applications of texture attribute analysis to 3d seismic data in this study texture attribute analysis application to 3d surface seismic data is presented this is done by choosing a cubic texel texture element from the seismic data to generate a gray level occurrence matrix which in turn is used to compute second order statistical measures of textural characteristics the cubic texel is then successively made to glide through the 3d seismic volume to transform it to a plurality of texture attributes application of texture attributes to two case studies from alberta confirm that these attributes enhance understanding of the reservoir by providing a clearer picture of the distribution volume and connectivity of the hydrocarbon bearing facies in the reservoir

provenance of the southern junggar basin in the jurassic evidence from detrital zircon geochronology and depositional environments abstract the goal of this paper is to study the provenance of the southern junggar basin during the late triassic to early cretaceous based on the detrital u pb geochronology petrography and depositional environments eight sandstone samples from the upper triassic to lower cretaceous were collected for detrital zircon u pb dating a total of 794 effective u pb ages was obtained and divided into four groups 488 2537 ma basement zircons 328 482 ma subduction related magmatic zircons 254 322 ma post collisional magmatic zircons and 135 250 ma syndepositional magmatic zircons these ages relate to three stages of basin evolution 1 from the early to middle jurassic tian shan experienced continued exhumation accompanied by progressive southward expansion of the junggar basin and a peneplain was formed by the time xishanyao formation was deposited organic rich sediments formed in a delta environment were well developed in the southern junggar basin with source rocks gradually switching from post collisional volcanic rocks 295 307 ma with a peak age of 300 ma of the southern north tian shan to post collisional volcanic rocks of the central tian shan 280 320 ma with a peak age of 316 ma and then to subduction related island arc rocks 402 423 ma with a peak age of 415 ma of the central tian shan 2 during deposition of the toutunhe and qigu formations large scale volcanic activities occurred along the north tian shan fault source rocks at this time include syndepositional volcanic rocks 151 161 ma and post collisional volcanic rocks 290 320 ma of the north tian shan by the time of deposition of the kalazha formation tian shan experienced rapid tectonic uplift leading to rapid lake regression alluvial fans were well developed in the southern junggar basin with source rocks being the underlying sedimentary strata of the north margin of the north tian shan 3 during the early cretaceous exhumation of the tian shan and lake transgression in the junggar basin happened again shallow lake sediments were developed in the southern junggar basin with source rocks being subduction related volcanic rocks 339 419 ma with a peak age of 415 ma of the central tian shan and post collisional volcanic rocks 254 305 ma with a peak age of 298 ma of the north tian shan

revisiting the use of seismic attributes as soft data for subseismic facies prediction proportions versus probabilities geostatistical modeling originated within the mining industry to estimate average minable ore grade from large support volumes given samples measured on small volume support in petroleum geostatistics the goal is more equivocal due to several different scales of support of input data which are often incongruent with the desired prediction scale more specifically the goal is to utilize indirect measurements e g seismic data from a scale larger than the prediction scale for fine scale spatial distributions of facies and petrophysical properties grounded by undersampled point data e g well log data note volume support is a geostatistical term that describes the size or resolution of the sample or measurement

calibration of prism and avnir 2 onboard alos daichi the advanced land observing satellite alos nicknamed ldquodaichirdquo was successfully launched on january 24 2006 and it continues to work very well this paper describes the calibrations of two optical instruments onboard alos which are the panchromatic remote sensing instrument for stereo mapping prism and advanced visible and near infrared radiometer type 2 avnir 2 prism consists of three panchromatic radiometers and is used to derive a digital surface model dsm with high spatial resolution which is an objective of the alos mission avnir 2 has four radiometric bands from blue to near infrared which are used for investigating regional environment issues such as land use and land cover classifications and disaster monitoring in this paper we introduce the calibration and validation plan methodologies accuracy assessments of the standard products image quality evaluations for prism and avnir 2 and their results geometric calibration is important in generating a precise dsm by a stereo pair image of prism the relative geometric calibrations of both prism and avnir 2 are conducted by evaluating accuracies within one scene and evaluating sensor alignments as absolute calibration for absolute geometric accuracies we achieved 8 1 m for nadir looking images and 9 3 m for forward and backward looking images of prism we also achieved 114 2 m for avnir 2 prism is also radiometrically calibrated both relatively and absolutely prism relative radiometric calibration is accomplished by using acquired images over homogeneous targets such as oceans deserts ice and snow areas as well as nighttime observation simultaneously observed images with calibrated avnir 2 are used for absolute radiometric calibration by cross calibration the absolute radiometric accuracy of the prism nadir looking radiometer is similar to that of avnir 2

stratal slicing of miocene pliocene sediments in vermilion block 50 tiger shoal area offshore louisiana many people have viewed modern land surfaces from commercial airplanes and marveled at the form and geometry of geomorphic features such as river channels deltas barrier islands and dune fields these views represent complete images of the modern time surfaces we can classify the depositional nature of features on these images by interpreting their planiform geometry and geographic context in fact modern 3 d seismic technology has made it possible for us to image similar but much older geomorphic or depositional features preserved in the rock record unfortunately although many reservoir scale well to well scale features can be detected in vertical seismic lines few such features can be resolved and interpreted in the vertical perspective because of the data s limited bandwidth only in the horizontal perspective are such depositional features large enough to be resolvable when displayed in map view on geologic time surfaces

three dimensional seismic geomorphology and analysis of the ordovician paleokarst drainage system in the central tabei uplift northern tarim basin western china high quality three dimensional seismic data acquired in the central tabei uplift tarim basin western china provide a rare opportunity to characterize in exceptional detail the three dimensional geomorphology of a deeply buried 5500 6500 m 18 045 21 325 ft ordovician unconformity and the related paleokarst drainage system an integrated approach was applied that emphasized integration of seismic data with available conventional core wireline logs and age equivalent outcrops the exceptional quality of the seismic data allowed a seismic detection limit of karstified features of less than 75 75 m 246 246 ft horizontally and 6 m 20 ft vertically interpreted geomorphologic and depositional elements include fluvial channels and canyons fluvial valleys sinkholes and tower karsts and hills the modern tower karst drainage system in guilin china is very similar to the mapped ordovician karst drainage system and is used as a modern analog the interaction between the surface karst drainage system and the shallow subsurface cave passage system is evidenced by the observation that surface canyons appear to initiate in areas associated with intense sinkhole development also surface river valleys tend to correspond to dip oriented surface depressions partly related to near surface cave collapse during burial into the deeper subsurface the combination of intrastratal collapse karstified strata and suprastratal collapse postkarst deposited strata created large damage zones hundreds of meters thick and kilometers wide coalesced collapsed paleocave systems can be interpreted from the unique circular pattern of faults observed in map view that are associated with seismic bright spots

three dimensional curvature analysis of seismic waveforms and its interpretational implications the idea of curvature analysis has been widely used in subsurface structure interpretation from three dimensional seismic data e g fault fracture detection and geomorphology delineation by measuring the lateral changes in the geometry of seismic events however such geometric curvature utilizes only the kinematic information two way traveltime of the available seismic signals while analysing the dynamic information waveform the traditional approaches e g complex trace analysis are often trace wise and thereby fail to take into account the seismic reflector continuity and deviate from the true direction of geologic deposition especially for steeply dipping formations this study proposes extending the three dimensional curvature analysis to the waveforms in a seismic profile here denoted as the waveform curvature and investigates the associated implications for assisting seismic interpretation applications to the f3 seismic dataset over the netherlands north sea demonstrate the added values of the proposed waveform curvature analysis in four aspects first the capability of the curvature operator in differentiating convex and concave bending allows automatic decomposition of a seismic image by the reflector types peaks troughs and zero crossings which can greatly facilitate computer aided horizon interpretation and modelling from three dimensional seismic data second the signed minimum curvature offers a new analytical approach for estimating the fundamental and important reflector dip attribute by searching the orientation associated with least waveform variation third the signed maximum curvature makes it possible to analyse the seismic signals along the normal direction of the reflection events finally the curvature analysis promotes the frequency bands of the seismic signals and thereby enhances the apparent resolution on identifying and interpreting subtle seismic features

seismic geomorphology based facies classification seismic facies analysis is a powerful yet largely subjective methodology for hydrocarbon exploration and development the term seismic facies means different things to different people for this study however seismic facies is defined as a seismic description of depositional facies confined in a seismically thin bed at a normal seismic sampling rate e g 4 ms making this study s seismic facies analysis different from classical seismic facies analysis of much thicker depositional sequences as a subjective interpretation of seismic attributes seismic facies analysis is often laborious and inconsistent especially if multiple mapping units are involved how to automate the process via computer pattern recognition so that consistency could be improved and the 3d cycle time reduced has been a hot topic in recent years

migration of widespread long lived volcanism across the galapagos volcanic province evidence for a broad hotspot melting anomaly abstract the well studied galapagos archipelago is a small part of the much larger galapagos volcanic province gvp consisting of the cocos carnegie coiba and malpelo aseismic ridges and related seamount provinces although these aseismic ridges and seamounts dominate the morphology of the region little is known about their origin due to a lack of direct age and geochemical information in order to establish how well the gvp fits with the predictions of the standard fixed hotspot and mantle plume hypotheses we conducted a first reconnaissance dredge grab sampling of submerged regions of the gvp we present here 40ar 39ar ages for many of these new basement samples and evaluate their implications for the various models put forward to explain the origin of the gvp correlating new and published sample site ages with distance from the western side of the galapagos islands show that volcanism has not progressed in narrow time progressive lines of seamounts and ridges as predicted by the conventional fixed hotspot and mantle plume hypothesis rather volcanism apparently migrated time progressively across the gvp in broad regions of long lived and possibly concurrent volcanism we propose that the most viable explanation for these observations is that the gvp is the product of cocos and nazca plate motions across a broad hotspot melt anomaly the complex spreading history of the cocos nazca spreading centre likely controlled the relative distribution of gvp volcanism between the cocos and nazca plates while creating lithosphere of variable age thickness across the region while the notion of a broad galapagos hotspot melting anomaly linked to a complex regional tectonic history requires significant testing it nevertheless highlights the need to test alternative mantle upwelling shapes and sizes compared to the widely accepted notion of a narrow continuous long lived galapagos mantle plume conduit defined by the size and location of a galapagos island

basin architecture from high resolution gravity gradient magnetic and seismic data king sound canning basin western australia an interpretation of geologic structure at king sound in the canning basin was completed using airborne gravity gradient magnetic and seismic data during the late devonian and mississippian periods the elevated part of the basement in the north was rimmed by carbonate reefs and redeposited carbonate debris whereas in the south siliciclastic submarine fans and turbidites were deposited along the margin of the basement in a deep marine environment three principal lithologic units were identified from the vertical gravity gradient gdd in the basin 1 the fairfield group carbonates of high density are interpreted to be the source of prominent positive gravity anomalies 2 forereef debris and carbonate clastics reworked from carbonates higher up the slope or from the carbonate platform are interpreted to be the source of medium density responses and 3 turbidites debris flows and associated clastic basinal sequences of low density are interpreted to be the source of prominent negative gravity anomalies depth slices of gdd indicate the channelized nature of turbidite flows in the lower section of the basin intrasedimentary intrusives were identified from magnetic gdd seismic and well data depth to magnetic basement calculation indicates that the surface of the archean to paleoproterozoic basement ranges from 3200 to 130 m 10 499 427 ft below sea level the northwest and northeast oriented south dipping faults cut the basement and propagate upward into the sediments a three dimensional geologic model constructed for king sound satisfies all known geologic constraints and is consistent with the gravity magnetic seismic and well data

evolution of atchafalaya lacustrine deltas south central louisiana abstract the entrenched pleistocene holocene mississippi alluvial valley was cut during the last low sea level stand and alluviation of the entrenched valley occurred during the holocene sea level rise regional gulf coast structures salt domes and faults have strongly influenced the morphology of the valley valley paleotopography has controlled depositional patterns and locations of major river courses as well as partially isolated large interdistributary basins within the alluvial deltaic plain interdistributary basin formation is further enhanced by distributary channel progradation switching and abandonment in conjunction with compactional subsidence of the alluvial plain surface geomorphology and sediment cores from the atchafalaya basin louisiana revealed that this basin has alternately accumulated fine grained organic rich sediments and terrigenous clastic dominated meander belt and lacustrine deposits basin subsidence and the presence of an active distributary channel in the basin are major determinants of the lithology of the sedimentary fill prograding lacustrine deltas of the atchafalaya river are the primary mechanism for filling the atchafalaya basin these upward coarsening deltas are relatively thin 3 m but are areally extensive tens to hundreds of kilometers and because they occur so frequently during the infilling process they account for a significant volume of the basin sequence the atchafalaya basin sequence documents lacustrine deltaic episodes dating from the early holocene maringouin and teche deltas to the present atchafalaya delta continued development of the atchafalaya river will rework portions of the backswamp and lacustrine deposits into meander belt deposits upon complete filling of the atchafalaya basin sediment will mostly bypass the basin and become deposited in the marine delta in atchafalaya bay

constraints on age and construction process of the foundation chain submarine volcanoes from magnetic modeling abstract the interaction between the foundation hotspot and the pacific antarctic ridge south pacific is one of the two known cases where a ridge is approaching a hotspot this ridge hotspot relative movement results in a change in the morphology of the volcanoes along the chain as the age of the lithosphere at the time of edifice formation progressively diminishes four hundred kilometers west of the pacific antarctic ridge axis volcanism is distributed along two sub parallel lines of volcanoes separated by distances diminishing from 100 km at the west to 50 km near the axis of the ridge the magnetic anomalies mapped on this part of the chain show a pattern clearly dominated by the magnetic signature of the seamounts the anomalies were forward modeled using a remanent magnetization of normal or reversed polarity within the volcano topography the resulting pattern of normal and reversed magnetization is consistent with the intervals of the geomagnetic polarity time scale for the last 5 ma the age of the oldest studied volcano these magnetic anomalies therefore represent an independent means of dating the volcanic edifices the ages deduced from the modeling are consistent with the hypothesis of volcanoes built by a hotspot on the fast moving pacific plate and are in good agreement with the published radiometric dates although these dates tend to correspond to the late constructional stages of the edifices the differences between magnetic and radiometric ages suggest that the average time span to build a volcano of the foundation chain is about 1 million years in agreement with other intraplate edifices the difference between the magnetic ages of the seamounts and of the underlying crust both deduced from the magnetic anomaly analysis show that the ridge has approached the hotspot at a rate of 40 km ma

detection and extraction of fault surfaces in 3d seismic data we propose an efficient method for detecting and extracting fault surfaces in 3d seismic volumes the seismic data are transformed into a volume of local fault extraction lfe estimates that represents the likelihood that a given point lies on a fault surface we partition the fault surfaces into relatively small linear portions which are identified by analyzing tilted and rotated subvolumes throughout the region of interest directional filtering and thresholding further enhance the seismic discontinuities that are attributable to fault surfaces subsequently the volume of lfe estimates is skeletonized and individual fault surfaces are extracted and labeled in the order of decreasing size the ultimate result obtained by the proposed procedure provides a visual and semantic representation of a set of well defined cleanly separated one pixel thick labeled fault surfaces that is readily usable for seismic interpretation

glacial lake inventory of bhutan using alos data methods and preliminary results the advanced land observing satellite alos is relatively new its optical sensors are capable of making high resolution digital surface models dsms for the first time the task of constructing a regional scale inventory of glacial lakes based on alos data has been undertaken this study presents the data processing methods and the results of validation and analysis on the alos based glacial lake inventory of bhutan in the himalaya the analysis based on gps measurements taken at metatshota lake in the mangde chu sub basin one of the glacial lakes assessed as presenting a potential flood danger shows a validation estimate of 9 5 m for the location of the alos based polygon with a root mean square of 11 7 m a comparison with digitized data from the international centre for integrated mountain development icimod shows that positioning and evaluation of terrain changes can be significantly improved using alos data preliminary analysis of the glacial lakes in four sub basins mo chu pho chu mangde chu and dangme chu reveals that the frequency distribution of lake sizes biases towards smaller lakes glacial lakes 0 01 0 05 km 2 in area account for 55 of the total number and occupy 13 of the total area together our results demonstrate the usefulness of high resolution alos data with accurate dsms for studying glacial lakes high priority must be given to continuously improving and updating the glacial lake inventory with high resolution satellite data

performance of aster and srtm dems and their potential for assessing glacial lakes in the lunana region bhutan himalaya to assess the potential volume of a glacial lake outburst flood glof more precisely than in previous studies we analyze ground survey data and remote sensing digital elevation models dems around glacial lakes in the lunana region bhutan based on a dem generated from differential gps ground surveys we first evaluate the relative accuracies of dems produced by the advanced spaceborne thermal emission and reflection radiometer aster and the shuttle radar topography mission srtm root mean square errors of the altitudinal difference between these dems and ground survey data were 11 0 m for aster and 11 3 m for srtm these errors are similar to those of previous studies we show that a topographical classification allows a better estimate of elevation on lakes ponds riverbeds and glaciers due to their flat surfaces while the relative accuracy is worse over moraines and hill slopes due to their narrow ridges and steep slopes using the optical satellite images and the ground survey data we re evaluate the glof volume in 1994 as 17 2 5 3 10 6 m 3 we show glof related information such as distance altitudinal difference and gradient at possible outburst points where the lake level is higher than the neighboring riverbed and or glacial lake

stratigraphic coordinates a coordinate system tailored to seismic interpretation in certain seismic data processing and interpretation tasks such as spiking deconvolution tuning analysis impedance inversion and spectral decomposition it is commonly assumed that the vertical direction is normal to reflectors this assumption is false in the case of dipping layers and may therefore lead to inaccurate results to overcome this limitation we propose a coordinate system in which geometry follows the shape of each reflector and the vertical direction corresponds to normal reflectivity we call this coordinate system stratigraphic coordinates we develop a constructive algorithm that transfers seismic images into the stratigraphic coordinate system the algorithm consists of two steps first local slopes of seismic events are estimated by plane wave destruction then structural information is spread along the estimated local slopes and horizons are picked everywhere in the seismic volume by the predictive painting algorithm these picked horizons represent level sets of the first axis of the stratigraphic coordinate system next an upwind finite difference scheme is used to find the two other axes which are perpendicular to the first axis by solving the appropriate gradient equations after seismic data are transformed into stratigraphic coordinates seismic horizons should appear flat and seismic traces should represent the direction normal to the reflectors immediate applications of the stratigraphic coordinate system are in seismic image flattening and spectral decomposition synthetic and real data examples demonstrate the effectiveness of stratigraphic coordinates

the support mechanism of the young foundation seamounts inferred from bathymetry and gravity summary the youngest volcanoes of the foundation volcanic chain were built on a plate less than 5 myr near the pacific antarctic ridge par axis the progressive approach of the spreading ridge to the hotspot during the last 10 myr resulted in the building of the edifices upon a progressively younger plate estimates of the effective elastic thickness te using two independent methods show that the elastic thickness of the plate diminishes towards the spreading ridge from 5 3 km to 2 0 km the spatial variation of te correlates with a significant change in both the morphology and the volume of the volcanoes suggesting an important control of the elastic thickness on the volcanic processes the reduction in te also explains conveniently the reduction in the distance between the north and the south systems the double volcanic line that characterizes the young part of the foundation chain in the direction of young loading ages the south system formed at the top of a flexural bulge created by the emplacement of the north system the main volcanic line the low te estimate for the south system and the shape of the bouguer anomalies confirm this model the effective elastic thicknesses obtained in this study are well matched by isotherms between 200 c and 300 c and support the hypothesis of a weak plate three mechanisms possibly acted to lower the plate rigidity re heating of a normal plate by the hotspot north system local fracturing south system and the creation of a thin lithosphere at the par axis by the coupling of a hotspot and the ridge related melting zones near ridge volcanoes

application of new seismic attributes to collapse chimneys in the fort worth basin three dimensional seismic volumes from the central fort worth basin display roughly circular collapse chimneys that extend vertically about 800 m from the ordovician ellenburger formation to the atokan middle pennsylvanian caddo limestone collapse chimneys in carbonates may be caused by subaerial karst hydrothermal or tectonic extensional processes we use 3d multitrace geometric attributes including coherence volumetric curvature and energy weighted coherent amplitude gradients to investigate details of the origin of these structures the ordovician ellenburger surface resembles a subaerial karst landscape of cockpits dolines and frying pan valleys while resistivity based wireline image logs record 50 m of karst breccia facies however images from coherence and long wavelength most positive and most negative curvature volumes show many of the 800 m collapse features are associated with basement faults or with subtle pennsylvanian and younger tectonic features rather than with intra ellenburg

plume ridge interaction revisited evidence for melt mixing from he ne and ar isotope and abundance systematics abstract submarine volcanic glass he ne and ar data from the pacific antarctic rise at its intersection with the foundation seamount chain have been obtained to further elucidate one of the main outstanding problems in plume ridge interaction studies the physical state in which mantle flow and mixing occur in those settings mixing of plume mantle and mid ocean ridge basalt source material may either be in the form of two solids of solid melt or of two melt phases only the positive correlation of 4 he 40 ar with 206 pb 204 pb as well as the negative correlation of 4 he 40 ar with 40 ar and 4 he concentrations combined with a lack of correlation between 4 he 40 ar and ridge depth or mgo concentration indicate that the enriched mantle plume material has been extensively degassed prior to mixing with the mid ocean ridge source material degassing of the plume source and mid ocean ridge source material prior to mixing is also suggested by the he versus pb isotope systematics however the occurrence of degassing processes requires the existence of melts implying that mixing between the plume and the mid ocean ridge material occurs in the physical form of melts

seismic characteristics of a reef carbonate reservoir and implications for hydrocarbon exploration in deepwater of the qiongdongnan basin northern south china sea our analysis of approximately 40 000 km of multichannel 2 d seismic data reef oil field seismic data and data from several boreholes led to the identification of two areas of reef carbonate reservoirs in deepwater areas water depth 500 in of the qiongdongnan basin qdnb northern south china sea high resolution sequence stratigraphic analysis revealed that the transgressive and highstand system tracts of the mid miocene meishan formation in the beijiao and ledong lingshui depressions developed reef carbonates the seismic features of the reef carbonates in these two areas include chaotic bedding intermittent internal reflections chaotic or blank reflections mounded reflections and apparent amplitude anomalies similar to the seismic characteristics of the lh11 1 reef reservoir in the dongsha uplift and island reef of the salawati basin indonesia which house large oil fields the impedance values of reefs in the beijiao and ledong lingshui depressions are 8000 9000 g cc x m s impedance sections reveal that the impedance of the lh11 1 reef reservoir in the northern south china sea is 800010000 g cc x m s whereas that of pure limestone in bd23 1 1 is 10000 g cc x m s the mid miocene paleogeography of the beijiao depression was dominated by offshore and neritic environments with only part of the southern beijiao uplift emergent at that time the input of terrigenous sediments was relatively minor in this area meaning that terrigenous source areas were insignificant in terms of the beijiao depression reef carbonates were probably widely distributed throughout the depression as with the ledong lingshui depression the combined geological and geophysical data indicate that shelf margin atolls were well developed in the beijiao depression as in the ledong lingshui depression where small scale patch or pinnacle reefs developed these reef carbonates are promising reservoirs representing important targets for deepwater hydrocarbon exploration c 2008 elsevier ltd all rights reserved

recommendations for the compilation of glacier inventory data from digital sources modern geoinformatic techniques allow the automated creation of detailed glacier inventory data from glacier outlines and digital terrain models dtms once glacier entities are defined and an appropriate dtm is available several methods exist to derive the inventory data e g minimum maximum and mean elevation mean slope and aspect for each glacier from digital intersection of both datasets compared to the former manual methods the new grid based statistical calculations are very fast and reproducible the major aim of this contribution is to help in standardizing the related calculations to enhance the integrity of the global land ice monitoring from space glims database the recommendations were prepared by a working group and also contribute to the european space agency project globglacier the document follows the former unesco manual for the production of the world glacier inventory published in 1970 identifies the potential pitfalls and describes the differences from the former methods of compilation the online background material for this paper see http www glims org contains example scripts for calculation of each parameter and will be updated when required

nonlinear 40ar 39ar age systematics along the gilbert ridge and tokelau seamount trail and the timing of the hawaii emperor bend over the last three decades the first order correlation in morphology and orientation of seamount trails has been called upon to support the concept of a fixed pacific hot spot frame of reference and to explain the hawaii emperor bend heb by a dramatic change in pacific plate motion in this paper however we present 40ar 39ar ages for the gilbert ridge and tokelau seamounts pacific that show similar changes or bends in their orientation but at different geological times up to 20 myr earlier than the heb changes in pacific plate motion alone cannot explain these observations because these asynchronous bends should have been reflected in the morphology of each of these seamount trails together with the lack of linear age progressions and inconsistent apparent local plate velocities of 131 and 87 mm yr we rule out a fixed hot spot origin for the gilbert ridge and tokelau seamount trails instead we invoke secondary or alternate processes to explain the complex age systematics and morphologies in these seamount trails we propose here that the heb type bends in these seamount trails were likely formed by short term jerk like plate extensions in the studied southwestern region of the pacific plate reactivating a preconditioned lithosphere that can be characterized by a complex structure and precursory magmatic impingements the remarkable differences observed in these colinear seamount trails fundamentally question the existence of heb type bends in the formation of pacific volcanic lineaments they also show us that applying geometric and morphologic observations alone is insufficient in constraining past plate motions nevertheless the need and search for alternate volcano tectonic mechanisms offer opportunities to better understand intraplate volcanism in general

en echelon volcanic elongate ridges connecting intraplate foundation chain volcanism to the pacific antarctic spreading center abstract the development of volcanic elongate ridges vers could be controlled in many cases by complex processes related to interaction between mantle plumes and spreading centers we report here measured ages for the foundation chain se pacific showing that volcanism along morphologically distinct vers can develop occasionally as rapidly formed continuous lines of coeval volcanism extending from a region of intraplate volcanism to the pacific antarctic spreading center but a significantly more dominant trend is for coeval yet structurally disconnected segments of foundation chain vers to develop in a series of en echelon ne sw elongate zones of coeval hotspot volcanism these elongate zones developed at intervals of approximately 1 myr while maintaining a basically steady state orientation and size as the pacific antarctic spreading center migrated continually closer to the foundation plume hotspot we infer from this new information that foundation chain ver development was controlled by an interplay between short lived local factors e g location of nearest spreading center segment lithospheric stress and long lived attributes of the foundation plume hotspot e g size orientation periodicity

seismic attribute technology for reservoir forecasting and monitoring during the 1970s and 1980s the seismic attributes most used in petroleum exploration were amplitude based instantaneous attributes however in the 1990s seismic attribute technology has dramatically advanced in several directions techniques now range from single trace instantaneous event attribute computations to more complex multitrace windowed seismic event attribute extractions to the generation of seismic attribute volumes applications run from simple amplitude anomaly detection to monitoring fluid front movement over time

non hotspot formation of volcanic chains control of tectonic and flexural stresses on magma transport the south pacific in the vicinity of both the superswell and the east pacific rise is repleat with volcanic chains that unlike the emperor hawaiian chain defy the hypothesis of formation via the relative motion of plates and hotspots we propose two nearly identical models for the origin of near axis and superswell chains assuming that both regions are underlain by significant quantities of more or less uniformly distributed partial melt given an initial volcanic load or a local anomaly in the melt source region volcanic chains form by magmatic hydrofracture at local tensile maxima of flexural and membrane stresses fracture wall erosion by magma flow provides a feedback which results in discrete edifices within the chains the model predicts island chains aligned with a deviatorically tensile tectonic stress near the ridge the elastic lithosphere is thin and observations and theoretical considerations indicate a strong deviatorically tensile stress field perpendicular to the ridge axis under such conditions the model results in parallel lines of volcanoes perpendicular to the spreading ridge later interstitial volcanism within the individual chains reduces the average spacing and results in nearly continuous ridges on the thicker lithosphere of the superswell membrane stresses are negligible and the model produces chains of much more widely spaced volcanoes a more isotropic stress field may result in broader chain like patterns of volcanoes in both cases the chains represent self propagating disturbances the resulting age progressions are thus independent of plate velocity but depend only on the dynamics of volcano formation and evolution

intraplate versus ridge volcanism on the pacific antarctic ridge near 37 s 111 w exploration of the foundation volcanic chain 33 s 131 w 37 s 111 w revealed the existence of different magmatic provinces with relation to their geological settings 1 the pacific antarctic ridge par is made up of several en echelon segments where both glassy midocean ridge basalts morbs with low incompatible elements k2o 150 ppm and ce 48 ppm at about 306 1300 km from the par axis 4 the old pacific seamounts built on a crust older than 23 m y located west of longitude 124 w 1300 km from the par axis consist of t and emorb on the par axis extensive crystal fractionation 65 produced the silicic lavas on the basis of pacific plate reconstruction using a half spreading rate of about 50 mm yr and integrating the observed compositional changes with respect to the structural settings it is inferred that the last volcanic events giving rise to the fs took place at about 110 km from the par axis about 5 m y ago the oblique ridges built between 5 m y and 23 m y with morb volcanics comparable to those of the the oblique ridge par provinces could also have been formed by an interaction between the foundation seamount dredge site 28 hotspot magmatism and that of an ancient accreting ridge magmatism precursor of the par

integrated seismic texture segmentation and cluster analysis applied to channel delineation and chert reservoir characterization in recent years 3d volumetric attributes have gained wide acceptance by seismic interpreters the early introduction of the single trace complex trace attribute was quickly followed by seismic sequence attribute mapping workflows three dimensional geometric attributes such as coherence and curvature are also widely used most of these attributes correspond to very simple easy to understand measures of a waveform or surface morphology however not all geologic features can be so easily quantified for this reason simple statistical measures of the seismic waveform such as rms amplitude and texture analysis techniques prove to be quite valuable in delineating more chaotic stratigraphy in this paper we coupled structure oriented texture analysis based on the gray level co occurrence matrix with self organizing maps clustering technology and applied it to classify seismic textures by this way we expect that our workflow should be more sensitive to lateral changes rather than vertical changes in ref

high frequency miocene sequence stratigraphy offshore louisiana cycle framework and influence on production distribution in a mature shelf province the regressive miocene succession of offshore louisiana comprises 10 third order sequences and no fewer than 58 fourth order sequences which average approximately 1 1 and 0 19 m y in duration respectively comparable to durations measured in the gulf coast basin and basins worldwide upper lower to middle miocene distal third order sequences comprise mostly lowstand prograding wedge slope fan and basin floor fan deposits in contrast middle to upper miocene medial sequences record progressively more landward systems tracts 1 the lateral transition between on shelf incised valley fills and the proximal parts of basinward thickening lowstand prograding wedges and 2 cyclic on shelf highstand and transgressive systems tracts upper miocene inner shelf and marginal marine systems tracts and more abundant incised valleys dominate the thinner proximal third order sequences this genetic framework has a major influence on hydrocarbon distribution although a strong structural trapping component is present in the fields more than 90 of cumulative production originates where fourth order systems tracts stack to form third order lowstand systems tracts in all 10 third order sequences the development of a high frequency sequence framework for the prolific miocene succession and the discovery that hydrocarbons are pooled within the miocene third order lowstand systems tracts yield a focused model for the development of abundant undiscovered miocene reserves in the mature northern gulf of mexico shelf province

prevention of outburst floods from periglacial lakes at grubengletscher valais swiss alps flood and debris flow hazards at grubengletscher near saas balen in the saas valley valais swiss alps result from the formation and growth of several lakes at the glacier margin and within the surrounding permafrost in order to prevent damage related to such hazards systematic investigations were carried out and practical measures taken the evolution of the polythermal glacier the creeping permafrost within the large adjacent rock glacier and the development of the various periglacial lakes were monitored and documented for the last 25 years by photogrammetric analysis of annually flown high resolution aerial photographs seismic refraction d c resistivity and gravimetry soundings were performed together with hydrological tracer experiments to determine the structure and stability of a moraine dam at a proglacial lake the results indicate a maximum moraine thickness of 100 m extremely high porosity and even ground caverns near the surface may have resulted from degradation of sub and periglacial permafrost following 19th 20th century retreat of the partially cold glacier tongue the safety and retention capacity of the proglacial lake were enhanced by deepening and reinforcing the outlet structure on top of the moraine complex the water level of an ice dammed lake was lowered and a thermokarst lake artficially drained

hybrid optimization for lithologic inversion and time lapse monitoring using a binary formulation we have developed a hybrid optimization algorithm for binary inversion of geophysical data associated with lithologic inversion and time lapse monitoring the binary condition is designed to invert geophysical data for well defined physical properties within discrete lithologic units such as a salt body within a sedimentary host or temporal changes in physical property associated with dynamic processes such as the density and conductivity change in an oil and gas reservoir or groundwater aquifer the solution of such inverse problems with discrete model values requires specialized optimization algorithms to meet this need we develop a hybrid optimization algorithm by combining a genetic algorithm with quenched simulated annealing the former allows for easy incorporation of prior geologic information and rapid buildup of large scale model features whereas the latter guides genetic algorithm to faster evolution by rapidly adjusting the finer model features in examining the performance of the hybrid

the foundation seamounts tectonic setting of a newly discovered seamount chain in the south pacific abstract large areas of the south pacific remain unsurveyed because they are so remote a major volcanic chain the foundation seamounts lies between 33 s and 39 s and between 111 w and 125 w poorly defined on conventional bathymetric charts it becomes very apparent when combining an analysis of conventional geophysical data with the satellite altimeter data the length of the seamount chain is 1350 km and the volcanoes are clustered within a 180 km wide band trending approximately n70w which is the direction of absolute motion of the pacific plate over a fixed reference system some of these volcanoes are so shallow that they may have emerged above the sea surface at an earlier time no dates are known for the seamounts surrounding the foundation seamounts chain the tectonic setting is that of the pacific plate at the time when the strike of the spreading ridge changed from a northwesterly direction to the present northeasterly one this episode of spreading reorganization involved the existence of a short lived microplate west of the pacific antarctic ridge a captured segment of nazca plate accounts for the large discrepancies in the magnetic anomalies offsets along the agassiz fracture zone large propagators like the adventure and kurchatov troughs are described the newly discovered western segment of the chile fracture zone is the pacific plate match of the chile fracture zone on the nazca plate

effective elastic thickness of the lithosphere along the easter seamount chain bathymetry and gravity data collected during legs 5 6 and 7 of the 1993 gloria expedition and the recently released 2 min altimetry derived global gravity grid are used to determine the effective elastic thickness of the lithosphere along the easter seamount chain esc forward modeling admittance and coherence methods yield consistent restfits with the exception of the eastern and western ends of the esc the effective elastic thickness along the chain is 1 4 km the thin elastic thickness for the majority of the esc seamounts is compatible with a young seafloor age at the time of loading derived from new radiometric ages of the seamounts along the chain and a magnetic isochron age interpretation of the nazca plate seafloor age the elastic thickness southeast of the nazca fracture zone is 6 km apparently because of the seafloor age discontinuity across the fracture zone the elastic thickness near the san felix island at the eastern end of the esc is even greater 11 km which is compatible with the estimated seafloor age at the time of loading a slight increase in the effective elastic thickness of the far western part of the esc suggests dynamic compensation or less thermal weakening of lithosphere above a plume channel versus directly above the plume center these findings combined with published geochemistry support a hotspot origin for the esc complicated by large scale plate boundary reorganizations and channeling of plume material to the east pacific rise

ridge hotspot interaction the pacific antarctic ridge and the foundation seamounts the study of different magmatic provinces between the resolution fracture zone 33 s 131 w and the pacific antarctic ridge par axis 37 s 111 w suggests that similar processes of interaction between hotspot and spreading axial magmatism occurred 20 25 ma and 0 5 ma ago there is evidence of this process from the changes in composition observed in the lavas erupted near 400 300 km between the present day par axis 37 s 111 w and the eastern tip of the foundation seamount fs hotspot near 36 20 s 114 w where the last alkali enriched volcanics k ti 0 30 zr y 6 and ce yb n 4 have erupted this transitional province between the par and the fs consists of volcanic cones built on several volcanic ridges 20 ma also built on volcanic ridges are identified west 1200 km from the par axis of a failed rift propagator frp forming the eastern boundary of the ancient selkirk microplate some of these seamounts made of alkali basalts were built during the initiation of the fs hotspot 20 23 ma ago the interaction and the influence thermal of mantle plume magmatism with the ancient spreading ridge of the farallon pacific plates was responsible for the eruptions of the t morbs and andesitic lavas this situation is comparable to that presently observed on the par axis where silicic lavas are also erupted in association with t morbs

stratal slicing benefits and challenges in the petroleum industry seismic interpretation meth odology varies according to a subject s scale in basinal to field scale hundreds of meters the goal is to map gross stratigraphic and structural features that are associated with petroleum systems including stratigraphy and depositional history hydrocarbon generation migration and entrapment seismic stratigraphy and sequence stratigraphy are common tools for this purpose at the reservoir scale meters to tens of meters the goal becomes characterizing distribution and physical properties related to volumetrics and production in a reservoir system in this task details are crucial seismic lithology and inversion seismic geomorphology and sedimentology and attribute analysis are some of the tools developed for this purpose

seismic attributes a historical perspective a seismic attribute is a quantitative measure of a seismic characteristic of interest analysis of attributes has been integral to reflection seismic interpretation since the 1930s when geophysicists started to pick traveltimes to coherent reflections on seismic field records there are now more than 50 distinct seismic attributes calculated from seismic data and applied to the interpretation of geologic structure stratigraphy and rock pore fluid properties the evolution of seismic attributes is closely linked to advances in computer technology as examples the advent of digital recording in the 1960s produced improved measurements of seismic amplitude and pointed out the correlation between hydrocarbon pore fluids and strong amplitudes bright spots the introduction of color printers in the early 1970s allowed color displays of reflection strength frequency phase and interval velocity to be overlain routinely on black and white seismic records interpretation workstations in the 1980s provided

bathymetric prediction from dense satellite altimetry and sparse shipboard bathymetry the southern oceans south of 30 s are densely covered with satellite derived gravity data track spacing 2 4 km and sparsely covered with shipboard depth soundings hundreds of kilometers between tracks in some areas flexural isostatic compensation theory suggests that bathymetry and downward continued gravity data may show linear correlation in a band of wave lengths 15 160 km if sediment cover is thin and seafloor relief is moderate at shorter wave lengths the gravity field is insensitive to seafloor topography because of upward continuation from the seafloor to the sea surface at longer wavelengths isostatic compensation cancels out most of the gravity field due to the seafloor topography we combine this theory with wiener optimization theory and empirical evidence for gravity noise to signal ratios to design low pass and band pass filters to use in predicting bathymetry from gravity the prediction combines long wavelengths 160 km from low pass filtered soundings with an intermediate wavelength solution obtained from multiplying downward continued band pass filtered 15 160 km gravity data by a scaling factor s s is empirically determined from the correlation between gravity data and existing soundings in the 15 160 km band by robust regression and varies at long wave lengths we find that areas with less than 200 m of sediment cover show correlation between gravity and bathymetry significant at the 99 level and s may be related to the density of seafloor materials in these areas the prediction has a horizontal resolution limit of 5 10 km in position and is within 100 m of actual soundings at 50 of grid points and within 240 m at 80 of these in areas of very rugged topography the prediction underestimates the peak amplitudes of seafloor features images of the prediction reveal many tectonic features not seen on any existing bathymetrie charts because the prediction relies on the gravity field at wavelengths 160 km it is insensitive to errors in the navigation of sounding lines but also cannot completely reproduce them therefore it may be used to locate tectonic features but should not be used to assess hazards to navigation the prediction is available from the national geophysical data center in both digital and printed form

interpretive advantages of 90 phase wavelets part 2 seismic applications we examine field seismic data to test the benefits of 90 phase wavelets in thin bed interpretation that are predicted by seismic modeling in part 1 of this paper in an interbedded sandstone shale miocene succession in the gulf of mexico basin a 90 phase shift of nearly zero phase seismic data significantly improves lithologic and stratigraphic interpretation a match between seismic and acoustic impedance ai profiles results in a better tie between seismic amplitude traces and lithology indicative logs better geometric imaging of ai units that does not use dual polarity seismic events results in easier and more accurate reservoir delineation less amplitude distortion and the stratigraphy independent nature of thin bed interference significantly improves stratigraphic resolution and seismic stratigraphic profiling for a ricker like wavelet having small side lobes stratigraphic resolution of 90 phase data is considerably higher than that of zero phase data in this specific case stratigraphic re

multiscale seismic attributes a wavelet based method and its application to high resolution seismic and ground truth data we propose a wavelet based method to characterize acoustic impedance discontinuities from a multiscale analysis of seismic reflected waves our approach relies on the analysis of ridge functions which contain most of the information of the wavelet transform in a sparse support this method falls in the framework of the wavelet response wr introduced by le gonidec et al which analyses the impedance multiscale behaviour by propagating dilated wavelets into the medium we further extend the wr by considering its application to broad band seismic data we take into account the bandpass filter effect related to the limited frequency range of the seismic source we apply the method to a deep water seismic experiment performed in 2008 during the erig3d cruise to demonstrate the potential of ridge functions as multiscale seismic attributes in conjunction to the analysis of seismic data acquired by the deep towed sysif system 200 2200 hz we use ground truth data to characterize the fine scale structure of superficial sediments by using the continuous wavelet transform cwt the availability of in situ measurements allows to validate the relationship between cwt andwr and to estimate the attenuation of seismic waves into the sediments once validated the method is applied on a whole seismic profile and wr ridge functions are computed for two particular reflectors the reflector thicknesses fall below the resolution limit of the seismic experiment making the wr seismic attributes a super resolution method

pulsing of a focused mantle plume evidence from the distribution of foundation chain hotspot volcanism 1 using the rare case of a hotspot chain crossing a fossil microplate we reveal fundamental mantle plume characteristics by comparing hotspot volcanism in a sequence of contrasting tectonic settings key new 40ar 39ar ages show that the foundation mantle plume pulses hot masses from depth with an apparent periodicity of one myr synchronous magmatism over large distances indicates that masses associated with individual pulses are focused initially into similarly sized zones under the pacific plate since the plume spreading on impact with the lithosphere influences a very wide area apparently unconnected hotspot volcanism can be produced simultaneously across wide swaths often crosscutting seamount chains our model might explain in part much of the midplate volcanism scattered across the pacific seafloor indicating the episodic addition of significantly greater masses of plume material into the upper mantle than suggested by the narrowness of major seamount chains

stratal slice the next generation vail and his colleagues 1977a b laid a foundation for seismic chronostratigraphy by analyzing the relative rise of sea level indicated by coastal onlap these workers invented a novel way of converting a stratigraphic cross section in the depth or traveltime domain to a chronostratigraphic chart in the wheeler domain figure 1a and figure 1b with the widespread use of seismic data in the industry such conversion can now be achieved conveniently with the proper software at the basinal regional or prospect scale figure 1c and figure 1d

a texture based region growing algorithm for volume extraction in seismic data we present a novel approach to automated volume extraction in seismic data and apply it to the detection of allochthonous salt bodies using a genetic algorithm we determine the optimal size of volume elements that statistically according to the u test best characterize the contrast between the textures inside and outside of the salt bodies through a principal component analysis approach this information was used to implement a seeded region growing algorithm to directly extract the bodies from the cube of seismic amplitudes we present the resulting three dimensional bodies and compare our final results to those of an interpreter showing encouraging results

migration rate of volcanism along the foundation chain se pacific abstract volcanism has migrated along the nw se trending foundation chain se pacific at a rate of 91 2 mm y for the past 21 million years my the foundation chain is at least 1900 km long and was erupted mostly in the interior of the pacific plate the linear migration of intraplate often geochemically enriched volcanism along the foundation chain can be explained by the theory of tectonic plate drift over a narrow stationary plume of hot mantle material upwelling from depth the present hotspot or at least its eastern extent generated by this foundation plume is now located on or close to the pacific antarctic spreading axis local spreading microplate boundaries have migrated systematically towards the foundation plume for at least the past 21 my a process that was however interrupted by the creation of the selkirk microplate the foundation chain has erupted therefore onto ocean crust ranging in age from 17 ma to 0 ma with distances between the foundation plume and local spreading microplate boundaries varying from 900 km to 0 km such interplay between the foundation plume and local seafloor spreading and microplate boundaries probably in combination with changing stresses in the lithosphere apparently induced major changes in the fabric and composition of the foundation chain e g the switch from individual seamounts to elongated en echelon ridges at 5 ma it can also explain why ages for a few foundation seamounts located at the edges of the selkirk microplate do not lie along the overall linear trend of migrating volcanism the linear velocity of the pacific plate over the foundation plume calculated on the basis of the migration rate of volcanism along the foundation chain is predicted by a number of rotation poles for the motion of the pacific plate in a fixed hotspot reference frame the fact that the measured migration rates of volcanism along the foundation and hawaiian chains are predicted by these rotation poles 1 confirms that the distribution of foundation chain ages records the absolute motion of the pacific plate and 2 supports the fundamental assumption of stationary mantle plumes in the case of hawaii versus foundation for at least the past 21 my the foundation chain was created by a weak plume primarily as relatively small probably rapidly erupted 1 my individual seamounts or seamount clusters at a rate of approximately one every my linear migration rates of volcanism are most likely defined unequivocally along such types of hotspot chain on the basis of age distance data it should also be easier to identify and characterize volcanism created as a result of plume interactions with local spreading microplate boundaries rotation poles for pacific plate drift show that the initial stages of volcanism along the southern austral chain 34 ma could have been created by the foundation plume suggesting that the path of pacific plate drift over the stationary foundation plume could be at least 3000 km long

application of multi seismic attributes analysis in the study of distributary channels abstract during the exploration of stratigraphic reservoirs the key to locating these reservoirs is to identify the sandstone distribution seismic data can be used to recognize large scale distributary channel sedimentary bodies however depiction of sedimentary bodies in small distributary channels using traditional interpretation data from seismic profiles is extremely difficult in the upper cretaceous first sandstone bed of the third member of the nenjiang formation called the nen 3 member for simplicity in the xb area of the southern songliao basin distributary channels are the main sedimentary facies the distributary channels migrate frequently therefore it is difficult to precisely depict the morphology of the channel and the distribution of sandstone in this study we investigated the deposition of distributary channels using equal scale formation plane seismic attributes such as post stack amplitude instantaneous amplitude and seismic waveform classification analyzed well logging data from target formations and mapped the distribution of distributary channels this study shows that seismic sedimentological study and stacking multiple attribute analysis can identify the distribution of distributary channels precisely and effectively the attributes of equal scale strata slices are evidently superior to those of time and horizon slices attribute extraction and selection of equal scale formation slices is an essential step the comprehensive selection of seismic attributes that show a good correlation to a single well can be used to clearly depict channel bodies the overlap of the 40 hz single frequency energy and the rms amplitude depicts the sedimentary characteristics and shapes of sandstone bodies in main channels as well as small scale distributary channels more clearly than a single attribute these attributes show that the first sandstone bed of the nen 3 member was from distributary channels with complex shapes the distributary channels cut across each other vertically and laterally it indicates that during the deposition of the nen 3 member in xb area the direction of the main channel is from north to south and the provenance could be from north and east the method of this paper may provide some helpful suggestions to the geologist using seismic attributes to undertake research on sedimentary environment at other places in the world

the pacific antarctic ridge foundation hotspot interaction a case study of a ridge approaching a hotspot the foundation hotspot pacific antarctic ridge par system is the best documented case of a fast spreading ridge approaching a hotspot and interacting with it the morphology crustal structure inferred from gravity anomalies and the chemical composition of the lavas of the axial area of the par show evidence of the influence of the hotspot that is presently located roughly 35 km west of the spreading ridge axis along axis variation in the mantle bouguer anomaly is about 28 mgal corresponding to a crustal thickening of 1 5 km where the hotspot is nearer to the par anomalous ridge elevation is 650 m and the along axis width of the chemical anomaly is 200 km a comparison of these axial parameters with those derived for other ridge hotspot systems suggests that the amount of plume material reaching the ridge axis is smaller for the foundation par system this implies a weaker connection between the plume and the ridge cumulative effects of a fast spreading rate and of a fast ridge hotspot relative motion can be responsible for this weak plume ridge flow the flow from the hotspot may be less efficiently channelled towards the ridge axis when a fast ridge is rapidly moving towards a hotspot

upper mantle heterogeneities and dynamics the width of geochemical and residual elevation anomalies along the mid ocean ridge system decrease as both the distance between migrating ridge segments and related hotspots and the local geochemical dispersion in the anomalies increase these observations provide further evidence that flows of mantle plumes in the upper mantle are deflected by migrating ridge sinks once they override hotspots

geologic significance of anomalous instantaneous frequency anomalous frequency spikes derived from complex trace analysis have long been considered more as a flaw of algorithms than a valuable seismic attribute however synthetic models and field data show that instantaneous frequency spikes are clearly linked to physical models that could help geologic interpretations of seismic data frequency spikes are related to relative amplitude minima along a seismic trace that occur either at the merging point of the top and base reflections of a wedge type i or at the tip of the wedge type ii a type ii spike is indicative of a seismically thin bed average 0 2 or thinner in this study denotes wavelength although the bed thickness tends to decrease with the data frequency and bed spacing in a multibed acoustic impedance profile in the range of 16 to 2 in this study interpretive values of instantaneous frequency include recognizing thin reservoirs that are otherwise difficult to detect mapping relative thickness changes of lithofacies detecting lithof

geochronology of galapagos seamounts lavas from seamounts of the central galapagos platform and the carnegie ridge increase in age with distance from the western edge of the platform consistent with a hotspot model for the generation of these features the areal distribution of seamount ages suggests that the pattern of dispersed volcanism seen on the present islands also prevailed between 5 and 6 ma age distance relationships are consistent with a decrease in the velocity of the nazca plate relative to the galapagos hotspot during the past 9 m y most likely at 5 ma when there was a change in pacific hotspot motion alternatively the plate velocity remained constant and volcanism at a single seamount endured up to 7 m y lavas from seamounts along the wolf darwin lineament to the northwest of the galapagos platform are young 1 ma with the youngest measured ages closest to the platform

a genetic algorithm for filter design to enhance features in seismic images abstract we present a novel method to enhance seismic data for manual and automatic interpretation we use a genetic algorithm to optimize a kernel that when convolved with the seismic image appears to enhance the internal characteristics of salt bodies and the sub salt stratigraphy the performance of the genetic algorithm was validated by the use of test images prior to its application on the seismic data we present the evolution of the resulting kernel and its convolved image this image was analysed by a seismic interpreter highlighting possible advantages over the original one the effects of the kernel were also subject to an automatic interpretation technique based on principal component analysis statistical comparison of these results with those from the original image by means of the mann whitney u test proved the convolved image to be more appropriate for automatic interpretation

mapping sediment dispersal patterns and associated systems tracts in fourth and fifth order sequences using seismic sedimentology example from corpus christi bay texas a seismic sedimentologic study was performed to map fourth and fifth order systems tracts in oligocene frio strata in corpus christi bay south texas guided by third order sequence stratigraphic correlations from seismic and wire line log data we prepared stratal slices from a three dimensional seismic volume to reveal high resolution 10 m 33 ft levels sediment dispersal patterns and associated systems tracts in a relative geologic time domain on average 1200 m 3940 ft of sediments were deposited in the third order lowstand expansion cycle and at least 16 higher order sequences fourth and fifth order sequences were recognized three types of depositional systems were identified in the frio stratigraphic section 1 offshelf lowstand slope fans that are best characterized by submarine channel and levee systems inside and outside incised submarine channels and by fan shaped sand body geometry 2 lowstand prograding deltaic systems that are composed of strike oriented and lobate deltaic sand bodies and 3 highstand systems that are represented by onshelf barrier lagoon and deltaic systems higher order sequence development was controlled by the interaction of relative sea level change sediment supply and gravity tectonics the top of sediment ridges was eroded or decapitated during many of the higher order sequences sand dispersal patterns are primarily controlled by accommodation resulting from rollover topography associated with growth faulting between the boundary fault and the hinge line atop rollover structures strike oriented sandstone bodies dominate within submarine channels and incised valleys and beyond the hinge line to the distal basin dip oriented sandstone bodies prevail sandstone thickness and dispersal patterns can be predicted by integrating wire line log measurements and seismic amplitude patterns

multivariate statistical analyses applied to seismic facies recognition one of the most important goals of seismic stratigraphy is to recognize and analyze seismic facies with regard to the geologic environment the first problem is to determine which seismic parameters are discriminant for characterizing the facies then to take into account all those parameters simultaneously the second problem is to be sure that there is a link between the seismic parameters and the geologic facies we are investigating this paper presents a methodology for automatic facies recognition based upon two steps the first or learning step begins with the definition of learning seismic traces for each facies we wish to recognize the choice of learning traces is based upon either well data or a seismic stratigraphic interpretation a large number of seismic parameters are then computed from the learning traces multidimensional analyses are carried out in order to validate the choice of learning traces and to select among all the available parameters those that discriminate best at this st

relative geologic time age volumes relating every seismic sample to a geologically reasonable horizon the age volume described in this paper can significantly increase the amount of useful geologic information extracted from a seismic data volume this paper has three goals the first is to introduce and describe the relative geologic time volume referred to herein as either an rgt volume or an age volume every seismic sample in an age volume contains an estimate of the relative geologic time for that sample which automatically relates every sample to a geologic horizon the second goal is to discuss some of the applications and advantages of using a rgt volume to store and access seismic interpretation for example it can be used to sculpt a seismic volume along a desired horizon or view depositional changes as a function of geologic time the third goal is to describe two methods for generating such a volume the first employing standard interpretation techniques and the second relying on unwrapping instantaneous phase unwrapping the instantaneous phase is a new holistic approach to interpreting seismic data that can produce a very detailed seismic interpretation the goal of building and using an rgt volume is to extract significantly more geologic information from the seismic data than is available from conventional methods the rgt volume is both a way of storing and retrieving seismic horizons to generate such a volume each seismic sample needs to be assigned an estimate of relative geologic time which in essence connects it to a geologically reasonable horizon in normal sections these relative geologic time values will increase with depth or traveltime high gradients in the rgt volume could be indicative of faults unconformities fluid contacts or interpretation errors while a constant value surface in a rgt volume is a seismic horizon figure 1 contains a portion of the seismic data used to illustrate the

geomorphology and structural segmentation of the crest of the southern pacific antarctic east pacific rise geomorphology of the boundary between pacific and antarctic plates was mapped with a sea beam multibeam echosounder and a seamarc ii bathymetric side scan sonar from the southern end of juan fernandez microplate at 35 s to heezen transform at 56 s there are six spreading center systems separated by two large left stepping nontransform offsets at 36 5 s and 41 5 s two right stepping transform fault systems and a left stepping hybrid structure with equally long strike slip and nontransform offsets axial rift zones spreading axes are generally within 1 of normal to the relative motion predicted by current plate rotation models most axial rift zones crop out along the crests of typical east pacific rise epr axial ridges which commonly have flat rather than humped long profiles about 2 of this fast spreading 84 100 mm yr rise crest has an axial rift valley instead of an axial ridge the longest rift valley segment is midway between menard and vacquier transforms near 51 s where an anomalously deep rise crest may mark a zone of below average mantle upwelling nontransform offsets structurally similar to those on the tropical epr but mostly formed by differential asymmetric spreading subdivide the four longest spreading center systems on the northern transform free two thirds of the rise net rift propagation at migrating offsets has been into the faster pacific plate this causes right steps to migrate north left steps to migrate south and crust to be transferred to the east flank this pattern has prevailed for several million years judging from the oblique fracture zones pseudofaults mapped on the rise flanks with older marine data and geosat altimetry on this rise crest the difference in stress on two plates with very different velocities may control the direction of offset migration

curvature attribute applications to 3d surface seismic data identifying subtle faults at or below the limits of seismic resolution and predicting fractures associated with folds and flexures is one of the major objectives of careful seismic interpretation with the advent of common use of 3d seismic in the late 1980s first derivative based horizon dip magnitude and dip azimuth were found to enhance faults that were otherwise difficult to see more recently second derivative based curvature maps have carried this process a step further horizon based curvature computation is now available in the commercial workstation environment putting these tools in the hands of geoscientists who do not have access to processing software and do not have time or inclination to program

lithospheric structure and compensation mechanisms of the galapagos archipelago volcanic islands of the galapagos archipelago are the most recent subaerial expression of the galapagos hotspot these islands and numerous seamounts are constructed mainly upon a broad volcanic platform that overlies very young 10 m y oceanic lithosphere just south of the active galapagos spreading center the 91 w fracture zone crosses the platform and creates an estimated 5 m y age discontinuity in the lithosphere major tectonic features of the galapagos include an unusually broad distribution of volcanic centers pronounced structural trends such as the nw se wolf darwin lineament wdl and a steep escarpment along the western and southern margins of the archipelago we use shipboard gravity and bathymetry data along with geosat geoid data to explain the tectonic and structural evolution of the galapagos region we model the gravity anomalies using a variety of compensation models including airy isostasy continuous elastic flexure of the lithosphere and an elastic plate with embedded weaknesses and we infer significant lithospheric strength variations across the archipelago the outboard parts of the southern and western escarpment are flexurally supported with an effective elastic thickness of 12 km this area includes the large shield volcanoes of fenandina and isabela islands where the lithosphere regionally supports these volcanic loads the central platform is weaker with an elastic thickness of 6 km or less and close to airy isostasy the greatest depths to the moho are located beneath eastern isabela island and the central platform thinner lithosphere in this region may account for the broad distribution of volcanoes the extended period of eruption of the central volcanoes and their reduced size the transition from strong to weak lithosphere along the southern escarpment appears to be abrupt within the resolution of our models and can be best represented by a free end or faultlike discontinuity also modeling the wdl as a lithospheric fault increases the match to the observed gravity anomalies the primary feature is the weak central platform whose existence is a logical convergence of several factors the 91 w transform age offset the possible increase in age of the lithosphere along the southern part of the platform due to ridge jumping and the formation of the central platform at a spreading ridge

the foundation seamount chain a first survey and sampling the foundation seamounts form a 1400 km long chain on the pacific plate from 32 s 127 w to the pacific antarctic spreading axis at 38 s 111 w previously only known from sparse single beam echosoundings and satellite altimetry we present here the first multibeam bathymetric survey and geological sampling results we confirm that the submarine topography correlates with the altimetry and that the chain is volcanic rather than tectonic or microcontinental in origin the chain can be divided up morphologically and geochemically into three section 1 west of 125 w large flat topped volcanoes composed of incompatible element depleted lavas 1 of a near ridge origin with little or no plume influence 2 between 125 and 115 w true intraplate volcanoes with incompatible element enrichment 1 9 generated over the foundation plume 3 east of 115 w e w trending volcanic ridges with compositions 2 0 0 3 suggestive of interaction between the plume and the pacific antarctic spreading axis on the spreading axis moderate incompatible element enrichments 0 8 cf 0 3 outside the foundation area also suggest plume influence it appears that the activity of the foundation plume in the last few million years has 1 significantly waned and 2 become wholly channeled towards the spreading axis the foundation plume may be in the process of dying

observations of ridge hotspot interactions in the southern ocean the evolution of ridge hotspot systems is not well understood in this investigation satellite derived marine gravity data are used in conjunction with underway bathymetric and magnetic anomaly profiles to investigate the nature of ridge hotspot interaction at four sparsely explored systems in the southern ocean these systems illustrate three different stages of ridge hotspot interaction in which a migrating spreading center approaches a hotspot pacific antarctic louisville passes over or is captured by the hotspot mid atlantic shona discovery and ultimately migrates away from the hotspot southeast indian kerguelen all of these systems show some evidence of discrete ridge jumps in the direction of the hotspot as the spreading center attempts to relocate toward the hotspot by asymmetric spreading interestingly these ridge jumps show no evidence of propagating offsets as have been seen on many other ridge hotspot systems a simple model predicts that typical plume excess temperatures can weaken the lithosphere sufficiently to promote asymmetric spreading and possibly allow a discrete ridge jump the presence of previously uncharted obliquely oriented aseismic ridges and gravity lineations between the ridge and the hotspot supports the notion of asthenospheric flux from the plume to the spreading center both before and after the time when the hotspot is ridge centered the azimuths of the aseismic ridges cannot be explained by plate kinematics alone they consistently extend from the ends toward the centers of the adjacent spreading segments suggesting some interaction between plume derived asthenospheric flux and local lithospheric structure the features discussed here also indicate that the transfer of asthenospheric material from the plume to the spreading center is influenced by the local plate boundary configuration and interaction with transform offsets

three holocene and late pleistocene glacial stages inferred from moraines in the lingshi and thanza village areas bhutan abstract moraines formed by valley glaciers in lingshi area northwestern bhutan constitute three distinct stages with contrasts in the spatial distribution and size of moraines and surface features such as clasts soils and vegetation moraines in the thanza village area northern bhutan show three stages with similar characteristics to those in the lingshi area using morphostratigraphic criteria these three stages correlate with some glacial stages in the khumbu himal eastern nepal dates from moraines in the khumbu himal provide a tentative chronological sequence of these three stages valley glaciers in bhutan expanded during the following periods 1 the takaphu and raphsthreng stages are the little ice age and late holocene glacial advances 2 the jykhuje and tenchey stages represent the late glacial and or early holocene glacial advances and 3 the lingshi dzong and lunana stages are coincident with the last glacial period

integrated seismic analysis of carbonate reservoirs from the framework to the volume attributes the recognition of the significance of seismic geometries and the depositional sequence concepts derived from them have revolutionized carbonate stratigraphy new insight into carbonate platform evolution has been gained from outcrops by describing subseismic geometric and facies relationships within a larger seismic scale chronostratigraphic framework integration of the outcrop and seismic and knowledge of the subseismic facies distributions has improved seismic stratigraphic prediction recently seismic analysis of carbonate strata has focused on the generation of more accurate and robust stratigraphic frameworks and large scale carbonate platform architecture delineating the depositional sequence framework provides a predictive way to map reservoir e g grainstone shoals reefal rudstones and floatstones etc source and seal lithofacies and to qualitatively delineate the early diagenetic history of a platform e g subaerial exposure at sequence boundaries pore systems are complex and reco

salt diapirs without well defined boundaries a feasibility study of semi automatic detection prestack depth imaging of seismic data in complex areas such as salt structures requires extensive velocity model updating in many cases salt boundaries can be difficult to identify due to lack of seismic reflectivity traditional amplitude based segmentation methods do not properly tackle this problem resulting in extensive manual editing this paper presents a selection of seismic attributes that can reveal texture differences between the salt diapirs and the surrounding geology as opposed to amplitude sensitive attributes that are used in case of well defined boundaries the approach consists of first extracting selected texture attributes then using these attributes to train a classifier to estimate the probability that each pixel in the data set belongs to one of the following classes near horizontal layering highly dipping areas and the inside of the salt that appears more like a low amplitude area with small variations in texture to find the border between the inside of the salt and the highly dipping surroundings the posterior probability of the class salt is input to a graph cut algorithm that produces a smooth continuous border an in line seismic section and a timeslice from a 3d north sea data set were employed to test the proposed approach comparisons between the automatically segmented salt contours and the corresponding contours as provided by an experienced interpreter showed a high degree of similarity

geometric attributes for seismic stratigraphic interpretation the application of sequence stratigraphy to seismic interpretation has proven to be fundamentally important in basin analysis it provides a framework for understanding strat igraphic evolution and is a key element in predicting the spatial distribution of reservoir seal and source rocks traditional methods of seismic se quence stratigraphy make use of observations such as stacking patterns seismic character of facies and their distribution to develop subsurface models we present a set of seismically derived geometric attributes that enhance and characterize these observations allowing a sequence stratigraphic framework to be developed in the earliest stages of interpretation