common conversion point stacking of receiver functions for estimating the geometry of dipping interfaces summary we develop a new method to estimate geometries of dipping seismic velocity discontinuities from common conversion point stacking of receiver functions the multistage fast marching method is applied to the ray tracing with refraction at dipping interfaces although geometry of interfaces dipping at 30 70 cannot be correctly estimated with a 1 d velocity model it can be correctly estimated when refraction at dipping interfaces is taken into account we apply this method to synthetic and observed data and confirm that geometries of dipping interfaces are successfully estimated this method will contribute to revealing the structures beneath subduction zones where dipping interfaces exist

seismic imaging of arc magma and fluids under the central part of northeastern japan abstract a dense seismic network was temporarily deployed during 1997 1999 in the central part of northeastern japan by japanese university research groups using the local earthquake arrival time data recorded by the network we have determined high resolution three dimensional images of p wave velocity vp s wave velocity vs and vp vs ratio in this area our results show that low vp low vs and high vp vs areas are extensively distributed in the uppermost mantle along the volcanic front in the lower crust low vp low vs and high vp vs areas are visible but they are confined to the individual volcanic areas in contrast the upper crust of volcanic areas shows low vp low vs and low vp vs rather than high vp vs these observations suggest that partial melting materials exist in the uppermost mantle along the volcanic front and they spread up to the midcrust of the volcanic areas low vp low vs and low vp vs in the upper crust of the volcanic areas suggest the presence of h2o rather than melt there deep low frequency microearthquakes perhaps caused by the rapid movement of fluids are located mostly at the edge of partial melting zones particularly at their upper surface distinct s wave reflectors bright spots with large reflection coefficients are distributed in the midcrust with slightly low vp vs suggesting that most of them are filled with h2o

p wave tomographic imaging of the crust and upper mantle beneath the japan islands more than 50 000 high accuracy arrival times from 1200 shallow and deep earthquakes selected from the japan university network earthquake catalog are used to investigate the three dimensional 3 d seismic velocity structure beneath japan travel times and ray paths are accurately calculated by using an efficient 3 d ray tracing technique p wave tomographic images of the crust and upper mantle to a depth of 500 km beneath the japan islands are determined with spatial resolutions of 25 50 km the obtained p wave velocity in the crust and uppermost mantle is slightly higher and relatively homogeneous in western japan in contrast with an average lower velocity and a large heterogeneity in eastern japan where many active volcanoes exist this feature correlates well with the distributions of heat flow and gravity anomalies low velocity low v zones are imaged in the crust and uppermost mantle beneath active volcanoes the low v zones in the mantle wedge dip toward the west and extend continuously to a depth of about 200 km a high velocity high v zone corresponding to the subducted pacific plate is delineated the thickness of the high v zone is estimated to be 80 90 km in southwestern japan the descending philippine sea plate is also delineated its thickness is estimated to be 30 km

short period fluctuations of the diurnal tide observed with low latitude mf and meteor radars during cadre evidence for gravity wave tidal interactions mf and meteor radar data from four equatorial and subtropical sites hawaii christmas island jakarta and adelaide are used to examine diurnal tide amplitude and phase variability at mesosphere and lower thermosphere altitudes all sites exhibit significant seasonal variability with the largest amplitude fluctuations occurring at hawaii and adelaide shorter term variability is found to occur primarily on timescales of 5 to 30 days amplitude and phase fluctuations are well correlated among different sites on occasion but in general the amplitude and phase coherences are low and suggest significant local influences on the tidal structures the temporal behavior of height variations of the diurnal tide amplitude and phase is also examined cross correlations and cross spectra of these tidal parameters especially between the amplitude and phase are examined closely the tendency for phase maxima to lead amplitude maxima is consistent with tidal modulation of gravity wave propagation and momentum fluxes with a corresponding feedback by the gravity wave momentum flux divergences on the observed tidal structures these results substantially extend previous more limited studies of gravity wave tidal interactions and provide a statistical basis for the possible importance of this interaction and its influences on the diurnal tidal structure

empirical model of 90 120 km horizontal winds from wind imaging interferometer green line measurements in 1992 1993 an empirical model of horizontal winds is developed based on wind imaging interferometer windii green line observations between 90 and 120 km in 1992 1993 the model includes mean winds solar diurnal and semidiurnal tides and some planetary wave components as well as annual and semiannual variations in these fields its formulation is similar to that of hwm 90 and hwm 93 of hedin et al 1991 1996 but greatly modified and extended to use the higher resolution global wind measurements now available from windii while the technique will only reach fruition when results can be combined from the wind measurements of several years by the different instruments on the uars satellite this interim but updated model provides improved representation of the temporal and geographic variations of the wind fields compared to the current reference models the model generated climatological mean wind diurnal tides and some samples of the entire wind motion fields are presented and compared with the windii measurements and analysis results obtained from the data sets by different methods to check the consistencies between the model representations and the observations this study also reveals a dual cell structure in the meridional component of the diurnal tides with two amplitude maxima centered around 95 and 102 km near 20 latitude and strongly symmetric about the equator at equinox large interannual variabilities are found to exist in both diurnal wind components with maximum amplitudes of 40 and 55 m s for the zonal and meridional respectively at the vernal equinox of 1992

local seismicity near the actively deforming corbetti volcano in the main ethiopian rift abstract corbetti is currently one of the fastest uplifting volcanoes globally with strong evidence from geodetic and gravity data for a subsurface inflating magma body a dense network of 18 stations has been deployed around corbetti and hawassa calderas between february 2016 and october 2017 to place seismic constraints on the magmatic hydrothermal and tectonic processes in the region we locate 122 events of magnitudes between 0 4 and 4 2 using a new local velocity model the seismicity is focused in two areas directly beneath corbetti caldera and beneath the city of hawassa the shallower 0 5 km depth below sea level b s l earthquakes beneath corbetti are mainly focused in ew to ns elongated clusters at urji and chabbi volcanic centres this distribution is interpreted to be mainly controlled by a northward propagation of hydrothermal fluids away from a cross rift pre existing fault source mechanisms are predominantly strike slip and different to the normal faulting away from the volcano suggesting a local rotation of the stress field these observations along with a low vp vs ratio are consistent with the inflation of a gas rich sill likely of silicic composition beneath corbetti in contrast the seismicity beneath hawassa extends to greater depth 16 km b s l these earthquakes are focused on 8 10 km long segmented faults which are active in seismic swarms one of these swarms in august 2016 is focused between 5 and 16 km depth b s l along a steep normal fault beneath the city of hawassa highlighting the earthquake hazard for the local population

seismic structure of the northeastern japan convergent margin a synthesis many studies recently made on the basis of seismic observations have revealed a detailed structure of the crust and the upper mantle beneath the northeastern japan arc and its relationship to seismic and volcanic activity spatial distributions of the depths to the conrad and the moho discontinuities estimated from shallow earthquake data and seismic explosion data show that both discontinuities are deep in the middle of the land area and shallow toward the coastlines of the japan sea and the pacific ocean the pn velocity has a lateral variation it is as low as 7 5 km s beneath the land area while that beneath the japan sea and the pacific ocean is 8 0 8 2 km s it changes abruptly at the transition zones which are located along the coastlines precise structure and location of the subducted pacific plate beneath the land area is inferred from converted or reflected seismic waves at the top or bottom of the plate the pacific plate is composed of a thin 5 km low velocity upper layer and a thick high velocity lower layer its total thickness being 80 90 km the upper plane seismicity of the double seismic zone is confined to the thin low velocity upper layer which probably corresponds to the subducted former oceanic crust the lower plane seismicity lies at the middle of the high velocity lower layer and the lower half of the plate below it is incapable of generating earthquakes the shallower portion of the upper surface of the plate beneath the pacific ocean along which major seismicity with low angle thrust faultings is actually occurring is also located by seismic observations on land and in the sea the pacific plate subducts at an extremely low angle of 5 for the first 25 km depth and then the dip steepens rather abruptly to 30 normal fault type events at the top of the plate have not been detected in the portion where the downward bending is the largest but have been ditected near the trench axis where it is rather small tomographic inversions for seismic velocity structure clearly delineate the inclined high velocity pacific plate with a thickness of 80 90 km and low velocity zones in the crust and the mantle wedge beneath active volcanoes seismic attenuation tomography also shows similar zones of low q value beneath active volcanoes although its spatial resolution is much lower the low velocity zones with 2 6 velocity lows are continuously distributed from the upper crust just beneath active volcanoes to a depth of 100 150 km in the mantle wedge and are approximately parallel to the dip of the underlying pacific plate these low velocity zones probably reflect the pathway of magma ascent from a depth in the mantle wedge to the earth s surface corresponding to a portion of the subduction induced secondary mantle wedge flow

morphology of the subducting slab boundary in the northeastern japan arc abstract the detection and location of the subducting slab boundary is crucial for a better understanding of the mechanical coupling between the subducting oceanic plate and the overlying continental plate and of the occurrence of large and destructive earthquakes on the main thrust zone in the forearc region of subduction zones it is also important for the understanding of the dehydration of the subducting slab and the genesis of island arc magmatism and volcanism in this study we have estimated the morphology of the upper surface of the subducting pacific plate under northeastern ne japan by using 1372 sp converted waves at the slab boundary and 666 earthquakes beneath the pacific ocean that are well located with sp depth phases we found that the pacific slab beneath ne japan subducts at a small dip angle of less than 10 for the first descent to about 20 km depth and has a steeper dip angle of 15 25 at 30 50 km depth and about 30 at deeper areas the slab depth is approximately 50 km under the pacific coast 150 km under the japan sea coast and nearly 100 km beneath the volcanic front at 60 150 km depths earthquakes in the lower plane of the double seismic zone occur in the central part of the slab while the upper plane events occur within 10 15 km beneath the slab boundary there is a change in the slab surface geometry around 38 n which corresponds to the landward extension of an oceanic fracture zone the strike of the slab is nne in the north and becomes ne in the south the southern part of the slab has a steeper dip angle than the northern part we believe that these features are related to the different patterns of interplate seismicity and mechanical coupling between the northern and southern parts of ne japan many great m8 0 8 5 interplate earthquakes have occured in northern ne japan during recorded history 830 1995 and microearthquakes show a wide distribution in the forearc region from the japan trench to the pacific coast suggesting strong interplate seismic coupling in that region in contrast only a few m7 0 7 5 class earthquakes have occurred in southern ne japan in the same period and microearthquakes tend to cluster in many small areas suggesting weaker interplate coupling there the subducted slab may be segmented by the oceanic fracture zones and the degree of seismic coupling changes from segment to segment the behavior of the segment in southern ne japan might be affected by the subducted seamounts so that the slab subducts at a steeper dip angle this interpretation is supported by geomagnetic topographic and geological studies which show that many small sized seamounts were subducted in the past from the southern part of the japan trench but almost no seamounts were subducted beneath the northern part

contrasting seismic reflectivity of the lower crust and uppermost mantle between ne japan and sw japan as illustrated by petrophysical analyses of mafic and ultramafic xenoliths 1 petrophysical analyses of mafic and ultramafic xenoliths reveal large contrasts in acoustic impedance between the lower crustal rocks and uppermost mantle rocks both beneath ichinomegata crater in ne japan and beneath oki dogo island in sw japan in contrast to minor contrasts in acoustic impedance both among the lower crustal rocks and among the uppermost mantle rocks beneath ichinomegata crater relatively large contrasts in acoustic impedance are present beneath oki dogo island between granulite and olivine gabbro in the lower crustal rocks as well as between plagioclase bearing wehrlite and other cumulus peridotites in the uppermost mantle rocks based on the existing petrologic models of the lower crust and uppermost mantle beneath ichinomegata crater and oki dogo island we then constructed model structures of the lower crust and uppermost mantle beneath these two areas composed of units with randomly arranged 100 m thick foliation parallel horizontal layers of xenolith samples and used these model structures to examine the seismic reflectivity beneath these two areas the results suggest the presence of strong seismic reflectors between the lower crust and the uppermost mantle in both areas although no other recognizable seismic reflector is expected beneath ichinomegata crater many seismic reflectors due to the above contrasts in acoustic impedance are expected both in the lower crust and in the uppermost mantle beneath oki dogo island thus a remarkable contrast in seismic reflectivity in the lower crust and uppermost mantle is likely present between these two areas as well as between ne japan and sw japan

deep low frequency microearthquakes in or around seismic low velocity zones beneath active volcanoes in northeastern japan abstract precise hypocenter relocations have been made for shallow intraplate microearthquakes beneath northeastern japan by applying source region station corrections the relocated hypocenter distribution shows that most of the events are confined to the upper 15 km of the crust which forms the brittle seismogenic zone in this volcanic arc it also shows that exceptionally deep microearthquakes well below the base of the seismic aseismic boundary occur at twelve locations of northeastern japan they occur in the lowermost crust or in the uppermost mantle where rheological properties of rocks are presumed to be in the ductile regime all the 153 events presently detected in the lowermost crust or in the uppermost mantle have anomalously low predominant frequencies 1 5 5 hz both for p and s waves in contrast to those 8 20 hz of normal shallow events in the brittle seismogenic zone the magnitudes of these events are small m 2 2 moreover all of these events are located beneath active volcanoes and or near p wave low velocity zones in the uppermost mantle the proximity of these events to the active volcanoes and other anomalous features suggest that these deep low frequency events are generated by magmatic activity of mantle diapirs in the uppermost mantle

diurnal nonmigrating tides from timed doppler interferometer wind data monthly climatologies and seasonal variations 1 timed doppler interferometer tidi measurements of zonal and meridional winds in the mesosphere lower thermosphere are analyzed for diurnal nonmigrating tides june 2002 to june 2005 climatologies of monthly mean amplitudes and phases for seven tidal components are presented at altitudes between 85 and 105 km and latitudes between 45 s and 45 n westward propagating wave numbers 2 3 and 4 the standing diurnal tide and eastward propagating wave numbers 1 2 and 3 the observed seasonal variations agree well with 1991 1994 uars results at 95 km comparisons between the tidi results and global scale wave model gswm and thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm tidal predictions indicate that the large eastward propagating wave number 3 amplitude is driven by tropical tropospheric latent heat release alone in contrast latent heating and planetary wave migrating tidal interactions are equally important to westward 2 and standing diurnal tidal forcing there is good quantitative agreement between tidi and the model predictions during equinox but the latter tend to underestimate the westward 2 and standing diurnal tide during solstice neither model reproduces the observed seasonal variations of the eastward propagating components

gravity wave interactions with the diurnal propagating tide observations of the diurnal propagating solar tide in the mesosphere and lower thermosphere 50 150 km indicate substantial annual variations in tidal amplitudes observations and modeling efforts suggest that interactions with internal gravity waves can result in significant modifications of the diurnal tide herein a two dimensional 2 d linear steady state tidal model is used in conjunction with hybrid lindzen matsuno gravity wave parameterization to examine the role of gravity wave interactions in the seasonal variability of the diurnal tide in the mlt the analysis indicates that annual variations of the background atmosphere result in significant annual variations in the eddy diffusion and the diurnal harmonic of the momentum flux divergence wave stress produced by breaking gravity waves the seasonal variability in these two mechanisms can explain the observed semi annual variability in the diurnal tide amplitude minima at solstice and maxima at equinox the relative roles of wave stress and diffusion are examined and it is shown that both play important roles in tidal modification by damping its amplitude the effects of varying inputs to the gravity wave parameterization are explored

the percolation phase transition in sea ice sea ice exhibits a marked transition in its fluid transport properties at a critical brine volume fraction p c of about 5 percent or temperature t c of about 5 c for salinity of 5 parts per thousand for temperatures warmer than t c brine carrying heat and nutrients can move through the ice whereas for colder temperatures the ice is impermeable this transition plays a key role in the geophysics biology and remote sensing of sea ice percolation theory can be used to understand this critical behavior of transport in sea ice the similarity of sea ice microstructure to compressed powders is used to theoretically predict p c of about 5 percent

effects of snow snowmelting and refreezing processes on air sea ice co2 flux the air sea ice co2 flux was measured in the ice covered saroma ko a lagoon on the northeastern coast of hokkaido japan using a chamber technique the air sea ice co2 flux ranged from 1 8 to 0 5 mg c m 2 h 1 where negative values indicate a sink for atmospheric co2 the partial pressure of co2 pco2 in the brine of sea ice was substantially lower than that of the atmosphere primarily because of the influence of the under ice plume from the saromabetsu river located in the southeastern part of the lagoon this suggests that the brine had the ability to take up atmospheric co2 into the sea ice however the snow deposited over the sea ice and the superimposed ice that formed from snowmelting and refreezing partially blocked co2 diffusion acting as an impermeable medium for co2 transfer our results suggest that the air sea ice co2 flux was dependent not only on the difference in pco2 between the brine and the overlying air but also on the status of the ice surface these results provide the necessary evidence for evaluation of the gas exchange processes in ice covered seas

three dimensional structure of vp vs and vp vs beneath northeastern japan implications for arc magmatism and fluids we estimated both p v p and s wave velocity v s structures beneath northeastern japan by applying a tomographic method to 169 712 p and 103 993 s wave arrival time data from 4338 local events the average value of v p v s ratio is 1 69 in the upper crust 1 75 in the lower crust and 1 77 in the uppermost mantle these differences in v p v s ratio may mainly reflect the lithological variations with depth low v p low v s and high v p v s zones are extensively distributed along the volcanic front in the uppermost mantle and are downward to the back arc side in the mantle wedge here the low v p low v s and high v p v s values are interpreted because of partial melting materials which imply the presence of a vast amount of melt in the uppermost mantle in the lower crust low v p low v s and high v p v s zones are not continuously visible along the volcanic front but are confined to individual volcanic areas which suggests that melting of lower crustal materials occurs just beneath each active volcano in contrast the upper crust beneath active volcanoes exhibits low v p low v s and low v p v s these results suggest that the partial melting zones under northeastern japan spread out from the uppermost mantle along the volcanic front up to the midcrust right beneath active volcanoes the low v p low v s and low v p v s features in the upper crust suggest the existence of h 2 o rather than melt right beneath active volcanoes

3 d seismic structure of kii peninsula in southwest japan evidence for slab dehydration in the forearc abstract kii peninsula is located in the forearc region of southwest japan and has distinct structural and tectonic features characterized by high seismicity in the crust and the subducting philippine sea slab high surface heat flow high 3he 4he isotopic ratio and a local change in the geometry of the subducting slab we have tried to determine detailed 3 d p and s wave velocity structures of this region using a large number of high quality arrival time data recorded by dense seismic networks on the japan islands from the obtained seismic velocities we further estimated 3 d distributions of poisson ratio crack density saturation rate and porosity parameter in the study area our results show significant heterogeneities in the crust and upper mantle wedge characterized by low seismic velocities high poisson ratio high values of crack density saturation rate and porosity these results suggest the existence of fluids in the crust and mantle wedge resulting from the dehydration of the subducting philippine sea slab which can explain the observed geophysical and geochemical features in kii peninsula

mesospheric momentum flux studies at adelaide australia observations and a gravity wave tidal interaction model abstract we present here the results of an analysis of gravity wave momentum fluxes in the mesosphere and lower thermosphere inferred using a dual beam doppler radar near adelaide australia during june 1984 our analysis reveals that over 70 of the momentum flux and of the inferred zonal drag was due to gravity waves with observed periods less than one hour this suggests that it is the gravity waves with high intrinsic frequencies and small horizontal scales that are most effective at transporting momentum into the middle atmosphere the temporal variations in the momentum flux and flux divergence due to high frequency motions were also examined in detail in addition to daily variability a strong diurnal modulation was observed to occur this was found to be correlated with the phase of large amplitude diurnal tidal motions as a result of these observations a gravity wave tidal interaction model was proposed which accounts for all of the major features of the observed data including a reduction i

equations for determining the gas and brine volumes in sea ice samples on a etabli des equations utilisables pour determiner le taux de gaz inclus dans la glace de mer a partir de mesures de densite de salinite et de temperature dans des gammes de temperatures entre 2 c et 30 c inversement ces relations peuvent etre utilisees pour calculer la densite de la glace de mer en fonction de la temperature et de la salinite en prenant en compte a la fois la presence de gaz et de cristaux de sel dans la glace on donne aussi des equations qui permettent le calcul du volume de gaz et d eau salee dans la glace a des temperatures autres que celle pour laquelle la densite a ete determinee

mountain wave drag in the stratosphere and mesosphere inferred from observed winds and a simple mountain wave parameterization scheme abstract a daily analysis of mountain wave propagation through observed global wind and temperature fields in january and august is presented winds and temperatures are obtained from the daily 18 level nmc climate analysis center mountain wave properties are deduced from a simple gravity wave parameterization scheme in which the effects of topographic anisotropy ridge orientation are explicitly included planetary waves in the northern winter stratosphere are found to play an important role in modulating the magnitude and distribution of inferred mountain wave drag in the middle atmosphere the aleutian anticyclone is found to effectively block mountain waves generated over western north america from reaching the mesosphere by inducing local mountain wave critical levels in the stratosphere stratospheric sudden warmings have a similar effect at all longitudes so that during months with sudden warmings have a similar effect at all longitudes so that during months with sudden warmings the average in

experimental evidence for carbonate precipitation and co2 degassing during sea ice formation chemical and stable carbon isotopic modifications during the freezing of artificial seawater were measured in four 4 m3 tank incubations three of the four incubations were inoculated with a non axenic antarctic diatom culture the 18 days of freezing resulted in 25 to 27 cm thick ice sheets overlying the residual seawater the ice phase was characterized by a decrease in temperature from 1 9 to 2 2oc in the under ice seawater down to 6 7oc in the upper 4 cm of the ice sheet with a concurrent increase in the salinity of the under ice seawater and brine inclusions of the ice sheet as a result of physical concentration of major dissolved salts by expulsion from the solid ice matrix measurements of ph total dissolved inorganic carbon ct and its stable isotopic composition d13ct all exhibited changes which suggest minimal effect by biological activity during the experiment a systematic drop in ph and salinity normalized ct by up to 0 37 phsws units and 376 mol c kg 1 respectively at the lowest temperature and highest salinity part of the ice sheet were coupled with an equally systematic 13c enrichment of the ct calculations based on the direct ph and ct measurements indicated a steady increase in the in situ concentration of dissolved carbon dioxide co2 aq with time and increasing salinity within the ice sheet partly due to changes in the dissociation constants of carbonic acid in the low temperature high salinity range within sea ice the combined effects of temperature and salinity on the solubility of co2 over the range of conditions encountered during this study was a slight net decrease in the equilibrium co2 aq concentration as a result of the salting out overriding the increase in solubility with decreasing temperature hence the increase in the in situ co2 aq concentration lead to saturation or supersaturation of the brine inclusions in the ice sheet with respect to atmospheric pco2 3 5x10 4 atm when all physico chemical processes are considered we expect co2 degassing and carbonate mineral precipitation from the brine inclusions of the ice sheet which were saturated or highly supersaturated with respect to both the anhydrous calcite aragonite vaterite and hydrated ikaite carbonate minerals

observational evidence of tidal gravity wave interactions using the uwo 2 mhz radar the degree of interaction between atmospheric gravity waves and tides is an issue which is of great importance in middle atmosphere studies it is especially important with regard to tidal variability which is frequently observed in the mesosphere and lower thermosphere but as yet has not been subject to adequate study in this paper we present some strong observational evidence of such interactions made with the uwo 2 mhz radar near london canada our observations show significant correlation between gravity waves and tides diurnal at certain times of the year and the nature of the correlation is intermittent and varies with time of year it is possible that differences between tidal amplitudes at sites with mesoscale separations may be explained in terms of such phenomena we also propose a simple model which is found to be consistent with the major features of the observed data

p and s wave travel time inversions for subducting slab under the island arcs of the northwest pacific we have observed slablike high p and s velocity anomalies around the wadati benioff zone under island arcs of the northwest pacific through travel time tomographic inversions nineteen years of international seismological centre travel time residuals for events and stations in this large region are used analyses of resolution and noise show that the images are generally well resolved the images illustrate that slab anomalies are continuous along strike in most parts of the upper mantle of the region and become contorted and generally broadened with depth near the bottom of the upper mantle fingering of the slabs including segmenting and spreading is indicated the fast anomalies associated with the japan izu bonin and mariana subduction zones tend to flatten to subhorizontal at depth while downward spreading may occur under parts of the mariana and kurile arcs the fast anomalies below 700 km are not in the shape of a single coherent sheet the principal compressional axes of focal mechanisms in the region consistently follow the downdip direction of the high velocity slab even when it bends to subhorizontal at depth the depth at which compression begins to dominate the downdip stress regime in the slab apparently depends on bending of the slab and its dip slab fingering and intense deep seismicity probably are the consequence of the slab encountering a barrier of some form around the 670 km discontinuity

three dimensional structure of p wave anisotropy beneath the tohoku district northeast japan 1 we retrieve three dimensional structures of isotropic and anisotropic velocities of p waves of the tohoku district from first p arrival time data assuming azimuthal anisotropy to be caused by hexagonal symmetry axes distributed horizontally in the earth the results show that the high velocity pacific slab is clearly imaged in the isotropic velocity structure even though the azimuthal anisotropy is taken into account in addition small scale low velocity regions and prominent low velocity anomalies are found just below the active volcanoes and in the mantle wedge above the high velocity pacific slab respectively the fast propagation axis of p waves is in mostly e w direction in the upper crust nearly n s and e w directions in the lower crust e w direction in the mantle wedge and n s direction in the descending pacific slab these features of the p wave anisotropy structure are consistent with those of lateral variations of the fast polarization directions measured previously by shear wave splitting observations the plausible factor that causes the crust anisotropy is interpreted as being alignment or preferred orientation of microcracks and crust minerals the mantle wedge anisotropy is attributed to lattice preferred orientation of the mantle minerals arising from present day mantle process such as the mantle wedge convection and the plate motion however the fast propagation axis of p waves in the slab is almost perpendicular to the magnetic lineation of the oceanic plate under the northwest pacific and thus the slab preserves the original anisotropic property that the pacific plate gained when it formed

direct observations of nonmigrating diurnal tides in the equatorial thermosphere 1 we present direct observations of nonmigrating diurnal tides in the 90 270 km range inferred from the upper atmosphere research satellite uars wind imaging interferometer windii a prominent zonal wavenumber 4 appears in daytime zonal winds extending to 180 km we interpret this signature as an eastward propagating diurnal wavenumber 3 de3 viewed from the satellite perspective this evidence of the extended upward propagation of de3 demonstrates that it acts as a direct coupling agent between the troposphere and the thermosphere and f region in addition to its role in the e region dynamo

seismic activity and deformation process of the overriding plate in the northeastern japan subduction zone abstract we estimated the temperature distribution within the crust of the northeastern japan arc from p wave velocity perturbations obtained by travel time tomography by comparing the estimated temperature distribution with the focal depth distribution of shallow precisely relocated microearthquakes we found that the brittle to ductile or stick slip to stable sliding transition occurs at the 400 c isotherm and that the transition depth has considerable lateral variations the brittle seismogenic zone the upper portion of the crust becomes locally thin in the p wave low velocity areas where the temperature is estimated to be relatively high concentration of shallow microearthquakes high topography and relatively large contractile deformation of the crust are also observed in these low velocity areas active faults are not distributed in the low velocity areas but lie just along the edge of those areas or outside them all these observations suggest that earthquake occurrence and deformation within the crust is governed to a considerable degree by the thermal regime of this volcanic arc which is characterized by a horizontally inhomogeneous distribution of temperature

global temperature stationary planetary waves extending from 20 to 120 km observed by timed saber version 1 07 temperature measurements from saber instrument on board of timed satellite during 2006 2007 are used to study the temperature stationary planetary waves spws from 20 to 120 km to cover the high latitudes in both hemispheres 80 degrees s 80 degrees n and most local times 120 day data are combined together into one data set the most pronounced spw features are the large amplitudes in the upper mesosphere and lower thermosphere umlt while the spws below 90 95 km share common features with previous observations in both hemispheric umlt spws amplitudes are large at middle and high latitudes throughout the year while their amplitudes in tropics are small wave 1 activity is generally stronger than the corresponding wave 2 activity with maximum amplitudes larger than 15 k occurring at about 60 degrees 70 degrees north or south at the altitudes between 112 km and 119 km wave 1 amplitudes are larger in the southern hemisphere sh than in the northern hemisphere nh their phases are normally tilt westward with increasing height below similar to 110 km above this altitude the wave 1 and wave 2 phases remain nearly unchanged with height indicating the in situ generations and no propagations comparisons between the observed spw structures and those from the nrlmsise 00 model have been done result shows their consistent features below similar to 80 km and that nrlmsise 00 model gives no spw information from 95 to 125 km but does have longitudinal variations above similar to 125 km that are similar to the observed spw features above similar to 110 km

evidence of gravity wave tidal interaction observed near the summer mesopause at poker flat alaska abstract an analysis of gravity wave tidal interaction observed near the mesopause by the mst radar at poker flat in july of 1986 is presented our observations revealed daily mean wind maxima of 60 m s 1 westward and 20 m s 1 southward with daily mean momentum fluxes contributed by gravity waves with periods less than 1 hour of 4 5 m2 s 2 eastward and 1 2 m2 s 2 northward considerable hourly height variability was found to exist for both winds and momentum fluxes a significant modulation of the fluxes by tidal winds was observed characterized by out of phase correlations over a number of heights diurnal and semidiurnal winds and momentum fluxes exhibited very similar height variations with amplitudes of 5 30 m s 1 and 1 5 m2 s 2 meridional winds leading zonal winds by 90 and maximum fluctuating winds and momentum fluxes at lower levels the observed variations in the amplitude and phase of winds and momentum fluxes provide some support to the gravity wave tidal interaction model proposed

solar tides as revealed by measurements of mesosphere temperature by the mls experiment on uars abstract temperatures between 25 and 86 km measured by the microwave limb sounder mls experiment on the upper atmosphere research satellite uars are analyzed to delineate diurnal semidiurnal and terdiurnal tidal structures and stationary planetary waves these fourier components are determined from temperatures averaged in bins covering 5 latitude 30 longitude and 1 h in local time this study confirms the presence of diurnal nonmigrating tides with zonal wavenumbers s 0 2 3 s 0 s 0 implying westward eastward propagation and semidiurnal tides with s 1 and 3 and some components of lesser importance that were previously determined from uars wind measurements near 95 km the seasonal latitudinal and height structures of these components are now revealed and utilized to aid in interpreting their behaviors and ascertaining their origins new discoveries include the terdiurnal s 2 and s 4 components and trapped nonmigrating diurnal tides with s 0 and s 2 the former are like

can the okhotsk plate be discriminated from the north american plate the plate geometry in northeast asia has been a long standing question with a major issue being whether the sea of okhotsk and northern japanese islands are better regarded as part of the north american plate or as a separate okhotsk plate this question has been difficult to resolve because earthquake slip vectors along the kuril and japan trenches are consistent with either pacific north america or pacific okhotsk plate motion to circumvent this difficulty we also use slip vectors of earthquakes along sakhalin island and the eastern margin of the japan sea and compare them to the predicted eurasia okhotsk and eurasia north america motions for a model with a separate okhotsk plate we invert 10 eurasia okhotsk and 255 pacific okhotsk slip vectors with pacific north america and eurasia north america nuvel 1 data alternatively for a model without an okhotsk plate those eurasia okhotsk and pacific okhotsk data are regarded as eurasia north america and pacific north america data respectively the model with an okhotsk plate fits the data better than one in which this region is treated as part of the north american plate because the improved fit exceeds that expected purely from the additional plate the data indicate that the okhotsk plate can be resolved from the north american plate the motions on the okhotsk plate s boundaries predicted by the best fitting euler vectors are generally consistent with the recent tectonics the eurasia okhotsk pole is located at northernmost sakhalin island and predicts right lateral strike slip motion on the nne striking fault plane of the may 27 1995 neftegorsk earthquake consistent with the centroid moment tensor focal mechanism and the surface faulting along the northern boundary of the okhotsk plate the north america okhotsk euler vector predicts left lateral strike slip consistent with the observed focal mechanisms on the nw boundary of the okhotsk plate the eurasia okhotsk euler vector predicts e w extension discordant with the limited focal mechanisms and geological data this misfit may imply that another plate is necessary west of the magadan region in southeast siberia but this possibility is hard to confirm without further data such as might be obtained from space based geodesy

evidence for significant protein like dissolved organic matter accumulation in sea of okhotsk sea ice absorption and fluorescence of chromophoric dissolved organic matter cdom in sea ice and surface waters in the southern sea of okhotsk was examined sea water cdom had featureless absorption increasing exponentially with shorter wavelengths sea ice showed distinct absorption peaks in the ultraviolet especially in younger ice older first year sea ice had relatively flat absorption spectra in the ultraviolet range parallel factor analysis parafac identified five fluorescent cdom components two humic like and three protein like sea water was largely governed by humic like fluorescence in sea ice protein like fluorescence was found in considerable excess relative to sea water the accumulation of protein like cdom fluorescence in sea ice is likely a result of biological activity within the ice nevertheless sea ice does not contribute excess cdom during melt but the material released will be of different composition than that present in the underlying waters thus at least transiently the cdom introduced during sea ice melt might provide a more labile source of fresher protein like dom to surface waters in the southern sea of okhotsk keywords sea ice sea ice ecology

southern argentina agile meteor radar system design and initial measurements of large scale winds and tides 1 the southern argentina agile meteor radar saamer was installed at rio grande on tierra del fuego 53 8 s 67 8 w in may 2008 and has been operational for 24 months this paper describes the motivations for the radar design and its placement at the southern tip of south america its operating modes and capabilities and observations of the mean winds planetary waves and tides during its first 20 months of operation saamer was specifically designed to provide very high resolution of large scale motions and hopefully enable direct measurements of the vertical momentum flux by gravity waves which have only been possible previously with dual or multiple beam radars and lidars or in situ measurements saamer was placed on tierra del fuego because it was a region devoid of similar measurements the latitude was anticipated to provide high sensitivity to an expected large semidiurnal tide and the region is now recognized to be a hot spot of small scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere perhaps the most dynamically active location on earth saamer was also intended to permit simultaneous enhanced meteor studies including head echo and nonspecular measurements which were previously possible only with high power large aperture radars initial measurements have defined the mean circulation and structure exhibited planetary waves at various periods and revealed large semidiurnal tide amplitudes and variability with maximum amplitudes at higher altitudes often exceeding 60 m s 1 and amplitude modulations at periods from a few to 30 days

high 3he emanation and seismic swarms observed in a nonvolcanic forearc region the 3he 4he and 4he 20ne ratios of gases emergent in the southwestern part of japan have been measured by a mass spectrometer the geographical distribution pattern of the 3he 4he ratios in the kinki district a non volcanic forearc region where microseismic activity at shallow depths has continued over a long period of time is strikingly different from those found in the rest of the japanese islands including the shikoku district which lies next to kinki anomalously high 3he 4he ratios up to 9 69 10 6 are found in the kinki district all the observed phenomena high emanation of 3he of magmatic origin high temperature hot springs high terrestrial heat flow hypocentral distribution of microearthquakes a local irregularity in the dip direction of the subducting philippine sea plate and the presence of molten materials inferred from the characteristic phases of sxp and sxs reflected waves in microseismograms strongly suggest the presence of a shallow magma body beneath the area

robust and exploratory analysis of active mesoscale tectonic zones in japan utilizing the nationwide gps array abstract a monitoring gps array recently developed in japan can yield nationwide maps of active inland tectonic zones atzs on a mesoscale approximately 70 to several hundred kilometers in lateral extent but it has been difficult to characterize atzs in japan as they are in fact operational on multiple scales and our efforts are often hindered by various irregularities in the data the key to overcoming these problems would be to gain an insight into the available data before any precise kinematic modeling is performed with indefinite assumptions in this study horizontal velocity fields deduced from the nationwide gps array were treated with a set of techniques in robust smoothing and exploratory data analysis that brought out exceptionally powerful mesoscale atzs and made them easier to characterize the resolved atzs were then retrospectively monitored to study their regional and temporal variations using a set of approx 840 observation stations about 30 km apart for a 4 year series of fixed observation time intervals 810 days each the smoothing operation involved three steps 1 imputation of the velocity fields for the purpose of anti aliasing 2 robust smoothing of the velocity fields with the median operative and 3 visualization of deformation rate distributions in several coordinate independent parameters and post filtering the geometrical resolvability of mesoscale atzs was confirmed by calibrating the smoothing scheme against synthetic tectonic boundary models before it was applied to the case study in japan atzs in japan which are essentially visible as systematic deviations in the velocity fields on the international terrestrial reference frame itrf and as strain rate anomalies were highlighted sharply along some known tectonic zones chains of active volcanoes and areas above low seismic velocity anomalies in the crust and upper mantle all of which generally paralleled the offshore trench axes the geometrical agreements among the mapped atzs and the physical anomalies in the crust are presumably due to their common structural weakness on the mesoscale in the four main islands of japan all but 30 40 of the strain rate anomalies persisted during the entire 6 years of the case study period while the rest sporadically appeared or disappeared in a period from several months to a few years the transient shifts in the deformation rates were remarkably synchronous with some nearby major tectonic episodes large earthquakes and slow events differential plate coupling strengths along the subduction zones can also be inferred from the persistent pattern of rotational strain rate anomalies forming clockwise and counterclockwise pairs along the pacific our empirical observations suggest that the first order features of interseismic crustal deformations in japan can be characterized as collateral processes behaving in response to fluctuations of the tectonic stresses on multiple scales likely influenced by changes of plate coupling strengths on the contiguous subduction faults

upper mantle velocity structure estimated from ps converted wave beneath the north eastern japan arc summary the upper boundary of the descending oceanic plate is located by using ps waves converted from p to s at the boundary in the tohoku district the north eastern part of honshu japan the observed ps p time data are well explained by a two layered oceanic plate model composed of a thin low velocity upper layer whose thickness is less than 10 km and a thick high velocity lower layer the upper and lower layers respectively have 6 per cent lower and 6 per cent higher velocity than the overriding mantle the estimated location of the upper boundary is just above the upper seismic plane of the double planed deep seismic zone this result indicates that events in the upper seismic plane at least in the depth range from 60 to 150 km occur within the thin low velocity layer on the surface of the oceanic plate

tidal gravity wave interactions and their influence on the large scale dynamics of the middle atmosphere model results results from a modified version of the quasi geostrophic model of mclandress and mcfarlane 1993 in combination with the tidal model of forbes 1982a b are used to delineate the role of tides in modulating gravity wave momentum fluxes and the ensuing effects on the large scale circulation of the middle atmosphere for solstice conditions the influence of the tidal wind fields on the location and strength of the gravity wave drag is strongest in the mesosphere and lower thermosphere where the tidal winds are of the same order as the zonal mean component due to the nonlinear dependence on the local wind speed the daily mean gravity wave drag in the model can differ significantly depending on whether or not tidal variations are included at middle and low latitudes these differences are largest and occur as a result of the filtering effects of the shorter vertical wavelength diurnal tide at more polar latitudes where the longer wavelength semidiurnal tide dominates a slight increase in drag occurs the interaction between the tidal wind fields and the localized orographic gravity wave momentum flux has important consequences for the in situ generation of planetary scale disturbances in particular the amplification of stationary planetary wavenumber 1 is enhanced by the presence of tides in addition forcing of nonmigrating tidal modes is predicted to occur as a result of the localized drag

effects of water and melt on seismic velocities and their application to characterization of seismic reflectors the effects of a silicate melt and water on seismic velocities are compared at relatively small fluid fraction less than 20 vol on the basis of a theoretical model of composite materials to show that the two fluids are clearly characterized by the velocity ratio vp vs for a silicate melt vp vs increases with increasing fluid fraction when a significant reflection is expected vp vs becomes much larger than 2 for water vp vs decreases as the fluid fraction increases to 10 vol then it increases but it remains similar to a solid state value about 1 8 unless the amount of water exceeds 15 vol this will be a good measure to distinguish between two candidates for seismic reflectors partially molten rocks and rocks containing free water if a reflector can be treated as a thin low velocity layer the velocity ratio in it can be estimated from the frequency dependence of reflection coefficient

three dimensional attenuation structure beneath the northeastern japan arc estimated from spectra of small earthquakes abstract a fine scale three dimensional attenuation structure beneath the northeastern japan arc has been obtained using a joint inversion for source parameters site response and q values data used for this study are p wave spectra of microearthquakes occurring in the subducting pacific plate the subducting plate is found to have higher q values than the overlying mantle there is an along arc variation in the distribution of low q zones in the crust and the mantle wedge within the study area for the southern part of the study area low q zones are distributed in the crust beneath the volcanic front they extend into the mantle wedge and become deep toward the west that is toward the backarc region on the other hand the northern part of the study area has low q zones at two depth ranges at shallower depths just beneath the volcanic front and at the deeper part of the mantle wedge beneath the backarc region the region without active volcanoes along the volcanic front has relatively high mantle q values seismic activity in the lower plane of the double planed deep seismic zone is high beneath this relatively high q region of the mantle wedge spatial distribution of low q zones found in the present study is nearly consistent with that of the low velocity zones estimated from studies of travel times tomography partial melting zones in the mantle wedge whose existence has been suggested from the study of seismic velocity structure and laboratory experiments are located in the low q zones obtained in the present study these results suggest that spatial distribution of q values is closely related to heterogeneous distribution of temperature in the mantle wedge

troposphere thermosphere tidal coupling as measured by the saber instrument on timed during july september 2002 1 coupling between the troposphere and lower thermosphere due to upward propagating tides is investigated using temperatures measured from the saber instrument on the timed satellite the data analyzed here are confined to 20 120 km altitude and 40 latitude during 20 july to 20 september 2002 apart from the migrating sun synchronous tidal components the predominant feature seen from the satellite frame during this period is a wave 4 structure in longitude with extrema of up to 40 50 k at 110 km amplitudes and longitudes of maxima of this structure evolve as the satellite precesses in local time and as the wave s responsible for this structure vary with time the primary wave responsible for the wave 4 pattern is the eastward propagating diurnal tide with zonal wave number s 3 de3 its average amplitude distribution over the interval is quasi symmetric about the equator similar to that of a kelvin wave with maximum of about 20 k at 5 s and 110 km de3 is primarily excited by latent heating due to deep tropical convection in the troposphere it is demonstrated that existence of de3 is intimately connected with the predominant wave 4 longitude distribution of topography and land sea difference at low latitudes and an analogy is drawn with the strong presence of de1 in mars atmosphere the predominant wave 2 topography on mars and the wave 2 patterns that dominate density measurements from the mars global surveyor mgs spacecraft near 130 km additional diurnal semidiurnal and terdiurnal nonmigrating tides are also revealed in the present study these tidal components are most likely excited by nonlinear interactions between their migrating counterparts and the stationary planetary wave with s 1 known to exist in the southern hemisphere during this period just prior to the austral midwinter stratospheric warming of 2002

melting and seismic structure beneath the northeast japan arc transportation of h2o associated with subduction of the pacific plate beneath the northeast japan arc is modeled to predict distribution of aqueous solution and melt and the consequent p wave velocity structure the observed velocity structure coincides well with the model for equilibrium transport of h2o most of h2o subducted is brought down to 150 200 km depth along the slab then the aqueous fluid generated ascends to initiate melting which explains the low velocity regions 6 reduction observed beneath the backarc rather than beneath the volcanic front if equilibrium transport of h2o occurs initiation of melting beneath the backarc with deep subduction of h2o is likely to be the case also for other subduction zones with slabs older than several tens of m y cold enough to stabilize serpentine to a great depth

shear wave splitting vp vs and gps during a time of enhanced activity at aso caldera kyushu 1 we performed shear wave splitting analyses and calculated vp vs ratios on local earthquakes recorded at seven stations around aso volcano japan between 2001 and 2008 the mean vp vs of 1 61 0 01 from all stations is among the lowest average values found anywhere in the world a temporal change of shear wave splitting fast polarization is observed at one station additionally spatial variations of shear wave splitting delay times and vp vs ratios show a correlation at three stations we suggest that stress controlled anisotropy dominates at these stations gps baselines and 2d strain reveal extension in the caldera in 2003 and compression before and after 2003 strain shortening axes indicate either a variation in regional stress or a local stress source that overprints the regional field in 2003 baseline changes correlate with periods of increased low frequency seismic activity located deeper than 15 km compaction and degassing of a previously reported sill at approximately 15 km depth could lead to constantly high pressure of volcanic gases over a wide area and explain the generally low vp vs ratios and the observed compression in the caldera we propose that a small volume of magma intruded into the sill in 2003 caused extension at the surface and triggered ash eruptions between 2003 and 2005 associated localized migration of gases in overpressured cracks with aspect ratios potentially 0 5 in the upper crust with porosities 0 1 could be the source of changes in seismic anisotropy and explain the slight variations observed in vp vs

late quaternary uplift rate inferred from marine terraces shimokita peninsula northeastern japan a preliminary investigation of the buried shoreline angle after estimating tectonic uplift rates along the northern part of the northeast japan forearc the overriding plate in the northeast japan subduction zone by mapping the elevation of the inner edges of marine terrace surfaces we refined this estimate through elevation measurements of the buried shoreline angle beneath well dated marine terrace surfaces from which we could derive more accurate paleo sea levels the uplift rate initially inferred from the inner edge of marine terrace t4 correlated with marine isotope stage mis 5e by tephrochronology increases eastward from 0 11 0 22 m ky 1 around the backarc volcanic front to 0 17 0 32 m ky 1 in the forearc on the peninsula of shiriyazaki we refined the uplift rates for t4 on the basis of the shoreline angle elevation from the reconstructed profile of the paleo sea cliff and wave cut platform on a rocky coast and the reconstructed profile of the swash zone sediments and terrace deposits on a sandy coast the refined uplift rates were 0 14 0 25 m ky 1 on the rocky coast and 0 14 0 23 m ky 1 on the sandy coast slightly slower than the rates we inferred from the height of t4 and about one half to three fourths of previously reported rates by extrapolation from the example of the sandy coast the refined uplift rate around the volcanic front was 0 09 0 18 m ky 1 the vertical deformation across the forearc of the shimokita peninsula since mis 5e is possibly associated with regional isostatic uplift of 0 09 0 18 m ky 1 and anticlinal deformation by an offshore fault interpreted from acoustic profiles of 0 05 0 07 m ky 1

3 d seismic velocity structure of the crust and the uppermost mantle in the northeastern japan arc 3 d seismic velocity structure of the crust and the uppermost mantle beneath the northeastern japan arc is investigated by using arrival time data from local earthquakes we use a velocity model composed of three layers corresponding to the upper crust the lower crust and the uppermost mantle respectively taking into account the observed regional variation of pn velocity the uppermost mantle is further divided into three parts by two pn velocity boundaries near the coasts of the japan sea and the pacific ocean the velocities within the upper crust the lower crust and the three parts of the uppermost mantle are assumed to be constant locations of two pn velocity boundaries and depth distributions of the conrad and the moho discontinuities are expressed by continuous functions of unknown parameters station corrections and hypocenters are also introduced to be unknowns these unknown parameters are determined by inverting arrival time data of p and s wave first arrivals and clear later arrivals of pg and p waves the pn velocity boundary between the land and the pacific ocean is located approximately along the pacific coastline and that between the land and the japan sea is nearly along the japan sea coastline the conrad and the moho discontinuities are at depths ranging from 14 to 20 km and from 27 to 36 km respectively the conrad and the moho depths have similar spatial distributions they are deep beneath the land and become shallower toward the western and the eastern coastlines beneath the land they are shallow in the central part of the tohoku district and become deeper toward both the north and the south directions in the north they become shallow again

mantle wedge structure in the miyagi prefecture forearc region central northeastern japan arc and its relation to corner flow pattern and interplate coupling 1 we applied three dimensional 3 d seismic tomography to both active source data and local earthquake data recorded at onshore and offshore seismic stations in the miyagi prefecture forearc region of central northeastern japan to obtain a detailed seismic velocity model of the mantle wedge the velocity model showed a clear boundary that divides the mantle wedge into an oceanward high velocity toe and a landward low velocity region that extends trenchward from beneath currently active arc volcanoes the top of the seaward dipping boundary is about 20 30 km landward from the coastline and its bottom is approximately beneath the coastline we consider that this velocity boundary represents the trenchward limit of corner flow and the high velocity toe represents a stagnant mantle wedge the high spatial resolution of the tomographic image we produced allowed us to identify a spatial correlation between velocity variations in the mantle wedge immediately above the plate boundary and the spatial extent of the rupture areas of the large interplate earthquakes that occur repeatedly in the region our results suggest that variations of the volume fraction of serpentinization in the mantle wedge cause the irregularity of rupture patterns of megathrust earthquake sequences we also identified a swarm of active microseismicity in the mantle wedge well above the seismogenic plate boundary this activity may be related to dehydration of a detached seamount

monthly tidal temperatures 20 120 km from timed saber 1 the saber instrument on the timed satellite provides unprecedented geographical coverage for the determination and study of atmospheric tides however the slow local time precession rate of timed can cause longer term temperature variations to alias into the tidal signals a new method of analyzing satellite data for tides has been developed to circumvent this difficulty but at the expense of temporal resolution of the tidal fields i e 120 day mean tidal structures are obtained in this work we apply this method to saber temperature data to derive a series of 120 day mean tidal structures extending between 20 and 120 km altitude 50 s 50 n latitude and centered on each month from september 2003 to september 2004 in addition to the migrating sun synchronous diurnal and semidiurnal tides a number of nonmigrating tides are revealed in the saber measurements some of these waves are thought to originate via nonlinear coupling between the migrating tides and the stationary planetary wave with zonal wave number s 1 other nonmigrating tidal components appear to be forced by latent heating due to deep tropical convection of the latter the eastward propagating diurnal tide with s 3 is dominant and is as large as the migrating diurnal tide during some months of particular interest is the wave 4 structure with respect to longitude that characterizes both the diurnal and semidiurnal total tidal fields this feature is a result of the predominant wave 4 topography land sea longitude dependence at the surface which is reflected in the diurnal and semidiurnal components of the latent heating rates due to deep tropical convection the ability of the global scale wave model gswm to approximate the observed tidal fields including the wave 4 total tidal structures is also assessed

fine structure beneath the tohoku district northeastern japan arc as derived by an inversion of p wave arrival times from local earthquakes abstract three dimensional p wave velocity structure beneath the tohoku district northeastern japan arc is investigated by an inversion of arrival times from local earthquakes using the method originally due to aki and lee 1976 in the crust 0 32 km depth a low velocity region is found along the volcanic front and its vicinity velocities at depths of 32 65 km are low beneath the regions where many quaternary volcanoes and geothermal areas are distributed in the region deeper than 65 km the subduction of the pacific plate is clearly revealed and the mantle structure above the descending plate is rather uniform these features suggest that volcanic activities have relation to the upper mantle structure the results obtained in this study will be helpful in investigating the mechanism of magma generation in a subduction zone

3he 4he ratio anomalies associated with the 1984 western nagano earthquake possibly induced by a diapiric magma a magnitude 6 8 earthquake occurred near ontake volcano in the western nagano prefecture of central honshu japan on september 14 1984 after the event 3he 4he ratios of bubbling gases in hot springs located less than 10 km from the newly formed fault were found to have increased significantly by up to 15 although the number of data is small considering that 3he can only be of magmatic origin we propose a model that the earthquake was triggered by an upward migration of 3he containing fluids associated with magma intrusion beneath the source region the proposed model is supported by the uplifting observed in the region since 1967 the continuation of seismic swarm activities in the area since 1976 an unprecedented eruption of ontake volcano in october 1978 and the existence of a small melted body in the lower crust beneath the present fault region

sources of nonmigrating tides in the tropical middle atmosphere 1 temperature measurements from the cryogenic infrared spectrometers and telescopes for the atmosphere crista experiment taken during the u s space shuttle mission sts 66 in november 1994 provide a variety of zonally symmetric and asymmetric tidal signatures in the altitude range from 40 90 km the most prominent zonally asymmetric tidal pattern is identified to be the westward propagating nonmigrating diurnal tide of zonal wavenumber 2 s 2 this mode has an amplitude of approximately half the amplitude of the migrating s 1 component of the diurnal tide the observational findings are compared to model results from the global scale wave model gswm and from the thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm gswm and time gcm account for different tidal sources and therefore allow an analysis of the tidal forcing responsible for the observed signatures the gswm tidal forcing in the model version used is based upon latent heat release associated with tropical deep convection while nonmigrating tides in the time gcm are predominantly forced by nonlinear interactions between the migrating diurnal tide and stationary planetary waves it is shown that the latter mechanism forces a large part of the s 2 mode while the stationary zonally uniform s 0 diurnal nonmigrating tide is mainly driven by latent heat release this result suggests that dynamical models for the mesosphere lower thermosphere mlt region need to account for the tropospheric latent heat source and stationary planetary wave activity in order to predict realistic longitudinal diurnal tidal variability

extensional structure in northern honshu arc as inferred from seismic refraction wide angle reflection profiling a recent extensive seismic wide angle experiment revealed a new image of crustal and uppermantle structure across northern honshu arc japan the western part of the arc recorded the crustal deformation by the miocene back arc spreading of the sea of japan the crust is composed of highly deformed tertiary sedimentary layers a relatively low velocity 5 75 5 9 km s crystalline basement and a 15 km thick lower crust with a velocity of 6 6 7 0 km s clear westward crustal thinning from 32 to 27 km represents the extensional deformation by the backarc spreading the crust attains the maximum thickness 32 35km east of the backbone range for which the magmatic intrusion underplating since 10 15 ma is a predominant factor the eastern part of the arc has a less deformed upper crust and a reflective middle lower crust probably remaining a stable block since the time of the backarc spreading

arctic ocean water mass balance from isotope data the distributions of the oxygen 18 and tritium isotopes and of salinity yield a residence time of 10 years for the surface and halocline waters of the arctic basin we find a yearly net production of 0 59 m of sea ice and an input of 1 16 m of freshwater from continental river runoff local precipitation and bering strait salinity deficiency using the basin area value with these numbers gives long term average total net production and transport rates of 0 15 sv of ice and 0 18 sv of meteoric component bering strait water not included if in addition a reasonable depth profile of relative current velocity is assumed for the outflow a yearly input of 2 8 sv of atlantic and bering strait water is needed to replenish the upper and halocline waters these numbers should be good to 20 and are multiyear averages the isotope data clearly indicate that the barents sea is an inflow area for atlantic water to the basin but that net export of ice occurs there

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

subducting plate boundary beneath the northeastern japan arc estimated from sp converted waves abstract in the tohoku district the northeastern part of honshu japan a conspicuous phase is frequently observed between p and s phases in seismograms for events in the lower seismic plane of the double planed deep seismic zone this phase is dominant in the vertical component and has an apparent velocity almost equal to or slightly smaller than the p phase we have never found this phase in seismograms for events in the upper seismic plane from these characteristics the phase is interpreted as sp converted from s to p at the upper boundary of the descending oceanic plate ubp using the travel times of the sp waves we estimated the location of the ubp beneath the tohoku district to be just above the upper seismic plane of the double planed deep seismic zone this position is consistent with those determined from the analyses of the travel times of the scsp and ps waves which are respectively the seismic wave converted from scs to p and that from p to s at the ubp

temporal change of the magma plumbing system at galeras volcano colombia revealed by repeated seismic tomography in 2009 2018 abstract we performed repeated three dimensional seismic tomography in 2009 2018 for the area influenced by the intersection of the silvia pijao buesaco and cauca almaguer fault systems beneath galeras volcano colombia we analyzed two periods 2009 2012 and 2013 2018 which were characterized by explosive eruptive activity and relative quiescence at galeras respectively we used p and s wave arrival times of 2848 2009 2012 and 2289 2013 2018 earthquakes that occurred beneath the volcano p and s wave velocity vp and vs respectively anomalies and their changes between the two periods were interpreted to be associated with magma movement in the volcanic plumbing system which was controlled by the intersection of the faults two possible pathways of magma ascent and accumulation were identified in the fault systems one located sw of the active crater consisted of areas with high vp vs values 1 9 at depths of 2 to 4 km below sea level and the other located ne of the active crater with high and low vp vs values the low vp vs

lateral variation of the cutoff depth of shallow earthquakes beneath the japan islands and its implications for seismogenesis abstract we estimated the spatial distribution of the cut off depth of shallow seismicity beneath the japan islands based on data from a recently constructed nationwide dense seismic network in order to avoid the effect of heterogeneous seismic velocity structure we determined the 3d seismic velocity structure for the whole of japan which was then used to relocate the hypocenters the cut off depth was determined by calculating d90 the depth above which 90 of the earthquakes occur a spatial distribution of estimated d90 values shows a considerable lateral variation ranging from about 5 km to about 40 km the d90 s are deep along the pacific coast of eastern japan locally shallow d90 s extend along belt like stretches of volcanic areas heat flow is low along the pacific coast in eastern japan and high in the volcanic areas this indicates that the lateral variation of d90 s is formed mainly by lateral geotherm variation cooling by the subducting old very cold pacific plate may cause the deep d90 s along the pacific coast in eastern japan heating by magma supplied from the mantle wedge below is considered to be the main cause of the shallow d90 s in the volcanic areas magma and or aqueous fluids derived from solidified magma contribute not only to locally shallow d90 s but also to the weakening of ambient rocks in the lower crust resulting in stress concentrations in the upper crust just above them large shallow inland earthquakes tend to occur in such areas suggesting that a model of shallow earthquake generation applied to tohoku can be used in other areas in japan as well

deep structure of japan subduction zone as derived from local regional and teleseismic events we have determined a detailed three dimensional p wave velocity structure of the japan subduction zone to 500 km depth by inverting local regional and teleseismic data simultaneously we used 45 318 p wave arrivals from 1241 shallow and deep earthquakes which occurred in and around the japan islands the arrival times are recorded by the japan university seismic network which covers the entire japan islands densely and uniformly we also used 4211 travel time residuals from 100 teleseismic events which are read from seismograms recorded by seismic stations in northeastern japan in comparison with the previous results obtained from only local and regional events the present result for the area around the lower plate boundary and the mantle below the plate is determined more reliably because of the addition of 7035 data from 100 teleseismic events and 41 very deep earthquakes in the crust and uppermost mantle low velocity zones are clearly visible beneath active volcanoes in the mantle wedge the low velocity zones generally parallel with the slab and exist continuously to a depth of about 200 km which is consistent with the petrological geochemical and geodynamic studies we consider that the existence of volcanism related low velocity anomalies in the mantle wedge is a general seismological characteristic of subduction zones in light of all the available tomographic results for many subduction zones in the world the pacific slab beneath japan is imaged more clearly than in previous studies as a high velocity zone with a thickness of 80 90 km and a p wave velocity 4 6 higher than the normal mantle lower velocity anomalies are found in the mantle below the slab

transport of chemical components in sea ice and under ice water during melting in the seasonally ice covered saroma ko lagoon hokkaido japan abstract physico chemical properties in the brine and under ice water were measured in saroma ko lagoon on the northeastern coast of hokkaido japan which is connected to the sea of okhotsk during the period from mid february through mid march 2006 the brine within brine channels of the sea ice was collected with a new sampling method examined in this study salinity dissolved inorganic carbon dic total alkalinity ta dissolved oxygen do nutrients and oxygen isotopic ratio 18 o contained in the brine within brine channels of the sea ice and in the under ice water varied largely in both time and space during the ice melt period when discharge from saromabetsu river located on the southeast of the lagoon increased markedly due to the onset of snow melting the under ice plume expands as far as 4 5 km from the river mouth at mid march 2006 transporting chemical components supplied from the river into the lagoon the under ice river water was likely transported into the sea ice through well developed brine channels in the sea ice due to upward flushing of water through brine channels occurred by loading of snowfalls deposited over the sea ice these results suggest that the river water plume plays an important role in supplying chemical components into the sea ice which may be a key process influencing the biogeochemical cycle in the seasonally ice covered saroma ko lagoon

three dimensional mapping of magma source and transport regions from seismic data the mantle wedge beneath northeastern japan we investigate the distribution of partial melt in island arc using the seismic velocity structure of the mantle wedge beneath northeastern japan the comparison of the seismic tomography with laboratory velocity data on a partially molten mantle rock yields estimates of melting zones in three dimensions we employ experimental data on the degree of partial melt in hydrous peridotite to give constraints on the melt fraction and temperature melting and magma rich zones derived from the velocity structure coincide with observed low q zones the results of the three dimensional mapping indicate that the source of magma in island arc is diapir like melting patches localized within the low velocity zones of the mantle wedge extensive volcanic activity along the volcanic front is due to the presence of vast magma rich zones just beneath the moho those melting zones in the uppermost mantle may in turn cause melting of lower crustal materials and produce felsic magma melt appears to stay at and beneath the moho where crystallization fractionation may proceed melt exists at greater depths in the back arc region which may correlate with across arc variations of chemical compositions of the volcanic rocks observed in northeastern japan we suggest that magma migration in the ductile lower crust may cause low frequency microearthquakes and magma penetration into the brittle upper crust may produce mid crustal s wave reflectors

non linear 3 d born shear waveform tomography in southeast asia s u m m a r ysoutheast se asia is a tectonically complex region surrounded by many active source re gions thus an ideal test bed for developments in seismic tomography much recent develop ment in tomography has been based on 3d sensitivity kernels based on the rst order bornapproximation but there are potential problems with this approach when applied to waveformdata in this study we develop a radially anisotropic model of se asia using long period multi mode waveforms we use a theoretical cascade approach starting with a large scale eurasianmodel developed using 2d nact sensitivity kernels and then using a modi ed born approxi mation nborn shown to be more accurate at modeling waveforms in order to invert a subsetof the data for structure in a subregion longitude 75

characteristics of the great whale river plume observations of the motion field and dilution effects associated with the plume of great whale river in hudson bay are presented for both open water and ice covered conditions in the summer months a distinct plume of about 100 km2 in area is formed offshore which is characterized by a 1 2 m thickness and large velocities directed away from the river mouth in contrast to slower currents parallel to the shore in the ambient waters underneath surface drifter results suggest that the outer boundary of plume may be a zone of frontal convergence under ice covered conditions the plume was significantly thicker and extended much farther offshore in spite of a marked reduction in river runoff at this time

satellite observations of thermospheric tides results from the wind imaging interferometer on uars thermospheric winds measured by the wind imaging interferometer windii on the upper atmosphere research satellite are analyzed for migrating solar tides the data cover a 2 year period commencing february 1992 and are obtained from the atomic oxygen o 1s 557 7 nm emission which provides observations of the 90 to 200 km altitude range during daytime and the 90 to 110 km range at night the subtropical lower thermosphere is dominated by the diurnal propagating tide which exhibits a vertical wavelength of approximately 22 km grows in amplitude up to 95 km and decays rapidly above where molecular diffusion greatly reduces the vertical shears although the phase remains fairly uniform throughout the year a pronounced semiannual oscillation is observed in the diurnal tide amplitude at both 20 n and 20 s the meridional and zonal wind components attain their maximum values at equinox of approximately 70 and 40 m s respectively while the solstitial minima are nearly a factor of 2 smaller at 35 n the diurnal tide semiannual amplitude oscillation is still present in the lower thermosphere but above 100 km it is replaced by an annual cycle with a maximum in july and august this contrasts with 35 s where the july august peak is absent and the semiannual oscillation extends to 110 km at midlatitudes the zonal and meridional winds are of similar magnitude and no significant hemispheric asymmetries in amplitudes are observed in the lower thermosphere the semidiurnal tide amplitude exhibits an annual oscillation with maximum values of 30 to 40 m s occurring in june july near 100 km at 35 n 35 s and the equator a bimodal structure in the seasonal variation of the semidiurnal phase is observed this feature is characterized by rapid equinoctial transitions and is particularly well defined at the equator examination of the equatorial middle thermosphere indicates that the semidiurnal tide attains its maximum amplitude at 140 km and exhibits a vertical wavelength of approximately 60 km these findings indicate the predominance of the antisymmetric 2 3 hough mode in the tropics

source and path of magma for volcanoes in the subduction zone of northeastern japan the assumption that the source of magma for volcanoes in subduction zones is located in the mantle immediately above the top of the subducting slab at approximately 100 km depth and straight beneath the volcanoes is incorrect in northeastern japan the combination of evidence from velocity tomography in the mantle wedge above the slab and mapping of earthquake size distribution within it strongly points to a source of fluids at the top of the slab at 140 to 150 km depth from where material rises along an inclined path to the volcanoes

flux of low salinity water from aniva bay sakhalin island to the southern okhotsk sea abstract in this study we examined the relationship between the low salinity water in the shelf region of the southern okhotsk sea which was seasonally sampled 0 200 m and fluxes of low salinity water from aniva bay to express the source of freshwater mixing in the surface layer we applied normalized total alkalinity nta and stable isotopes of seawater as chemical tracers nta s diagrams indicate that nta of low salinity water in the upper 30 m layer just off the soya warm current is clearly higher than in the far offshore region in summer and autumn using nta s regression lines we could deduce that the low salinity and high nta water in the upper layer originates from aniva bay for convenience we defined this water as the aniva surface water asw with values s 2450 mol kg 1 formation and transport processes of asw are discussed using historical data the interaction between the maximum core of high nta water on the bottom slope of eastern aniva bay and an anticyclonic eddy at the mouth of aniva bay are concluded to control asw formation upwelling of the cold water belt water at the tip of cape krillion is considered to cause asw outflow from aniva bay

three dimensional velocity structure seismicity and fault structure in the parkfield region central california this study examines the three dimensional velocity structure in a 60 by 80 km region containing the parkfield segment of the san andreas fault we use local earthquake and shot p arrival times in an iterative simultaneous inversion for velocity and hypocentral parameters using the three dimensional model we relocated 5251 events that occurred from 1969 to 1991 as well as the 1966 aftershocks and computed 664 fault plane solutions the san andreas fault saf characterized by a sharp across fault velocity gradient is the primary feature in the velocity solution there is a 5 20 lateral change in velocity over a 4 km width the contrast being sharper where there is better resolution the model also shows significant variations in the velocity and in the complexity of the velocity patterns along the saf the largest across fault velocity difference is below middle mountain where a large volume of low velocity material impinges on the saf from the northeast this material is inferred to be overpressured and may be key to understanding the unusual behavior in the parkfield preparation zone a 20 km long high velocity slice is imaged northeast of the saf near gold hill its along fault length corresponds to the length of the maximum slip in 1966 the relocated seismicity shows that the san andreas fault is a planar vertical fault zone at seismogenic depths ninety percent of the fault plane solutions that are on or near the saf were right lateral strike slip on subvertical fault planes that parallel the saf thus the surface fault complexities do not appear to extend to depth and therefore do not explain the rupture character at parkfield at parkfield variations in material properties play a key role in fault segmentation and deformation style our observations suggest that there may be a general relation between increasing velocity and increasing ability of the rocks to store strain energy and release it as brittle failure

co2 system development in young sea ice and co2 gas exchange at the ice air interface mediated by brine and frost flowers in kongsfjorden spitsbergen in march and april 2010 we investigated the development of young landfast sea ice in kongsfjorden spitsbergen svalbard we sampled the vertical column including sea ice brine frost flowers and sea water to determine the co2 system nutrients salinity and bacterial and ice algae production during a 13 day interval of ice growth apart from the changes due to salinity and brine rejection the sea ice concentrations of total inorganic carbon c t total alkalinity a t co2 and carbonate ions co3 2 in melted ice were influenced by dissolution of calcium carbonate caco3 precipitates 25 55 mol kg 1 and played the largest role in the changes to the co2 system the c t values were also influenced by co2 gas flux bacterial carbon production and primary production which had a small impact on the c t the only exception was the uppermost ice layer in the top 0 05 m of the ice there was a co2 loss of 20 mol kg 1 melted ice 1 mmol m 2 from the ice to the atmosphere frost flowers on newly formed sea ice were important in promoting ice air co2 gas flux causing a co2 loss to the atmosphere of 140 800 mol kg 1 d 1 melted frost flowers 7 40 mmol m 2 d 1

drake antarctic agile meteor radar first results configuration and comparison of mean and tidal wind and gravity wave momentum flux measurements with southern argentina agile meteor radar 1 a new generation meteor radar was installed at the brazilian antarctic comandante ferraz base 62 1 s in march 2010 this paper describes the motivations for the radar location its measurement capabilities and comparisons of measured mean winds tides and gravity wave momentum fluxes from april to june of 2010 and 2011 with those by a similar radar on tierra del fuego 53 8 s motivations for the radars include the hotspot of small scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere mlt centered over the drake passage the maximum of the semidiurnal tide at these latitudes and the lack of other mlt wind measurements in this latitude band mean winds are seen to be strongly modulated at planetary wave and longer periods and to exhibit strong coherence over the two radars at shorter time scales as well as systematic seasonal variations the semidiurnal tide contributes most to the large scale winds over both radars with maximum tidal amplitudes during may and maxima at the highest altitudes varying from 20 to 70 ms 1 in contrast the diurnal tide and various planetary waves achieve maximum winds of 10 to 20 ms 1 monthly mean gravity wave momentum fluxes appear to reflect the occurrence of significant sources at lower altitudes with relatively small zonal fluxes over both radars but with significant and opposite meridional momentum fluxes below 85 km these suggest gravity waves propagating away from the drake passage at both sites and may indicate an important source region accounting in part for this hotspot

imaging the fault zones of the 2000 western tottori earthquake by a new inversion method to estimate three dimensional distribution of the scattering coefficient 1 we developed an inversion method to estimate the spatial variation of scattering coefficient from observed envelopes of s coda waves synthetic envelopes are calculated on the basis of the single scattering theory assuming double couple sources and a one dimensional depth dependent velocity structure in our algorithm we evaluated scattering attenuation taking spatial variation of scattering coefficient into consideration in order to model energy attenuation by passing through the localized anomalous zones with high scattering coefficients the inversion method was applied to the seismograms in and around the focal area of the 2000 western tottori earthquake with m 7 3 obtained results show that there exist several zones with large scattering coefficient zones lszs one of the most predominant lsz is located along and around the fault zone of the m 7 3 earthquake in the upper crust this lsz suggests the existence of damaged zones in the main shock fault within this lsz an exceptionally small scattering coefficient area was detected this area corresponds to an asperity with a large amount of coseismic slip of the main shock other prominent lszs are detected in the mid to lower crust below the northwestern part of the main shock fault in addition lszs are distributed in a seismic low velocity zone near quaternary volcanoes and near hypocenters of deep low frequency microearthquakes some of the imaged lszs are probably related to local concentration of fluid in the crust

spatial variations in 3he 4he ratios along a high strain rate zone central japan abstract a linear zone with high strain rates along the japan sea coast the niigata kobe tectonic zone nktz is considered to be associated with rheological heterogeneities in the lower crust and or upper mantle helium isotope variations along the nktz reveal a close association with the geophysical evidence for rheological heterogeneities in the crust and mantle in the southern nktz the 3 he 4 he ratios lower than 3 4 ra ra denotes the atmospheric 3 he 4 he ratio of 1 4 10 6 could be interpreted as a two component mixture of helium stored in aqueous fluids driven off the subducting oceanic crust and radiogenic crustal helium higher 3 he 4 he ratios are observed in the central nktz where quaternary volcanoes and high temperature hot springs are concentrated suggesting that the 3 he emanation manifest in the central nktz results from the effective transfer of mantle helium by intrusion and degassing of mantle derived magma in the crust in the northern nktz where two large inland earthquakes occurred recently there appears to be many samples with 3 he 4 he ratios significantly higher than those observed in the fore arc side of northeast japan a plausible source of mantle helium could be attributed to upward mobilization of aqueous fluids generated by dehydration of the subducting pacific plate slab

deep structure of the northeastern japan arc and its relationship to seismic and volcanic activity evidence for possible deep seated magmatic activity beneath northeastern japan can be obtained from seismic observations tomographic inversions of p wave velocity data show low velocity zones distributed in the crust and upper mantle beneath active volcanoes in or around these zones anomalously low frequency micro earthquakes perhaps caused by magmatic activity are found at depths of 25 40 km distinct s wave reflectors corresponding to the upper surfaces of magma bodies are found at depths of 10 18 km large crustal earthquakes also occur around the low velocity zones these observations reveal the distribution of magma reservoirs at depths and elucidate its relation with shallow seismicity beneath volcanic arcs

simultaneous estimation of attenuation structure source parameters and site response spectra application to the northeastern part of honshu japan abstract we have developed an inversion method for estimating q structure by the use of a large number of waveform data from earthquakes we divide an area to be analyzed into small blocks and simultaneously estimate the q value in each block source parameters for each event and site response spectrum for each station the source spectrum is assumed to be expressed by the 2 model and values of corner frequencies and low frequency levels of source spectra are estimated amplitudes are calculated by taking the orientation of focal mechanism solutions into account a trade off among estimated parameters is tested by numerical experiments using three sets of artificial data in a case when artificial data include error of 15 in the orientation of the p axis of focal mechanism solutions the inverted result shows that the original checkerboard pattern of q structure is well reconstructed although estimated q 1 values are about 10 higher than those of the original one the result without the corrections for radiation effect shows that the checkerboard pattern is only reconstructed in the blocks having a sufficient number of ray paths we applied this inversion method to a real data set in the northeastern part of honshu japan estimated q p structure shows that low q p regions are distributed beneath the volcanic front and they move towards the west with increasing depth previous studies of three dimensional seismic velocity structure in this area show that p wave low velocity regions exist in the crust beneath the volcanic front and they are inclined towards the west in the mantle wedge the low q p regions estimated in this study coincide in general with the p wave low velocity regions

highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events first results the first observations of lowering of mesopause temperature during counter electrojet cej events over a narrow region of 150 km centered at around magnetic equator are presented the daytime mesopause temperature is measured over trivandrum 8 5 n 77 e dip lat 0 5 n india using the ground based multiwavelength dayglow photometer the unique meridional scanning capability of the instrument is extensively used in this study a lowering of temperature by as much as 25 k has been observed during certain cej events which includes a few partial cejs the gravity wave tidal interaction through vertically upward wind is proposed to be manifesting as lowering in the mesopause temperature and also as cej these observations are new and address to the issues concerning the vertical coupling processes prevailing in the equatorial mesosphere lower thermosphere ionosphere mlti region citation vineeth c t k pant c v devasia and r sridharan 2007 highly localized cooling in daytime mesopause temperature over the dip equator during counter electrojet events

depth extent of the lau back arc spreading center and its relation to subduction processes seismic tomography and wave form inversion revealed that very slow velocity anomalies 5 to 7 percent beneath the active lau spreading center extend to 100 kilometer depth and are connected to moderately slow anomalies 2 to 4 percent in the mantle wedge to 400 kilometer depth these results indicate that geodynamic systems associated with back arc spreading are related to deep processes such as the convective circulation in the mantle wedge and deep dehydration reactions in the subducting slab the slow regions associated with the tonga arc and the lau back arc are separated at shallow levels but merge at depths greater than 100 kilometers suggesting that slab components of back arc magmas occur through mixing at these depths

stationary planetary waves inferred from windii wind data taken within altitudes 90 120 km during 1991 96 abstract a climatology of stationary planetary waves spws in horizontal winds at latitudes 70 s 70 n and altitudes 90 120 km is obtained from wind imaging interferometer windii green line measurements in december january and march april of 1991 96 the observed solstitial spw fields are relatively stronger and dominated by zonal wavenumber 1 variations in contrast the equinoctial spw fields are weaker and characterized by zonal wavenumber 2 variations the zonal amplitude maxima of 10 25 m s 1 are generally centered at the midlatitudes of 35 40 in both hemispheres around 96 km with the eastward perturbation velocity maxima around 90 e for wavenumber 1 and 60 and 240 e for wavenumber 2 the meridional amplitude maxima are about 5 15 m s 1 and show more variabilities in their latitude height distributions the meridional phases indicated that eliassen palm ep fluxes were downward poleward for the winter maxima vertically varying poleward for the summer maxima and more variable during march apr

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

vp vs ratios in the yellowstone national park region wyoming abstract in this paper we study the variation of v p v s and poisson s ratio in the yellowstone national park region using earthquakes which were well recorded by a local seismic network we find that the average v p v s value within the geothermally active yellowstone caldera is about 7 lower than in the area outside the caldera within the caldera itself there may be a further 2 7 reduction of v p v s in the hydrothermally active norris geyser basin the upper and lower geyser basins and the yellowstone lake and mud volcano regions after considering various possible causes for v p v s changes such as geologic and structural differences thermal effects partial melting and hydrothermal activity we conclude that the most plausible explanation for the observed v p v s reduction is the presence of hot water at temperatures and pore pressures near the water steam transition in the caldera geothermal reservoirs