geometry and evolution of salt structures in a marginal rift basin of the gulf of mexico east texas the geometry and distribution of salt structures in the east texas basin shown in an isometric block diagram reveal that a minimum of 1 500 m of mid jurassic louann salt accumulated in a north northeast trending trough floored by thinned continental crust above a threshold thickness of 600 m salt was mobilized by 1 loading beneath a carbonate wedge 2 differential loading by prograding terrigenous clastics and 3 basin edge tilting and erosion salt structures evolved from salt pillows to active diapirs with maximum gross growth rates of 400 to 530 m m y each stage lasted 10 to 30 m y three generations of diapirs were successively activated in different areas by different forces

postglacial relative sea level histories along the eastern canadian coastline abstract we have assembled a database of relative sea level rsl data points from the eastern coast of canada from hudson bay to the border with the usa in compiling this database we have critically reviewed 1092 radiocarbon dated samples from raised beaches isolation basins intertidal and marine deposits and archaeological indicators to produce 405 sea level index points and 687 sea level limiting points our comprehensive systematic and quality controlled rsl database allowed for the reconstruction of the postglacial evolution of 34 regions of eastern canada providing new basin scale insights into the processes driving rsl changes in the last 16 ka the combination of a database of sea level index points with an innovative empirical bayesian spatio temporal statistical model provided new insights into rates and magnitude of the spatially variable glacial isostatic adjustment gia which dominated the postglacial rsl evolution in this sector of north america a continuous postglacial rsl fall is observed at latitudes 50 n with higher rates up to 35 mm a 1 recorded in southeastern hudson bay at lower latitudes the evolution is non monotonic with rsl that dropped to a spatially variable early holocene lowstand followed by a mid holocene highstand and eventually a gradual drop to present rsl this pattern is particularly evident in the st lawrence corridor along the majority of the newfoundland new brunswick and western nova scotia coasts a late pleistocene early holocene rsl lowstand was followed by a continuous rise through the holocene at the margin of the former ice sheet i e eastern nova scotia our data identify a continuous rsl rise through the holocene these records are characterized by decreasing rates of rsl rise through time commencing with a rapid rise during the early holocene up to 17 mm a 1 a slowdown in the mid holocene average rates 9 mm a 1 and a further reduction in the late holocene average rates

early holocene greenland ice mass loss likely triggered earthquakes and tsunami abstract due to their large mass ice sheets induce significant stresses in the earth s crust stress release during deglaciation can trigger large magnitude earthquakes as indicated by surface faults in northern europe although glacially induced stresses have been analyzed in northern europe they have not yet been analyzed for greenland we know that the greenland ice sheet experienced a large melting period in the early holocene and so here we analyze glacially induced stresses during deglaciation for greenland for the first time instability occurs in southern greenland where we use a combined analysis of past sea level indicators and a model of glacially induced fault reactivation to show that deglaciation of the greenland ice sheet may have caused a large magnitude earthquake or a series of smaller magnitude earthquakes around 10 600 years ago offshore south western greenland the earthquake s may have shifted relative sea level observations by several meters if the earthquake induced stress release was created during a single event it could have produced a tsunami in the north atlantic ocean with runup heights of up to 7 2 m in the british isles and up to 7 8 m along canadian coasts

using relative sea level data to constrain the deglacial and holocene history of southern greenland this paper presents new holocene relative sea level rsl data collected from isolation basins close to the town of paamiut in south west greenland the data shows a rapid fall from a marine limit of c 52 m asl at c 10 9 cal ka bp to close to present by c 9 5 cal ka bp at rates of up to c 32 mm yr falling below present for the majority of the holocene before rising to present in the last 2000 years the elevation of the rsl lowstand is not well constrained but was at least below 3 m this pattern of rapid rsl fall during the early holocene matches the pattern seen at other southern greenland locations suggesting rapid largely simultaneous ice retreat from the area surrounding the qassimiut lobe at the start of the holocene occurring c 2000 years after the initial deglaciation of the extreme southern tip of greenland the rsl histories from this and other southern greenland locations are distinct to those recorded further north along the west coast and are in broad agreement with a pattern of vertical land motion and rsl predicted by the huy2 model simpson et al 2009 which predicts an 80 m drop in the contribution of vertical land motion to rsl at 10 cal ka bp between sisimiut and paamiut on the west coast despite this broad scale spatial agreement between the rsl data and the huy2 model it fails to satisfactorily predict the holocene rsl histories at paamiut and other southern greenland locations sensitivity tests indicate that the data model misfits are most likely due to an over estimate of the forcing during the holocene thermal maximum or the response to this forcing in southern greenland and error in the north american ice sheets component of the background deglaciation model our new data suggests that much of the southern part of the ice sheet acted differently to the area further north however rsl changes at paamiut are also largely impacted by regional and larger scale processes including a bulls eye of uplift centred on the west the impact of the holocene thermal maximum and the influence of the collapse of the north american ice sheets

evolution of salt structures during burial of salt sheets on the slope northern gulf of mexico abstract shallow buried allochthonous salt sheets are the dominant type of salt structure along the lower slope of the northern gulf of mexico trailing landward margins of the sheets are buried during continental margin progradation while their leading edges advance basinward under thin cover during burial a series of daughter structures including stocks massifs and remnant structures evolved as the sheet was segmented by extension and differential loading during extension fault bound basins on the upper surface of the sheet initiated the growth of salt rollers some rollers matured into stocks and massifs as sediment accumulated rapidly in circular salt withdrawal basins that were localized over the initial fault bound basins lateral extension is a key mechanism in initiating salt structural evolution however simple vertical subsidence of sediments is the primary displacement mechanism where the salt is completely displaced a salt weld discontinuity identifies its former stratigraphic position a variety of structures in the eastern green canyon area have been identified overlying a neogene salt weld including remnant salt structures mature stocks massifs and sedimentary structures such as turtle structure anticlines

style and timing of salt movement in the persian gulf basin offshore iran insights from halokinetic sequences adjacent to the tonb e bozorg salt diapir abstract the variations in the rate of salt rise is reflected in the sedimentary sequences adjacent to salt diapirs and provides insights into the style of salt movement sedimentation interaction and the timing of halokinetic phases episodic movement of salt diapir is defined by wedge and tabular shaped salt related sedimentary strata halokinetic sequences adjacent to the diapir detailed mapping of depositional strata on 2d seismic sections adjacent to salt diapirs on the tonb e bozorg island persian gulf sw iran reveals the presence of a series of sedimentary sequences related to the halokinetic activity of two salt source layers the hormuz and fars salts respectively the hormuz salt deposited in the uppermost proterozoic mobilized in the lower paleozoic and then continued to move periodically to present and to create the deep salt structures in the tonb e bozorg region the fars salt deposited in the lower miocene and then started rising and created the central salt structure the tonb e bozorg island and several peripheral ring like salt structures around the island our results reveal that both the salt layers within the tonb e bozorg region grew by downbuilding and continued to move periodically by passive and active diapirism to the present salt movement sedimentation interaction during salt diapirism influences petroleum play and therefore is of interest in petroleum geoscience

structure and quantification of processes controlling the evolution of the inverted ne german basin abstract a ne sw reflection seismic transect crossing the entire ne german basin negb was investigated in detail to study the interaction between tectonics and sedimentation during the multiphase evolution of the region by restoring a geological section across the post rotliegend the kinematic evolution was reconstructed and rates of important geological processes such as erosion or basin shortening were quantified the present day structural style of the negb is the result of several major deformation events 1 regional subsidence accompanied by local thin skinned e w extension during the permo triassic jurassic was followed by basin inversions at the 2 jurassic cretaceous and at the 3 cretaceous tertiary boundary zechstein salt played an important role since mobile zechstein evaporites decoupled the supra salt from the sub salt succession and allowed the transmission of deformation over a large distance of major significance to the late cretaceous structural development was the crustal scale upthrusting of the calfoerde block along the gardelegen fault at the southern basin margin the accompanying horizontal shortening has a minimum value of 9 km and led to the development of thrusts and folds within the post zechstein succession

surface fault slip associated with the 2004 parkfield california earthquake surface fracturing occurred along the san andreas fault the subparallel southwest fracture zone and six secondary faults in association with the 28 september 2004 m 6 0 parkfield earthquake fractures formed discontinuous breaks along a 32 km long stretch of the san andreas fault sense of slip was right lateral only locally was there a minor 1 11 mm vertical component of slip right lateral slip in the first few weeks after the event early in its afterslip period ranged from 1 to 44 mm our observations in the weeks following the earthquake indicated that the highest slip values are in the middle mountain area northwest of the mainshock epicenter creepmeter measurements indicate a similar distribution of slip surface slip along the san andreas fault developed soon after the mainshock field checks in the area near parkfield and about 5 km to the southeast indicated that surface slip developed more than 1 hr but generally less than 1 day after the event slip along the southwest fracture zone developed coseismically and extended about 8 km sense of slip was right lateral locally there was a minor to moderate 1 29 mm vertical component of slip right lateral slip ranged from 1 to 41 mm surface slip along secondary faults was right lateral the right lateral component of slip ranged from 3 to 5 mm surface slip in the 1966 and 2004 events occurred along both the san andreas fault and the southwest fracture zone in 1966 the length of ground breakage along the san andreas fault extended 5 km longer than that mapped in 2004 in contrast the length of ground breakage along the southwest fracture zone was the same in both events yet the surface fractures were more continuous in 2004 surface slip on secondary faults in 2004 indicated previously unmapped structural connections between the san andreas fault and the southwest fracture zone further revealing aspects of the structural setting and fault interactions in the parkfield area

the world stress map database release 2016 crustal stress pattern across scales abstract knowledge of the present day crustal in situ stress field is a key for the understanding of geodynamic processes such as global plate tectonics and earthquakes it is also essential for the management of geo reservoirs and underground storage sites for energy and waste since 1986 the world stress map wsm project has systematically compiled the orientation of maximum horizontal stress shmax for the 30th anniversary of the project the wsm database has been updated significantly with 42 870 data records which is double the amount of data in comparison to the database release in 2008 the update focuses on areas with previously sparse data coverage to resolve the stress pattern on different spatial scales in this paper we present details of the new wsm database release 2016 and an analysis of global and regional stress pattern with the higher data density we can now resolve stress pattern heterogeneities from plate wide to local scales in particular we show two examples of 40 60 shmax rotations within 70 km these rotations can be used as proxies to better understand the relative importance of plate boundary forces that control the long wave length pattern in comparison to regional and local controls of the crustal stress state in the new wsm project phase iv that started in 2017 we will continue to further refine the information on the shmax orientation and the stress regime however we will also focus on the compilation of stress magnitude data as this information is essential for the calibration of geomechanical numerical models this enables us to derive a 3 d continuous description of the stress tensor from point wise and incomplete stress tensor information provided with the wsm database such forward models are required for safety aspects of anthropogenic activities in the underground and for a better understanding of tectonic processes such as the earthquake cycle

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

a systematic technique for the sequential restoration of salt structures abstract a method is described for the sequential restoration of cross sections in areas of salt tectonics where deformation is confined to the salt and higher layers the subsurface geometry evolves with time through the interaction of various processes sedimentation compaction isostatic adjustment thermal subsidence if present faulting and salt withdrawal diapirism the technique systematically calculates and removes the effects of each of these processes during specified time intervals defined by the interpreted horizons it makes no assumptions about salt kinematics and generally results in the area of the salt layer changing through time the method is described for restoration of extensional terranes but it is also suitable for areas of contractional salt tectonics with only minor modifications after converting an interpreted seismic profile to depth the top layer is stripped off and the underlying section is decompacted according to standard porosity depth functions a deep baseline unaffected by compaction or deformation is used to restore any isostatic compensation or thermal subsidence isostasy is calculated according to the airy model and differential sedimentary loading across a section is shown to be approximately balanced by changes in salt thickness so that the load is evenly distributed after these processes have been reversed the resulting geometry and the seismic data are used to create the sea floor template for structural restoration fault offsets are removed and the layers down to the top salt are restored to this template while the base salt remains fixed the resulting space between the restored top salt and the fixed base salt defines the restored salt geometry in addition the difference between the sea floor template and a fixed sea level provides a measure of the change in water depth ignoring eustatic changes in sea level the technique is applied to an interpreted seismic profile from the eastern green canyon ewing bank area of offshore louisiana the section is characterized by a variety of salt structures including salt rollers a diapiric massif a remnant salt sheet and a salt weld which are shown to have derived from an originally continuous salt sheet which has been modified by sedimentary loading early loading created vertical basin growth that was accommodated primarily by salt withdrawal and associated diapiric rise through the process of downbuilding once the salt weld formed continued sedimentation was accommodated by a lateral increase in basin size caused by down dip extension on listric growth faults

a high resolution record of greenland mass balance we map recent greenland ice sheet elevation change at high spatial 5 km and temporal monthly resolution using cryosat 2 altimetry after correcting for the impact of changing snowpack properties associated with unprecedented surface melting in 2012 we nd good agreement 3 cm yr bias with airborne measurements with the aid of regional climate and rn modeling we compute high spatial and temporal resolution records of greenland mass evolution which correlate r 0 96 with monthly satellite gravimetry and reveal glacier dynamic imbalance during 2011 2014 greenland mass loss averaged 269 51 gt yr atmospherically driven losses were widespread with surface melt variability driving large uctuations in the annual mass de cit terminus regions of ve dynamically thinning glaciers which constitute less than 1 of greenland s area contributed more than 12 of the net ice loss this high resolution record demonstrates that mass de cits extending over small spatial and temporal scales have made a relatively large contribution to recent ice sheet imbalance

microearthquakes illuminate the deep structure of the endglacial parvie fault northern sweden at 155 km the parvie fault is the world s longest known endglacial fault egf it is located in northernmost sweden in a region where several kilometre scale egfs have been identified based on s

evolution of stocks and massifs from burial of salt sheets continental slope northern gulf of mexico salt structures in a 4000 km sup 2 region of the continental slope the northeast green canyon area include stocks massifs remnant structures and an allochthonous sheet salt withdrawal basins include typical semicircular basins and an extensive linear trough that is largely salt free counterregional growth faults truncate the landward margin of salt sheets that extend 30 50 km to the sigsbee escarpment the withdrawal basins stocks and massifs occur within a large graben between an east northeast trending landward zone of shelf margin growth faults and a parallel trend of counterregional growth faults located 48 64 km basinward the graben formed by extension and subsidence as burial of the updip portion of a thick salt sheet produced massifs and stocks by downbuilding differential loading segmented the updip margin of the salt sheet into stocks and massifs separated by salt withdrawal basins initially low relief structures evolved by trap door growth as half graben basins buried the salt sheet remnant salt structures and a turtle structure anticline overlay a salt weld disconformity in sediments formerly separated by a salt sheet age of sediments below the weld is inferred to be be late miocene to early pliocene 4 6 5 3 ma age of sediments above the weld is late pliocene 2 8 3 5 ma the missing interval of time 1 2 5 ma more is the duration between emplacement of the salt sheet and burial of the sheet sheet extrusion began in the late miocene to early pliocene and sheet burial began in the late pliocene in the area of the submarine trough to early pleistocene in the area of the massifs less

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

pre break up palaeostress state along the east greenland margin this paper describes intraplate deformation and the palaeostress state along the east greenland margin during the paleocene between 65 and 55 myr ago prior to the onset of the ne atlantic spreading it is shown that the pre break up deformation is the result of dip oblique strike slip tectonics in the se and compressive tectonics in the north the reduced palaeostress tensors derived from inversion of the fault slip data show that the maximum horizontal stress 1 is compressive and the orientations of 1 change from ene wsw in the south to nne ssw in the north the reconstructed palaeostress trajectory map demonstrates that the 1 orientations reflect the plate motion path and define small circles whereas the trends of the minimum horizontal stress 3 converge and cluster around an area in the arctic that is interpreted as the rotation pole of greenland the intraplate deformation folding and uplift that affected the greenland and european margins the barents sea and the north sea during the paleocene can be explained by the counter clockwise rotation of greenland the present paper calculates the pole of rotation of greenland using the kinematics of brittle faults along the plate margin and the palaeostress derived from inversion of fault slip data analysis as an indicator of motion path

intraplate volcanism off south greenland caused by glacial rebound plate tectonic mechanisms explain most of the dominant types of volcanism intraplate volcanism has been attributed to hot spots associated with mantle plumes though alternative explanations have been proposed for settings not fed by plumes we report young intraplate volcanism in an amagmatic margin south of greenland in a 40 ma old plate an elongated structure with a length of 110 km and a height of 2500 m above basement extends at an oblique angle to the mid atlantic ridge and the fracture zones we propose that this structure is related to reactivation of a rudimentary fracture zone by edge driven convection across minna fracture zone and partial melting caused by glacial rebound during the periodic melting of ice on greenland in the last 3 ma

constraints on the greenland ice sheet since the last glacial maximum from sea level observations and glacial rebound models abstract geomorphological descriptions of changes in the extent of the greenland ice sheet gis have been combined with glacial isostatic adjustment models to reproduce the sea level history of greenland since the last glacial maximum lgm the contribution to past sea level change around greenland due to ice load changes outside of that region has been considerable 10 s of meters while still contributing a rise of several mm yr 1 today the isostatic contribution to relative sea level around greenland from changes in the gis is found by iteratively perturbing preliminary ice models with different lgm extents and deglaciation starting times the resulting first order model that provides the best agreement between observed and predicted sea level contributes 3 1 and 1 9 m water equivalent of additional ice relative to present day ice volumes at the lgm and younger dryas respectively the gis in most areas does not appear to have extended far onto the continental shelf the exceptions being southern most southwest greenland and northern east greenland as well as at the coalescence of the northwest greenland and innuitian ice sheets changes in ice thickness since the lgm were 500 m along the present day outer coast and 1500 m along some parts of the present day ice margin the observed mid to late holocene fall in sea level to below the present day level and the subsequent transgression seen in some areas implies that the gis retreated behind the present day margin by distances of the order of 40 km before readvancing

gravitational viscoelastic postseismic relaxation on a layered spherical earth viscoelastic relaxation of a ductile asthenosphere underlying a purely elastic plate is a strong candidate process for explaining anomalous rates of crustal deformation observed following large earthquakes the nongravitational treatment of pollitz 1992 which is valid on a global scale and includes the effects of compressibility is here extended to permit the calculation of gravitational viscoelastic relaxation for a specified spherically layered viscoelastic rheology following an earthquake in an elastic layer the simple approximations we adopt make the resulting treatment particularly suitable for near field calculations for an asthenosphere with a maxwell rheology the effect of gravitational coupling is manifested only many relaxation times after the earthquake as obtained by previous investigators its effect is generally to speed up the long wavelength component of the relaxation process and attenuate the overall vertical displacement pattern several subtle features common to the relaxation behavior from several different fault types thrust rift and strike slip are identified the effect of gravitational coupling on horizontal displacements is consistent with flexure of the upper elastic plate driven by the corresponding effects on the vertical displacement stress diffusion away from the source region generally exhibits pulse like behavior which is dispersive in both space and time if the asthenosphere is confined to a relatively narrow channel then the dispersion branches governing relaxation are radically altered and stress diffusion effects far from the coseismic rupture zone exhibit a complicated time dependence reflecting the competing tendencies of toroidal and spheroidal mode relaxation

restoration of cross sections to constrain deformation processes of extensional terranes abstract restoring balanced cross sections constrains the possible deformation processes affecting extensional terranes with a ductile substratum such as salt and syndeformational sedimentation cross sections are divided into fault blocks and shear domains each of which can be undeformed with a different set of parameters the success of restorations is judged by compatibility between the blocks and the reasonableness of the restored structures fault blocks in physical models restore with simple shear at about 60 dipping in the direction which removes extension corresponding to an antithetic orientation in the hangingwalls of normal growth faults and subparallel to the fault in the footwall other components of the deformation are rigid rotation translation and decompaction shear angles inferred from natural examples are more varied ranging from vertical to moderately inclined nearly always dipping in a direction that removes extension

using commercial finite element packages for the study of earth deformations sea levels and the state of stress summary modifications to commercial finite element fe packages must be applied before they can be used for geophysical studies involving long wavelength deformation or viscoelasticity this paper provides in detail how and why the commercial codes have to be modified when incompressibility is assumed both the non self gravitating flat earth and self gravitating spherical earth will be considered the latter involves an iterative procedure which converges within 5 iterations this is demonstrated both analytically and numerically in addition implementation of the gravitationally self consistent sea level equation on a self gravitating spherical earth is also described good agreement between numerical results obtained with this coupled finiteelement method and the conventional spectral method is also demonstrated in all cases the interpretation of the outputs of fe models are particularly important in modelling the state of stress

a data calibrated distribution of deglacial chronologies for the north american ice complex from glaciological modeling article i nfo past deglacial ice sheet reconstructions have generally relied upon discipline specific constraints with no at tention given to the determination of objective confidence intervals reconstructions based on geophysical inversion of relative sea level rsl data have the advantage of large sets of proxy data but lack ice mechanical constraints conversely reconstructions based on dynamical ice sheet models are glaciologically self consistent but depend on poorly constrained climate forcings and sub glacial processes as an example of a much better constrained methodology that computes explicit error bars we present a dis tribution of high resolution glaciologically self consistent deglacial histories for the north american ice com plex calibrated against a large set of rsl marine limit and geodetic data the history is derived from ensemble based analyses using the 3d mun glacial systems model and a high resolution ice margin chronol ogy derived from geological and geomorphological observations isostatic response is computed with the vm5a viscosity structure bayesian calibration of the model is carried out using markov chain monte carlo methods in combination with artificial neural networks trained to the model results the calibration provides a posterior distribution for model parameters and thereby modeled glacial histories given the observational data sets that takes data uncertainty into account final ensemble results also account for fits between com puted and observed strandlines and marine limits given the model including choice of calibration parameters input and constraint data sets and vm5a earth rhe ology we find the north american contribution to mwp1a was likely between 9 4 and 13 2 m eustatic over a 500 year interval this is more than half of the total 16 to 26 m meltwater pulse over 500 to 700 years with lower values being more probable indicated by the barbados coral record fairbanks 1989 peltier and fairbanks 2006 if one assumes a 5 meter living range for the acropora palmata coral 20 ka ice volume for north america was likely 70 1 2 0 m eustatic or about 60 of the total contribution to eustatic sea level change we suspect that the potentially most critical unquantified uncertainties in our analyses are those related to model structure especially climate forcing deglacial ice margin chronology and earth rheology

evidence for and implications of self healing pulses of slip in earthquake rupture dislocation time histories of models derived from waveforms of seven earthquakes are discussed in each model dislocation rise times the duration of slip for a given point on the fault are found to be short compared to the overall duration of the earthquake 10 however in many crack like numerical models of dynamic rupture the slip duration at a given point is comparable to the overall duration of the rupture i e slip at a given point continues until information is received that the rupture has stopped propagating alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are 1 the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes 2 earthquakes are composed of a sequence of small dimension short duration events that are separated by locked regions barriers 3 rupture occurs in a narrow self healing pulse of slip that travels along the fault surface evidence is discussed that suggests that slip durations are indeed short and that the self healing slip pulse model is the most appropriate explanation a qualitative model is presented that produces self healing slip pulses the key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity the model has the following features high static strength of materials kilobar range low static stress drops in the range of tens of bars and relatively low frictional stress during slip less than several hundreds of bars it is suggested that the reason that the average dislocation scales with fault length is because large amplitude slip pulses are difficult to stop and hence tend to propagate large distances this model may explain why seismicity and ambient stress are low along fault segments that have experienced large earthquakes it also qualitatively explains why the recurrence time for large earthquakes may be irregular

reply to comment by hampel et al on stress and fault parameters affecting fault slip magnitude and activation time during a glacial cycle reply to comment by hampel et al on stress and fault parameters affecting fault slip magnitude and activation time during a glacial cycle

allochthonous salt structure and stratigraphy of the north eastern gulf of mexico ii structure the kinematic evolution of allochthonous salt in the north eastern gulf of mexico proceeds in three stages 1 since its middle jurassic deposition the louann salt was loaded by sediments causing episodic basinward movement of salt ultimately leading to large concentrations of salt masses in a slope environment by the end of the lower cretaceous 2 a regime of starved sedimentation during late cretaceous and early oligocene is responsible for the stabilization of these early salt accumulations 3 with renewed rapid accumulation of sediments during the neogene and pliocene extensive allochthonous salt tongues and sheets formed by gravity spreading within the younger sediments of the slope

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

directly dating postglacial greenlandic land surface emergence at high resolution using in situ 10be postglacial emergence curves are used to infer mantle rheology delimit ice extent and test models of the solid earth response to changing ice and water loads such curves are rarely produced by direct dating of land emergence rather most rely on the presence of radiocarbon datable organic material and inferences made between the age of sedimentary deposits and landforms indicative of former sea level here we demonstrate a new approach 10 be dating to determine rates of postglacial land emergence in two different settings in southern greenland narsarsuaq igaliku we date directly the exposure as relative sea level fell of gravel beaches and rocky outcrops allowing determination of rapid post younger dryas emergence in western greenland kangerlussuaq we constrain holocene isostatic response by dating the sequential stripping of terrace sediment driven by land surface uplift relative sea level fall and resulting fluvial incision the technique we employ provides high temporal and elevation resolution important for quantifying rapid emergence immediately after deglaciation and less rapid uplift during the middle holocene 10 be constrained emergence curves can improve knowledge of relative sea level change by dating land emergence along rocky coasts at elevations and locations where radiocarbon datable sediments are not present and without the lag time needed for organic material to accumulate

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

induced stresses and fault potential in eastern canada due to a realistic load a preliminary analysis summary in order to understand the causal relation between postglacial rebound and earthquakes a simple disc load model is used to 1 calculate stresses induced in the lithosphere and mantle by glacial loading melting and postglacial rebound and 2 evaluate the effect of glacial loading rebound on the failure potential for earthquakes in the upper crust the dependence of the failure potential and the actual mode of failure on the coefficient of friction the ambient tectonic stress magnitude direction the stress due to the overlying rocks and lithospheric thickness are investigated prominent features of this paper are the inclusion of 1 a viscoelastic mantle and thus the migration of stress and 2 the ambient tectonic stress and overburden stress contributions in the calculation of the total stress field it is assumed that throughout the earth there are optimally oriented pre existing virtual faults that are initially close to but not at failure thus a time dependent quantity called dfsm related to the coulomb mohr failure criterion can be defined such that a negative value of dfsm would advocate faulting or earthquake activities whereas a positive value of dfsm would promote stability the results indicate that under all combinations of tectonic stress magnitude and overburden stress crustal loading promotes fault stability directly underneath the load upon the removal of the load thrust faulting is predicted within the ice margin if the horizontal stress s induced by the overburden is greater than or equal to the vertical component s of the overburden stress 121 where sjs under this condition theory predicts that faulting or earthquake activity should have reached a maximum immediately after deglaciation if the horizontal stress induced by the overburden is less than the vertical component of the overburden stress 1 l then theory predicts fault stability within the ice margin the theory predicts fault instability both north and south of the ice margin the mode of failure however is completely determined by the value of i the trade off between the tectonic stress magnitude and the overburden stress parameter 1 is also investigated it is shown that a larger tectonic stress magnitude can be used to compensate a smaller value of 1 the results of this analysis show that variations in the coefficient of friction lithospheric thickness and a ductile zone below the upper crust do not significantly affect the above conclusions

geologically constrained seismic imaging workflow we present the geologically constrained workflow for velocity model building as a case study from offshore brazil the workflow involves basin reconstruction gravity modeling and seismic interpretation in addition to standard prestack depth migration psdm model building tools building a salt model based on seismic evidence can be highly nonunique in a geologically constrained seismic processing workflow the main aim is to use geologic understanding with geophysical models and datasets to improve an input velocity realization for the psdm loop thereby improving image quality all of these methods are inherently uncertain and a final model is based on a range of subjective choices thus a final result that agrees with all sciences still can be completely wrong however an understanding of these choices enables a unique way of testing and constraining the number of antimodels velocity models that fit the observations but are different from the final result this can reduce time spent and uncertainty in geologic evaluation

allochthonous salt structure and stratigraphy of the north eastern gulf of mexico part ii structure abstract the kinematic evolution of allochthonous salt in the north eastern gulf of mexico proceeds in three stages 1 since its middle jurassic deposition the louann salt was loaded by sediments causing episodic basinward movement of salt ultimately leading to large concentrations of salt masses in a slope environment by the end of the lower cretaceous 2 a regime of starved sedimentation during late cretaceous and early oligocene is responsible for the stabilization of these early salt accumulations 3 with renewed rapid accumulation of sediments during the neogene and pliocene extensive allochthonous salt tongues and sheets formed by gravity spreading within the younger sediments of the slope autochthonous salt allochthonous salt and detached allochthonous salt are typical stages of evolution major down to the basin growth faults separate allochthonous salt sheets from their original feeder stocks extension along down to the basin master growth faults is compensated mainly by salt withdrawal and partly by basinward shortening

paleogeographic evolution of early deep water gulf of mexico and margins jurassic to middle cretaceous comanchean the paleobathymetric configuration of the early gulf of mexico is inferred from 1 cretaceous carbonate shelf margins interpreted from seismic profiles and other stratigraphic data 2 distribution of jurassic and cretaceous platform and basinal facies and 3 hindcasting of subsidence history in the central basin substantial paleogeographic ambiguity results from uncertainty about 1 kinematics and timing of late triassic to jurassic extensional opening of the gulf basin which probably involved major strike slip faulting 2 the magnitude of subsequent compressive deformation on the western and southern basin margins and 3 possible accretion of allochthonous terranes the initial sub sea level topographic depression created by crustal extension is manifested by the distribution of callovian pre marine salt and oxfordian basinal marine facies late jurassic sea floor spreading split the main salt body and created a central deep water 1 km trough from the oxfordian to early neocomian ramp like platform margins generally underwent net retreat except in the northern gulf where major clastic progradation took place carbonate platform margins with sufficient paleorelief for geometric expression on seismic profiles developed early in the cretaceous these cretaceous carbonate margins exhibit a variety of architectural styles including 1 in the northwestern gulf two cycles of progradation coahuilan and comanchean terminated by drowning events 2 in the southwestern gulf a single cycle of progradation 3 continuous aggradation along the florida and campeche escarpments paleobathymetric relief across cretaceous carbonate margins ranges from high and steep to low relief to ramplike the close of comanchean drowning event greatly and permanently reduced the extent of circum gulf carbonate platforms and especially rimmed margins locations of cretaceous carbonate margins were influenced by basement hinge zones and paleohighs developed on attenuated continental crust by the distribution of salt and by clastic progradation eustacy is commonly invoked to explain behavior and architecture of carbonate margins in the gulf but other paleoenvironmental variables such as nutrient abundance are probably important as well

viscous gravitational relaxation summary this paper is concerned with a detailed examination of the response of maxwell models of the planet to surface mass loads particular attention is devoted to an examination of the factors which determine the isostatic response since the understanding of this response is crucial in a number of different geodynamic problems one particular example which we discuss in detail is concerned with the prediction of free air gravity anomalies produced by large scale deglaciation events using the methods developed here we are able to provide the first direct assessment of the importance of initial isostatic disequilibrium on the observed relative sea level variations and free air gravity anomalies forced by the melting of the laurentide ice sheet we are therefore able to estimate the extent to which such initial disequilibrium might influence the inference of mantle viscosity from isostatic adjustment data our calculations establish that free air gravity data although they are sensitive to the degree of initial disequilibrium provide an extremely high quality constraint upon the viscosity of the lower mantle

a model of greenland ice sheet deglaciation constrained by observations of relative sea level and ice extent an ice sheet model was constrained to reconstruct the evolution of the greenland ice sheet gris from the last glacial maximum lgm to present to improve our understanding of its response to climate change the study involved applying a glaciological model in series with a glacial isostatic adjustment and relative sea level rsl model the model reconstruction builds upon the work of simpson et al 2009 through four main extensions 1 a larger constraint database consisting of rsl and ice extent data model improvements to the 2 climate and 3 sea level forcing components 4 accounting for uncertainties in non greenland ice the research was conducted primarily to address data model misfits and to quantify inherent model uncertainties with the earth structure and non greenland ice our new model termed huy3 fits the majority of observations and is characterised by a number of defining features during the lgm the ice sheet had an excess of 4 7 m ice equivalent sea level iesl which reached a maximum volume of 5 1 m iesl at 16 5 cal ka bp modelled retreat of ice from the continental shelf progressed at different rates and timings in different sectors southwest and southeast greenland began to retreat from the continental shelf by 16 to 14 cal ka bp thus responding in part to the bolling allerod warm event c 14 5 cal ka bp subsequently ice at the southern tip of greenland readvanced during the younger dryas cold event in northern greenland the ice retreated rapidly from the continental shelf upon the climatic recovery out of the younger dryas to present day conditions upon entering the holocene 11 7 cal ka bp the ice sheet soon became land based during the holocene thermal maximum htm 9 5 cal ka bp air temperatures across greenland were marginally higher than those at present and the gris margin retreated inland of its present day southwest position by 40 60 km at 4 cal ka bp which produced a deficit volume of 0 16 m iesl relative to present in response to the htm warmth our optimal model reconstruction lost mass at a maximum centennial rate of c 103 4 gt yr our results suggest that remaining data model discrepancies are affiliated with missing physics and sub grid processes of the glaciological model uncertainties in the climate forcing lateral earth structure and non greenland ice particularly the north american component finally applying the huy3 greenland reconstruction with our optimal earth model we generate present day uplift rates across greenland due to past changes in the ocean and ice loads with explicit error bars due to uncertainties in the earth structure present day uplift rates due to past changes are spatially variable and range from 3 5 to 7 mm a including earth model uncertainty

suppression of earthquakes by large continental ice sheets the interior regions of antarctica and greenland are aseismic no earthquake larger than body wave magnitude 4 5 5 0 is known for either except along coastal zones or continental shelves here i advance an explanation for this lack of seismic activity in terms of pressure effects produced by the continental ice sheets that mantle both continents

model for salt deformation on deep margin of central gulf of mexico basin based on available nonexclusive seismic data a preliminary model has been developed for salt deformation on the deep margin of the central gulf of mexico basin in this model the tertiary clastic wedge prograded to the basinward limit of original jurassic salt by the middle miocene as the salt and overburden thinned basinward lateral flow combined with a strong component of downward force exerted by subsiding voluminous middle miocene loading caused the basinward limit of the louann salt to effectively shear off deposition of the upper miocene and pliocene sediments was confined primarily shoreward of an incipient salt swell but pleistocene sediments were eventually able to breach the barrier deformation of the detached salt produced the features present on the slope today preliminary work indicates that most of the detached salt was propelled basinward and upsection toward the present sigsbee escarpment leaving pinch and swell salt structures behind the various types of residual salt structures have been formed as a result of differences in the history of sedimentary loading different stages of development of pinch and swell structures shown on seismic sections illustrate this model

validating velocities in the geoclaw tsunami model using observations near hawaii from the 2011 tohoku tsunami the ability to measure predict and compute tsunami flow velocities is of importance in risk assessment and hazard mitigation substantial damage can be done by high velocity flows particularly in harbors and bays even when the wave height is small moreover advancing the study of sediment transport and tsunami deposits depends on the accurate interpretation and modeling of tsunami flow velocities and accelerations until recently few direct measurements of tsunami velocities existed to compare with model results during the 11 march 2011 tohoku tsunami 328 current meters were in place around the hawaiian islands usa that captured time series of water velocity in 18 locations in both harbors and deep channels at a series of depths we compare several of these velocity records against numerical simulations performed using the geoclaw numerical tsunami model based on solving the depth averaged shallow water equations with adaptive mesh refinement to confirm that this model can accurately predict velocities at nearshore locations model results demonstrate tsunami current velocity is more spatially variable than waveform or height and therefore may be a more sensitive variable for model validation

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

estimates of south greenland late glacial ice limits from a new relative sea level curve abstract marine lacustrine isolation contacts from seven basins in the nanortalik area south greenland have been analysed and dated the basins were isolated from the sea as a consequence of isostatic rebound following deglaciation the isolation contacts were identified with litho and biostratigraphical analyses especially sedimentary changes grey scale analyses and analyses of macroscopical remains of plants and animals dating was performed by analytical mass spectroscopy radiocarbon dating of macrofossils and bulk sediment samples a slow initial relative sea level fall that begins at 13 8 cal ka bp changes to a rapid relative sea level fall before the sea level fell below the present day sea level just prior to 10 cal ka bp the emergence curve goes further back in time than any previous emergence curve constructed from greenland which reflects the early deglaciation of the studied region the glacio isostatic crustal rebound following deglaciation was around 110 m the sea level history indicates that the margin of the greenland ice sheet probably extended out to the shelf margin during the last glacial maximum and that the ice thickness must have been at least 1500 m over the outer coast thus the highest coastal mountains would have been ice covered which is surprising given their alpine character in addition the major part of the recession of the ice must have occurred relatively late and quickly maybe from 14 to 12 cal ka bp the late holocene transgression may at least in part be due to increased isostatic loading as a consequence of advancing glaciers during the neoglaciation

a forward modeling strategy for balancing cross sections 1 a strategy to balance cross sections of complex structures is documented and illustrated by the interpretation of a compressional structure in the deep water gulf of mexico the strategy is applicable to structures formed in sedimentary rocks under low temperatures in both compressional and extensional environments and involves the comparison of the observed structure with simple balanced forward models forward models generated using fault related fold theory help in understanding the processes and kinematics involved in the deformation further forward models are completely constrained and easy to balance whereas it is difficult to balance data therefore forward models are useful in evaluating ideas without completely solving the structure models are constructed assuming parallel behavior preservation of layer thickness no net distortion where layers are horizontal and conservation of bed length unmetamorphosed sedimentary rocks are generally observed to deform obeying the assumptions of parallel behavior in field map well and seismic data