validation of elastic wave measurements of rock fracture compliance using numerical discrete particle simulations we test various methods of quantifying the compliance of single and multiple rock fractures from synthetic ultrasonic data the data are generated with a 2d discrete particle scheme which has previously been shown to treat fractures in agreement with linear slip theory studying single fractures we find that delays derived from peak amplitudes do not correspond to group delays as might be expected this is due to waveform distortion caused by the frequency dependent transmission across the fracture instead the delays correspond to an expression for phase delays which we derive from linear slip theory phase delays are a unique function of compliance whereas group delays are non uniquely related to compliance we believe that this property of group delays has hindered the wider application of deriving fracture compliances from traveltimes we further show that transmission coefficients derived from waveform spectra yield more accurate fracture compliances than those obtained from ratios of signal peak amplitudes we also investigate the compliance of a set of parallel fractures fracture compliance can only be determined from transmission coefficients if the fracture spacing is so large that the first arriving pulse is not contaminated by reverberations in the case of contamination the direct measurement of group or phase delays is not practical however we demonstrate that in such cases of strong waveform distortion the coda wave interferometry method is very effective for determining relative fracture compliance first break delays in the fracture set data are related to those observed in single fracture simulations this means that fracture set compliance can be estimated from first break data if used together with numerical simulations

strength and anisotropy of foliated rocks with varied mica contents abstract we have shortened 15 schists and gneisses with varying compositions 15 75 mica by volume at angles of 45 and 90 to foliation s to investigate the influence of micas on the strength and anisotropy of foliated rocks at the conditions tested t 25 c p c 200 mpa and e 10 5 s 1 compressive strengths vary by a factor 4 in the 45 and 90 orientations and individual rock types exhibit directional responses ranging from isotropic to strongly anisotropic trends of decreasing strength decreasing anisotropy and increasing ductility are observed with increasing mica content strains in all samples were localized within inclined shear zones accommodated by dislocation slip and grain scale microkinking in micas and microcracking in all other silicates stress strain response and grain scale deformation microstructures both indicate that mechanical behavior is strongly influenced by the concentration and spatial arrangement of micas shear zone formation is associated either with discrete brittle fracture transitional strain softening or steady strength ductile shear in both brittle and transitional samples extensive microcracking of strong quartzo feldspathic bridges occurs and stress drop magnitudes decrease with decreasing spacing and increasing overlap of adjacent critically oriented micas steady strength ductile shear zones develop in samples containing domains of interconnected micas and isotropic mechanical response is observed in those in which micas are contiguous in nearly all directions

reservoir compartmentalization an introduction reservoir compartmentalization the segregation of a petroleum accumulation into a number of individual fluid pressure compartments occurs when flow is prevented across sealed boundaries in the reservoir these boundaries are caused by a variety of geological and fluid dynamic factors but there are two basic types static seals that are completely sealed and capable of withholding trapping petroleum columns over geological time and dynamic seals that are low to very low permeability flow baffles that reduce petroleum crossflow to infinitesimally slow rates the latter allow fluids and pressures to equilibrate across a boundary over geological time scales but act as seals over production time scales because they prevent crossflow at normal production rates such that fluid contacts saturations and pressures progressively segregate into dynamic compartments thus reservoir compartmentalization impacts the volume of moveable produceable oil or gas that might be connected to any given well drilled in a field which restricts the volume of reserves that can be booked for that field booking of reserves is tightly regulated by government authorities because it is a key measure used by stock analysts and investors to value an oil company this places reservoir compartmentalization studies and the predictive science and technology applied to them at the heart of company valuation unexpected compartmentalization can also seriously impact the profitability of a field with more data acquisition more study more wells more time being required to produce less oil and gas than was originally anticipated in extreme cases this might even lead to early field abandonment however unexpected or misunderstood reservoir compartmentalization has been an industrywide experience for over 30 years and it is clear that there is great value in learning from past often expensive mistakes e g smith 2008 this learning process has often driven developments in geoscience engineering and related technology enabling operating companies to identify and predict new untapped volumes in old fields make general improvements to field management e g gainski et al wonham et al and apply this knowledge to other similar but lessmature fields in their portfolio reservoir compartmentalization is therefore a major uncertainty that should be accurately assessed during the appraisal of petroleum reservoirs in order to avoid unexpected compartmentalization at the production stage in the past few decades there have been major advances in data detection and surveillance methods and our geoscience and reservoir engineering approaches however reservoir compartmentalization can still be underestimated during field appraisal and can still give surprises that force a re think of the field development and production plan e g smith 2008 this is not necessarily a defect in the science or technology but rather it may also be a result of ineffectual data appraisal or discipline integration within subsurface workflows thus it is not unusual for subsurface teams to place too much emphasis on one aspect of the evidence or to make early assumptions that bias data acquisition analyses and interpretations later on for example fisher jolley 2007 point out that non existent faults or improbable fault seal capacities might be invoked to explain variable petroleum contacts and dynamic fluid pressure behaviour when an alternative or combination of factors or other unrelated explanations might be more appropriate for the data e g hydrodynamic tilting of petroleum contacts tozer borthwick research initiatives and collaborations between oil companies service groups and academic institutions vary considerably in scope and content and there is often a creative tension between the competitive advantages motivations and knowledge gaps perceived by the sponsoring companies and their research partners in addition to this the scientific insights that can be gained from the

rock slope instabilities in sogn and fjordane county norway a detailed structural and geomorphological analysis rock slope failures form a frequent hazard to many populated mountain regions especially in western norway the topographical and meteorological characteristics increase the vulnerability for rock slope failures a major focus for studies in norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters the determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition in addition a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures the primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western norway it is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region the implemented approaches range from regional scale statistical analyses towards site specic numerical modelling while a focus is set on quantitative analyses within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of sogn fjordane western norway it is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits the degree of tectonic deformation and the geological lineament density large rock slope instabilities develop preferentially within relatively weak rock units such as phyllites or weathered mac gneisses and at convex slope breaks looking more into detail a strong structural control is conrmed by numerical modelling for the unstable rock slope at stampa susceptibility and hazard are assessed at dierent scales and with dierent measures quantitative rockfall susceptibility is mapped on a regional scale for the entire county of sogn fjordane based on the statistical analysis of a set of controlling factors in addition this statistical susceptibility model is combined with a physically based model restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source this combination allows using road inventories with registered impact points instead of release areas for susceptibility modelling in contrast relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at stampa based on morphology and past activity present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the storfjord region in western norway based on magnitude frequency analyses furthermore a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region this phd thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in norway it is shown that susceptibility and hazard can be assessed with dierent measures forming the basis for further decisions regarding risk assessment and mitigation

structural features and the evolutionary mechanisms of the basal shear zone of a rockslide abstract rockslides commonly form a shear zone to accommodate their displacements as such the landslide history and mechanism must be recorded in the structural features of the shear zone we investigated the basal shear zone of a 60 m thick rockslide body with a lateral displacement of 200 m on a dip slope and found the evolutionary mechanisms of a basal shear zone of a rockslide a basal shear zone on a dip slope is initiated along a lithologic boundary that is characterized by a high competency contrast such as pelitic rock and greenstone or chert and develops in the weaker rock which was pelitic rock in the present study the basal shear zone first develops with fracture of the rock mass followed by intragranular fracturing of rock fragments shear strain by landslide gradually localizes to a narrow zone in the fractured zone to form a clayey layer by cataclasis of rock fragments the rock fragments in the clayey layer become rounded by attrition and the clayey layer finally obtains shear surfaces with slickensides

on facies belts and facies mosaics holocene isolated platforms south china sea although the general criteria for recognition and environmental interpretation of different carbonate facies are well established a predictive understanding of the areal extent and spatial patterning of facies bodies and why they might organize into facies belts or facies mosaics is poorly constrained to explore patterns and process dynamics of facies on isolated carbonate platforms quantitative analysis of thematic maps derived from remote sensing images of 27 holocene atolls of the paracel and spratly chains in the south china sea explores variability within and among platforms on these systems most annular shelf margin reefs are less than 500 m wide on both chains inboard of the reefs reef sand aprons range up to 500 m spratlys and 1000 m paracels wide around individual platforms spratly chain sand apron widths are wider to north west whereas apron widths in the paracel chain are more symmetrical collectively data indicate log normal width exceedance probability distributions platform interior patch reefs include area exceedance probability distributions and gap size distributions lacunarity consistent within chains but distinct between the chains to understand the processes underlying distinct distributions simulations explored distinct growth scenarios results suggest that differences may represent distinct process classes proportional growth processes with multiplicative random effects reef sand aprons belts versus non linear size proportional growth of randomly aged and distributed elements patch reefs mosaics the probabilistically distinct sizes and spatial patterns of geomorphic elements within these general process classes are interpreted to represent variations on themes related to different impacts of tropical storms winter cold fronts and circulation in each chain the results highlight fundamentally different growth patterns impacting the sizes and distribution of facies belts and mosaics on isolated carbonate platforms because these bodies ultimately construct stratigraphy the themes could be applied to understand and predict variability in the architecture of subsurface reservoir analogues this article is protected by copyright all rights reserved

what matters for flow and recovery in carbonate gas reservoirs insights from the mature central luconia province offshore sarawak malaysia miocene carbonate reservoirs in central luconia offshore sarawak malaysia have been delivering gas for over 30 yr in this paper learnings from that period of production are used to understand the key drivers affecting flow during production and recovery optimization in existing fields as well as development decisions for new discoveries the large data set generated over more than 40 yr was analyzed in a consistent manner through a holistic database constrained by a stratigraphic framework to allow reservoir units to be compared like for like integrated knowledge base ikb concept carbonate reservoir heterogeneities impacting flow are grouped into horizontal heterogeneities argillaceous flooding layers and exposure related karst and vertical heterogeneities large scale architectural elements found especially along platform margins both types of heterogeneities control water ingress during production and influence the recovery mechanism argillaceous flooding layers can act as baffles holding back water rise during production or can form pressure compartments long lived fault bounded reef margins carbonate shoals islands and karsts can be vertical conduits for aquifer inflow platform shape and architecture impact column height and hence recovery efficiency additional drivers impacting recovery were found to be gas column height aquifer size and permeability pressure connection to neighboring fields and field development concepts all drivers identified impact decisions throughout the field life e g well count and design intervention capabilities evaluation and mitigation of early water breakthrough reservoir management selecting enhanced recovery methods and abandonment pressure the ikb allowed to derive big rules on what matters for flow which were used to decide on development strategies for greenfields in central luconia the presented outcomes can be extrapolated to comparable carbonate systems whereas the ikb approach can be adapted and applied to other mature basins and reservoir types where equally vast and historic data sets are awaiting to be used in the current era of digitalization

fractal analysis applied to cataclastic rocks abstract cataclastic rocks can be characterized by their fractal dimension which is dependent on the mode of fragmentation a mode of fragmentation may be defined in terms of base b and the number of fragile elements n f fractal dimension of a cataclastic rock can be obtained by finding the slope of the least square fit straight line of particle size frequency area frequency and volume frequency distribution in a log log coordinate system the relationships are d slope size frequency d 2slope area frequency and d 3slope volume frequency respectively in the analyses particle shape does not affect fractal dimension and neither does the diameter measured for a cataclastic rock

long term gravitational deformation of rocks by mass rock creep abstract subsurface rocks beneath slopes are deformed to various degrees in various ways by mass rock creep mrc when they are subjected to a gravitationally unstable state for a long period mrc forms folds faults and numerous kinds of fractures such deformation is one of the main factors for deteriorating rock masses on slopes and also precursors of many landslides mrc deformations which have often been ascribed to tectonic origins can be distinguished from tectonic ones by their deformational features landforms and relationships between slope morphology and subsurface structures mrc folds are flexural slip folds that have the following mesoscopic to microscopic characteristics their axial surfaces are not smooth but are jagged and many visible openings or open fractures develop in association with the folds the jagged axial surfaces become smoother at depth and openings decrease in width with increasing overburden at the deformation site macroscopic types of mrc folds change according to the relationship between foliations and slopes buckling folds form in consequent slopes drag folds form in a deeper part of obsequent slopes and bending folds form in slopes with steep dipping foliations consequent or obsequent by downslope bowing of foliations shear fractures and tension fractures are the main deformational structures formed by mrc in massive rocks among shear fractures those of listric origin are remarkable tension fractures in general occur either in networks dividing rocks into fragments that slip and rotate irregularly in relation to each other or in parallel arrays of steeply dipping fractures an mrc fault has a shear zone consisting of a pulverized zone with gouge and a phyllitic or brecciated zone in a densely foliated rock the phyllitic zone is formed by microscopic slip along foliations in a sparsely foliated rock the brecciated zone is formed by random crushing except for the faults made through the shear fractures in massive rocks landforms due to mrc are gentle slopes bounded by horseshoe knicklines upslope convex slopes ridge top depressions multiple ridges uphill facing scarps and ridge crossing depressions

ring shear studies of till deformation coulomb plastic behavior and distributed strain in glacier beds a ring shear device was used to study the factors that control the ultimate steady strength of till at high shear strains tests at a steady strain rate and at different stresses normal to the shearing direction yielded ultimate friction angles of 26 3 and 18 6 for tills containing 4 and 30 clay sized particles respectively other tests at steady normal stresses and variable shear strain rates indicated a tendency for both tills to weaken slightly with increasing strain rate this weakening may be due to small increases in till porosity these results provide no evidence of viscous behavior and suggest that a coulomb plastic idealization is reasonable for till deformation however viscous behavior has often been suggested on the basis of distributed shear strain observed in subglacial till we hypothesize that deformation may become distributed in till that is deformed cyclically in response to fluctuations in basal water pressure during a deformation event transient dilation ofdiscrete shear zones should cause a reduction in internal pore water pressure that should strengthen these zones relative to the surrounding till a process called dilatant hardening consequent changes in shear zone position when integrated over time may yield the observed distributed strain

surfaces with a long history the aptian top shu aiba formation unconformity sultanate of oman discontinuity surfaces in shallow marine carbonate successions may represent significant time gaps in the geological record of ancient epeiric neritic seas understanding the hidden geological information contained in major discontinuities is thus of key significance in palaeo environmental analysis sequence stratigraphy reconstructions of sea level change and basin evolution in the present paper the aptian top lower shu aiba formation discontinuity in the sultanate of oman is taken as a prominent example of a regionally extensive 100 000 km2 surface with a long up to 10 myr and complex geological history the top shu aiba discontinuity formed on the topographically elevated domain of the oman platform and represents in essence the late aptian time interval coeval carbonates in the intrashelf bab basin and oceanic rim indicate forced regression and sequence wise gradual down stepping available regional sedimentological sequence stratigraphic petrographic palaeontological and geochemical evidence from outcrops and cored wells in oman is summarized in part complemented by new data and reviewed in a process oriented context in the field the discontinuity is expressed as a low relief stained surface with evidence for a marine hardground stage being dominant indistinct features that indicate a transient meteoric precursor stage isotope shifts meteoric cements circumgranular cracks etc are present but their interpretation requires careful and detailed work this feature is remarkable as a series of relative sea level falls with amplitudes of up to several tens of metres from the early to late aptian boundary to the end of the aptian are reported from the middle east and elsewhere despite the palaeogeographic position of the study area in the tropical climate zone evidence of deep cutting karst features characteristic for many long term exposure surfaces worldwide is scarce acknowledging the fact that the modern world offers no genuine analogues for the lower aptian carbonate system in oman morphological similarities between actualistic wave eroded coastal terraces and the top shu aiba discontinuity are discussed critically this discussion may imply that during an exposure time of several million years the top shu aiba discontinuity experienced repeated stages of shallow flooding and emergence with each transgression removing portions of the underlying rock record the data shown here exemplify the complexity of hiatal surfaces in epeiric neritic carbonates and may serve as a case example for other major discontinuities

rock fragmentation and particle size in crushed zones by faulting abstract the size distribution of fragments in the crushed zone adjacent to a fault and that of grains in a zone of very fine grained particles the fault gouge was determined for two different faults in central japan one fault has a wide ca 100 m zone of rock fragmentation between the fault gouge zone and the basement rock formation dimensions of the 50 largest rock fragments were measured in the field at locations within a continuous outcrop of this fault at some places bulk samples were also collected and the particle fragment and grain size distributions were determined in the laboratory the relationship between the logarithmic mean of the sizes of the largest 50 fragments and their distances from the fault suggests that size reduction of fragments is due to bulk crushing away from the fault and to surface grinding near the fault the other fault has no crushed zone of basement rocks but does have a 5 m wide zone of fault gouge ten samples of ca 200 g each and three bulk samples of ca

mapping bathymetry and depositional facies on great bahama bank satellite imagery and an extensive set of water depth measurements have been used to map and critically evaluate the magnitude and patterns of bathymetry across great bahama bank descriptions of previously collected sediment samples were combined with satellite imagery to map and refine the interpreted distribution of surficial carbonate sediments depositional facies data reveal that 60 of great bahama bank lies in 5 m or less of water the deep portion occurs mainly in a generally east west trending area in the southern portion of the platform the re evaluation of the facies reveals that great bahama bank is essentially a very grainy platform with muddier accumulations primarily in the lee of andros island this area of great bahama bank also experiences currents related to an excursion of the florida current onto the platform top possibly enhancing sediment mud production through the generation of whitings sediment equivalents to mudstones wackestones and mud rich packstones cover 8 5 and 14 respectively of the platform top whereas sediment equivalents to mud poor packstones grainstones and rudstones account for 20 45 and 3 of the surface area boundstones reefs were not specifically mapped in this study due to the resolution of the mapping there is a poor relationship between the occurrence of the depositional texture and water depth in that the grainier sediment types are abundant across the full range of water depths the most abrupt lateral facies changes portrayed on the facies maps are observed leeward of islands areas which also hold the highest diversity in facies type the majority of the islands on the platform align with the north west south east strike of the platform margin and these islands in turn exert control on the shape and orientation of facies belts that develop in proximity to them for this reason regions of the platform that contain principal islands host facies belts that align with the principal axis of the platform whereas for regions lacking islands the facies belts adopt an east west trend consistent with prevailing winds and currents there is a clear trend that the wide southern portion of the platform hosts the most continuous expanses of grain rich sediments

anisotropy in seismic velocities and amplitudes from multiple parallel fractures many rock structures include multiple near parallel planar discontinuities such as bedding planes or joints the effects of these nonwelded interfaces on seismic wave propagation are often analyzed using effective moduli in terms of which seismic wave propagation is independent of frequency and without loss unless the moduli include imaginary terms an alternative approach is to treat these interfaces as a boundary condition in the seismic wave equation across which seismic stress is continuous but seismic particle displacements are discontinuous the ratio of the stress to displacement is called the specific stiffness of the interface and characterizes the elastic properties of a fracture for a completely elastic system this results in frequency dependent reflection and transmission coefficients for each interface as well as a frequency dependent group time delay using multiple parallel displacement discontinuities and ignoring converted and reflected waves expressions derived for transmitted wave amplitudes and group velocities show that these depend on frequency angle of incidence and polarization in the case of shear waves measurements on a laminated steel block show that shear pulses propagating parallel to the laminations and polarized parallel and perpendicular to the plane of the laminations both travel at the velocity for solid steel although the spectra of these pulses differ considerably however the energy of the pulse polarized perpendicular to the laminations may propagate as an interface wave between each pair of laminations predictions of the displacement discontinuity model have features quite distinct from many crustal observations to date we suggest that we are able to model dense populations of coplanar cracks that cannot be treated by effective moduli methods which require a dilute concentration of cracks

onshore to offshore trends in carbonate sequence development diagenesis and reservoir quality across a land attached shelf in se asia abstract although isolated miocene buildups in se asia commonly form prolific hydrocarbon reservoirs their equivalents on clastic dominated land attached shelves remain poorly known and underexplored here onshore to offshore trends in carbonate development and reservoir quality are assessed across the nw borneo shelf through study of surface outcrops and subsurface wells a multidisciplinary programme of fieldwork petrography and geochemical analyses allowed evaluation of spatio temporal variations in deposition diagenesis and pore system development together with an assessment of controlling influences in addition to field logging and sample collection 200 samples were studied via transmitted light cathodoluminescent and scanning electron microscopy together with stable isotopic characterisation o c and sr carbonates developed as localised low and higher relief buildups as well as more continuous sheet like deposits in near coast to shelf margin positions molluscs corals larger benthic foraminifera and coralline algae are common constituents most samples show evidence for marine micritisation and just in shelf margin positions isopachous cements however burial diagenesis predominates in the form of compaction neomorphism fracturing late leaching and dolomitisation near coastal carbonates commonly contain siliciclastics as do some shelf margin deposits that interdigitate with or are covered in siliciclastics some early probable meteoric leaching affected inner shelf deposits prior to pervasive neomorphic to blocky poikilotopic calcite cement formation on the basis of 18 o v pdb values of 4 5 to 7 9 equivalent to 18 o v smow values of 0 to 4 at 25 40 c and 13 c v pdb values of 0 6 to 1 6 cementation probably reflects alteration from terrestrial groundwaters in meteoric aquifers derived from the humid landmass of borneo despite this cementation moderate energy inner to mid shelf grainstones from the core of mounded carbonates still retain or have enhanced porosity 18 o v pdb values of 3 6 to 5 4 those for the late dolomites are suggestive of fluids of meteoric origin 18 o v pdb values of 5 2 to 7 4 equivalent to values of 0 3 to 6 3 v smow at 40 60 c critical factors for reservoir quality development in carbonates from siliciclastic dominated shelves in the equatorial tropics are 1 development and preservation of primary porosity 2 cementation associated with meteoric aquifers draining large humid equatorial landmasses and 3 burial leaching and fluid pathways

a 3d discrete numerical elastic lattice method for seismic wave propagation in heterogeneous media with topography 1 a three dimensional elastic lattice method for the simulation of seismic waves is presented the model consists of particles arranged on a cubic lattice which interact through a central force term and a bond bending force particle disturbances are followed through space by numerically solving their equations of motion a vacuum free surface boundary condition is implicit in the method we demonstrate that a numerical implementation of the method is capable of modelling seismic wave propagation with complex topography this is achieved by comparing the scheme against a finite difference solution to the elastodynamic wave equation the results indicate that the scheme offers an alternative 3d method for modelling wave propagation in the presence of strong topography and subsurface heterogeneity we apply the method to seismic wave propagation on mount etna to illustrate its applicability in modelling a physical system

architecture and growth history of a miocene carbonate platform from 3d seismic reflection data luconia province offshore sarawak malaysia using 3d seismic reflection data and wireline logs we reconstruct in detail the architecture and growth history of a miocene carbonate platform in the luconia province offshore sarawak malaysia platform growth started in the late oligocene to early miocene by coalescence of isolated patch reefs the growth history includes phases of progradation backstepping and occasional collapsing of platform flanks guided by syndepositional faulting the most pronounced seismic reflections in the platform correspond to flooding events thin transgressive systems tracts subaerial exposure preceding the flooding could be demonstrated in only one case platform growth was terminated by gradual submergence drowning indicated by smooth concentric seismic reflectors forming a convex mound

wings mushrooms and christmas trees the carbonate seismic geomorphology of central luconia miocene present offshore sarawak northwest borneo central luconia is a geological province of the sarawak basin offshore northwest borneo characterized by extensive development of miocene to holocene carbonate buildups the buildups are up to 2 km 1 mi thick and reveal complex seismic geomorphologies including out building in building carbonate siliciclastic intercalations and coalescence of neighboring carbonate bodies intermittent carbonate and siliciclastic deposition is interpreted to have been governed by frequently oscillating sea level and variable siliciclastic input location of the buildups with respect to deltaic facies and the seismic expressions of marginal carbonate strata locally known as wings are used here to classify carbonate seismic geomorphologies buildups encompassed by deltaic topsets are said to reside onshelf and are flanked by marginal carbonate deposits conformable with the onlapping siliciclastics and interpreted as thin carbonate platforms deposited in situ over prominent erosional unconformities and flooding surfaces such marginal facies are described on the basis of their appearance as open wings in contrast buildups downlapped by prodelta foresets or bottomsets or those draped by pelagic sediments are said to reside offshelf and are characterized by high relief steeply dipping marginal carbonate strata discordant with respect to the relatively flat lying platform carbonates as well as the onlapping siliciclastics these marginal strata have an appearance of closed wings and are interpreted as slope aprons composed of carbonate material derived from the productive platform tops and deposited off platform in deeper water carbonate geometries range from contracting upward pinnacles to expanding upward platforms in onshelf settings whereas buildups located offshelf have mostly contracting upward or aggrading morphologies buildups deposited onshelf have generally maintained a similar height of depositional slopes as they evolved reflecting rates of background siliciclastic deposition approximating those of carbonate growth in contrast depositional slopes of offshelf buildups have become progressively higher owing to limited siliciclastic input observations presented here on carbonate geomorphology and adjacent siliciclastic stratigraphy provide important clues for the understanding of the geology of the province because carbonates and siliciclastics intercalate frequently siliciclastic biostratigraphy can be used to precisely date and correlate geographically remote carbonate reservoir intervals and intrareservoir depositional and diagenetic events such as marine transgressive or exposure surfaces or karst networks conversely basin paleobathymetry can be measured by the size of carbonate clinoforms and the thickness of buildups established over flooded siliciclastic surfaces deposition of low relief carbonate platforms over siliciclastic substrates indicates shallow marine conditions as opposed to the prevalent notion of kilometer scale paleobathymetry these interpretations have important implications for understanding of the sedimentology and lithology of the ambient basinal siliciclastics with fundamental applications to hydrocarbon exploration

sea level changes shoreline journeys and the seismic stratigraphy of central luconia miocene present offshore sarawak nw borneo abstract central luconia is a geological province of the sarawak basin offshore nw borneo characterised by extensive development of miocene to recent carbonate build ups in the subsurface many of these build ups are reservoirs for hydrocarbons this study focuses on shelf wide stratigraphic architecture from which implications are drawn for the stratigraphic sealing potential of the deltaic clastics a stratigraphic model is proposed whereby clastic sediments surrounding the carbonate build ups are interpreted as stacked low relief deltas deposited in response to high frequency oscillation of the sea level the deltas are shown to have frequently prograded beyond carbonate build ups as a result of interaction between eustacy and deposition deltaic topsets are juxtaposed against carbonate build ups providing migration routes for hydrocarbons most of the carbonate reservoirs are consequently underfilled with hydrocarbon columns limited to the youngest onlapping stratigraphic sequence

unconformities and porosity development in carbonate strata ideas from a hedberg conference the purpose of this paper is to highlight ideas from a hedberg conference concerning detection of unconformities and associated porosity in carbonate strata many types of information including cores and outcrops seismic data eustatic sea level curves wireline logs biostratigraphic data stable isotope trends cycle stacking patterns and tectonic and basin evolution models can be used to predict and or detect subaerial unconformities all methods of detecting subaerial exposure with these types of information have limits and pitfalls detailed analysis of the stratigraphy sedimentology and diagenetic history of a rock sequence from outcrop or core data is considered the most reliable means of detecting subaerial exposure though an integrated approach using all a ailable information is recommended the relationship between subaerial exposure and subsurface porosity in carbonates is not simple or easily predicted subsurface porosity is the product of many factors operating during deposition subaerial exposure and burial several concepts should be recognized when evaluating porosity associated with subaerial unconformities 1 carbonate diagenesis during subaerial exposure rearranges pore networks but usually does not increase the total porosity near surface dissolution can simply lower a topographic surface without increasing porosity within the host limestone in many cases total porosity in carbonates under unconformities is actually reduced during subaerial exposure 2 permeability is likely to change more than porosity during subaerial exposure increasing in some c ses but decreasing in others 3 pore systems evolve with time during subaerial exposure short periods of subaerial exposure 10 000 400 000 yr are often associated with greater porosity than long intervals of subaerial exposure 1 20 million yr prolonged subaerial exposure may change permeability less than porosity because high permeability karst related conduits can form quickly and persist for millions of years 4 many carbonates subjected to subaerial exposure have little or no porosity in the deep subsurface because compaction cementation and stratal collapse reduce porosity during burial 5 unconformity related diagenesis may enhance reservoir potential by creating pore systems that are resistant to compaction during deeper burial 6 vugs caverns and breccias can fo m in the deep subsurface because of dissolution by basinal fluids independent of subaerial exposure 7 lithologic changes at unconformities like shales overlying carbonates can influence the flow of subsurface fluids during end page 857 deeper burial resulting in deep burial dissolution localized along unconformities if subaerial exposure and exposure surfaces are integrated into a sequence stratigraphic paleogeographic and climatic framework systematic and hopefully predictable patterns will emerge however we do not fully understand the complex interplay between the factors critical to creating and preserving porosity in carbonates additional research is needed to quantify critical processes and products so we can reliably predict porosity associated with subaerial exposure during exploration in frontier basins and on a smaller scale during reservoir analysis

fault gouge evolution in highly overconsolidated claystones processes of fault gouge evolution in hard claystones start with cataclasis that produces a soft clay gouge which fills the space between the initial fragments this re seals the initially highly porous and permeable damage zone without diagenetic processes we studied this process in shales and sandstones deformed in normal faults after uplift to shallow crustal depths in the ardennes and eifel detailed mapping shows four different lithotypes from intact shale in the wall rock broken wall rock fragments with various amounts of clay to a fully reworked gouge these lithotypes reflect different evolutionary stages the similar mineralogy of the different lithotypes suggests that the main process involved is mechanical fragmentation with minor contribution by diagenetic changes or weathering accompanied by large changes in microstructure porosity and transport properties while the wall rock has a very low porosity and permeability initial deformation results in a much higher porosity with large pores the reworked clay gouge also has a high porosity but its pore size corresponds to a lower permeability and higher capillary seal capacity in upper crustal fault zones in strong brittle lithologies this early re sealing in sections consisting of claystone will lead to local barriers to along fault fluid flow

marginal basin evolution the southern south china sea abstract the southern south china sea is divided into contrasting morphology by the west baram line to the west is the sundaland extinct passive margin in which rifting began in the eocene 46 ma and ceased at 19 21 ma anomaly 6 where sea floor spreading began much later than along the shelf of china the break up hiatus lasted 3 5 ma marked by the mid miocene unconformity also preserved on land sarawak the post rift strata date from 16 ma and drape over the rifted topography to the east is a convergent margin that became a collision zone in the middle miocene the sunda shelf is of uniform 30 km thickness except in localised deep basins and extends to a water depth of 200 m the continental slope is narrow the continental rise dangerous grounds is covered by water ranging from 500 m to 3 5 km depth at the continent ocean transition its width ranges from 170 to 330 km the rajang delta extends over the shelf and continental slope its post rift sediments drape over the rifted proximal topography of the dangerous grounds to the east the drape is thinner and has not completely buried the rifted topography the cuestas appear to have supported the carbonate build up infrastructures of the spratly islands whose slopes rise abruptly from a sea floor of 2 3 km depth the sabah and brunei margin is a collision zone that was formerly convergent the on land geology indicates a mesozoic ophiolitic basement the main collision feature is the western cordillera constructed mainly of sandy eocene to lower miocene turbidites predominantly oligocene to lower miocene in the west crocker 32 18 ma uplifted episodically throughout the upper miocene and pliocene 14 8 ma the 2 km deep northwest borneo trough may be a relict of the convergence phase but could also be a collisional foredeep the oil prolific baram delta resulting from uplift and erosion of the western cordillera has built out as far as the northwest borneo trough it is suggested that the passive margin continental rise dangerous grounds has been underthrust beneath sabah to cause uplift of the western cordillera the west baram line accordingly abruptly separates the collision zone from the western extinct passive margin and is a now extinct major right lateral transform fault

fracturing and hydrothermal alteration in normal fault zones large normal fault zones are characterized by intense fracturing and hydrothermal alteration displacement is localized in a slip zone of cataclasite breccia and phyllonite surrounding corrugated and striated fault surfaces slip zone rock grades into fractured but less comminuted and hydrothermally altered rock in the transition zone which in turn grades abruptly into the wall rock fracturing and fluid flow is episodic because permeability generated during earthquakes is destroyed by hydrothermal processes during the time between earthquakes

origin of seismic reflections in a carbonate gas field lower miocene offshore myanmar abstract the geological origin of seismic reflections within a carbonate gas reservoir has been determined on the basis of an integrative analysis of cores well logs pre production and 4d time lapse seismic data the gas reservoir is subdivided into meter to decameter thick diagenetic units which are characterized by distinct acoustic properties low impedance units are dominant and consist of highly microporous and vuggy foraminiferal coralline algal floatstones intervals whose porosity has been significantly enhanced in burial diagenetic environments high to moderate acoustic impedance units thickness 1 20 m are related to various depositional and diagenetic fabrics 1 early lithified coral floatstones 2 foraminiferal rudstone whose intergranular space is occluded by shallow burial sparry calcite and 3 carbonate breccia with neomorphosed corals occurring below an intra formational subaerial exposure surface within the gas zone seismic reflection horizons may form at the boundary between two diagenetic units with contrasted acoustic impedance or may result from the interference between reflection at base and top of such intervals a stratigraphy cross cutting reflection horizon has been shown to form at a major and laterally continuous shift in porosity which is related to a differential diagenetic evolution between the gas and the water zone during or after hydrocarbon emplacement finally the analysis of the geological origin of seismic reflections has been proved to help predicting and mapping the major heterogeneities with significant impact on flow during production

structural constraints on deep seated slope deformation kinematics abstract a significant sackung type deep seated slope gravitational deformation dsgsd was recognised for the first time by the authors in the middle part of valfurva east of bormio rhaetian alps italy the reconstruction of its kinematics age and state of activity is presented through a detailed description of its morphological geomechanical and structural features an integrated multi disciplinary approach was performed to achieve a clear comprehension of the phenomenon field surveys and aero photo interpretation were carried out in order to clarify the structural geological and geomorphological setting in which the dsgsd developed a kinematic conceptual model of the slope deformation was developed through the analysis of morpho structures of their significance and relationships with lithological markers and quaternary deposits after a geomechanical characterisation of the rock mass involved in the slope deformation numerical modelling was performed to verify the hypotheses made on kinematics and driving factors of the phenomenon the sackung affects pre permian metapelites metabasites and marbles belonging to the upper austroalpine basement of the campo nappe as well as late pleistocene and holocene glacial and rock glacier deposits the deformation started after the late wurmian age 15 000 11 000 years b p and continued until few centuries ago not excluding a present day low rate activity deformation consists in a large oblique sagging along a deep confined sliding surface associated with gravitational reactivation of pre existing late alpine and recent tectonic brittle structures leading to the formation of n s and wnw ese trending gravitational morpho structures the evolution of the wnw ese trending system resulting in asymmetric trenches led to progressive failure of the lower part of the slope during the last 10 000 years as testified by large paleo landslide accumulations and it is still in progress numerical modelling indicates post glacial unloading as the main triggering factor of the slope deformation the importance of this deep seated slope deformation is enhanced by the occurrence of the 30 mm 3 active ruinon landslide in the lower part of the slope such landslide is subjected to rapid evolution and threatens the valley floor establishing an important risk factor connected to human lives and socio economic activities

geological model of the aknes rockslide western norway abstract aknes is known as the most hazardous rockslide area in norway at present and is among the most investigated rockslides in the world representing an exceptional natural laboratory this study focuses on structural geology and the usage of geophysical methods to interpret and understand the structural geometry of the rockslide area the interpretations are further used to build a geological model of the site this is a large rockslide with an estimated volume of 35 40 million m 3 derron et al 2005 defined by a back scarp a basal shear zone at about 50 m depth and an interpreted toe zone where the sliding surface daylights the surface the rockslide is divided into four sub domains experiencing extension in the upper part and compression in the lower part structural mapping of the area indicates that the foliation of the gneiss plays an important role in the development of this rockslide the upper boundary zone of the rockslide is seen as a back scarp that is controlled by and parallel to the pre existing steep foliation planes where the foliation is not favourably orientated in regard to the extensional trend the back scarp follows a pre existing fracture set or forms a relay structure the foliation in the lower part dipping 30 to 35 to s sse seems to control the development of the basal sliding surface with its subordinate low angle trust surfaces which daylights at different levels the sliding surfaces are sub parallel to the topographic slope and are located along mica rich layers in the foliation geophysical surveys using ground penetrating radar gpr refraction seismic and 2d resistivity profiling give a coherent understanding of undulating basal sliding surface in the subsurface the geophysical surveys map the subsurface in great detail to a depth ranging from 30 40 m for gpr to approximately 125 m for refraction seismic and 2d resistivity profiling this gives a good control on the depth and lateral extent of the basal sliding surface and its subordinate low angle thrusts drill cores and borehole logging add important information with regard to geological understanding of the subsurface fracture frequency fault rock occurrences geophysical properties and groundwater conditions both in outcrops and or drill cores constrain the geometrical and kinematic model of aknes rockslide

morphological indicators of structural control relative sea level fluctuations and platform drowning on present day and miocene carbonate platforms abstract the morphology of carbonate platforms may be influenced by tectonic activity and eustatic variations 3d seismic data and satellite imagery are used in order to investigate the morphological similarities between present day carbonates platforms east of borneo island and miocene carbonate platforms of the south china sea the morphological similarities exhibit platform fragmentation that could be caused by subtle faulting sufficient to drown reef rims platform contraction which is a result of back stepping of the reef margin during a relative sea level rise and polygonal patterns in internal lagoons described as mesh reefs in modern platforms and possibly interpreted as karst in miocene platforms vertical movements may trigger the formation of new geomorphological conditions that modify the distribution of coral growth with respect to the new hydrodynamic conditions in space and time these movements uplift and tilting reduce and localize the space necessary for the coral ecosystem explaining the contraction leading to drowning of parts of and ultimately the whole platform

time lapse monitoring of rock properties with coda wave interferometry 1 the coda of seismic waves consists of that part of the signal after the directly arriving phases in a finite medium or in one that is strongly heterogeneous the coda is dominated by waves which have repeatedly sampled the medium small changes in a medium which may have no detectable influence on the first arrivals are amplified by this repeated sampling and may thus be detectable in the coda we refer to this use of multiple sampling coda waveforms as coda wave interferometry we have exploited ultrasonic coda waves to monitor time varying rock properties in a laboratory environment we have studied the dependence of velocity on uniaxial stress in berea sandstone the temperature dependence of velocity in granite and in aluminum and the change in velocity due to an increase of water saturation in sandstone there are many other possible applications of coda wave interferometry in geophysics including dam and volcano monitoring time lapse reservoir characterization earthquake relocation and stress monitoring in mining and rock physics

coda wave interferometric detection of seismic velocity changes associated with the 1999 m 3 6 event at mt vesuvius 1 we detect seismic wave velocity changes at mt vesuvius using doublets and the coda wave interferometry method the high sensitivity of multiply scattered coda waves to temporal changes in the medium allows us to detect velocity variation smaller than 0 4 we use 17 doublets some of them grouped in families of multiplets spanning january 1996 to december 1999 data show a systematic increase in velocity from 1996 to end september 1999 followed by a rapid drop in velocity this drop immediately precedes a sustained swarm of vt type earthquakes including the 9th october 1999 m 3 6 event the largest in the region since at least 1972 we propose a long term fluid pressurization followed by influx as a possible causative mechanism

seismic anisotropy of fractured rock a simple method for including the effects of geologically realistic fractures on the seismic propagation through fractured rocks can be obtained by writing the effective compliance tensor of the fractured rock as the sum of the compliance tensor of the unfractured background rock and the compliance tensors for each set of parallel fractures or aligned fractures the compliance tensor of each fracture set is derivable from a second rank fracture compliance tensor for a rotationally symmetric set of fractures the fracture compliance tensor depends on only two fracture compliances one controlling fracture compliance normal the other tangential to the plane of the fractures the stiffness tensor which is more useful in the consideration of elastic wave propagation through rocks can then be obtained by inversion the components of the excess fracture compliance tensor represent the maximum amount of information that can be obtained from seismic data if the background rock is isotropic and the normal a

development of deep seated gravitational slope deformation on a shale dip slope observations from high quality drill cores abstract we analyzed high quality drill cores with 100 recovery drilled into a gravitationally deformed dip slope of a shale dominated sequence of sediments in japan the slope had undulating surfaces but no well defined landslide scarps suggesting that parts of the slope had undergone gravitational deformation but had not completely separated from the surrounding bedrock the gravitational deformation of shale and sandstone is characterized by disintegration and brecciation of sediments and the formation of pulverized zones with poorly developed planar structures jigsaw like structures and fracture openings shear zones are distributed intermittently within the slope but have not merged discernably into a through going master sliding surface incipient landslide shear zones form openings within coherent rock by shearing along bedding with these shear zones potentially developing downward in a stepwise manner which may be related to stress redistribution induced by river incision

coseismic velocity variations caused by static stress changes associated with the 2001 mw 4 3 agios ioanis earthquake in the gulf of corinth greece 1 the analysis of temporal variations in the seismic velocity across faults can be used to estimate in situ stress changes seismic velocity of propagation depends on the fault stiffness which is a function of stress the coda wave interferometry technique is applied to seven families of repeating earthquakes multiplets recorded on the southern shore of the gulf of corinth greece to estimate high precision velocity changes in the earth s crust associated with the mw 4 3 agios ioanis earthquake results show that the agios ioanis event causes a perturbation in elastic properties at seismogenic depth resulting in a reduction of 0 2 in the seismic velocity the results are not consistent with either damage induced by dynamic stresses nor a fluid transient origin in contrast both the spatial distribution and magnitude of the velocity perturbation correlate well with modeled static stress variations this suggests that the measured changes in the mechanical properties of the seismogenic crust can be attributed to a change in static stress field associated with the mw 4 3 agios ioanis earthquake the velocity changes indicate an unclamping of the pyrgaki fault at depth which has local hazard implications

experimental investigation into the microstructural and mechanical evolution of phyllosilicate bearing fault rock under conditions favouring pressure solution abstract mature crustal fault zones are known to be zones of persistent weakness this weakness is believed to result from microstructural modifications during deformation such as grain size reduction and foliation development around the brittle ductile transition phyllosilicates are expected to have a significant effect on fault strength in particular under conditions favouring pressure solution to study such effects we performed rotary shear experiments on brine saturated halite kaolinite mixtures aimed at investigating the relation between microstructural and mechanical evolution in a system where pressure solution and cataclasis dominate the results show significant strain weakening and a transition with progressive strain towards more rate sensitive and less normal stress sensitive behaviour this was accompanied by a microstructural evolution from a purely cataclastic microstructure to a mylonitic microstructure consisting of elongate asymmetric clasts in a fine grained foliated matrix the results demonstrate that strain weakening and the development of a typical mylonitic microstructure can occur as a consequence of grain size reduction by cataclasis and a transition to pressure solution accommodated deformation even in the absence of dislocation creep the data raise questions regarding the reliability of microstructures as rheology indicators as well as on the use of low strain monomineralic flow laws for modelling crustal dynamics

neotectonic faulting in northern norway the stuoragurra and nordmannvikdalen postglacial faults abstract a systematic compilation and characterisation of many reports of neotectonic crustal deformation in norway both on local and regional scales has identified two neotectonic faults in northern norway the stuoragurra fault is a large reverse fault in finnmark county the nordmannvikdalen fault is a much smaller normal fault in troms county the stuoragurra postglacial fault can be followed in several discontinuous sections for 80 km in a ne sw direction the fault has up to 10 m of displacement during 1998 two trenches were made across the fault the hanging wall was seen to be thrust upwards over the footwall with 7 m vertical displacement evident from displaced glacial contacts the fault did not penetrate the overlying glacial materials but rather folded them forming a blind thrust large liquefaction and other deformation structures were found in the glaciofluvial sediments in both trenches veins of angular and subangular pebbles from the local bedrock penetrate more than 10 m laterally from the thrust plane and into the sediments in the footwall it is thought that these veins were injected during the fault activity the major deformation of the sediments has a decollement plane that continues laterally in the e b horizon contact of the modern soil on top of the footwall this may indicate that an initial pedogenesis had taken place before the fault activity occurred however no macro plant fossils to support this were found in the possible buried soil deformational structures seen in the trench can be explained as a result of one major fault event the nordmannvikdalen postglacial fault is a nw se trending normal fault dipping to the ne the fault offsets till on the nw slope of nordmannvikdalen the escarpment varies in height from 0 5 to 1 5 m with a trench often present between the hanging wall and the footwall the fault locally splits into two subparallel branches however this is probably only in the glacial overburden ground penetrating radar gpr profiles show two prominent bedrock reflectors dipping approximately 40 to the ne an upward extrapolation of the northernmost reflector through the overburden coincides with the position of the surface scarp the bedrock is well exposed along a streamed parallel to the gpr profiles bedding and foliation cannot be responsible for the reflectors visible in the gpr profiles gravitational forces have been ruled out as the origin of the fault although both faults probably formed shortly after weichselian deglaciation there is evidence that isostatic uplift was not the only force acting quaternary tilting of fennoscandia due to ridge push or mantle convection may also play a role in neotectonic activity in norway

shear strength of soils containing amorphous clay size materials in a slow moving landslide abstract the shear behavior of soils rich in amorphous clay size materials was not well reported in the literature this study analyzed the direct shear and ring shear test data of soil samples containing 55 74 amorphous materials in the clay fraction from a slow moving landslide in eastern honolulu hi the direct shear test results showed that the undisturbed soil samples when not sheared internally had peak cohesion c of about 50 kpa and internal friction angle o of about 10 this implies that the amorphous clay size materials provided strong interparticle bonds for the soils breaking of the bonds during the softening process and redistribution of the amorphous clay size materials were primarily responsible for the drop from the peak strength to the residual strength c 0 o 10 from back calculation with slope w and c 0 o 5 7 from the ring shear test the drained residual failure envelope is stress dependent due to the interaction of the gel like amorphous clay size materials with crystalline silt and sand sized particles the amorphous clay size materials act as the contact between crystalline particles the contact increases with increasing consolidation stress resulting in a decrease in the shear strength and the residual friction angle

correlation between velocity dependence of friction and strain localization in large displacement experiments on feldspar muscovite and biotite gouge abstract room temperature rotary shear experiments on rock powders of albite feldspar and muscovite and biotite micas show that the degree of localization of shear strain in these materials correlates with the frictional behavior in both feldspar and mica experiments increasing localization correlates with a lower coefficient of friction and a more negative velocity dependence of friction feldspar gouges tend to have localized deformation along one or more boundary parallel shears and a negative velocity dependence more localized deformation correlates with a lower coefficient of friction and a more negative velocity dependence in general micas deform throughout a broader zone than feldspar and have a lower coefficient of friction compared to muscovite biotite is weaker has a negative rather than a positive velocity dependence and shows more localized deformation for materials as diverse as feldspars and micas localization along boundary parallel shears correlates with negative velocity dependence along compliant natural faults a negative velocity dependence would result in a greater tendency for unstable sliding thus localized boundary parallel shears may indicate negative velocity dependence and slip by earthquakes on natural faults

the role of fault reactivation and growth in the uplift of western fennoscandia new structural data published aft data and topographic data suggest that the latest cretaceous cenozoic uplift of western norway was associated with normal reactivation of the more trondelag fault complex reactivation focused along the base of today9s topographic rise with maximum displacements in the order of 2 3 km structural and aft data indicate that reactivation occurred along a displacement gradient with least normal displacement in the ne and increasing displacements towards the sw reactivation commenced in connection with the triassic to earliest cretaceous phases of rifting on the norwegian margin and probably continued through most of the tertiary the late cretaceous to cenozoic topographic development of the scandes mountains followed structurally induced templates such as those described from other areas of active normal faulting a fault model for the cenozoic uplift of the norwegian mainland provides a framework for provenance erosion and transport of sediments eventually deposited in the offshore post rift basins in the latest cretaceous palaeogene and neogene the asymmetric topographic profile of fennoscandia is reflected in the aft data and suggests that lithospheric flexure places a first order control on the shape of the scandes mountains and the central fennoscandian craton

a field investigation of fracture compliance a field measurement of fracture compliance is described the aim was to determine how compliance scales with fracture size and specifically how laboratory measurements of fracture compliance compared with field estimates from sonic and seismic data a test site was constructed consisting of three 40 m vertical boreholes drilled in the floor of a carboniferous limestone quarry detailed knowledge of the rocks in the test area was obtained from core analysis wireline logging and local area fracture mapping seismic cross hole surveys were performed using a sparker source with a dominant frequency of 2000 hz and hydrophone receivers the rocks had a compressional wave velocity anisotropy of 10 which was attributed to the presence of predominantly horizontal partially open fractures estimates of normal fracture compliance within a range from 2 5 10 13 m pa to 3 5 10 12 m pa were obtained from both the cross hole data and the sonic log data this is an order of magnitude greater than values obtained from laboratory experiments which are reported elsewhere

rock fracture compliance derived from time delays of elastic waves the purpose of this study is to compare the reliability of various methods of estimating normal rock fracture compliance from elastic wave measurements we compare ultrasonic through transmission laboratory measurements for a smooth fracture in a westerly granite specimen with numerical simulations and analytical solutions the focus is on deriving compliance from time delays the influence of specimen and source transducer width was constrained using numerical wave simulations we find that measured ultrasonic phase delays are better suited to estimate the fracture compliance than group delays using the frequency domain instead of the time domain increases the accuracy of the fracture compliance estimates we further show that for cases where precise phase delay measurements are unavailable employing first break times in conjunction with numerical simulations can be considered as an alternative

long term observation of in situ seismic velocity and attenuation 1 we conducted 1 year continuous measurements of in situ compressional wave velocity and attenuation across a distance of 12 m in a vault at the coast of miura bay japan using a piezoelectric transducer as the ultrasonic wave source we detected for the first time periodic variations in both velocity and attenuation with amplitudes of 0 3 and of 4 respectively corresponding to the diurnal and semidiurnal lunar and solar tides these variations correlate well with the in situ areal strain change due to tidal ocean loading estimated from the strain records about 100 m away from the observational site relative minimum velocity and relative maximum attenuation occur at every time of relative maximum areal strain expansion suggesting that opening closure of pores or cracks of in situ rocks is responsible for these periodic variations the velocity variation shows a remarkable 14 day periodicity corresponding to the spring and neap tides arising from a nonlinear response of the velocity change to tidal strain change such that the velocity change depends on how slowly the tidal dilatation departs from its peak value

comparison of residual shear strengths from back analysis and ring shear tests on undisturbed and remolded specimens slope stabilization procedures for six landslides in the niigata prefecture in japan afforded an excellent opportunity to examine the residual drained shear strength of weathered mudstones installation of 3 m diameter drainage galleries allowed undisturbed block samples to be collected which contained the slickenside surface of the failure plane ring shear tests were conducted on undisturbed samples and remolded samples of the same material in addition to the laboratory testing back analysis was performed to calculate the residual shear strength parameters of the slopes good agreement was found between the residual friction angles determined from back analysis tests on undisturbed samples and tests on remolded specimens many of the landslide materials exhibited a small cohesion at low values of effective normal stress but the secant friction angle achieved a constant value at higher normal stresses

the compliance of macrofractures seismic anisotropy in reservoir rocks can result from the alignment of fractures of any size from grain scale to lengths of meters or tens of meters provided the seismic wavelength is long relative to the size and spatial distribution of the fractures it can also be caused by correlated pore space alignment of minerals or grains or any combination of the above it is of huge practical importance to determine the primary cause of observed seismic anisotropy since the presence or otherwise of a limited number of open macrofractures is likely to greatly influence the calculations of fluid flow within a reservoir for the purposes of this article macrofractures are defined as having lengths of approximately a meter to tens of meters but to be of subseismic scale meaning that they are not individually imaged within a seismic reflection section

characteristics of crushed rocks observed in drilled cores in landslide bodies located in accretionary complexes abstract the recent development of high quality boring which uses foam surfactants has made it possible to examine the detailed geological constitution and structure of landslide bodies however geological information related to landslides has not been obtained appropriately even from undisturbed high quality drilled cores moreover it has been difficult to distinguish between rocks crushed by landslide movement and the fault breccia in accretionary complexes we examined the detailed geology of high quality drilled cores of landslide bodies on the shimanto belt and the chichibu belt the fault breccia near the landslide bodies was found to exhibit planar fabrics while the crushed breccias in the landslide bodies showed a random fabric we discovered that classifying the degree of crushing and inspecting the planar fabrics of rocks are effective in the geological determination of landslide bodies

the tjellefonna fault system of western norway linking late caledonian extension post caledonian normal faulting and tertiary rock column uplift with the landslide generated tsunami event of 1756 abstract on february 22 1756 approximately 15 7 million cubic meters of bedrock were catastrophically released as a giant rockslide into the langfjorden subsequently three 40 meter high tsunami waves overwhelmed the village of tjelle and several other local communities inherited structures had isolated a compartment in the hanging wall damage zone of the fjord dwelling tjellefonna fault because the region is seismically active in oblique normal mode and in accordance with scant historical sources we speculate that an earthquake on a nearby fault may have caused the already weakened tjelle hillside to fail from interpretation of structural geomorphic and thermo chronological data we suggest that today s escarpment topography of more og trondelag is controlled to a first order by post rift reactivation of faults parallel to the mesozoic passive margin in turn a number of these faults reactivated late caledonian or early post caledonian fabrics normal sense reactivation of inherited structures along much of coastal norway suggests that a structural link exists between the processes that destroy today s mountains and those that created them the paleozoic more trondelag fault complex was reactivated as a normal fault during the mesozoic and probably throughout the cenozoic until the present day its ne sw trending strands crop out between the coast and the base of a c 1 7 km high nw facing topographic great escarpment well preserved kinematic indicators and multiple generations of fault products are exposed along the tjellefonna fault a well defined structural and topographic lineament parallel to both the langfjorden and the great escarpment the slope instability that was formerly present at tjelle and additional instabilities currently present throughout the region may be viewed as the direct product of past and ongoing development of tectonic topography in more og trondelag county in the langfjorden region in particular structural geometry suggests additional unreleased rock compartments may be isolated and under normal fault control although post glacial rebound and topographically derived horizontal spreading stresses might in part help drive present day oblique normal seismicity the normal fault controlled escarpments of norway were at least partly erected in pre glacial times cretaceous to early tertiary post rift subsidence was interrupted by normal faulting at the innermost portion of the passive margin imposing a strong tectonic empreinte on the developing landscape

triaxial testing of lopez fault gouge at 150 mpa mean effective stress triaxial compression experiments were performed on samples of natural granular fault gouge from the lopez fault in southern california this material consists primarily of quartz and has a self similar grain size distribution thought to result from natural cataclasis the experiments were performed at a constant mean effective stress of 150 mpa to expose the volumetric strains associated with shear failure the failure strength is parameterized by the coefficient of internal friction based on the mohr coulomb failure criterion

geological mapping of rapid mass movement deposits as an aid to land use planning abstract rapid mass movements are common features of hilly or mountainous terrains and depending on the type of movements or processes involved these give rise to characteristic deposits identification of these deposits in mapping programmes gives a clue as to their mode of origin rockslide rockfall snow avalanche debris flow fluidal sediment flow and this can be used to predict rapid mass movements in the future a case story from western norway is described and the value of mapping such deposits for land use planning and hazard estimation stressed

behavior of a landslide prior to inducing a viaduct failure caracas la guaira highway venezuela a reactivation of a large ancient landslide identified in 1987 began to progressively damage the southern side of an important prestressed concrete span structure of a highway connecting caracas capital of venezuela with its main port and airport this paper deals with the behavior of the landslide over a period of 19 years and the final failure of the structure in march 19 2006 results of geotechnical investigation evaluation of inclinometer readings and surface control point displacements as well as behavior of the structure subjected to the slide thrust are discussed several causes that may explain the reactivation and behavior of the landslide and some aspects about failure time prediction are also described

large sackung along major tectonic features in the central italian alps deep seated gravitational slope deformation sackung is common in alpine mountain belts it is controlled by lithological geomorphological and structural features we describe and discuss five examples of dsgsd along the insubric line periadriatic fault in the central italian alps the five examples are different in morphology size state of activity and distribution and are located along both primary and secondary valleys we demonstrate relations between structural and gravitational features and discuss the possibility that structural has both passive and active roles in sackung development analysis of ps sar data shows that the studied examples are not active today numerical modelling demonstrates the importance of lithological and structural constraints postglacial debuttressing groundwater fluctuations and weathering on sackung triggering and development

giant rockslides from the inside the growing body of research on large scale mass wasting events so far has only scarcely investigated the sedimentology of chaotic deposits from non volcanic terrestrial landslides such that any overarching and systematic terminological framework remains elusive yet recent work has emphasized the need for better understanding the internal structure and composition of rockslide deposits as a means to characterise the mechanics during the final stages of runout and emplacement we offer a comprehensive overview on the occurrence of rock fragmentation and frictional melt both at different geographic locations and different sections within large 10 6 m 3 rockslide masses we argue that exposures of pervasively fragmented and interlocked jigsaw cracked rock masses basal melange containing rip up clasts and phantom blocks micro breccia and thin bands of basal frictionite are indispensable clues for identifying deposits from giant rockslides that may remain morphologically inconspicuous otherwise these sedimentary assemblages are diagnostic tools for distinguishing large rockslide debris from macro and microscopically similar glacial deposits tectonic fault zone breccias and impact breccias and thus help avoid palaeoclimatic and tectonic misinterpretations let alone misestimates of the hazard from giant rockslides moreover experimental results from mossbauer spectroscopy of frictionite samples support visual interpretations of thin sections and demonstrate that short lived 1500 degrees c in the absence of water occurred at the base of several giant moving rockslides this finding supports previous theories of dry excess runout accompanied by comminution of rock masses down to gm scale and indicates that catastrophic motion of large fragmenting rock masses does not require water as a potential lubricant

forward modeling of fracture induced sonic anisotropy using a combination of borehole image and sonic logs we develop a methodology to model and interpret borehole dipole sonic anisotropy related to the effect of geologic fractures using a forward modeling approach we use a classical excess compliance fracture model that relies on the orientation of the individual fractures the elastic properties of the host rock and the normal and tangential fracture compliance parameters orientations of individual fractures are extracted from borehole image log analysis the model is validated using borehole resistivity image and sonic logs in a gas sand reservoir over a 160 ft 50 m vertical interval of a well significant amounts of sonic anisotropy are observed at three zones with a fast shear azimuth fsa exhibiting 60 of variation and slowness difference between 2 and 16 numerous quasivertical fractures with varying dip azimuths are identified on the image log at the locations of strong sonic anisotropy the maximum horizontal stress direction given by breakouts and drilling induced fractures is shown not

self similar cataclasis in the saltville thrust zone knoxville tennessee fault rocks from the saltville thrust zone knoxville tennessee display a fractal geometry of clast size over 3 orders of magnitude the cataclastic fractal geometry occurs at each magnification in different clast size classes and at combined magnifications the mean of the fractal dimension d measured at each of the optical photomicrographs is generally smaller than that of the scanning electron microscopy images because of the smaller clast density in the optical sections the fractal dimensions measured on randomly selected areas of the sections cut parallel to the thrust and normal to the thrust along the dip and strike show a normal distribution with its mean median and mode that correlate closely with the dimension of ideal fractal cataclasis di based on the sierpinski carpet model the cataclasis was a statistical random isotropic and homogeneous fractal process that deformed the carbonates similarly parallel and normal to the thrust plane and in different parts of the thrust zone

the intrinsic effect of shape on the retrogradation motif and timing of drowning of carbonate patch reef systems lower frasnian bugle gap canning basin western australia the evolution and architecture of a set of retreating lower frasnian patch reef outcrops in the canning basin of western australia were evaluated and their depositional and stratigraphic contacts spatially recorded using digital surveying tools the geological data together with high resolution digital elevation models were assembled in three dimensional visualization and modelling software and subsequently used for building two dimensional surface models and three dimensional volumetric models numerical data on geometry and shape were extracted from these models and used to quantitatively assess the retrogradation motif of patch reef development the development of the patch reefs comprises three stages during stages 1 and 2 the patch reefs exhibited an overall retrogradational escarpment type configuration displayed by on average 60 steep reef margin walls that lacked the support of coeval slope deposits the subdivision between stages 1 and 2 is based on minor backstepping reducing less than 10 of the platform top area the onset of stage 3 is recognized by stromatolite development fringing reef margin walls during stage 3 an aggrading accretionary reef margin developed comprising allochthonous and autochthonous slope deposits both types of slope deposit onlap the previous stages and are distributed unevenly with allochthonous slope deposits being noticeably absent around the smaller and more elongate patch reefs the variation in distribution of slope sediment type can be explained by the amount linked to platform size of platform top shedding small patch reefs were unable to fill the available accommodation adjacent to escarpments with allochthonous slope sediments and were thus encroached by autochthonous slope sediments the variation which cannot be explained by the size difference in the platform top factory has been related to the difference in perimeter length for patch reefs with similar platform top production areas a more elongate patch reef inherits a longer perimeter and a proportionally smaller volume of allochthonous slope sediment per margin length will be transported to the flanks thus the more elongate patch reef intrinsically contained more sites within which autochthonous slope sediments developed digital outcrop modelling and numerical evaluation of the evolution of the patch reefs revealed the major differences in retrogradation motif the quantified variations in progressive decline of platform top area with height were confirmed by hypothetical decline curves for ellipse shaped carbonate systems for which aspect ratio ratio between length and width varied this mathematical model demonstrates that the progressive decline of the production area is highly sensitive to shape and can be used to numerically assess and predict the relative timing of drowning i e when the platform top production area becomes nil of retrogradational isolated carbonate platforms that are controlled by high accommodation wider implications can be surmised for highstand systems tracts and prograding carbonate systems for example for equally sized platforms with hypothetically similar carbonate factories and identical external forces the potential to prograde by platform top shedding is higher with a smaller aspect ratio because the shorter perimeter implies less accommodation space needing to be filled up to commence slope progradation clearly there are intrinsic effects of shape on the development of carbonate platform systems

rock mass movements across bedding in kananaskis country alberta rock mass movements in sedimentary rocks across bedding in kananaskis country alberta are controlled by discontinuity orientations and topography when bedding planes dip at less than 50 small

spatial orientation and distribution of reservoir fractures from scattered seismic energy wepresentthedetailsofanewmethodfordeterminingthereflection and scattering characteristics of seismic energy from subsurface fractured formations the method is based upon observations we have made from 3d finite difference modeling of the reflected and scattered seismic energy over discrete systems of vertical fractures regularly spaced discrete vertical fracture corridors impart a coda signature which is a ringing tail of scatteredenergy toanyseismicwaveswhicharetransmittedthrough or reflected off of them this signature varies in amplitude and coherence as a function of several parameters including 1 the difference in angle between the orientation of the fractures and the acquisition direction 2 the fracture spacing 3 the wavelength of the illuminating seismic energy and 4 the compliance or stiffness of the fractures this coda energy is most coherent when the acquisition direction is parallel to the strike of thefractures ithasthelargestamplitudewhentheseismicwavelengths are tuned to the fracture spacing and when the fractures have low stiffness our method uses surface seismic reflection tracestoderiveatransferfunctionthatquantifiesthechangeinan apparent source wavelet before and after propagating through a fracturedinterval thetransferfunctionforanintervalwithnoor low amounts of scattering will be more spikelike and temporally compact the transfer function for an interval with high scattering will ring and be less temporally compact when a 3d survey is acquired with a full range of azimuths the variation in the derived transfer functions allows us to identify subsurface areas with high fracturing and to determine the strike of those fractures wecalibratedthemethodwithmodeldataandthenapplied ittotheemiliofieldwithafracturedreservoir themethodyielded results which agree with known field measurements and previously published fracture orientations derived from ps anisotropy

fault related rocks suggestions for terminology many traditional terms for fault related rocks have undergone recent dynamic metamorphism under high pressure discussions by various groups of specialists a generally acceptable simplified framework encompassing these and associated structural terms is now needed for many geologic engineering and legal purposes such a framework is proposed here focusing on a rate of strain versus rate of recovery diagram and relating this framework to the products of brittle and ductile deformation along faults

the relationship between particle characteristics and frictional strength in basal fault breccias implications for fault rock evolution and rockslide susceptibility abstract microstructural analysis of fault rock breccias along the basal shear zone bsz of potential rock slope failures in norway demonstrates that particle size distribution curves show a spectrum from particle to matrix supported we demonstrate that variation in residual shear strength from 450 to 700 kpa is directly related to particle size and shape characteristics we also show that these characteristics are dependent on the fault rock evolution and breakdown mechanism and demonstrate this with simulated examples particle supported fault rocks have higher residual strength than matrix supported samples as the amount of fine material increases the residual shear strength of the fault material decreases particle aspect ratio is variable suggesting different comminution mechanisms and fault zone evolution as particle size decreases below 10 20 m particle aspect ratio approaches 1 1 suggesting that as the fault rock evolves the particles become rounder as aspect ratio increases fault strength decreases we contend that the susceptibility of potential rock slope failures is fundamentally linked to and depends partly on the microscopic properties of the underlying fault rocks and is linked to their comminution history

assessing controls on isolated carbonate platform development in central luconia nw borneo from a regional 3d seismic facies and geomorphology investigation

deformation processes and weakening mechanisms within the frictional viscous transition zone of major crustal scale faults insights from the great glen fault zone scotland abstract the great glen fault zone ggfz scotland is a typical example of a crustal scale reactivated strike slip fault within the continental crust analysis of intensely strained fault rocks from the core of the ggfz near fort william provides a unique insight into the nature of deformation associated with the main phase of sinistral movements along the fault zone in this region an exhumed sequence of complex mid crustal deformation textures that developed in the region of the frictional viscous transition ca 8 15 km depth is preserved fault rock fabrics vary from mylonitic in quartzites to cataclastic in micaceous shear zones and feldspathic psammites protolith mineralogy exerted a strong control on the initial textural development and distribution of the fault rocks at lower strains crystal plastic deformation occurred in quartz dominated lithologies to produce mylonites simultaneously with widespread fracturing and cataclasis in feldspar and mica dominated rocks at higher strains shearing appears to increasingly localise into interconnected networks of cataclastic shear zones many of which are strongly foliated textures indicative of fluid assisted diffusive mass transfer mechanisms are widespread in such regions and suggest that a hydrous fluid assisted grainsize controlled switch in deformation behaviour followed the brittle comminution of grains the fault zone textural evolution implies that a strain induced fluid assisted shallowing and narrowing of the frictional viscous transition occurred with increasing strain it is proposed that this led to an overall weakening of the fault zone and that equivalent processes may occur along many other long lived crustal scale dislocations

transmission of seismic waves across single natural fractures fractures and other nonwelded contacts are important mechanical and hydrological features of rock masses their effects on seismic wave propagation can be modeled as a boundary condition in the seismic wave equation seismic stress is continuous across such a boundary but seismic particle displacement and seismic particle velocity are not the complete solutions for seismic wave reflection conversion and transmission across a displacement and velocity discontinuity between two half spaces with different densities and elastic properties are derived for all angles of the incident wave the ratio between the seismic stress across this boundary and the seismic particle displacement and velocity are described by a specific stiffness and a specific viscosity respectively a displacement discontinuity results in frequency dependent reflection and transmission coefficients and a frequency dependent group time delay the velocity discontinuity results in frequency independent coefficients and zero delay results of laboratory experiments on compressional and shear wave transmission across three different natural fractures in a quartz monzonite are described measurements were made at different effective stresses under dry and saturated conditions at room temperature it is shown that the effect of these fractures on the spectral amplitudes for compressional and shear pulses transmitted across these fractures are described well by a displacement discontinuity for compressional pulses under dry and saturated conditions and by a combined displacement and velocity discontinuity for shear wave pulses under dry and saturated conditions values of specific stiffness and specific viscosity vary between fractures and increase with increasing effective stress as does the static specific stiffness of these fractures changes in the spectral amplitudes of transmitted pulses are also analyzed in terms of attenuation using the seismic quality factor q which is found to be a function of frequency