self weight consolidation of soft soils an experimental and theoretical study soil is laid down by sedimentation through water passing through the phases of a fluid supported suspension through a loose structure to a soft soil the stiffness of which then gradually increases under additional load consolidation is caused by the self weight of the soil and while the sediment is soft is accompanied by large strains to predict magnitudes and rates of movement the physical processes must be understood and used as the basis of a theoretical model this paper describes laboratory experiments on the development and consolidation of a soft soil in settling columns with measurement of density using an accurate non destructive x ray technique total stress pore pressure and settlement the results are compared with an earlier theoretical model modifications made to the model in the light of observed experimental features allow it to be used to predict the laboratory consolidation le sol est depose par sedimentation a travers l eau il a d abord la forme d une suspension soutenue

frechet kernels for imaging regional earth structure based on three dimensional reference models high resolution images of three dimensional 3d seismicstructuresare not only of scientific interest but also of practical importance in predicting strong ground motion after large earthquakes given the source and station distributions resolutions in current regional seismic tomography studies have been limited by two types of simplifying practices the adoption of high frequency approximations such as the ray theory and the use of one dimensional 1d reference starting models we have developed a new approach to compute accurate finite frequency 3d frechet sensitivity kernels of observed travel time and amplitude anomalies relative to 3d reference models in our approach we use a fourth order staggered grid finite difference method to model the seismic wave propagation in 3d media and the reciprocity property of the green s tensor to reduce the number of numerical simu lations this approach accounts for the perturbations in compressional and shear wave speeds in the same way leading to a capability of inverting for the shear wave speed directly from seismic data the algorithm is readily parallelized to allow for realistic regional high resolution 3d tomography inversions we have implemented the algorithm for the southern california earthquake center scec community velocity model scec cvm 3 0 a complex 3d model for southern california in cluding a number of sedimentary basins by enabling the inversion of 3d structural perturbations to 3d reference models our approach provides a practical means of iteratively solving the nonlinear regional tomography problems

integrated model of the crustal structure in the gulf of california extensional province abstract a method of constructing 3d earth models from a suite of 1d profiles is demonstrated using delaunay triangulation accurate crustal models are required to correct for crustal contamination in seismic tomography of the mantle and can be used as starting points for higher resolution tomography of the lithosphere and asthenosphere using a simple input data set 1d vertical profiles provides for rapid prototyping model building and modification any structural length scale in the final 3d model is possible using this method through precise placement of 1d profiles and triangulation collections of layers within the 1d profiles are grouped and identified by keys called superlayers allowing for 3d discontinuities and variations along these important interfaces the method was applied to the gulf extensional province and baja california regions to account for the laterally discontinuous crustal variations during a tomographic inversion for mantle structure use of the 3d model and appropriate regional crustal wave speeds minimizes wave speed variations in the tomographic model and assists interpretation of the final model

reflection and transmission of surface waves at a vertical discontinuity and imaging of lateral heterogeneity using reflected fundamental rayleigh waves we present a technique for the determination of approximate reflection and transmission coefficients of surface wave modes for a vertical plane discontinuity that is simple to use it is applied to different models of lateral heterogeneity furthermore a method for the localization of lateral heterogeneity using the coda of the fundamental rayleigh mode is proposed in particular the frequency content of surface waves enables the investigation of the lower crust and the uppermost mantle lateral changes of the s wave velocity density and p wave velocity lead to the formation of the coda of the fundamental rayleigh mode that contains delayed surface waves that reach the recording station indirectly the complicated structure of the coda makes it impossible to identify reflected surface waves visually using a small number of recordings only coda waveforms of a large number of source station pairs are inverted simultaneously for experimental reflection coefficients the method is successfully tested using an ultrasonic model experiment finally it is applied to central europe and especially to the tornquist zone tz mainly using records of the german regional seismological network grsn the resulting reflection coefficients depend on frequency and give an image of the location of reflectors

the middle miocene yallourn coal seam the last coal in australia abstract the 100 m thick middle miocene yallourn brown coal seam was the last of the major latrobe valley group seams to form in the gippsland basin southeastern australia and the final major coal to form in australia coal deposition coincided with the middle miocene climatic optimum during this warm period of relatively high sea levels high water tables and relatively high subsidence rates a 565 km 2 area of alternating eutrophic and ombrogenous peat swamp developed at the western end of the latrobe valley to form the yallourn seam stratigraphic units of the seam contain a high sclerophyll plant component and abundant charcoal suggesting seasonal dry periods alternated with wet warm conditions characterised by abundant rushes and dense kauri forests iron content in parts of the yallourn seam is relatively high and a strong correlation exists between the iron distribution and the abundance of proteoid roots mainly proteaceae an indicator of seasonal dry periods the contemporaneous carbonates of the wuk wuk marl were deposited in a high productivity upwelling warmer water subtropical environment a new carbon isotope profile at 1 m intervals through the yallourn seam shows a poor relationship between 13 c isotopes and coal colour but some correlation with gymnosperm abundance the 13 c record also correlates well with long term secular changes in climate the presence of global carbon maxima cm2 cm4 and with the deep sea 13 c marine organic record thick coal seam development ended near the end of the middle miocene climatic optimum the termination of coal seam deposition in latrobe valley was primarily the result of tectonic compression uplift and development of adjacent highland relief and erosion at the end of the miocene

crustal and upper mantle responses to lithospheric segmentation in the northern apennines lithospheric tear faults are expected to develop in response to along strike variations in the rates of slab rollback however the exact geometry of such structures and their crustal and upper mantle expressions are still debated we present an analysis of seismic structural and morphological features that possibly represent the expression of lithospheric segmentation in the northern apennines geophysical observations show evidence for the existence of a discontinuity in the lithospheric structure beneath the northern apennines characterized by a change in the spatial distribution of intermediate depth seismicity along strike variations in the pattern of crustal seismicity and a bend in the moho topography the near surface expression of this discontinuity is associated with an abrupt change in the morphology and exhumation history of the northern apennines in the proximity of the livorno sillaro lineament we interpret these features as evidence for incipient tearing of the lithospheric slab beneath the northern apennines marking the boundary between domains that underwent contrasting styles of lithospheric deformation which are either associated with different rates of slab rollback or a transition from underplating to retreat we suggest that similar types of structures may play a crucial role in the evolution of convergent plate boundaries allowing segmentation of orogenic belts and facilitating the development of orogenic curvatures ultimately further tearing along such structures could potentially lead to the occurrence of tear related magmatism and the formation of slab windows

silica burp in the eocene ocean the eocene was a time of greatly increased silica accumulation in the ocean and the peak was in the early middle eocene at about 50 ma the responsible geohistorical configuration included the following elements extensive volcanism about 4 m y earlier as part of the chron 24 plate reorganization early eocene warming with deep weathering to high latitudes and accumulation of the released silica in a sluggish ocean and sharp cooling in the earliest middle eocene stimulating oceanic upwelling and biosilicification it is possible on the evidence of carbon and oxygen isotopic patterns that the trigger for the exhalation of silica was a reverse greenhouse effect

imaging lateral heterogeneity in the northern apennines from time reversal of reflected surface waves summary prominent arrivals in the coda of seismograms from the wider alpine area can be associated with lateral reflections of love waves at the northern apennines mountain chain italy where structural heterogeneity causes an abrupt contrast in phase velocity we discuss an approach to image lateral heterogeneity from reflected surface waves using intermediate period threecomponent coda waveforms as sources for an adjoint wavefield that propagates the reflections backward in time we numerically compute three dimensional sensitivity kernels for the dependence of coda waveforms on p velocity s velocity and density based upon correlations between the adjoint and the regular forward wavefields we consider synthetic coda waveforms for a simplified model of the northern apennines as well as real coda observations from five moderate magnitude earthquakes m w 4 6 5 6 in the southern alps wave propagation is simulated using the spectral element method for which a 3 d regional earth model is used in the case of real data single and combined event sensitivity kernels provide clear images of the reflectivity associated with the northern apennines in kernels for density and s wave speed the kernels show that surface wave reflections occur near the axial zone of the mountain chain apart from the apennines the approach is able to image other smaller reflectivity patches from the coda waveforms like the ivrea zone in the southern alps our coda misfit kernels can be integrated in a gradient based waveform tomography where they could enhance the sharpness of the model at lateral discontinuities

time reversal imaging of seismic sources and application to the great sumatra earthquake the increasing power of computers and numerical methods like spectral element methods allows continuously improving modelization of the propagation of seismic waves in heterogeneous media and the development of new applications in particular time reversal in the three dimensional earth the concept of time reversal hereafter referred to as tr was previously successfully applied for acoustic waves in many fields like medical imaging underwater acoustics and non destructive testing we present here the first application at the global scale of tr with associated reverse movies of seismic waves propagation by sending back long period time reversed seismograms we show that seismic wave energy is refocused at the right location and the right time of the earthquake when tr is applied to the sumatra andaman earthquake 26 dec 2004 the migration of the rupture from the south towards the north is retrieved therefore tr is potentially interesting for constraining the spatio temporal history of complex earthquakes

the nature and evolution of lithotypes in the tertiary brown coals of the latrobe valley southeastern australia abstract lithotype banding identified on colour and texture of the coal occurs in all seams covering the period mid eocene to late miocene in the latrobe valley preliminary palaeobotanical studies on both pollen and plant macrofossil components of the youngest seams indicated strong relationships between lithotype vegetation and inferred depositional environment with the lithotype gradient from lightest to darkest coals corresponding with hydroseral stages from unvegetated open water through swamp forest to raised bog communities subsequent studies on the older seams failed to show such close correspondence between lithotype and vegetation the analysis of palynological and petrological data from all seams in this paper adds support to the original hypothesis of lithotype formation however it also demonstrates a gradual differentiation of lithotypes through the coal forming period this most likely involved the progressive development of vegetation communities adapted to the range of swamp environments with the peatforming environment of particular significance is the development of a community with a significant sclerophyll component within the predominant rainforest vegetation which colonised the raised bogs of the youngest seams the process may have been facilitated or accelerated by an increasingly variable climate and the increased importance of fire within the region

time reversal imaging of synthetic volcanic tremor sources 1 time reversal of seismic wavefields recorded at active volcanoes may provide images of the source process for long period lp or volcanic tremor events directly independent of assumptions about extent geometry and mechanics of the source time reversal methods involve propagating the original time series from many receiver locations back into the medium the reversed signals then focus at their origin due to constructive interference elucidating the source location extent and radiation pattern in practice focusing may be blurred due to inaccurate earth models or sparse sampling of the wavefield at the surface here we investigate the feasibility of this method for several synthetic volcanic tremor sources and present a gallery of time reversal source images wave propagation is computed numerically in a 2d volcano model with realistic topography our results indicate that time reversal may be applicable in volcanic settings possibly yielding new insights into volcano seismic lp or tremor sources

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

images of the iberian lithosphere from one local earthquake abstract on 12 august 2007 a magnitude m w 4 7 intraplate earthquake occurred near the center of the iberian peninsula an area characterized by comparably simple crustal structure within the complex iberia maghreb plate boundary zone and characterized by complete azimuthal coverage with seismic broadband stations we analyze regional intermediate period 20 to 50 s coda waveforms for this earthquake they contain energy representing late arriving surface waves that have been reflected laterally at lithospheric heterogeneities in or around iberia but complexity of the coda waveforms hampers a direct interpretation we use coda recordings as the source for a back propagating adjoint wave field and compute 3d born sensitivity kernels for the dependence of least squares waveform misfits of coda waves on wave speed variations we hereby image the origin of single scattering recorded in the coda misfit kernels for p and s wave velocity show azimuth dependent intensity variation as a result of source radiation and an appropriate compensation significantly improves imaging quality thereby revealing several clear lineaments these are interpreted as surface wave reflectors due to deep rooted heterogeneity such as terrain boundaries or moho topography demonstrating the ability of the approach to unravel complex waveforms and providing a new point of view on regional lithospheric structure

atmospheric carbon dioxide through the eocene oligocene climate transition geological and geochemical evidence1 2 3 indicates that the antarctic ice sheet formed during the eocene oligocene transition4 33 5 34 0 million years ago modelling studies5 6 suggest that such ice sheet formation might have been triggered when atmospheric carbon dioxide levels fell below a critical threshold of 750 p p m v but the timing and magnitude of relative to the evolution of the ice sheet has remained unclear here we use the boron isotope ph proxy7 8 on exceptionally well preserved carbonate microfossils from a recently discovered geological section in tanzania9 10 to estimate before during and after the climate transition our data suggest that a reduction in occurred before the main phase of ice growth followed by a sharp recovery to pre transition values and then a more gradual decline during maximum ice sheet growth was between 450 and 1 500 p p m v with a central estimate of 760 p p m v the ice cap survived the period of recovery although possibly with some reduction in its volume implying as models predict11 a nonlinear response to climate forcing during melting overall our results confirm the central role of declining in the development of the antarctic ice sheet in broad agreement with carbon cycle modelling12 and help to constrain mechanisms and feedbacks associated with the earth s biggest climate switch of the past 65 myr

time reverse location of seismic long period events recorded on mt etna we present the first application of a time reverse location method in a volcanic setting for a family of long period lp events recorded on mt etna results are compared with locations determined using a full moment tensor grid search inversion and cross correlation method from 2008 june 18 to july 3 50 broad band seismic stations were deployed on mt etna italy in close proximity to the summit two families of lp events were detected with dominant spectral peaks around 0 9 hz the large number of stations close to the summit allowed us to locate all events in both families using a time reversal location method the method involves taking the seismic signal reversing it in time and using it as a seismic source in a numerical seismic wave simulator where the reversed signals propagate through the numerical model interfere constructively and destructively and focus on the original source location the source location is the computational cell with the largest displacement magnitude at the time of maximum energy current density inside the grid before we located the two lp families we first applied the method to two synthetic data sets and found a good fit between the time reverse location and true synthetic location for a known velocity model the time reverse location results of the two families show a shallow seismic region close to the summit in agreement with the locations using a moment tensor full waveform inversion method and a cross correlation location method

seismic tomography of the southern california crust based on spectral element and adjoint methods we iteratively improve a 3 d tomographic model of the southern california crust using numerical simulations of seismic wave propagation based on a spectral element method sem in combination with an adjoint method the initial 3 d model is provided by the southern california earthquake center the data set comprises three component seismic waveforms i e both body and surface waves filtered over the period range 2 30 s from 143 local earthquakes recorded by a network of 203 stations time windows for measurements are automatically selected by the flexwin algorithm the misfit function in the tomographic inversion is based on frequency dependent multitaper traveltime differences the gradient of the misfit function and related finite frequency sensitivity kernels for each earthquake are computed using an adjoint technique the kernels are combined using a source subspace projection method to compute a model update at each iteration of a gradient based minimization algorithm the inversion involved 16 iterations which required 6800 wavefield simulations the new crustal model m 16 is described in terms of independent shear v s and bulk sound v b wave speed variations it exhibits strong heterogeneity including local changes of 30 per cent with respect to the initial 3 d model the model reveals several features that relate to geological observations such as sedimentary basins exhumed batholiths and contrasting lithologies across faults the quality of the new model is validated by quantifying waveform misfits of full length seismograms from 91 earthquakes that were not used in the tomographic inversion the new model provides more accurate synthetic seismograms that will benefit seismic hazard assessment

sequence stratigraphic analysis and the origins of tertiary brown coal lithotypes latrobe valley gippsland basin australia abstract the methods of sequence analysis have been applied to the onshore gippsland basin and in particular to the latrobe valley group coal measures which include up to five coal seams each exceeding 100 m in thickness the methods appear to provide new depositional concepts to the evolution of these seams and the development of coal lithotypes in the eastern half of the latrobe valley evidence for marine transgressions into the coal measures are recorded in most of the interseam sediment splits by the presence of contained foraminifera and dinoflagellates to the west inland these splits pinch out into continuous coal however they can be followed westwards as enhanced organic sulphur levels along sharply defined boundaries between light coal lithotypes below and dark coal lithotypes above the dark lithotype immediately overlying each of these boundaries contains the highest sulphur value and warmer climate pollen assemblages sluiter et al 1995 this volume colorimeter and lithotype logging strongly supports an upwards lightening cyclicity to coal colour at 12 20 m intervals through the approx 100 m thick seams with cycle boundaries defined at sharp planar to undulating surfaces the lightening upward lithotype cycles together with their unique boundary conditions i e enhanced organic sulphur levels warm climatic indicators and laterally equivalent marine clay splits are interpreted as parasequences and parasequence boundaries respectively each major coal seam can comprise up to five parasequences and is interpreted to represent deposition during an outbuilding high stand systems tract at one of several maximum periods of tertiary coastal onlap the top of each major seam shows evidence of truncation erosion on a regional scale and these surfaces are interpreted to represent the sequence boundaries the major seams are usually conformably underlain by marine clays and extensive aquifer sands being deposits of the late transgressive systems tracts the low stands and early parts of the transgressive systems tracts appear not to be represented in the latrobe valley due to its more basin margin location but are probably present down dip in the equivalent marine facies of the seaspray group stratigraphic correlation of the sequence boundaries identified in the coal measures to the adjacent internationally dated marine seaspray group provides a basis for chronostratigraphic correlation of the coal successions to the coastal onlap charts of haq et al exon mesozoic cenozoic chronostratigraphic chart version january 1988 and august 1989 from this dating it appears that each major seam is confined to high stands of third order eustatic cycles it therefore follows that the lithotype cycles parasequences that comprise each seam are related to fourth order eustatic cycles by analogy all the coal cycles may have developed under subtropical conditions as ombrogenous forested peat swamps in a similar manner to the holocene though tropical swamps of indonesia

eocene circulation of the southern ocean was antarctica kept warm by subtropical waters 1 near the eocene s close 34 million years ago the climate system underwent one of the largest shifts in earth s history antarctic terrestrial ice sheets suddenly grew and ocean productivity patterns changed previous studies conjectured that poleward penetration of warm subtropical currents the east australian current eac in particular caused eocene antarctic warmth late eocene opening of an ocean gateway between australia and antarctica was conjectured to have disrupted the eac cooled antarctica and allowed ice sheets to develop here we reconstruct eocene paleoceanographic circulation in the tasmanian region using 1 biogeographical distributions of phytoplankton including data from recently drilled ocean drilling program leg 189 sites and 2 fully coupled climate model simulations we find that the eac did not penetrate to high latitudes and ocean heat transport in the region was not greater than modern our results do not support changes in thermal isolation as the primary driver of the eocene oligocene climatic transition

how normal faulting and sedimentation interact to produce listric fault profiles and stratigraphic wedges abstract in a series of scale experiments we generated listric normal faults by extending models composed of colored sand layers deposited at regular time intervals throughout deformation during syntectonic sedimentation progressive bulk extension along a single set of faults caused domino type tilting of fault blocks underlying tilted faults propagated upwards with constant dips into newly sedimented layers hence fault profiles become progressively more listric tilting of the free surface resulted in asymmetrical depressions and in fan shaped deposits stepwise or continuous geometric models of domino tilting and synchronous sedimentation yield the same structural and stratigraphic features as observed in the sand models the continuous geometric model shows that a critical parameter governing fault curvature is the ratio r between rates of bulk strain and sedimentation both types of models reveal that synchronous sedimentation and bulk extension are capable by themselves of generating listric normal faults

source parameters and stress release of seismic sequences occurred in the friuli venezia giulia region northeastern italy and in western slovenia abstract the source parameters of the major events of a swarm and of two seismic sequences occurred in the friuli area northeastern italy and in western slovenia were estimated the claut swarm c96 occurred since the end of january to june 1996 with a md 4 3 major shock and it appears composed of three sub sequences the two sequences are the kobarid sequence k98 started on april 12 1998 with a md 5 6 mainshock and the m te sernio s02 sequence caused by the february 14 2002 earthquake md 4 9 acceleration and velocity data recorded by the local seismic network of the istituto nazionale di oceanografia e di geofisica sperimenale ogs and corrected for attenuation were employed to estimate seismic moments and radiated energies source dimensions were inferred from the computed corner frequencies and the stress release was estimated from the brune stress drop the apparent stress and the rms stress drop on the whole seismic moments range from 1 7 1012 to 1 1 1017 n m and radiated energies are in the range 106 1013 j brune stress drops are scattered and do not show any evidence of a self similarity breakdown for sources down to 130 m radius the radiated seismic energy scales as a function of seismic moment with a slope of the scaling relation that decreases for increasing seismic moments the mechanism of stress release was analyzed by computing the parameter of zuniga zuniga r 1993 frictional overshoot and partial stress drop which one bull seismol soc am 83 939 944 the k98 and s02 sequences are characterized by a wide range of the parameter with stress drop mechanism varying from partial locking to overshoot cases the values of the c96 swarm are more homogeneous and close to the orowan s condition the radiated seismic energy and the ratio of stress drop between mainshock and aftershocks appear different among the analyzed cases we therefore investigated the relationship between the stress parameters of the main shock and the energy radiated by the aftershock sequences for this purpose we also estimated the source parameters of two other sequences occurred in the area with mainshocks of md 4 1 and 5 1 respectively we found a positive correlation between the brune stress drop of the mainshock and the ratio between the radiated energy of the mainshock and the summation of the energies radiated by the aftershocks

a near field sea level record of east antarctic ice sheet instability from 32 to 27 myr 1 fossil facies and isotope analyses of an early high paleolatitude 55 s section suggests a highly unstable east antarctic ice sheet from 32 to 27 myr the waxing and waning of this ice sheet from 140 to 40 of its present volume caused sea level changes of 25 m ranging from 30 to 50 m related to periodic glacial 100 000 to 200 000 years and shorter interglacial events the near field gippsland sea level gsl curve shares many similarities to the far field new jersey sea level njsl estimates however there are possible resolution errors due to biochronology taphonomy and paleodepth estimates and the relative lack of lowstand deposits in njsl that prevent detailed correlations with gsl nevertheless the lateral variations in sea level between the gsl section and njsl record that suggest ocean siphoning and antisiphoning may have propagated synchronous yet variable sea levels

rapid cenozoic glaciation of antarctica induced by declining atmospheric co2 the sudden widespread glaciation of antarctica and the associated shift towards colder temperatures at the eocene oligocene boundary 34 million years ago refs 1 4 is one of the most fundamental reorganizations of global climate known in the geologic record the glaciation of antarctica has hitherto been thought to result from the tectonic opening of southern ocean gateways which enabled the formation of the antarctic circumpolar current and the subsequent thermal isolation of the antarctic continent5 here we simulate the glacial inception and early growth of the east antarctic ice sheet using a general circulation model with coupled components for atmosphere ocean ice sheet and sediment and which incorporates palaeogeography greenhouse gas changing orbital parameters and varying ocean heat transport in our model declining cenozoic co2 first leads to the formation of small highly dynamic ice caps on high antarctic plateaux at a later time a co2 threshold is crossed initiating ice sheet height mass balance feedbacks that cause the ice caps to expand rapidly with large orbital variations eventually coalescing into a continental scale east antarctic ice sheet according to our simulation the opening of southern ocean gateways plays a secondary role in this transition relative to co2 concentration

glacial climates in the antarctic region during the late paleogene evidence from northwest tasmania australia published data suggest that ice buildup commenced in antarctica during the late middle eocene this predates by 30 m y the earliest evidence of cenozoic glaciation on other fragments of gondwana although several of these were at high latitudes during the paleogene we provide new evidence for local glacier development during the late paleogene in tasmania then a mountainous peninsula at about lat 55 63 s projecting into the circum antarctic ocean the date of glaciation is not precisely known but an earliest oligocene age is indicated we suggest that episode may correlate with abrupt cooling of the sea surface surrounding antarctica during the earliest oligocene 36 ma

three dimensional interface modelling with two dimensional seismic data the alpine crust mantle boundary summary we present a new approach to determine the 3 d topography and lateral continuity of seismic interfaces using 2 d derived controlled source seismic reflector data the aim of the approach is to give the simplest possible structure consistent with all reflector data and error estimates we define simplicity of seismic interfaces by the degree of interface continuity i e shortest length of ovsets and by the degree of interface roughness least surface roughness the method is applied to structural information of the crust mantle boundary moho obtained from over 250 controlled source seismic reflection and refraction profiles in the greater alpine region the reflected and refracted phases from the moho interface and their interpretation regarding crustal thickness are reviewed and their reliability weighted weights assigned to each reflector element are transformed to depth errors considering fresnel volumes the 2 d derived reflector elements are relocated in space 3 d migration and interpolation is performed between the observed reflector elements to obtain continuity of model parameters interface ovsets are introduced only where required according to the principle of simplicity the resulting 3 d model of the alpine crust mantle boundary shows two ovsets that divide the interface into a european an adriatic and a ligurian moho with the european moho subducting below the adriatic moho and with the adriatic moho underthrusting the ligurian moho each sub interface depicts the smoothest possible i e simplest surface fitting the reflector data within their assigned errors the results are consistent with previous studies for those regions with dense and reliable controlledsource seismic data the newly derived alpine moho interface however surpasses earlier studies by its lateral extent over an area of about 600 km by 600 km by quantifying reliability estimates along the interface and by obeying the principle of being consistently as simple as possible

a review of the traralgon formation in the gippsland basin a world class brown coal resource the traralgon formation contains by far the largest brown coal resources in the gippsland basin and is probably unequalled in the world for any single basin deposit of its type out of an indicated resource of 345 billion tonnes gt approximately 10 gt are currently listed as economically recoverable reserves low ash content ave 2 9 db but higher organic sulphur contents ave 1 72 db largely reflect the near coastal depositional environments under which much of the original extensive peat swamps accumulated the contained plant matter and coal types indicate a high latitude rainforest environment where rainfall and temperatures were higher than present and where lithotype cycling occurs the coals appear to have accumulated at specific high stand periods of coastal onlap towards the end of the middle and late eocene and eustatic sea level changes play an important role in development of the coal seams the timing for maximum coal accumulation takes place at the apogee of a greenhouse world shortly before the cooling trends into the early oligocene during this time over 100 gt of carbon was sequestered into these coal deposits

inverting interpolated receiver functions with surface wave dispersion and gravity application to the western u s and adjacent canada and mexico we use p wave receiver functions from the western u s and adjacent regions to construct a receiver function wavefield interpolation scheme that helps to equalize the lateral sampling of the receiver functions and the surface wave dispersion and to greatly simplify the receiver functions spatial interpolation and smoothing suppress poorly sampled and difficult to interpret back azimuthal variations and allow the extraction of the first order features in the receiver function wavefield including observations from several ray parameter ranges we combine the interpolated receiver functions with rayleigh wave dispersion estimates and surface gravity observations to estimate the 3 d shear wave speed beneath the region speed variations in the 3 d model correlate strongly with expected geologic variations and illuminate broad scale features of the western u s crust and upper mantle the model is smooth self consistent and demonstrates the compatibility of the interpolated receiver functions and dispersion observations

measurement of diagenetic compaction strain from quantitative analysis of fault plane dip we developed a new technique for quantifying the amount of porosity loss during diagenetic transformation of opal a to opal ct the technique is based on 3d seismic data from offshore norway where the widely developed biosiliceous sediments of the brygge formation are deformed by a polygonal fault system evidence is shown from two study areas that the dip of the polygonal fault planes reduces abruptly across the opal a to opal ct diagenetic boundary suggesting that the fault planes were passively rotated into shallower dips due to diagenesis the reduction of fault plane dip was used to quantify the vertical compaction strain due to diagenesis using an independent assessment of the magnitude of the porosity loss we are able to validate the method based on fault plane dips and also to evaluate whether the porosity loss results in an exclusively vertical strain additionally the impact of silica diagenesis on the shear strength of the sediments and fault growth is investigated we present evidence suggesting that deviations from classical mohr coulomb behaviour may be expected during the combined processes of diagenesis and porosity collapse and may indeed be sufficient to promote continued fault growth

biogeographic impact of the leeuwin current in southern australia since the late middle eocene abstract the leeuwin current can be tracked from the western margin of the australian continent to the southern margin by the record of fossilized organisms typical of warm water marine environments this transport smudges the normal latitudinal asymmetry in the biotas of opposing oceanic and continental margins in which the eastern margins of oceans are cooler than the western margins and warmer biotas are restricted to lower latitudes in the east the most comprehensive record is in the large benthic foraminifera although fossils of benthic invertebrates nektonic nautiloids and planktonic protists are also informative in addition organic biomarker hydrocarbons in stranded bitumens and resins demonstrate that they have travelled the same route from their ultimate sources in cenozoic sedimentary basins and modern tropical rainforests of the indonesian archipelago the earliest spoor of the current is in the later middle eocene at which time the part deflection of counter gyral circulation in the indian ocean to the southeast was stimulated by the accelerated opening of the oceanic gap between australia and antarctica thus the origin of the leeuwin current is twice the age of the previously suggested origin in the miocene the current turns on and turns off in the great australian bight during the late quaternary in concert with the interglacials and the glacials at scales of 10 5 yr the switch can be seen in the faunal succession of planktonic foraminifera which are consistent with the neritic benthic faunas of the central gulfs both communities show that at the warm peak of the last interglacial the current transported biota across the bight more strongly than it has during the holocene the cenozoic record of the past 40 ma is in the same mode at 10 6 yr scales the relevant fossils are found concurrently at major marine transgressions and warming reversals of the overall fall in global temperature however the fossil pattern is due to transport on the activated leeuwin current not merely to general warming and the spread of friendly environments to higher latitudes

volume change during sediment diagenesis and the development of growth faults abstract the stress system induced the weight of a sediment and the pore fluid it contains termed the passive stress system is capable of deforming the sediment this volumetric deformation is examined with respect to the evolution of porosity and permeability during burial the effect of this self deformation on the shape of growth faults and normal faults in extensional terrains is considered

rayleigh wave multipathing along the west coast of north america we have created a movie of surface ground motion for the 3 november 2002 denali fault earthquake based on spectral element simulations using crustal model crust2 0 mantle model s20rts topography and bathymetry model etopo5 and a finite fault slip model the movie features two anomalous wave packets that travel along the west coast of the north american plate following off great circle paths these wave packets are rayleigh waves with dominant periods around 20 sec which are also found in seismograms recorded by the southern cali fornia seismic network one of these packets is the direct surface wave whose group arrival time changes laterally as dictated by the shape of the oregon coast the other packet is a surface wave reflected by a lateral interface underneath the rocky moun tains a linear reflector parallel to the canadian coast offsetting it by a few hundred kilometers can explain its arrival time but the offsetting distance derived from the synthetic seismograms puts the reflector 350 km northeast of the result obtained from the data indicating a need to update the crustal and mantle models in this area online material animation of normalized simulated vertical displacement for the 2002 denali earthquake

reflection of seismic surface waves at the northern apennines abstract seismic surface waves with periods of 15 to 20 s are reflected laterally at the northern apennines for earthquakes originated and recorded in the wider alpine area a few hundred kilometres north of the apennines we can directly observe late arrivals of reflected regional surface waves these have a characteristic polarization of particle motion and often dominate the intermediate period surface wave coda love waves are the most prominent coda arrivals while reflected rayleigh waves show smaller amplitudes and become clear only after rotation of the recordings to the reflection incidence direction we can track the development of the love wave reflection along a temporary broad band transect across the northern apennines indicating the location of the reflector near to the highest topography from spectral element simulations of three dimensional wave propagation we attribute the reflection to a continuous 270 km long offset in the crust mantle boundary under the mountain belt with vertical throw of 20 km thus supporting a deep crustal root under the outer side of the apennines fold and thrust belt and significant crustal thinning on the inner side amplitude reflection coefficients for near normal incidence can be estimated as 7 for both love and rayleigh waves

constraining s wave velocity using rayleigh wave ellipticity from polarization analysis of seismic noise we develop a new method for measuring ellipticity of rayleigh waves from ambient noise records by degree of polarization dop analysis the new method named dop e shows a good capability to retrieve accurate ellipticity curves separated from incoherent noise in order to validate the method we perform synthetic tests simulating noise in a 1 d earth model we also perform measurements on real data from antarctica and northern italy observed curves show a good fit with measurements from earthquake records and with theoretical ellipticity curves the inversion of real data measurements for vs structure shows a good agreement with previous models in particular the shear wave structure beneath concordia station shows no evidence of a significant layer of liquid water at the base of the ice the new method can be used to measure ellipticity at high frequency and therefore it will allow the imaging of near surface structure and possibly of temporal changes in subsurface properties it promises to be useful to study near surface processes in a wide range of geological settings such as volcanoes fault zones and glaciers

structural stratigraphic models for extensional basins of half graben type abstract the equations describing subsidence in isostatically compensated basins formed by lithospheric stretching can be modified to define a notional depth to decollement which relates subsidence to the stretching factor in much the same way as the depth to a physical sole fault relates subsidence to extension in uncompensated thin skinned basins for a constant density basin fill this notional depth to decollement corresponds to the level of no vertical motion within the lithosphere in general the physical sole to a system of detached normal faults will not lie at the notional depth to decollement and must move vertically during extension this vertical movement must be implicitly corrected for before area bed length balancing is used to determine the depth to a physical sole fault the notional depth to decollement has been calculated numerically for an extensional basin loaded by sediments which follow a north sea shaly sand compaction law and increases with from 5 to 9 km a set of model half grabens has been constructed by combining subsidence curves generated by this shaly sand model with geometric relationships inherent in the rotated planar domino mechanism of upper crustal faulting for comparison a similar set of half grabens was constructed for an uncompensated basin with a sole fault at 7 5 km depth in both cases large fault to fault spacings give rise to large basement relief and consequent footwall uplift and erosion small fault spacings give rise to simple listric growth faults intermediate values generate more complex uplift subsidence histories which are capable of giving rise to such commonly observed features as rounded eroded fault block shoulders local regression followed by onlap or exponentially increasing subsidence at the crest of the fault block

finite frequency kernels for wave propagation in porous media based upon adjoint methods s u m m a r y we determine finite frequency kernels for wave propagation in porous media based upon adjoint methods these sensitivity kernels may be obtained based upon two numerical simulations for each source one calculation for the current model and a second adjoint calculation that uses time reversed signals at the receivers as simultaneous fictitious sources the adjoint equations for a porous medium are identical to the usual biot equations with the exception of the adjoint source term which involves time reversed measurements of the differences between simulations and data isotropic poroelastic wave propagation is governed by eight primary model parameters which appear in the original biot equations these parameters include four moduli the shear modulus of the frame plus three bulk moduli we consider two alternative parameterizations one involving density normalized moduli corresponding to squared wave speeds and a second involving the poroelastic shear and compressional wave speeds the alternative parameterizations lead to density sensitivity kernels that are small reflecting the fact that the traveltime of a poroelastic wave is governed by wave speed not density we systematically investigate and illustrate the sensitivity of the fast and slow compressional waves and the shear wave to the poroelastic model parameters using a 2 d spectral element method the poroelastic sensitivity kernels presented herein form the basis of tomographic imaging and inversion in porous media

the geometrical evolution of normal fault systems abstract the purpose of this paper is to examine the kinematic behaviour of normal fault systems and see what general conditions govern their geometrical evolution we pay particular attention to seismological and surface data from regions of present day active normal faulting as the instantaneous three dimensional geometry at the time of fault movement is better known in active regions than in areas where the faults are now static most normal faults are concave upward or listric this shape can be produced by geometric constraints either because the faults reactivate curved thrusts or because they must be curved to accommodate rotations another effect which will produce curved faults is the variation of rheology with depth brittle failure at shallow depths produces less fault rotation than does distributed creep in the lower part of the crust an important geometric feature of normal faulting is the uplift of the footwall the amount of such uplift is related not only to the elastic properties of the lithosphere but also to the throw and dip of the fault a striking feature of active normal faults is that they occur in groups in which all the faults dip in the same direction this behaviour arises because the faults cannot intersect if they do one must cease to be active the rotation which such fault systems produce reduces the dip of the faults until a new steeply dipping fault is formed once a new fault cuts pre existing faults the earlier faults become locked and a new set of faults must propagate rapidly across the whole region involved many of these geometric constraints also apply to thrust faulting

abrupt climate change and transient climates during the paleogene a marine perspective detailed investigations of high latitude sequences recently collected by the ocean drilling program odp indicate that periods of rapid climate change often culminated in brief transient climates with more extreme conditions than subsequent long term climates two examples of such events have been identified in the paleogene the first in latest paleocene time in the middle of a warming trend that began several million years earlier the second in earliest oligocene time near the end of a middle eocene to late oligocene global cooling trend superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice sheet on antarctica in both cases the climate extremes were not stable lasting for less than a few hundred thousand years indicating a temporary or transient climate state geochemical and sedimentolog

reverse propagation of surface waves reflected from seamounts in the northwestern pacific abstract the reverse propagation of a surface wave traveling through the japanese islands from southwest to northeast was detected for major shallow earthquakes that occurred in northeastern japan the wave is predominant in the transverse component having a period of 20 sec and lasting longer than 200 sec the propagation velocity is around 3 8 km sec which is characteristic of a typical surface wave semblance analysis using a dense seismograph network shows that the wave was generated near the kyushu palau ridge southeast of kyushu island numerical simulation with a 3d finite element method can explain the surface wave reflection predominant in the transverse component as reflection from seamounts with a crustal root 10 km deeper than the moho discontinuity at the surrounding ocean floor the observed long duration of the reverse propagating surface wave might represent the superposition of a reflected wave from other seamounts and or the thick sedimentary layer along the nankai trough

on changes in porosity and volume during burial of argillaceous sediments abstract the porosity and hence volume of argillaceous sediments is determined by 1 the magnitude of the effective stress acting within the sediment 2 the previous stress history of the sediment and 3 at shallow depths of burial by features such as the mineralogy and the nature of the depositional environment stress paths and the critical state diagrams for a number of clays are used to investigate the range of porosities possible in argillaceous sediments as the effective stresses increase it is found that all porosity effective stress curves converge at large stresses the change in porosity is strongly dependent on the mean effective stress but largely independent of the deviatoric stress and thus is largely independent of the nature of the stress field acting on the basin compressional extensional etc because of the dependence of porosity on the mean effective stress no simple relationship exists between porosity and depth of burial but in the absence of overpressured pore fluids and assuming the sediment is not overconsolidated it is possible to contour the porosity effective stress diagram in terms of burial depths these data should assist in recalculating stratigraphic thicknesses for basin reconstruction and stratigraphic correlation studies

spectral element simulations of seismic waves generated by the 2009 l aquila earthquake abstract we adopt a spectral element method sem to perform numerical simulations of the complex wavefield generated by the 6 april 2009 m w 6 3 l aquila earthquake in central italy the mainshock is represented by a finite fault solution obtained by inverting strong motion and global positioning system data testing both 1d and 3d wavespeed models for central italy surface topography attenuation and the moho discontinuity are also accommodated including these complexities is essential to accurately simulate seismic wave propagation three component synthetic waveforms are compared to corresponding velocimeter and strong motion recordings the results show a favorable match between data and synthetics up to 0 5 hz in a 200 km 200 km 60 km model volume capturing features mainly related to topography or low wavespeed basins we construct synthetic peak ground velocity maps that for the 3d model are in good agreement with observations thus providing valuable information for seismic hazard assessment exploiting the sem in combination with an adjoint method we calculate finite frequency kernels for specific seismic arrivals these kernels capture the volumetric sensitivity associated with the selected waveform and highlight prominent effects of topography on seismic wave propagation in central italy online material movie of wave propagation waveform fits and stable of station parameters

glacial eustasy during the cenozoic sequence stratigraphic implications a newly constructed composite oxygen isotope record is a proxy for eustasy that extends back to the cretaceous tertiary boundary and provides an independent test of sequence stratigraphic based eustatic curves the isotope record shows several eustatic episodes that are consistent with the geological record of ice sheet evolution the first evidence for the existence of an ice sheet in east antarctica occurs near the lower middle eocene boundary base of the lutetian stage there is no evidence for a large ice sheet on antarctica prior to this time however strata of this age are lacking over most of the continent the isotope curve also indicates that the ice sheet experienced phases of growth during the late eocene and middle oligocene followed by a decrease in volume in the early miocene the ross sea stratigraphic record indicates initial evolution of the west antarctica ice sheet during the early miocene by the middle miocene the ice sheet spread across the ross sea weddell sea and antarctic peninsula continental shelves the pliocene pleistocene record of glaciation in antarctica includes numerous glacial erosion surfaces on the continental shelf indicating repeated advance and retreat of both east and west antarctica ice sheets these volume changes in the antarctica ice sheet were in response to the rise and fall of sea level caused by expanding and contracting northern hemisphere ice sheets there is a reasonable correlation between eustatic curves derived from sequence stratigraphic studies and the composite oxygen isotope record since the middle eocene this correlation indicates that glacial eustasy has been the principal factor regulating stratal stacking patterns on a global scale since the middle eocene

balanced cross section construction from seismic sections in areas of extensional tectonics abstract the application of the technique of balanced section construction initially developed for areas of compressional folding and faulting is reviewed with reference to extensional tectonics a number of examples are discussed where these techniques have been successfully applied in the north sea the interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions the nature of seismic sections however places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion the rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information

chronostratigraphic framework for the iodp expedition 318 cores from the wilkes land margin constraints for paleoceanographic reconstruction the integrated ocean drilling program expedition 318 to the wilkes land margin of antarctica recovered a sedimentary succession ranging in age from lower eocene to the holocene excellent stratigraphic control is key to understanding the timing of paleoceanographic events through critical climate intervals drill sites recovered the lower and middle eocene nearly the entire oligocene the miocene from about 17 ma the entire pliocene and much of the pleistocene the paleomagnetic properties are generally suitable for magnetostratigraphic interpretation with well behaved demagnetization diagrams uniform distribution of declinations and a clear separation into two inclination modes although the sequences were discontinuously recovered with many gaps due to coring and there are hiatuses from sedimentary and tectonic processes the magnetostratigraphic patterns are in general readily interpretable our interpretations are integrated with the diatom radiolarian calcareous nannofossils and dinoflagellate cyst dinocyst biostratigraphy the magnetostratigraphy significantly improves the resolution of the chronostratigraphy particularly in intervals with poor biostratigraphic control however southern ocean records with reliable magnetostratigraphies are notably scarce and the data reported here provide an opportunity for improved calibration of the biostratigraphic records in particular we provide a rare magnetostratigraphic calibration for dinocyst biostratigraphy in the paleogene and a substantially improved diatom calibration for the pliocene this paper presents the stratigraphic framework for future paleoceanographic proxy records which are being developed for the wilkes land margin cores it further provides tight constraints on the duration of regional hiatuses inferred from seismic surveys of the region

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

eocene oligocene coals of the gippsland and australo antarctic basins paleoclimatic and paleogeographic context and implications for the earliest cenozoic glaciations abstract australia s gippsland basin contains a semi continuous eocene oligocene 41 5 28 4 ma near coastal coal record that formed adjacent to pacific ocean traralgon and morwell formation brown coals include 4 main seams t2 t1 t0 m2 coal seam palynology records show late middle eocene t2 coals formed under megathermic conditions characterized by high gymnosperm contents late eocene t1 coals formed under mesothermic conditions characterized by reduced gymnosperm contents and earliest indications of palaeoclimate cooling earliest oligocene t0 coal record 33 9 31 5 ma contains high gymnosperm palynology profile very similar to the t2 coals the earliest indication of cooler climes only begins after this coal formed as indicated by low gymnosperm high nothofagus southern beech pollen proportions we suggest in gippsland the earliest evidence for major glacial cooling by inference the oi1 event be placed immediately above the t0 coal seam where early to late oligocene morwell formation sands clays and coals contain low counts of gymnosperms a number of contemporaneous middle to late eocene brown coals occurred in near coastal settings across 1200 km of southern australia palaeogeographically all these coal basins faced the australo antarctic gulf and have a much lower gymnosperm proportion

kinematic analysis of a growth fault system in the niger delta from restoration in map view by restoring six stratigraphic markers in map view we have studied the kinematics of a growth fault system involving a major fault its antithetic and a faulted roll over located within the niger delta offshore nigeria restoration yields for each marker the horizontal displacements due to normal faulting and the associated fields of block rotation about vertical axes as expected for a continuous history of growth faulting the amount of extension computed for each stratigraphic marker increases with depth from the fields of finite displacement and block rotation we find that horizontal extension perpendicular to fault traces is associated with a minor amount of bulk left lateral wrenching accommodated by counterclockwise rotation of blocks because the overall deformation differs from a plane strain balancing of cross sections alone would lead to some errors we also computed incremental displacement fields for time intervals between successive stratigraphic markers according to our results during the first stages of growth faulting displacement occurred only on the major faults whereas during later stages larger horizontal displacements were accommodated by numerous small faults probably responsible for the collapse of the roll over

biogeographic ecological and stratigraphic relationships of the miocene brown coal floras latrobe valley victoria australia abstract palaeobotanical studies of the brown coal deposits of the latrobe valley have contributed significantly towards an understanding of the age of the deposits existing climatic conditions and detailed depositional environments this paper re assesses some past reconstructions for the early to mid miocene coals using recent information on plant distributions and their bioclimatic significance and on a marine incursion model for coal lithotype formation the brown coal flora is composed overwhelmingly of rainforest taxa that presently cover a range of different environments within the australasian region the application of a bioclimatic prediction model to these taxa allows the construction of consistent and quantitative estimates of climates during coal forming phases it is considered that rainfall in the area was more than twice the 850 mm received today with significant seasonal variation the mean annual temperature estimate of about 19 c indicating a mesothermal or subtropical environment is some 2 5c higher than present and higher than previous estimates it does however correspond with sea surface temperature estimates for the southern ocean at this time the original model of lithotype formation which suggests that lithotypes conform to a successional sequence from open water in the lightest coloured lithotypes to raised bog in the darkest lithotypes is considered to be inconsistent with the evidence for lightening upwards sequences within the coals a central feature of the proposed marine incursion model of coal formation the two models are reconciled to some degree by a reinterpretation of the palaeobotanical data and by the postulation of climatic rather than autogenic successional control over lithotype formation

fluid flow pathways in actively deforming sediments the role of pore fluid pressures and volume change abstract the manner in which sediments respond to burial and shear depends largely on the ease with which fluids can escape rapid increase of overburden pressure or shear prevents efficient dewatering and can lead to the generation of excess pore fluid pressures a principal control on the development of overpressure and hence mechanical strength is the sediments permeability observations from modern plate margin accretionary prisms indicate that many faults are associated with both overpressuring and efficient fluid flow that operates in pulses indicative of permeability that is constantly changing we present the results of laboratory experiments exploring how the permeability of sediment retrieved from the barbados accretionary prism and laboratory analogues varies with progressive strain volume changes are linked to permeability fluctuations and the drainage capacity of the material we investigate the importance of the previous stress history imparted on the sediment and quantify the extent to which different deformation structures can acts as conduits for fluid flow under conditions of fluctuating effective stress material that has been initially consolidated and then subjected to reduction of effective stress either by raised fluid pressure or reduction of load inducing overconsolidation dilates during shear zone formation and displays an increase in permeability during strain shear fabrics can localise flow further where the principal mode of deformation is intensely localised and brittle and effective stress approaches zero conversely normally consolidated sediments deform by bulk volume loss without generating discrete fabrics and hence do not enhance flow under reduced effective stress conditions permeability can increase during strain by up to one order of magnitude when deformation results in sudden porosity collapse and pore water expulsion microstructural analysis and permeability testing before during and after shear have helped constrain the principal factors that control the evolution of flow conduits in fine grained low permeability sediments

volume changes during diagenesis abstract the literature pertaining to volume change during diagenesis of clastic sediments is reviewed with respect to the problem of calculating pre and syn compaction thicknesses of sediments for basin reconstruction and stragraphic correlation studies four major mechanisms for volume change are identified mechanical compaction mechanical dissolution chemical dissolution and phase change the first two of these are found to be strongly dependent on the effective stress whilst the latter two show at least a pressure dependence quantification of the relationships between porosity and depth of burial of a sediment seems to be possible only for specific examples of the first of these processes at present this quantification is dealt with in the accompanying related publication

ellipticity of rayleigh waves in basin and hard rock sites in northern italy we measure ellipticity of teleseismic rayleigh waves at 95 seismic stations in northern italy for wave period between 10 and 110 s using an automatic technique and a large volume of high quality seismic recordings from over 500 global earthquakes that occurred in 2008 2014 northern italy includes a wide range of crustal structures from the wide and deep po plain sedimentary basin to outcropping sedimentary and crystalline rocks in the northern apennines and alps it thus provides an excellent case for studying the influence of shallow earth structure on polarization of surface waves the ellipticity measurements show excellent spatial correlation with geological features in the region such as high ellipticity associated with regions of low seismic velocity in the po plain and low ellipticity values in faster hard rock regions in the alps and apennine mountains moreover the observed ellipticity values also relate to the thickness of the basement as highlighted by observed differences beneath the alps and the apennines comparison between observations and predicted ellipticity from a reference crustal model of the region show substantial fit particularly for t 38 s data discrepancy for shorter wave period suggests that slight modifications of the model are needed and that the ellipticity measurements could help to better constrain the shallow crustal structure of the region predictions for the po plain are larger than the observations by a factor of four or more and transition from retrograde to prograde rayleigh wave motion at the surface for periods of t 10 13 s is predicted for seismic stations in the plain analysis of corresponding real data indicates a possible detection of teleseismic prograde particle motion but the weak teleseismic earthquake signals are mixed with ambient noise signals at the predicted short transition periods detection of the period of polarity inversion from the joint analysis of earthquake and ambient noise ellipticity measurements may provide further stringent constraints on the structure of sedimentary basins

timing and nature of the deepening of the tasmanian gateway 1 tectonic changes that produced a deep tasmanian gateway between australia and antarctica are widely invoked as the major mechanism for antarctic cryosphere growth and antarctic circumpolar current acc development during the eocene oligocene e o transition 34 33 ma ocean drilling program odp leg 189 recovered near continuous marine sedimentary records across the e o transition interval at four sites around tasmania these records are largely barren of calcareous microfossils but contain a rich record of siliceous and organic walled marine microfossils in this study we integrate micropaleontological sedimentological geochemical and paleomagnetic data from site 1172 east tasman plateau to identify four distinct phases a d in the e o tasmanian gateway deepening that are correlative among odp leg 189 sites phase a prior to 35 5 ma minor initial deepening characterized by a shallow marine prodeltaic setting with initial condensation episodes phase b 35 5 33 5 ma increased deepening marked by the onset of major glauconitic deposition and inception of energetic bottom water currents phase c 33 5 30 2 ma further deepening to bathyal depths with episodic erosion by increasingly energetic bottom water currents phase d 30 2 ma establishment of stable open ocean warm temperate oligotrophic settings characterized by siliceous carbonate ooze deposition our combined evidence indicates that this early oligocene tasmanian gateway deepening initially produced an eastward flow of relatively warm surface waters from the australo antarctic gulf into the southwestern pacific ocean this proto leeuwin current fundamentally differs from previous regional reconstructions of eastward flowing cool water e g a proto acc during the early oligocene and thereby represents an important new constraint for reconstructing regional to global scale dynamics for this major global change event

persistent near tropical warmth on the antarctic continent during the early eocene epoch the warmest global climates of the past 65 million years occurred during the early eocene epoch about 55 to 48 million years ago when the equator to pole temperature gradients were much smaller than today1 2 and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume3 4 recently the early eocene has received considerable interest because it may provide insight into the response of earth s climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future5 as a consequence of unabated anthropogenic carbon emissions4 6 climatic conditions of the early eocene greenhouse world however are poorly constrained in critical regions particularly antarctica here we present a well dated record of early eocene climate on antarctica from an ocean sediment core recovered off the wilkes land coast of east antarctica the information from biotic climate proxies pollen and spores and independent organic geochemical climate proxies indices based on branched tetraether lipids yields quantitative seasonal temperature reconstructions for the early eocene greenhouse world on antarctica we show that the climate in lowland settings along the wilkes land coast at a palaeolatitude of about 70 south supported the growth of highly diverse near tropical forests characterized by mesothermal to megathermal floral elements including palms and bombacoideae notably winters were extremely mild warmer than 10 c and essentially frost free despite polar darkness which provides a critical new constraint for the validation of climate models and for understanding the response of high latitude terrestrial ecosystems to increased carbon dioxide forcing

was the oligocene miocene a time of fire and rain insights from brown coals of the southeastern australia gippsland basin abstract lithotype cycles ranging from 10 to 30 m thick in the brown coals of the latrobe valley gippsland basin australia display well developed lightening upward trends cycle tops are characterized by abrupt and unconformable boundaries with the overlying cycle geological geochemical palynological and macrofossil evidence is consistent with a relative drying terrestrialization upward depositional model for the cycles the abundance of charcoal in dark lithotypes near the cycle bases is explained by the fire prone and highly flammable nature of the herbaceous reed wetlands in common with similar modern wetlands in modern australasia in which the dark lithotypes are suggested to have formed this together with the greater preservation potential of charcoal in subaqueous environments results in the wettest facies of the latrobe valley coals having the highest charcoal contents despite prevailing warm wet climate conditions and the predominance of rainforests that are suggested to have characterized the cenozoic of southern australia some swamp taxa were clearly already pre adapted to tolerate fire and are likely to have been the ancestors of the fire adapted floral communities of modern arid australia

evolution of early cenozoic marine temperatures the equator to high southern latitude sea surface and vertical temperature gradients are reconstructed from oxygen isotope values of planktonic and benthic foraminifers for the following five time intervals late paleocene early eocene early middle eocene late eocene and early oligocene paleotemperatures are calculated using standard oxygen isotope temperature equations with adjustments to account for 1 variations in sea water 18o related to changes in global ice volume over time and 2 latitudinal gradients in surface water 18o these reconstructions indicate that sea surface temperatures sst of the southern oceans in the early eocene were as high as 15 c whereas temperatures during the late paleocene and early middle eocene reached maximum levels of 10 12 c by the late eocene and early oligocene high latitude sst had declined to 6 and 4 c respectively for most of the early paleogene low latitude sub tropical temperatures remained constant and well within the range of holocene temperatures 24 ndash 25 c but by the late eocene and early oligocene declined to values in the range of 18 to 22 c the late paleogene apparent decline in tropical temperatures however might be artificial because of dissolution of near surface foraminifera tests which biased sediment assemblages toward deeper dwelling foraminifera moreover according to recent plate reconstructions it appears that the majority of sites upon which the late eocene and early oligocene tropical temperatures were previously established were located either in or near regions likely to have been influenced by upwelling global deepwater temperature on average paralleled southern ocean sst for most of the paleogene we speculate based on the overall timing and character of marine sea surface temperature variation during the paleogene that some combination of both higher levels of greenhouse gases and increased heat transport was responsible for the exceptional high latitude warmth of the early eocene

the arc of the western alps in the light of geophysical data on deep crustal structure recently two international deep seismic campaigns in the western and central alps etude continentale et oceanique par reflexion et refraction sismique progetto strategico crosta profonda ecors crop roure et al 1996b and national research program 20 nrp 20 pfiffner et al 1997 have been completed here we present a synoptic interpretation of the wealth of geophysical data about deep crustal structure of the alps collected during the past 40 years including the two above mentioned geophysical projects the tectonic reinterpretation of the ecors crop high resolution seismic transect is based on an evaluation of the deep crustal structure by integrating new and literature data on surface geology combined with previously published interpretations regarding the central alps schmid et al 1996 this study reveals substantial differences in geometry and kinematics between transects across the western and central alps respectively at depth the transition between the central and western alps is marked by the western limits of an adriatic lower crustal wedge shaped structure and the northeastern limits of a similar structure made of european lower crustal material at the surface it coincides with a corridor of dextral strike slip along the tonale and simplon lines in addition the thickness of the seismogenic zone shows a remarkable variation from over 40 km beneath the penninic realm of the western alps to less than 20 km in the central alps the formation of the western alpine arc was initiated during convergence and collision before 35 myr ago when the adriatic micro plate moving northward with respect to the european foreland caused sinistral transpression in the western alps while the central and eastern alps underwent head on convergence and collision during the post collisional stage i e after 35 myr ago the arcuate shape of the western alps was accentuated by wnw directed movement and anticlockwise rotation of the adriatic microplate decoupled from the central and eastern alps along the tonale simplon dextral shear zone this led to wedging of lower crustal slices both in the western alps and in the central alps the new tectonic interpretation of the ecors crop transect allows a kinematic model to be established for crustal shortening in the western alps during the past 35 myr the ivrea mantle plays the role of a backstop in our tectonic model we distinguish three episodes of post collisional crustal shortening along the ecors crop transect from 35 to 30 ma the brianconnais basement was back thrusted over the gran paradiso units leading to 30 km of crustal shortening first episode in the early miocene movements concentrated mainly along the penninic frontal thrust and resulted in about 60 km shortening second episode post 12 ma shortening within the external massifs is associated with folding in the jura mountains when the crust was shortened by an additional 30 km third episode

effect of the deepening of the tasman gateway on the global ocean 1 we examine the effect of the deepening of the tasman seaway at the end of the eocene in a climate model with realistic late eocene bathymetry and winds for this we have constructed an eocene numerical model based on the university of victoria climate model with wind forcing derived from a fully coupled eocene simulation the model climate state is characterized by an oceanic meridional overturning circulation moc involving southern hemisphere sinking and a northward atmospheric moisture transport across the equator the deepening of the tasman seaway in the presence of an open drake passage and the associated establishment of the antarctic circumpolar current acc have a limited climatic impact on antarctica nonetheless the antarctic deep sinking regions cool sufficiently to lead to a global deep ocean cooling of 3 c no initiation of northern component water is found indicating that this may require the development of a more mature acc previous studies suggest that the ross sea gyre cools the east coast of australia and expected the deepening of the tasman seaway to lead to a warming east of australia due to the introduction of warmer water from the australo antarctic gulf we here find that this warming is limited to close to the australian coast and that widespread cooling prevails further off shore

the mid pleistocene transition in the subtropical southwest pacific 1 reconstructions of subtropical southwest pacific climate variability over the pleistocene were derived from coupled planktic foraminiferal 18o mg ca measurements taken from a southern coral sea sediment core a clear shift from 40 kyr to 100 kyr modes of reconstructed glacial interglacial sea surface temperature sst variability is seen over the mid pleistocene transition and these fluctuations are shown to have remained coherent with the orbital obliquity cycle across the transition the likely origin of this strong obliquity signal in subtropical southwest pacific sst is shown to be the southern high latitudes and comparison with existing sst reconstructions from the equatorial pacific is consistent with the communication of the signal occurring principally by greenhouse gas forcing in contrast to the sst reconstruction regional hydrological cycle variability based on the calculated local component of 18osw change does not show significant coherence with obliquity after 1000 ka the decoupling of the sst and hydrological cycle responses over the mid pleistocene transition allows constraints to be placed on the evolution and extent of orbitally paced fluctuations within the coupled low latitude ocean atmosphere system

global implications of lower to middle eocene sequence boundaries on the new jersey coastal plain the icehouse cometh wedocumentninelower middleeocenesequencesonthenewjerseycoastalplainand comparethemwithglobal d 18 oandhaqetal records earlyeocenehiatusesdonotmatch d 18 ochanges anditisunlikelythattheyaretheresultofglacioeustasy consistentwithan ice free early eocene early middle eocene 49 43 ma evidence for a link between sequencesand d 18 oisequivocal andthepresenceoflargeicesheetsisuncertain beginning in the late middle eocene 43 42 ma concomitant increases in planktonic and benthic d 18 o records coincide with the timing of hiatuses on the new jersey coastal plain and a change from carbonate dominated to siliciclastic dominated sedimentation these represent the development of the antarctic ice cap and the beginning of the icehouse world of the 14 sequences predicted by haq et al for this interval 9 are resolvable on the new jersey margin and the other 5 appear to be combined with others we conclude that although ice volume changes controlled sequences since at least 42 ma mechanisms for sea level change prior to then are still not fully understood

the eocene oligocene transition changes in sea level temperature or both abstract the eocene oligocene transition eot 34 ma reflects the onset of major antarctic glaciation the primary geochemical signature of the eot is two 300 kyr spaced shifts in increasing deep sea oxygen isotope values possibly reflecting both global cooling and or increasing ice volume a way to assess the respective contribution of continental ice is to quantify concomitant glacio eustatic sea level change this is usually expressed in relatively shallow marine depositional settings one potentially suitable region is in the vicentinian alps ne italy where marginal marine deposits document sea level changes during the eot by correlating stable isotope bio and magnetostratigraphic information between three distant regions we are able to relate the shallow marine sections to the pacific oxygen isotope record from ocean drilling program odp site 1218 of coxall et al 2005 microfacies sedimentological and biotic analysis suggests that associated with the first isotope shift eot 1 sea level fell 20 m and with the ultimate shift the oligocene isotope event 1 oi 1 sea level fell some 50 60 m distribution patterns of temperature sensitive dinoflagellates from a coeval central italian section reveal that the early stages of the eot were accompanied by sea surface cooling whereas no sustained cooling is noted in association with the oi 1 this suggests that the initial eot shift s reflect a mixed signal of ice volume and temperature whereas the oi 1 primarily reflects expansion of the antarctic cryosphere

oligocene climate dynamics a planktonic and benthic foraminiferal stable isotope stratigraphy of the oligocene equatorial pacific ocean drilling program site 1218 was generated at 6 kyr resolution between magnetochrons c9n and c11n 2n 26 4 30 ma on a newly developed astronomically calibrated timescale our data allow a detailed examination of oligocene paleoceanography the evolution of the early cryosphere and the influence of orbital forcing on glacioeustatic sea level variations spectral analysis reveals power and coherency for obliquity 40 kyr period and eccentricity 110 405 kyr orbital bands with an additional strong imprint of the eccentricity and 1 2 myr obliquity amplitude cycle driving ice sheet oscillations in the southern hemisphere planktonic and benthic foraminifera 18o are used to constrain the magnitude and timing of major fluctuations in ice volume and global sea level change glacial episodes related to obliquity and eccentricity variations occurred at 29 16 27 91 and 26 76 ma corresponding to glacioeustatic sea level fluctuations of 50 65 m alteration of high latitude temperatures and antarctic ice volume had a significant impact on the global carbon burial and equatorial productivity as cyclic variations are also recorded in the carbon isotope signal of planktonic and benthic foraminifera the water column carbon isotope gradient and estimated percent carbonate of bulk sediment we also investigate the implications of a close correspondence between oxygen and carbon isotope events and long term amplitude envelope extrema in astronomical calculations during the oligocene and develop a new naming scheme for stable isotope events on the basis of the 405 kyr eccentricity cycle count

centroid moment tensor solutions for april june 1998 abstract centroid moment tensor solutions are presented for 219 earthquakes that occurred during the second quarter of 1998 the solutions are obtained using corrections for aspherical earth structure represented by a whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l 1992 acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging plenum vol 19 pp 785 797 a new model of anelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of anelasticity consistent with long period surface wave attenuation bull seismol soc am 86 144 158 is used to predict the decay of the waveforms

on the hydro mechanical behaviour of remoulded and natural opalinus clay shale the geo energy sector makes use of advanced technologies such as shale gas extraction co2 sequestration and nuclear waste geological disposal that rely on the exploitation of shale formations due to the great depths involved in these applications and the difficulties in retrieving intact samples remoulded shale specimens are often adopted for hydro mechanical testing remoulded and intact shales may substantially differ in their hydro mechanical behaviour due to the particular structure of the natural material which is the result of diagenesis and burial history this paper presents an experimental campaign aimed at i characterizing the role of diagenesis and depth for opalinus clay shale and their impact on the hydro mechanical behaviour of the material and ii understanding how representative the behaviour of the remoulded material is with respect to that of the natural shale in this paper the hydro mechanical behaviour of remoulded and intact specimens from the opalinus clay shale formation is investigated by means of a comprehensive oedometric testing campaign the effects of depth and diagenesis on the material behaviour are analysed by testing intact specimens that come from two different sites and depths of the considered shale formation the results highlight a considerably greater stiffness for the natural opalinus clay with respect to the remoulded specimens when the same vertical effective stress is considered together with a significantly lower porosity for the former which is shown to be the result of diagenetic processes rather than solely mechanical compaction a lower swelling sensitivity is also manifested by the natural material with respect to the remoulded specimens as a result of the formation of bonding on the other hand the diagenetic processes do not seem to have a strong impact on the permeability of the material finally creep effects are reduced when diagenesis occurs while they become more relevant when the material is disturbed or remoulded the obtained results provide significant insight into the roles of depth diagenesis and structural disturbance on the hydro mechanical behaviour of the opalinus clay shale

environmental forcings of paleogene southern ocean dinoflagellate biogeography 1 despite warm polar climates and low meridional temperature gradients a number of different high latitude plankton assemblages were to varying extents dominated by endemic species during most of the paleogene to better understand the evolution of paleogene plankton endemism in the high southern latitudes we investigate the spatiotemporal distribution of the fossil remains of dinoflagellates i e organic walled cysts dinocysts and their response to changes in regional sea surface temperature sst we show that paleocene and early eocene 65 50 ma southern ocean dinocyst assemblages were largely cosmopolitan in nature but that a distinct switch from cosmopolitan dominated to endemic dominated assemblages the so called transantarctic flora occurred around the early middle eocene boundary 50 ma the spatial distribution and relative abundance patterns of this transantarctic flora correspond well with surface water circulation patterns as reconstructed through general circulation model experiments throughout the eocene we quantitatively compare dinocyst assemblages with previously published tex86 based sst reconstructions through the early and middle eocene from a key locality in the southwest pacific ocean odp leg 189 site 1172 on the east tasman plateau we conclude that the middle eocene onset of the proliferation of the transantarctic flora is not linearly correlated with regional sst records and that only after the transantarctic flora became fully established later in the middle eocene possibly triggered by large scale changes in surface ocean nutrient availability were abundances of endemic dinocysts modulated by regional sst variations

displacive widening of calcite veins in shale insights into the force of crystallization abstract the geometry microtextures and c axis fabrics of calcite beef veins in the lower jurassic black shales wessex basin uk were characterized to investigate the mechanism responsible for widening following fracture propagation isolated beef veins exhibit planar tapering tips whereas closely spaced veins are characterized by blunt tips vein surfaces are generally smooth and flat however circular ridges appear on vein surfaces that protrude into the host clays where there are solid inclusions below or above the ridges fossils with well preserved morphologies which are separated by subvertical calcite fibers are observed on both the lower and upper surfaces of single veins the shale laminations around beef veins are folded and parallel to vein margins the beef veins commonly contain blocky zones of small equant calcite crystals pyrite and organic matter the fibers exhibit a preferred subvertical c axis orientation whilst crystals in the median zones and blocky zones have random c axis orientations the different crystal sizes morphologies and c axis orientations of the fibers from the blocky crystals suggest that the fibers grew without competition with each other under a nonhydrostatic stress field the displacive widening of calcite beef veins which is evident from vein interactions and deformation of individual fossil skeletons demonstrates that fibers grew incrementally because the crystallization pressure of calcite exceeded the overburden load the force of crystallization is suggested to be responsible for the c axis orientations of calcite fibers whereby crystals with free surfaces normal to c axis orientations grew preferentially the present study suggests that the fibrous widening of calcite veins in shale postdates their initiation and may result from displacive crystallization rather than fluid overpressure