shear wave polarization anisotropy in the mantle wedge above the subducting pacific plate abstract research of azimuthal anisotropy in the mantle wedge above subduction zones opens up a new source of information about rising magma in the region because the physical property estimated from shear wave anisotropy is related to dynamic processes inside the earth regional variation in shear wave polarization is investigated from a teleseismic event and some local deep earthquakes using a spatially dense seismic array of the nied located in the central part of japan a characteristic pattern is found on the spatial distribution of shear wave polarization data obtained from scs waves large and small values of shear wave polarization anisotropy are observed at seismic stations located to the west and east of the volcanic front respectively the anisotropic zone with maximum velocity in n s direction is localized in the wedge portion between the surface and subducting slab using the data of the local deep events the location of the anisotropic zone corresponds with a low q zone obtained from seismic tomography data we conclude that the azimuthal anisotropic zone in the mantle wedge is caused by melt filled cracks which is consistent with models obtained by petrological studies

on the equipotential surface hypothesis of lunar maria floors the equipotential surface hypothesis suggests that lunar maria floors lie on a surface parallel to the selenoid this is examined using the spherical harmonic representations of the clementine topography and lunar prospector gravity data it is demonstrated that the floors of both circular and noncircular maria significantly deviate from an equipotential surface deeper circular maria and the deeper part of the noncircular maxe tranquillitatis have been subsided under larger mass loads in the crust we calculate the mass beneath the maria to be in excess to the mass required for isostatic compensation of the topography at 60 km depth a global map of this excess mass shows that the noncircular maria are isostatically compensated unlike the circular maria the map also reveals seven new sizable mascons the three largest are associated with mendel rydberg mare humboldtianum and mare moscoviense

shear wave splitting and subcontinental mantle deformation splitting observations are interpreted in terms of the strain induced lattice preferred orientation of mantle minerals especially olivine we consider three hypotheses concerning the origin of the continental anlsotropy 1 strain associated with absolute plate motion as in the oceanic upper mantle 2 crustal stress and 3 the past and present internal deformation of the subcontinental upper mantle by tectonic episodes it is found that the last hypothesis is the most successful namely that the most recent significant episode of internal deformation appears to be the best predictor of q for stable continental regions this is interpreted as fossil anisotropy whereas for presently active regions such as alaska the anisotropy reflects present day tectonic activity in the stable portion of north america there is a good correlation between delay time and lithospheric thickness this is consistent with the anisotropy being localized in the subcontinental lithosphere and suggests that intrinsic anisotropy is approximately constant the acceptance of this hypothesis has several implications for subcontinental mantle deformation first it argues for coherent deformation of the continental lithosphere crust and mantle during orogenies this implies that the anisotropic portion of the lithosphere was present since the deformational episode and rules out the addition of undeformed material to this layer by subsequent underplating or conductive growth of the thermal boundary layer one of the most important issues in the study of orogenies is the need to reconcile the formation of thickened lithosphere with the paradoxically high mantle temperatures often associated with orogenic episodes most efforts to date have focussed on modes of deformation whereby the cold lithospheric mantle is removed by convective instability or delamination and replaced by warm asthenosphere these models however are incompatible with the evidence for preserved coherent lithospheric deformation rather the deformed mantle appears to have been heated in place we suggest that the elevated mantle temperatures may be due to the strain heating accompanying the deformation

mantle flow in regions of complex tectonics insights from indonesia 1 indonesia is arguably one of the tectonically most complex regions on earth today due to its location at the junction of several major tectonic plates and its long history of collision and accretion it is thus an ideal location to study the interaction between subducting plates and mantle convection seismic anisotropy can serve as a diagnostic tool for identifying various subsurface deformational processes such as mantle flow for example here we present novel shear wave splitting results across the indonesian region using three different shear phases local s sks and downgoing s to improve spatial resolution of anisotropic fabrics allows us to distinguish several deformational features for example the block rotation history of borneo is reflected in coast parallel fast directions which we attribute to fossil anisotropy furthermore we are able to unravel the mantle flow pattern in the sulawesi and banda region we detect toroidal flow around the celebes sea slab oblique corner flow in the banda wedge and sub slab mantle flow around the arcuate banda slab we present evidence for deep sub 520 km anisotropy at the java subduction zone in the sumatran backarc we measure trench perpendicular fast orientations which we assume to be due to mantle flow beneath the overriding eurasian plate these observations will allow to test ideas of for example slab mantle coupling in subduction regions

the influence of microstructure on seismic wave speed anisotropy in the crust computational analysis of quartz muscovite rocks summary we study the influence of microstructural variables on seismic wave speed anisotropy in crustal rocks the bulk elastic properties and corresponding wave velocities are calculated for synthetic rock samples with varying amounts of muscovite and quartz different muscovite and quartzgrainorientationsandvaryingspatialdistributionsofthemuscovitegrainstoinvestigate the sensitivity of seismic wave speed anisotropy on these characteristics the asymptotic expansionhomogenizationmethodcombinedwithfiniteelementmodellingisusedtocalculate bulk stiffness tensors for representative rock volumes and the wave velocities are obtained from these tensors using the christoffel equation the aim of this paper is to 1 demonstrate how wave speeds computed from the rigorous asymptotic expansion homogenization method compare with those generated using stiffness tensors derived from commonly applied analytic estimates and 2 explore how different microstructural variables influence seismic wave speeds our results show that the muscovite grain orientations have a significant influence on the wave speeds increasing the modal fraction and alignment of muscovite grains leads to greater seismic anisotropy of the rock the p wave speed at an incidence angle of 45 between the

major lunar crustal terranes surface expressions and crust mantle origins in light of global remotely sensed data the igneous crust of the moon can no longer be viewed as a simple globally stratified cumulus structure composed of a flotation upper crust of anorthosite underlain by progressively more mafic rocks and a residual melt kreep sandwich horizon near the base of the lower crust instead global geochemical information derived from clementine multispectral data and lunar prospector gamma ray data reveals at least three distinct provinces whose geochemistry and petrologic history make them geologically unique 1 the procellarum kreep terrane pkt 2 the feldspathic high lands terrane fht and 3 the south pole aitken terrane spat the pkt is a mafic province coincident with the largely resurfaced area in the procellarum imbrium region whose petrogenesis relates to the early differentiation of the moon here some 40 of the th in the moon s crust is concentrated into a region that constitutes only about 10 of the crustal volume this concentration of th average 5 ppm and by implication the other heat producing elements u and k led to a fundamentally different thermal and igneous evolution within this region compared to other parts of the lunar crust lower crustal materials within the pkt likely interacted with underlying mantle materials to produce hybrid magmatism leading to the magnesian suite of lunar rocks and possibly kreep basalt although rare in the apollo sample collection widespread mare volcanic rocks having substantial th enrichment are indicated by the remote data and may reflect further interaction between enriched crustal residues and mantle sources the fht is characterized by a central anorthositic region that constitutes the remnant of an anorthositic craton resulting from early lunar differentiation basin impacts into this region do not excavate significantly more mafic material suggesting a thickness of tens of kilometers of anorthositic crust the feldspathic lunar meteorites may represent samples from the anorthositic central region of the fht ejecta from deep penetrating basin impacts outside of the central anorthositic region however indicate an increasingly mafic composition with depth the spat a mafic anomaly of great magnitude may include material of the upper mantle as well as lower crust thus it is designated a separate terrane whether the spa basin impact simply uncovered lower crust such as we infer for the fht remains to be determined

morphology and micromorphology of the loess paleosol sequences in the south of the east european plain mis 1 mis 17 abstract the micro and macromorphological studies performed on the loess soil sequences in the south of the east european plain permitted to identify and describe the type of soil formation processes that took part in the development of interstadial and interglacial paleosols four paleosol complexes are distinctly identified within the limits of the studied region vorona mis 13 15 inzhavino mis 8 9 or mis 10 11 kamenka mis 6 7 or mis 8 9 mezin mis 5 besides there are the bryansk interstadial paleosol mis 3 and rzhaksa interglacial paleosol mis 17 both well identifiable in the region the results obtained are in general agreement with the earlier conclusions by velichko et al 2012 about a general reduction of heat and moisture supply and an increase in aridity from the earlier towards later stages of the pleistocene the new data revealed however a few differences from the earlier concept to mention but one example we have found that the kamenka interglacial mis 7 or mis 9 paleosols formed in environments more humid than those of the likhvin interglacial mis 9 or mis 11

experimental determination of elastic constants of oshima granite barre granite and chelmsford granite employing polyhedral specimens longitudinal and shear wave velocities were measured in various directions of propagation and polarization sound velocities showed orthorhombic elasticity in all of the rocks with the assumption of orthorhombic elasticity the nine stiffness constants of all samples were determined by the sound velocities under atmospheric pressure and kelvin christoffel s equation twenty one stiffness constants of oshima granite determined without assuming any symmetry also showed orthorhombic features directions of the symmetry axes agreed well with the orientation of the preexisting cracks akaike s information criterion showed that the orthorhombic model with nine nonzero elastic stiffnesses was better than the model having 21 nonzero elastic stiffnesses for oshima granite the polyhedrons of two granitic rocks were loaded under hydrostatic pressure all components of the stiffness constants increased with pressure under pressure of more than 120 mpa two granitic rocks were approximately isotropic the results show that oriented microcracks are mainly responsible for the orthorhombic elasticity of the granitic rocks and also indicate that dry oriented cracks can not be a cause for the anisotropic elasticity of granites at depths of more than 6 8 km

p wave anisotropic tomography of the nankai subduction zone in southwest japan 1 the active subduction of the young philippine sea phs plate and the old pacific plate has resulted in significant seismic heterogeneity and anisotropy in southwest sw japan in this work we determined a detailed 3 d p wave anisotropic tomography of the crust and upper mantle beneath sw japan using 540 000 p wave arrival times from 5 249 local earthquakes recorded by 1095 stations the phs slab is imaged clearly as a high velocity high v anomaly which exhibits considerable lateral variations significant low velocity low v anomalies are revealed above and below the phs slab the low v anomalies above the phs slab may reflect the upwelling flow in the mantle wedge and the phs slab dehydration and they form the source zone of the arc volcanoes in sw japan the low v zones under the phs slab may reflect the upwelling flow in the big mantle wedge above the pacific slab the anisotropy in the crust and upper mantle is complex in kyushu the p wave fast velocity direction fvd is generally trench normal in the mantle wedge under the back arc which is consistent with the corner flow driven by the phs slab subduction the fvd is trench parallel in the subducting phs slab under kyushu we think that the intraslab seismicity is a potential indicator to the slab anisotropy that is the phs slab with seismicity has kept its original fossil anisotropy formed at the mid ocean ridge while the aseismic phs slab has reproduced the anisotropy according to its current deformation

observation of shear wave splitting from natural events south moat of long valley caldera california june 29 to august 12 1982 three component seismograms from local earthquakes recorded by three university of wisconsin stations in the south moat of long valley caldera in 1982 have been analyzed for shear wave splitting the average polarization direction of the first arriving shear waves observed at the two stations south of the resurgent dome is nnw sse time delays between the fast and slow shear waves are proportional to hypocentral distances and the maximum velocity anisotropy inferred is 6 4 the average shear wave polarization observed at the station above the resurgent dome is north south the time delays there are not a function of hypocentral distance and the normalized time delays ms km from events at the southwest boundary of the caldera are larger than those at other azimuths indicating maximum 9 6 velocity anisotropy the east west to ene wsw variation of the tensional stress fields implied by the shear wave polarizations indicates the interaction between the inflating caldera and the sierra nevada range front faults under the generally wnw ese tension expected from the regional tectonics

geological and industrial implications of extensive dilatancy anisotropy extensive dilatancy anisotropy is the hypothesized distribution of stress aligned fluid filled microcracks pervading most rocks in the earth s crust the geometry of the cracks and the aligning stress field can be monitored by analysing the waveforms of shear waves propagating through the rockmass the ability to estimate some of the parameters of the crack and stress geometry by analysing shear wave particle displacements has widespread implications

the role of magma buoyancy on the eruption of lunar basalts it has long been recognized that mare basalts on the moon are preferentially located both on the earth facing hemisphere and within large impact basins a popular model that accounts for this observation assumes that these magmas were denser than the lunar crust that they accumulated at the crust mantle interface and that eruptions occurred only when this magma chamber became overpressurized in this paper we re evaluate this model and argue that it is not consistent with the available data nor with models of dike propagation as an alternative hypothesis we propose that magma buoyancy is the predominant factor that determines whether mare basalts erupt at the surface or form crustal intrusions instead we have computed the densities of mare basaltic magmas and find that some are in fact less dense than the moon s upper anorthositic crust based on the widely accepted view that the lunar crust becomes more mafic with depth we also show that all mare basaltic magmas should be less dense than the lower portion of the crust thus if the upper anorthositic crust was regionally removed by an impact event then any mare basaltic magma could have risen to the surface there based on buoyancy considerations alone in support of this model we note that mare basalts are indeed found wherever geophysical crustal thickness models predict the upper crust to be absent furthermore many of the basalts that erupted within the anorthositic highlands are predicted to be less dense than the underlying crust based on remote sensing data the high titanium flows within oceanus procellarum are somewhat problematical to our model in that an anorthositic crust is predicted to be present beneath them using results from recent lunar thermal models we suggest that these magmas may have overcome their negative buoyancy in the crust by possessing superliquidus temperatures if magma buoyancy does indeed control whether or not a basaltic eruption will occur then this implies that the quantity of magma produced beneath the south pole aitken basin was about 10 times less than that of the nearside fl 2001 elsevier science b v all rights reserved

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

the clementine mission to the moon scientific overview in the course of 71 days in lunar orbit from 19 february to 3 may 1994 the clementine spacecraft acquired just under two million digital images of the moon at visible and infrared wavelengths these data are enabling the global mapping of the rock types of the lunar crust and the first detailed investigation of the geology of the lunar polar regions and the lunar far side in addition laser ranging measurements provided the first view of the global topographic figure of the moon the topography of many ancient impact basins has been measured and a global map of the thickness of the lunar crust has been derived from the topography and gravity

an anomalous spatial pattern of shear wave splitting observed in ocean bottom seismic data above a subducting seamount in the nankai trough in the summer of 2000 an ocean bottom seismometer obs array was deployed along the western end of the nankai trough off cape muroto the array crosses an area where a buried subducting seamount was identified under the nankai accretionary prism sediments during a multichannel seismic mcs reflection survey in this paper we report the first results of shear wave splitting sws analysis of the three component obs data one interesting result is a peculiar anomaly in the behaviour of shear wave polarizations observed near the subducting seamount we attempt to explain the observed spatial pattern in shear wave polarizations by complex structure of stress field in accretionary prism sediments around seamount we conclude that the spatial pattern of sws consistent with expected stress perturbations around seamounts but there are several other reasons that can result in a similar type of seismic anisotropy finally we have a somewhat broader look at the spatial pattern of shear wave polarizations observed with another obs array near the active front of nankai trough

topographic compositional units on the moon and the early evolution of the lunar crust the distribution of elevations on the moon determined by clementine deviates strongly from a normal distribution suggesting that several geologic processes have influenced the topography the hypsograms for the near side and far side of the moon are distinctly different and these differences correlate with differences in composition as determined by apollo orbital geochemistry clementine global multispectral imaging and ground based spectroscopy the hypsograms and compositional data indicate the presence of at least five compositional altimetric units the lack of fill of the south pole aitken basin by mare basalts suggests poor production efficiency of mare basalt in the mantle of this area of the moon

shear wave polarizations near the north anatolian fault i evidence for anisotropy induced shear wave splitting summary the turkish dilatancy projects tdp1 in 1979 and tdp2 in 1980 recorded small earthquakes near the north anatolian fault with closely spaced networks of three component seismometers in order to investigate the possibility of diagnosing dilatancy from its effects of shear wave propagation this paper examines the polarizations of shear wavetrains recorded in the shear wave window immediately above the earthquake foci abrupt changes in the orientation and or ellipticity of the shear wave polarizations are almost always observed during the first few cycles following the initial shear wave arrival on each seismogram the horizontal projections of the polarizations of the first shear wave arrivals at any given station show nearly parallel alignments with approximately the same orientations at each of the recording sites with one exception it is difficult to explain this uniform alignment over a wide area in terms of scattering at the irregular surface topography or by earthquake focal mechanisms we demonstrate that the shear wave splitting is likely to be the result of anisotropy in the region above the earthquake foci which could produce polarizations displaying the observed alignments the temporal change of the azimuth of alignment observed at one locality between 1979 and 1980 may be due to the release of a local stress anomaly by a very near earthquake

progressively cooler drier interglacials in southern russia through the quaternary evidence from the sea of azov region loess palaeosol exposures along taganrog bay sea of azov in southern russia reveal a complex succession of quaternary palaeoenvironments over the past 0 7 million years the deposits overlie marine sediments of tiraspolian cromerian age at the key section of semibalki 1 four palaeosol complexes are identified within the series the earliest palaeosol complex in the semibalki 1 section is correlated with the late muchkap interglacial the vorona palaeosol the soil type resembled modern subtropical mediterranean region soils the later middle pleistocene palaeosols bear evidence of soil forming processes typical of various temperate zone environments with a gradual transition to increasingly cooler drier conditions soils suggesting transitional development between kastenozems and chernozems developed during the likhvin interglacial inzhavino pc pc 2 kamenka interglacial is typified by eluviated luvic chernozemic soils possibly formed under prairie parkland conditions finally the mikulino integlacial of the late pleistocene mezin pc is represented by chernozems similar to the modern holocene soils of the region but showing enhanced podzolization and fewer seasonal frost features a succession of environmental changes has been traced in the study region from semi humid subtropical environments at the end of the early pleistocene to prairie environments then to boreal mild temperate during the middle pleistocene and finally towards landscapes with typical steppe soils in the late pleistocene and holocene the sequence indicates that moisture supply and temperatures during successive interglacials shifted progressively towards increasingly cooler somewhat drier climates influencing soil formation

p wave anisotropic tomography of the crust and upper mantle under hokkaido japan abstract we determined a 3 d anisotropic velocity structure beneath hokkaido in northern japan using a large number of first p wave arrival times the travel time inversion is parameterized with an isotropic component and two anisotropic parameters for each grid node by assuming p wave azimuthal anisotropy with hexagonal symmetry axis distributed horizontally the geometries of the conrad and moho discontinuities and the upper boundary of the subducting pacific plate are taken into account in the model our results show that low velocity zones exist beneath active arc volcanoes in the crust and in the central portion of mantle wedge above the high velocity pacific slab which are similar to the previous tomographic images p wave anisotropy is revealed in the crust mantle wedge and the subducting pacific slab in the upper crust the anisotropy is possibly caused by microcracks and cracks in the lower crust the anisotropic structure is different from that in the upper crust and it may be affected considerably by the plastic flow deformation in the mantle wedge the fast velocity direction fvd is generally trench normal in most of the study area while it becomes trench parallel in the pacific coast areas close to the trench which agrees with the shear wave splitting results beneath the volcanic front the fvd is also trench parallel which may suggest the existence of complex 3 d mantle flow in the mantle wedge the fvd in the subducting pacific slab is nearly north south which likely keeps the original fossil anisotropy of the pacific plate formed at the mid ocean ridge or is affected by the olivine fabric transition from a type to b type fabric due to the changes in water content stress and temperature

seismic anisotropy and shear wave splitting in lower crustal and upper mantle rocks from the ivrea zone experimental and calculated data to quantify the relationships between anisotropy s wave splitting and tectonics we determined the seismic properties of lower crustal and upper mantle rocks outcropping in the ivrea zone northern italy we obtained p and s wave seismic velocities by laboratory direct velocity measurements and or by calculations based on the modal compositions of the rocks the lattice preferred orientations lpos and the single crystal stiffness coefficients measured p and s wave velocities 6 0 7 5 km s 1 and 3 6 4 2 km s 1 are typical of the lower crust the p wave anisotropy is in the range 0 10 shear wave birefringence is in the range 0 0 0 6 km s 1 with typical values between 0 0 and 0 2 km s 1 in many cases the birefringence is clearly related to fabric elements foliation lineation mafic rocks such as anorthosite or pyroxene bearing gabbros exhibit low p wave anisotropies 5 and low shear wave birefringences less than 0 1 km s 1 in contrast the seismic properties of felsic rocks such as biotite bearing gneisses and mafic rocks such as amphibolites display high vp anisotropy 10 and strong birefringence 0 3 km s 1 biotite and amphibole preferred orientations clearly control seismic anisotropy and particularly shear wave splitting in these rocks maximum splitting is observed in directions parallel to the foliation with the fast split shear wave polarized parallel to the foliation plane to have an overview of the seismic properties of this lower crustal section at a broader scale we calculated from our data the anisotropic seismic properties of several hypothetical samples that are perhaps more representative of the regional anisotropy than each sample individually for instance the average lower crustal sample displays an anisotropy of 5 5 for p waves and a birefringence around 0 14 km s 1 for s waves propagating parallel to the foliation we observe little splitting for waves propagating at high angle to the foliation

control of the 2009 l aquila earthquake central italy by a high velocity structure a receiver function study 1 receiver functions rfs analyzed at two permanent broadband seismic stations operating in the epicentral area of the mw 6 3 2009 l aquila earthquake central italy yield insight on crustal structure along the fault rupture the harmonic decomposition of rfs highlights a subsurface structure in which both isotropic and anisotropic features are present we model the waveforms using recently developed monte carlo methods the retrieved models display a common depth structure between 10 and 40 km depth consistent with the under thrusting of the adria lithosphere underneath the apennines belt along the fault in the uppermost crust the s wave velocity structure is laterally heterogeneous right above the hypocenter we find a 4 6 km thick very high s wave velocity body vs as high as 4 2 km s that is absent in the se portion of the fault where the earthquake propagated the high vs body is coincident with the area of fewer aftershocks and is anticorrelated with the maximum slip patches of the earthquake as modeled by differential interferometric synthetic aperture radar dinsar and strong motion data we interpret this high vs body as a high strength barrier responsible for the high peak ground motion in the near field observed in the l aquila city and surroundings and for the complexity in the rupture evolution the retrieved seismic s wave velocity of this body far exceeds common vs values in the upper crust and it is more compatible with values observed in mafic basement rocks

shear wave polarization anisotropy in the upper mantle from a deep earthquake abstract shear wave polarization anisotropy in the upper mantle is investigated at the spatially dense seismic stations of the national research institute for earth science and disaster prevention located in central japan by the use of the scs wave of a deep earthquake which occurred beneath sakhalin island on 12 may 1990 a characteristic pattern is found small and large shear wave anisotropy values are observed at seismic stations located on the east and west sides of the volcanic front respectively

azimuthal variation of pg velocity in the moldanubian czech republic observations based on a multi azimuthal common shot experiment westudytheazimuthalvelocityvariationofpg wavesinthemoldanubian whichisacrystallinesegmentwithinthebohemian massif in the czech republic we use the data from a multi azimuthal common shot experiment performed as part of the alp 2002 refraction experiment complemented by profile refraction data from the celebration 2000 experiment we analyze the traveltimesofwavesrecordedby72portableseismicstationsdeployedalongtwocircleswithradiiof35and45kmaroundashot the observed travel times display an azimuthal variation indicating anisotropy of 2 the minimum and maximum velocity values are 5 83 and 5 95 km s respectively the direction of the maximum velocity is n508e these values characterize horizontal anisotropy of the uppermost crust down to 3 km the strength and orientation of uppermost crustal anisotropy in the moldanubian is consistent with the overall upper crustal anisotropy in the entire bohemian massif the high velocity direction is roughly perpendicular to the present day maximum compressive stress in the bohemian massif and central europe and coincides with the orientation of structures formed by the main variscan tectonic events in the area this indicates that the anisotropy is caused predominantly by alignment of textural elements and minerals in the rocks which developed in early geological stages

pedosedimentary division rock magnetism and chronology of the loess palaeosol sequence at roxolany ukraine abstract the loess mantle of the viii dniestre terrace at roxolany in the black sea area of ukraine is subdivided into six units which encompass the following palaeosol taxons pedocomplexes pk with evidence for several soil forming and sedimentary episodes incipient monogenetic palaeosols and horizons of carbonate concretions these cyclical loess palaeosol units provide a depositional record from the end of the matuyama chron through the holocene the detailed pedosedimentary subdivision of loesses at roxolany is generally consistent with magnetic susceptibility depth functions and seems to reflect global climatic variations earlier chronologies guidebook of the international geological congress xxvii session 1984 are re estimated on the basis of a revised position of the matuyama brunhes boundary and by detailed rock magnetic and micromorphological studies the strongly developed chernosem of pk 4 at approximately 22 m depth showing features of rubefication and the highest magnetic susceptibility value is viewed as a good stratigraphic marker of the late cromerian and seems to represent the climatic optimum of the brunhes chron oxygen isotope stage 13 the uppermost pk 2 is represented in the lower part by a chernosem analogous to surface soils of the area and is argued to be no younger than the last interglacial oxygen isotope stage 5e the poor preservation of pk 2 seems to result from processes of soil degradation and deflation at the time of interglacial glacial transition the closely spaced palaeosols between pk 2 and pk 4 seem to relate to three independent interglacials highest resolution of the palaeoclimatic record is found at the final matuyama chron from pk 9 to pk 8 and in incipient soils that contain either humic horizons with enhanced magnetic susceptibility or only horizons of large carbonate concretions

40ar 39ar dating of the brunhes matuyama geomagnetic field reversal magnetostratigraphic studies are widely used in conjunction with the geomagnetic polarity time scale gpts to date events in the range 0 to 5 million years ago a critical tie point on the gpts is the potassium argon age of the most recent brunhes matuyama geomagnetic field reversal astronomical values for the forcing frequencies observed in the oxygen isotope record in ocean drilling project site 677 suggest that the age of this last reversal is 780 ka thousand years ago whereas the potassium argon based estimate is 730 ka results from 4039 ar incremental heating studies on a series of lavas from maui that straddle the brunhes matuyama reversal give an age of 783 11 ka in agreement with the astronomically derived value the astronomically based technique appears to be a viable tool for dating young sedimentary sequences

modeling of three component lg waves in anisotropic crustal models abstract lg wave synthetic seismograms are presented in order to analyze the influence of anisotropy in the continental crust on their three component waveforms the effect of dry and liquid filled open cracks in the upper crust and petrological anisotropy in the lower crust on waves produced by surface explosions and crustal earthquakes is examined the polarization and especially the amplitude of the transverse component proves to be very sensitive to introduction of weak anisotropy in the crust comparisons of the modeling with lg wave data produced by explosions in southern scandinavia show that a realistic crustal anisotropy can explain observations that the transverse components of these waves are as large as their vertical ones a 10 km thick surficial layer with liquid filled open cracks is our perferred model for southern scandinavia

geoid anomalies in a dynamic earth in order to obtain a dynamically consistent relationship between the geoid and the earth s response to internal buoyancy forces we have calculated potential and surface deformation love numbers for internal loading these quantities depend on the depth and harmonic degree of loading they can be integrated as green functions to obtain the dynamic response due to an arbitrary distribution of internal density contrasts spherically symmetric self gravitating flow models are constructed for a variety of radial newtonian viscosity variations and flow configurations including both whole mantle and layered convection we demonstrate that boundary deformation due to internal loading reaches its equilibrium value on the same time scale as postglacial rebound much less than the time scale for significant change in the convective flow pattern by calculating relaxation times for a series of spherically symmetric viscous earth models for uniform mantle viscosity the geoid signature due to boundary deformations is larger than that due to internal loads resulting in net negative geoid anomalies for positive density contrasts geoid anomalies from intermediate wavelength density contrasts are amplified by up to an order of magnitude geoid anomalies are primarily the result of density contrasts in the interior of convecting layers density contrasts near layer boundaries are almost completely compensated layered mantle convection results in smaller geoid anomalies than mantle wide flow for a given density contrast viscosity stratification leads to more complicated spectral signatures because of the sensitivity of the dynamic response functions to model parameters forward models for the geoid can be used to combine several sources of geophysical data e g subducted slab locations seismic velocity anomalies surface topography to constrain better the structure and viscosity of the mantle

the deep structure of lunar basins implications for basin formation and modification we present models for the structure of the crust and upper mantle beneath lunar impact basins from an inversion of gravity and topographic data from the nearside of the moon all basin models display a thinner crust and an elevated moho beneath the central basin region compared to surrounding areas a signature of the processes of basin excavation and mantle uplift during collapse of the transient cavity there is a general decrease in the magnitude of apparent uplift of mantle material with increasing basin age we attribute this relation primarily to enhanced rates of ductile flow of crustal material early in lunar history when crustal temperatures were relatively high and the effective elastic lithosphere was thin the more relaxed topographic and moho relief associated with older basins on the central nearside may in particular be at least partly a consequence of the extensive subsurface heating associated with the formation of the large procellarum basin the deep structure of the youngest basins constrains the geometry of the cavity of excavation and the amount of crustal material ejected beyond the basin rim from the volumes of the topographic basin of mare basalt fill and of uplifted mantle material the volume of crustal material ejected beyond the basin rim for an orientale sized event was of the order of 107 km 3 a near constant thickness of nonmare crustal material beneath the central regions of young basins of various diameters and preimpact crustal thicknesses suggests that the transient cavity excavated to at least the base of the crust for the largest basins significant excavation into the mantle may have been impeded by an abrupt increase in strength at the lunar moho

sarykul paleosol in southern urals sediments russia abstract sarykul paleosols in the southern urals russia with a stable position in geological sediments are considered the brunhes matuyama boundary was found in these paleosols and they were used as a source of information on the environment data were obtained during the study of the sarykul paleosols in four sections located in the mountain part of the southern urals on the miass river erosion accumulation terrace and at the eastern edge on the trans uralian peneplain saykul paleosols have a relatively thick and compact humic horizon with a tongued lower boundary the paleosols are dark grey with high toc content that is not usual for the early pleistocene paleosols the materials showed that sarykul paleosols formed on different parent rocks may have various characteristics of the mineral part texture ph magnetic susceptibility carbonate content ratio of exchangeable cations while their humic substances characteristics humic and fulvic acid ratio humic acid characteristics of elemental composition and structure are very similar climate conditions during sarykul paleosol formation changed from relatively warm and humid to less warm and more humid the study of southern urals sarykul paleosols has shown that they can serve as a reliable marker of the final early pleistocene due to their specific characteristics not analogous to the modern soils

numerical modelling of the three dimensional stress field in southwestern japan abstract it has been inferred from the focal mechanism of earthquakes and their hypocenter distribution shiono 1977 that the stress field in southwestern japan indicates complicated features a nw se compression at shallow depths along the nankai trough an e w or ese wnw compression in the inland crust an extension parallel to the leading edge of the philippine sea plate at subcrustal depths in the region from the southern chubu to northwestern shikoku and a down dip tension beneath the kyushu island in order to investigate possible sources of these complex features of the stress state a three dimensional finite element method is employed to model the configuration of the subducting philippine sea plate taking into consideration the following three possible types of forces 1 1 a negative buoyancy due to the density contrast between the subducting plate and the surrounding mantle 2 2 a northwestward compressive force generated by the movement of the philippine sea plate 3 3 a westward compressive force due to the movement of the pacific plate for various combinations of different magnitudes of these forces and of different elastic moduli the stresses at a number of selected sites are calculated and their directions are compared with those inferred from the focal mechanism and other geophysical information it is found that the observed extensional stresses parallel to the leading edge of the subducting philippine sea plate may be caused mainly by the negative buoyancy the northwestward compressive force may not play an important role in generating the complex stress field in southwestern japan the observed e w compressional stress field prevailing in the inland region appears to result mainly from the westward moving pacific plate the present results suggest that if a thin low velocity transitional layer exists just above the subducting philippine sea plate it could give appreciable effects on the mechanism of low angled thrust faulting off the kii peninsula and the shikoku island the magnitude of the shear stress in the continental crust and in the subducting plate is estimated to be of the order of several hundred bars although the calculated shear stresses are considerably affected by the configuration of the subducting plate and also by the applied forces it is interesting that the stress distribution appears to have some relations to seismicity of subcrustal earthquakes and to the rupture process of large thrust earthquakes along the plate boundary

the lunar mascons revisited the entire spectra of the surface topography and gravity field of lunar mascons are well presented by the high resolution clementine data the negative correlation between the topography and gravitational potential of the mascons suggests that they are dynamically supported both elastic support and viscous decay models are examined for the elastic support models the spectral characteristics and the lateral variations of the thickness of the elastic layer are determined on the basis of the thin spherical shell flexure formulation and using only the antivarying harmonics of the topography and potential an elastic layer thickness of about 50 km is required to support imbrium serenitatis and nectaris mascons about 35 km for crisium mascon and about 30 km for smythii and humorum mascons a layer of about 20 km thickness can support orientale mascon the strength envelopes of the upper 100 km of the moon within 4 3 gyr ago show that the elastic layer was not thick enough to support the mascons in the early history they decayed through viscous deformation of the lunar interior a lower limit of 6 1024 pa s is estimated for the lunar viscosity within 3 6 3 gyr ago we also determine the thicknesses of the crust and mare flows of the mascon basins on the basis of the assumption that the basins were isostatically compensated prior to the mascon formation the crust beneath the mascon basins is about 30 40 km except for crisium and orientale where the crust is about 20 km the mare flows of about 3 6 km are obtained for almost all of the mascon basins the topography and gravitational potential of aitken basin shows that the basin is compensated at 52 54 km depth the mantle beneath the basin has rebounded upward by about 20 30 km and is overlain by about 20 25 km of a mixture of the excavated crustal and mantle material the lack of a mascon and pervasive mare flows in the basin brings into question the current models of the mascon formation

an analysis of split shear waves observed above crustal and uppermost mantle earthquakes beneath shikoku japan implications in effective depth extent of seismic anisotropy shear wave splitting has been detected in three component seismograms from a number of small earthquakes taking place either within the upper crust or the uppermost mantle beneath the shikoku area japan the faster shear waves are polarized nearly in e w at the stations in the central part of shikoku and in nen sws at the southern stations the arrivals of slower shear waves polarized orthogonally to the faster ones are also clearly recognized in many seismograms at one of the stations the faster shear wave polarizations at the stations in the central part of shikoku and the pattern of travel time differences between split shear waves are successfully explained in terms of crustal anisotropy generated by vertical alignment of stress induced microcracks the difference in polarization directions suggests that the tectonic stress state beneath the southern shikoku region is significantly different from that beneath the central part of shikoku a quantitative analysis of travel time differences between split shear waves suggests that the presence of seismic anisotropy which causes the observed shear wave splitting is limited to the upper 10 or 15 km of the crust nevertheless the possibility that anisotropy is concentrated in a much thinner surface layer cannot be ruled out the average aspect ratio of crack might be greater than of the order of 10 2 or the cracks may not be purely vertical but have some fluctuations in the dip angle

matuyama brunhes boundary in key sections of the loess paleosol glacial formations on the east european plain abstract multidisciplinary studies of two key sections parastratotypes of the loess soil glacial formation strelitsa and sebryakovo mikhailovka sections located in the central part of the east european plain placed the matuyama brunhes reversal well below the lower pleistocene till the till attributed to the don glaciation maximum glaciation on the east european plain is separated from the m b reversal by several units as follows 1 a horizon of humified loam of still uncertain stratigraphic position 2 a loess horizon and 3 a paleosol complex rzhaksa the polarity reversal is within a transitional zone which includes the base of the lower bobrov loess and the upper portion of the underlying soil complex balashov the primary constituent of remanent magnetization has been identified using two methods demagnetization by heating and by alternating magnetic field such a technique ensures a high degree of reliability

quantitative measurements of shear wave polarizations at the anza seismic network southern california implications for shear wave splitting and earthquake prediction we analyze shear wave polarizations from local earthquakes recorded by the anza network in southern california using an automated method which provides unbiased and quantitative measurements of the polarization and the duration of linear motion following the shear wave arrival the linearity interval initial shear wave particle motions are strongly aligned at four stations a feature that is not predicted by focal mechanisms the particle motion alignment is most likely caused by shear wave splitting due to anisotropy beneath these stations a result supported by the clear shear wave splitting seen in a borehole recording near one of the anza stations these results are consistent with an earlier analysis of these data by peacock et al 1988 however our analysis does not support claims by crampin et al 1990 that shear wave splitting delay times at station knw exhibit temporal variations which can be correlated with the occurrence of the north palm springs earthquake ml 5 6 of july 8 1986 automatically determined linearity intervals scatter widely from 0 02 to 0 15 s and exhibit no clear temporal trends we find a correlation between earthquake moment and the linearity interval possibly a result of longer effective source time functions for the larger events the inability to identify a distinct slow quasi shear wave pulse for the vast majority of these events indicates that scattering strongly affects the particle motion even in the very early shear wave coda analysis of earthquake clusters with similar waveforms recorded at knw shows that seismic green functions are stable throughout the observational period and that most linearity interval variation is due to source and ray path differences between events if shear wave splitting is causing the observed delay times between horizontal components the waveform stability for events in these clusters restricts any temporal changes in shear wave splitting delay times to less than 5 10

origin of crustal anisotropy shear wave splitting studies in japan shear wave splitting manifested as leading shear wave polarization that is parallel alignment of leading shear wave particle motions from a variety of sources has been observed at a number of seismograph stations in japan detected on shear wave seismograms from crustal earthquakes over a wide range of source zones and source receiver azimuths the shear wave splitting can be attributed to crustal anisotropy this paper discusses the relation between leading shear wave polarization directions and tectonic features of japan to explain the observed shear wave splitting the author proposes that at least three phenomena should be taken into account stress induced microcracks primarily aligned in vertical or subvertical planes cracks or fractures in the vicinity of active faults having their orientation parallel to the fault planes and intrinsic rock anisotropy resulting from preferred orientation of minerals travel time differences between leading and slower split shear waves from crustal and upper mantle earthquakes analyzed for about one third of the stations suggest that the crustal anisotropy which causes the observed shear wave splitting may be limited to the upper 15 25 km this implies that the density of nonhorizontally aligned cracks or fractures below 15 25 km and into the upper mantle is muchmore smaller than that in the crust above 15 25 km less

crustal anisotropy in the bohemian massif czech republic observations based on central european lithospheric experiment based on refraction celebration 2000 1 we study the azimuthal velocity variation of pg waves in the bohemian massif using data collected during central european lithospheric experiment based on refraction celebration 2000 we analyze travel times of waves generated by 28 shots and recorded by 256 portable and 19 permanent seismic stations deployed on the territory of the czech republic and in adjacent areas we use recording offset ranging from 30 to 190 km with azimuths covering the whole interval of angles the observed travel times are inverted for parameters of a velocity model formed by an isotropic low velocity subsurface layer with a varying depth lying on a homogeneous transversely isotropic half space with a horizontal axis of symmetry the recovered velocity displays a systematic azimuthal variation indicating a regional scale intrinsic or effective anisotropy in the bohemian massif the mean minimum and maximum values of the velocity are vmean 6 03 km s vmin 5 98 km s vmax 6 10 km s respectively indicating an anisotropy of 1 5 2 5 the direction of the maximum propagation velocity is n35 e being approximately perpendicular to the present maximum compression in the earth crust in central europe the observed anisotropy cannot be induced by stress aligned cracks in the crust because the crack models predict azimuthal velocity variations completely inconsistent with the observed one therefore we suggest the crustal anisotropy to be induced by a preferred orientation of rock forming minerals and large scale intrusion fabrics developed during a tectonic evolution of the bohemian massif

percolation in the crust considering the earth s crust as a heterogeneous medium we show here that the general features of the seismic electrical and mechanical properties of the crust can be conveniently described with a unified model derived from percolation theory the basic assumption is that fracture density is a variable parameter which decreases with depth and as a result there exists a critical threshold below which fractures are only connected within finite clusters this threshold corresponds to a critical fracture density and to a critical depth fluids circulate through a connected network of fractures down to the critical depth zc below zc anisotropic fracture clusters result in seismic reflectors and high electrical conductivity earthquakes are restricted to depths shallower than zc where friction controls the mechanical resistance to fluid infiltrated pre existing fractures

a decade of shear wave splitting in the earth s crust what does it mean what use can we make of it and what should we do next it is 10 years since shear wave splitting throught to be diagnostic of some form of seismic anisotropy was first positively identified in the earth s crust from the beginning it was argued that the splitting was probably associated with the presence of stress aligned cracks inclusions in the crust and that this would provide the opportunity for monitoring the in situ geometry of cracks and stress in a variety of different circumstances and in a variety of different applications

topography of the moon from the clementine lidar range measurements from the lidar instrument carried aboard the clementine spacecraft have been used to produce an accurate global topographic model of the moon this paper discusses the function of the lidar the acquisition processing and filtering of observations to produce a global topographic model and the determination of parameters that define the fundamental shape of the moon our topographic model a 72nd degree and order spherical harmonic expansion of lunar radii is designated goddard lunar topography model 2 gltm 2 this topographic field has an absolute vertical accuracy of approximately 100 m and a spatial resolution of 2 5 the field shows that the moon can be described as a sphere with maximum positive and negative deviations of 8 km both occurring on the farside in the areas of the korolev and south pole aitken s p aitken basins the amplitude spectrum of the topography shows more power at longer wavelengths as compared to previous models owing to more complete sampling of the surface particularly the farside a comparison of elevations derived from the clementine lidar to control point elevations from the apollo laser altimeters indicates that measured relative topographic heights generally agree to within 200 m over the maria while the major axis of the lunar gravity field is aligned in the earth moon direction the major axis of topography is displaced from this line by approximately 10 to the east and intersects the farside 24 north of the equator the magnitude of impact basin topography is greater than the lunar flattening 2 km and equatorial ellipticity 800 m which imposes a significant challenge to interpreting the lunar figure the floors of mare basins are shown to lie close to an equipotential surface while the floors of unflooded large basins except for s p aitken lie above this equipotential the radii of basin floors are thus consistent with a hydrostatic mechanism for the absence of significant farside maria except for s p aitken whose depth and lack of mare require significant internal compositional and or thermal heterogeneity a macroscale surface roughness map shows that roughness at length scales of 10 1 10 2 km correlates with elevation and surface age

crustal diversity of the moon compositional analyses of galileo solid state imaging data the multispectral images of the lunar limb and farside obtained by the solid state imaging ssi system on board the galileo spacecraft provide the first new pulse of compositional data of the moon by a spacecraft in well over a decade the wavelength range covered by ssi filters 0 4 1 0 m is particularly sensitive to the composition of mare basalts the abundance of mafic ferrous minerals and the maturity of the regolith to a first order the limb and farside material is consistent with previous characterization of nearside lunar spectral types for mare and highland soils and craters most basalts are of an intermediate tio 2 composition and most of the highland crust is feldspathic with local variations in mafic content identified principally at impact craters dark manfling material on the farside can be interpreted in terms of known properties of lunar pyroclastic glass regions of cryptornate are shown to have spectral properties intermediate between those of highland and mare soils as would be expected from a mixture of the two there are several important exceptions and surprises however unlike the basalt types identified on the nearside limb and farside basalts exhibit an exceptionally weak 1 xm ferrous absorption band this may indicate a compositionally distinct lunar basalt group that for example is more mg rich than most basalts of the nearside some of the most notable compositional anomalies are associated with south pole aitken basin this large region has a much lower albedo than surrounding highlands the inner darkest portion of the basin exhibits optical properties indistinguishable low ti basalts deposits to the south exhibit unique properties with a strong and broad ferrous 1 xrn absorption most consistent with abundant olivine the unusual compositions associated with south pole aitken and their spatial e3tent suggests the impact creating this huge lunar basin excavated mafic rich lower crust or perhaps mantle material 1 intro oucri ion

evidence from shear wave splitting for the restriction of seismic anisotropy to the upper crust the existence of anistropy in the propagation speed of seismic waves through the earth s crust has been attributed to the non random alignment of microcracks in the crust1 for sparsely distributed parallel vertical cracks perturbation theory predicts the splitting of a shear wave into two orthogonally polarized waves2 4 here we present extremely clear evidence for shear wave splitting in three component seismograms from crustal and sub crustal microearthquakes recorded in the shikoku district of japan quantitative analysis of travel time differences between split shear waves leads to the conclusion that the observed anisotropy is limited to the upper crust shallower than 10 15 km this model is consistent with recent results from reflection seismology5 and implies that microcrack density or orientation changes from the upper to the lower crust

coincident seismic reflection refraction studies of the continental lithosphere a global review summary vertical incidence reflection profiling has identified several characteristic features of the continental iithosphere including a generally transparent upper crust a reflective lower crust reflections from the crust mantle boundary and a commonly transparent upper mantle the underlying physical causes of these characteristic features remain poorly understood this review summarizes additional information brought to bear on the physical properties of these characteristic crustal structures through the use of coincident wide angle refraction profiling

geology of the smythii and marginis region of the moon using integrated remotely sensed data we characterized the diverse and complex geology of the eastern limb region of the moon using a trio of remote sensing data sets clementine lunar prospector and apollo on the basis of clementine derived iron and titanium maps we classify the highlands into low iron 3 6 wt feo and high iron 6 9 wt feo units the association of the latter with basalt deposits west of smythii basin suggests that the highland chemical variation is the result of mixing between basalt and highland lithologies mare smythii and mare marginis soils are compositionally similar containing moderate iron 15 18 wt feo and titanium 2 5 3 5 wt tio2 smythii basin in addition to the basalt deposits contains an older moderate albedo plains unit our investigation reveals that the dark basin plains unit has a distinct albedo chemistry and surface texture and formed as a result of impact mixing between highland and mare lithologies in approximately equal proportions clementine iron and maturity maps show that swirls along the northern margin of mare marginis have the same iron composition as the surrounding nonswirl material and indicate that the swirl material is bright because of its low agglutinate content gravity data for the eastern limb show high positive bouguer gravity anomalies for areas of thin basalt cover e g smythii basin and complex craters joliot lomonosov and neper we deduce that the uplift of dense mantle material is the primary and mare basaltic fill the secondary source for generating the concentration of mass beneath large craters and basins

shear wave polarization anisotropy observed in a rift zone in japan abstract we have found polarization anisotropy in shear waves from small earthquakes both in the upper crust and in the uppermost mantle beneath a rift zone in central kyushu japan we have recognized two different directions in the polarization of the faster shear waves about e w directions at three stations located in the rift zone and about n s at two stations possibly located outside and close to the edge of the rift zone the former case e w is consistent with a hypothesis that shear wave splitting is caused by vertical cracks or fractures striking in the e w direction which have formed under the present tectonic stress inside a rift zone extending in the n s direction with the maximum horizontal compressive stress striking in the direction about e w and the minimum compressive stress vertical in contrast the latter case n s is inconsistent with the above hypothesis this inconsistency in the polarization direction may be due to a complicated pattern of crack distribution around the stations outside the rift zone alternatively it may result from a complicated stress regime within the crust close to the edge of the rift zone arrival time differences between the faster and slower split shear waves from the upper crustal earthquakes are less than about 0 12 s while those from the upper mantle events are less than about 0 25 s the relatively small arrival time differences from the upper mantle events with respect to their hypocentral distances could result from a small crack density in the lower crust and upper mantle compared with that in the upper crust

anisotropic structures of oceanic slab and mantle wedge in a deep low frequency tremor zone beneath the kii peninsula sw japan 1 anisotropy is an important feature of elastic wave propagation in the earth and can arise from a variety of ordered architectures such as fractures with preferential alignments or preferred crystal orientations we studied the regional variations in shear wave anisotropy around a deep low frequency earthquake lfe zone beneath the kii peninsula sw japan using waveforms of local earthquakes observed by a dense linear array along the lfe zone the fast directions of polarization are subparallel to the strike of the margin for both crustal and intraslab earthquakes the delay time of the split shear waves in intraslab earthquakes is larger than that in crustal earthquakes and shows a down dip variation across the lfe zone this indicates that anisotropy exists in the mantle wedge and in the lower crust and or oceanic slab we explain the observed delay time of 0 015 0 045 s by suggesting that the mantle wedge consists of a deformed 1 15 km thick serpentine layer if the mantle wedge is completely serpentinized in addition to high fluid pressures within the oceanic crust the sheared serpentine layer may be a key factor driving lfes in subduction zones

velocity and anisotropy structure of the crust in the dabieshan orogenic belt from wide angle seismic data abstract in order to investigate the crust and upper mantle structure of velocity and anisotropy for dabieshan orogenic belt a wide angle reflection refraction survey from anyi jiangxi province to zhuangmu anhui province pr china was undertaken in 1994 we reconstructed initial images of p and s wave velocities and two anisotropy factors with anderson s notation by using multi parameter velocity analysis technique in 2d anisotropic media and fitted the observed traveltimes for p and s reflecting waves to that calculated by forward modelling and produced the final models of p and s wave velocity and two anderson s anisotropy factors the structures of two anisotropy factors are very different from the structures of p and s wave velocities the structures of p and s wave velocities show the characteristic of layering and blocking and the structures of anderson s anisotropy factors displays the characteristics of chimney structure the thickness of the crust in the studied area varies in the 34 41 km range with a mountain root beneath the dabieshan orogenic belt the average p wave and s wave velocity in the upper middle and lower crust are 5 6 6 0 km s about 3 4 km s 6 2 6 3 km s about 3 6 km s and 6 4 6 8 km s about 4 0 km s respectively the poisson ratio varies from 0 24 to 0 29 with the polarization analysis to the phase s g we find that the fast polarization directions for the yangtze block dabie block and northern china block are about n77 e n18 w and n53 e respectively the seismic anisotropy factors are up to about 5 the zone with strong anisotropy shows the chimney structure which indicates force direction endured by materials flowed upward we inferred that the subduction of the yangtze plate and the mantle flow of materials have played important role in exhuming the ultra high pressure metamorphic rocks of the dabieshan orogenic belt

in situ stress state from walkaround vsp anisotropy in the kumano basin southeast of the kii peninsula japan to reveal the stress state within the kumano basin which overlies the nankai accretionary prism we estimated seismic anisotropy from walkaround vertical seismic profiling vsp data recorded at site c0009 during integrated ocean drilling program iodp expedition 319 we obtained the following anisotropic parameters 1 p wave velocity anisotropy derived from azimuthal normal moveout nmo velocity analysis 2 p wave amplitude variation with azimuth and 3 axes of symmetry of s wave splitting azimuthal variations of p wave velocity by ellipsoidal fitting analysis showed that p wave velocity anisotropy within sediments of the kumano basin was 5 both the directions of fast p wave velocity and strong amplitude are aligned with the convergence vector of the philippine sea plate furthermore s wave splitting analysis indicated that s wave polarization axes were parallel to and normal to the direction of plate subduction these results indicate that the maximum horizontal stress at site c0009 in the kumano basin is in the direction of plate subduction the horizontal differential stress estimated from the p wave velocity anisotropy 2 7 5 5 mpa indicates that the maximum horizontal stress is similar in magnitude to or a little higher than the vertical stress

lunar multiring basins and the cratering process abstract numerous studies of the lunar gravity field have concluded that the lunar moho is substantially uplifted beneath the young multiring basins this uplift is presumably due to the excavation of large quantities of crustal material during the cratering process and subsequent rebound of the impact basin floor using a new dual layered crustal thickness model of the moon the excavation cavities of some nearside multiring basins grimaldi and larger and younger than tranquillitatis were reconstructed by restoring the uplifted moho to its preimpact location the farside south pole aitken spa basin was also considered due to its importance in deciphering lunar evolution restoring the moho to its preimpact position beneath these basins resulted in a roughly parabolic depression from which the depth and diameter of the excavation cavity could be determined using these reconstructed excavation cavities the basin forming process was investigated excavation cavity diameters were generally found to be on the small side of most previous estimates for orientale the modeled excavation cavity lies within the inner rook ring additionally with the exception of the three largest basins serenitatis imbrium and south pole aitken the depth diameter ratios of the excavation cavities were found to be 0 115 0 005 a value consistent with theoretical and experimental results for impact craters orders of magnitude smaller in size the three largest basins however appear to have significantly shallower depths of excavation compared to this trend it is possible that this may reflect a different physical process of crater formation e g nonproportional scaling special impact conditions or postimpact modification processes the crustal thickness model also shows that each basin is surrounded by an annulus of thickened crust we interpret this thickened crust as representing thick basin ejecta deposits and we show that the radial variation in the thickness of these deposits is consistent with scaling laws obtained from small scale experimental studies if multiring basins ever possessed a terraced main crater rim this terraced zone may be presently unrecognizable at the surface due to the emplacement of ejecta deposits that exceed a few kilometers in thickness exterior to the excavation cavity rim we also show that the interiors of many basins were superisostatic before mare volcanism commenced those basins that were closest to approaching a premare isostatic state lie close to or within an anomalous geochemical province rich in heat producing elements

basalt thickness in mare humorum the crater excavation method basalt thicknesses in mare basins have been determined using assumptions about the premare topography of partly buried craters and by comparison to the orientale basin differences in those assumptions have led to a factor of 4 difference in mare thickness estimates further knowledge of thickness is restricted to areas in which buried craters are present using mixing models applied to multispectral images acquired by the clementine spacecraft we have shown that craters in the mare sometimes excavate highland material from below the mare cover using such craters and assumptions about their depth of excavation we obtain independent estimates of basalt thickness our results are in agreement with the lowest of previous thickness estimates we derive a volume of 40 000 km 3 for basalts in mare humorum considerably less than the 110 000 km 3 from previous estimates we also confirm a diameter of 425 km for thc humorum multiring basin based on the clementine gridded global topography assuming an original morphology like orientale

apollo lunar seismic experiment final summary processing and initial analysis of the entire set of apollo lunar seismic data collected continuously from 1969 through 1977 have now been completed recent results include 1 better defined deep moonquake locations which appear to be bounded rather sharply between about 800 km and 1000 km depths with concentrations near both boundaries and 2 middle mantle 500 to 1000 km depth seismic velocities of vp 8 3 0 4 km sec and vs 4 6 0 2 km sec which are significantly higher than previous estimates and represent an increase of velocities from the upper mantle as opposed to a decrease in previous estimates

crustal anisotropy in the forearc of the northern cascadia subduction zone british columbia summary this paper aims to identify sources and variations of crustal anisotropy from shear wave splitting measurements in the forearc of the northern cascadia subduction zone of southwest british columbia over 20 permanent stations and 15 temporary stations were available for shear wave splitting analysis on 4500 event station pairs for local crustal earthquakes results from 1100 useable shear wave splitting measurements show spatial variations in fast directions with margin parallel fast directions at most stations and margin perpendicular fast directions at stations in the northeast of the region crustal anisotropy is often attributed to stress and has been interpreted as the fast direction being related to the orientation of the maximum horizontal compressive stress however studies have also shown anisotropy can be complicated by crustal structure southwest british columbia is a complex region of crustal deformation and some of the stations are located near large ancient faults to use seismic anisotropy as a stress indicator requires identifying which stations are influenced by stress and which by structure we determine the source of anisotropy at each station by comparing fast directions from shear wave splitting results to the maximum horizontal compressive stress orientation determined from earthquake focal mechanism inversion most stations show agreement between the fast direction and the maximum horizontal compressive stress this suggests that anisotropy is related to stress aligned fluid filled microcracks based on extensive dilatancy anisotropy these stations are further analysed for temporal variations to lay groundwork for monitoring temporal changes in the stress over extended time periods determining the sources of variability in anisotropy can lead to a better understanding of the crustal structure and stress and in the future may be used as a monitoring and mapping tool

the great lunar hot spot and the composition and origin of the apollo mafic lkfm impact melt breccias thorium rich mafic impact melt breccias from the apollo 14 17 missions that is those breccias identified with the composition known as lkfm are regarded largely as products of basin forming impacts that penetrated the feldspathic crust and sampled underlying mafic material and magma ocean residuum carrying the compositional signature of kreep potassium rare earth elements phosphorous despite considerable compositional variation among such breccias compositions of all of them correspond to mixtures of only four components 1 a norite with composition generally similar to that of apollo 15 basalt mean abundance 58 range 30 95 2 fo 90 dunite mean 13 range 1 27 3 feldspathic upper crust mean 29 range 4 50 and feni metal 0 1 1 7 petrographic evidence has shown that much of the feldspathic component but none of the kreep component is clastic this observation and the high proportion of kreep norite component in the breccias suggest that the melt zone of the impact or impacts forming the breccias contained little feldspathic material but consisted predominantly of material with the average composition of kreep norite the dunite component probably derives ultimately from the upper mantle these conclusions support the hypothesis that the breccias were not formed in typical feldspathic crust but instead by one or more impacts into what is designated here the great lunar hot spot that is the anomalous th rich terrane in the imbrium procellarum area identified by the apollo and lunar prospector gamma ray spectrometers the lkfm composition is a special product of the great lunar hot spot and is not the average composition of the lower crust in typical feldspathic highlands similarly mg suite and alkali suite plutonic rocks of the apollo collection are likely all differentiation products of the hot spot not of plutons that might occur in typical feldspathic crust

seismic anisotropy in the eastern united states deep structure of a complex continental plate we have analyzed shear wave splitting recorded by portable and permanent broadband and long period stations located in the eastern united states teleseismic shear waves sks skks and pks were used to retrieve the splitting parameters the orientation of the fast wave polarization plane and the delay time t in total 120 seismic events were processed allowing for more than 600 splitting measurements within the appalachians stations located in the western external part are characterized by t 1s and trending n50 70 e in the south and central regions and n30 40 e in the north closely following the trend of the orogenic belt in these areas the transition region between north and central is characterized by t 1 1 3 s and by e w trending that are at a high angle to the regional geologic trend measurements at two stations located in the eastern internal part of the belt indicate very weak anisotropy the large scale pattern of anisotropy is not consistent with that predicted for simple asthenospheric flow beneath the plate splitting along the southern and eastern margins of the continent is consistent with that expected for grenvillian deformation an alternative model of asthenospheric flow around the cratonic keel cannot be ruled out within the cratonic core the correlation between t and lithospheric thickness suggests a lithospheric anisotropy smaller length scale variations also argue for a significant contribution of lithospheric structures the fabric responsible for shear wave splitting may have formed during tectonic episodes that affected the eastern united states i e the grenville and appalachian orogenies and the subsequent rifting of the north atlantic ocean our observations in the western appalachians suggest that the anisotropy may be preserved since the grenvillian orogeny the absence of detectable splitting in the two stations in the eastern appalachians is attributed to the igneous intrusions related to the atlantic rifting the measurements in the transition between the northern and central southern appalachians constitute an intriguing anomaly whose e w have little obvious relation to the regional surface geology we suggest two possible causes 1 the local dominance of asthenospheric flow motivated by the proximity of a pervasive low velocity anomaly and 2 lithospheric deformation in a transcontinental strike slip fault zone active during the appalachian collision

deformation and mantle flow beneath the sangihe subduction zone from seismic anisotropy abstract subduction of oceanic lithosphere is the most direct feedback between the earth s surface and deep interior however the detail of its interaction with the broader convecting mantle is still unclear mantle flow around subduction zones can be constrained using seismic anisotropy but despite many such studies a simple global picture is lacking the sangihe subduction zone where the molucca sea microplate is subducting westward beneath the eurasian plate is part of the tectonically complex sulawesi philippine region and an ideal natural laboratory to study complex subduction processes we investigate the anisotropic structure of the sangihe subduction zone with shear wave splitting measurements of local s and sks phases at two stations mni in sulawesi dav in the philippines as well as downgoing s phases at five stations at teleseismic distances combining different phases allows a better vertical resolution of anisotropic fabrics than is possible with a single phase the broad depth distribution of local events 60 630 km allows us to observe a change in splitting behaviour at 380 km depth above fast directions are trench parallel and delay times t are 0 34 0 53 s with no increase with depth we suggest this anisotropy is caused by aligned cracks possibly melt filled beneath the volcanic arc and fossil anisotropy in the overriding plate below 380 km is predominantly trench normal and t are slightly higher 0 53 0 65 s as no correlation is observed with inferred distance travelled inside the slab we attribute this anisotropy to shear layers atop the slab which are coherent from 200 to 400 km depth and perhaps extend into the transition zone sks and source side measurements show larger t 1 53 and 1 33 s respectively and trench parallel since these phases predominantly sample sub slab mantle we consider along strike lateral flow associated with the double sided subduction of the molucca sea microplate to be the most likely explanation we thus infer three dominant regions of anisotropy at the sangihe subduction zone one within the overriding lithosphere one along the slab wedge interface and one below the subducting molucca sea slab the mantle wedge above 200 km depth and the slab itself do not seem to contribute notably to the measured anisotropy this study demonstrates the insight seismic anisotropy can provide into mantle dynamics even in tectonically complex subduction systems

focal mechanisms in anisotropic media summary focal mechanisms of seismic sources in anisotropic media are more complicated than in isotropic media planar shear faulting produces pure double couple dc mechanism in isotropy but generally non double couple non dc mechanism in anisotropy the non dc mechanism can comprise both the isotropic iso and compensated linear vector dipole clvd components the amount of the iso and clvd components depends on strength and symmetry of anisotropy and on the orientation of faulting shear faulting in anisotropy generates a pure dc mechanism provided that faulting is situated in symmetry planes of orthorhombic or of higher anisotropy symmetries the fault plane solution i e the orientation of the fault normal and the slip direction can be retrieved from the seismic moment tensor and from elastic parameters describing anisotropy at the source numerical modelling shows that shear faulting in anisotropic rocks present in the earth crust the earth mantle or in the subduction zones can produce mostly mechanisms with the clvd up to 30 per cent and with the iso up to 15 per cent the fault plane solutions calculated under the assumption of isotropy typically deviate from the true solutions by an angle of 5 to 10

the lunar crust global structure and signature of major basins new lunar gravity and topography data from the clementine mission provide a global bouguer anomaly map corrected for the gravitational attraction of mare fill in mascon basins most of the gravity signal remaining after corrections for the attraction of topography and mare fill can be attributed to variations in depth to the lunar moho and therefore crustal thickness the large range of global crustal thickness 20 120 km is indicative of major spatial variations in melting of the lunar exterior and or significant impact related redistribution the 61 km average crustal thickness constrained by a depth to moho measured during the apollo 12 and 14 missions is preferentially distributed toward the farside accounting for much of the offset in center of figure from the center of mass while the average farside thickness is 12 km greater than the nearside the distribution is nonuniform with dramatic thinning beneath the farside south pole aitken basin with the global crustal thickness map as a constraint regional inversions of gravity and topography resolve the crustal structure of major mascon basins to half wavelengths of 150 km in order to yield crustal thickness maps with the maximum horizontal resolution permitted by the data the downward continuation of the bouguer gravity is stabilized by a three dimensional minimum slope and curvature algorithm both mare and non mare basins are characterized by a central upwarped moho that is surrounded by rings of thickened crust lying mainly within the basin rims the inferred relief at this density interface suggests a deep structural component to the surficial features of multiring lunar impact basins for large 300 km diameter basins moho relief appears uncorrelated with diameter but is negatively correlated with basin age in several cases it appears that the multiring structures were out of isostatic equilibrium prior to mare emplacement suggesting that the lithosphere was strong enough to maintain their state of stress to the present

calibration of shear wave splitting in the subcontinental upper mantle beneath active orogenic belts using ultramafic xenoliths from the canadian cordillera and alaska abstract despite the abundance of measurements of shear wave splitting around the world some fundamental questions about its geological interpretation have not yet been answered in order to constrain 1 i the orientation and magnitude of s wave anisotropy 2 ii the thickness of the anisotropic layer and 3 iii the possible variation of the anisotropy with depth in the subcontinental upper mantle beneath active orogenic belts we have carried out a systematic investigation on shear wave properties of mantle xenoliths from recent alkaline basalts of the canadian cordillera and alaska it is found that the polarization direction of the fast s wave as well as the time delay t between the two arrivals are strongly dependent on the propagation direction with respect to the structural frame at a single station the variations of measured and t values for sks phases from different events can result from this dependence because the average grain size of olivine in upper mantle samples is commonly larger than 0 5 mm dislocation creep prevails over a thickness of at least 250 km and results in olivine lpo and hence anisotropy and shear wave splitting a single thick anisotropic layer in mountain parallel subvertical shear zones may cause high values of tgd while multiple subhorizontal layers will produce multiple splitting making the measurement and interpretation of s wave splitting difficult our results also suggest that the s wave splitting observed in cold old stable cratons such as the canadian shield is likely dominated by fossil anisotropy whereas that observed in hot active orogenic regions such as the northwest american cordillera and the tibetan plateau may be dominated by modern tectonic deformation in the lithosphere and flow in the asthenosphere

impact induced mass flow effects on lunar shape and the elevation dependence of nearside maria with longitude abstract lunar mass flow patterns due to bolide impacts were inferred from a spectral correlation analysis of the lp75g gravity and gltm 2 topographic models for insight on the development of the moon s shape and elevation dependence of nearside circular maria with longitude the results suggest that in compensating for massive crustal unloading by bolide impacts subsurface mass flows were constrained by the dichotomized thickness and mechanical attributes of the lunar near and far sides on the nearside a regionally positive selenoid reflects positive mass anomalies at the moho as well as the lithosphere asthenosphere and core mantle boundaries beneath the giant ancient pre nectarian procellarum basin and the superposed imbrium basin the elevations of nearside circular maria for the lunar multi ring basins exhibit a first order decrease of roughly 2 km from 270 e to 90 e and a possible second order effect that is highly correlated with the lunar selenoid the linear trend in the surface elevations of the maria reflects the greater excavation depths of the younger basins while the second order effect suggests that the selenoid may have constrained the mare flooding of the multi ring basins

clay illuviation in red mediterranean soils abstract theories regarding pedogenesis in red mediterranean soils have undergone several stages of development the concept of clay illuviation in these soils was not a part of early theories and it is not yet unanimously accepted as a leading soil forming process a methodology is presented for studying the illuviation of clay in these soils emphasizing typology of textural features and fabrics the problem of age determination is also addressed through the use of radiometric dates and correlation with archaeological artifacts clay illuviation in red mediterranean soils under present day environmental conditions suggests that it occurs presently only on humid and sub humid margins of the mediterranean basin elsewhere illuvila clay accumulations are inherited from interglacial periods red mediterranean soils during glacial periods were eroded coluviated aggraded with aeolian dust calcitic fraction of which was redistributed in form of calcitic features and eventually were affected by water logging an example of water logging of red mediterranean soils mamora morocco which took place during the last glacial cycle consists of yellow illuvial clays accompanied by a yellowing of the ground mass during earlier cycles water logging resulted in whitish grey stains in which hydromorphic textural features were deposited

evidence for shallow and pervasive seismic anisotropy in the wellington region new zealand the shear waves of local earthquakes were recorded during a 5 month deployment of seven three component digital seismographs on the wellington peninsula new zealand the seismographs were spaced an average of less than 5 km apart and over 300 local earthquakes were recorded with phase arrivals within the shear wave window a significant number 37 of the earthquakes recorded showed clear evidence of shear wave splitting identifiable fast and slow shear wave arrivals with similar pulse shapes consistent polarization directions at particular stations were also observed even when poor signal to noise ratio or scattering meant that no slow shear wave arrival could be identified however there were large station to station differences in the polarization directions correcting for the observed shear wave splitting improved the fit between the measured shear wave polarizations and those calculated assuming a double couple focal mechanism the cause of the observed shear wave splitting is therefore most likely to be seismic anisotropy large station to station differences in the polarization alignments ranging from 61 24 to 137 18 suggest that most anisotropy is confined to the top 2 3 km of the crust however there is evidence from one station for a small amount of pervasive anisotropy if such a trend existed on the other stations it could not be identified because of the large scatter in the data points the measured delay times between split shear waves vary from 0 02 to 0 22 s with a mean value of 0 1 0 06 s this translates to a near surface shear wave velocity anisotropy of about 10 with up to 2 pervasive anisotropy possible throughout the crust this data set indicates that extensive dilatancy anisotropy cannot be the sole cause of crustal seismic anisotropy and that foliations in the rock fabric and the fracture zones of active faults may also be important there is no evidence for temporal change in the shear wave splitting parameters during the period of the experiment

azimuthal seismic anisotropy in the upper crust of the japanese islands induced by the 2011 tohoku oki megathrust earthquake

seismic anisotropy estimated from p wave arrival times in crosshole measurements summary seismic anisotropy is evidenced in the inner core upper mantle and the lower crust in large scale and the evidence is generally provided by shear wave splitting analysis here this paper searches for the evidence of anisotropy in the uppermost crust by using p wave arrival times from crosshole seismic measurement to directly estimate velocity anisotropy associated with the fine layering effect of multiple sedimentary beds conceptually fine layering causes the so called vti vertical transverse isotropy anisotropy with a vertical symmetry and the effect is parametrized by the horizontal and vertical velocity ratio it is found however that the vti anisotropic parameter does not have a simple vertical symmetry but is also azimuth dependent this azimuthal anisotropy may reflect the fracture orientation due to large scale tectonic movements and is very important in the production of oil reservoirs as the seismically fast directions can indicate preferred directions of fluid flow this paper presents innovative methods for anisotropy analysis in both vertical and horizontal plane integrated seismic anisotropy interpretation clearly indicates distinguished strain orientations forming fractures in oligocenic miocenic and pliocenic sediment in the edge of the extensional basin immediately next to tan lu fault an active continental strike slip fault zone

significant seismic anisotropy beneath the southern lhasa terrane tibetan plateau 1 shear wave splitting measurements using teleseismic pks skks and sks phases recorded by station lsa on the southern part of the lhasa terrane of the tibetan plateau reveal significant azimuthal anisotropy with a splitting time of up to 1 5 s a conclusion that is contradictory to previous studies which suggested isotropy or weak anisotropy in addition systematic variations of the splitting parameters fast polarization direction and splitting time with the arriving azimuth of the seismic ray path are observed suggesting a model of anisotropy that is more complicated than a single layer with horizontal axis of symmetry the measurements are consistent with a model with two layers of anisotropy the top layer has a ne sw fast direction which is consistent with gps revealed direction of surface movement and can be associated with lattice preferred orientation of middle lower crustal minerals such as amphibole the lower layer has a nearly e w fast direction and can be the consequence of either the n s directed compressional stress originated from the india eurasia collision or flow in the asthenosphere related to the absolute motion of eurasia this study underlines the importance of a long duration of deployment of seismic stations in resolving complex anisotropy

seismic anisotropy of the pacific slab and mantle wedge beneath the japanese islands 1 the mantle beneath the japanese islands is complex because of subduction of the pacific and philippine sea plates and the deformation associated with it detection of seismic anisotropy should be useful for understanding the processes occurring in such mantle here we resolve seismic anisotropy of the mantle wedge from that of the underlying subducted pacific slab using a large number of measurements of shear wave splitting for a family of core reflected shear phases scs sscs scs2 and sscs2 the anisotropy of the mantle wedge changes sharply across the volcanic front on the pacific side of the volcanic front a vertically propagating shear wave is polarized with the fast direction approximately parallel to the trench whereas on the back arc side it is polarized with the fast direction approximately parallel to the plate convergence direction the pacific slab is uniformly anisotropic with the nnw fast direction consistent with the paleospreading direction of the northwestern pacific seafloor the preferential alignment of anisotropic crystals frozen in the plate at the time of its formation appears to be preserved down to depths beyond 400 km within the slab

p wave anisotropic tomography beneath northeast japan we determined a 3 d p wave anisotropic tomography beneath northeast japan by using first p arrival times the travel time inversion is parameterized with an isotropic component and two anisotropic parameters for each grid node by assuming p wave azimuthal anisotropy with hexagonal symmetry axis distributed horizontally the geometries of the conrad and moho discontinuities and the upper boundary of the subducting pacific plate are taken into account in the model our extensive synthetic tests show that the anisotropic velocity inversion method is reliable our results show that low velocity zones exist below active volcanoes in the crust in the fore arc mantle wedge and in the central portion of the mantle wedge above the high velocity pacific slab which are similar to the previous tomographic images anisotropic velocity variations are revealed in the crust mantle wedge and the subducting pacific slab the anisotropic patterns are complex and different in the upper and lower crust in the mantle wedge the fast direction of p velocity is generally trench parallel in the fore arc area while it becomes trench normal in the back arc area which agree well with the shear wave splitting results the trench parallel fast direction is revealed beneath the volcanic front which may suggest the existence of complex 3 d mantle flows in the mantle wedge the fast velocity direction in the subducting pacific slab is mostly n s which is likely due to the original fossil anisotropy of the pacific plate formed at the mid ocean ridge our result also suggests that the anisotropy is weak in the upper crust and the average amplitude of the velocity anisotropy in the mantle is no larger than 4

lunar impact basins new data for the western limb and far side orientale and south pole aitken basins from the first galileo flyby compositional aspects of impact basin materials can be analyzed using multispectral image data acquired by the galileo solid state imaging ssi experiment during the december 1990 lunar encounter these data provide important information on the spectral properties of the western lunar limb and parts of the far side the ssi images cover the wavelength range 0 4 1 0 m allowing measurement of spectral slope and estimation of the strength of the 1 m absorption due to iron in the mafic minerals olivine and pyroxene among deposits of the 930 km diameter orientale basin exterior ejecta comprising the hevelius formation is relatively homogeneous and spectrally similar to mature apollo 16 soils suggesting an upper crustal source the centrally located maunder formation is distinct from the younger mare basalts but comparable to the hevelius formation in its spectral reflectance properties supporting an interpretation as basin impact melt the montes rook formation located in an annulus between the maunder and the hevelius shows a slightly stronger mafic absorption and may be the deepest crustal material excavated the distal orientale deposits show local mafic enhancements in the schiller schickard and mendel rydberg regions interpreted to represent pre orientale mare deposits or cryptomaria intermixed with overlying basin ejecta in this case maria of sizes comparable to those presently observed were widespread in this region before the orientale impact mixing model analyses are consistent with the ballistic erosion and sedimentation model for ejecta emplacement in the distal regions beyond the continuous ejecta deposit on the southern lunar farside a huge area with an enhanced mafic absorption corresponds to the interior and rim of the pre nectarian south pole aitken impact basin 2000 2500 km in diameter the anomaly is interpreted to be due to several factors including excavation into the more mafic lower crust and the presence of extensive early volcanic fill cryptomare similar to that seen in ancient basins such as smythii and australe these results show that although basin forming events are an important factor in producing lateral heterogeneities in crustal composition and in modifying preexisting deposits such as cryptomaria the majority of material in even the largest basins was excavated from crustal levels our results suggest a gradational vertical crustal stratigraphy consisting of an uppermost mixed crustal layer of anorthosite basin ejecta and cryptomaria deposits generally corresponding to the megaregolith an upper crustal layer of anorthosite and a lower more noritic layer many of the basic questions remaining from this study could be addressed by global high resolution geochemical and mineralogical data obtained by polar orbiting spacecraft

numerical modeling of mantle flow beneath madagascar to constrain upper mantle rheology beneath continental regions over the past few decades azimuthal seismic anisotropy measurements have been widely used proxy to study past and present day deformation of the lithosphere and to characterize convection in the mantle beneath continental regions distinguishing between shallow and deep sources of anisotropy remains difficult due to poor depth constraints of measurements and a lack of regional scale geodynamic modeling here we constrain the sources of seismic anisotropy beneath madagascar where a complex pattern cannot be explained by a single process such as absolute plate motion global mantle flow or geology we test the hypotheses that either edge driven convection edc or mantle flow derived from mantle wind interactions with lithospheric topography is the dominant source of anisotropy beneath madagascar we therefore simulate two sets of mantle convection models using regional scale 3 d computational modeling we then calculate lattice preferred orientation that develops along pathlines of the mantle flow models and use them to calculate synthetic splitting parameters comparison of predicted with observed seismic anisotropy shows a good fit in northern and southern madagascar for the edc model but the mantle wind case only fits well in northern madagascar this result suggests the dominant control of the measured anisotropy may be from edc but the role of localized fossil anisotropy in narrow shear zones cannot be ruled out in southern madagascar our results suggest that the asthenosphere beneath northern and southern madagascar is dominated by dislocation creep dislocation creep rheology may be dominant in the upper asthenosphere beneath other regions of continental lithosphere

seismic anisotropy beneath the continents probing the depths of geology seismic anisotropy beneath continents is analyzed from shear wave splitting recorded at more than 300 continental seismic stations anisotropy is found to be a ubiquitous property that is due to mantle deformation from past and present orogenic activity the observed coherence with crustal deformation implies that the mantle plays a major if not dominant role in orogenies no evidence is found for a continental asthenospheric decoupling zone suggesting that continents are coupled to general mantle circulation

shear wave splitting above small earthquakes in the kinki district of japan abstract we have identified shear wave splitting diagnostic of the effective anisotropy induced by aligned microcracks in the wavetrains of micro earthquakes at four stations of the abuyama network in the kinki district of japan we find that the directions of polarization of the faster split shear waves are nearly parallel for all azimuths of arrival and for all angles of incidence less than the critical angle at three of the four stations these directions of polarization are consistent with the axis of maximum compression obtained from earthquake fault plane mechanisms and also agree with the directions of the general trends of geological structures which represent the orientations of the cleavage or lamination these results suggest that crack induced anisotropy is present in the brittle upper crust beneath japan as has been found elsewhere but we could not distinguish whether this reflects the distributions of cracks induced by the present stress field or results from the general trends of surface geology although the delay times between faster and slower shear waves are difficult to estimate reliably because of their high sensitivity to internal interfaces the delay times can be interpreted as the result of a distribution of parallel vertical cracks with a crack density of about 0 04 the consistency or lack of consistency of the directions of the shear wave polarizations at the four stations demonstrates the effects of surface topography and near surface layering on the shear wave polarizations

vp vs ratio and shear wave splitting in the nankai trough seismogenic zone insights into effective stress pore pressure and sediment consolidation to estimate variation of stress state and sediment consolidation in the nankai plate subduction zone off southwest japan we measured the p wave to s wave velocity ratio vp vs and s wave splitting along the seismic line extending from the trench to the seismogenic zone for this purpose we used active source seismic data recorded by multicomponent ocean bottom seismometers obs because it is difficult to identify the ps converted reflection waveforms for each of the geological boundaries in this deep offshore region we focused on the more easily identified pps refracted waveforms that register the conversion of the up going p waves to s waves at the igneous crust surface we estimated the average vp vs ratio within the sedimentary section by using the time lag between the p refracted waves and pps converted waves this vp vs ratio changes abruptly at the trough axis i e the deformation front of the accretionary prism arguably because of compaction associated with the accretion process we observ

geophysical constraints on lunar bulk composition and structure a reassessment theoretical lunar mantle seismic velocity and density profiles are calculated for a series of proposed bulk compositions present day selenotherms and models for early differentiation and evolution the seismic velocity profiles are compared to the most recent observational model derived from the complete apollo data set to evaluate compositional implications the mantle density profiles are compared to mean density moment of inertia and crustal density thickness constraints to evaluate the need for a metallic core the calculated seismic velocity profiles are in qualitative agreement with the observational model in two general respects 1 a quasicontinuous velocity decrease occurs in the upper mantle due to the large thermal gradients that characterize all three of the considered thermal models 2 a discontinuous velocity increase occurs at the spinel to garnet transition approximately 500 km depth due mainly to the higher garnet velocities as compared to olivine and orthopyroxene in the upper mantle all four of the considered bulk compositions spanning a range of plausible feo and al2o3 contents are allowed when uncertainties in the temperature profile and depth of differentiation are taken into account however in the middle mantle depths 500 km the most aluminous models those with larger garnet abundances consistently produce larger velocity increases that are most nearly in accord with the observational model in general models that assume differentiation of the upper mantle only that are more aluminous in bulk composition and that have strong thermal gradients in the upper mantle but smaller gradients in the middle mantle result in calculated velocity profiles that most nearly agree with the observational velocity model an alternate differentiation model in which the middle mantle is dominated by mgo rich mafic silicates is also in accord with the observational seismic velocity model but results in density decreases that appear to violate stability arguments in every case calculated mantle density increases are insufficient to match the one standard deviation upper limit on the moment of inertia even when the most favorable combinations of allowed crustal thickness and density are assumed agreement with the moment of inertia upper limit is obtained if metallic cores representing 1 4 of the lunar mass are added to the bulk composition such cores are larger than needed to explain the observed depletions of lunar siderophile elements if the moon formed entirely from terrestrial mantle material

galileo imaging observations of lunar maria and related deposits the galileo spacecraft imaged parts of the western limb and far side of the moon in december 1990 ratios of 0 41 0 56 gin filter images from the solid state hnaging ssi experiment provided information on the titanium content of mare deposits ratios of the 0 76 0 99 gm images indicated 1 gin absorptions associated with fe 2 in mafic minerals mare ages were derived froin crater statistics obtained from lunar orbiter images results on mare coinpositions in western oceanus procellarum and the humorurn basin are consistent with previous earth based observations thus providing confidence in the use of galileo data to extract compositional information mare units in the grimaldi and riccioli basins range in age froin 3 25 to 3 48 ga and consist of medium to medium high titanium 4 to 7 tio2 content lavas the schiller zucchius basin shows a higher 0 76 0 99 gm ratio than the surrounding highlands indicating a potentially higher mafic mineral content consistent with previous interpretations that the area includes mare deposits blanketed by highland ejecta and light plains materials the oldest mare materials in the orientale basin occur in south central mare orientale and are 3 7 ga old youngest mare materials are in lacus autumni and are 2 85 ga old these units are medium to medium high titanium 4 to 7 tio2 basalts thus volcanism was active in orientale for 0 85 ca but lavas were relatively constant in composition galileo data suggest that mendel rydberg mare is similar to mare orientale cryptomare are present as well thus the mare lavas on the western limb and far side to 178oe are remarkably uniform in coinposition being generally of medium to medium high titanium content and having relatively low 0 76 0 99 gin ratios this region of the moon is between two postulated large impact structures the procellarum and the south pole aitken basins and may have a relatively thick crust in areas underlain by an inferred thinner crust i e zones within large basins as at apollo titanium content is often higher however no mare deposits with titanium abundances approaching those of the high titanium 9 to 14 tio2 apollo 11 and 17 basalts nor of the high titanium regions of central oceanus procellarum are seen on the western limb or eastern far side light plains deposits are generally indistinct froin the surrounding highlands in the ssi data and are inferred to be derived primarily from the same material that forins the highlands some of the light plains are too young to be related to basin forming impacts suggesting possible volcanic origin dark mantle deposit compositions derived from ssi data are consistent with earth based observations of similar near side deposits and are interpreted to be pyroclastic materials however the modernitc albedo and 1 gin absorption of the dark mantle deposit on the southwest margin of the orientale basin suggest it is a local pyroclastic deposit contaminated with underlying highland materials from the orientale impact

seismic velocity structure of the lunar mantle i have inverted the recently completed set of seismic arrival times from the apollo lunar seismic network to estimate the average seismic velocities in three sections of the lunar mantle two for the upper mantle and one for the middle mantle the method used is a variation of the linearized least squares inversion where the inversion is accomplished in steps the estimated average velocities in the upper mantle decrease from vp 7 74 km s and vs 4 49 km s in the section above 270 km depth to vp 7 46 km s and vs 4 25 km s in the section between 270 and 500 km depth confirming the earlier finding of negative gradients based on seismic amplitude variations the average velocities in the middle mantle between the depths of 500 km and 1000 km of vp 8 26 km s and vs 4 65 km s are significantly higher than those in the upper mantle contradicting earlier estimates based on more limited data the higher velocities may suggest initial melting of the moon down to at least 1000 km depth

crustal anisotropy beneath hudson bay from ambient noise tomography evidence for post orogenic lower crustal flow the crust underlying hudson bay canada records a long and complex tectonic history in this study we investigate this region using tomographic inversion based on continuous ambient noise recordings from 37 broadband seismograph stations that encircle hudson bay the ambient noise data were processed to obtain group velocity dispersion measurements from 10 35 s period which were inverted using an algorithm that incorporates the effects of anisotropy this work is among the first in which ambient noise data have been used to investigate azimuthal anisotropy the inversion method uses smoothing and damping to regularize the solution due to the significantly increased number of model parameters relative to the isotropic case we performed a careful analysis for parameter selection to determine whether leakage occurs between isotropic and anisotropic model parameters we observe a robust pattern of anisotropic fast directions in the mid crust that are consistent with large scale tectonic trends based on magnetic anomaly patterns in particular a distinctive double indentor shape for the superior craton is clearly expressed in both data sets this pattern breaks down deeper in the crust suggesting that some degree of lithospheric decoupling in the lower crust such as channel flow occurred during orogenesis given regional evidence for vertically coherent deformation in the crust and underlying mantle we interpret this pattern in the lower crust as a tectonic overprint that post dates the main phase of trans hudson deformation at most levels in the crust we observe a profound change in direction of anisotropic fast direction across an inferred suture beneath hudson bay