the q structure of the upper mantle constraints from rayleigh wave amplitudes 1 the three dimensional shear attenuation or q structure of the upper mantle is still poorly understood despite the increasing accuracy and sophistication of velocity models of the same part of the earth here we present a set of three dimensional q models of the upper mantle based on amplitude measurement of minor and major arc rayleigh waves in the period range 70 170 s the models show that areas of low attenuation underlie continents to a depth of around 300 km and areas of high attenuation are associated with oceans and plate boundaries particularly in the top 200 km below 350 km the sensitivity of the data to attenuation structure decreases rapidly it is well known that the amplitudes of surface waves can be strongly influenced by factors other than attenuation in particular focusing due to elastic structure and errors in source mechanisms we consider the effects of focusing by discussing the implications of the results of selby and woodhouse 2000 comparisons with focusing predictions using phase velocity maps allow us to identify features due to focusing in maps of attenuation distribution the influence of the source on the observed attenuation distribution is investigated by including a source term in the model inversion we find that successfully combining the data at each frequency into one three dimensional model requires that this source term must vary with frequency suggesting that a simple correction to the scalar moment of each event cannot explain the observations although the effects of focusing and the source can be significant we find that the observed attenuation pattern is robust up to degree 8 however shorter wavelength structure can be strongly influenced by other controls finally we use one of the models to predict the degree 2 attenuation pattern for 250 s rayleigh waves the observed pattern suggests that existing normal mode observations may be explainable in terms of structure above 350 km depth

episodic graben formation and extensional neotectonic regime in west central anatolia and the isparta angle a case study in the aksehir afyon graben turkey

global sea level rise published values for the long term global mean sea level rise determined from tide gauge records exhibit considerable scatter from about 1 mm to 3 mm yr this disparity is not attributable to instrument error long term trends computed at adjacent sites often agree to within a few tenths of a millimeter per year instead the differing estimates of global sea level rise appear to be in large part due to authors using data from gauges located at convergent tectonic plate boundaries where changes of land elevation give fictitious sea level trends in addition virtually all gauges undergo subsidence or uplift due to postglacial rebound pgr from the last deglaciation at a rate comparable to or greater than the secular rise of sea level modeling pgr by the ice 3g model of tushingham and peltier 1991 and avoiding tide gauge records in areas of converging tectonic plates produces a highly consistent set of long sea level records the value for mean sea level rise obtained from a global set of 21 such stations in nine oceanic regions with an average record length of 76 years during the period 1880 1980 is 1 8 mm yr 0 1 this result provides confidence that carefully selected long tide gauge records measure the same underlying trend of sea level and that many old tide gauge records are of very high quality

localization of the gravity field and the signature of glacial rebound the negative free air gravity anomaly centred on hudson bay canada shows a remarkable correlation with the location of the laurentide ice sheet suggesting that this gravity anomaly is the result of incomplete post glacial rebound this region however is also underlain by higher than average mantle seismic velocities suggesting that the gravity low might result instead from dynamic topography associated with convective downwellings here we analyse the global gravity field as a simultaneous function of geographic location and spectral content we find that the hudson bay gravity low is unique with anomalously high amplitude in the spectral band where the power from the laurentide ice load is greatest and the relaxation times predicted for viable models of viscous relaxation are longest we estimate that about half of the hudson bay gravity anomaly is the result of incomplete post glacial rebound and derive a mantle viscosity model that explains both this gravity signature and the characteristic uplift rates for the central laurentide and fennoscandian regions this model has a jump in viscosity at 670 km depth comparable to that in dynamic models of the geoid highs over subducted slabs but lacks a low viscosity asthenosphere consistent with a higher viscosity in the upper mantle beneath shields than in oceanic regions

abraded sand volcanoes as a tool for recognizing paleo earthquakes with examples from the cisuralian talchir formation near angul orissa eastern india abstract one of the bedding planes of a sandstone unit belonging to the cisuralian talchir formation is well exposed along the nandir jhor river in eastern india it shows a few dozens of circular structures commonly with diameters of a few decimetres a concentration is found in an area of some 50 m 2 where 12 well developed specimens occur the structures are interpreted as abraded sand volcanoes which interpretation is supported by the occurrence on the same bedding plane of a sand volcano with a diameter of over a meter the concentrated structures thus represent a sand volcano field a phenomenon that has not been recognized earlier in the pre holocene geological record but that in recent times seems always to be related to an earthquake the structures described here might therefore help to recognize earthquakes that occurred in the geological past

constraining the kinetics of mantle phase changes with seismic data summary in a system where two phases coexist a seismic wave can disrupt the pre existing equilibrium and induce a re equilibration process because the kinetics of the phase change is not instantaneous the transformation induces an attenuation of the wave that can be quantified using an appropriate physical theory kinetics of earth s phase transitions are not well known in this paper we show that they can be constrained by seismic attenuation data we quantify the influence of a phase transition upon seismic mode attenuation and body wave reflexion coefficient we perform a numerical application for the olivine to wadsleyite transition at 410 km depth assuming a phase loop thickness of 10 km we show that the relaxation time that controls the frequency band of attenuation and the velocity at which the interface evolves when submitted to a pressure disequilibrium is likely larger than 7000 s for this kinetics slower than typical seismic waves periods the transformation loop does not affect s waves attenuation but potentially that of p waves and normal modes

global maps of rayleigh wave attenuation for periods between 40 and 150 seconds studies of seismic attenuation must account for the large amplitude deviations caused by elastic focusing of energy in a new approach we jointly invert phase and amplitude measurements of 19 000 minor arc rayleigh waves between periods of 40 and 150 seconds the simultaneous inversion ensures that attenuation and phase velocity are mutually consistent because the phase and focusing term of amplitude are modelled using a common elastic model at the shortest periods the maps show a good correlation between attenuation and phase velocity suggesting a common cause in the uppermost mantle most probably thermal in origin this correlation is lost at longer periods the main signal beyond periods of 100 seconds is a strongly attenuating circum pacific zone and a pronounced ring of high attenuation around africa this feature seems reliable in our attenuation maps but not correlated to an equivalent structure in phase velocity we thus favour scattering of wave energy on large size structures as a possible cause

an overview of geotechnical aspects of the cay eber turkey earthquake abstract the cay eber earthquake md 6 0 occurred in the afyon province in the western part of turkey on 3 february 2002 and resulted in the loss of 42 lives and damage to buildings in the settlements particularly close to the epicenter in this study characteristics of the main shock and its geotechnical aspects such as local site conditions and their effects liquefaction phenomena and natural slope failures are evaluated the causative fault is a normal fault with a slight left lateral component and produced very short surface ruptures due to the presence of top soft and thick alluvial sequence filled the earthquake affected basin horizontal acceleration time histories and collapse direction of various buildings show a good agreement and indicate directivity effect the earthquake caused soil liquefaction and limited rock falls the presence of fine grained and low permeability topsoil layers in the alluvial sequence prevented a widespread liquefaction and associated ground deformations based on the back analysis of liquefaction data and the results of cyclic triaxial testing values of peak horizontal ground acceleration to initiate liquefaction are inferred in addition for selected sites the assessments based on the soil amplification factors estimated from equivalent shear wave velocities and available microtremor data and acceleration response spectra revealed that the resonance phenomena was one of the contributing factors in the damage sustained by some buildings

soil liquefaction susceptibility and hazard mapping in the residential area of kutahya turkey this study presents the results of both field and laboratory tests that have been undertaken to assess liquefaction susceptibilities of the soils in kutahya city located in the well known seismically active fault zone liquefaction potentials of the sub surface materials at kutahya city were estimated by using the geological aspect and geotechnical methods such as spt method of field testing and the data obtained have been mapped according to susceptibility and hazard the susceptibility map indicated liquefable and marginally liquefable areas in alluvium and non liquefable areas in neogene unit for the magnitude of earthquake of m 6 5 whereas liquefaction hazard map produced by using of liquefaction potential index showed the severity categories from very low to high however a large area in the study area is prone to liquefy according to liquefaction susceptibility map the large parts of the liquefable horizon are mapped as low class of severity by the use of the liquefaction potential index it can be said that hazard mapping of liquefaction for a given site is crucial than producing liquefaction susceptibility map for estimating the severity both the susceptibility and hazard maps should be produced and correlated with each other for planning in an engineering point of view

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

global models of surface wave attenuation 1 a large data set of fundamental mode rayleigh wave amplitudes is analyzed to derive global models of surface wave attenuation 1 q the data set consists of measurements of rayleigh wave amplitude anomalies in the period range 50 250 s for 347 earthquakes observed at 179 seismic stations the amplitude anomalies are considered to depend on four factors intrinsic attenuation along the ray path elastic focusing effects along the ray path a source factor accounting for uncertainties in the strength of excitation and a receiver factor accounting for uncertainties in the response at the station the amplitude data are inverted simultaneously for global maps of attenuation expanded in spherical harmonics up to degree 12 global maps of phase velocity expanded to degree 20 and source and receiver correction factors all four variable types are shown to be important in explaining the amplitude anomalies a data set of phase delay measurements provides additional constraints on velocity structure the maps of attenuation obtained by simultaneous inversion for elastic and anelastic models contain important features that are not robustly imaged when the effect of focusing on wave amplitude is ignored these include high attenuation along western north america and along the east pacific rise and other ridge systems and low attenuation associated with stable continental interiors the global attenuation maps exhibit a strong correlation with phase velocity maps corrected for the effect of the crust particularly for periods 200 s the correlation suggests that the variability in both q and velocity in the shallow upper mantle is primarily thermal in origin

attenuation tomography of the upper mantle we present qsadr17 a global shear wave attenuation model of the upper mantle synthetic tests confirm that large scale shear attenuation anomalies are resolved in the whole upper mantle with limited vertical smearing 50 km qsadr17 shows strong correlation with surface tectonics down to 200 km depth with low attenuation beneath continents and high attenuation beneath oceans the attenuation signal near 250 km depth is dominated by a high quality factor along subduction zones attenuating anomalies are found beneath mid ocean ridges down to 150 km and under most pacific hotspots from the lithosphere down to the transition zone the presence of broad attenuating anomalies at 150 km depth in the pacific ocean suggests that several thermal plumes pond in the asthenosphere evidence for compositional heterogeneities is found in the lithosphere at the base of cratons and in a number of active regions

investigation of glacial isostatic adjustment in the northeast u s using gps measurements 1 we have been observing three dimensional site velocities at over 60 permanent gps stations in the northeastern u s for the purpose of inferring mantle viscosity and thus improving current models of glacial isostatic adjustment gia we estimate the upper and lower mantle viscosity by comparing radial site velocities from a subset of continuous gps measurements with numerical gia predictions our inferences are consistent with previous esti mates obtained using different methods and data sets

q tomography of the upper mantle using three component long period waveforms summary we present a degree 8 3 d q model qrlw8 of the upper mantle derived from three component surface waveform data in the period range 60 400 s the inversion procedure involves two steps in the first step 3 d whole mantle velocity models are derived separately for elastic sh transverse component and sv vertical and longitudinal component velocity models using both surface and body waveforms and the non linear asymptotic coupling theory nact approach in the second step the surface waveforms thus aligned in phase are inverted to obtain a 3 d q model in the depth range 80 670 km various stability tests are performed to assess the quality of the resulting q model and in particular to assess possible contamination from focusing effects we find that the 3 d patterns obtained are stable but the amplitude of the lateral variations in q is not well constrained because large damping is necessary to extract the weak q signal from data the model obtained agrees with previous results in that a strong correlation of q with tectonics is observed in the first 250 km of the upper mantle with high attenuation under oceanic regions and low attenuation under continental shields it is gradually replaced by a simpler pattern at larger depth at the depths below 400 km the q distribution is generally dominated by two strong minima one under the southern pacific and one under africa yielding a strong degree 2 pattern most hotspots are located above regions of low q at this depth ridges are shallow features in both velocity and q models

the three dimensional seismological model a priori constrained confrontation with seismic data we compare the predictions of an a priori model of the upper mantle with seismic observations of surface waves and eigenmodes the 3 dimensional seismological model a priori constrained 3smac has been developed by natal and ricard 1996 it is based on the interpretation by geodynamicists of the near surface layers of the earth on distributions of temperature pressure and composition as a function of depth and then on estimates of seismic parameters density velocities attenuations from solid state laboratory measurements as a function of temperature and pressure the 3smac predictions are confronted with observations consisting of phase velocities for love and rayleigh waves in the period range of 70 250 s montagner and taniraoto 1990 we first show that tomographic inversions applied to 3smac synthetics induce a strong smoothing of the heterogeneities this ca sts doubt on the meaning of the spectra of mantle heterogeneities revealed by tomography we then show that most of the love and rayleigh fundamental mode observations for periods less than 200 s are satisfactorily predicted by 3smac the major differences come from the seismic velocities under the red sea and southeast china which are much slower than what is estimated from 3smac as well as those under greenland which are not as fast as the other cratonic areas because the lithosphere is thinner than 100 km under oceans and thinner than 300 km under continents in 3smac we suggest that the existence of deeper lithospheric anomalies as proposed in many tomographic models is mostly due to a spurious effect of the inversion rather than implied by surface wave data half of the variance of the degree 2 anomaly mapped by low degree eigenmode observations can be explained by lithospheric velocity structures the other half is highly correlated with the distribution of deep slabs but its amplitude is a factor of 3 or 4 larger than that predicted by 3smac the lithospheric anomalies present a degree 6 pattern well correlated with the distribution of hotspots even when the thermal anomalies that could be associated with plumes are not included in 3smac our results emphasize the importance of giving very close attention to surface corrections in tomographic models

global seismic attenuation imaging using full waveform inversion a comparative assessment of different choices of misfit functionals author s karaoglu h romanowicz b abstract the authors 2017 published by oxford university press on behalf of the royal astronomical society we present the results of synthetic tests that aim at evaluating the relative performance of three different definitions of misfit functionals in the context of 3 d imaging of shear wave attenuation in the earth s upper mantle at the global scale using long period full waveform data the synthetic tests are conducted with simple hypothetical upper mantle models that contain q anomalies centred at different depths and locations with or without additional seismic velocity anomalies to build synthetic waveform data sets we performed simulations of 50 events in the hypothetical target models using the spectral element method filtered in the period range 60 400 s the selected events are chosen among 273 events used in the development of radially anisotropic model semucb wm1 and recorded at 495 stations worldwide the synthetic z component waveforms correspond to paths and time intervals fundamental mode and overtone rayleigh waves that exist in the real waveform data set the inversions for shear attenuation structure are carried out using a gauss newton optimization scheme in which the gradient and hessian are computed using normal mode perturbation theory the three different misfit functionals considered are based on time domain waveform wf and waveform envelope e wf differences as well as spectral amplitude ratios sa between observed and predicted waveforms we evaluate the performance of the three misfit functional definitions in the presence of seismic noise and unresolved s wave velocity heterogeneity and discuss the relative importance of physical dispersion effects due to 3 d q structure we observed that the performance of wf is poorer than the other two misfit functionals in recovering attenuation structure unless anelastic dispersion effects are taken into account in the calculation of partial derivatives wf also turns out to be more sensitive to seismic noise than e wf and sa overall sa performs best for attenuation imaging our tests show that it is important to account for 3 d elastic effects focusing before inverting for q additionally we show that including high signal to noise ratio overtone wave packets is necessary to resolve q structure at depths greater than 250 km

sea level change glacial rebound and mantle viscosity fornorthern europe northwestern europe remains a key region for testing models of glacial isostasy because of the good geological record of crustal response to the glacial unloading since the time of the last glacial maximum models for this rebound and associated sea level change require a detailed knowledge of the ice sheet geometry including the ice thickness through time existing ice sheet reconstructions are strongly model dependent and inversions of sea level data for the mantle response may be a function of the model assumptions thus inverse solutions for the sea level data are sought that include both ice and earth model parameters as unknowns sea level data from fennoscandia the north sea the british isles and the atlantic and english channel coasts have been evaluated and incorporated into the solutions the starting ice sheet for fennoscandia is based on a reconstruction of a model by denton hughes 1981 that is characterized by quasi parabolic cross sections and symmetry about the load centre both global northwestern europe as a whole and regional subsets of the data solutions have been made for earth model parameters and ice height scaling parameters the key results are as follows 1 the response of the upper mantle to the changing ice and water loads is spatially relatively homogenous across scandinavia the north sea and the british isles 2 this response can be adequately modelled by an effective elastic lithosphere of thickness 65 85 km and by an effective upper mantle viscosity from the base of the lithosphere to the 670 km depth seismic discontinuity of about 3 4 1020 pa s the effective lower mantle viscosity is at least an order of magnitude greater 3 the ice thickness over scandinavia at the time of maximum glaciation was only about 2000 m much less than the 3400 m assumed in the denton hughes model 4 the ice profiles are asymmetric about the centre of the ice sheet with those over the western part being consistent with quasi parabolic functions whereas the ice heights over the eastern and southern regions increase much more slowly with distance inwards from the ice margin

a global tomographic model of shear attenuation in the upper mantle we present a global three dimensional model of shear attenuation in the upper mantle based on the measurement of amplitudes of low frequency 100 300s rayleigh waves observed at stations of the geoscope and iris networks attenuation coefficients are measured on r1 and r2 paths using a method which minimizes the effects of focussing due to propagation in a three dimensional elastic earth through a series of tests which in particular involve the computation of synthetic models of attenuation and focussing we demonstrate that long wavelength lateral variations in attenuation in the first 400 500 km of the mantle can indeed be resolved the model is obtained in a two step procedure the first step consists in the computation of maps of rayleigh wave attenuation at different periods using an inversion method without a priori parametrisation which involves the introduction of a correlation length chosen here at 3000 km to optimize the trade off between resolution and variance in the model in the second step after corrections for shallow structure an inversion with depth is performed assuming lateral heterogeneity is confined to depths between 80 and 650 km the resulting model presents lateral variations in qp that are correlated with tectonic features in particular ridges and shields in the first 250 km of the upper mantle below that depth the pattern shifts and becomes correlated with the hotspot distribution particularly so if the buoyancy strength of hotspots is taken into account two major low velocity zones appear to be located in the central pacific and beneath northern africa in the depth range 300 500 km this pattern seems to continue at greater depth but resolution becomes insufficient below 500 km to draw definitive conclusions the smooth lateral variations retrieved are on the order of 50 down to 400 km we propose an interpretation in terms of plume lithosphere ridge interaction in the upper mantle arguing for deflection of the bulk of hot upwelling material from plumes towards ridges which may be occurring between 200 and 300 km depth

upper mantle seismic wave attenuation effects of realistic partial melt distribution frequency dependence of seismic velocity and attenuation resulting from viscoelastic relaxation of partially molten mantle is estimated we consider the contribution of the melt squirt mechanism through which pressure differences between disk shaped inclusions are equalized by melt passing through connecting tubes the pressure differences arise as a result of shear strain compressing disk shaped pores differently on the basis of disk orientation with respect to the applied shear the frequencies over which the transition from the unrelaxed to the relaxed states occurs are determined by representing the melt as a network of tubes connecting oblate ellipsoidal pores the pressure equalization process is modeled by a system of first order linear differential equations whose eigenvalues are the characteristic frequencies for melt squirt relaxation it is shown that in this framework the set of frequencies is invariant to the absolute scale of the system but is sensitive to melt bulk modulus and viscosity as well as distribution of melt inside pores and conduits use of realistic solid and melt physical properties and pore and conduit geometries demonstrates that it is the relaxed modulus that is most likely excited in the seismic band and that melt mobility has little effect on seismic attenuation some conceivable melt distributions however would result in detectable attenuation in the seismic band in all cases investigated attenuation increases with frequency indicating that melt squirt is not responsible for global upper mantle q observations

seismic observations of large scale deformation at the bottom of fast moving plates abstract we present a new tomographic model of azimuthal anisotropy in the upper mantle dr2012 and discuss in details the geodynamical causes of this anisotropy our model improves upon dkp2005 seismic model debayle et al 2005 through a larger dataset expanded by a factor 3 7 and a new approach which allows us to better extract fundamental and higher mode information our results confirm that on average azimuthal anisotropy is only significant in the uppermost 200 250 km of the upper mantle where it decreases regularly with depth we do not see a significant difference in the amplitude of anisotropy beneath fast oceanic plates slow oceanic plates or continents the anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity it peaks in the asthenosphere around 150 km depth it is very weak for plate velocities smaller than 3 cm yr 1 increases significantly between 3 and 5 cm yr 1 and saturates for plate velocities larger than 5 cm yr 1 plate scale present day deformation is remarkably well and uniformly recorded beneath the fastest moving plates india coco nazca australia philippine sea and pacific plates beneath slower plates plate motion parallel anisotropy is only observed locally which suggests that the mantle flow below these plates is not controlled by the lithospheric motion a minimum plate velocity of around 4 cm yr 1 is necessary for a plate to organize the flow in its underlying asthenosphere the correlation of oceanic anisotropy with the actual plate motion in the shallow lithosphere is very weak a better correlation is obtained with the fossil accretion velocity recorded by the gradient of local seafloor age the transition between frozen in and active anisotropy occurs across the typical age isotherm that defines the bottom of the thermal lithosphere around 1100 c under fast continents mostly under australia and india the present day velocity orients also the anisotropy in a depth range around 150 200 km depth which is not deeper than what is observed under oceans

upper mantle seismic wave velocity effects of realistic partial melt geometries we investigate seismic wave velocity reduction resulting from the presence of partial melt in the upper mantle the amount of shear and bulk modulus reduction produced by the presence of a connected network of realistically shaped and naturally organized melt inclusions is found using finite element calculations the geometries of the inclusions are taken directly from laboratory experiments of mantle melting with finite element meshes constructed to conform to these shapes the shear and bulk moduli of the composite material are found for both the unrelaxed isolated inclusions and relaxed pressure equalized inclusions cases by assigning appropriate material properties to the fluid modulus reduction from deformation simulations of a solid containing realistically shaped and ellipse shaped melt inclusions quantify the effect of melt pocket cuspateness and melt pocket organization on seismic velocity reduction the three dimensional response is estimated from two dimensional distributions of the melt phase by determining the mode ii and mode iii components of elastic modulus reduction separately and summing their effects in general cuspate and naturally organized melt inclusions cause greater velocity reduction it is shown that v and vs reduction per percent partial melt are at least 3 6 and 7 9 respectively even higher values for velocity reduction are possible above 1 melt fraction if melt exists only in tubules below 1 melt fraction the lower more conservative values of velocity reduction are 070 greater for vp and 84 greater for vs than the analytically determined values for ellipsoidal inclusions somewhat greater effects are possible if nonrandom organization of melt occurs on scales greater than our model

seismic attenuation near the east pacific rise and the origin of the low velocity zone abstract low shear wave velocities beneath mid ocean ridges and in the low velocity zone beneath oceanic plates commonly have been attributed to the presence of melt or dissolved water but several recent studies have challenged that interpretation the alternative is that the anelastic effects of increasing temperature may cause the observed drop in velocity along with a predicted increase in attenuation we report the first measurements of surface wave attenuation within regional arrays of seismometers on the seafloor near the east pacific rise there is much less attenuation than is predicted by models in which the velocity is controlled solely by the direct elastic and anelastic effects of changing temperature suggesting that melt and water concentration do play an important role there also is somewhat less attenuation than is found in global studies we speculate that scattering from unresolved velocity heterogeneities contribute to the apparent attenuation in global studies

back analysis of a seismically induced highway embankment failure during the 1999 duzce earthquake an earthquake of magnitude 7 2 on the richter scale occurred on 12 november 1999 in the duzce bolu region of turkey the region was also hit approximately 3 months before during the devastating kocaeli earthquake of 17 august 1999 besides high casualties and damage to various engineering structures and buildings slope and embankment failures on the highway and the country roads occurred in this study the authors are concerned with the back analysis of an embankment failure that occurred on the four lanes e 5 highway connecting ankara to istanbul at bakacak in the bolu province during the 1999 duzce earthquake both pseudo dynamic and dynamic limiting equilibrium methods are used to back analyse the conditions for the initiation of failure and also displacement responses of the embankment during the earthquake shaking after having given a brief summary of the investigations on the post failure state the geology and geotechnical characteristics of the site and the dynamic limiting equilibrium method developed and used for analyses are described the results of the back analysis based on a pseudo dynamic approach revealed that the maximum ground acceleration to initiate the failure of the embankment was probably about 0 125 g on the other hand the application of a method for computing the displacement and velocity responses of the failed embankment showed that the failure was possible when the embankment was subjected to ground accelerations similar to that recorded at the duzce station in addition the computations also revealed that the time history of accelerations could be very important for the failure of slopes and embankments

is there seismic attenuation in the mantle article history the small scale heterogeneity of the mantle is mostly due to the mixing of petrological heterogeneities by a smooth but chaotic convection and should consist in a laminated structure marble cake with a power spectrums k varying as 1 k w herekis the wavenumber of the anomalies this distribution of heterogeneities during convective stirring with negligible diffusion called batchelor regime is documented by fluid dynamic experiments and corresponds to what can be inferred from geochemistry and seismic tomography this laminated structure imposes density seismic velocity and potentially anisotropic heterogeneities with similar 1 kspectra a seismic wave of wavenumberk 0 crossing such a medium is partly reflected by the heterogeneities and we show that the scattered energy is proportional tok 0 s 2k 0 t he reduction of energy for the propagating wave appears therefore equivalent to aq uality factor 1 q k 0 s 2k 0 w ith the specif ic 1 kspectrum of the mantle the resulting apparent attenuation should therefore be frequency independent we show that the total contribution of 6 9 rms density velocity and anisotropy would explain the observed s and p attenuation of the mantle although these values are large they are not unreasonable and we discuss how they depend on the range of frequencies over which the attenuation is explained if such a level of heterogeneity were present most of the attenuation of the earth would be due to small scale scattering by laminations not by intrinsic dissipation intrinsic dissipation must certainly exist but might correspond to a larger yet unobservedq this provocative result would explain the very weak frequency dependence of the attenuation and the fact that bulk attenuation seems negligible two observations that have been difficult to explain for 50 years

a global shear velocity model of the upper mantle from fundamental and higher rayleigh mode measurements we present dr2012 a global sv wave tomographic model of the upper mantle we use an extension of the automated waveform inversion approach of debayle 1999 which improves our mapping of the transition zone with extraction of fundamental and higher mode information the new approach is fully automated and has been successfully used to match approximately 375 000 rayleigh waveforms for each seismogram we obtain a path average shear velocity and quality factor model and a set of fundamental and higher mode dispersion and attenuation curves we incorporate the resulting set of path average shear velocity models into a tomographic inversion in the uppermost 200 km of the mantle sv wave heterogeneities correlate with surface tectonics the high velocity signature of cratons is slightly shallower approximate to 200 km than in other seismic models thicker continental roots are not required by our data but can be produced by imposing a priori a smoother model in the vertical direction regions deeper than 200 km show no velocity contrasts larger than 1 at large scale except for high velocity slabs within the transition zone comparisons with other seismic models show that current surface wave datasets allow to build consistent models up to degrees 40 in the upper 200 km of the mantle the agreement is poorer in the transition zone and confined to low harmonic degrees 10

surface fault breaks aftershock distribution and rupture process of the 17 august 1999 izmit turkey earthquake the results obtained from field studies of surface fault breaks on land aftershock studies and analysis of complex teleseismic body waves of the 17 august 1999 izmit earthquake m w 7 4 indicate that the northern strand of the north anatolian fault zone had been ruptured between 29 1 e and 31 1 e with a maximum total fault rupture length of about 200 km the 12 november 1999 duzce earthquake m w 7 2 extended the surface fault break an additional 41 km to the east alignment of the aftershocks delineates the fault rupture on land and extends it to the west of the hersek delta well into the marmara sea to 29 1 e longitude we have identified six fault rupture segments two of them are located to the west of the hersek delta and four are located to the east rupture process analysis suggests two stages of rupture separated in space and time with an estimated total scalar seismic moment of 2 42 1020 n m the first stage initiated at the epicenter near izmit and propagated asymmetrically first eastward and then westward with a total scalar moment of 1 6 1020 n m showing predominantly right lateral strike slip faulting followed by a minor subevent extending the rupture further east the second stage took place at the western and eastern ends of the source area rupturing two segments within the marmara sea west of the hersek delta and two segments between akyazi and golyaka the rupture process analysis indicates that six fault segments were ruptured during the mainshock four of them on land and two within the marmara sea the major moment release of 1 2 1020 n m is found on the 64 km long sapanca segments located between the easternmost tip of the gulf of izmit and akyazi with an estimated maximum slip of 5 3 m the moment release on the golcuk segment with a length of 30 km is about 3 7 1019 n m and the estimated slip on this segment is 4 1 m rupture process analysis suggests two 20 km long segments between akyazi and golyaka striking n70 e the scalar moment releases on these segments are 2 7 1019 and 1 9 1019 n m with estimated offsets of 2 2 and 1 6 m respectively the last two subevents took place to the west of the hersek delta on the yalova segment and within the marmara sea with estimated offsets of 1 3 and 1 0 m respectively manuscript received 20 august 2000

stagnant slab wet plumes and cenozoic volcanism in east asia abstract data from seismology and mineral physics indicate the existence of low velocity zones in the deep part of the upper mantle wedge and the mantle transition zone under east asia zhao and ohtani 2009 zhao et al 2009 it suggests a link between the deep subduction and stagnation and deep dehydration of the pacific slab below this area and the cenozoic volcanism observed at the surface here we present a numerical model describing the dynamics of a hydrated layer covering a slab that is stagnating in the earth tm s mantle transition zone specifically our model includes the effects of water on density and viscosity of the mantle minerals we conclude that the presence of water is likely to induce rayleigh taylor type instabilities wet plumes that are able to transport water up to the base of the surficial lithosphere in a relatively short time scale a few million years under initial conditions representative of the subducting pacific slab under east asia melting is induced where wet plumes reach the base of the lithosphere according to our results and analysis of the known composition of cenozoic basalts from southwest japan iwamori 1991 iwamori 1992 wet plumes and their melting induced by water related to the stagnant slab provides an appealing hypothesis to explain cenozoic volcanism in east asia

a comparison of vlbi data with the ice 3g glacial rebound model crustal motion predicted by the ice 3g glacial rebound model exhibits a pattern of tangential horizontal divergence away from the centres of uplift which in north america and europe are located around hudson bay and the gulf of bothnia tangential velocities reach peak magnitudes of 1 2 mm yr and must be included when predicting very long baseline interferometry vlbi baseline length change rates due to post glacial rebound out of 18 observed vlbi baselines examined 3 are situated such that their predicted length rates are around their 2 uncertainties or greater it is encouraging that 2 of these baselines exhibit predicted length rates within 2 of the observed rates

geometric effects of global lateral heterogeneity on long period surface wave propagation long period rayleigh waves from iranian earthquakes have large amplitude asymmetries between minor arc and major arc arrivals e g r 2 and r 3 at digital stations in the azimuth range n20 w to n60 e these asymmetries are as large as a factor of 2 at a period of 256 s and persist to periods greater than 300 s in some cases the entire rayleigh wave group arrival spanning periods from 100 to 300 s is either uniformly enhanced in amplitude or diminished to such a degree that the group arrival appears to be missing the amplitude anomalies are generally not accompanied by significant phase anomalies the irregular azimuthal distribution of the amplitude asymmetries and their occurrence for events with different focal mechanisms and epicentral separations of several hundred kilometers preclude an explanation of these observations by source complexity events in the mediterranean and nepal do not produce similar amplitude asymmetries at the same stations the anomalies are thus most likely due to focusing and defocusing propagation effects as a preliminary investigation of the effects of lateral heterogeneity of upper mantle velocity structure on long period surface wave amplitudes surface wave ray tracing calculations are performed using recently proposed global phase velocity distributions dramatic deviations from great circle paths are predicted for long propagation paths e g r 3 the particular spatial distribution of lateral velocity gradients around a given source location determines whether substantial amplitude asymmetries will be observed between minor arc and major arc arrivals and whether these will persist for sequential great circle orbits the 200 s period amplitude asymmetry observed at kip for the iranian source region r 2 4 r 3 is well predicted by the ray tracing results the absence of this anomaly for the other source regions is also predicted other observed anomalies are not all well predicted but it is clear that geometric effects can contribute significantly to the observed variations of rayleigh and love wave amplitudes this is the probable explanation for the instability of q estimates made from surface waves other source regions producing large surface wave amplitude anomalies include japan and southeastern alaska

mapping lateral variations in upper mantle attenuation by stacking p and pp spectra 1 we study the lateral variations in p wave attenuation in the upper mantle at frequencies between 0 16 and 0 86 hz by analyzing the spectra from 18 000 p and 14 000 pp arrivals we select seismograms from shallow earthquakes at epicentral distances of 40 80 for p waves and 80 160 for pp waves each spectrum is the product of source receiver and propagation response functions as well as local source and receiver side effects we correct each spectrum for average source and attenuation models since there are multiple receivers for each source and multiple sources for each receiver we can approximate the source and receiver side terms by stacking the appropriate p log spectra the resulting source specific response functions include any remaining source spectrum and near source q structure the receiver stacks include the site response and near receiver q structure we correct the pp log spectra for the appropriate source and receiver side stacks since attenuation in the lower mantle is small the residual log spectrum approximates attenuation in the upper mantle near the pp bounce point and is used to estimate we constrain the anomalies to the top 220 km of the mantle as suggested by previous q studies and translate the measurements to variations in 1000 q the patterns of more and less attenuating regions generally correlate with previously published shear attenuation models and surface tectonics continents are usually less attenuating than the global average whereas oceanic regions tend to be more attenuating there are interesting exceptions to this tectonic pattern such as an attenuating region beneath southern africa

ice 3g a new global model of late pleistocene deglaciation based upon geophysical predictions of post glacial relative sea level change a new high resolution global model of late pleistocene deglaciation is inferred on the basis of geophysical predictions of postglacial relative sea level variations in which the ice ocean solid earth interaction is treated in a gravitationally self consistent fashion for the purpose of these analyses the radial viscoelastic structure of the planet is assumed known on the basis of previously published sensitivity tests on solutions of the forward problem only radiocarbon controlled relative sea level histories from sites that were actually ice covered with one or two additions are employed to constrain the model leaving relative sea level rsl data from sites that were not ice covered to be employed to confirm its consistency results for these confirmatory analyses are reported elsewhere here the new deglaciation model referred to as ice 3g is compared to previous models derived by several independent means and tested against a number of additional observations other than sea level histories including geologically controlled retreat isochrones oxygen isotope data from deep sea sedimentary cores and coral terrace elevations the latter two observations strongly constrain the net sea level rise that has occurred since the onset of deglaciation and therefore the mass of ice that melted during the last glacial interglacial transition

multimode surface waveform tomography of the pacific ocean a closer look at the lithospheric cooling signature summary we present a regional surface waveform tomography of the pacific upper mantle obtained using an automated multimode surface waveform inversion technique on fundamental and higher mode rayleigh waves to constrain the vsv structure down to 400 km depth we have improved on previous implementations of this technique by robustly accounting for the effects of uncertainties in earthquake source parameters in the tomographic inversion we have furthermore improved path coverage in the south pacific region by including rayleigh wave observations from the french polynesian pacific lithosphere and upper mantle experiment deployment this improvement has led to imaging of vertical low velocity structures associated with hotspots within the south pacific super swell region we have produced an age dependent average cross section for the pacific ocean lithosphere and found that the increase in vsv with age is broadly compatible with a half space cooling model of oceanic lithosphere formation we cannot confirm evidence for a pacific wide reheating event our synthetic tests show that detailed interpretation of average vsv trends across the pacific ocean may be misleading unless lateral resolution and amplitude recovery are uniform across the region a condition that is difficult to achieve in such a large oceanic basin with current seismic stations

the upper mantle degree 2 constraints and inferences from global mantle wave attenuation measurements we present the results of an analysis of global lateral variations in anelasticity of the upper mantle as measured from very long period rayleigh waves observed on the geoscope network four consecutive wave trains are used on each record to eliminate uncertainty on the amplitude at the source and to take into account in a linear manner focussing effects due to lateral variations in elastic parameters local estimates of attenuation are obtained using an inversion method based on the introduction of a correlation length as an alternative to spherical harmonics expansion comparison of phase velocity and attenuation maps obtained at various periods shows a strong correlation of high q and high velocity regions respectively low q and low velocity both for great circle and minor arc data at periods around 200 s the detailed analysis of the degree 2 pattern well resolved in the attenuation maps around this period shows that it originates in the depth range 250 500 km and indicates that of the upper mantle degree 2 pattern observed in shear velocity is likely to be of thermal origin possibly related to the topmost part of the large scale convective system corrections for dispersion due to anelastic attenuation in degree 2 lead to significant decrease of corresponding lateral variations in shear velocity and a better agreement in phase and amplitude of the upper mantle degree 2 pattern with that observed in the geoid this study shows that it is important to consider correcting presently available upper mantle tomographic models for the effects of intrinsic attenuation at long periods before performing any comparison with short period data or other geophysical parameters

the global attenuation structure of the upper mantle 1 a large data set of fundamental mode rayleigh wave amplitudes is analyzed to derive a new global three dimensional model of shear wave attenuation in the upper mantle the amplitude observations span a range of periods between 50 and 250 s and are derived from earthquakes with mw 6 0 that occurred between 1993 and 2005 four separate factors may influence an amplitude anomaly intrinsic attenuation along the raypath elastic focusing effects along the raypath uncertainties in the strength of excitation and uncertainties in the response at the station in an earlier paper dalton and ekstrom 2006a dependence of the retrieved attenuation structure on these terms was shown to be significant and an approach was developed to invert the amplitudes simultaneously for each term the new three dimensional attenuation model qrfsi12 which is the subject of this paper is derived using this method the model contains large lateral variations in upper mantle attenuation 60 to 100 and exhibits strong agreement with surface tectonic features at depths shallower than 200 km at greater depth qrfsi12 is dominated by high attenuation in the southeastern pacific and eastern africa and low attenuation along many subduction zones in the western pacific resolution tests confirm that the change in pattern of attenuation above and below 200 km depth can be determined with confidence using the fundamental mode data set the new model is highly correlated with global models of shear wave velocity particularly in the uppermost mantle suggesting that the same factors may control both seismic attenuation and velocity in this depth range however forcing the lateral perturbations in attenuation to match those found in global velocity models decreases the data variance reduction which suggests that subtle differences between patterns of attenuation and velocity are robust

waveform inversion using secondary observables a new method is proposed for inverting single station surface wave seismograms instead of inverting directly the time signal use is made of secondary observables built up from a set of time frequency images this allows us to enhance the signal to noise ratio and to make more linear the relationship between the model parameters and the inverted observables the feasibility of the method is checked on multimode synthetics prior to present the inversion of a long period multimode seismogram related to the pacific ocean

even degree lateral variations in the earth s mantle constrained by free oscillations and the free air gravity anomaly the recent occurrence of several large earthquakes in particular the 1994 june 9 bolivia event has motivated a re examination of the earth s large scale heterogeneity from a normal mode or free oscillation perspective compared to earlier studies the number of normal mode constraints on lateral variations in the mantle has increased five fold and toroidal and cross coupled modes complement the traditional spheroidal mode data set it is demonstrated that this large collection of mode data combined with the free air gravity anomaly can reliably constrain even degree lateral variations in wave velocities as well as density we present the first whole mantle density model constrained by seismology our shear and compressional velocity models are consistent with existing models based upon traveltimes and waveforms and are reasonably well correlated throughout the mantle shear and bulk sound velocity models exhibit a gradual decrease in correlation with depth and are anti correlated near the core mantle boundary we find that lateral variations in density are poorly correlated with wave velocities and are locally anti correlated with shear velocity in the lowermost mantle the correlations between wave velocities and density suggest both a thermal and a compositional origin to lateral heterogeneity in addition to traditional maps of lateral variations in wave velocity we also present maps of lateral variations in shear and bulk moduli the inversion puts weak constraints on even degree topographic variations on the core mantle boundary the 660 km discontinuity and dynamic free surface topography finally we determine both radially and laterally varying scaling relationships including poisson s ratio

present day post glacial sea level change far from the late pleistocene ice sheets implications for recent analyses of tide gauge records we examine the sensitivity of predictions of the present day rate of sea level change due to glacial isostatic adjustment gia in two regions located within the far field of the late pleistocene ice sheets europe north africa and the western pacific caribbean to variations in the mantle viscosity profile the regions considered here encompass the location of 11 of 21 sites used in a recent determination based on gia corrected tide gauge records of the global rate of secular sea level change our analysis suggests that the mean gia correction at the 11 far field sites may vary by as much as 0 5 mm yr depending on the adopted earth model and we derive a bound on the residual secular sea level rise of 1 1 to 1 6 mm yr this bound is consistent with our analysis of the tide gauge record from the u s east coast and it suggests that previous estimates of the residual sea level rise represent an upper bound