wind than do the monostatic single station vector wind fields routinely inferred by these instruments here we present comparisons between both the independently derived monostatic wind fields from each instrument and the bistatic wind estimates inferred in their common observing volumes data are presented from observations on three nights during 2010 two principal findings have emerged from this study first the monostatic technique was found to be capable of estimating the actual large scale wind field reliably under a large range of geophysical conditions and is well suited to applications requiring only a large scale big picture approximation of the wind flow secondly the bistatic or tristatic technique is essential for applications requiring detailed knowledge of the small scale behavior of the wind as for example is required when searching for gravity waves

aspherical earth structure from fundamental spheroidal mode data free oscillation data reveal heterogeneity in the earth s mantle whose geographical pattern is dominated by spherical harmonics of angular degree two and correlates well with the hydrostatically referenced geoid the heterogeneity can be modelled as localized in the transition zone 420 670 km depth and may be related to a large scale component of mantle convection

the nars deep project the nars deep project involves the deployment of broadband seismological stations in russia belarus and the ukraine six stations were installed in 1995 two in 1997 and more stations were to be installed from 1998 onwards the nars deep project was initiated as a temporary deployment but funding from the european community enabled the stations to become permanent in this paper we present first results of the nars deep project a surface waveform inversion for the upper mantle structure along a profile from egypt to spitsbergen shows evidence for strong variations in the shear velocity structure for the different tectonic units the most striking features of the model comprise strong lithospheric anisotropy beneath the eastern mediterranean and a lithospheric thickness of approximately 200 km beneath the shield areas the crustal structure beneath the seismic station in st petersburg was investigated using the receiver function method the results of a monte carlo inversion for the receiver functions of this station show evidence for a sedimentary layer with a thickness of less than 1 km overlying an upper crustal layer extending to a depth of approximately 16 km the moho depth cannot be resolved from the receiver functions of this station

spatial structure in the thermospheric horizontal wind above poker flat alaska during solar minimum a new all sky imaging wavelength scanning fabry perot spectrometer was used to record high resolution r 200 000 spectra of the 630 nm thermospheric optical emission above poker flat alaska these spectra were used to derive spatially resolved maps of the horizontal wind vector at approximately 250 km altitude we describe the procedure used to infer vector winds from line of sight doppler shifts along with its limitations we present the time evolution of the vector wind fields obtained from this method for 6 nights of observation five of the 6 nights contained periods when we inferred the existence of significant curvature divergence or shear in the thermospheric wind across our instrument s 1000 km diameter field of view the sixth night exhibited little spatial structure and is shown for comparison we compare these results with a generic solar minimum winter time run of the national center for atmospheric research s thermosphere ionosphere and electrodynamics general circulation model while agreement was good at the start and end of the night considerable differences were found in the late evening and midnight sectors some possible origins for these discrepancies are proposed in particular we suggest that the f region horizontal wind may be deflected by upwelling vertical winds which are in turn driven by e region heating in the auroral zone we note that both the instrument used and our high latitude implementation of the analysis procedure are new experimental techniques thus the data presented here should be regarded as preliminary and if possible be validated by comparison with results from other techniques

least squares fitting of marine seismic refraction data summary an iterative procedure is presented for fitting waveform data from a marine seismic refraction experiment the wavefunction from the explosive source is known and the crustal structure is refined using the damped least squares procedure the damping parameter serves the dual purpose of stabilizing an under constrained inversion and improving the linearity by suppressing high frequencies the synthetic seismograms and their model differentials are calculated using the wkbj seismogram method both the synthetic seismograms and the linear algebra are sufficiently straightforward that the computations can be performed on an array processor the inversion procedure is then sufficiently rapid that interactive computations are possible the technique is illustrated using the ff2 refraction data from the fanfare cruise of the scripps institution of oceanography these data had been interpreted previously by trial and error using the reflectivity method starting from two different simple models the inversion procedure obtains essentially one unique model its features are very similar to the previous model

new constraints on the rupture process of the 1999 august 17 izmit earthquake deduced from estimates of stress glut rate moments summary this paper illustrates the use of integral estimates given by the stress glut rate moments of total degree 2 for constraining the rupture scenario of a large earthquake in the particular case of the 1999 izmit mainshock we determine the integral estimates of the geometry source duration and rupture propagation given by the stress glut rate moments of total degree 2 by inverting long period surface wave lpsw amplitude spectra kinematic and static models of the izmit earthquake published in the literature are quite different from one another in order to extract the characteristic features of this event we calculate the same integral estimates directly from those models and compare them with those deduced from our inversion while the equivalent rupture zone and the eastward directivity are consistent among all models the lpsw solution displays a strong unilateral character of the rupture associated with a short rupture duration that is not compatible with the solutions deduced from the published models with the aim of understand this discrepancy we use simple equivalent kinematic models to reproduce the integral estimates of the considered rupture processes including ours by adjusting a few free parameters controlling the western and eastern parts of the rupture we show that the joint analysis of the lpsw solution and source tomographies allows us to elucidate the scattering of source processes published for this earthquake and to discriminate between the models our results strongly suggest that 1 there was significant moment released on the eastern segment of the activated fault system during the izmit earthquake 2 the apparent rupture velocity decreases on this segment

a study of the barisakho georgia earthquake of 1992 october 23 from broad band surface and body waves summary we study the 1992 october georgian earthquake located in the centra part of the great caucasus this is the last strong ms 6 5 shallow earthquake of a series of three that struck this region in the two year period of 1991 1992 in order to determine the source parameters we analysed surface and body waves from the iris and geoscope very broad band digital networks the fundamental mode of surface waves was retrieved using frequency time analysis ftan a technique that makes inversion more stable and enables the measurement of the spectral features from the signal in the presence of stationary noise we used long period surface waves 60 150 s to obtain the seismic moment mo 4 8 10 n m and the focal mechanism strike 8 300 dip 6 15 and rake a 135 the space time distribution of the source moment density tensor was determined from intermediate period 35 60 s surface waves we found the following results duration 6 s rupture velocity 3 2 km s i major and minor axes of the fault surface i 32 km and zmin 20 km respectively for the inversion of body waves we performed a shape waveform modelling using the gradient method of nabelek we considered the source as a point source of 6 s duration the results of body wave inversion mo 3 0 10 n m 8 300 6 17 and 1 137 are in good agreement with estimates from surface waves one of the nodal planes of the fault plane solution corresponds to a thrust fault which agrees with the general seismotectonic features of the region of the kartli and kokheti ridges in the central part of the great caucasus the southern slope of the great caucasus strikes wnw ese and the underlying crystalline basement plunges towards the nne under the main axial zone the source plane coincides with the location of the contact between the crystalline basement and the upper block overthrust

neighbourhood inversion of teleseismic ps conversions for anisotropy and layer dip summary the inversion of teleseismic receiver functions for lithospheric structure is difficult due to the non linearity of the problem which is greatly increased in the presence of dipping interfaces and layer anisotropy given an efficient ray theoretical tool for forward modelling teleseismic seismograms we perform a directed monte carlo search technique using the neighbourhood algorithm of sambridge enabling us to search 20 30 parameters in a reasonable amount of computer time tests on synthetic data reveal inherent velocity depth trade offs in typical data sets due to the limited moveout present in teleseismic ps the azimuth of the anisotropic symmetry axis and the strike of a dipping interface prove to be well resolved given adequate backazimuthal coverage we apply this technique to two single station data sets the first from permanent station pgc vancouver island british columbia displays dipping low velocity sediment layers in the mid crust the second from a station at the northern end of the tibetan plateau operating in 1991 and 1992 requires a sequence of thick crustal anisotropic layers to explain the observed pattern of receiver function arrivals

partitioned waveform inversion and two dimensional structure under the network of autonomously recording seismographs nonlinear optimization methods are very effective in finding models that predict optimal waveform fits to observed seismograms provided the number of model parameters is small to reduce the size of the large scale two or three dimensional seismic modelling problem path integrals over seismic velocities may be defined as model parameters instead of the seismic velocities themselves this partitions the large scale optimization problem into a number of independent small scale problems and reduces the computational effort by several orders of magnitude the path integral parameters are transformed such that their correlation matrix becomes diagonal a linear inversion performs the mapping from the space of path integral parameters into the model space of seismic velocities and makes backus gilbert resolution analysis possible the method has been applied to body wave and surface wave data from the broadband portable network of autonomously recording seismographs nars in western europe using a surface wave ray approximation to generate synthetics by mode summation waveforms were fitted for frequencies as high as 50 mhz variations in s velocity as large as 6 1 have been established with a vertical resolution of 100 150 km and a horizontal resolution as small as 400 km in parts of the model although a low velocity layer is present under the southern part of the nars array such layer is very weak or absent north of the paris basin horizontal velocity gradients are well resolved down to 400 km depth

simultaneous fpi and tma measurements of the lower thermospheric wind in the vicinity of the poleward expanding aurora after substorm onset

higher degree moment tensor inversion using far field broad band recordings theory and evaluation of the method with application to the 1994 bolivia deep earthquake summary we present a method to estimate parameters of the extended earthquake source using higher degree moment tensors at 27 centroid locations we show that a taylor series expansion of green s functions around a single centroid is not accurate enough when working with seismic wave periods and wavelengths in the range of the rupture duration and spatial extent of the fault respectively introducing a grid of 27 centroid locations on the fault and using higher degree moment tensors we are able to model adequately body and surface waves with periods and wavelengths smaller than the rupture duration and fault dimensions under simplifying assumptions an iterative inversion scheme is coded to estimate parameters of planar haskell type faults realistic inversion examples for deep and shallow earthquakes show that uni and bidirectional rupture models rupture direction fault and auxiliary plane and kinematic source dimensions and can be constrained with teleseismic body and or surface waves the application to the deep bolivia event indicates a subhorizontal fault plane unidirectional rupture to the north is slightly preferred the rupture duration of 25 s and fault dimensions of 47 25 km agree well with the estimates for the main pulse moment release given in other studies

a seismic cross section through the east european continent summary a 2 d pro le for the shear wave velocity and anisotropybetween egypt and spitsbergen is presented the pro le is constructed using fundamental and higher mode love and rayleigh waves recorded by stations of the nars deep iris and geofon networks the surface wave data have been inverted for shear velocity and anisotropy using a waveform inversion in the eastern mediterranean lithosphere we observe a large diierence 7 per cent between sh and sv velocities we interpret this anomaly as an anisotropic oceanic lithosphere beneath the eastern mediterranean an interpretation which is consistent with tectonic reconstructions of the region the east european continent is imaged as a high velocity body whose thickness increases with the estimated age of the lithosphere the continental root of the ukrainian and baltic shields and east european platform extends to a depth of 200 km this is in contrast to the surrounding younger continental regions which appear to be less than 100 km thick we further studied the structure of the continental lithosphere by investigating a possible relation between seismic velocities and tectonic age both a logarithmic and a square root relation have been tted to the average seismic velocities in each tectonic region the data slightly favour a logarithmic relation but a square root relation cannot be excluded

the anisotropic seismic structure of the east european platform 1 we present models for the p and s velocity structure of the upper mantle beneath the east european platform including measurements of radial anisotropy the models were obtained by full waveform inversion of 3 component broadband seismograms from strike slip earthquakes located near the edge of the platform and recorded in russia and europe we used direct and multiply reflected body wave arrivals s ss p pp combined with fundamental mode love and rayleigh waves at source receiver distances between 15 and 50 to resolve mantle structure down to the 410 km discontinuity the platform is underlain by a radially anisotropic mantle lid extending to a depth of 200 km with a largely isotropic mantle below the model has a positive velocity gradient from 41 km to 100 km depth and a relatively uniform velocity structure from 100 km to 200 km depth with high sh and ph velocities 4 77 km s 8 45 km s shear anisotropy is uniform at 5 h v from 41 to 200 km depth drops to 2 from 200 to 250 km and is isotropic below that the average shear velocity from 100 to 250 km is also uniform at 4 65 km s and the drop in anisotropy is matched by a drop in h to 4 70 km s combined with an increase in v to 4 60 km s below 250 km there is a positive velocity gradient in both p and s velocity down to 410 km p anisotropy is not well resolved but p structure mimics the sh velocity structure suggesting that p is also anisotropic within the lid

assimilated observations of thermospheric winds the aurora and ionospheric currents over alaska we present simultaneous measurements of thermospheric winds auroral emissions and ionospheric currents over alaska obtained from four separate instruments thermospheric f region wind maps were recorded by an all sky imaging fabry perot spectrometer located at poker flat and observing at 630 0 nm auroral images at 557 7 nm were obtained from the low resolution visible imager on board the polar satellite white light all sky auroral images were recorded by ground based all sky cameras located in alaska at poker flat 65 07 n 212 34 e and at kaktovik 70 06 n 217 24 e finally the east west component of the ionospheric f region plasma convection was inferred using the alaskan meridian chain of magnetometers montage images of these four data sets are presented projected onto a geographic map of the alaskan region we examine a 10 hour period during the alaskan local nighttime of february 10 1997 these montages illustrate a close relationship between spatial structures occurring in the aurora in the ionospheric plasma convection and in the f region wind field latitudinal shear of the geomagnetic zonal wind often observed in the premidnight time sector was seen to be associated with both the equatorward and poleward boundaries of the discrete aurora we focus particularly on a period commencing just after 0900 ut when a strong shear in the zonal wind was observed to sweep southward across alaska after magnetic midnight the wind field was dominated by the emergence of the cross polar jet from the polar cap this overwhelmed any wind features associated with local auroral processes

optical observations of thermospheric dynamics at arecibo observations of thermospheric neutral winds have been made at arecibo puerto rico by using a fabry perot interferometer to measure the doppler shift of the nighttime o d 630 nm emission we have developed a scheme of making observations at eight equally spaced azimuth positions with a constant zenith angle this technique allows us to determine the mean neutral wind velocities in the meridional and zonal directions as well as any horizontal gradients in the wind field it also provides a good means of simultaneously monitoring any spatial variations in neutral temperature and the intensity of the o d emission in general the highest equatorward wind velocity is observed at about 2100 lst the meridional wind velocity usually lessens as midnight approaches and sometimes but by no means always reverses after midnight the magnitude of the equatorward velocity is greater in summer than in winter months for winter and spring months the zonal wind blows eastward throughout the night with the velocity tending to decrease in a fairly regular fashion from about 125 m s 1 at 2100 lst towards zero by 0400 lst in summer the pattern is similar but the eastward flow usually reverses earlier and a westward velocity of some 50 m s 1 may be attained by 0400 lst significant horizontal wind gradients are often observed in the meridional direction but not in the zonal direction near midnight especially during both the equinox and summer months the equatorward wind is often greater to the north of arecibo than to the south we interpret this as being an effect of the passage of the midnight equatorial pressure maximum to the south of the station measurements of neutral temperature with the interferometer do indeed show that between 0100 0200 lst the neutral temperature to the south of arecibo is enhanced by some 40 k over that to the north

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

estimation of mesoscale thermospheric wind structure using a network of interferometers we introduce a technique for estimating the regional thermospheric wind field from measurements made by a network of interferometers unlike previous work this technique does not make assumptions about the functional form of the wind field and instead uses inverse theory to find the smoothest wind field that agrees with the measurements this technique is general and applies to any network making radial velocity measurements we show reconstructions of the thermospheric wind field over the eastern united states and over eastern brazil using data from two distinct networks of fabry perot interferometers measuring the doppler shift of the 630 0 nm airglow emission in brazil we find direct evidence of a convergent wind field during the period of rapid thermospheric temperature increase associated with the equatorial midnight temperature maximum

braided rivers within an arid alluvial plain example from the lower triassic western german basin recognition criteria and expression of stratigraphic cycles based on a detailed sedimentological analysis of lower triassic continental deposits in the western germanic sag basin i e the eastern part of the present day paris basin the conglomerat basal gres vosgien and conglomerat principal formations three main depositional environments were identified i braided rivers in an arid alluvial plain with some preserved aeolian dunes and very few floodplain deposits ii marginal erg i e braided rivers aeolian dunes and aeolian sand sheets and iii playa lake an ephemeral lake environment with fluvial and aeolian sediments most of the time aeolian deposits in arid environments that are dominated by fluvial systems are poorly preserved and particular attention should be paid to any sedimentological marker of aridity such as wind worn pebbles ventifacts sand drift surfaces and aeolian sand sheets in such arid continental environments stratigraphic surfaces of allocyclic origin correspond to bounding surfaces of regional extension elementary stratigraphic cycles i e the genetic units have been identified for the three main continental environments the fluvial type fluvial aeolian type and fluvial playa lake type at the time scale of tens to hundreds of thousands of years these high frequency cycles of climatic origin are controlled either by the groundwater level in the basin or by the fluvial siliciclastic sediment input supplied from the highland lower triassic deposits from the germanic basin are preserved mostly in endoreic basins the central part of the basin is arid but the rivers are supplied with water by precipitation falling on the remnants of the hercynian variscan appalachian mountains consequently a detailed study of alluvial plain facies provides indications of local climatic conditions in the place of deposition whereas fluvial systems only reflect climatic conditions of the upstream erosional catchments

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

determination of stress glut moments of total degree 2 from teleseismic surface wave amplitude spectra abstract a special case of the seismic source where the stress glut tensor can be expressed as a product of a uniform moment tensor and a scalar function of spatial coordinates and time is considered for such a source a technique of determining stress glut moments of total degree 2 from surface wave amplitude spectra is described the results of application of this technique for the estimation of spatio temporal characteristics of the georgian earthquake 29 04 91 are presented

uniformitarianism as a guide to rocky shore ecosystems in the geological record literature on pleistocene and neogene rocky shores is reviewed from a uniformitarian perspective to assess the fidelity of physical and biological information entrained in the geological record through present day processes coverage by latitude spans tropical to subarctic shores variations in paleotopography are illustrated by unconformities between sedimentary accumulations and rocks of igneous or non igneous origin former rocky shores occur across a range of geographic scales that include i spot localities ii embayments with continuous transition from exposed outer to protected inner shores and iii entire islands with windward and leeward shores differences in rate and mag nitude of sea level change affect rocky shore physiography terrace deposits characterize the pleistocene but ramp de posits typify older neogene shores on average species with hard parts account for about 50 of the modern rocky intertidal fauna on a regional basis regardless of latitude biodiversity is highest in mid latitudes fixed organisms with encrusting wedging or boring habits corals barnacles oysters other bivalves and vermetid gastropods show high potential for fossilization in growth position mobile organisms that cling to rocks gastropods crabs and echinoids suffer post mortem transport but may be immured within neptunian dikes or interstices among cobbles and boulders at best localized fossil deposits from the pleistocene reflect 30 of the biodiversity of skeletonized organisms tabulated from modern rocky shores on a regional basis uniformitarianism provides little insight into the diversity of soft bodied organisms excluding stromatolites that joined the ecosystem in precambrian times and the extent to which soft bodied organisms dominated shore life through later times

interpretation of ancient epikarst features in carbonate successions a note of caution abstract in shallow marine carbonate successions of the phanerozoic evidence for shorter lived subaerial exposure stages of ancient carbonate seafloors is commonly found in the presence of small scale epi karst solution pits in discontinuity surfaces under favorable conditions these solution features are accompanied by soil features including calcretes or root traces alveolar septal structures petrographic evidence such as pendant cements circumgranular cracks or pisoliths bleaching and staining of carbonate rocks or circumstantial geochemical evidence perhaps more often however ancient carbonate successions lack undisputable evidence for meteoric karsting using a well exposed case example from the aptian of oman we here document that the superficial visual field inspection of solution pits in discontinuity surfaces may lead to erroneous interpretations outcrops at jabal madar a diapiric structure allow for an in depth analysis of dissolution features in the regionally extensive top shu aiba discontinuity the solution pits discussed here were investigated for their stratigraphic position their orientation relative to bedding planes diagenetic and petrographic features and their potential relation to extensional fractures related to the updoming of jabal madar the main message brought forward is that under burial conditions spatially localized hypogenic carbonate leaching may form features that are easily mistaken for ancient meteoric epikarst these features preferentially form in interstratal positions where fractured massive carbonate rocks are capped by a major discontinuity surface overlain by non fractured argillaceous sediments thus while dissolution reprecipitation processes in the burial phreatic realm are omni directional in permeable carbonates low permeability argillaceous fines are not or to a much lesser extent prone to chemical corrosion as a consequence carbonate aggressive burial fluids leach out pits at the carbonate shale interface these appear to protrude perpendicular as bowl shaped depressions into the underlying limestones and are in the case examples documented here preferentially aligned along factures these findings have significance for the interpretation of ancient epikarst features in shallow marine carbonate successions

predominance of unilateral rupture for a global catalog of large earthquakes the manner in which an earthquake rupture propagates across a fault reflects both the initial properties of the fault and the dynamical stresses produced by the rupture we quantify the propagation of an earthquake rupture using the second moments of the earthquake space time distribution in particular the second moments provide a simple way to differentiate between approximately bilateral and predominantly unilateral ruptures we determined the second moments for a catalog of m w 7 earthquakes that have occurred since 1994 the results show that approximately 80 of large shallow ruptures are predominantly unilateral our result agrees well with strong motion inversions from previous studies on moderate and large earthquakes the predominance of unilateral propagation in large earthquakes is explained by a simple characteristic earthquake model in which large events rupture an entire structurally defined fault segment and nucleation points are uniformly distributed along the fault the predominance of unilateral rupture may also be enhanced by the dynamic stress field produced by contrasts in the elastic properties between the two sides of plate boundary faults manuscript received 16 november 2001

non linear dynamics of the lithosphere and intermediate term earthquake prediction abstract the lithosphere of the earth is structured as a hierarchical system of volumes of different sizes from about 10 tectonic plates to about 10 25 grains of rock their relative movement against the forces of friction and cohesion is realized to a large extent through earthquakes the movement is controlled by a wide variety of independent processes concentrated in the thin boundary zones between the volumes the boundary zone has a similar hierarchical structure consisting of volumes separated by boundary zones etc altogether this hierarchy of volumes and multitude of processes compose the lithosphere into a large non linear complex system upon coarse graining the integral mesoscale empirical regularities emerge indicating a wide range of similarity collective behavior and the possibility of earthquake prediction this approach led to new paradigms in the dynamics of the lithosphere and on the practical side created a capacity to predict from 70 to 90 of large earthquakes with alarms occupying 10 20 of the time space considered such predictions may be used to undertake earthquake preparedness measures which would prevent a considerable part of the damage although far from the total damage the methodology linking prediction with preparedness was developed it may help a disaster management authority to choose the preparedness measures allowing for the currently realistic accuracy of predictions a large scale experiment in advance prediction of large earthquakes worldwide has been launched to test the prediction algorithms the test is unprecedented in rigor and coverage the forecasts are communicated with due discretion to several dozen leading scientists and administrators in many countries among already predicted earthquakes are all the last eight great ones with magnitude 8 and more the major drawback is the rate of false alarms the possibility is outlined to develop a new generation of prediction methods with fivefold increase in accuracy and the transition to short term prediction the links with prediction of geotechnical and engineering disasters are established scenarios of transitions to a large earthquake happen to share some features with a broader class of catastrophes this experience now opens as yet untapped possibilities for reduction of technological disasters

thermal anomalies and magmatism due to lithospheric doubling and shifting abstract we present some thermal and magmatic consequences of the processes of lithospheric doubling and lithospheric shifting lithospheric doubling concerns the obduction of a cold continental or old oceanic lithospheric plate over a young and hot oceanic lithosphere upper mantle system including an oceanic ridge lithospheric shifting concerns the translation and rotation of a lithospheric plate relative to the upper mantle in both cases the resulting thermal state of the upper mantle below the obducting or shifting lithosphere may be perturbed relative to a normal continental or oceanic geothermal situation the perturbed geothermal state gives rise to a density inversion at depth and thus induces a vertical gravitational instability which favours magmatism we speculate about the magmatic consequences of this situation and infer that in the case of lithospheric doubling our model may account for the petrology and geochemistry of the resulting magma the original layering and composition of the overridden young oceanic lithosphere may strongly influence magmatic processes we dwell shortly on the genesis of kimberlites within the framework of our lithospheric doubling model and on magmatism in general lithospheric recycling is inherent to the mechanism of lithospheric doubling

palaeoecology and evolution of marine hard substrate communities abstract marine organisms have occupied hard substrates since the archaean shells rocks wood and sedimentary hardgrounds offer relatively stable habitats compared to unconsolidated sediments but the plants and animals which inhabit them must develop means to gain and defend this premium attachment space hard substrate communities are formed by organisms with a variety of strategies for adhering to and or excavating the substrates they inhabit while mobile grazers organically attached and even soft bodied organisms may leave evidence of their former presence in ancient hard substrate communities a superior fossil record is left by sessile encrusters with mineralised skeletons and by borers which leave trace fossils furthermore encrusters and borers are preserved in situ retaining their spatial relationships to one another and to the substrate spatial competition ecological succession oriented growth and differential utilisation of exposed vs hidden substrate surfaces can all be observed or inferred hard substrate communities are thus excellent systems with which to study community evolution over hundreds of millions of years here we review the research on modern and ancient hard substrate communities and point to some changes that have affected them over geological time scales such changes include a general increase in bioerosion of hard substrates particularly carbonate surfaces through the phanerozoic this is at least in part analogous to the infaunalisation trends seen in soft substrate communities encrusting forms show an increase in skeletalisation from the palaeozoic into the mesozoic and cenozoic which may be a response to increasing levels of predation hard substrate communities considering borers and encrusters together show a rough increase in tiering through the phanerozoic which again parallels trends seen in soft substrate communities this extensive review of the literature on living and fossil hard substrate organisms shows that many opportunities remain for large scale studies of trends through time at the community and clade levels palaeontologists will especially benefit by closer integration of their work with that of neontologists particularly in aspects of ecology such as larval recruitment competition and succession

tracing the influence of the trans european suture zone into the mantle transition zone cratons with their thick lithospheric roots can influence the thermal structure and thus the convective flow in the surrounding mantle as mantle temperatures are hard to measure directly depth variations in the mantle transition zone mtz discontinuities are often employed as a proxy here we use a large new data set of p receiver functions to map the 410 km and 660 km discontinuities beneath the western edge of the east european craton and adjacent phanerozoic europe across the most fundamental lithospheric boundary in europe the trans european suture zone tesz we observe significantly shorter travel times for conversions from both mtz discontinuities within the craton caused by the high velocities of the cratonic root by contrast the differential travel time across the mtz is normal to only slightly raised this implies that any insulating effect of the cratonic keel does not reach the mtz in contrast to earlier observations in siberia we do not find any trace of a discontinuity at 520 km depth which indicates a rather dry mtz beneath the western edge of the craton within most of covered phanerozoic europe the mtz differential travel time is remarkably uniform and in agreement with standard earth models no widespread thermal effects of the various episodes of caledonian and variscan subduction that took place during the amalgamation of the continent remain only more recent tectonic events related to alpine subduction and quarternary volcanism in the eifel area can be traced while the east european craton shows no distinct imprint into the mtz we discover the signature of the tesz in the mtz in the form of a linear region of about 350 km width with a 1 5 s increase in differential travel time which could either be caused by high water content or decreased temperature taking into account results of recent s wave tomographies raised water content in the mtz cannot be the main cause for this observation accordingly we explain the increase equivalent to a 15 km thicker mtz by a temperature decrease of about 80 k we discuss two alternative models for this temperature reduction either a remnant of subduction or an indication of downwelling due to small scale edge driven convection caused by the contrast in lithospheric thickness across the tesz any subducted lithosphere found in the mtz at this location is unlikely to be related to variscan subduction along the tesz though as eurasia has moved significantly northward since the variscan orogeny

large scale waveform inversions of surface waves for lateral heterogeneity 2 application to surface waves in europe and the mediterranean linear surface wave scattering theory is used to reconstruct the lateral heterogeneity under europe and the mediterranean using surface wave data recorded with the network of autonomously recording seismographs nars the waveform inversion of the phase and the amplitude of the direct surface wave leads to a variance reduction of approximately 40 and results in phase velocity maps in the period ranges 30 40 s 40 60 s and 60 100 s a resolution analysis is performed in order to establish the lateral resolution of these inversions using the phase velocity perturbations of the three period bands a two layer model for the s velocity under europe and the mediterranean is constructed the s velocity perturbations in the deepest layer 100 200 km are much more pronounced than in the top layer 0 100 km which confirms that the low velocity zone exhibits pronounced lateral variations in both layers the s velocity is low under the western mediterranean while the s velocity is high under the scandinavian shield in the deepest layer a high s velocity region extends from greece under the adriatic to northern italy several interesting smaller features such as the massif central are reconstructed one of the spectacular features of the reconstructed models is a sharp transition in the layer between 100 and 200 km near the tornquist tesseyre zone this would indicate that there is a sharp transition at depth between central europe and the east european platform the waveform inversion of the surface wave coda leads to good waveform fits but the reconstructed models are chaotic this is due both to a lack of sufficient data for a good imaging of the surface wave energy on the heterogeneities and to an appreciable noise component in the surface wave coda

automatic 1 d waveform inversion of marine seismic refraction data summary full waveform synthetic seismograms are now used as standard in the interpretation of marine refraction data but only with a laborious trial and error fitting procedure we show how the matching of observed waveforms with wkbj synthetic seismograms can be efficiently and automatically performed for 1 d earth models automation of the inversion is difficult because of the multi modal irregular form of the misfit of data and synthetics a sequence of three steps is required for a complete inversion location of the deepest valley of the misfit function descent to the global minimum and description of the neighbourhood of the minimum for error analysis the first step is accomplished with a monte carlo search through a very large model space defined by poor prior knowledge of velocities and gradients of the solution weak traveltime constraints are used to eliminate poorly fitting models from waveform calculations a comparison of the traveltime and waveform misfits of the monte carlo models clearly illustrates that waveforms are providing more information than traveltimes alone bayesian statistics are used to construct marginal probability distributions and the covariance matrix which give a rough preliminary error analysis in the second step damped least squares linearized inversion makes small adjustments to the best fitting monte carlo model as it descends to the global minimum finally the immediate neighbourhood of the global minimum is explored with constrained least squares inversion realistic error bounds on each parameter are defined from the resulting slices through the misfit function these bounds are much narrower than traveltime inversion provides correlations between parameters are obtained from the covariance matrix constructed from models examined during this error analysis the inversion methods are illustrated on the ff2 refraction data set of the scripps institution of oceanography the monte carlo search successfully locates the valley of the global minimum as well as a nearby secondary minimum the error analysis puts realistic error bounds on the detailed inversion of this data set by spudich orcutt

the co occurence of trypanites and glossifungites substrate controlled trace fossil assemblages in a triassic mixed siliciclastic carbonate depositional system baldonnel formation williston lake b c canada abstract detailed outcrop analysis of an upper triassic shallow marine mixed siliciclastic carbonate ramp succession in northwestern canada reveals numerous disconformities that are characterized by substrate controlled trace fossil assemblages although glossifungites assemblages and to a lesser extent trypanites assemblages are common in the upper carnian baldonnel formation in several horizons a pattern of paired trypanites glossifungites demarcated discontinuity surfaces occurs these paired surfaces occur in the same overall environmental setting and are interpreted to have the same general stratigraphic implications in each case the trypanites surfaces invariably occur lower in the section they penetrate into sandy bioclastic limestone and are infilled and overlain by a coarse grained detrital lag their development indicates early cementation in a coastal setting the trypanites surfaces form coplanar maximum regressive surfaces and transgressive surfaces of erosion and are correlatable on a regional scale the lags are overlain in turn by laminated calcareous siltstone denoting offshore deposition and bioclastic sandstone a return to shoreface depositional conditions the siltstone sandstone contacts are characterized by low diversity glossifungites assemblages which are interpreted as an amalgamated succession of storm induced wave ravinement surfaces emplaced in front of a rapidly prograding shoreface paired trypanites glossifungites surfaces in the baldonnel formation reflect fluctuations in relative sea level and sediment input in an overall low accommodation mixed siliciclastic carbonate ramp setting

lateral heterogeneity of europe s upper mantle as inferred from modelling of broad band body waves summary the upper mantle velocity structure beneath europe is investigated by body wave modelling of broad band seismograms from earthquakes in the eastern mediterranean recorded by stations in north west europe the gross features of the p and s wave velocity distribution as inferred from the data show a high velocity lid a low velocity zone and two discontinuities at depths of approximately 420 and 650 km the seismograms also present evidence for lateral heterogeneity of at least a few per cent 2 5 per cent for p 4 per cent for s to a depth of approximately 400 km many of the inferred velocity variations can be related to the tectonic setting of the region between source and receiver broad band seismograms are essential for such detailed study of upper mantle structure using body wave modelling

neutral thermospheric dynamics observed with two scanning doppler imagers 2 vertical winds 1 this article is the second in a series of three papers reporting on observations of the 630 0 nm thermospheric airglow emission by two spatially separated scanning doppler imagers sdi s in alaska in this article line of sight wind measurements from these instruments in four common volume regions lying along the great circle joining the two observatories have been used to derive estimates of the vertical wind in those common volumes these estimates are combined with the vertical winds measured directly in each of the station zeniths to resolve both the spatial and temporal variations of the vertical wind field data from four nights are presented as examples of the wave like oscillations and frequently high spatial correlations that are observed a statistical study of data from the full 19 night data set showed that the frequency of observing statistically significant correlation between vertical winds measured at separate locations decreased linearly with increasing separation a linear fit to this trend indicated that for this particular location and orientation the largest separation over which statistically significant correlation would be expected to occur is approximately 540 km

imaging coseismic rupture in far field by slip patches summary since the end of the 1970s teleseismic waves are used routinely to infer the first order characteristics of the event location depth duration focal mechanism but finding the second order kinematic parameters spatial distribution of slip rupture velocity and more basically the discrimination between the fault plane and the other nodal plane of distant events remains a difficult task classically these events are studied by two different methods either they are seen as a succession of subevents each of which is considered as a point source or like in near field as extended sources where the kinematic parameters are retrieved on a grid the first approach is not physically satisfactory and can lead to erroneous interpretations of the

source parameters and tectonic origin of the 1996 june 1 tianzhu mw 5 2 and 1995 july 21 yongden mw 5 6 earthquakes near the haiyuan fault gansu china summary the 1996 june 1 tianzhu mw 5 2 ms 4 9 and the 1995 july 21 yongden mw 5 6 ms 5 4 earthquakes are the two largest events recorded in the last 10 years between the 1990 october 20 ms 5 8 and the recent 2000 june 6 ms 5 6 earthquakes near the tianzhu seismic gap on the haiyuan fault in northeastern tibet we use frequency time analysis ftan to extract the fundamental modes of love and rayleigh waves from digital records a joint inversion of their amplitude spectra and of p wave first motion polarities is then performed to calculate the source parameters focal mechanisms depths and seismic moments of these two ms 5 earthquakes such a joint inversion is tested for the first time we use iris and geoscope network records for period ranges of 20 40 s for the former event and 35 70 s for the latter the inversion of the tianzhu earthquake yields nodal planes with strike dip and slip of 282 72 and 3 and 191 87 and 162 respectively a focal depth around 12 km and a seismic moment of 0 56 1017 n m consistent with the harvard cmt calculation and the alignment and depths of the aftershocks recorded by a local network we propose two possible tectonic interpretations for this off fault event the solution for the yongden earthquake is consistent with a thrust with strike dip and slip of 105 45 and 75 respectively a focal depth around 6 km and a seismic moment of 2 4 1017 n m also in agreement with the harvard cmt mechanism the distribution of the aftershocks recorded by a regional network and the general tectonic setting that we refine

directly estimating earthquake rupture area using second moments to reduce the uncertainty in stress drop author posting the author s 2018 this article is posted here by permission of oxford university press for personal use not for redistribution the definitive version was published in geophysical journal international 214 2018 2224 2235 doi 10 1093 gji ggy201

waveform inversion of seismic refraction data and applications to young pacific crust summary we present a method for constraining the velocity depth structure in the earth using seismic refraction waveform data we test the method with synthetic data from known models and apply it to a set of data collected in 1982 june from the east pacific rise at 13 n from the magma expedition in this iterative process wkbj seismograms are computed for a starting model the difference between these and the observed seismograms is used to update the model subject to physical constraints an important first step in the inverse scheme is the linearization of the wkbj seismogram equation allowing us to compute differential seismograms partial derivatives of the synthetic seismogram with respect to specific model parameters this linearization provides the means for estimating required model perturbations based on the misfit in the seismograms the choice of a suitable numerical strategy for computing an updated model is a crucial second step in formulating a working algorithm because the data contain noise synthetic seismograms can only fit the data to this noise level in this case infinitely many models fit the data to this tolerance and some of these estimates are non physical involving negative layer thicknesses a successful strategy must choose from among these possibilities a well defined physically reasonable new model in a commonly used approach to solving non linear problems the perturbation to the starting model is minimized while improving the fit to the data after several iterations the final model which possesses no special properties still tends to resemble the starting model when used with the magma data this technique essentially does not perturb the model at all a method we find much more satisfactory involves solving for the new model directly while applying physically important constraints as constraints we require the velocity gradient remain below a fixed value and penalize the roughness of the new model we thus solve for the smoothest model fitting the data to the specified misfit

3 dimensional structure of the indian ocean inferred from long period surface waves to improve the lateral resolution of the first global 3 dimensional models of seismic wave velocities regional studies have to be undertaken the dispersion of rayleigh waves along 86 paths across the indian ocean and surrounding regions is investigated in the period range 40 300 s the regionalization of group velocity according to the age of the sea floor shows an increase of velocity with age up to 150 s only similar to the results in the pacific ocean but here this relationship vanishes more quickly at long period therefore the correlation of the deep structure with surface tectonics seems to be shallower in the indian ocean than in the pacific ocean a tomographic method is applied to compute the geographical distributions of group velocity and azimuthal anisotropy and then the 3 d structure of s wave velocity horizontal wavelengths of 2000 km for velocity and 3000 km for azimuthal anisotropy distribution can be resolved except for the central part of the south east indian ridge which displays high velocities at all depths the inversion corroborates a good correlation between lithospheric structure down to 120 km and surface tectonics low velocities along the central and southeast indian ridges velocity increasing with the age of the sea floor high velocities under african indian and australian shields at greater depths the low velocity zones under the gulf of aden and the western part of the southeast indian ridges hold but the low velocity anomaly of the central indian ridge is offset eastward the low velocity anomalies suggest uprising material and complex plate boundary

dynamic inversion of the 2000 tottori earthquake based on elliptical subfault approximations 1 we propose a simplified nonlinear method for the kinematic and dynamic inversion of near field strong motion data at low frequencies using a few elliptical patches we reduce the number of independent parameters of the inverse problem we apply this method to the dynamic inversion of the western tottori japan earthquake mw 6 6 6 8 of 6 october 2000 using unfiltered records we relocated the hypocenter close to 14 km in depth fifteen records obtained by the kik net and k net accelerometer networks were then filtered to the 0 1 0 5 hz frequency range and integrated to displacement we compare observed and synthetic records using the 2 norm a nonlinear kinematic inversion for the elliptical subfaults is first computed using the neighborhood algorithm na inversion converges to a slip distribution modeled by just two elliptical patches we then propose a dynamic inversion method based on the same simple geometrical ideas dynamic rupture propagation is computed by finite differences on a coarse numerical grid rupture propagation is controlled by a classical slip weakening friction law inversion is implemented with the na for a barrier model in this model prestress is uniform and rupture propagation is arrested by a simple distribution of barriers inversion converges to a model with two elliptical barriers synthetics computed for the dynamic inversion fit the observed data reducing the variance by nearly 60 by making different assumptions about the rupture process we illustrate the nonuniqueness of the solution to dynamic inversion

revised global model of thermosphere winds using satellite and ground based observations thermospheric wind data obtained from the atmosphere explorer e and dynamics explorer 2 satellites have been combined with wind data for the lower and upper thermosphere from ground based incoherent scatter radar and fabry perot optical interferometers to generate a revision hwm90 of the hwm87 empirical model and extend its applicability to 100 km comparison of the various data sets with the aid of the model shows in general remarkable agreement particularly at mid and low latitudes the ground based data allow modeling of seasonal diurnal variations which are most distinct at mid latitudes while solar activity variations are now included they are found to be small and not always very clearly delineated by the current data they are most obvious at the higher latitudes the model describes the transition from predominately diurnal variations in the upper thermosphere to semidiurnal variations in the lower thermosphere and a transition from summer to winter flow above 140 km to winter to summer flow below significant altitude gradients in the wind are found to extend to 300 km at some local times and pose complications for interpretation of fabry perot observations

spatial sampling of the thermospheric vertical wind field at auroral latitudes 1 results are presented from two nights of bistatic doppler measurements of neutral thermospheric winds using fabry perot spectrometers at mawson and davis stations in antarctica a scanning doppler imager sdi at mawson and a narrow field fabry perot spectrometer fps at davis have been used to estimate the vertical wind at three locations along the great circle joining the two stations in addition to the vertical wind routinely observed above each station these data were obtained from observations of the 630 0 nm airglow line of atomic oxygen at a nominal altitude of 240 km low resolution all sky images produced by the mawson sdi have been used to relate disturbances in the measured vertical wind field to auroral activity and divergence in the horizontal wind field correlated vertical wind responses were observed on a range of horizontal scales from 150 to 480 km in general the behavior of the vertical wind was in agreement with earlier studies with strong upward winds observed poleward of the optical aurora and sustained though weak downward winds observed early in the night the relation between vertical wind and horizontal divergence was seen to follow the general trend predicted by burnside et al 1981 whereby upward vertical winds were associated with positive divergence and vice versa however a scale height approximately 3 4 times greater than that modeled by nrlmsise 00 was required to best fit the data using this relation

pedogenesis of late quaternary deposits northern kyonggi bay korea implications for relative sea level change and regional stratigraphic correlation abstract late pleistocene and early holocene paleosols are described from construction pits and boreholes in the northern kyonggi bay west coast of korea thin section petrography chemistry clay mineralogy and geotechnical properties of the paleosols were examined to infer relative sea level fluctuations during the late quaternary relict laminae and gradational contacts with underlying tidal rhythmites confirm that the late pleistocene paleosol is a pedogenically altered tidal deposit illuvial clay coatings rootlets and enrichment of kaolinite and chemically stable oxides indicate that pedogenesis occurred on a well drained stable surface during the last glacial period redoximorphic features such as drab colored root traces and sphaerosiderite however suggest that waterlogged conditions developed temporarily due to a rise of the water table at the end of the last glacial period as sea level rose an early holocene paleosol formed in freshwater bog deposits burying the late pleistocene paleosol the early holocene paleosol has abundant sphaerosiderites and organic material the presence of weakly developed illuvial clay coatings oxidized siderites and pellets however indicates oxidizing condition associated with water table fall occurred during the early holocene despite the similarity in the degree of chemical and clay mineralogical weathering the late pleistocene paleosol is distinguished from its early holocene counterpart by thicker and more abundant illuvial clay coatings more fe 2 o 3 and a greater degree of consolidation duration of pedogenesis might be a primary cause for the difference of the pedofeatures with climate playing a secondary role the widespread presence of similar late pleistocene paleosols highlights its significance as a key stratigraphic marker for regional correlations along the west coast of korea

teleseismic inversion for the second degree moments of earthquake space time distributions summary determining detailed descriptions of the space time distribution of an earthquake s rupture using only teleseismic data is often a difficult and non unique process however a description of an earthquake that goes beyond a point source is often needed for many seismotectonic problems we have developed a method that inverts measurements of the shifts in traveltime and amplitude of various seismic phases at global stations for the second degree polynomial moments of an event s space time distribution our values for the second moments of the 1995 mw 8 0 jalisco mexico thrust event correspond to a characteristic rupture length of 121t10 km along strike a characteristic rupture width of 76t11 km downdip a characteristic duration of 29t2 s and a direction of rupture propagation along the strike of the subduction zone to the nw for the 1995 mw 7 2 gulf of aqaba earthquake our estimates of the second moments correspond to a characteristic rupture length of 53t2 km a characteristic duration of 12t1 s and rupture propagation to the ne along the strike of the dead sea transform our estimates of the first and second moments agree well with values from local seismic and geodetic networks for both the jalisco and aqaba events we are able to resolve the fault plane ambiguity associated with the events moment tensors using our estimates of the second spatial moment

a new absolute arrival time data set for europe summary the main aim of this study is to create a data set of accurate absolute arrival times for stations in europe which do not report to the international seismological centre isc waveforms were obtained from data centres and temporary experiments and a semi automatic picking method was applied to determine absolute arrival times for p and s phases 85 000 arrival times were picked whose distribution of residuals shows generally low standard deviations on the order of 0 5 0 7 s furthermore mean teleseismic station residuals reflect the properties of the underlying crust and uppermost mantle comparison to isc data for matching event stationphase combinations also confirms the good quality of the new absolute arrival time picks most importantly this data set complements the isc data as it fills regional data coverage gaps in europe

paleosols in clastic sedimentary rocks their geologic applications interest in pre quaternary paleosols has increased over the past decade in large part because they have proved to be beneficial in solving diverse geological problems the majority of paleosols are described from continental deposits most commonly from alluvial strata criteria for recognizing these paleosols have been extensively described however classifying them has proved more complicated pre quaternary paleosols are generally classified according to one or more modern soil classification systems although one new classification has been proposed exclusively for paleosols to avoid problems using the modern soil classifications in addition to taxonomic classification paleosols can be categorized according to the interplay among deposition erosion and the rate of pedogenesis when they formed paleosols can be solitary if they formed during a period of landscape stability following the development of an unconformity such paleosols are commonly thick and extremely well developed more commonly paleosols are vertically stacked or multistory because they formed in sedimentary systems undergoing net aggradation if erosion was insignificant and sedimentation was rapid and unsteady compound paleosols generally formed if the rate of pedogenesis exceeded the rate of deposition composite paleosols developed thick cumulative paleosols indicate that erosion was insignificant and that sedimentation was relatively steady both autogenic and allogenic processes can influence depositional and erosion patterns and thus affect the kinds of soils that form consequently paleosols can help to interpret the history of sediment deposition and the autogenic and allogenic processes that influenced a sedimentary basin paleosols are also helpful in stratigraphic studies including sequence stratigraphic analyses they are used for stratigraphic correlations at the local and basinal scale and some workers have calculated sediment accumulation rates based on the degree of paleosol development in addition to their stratigraphic applications paleosols can be used to interpret landscapes of the past by analyzing paleosol landscape associations at different spatial scales ranging from local to basin wide in scope at the local scale lateral changes in paleosol properties are largely the result of variations in grain size and topography at the scale of the sedimentary basin paleosols in different locations differ because of basinal variations in topography grain size climate and subsidence rate paleosols are used to reconstruct ancient climates even to estimate ancient mean annual precipitation map and mean annual temperature mat ancient climatic conditions can be interpreted from modern soil analogs or by identifying particular pedogenic properties that modern studies show to have climatic significance stable carbon and oxygen isotopes are also used to interpret ancient climate and some effort has been made to estimate mat from isotopic composition on the basis of

waveform inversion of time corrected refraction data summary seismic refraction data collected in land or marine surveys are often complicated by small near random time shifts of the individual seismograms relative to one another for the case of fixed receiver geometry these shifts arise primarily from basement topography often masked by sediments beneath each source although a topographic timing correction is normally applied to the seismograms the effects of poorly known topography produce residual shifts in the seismograms the application of additional time corrections statics can bias solutions computed using iterative waveform inversion because a suitable set of statics can make a poor starting velocity model appear to match the data without any correction however seismograms computed from even the best fitting laterally homogeneous model may not agree with the data to within one half period in this paper i present a formalism for iterative waveform inversion of refraction data containing residual time shifts in this method the statics are directly modelled in the synthetic seismograms and new values estimated in the inversion together with new velocity model parameters the method is similar to studies of statics in seismic reflection data but in this case values for the statics are estimated simultaneously with the velocity model with the use of suitable norms the new velocity model is required to be smooth and the statics required to be small convergence is achieved when the velocity profile s roughness the rms size of the statics and the waveform misfit are in equilibrium because the starting synthetics need not match the data to within one half period a much larger set of velocity models used for an initial guess will converge on the family of solutions than for waveform inversions in which time shifts are not used the original arbitrary starting model loses its importance after the first iteration and solutions meeting the convergence criterion appear to be independent of the particular choice of starting model numerical tests show the method to be robust an inaccurate starting model that fits the data only through a biased set of statics is accurately corrected the method is illustrated on a set of refraction data collected in the vicinity of the east pacific rise in this application two quite different starting velocity models converge to a common family of solutions

preliminary results from higher mode surface wave measurements in western europe using the nars array abstract for the first time fundamental and higher mode rayleigh wave phase velocity data for the west european platform have been measured using teleseismic recordings from the mobile broad band nars array measurements could be obtained from 30 to 70 mhz this is an extension of 30 mhz towards higher frequencies with regard to previous measurements in the frequency range of 10 to 40 mhz for western europe including the scandinavian shield nolet 1977 inversion of the new data for isotropic shear wave velocity and density model wepl1 shows a broad low shear wave velocity layer from 120 to 260 km depth without a lehmann discontinuity at larger depths the model resembles the m7 model nolet 1977 the density model shows a steep positive gradient from 60 to 100 km depth followed by a slight decrease down to 300 km depth no pronounced low density layer as present in the m7 model could be resolved reinversion of nolet s data using the same starting model as for the wepl1 model and calculation of the difference structure yields a model for the scandinavian shield scsh1 the shield has higher shear wave velocities than the west european platform down to about 300 km depth

self consistent retrieval of source parameters using mantle waves the large number of high quality stations from global networks e g iris geoscope allows for rapid and robust recovery of source parameters of large earthquakes we present a self consistent analysis of surface waves in terms of directivity parameters the boxcar is often used to recover source parameters but is rarely a faithful representation of an event s time function we demonstrate that more reliable estimates of directivity parameters can be obtained when we take into account the source time function stf of the event a low frequency stf is obtained from first r1 and second r2 orbit rayleigh waves in the range 2 to 15 mhz with a spectral synthesis and inversion method we measure the differential amplitudes between data and 3d synthetics we use the r1 r2 ratio of differential amplitudes to invert in a single narrow frequency band for the event s apparent rupture azimuth and velocity for the mw 8 1 chile 1995 event data are consistent with unilateral southward propagation with a velocity of about 2 4 km sec for the mw 7 9 mexico 1995 earthquake the rupture propagated toward the nw at about 2 0 km sec our low frequency estimates agree with broadband studies of both events and can be retrieved rapidly on a routine basis after a large earthquake

seasonal dependence of northern high latitude upper thermospheric winds a quiet time climatological study based on ground based and space based measurements this paper investigates the large scale seasonal dependence of geomagnetically quiet time northern high latitude f region thermospheric winds by combining extensive observations from eight ground based optical remote sensing and three space based optical remote sensing and in situ instruments to provide a comprehensive picture of the wind morphology data are assimilated into a seasonal empirical vector wind model as a function of season latitude and local time in magnetic coordinates the model accurately represents the behavior of the constituent data sets there is good general agreement among the various data sets but there are some major offsets between goce and the other data sets especially on the duskside the assimilated wind patterns exhibit a strong and large duskside anticyclonic circulation cell sharp latitudinal gradients in the duskside auroral zone strong antisunward winds in the polar cap and a weaker tendency toward a dawnside cyclonic circulation cell the high latitude wind system shows a progressive intensification of wind patterns from winter to equinox to summer the latitudinal extent of the duskside circulation cell does not depend strongly on season zonal winds show a mainly diurnal variation two extrema around polar and middle latitudes and semidiurnal variation four extrema at auroral latitudes meridional winds are primarily diurnal at all high latitudes the strength of zonal winds channeling through the auroral zone on the duskside is strongest in the summer season the vorticity of the wind pattern increases from winter to summer whereas divergence is maximum in equinox in all three seasons divergence is weaker than vorticity

investigating microearthquake finite source attributes with iris community wavefield demonstration experiment in oklahoma author posting the authors 2018 this article is posted here by permission of the royal astronomical society for personal use not for redistribution the definitive version was published in geophysical journal international 215 2018 1072 1087 doi 10 1093 gji ggy203