influence of a pre existing basement weakness on normal fault growth during oblique extension insights from discrete element modeling abstract we use discrete element modeling to investigate three dimensional fault geometry and the three dimensional evolution of a fault network that develops above a 60 dipping planar pre existing weakness striking 60 relative to the extension direction the evolution of the fault network comprises three stages i reactivation of pre existing structure and nucleation of new faults 0 10 extension ii radial propagation and interaction between reactivated structure and new faults 15 20 extension and iii linkage between reactivated structure and adjacent faults 20 25 extension during the first stage the pre existing structure mostly reactivates forming a long and under displaced fault new faults are mainly extension perpendicular and dip at 60 during the second stage saw tooth fringes grow upwards from the upper tip of the reactivated structure which becomes the major fault and influence the density and orientation of surrounding faults during the third stage the reactivated structure links laterally and vertically with adjacent faults creating non planar fault geometries following linkage the reactivated structure enhances the displacement of linked faults along branch lines our study demonstrates that pre existing weak faults can be reactivated propagating upwards in an irregular saw tooth pattern and affecting fault density orientation dip and displacement and providing the nucleation site of new faults

geometry mechanisms and significance of extensional folds from examples in the rocky mountain basin and range province u s a abstract geologic mapping and structural analysis in paleogene half graben of idaho and montana have revealed over 70 extensional folds that form orthogonal sets with mostly ne and se trending axes on a regional scale they parallel or lie perpendicular to the strikes of the largest normal faults transverse folds at a high angle to the fault and folds oblique to the fault comprise more than half of the folds and reflect the highly three dimensional nature of the bulk strain detailed geometric analysis of 15 folds in the salmon horse prairie and medicine lodge basins shows that they typically have an upright to steeply inclined bisecting surface an interlimb angle of 141 and a plunge of 19 based on our synthesis of the eight common mechanisms of extensional folding and their distinguishing characteristics we were able to determine how some of the investigated folds formed fault bend folding above both fault parallel and fault perpendicular bends in the underlying normal fault produced most of the folds in the study area but displacement gradients along normal faults fault drag isostatic adjustments and transtension were also factors in the deformation most of the compound folds which result from more than one mechanism of folding are oblique to all adjacent normal faults recognition of such extensional folds is critical because they might be misinterpreted as contractional structures they influence sediment thickness patterns and dispersal in rift basins and may control the migration and trapping of petroleum and groundwater resources

forced folding and fracturing induced by differential compaction during post depositional inflation of sandbodies insights from numerical modelling abstract three series of numerical models based on the discrete element method were constructed to simulate forced folding and fracturing triggered by postdepositional inflation of fluidised sandbody the models consist of numerous particles that have relatively low to high interparticle bonds to represent overburden sediments with a relatively low to high cohesion and cohesionless frictionless particles to represent fluidised sands the modelling results show that normal faults were produced due to the upward inflation of sand domes and the resulting flexed overburden when the cohesion of the host sediments is low opening voids were created as a result of strata collapse when the intrusion related normal faults terminated within the host sediments as blind faults conical fractures that are aligned along sandbody margins were produced which consist of closed lower segments with a reverse displacement and opening middle upper segments with a minor to zero shear component forced folds were generated in most models with a moderate to high cohesion resulting in differential compaction in the overlying sediments that can account for the formation of fold related fractures which are either shear hybrid or pure tensile depending on their structural positions the amplitude of forced folds is closely associated with both cohesion and thickness of sediments in the overburden whilst fold wavelength is mainly controlled by sediment cohesion based on the modelling results three types of preferential sites for the storage of injected sands were suggested which are believed to be instructive for subsurface sandbody detection and prediction this study demonstrates that differential compaction induced by sand inflation can play an important role in overburden folding and fracturing

localisation of normal faults in multilayer sequences abstract existing conceptual growth models for faults in layered sequences suggest that faults first localise in strong and brittle layers and are later linked in weak and ductile layers we use the discrete element method for modelling the growth of a normal fault in a brittle ductile multilayer sequence the modelling reveals that faults in brittle ductile sequences at low confining pressure and high strength contrast localise first as mode i fractures in the brittle layers low amplitude monoclinal folding prior to failure is accommodated by ductile flow in the weak layers the initially vertically segmented fault arrays are later linked via shallow dipping faults in the weak layers faults localise therefore as geometrically and kinematically coherent arrays of fault segments in which abandoned fault tips or splays are a product of the strain localisation process and do not necessarily indicate linkage of initially isolated faults the modelling suggests that fault tip lines in layered sequences are more advanced in the strong layers compared with weak layers where the difference in propagation distance is most likely related to strength and or ductility contrast layer dependent variations in fault localisation rates generate fringed rather than smooth fault tip lines in multilayers

deformation and fault activity in space and time in high resolution numerical models of doubly vergent thrust wedges a discrete element model is used to investigate the manner in which deformation and fault activity change in space and time during the development of a doubly vergent thrust wedge in the upper crust deformation is a result of shortening at a subduction slot in the base of the model a configuration which produces a dynamic backstop within the cohesionless frictional cover material a series of experiments with differing basal decollement friction are performed the distinct manners in which thrust wedges grow and the variability of fault development and activity in space and time are then examined both predicted large scale wedge geometries and individual fault fold structures are similar to those observed in sandbox models and show the complex manner in which shortening is accommodated and localized during the development of the thrust wedge when compared to a sandbox model with similar boundary conditions model results are strikingly similar in all cases deformation initiates above the subduction slot with the formation of an axial zone the wedge is then developed by displacement on a retro wedge thrust and propagation of deformation into the pro wedge region models with low coefficients of basal friction typically develop wide shallow wedges with distributed spaced deformation and rather symmetric box like structures whereas those with high coefficients of basal friction develop narrower steeper wedges consisting of a series of stacked pro wedge thrust sheets and a high displacement retro wedge thrust in general fault initiation and linkage is extremely complex in our models with several smaller faults operating until linkage occurs to form a major through going structure of particular interest is the observation that many of the faults do not develop at the basal decollement and propagate upwards through the cover but rather initiate at high levels in the cover and propagate link downwards with other deeper structures results also indicate the utility of the discrete element approach in modelling large displacement complex deformation of geological materials

forced folding and basement detached normal faulting in the haltenbanken area offshore norway triassic evaporites affected the structural development of the haltenbanken area of offshore norway during the late jurassic and early cretaceous by mechanically isolating triassic and younger strata from older strata and basement many folds in the haltenbanken area are forced folds above basement involved normal faults forced folds formed at least in part because triassic evaporites behaved ductilely decoupling overlying strata from underlying faulted strata and basement seismic data show that these forced folds are asymmetric flexures that affect lower cretaceous jurassic and triassic strata strata beneath the traiassic evaporites are faulted some forced folds die out along strike into and are cut by basement involved normal faults folding predominated above salt swells where decoupling was enhanced whereas faulting occurred on the flanks of salt swells where salt thicknesses were reduced and decoupling was less effective many normal faults in the haltenbanken area are basement detached and flatten within the triassic evaporites seismic data show that rollover anticlines and antithetic normal faults affect lower cretaceous jurassic and triassic strata within the hanging walls of these basement detached normal faults strata beneath the evaporites are not affected by this deformation some basement detached normal faults may be secondary structures associated with forced folding others especially thosemore with large displacements may have formed in response to gravity sliding less

kinematic models of basement cover interaction insights from the malargue fold and thrust belt mendoza argentina abstract we investigate through natural examples from the malargue fold and thrust belt the manner in which the basement structures interact with the cover in a thick skinned fold and thrust belt our work suggests that there is a broad spectrum of basement cover interaction mechanisms with two end members coupled and uncoupled interactions the kind of bonding between basement and cover is related to the propagation to slip ratio p s because high values of this ratio indicate rapid forward propagation of shortening into the cover while low values favour welding between basement and cover structures we analyse the factors controlling the kinematics of basement cover deformation and find that not only the strength of the cover its thickness and its mechanical anisotropy control the p s and basement cover bonding but also the strain rate the thickness of synorogenic strata and the presence of pre existing faults

cybertectonic earth and gaia s weak hand sedimentary geology sediment cycling and the earth system tectonics climate and sea level are dominant controls on the nature and distribution of sedimentary environments by inverse logic recognition of influences on sedimentation from the stratigraphic record as a result of perturbations in these variables leads to clarification of past environmental and structural change the succession of sedimentary environments in time and place is determined by a wider combination of variables namely sediment flux biological evolution atmosphere and water body productivity and chemistry the feedbacks and interrelationships between all variables cause the complexity seen in sedimentation processes over geological time the processes of global tectonics that cause widespread mountain belt and continental plateau uplift have produced numerous severe events during earth history these often random workings out of the plate tectonic cycle define the state of cybertectonic earth from cyber after the greek kubernan to steer or govern this has worked within a usually zonally arranged series of climatic belts and within the framework provided by biological evolution at certain times in the geological past a combination of factors arose as a response to continental uplift and have acted to cause certain earth surface conditions and variables notably mean global surface temperature atmospheric p co 2 p o 2 to have varied by very large amounts 2 10 compared with present values these large fluctuations such as those responsible for the neoproterozoic late palaeozoic and late tertiary glaciations lead one to doubt the reality of homeostatic control of surface conditions as proposed in lovelock9s gaia hypothesis the gaian kuberne0te0s steersman had a weak hand on the helm frequently unable to prevent vast areas of the globe experiencing rapid fluctuations in environmental conditions and inimical conditions to life for very long periods during neoproterozoic and phanerozoic times at the same time biogenic and abiogenic processes have proved capable of returning earth to states of mean stability although biogeochemical cycling models seem alarmingly ad hoc and largely untestable as scientific hypotheses in any true geological sense

structure of the mountain front flexure along the anaran anticline in the pusht e kuh arc nw zagros iran insights from sand box models this is a contribution of the group of dynamics of the lithosphere gdl financed by a collaborative project between the institute of earth sciences jaume almera csic of barcelona spain and statoilhydro tehran and statoilhydro research centre with the partial support of project team consolider ingenio 2010 no csd 2006 00041

subsurface structural interpretation by applying trishear algorithm an example from the lenghu5 fold and thrust belt qaidam basin northern tibetan plateau abstract the application of trishear algorithm in which deformation occurs in a triangle zone in front of a propagating fault tip is often used to understand fault related folding in comparison to kink band methods a key characteristic of trishear algorithm is that non uniform deformation within the triangle zone allows the layer thickness and horizon length to change during deformation which is commonly observed in natural structures an example from the lenghu5 fold and thrust belt qaidam basin northern tibetan plateau is interpreted to help understand how to employ trishear forward modelling to improve the accuracy of seismic interpretation high resolution fieldwork data including high angle dips dragging structures thinning hanging wall and thickening footwall are used to determined best fit trishear model to explain the deformation happened to the lenghu5 fold and thrust belt we also consider the factors that increase the complexity of trishear models including a fault dip changes and b pre existing faults we integrate fault dip change and pre existing faults to predict subsurface structures that are apparently under seismic resolution the analogue analysis by trishear models indicates that the lenghu5 fold and thrust belt is controlled by an upward steepening reverse fault above a pre existing opposite thrusting fault in deeper subsurface the validity of the trishear model is confirmed by the high accordance between the model and the high resolution fieldwork the validated trishear forward model provides geometric constraints to the faults and horizons in the seismic section e g fault cutoffs and fault tip position faults intersecting relationship and horizon fault cross cutting relationship the subsurface prediction using trishear algorithm can significantly increase the accuracy of seismic interpretation particularly in seismic sections with low signal noise ratio

mechanical analysis of the geometry of forced folds a mechanical model of forced folding comprised of an anisotropic cover overlying displaced rigid basement blocks is used to investigate the influence of various parameters on theoretical fold form shape and dip of basement fault strength of basement cover contact and degree of anisotropy of the cover we show that the degree of anisotropy in the cover largely influences the geometry of the forelimb of the forced fold folds produced in isotropic cover display forelimbs that taper from large dip angles near the basement cover contact to low dip angles at the ground surface in contrast dips in the forelimbs of folds in anisotropic cover are nearly uniform with depth we show that the basement cover contact and the shape of the basement fault largely influence the geometry of the backlimb backlimb rotation occurs in cover welded to the basement and in cover underlying curved basement faults in addition the kinematic features of the theoretical folds are compared with the fold geometry generated by parallel kink and trishear models folds in isotropic cover overlying straight basement faults closely resemble the fold forms produced by the trishear kinematic model while fold forms in anisotropic cover more closely resemble folds produced by parallel kink geometric constructions

paleoseismology of the mount narryer fault zone western australia a multistrand intraplate fault system our paleoseismological study of faults and fault related folds comprising the mount narryer fault zone reveals a mid to late quaternary history of repeated morphogenic earthquakes that have influenced the planform and course of the murchison roderick and sanford rivers western australia the dominant style of deformation involves folding of near surface sediments overlying discrete basement faults carbon 14 optically stimulated luminescence and in situ produced 10 be constrain the timing of the events and late quaternary slip rates associated with fault propagation folds in tectonically uplifted and deformed alluvial channel deposits a flight of five inset fluvial terraces is preserved where the murchison river flows across the roderick river fault these terraces which we infer to be coseismic are consistent with at least four late quaternary seismic events on the order of moment magnitude m w 7 1 within the last 240 k y secondary shears expressed on the folds indicate a component of dextral strike slip displacement quaternary slip rates on the underlying faults range from 0 01 to 0 07 mm yr 1 with a total slip rate for the zone between 0 04 and 0 11 mm yr 1 these rates are intermediate to those in the adjacent mesozoic basin 0 1 mm yr 1 and precambrian craton 1 and so provide insight into how tectonic strain is partitioned and transferred across a craton margin

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

the roles of complex mechanical stratigraphy and syn kinematic sedimentation in fold development insights from discrete element modelling and application to the pico del aguila anticline external sierras southern pyrenees

progressive evolution of a fault related fold pair from growth strata geometries sant llorenc de morunys se pyrenees abstract new structural stratigraphical mapping constrains the three dimensional kinematics and mechanisms of eocene oligocene growth folding at sant llorenc de morunys ne ebro basin spain a 1 km wide sub vertical panel of syntectonic alluvial gravels passes southwards via a highly asymmetrical growth fold pair to shallowlydipping strata the axial surface of the anticline comprises either continuous or en echelon segments while that of the syncline is concave and usually continuous while converging upwards the axial surfaces do not define growth triangles principal and subsidiary growth unconformities and thickness changes occur across both axial surfaces and the common limb dips within the common limb decrease up stratigraphy and up dip mesostructures indicate that internal deformation was ongoing during folding at all stratigraphical levels and concentration of cleavage in the syncline indicates that this hinge was essentially fixed sequential restoration of three profiles shows that folds amplified principally by limb rotation but incorporated minor passive hinge migration particle movement vectors generated by section restoration are arcuate about a hinterland pinpoint a new trishear model of fault propagation folding involving non rigid limb rotation reproduces the rounded hinge forms thickening geometries and limb dip variations observed simple kink band migration models fixed axis and constant thickness theories do not replicate these features

mechanical stratigraphy and the transition from trishear to kink band fault propagation fold forms above blind basement thrust faults a discrete element study abstract we employ a discrete element technique to investigate the influence of mechanical stratigraphy on the transition from trishear to kink band fault propagation fold forms above a blind basement thrust fault we find that a classic trishear fold consisting of a broad upwards widening monocline with limb dips increasing towards the fault tip occurs where the cover stratigraphy is weak and has no strong mechanical layering in contrast we find that marked bedding parallel mechanical layering in the cover promotes much narrower kink like fold geometries with more constant limb widths and dips we discuss the modelling results in terms of their implications for structural interpretation and the application of kinematic models of fault related folding in contractional settings

a new strategy for discrete element numerical models 2 sandbox applications 1 here we present a series of numerical experiments using a new formulation of the discrete element method dem that improves performance in modeling faults and shear zones in the new method named the stress based discrete element method sdem which is introduced in the companion paper by egholm stress tensors are stored at each circular particle further sdem includes rotational resistivity of particles and elastoplastic constitutive rules for governing particle deformation when combining these new features the sdem is capable of reproducing the friction properties of rocks and soils without the need for the ad hoc calibration routines normally associated with dem in contrast to the conventional dem the friction properties of a sdem particle system are in agreement with the mohr coulomb constitutive model with friction angles specified on a particle level benchmark sandbox models show that unlike most commonly used numerical methods sdem faults and shear zones develop at angles in agreement with general observations from structural geology and analogue modeling studies citation egholm d l m sandiford o r clausen and s b nielsen 2007 a new strategy for discrete element numerical models 2 sandbox applications j geophys res 112 b05204 doi 10 1029 2006jb004558

barotropic models of the extratropical response to el nino abstract a series of linear and nonlinear barotropic models are used to interpret the extratropical response to el niflo equatorial surface temperatures as simulated by an atmospheric general circulation model gcm the divergence time mean vorticity tendency due to transients and the zonal mean tlow are specified from the gcm and the deviation of the streamfunction from its zonal mean at an upper tropospheric level is predicted nonlinearsteady state models suggest that the extratropical wave train is primarily forced from the central rather than the western pacific and that subtropical divergence anomalies are of more importance than tropical anomalies these nonlinear solutions can be reproduced with little loss in accuracy by linearizing about the zonally asymmetric climatological flow if one linearizes about the zonally symmetric flow the part of the solution forced from thewestern pacific deteriorates significantly the solution in the tropics and subtropics also deteriorates if advection of v

geometry and kinematics of fault propagation folds with variable interlimb angle abstract several conceptual approaches have been proposed to account for the development of fault propagation folds whose geometry and kinematics depend on the amount of displacement along a basal decollement level the ramp angle and the slip to propagation ratio among these the variable interlimb angle model of mitra 1990 is able to explain open and close natural folds but its application is limited because the fold geometry and bed thickness evolution rely on imposed parameters that cannot be measured directly here we use the ramp and the interlimb angles as input data to develop a forward fold model that accounts for thickness variations in the forelimb the relationship between the fold amplitude and fold wavelength is subsequently applied to construct balanced geological cross sections from surface parameters only and to propose a kinematic restoration of the folding through time the model can catter for a wide variety of folds reconstruct the deep architecture of anticlines and deduce the kinematic evolution of the folding with time we consider three natural examples to validate the variable interlimb angle model along strike thickness variation in the forelimb of the turner valley anticline in the alberta foothills of canada precisely corresponds to the theoretical values proposed by our model reconstruction at depth of the alima anticline in the southern tunisian atlas implies that the decollement level is localised in the triassic liassic series as highlighted by seismic imaging the kinematic reconstruction of the ucero anticline in the spanish castilian mountains is also in agreement with the fold geometry derived from two cross sections the variable interlimb angle model predicts that the fault propagation fold can be symmetric normal asymmetric with a greater dip value in the forelimb than in the backlimb or reverse asymmetric with greater dip in the backlimb depending on the shortening amount

fault propagation folding in extensional settings examples of structural style and synrift sedimentary response from the suez rift sinai egypt field data from the oligocene miocene gulf of suez rift demonstrate that coeval growth faults folds and transfer zones exerted a major control on synrift stratigraphic sequence development growth folds in the suez rift are related to steeply dipping normal faults that propagated upward resulting in broad upward widening monoclines in overlying strata folding during fault propagation was accommodated by layer parallel slip and detachment along mudstone horizons as well as by normal and rare reverse secondary faults that propagated away from the master fault the eventual propagation of the master fault through to the surface left the steep limb of the monocline and most of the secondary faults in the hanging wall this evolving structural style exerted a marked control on the geometry and stacking patterns of coeval synrift sediments synrift sediments display onlap and intraformational unconformities toward the growth monoclines and buried faults whereas they diverge into broadly synclinal expanded sections away from the growth monocline continued movement across buried faults resulted in the progressive rotation of the monoclinal limb and associated synrift sediments each successively younger sequence dipping basinward at a shallower angle than the previous one the resulting synrift geometries differ significantly from stratal geometries normally anticipated adjacent to normal faults along strike variations in facies stacking patterns are also commonly associated with decreasing displacement across faults and associated folds toward low relief transfer zones data from other rift basins indicate that fault propagation folds are not unique to the gulf of suez

numerical modeling of trishear fault propagation folding in contrast to kink band migration modeling methods trishear numerical models produce fault propagation folds with smooth profiles and rounded hinges modeled fold hinges tighten and converge downward within a triangular zone of distributed deformation which is focused on the fault tip such features have been reported from field studies and are also seen in analogue models of compressional deformation however apart from its initial application to laramide folds little quantitative work has been undertaken on trishear fault propagation folding in other settings in addition no study has been undertaken into the growth strata which might be associated with such structures this paper uses an equivalent velocity description of the geometric model of trishear together with models of erosion and sedimentation to investigate trishear fault propagation folding of both pregrowth and growth strata the trishear model is generalized to include a variety of fault propagation to slip ratios and fault propagation from a flat decollement the models show continuous rotation of the forelimb with the characteristic development of cumulative wedges within growth strata when total slip on a structure is high the model predicts overturned pregrowth and growth strata during the initial stages of deformation beds in the forelimb thicken but later thin when they become steep or overturned the effect of variations in fault propagation to slip ratios on two dimensional finite strain in the models is assessed by the use of initially circular strain markers high fault propagation to slip p s ratios lead to narrow zones of high finite strain while lower p s ratios lead to more ductile deformation and broader zones of high strain in all cases hanging wall anticlines and footwall synclines originate as early ductile folds which are later cut by the propagating fault modeled structures are compared with natural examples

foreland basement involved structures basement involved structures commonly occur as long irregular chains of uplifts in foreland basins these structures commonly contain significant hydrocarbon accumulations with most major fields located on the broad crests of these structures the search for complex traps in deeper targets and in subthrust structures requires an improved understanding of the geometry and evolution of these structures characteristic features of basement structures include deformation zones within the sedimentary cover that dissipate significant fault slip and gently dipping frontlimbs and backlimbs fault slip in the basement is usually accommodated in the cover by a triangular widening upward deformation zone on the forelimb with the nature of deformation controlled primarily by the mechanical stratigraphy if the cover contains interlayered competent and incompetent units the incompetent units are characterized by significant penetrative deformation whereas the competent units are faulted after a relatively small amount of penetrative deformation depending on the competency contrast between the basement and cover the nature of basement and the physical conditions of deformation the deformation zone may also propagate downward into the basement gently dipping backlimb and frontlimb panels are related to movement of the hanging wall over synclinal and anticlinal bends in the major fault respectively many basement faults are characterized by a number of synclinal fault bends within the basement which result in long and gently dipping backlimbs forelimb panels are related to anticlinal bends that typically occur at the basement cover interface as well as at one or more locations in the sedimentary cover case studies of well constrained examples of structures from the bighorn and uinta basins and the central basin platform demonstrate the development of these characteristic features and their strong dependence on the mechanical stratigraphy these models and case studies will be useful in interpreting foreland basement structures in areas with poor or limited data

numerical investigation of dip slip fault propagation effects on offshore seabed sediments abstract an enhanced understanding of the phenomenon of dip slip fault propagation through young unconsolidated offshore sediments is essential for the evaluation of the response of shallow offshore structures and subsea oil gas pipelines substantial and permanent seafloor deformation constitutes a severe geohazard for these marine structures and associated offshore elements components this paper addresses the response of seabed sand deposits subjected to underlying dip slip fault movement the resulting propagation of the faulting offset in seabed sediments is explored using 2d finite element modeling in abaqus while accounting for nonlinear soil behavior with strain softening a 2d plain strain fem seabed model is adopted to investigate the effect of different seabed soil properties and layer thicknesses on the extent and magnitude of seabed surface deformation induced by normal and reverse faults with different dip angles the results indicate that 1 the adoption of sand properties that depend on depth is necessary to realistically model the fault propagation mechanism particularly for fault propagation through thick and dense sand deposits 2 the presentation of fault propagation results in a normalized manner with respect to sand cover thickness does not eliminate the dependency on the actual layer thickness and 3 the deformation of the beds in the cover as a result of basement faulting can be modeled realistically using trishear kinematic approaches

nonlinear planetary wave reflection in an atmospheric gcm the nonlinear behavior of planetary waves excited by midlatitude topography is considered in an atmospheric gcm the gcm is run at standard resolution t42 and includes all of the complexity normally associated with a gcm only two simplifications are made to the model first it is run in perpetual january mode so that the solar radiation takes the diurnally varying value associated with 15 january second the lower boundary is simplified so that it is entirely ocean with zonally symmetric ssts planetary waves are excited by gaussian shaped topography centered at 45 n 90 w as in earlier studies the excited wave train propagates toward low latitudes where for sufficiently large forcing amplitude i e height of topography the wave will break several different experiments are run with different mountain heights each experiment is run for a total of 4015 days the response of the model depends on the height of the mountain for the small amplitude mountain 500 m the wave is dissipated at low latitudes near its critical latitude for large amplitude mountains 2000 3000 and 4000 m wave breaking and nonlinear reflection out of the wave breaking region is observed the spatial character of the reflected wave train is similar to that detected in earlier studies with more idealized models

discrete element modelling of contractional fault propagation folding above rigid basement fault blocks many studies have shown that discrete blind faults at depth are commonly linked to more distributed deformation in particular folding at higher levels one category of fault related folds forced folds is common where there is a distinct mechanical contrast between faulted basement and sedimentary cover outcrop numerical and analogue modelling studies indicate that such folds form as upward widening zones of distributed deformation monoclines above discrete faults at depth with increasing displacement the folds are often cut by faults as they propagate upwards into the cover while the trishear kinematic model of fault propagation folding appears to approximately represent the geometric development of such structures comparatively little is known of the mechanical controls on their development here we present a 2d discrete element model of sedimentary cover deformation above a contractional fault in rigid basement the elements consist of a series of soft spheres that obey newton s equations of motion and initially interact with elastic forces under the influence of gravity particles are bonded until the separation between them exceeds a defined breaking strain at which time the bond breaks simulated by the transition from repulsive attractive forces to solely repulsive forces the model is used to investigate the influence of basement fault dip and sedimentary cover strength on the geometry of the folds developed and the rate of fault propagation in all cases an upward widening monocline occurs above the basement fault we find that shallow basement fault dips produce homogenous thickening of the monocline limb while steeper dips produce contemporaneous thinning and thickening within the monocline thinning and thickening within the monocline are accommodated by a combination of small scale faulting and folding with decreasing cover strength the zone of deformation becomes wider localization does not occur on a single fault and fold geometries resemble trishear fold profiles with low propagation to slip ratios p s 1 in contrast a stronger cover produces a narrower zone of deformation localization on a single fault and more rapid fault propagation similar to trishear fold profiles where p s 2 3 the fault propagates into the cover at approximately the same angle as the basement fault the model reproduces well many of the features observed in analogue modelling and reported from outcrop and seismic studies

the deformation of overburden soil induced by thrust faulting and its impact on underground tunnels overburden soil beds situated above a fault are often deformed by propagation of bedrock thrusting from the fault during large earthquake the deformed beds formed a triangular shear zone this coseismic faulting often causes damage to underground tunnels located in the shear zone the present research studies the deformation behavior of the overburden soil beds and the tunnel the associated mechanism and the impact on the safety of tunnel linings induced by a large blind thrust slip based on sandbox experimental and numerical studies it is found that results from numerical analysis are in agreement with the sandbox model tests with regard to growths of the shear zones within the soil beds location of the tunnel in this shear zone and deformations of the tunnel the potential major shear zone may be bent or bifurcated into two sub shear zones owing to existence of a tunnel inside the shear zone furthermore the occurrence of back thrust faulting will threaten the safety of nearby structures it was also identified that stiffness of the soil and the fault dip angles are among the major factors controlling the configuration of shear zones the stresses within the soil and the loads on tunnel linings based on the identified mechanisms the strategies for hazard prevention are accordingly suggested and discussed

mathematical block motion model for deformation of a layer above a buried fault of arbitrary dip and sense of slip abstract an analytic series solution is obtained for the stress and deformation in an isotropic viscous or incompressible elastic layer subjected to rigid block motion at its base the block motion approximates slip on a pre existing basement fault of arbitrary dip and sense of slip deformation in the layer due to horizontally separating and horizontally converging blocks slip on a vertical basement fault and slip on 45 dipping reverse and normal basement faults is examined above horizontally diverging and converging blocks a symmetric syncline and anticline form respectively monoclines form above dipping basement faults the location of the monocline and to a lesser degree its form vary systematically with fault attitude and sense of slip for a given fault displacement the region of brittle failure in a basement normal fault model is larger than that in a reverse fault model new faults formed in the layer are arcuate in profile model results agree with observations of stress orientation and deformation from laboratory models

geometry and architecture of faults in a syn rift normal fault array the nukhul half graben suez rift egypt the geometry and architecture of a well exposed syn rift normal fault array in the suez rift is examined at pre rift level the nukhul fault consists of a single zone of intense deformation up to 10 m wide with a significant monocline in the hanging wall and much more limited folding in the footwall at syn rift level the fault zone is characterised by a single discrete fault zone less than 2 m wide with damage zone faults up to approximately 200 m into the hanging wall and with no significant monocline developed the evolution of the fault from a buried structure with associated fault propagation folding to a surface breaking structure with associated surface faulting has led to enhanced bedding parallel slip at lower levels that is absent at higher levels strain is enhanced at breached relay ramps and bends inherited from pre existing structures that were reactivated during rifting damage zone faults observed within the pre rift show ramp flat geometries associated with contrast in competency of the layers cut and commonly contain zones of scaly shale or clay smear damage zone faults within the syn rift are commonly very straight and may be discrete fault planes with no visible fault rock at the scale of observation or contain relatively thin and simple zones of scaly shale or gouge the geometric and architectural evolution of the fault array is interpreted to be the result of i the evolution from distributed trishear deformation during upward propagation of buried fault tips to surface faulting after faults breach the surface ii differences in deformation response between lithified pre rift units that display high competence contrasts during deformation and unlithified syn rift units that display low competence contrasts during deformation and iii the history of segmentation growth and linkage of the faults that make up the fault array this has important implications for fluid flow in fault zones

discrete element modelling of hanging wall deformation along the d 1 fault system danish north sea with implications for gas chimney interpretations abstract this study uses 3d seismic mapping nncc attribute analysis and 2d sdem modelling of soft sediment deformation to analyse hanging wall deformation related to faulting across a listric fault detaching along the top of a major salt roller the computational model experiments used the overall fault and salt structure evolution as boundary conditions to predict the distribution of faults within the hanging wall the modelling successfully reproduced geometries similar to the syn and antithetic faults that are visible on seismics but it also showed the presence of well defined vertical deformation zones both in the hanging wall and the foot wall of the listric fault in the model salt movement controls the formation of the deformation zones the similarity of nncc inferred vertical chimneys and the modelled deformation zones suggests that the subtle vertical chimneys identified in the 3d seismic data might actually be related to vertical to sub vertical deformation zones caused by the presence and movement of the salt structure

seasonality in the local and remote atmospheric response to sea surface temperature anomalies abstract two apparently contradictory situations are provided by observations of the atmospheric response to sea surface temperature anomalies these are i the extratropical regions of the winter hemisphere appear to possess strong teleconnections with equatorial forcing but weak or non existent connections with local extratropical heating anomalies ii the extratropical regions of the summer hemisphere are quite sensitive to local thermal forcing but apparently unaffected by the remote forcing from equatorial regions an attempt is made to provide a consistent physical picture which simultaneously embraces these two situations with the aid of a simple linear model it is shown that the summer hemisphere is more sensitive to local forcing than the winter hemisphere because it is closer to the diabatic limit of webster 1981 thus allowing an efficient energy generation the winter hemisphere is much closer to the adjective limit the sensitivity of the midlatitudes to remote equatorial forcing

three dimensional distinct element modelling of relay growth and breaching along normal faults three dimensional numerical models of neutral i e slip parallel relay zones on normal faults that cut massive sandstone host rocks have been constructed using the distinct element method code particle flow code in 3 d pfc3d the models successfully reproduce the geometries displacement profiles and strains observed in natural relay zones in contrast to boundary element method simulations the modelled relay ramps dip towards the hanging wall consistent with observations of most natural relay zones the modelling shows that relay zones are stable structures that grow by progressive rotation of an approximately planar relay ramp without significant propagation of the relay bounding faults prior to breaching stable growth is terminated when a breaching fault propagates across the top or bottom of the relay ramp breaching fault propagation is not instantaneous and the ramp continues to rotate and therefore transfer displacement between the relay bounding faults until they become fully hard linked following hard linkage displacement is accommodated by slip on the through going fault surface the modelling results confirm previous conceptual models of relay growth and breaching based on geometric and kinematic analysis of natural relay zones

an elusive blind thrust fault beneath metropolitan los angeles seismic reflection profiles petroleum wells and relocated earthquakes reveal the presence of an active blind thrust fault beneath metropolitan los angeles a segment of this fault likely caused the 1987 whittier narrows magnitude 6 0 earthquake mapped sizes of other fault segments suggest that the system is capable of much larger magnitude 6 5 to 7 and more destructive earthquakes

trishear for curved faults abstract fault propagation folds form an important trapping element in both onshore and offshore fold thrust belts and as such benefit from reliable interpretation building an accurate geologic interpretation of such structures requires palinspastic restorations which are made more challenging by the interplay between folding and faulting trishear erslev 1991 allmendinger 1998 is a useful tool to unravel this relationship kinematically but is limited by a restriction to planar fault geometries or at least planar fault segments here new methods are presented for trishear along continuously curved reverse faults defining a flat ramp transition in these methods rotation of the hanging wall above a curved fault is coupled to translation along a horizontal detachment including hanging wall rotation allows for investigation of structures with progressive backlimb rotation application of the new algorithms are shown for two fault propagation fold structures the turner valley anticline in southwestern alberta and the alpha structure in the niger delta

mechanical models of trishear like folds previous workers have formulated velocity descriptions of the trishear kinematic model of fault propagation folds which are inherently non unique we present two complete mechanical models of fault related folding and assess the validity of the assumptions used in the assignment of velocities in the trishear description and to eliminate the untenable situation of an infinite number of possible solutions for velocity fields the mechanical model of forced folding forced fold based on viscous folding theory is used to derive the velocity fields in an anisotropic sedimentary cover overlying faulted and displaced rigid basement blocks the solution of displacements around a stress free fault in an elastic body is used to model fault arrest folds that form around a fault imbedded in a deformed medium the results indicate that the velocity fields assumed in the trishear model more closely resemble the velocities derived in the mechanical forced fold model than the mechanical model of fault arrest folding the forced fold model produces a triangular region of concentrated deformation similar to the trishear region assumed in the kinematic models while the deformation produced by the fault arrest model is not concentrated within a triangular zone

physical modeling of deformation patterns in monoclines above oblique slip faults abstract many basement involved fault related folds are thought to form by reactivation of pre existing faults although oblique slip is expected on such structures it is often difficult to identify because the underlying faults are blind paleomagnetic records are ambiguous and mesoscopic deformation patterns in the associated monoclines are often incompletely exposed or difficult to interpret this study seeks to establish a relationship between oblique slip on a basement reverse fault and the deformation patterns in the overlying folded rock layers using scaled physical models of wet clay overlying a rigid basement we create a suite of laramide style folds over basement faults with variable obliquity precise displacements and strains on the surface of the clay are recorded using close range photogrammetry we use these measurements to predict deformation patterns that we would expect to find in analogous natural structures the results of our models show that there are three general strain zones that form in monoclines that form above oblique slip faults the upper hinge region of the monocline is dominated by extension the lower hinge region by contraction and the middle of the fold limb is dominated by shear strains the boundaries of these three zones as well as the magnitude of strain in each of the zones vary with the amount of oblique slip and fault throw deformation should be dominated by joints and extensional faults in the extensional zone by contractional faults and cleavage in the contractional zone and may contain extensional contractional or strike slip faults along with joints and cleavage arranged in riedel style geometries in the shear strain dominated zone at fault obliquities above 45 there is significant overlap of the different strain zones and deformation patterns in these regions can consequently be very complex involving reactivation or overprinting of earlier structures or the formation of mixed mode structures displacements on the surface of our model monoclines suggest that previous paleomagnetic interpretations of vertical axis rotations on natural monoclines may need to be re evaluated although such rotations increase with increasing fault obliquity the magnitude of these rotations will vary significantly with position across a monocline

drape folding of compressible elastic layers i analytical solutions for vertical uplift abstract two new analytical solutions allow the effects of layer thickness vertical fault zone width and throw layer compressibility and basal slip on drape fold geometry to be investigated welded case i and non welded case ii lower contacts with step vertical displacement functions and an upper free surface are used as boundary conditions comparison of fold profiles displacement fields and principal stress trajectory fields suggests that fold form yields relatively little information about lower boundary geometry or stress conditions drape folds with non welded contacts however are distinctly asymmetric along their lower boundaries displacement and principal stress trajectory fields on the other hand can be used to distinguish which of the two boundary conditions was used to produce a given theoretical fold values of maximum shear stress are much higher along welded contacts than along non welded contacts suggesting that faulting and brecciation should be more prevalent along welded contacts these findings are consistent with published field observations and suggest that some attributes of theoretical folds for example lower boundary geometry and minor fracture orientation may be used to infer the conditions under which real drape folds were formed

structural styles and decoupling in stratigraphic sequences with double decollements during thin skinned contractional tectonics insights from numerical modelling abstract six series of particle based numerical experiments were performed to simulate thin skinned contractional tectonics in stratigraphic sequences with double decollements during horizontal shortening the models were assigned with varying rock competence depth and thickness of the upper decollement which resulted in significantly different styles of deformation and decoupling characteristics above and below the upper decollement the models composed of the least competent material produced distributed sinusoidal detachment folds with many shallow structures profoundly decoupled from the deep seated folds the models composed of a more competent material are dominated by faulted box folds with minor disharmonic folds developed in their limbs in contrast the results of models composed of the most competent material are characterised by localised piggyback thrusts fault bend folds and pop up structures with tensile fractures developed in fold hinges depth of the upper decollements also plays an important role in controlling structural decoupling i e the shallower the upper decollements the higher the degree of decoupling becomes thicker upper decollements can provide sufficient mobile materials to fill fold cores and contribute to the formation of secondary disharmonic folds helping enhance structural decoupling our modelling results are comparable to the structural features exhibited in the dezful embayment of the zagros fold and thrust belt with the miocene gachsaran formation acting as the shallow upper decollement and the fars with the triassic dashtak formation as its intermediate decollement this study demonstrates that rock competence depth and thickness of the upper decollements can jointly affect the structural styles and decoupling our modelling results are instructive for structural interpretation of deep zones in fold and thrust belts that exhibit distinct structural decoupling features

discrete element modeling of stick slip instability and induced microseismicity using particle flow code a discrete element model is presented in this paper that allows direct modeling of stick slip behavior in pre existing weak planes such as joints beddings and faults the model is used to simulate a biaxial sliding experiment from literature on a saw cut specimen of sierra granite with a single fault the fault is represented by the smooth joint contact model also an algorithm is developed to record the stick slip induced microseismic events along the fault once the results compared well with laboratory data a parametric study was conducted to investigate the evolution of the model s behavior due to varying factors such as resolution of the model particle elasticity fault coefficient of friction fault stiffness and normal stress the results show a decrease in shear strength of the fault in the models with smaller particles smaller coefficient of friction of the fault harder fault surroundings softer faults and smaller normal stress on the fault also a higher rate of displacement was observed for conditions resulting in smaller shear strength an increase in b values was observed by increasing the resolution or decreasing the normal stress on the fault while b values were not sensitive to changes in elasticity of the fault or its surrounding region a larger number of recorded events were observed for the models with finer particles smaller coefficient of friction of the fault harder fault surroundings harder fault and smaller normal stress on the fault the results suggest that it is possible for the two ends of a fault to be still while there are patches along the fault undergoing stick slips such local stick slips seem to provide a softer surrounding for their neighbor patches facilitating their subsequent stick slips

linked sequence stratigraphic and structural evolution of propagating normal faults two distinct phases in the structural evolution of normal faults can be identified in the miocene gulf of suez rift 1 an initial growth fold stage when the fault is a buried structure and 2 a subsequent surface faulting stage during the growth fold stage strata thin and become truncated toward the fault zone and are rotated and diverge away from the buried fault into growth synclines in contrast once the fault breaks surface strata form a divergent wedge which is rotated and thickens into the fault the two tectono stratigraphic styles also occur contemporaneously along the length of a single fault segment growth folding characterizes deformation around the ends of fault segments where the fault is blind whereas the center of fault segments are characterized by surface faulting these observations suggest that marked along strike variation in stratal surfaces and facies stacking patterns will occur in depositional sequences in areas of normal faulting

numerical simulation of faults and shear zones summary a numerical model is developed to simulate faults and shear zones in rocks it consists of a 2 d set of soft spheres in plane strain compression tests the soft spheres obey newton s equations of motion and initially interact with viscoelastic forces the fracturing process is simulated by the transition from attractive repulsive forces to solely repulsive forces the behaviour of the solid is studied by varying two independent parameters the density of pre existing fractures and the confining pressure the density of pre existing fractures controls the intrinsic cohesion of the rock a transition from brittle to ductile behaviour is generated by letting this parameter vary the deformation is localized along narrow shear zones when the solid is intact as the cohesion decreases the deformation becomes more homogeneous the effect of the confining pressure is then studied for different cohesions in loose media a variation of the stress drop in stress strain curves is observed

the role of bed parallel slip in the formation of blind thrust faults abstract a finite element code is used to model the mechanical behaviour of elastoplastic sedimentary layers that are deformed by the movement of a faulted deformable basement the propagation of the blind thrust fault is analysed in terms of the evolution of strain localization in the elastoplastic layers of strain softening and strain hardening materials the role of layer thickness bedding parallel slip and fault dip are also studied we found that if no interlayer slip is allowed blind thrusts tend to propagate with constant dip regardless of the rheological properties of the sediment layers however if bedding parallel slip is present a mechanical decoupling appears between layers allowing stress transfers along large distances and favouring the formation of backthrusts fault dip also has significant influence on the qualitative behaviour when interlayer slip is possible a steep fault will tend to split

deformation of overburden soil induced by thrust fault slip abstract when the blind thrust fault slips due to earthquakes overburden soil strata may deform and fail leading to a development of a coseismic fault zone how overburden soil strata will deform or be faulted is an essential issue in the evaluation on the safety of ground underground infrastructures located near the potential plastic zone on the basis of previous work by cole and lade cole d a lade p v 1984 influence zones in alluvium over dip slip faults journal of geotechnical engineering 110 599 615 this research further explores the processes of thrust faulting within overburden soil and examines the influences of corresponding factors or parameters under a range of boundary conditions using physical models and numerical analysis for both small scale and full scale configurations factors explored include uplifting rate fault dip angle dilation angle of plastic flow young s modulus poisson ratio cohesive strength frictional angle scaling as well as the location of ground loadings applied on ground surface the experimental results indicate that although one major fault slip surface can be developed subsidiary faults may also form which requires special attention when defining stain patterns young s modulus and the dilation angle are the most influential parameters in our models a stiffer e leads to early fault propagation and the occurrence of back thrusts and causes more significant discrepancies in the deformation behaviors of models with different scales a greater dilation angle of the overburden soil leads to a wider fault zone the above mentioned phenomena highlight that a careful consideration of the applicable young s modulus and the dilation angle is essential in a proper simulation or prediction of the fault zone development for small scale physical models used to simulate the fault development for a full scale problem the stiffness of model soil should be properly scaled down which still requires further study

northern winter stationary waves theory and modeling a review is provided of stationary wave theory the theory for the deviations from zonal symmetry of the climate to help focus the discussion the authors concentrate exclusively on northern winter several theoretical issues including the external rossby wave dispersion relation and vertical structure critical latitude absorption the nonlinear response to orography and the interaction of forced wave trains with preexisting zonal asymmetries are chosen for discussion while simultaneously presenting a decomposition of the wintertime stationary wave field using a nonlinear steady state model

volcanotectonic interactions between mauna loa and kilauea insights from 2 d discrete element simulations abstract numerical simulations using the discrete element method dem are carried out to examine the dynamics and internal deformation of overlapping volcanoes constructed upon a weak decollement horizon as analogs to the kilauea mauna loa system of volcanoes in hawaii employing a frictional rheology the dem simulations capture much of the complex deformation behavior of mauna loa and kilauea volcanoes here referred to as the primary and secondary edifices respectively the models demonstrate incremental displacements of the outer flanks of the volcanoes and concurrent summit subsidence leading to characteristic low slopes and inward dipping strata slip discontinuities that develop within the piles define steeply dipping normal faults along the upper flanks and beneath the edifice summits that accommodate subsidence and flank spreading edifice overlap influences dynamic behavior significantly even small topographic perturbations restrict the internal deformation and spreading of the confined flanks the degree of buttressing depends on the relative positions of the two edifices if the secondary edifice grows high upon the flanks of the primary edifice outward spreading of the underlying flank is enhanced if the secondary edifice is built low upon the primary flanks spreading of the underlying flank is effectively prevented or possibly reversed furthermore as the second edifice grows it subsides into the underlying flank partitioning it into a mobile downslope region entrained by spreading of the second edifice and a comparatively stable upper flank region these results suggest that much of the mass of kilauea volcano may lie deeply buried within the underlying flank of mauna loa while older mauna loa rocks may lie far from their source beneath the mobile flank of the younger volcano

critical state finite element models of contractional fault related folding part 2 mechanical analysis abstract finite element modeling of contractional fault related folding with critical state mechanics concepts reveals fundamentally different behaviors at two levels depending on 1 mechanical stratigraphy and 2 initial fault geometry deviatoric plastic strain rate and strain patterns show that strong layers like normally consolidated sandstone or overconsolidated shale develop strain localization in form of narrow plastic shear bands soft layers like normally consolidated shale fail to develop localizations and respond by diffuse distributed plastic strain inter layered overburdens display both deformation modes models with listric thrust fault seeds develop basement cored anticlines in the hangingwall that are characterized by locally tensile stress regimes within overall compressive regional stress fields the anticline crests of these models show evidence for strain softening by contrast anticlines emerging in detached fault related fold models are subject to locally compressive stress regimes consistent with the applied far field shortening these anticline crests strain harden during deformation stresses resulting from the finite element models deviate from stress estimates based on integrated densities the discrepancy is small for basement involved models but significant for detached style models suggesting that stress predictions based on integrated densities may be inaccurate for contractional systems first order predictions of plastic deformation suggest that footwall synclines in basement involved fold styles may host reservoirs with relatively poor quality owing to horizontal and vertical compaction anticlines found in detached deformation styles are bounded by compactive domains whereas the crestal regions are less affected by volumetric plastic deformation thus producing relatively better reservoir quality

numerical modelling of syntectonic subaqueous sedimentation the effect of normal faulting and a relay ramp on sediment dispersal abstract relay ramps are common in extensional settings and play a significant role in sediment dispersal as they control sedimentary pathways unlike for subaerial settings the impact of subaqueous relay ramps on sediment dispersal and clastic sedimentation is less studied in these subaqueous cases numerical approximations could be a good approach to understand syntectonic sedimentation considering this a numerical model is used to study the sedimentary infill in an extensional basin specifically related to a relay ramp system the study is carried out using a novel program that merges a discrete element code for tectonic deformation and a stratigraphic modelling code for sedimentation to perform a test study two configurations are designed with one normal fault and with two overlapping normal faults linked by a relay ramp to these initial configurations three different deformation velocities 10 5 and 2 cm y are applied in dip slip direction these scenarios are considered as initially submerged the same incoming amount of three different terrigenous sediments is considered in all the experiments these sediments are transported basinward in suspension by processes of advection dispersion and diffusion finally these examples also include four different boundary conditions for the sedimentary model which define the source area location for the incoming water and sediment results show that the source area location in relation to the available accommodation space plays the major role in the distribution of different sediment types into the basin nonetheless when the source area for water and sediment is defined as regional and parallel to the fault the grain size distribution obtained by the two overlapping faults configuration has clear asymmetries when compared with the ones obtained by one fault configurations therefore the different extensional experiments allow concluding that the relay ramp configuration can play an important role in the distribution of the sediments into the basin

anthropogenic changes in the walker circulation and their impact on the extra tropical planetary wave structure in the northern hemisphere a robust change in the tropical circulation induced by anthropogenic warming in cmip3 models is a weakening of the walker circulation this weakening affects the upper tropospheric divergence thereby modifying the propagation of rossby waves from the tropics into the extra tropics it can be modeled by the barotropic vorticity equation forced with a rossby wave source that is computed from the upper tropospheric divergence using the bve as a diagnostic tool it is demonstrated for the cmip3 models that the weakening of the walker circulation has a significant impact on the extra tropical planetary wave structure and to a large extent explains the projected changes in the mid tropospheric meridional wind in the cmip3 models the dominant response is a wave number five pattern similar to the circumglobal waveguide pattern this analysis implies that a correct simulation of the walker circulation and its response to anthropogenic changes are crucial for a correct simulation of the anthropogenic change in the extra tropical planetary wave structure structure and intensity of the walker circulation of the cmip3 models show significant deviations from the walker circulation as diagnosed from the era interim and ncep ncar reanalysis improving the simulation of the walker circulation is a prerequisite to narrow the uncertainty in the projected anthropogenic change in the extra tropical planetary wave structure

an experimental and theoretical study of rare earth element partitioning between sulfides fes cas and silicate and applications to enstatite achondrites abstract partition coefficients of the rare earth elements ree between sulfides fes or cas and silicate melt were determined experimentally at 1200 1300 c the ree sulfide silicate partition coefficients d are 1 under the experimental o and s fugacities which demonstrates that the ree are mainly located in the silicate phase rare earth element partition coefficients in the fes silicate system decrease from light to heavy ree while the opposite behavior is found for the cas silicate system where partition coefficients increase from light to heavy ree in both sulfide systems eu is preferentially incorporated into the sulfide phases as also expected from thermodynamic calculations the eu sulfide silicate partition coefficient is about a factor of ten higher than that of neighboring sm and gd in accordance with thermodynamic predictions of ree sulfide silicate partition coefficients the low sulfide silicate partition coefficients indicate that cas oldhamite in enstatite achondrites aubrites cannot have gained its high ree concentrations during igneous differentiation processes the high ree concentrations and the ree patterns in aubritic oldhamite are more plausibly explained by ree condensation into refractory cas the refractory nature of cas prevented major exchange reactions of the oldhamite with other aubritic minerals during the short differentiation and metamorphism period on the aubrite parent body thus oldhamite in aubrites may be relict condensates altered to different degrees during short heating events as originally suggested by lodders and palme 1990

effect of increased shear stress along a plate boundary fault on the formation of an out of sequence thrust and a break in surface slope within an accretionary wedge based on numerical simulations abstract we investigated the effect on accretionary wedge structure of increased shear stress which describes the frictional sliding resistance along a decollement arising from an increase in material friction or reduction in pore pressure to clarify the nature of the effect we performed numerical simulations using two models a stable friction model and an increased friction model the stable friction model produced a low angle smooth surface slope and an in sequence thrust whereas the increased friction model produced a break in surface slope scarp and an out of sequence thrust ost that cuts through the thrust sheet the ost formed via the connection of segments of two adjacent thrusts and its formation resulted in a change in the thickening mode of the wedge from thrust sheet rotation and back thrust activity to underplating this contrast in thickening mode between the landward high friction zone and seaward low friction zone resulted in the formation of a clear break in slope as the landward zone is steeper than the seaward zone consistent with critical taper theory the subduction of a basement slice or seamount can produce similar structures arising from an increase in resistance to basal shear sliding however the distinctive structures arising in an accretionary wedge as a result of increased shear sliding resistance include a flat basal plane and absence of slope failure sediments beneath the ost these structural features are observed in accretionary wedges of the nankai trough off muroto japan the sunda strait and the barbados ridge

seismicity and stress rotation in a granular model of the brittle crust the basic mechanical process responsible for earthquakes and faulting is not known the intuitive notion of frictional slip on faults between elastic crustal blocks cannot be reconciled with laboratory measurements of the strength of rocks1 field observations of heat flow2 3 and stress orientation4 around the san andreas fault in california and seismological estimates of the energy radiated by earthquakes5 the weakening of large faults by elevated pore fluid pressure6 has been suggested as one solution to this paradox but places severe constraints on the hydrological conditions of the faults concerned here i propose an alternative model for earthquake mechanics in which the crust is treated as a system of many interlocking blocks divided by many faults7 the model combines this random granular structure with simple deterministic mechanical interactions numerical simulations of the deformation of an aggregate of rough grains under compressive stress show earthquake like elastodynamic failures without frictional heat production and substantial rotation of stresses across shear zones which mimics field observations there remain problems of scale in comparing these simulations with nature but a seismological test of the model may be possible

simulation of the frictional stick slip instability a lattice solid model capable of simulating rock friction fracture and the associated seismic wave radiation is developed in order to study the origin of the stick slip instability that is responsible for earthquakes the model consists of a lattice of interacting particles in order to study the effect of surface roughness on the frictional behavior of elastic blocks being rubbed past one another the simplest possible particle interactions were specified corresponding to radially dependent elastic brittle bonds the model material can therefore be considered as round elastic grains with negligible friction between their surfaces although breaking of the bonds can occur fracturing energy is not considered stick slip behavior is observed in a numerical experiment involving 2d blocks with rough surfaces being rubbed past one another at a constant rate slip is initiated when two interlocking asperities push past one another exciting a slip pulse the pulse fronts propagate with speeds ranging from the rayleigh wave speed up to a value between the shear and compressional wave speeds in agreement with field observations and theoretical analyses of mode ii rupture slip rates are comparable to seismic rates in the initial part of one slip pulse whose front propagates at the rayleigh wave speed however the slip rate is an order of magnitude higher in the main part of pulses possibly because of the simplified model description that neglected intrinsic friction and the high rates at which the blocks were driven or alternatively uncertainty in slip rates obtained through the inversion of seismograms particle trajectories during slip have motions normal to the fault indicating that the fault surfaces jump apart during the passage of the slip pulse normal motion is expected as the asperities on the two surfaces ride over one another the form of the particle trajectories is similar to those observed in stick slip experiments involving foam rubber blocks bruneet al 1993 additional work is required to determine whether the slip pulses relate to the interface waves proposed by brune and co workers to explain the heat flow paradox and whether they are capable of inducing a significant local reduction in the normal stress it is hoped that the progressive development of the lattice solid model will lead to realistic simulations of earthquake dynamics and ultimately provide clues as to whether or not earthquakes are predictable

discrete element modelling of the influence of cover strength on basement involved fault propagation folding abstract a discrete element model is used to investigate the influence of sedimentary cover strength on the development of basement involved fault propagation folds we find that uniformly weak cover best promotes the development of classical trishear like fault related folds showing marked anticlinal thinning and synclinal thickening with cover dips increasing downwards towards the fault tip uniformly strong cover results in more rounded fold forms with only minor hinge thickening thinning and significant basement fault propagation into the sedimentary cover heterogeneous layered cover sequences with marked differences in strength promote the development of more complex and variable fold forms with a close juxtaposition of brittle and macroscopically ductile features which diverge from the predictions of simple kinematic models in these structures the upper layers are often poor indicators of deeper structure in addition we find that in layered cover sequences fault propagation into the cover is a complex process and is strongly buffered by the weaker cover units

the eastward shift of the walker circulation in response to global warming and its relationship to enso variability this study investigates the global warming response of the walker circulation and the other zonal circulation cells represented by the zonal stream function in cmip3 and cmip5 climate models the changes in the mean state are presented as well as the changes in the modes of variability the mean zonal circulation weakens in the multi model ensembles nearly everywhere along the equator under both the rcp4 5 and sres a1b scenarios over the pacific the walker circulation also shows a significant eastward shift these changes in the mean circulation are very similar to the leading mode of interannual variability in the tropical zonal circulation cells which is dominated by el nino southern oscillation variability during an el nino event the circulation weakens and the rising branch over the maritime continent shifts to the east in comparison to neutral conditions vice versa for a la nina event two thirds of the global warming forced trend of the walker circulation can be explained by a long term trend in this interannual variability pattern i e a shift towards more el nino like conditions in the multi model mean under global warming further interannual variability in the zonal circulation exhibits an asymmetry between el nino and la nina events el nino anomalies are located more to the east compared with la nina anomalies consistent with this asymmetry we find a shift to the east of the dominant mode of variability of zonal stream function under global warming all these results vary among the individual models but the multi model ensembles of cmip3 and cmip5 show in nearly all aspects very similar results which underline the robustness of these results the observed data era interim reanalysis from 1979 to 2012 shows a westward shift and strengthening of the walker circulation this is opposite to what the results in the cmip models reveal however 75 of the trend of the walker circulation can again be explained by a shift of the dominant mode of variability but here towards more la nina like conditions thus in both climate change projections and observations the long term trends of the walker circulation seem to follow to a large part the pre existing dominant mode of internal variability

expansion of the hadley cell under global warming 1 a consistent weakening and poleward expansion of the hadley circulation is diagnosed in the climate change simulations of the ipcc ar4 project associated with this widening is a poleward expansion of the subtropical dry zone simple scaling analysis supports the notion that the poleward extent of the hadley cell is set by the location where the thermally driven jet first becomes baroclinically unstable the expansion of the hadley cell is caused by an increase in the subtropical static stability which pushes poleward the baroclinic instability zone and hence the outer boundary of the hadley cell

multiple geometries and modes of fault propagation folding in the canadian thrust belt abstract a multitude of fold models have been proposed to explain the variety of fold geometries which develop in front of thrust faults detailed field fabric and photogrammetric studies of 4 fault cored asymmetrical folds in the thin skinned canadian thrust belt were used to test models of fault propagation folding fold geometries include combinations of angular and rounded fold surfaces highly contorted anticlinal hinge areas and minimal penetrative deformation or changes in bedding thickness interlimb angles generally decrease with increasing shortening indicating progressive fold tightening about fixed anticlinal hinges extensive flexural slip thrusting toward the anticlinal axes of angular folds suggests that kink folding in thin skinned thrust belts is aided by material transfer from both fold limbs into hinge areas fold geometries change dramatically along the strike of individual structures demonstrating the non uniqueness of fault propagation fold geometries no single mode of fault propagation folding can explain the diverse fold geometries seen in the canadian thrust belt this geometric variability can be ascribed to the complex interplay of multiple modes of folding in strata near the causal thrusts oblique shear and flexural slip in triangular shear zones distribute thrust displacements into both rounded and angular folds simultaneous angular folding of overlying strata commonly occurs by progressive kink folding where folds tighten by flexural slip on all fold limbs until the thrust breaks through the fold regional and local differences in the amount of pervasive top to the craton shear needed for progressive kink folding may be partially responsible for the variability of fault propagation fold geometries in thin and thick skinned orogens world wide

a discrete element model for orogenesis and accretionary wedge growth 1 we develop a two dimensional discrete element model to investigate the evolution of doubly vergent orogenic and accretionary wedges this generates the localization of deformation across persistent structures as emergent phenomena unlike many continuum models that require predefined weaknesses to localize strain the model is used to study how deformation processes evolve for two different boundary conditions drawing strong comparisons with previous sandbox analogues and computational approaches the deformational history of the modeled wedges is characterized by three stages defined by an evolution in the mechanisms available to accommodate shortening the first stage develops a strong retrovergent thrust that initiates at the subduction point the second stage shows a change in vergence of deformation as thin skinned thrusting propagates into material carried on the subducting plate thus evolving a folded and thrusted prowedge finally a second shallower retrowedge develops in the overriding plate through accretion this final stage is not present in all sand analogue modeling approaches and defines a difference in the deformation style thresholds in geometry and size regulate the localization and style of deformation and hence the progression through the three stages the wedges produced show periodicity in the modes of accretion to maintain a geometric form with deformation localizing across structures that are internally reactivated thus prowedges and retrowedges are seen to oscillate about constant taper angles

inference of trishear faulting processes from deformed pregrowth and growth strata near surface strata deformed by propagation of a fault situated underneath these strata hold explicit records of fault activities the delicate deformed strata exposed in investigation trenches for paleoseismologic study conform to fault propagation folds growing above a blind thrust growth strata deposited subsequently across the coseismic fold scarps are preserved by onlap and unconformities information from these sedimentary and folding processes was used in conjunction with inverse modeling using the trishear model technique proposed by allmendinger allmendinger r w 1998 inverse and forward numerical modeling of trishear fault propagation folds tectonics 17 640e656 in estimating the times and amounts of slips this methodology becomes necessary especially when the extent of a deformed profile is insufficiently exposed to observation or the location of the fault tip is invisible the proposed method can deal with growth strata that can be selectively removed during fold restoration the interpretations on the deformation history obtained by inverse analysis and trench investigation were then compared the combination of these two approaches seemed to enhance and complement each other and allows a better and more complete understanding of the trishear faulting processes and is useful in seismic hazard assessment 2007 published by elsevier ltd

estimation of fault propagation distance from fold shape implications for earthquake hazard assessment a numerical grid search using the trishear kinematic model can be used to extract both slip and the distance that a fault tip line has propagated during growth of a fault propagation fold the propagation distance defines the initial position of the tip line at the onset of slip in the santa fe springs anticline of the los angeles basin we show that the tip line of the underlying puente hills thrust fault initiated at the same position as the 1987 magnitude 6 0 whittier narrows earthquake

mechanical models of fault propagation folds and comparison to the trishear kinematic model abstract faults propagating through the earth generate a wave of deformation ahead of their tip lines we have modeled this process to understand the relationship between fold geometry and fault propagation using finite element modeling fem we investigate the response of incompressible frictionless and frictional materials and a compressible frictional material with associated flow to vertical and dipping faults whose tip lines propagate at rates 3 3 5 times their slip rates the fold geometries finite strain and velocity fields in models with incompressible materials are very similar to those produced by the trishear kinematic model even though the latter uses a purely ad hoc linear velocity field furthermore when the trishear grid search is applied to the final geometry of the mechanical folds the best fit kinematic models have approximately the same propagation to slip ratio as was used in the fem experiments however when the compressible frictional material is used the mechanical models exhibit a main triangular shear band in front of the tip line and a conjugate shear band in the fold backlimb both migrating with the propagating tip line the conjugate shear band antithetic to the fault produces a gentle anticlinal back limb even though there is not a bend in the fault

drape folding of compressible elastic layers ii matrix solution for two layer folds abstract a matrix solution for two layer drape folds in compressible elastic media is used to examine the relative importance of layer compressibility layer stiffness and the presence or absence of lower boundary shear on fold form principal stress direction and maximum shear stress distribution the most obvious effect of decreasing the shear modulus of the lower layer is a change in principal stress orientation accompanied by a decrease in maximum shear stress principal stress orientation and to a lesser degree fold shape can be further altered by changing the compressibility of an easily sheared basal layer characteristics of drape folds with welded and non welded basal contacts as observed in the field and predicted by a single layer model of drape folding are also further explored with the two layer model

3d simulations of salt tectonics in the kwanza basin insights from analogue and discrete element numerical modeling abstract the kwanza basin is located at the passive margin of west africa in the central segment of the south atlantic and is an important area for oil and gas exploration the distribution and deformation characteristics of thick lower cretaceous aptian salt deposits in the basin have significant impacts on hydrocarbon accumulation however reports on their 3d interpretation together with an understanding of the genesis and evolution of salt tectonics in this area are scarce in the literature in this paper 3d analogue experiments and 3d discrete element numerical simulations are carried out to analyze the zonal characteristics extension translation contraction the main control factors and to develop a kinematic model of salt tectonics in the basin according to our modeling we make the following conclusions 1 the zonal characteristics of salt tectonics formed in the basin reflect the superposition of gravity gliding and gravity spreading the main control factor of basin scale salt deformation is basement structural activity which can be summarized into three points early post salt basement extension initial presence of local variation of base of salt gradient and more recent differential subsidence between landward side and seaward side 2 salt deformation is episodic having experienced one stage of regional deformation late aptian to albian and two stages of inherited developmental deformation campanian and eocene to miocene mainly resulting in forward expansion towards the ocean 3 during the early stage of salt deformation faults developed in suprasalt layers in the extensional and translational zones of the basin resulting in local high velocity areas and a large vertical upward velocity component in the salt layer later due to blocking by the outer high region and increasing overburden salt in contact with the outer high developed a vertical upward velocity component gradually forming thrust structures 4 3d analysis highlights the pervasive lateral deformation of the salt the main factors governing it are the distribution of accommodation in the salt basin and the initial morphology of the salt layer in the early stages salt layer had a velocity component to the salt scarce side from north to south whereas in the later stages it developed a velocity component to the wide side of the basin from south to north leading to the gradual accumulation of salt in the north of the basin we have shown that 3d simulations can complete the analysis of salt deformation both parallel and perpendicular to the slope in a passive margin basin this may provide guidance for the exploration of oil and gas reservoirs in the context of salt tectonics especially in asymmetrical basins where seismic imaging is poor and has to be supplemented by strong geological concepts including understanding 3d movement of salt

experimental clay models of inversion structures abstract experimental modeling is used to study the geometry and evolution of inversion structures two main types of inversion structures are analyzed 1 1 structures formed by fault propagation folding and 2 2 structures formed by fault bend folding on listric faults fault propagation inversion structures initially develop as broad drape folds with possible fault breakthrough during an early extensional phase syn extensional strata deposited in the hanging wall typically thicken away from the fault compressional reactivation results in reversal of slip on the master and secondary faults their rotation to shallower dips and the development of a compressional fault propagation fold key features of the fault propagation fold are basinward thickening of syn extensional units and resulting steep dips of the front limb of the structure fault bend inversion structures initiate as rollover folds within extensional half graben deformation is primarily localized along a system of antithetic faults syn extensional strata typically thicken across the fault but also thin basinward away from the fault during compression the extensional rollover folds are folded into compressional fault bend folds key features of this structure are thinning of syn extensional units into the basin inversion of more symmetric graben results in a doubly convex geometry of syn extensional units these observations of bed geometry and thickness provide predictive models for interpreting the geometries of inversion structures in areas of poor data quality

factors that control the development of fault bend versus fault propagation folds insights from mechanical models based on the discrete element method dem abstract we investigate the role and relative importance of a range of geometric and mechanical factors in the development of contractional fault related folds with an emphasis on defining the factors that promote the development of fault bend and fault propagation folds we construct a series of discrete element mechanical models in order to test the effects of fault dip bulk material strength mechanical layer anisotropy and spacing sedimentation rate and boundary conditions on the style of fault related fold that develops we find that fault bend folding is most favored at low fault ramp dips with thinly spaced mechanical layers and strong layer strength contrasts in contrast conditions that inhibit slip on a potential upper detachment surface such as increased friction and a fixed foreland boundary encourage the development of fault propagation folds additionally steeper fault dips more widely spaced mechanical layers and decreased layer strength contrast favor the increased localization of shear during the growth of structures this leads to structures that deform by a mixture of fault bend and fault propagation folding styles observations of the distortional strains that develop in the model provide insight into the relationship between the different deformation mechanisms such as flexural slip and localized shear which accommodate structural growth and ultimately determine fault related folding style thus these models provide a context for understanding how rock and fault properties influence whether structures evolve as fault bend or fault propagation folds or as combinations of these end members we apply these insights to interpret two natural examples from the offshore niger delta outer fold and thrust belt that exhibit changes in structural style through time as a result of changes in fault properties and syntectonic sedimentation

fault related folding a review of kinematic models and their application abstract folding that is directly related to fault activity is an important deformation feature that occurs all over the world in mountain belts accretionary wedges fold and thrust belts and intra plate settings in either strike slip compressional or extensional regimes due to their widespread occurrence knowledge about the development of these structures is important to a broad spectrum of geoscience sub disciplines such as structural geology seismology geomorphology petroleum geology and quaternary geology fault related folding has been analyzed intensively over the last 140 years for the sake of this review we divide the folds according to the way the faults and the folds form that is into detachment fault bend and fault propagation folds all fault related folds are caused by changes in fault parameters the simplest method to produce folds is to transport material along faults that have stepped flat ramp flat geometries fault bend fold alternatively the slip can decrease along the length of the fault and depending on whether the fault remains within a detachment layer or steps up through mechanical stratigraphy either a detachment fold or a fault propagation fold is formed respectively detachment folding was first investigated in the early 20th century whereas the full significance of fault propagation folds was recognized quite late in the 1980s seminal work on fault related folding was carried out in the 1930s but quantitative kinematic models have only been available in the last 30 years these models are extremely valuable because they allow a comprehensive understanding of the evolution of fault related folds and lead to more accurate predictions of the sub surface structure from the mid 1990s onwards numerical simulations have been used to identify how fault parameters such as dip and fault bend angle propagation to slip ratio and shape of the trishear zone influence the geometry of the related folding this is directly applicable to the analysis of the shape of anticlines produced however this does not mean that fold geometry is uniquely related to fault geometry on the contrary different kinematic approaches can lead to a similar fold shape

the influence of shortening and sedimentation on rejuvenation of salt diapirs a new discrete element modelling approach abstract this study employs a novel discrete element modelling approach to investigate the interplay of sedimentation with rejuvenation of diapirs by shortening the inherent complexity of salt tectonics the complications encountered when imaging structures beneath salt and the lack of outcrop analogues coupled with its importance to petroleum systems make salt tectonics one of the most interesting and debated topics in basin studies model results successfully reproduce the geometric and dynamic behaviour of active diapirism and show the effects of sedimentation thickness rate and timing on the generation of distinct diapir geometries including i salt tongues and ii squeezed upright diapirs models with late sedimentation or a lower sedimentation rate relative to salt mobility show development of asymmetric diapirs with allochthonous salt tongues whereas models with earlier sedimentation or a faster sedimentation rate generate upright squeezed diapirs early sedimentation at a moderate rate results in a symmetrical hour glass shaped structure resembling a tear drop diapir results are fully reproducible and comparable with many natural examples and include overburden deformation which is difficult to simulate using other numerical techniques extending this approach to different problems and basinal contexts could improve our understanding of deformation mechanisms and sediment distribution around salt structures

experimental models of extensional forced folds we have used single layer and multilayer clay models to study the development of forced folds above normal faults our modeling results show that the deformation patterns associated with extensional forced folding depend on the dip of the underlying normal fault and the presence of layer parallel detachments in single layer clay models extensional forced folds are upward widening monoclines anticlinal axial surfaces dip in the same direction as underlying master normal faults and synclinal axial surfaces dip in the opposite direction of master normal faults most secondary faults are upward steepening normal faults if master normal faults are steeply dipping however many secondary normal faults become high angle reverse faults at shallow depths the propagation and linkage of secondary faults into through going normal faults terminates the development of extensional forced folds more folding occurs prior to fault linkage if the master normal fault is steeply dipping rather than gently dipping most dipping beds and secondary faults are preserved in the hanging walls of the through oing normal faults in multilayer clay models with layer parallel detachments extensional forced folds are also upward widening monoclines slip on the lowest detachment laterally transfers extension induced by normal faulting and forced folding from the master normal fault to the detachment edge slip on overlying detachments accommodates minor thickness changes associated with upward widening of the fold secondary faults include low angle normal faults near the anticlinal axial surface minor thrust faults near the synclinal axial surface and high angle normal faults above the detachment edge the model predicted deformation patterns are similar to those of extensional forced folds from the gulf of suez and offshore norway this similarity suggests that our modeling results apply to extensional forced folds and can provide guidelines for interpreting field well and seismic data

discrete element modeling of the faulting in the sedimentary cover above an active salt diapir geological mapping seismic analyses and analogue experiments show that active salt diapirism results in significant faulting in the overburden strata faults associated with active diapirism generally develop over the crest of the dome and form a radial pattern in this study we have created a 3 d discrete element model and used this model to investigate the fault system over active diapirs the model reproduces some common features observed in physical experiments and natural examples the discrete element results show that most faults initiate near the model surface and have displacement decreasing downward in addition model results indicate that the earliest fault working as the master fault has a strong influence on the subsequent fault pattern the footwall of the master fault is mainly deformed by arc parallel stretching and develops a subradial fault pattern whereas the hanging wall is deformed by both arc parallel stretching and gliding along the master fault and top of salt and hence develops both parallel and oblique faults model results replicate the fault pattern and deformation mechanism of the reitbrook dome germany

kinematic modelling of extensional fault propagation folding abstract many studies have shown that in extensional basins discrete faulting at depth is commonly linked to more distributed deformation in particular folding at higher levels such extensional fault propagation folds are particularly common where there is a distinct mechanical contrast between faulted basement and sedimentary cover outcrop and analogue modelling studies indicate that such folds form as upward widening zones of distributed deformation monoclines above discrete faults at depth with increasing displacement strain the folds are cut by faults as they propagate upwards into the cover to date however there has been little investigation into the kinematics of linked basement faulting and extensional fault propagation folding here we present a two dimensional kinematic model of linked basement faulting and fault propagation folding which is based upon trishear the model allows investigation of the influence of shear zone geometry and the rate of fault propagation upon the style of folds and the strains associated with them the evolution of linked basement faulting and folding predicted by the model is compared in detail to that observed in an analogue model the kinematic model reproduces well many of the features seen both in the analogue model and reported from outcrop and seismic studies

discrete element simulations of gravitational volcanic deformation 1 deformation structures and geometries 1 we have carried out two dimensional particle dynamics simulations of granular piles subject to frictional coulomb failure criteria to gain a first order understanding of different modes of gravitational deformation within volcanoes under uniform basal and internal strength conditions granular piles grow self similarly developing distinctive stratigraphies morphologies and structures piles constructed upon cohesive substrates exhibit particle avalanching forming outward dipping strata and angle of repose slopes systematic decreases in basal strength lead to progressively deeper and steeper internal detachment faults and slip along a basal decollement landslide forms grade from shallow slumps to deep seated landslide and finally to axial subsidence and outward flank displacements or volcanic spreading surface slopes decrease and develop concave up morphologies with decreasing decollement strength depositional layers tilt progressively inward spatial variations in basal strength cause lateral transitions in pile structure stratigraphy and morphology this approximation of volcanoes as coulomb granular piles reproduces the richness of deformational structures and surface morphologies in many volcanic settings the gentle slopes of hawaiian volcanoes and olympus mons on mars suggest weak basal decollements that enable volcanic spreading high angle normal faults favored above weak decollements are interpreted in both settings and may explain catastrophic sector collapse in hawaii and broad aureole deposits surrounding olympus mons in contrast steeper slopes and shallow detachment faults predominate in the canary islands thought to lack a weak decollement favoring smaller more frequent slope failures than predicted for hawaii the numerical results provide a useful predictive tool for interpreting dynamic behavior and associated geologic hazards of active volcanoes

novel three pattern decomposition of global atmospheric circulation generalization of traditional two dimensional decomposition this study investigates the differences and connections between the three pattern decomposition of global atmospheric circulation the representation of the horizontal vortex circulation in the middle high latitudes and the local partitioning of the overturning circulation in the tropics it concludes that the latter two methods are based on the traditional two dimensional 2d decomposition of the vortex and divergent circulations in the fluid dynamics and that the three pattern decomposition model is not a simple superposition of the two traditional methods but a new three dimensional 3d decomposition of global atmospheric circulation the three pattern decomposition model can decompose the vertical vorticity of atmosphere into three parts one part is caused by the horizontal circulation whereas the other two parts are induced by divergent motions which correspond to the zonal and meridional circulations the diagnostic results from the decomposed vertical vorticities accord well with the classic theory the atmospheric motion at 500 hpa is quasi horizontal and nondivergent and can represent the vertical mean state of the entire atmosphere the analysis of the climate characteristics shows that the vertical vorticities of the zonal and meridional circulations are the main cause of the differences between the three pattern circulations and traditional circulations the decomposition of the vertical vorticity by the three pattern decomposition model offers new opportunities to quantitatively study the interaction mechanisms of the rossby hadley and walker circulations using the vorticity equation