present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

sharpening the tomographic image of the subducting slab below sumatra the andaman islands and burma summary taking advantage of the increased ray coverage due to seismicity following the 2004 december and 2005 march great earthquakes an improved iterative regional global tomographic method was applied to the sumatra andaman and adjacent regions to better constrain the 3 d mantle velocity heterogeneity in the region velocity and hypocentral parameters were iteratively perturbed to sharpen the image of the subducted slab several iterations were performed and the effects of source mislocation were considered in the iterative process an issue usually neglected in global tomography we find that source relocation between iterations increases the amplitudes of slab anomalies and sharpens the definition of slab geometry beyond what can be achieved by a fixed source iterative inversion alone in addition extensive restoration tests of synthetic data were conducted that emphasize enhancements obtained by our iterative process these tests show significant increases in amplitude and decreased smearing of synthetic slab features thus when applied to the real data similar enhancements are inferred in the resulting model which better illustrates the complex slab geometry in the upper mantle and transition zone regions along the sumatra andaman and burma subduction zones

ichnodiversity and ichnoabundance revealing depositional trends in a confined turbidite system ichnological studies are still in their infancy when it comes to the interpretation of deep marine deposits the eocene oligocene turbidite system of the gres d annot formation in south east france is well studied sedimentologically but its trace fossil content is poorly known here an integrated ichnological sedimentological study is presented from the annot sub basin for the first time which demonstrates its value for interpreting proximal to distal and axial to marginal trends in confined turbidite systems a comprehensive trace fossil data set was collected from seven outcrops situated in the southern part of the basin these data are presented following a morphology based classification scheme to allow easy recognition and characterization of ichnotaxa ichnodiversity and the abundance of ichnotaxa are regarded as important parameters in such interpretations instead of simply counting ichnotaxa per outcrop or stratigraphic unit an equation has been developed in which the ichnoabundance new term of each counted ichnotaxon is calculated an exponential growth factor is applied to the increase of the frequency of trace fossils and is assumed in this equation to better reflect the population dynamics of benthic organisms a comparison of the solution for pre turbidite and post turbidite trace fossil suites seems to be more suitable for revealing regional and stratigraphic trends compared with conventional approaches despite varying size and conditions of the studied outcrops the results achieved from the gres d annot formation can help in the reconstruction of sedimentary processes acting in this confined turbidite basin

an experimental investigation of density stratified inertial gravity currents turbidity currents and pyroclastic density currents may originate as stratified flows or develop stratification during propagation analogue density stratified laboratory currents are described using layers of salt solutions with different concentrations and depths to create the initial vertical stratification the evolving structure of the flow depends on the distribution of the driving buoyancy between the layers b proportional to the layer volumes and densities and their density ratio q when the lower layer contains more salt than the upper layer and so has a greater proportion of the driving buoyancy b 0 ae5 this layer travels to the nose of the current by mixing into the back of the head along the body wake density interface to produce a homogeneous flow q fi 1 or overtaking leading to streamwise stratification q fi 0 timescales describing the mixing between the layers and the streamwise separation of the layers are used to understand these flow behaviours and are in accordance with the experimental observations distance time measurements of the flow front show that strongly stratified flows initially travel faster than weakly stratified flows but during their later stages they travel more slowly in natural flows that are stratified in concentration and grain size internal features such as stepwise grading gradual upward fining and reverse grading could be produced depending on b and q stratification may also be expected to affect interactions with topography and overall fan architecture

convergence rate across the nepal himalaya and interseismic coupling on the main himalayan thrust implications for seismic hazard we document geodetic strain across the nepal himalaya using gps times series from 30 stations in nepal and southern tibet in addition to previously published campaign gps points and leveling data and determine the pattern of interseismic coupling on the main himalayan thrust fault mht the noise on the daily gps positions is modeled as a combination of white and colored noise in order to infer secular velocities at the stations with consistent uncertainties we then locate the pole of rotation of the indian plate in the itrf 2005 reference frame at longitude 1 34 3 31 latitude 51 4 0 3 with an angular velocity of 0 5029 0 0072 myr the pattern of coupling on the mht is computed on a fault dipping 10 to the north and whose strike roughly follows the arcuate shape of the himalaya the model indicates that the mht is locked from the surface to a distance of approximately 100 km down dip corresponding to a depth of 15 to 20 km in map view the transition zone between the locked portion of the mht and the portion which is creeping at the long term slip rate seems to be at the most a few tens of kilometers wide and coincides with the belt of midcrustal microseismicity underneath the himalaya according to a previous study based on thermokinematic modeling of thermochronological and thermobarometric data this transition seems to happen in a zone where the temperature reaches 350 c the convergence between india and south tibet proceeds at a rate of 17 8 0 5 mm yr in central and eastern nepal and 20 5 1 mm yr in western nepal the moment deficit due to locking of the mht in the interseismic period accrues at a rate of 6 6 0 4 10 19 nm yr on the mht underneath nepal for comparison the moment released by the seismicity over the past 500 years including 14 m w 7 earthquakes with moment magnitudes up to 8 5 amounts to only 0 9 10 19 nm yr indicating a large deficit of seismic slip over that period or very infrequent large slow slip events no large slow slip event has been observed however over the 20 years covered by geodetic measurements in the nepal himalaya we discuss the magnitude and return period of m 8 earthquakes required to balance the long term slip budget on the mht

first global positioning system results in northern myanmar constant and localized slip rate along the sagaing fault we present the first recorded global positioning system gps data from myanmar measured at the northern tip of the sagaing fault this area is in a very complex geodynamic context where rigid and semirigid plates interact the 12 gps sites measured in 2005 and 2008 in northern myanmar show that the slip rate is 18 mm yr and is localized along a single active narrow fault trace 20 km wide the same rate was previously demonstrated and remeasured 500 km southward in central myanmar despite the geodynamic regional complexity induced by interaction between the sunda and india plates the burma microplate and the highly deformable eastern himalayan syntaxis the slip rate remains surprisingly constant along this fault however the modeled locking depth varies from 20 km in central myanmar to 5 km in the north

seismic modelling for reservoir studies a comparison between convolutional and full waveform methods for a deep water turbidite sandstone reservoir abstract two seismic modelling approaches that is two dimensional pre stack elastic finite difference and one dimensional convolution methods are compared in a modelling exercise over the fluid flow simulation model of a producing deep water turbidite sandstone reservoir in the west of shetland basin if the appropriate parameterization for one dimensional convolution is used the differences in three dimensional and four dimensional seismic responses from the two methods are negligible the key parameters to ensure an accurate seismic response are a representative wavelet the distribution of common depth points and their associated angles of incidence conventional seismic images generated by the one dimensional convolutional model suffer from lack of continuity because it only accounts for vertical resolution after application of a lateral resolution function the convolutional and finite difference seismic images are very similar although transmission effects internal multiples and p to s conversions are not included in our convolutional modelling the subtle differences between images from the two methods indicates that such effects are of secondary nature in our study a quantitative comparison of the normalized root mean square amplitude attributes and waveform kinematics indicates that the finite difference approach does not offer any tangible benefit in our target oriented seismic modelling case study and the potential errors from one dimensional convolution modelling are comparatively much smaller than the production induced time lapse changes

jurassic to miocene magmatism and metamorphism in the mogok metamorphic belt and the india eurasia collision in myanmar situated south of the eastern himalayan syntaxis at the western margin of the shan thai terrane the highgrade mogok metamorphic belt mmb in myanmar occupies a key position in the tectonic evolution of southeast asia the first sensitive high resolution ion microprobe u pb in zircon geochronology for the mmb shows that strongly deformed granitic orthogneisses near mandalay contain jurassic 170 ma zircons that have partly recrystallized during 43 ma high grade metamorphism a hornblende syenite from mandalay hill also contains jurassic zircons with evidence of eocene metamorphic recrystallization rimmed by thin zones of 30 9 plus or minus 0 7 ma magmatic zircon the relative abundance of jurassic zircons in these rocks is consistent with suggestions that southern eurasia had an andean type margin at that time mid cretaceous to earliest eocene 120 to 50 ma i type granitoids in the mmb myeik archipelago and western myanmar confirm that prior to the collision of india an up to 200 km wide magmatic belt extended along the eurasian margin from pakistan to sumatra metamorphic overgrowths to zircons in the orthogneiss near mandalay date a period of eocene 43 ma high grade metamorphism possibly during crustal thickening related to the initial collision between india and eurasia at 65 to 55 ma this was followed by emplacement of syntectonic hornblende syenites and leucogranites between 35 and 23 ma similar syntectonic syenites and leucogranites intruded the ailao shan red river shear belt in southern china and vietnam during the eocene oligocene to miocene and the wang chao and three pagodas faults in northern thailand that most likely link with the mmb were also active at this time the complex history of eocene to early miocene metamorphism deformation and magmatism in the mmb provides evidence that it may have played a key role in the network of deformation zones that accommodated strain during the northwards movement of india and resulting extrusion or rotation of indochina

topographic controls on the development of contemporaneous but contrasting basin floor depositional architectures abstract sediment laden gravity driven flow deposits on the basin floor are typically considered to form either discrete lobes that stack compensationally or packages of laterally extensive beds commonly termed sheets these end member stacking patterns are documented in several basinfills however whether they can coexist in a single basin or there are intermediate or transitional stacking patterns is poorly understood an analysis of depositional architecture and stacking patterns along a 70 km dip oriented transect in the upper broto turbidite system jaca basin south central pyrenees spain which displays disparate stacking patterns in contemporaneous strata is presented proximal and medial deposits are characterized by discrete packages of clean sandstones with sharp bed tops which exhibit predictable lateral and longitudinal facies changes and are interpreted as lobes distal deposits comprise both relatively clean sandstones and hybrid beds that do not stack to form lobes instead localized relatively thick hybrid beds are inferred to have inhibited the development of lobes hybrid beds developed under flows which were deflected and entrained carbonate mud substrate off a carbonate slope that bounded the basin to the south evidence for this interpretation includes 1 divergent paleoflow indicators and hummock like features in individual beds 2 a decrease in hybrid bed thickness and abundance away from the lateral confining slope 3 a carbonate rich upper division not seen in more proximal turbidites the study demonstrates the co occurrence of different styles of basin floor stacking patterns in the same stratigraphic interval and suggests that characterization of deep water systems as either lobes or sheets is a false dichotomy

oblique reflection of turbidity currents turbidity currents meeting obstacles for example the margins of a confined basin are subject to reflection the consequent change in flow direction is expressed in the sequence of depositional structures of the resulting bed of sediment putative examples of orthogonal reflection have been described based on 180 opposed current directions we present field evidence for the more general case of oblique reflection of turbidites and we report the results of flume experiments indicating a mechanism involving generation of internal solitary waves at an oblique ramp these propagate normal to the ramp regardless of the angle of incidence flow directions in reflected turbidites may indicate the orientation of reflecting surfaces such as basin margin slopes and thus may be of considerable help in paleogeographic and tectonic reconstructions

compound seismic modelling of the ainsa ii turbidite system spain application to deep water channel systems offshore angola abstract seismic models of outcrops are essential for qualifying petroleum targets because they bridge a critical gap in both resolution and scale between architectural geometries observed in outcrops and in seismic data the paper describes how a seismic model of the deep marine ainsa ii turbidite system of the st vicente formation in the southern pyrenees spain is developed and used as an analogue for exploration prospects in the quifangondo formation lower congo basin offshore angola first geometry and lithology information from the ainsa ii outcrop were utilised to construct a detailed earth model the ainsa ii turbidite system consists of at least five clastic turbidite units bounded by erosional surfaces where only the youngest unit is steep sided the input geo model earth model includes stratigraphic information such as truncations onlaps thickening thinning of beds condensed sections and detailed lateral changes in lithology second subsurface petrophysical properties velocity and density logs necessary to build the forward seismic models were extracted from an offshore well in angola this allowed us to utilise the outcrop as a seismic analogue for a relatively narrow laterally aggrading turbidite system offshore angola the seismic models showed that it is difficult to image and identify amalgamated beds inside a larger unit particularly if beds have predominantly the same facies associations and weakly dipping basal boundaries as in the lower part of the ainsa ii system second seismic modelling helped to highlight areas where it is difficult to distinguish between seismic onlap and true stratigraphic onlap information which decides when evaluating stratigraphic traps we also found that lateral degradation in amplitude may represent a lateral change in lithology e g from sandy channel deposits to levee overbank heterolithics integration of outcrop mapping well data 3d seismic interpretation and forward seismic modelling has enabled us to study deep water depositional elements at a sub seismic scale this has resulted in enhanced prediction of the lithology distribution and architecture of the turbidite system offshore angola and gives new insights into the 3d geometry of the ainsa ii system

fused spectral decomposition seismic attributes and forward seismic modelling to predict sand bodies in meandering fluvial reservoirs abstract understanding the hierarchical architectural elements of fluvial sand bodies is important for planning their development strategy and to enhance oil recovery red green blue rgb blending of multiple seismic attributes and forwarding seismic modelling are commonly used in the analysis of compound sand bodies however rgb blending of multiple seismic attributes can only qualitatively describe the boundaries and thickness of sand bodies the forward seismic modelling techniques previously documented in the literature are not effective when depicting the geometry of and stacking relationships between sand bodies i e reservoir compartmentalisation hence we propose in this work a new workflow that combines fused spectral decomposition seismic attributes sdsas and forwarding seismic modelling to quantitatively predict sand thickness and to characterise stacking relationships between sand bodies first we employ a support vector machine svm algorithm to fuse high middle and low frequency components attributes of seismic data so as to quantitatively predict the thickness of sand bodies second we define the seismic waveform response patterns corresponding to the typical conceptual stacked sand bodies with the constraints of waveform patterns and predicted sand thickness fused sdsas the geometry and stacking relationships of the sand bodies are characterised by forward seismic modelling to illustrate the effectiveness of our proposed workflow we apply it to the neogene minghuazhen formation nm of the qhd 32 6 oil field bohai bay basin china we define five architectural elements of a meandering fluvial reservoir by analysing the hierarchy of sand bodies using our workflow the predicted sand bodies in this workflow were further proven by horizontal drilling and production data

horizontal motion in elastic response to seasonal loading of rain water in the amazon basin and monsoon water in southeast asia observed by gps and inferred from grace 1 we find seasonal horizontal crustal motions observed by gps positioning in elastic response to heavy rainfall in the amazon basin and to monsoons in southeast asia to be consistent with those inferred from gravity recovery and climate experiment grace gravity observations of water mass loading solid earth moves toward the amazon during heavy spring rainfall and toward southeast asia during summer monsoons and back away from these areas 6 months later when the water load is minimum vertical oscillations observed by gps and inferred from grace are 2 to 3 times larger than horizontal oscillation near the margins of the areas of large mass loading some discrepancies between gps and grace are probably caused by local effects that influence gps measurements because the gps sites that show significant discrepancies also do not match nearby gps sites however when the load is short wavelength the limited spatial resolution of grace can cause systematic misfits

rigid indian plate constraints from gps measurements abstract we analyze gps data from 26 sites located on the indian plate and along its boundary the large spatial coverage of the indian plate by these sites and longer data duration helped us in refining the earlier estimates of the euler pole for the indian plate rotation our analysis suggests that the internal deformation of the indian plate is very low

present day crustal deformation around sagaing fault myanmar 1 global positioning system gps measurement campaigns in myanmar conducted in 1998 and 2000 allow quantifying the present day crustal deformation around the sagaing fault system in central myanmar both a regional network installed at four points within the country and a local 18 station network centered on the city of mandalay across the sagaing fault demonstrate that active deformation related to the northward motion of india is distributed across myanmar in a platelet that extends from the western edge of the shan plateau in the east to the andaman trench in the west in this platelet deformation is rather diffuse and distributed over distinct fault systems in the east the sagaing shan scarp fault system absorbs 10 mm yr this gps study combined with an on land geotectonic survey demonstrate that oblique slip of india along the rigid sundaland block is accommodated by a partitioned system characterized by distribution of deformation over a wide zone index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8110 tectonophysics continental tectonics general 0905 8158 tectonophysics plate motions present and recent 3040 keywords tectonics gps fault southeast asia

inflation of ponded particulate laden density currents field based physical modeling and analytical research approaches currently suggest that topographically confined particle laden density currents commonly inflate to produce suspension clouds that generate tabular and texturally homogeneous sedimentary deposits here a novel three dimensional theoretical model details a phase space of the criteria for inflation as a function of flow duration basin size and geometry total mass transport sediment concentration and particle grain size it shows that under most circumstances cloud inflation is unlikely at real world scales even where inflation is possible inflation relative to initial flow height is small except for suspensions of silt or finer grained sediment tabular deposits therefore either arise from processes other than flow ponding or deposits in confined settings may be significantly more complex than are currently understood due to processes of autogenic compensation and channelization with associated implications for reservoir characterization in applied contexts this study illustrates the potential of analytical flow modeling as a powerful complement to other research approaches

the influence of lateral basinal slopes on turbidite sedimentation in the annot sandstones of se france abstract the deep water deposits of the lower oligocene annot sandstones of se france were deposited in topographically dissected basins axially derived turbidites show marked lateral onlap onto the underlying marls the original lateral slopes were at least 250 m high and up to 12 prior to compaction induced steepening they commonly show a stepped or undulatory profile lateral tracing of individual beds away from their position of onlap termination down the paleoslope reveals a characteristic succession of microfacies thin bedded nongraded fine sandstones with upper flow regime planar lamination pass downslope into medium bedded partially graded medium sandstones with ripple and planar lamination at the base of the depositional slope the turbidites become thick to very thick bed ed fully graded commonly stepwise coarse sandstones to mudstones the most likely interpretation of the lateral transition from lower flow regime to upper flow regime conditions from the axial trough to the lateral margin of the basin involves pulsatory flow conditions episodes of increased flow thickness and velocity deposited upper flow regime bed forms on the higher parts of lateral ramps while periods of waning current deposited lower flow regime bed forms in the axial trough during accumulation of the sands the underlying marls were differentially compacted with maximum compaction under the axis of the basin decreasing to zero compaction at the edges of the basin this resulted in secondary slopes on the upper surface of the sandstones overlying the marl slopes which may have been important in controlling the accumulation of successive sand packages successive onlap and overstep of sand layers onto the marls resulted in a vertical profile that shows the same succession of facies as traced downslope in individual beds the resulting vertical sections coarsen and thicken upwards over 5 10 m the characteristics of the thin bedded fine sandstones at the base of cycles may be used to distinguish between prograding and laterally onlapping turbidite packages sandstone packages in the basin axis are thick 30 60 m sharp based and sandstone rich the laterally equivalent part of a package overlying a confining slope is thinner asymmetric with a coarsening upward signature and more mudstone rich

submarine transitional flow deposits in the paleogene gulf of mexico gravity driven flows on the seafloor are the largest yet least well understood sediment transport agents on earth recent exploration wells in ultradeep basins have revealed the presence of large sandy submarine fan systems of enigmatic facies types many hundreds of kilometers from paleocoastlines these sedimentary deposits often defy conventional turbidite or debrite interpretations having a character suggestive of deposition from flows with transient turbulent laminar rheologies in the wilcox formation gulf of mexico inferred transitional flow deposits have distinctive stratigraphic stacking patterns from fine grained debrites to coarser grained turbidites the vertical sequence of beds is here inferred to reflect the longitudinal bed distribution in response to lobe progradation and demonstrates a transition from well mixed turbulent flow to progressively more rheologically stratified flow and eventually to fully laminar flow the progressive development of internal rheological boundaries resulted in a high concentration but fluidal basal layer and an upper quasi laminar layer with an overriding sheared dilute turbidity current the long runout of the flows is linked to their high silt and clay content it is most likely flow expansion at the channel lobe transition that drives flow transformation this process based model may be applicable to many deep water settings and provides a framework within which to interpret the stratigraphic and spatial distribution of these complex deposits

subduction of the indian lithosphere beneath the tibetan plateau and burma abstract subduction of the indian lithosphere under eurasia plays an important role in the tectonic evolution of the tibetan plateau and surrounding regions to improve our knowledge of pertinent mantle structures through tomographic imaging we combine p wave arrival time data from temporary arrays in tibet and stations of the chinese seismograph network with reprocessed data from the international seismological centre the new images reveal considerable spatial variations in mantle structure along the collision zone and the horizontal distance over which presumed continental indian lithosphere slides northward beneath the plateau decreases from west where it underlies the himalayas and the entire plateau to east where no indication is found for present day underthrusting beyond the himalayan block and indus tsangpo suture p wavespeed appears low in the shallow mantle beneath much of central and eastern tibet these observations suggest that indian lithosphere underlies only the southwestern part of the plateau and that the central and northeastern part is underlain by lithosphere of asian origin the continental parts of the indian plate that currently underthrust or subduct below the plateau appear generally detached from the oceanic slab fragments that subducted longer ago and that have been detected deeper in the mantle except perhaps in the central part of the collision zone 80 90 e this suggests that ongoing india eurasia collision must increasingly be driven by other forces such as subduction of the indian plate further west and east e g beneath indochina our images reveal structures associated with eastward subduction along the burmese arc southeast of the eastern himalayan syntaxis the tengchong volcanic complex in southwest china is marked by slow wave propagation to 150 km depth suggesting a causal link to subduction along the burmese arc the low velocities beneath the red river fault region extend to greater depth and may be related to upper mantle processes further southeast

open ocean convection observations theory and models we review what is known about the convective process in the open ocean in which the properties of large volumes of water are changed by intermittent deep reaching convection triggered by winter storms observational laboratory and modeling studies reveal a fascinating and complex interplay of convective and geostrophic scales the large scale circulation of the ocean and the prevailing meteorology two aspects make ocean convection interesting from a theoretical point of view first the timescales of the convective process in the ocean are sufficiently long that it may be modified by the earth s rotation second the convective process is localized in space so that vertical buoyancy transfer by upright convection can give way to slantwise transfer by baroclinic instability moreover the convective and geostrophic scales are not very disparate from one another detailed observations of the process in the labrador greenland and mediterranean seas are described which were made possible by new observing technology when interpreted in terms of underlying dynamics and theory and the context provided by laboratory and numerical experiments of rotating convection great progress in our description and understanding of the processes at work is being made

stable creeping fault segments can become destructive as a result of dynamic weakening faults in earth s crust accommodate slow relative motion between tectonic plates through either similarly slow slip or fast seismic wave producing rupture events perceived as earthquakes these types of behaviour are often assumed to be separated in space and to occur on two different types of fault segment one with stable rate strengthening friction and the other with rate weakening friction that leads to stick slip the 2011 tohoku oki earthquake with moment magnitude m w 9 0 challenged such assumptions by accumulating its largest seismic slip in the area that had been assumed to be creeping here we propose a model in which stable rate strengthening behaviour at low slip rates is combined with coseismic weakening due to rapid shear heating of pore fluids allowing unstable slip to occur in segments that can creep between events the model parameters are based on laboratory measurements on samples from the fault of the m w 7 6 1999 chi chi earthquake the long term slip behaviour of the model which we examine using a unique numerical approach that includes all wave effects reproduces and explains a number of both long term and coseismic observations some of them seemingly contradictory about the faults at which the tohoku oki and chi chi earthquakes occurred including there being more high frequency radiation from areas of lower slip the largest seismic slip in the tohoku oki earthquake having occurred in a potentially creeping segment the overall pattern of previous events in the area and the complexity of the tohoku oki rupture the implication that earthquake rupture may break through large portions of creeping segments which are at present considered to be barriers requires a re evaluation of seismic hazard in many areas

structure and kinematics of the indo burmese wedge recent and fast growth of the outer wedge 1 the northern sunda subduction zone offshore burma and the associated indo burmese wedge mark the active eastern boundary of the burma platelet jammed between the india plate and the sunda plate the aim of this paper is to provide a structural and kinematics analysis of the indo burmese wedge based on seismic reflection geodetic and geological field data we found out that the indo burmese wedge is the place of diffuse strain partitioning right lateral shearing in the innermost part and e w shortening in the outermost part in the outer wedge thick skinned deformation overprints thin skinned deformation it can be explained by the required preservation of the critical taper after the fast westward propagation of the outer wedge above a very efficient clayey decollement layer the thick skinned deformation is here characterized by major right lateral strike slip faults the kaladan fault and the chittagong coastal fault and yet a typical internal deformation of the indo burmese wedge we suggest that the westward migration of internal right lateral shear deformation allows preservation of the strain partitioning ratios between internal n s trending right lateral shearing and external e w shortening some seismic lines show that the outer wedge deformation is not older than 2 ma its propagation could have been enhanced by the large amount of sediments filling up the sylhet flexural basin formed after the pliocene tectonic uplift of the shillong plateau

frontal and lateral submarine lobe fringes comparing sedimentary facies architecture and flow processes submarine lobe fringe deposits form heterolithic successions that may include a high proportion of hybrid beds the identification of lobe fringe successions aids interpretation of paleogeographic setting and the degree of basin confinement here for the first time the sedimentological and architectural differences between frontal and lateral lobe fringe deposits are investigated extensive outcrop and core data from fan 4 skoorsteenberg formation karoo basin south africa allow the rates and style of facies changes from axis to fringe settings of lobes and lobe complexes in both down dip frontal and across strike lateral directions to be tightly constrained over an 800 km2 study area fan 4 comprises three sand prone divisions that form compensationally stacked lobe complexes separated by thick packages of thin bedded siltstone and sandstone intercalated with muddy siltstone interpreted as the fringes of lobe complexes lobe fringe facies associations comprise i thick bedded structureless or planar laminated sandstones that pinch and swell and are associated with underlying debrites ii argillaceous and mudclast rich hybrid beds and iii current ripple laminated sandstones and siltstones typically frontal fringes contain high proportions of hybrid beds and transition from thick bedded sandstones over length scales of 1 to 2 km in contrast lateral fringe deposits tend to comprise current ripple laminated sandstones that transition to thick bedded sandstones in the lobe axis over several kilometers variability of primary flow processes are interpreted to control the documented differences in facies association preferential deposition of hybrid beds in frontal fringe positions is related to the dominantly downstream momentum of the high density core of the flow in contrast the ripple laminated thin beds in lateral fringe positions are interpreted to be deposited by more dilute low density parts of the flows the development of recognition criteria to distinguish between frontal and lateral lobe fringe successions is critical to improving paleogeographic reconstructions of submarine fans at outcrop and in the subsurface and will help to reduce uncertainty during hydrocarbon field appraisal and development

on traction carpet sedimentation traction carpets are highly concentrated bedload layers that are developed beneath and driven by turbulent overlying flows they have a convex up velocity profile and comprise a lower frictional and an upper collisional region the frictional region having a particle concentration more than 80 of the packed bed is characterized by nearly continuous grain contacts low strain rate and hampered grain segregation on the other hand the collisional region has a particle concentration between 15 and 80 of the packed bed and is characterized by active grain collisions and higher strain rate deposition from the traction carpets occurs via progressive aggradation of the bed rather than via en masse freezing while the downward grain flux from the overlying flow maintains them the thickness of a traction carpet stratum is therefore determined by the cumulative amount of sediment settled during the lifespan of a traction carpet and can be much larger than the thickness of a moving traction carpet inverse grading can be produced in the collisional region by the vertical gradient of dispersive pressure which is related to nonuniform distribution of particles when a thick frictional region develops however the inverse size distribution in the collisional region is poorly recorded in the deposits depositional features of traction carpet strata are therefore determined by the duration of a traction carpet and the thickness ratio of collisional to frictional regions the thickness ratio is further controlled by the applied shear stress sediment fallout rate and grain size generally a collisional region is better developed beneath a highly competent and coarse grained gravelly flow whereas a thick frictional region is developed beneath a heavily sediment laden fine grained sandy flow this explains the more common occurrence of inverse grading in coarse grained deposits

submarine channel response to intrabasinal tectonics the influence of lateral tilt lateral tilting is a common deformation style in extensional basins its influence on subaerial channels is to a degree understood and may be significant controlling the style of channel development and the resultant sand body architecture growth faulting and lateral tilting in turbidite channel systems have been demonstrated from three dimensional seismic data but the resultant architecture of channels within these settings has not yet been documented in the carboniferous of northern england a sand rich slope channel developed within a basin undergoing late stage extension underwent progressive and unidirectional migration toward a topographic low on a laterally tilting block the resultant sandstone body is wedge shaped in cross section and composed dominantly of sigmoidal lateral accretion deposits the channel returned to an axial course before undergoing lateral migration in the same direction creating a multistory multilateral channel sandstone body the repeated unidirectional migration combined with evidence of syndepositional deformation suggests that active tectonism strongly influenced channel evolution and deposition a model of submarine channel evolution in extensional basins is presented in systems where large displacements occur the channel system may avulse creating isolated sand ribbons which are connected updip where the lateral dip is always more influential than the regional dip the system may pond in the hanging wall syncline the model is compared to a subsurface channel within the pliocene of the nile delta slope which was influenced by syndepositional fault movement application of the outcrop derived model allows some simple architectural interpretations to be made

contained reflected turbidity currents from the middle ordovician cloridorme formation quebec canada an alternative to the antidune hypothesis the parautochthonous cloridorme formation is a syn orogenic flysch succession that was deposited in an elongate foredeep basin as mainly lower middle fan outer fan and basin floor deposits the basin floor deposits about 1 5 km thick are confined to members 1 2 and 1 and are characterized by graded thick 1 10 m mud rich calcareous greywacke beds previously interpreted as deposits of concentrated muddy unidirectional turbidity currents that locally generated backset antidune lamination in internally stratified flows the dominant flow directions were from east to west but west to east transport also occurred as seen in the orientation of ripples climbing ripples flutes consistently overturned flames and grain imbrication we believe that the flows that deposited these thick calcareous greywacke beds reversed by roughly 180 one or more times during deposition of the lower sandy part of the beds flow reversals are consistent with the sharp grain size breaks and mud partings within sandy divisions measurement of grain fabric relative to stratification in the most celebrated antidune bedforms indicates flow from west to east thus the bedforms were produced by west to east migration of megaripples not by the upcurrent migration of antidunes the thick muddy beds were deposited by large volume muddy flows that were deflected and reflected from the side slopes and internal topographic highs of a confined basin floor much like the contessa and similar beds of the italian apennines large quantities of suspended mud were ponded above the irregular basin floor and settled to produce the thick silty mudstone caps seen on each bed because of their mode of emplacement we propose that these beds be called contained turbidites

flow behavior of ponded turbidity currents abstract sea floor topography can constrict deflect or reflect turbidity currents resulting in a range of distinctive deposits where flows rebound off slopes and a suspension cloud collects in an enclosed basin ponded or contained turbidites are deposited ponded turbidites have been widely recognized in slope mini basins and on small structurally confined basin floors in strike slip and foreland basin settings they can have a variable internal structure the significance of which remains poorly understood in terms of flow behavior new experiments demonstrate that the ponding process can comprise up to four phases 1 cloud establishment 2 inflation 3 steady state maintenance and 4 collapse the experiments explored the behavior of sustained turbidity currents draining into small basins and show that the ponded suspensions that form are characterized by an important internal interface this divides a lower outbound moving layer from an upper return layer the basal layer evolves to constant concentration and grain size whereas the upper layer is graded concentration and grain size decrease upward during the cloud inflation stage the concentration and velocity profiles of the ponded suspension evolve and this phase can dominate the resulting deposit outbound internal waves can travel along the interface between the outbound and return layers and impinge against the confining slope and their amplitude is highest when the density contrast between layers is greatest e g when the input flows are thin and dense the experiments show that flow reversals can arise in several ways initial rebound episodic collapse of the wedge of fluid above the counter slope grounding of the internal velocity interface and that despite steady input velocities decay and the deposit grades upwards internal waves emanate from the input point i e do not form as reflections off the counter slope the internal grain size interface within the suspension may dictate textural trends in sands onlapping the confining slopes where flows are partially ponded internal waves can generate pulsing overspill to basins down dip

process controls on the development of stratigraphic trap potential on the margins of confined turbidite systems and aids to reservoir evaluation stratigraphic trapping at pinch out margins is a key feature of many turbidite hosted hydrocarbon reservoirs in systems confined by lateral or oblique frontal slopes outcrop studies show that there is a continuum between two geometries of pinch out configuration in type a turbidites thin onto the confining surface although the final sandstone pinch out is commonly abrupt and individual beds tend not to erode into earlier deposits in type b turbidite sandstones commonly thicken toward the confining slope and beds may incise into earlier deposits these two types may occur in combination to give a wide spectrum of pinch out characteristics our analysis suggests the principal control in determining pinch out character is flow magnitude with smaller flows producing type a and larger flows producing type b in areas of poor seismic control it can be difficult to assess either pinch out character or the proximity of wells to confining slopes because estimates of paleoflow magnitude can be made from core or high quality log image data however it is possible to make reasonable estimates of pinch out character even from wells such as exploration wells which may be placed conservatively away from the field margins furthermore systematic paleoflow variations and thickness trends are commonly seen in individual turbidite sandstones as they approach confining slopes for example dispersal directions indicate flow deflection parallel with the strike of confining topography beds thin toward type a onlaps and thicken toward type b onlaps these relationships can be exploited via analysis of vertical successions to constrain well position with respect to the slope similarly the presence location and frequency of locally derived debrites can provide information on the presence and proximity of confining slopes begin page 972

upslope flow of turbidity currents a comparison among field observations theory and laboratory models field observations from the marine realm indicate that turbidity currents are capable of transferring detritus considerable distances upslope onto bathymetric highs upslope deposition occurs because of the combined effects of flow thickness tilting of the cross flow surface slope and a vertical shift in the flow s center of gravity numerical analysis and laboratory experiments indicate that the maximum run up elevation of a subcritical turbidity current is approximately equal to 1 53 times the flow thickness

seismic modeling in the analysis of deep water sandstone termination styles innovative seismic forward modeling is used to illustrate the sensitivity within seismic data and its application in the interpretation of onlap and pinch out of terminating deep water sandstones two critical components in deep water exploration and production sandstone quality net to gross estimates volume calculations vertical connectivity and stratigraphic trapping are all dependent on the sandstone extent and their seismic characteristics in these settings however seismic resolution is commonly insufficient to resolve the critical reservoir parameters seismic modeling of termination styles based on integrated outcrop and subsurface properties allows for depth and resolution focused predictive models to be built for improved subsurface analysis this technique is currently underused as a method to better understand the sensitivity of seismic data to the target lithologies and their geometries the gres d annot formation is a well studied sand prone deep water system of paleogene age deposited in a bathymetrically complex setting six end member termination styles are discussed including three sand prone styles simple onlap o s draping onlap o d and bed thickening o t and three heterolithic styles advancing pinch out p a convergent pinch out p c and convergent thickening and pinch out p ct local thickening close to the system margins is common in both sand prone and heterolithic terminating strata and plays an important function in the appropriate distribution of sandstone the outcrops are interpreted as potential process analogs for the complex sandstone distribution and termination patterns observed in plays like the paleogene of the gulf of mexico and the jurassic of the northern north sea

collision of the ganges brahmaputra delta with the burma arc implications for earthquake hazard abstract we take a fresh look at the topography structure and seismicity of the ganges brahmaputra delta gbd burma arc collision zone in order to reevaluate the nature of the accretionary prism and its seismic potential the gbd the world s largest delta has been built from sediments eroded from the himalayan collision these sediments prograded the continental margin of the indian subcontinent by 400 km forming a huge sediment pile that is now entering the burma arc subduction zone subduction of oceanic lithosphere with 20 km sediment thickness is fueling the growth of an active accretionary prism exposed on land the prism starts at an apex south of the gbd shelf edge at 18 n and widens northwards to form a broad triangle that may be up to 300 km wide at its northern limit the front of the prism is blind buried by the gbd sediments thus the deformation front extends 100 km west of the surface fold belt beneath the comilla tract which is uplifted by 3 4 m relative to the delta this accretionary prism has the lowest surface slope of any active subduction zone the gradient of the prism is only 0 1 rising to 0 5 in the forearc region to the east this low slope is consistent with the high level of overpressure found in the subsurface and indicates a very weak detachment since its onset the collision of the gbd and burma arc has expanded westward at 2 cm yr and propagated southwards at 5 cm yr seismic hazard in the gbd is largely unknown intermediate size earthquakes are associated with surface ruptures and fold growth in the external part of the prism however the possibility of large subduction ruptures has not been accounted for and may be higher than generally believed although sediment clogged systems are thought to not be able to sustain the stresses and strain weakening behavior required for great earthquakes some of the largest known earthquakes have occurred in heavily sedimented subduction zones a large earthquake in 1762 ruptured 250 km of the southern part of the gbd suggesting large earthquakes are possible there a large but poorly documented earthquake in 1548 damaged population centers at the northern and southern ends of the onshore prism and is the only known candidate for a rupture of the plate boundary along the subaerial part of the gbd burma arc collision zone

flash weakening of serpentinite at near seismic slip rates 1 to investigate the processes responsible for dynamic frictional weakening in antigorite serpentinite we conducted single velocity and velocity stepping friction experiments at slip rates v from 0 01 to 0 4 m s 1 sliding displacements up to 40 mm and a normal stress of 5 mpa single velocity experiments demonstrate an approximately 1 v dependence of friction on velocity above a characteristic weakening velocity vw 0 1 m s 1 consistent with theoretical predictions for flash heating and subsequent weakening of asperities velocity stepping experiments impose stepwise increases in slip rate show stepwise weakening at slip rates above vw scanning electron microscopy of experimental fault surfaces reveals nanoparticle gouge textures at raised sites 10 m in diameter in tests that exhibit dramatic weakening furthermore x ray diffraction analyses of fault gouge from the sliding surface document the formation of significant talc in these tests indicating that weakening temperatures reached 500 c 700 c in contrast no talc is observed in samples for which v remained significantly below vw the observed value for vw is consistent with published microphysical models for flash weakening when independent constraints on the thermal stability and contact strength of antigorite are considered finally while serpentinite displays velocity strengthening behavior at plate tectonic slip rates our results indicate that seismic ruptures propagating into serpentinized regions in the shallow lithosphere may trigger seismicity or slow earthquakes after limited amounts of displacement

nature of ophiolite occurrences along the eastern margin of the indian plate and their tectonic significance upper mesozoic to lower eocene ophiolitic rocks occur in two parallel belts along the eastern margin of the indian plate the eastern belt passes through central burma sumatra and java and coincides with a zone of gravity highs resulting from steeply dipping mafic rocks it denotes the locus of the subduction where these ophiolites were accreted just prior to middle eocene time in contrast the western belt which passes through nagaland manipur western burma and andaman is flanked to the east by a negative gravity anomaly zone in it the ophiolites occur as rootless subhorizontal bodies tectonically overlying eocene oligocene flysch sedimentary rocks they are inferred to be nappes that propagated westward from the eastern belt during late oligocene terminal collision of the indian and eurasian continental blocks ophiolite occurrences in andaman and mentawai islands belonging to the western belt are generally linked with active subduction west of the island arc this subduction began only in late miocene time and thus it could not have produced the ophiolites which had been emplaced on land much earlier

momentum transport by a line of cumulonimbus abstract the vertical transport of horizontal momentum normal to a line of cumulonimbus observed during gate on 14 september 1974 is against the vertical momentum gradient contrary to the predictions of mixing length theory data from repeated aircraft passes normal to the line s axis at heights from 0 15 to 5 5 km are used to document the flux and determine its source the flux is concentrated in roughly a 25 km wide active zone just behind the leading edge of the line in kilometer scale convective updrafts accelerated upward by buoyancy and toward the rear of the line by mesoscale pressure forces the fall in mesoscale pressure from the leading edge to the rear of the active zone is mainly hydrostatic resulting from relatively high virtual temperatures and the 60 degree tilt of the leading edge from the vertical with the clouds at the surface well ahead of those aloft evaluation of the terms in the momentum flux generation equation confirms that the above process reflected by the velocity buoyan

an ocean largeheddy simulation model with application to deep convection in the greenland sea a nonhydrostatic boussinesq threehdimensional model the ocean largeheddy simulation model lolemr has been developed to study deep oceanic convection the model uses a subgridhscale parameterization of turbulence developed for largeheddy simulation models and the advection of scalars is accomplished using a monotonic scheme a set of experiments was performed using olem to provide a direct comparison with laboratory results and aircraft measurements of the atmospheric convective boundary layer the results from these experiments are in excellent agreement with laboratory and atmospheric convective boundary layer measurements of the mean profiles of zonal and vertical velocity variance potential temperature variance and heat flux the horizontal wavenumber spectra of zonal and vertical velocity are also in good agreement with laboratory measurements and kolmogorov s theoretical inertial subrange spectrum a set of experiments using a potential temperaturehsalinity profile from the central greenland sea for model initialization was conducted to study the effect of the thermobaric instability and rotation on the structure and evolution of deep oceanic convection the artificial removal of the thermobaric instability suppresses penetrative convection which is responsible for rapid changes in water properties at depths much greater than occurs for convective mixedhlayer deepening the vertical velocity and diameter 0 08 m s 1 and 300 m respectively of the penetrative plumes are in good agreement with observations from the greenland sea a period of strong penetrative convection is followed by a gradual transition to convective mixedhlayer deepening during penetrative convection the values of heat flux are about 2 times greater than convective mixedhlayer deepening in the absence of rotation the evolution of penetrative convection occurs more rapidly and vertical motions are more vigorous the presence of the horizontal component of rotation forces asymmetries in the circulation around a penetrative plume these experiments clearly demonstrate the importance of thermobaric instability and rotation on deep convection to properly model largehscale flows in regions of penetrative convection it is necessary to include these effects in the vertical mixing parameterization