china s yangtze estuary ii phosphorus and polycyclic aromatic hydrocarbons in tidal flat sediments abstract concentrations of phosphorus p and polycyclic aromatic hydrocarbons pahs were determined in tidal flat sediments from the yangtze estuary and hangzhou bay the amount of total p in surface sediments ranges from 18 0 to 31 4 mol g 1 along the southern coast the spatial and temporal distribution of p in tidal flats is closely related to geomorphological location and contaminant input especially in association with variations in hydrodynamic conditions speciation of p in sediments was extracted sequentially results show that calcium phases are dominant in the total p of tidal flat sediments which is similar to marine sediments the main diffusion of dissolved p is from overlying water to sediment in the coastal environment of the yangtze estuary two sediment cores from the baoshan bs and donghai dh sites were extracted for pah analysis the total concentration of pahs ranges from 0 061 to 7 618 g g 1 at the bs site and from 0 005 to 2 370 g g 1 at the dh site the distribution of total and individual pahs in the sediment shows a subsurface maximum following by decreased levels to the surface and with depth the pattern of pah abundance suggests that there has been significant petroleum contamination in the yangtze estuary a few individual pahs such as acenaphthalene and anthracene in surface samples of the two cores are in excess of current sediment quality criteria in the yangtze estuary the present study suggests that anthropogenic activities enhance contaminant inputs to the estuary

a fractal model for crustal deformation abstract we hypothesize that crustal deformation occurs on a scale invariant matrix of faults for simplicity we consider a two dimensional pattern of hexagons on which strike slip faulting occurs the behavior of the system is controlled by a single parameter the fractal dimension deformation occurs on all scales of faults the fractal dimension determines the fraction of the total displacement that occurs on the first order or primary faults the value of the fractal dimension can be obtained from the frequency magnitude relation for earthquakes our results are applied to the san andreas fault system in central california earthquake studies give d 1 90 we associate the main strand of the san andreas fault with the primary faults of our fractal system we predict that the relative velocity across the main strand is 2 93 cm yr the remainder of the relative velocity of 5 5 cm yr between the pacific and north american plates occurs on higher order faults the predicted value is in reasonably good agreement with the value 3 39 0 29 cm yr obtained from geological studies

orogen parallel flow during continental convergence numerical experiments and archean field examples using triaxial numerical experiments we investigated the evolution of the state of stress and that of the bulk instantaneous and fi nite strain during ongoing convergence and subsequent progressive tectonic unloading of a warm and buoyant continental lithosphere various unloading histories of the driving tectonic force were considered as the tectonic force progressively declines the instantaneous strain evolves from plane strain to horizontal constriction in a direction perpendicular to that of convergence and fi nally to horizontal fl attening during the progressive unloading of the tectonic force driving convergence bulk constrictional strain accommodates the release of accumulated gravitational stress the decline of the triaxial strain rates to low values reduces the potential for the orogen parallel linear fabric to be erased by horizontal fl attening this is confi rmed by the fi nite strain ellipsoid that evolves toward plane strain with a long axis parallel to the orogen in the ca 2 5 ga gawler and terre adelie cratons we have identifi ed a well preserved and widespread horizontal linear fabric as suggested by our numerical experiments we associate the development of this linear fabric with the waning stages of late archean convergence

high speed rupture in the first 20 s of the 2011 tohoku earthquake japan 1 the 2011 tohoku earthquake produced tens of meters of fault slip near the japan trench which generated devastating tsunami the rupture process before the huge slip is still unclear due to a lack of resolution here i perform a multiscale slip inversion analysis to examine the first 10 and 20 s of the rupture process and the whole rupture process at different scales the result shows that 4 s after the initiation this earthquake started with a relatively high speed rupture that had a peak slip rate faster than 1 m s and a rupture velocity comparable to 3 km s fourteen seconds after the initiation the rupture propagation direction changed from northward to westward near the edge of the m 7 3 foreshock coseismic slip area the stress release by the foreshock may contribute to the complex small scale rupture propagation which may appear to be slow rupture propagation when only looking at long period data

grain size effect on multi element concentrations in sediments from the intertidal flats of bohai bay china abstract in the intertidal flats of bohai bay china the spatial distribution of the grain size of sediments becomes coarser from landward to seaward to study the grain size effect on multi element concentrations in sediments samples along the coastline and 3 horizontal cross sections were collected from the intertidal flats of bohai bay china in 1998 total concentrations of 49 elements including alkali alkaline earth trace metal rare and rare earth elements were measured by icp aes icp ms and inaa the results show that sediment texture plays a controlling role on the concentrations and their spatial distribution principal component analysis and cluster analysis were carried out based on the grain sizes of the sediments and the samples were classified into 3 groups mud silt mud and silt significant differences among the element concentrations in the 3 groups were observed and the concentrations of the elements in each group are reported in this study most of the elements have their highest concentrations in the fine grained mud samples in comparison with the silt and silt mud samples with clay minerals possibly playing an important role in contrast concentrations of ba sr hf and zr are elevated in the coarse silt samples ba and sr may reside in feldspars while zr and hf are present in zircons landward to seaward spatial variation of element concentrations in the sediments is observed which is in line with the spatial distribution of the grain size and is related to the seawater hydrological dynamics in the intertidal flats

infrasonic forerunners exceptionally fast acoustic phases 1 a vapor cloud explosion occurred at an oil depot near buncefield in the uk in 2005 three infrasound arrays in the netherlands detected various stratospheric phases some of these phases appeared with celerities i e horizontal propagation velocity in the conventional range of 0 28 to 0 31 km s exceptionally fast arrivals infrasonic forerunners were identified with celerities of 0 31 to 0 36 km s these phases could be explained by head wave like propagation in a high velocity acoustic channel between 40 and 50 km height where stratospheric zonal winds reached values of 120 m s the manifestation of infrasonic forerunners is validated by modeling with raytracing through actual atmospheric models and determining the celerity apparent velocity and back azimuth one phase occurred with a celerity of 0 25 km s hence we propose a new celerity range for fast stratospheric phases of 0 31 to 0 36 km s and to lower the limit of the conventional range to 0 25 km s

stable and unstable damage evolution in rocks with implications to fracturing of granite summary we address the relation between the rock rigidity and crack density by comparing predictions of a viscoelastic damage rheology model to laboratory data that include direct microscopic mapping of cracks the damage rheology provides a generalization of hookean elasticity to a non linear continuum mechanics framework incorporating degradation and recovery of the effective elastic properties transition from stable to unstable fracturing and gradual accumulation of irreversible deformation this approach is based on the assumption that the density of microcracks is uniform over a length scale much larger than the length of a typical crack yet much smaller than the size of the entire deforming domain for a system with a sufficiently large number of cracks one can define a representative volume in which the crack density is uniform and introduce an intensive damage variable for this volume we tested our viscoelastic damage rheology against sets of laboratory experiments done on mount scott granite based on fitting the entire stress strain records the damage variable is constrained and found to be a linear function of the crack density an advantage of these sets experiments is that they were preformed with different loading paths and explicitly demonstrated the existence of stable and unstable fracturing regimes we demonstrate that the viscoelastic damage rheology provides an adequate quantitative description of the brittle rock deformation and simulates both the stable and unstable damage evolution under various loading conditions comparison between the presented data analysis of experiments with mount scott granite and previous results with westerly granite and berea sandstone indicates that granular or porous rocks have lower seismic coupling this implies that the portion of elastic strain released during a seismic cycle as brittle deformation depends on the lithology of the region hence upper crustal regions with thick sedimentary cover or fault zones with high degree of damage are expected to undergo a more significant inelastic deformation in the interseismic period compared to intact crystalline rocks

sulphur organic carbon and iron relationships in estuarine and freshwater sediments effects of sedimentation rate abstract concentrations of s organic c and fe were investigated in profiles of sediments from two estuarine systems in the sw of western australia in marine affected sediments inorganic s dominates total s and concentrations of total s correlate with fe and not with organic c in freshwater sediments organic s dominates total s and concentrations of total s correlate with organic c and not with fe molar fe s ratios in the estuarine sediments decrease with increasing salinity and approach unity for marine conditions net accumulation rates of s in sediments were estimated with a numerical computer model calibrated with published data on profiles of marine sediments for diffusion of so2 4 sedimentation rates and distributions of s measured depth integrated reduction rates of so2 4 in the marine affected estuarine sediments approach those obtained for fe limited marine conditions at similar rates of sedimentation measured concentrations of inorganic s in anoxic freshwater sediments fit a numerically calculated relationship between inorganic s and sedimentation rate

micro and macroscopic models of rock fracture summary the anelastic deformation of solids is often treated using continuum damage mechanics an alternative approach to the brittle failure of a solid is provided by the discrete fiber bundle model here we show that the continuum damage model can give exactly the same solution for material failure as the fiber bundle model we compare both models with laboratory experiments on the time dependent failure of chipboard and fiberglass the power law scaling obtained in both models and in the experiments is consistent with the power law seismic activation observed prior to some earthquakes

sedimentary iron phosphorus cycling under contrasting redox conditions in a eutrophic estuary abstract phosphorus p is often a limiting nutrient within freshwater and estuarine systems thus excess inputs of p from anthropogenic activities dominantly agriculture can induce eutrophication in receiving water bodies the sequestration of p within estuarine sediments is controlled by sorption and precipitation processes which are impacted by local redox conditions and burial environment despite the global spread of oxygen depletion in coastal marine systems p burial under reducing conditions remains poorly understood we investigated p cycling in relation to iron fe redox chemistry in sediments from the eutrophic peel harvey estuary in western australia using a combination of porewater analysis sequential chemical p extractions synchrotron based micro scale x ray fluorescence mapping and fe k edge x ray absorption spectroscopy and po43 sorption experiments the sediments represented redox regimes varying from strongly reducing organic rich sediments with little or no reactive fe iii oxyhydr oxides to oxygenated sediments that were enriched in reactive fe iii phases organic p and fe associated p were the main p burial phases and the latter was quantitatively important even in sediments with an overall strongly reducing character we attribute this to adsorption of p onto micro scale fe iii oxyhydroxide enrichments and or fe bearing clay minerals the organic rich sediments showed a strong decline in p contents with depth p was released from organic matter and fe phases but apatite precipitation was apparently inhibited in these sediments despite greater and stronger po43 sorption capacity the oxic sediments contained relatively little p due to a lack of the primary p source in marine sediments organic matter our results provide detailed insight into p burial in dynamic estuarine sediments and show that micro scale spectroscopic analyses greatly advance our understanding of p sequestration processes

infrasound radiated by the gerdec and chelopechene explosions propagation along unexpected paths summary infrasound propagation paths through the atmosphere are controlled by the temporally and spatially varying sound speed and wind speed amplitudes because of the complexity of atmospheric acoustic propagation it is often difficult to reconcile observed infrasonic arrivals with the sound speed profiles predicted by meteorological specifications this paper provides analyses of unexpected arrivals recorded in europe and north africa from two series of accidental munitions dump explosions recorded at ranges greater than 1000 km two explosions at gerdec albania on 2008 march 15 and four explosions at chelopechene bulgaria on 2008 july 3 the recorded signal characteristics include multiple pulsed arrivals celerities between 0 24 and 0 34 km s 1 and some signal frequency content above 1 hz often such characteristics are associated with waves that have propagated within a ground to stratosphere waveguide although the observed celerities extend both above and below the conventional range for stratospheric arrivals however state of the art meteorological specifications indicate that either weak or no ground to stratosphere waveguides are present along the source to receiver paths by incorporating realistic gravity wave induced horizontal velocity fluctuations into time domain parabolic equation models the pulsed nature of the signals is simulated and arrival times are predicted to within 30 s of the observed values 1 per cent of the source to receiver transit time modelling amplitudes is highly dependent upon estimates of the unknown acoustic source strength or equivalent chemical explosive yield current empirical explosive yield relationships derived from infrasonic amplitude measurements from point source chemical explosions suggest that the equivalent chemical yield of the largest gerdec explosion was of the order of 1 kt and the largest chelopechene explosion was of the order of 100 t when incorporating these assumed yields the parabolic equation simulations predict peak signal amplitudes to within an order of magnitude of the observed values as gravity wave velocity perturbations can significantly influence both infrasonic arrival times and signal amplitudes they need to be accounted for in source location and yield estimation routines both of which are important for explosion monitoring especially in the context of the comprehensive nuclear test ban treaty

a model for complex aftershock sequences the decay rate of aftershocks is commonly very well described by the modified omori law n t t p where n t is the number of aftershocks per unit time t is the time after the main shock and p is a constant in the range 0 9 p 1 5 and usually close to 1 however there are also more complex aftershock sequences for which the omori law can be considered only as a first approximation one of these complex aftershock sequences took place in the eastern pyrenees on february 18 1996 and was described in detail by correig et al 1997 in this paper we propose a new model inspired by dynamic fiber bundle models to interpret this type of complex aftershock sequences with sudden increases in the rate of aftershock production not directly related to the magnitude of the aftershocks as in the epidemic type aftershock sequences the model is a simple discrete stochastic fracture model where the elements asperities or barriers break because of static fatigue transfer stress according to a local load sharing rule and then are regenerated we find a very good agreement between the model and the eastern pyrenees aftershock sequence and we propose that the key mechanism for explaining aftershocks apart from a time dependent rock strength is the presence of dynamic stress fluctuations which constantly reset the initial conditions for the next aftershock in the sequence

experimental characterization of seasonal variations in infrasonic traveltimes on the korean peninsula with implications for infrasound event location summary the dependence of infrasound propagation on the season and path environment was quantified by the analysis of more than 1000 repetitive infrasonic ground truth events at an active open pit mine over two years blast associated infrasonic signals were analysed from two infrasound arrays chnar and uldar located at similar distances of 181 and 169 km respectively from the source but in different azimuthal directions and with different path environments the chnar array is located to the nw of the source area with primarily a continental path whereas the uldar is located east of the source with a path dominated by open ocean as a result chnar observations were dominated by stratospheric phases with characteristic celerities of 260 289 m s 1 and large seasonal variations in the traveltime whereas data from uldar consisted primarily of tropospheric phases with larger celerities from 322 to 361 m s 1 and larger daily than seasonal variation in the traveltime the interpretation of these observations is verified by ray tracing using atmospheric models incorporating daily weather balloon data that characterizes the shallow atmosphere for the two years of the study finally experimental celerity models that included seasonal path effects were constructed from the long term data set these experimental celerity models were used to constrain traveltime variations in infrasonic location algorithms providing improved location estimates as illustrated with the empirical data set

atmospheric boundary waves excited by the tsunami generation related to the 2011 great tohoku oki earthquake 1 atmospheric pressure changes caused by the 2011 off the pacific coast of tohoku japan earthquake mw 9 0 are investigated sensitive microbarographs in and around japan recorded unequivocal signals associated with the tsunami we identify them as atmospheric boundary waves excited by the uplift and subsidence of the ocean surface on the basis of the waveform characteristics as well as similarity with the data from ocean bottom pressure gauges potential usefulness of an observation network of atmospheric pressure is discussed regarding the improvement of the tsunami warning system

rheology of the upper mantle a synthesis rheological properties of the upper mantle of the earth play an important role in the dynamics of the lithosphere and asthenosphere however such fundamental issues as the dominant mechanisms of flow have not been well resolved a synthesis of laboratory studies and geophysical and geological observations shows that transitions between diffusion and dislocation creep likely occur in the earth s upper mantle the hot and shallow upper mantle flows by dislocation creep whereas cold and shallow or deep upper mantle may flow by diffusion creep when the stress increases grain size is reduced and the upper mantle near the transition between these two regimes is weakened consequently deformation is localized and the upper mantle is decoupled mechanically near these depths

a damage model for the continuum rheology of the upper continental crust abstract in orogenic zones it is often considered appropriate to use a continuum rheology to model the deformation of the upper continental crust in this paper we derive an applicable rheology utilizing fiber bundle and continuum damage models we show that the results are identical and yield a power relation between stress and strain rate e of the form e 1 we constrain the applicable values of utilizing omori s law for the decay of aftershocks and conclude that 1 is in the range of 5 15 with this strong nonlinear viscous rheology the behavior of the deforming upper crust approaches that of a perfect plastic material

fractal dimension of fault systems in japan fractal structure in rock fracture geometry at various scales based on fault maps whether or not the fracture geometry of rocks is self similar was examined by using a box counting algorithm the statistical self similarity fractal structure of the fault fracture systems holds well at the scale of about 2 to 20 km the fractal dimension in japan varied from 1 05 to 1 60 the fractal dimension is about 1 5 1 6 at the central part of the japan arc and decreases with distance from the center at a smaller scale the fractal structure also holds well in the rock fracture geometry the fractal dimension of the north izu peninsula fault system branching faults is 1 49 at the scale of 0 625 to 10 km the fractal dimension of rock fracture geometry at the scale order of 10 1 to 10 2 meters is about 1 49 1 61 the upper limit of the fractal dimension of rock fracture geometry is about 1 6 judging from the estimation of fractal dimension on actual fracture geometry of rocks this value may impose a restraint on modeling of faulting and the fracture process of rocks

a seismoacoustic analysis of the gas pipeline explosion near ghislenghien in belgium a high pressure gas pipeline exploded near ghislenghien in belgium on 30 july 2004 seismic energy of this event was recorded at three nearby seismometers the origin time of the explosion was determined by analyzing the rayleigh waves and found to be 06h55m27 2sec coordinated universal time utc ground truth of the explosion was invoked to assess the accuracy of the location derived from infrasound data recorded over western europe different infrasonic phases were identified by using array processing techniques and raytracing through atmospheric models the analysis showed that the derived location was situated 13 km from the true location the total area of the uncertainty ellipse or area to be searched if the source was of unknown origin was 690 km 2 after the origin time and location the yield was calculated by comparing infrasonic stratospheric amplitudes with those from a high explosives dataset and was estimated at 40 9 tons high explosives equivalent in summary this study illustrates the capability of seismic and infrasound data in forensic investigations furthermore the potential of infrasound as a monitoring or verification technique is addressed

evolution of pinch and swell structures in a power law layer analytical and finite element fem solutions for the necking of a single power law layer up to large finite amplitude are obtained continuous necking of the layer produces pinch and swell structures the layer is either a free plate or embedded in a homogeneous medium an analytical solution for finite amplitude necking based on the assumption that plane sections remain plane psrp agrees well with the fem result for a layer power law stress exponent n 5 and for a ratio of layer to medium effective viscosities m 100 fem simulations for embedded layers verify that psrp for m 20 the presented numerical experiments generate localized necking and pinch and swell structures similar to natural ones for n 5 and m 20 additional weakening mechanisms such as strain softening although likely to be operative in nature are not required to generate natural pinch and swell structures fem experiments with random perturbation of the layer interfaces show that even with strong necking instability the layer is thinned at the swell as well as at the necks affecting strain estimation from pinch and swell geometry 2008 elsevier ltd all rights reserved

a model of damage mechanics for the deformation of the continental crust 1 we derive a continuum rheology for the deformation of the continental crust using continuum damage mechanics it is hypothesized that when a constant strain rate is applied to a solid material the stress and damage increase until failure occurs which is analogous to an earthquake we further assume that this process is repeated in analogy to the reoccurrence of earthquakes on a fault our model assumes that the continental crust behaves elastically below a yield stress y above this stress the continuum deformations can be modeled as a non newtonian viscous flow with y n where n is constant we derive the modified omori s law for aftershock decay using a viscoelastic version of our model and get good agreement with observations taking n 6 using parameter values appropriate for aftershocks we obtain a continuum crustal rheology that can explain major orogenies such as the indian asian collision

a thin viscous sheet model for continental deformation summary for the purposes of describing its large scale and long term deformation the continental lithosphere is regarded as a continuum obeying a newtonian or a power law rheology the flow of a thin sheet of power law material overlying an inviscid substrate is studied under the assumption that vertical gradients of the horizontal velocity are negligible a numerical model is used to investigate the deformation of such a sheet under conditions approximating those of continent continent collision the material flows in response to forces applied to its boundaries for example the indenting of one continent by another and to forces in its interior arising from gradients in crustal thickness the horizontal divergence of the flow produces changes in the crustal thickness and hence a time dependent form to the flow itself for a given set of boundary conditions the flow depends on the stress exponent in the power law rheology n and on the argand number which is a measure of the ratio between the stress arising from crustal thickness contrasts and the stress required to deform the material at the ambient strain rates when the effective viscosity of the medium is very high ar o crustal thickness variations do not influence the flow if the material is newtonian n l the deformation associated with an influx of material approximating an indenter is of much greater lateral dimension than the width of the indenter whereas when material has a power law rheology n 3 5 are used the deformation is confined to a region of lateral extent comparable to that of the indenter as ar increases the forces arising from crustal thickness contrasts exert more influence on the flow and the maximum crustal thickness that can be sustained by a given influx of material is related by a simple expression to the effective viscosity of the medium at the ambient strain rates in the limit of a very weak medium ar 10 the lithosphere is unable to sustain appreciable crustal elevation contrasts the results of these numerical experiments show that systems in which the effective viscosities are such that the maximum deviatoric stresses are between 1 kbar

analytic models for orogenic collapse abstract orogenic plateaus and collisional mountain belts are formed by tectonic driving forces such as those associated with a continental collision and magmatism when the horizontal driving forces are removed e g at the conclusion of an orogeny the elevation of the plateau or collisional orogen will relax by one or both of two processes the first of these is erosion which removes the near surface rocks and allows uplift the second is the gravitational collapse of elevated topography in this paper we consider a simplified analysis in order to quantify the relative importance of erosion and gravitational collapse in the removal of topography we treat the erosion problem using the culling diffusion equation approach the basic assumption is that the material transport down slope is proportional to the slope with the equivalent coefficient of diffusion k the constant of proportionality the parameter k quantifies the rate of erosion it is applicable whether or not the topography is compensated for the gravitational collapse problem we use the thin viscous sheet approximation and assume a linear viscous rheology to simplify the analysis we assume the thickness of the continental crust approximates the thickness of the highly viscous lithosphere and that the crust overlies a much lower viscosity mantle we also assume the topography is harmonic with a wavelength the viscosity quantifies the thinning of the crust due to the buoyancy driven lateral flow our results indicate an exponential decay of topography with time and show that the relative role of erosion versus gravitational collapse for compensated topography is controlled by the value of the non dimensional collapse number c gh o 2 c 16 k 2 where g is the acceleration due to gravity h o is a reference thickness of the crust c is the density of the crust and k and are as defined above if c is large compared with unity gravitational collapse dominates if c is small compared with unity erosion dominates

finite strain calculations of continental deformation 2 comparison with the india asia collision zone numerical experiments on a thin viscous sheet model for deformation of continental lithosphere subjected to an indenting boundary condition yield distributions of crustal thickness of stress and strain rate and of latitudinal displacements that may be compared with observations in the india asia collision zone a simple indenting boundary condition applied to initially laterally homogeneous sheets obeying a power law rheology produces results that are in broad agreement with the observations provided that the power law exponent is three or greater and the sheet can support vertically integrated stress differences of 2 1013 5 1012 n m 1 in regions in front of the indenter under these conditions the calculated deformation shows accommodation of convergence primarily by crustal thickening to produce a plateau in front of the indenter palaeomagnetic data from india and tibet and the observed distribution of topography suggest that much of the post eocene convergence of india with asia has been taken up by deformation within asia that involved crustal thickening the principal difference between calculation and observation is the absence from the calculated strain rate fields of east west extension of the plateau in front of the indenting boundary the calculations show that once such a plateau is formed the buoyancy force associated with the crustal thickness contrast inhibits further thickening and the plateau strains at less than half the rate of its immediate surroundings seismically determined regional strain rates exhibit a similar distribution with the tibetan plateau straining at about one quarter the rate of the tien shan and ningxia gansu regions calculated principal compressive stress orientations and regional strain rates agree with the seismically determined quantities in the mongolia baikal tien shan tibet and ningxia gansu regions of asia to within the uncertainty of the latter the vertically integrated stresses that are calculated for the viscous sheet are comparable with those that can be supported by a theologically stratified continental lithosphere obeying laboratory determined flow laws we suggest that the thin viscous sheet model described in this paper and its companion gives a simple and physically plausible description of the observed deformation in central asia in this description the predominant mechanism of accommodation of continental convergence is diffuse crustal thickening with shear on vertical planes playing a subsidiary role once large crustal thickness contrasts have been established

accumulation of phosphorus and heavy metals in the peel harvey estuary in western australia results of a preliminary study abstract concentrations of p and of heavy metals zn cd pb cu were determined in sediment cores from the peel harvey estuary in western australia two cores were extracted each representing one of the two basins of the estuary sediments were dated by surplus 210 pb by 137 cs and by changes in the fe s ratio increasing exports of p from the mainly agricultural catchments have resulted in more than a doubling of both total p and acid extractable inorganic p in sediments of the estuary accumulation of p in the estuary is less than expected for complete retention of inputs of p from the major tributaries historical data show that since 1950 average concentrations of dissolved inorganic p have approximately doubled in the peel inlet and increased by times seven in the harvey estuary increases in concentrations in surface sediments of acid extractable zn cd pb and cu are noticeable in the peel inlet and of zn and cd in the harvey estuary the greatest increase relative to background is shown by zn concentrations of extractable zn and cd in surface sediments are similar to those estimated from average concentrations in the water column for equilibrium adsorption to organic matter in sediments extractable pb is greater than estimated for equilibrium adsorption to sediments extractable cu is of the order of what can be expected for equilibrium adsorption to sediments in the peel inlet but is less than expected in the harvey estuary

phosphorus speciation in the sediment and mass balance for the central region of the great barrier reef continental shelf australia abstract solid phase p speciation has been determined in sediments from a transect across the central section of the continental shelf and slope of the great barrier reef gbr lagoon this region is characterized by a gradient of riverine aluminosilicate clay and silt nearshore seawards of which biogenic carbonate sediment predominates phosphorus speciation results show large variations along this transect organic p and authigenic apatite p are the major chemical forms of phosphorus in the central gbr continental shelf sediments post depositional reorganization of p was also observed converting organic p and iron bound p fe p to authigenic apatite p phosphorus burial rate was estimated from measurements of total p concentration and excess 210pb sediment mass accumulation rates burial efficiency varies significantly over the shelf inshore areas showed significant p remobilization from sediments to the water column up to 50 the mid and the outer shelf showed little evidence for remobilization except for coral reef platform sediments with more of the sediment p being in the less reactive authigenic apatite phases an appreciable fraction of this non labile authigenic apatite phase was identified as fish bone p sources and sinks over the central part of the gbr shelf were quantified using a mass balance approach this showed that coral sea shelf edge upwelling events are essential to satisfy the large p nutrient demand of the whole gbr lagoon p inputs due to upwelling events were greater than those contributed by local rivers over an average year

distributed damage faulting and friction we present a formulation for mechanical modeling of geological processes in the seismogenic crust using damage rheology the seismogenic layer is treated as an elastic medium where distributed damage modifying the elastic stiffness evolves as a function of the deformation history the model damage rheology is based on thermodynamic principles and fundamental observations of rock deformation the theoretical analysis leads to a kinetic equation for damage evolution having two principal coefficients the first is a criterion for the transition between strength degradation and recovering healing and is related to friction the second is a rate coefficient of damage evolution which can have different values or functional forms for positive degradation and negative healing evolution we constrain these coefficients by fitting model predictions to laboratory data including coefficient of friction in sawcut setting intact strength in fracture experiments first yielding in faulting experiments under three dimensional strain onset and evolution of acoustic emission and dynamic instability the model damage rheology accounts for many realistic features of three dimensional deformation fields associated with an earthquake cycle these include aseismic deformation gradual strength degradation development of process zones and branching faults around high damage areas strain localization brittle failure and state dependent friction some properties of the model damage rheology e g cyclic stick slip behavior with possible accompanying creep are illustrated with simplified analytical results the developments of the paper provide an internally consistent framework for simulating long histories of crustal deformation and studying the coupled evolution of regional earthquakes and faults this is done in a follow up work

rheology of the lithosphere selected topics we review recent results concerning the rheology of the lithosphere with special attention to the following topics 1 the flexure of the oceanic lithosphere 2 deformation of the continental lithosphere resulting from vertical surface loads and forces applied at plate margins 3 the rheological stratification of the continents 4 strain localization and shear zone development and 5 strain induced crystallographic preferred orientations and anisotropies in body wave velocities we conclude with a section citing the 1983 1986 rock mechanics literature by category

precursory seismic activation and critical point phenomena in this paper we relate the behavior of seismicity prior to a characteristic earthquake to the excitation in proximity to a spinodal instability we illustrate the spinodal instability as the upper limit of superheated water prior to a steam explosion we draw an analogy between the steam explosion and a characteristic earthquake and show that the power law activation associated with the spinodal instability is essentially identical to the power law increase in benioff strain observed prior to characteristic earthquakes we find that theory and actual data give very similar results

accelerated seismic release and related aspects of seismicity patterns on earthquake faults observational studies indicate that large earthquakes are sometimes preceded by phases of accelerated seismic release asr characterized by cumulative benioff strain following a power law timeto failure relation with a term tf t m where tr is the failure time of the large event and observed values of m are close to 0 3 we discuss properties of asr and related aspects of seismicity patterns associated with several theoretical frameworks the subcritical crack growth approach developed to describe deformation on a crack prior to the occurrence of dynamic rupture predicts great variability and low asymptotic values of the exponent m that are not compatible with observed asr phases statistical physics studies assuming that system size failures in a deforming region correspond to critical phase transitions predict establishment of long range correlations of dynamic variables and power law statistics before large events using stress and earthquake histories simulated by the model of ben zion 1996 for a discrete fault with quenched heterogeneities in a 3 d elastic half space we show that large model earthquakes are associated with nonrepeating cyclical establishment and destruction of long range stress correlations accompanied by nonstationary cumulative benioff strain release we then analyze results associated with a regional lithospheric model consisting of a seismogenic upper crust governed by the damage rheology of lyakhovsky et al 39 over a viscoelastic substrate we demonstrate analytically for a simplified 1 d case that the employed damage rheology leads to a singular power law equation for strain proportional to t f t 1 3 and a nonsingular power law relation for cumulative benioff strain proportional to t f t 1 3 a simple approximate generalization of the latter for regional cumulative benioff strain is obtained by adding to the result a linear function of time representing a stationary background release to go beyond the analytical expectations we examine results generated by various realizations of the regional lithospheric model producing seismicity following the characteristic frequency size statistics gutenberg richter power law distribution and mode switching activity we find that phases of asr exist only when the seismicity preceding a given large event has broad frequency size statistics in such cases the simulated asr phases can be fitted well by the singular analytical relation with m 1 3 the nonsingular equation with m 0 2 and the generalized version of the latter including a linear term with m 1 3 the obtained good fits with all three relations highlight the difficulty of deriving reliable information on functional forms and parameter values from such data sets the activation process in the simulated asr phases is found to be accommodated both by increasing rates of moderate events and increasing average event size with the former starting a few years earlier than the latter the lack of asr in portions of the seismicity not having broad frequency size statistics may explain why some large earthquakes are preceded by asr and other are not the results suggest that observations of moderate and large events contain two complementary end member predictive signals on the time of future large earthquakes in portions of seismicity following the characteristic earthquake distribution such information exists directly in the associated quasi periodic temporal distribution of large events in portions of seismicity having broad frequency size statistics withrandom or clustered temporal distribution of large events the asr phases have predictive information the extent to which natural seismicity may be understood in terms of these end member cases remains to be clarified continuing studies of evolving stress and other dynamic variables in model calculations combined with advanced analyses of simulated and observed seismicity patterns may lead to improvements in existing forecasting strategies

finite strain calculations of continental deformation 1 method and general results for convergent zones a finite element method is used to calculate stresses and strain rates in a thin viscous sheet representing the continental lithosphere that is bordered in one part by an indenting boundary we calculate solutions for velocity fields crustal thickness distributions strain rates rotation time integrated vorticity and finite strain ellipsoids to show the dependence of these quantities on the controlling parameters the stress strain exponent n and the strength of the sheet relative to the gravitational forces which may be expressed as a dimensionless number the argand number ar for n 3 and ar between 1 and 10 a plateau of thickened crust is formed in front of the indenter the strain histories of individual elements within the viscous sheet may be quite complex and the finite strain at the end of deformation may bear no obvious relation to the principal stress orientations during the deformation the strain rate fields are interpreted in terms of the style of faulting that would be expected in the brittle upper crust if it were coupled to the ductile but stronger upper mantle in general the length scale of deformation increases with ar and time since the start of the collision and decreases with n for ar 3 the increase in length scale is accompanied by a change in the style of deformation from predominantly crustal thickening with thrust faulting in the brittle layer to predominantly transcurrent deformation strike slip faulting in the brittle layer

the growth of geological structures by repeated earthquakes 1 conceptual framework in many places earthquakes with similar characteristics have been shown to recur if this is common then relatively small deformations associated with individual earthquake cycles should accumulate over time to create geological structures following this paradigm we show that existing models developed to describe leveling line changes associated with the seismic cycle can be adapted to explain geological features associated with a fault in these models an elastic layer containing the fault overlies a viscous half space with a different density fault motion associated with an earthquake results in immediate deformation followed by a long period of readjustment as stresses relax in the viscous layer and isostatic equilibrium is restored deformation is also caused as a result of the loading and unloading due to sediment deposition and erosion in this paper the parameters that control the growth of dip slip structures are identified we find that the flexural rigidity of the crust or the apparent elastic thickness provides the main control of the width of a structure the loading due to erosion and deposition of sediment determines the ratio of uplift to subsidence between the two sides of the fault the flexure due to sediment load is much more important in this respect than whether the fault is normal or reverse in character we find that in general real structures are associated with apparent elastic thicknesses of 4 km or less and thus with very low flexural rigidities

infrasound monitoring of volcanoes to probe high altitude winds 1 active volcanoes in the vanuatu archipelago permanently generate infrasonic waves their monitoring over 1 year exhibits clear seasonal trends in the direction of arrival of the detected signals from summer to winter the azimuth variation reaches 15 this deviation is essentially due to the reversibility of the zonal stratospheric wind with season which strongly affects the deflection of the ray direction a three dimensional 3 d ray tracing modeling roughly explains the observed seasonal trend in the azimuth variation but underestimates its amplitude the discrepancy between the measurements and the results of simulation is explained by undervalued wind speeds in the upper atmosphere infrasonic observations are used as input of an inversion scheme for adjusting the vertical structure of the wind in the upper stratosphere and mesosphere it is shown that the mesospheric zonal winds are underestimated by at least 20 m s throughout the year with differences reaching 50 m s

damage in step overs may enable large cascading earthquakes seismic hazard analysis relies on the ability to predict whether an earthquake will terminate at a fault tip or propagate onto adjacent faults cascading into a larger more devastating event while ruptures are expected to arrest at fault discontinuities larger than 4 5 km scientists are often puzzled by much larger rupture jumps here we show that material properties between faults significantly affect the ability to arrest propagating ruptures earthquake simulations accounting for fault step over zones weakened by accumulated damage provide new insights into rupture propagation revealing that lowered rigidity and material interfaces promote rupture propagation our models show for the first time that step overs as wide as 10 km may not constitute effective earthquake barriers our results call for re evaluation of seismic hazard analyses that predict rupture length and earthquake magnitude based on historic records and fault segmentation models

western u s infrasonic catalog illuminating infrasonic hot spots with the usarray 1 in this study reverse time migration is applied to signals recorded by the 2007 08 usarray presumably due to acoustic to seismic coupling to detect and locate in two dimensional space and time 901 sources of atmospheric infrasound defining the western united states infrasonic catalog wusic the detections are visually inspected and ranked uncertainties are estimated using a bootstrap technique the method correctly locates most rocket motor detonations in utah and a bolide explosion in oregon with an average spatial accuracy of 50 km and 25 km respectively the origin time statistics for 2007 and 2008 events are nearly identical and suggest a predominant human origin the event locations illuminate repeating sources of infrasound or infrasonic hot spots in nevada utah and idaho that are spatially associated with active military areas the infrasonic arrivals comprise several branches that are observed to a range between 200 and 1500 km to the east and west of the epicenter in the winter and summer respectively the optimum group velocities are gaussian distributed and centered at 295 m s a seasonal variation in optimum group velocities exhibits good correlation with atmospheric temperature the results show that relatively dense seismic networks fill in the gaps between sparsely located infrasound arrays and provide valuable information for regional infrasonic source location and propagation studies specifically the catalogs presented here can be used to statistically validate and improve propagation models especially above the middle stratosphere where winds are not directly measured by ground based weather stations or meteorological satellites

damage formation associated with bending under a constant moment abstract deformation within the earth s lithosphere is largely controlled by the rheology of the rock fracture and faulting are characterized by elastic rheologies with brittle mechanisms while folding and flow are characterized by plastic and or viscous rheologies due to ductile mechanisms however it has been recognized that deformation that resembles ductile behavior can be produced within the confines of the brittle lithosphere specific examples are folds that form in the shallow crust steep hinges at subduction zones that are accompanied by seismicity and large scale deformation at plate boundaries in these cases the brittle lithosphere behaves elastically with fracture and faulting yet produces ductile behavior in this paper we attempt to simulate such ductile behavior in elastic materials using continuum damage mechanics engineers utilize damage mechanics to model the continuum deformation of brittle materials we utilize a modified form of damage mechanics that represents a reduction in frictional strength of preexisting fractures and faults we use this empirical approach to simulate the bending of the lithosphere under the application of a constant moment we use numerical simulations to obtain elastostatic solutions for plate bending and where the longitudinal stress at a particular node exceeds a yield stress we apply damage to reduce young s modulus at the node damage is calculated at each time step by a power law relationship of the ratio of the yield stress to the longitudinal stress and the yield strain to the longitudinal strain this results in the relaxation of the material due to increasing damage to test our method we apply our damage rheology to an infinite plate deforming under a constant bending moment we simulate a wide range of behaviors from slow relaxation to instantaneous failure over timescales that span six orders of magnitude using this method stress relaxation produces elastic perfectly plastic behavior in cases where failure does not occur for cases of failure we observe a rapid increase in damage leading to failure analogous to the acceleration of microcrack formation and acoustic emissions prior to failure the changes in the rate of damage accumulation in failure cases are similar to the changes in b values of acoustic emissions observed in triaxial compression tests of fractured rock and b value changes prior to some large earthquakes thus continuum damage mechanics can simulate the phenomenon of ductile behavior due to brittle mechanisms as well as observations of laboratory experiments and seismicity

microplate versus continuum descriptions of active tectonic deformation whether deformation of continents is more accurately described by the motions of a few small rigid plates or by quasi continuous flow has important implications for lithospheric dynamics fault mechanics and earthquake hazard assessment actively deforming regions of the western united states central asia japan and new zealand show features that argue for both styles of movement but new observations are necessary to determine which is most appropriate and at what scale the description applies geologic geodetic seismic and paleomagnetic measurements tend to sample complementary aspects of the deformation field so an integrated observation program can utilize the strengths of each method and overcome their separate spatial or temporal biases provided the total relative motion across each region is known and the distribution of active faults is well mapped determination of fault slip rates can provide potentially decisive constraints reconnaissance geological studies supply useful slip rate estimates but precise values depend upon detailed intensive investigation of individual sites geodetic survey measurements can determine the spatial pattern of contemporary movements and extract slip rate information but the sometimes elusive effects of cyclic elastic strain buildup and relief must be accounted for in relating current movements to the long term deformation pattern earthquake catalogs can be applied to determine seismic strain rates and relative velocities but must be averaged over large regions and are usually limited by the inadequate duration of historical or instrumental seismicity catalogs paleomagnetic determinations of vertical axis rotations provide estimates of block rotation rates but are often locally variable and averaged over many millions of years which of the two descriptions of continental tectonics is more nearly correct depends on the local rheological stratification of the lithosphere especially the strength and thickness of the elastic crust relative to the ductile lithosphere and dynamical models can provide contrasting forecasts of observable features with testable consequences

real time inversion of gps data for finite fault modeling and rapid hazard assessment 1 responses to recent great earthquakes and ensuing tsunamis in sumatra chile and japan with the resulting loss of life and damage to infrastructure demonstrate that our ability to ascertain the full extent of slip of catastrophic earthquakes and their tsunamigenic potential in the first minutes after the initiation of rupture is problematic regional gps networks such as those in western north america and japan are complementary to seismic networks by being able to directly measure displacements close to the source during large earthquakes in real time we report on rapid modeling of two large earthquakes the 2003 mw 8 3 tokachi oki earthquake 100 km offshore hokkaido island using 356 geonet stations and the 2010 mw 7 2 el mayor cucapah earthquake in northern baja california using 95 crtn stations in southern california about 75 km northwest of the epicenter working in a simulated real time mode we invert for finite fault slip in a homogeneous elastic half space using green s functions obtained from okada s formulation we compare two approaches the first starts with a catalog of pre defined faults while the second uses a rapid centroid moment tensor solution to provide an initial estimate of the ruptured fault plane in either case we are able to characterize both earthquakes in less than two minutes reducing the time necessary to obtain finite fault slip and moment magnitude for medium and greater earthquakes compared to traditional methods by an order of magnitude

crustal thickening versus lateral expulsion in the indian asian continental collision since the beginning of the continental collision between india and asia there has been about 2500 km of convergence and the northward movement of india has been accommodated by major internal deformation of the asian lithosphere the crustal thickening in and around the tibetan plateau is clearly a direct consequence of this collision but there is considerable debate as to whether a large fraction of the indentation has been accommodated by eastward motion of the lithospheric blocks of southeastern asia and southern china numerical experiments described here test this hypothesis for a range of indentation geometries and rheological models of the lithosphere we employ a thin viscous sheet model of the lithosphere with a depth averaged nonlinear viscous rheology described by a stress strain rate exponent n and including gravitational buoyancy forces scaled by the dimensionless argand number ar the eastern boundary for the collision region is described as a lithostatic boundary the precollision normal stress is determined by static balance and that constant stress is applied throughout the collision the experiments show that during collision the eastern boundary is smoothly displaced to the east at a rate about 1 4 of the indentation rate with only minor variation due to geometry or rheology crustal thickening rates in the region of the plateau are reduced by between 10 and 25 of the corresponding rates determined for similar experiments with a rigid eastern boundary to generalize from the results of these experiments the total north south shortening strain produced by the collision is partitioned between crustal thickening and eastward displacement in the ratio of at least 3 1 and more probably 4 1

speculations on the geometry of the initiation and termination processes of earthquake rupture and its relation to morphology and geological structure earthquake initiation and termination processes are commonly described in terms of barriers and asperities barriers fall into two classes geometric barriers are associated with places where the orientation of a failure surface changes and relaxation barriers where stress is low because aseismic creep processes outpace tectonic loading geometric barriers fall into conservative and nonconservative subgroups according to whether finite fault motion can proceed without the creation of new structures or whether it demands the creation of new faulting or void space the multiple faulting or fragmentation associated with some nonconservative barriers can disrupt fault planes and form asperities by means of selected examples it is shown that a description in terms of these barriers can help one to visualise the processes of earthquake rupture and its relation to the geological environment

the accommodation of large strains in the upper lithosphere of the earth and other solids by self similar fault systems the geometrical origin of b value plate tectonics has provided a method of visualizing the geometry of the deformation of the earth s lithosphere on a large scale the description is so concise that for many purposes it provides an explanation of geological processes that overshadows the need to understand the driving processes the mechanics of the zones between the plates are less well understood particularly in continental regions where large areas are subject to deformation both continuous and discontinuous models have been tried but both have obvious drawbacks

cumulative benioff strain release modified omori s law and transient behaviour of rocks abstract irreversible thermodynamic theories with internal state variables can be used to derive a general constitutive law for both transient and steady state behaviours of rocks this constitutive law can represent the concepts of damage and damage evolution in either the fibre bundle model or continuum damage mechanics we have previously proposed an empirically based constitutive law for both the transient and steady state behaviours of rocks ultimately derived from laboratory experimental data we show here that this law is concordant with the general constitutive law derived from irreversible thermodynamic theories and that the relaxation modulus has a temporal power law that depends on a structural fractal property of rocks our constitutive law predicts forms for the cumulative benioff strain release for precursory seismic activations and the modified omori s laws of aftershocks both aspects of the temporal fractal properties of seismicity these seismic properties can also be derived by the fibre bundle model or continuum damage mechanics our model suggests that these time scale invariant processes of seismicity may be regulated by the fractal structures of crustal rocks

a study of infrasound propagation using dense seismic network recordings of surface explosions abstract we use dense seismic network recordings of accurately located surface explosions in northern utah to shed light on the propagation of infrasound through the stratosphere the data clearly show propagation of infrasound downwind from the source as expected the data also clearly show the penetration of infrasound into geometric shadow zones near the source and the spread of infrasound to a distance of 800 km from the source the spread of infrasound both toward and away from the source is not predicted by applying either ray theory or the full wave finite difference technique to smooth ground to space g2s models the mismatch between synthetics and data suggest a missing component in these models possibly a small scale gravity wave structure comparison of the network recordings of approximately 1500 infrasound signals with travel time predictions based on rays shows no significant average bias in the travel times on average recorded signals arrived 1 s earlier than predictions travel time residuals are normally distributed about the mean with a standard deviation of 15 s the small bias of the travel time predictions indicates that despite the fact that small scale structure is averaged out of commonly used g2s models the large scale structure of the atmosphere is accurately represented the scatter of travel time residuals is suggestive of small scale structure missing from the models that we used to make the predictions but firm conclusions would require a more in depth study

block versus continuum deformation in the western united states abstract the relative role of block versus continuum deformation of continental lithosphere is a current subject of debate continuous deformation is suggested by distributed seismicity at continental plate margins and by cumulative seismic moment sums which yield slip estimates that are less than estimates from plate motion studies in contrast block models are favored by geologic studies of displacement in places like asia a problem in this debate is a lack of data from which unequivocal conclusions may be reached in this paper we apply the techniques of study used in regions such as the alpine himalayan belt to an area with a wealth of instrumental data the western united states by comparing plate rates to seismic moment release rates and assuming a typical seismogenic layer thickness of 15 km it appears that since 1850 about 60 of the pacific north america motion across the plate boundary in california and nevada has occurred seismically and 40 aseismically the san francisco bay area shows similar partitioning between seismic and aseismic deformation and it can be shown that within the seismogenic depth range aseismic deformation is concentrated near the surface and at depth in some cases this deformation can be located on creeping surface faults but elsewhere it is spread over a several kilometer wide zone adjacent to the fault these superficial creeping deformation zones may be responsible for the palaeomagnetic rotations that have been ascribed elsewhere to the surface expression of continuum deformation in the lithosphere our results support the dominant role of non continuum deformation processes with the implication that deformation localization by strain softening must occur in the lower crust and probably the upper mantle our conclusions apply only to the regions where the data are good and even within the western united states i e the basin and range deformation styles remain poorly resolved nonetheless we maintain that block motion is the deformation style of choice for those continental regions where the data are best

physical basis for statistical patterns in complex earthquake populations models predictions and tests understanding the physics of earthquakes and the space time patterns they produce is illuminated by the use of coarse grained models and simulations that capture the basic physical processes and that are amenable to analysis we present a summary of ideas that describe the nucleation growth and arrest of earthquakes on individual faults under shear loading we find that faults reside in a metastable state near a classical spinodal that governs the nucleation and growth of slip events the roughness of an associated stress distribution field x t determines whether slip events are confined within the initial high stress patch or break away and grow to become very large we find a critical value of roughness that is associated with a first order order disorder transition we also give a number of predictions examples and applications of these ideas and indicate how they might be tested through systematic observational programs

a constitutive law for rate of earthquake production and its application to earthquake clustering seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stress ing history control the timing of earthquakes the model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate and state dependent fault properties this yields a general state variable constitutive formulation for rate of earthquake production resulting from an applied stressing history to illustrate and test the model some characteristics of seismicity following a stress step have been explored it is proposed that various features of earthquake clustering arise from sensi tivity of nucleation times to the stress changes induced by prior earthquakes the model gives the characteristic omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate earthquake data appear to support a model prediction that aftershock duration defined as the time for rates to return to the back ground seismicity rate is proportional to mainshock recurrence time observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial depen dence of stress changes of the first event of the pair and stress sensitive time dependent nucleation applications of the constitutive formulation are not restricted to the simple stress step models investigated here it may be applied to stressing histories of arbitrary complexity the apparent success at modeling clustering phenomena suggests the possibil ity of using the formulation to estimate short to intermediate term earthquake probabil ities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress

shear heating in extensional detachments implications for the thermal history of the devonian basins of w norway article i nfo the supra detachment basins in western norway were formed during lower to middle devonian in the hangingwall of the extensional system of detachments known as the nordfjord sogn detachment zone nsdz the basins experienced elevated peak temperatures up to 345 c adjacent to the main detachment fault during the terminal stages of the extension in this study we show that the heat generated by the de formation of the rocks within the shear zone of the detachment also known as shear heating played a role in the thermal evolution of the entire region during the extension and could have induced the elevated peak temperatures of the supra detachment basins we numerically analyse the influence of the rheology and the deformation style within the shear zone the rate of exhumation of the footwall and the thickness of the sedimentary accumulation on the top of the system the model reproduces the elevated temperatures recorded in the supra detachment basins where locally 100 c and 25 of the total heat budget can be attrib uted to shear heating we show that this additional heat source may increase the peak temperatures of the hangingwall as far as 5 km away from the detachment

theory of time dependent rupture in the earth at a velocity x which is a well defined function of k this propagation is stable and quasi static and is referred to as subcritical crack growth we shall use the terms stable quasistatic and subcritical to mean propagation at velocities much less than the sonic velocities of the medium this behavior results from stress induced corrosion at the crack tip the principal corrodent for the present application being h20 this behavior has been firmly established in the laboratory for mode i tensile cracks in a wide variety of materials ineluding silicates and silicate glasses see cholz 1968a 1972a martin 1972 wiederhorn and bolz 1970 atkinson 1979 lawn and wilshaw 1975 knott 1973 the form of the relationship between k and x does not vary significantly with the material only the parameters in the law vary as an example we show in figure 1 data on subcritical crack growth in quartz after atkinson 1979 the empirical relationship is found to take the form

pulsating continents on venus an explanation for crustal plateaus and tessera terrains we propose that tessera terrains on venus represent continental crust that does not participate in the periodic recycling of the lithosphere through global subduction events we have studied the force balance on the boundary of a continental area that survives a global subduction event using an analytical model in the proposed model the ratio between the crustal and lithospheric mantle thicknesses controls the force balance if the crust thickness is less than 2 5 of the lithospheric mantle thickness the continental area will be compressed but if the crustal thickness is higher than 2 5 of the lithospheric mantle thickness the continental area will spread out and collapse consequently if the lithospheric mantle beneath a continental region is delaminated during a global subduction event the continent will collapse generating tessera inliers dominated by extensional tectonics but if a significant portion of lithospheric mantle remains then the continental area will be compressed generating a plateau by crustal shortening the observed plateau heights can be explained by this model a 2 km height plateau can be generated by a lithospheric mantle thickness of 40 km while a 4 km height plateau can be generated by a 90 km thick lithospheric mantle we have modelled this crustal thickening of a continental area by tectonic contraction using a thin viscous sheet approach with a newtonian viscosity for the crust the force from a hot mantle elevated during a global subduction event is enough to build up a plateau by compression in 50 ma using a viscosity for the continental crust of 1021 pa s and 200 ma for 5 1021 pa s during this compressional stage concentric fold and thrust belts are generated in the plateau continent erasing any impact craters that were present the subsequent stabilization of a new crust and lithosphere in the surrounding mantle changes the force balance allowing a moderate gravitational collapse of the plateau continent accommodated by radial grabens the pulsating continent model links for the first time the generation of crustal plateaus and the origin of the volcanic plains predicting the observed equivalent effective crater density for both terrains

an analysis of ground shaking and transmission loss from infrasound generated by the 2011 tohoku earthquake 1 the 2011 mw9 0 tohoku earthquake generated infrasound that was recorded by nine infrasonic arrays most arrays recorded a back azimuth variation with time due to the expanse of the source region we use ray tracing to predict group velocities and back azimuth wind corrections a japan accelerometer network recorded ground shaking in unprecedented spatial resolution we back projected infrasound from arrays is44 kamchatka and is30 tokyo to the source region and compare these results with acceleration data is44 illuminates the complex geometry of land areas that experienced shaking is30 illuminates two volcanoes and a flat area around the city of sendai where the maximum accelerations occurred the arrays and epicentral region define three source receiver profiles the observed broadband energy transmission loss tl follows an exponential decay law the best fitting model which has parameters that are interpreted to include the effects of geometric spreading scattering and the maximum ratio of the effective sound speed in the stratosphere to that at the ground accounts for stratospheric wind speed yields a 65 variance reduction relative to predictions from a traditional tl relationship this model is a simplified version of the model of le pichon et al 2012 which yields an 83 variance reduction for a single frequency implying that fine scale atmospheric structure is required to explain the tl for stratospheric upwind propagation our results show that infrasonic arrays are sensitive to ground acceleration in the source region of megathrust earthquakes the tl results may improve infrasonic amplitude scaling laws for explosive yield