a study of mantle layering beneath the western pacific the reverberative interval of the seismogram defined as the portion following the surface wave train propagating along the minor arc and ending with the first body wave arrivals from the major arc provides an excellent window in which to observe subcritical reflections from mantle discontinuities on an sh polarized seismogram the intervals between scsn and sscsn wave groups zeroth order reverberations are approximately 15 min long and consist almost entirely of waves reflected one or more times from mantle discontinuities first and higher order reverberations we have developed signal enhancement and waveform inversion schemes to progressively extract information pertaining to mantle layering from the waveforms of zeroth and first order reverberations and have applied them to a data set of long period digital seismograms drawn from a number of tectonic regions in and around the western pacific the results place important constraints on the nature of the transition zone discontinuities measurements of the two way vertical shear wave travel time from the free surface to the 400 km and 650 km discontinuities 400 and 650 respectively yield estimates of transition zone travel time tz largely uncontaminated by outside heterogeneity variations in the path averaged estimates of tz are of the order of 5 4 s indicating significant lateral heterogeneity in the transition zone correlations of tz with 400 and lm travel time through the lower mantle are consistent with but do not require the thermal deflection of an exothermic phase transition near 400 km and an endothermic transition at 650 km with 12 km of long wavelength 500 5000 km topography on each the amount of topography estimated for the 650 km discontinuity is significantly less than predicted for a rigorously stratified mantle 100 km in a search for other mantle discontinuities we find evidence for a strong reflector possibly associated with the onset of partial melting in the upper mantle average depth of 86 km due to ambiguity inherent to the method this feature can also be interpreted as an impedance increase in the d region of the lower mantle 70 170 km above the core mantle boundary no evidence is found for a 220 km discontinuity or the d discontinuity proposed by lay and helmberger 1983 suggesting that if such features are present in the western pacific they are either small normal incidence sh reflection coefficient r 1 5 or intermittent or have lateral depth variations well in excess of 50 km

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

comparison of the quaternary travertine sites in the denizli extensional basin based on their depositional and geochemical data abstract in the denizli basin turkey located in the western anatolian extensional province travertine and tufa deposition has been an ongoing process for at least 600 000 years travertine bodies which are 30 to 75 m thick and each covers areas of 1 to 34 km2 are up to 1 km3 in volume today spring waters in this area have temperatures of 19 to 57 c are of the ca mg hco3 so4 type in the pamukkale kelkaya and pinarbasi areas and the ca mg so4 hco3 type at cukurbag thermal waters along the northern margin of the basin are generally hotter than those in the east southeast and south the 18o and d values of the spring waters indicate a meteoric origin the average temperatures of the hydrothermal systems in the denizli basin appear to have decreased from pleistocene to holocene travertine which formed from the hotter water is more widespread than the tufa that formed in the cooler spring waters deposition of the travertine which formed largely on slopes in depressions and along fissure ridges mostly on northern basin margins was controlled by the interplay between various intrinsic and extrinsic parameters the travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded crystalline crust raft and pisoid travertines found in some of the northern sites the aragonitic samples rich in sr are typically found around the spring orifices and along the central axis of the fissure ridges the stable isotope values of the travertine found in the northwest and southeast parts of the basin are different the 13c values of the northern travertine deposits are more positive 3 7 to 11 7 vpbd than those found in the south southeast areas 4 to 5 8 vpdb in contrast the travertine and tufa in the southeastern areas have higher 18o values 15 2 to 7 8 vpdb than those of the northern areas 16 6 to 4 8 vpdb available evidence indicates that spring activity and associated travertine precipitation in the denizli basin were controlled largely by tectonic activity rather than by climatic conditions

global anisotropy in the upper mantle inferred from the regionalization of phase velocities a data set of 2600 paths for rayleigh waves and 2170 paths for love waves was selected in order to resolve azimuthal anisotropy of surface waves in the period range 70 250 s the epicenters were chosen so that the paths provide uniform spatial and azimuthal coverage of earth a synthetic seismogram is computed for each path and compared to the observed seismogram in order to infer the phase velocity along each path to process such a large data set a new tomographic technique is designed a good correlation is found with surface tectonics in the whole period range for love waves and at shorter periods for rayleigh waves the directions of maximum velocities are also well correlated with plate tectonics motions for the 2 azimuthal term of rayleigh waves when the power spectrum of heterogeneities is computed it is found that for love waves the even orders are usually larger than the odd orders for rayleigh waves the degrees 2 and 6 dominate only at long periods suggesting a deep origin for these components

origin of the anomalies of gravity and its vertical gradient over cavities in brittle rock investigations show that the depth range of the gravity method for detecting cavities is considerably greater than expected on the basis of theoretical calculations that consider only the depth and shape of the cavity the cavity generates its own gravity field that is the sum of the activity of the cavity itself and the density changes caused in the surrounding rocks by the process of their destruction as a result of the cavity s expansion the latter factor is decisive for the cavity s detection by the gravity method in several cases the extent of the zones of change density in the surrounding rocks and their actual shape depend on many parameters thus the determination of the depth of the cavity cannot be made by comparing measured and theoretical curves of gravity anomalies the location of the center of gravity of the area disturbed by the cavity or upper boundary of its development towards the ground surface can be determined by denoting the singular point of gravity as a result of the downward analytical continuation of ag the strakhov grigorieva lapina 1977 method fulfils the necessary conditions in the field

attenuation tomography of the earth s mantle a review of current status resolving the lateral variations of attenuation in the deep mantle by tomographic methods holds potential for constraining its thermal structure and dynamics it is a challenging subject which has been addressed by only a few studies until now we here review the main motivations behind pursuing this challenge the difficult issues involved in separating effects of anelastic attenuation from scattering and focusing due to propagation in 3 d elastic structure and finally discuss the current status of global attenuation tomography

induced gravity anomalies and seismic energy as a basis for prediction of mining tremors the results of prediction of occurrence of mining tremors and bursts in the course of the exploitation of the remaining part of the hard coal in seam 510 of the mine pstrowski upper silesia have been presented in the paper the exploitation has taken place under extremely difficult conditions hazardous for the mining crew

the upper mantle degree two pattern constraints from geoscope fundamental spheroidal mode eigenfrequency and attenuation measurements we have analyzed fundamental spheroidal mode spectra obtained from very long period geoscope records in terms of global distribution of eigenfrequencies and attenuation with a new data set and a different data processing approach involving time variable filtering and the removal of higher order effects in the spectra we confirm the strong upper mantle degree two signature in the eigenfrequency data the higher frequency content of the geoscope spectra allows us to put better constraints on the depth range at which this pattern originates which appears to be somewhat shallower than was proposed before while some effect may persist down to the bottom of the transition zone the frequency signature of the strongest degree two pattern requires an s velocity heterogeneity concentrated in the depth range 300 500 km and this signature is also apparent in the distribution of q which is indicative of a probable thermal origin the data also resolve a shallow degree 2 pattern well explained by heterogeneity spanning from the surface to depths of about 300 km and associated with the distribution of tectonic provinces it is shifted by about 45 with respect to the deep degree 2 pattern and its expression in the q data is not clear

paleoseismic evidence of legendary earthquakes the apparition of archangel michael at monte sant angelo italy abstract the gargano promontory a carbonate massif belonging to the adria microplate the foreland of both the apenninic and dinaric mountain chains is a well known seismogenic area with historic earthquake up to i max x mcs july 30 1627 m 6 7 nevertheless paleoseismic data on the region are still scarce and no trench fault stratigraphy has been analysed along the major e w trending right lateral strike slip fault system that cuts through the whole massif the south gargano line sgl the over 60 km long on shore trace of the sgl the mattinata fault is clearly segmented this study focused on the eastern active fault segment the monte sant angelo fault msa to verify the associated seismic potential analysis of contemporary descriptions of the august 10 1893 earthquake m 5 2 coupled with field work allowed identification of surface faulting along the msa along the fault there is paleoseismic evidence of the occurrence of larger earthquakes after collecting geomorphic evidence of paleo earthquakes we selected two trench sites at the base of two prominent fault escarpments where the msa is characterized by significant vertical components of fault displacement the preliminary results demonstrate that i the recent vertical slip rate of the msa range between 0 2 0 3 and 0 7 mm yr ii the msa moves with incremental slip episodes with vertical surface offset up to several decimeters iii based on the stratigraphic and geomorphic evidence of surface faulting observed and assuming a rupture length of around 20 km the seismic potential of the msa segment would be similar to that displayed by the western sgl segment during the 1627 event a large earthquake on the msa is reported only in ancient legends the most relevant of which being the one describing the apparition of archangel michael at monte sant angelo traditionally dated ad 493 using a multidisciplinary approach combining paleoseismic and historical data it has been possible to interpret the legend and hereby identify an event of surface faulting before 8th century ad a recent scarplet up to 1 m high on the msa can be seen to be related to this legendary earthquake which in turn seems to correspond to the maximum possible magnitude geologic phenomena observed during the earthquake at the site of the sanctuary appear to lie at the very origin of the veneration of the place

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

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

origin and evolution of the thermal waters from the pamukkale geothermal field denizli basin sw anatolia turkey insights from hydrogeochemistry and geothermometry abstract the pamukkale geothermal field pgf of the denizli basin sw turkey is one of the most distinguished active geothermal fields known in the world the thermal waters from the pgf are subdivided into two groups group 1a ca hco3 and group 1b ca so4 types the cold waters are also classified into two groups group 2a ca hco3 and group 2b mg hco3 types the hydrogeochemical properties of the pgf thermal waters suggest interactions with the basal metamorphic rocks of the menderes massif tectonically overriding by the carbonate rocks of the lycian nappes and sedimentary rocks of the neogene formations the bedrock units are stratigraphically overlain by the neogene sedimentary units of the denizli group the thermal springs of the pgf are affected by several hydrothermal processes including mixing water rock interaction and input of mantle volatiles the thermal water plots of the pgf deviate from the full equilibrium line indicating a low water maturity and or mixing processes mixing models and na k mg ternary diagram suggest mixing between meteoric and thermal waters during the uprising of the deep originated fluids the water rock interaction leads saturation of calcite and induces travertine precipitation in the discharge area low tritium this study proposes a conceptual hydrogeological hydrogeochemical tectonic model for the pgf the thermal waters are derived from the infiltration of rainwater through fractures and faults in high recharge areas to the deep hot reservoir heating produced by the high geothermal gradient is interpreted in relation with the regional crustal thinning thermal waters upwell along wnw ese trending deep faults and fractures the pamukkale fault system that act as hydrothermal pathways favouring migration of a huge amount of co2 rich gas from deep geothermal reservoir the geochemical and isotopic data of the thermal waters and gas indicate that the degassing of both metamorphic co2 and mantle derived co2 occurs in the pgf helium isotope data indicate that mantle volatiles produce possibly an upwelling into asthenosphere and ascent along these tectonic discontinuities in this context the pgf is one of the best example of geothermal fields as an interaction of active magmatism in the actively extending crustal setting

mantle layering from scs reverberations 2 the transition zone this is the second paper in a four part sequence that examines the nature of mantle layering using the scsn phases and internal reflections observed within the reverberative interval of sh polarized seismograms mantle reflectivity profiles for 18 seismic corridors sampling portions of indonesia australia and the western and central pacific are constructed from low frequency 25 mhz scs reverberations i e scsn type phases reflected once from internal mantle discontinuities modeling the reflectivity profiles using synthetic seismograms yields precise path specific estimates of the travel times to the 410 km and 660 km discontinuities and their reflection coefficients the data are consistent with an olivine dominated model of the transition zone marked by two major phase transitions having average apparent depths of 414 2 km and 660 2 km and impedance contrasts of 0 046 0 010 and 0 072 0 010 respectively the interpath variations observed in the reverberation travel times imply that the topography on the two discontinuities is of the order of 20 km peak to peak and is negatively correlated consistent with an endothermic transition at 660 km whose clapeyron slope magnitude is comparable to that of the 410 km exothermic transition in the case of the 660 km discontinuity we have been able to supplement these long wavelength 1500 5000 km observations with an estimate of intrapath topography inferred from the frequency dependence of the 660 km reflection coefficient which gives peak to peak variations less than 40 km on scale lengths of 500 1500 km for the 660 km discontinuity the observed topography is significantly less than the dynamic topography expected for a simple compositional interface in regions of subduction however we do observed an intriguing negative correlation between the apparent depth and the reflection coefficient of the 660 km discontinuity which may involve small compositional variations plausible explanations for this correlation include heating of an initially cool chemical boundary layer gravitationally trapped above an endothermic phase transition loss of reflected energy due to local curvature or roughness of the reflector and or extreme topography occurring on a small compositional component to the discontinuity 40 of the total impedance contrast by stripping the 410 km and 660 km peaks from the composite path reflectivity profile we identify three minor reflectors at mean depths of 520 710 and 900 km the shallowest may mark the phase spinel phase transition the 710 km discontinuity can be attributed to the ilmenite gamet perovskite phase transition although changes in perovskite symmetry can potentially provide explanations for both the 710 km and 900 km features

induced gravity anomalies and rock burst risk in coal mines a case history1 the use of the gravity method to predict rock bursts in mines is based on the relationship between the development of a dilatancy process in the exploited rock mass and the time dependent gravity anomalies induced by this phenomenon the differences between successive observations of anomalies and the time behaviour of their trend amplitudes as precursors of preceding changes of rock stability are interpreted the centres of zones of induced rock density variation are determined by computing the position of singular points of the differences between anomalies two gravity surveys have been carried out in the radbod coal mine germany the first survey took place at the level of the dickebank seam depth 1030 m the second in the sonnenschein seam depth 1090 m the observations were made with worden and lacoste romberg d type gravimeters the differences between successive anomalies were less than 100 gal in the case of the dickebank seam the position of singular points demonstrates the effect of two approaching longwalls on a previously mined out seam and on the gallery in which the gravity observations were made in the case of the sonnenschein seam the trend amplitudes show distinct variations in the formation of the approaching longwall below the edges of all previously mined out seams in particular the effect of a remnant pillar has caused the largest gravity gradients this result corresponds to the existence of a zone of rock burst hazard known from test drilling the computed singular points are grouped together under the remnant pillar indicating two local hazard zones both results the observed development of rock instability with time and the information about the position of the disturbed rock mass relative to the mine workings are of importance subsurface gravity surveying can therefore be a valuable tool for predicting rock bursts

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

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

test of tectonic models by great circle rayleigh waves summary a large set of published great circle rayleigh wave phase velocities in the period range 125 350s is used to compare three recent tectonic models okal leveque jordan prior to any regionalization the symmetry property of the great circle integrals is used to obtain a lower limit of the signal noise ratio in the data it turns out that the signal is responsible for at least 30 per cent of the data variance in the period range 175 300s a standard regression method is applied for computing the pure path velocities and the model efficiency is derived from a variance analysis it is shown that even at great depth none of the three models explains more than 60 per cent of the energy due to the long wavelength lateral heterogeneities 6500 km the three models have nearly the same efficiency for explaining the short period data t 125s between 200 and 300s the higher performance of okal s model indicates that it is important to separate the subduction zones from the other orogenic zones by perturbing the lateral extension of the subduction zones it comes out that they constitute on both sides of the subducting slabs wider anomalies than often assumed suggesting large downgoing flows on the contrary the effect of surface features such as marginal seas are restricted to a close region in front of the trenches finally the anomalous ellipticity values deduced directly from great circle data are partly explained by a coupling between tectonics and ellipticity

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

the effects of the theoretical formalism and data selection on mantle models derived from waveform tomography summary most global tomographic models to date are derived using a combination of surface wave or normal mode data and body wave traveltime data the traveltime approach limits the number of phases available for inversion by requiring them to be isolated on the seismogram this may ultimately result in limiting the resolution of 3 d structure at least in some depth ranges in the mantle in a previous study we successfully derived a degree 12 whole mantle sh velocity tomographic model saw12d using exclusively waveform data in that inversion a normal mode formalism suitable for body waveforms the non linear asymptotic coupling theory nact was combined with a body wave windowing scheme referred to as the individual wavepacket iw technique which allows one to assign individual weights to different body wave energy packets we here compare the relative merits of this choice of theoretical formalism and windowing scheme at different depth ranges in the mantle choosing as the reference a model obtained using 7500 transverse component body wave and 8000 surface wave seismograms and the nact and iw approaches we discuss the relative performance of the path average approximation pava a zeroth order theoretical approximation appropriate for single mode surface waves relative to nact and compare the iw windowing scheme with a more standard full window fw approach in which a single time window is considered from the first body wave arrival to the fundamental mode surface waves the combination pava fw is often used in global tomography to supplement the traveltime data we show that although the quality of the image derived under the pava fw formalism is very similar to that derived under nact iw in the first 300 km of the upper mantle where the resolution is dominated by surface waves it deteriorates at greater depths images of the lower mantle are shown to be strongly sensitive to the theoretical formalism in contrast the resolution of structure near the core mantle boundary depends mostly on the windowing scheme this is because this resolution is controlled by low amplitude phases such as sdiff which are downweighted in the fw scheme whilst the image obtained in d using the combination nact iw is in good agreement with images obtained by other authors using both waveforms and traveltimes we show that when using fw uppermost mantle structure can be mapped into d this result is confirmed by synthetic tests performed on a composite of the upper mantle geodynamic model 3smac we also show based on synthetic tests that for structures in the upper mantle with sharp boundaries differences are observed between nact and pava whilst a combination of traveltimes and surface wave data is adequate for resolving relatively smooth features in the mantle our results show that by potentially increasing the achievable sampling the waveform approach shows great promise for future high resolution tomographic modelling of mantle structure if cast in an appropriate theoretical framework

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

upper mantle structure from long period differential traveltimes and free oscillation data summary we have performed an inversion to model upper mantle structure using ss s differential traveltime residuals in conjunction with previously reported structure coefficient estimates obtained from free oscillation frequency and attenuation measurements the model we obtain is consistent with both the differential traveltime and structure coefficient data sets and provides nearly the same level of fit as independent inversions of these data sets we find that a relatively simple model parametrization appears to be adequate for the data used upper mantle velocity perturbations and lateral variations in the radii of boundaries at 400 and 670 km depth are parametrized with spherical harmonic expansions up to degree and order 8 the expansions are fixed at specific depth knots separated by roughly 200 km spanning the range 20 670 km radial variations in velocity are obtained by linear interpolation between these depth knots smoothness constraints were applied as part of the inversion procedure as well as corrections for the thickness and velocity variations of the crust the smoothness constraints were adjusted to require a smoother structure in the bottom portion 400 to 670 km depth of the model where the structure coefficients have the greatest sensitivity the upper part of the model is primarily constrained by the differential traveltime data the resulting misfit of the final model shows that on average the individual structure coefficients and ss s measurements are fit to within approximately 1 5 standard deviations we suggest that some of the misfit is due to lower mantle structure which is not included in the modelling the power as a function of harmonic degree for the top portion of the model 20 to 220 km depth does not fall off significantly at the higher harmonic degrees suggesting that the differential traveltime data may require models which include structure for degrees greater than 8 boundary perturbations at depths of 400 and 670 km trade off strongly with the velocity variations allowing variations of the order of f10 km in the radii of the discontinuities at 400 and 670 km provides a slight improvement to the data fit comparisons of several depths of our upper mantle velocity model to the geoid show the strongest correlation at degree 2 for structure near 670 km depth the distribution of slab structures is highly correlated to the degree 2 components of the model for depths of 200 to 670 km examination of the model in the vicinity of hotspots shows no consistent hotspot related signal

scent of a myth tectonics geochemistry and geomythology at delphi greece extensive geochemical investigation of water travertine soil and diffuse gas coupled with geo structural analysis provides new insights into local fault fluid interaction and allows us to pinpoint basic elements in the geological origin or geomythology of the delphic oracle still debated by geologists delphi hosted the most famous oracle of antiquity supposed to prophesy under the effects of intoxicating gas exhaling from a chasm in the ground co 2 h 2 s rich ethylene rich or ch 4 rich gases have been invoked to explain the mantic vapours although previous interpretations dismissed the results achieved by classical scholars this study fits together history archaeology mythology and geology in a single coherent frame we highlight that no hydrocarbon gas discharges are released at present to the surface in the area the lack of any geochemical anomaly indicates that the delphi active fault does not at present constitute a preferential route for the circulation of thermogenic deep fluids the mythological gas exhaling chasm can plausibly be related to episodic seismic ruptures in the ancient past which affected for a limited time gas pockets fed by a relatively deep confined hydrothermal system the delphi fault has produced shocks up to ms 6 7 1 august 1870 and similar seismic faulting events in the past could have episodically triggered co 2 h 2 s rich emissions

what patterns of heterogeneity in the earth s mantle can be revealed by seismic travel time tomography abstract we investigate which patterns of seismic heterogeneity in the mantle would be returned reliably by a tomographic inversion in which the model mantle is parametrized by a set of discrete non overlapping voxels we construct synthetic data sets based on real ray sampling of the mantle by introducing spherical harmonic patterns of velocity heterogeneity and perform inversions of the synthetic data we expand the resulting voxel model in spherical harmonics and compare the power at each degree and in each model layer with the input spherical harmonics in order to determine which patterns produced by inversions of real data may be deemed reliable and to identify patterns which must be viewed with skepticism we find that while the power input to a particular pattern of heterogeneity in the 0 200 km layer is generally recovered accurately the pattern itself is poorly determined in this layer a pattern in the 200 400 km layer is more precisely determined though the power contained in the pattern is consistently underestimated and more leakage occurs to the layers above and below the transition zone 400 670 km shows similarly strong control of lateral heterogeneity patterns but tests return a more accurate estimate of input powre than for the second layer the l 2 4 and 6 components all show accurate recovery in the 400 670 km layer this result supports previous findings from inversions with real data that l 2 is a significant pattern of heterogeneity in the mantle s transition zone and that l 4 is not a significant pattern for the entire upper mantle l 6 would be retrieved reliably and its constructive behavior in upper mantle models derived with real data is confirmed these tests also demonstrate the inability of our inversion procedure to retrieve shorter wavelength features in the lower mantle the results for our lowermost layer d must be considered suspect due to the inadequate constraints placed on model values by our ray coverage and the sensitivity of these results to noise in the data

a possible normal fault rupture for the 464 bc sparta earthquake surface ruptures have been identified for some normal faulting earthquakes in the aegean region1 3 but for most historical earthquakes the associated faults are unknown this hampers the evaluation of the rates and styles of present day deformation and the assessment of seismic hazard in the region4 here we examine the famous earthquake that destroyed sparta in 464 bc using spot satellite images and fieldwork we have mapped a 20 km long normal fault scarp trending approximately north south a few kilometres east of the ancient city our observations combined with an examination of historical descriptions of the earthquake damage suggest that the sparta earthquake ruptured this fault scarp in an event of magnitude ms 7 2 the holocene slip rate and the recurrence time for such large events on the sparta fault would be 1 mm yr 1 and 3 000 yr respectively

the ad 60 denizli basin earthquake and the apparition of archangel michael at colossae aegean turkey this paper illustrates the results of a multidisciplinary study on the active tectonics of hierapolis and colossae in aegean turkey tectonic analysis is combined with a study of historical seismicity highlighting the use of historical sources from oral tradition legends and myths to derive important geological information for which the legendary account is the only witness strong correlation between tectonic and historical mythological data suggests that the legendary narration is based on real geological events this allows a better understanding of the local active tectonics and seismic history at hierapolis it is possible to recognize evidence of surface faulting from the ad 60 earthquake at colossae we can reconstruct the local geomorphic evolution and show its relationship to the ad 60 earthquake in particular cases deciphering local folk tales legends and myths may provide useful data on the historical seismicity of an area this subject has only recently been investigated by geologists bentor 1989 guidoboni 1989 armijo et al 1991 nur 1991 piccardi 2000 2005 but is still complicated because it deals with documents derived from oral tradition many of these documents are based on a codified religious terminology which sounds unfamiliar today and contributes to the lack of precision in specific cases where geological phenomena are clearly quoted geological analysis can be used as an interpretative key of legends this study presents a case history where legendary narrations from the denizli basin aegean turkey fig 1a provide useful geological and palaeoseismological information in particular traditions related to a famous earthquake that occurred in ad 60 and two famous ancient sanctuaries of this area colossae located at the southern margin of the basin and hierapolis about 15 km to the nw are examined fig 1b early christian and medieval legends based on geological events are attached to these two places the apparition of archangel michael at colossae and the apocryphal account of the arrival of st philip at hierapolis both legends were later commemorated by famous sanctuaries that have attracted pilgrims through the centuries moreover at hierapolis the geological basis for these legends constituted the source event for local religious rituals also at an earlier level in the greek roman sanctuary of apollo only sparse descriptions about the effects of the ad 60 earthquake are available in historical documents thus oral tradition is the only source of further information the natural phenomena that led to these legends are coseismic geomorphic effects related to that strong earthquake for which legend is the only existent testimony the cases illustrated here are clear examples of how particular hagiographic legends can constitute quasi historical documents following a tectonic study of the area and review of historical accounts this paper focuses on two main aspects of local myths and geology the first recovers important information to reconstruct the seismotectonic parameters of the ad 60 earthquake in particular identifying its source as being the master fault of the denizli basin and the second gains insight into the true origin of particular legends and the reasons for sacred site selection in addition this multidisciplinary approach sheds light on important developments in the evolution of western religious thought

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

recent developments in underground gravity surveys1 underground gravity observations in deep coal mines using the conventional gravity meters worden type master and lacoste romberg model d both of which have been adapted to the fire damp regulations can be accurate to 10 and 3 gal respectively for underground determination of the vertical gradient of gravity the lacoste romberg meter is used together with a specially designed measuring tower using this euipment an accuracy in tower gradient observations of 30 e was obtained to apply the equipment to precision gravity observations in underground situations an additional correction i e a gallery correction is needed high accuracy in correction is achieved by a new method of three dimensional modelling the gravity effect is computed for bodies with a surface approximated by triangular elements which are generated from corner points of the body the combination of gallery correction with tower gradient data leads to a new method for in situ density determination it offers the possibility of horizontal instead of vertical density profiling to demonstrate the effectiveness of the developments in underground observations the localization of a pump room is presented microgravity and tower gradient observations were carried out to detect the cavity the horizontal gradient was also calculated to give a more reliable location

pleistocene holocene tectonic reconstruction of the ballik travertine denizli graben sw turkey de formation of large travertine geobodies at intersecting grabens abstract travertine geobodies have been identified as potential reservoir analogues to carbonate build ups in pre salt hydrocarbon systems to investigate travertine geobody deformation faults were mapped in 35 travertine quarries that excavate the ballik travertine i e a c 12 5 km2 large travertine geobody that precipitated at the intersection of the ne margin of the denizli basin and neighbouring baklan graben sw turkey this travertine precipitated from cooling carbonate saturated thermal spring waters that resurfaced along the margin fracture fault network and through neogene unconsolidated underlying sediments from the denizli basin floor to the uplifted graben shoulders fault orientation is dominantly wnw ese oriented with major basin faults showing a left stepping trend along the upper denizli margin travertine is only deformed by extensional normal faults along the lower margin travertine starts with a subhorizontal facies but evolves to a travertine facies formed by a sloping topography with a domal architecture paleostress inversion of fault slip data reveals that an early pleistocene nne ssw extensional transtensional phase initiated the wnw ese oriented graben facing normal fault network in the middle pleistocene the ballik fault network was left lateral strike slip reactivated because it acted as a transfer zone between the nw se extending neighbouring baklan basin and nw se extension along ne sw oriented margin faults of the dghs in this stress configuration travertine precipitated along the sw margin fault of the baklan graben after strike slip reactivation a late pleistocene to current nne ssw extensional stress regime reinstalled during which margin faults widened and active travertine precipitation moved to more central parts of the dghs as different tectonic regimes affect graben intersections reservoir analogues can have a complex deformation history driven by fault reactivation and recurrent stress permutations this study concludes that large travertine geobodies can form at graben intersections because of their susceptibility to enhanced fluid flow through the complex fault fracture network

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

geological events in the bible the books of the bible contain numerous frequently very exact descriptions of geological events some of these are discussed here earthquakes and their accompanying landslides the crossing of the river jordan seiches and tsunamis the flood flooding sodom and gomorrah faulting burning gas seepages the burning bush and volcanism mount sinai these geological events appear in the biblical text mainly for artistic reasons they serve as a suitable background to dramatize the biblical account they create a supernatural atmosphere for the main stories but the time and place at which they occurred are of no importance to the narrator and might be shifted freely

deep seismic expression of an ancient plate boundary in europe seismological results on the structure of the upper mantle below europe reveal a marked contrast in seismic properties between precambrian and younger parts of europe the precambrian craton in eastern europe is characterized by high shear wave velocities which can be explained by low temperatures the transition to low seismic velocities below phanerozoic europe coincides with the crustal boundary zone of the craton and exists to depths of at least 140 kilometers despite the long and complex tectonic history of the plate boundary zone the transition is remarkably sharp which rules out any significant lateral transport of asthenospheric material across the suture zone

evidence from the gediz graben for episodic two stage extension in western turkey western turkey falls within a wide belt of nne ssw directed active continental extension generally similar to the basin and range province of the usa it comprises a zone of wnw ese trending major grabens detailed study of the gediz graben reveals two contrasting infills that represent two distinct extensional stages separated by a short phase of compression the older infill consists of an 800 m thick folded and exhumed continental sedimentary sequence with intercalated calc alkaline volcanics it accumulated in a basin formed in the northern hanging wall of a detachment fault during miocene early pliocene times the younger infill rests on the older infill with angular unconformity and consists of about 170 m of undeformed terraced continental sediments and basaltic lavas it accumulated during plio quaternary times in an asymmetric graben bounded by step like normal faults this later extension was probably triggered by the commencement of sea floor spreading along the red sea in early pliocene times and has persisted to the present almost all the grabens in western turkey are best explained by this episodic two stage graben model with an intervening phase of short term compression which differs from the progressive evolution inferred for the basin and range province of the usa

3 d upper mantle shear velocity and attenuation from fundamental mode free oscillation data summary we present the results of global measurements of spheroidal and toroidal fundamental mode eigenfrequencies as well as fundamental spheroidal mode attenuation made from a data set consisting primarily of records from the geoscope network data processing includes variable filtering and account is taken of higher order effects along the dispersion branch local frequency and attenuation maps are first obtained as a function of angular order by a regionalization scheme based on the introduction of a correlation length in a second step after correction for shallow layer effects shear velocity maps at different depths in the mantle are obtained by simultaneous inversion of spheroidal and toroidal local frequency maps the results confirm the correlation of shear velocity with large scale tectonic features in the first 200 km of the mantle below that depth the maps are dominated by a degree 2 pattern whose power is peaked around a depth of 300 km shallower than inferred in the first 3 d global studies of the upper mantle and correlated with a degree 2 in attenuation thus confirming the results of our earlier study of degree 2 in the upper mantle we also report estimates of spherically averaged eigenfrequencies for fundamental spheroidal and toroidal mode branches

3 d imaging of the upper crust beneath the denizli geothermal region by local earthquake tomography western turkey abstract the denizli basin and its surroundings are one of the regions that have high seismic activity and rich geothermal fields in western anatolia in the first half of year 2000 an increasing seismic activity was observed around the denizli basin without a large mainshock occurrence a temporary seismic network consisting of 28 stations were deployed to observe the seismic activity in the region by the scientific and technological research council of turkey marmara research center earth and marine science institute tubitak mam emsi in this study one and three dimensional vp and vp vs structure of the denizli basin have been determined by using the travel times of the 635 recorded earthquake data firstly one dimensional inversion schema was performed to stabilize initial velocity model and to have more reliable hypocentral locations then an iterative and simultaneous three dimensional inversion procedure was carried out to obtain 3 d high resolution seismic velocity models furthermore to assess the solution quality of our inversion we conducted a series of resolution tests we concluded high resolution 3 d vp and vp vs seismic velocity models for the upper 20 km of the crust beneath the denizli basin and surroundings and interpreted the results in the context of known geologic and tectonic units the resulting 3 d vp models define the geometry of the basin sediment thickness and intrusive magmatic bodies as well as regions of anomalous velocity the vp vs models help to constrain the location and geometry of the faults zones of weakness and gas or fluid saturated formations with high pore pressure zones all tomographic results show that there is a strong correlation between local seismicity and the high vp and vp vs anomalies consequently this relationship indicates that the reason of the high seismicity in the denizli basin depends on activity of hydrothermal system as well as tectonic regime

three dimensional structure of the upper mantle beneath the atlantic ocean inferred from long period rayleigh waves 1 group and phase velocity distributions group and phase velocity distributions of rayleigh wave fundamental modes are determined in the atlantic ocean using a method of regionalization without a priori constraints for a period range from 50 to 200 s eighty six direct source station paths are studied and 38 out of the best data from weidner s 1974 phase velocities are added to our data set for periods lower than 100 s the importance of shallow layer corrections is described in detail the general features of the distributions agree with global models and smaller scale heterogeneities are revealed a spatial resolution of 1500 km is needed to detect fine lateral heterogeneities in the atlantic the small lateral extent of young oceanic regions and strong lateral velocity gradients do not allow to quantify velocity versus age relationships using our data set on the other hand the regionalization without a priori constraints of phase velocities confirms the presence of a high velocity anomaly beneath the central part of the atlantic for periods greater than 100 s

tomography the geoid and plate motions the dynamics of the earth s mantle and its relationship to mantle structure as revealed by seismic tomography the geoid and plate motions are discussed in a critical review of u s research from the period 1987 1990 sections are devoted to plates and mantle convection seismic anomalies flow and the geoid subducted slabs and the 670 km discontinuity the physical properties of the mantle plumes and computational and experimental modeling efforts also included is a comprehensive bibliography for the period 248 refs

measurements of mantle wave velocities and inversion for lateral heterogeneities and anisotropy 3 inversion lateral heterogeneity in the earth s upper mantle is investigated by inverting dispersion curves of long period surface waves 100 330 s models for seven different tectonic regions are derived by inversion of regionalized great circle phase velocity measurements from our previous studies we also obtain a representation of upper mantle heterogeneities with no a priori regionalization from the inversion of the degree 6 spherical harmonic expansion of phase and group velocities the data are from the observation of about 200 paths for love waves and 250 paths for rayleigh waves for both the regionalized and the spherical harmonic inversions corrections are applied to take into account lateral variations in crustal thickness and other shallow parameters these corrections are found to be important especially at low spherical harmonic order the trench region and fast velocities down to 250 km under shields below 200 km under the oceans both s velocity and s anisotropy support a model of small scale convection in which cold blobs detach from the bottom of the lithosphere when its age is large enough the spherical harmonic models clearly demonstrate a posteriori the relation between surface tectonics and s velocity heterogeneities in the first 250 km all shields are fast most ridges are slow below 300 km a belt of fast mantle follows the pacific subduction zones however at greater depths large scale heterogeneities that seem to bear no relationship to surface tectonics are observed the most prominent feature at 450 km is a fast velocity region under the south atlantic ocean smaller scale heterogeneities that are not related to surface tectonics are also mapped at shallower depths an anomalously slow region centered in the south central pacific is possibly linked to intense hot spot activity a very fast region southeast of south america may be related to subduction of old pacific plate between 200 and 400 km a belt of sv sh anisotropy follows part of the ridge and subduction systems indicating vertical mantle flow in these regions the spherical harmonic results open new horizons for the understanding of convection in the mantle perspectives for the improvement of the models presented are discussed

travitonics using travertines in active fault studies abstract late quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures on the basis of field studies in the aegean region turkey and greece the northern apennines italy and the basin and range province usa we conclude that the following relationships are of predictive value i travertine deposits are preferentially located along fracture traces either immediately above extensional fissures or in the hanging walls of normal faults ii the locations of many travertine fissure ridge deposits coincide with step over zones relay ramps between fault segments networks of intersecting tensional fissures reflecting the complex strains experienced in such settings are probably responsible for enhancing hydrothermal flow iii the morphology of travertine deposits overlying extensional fissures is controlled by the rheology of the underlying materials tufa cones towers pinnacles form on former and present lake floors where fissures underlie unconsolidated sediments whereas fissure ridges develop where fissures cut bedrocks at the surface iv fissure ridges comprise outwardly dipping bedded travertine flanking a central tensional fissure filled by vertically banded travertines fissures can be used to infer local stretching directions v where there are travertines datable by the u series method it is possible to calculate time averaged dilation and lateral propagation rates for individual fissures vi most fissures cutting fissure ridges comprise self similar angular segments with fractal dimensions in the range 1 00 1 12 the properties of bedded travertine combined with stress perturbations at fissure tips probably being responsible for such similar fractal dimensions being inferred from such a wide range of locations fissures gradually increasing in width with depth are products of continuous fracture dilation in contrast to those that form during episodic dilation which display stepped increases of width with depth vii travertine deposited from springs along fault zones accumulate in terraced mounds sited down slope of the spring line viii many post depositional fractures cutting travertine deposits are locally oriented at right angles to deposit margins and ix systematic joints in travertines are restricted to those parts of eroded sheet deposits that have been exhumed

neogene evolution of the denizli region of western turkey the denizli region contains one of the easternmost neogene sedimentary basins in the part of western turkey that takes up ssw extension this isolated active normal fault zone which contains closely spaced en echelon normal fault branches is investigated using field measurements of fault exposures and tilted sediments and seismological observations as a case study to address its style of extension the denizli basin is no more than 1 km thick and has accommodated up to 4 km of extension substantial 20 sediment dips are readily explicable assuming extension is accompanied by distributed vertical simple shear with initial and present day dips of the main normal faults that control extension most likely 54 57 and 45 50 other aspects of the form of this basin require regional uplift at 0 1 mm yr 1 providing the first indication of major tectonic elevation changes in this actively extending region that are not directly related to throw on normal faults

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

active faulting at delphi greece seismotectonic remarks and a hypothesis for the geologic environment of a myth historical data are fundamental to the understanding of the seismic history of an area at the same time knowledge of the active tectonic processes allows us to understand how earthquakes have been perceived by past cultures delphi is one of the principal archaeological sites of greece the main oracle of apollo it was by far the most venerated oracle of the greek ancient world according to tradition the mantic proprieties of the oracle were obtained from an open chasm in the earth delphi is directly above one of the main antithetic active faults of the gulf of corinth rift which bounds mount parnassus to the south the geometry of the fault and slip parallel lineations on the main fault plane indicate normal movement with minor right lateral slip component combining tectonic data archaeological evidence historical sources and a reexamination of myths it appears that the helice earthquake of 373 b c ruptured not only the master fault of the gulf of corinth rift at helice but also the antithetic fault at delphi similarly to the corinth earthquake of 1981 moreover the presence of an active fault directly below the temples of the oldest sanctuary suggests that the mythological oracular chasm might well have been an ancient tectonic surface rupture

dispersion of very long period rayleigh waves along the east pacific rise evidence for s wave velocity anomalies to 450 km depth the phase dispersion of fundamental mode rayleigh waves from the second gazli earthquake has been measured at periods between 40 and 400 s between los angeles and the south pole over most of its length the path between the two stations is parallel and close to the east pacific rise the phase velocities we have observed are significantly lower than the global averages the inversion for the oceanic part of the path gives a shear wave velocity model with 1 unusually low velocities down to a depth of about 200 km with a minimum of 4 1 km s around 100 km 2 normal or slightly less than normal velocities between depths of 200 km and about 400 km and 3 a depression of the olivine spinel phase boundary by about 50 km or an equivalent velocity reduction around a depth of 450 km in a model without mantle discontinuities we can make no definitive assertions regarding deeper anomalies in the mantle the velocity anomalies below a depth of 200 km are consistent with the assumption that the temperature of the upper mantle between the low velocity zone and the spineloxide transition at 671 km in model 1066b is elevated by 140 k relative to the average earth corrections to customary data processing procedures are offered that are designed to eliminate bias in estimates of dispersion at periods greater than 240 s

the spectrum of tomographic earth models summary the properties of mantle convection are expected to generate characteristic signatures in the spectrum of mantle heterogeneities and in its dependence on depth the investigation of present tomographic models and the associated spectra of seismic velocity perturbations can provide insight into this problem the characterization of heterogeneities in the mantle at all scales involves combining and comparing tomographic models at both global and regional scales the former are expanded into the spherical harmonics domain while the latter are expanded into the fourier domain the comparison of both types of expansions is possible if we consider power spectral density per unit surface such a comparison should be carried out with great care and the scaling factors are derived to make it meaningful the method is applied to recent global and regional tomographic models it is shown that contrary to previous assertions there is an overall agreement between both kinds of models

structure of the inner core inferred from observations of its spheroidal shear modes spheroidal modes of elastic gravitational oscillation that have an energy partition dominated by shear energy in the inner core are called core modes recordings from the ida gravimeter network of an earthquake in the tonga region on june 22 1977 have provided the first unambiguous observations of core modes they conclusively show that at low frequencies the inner core has a very high q about 3500 they also tightly constrain the ratio of the inner core radius to the mean shear velocity to be 345s with an uncertainty of 0 5

effect of sharp lateral heterogeneity on the earth s normal modes when inverting normal mode data for global large scale heterogeneity possible biases due to small scale structure are commonly ignored the authors conducted two experiments in the first one they calculated with a recently developed first order scattering formalism the effect of a simplified subduction zone model on the eigenfrequencies of the fundamental spheroidal mode branch the frequency shifts induced by this single subduction zone appear to be smaller by only a factor of 3 to 4 than shifts observed on long period seismograms or than shifts induced by existing models of global upper mantle inhomogeneity the second experiment involved a model of a hot spot plume on the core mantle boundary solving the variational problem with many coupling terms included the authors calculated the effect of such a plume on the amplitude of some low angular order modes the results suggest an effect at least as large as that due to available large scale mantle modes it thus appears that relatively small scale sharp lateral structure in different depth ranges of the earth may have an important effect on normal mode observations and that these effects may not be ignored in inversions of normal mode data

three dimensional structure of the upper mantle beneath the atlantic ocean inferred from long period rayleigh waves 2 inversion the three dimensional shear wave velocity structure of the upper mantle beneath the atlantic ocean is investigated by inversion of fundamental mode of rayleigh wave group and phase velocities the results are reliable down to 300 km depth and improve upon the image of upper mantle structure given by global tomographic models the inversion of two dimensional lateral distributions of group and phase velocities regionalized without a priori constraints shows that shear wave velocities are correlated with lithospheric age beneath the north atlantic our data set fails to quantify the correlation between shear velocities and lithospheric age because of the small lateral extent of young regions 22 ma and of strong transverse gradients in contrast with similar studies in the indian and pacific oceans slow velocities associated with the location of the mid atlantic ridge are restricted to the lithosphere therefore the atlantic mid oceanic ridge behaves as a shallow structure which is weakly related to deep upwelling asthenospheric flows at depths greater than 200 km the central part of the atlantic is characterized by the highest velocity anomaly this anomaly can be interpreted in different ways part of this anomaly might correspond to a negative vsh vsv vsv ratio implicitely included in the isotropic inversion we also tentatively interpret this anomaly as an important contributor to a shallow degree two pattern of shear wave velocity distribution for the atlantic area

active tectonics of the aegean region the aegean sea and its surrounding regions comprise one of the most rapidly deforming parts of the alpine himalayan mountain belt though the deformation of the belt as a whole is related to thc northward move ment of africa arabia and india relative to eurasia the tectonics of the aegean region itself is dominated by strike slip and extensional motions the actively deforming part of the aegean region is not large about 700 x 700 km2 compared with that in asia yet it has had an influence on our views of continental tectonics disproportionate to its size and comparable perhaps only to tibet fundamental contributions from the aegean have been made to many topics including