self driven mode switching of earthquake activity on a fault system theoretical results based on two different modeling approaches indicate that the seismic response of a fault system to steady tectonic loading can exhibit persisting fluctuations in the form of self driven switching of the response back and forth between two distinct modes of activity the first mode is associated with clusters of intense seismic activity including the largest possible earthquakes in the system and frequency size event statistics compatible with the characteristic earthquake distribution the second mode is characterized by relatively low moment release consisting only of small and intermediate size earthquakes and frequency size event statistics following a truncated power law the average duration of each activity mode scales with the time interval of a large earthquake cycle in the system the results are compatible with various long geologic paleoseismic and historical records the mode switching phenomenon may also exist in responses of other systems with many degrees of freedom and nonlinear dynamics 1999 elsevier science b v all rights reserved

carbonate factories a conundrum in sedimentary geology abstract describing characterizing and interpreting the nearly infinite variety of carbonate rocks are conundrums intricate and difficult problems having only conjectural answers that have occupied geologists for more than two centuries depositional features including components rock textures lithofacies platform types and architecture all vary in space and time as do the results of diagenetic processes on those primary features approaches to the study of carbonate rocks have become progressively more analytical one focus has evolved from efforts to build reference models for specific phanerozoic windows to scrutinize the effect of climate and long term oscillations of the ocean atmosphere system in influencing the mineralogy of carbonate components this paper adds to the ongoing lively debates by attempting to understand changes in the predominant types of carbonate producing organisms during the mesozoic cenozoic while striving to minimize the uniformitarian bias our approach integrates estimates of changes in ca2 concentration in seawater and atmospheric co2 with biological evolution and ecological requirements of characteristic carbonate producing marine communities the underlying rationale for our approach is the fact that co2 is basic to both carbonates and organic matter and that photosynthesis is a fundamental biological process responsible for both primary production of organic matter and providing chemical environments that promote calcification gross photosynthesis and hypercalcification are dependent largely upon sunlight while net primary production and e g subsequent burial of organic matter typically requires sources of new nutrients n p and trace elements our approach plausibly explains the changing character of carbonate production as an evolving response to changing environmental conditions driven by the geotectonic cycle while identifying uncertainties that deserve further research with metazoan consumer diversity reduced by the end permian extinctions excess photosynthesis by phytoplankton and microbial assemblages in surface waters induced by moderately high co2 and temperature during the early mesozoic supported proliferation of non tissular metazoans e g sponges and heterotrophic bacteria at the sea floor metabolic activity by those microbes especially sulfate reduction resulted in abundant biologically induced geochemical carbonate precipitation on and within the sea floor for example with the opening of tethyan seaways during the triassic massive sponge microbe boundstones the benthic automicrite factory formed steep massive and thick progradational slopes and locally mud mounds as tectonic processes created shallow epicontinental seas photosynthesis drove lime mud precipitation in the illuminated zone of the water column the resulting neritic lime mud component of the shallow water carbonate factory became predominant during the jurassic paralleling the increase in atmospheric pco2 while the decreasing importance of the benthic automicrite factory parallels the diversification of calcifying metazoans phytoplankton and zooplankton with atmospheric pco2 declining through the cretaceous the potential habitats for neritic lime mud precipitation declined at the same time peak oceanic ca2 concentrations promoted biotically controlled calcification by the skeletal factory with changes produced by extinctions and turnovers at the cretaceous tertiary boundary adaptations to decreasing ca2 and pco2 coupled with increasing global temperature gradients i e high latitude and deep water cooling and strategies that efficiently linked photosynthesis and calcification promoted successive changes of the dominant skeletal factory through the cenozoic larger benthic foraminifers protist protist symbiosis during the paleogene red algae during the miocene and modern coral reefs metazoan protist symbiosis since late miocene

inorganic and organic carbon biogeochemistry in the gautami godavari estuary andhra pradesh india during pre monsoon the local impact of extensive mangrove forests tidal mangrove creeks in the delta here variations in the concentration and d 13 co f the dic pool were shown to result largely from the mineralization of organic matter the present study clearly identifies the mangrove creeks as an active site of mineralization and co2 efflux to the atmosphere but shows that these changes in the aquatic biogeochemistry are a localized feature rapidly fading in the adjacent kakinada bay our data indicate that mineralization of dissolved organic carbon doc of mangrove origin and its subsequent efflux as co2 to the atmosphere may represent an important fate for mangrove carbon although further quantification of this process in a variety of systems is required we suggest that some of the current ideas on the role of mangroves in the carbon budget of the coastal zone may need to be reconsidered index terms 4235 oceanography general estuarine processes 4504 oceanography physical air sea interactions 0312 4805 oceanography biological and chemical biogeochemical cycles 1615 4815 oceanography biological and chemical ecosystems structure and dynamics keywords mangroves mineralization stable isotopes

strontium hydrothermal systems and steady state chemical weathering in active mountain belts abstract hydrothermal systems are a common feature of active collisional orogens these systems can have a profound effect on the sr fluxes and sr isotopic composition of riverine waters through the direct input of sr from hot springs and groundwaters and the chemical weathering of hydrothermal calcite in an effort to quantify the role of calcite weathering we present an analytical model that examines the relationship between rock uplift and steady state chemical weathering of granites and greywackes that contain trace amounts we compare model results with sr fluxes and isotopic composition of riverine waters from the southern alps of new zealand an area that is frequently used as an example of a steady state collisional orogen as our model predicts roughly 50 of sr flux is from the weathering of calcite in the areas of highest uplift along the west flank of the southern alps this proportion decreases substantially

the climatology of zonal wave numbers 1 and 2 planetary wave structure in the mlt using a chain of northern hemisphere superdarn radars the zonal wave components 1 and 2 were extracted from the meridional wind along the latitude band of 51 66 n for the years 2000 2008 using eight super dual auroral radar network superdarn radars spanning longitudes from 25 e to 150 w each extracted zonal component represents the superposition of all temporal periods with that zonal structure and indicates the total planetary wave energy available with that wave number the hovmoller diagrams show stationary as well as eastward and westward traveling planetary waves propagating in the background wind the method used to detect the zonal planetary wave components in the superdarn data are detailed and validated using uk meteorological office data which allows the evolution of s1 and s2 planetary wave energy between the stratosphere and mesosphere to be assessed the climatology of zonal wave number 1 and 2 planetary wave activity in the mesosphere lower thermosphere mlt is presented and compared to the activity in the stratosphere the mlt climatology of the mean wind anomalies shows stronger planetary wave activity during winter and weaker activity during summer with enhancement around midsummer and autumn equinox the climatology of the mean wind displays similar amplitudes apart from very strong s1 planetary wave amplitudes during summer in addition planetary wave activity during winters with major and minor stratospheric warming events are examined and contrasted

velocity contrast across the 1944 rupture zone of the north anatolian fault east of ismetpasa from analysis of teleseismic arrivals 1 we use differences between arrival times of teleseismic events at sets of stations crossing the north anatolian fault east of ismetpasa where shallow creep has been observed to detect and quantify a contrast of seismic velocities across the fault waveform cross correlations are utilized to calculate phase delays of p waves with respect to expected teleseismic arrivals with incident angles corresponding to the generating events compiled delay times associated with 121 teleseismic events indicate about 4 3 average p wave velocity contrast across the fault over the top 36 km with faster velocity on the north side the estimated contrast is about 8 3 if the velocity contrast is limited to the top 18 km the sense of velocity contrast is consistent with the overall tectonic setting and inference made for the examined fault section based on theoretical expectations for bimaterial ruptures and observed asymmetry of rock damage across the fault our data indicate lack of significant microseismicity near the fault suggesting that creep in the area is limited to the depth section above the seismogenic zone

the geometry of echelon fractures in rock implications from laboratory and numerical experiments abstract the traces of echelon joints veins and dikes in rock range from curving to straight theoretical analyses using boundary element numerical methods have concluded that straight open fractures imply a significant remote differential stress whereas curving traces imply a more nearly isotropic stress we present a series of laboratory experiments which investigate the two dimensional propagation paths of echelon fractures in pmma plates as a function of the applied biaxial loading and the initial geometry of a simple fracture array the experimental results support the theoretical conclusions and verify the accuracy of the numerical method at the grain scale rock does not rigorously conform to the assumptions of isotropy homogeneity and linear elasticity demanded by the numerical method nevertheless results from crack path stability theory suggest that small scale deviations of a fracture from the ideal path generally do not affect its large scale behavior fracture paths which become kinked or curved by local heterogeneities are found to self correct to a path governed by competition between the fracture tip and remote stress fields provided the remote differential stress is non zero this enhances our confidence that the numerical method can be used to produce and explain realistic fracture geometries in rock an unexpected experimental result is the non perpendicular intersection of fractures grown in the laboratory free surface boundary conditions require that the walls of an open fracture be free of shear stress the principal stresses are therefore aligned with the crack wall and we might consequently expect an approaching opening mode fracture either to intersect the free surface at a right angle or to turn away and follow an asymptotic nonintersecting path experimental and numerical modeling however shows how the near tip stresses generated by an approaching fracture dominate the local stress field and allow it to propagate along an oblique path very close to intersection with the adjacent free surface

temporal transport of major and trace elements in the upper reaches of the xijiang river sw china this study investigated the temporal variations of major and trace element contents and controlling factors in the upper reaches of the xijiang river sw china the results showed the major ions principally derived from the weathering of carbonate and silicate rocks with a seasonal variation impacted by the monsoonal climate the contents of dissolved trace elements also varied seasonally in the two main tributaries the nanpan and beipan rivers most dissolved trace elements such as mn zn and pb being affected by anthropogenic contributions displayed a large seasonal variability from onefold to hundred fold while v rb and u show a relative stable trend uncorrelated with the different seasons suggesting a natural origin by rock weathering suspended particle matter in the nanpan and beipan rivers was depleted in ca mg na k and sr but enriched in al fe and sb compared to the upper crust uc values a binary mixture of silicate rich and carbonate rich sources dominates the behavior of elements such as ca and sr in riverine sediments while a third end member with an anthropogenic signature influenced the content of trace elements like mn sb pb zn cd cr and cu the enrichments of sb relative to the uc would be related to the mining activity in the studied area the study highlights the importance of investigating temporal variations of major and trace element contents of rivers controlled by the monsoon climate and impacted by human activity

imaging surface contacts power law contact distributions and contact stresses in quartz calcite glass and acrylic plastic a procedure has been developed to obtain microscope images of regions of contact between roughened surfaces of transparent materials while the surfaces are subjected to static loads or undergoing frictional slip static loading experiments with quartz calcite soda lime glass and acrylic plastic at normal stresses to 30 mpa yield power law distributions of contact areas from the smallest contacts that can be resolved 3 5 m2 up to a limiting size that correlates with the grain size of the abrasive grit used to roughen the surfaces in each material increasing normal stress results in a roughly linear increase of the real area of contact mechanisms of contact area increase are by growth of existing contacts coalescence of contacts and appearance of new contacts mean contacts stresses are consistent with the indentation strength of each material contact size distributions are insensitive to normal stress indicating that the increase of contact area is approximately self similar the contact images and contact distributions are modeled using simulations of surfaces with random fractal topographies the contact process for model fractal surfaces is represented by the simple expedient of removing material at regions where surface irregularities overlap synthetic contact images created by this approach reproduce observed characteristics of the contacts and demonstrate that the exponent in the power law distributions depends on the scaling exponent used to generate the surface topography

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

scaling relations of earthquakes and aseismic deformation in a damage rheology model summary we perform analytical and numerical studies of scaling relations of earthquakes and partition of elastic strain energy between seismic and aseismic components using a thermodynamically based continuum damage model brittle instabilities occur in the model at critical damage level associated with loss of convexity of the strain energy function a new procedure is developed for calculating stress drop and plastic strain in regions sustaining brittle instabilities the formulation connects the damage rheology parameters with dynamic friction of simpler frameworks and the plastic strain accumulation is governed by a procedure that is equivalent to drucker prager plasticity the numerical simulations use variable boundary forces proportional to the slip deficit between the assumed far field plate motion and displacement of the boundary nodes these boundary conditions account for the evolution of elastic properties and plastic strain in the model region 3 d simulations of earthquakes in a model with a large strike slip fault produce scaling relations between the scalar seismic potency rupture area and stress drop values that are in good agreement with observations and other theoretical studies the area and potency of the simulated earthquakes generally follow a linear log log relation with a slope of 2 3 and are associated with stress drop values between 1 and 10 mpa a parameter space study shows that the area potency scaling is shifted to higher stress drops in simulations with parameters corresponding to lower dynamic friction more efficient healing and higher degree of seismic coupling

a rheological model of a fractured solid abstract experiments to study the behavior of various materials point to the relation that exists between elastic properties and the type of stress the influence of the state of stress on the elasticity of a fractured material will be discussed for a physically non linear model of an elastic solid the strain dependent moduli model of material presented in this paper makes it possible to describe this feature of a solid it also permits to simulate a dilatancy of rocks a damage parameter introduced into the model using a thermodynamical approach allows to describe a rheological transition from the ductile regime to the brittle one and to simulate the rock s memory narrow fracture zone creation and strain rate localization additionally the model enables the investigation of the final geometry of fracture zones and also to simulate their creation process taking into account pre existing fracture zones the process of narrow fracture zone creation and strain rate localization was simulated numerically for single axis compression and shear flow

mesospheric planetary waves at northern hemisphere fall equinox northern hemisphere planetary waves are strong in the winter and weak in the summer and they go through a fast transition around equinox this transition is studied here using ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm simulations with 1997 national centers for environmental prediction ncep analysis the planetary wave variability during the transition and its effect on the temperature and winds in the mesosphere are examined the simulated planetary wave structure agrees with climatological studies and the fast transition of the planetary waves is captured by the model the wave variability produces large temperature changes in the upper atmosphere above local stations in middle and high latitudes the qualitative behavior of the model is in excellent agreement with recent observations of a major perturbation in oh mesospheric temperatures from ft collins taylor et al 2001 although the smaller calculated magnitude suggests that the planetary wave amplitude might be underestimated by the model

spatial heterogeneity in earthquake fault like systems the inhomogeneity of materials with different physical properties is responsible for a wide variety of spatial and temporal behavior in this work we studied an earthquake fault model based on the olami feder christensen and rundle jackson brown cellular automata models with particular aspects of spatial heterogeneities and long range stress interactions in our model some localized stress accumulators were added into the system by converting a percentage of randomly selected sites into stronger sites that are called asperity cells these asperity cells support much higher failure stresses than the surrounding regular lattice sites but eventually rupture when applied stress reaches their threshold stress we found that changing the spatial configuration of those stronger sites generally increased the ability of the fault system to generate larger events but that the total percentage of asperities is important as well we also observed an increasing number of larger events associated with the total number of asperities in the lattice

nonlinear dynamics granular media and dynamic earthquake triggering the landers earthquake of 1992 triggered a series of earthquakes in other parts of california focusing attention on the mechanism of remote triggering laboratory experiments on granular material under pressure suggest that triggering is a result of seismic waves impinging on a fault and inducing elastic nonlinear behaviour of the fault core accompanied by instantaneous weakening and failure the resulting softening to weakening model fits in well with field observations of real earthquakes the 1992 magnitude 7 3 landers earthquake triggered an exceptional number of additional earthquakes within california and as far north as yellowstone and montana1 2 3 since this observation other large earthquakes have been shown to induce dynamic triggering at remote distances for example after the 1999 magnitude 7 1 hector mine1 and the 2002 magnitude 7 9 denali4 earthquakes and in the near field as aftershocks5 the physical origin of dynamic triggering however remains one of the least understood aspects of earthquake nucleation1 2 3 4 5 the dynamic strain amplitudes from a large earthquake are exceedingly small once the waves have propagated more than several fault radii for example a strain wave amplitude of 10 6 and wavelength 1 m corresponds to a displacement amplitude of about 10 7 m here we show that the dynamic elastic nonlinear behaviour of fault gouge perturbed by a seismic wave may trigger earthquakes even with such small strains we base our hypothesis on recent laboratory dynamic experiments conducted in granular media a fault gouge surrogate6 7 from these we infer that if the fault is weak8 9 10 seismic waves cause the fault core modulus to decrease abruptly and weaken further if the fault is already near failure this process could therefore induce fault slip

dissolved inorganic carbon in the xijiang river concentration and stable isotopic composition dissolved inorganic carbon dic is one the major products of chemical weathering of the land and it is also one of the most active components in the riverine carbon species concentration and stable isotopic composition of dic in the mainstream of the xijiang river xjr and its two tributaries the guijiang and hejiang rivers were investigated during a hydrological year and a massive flooding dic concentration of most selected sections of the xjr system varied from 750 to 2 400 m with an average of 1 630 390 m dic was significantly diluted in the massive flooding period the stable isotopic composition of dic 13cdic varied from 14 75 to 8 25 with an average of 11 19 1 18 from 17 22 to 10 65 with an average of 13 00 1 86 and from 15 94 to 9 71 with an average of 12 68 1 28 in the mainstream of the xjr the guijiang river and the hejiang river respectively this is jointly determined by the outcrop area of carbonate rocks and the properties of soil organic carbon within the catchments 13cdic is less negative in the dry season because of the increasing contribution from karst groundwater and more negative in the wet season because of the increasing contribution from surface soil water calcite was saturated sometimes at the mainstream sections of the xjr carbonate sourced dic contributes 10 32 43 95 with an average of about 27 69 6 03 of the riverine dic for the xjr the xjr exports about 4 27 1012 g of dic in the surveyed year of which about 83 occurred in the wet season

observational evidence for temporary planetary wave forcing of the mlt during fall equinox we present direct observations of zonal wave numbers 1 and 2 planetary wave activity in the mesopause region derived from a longitudinal chain of high latitude northern hemisphere 51 66 n super dual auroral radar network radars over a 9 year period 2000 2008 the planetary wave activity observed shows a consistent increase around the fall equinox this is shown to be coincident with a minimum in the magnitude of the stratospheric winds and consequently a minimum in the stratospheric gravity wave filtering and the subsequent momentum deposition in the mesopause region despite this the observed meridional winds are shown to be perturbed poleward and mesopause temperatures rise temporarily suggesting that westward momentum deposition from planetary waves temporarily becomes the dominant forcing on the mesopause region each fall equinox

carbon flux and c s isotopic characteristics of river waters from a karstic and a granitic terrain in the yangtze river system abstract we analyzed dissolved major elements 13 c dic and 34 s so4 in river waters from a karstic and a granitic terrain to examine weathering processes and the influence of basin geology on water quality and associated riverine alkalinity transport results show that waters from the karstic terrain have higher total dissolved solids tds major ion concentrations and 13 c dic values but lower k na and si concentration and 34 s so4 values than that from the granitic terrain the compositions of major ions and isotopes indicate that the solutes of the granitic terrain are controlled by processes of silicate and carbonate dissolution by carbonic acid however carbonate dissolution by both carbonic and sulfuric acid are dominant processes in karstic terrain total erosion rates dissolved inorganic carbon dic flux and co 2 uptake were 28 0 t km 2 yr 1 2 9 10 5 mol km 2 yr 1 and 2 3 10 5 mol km 2 yr 1 for the granitic terrain and 70 2 t km 2 yr 1 11 9 10 5 mol km 2 yr 1 and 6 4 10 5 mol km 2 yr 1 for the karstic terrain respectively these results indicated the karstic area plays an important role in uptake of co 2 and dic flux along the yangzte river basin our results also revealed that co 2 uptake due to carbonate chemical weathering in both karstic and granitic terrain is very high and provide as much or more dic flux than that from silicate chemical weathering

chemical weathering and atmospheric soil co2 uptake in the andean and foreland amazon basins abstract this study is a geochemical investigation of the andean and foreland basins of the amazon river at high spatial and time resolution carried out within the framework of the hybam research program hydro geodynamics of the amazon basin monthly sampling was carried out at 27 gauging stations located in the upper tributaries of the amazon basin from north to south the napo maranon ucayali madre de dios beni and mamore rivers the aim of this paper is to estimate the present day chemical weathering rate cwr as well as the flux of co 2 consumption from total and silicate weathering in the andes and foreland amazon basins and to discuss their distribution as a function of geomorphic and structural parameters based on the forward method the napo and other ecuadorian basins present high silicate weathering rates in comparison with the other basins we confirm that the maranon and ucayali rivers control the amazon hydrochemistry due to the presence of salt rocks and carbonates in these basins the madre de dios beni and mamore basins do not contribute much to the amazon dissolved load this north to south cwr gradient can be explained by the combination of decreasing weatherable lithology surface and decreasing runoff rates from the north to the south the foreland part of the basins or mountain lowland transition accounts for nearly the same proportion of the amazon silicate chemical weathering and carbonate chemical weathering fluxes as the andean part this result demonstrates the importance of the sediment accumulation areas in the amazon basin weathering budget and can be explained by the occurrence of a higher temperature the deposition of fresh sediments from andean erosion and a higher sediment residence time than in the upper part of the basin with a total co 2 consumption rate of 744 10 3 moles km year 1 and a silicate co 2 consumption rate of 300 10 3 moles km year 1 the upper amazon river andes foreland part is the most intense part of the amazon basin in terms of atmospheric co 2 consumption by weathering processes it is an important co 2 sink by weathering processes but accounts for only somewhat more than half of the co 2 consumption by silicate weathering of the amazon basin this result points out the importance of the lowland part of the basin in the inorganic c silicate budget the upper amazon accounts for 2 4 of the world s silicate co 2 consumption which is the same proportion as for the southern and southern east himalaya and tibetan plateau

ultrasonic velocities acoustic emission characteristics and crack damage of basalt and granite acoustic emissions ae compressional p shear s wave velocities and volumetric strain of etna basalt and aue granite were measured simultaneously during triaxial compression tests deformation induced ae activity and velocity changes were monitored using twelve p wave sensors and eight orthogonally polarized s wave piezoelectric sensors volumetric strain was measured using two pairs of orthogonal strain gages glued directly to the rock surface p wave velocity in basalt is about 3 km s at atmospheric pressure but increases by 50 when the hydrostatic pressure is increased to 120 mpa in granite samples initial p wave velocity is 5 km s and increases with pressure by 20 the pressure induced changes of elastic wave speed indicate dominantly compliant low aspect ratio pores in both materials in addition etna basalt also contains high aspect ratio voids in triaxial loading stress induced anisotropy of p wave velocities was significantly higher for basalt than for granite with vertical velocity components being faster than horizontal velocities however with increasing axial load horizontal velocities show a small increase for basalt but a significant decrease for granite using first motion polarity we determined ae source types generated during triaxial loading of the samples with increasing differential stress ae activity in granite and basalt increased with a significant contribution of tensile events close to failure the relative contribution of tensile events and horizontal wave velocities decreased significantly a concomitant increase of double couple events indicating shear suggests shear cracks linking previously formed tensile cracks

comparative study of short term diurnal tidal variability examination of the simultaneous temperature measurement from the sounding of the atmosphere using broadband emission radiometry saber instrument on board the thermosphere ionosphere mesosphere energetics and dynamics timed satellite not only confirms the existence of the inversion layer but also reveals the global nature of the inversion suggesting the presence of a transient planetary wave in the mesosphere the large tidal variability therefore is probably a consequence of the interaction between the transient planetary wave and tides this possibility is investigated by using the ncar thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm and by comparing model results with the lidar saber and timed doppler interferometer tidi measurements with a large transient planetary wave specified at the model lower boundary the model is able to produce strong diurnal tidal variability comparable to that from the lidar observation and the modeled temperature inversion is similar to that from the saber measurement the model results suggest that the planetary tidal wave interaction excites nonmigrating tides and modulates the gravity modes and or the rotational modes of the diurnal migrating tide among the nonmigrating tides the diurnal zonally symmetric s 0 component is the strongest and its interaction with the planetary wave leads to a strong diurnal eastward wave number 1 component

characterization of fault zones there are currently three major competing views on the essential geometrical mechanical and mathematical nature of faults the standard view is that faults are possibly segmented and heterogeneous euclidean zones in a continuum solid the continuum euclidean view is supported by seismic gravity and electromagnetic imaging studies by successful modeling of observed seismic radiation geodetic data and changes in seismicity patterns by detailed field studies of earthquake rupture zones and exhumed faults and by recent high resolution hypocenter distributions along several faults the second view focuses on granular aspects of fault structures and deformation fields the granular view is supported by observations of rock particles in fault zone gouge by studies of block rotations and the mosaic structure of the lithosphere which includes the overall geometry of plate tectonics by concentration of deformation signals along block boundaries by correlation of seismicity patterns on scales several times larger than those compatible with a continuum framework and by strongly heterogeneous wave propagation effects on the earth s surface the third view is that faults are fractal objects with rough surfaces and branching geometry the fractal view is supported by some statistical analysis of regional hypocenter locations by long range correlation of various measurements in geophysical boreholes by the fact that observed power law statistics of earthquakes are compatible with an underlying scale invariant geometrical structure by geometrical analysis of fault traces at the earth s surface and by measurements of joint and fault surfaces topography

longitudinal variations in mesospheric winds evidence for gravity wave filtering by planetary waves abstract mesospheric horizontal wind data from the high resolution doppler image hrdi satellite instrument are used to investigate the longitudinal variation of nontidal winds in the upper mesosphere and their relationship with winds in the stratosphere the period covered by the study is late winter february mid march for 1992 1994 the results indicate that there is a negative correlation between longitudinal variations of the zonal winds in the stratosphere and those in the mesosphere and between longitudinal variations of the meridional winds in the stratosphere and mesosphere the data are examined to determine which of several possible causes is responsible the possibilities are 1 that planetary scale disturbances are produced in situ by gravity wave drag in the mesosphere that is not zonally symmetric because of filtering by the planetary waves in the stratosphere 2 that asymmetries are caused by longitudinal variations in gravity wave drag due to azonal source distributions that are coinc

silicate rock weathering and atmospheric soil co2 uptake in the amazon basin estimated from river water geochemistry seasonal and spatial variations abstract using the data of the camrex project 1982 1984 on the water geochemistry of the amazon river and its main tributaries it was possible to assess the silicate rock weathering processes and the associated consumption of atmospheric soil co2 taking into account seasonal and spatial variations this study confirms the important role of the andes in the fluvial transport of dissolved and particulate material by the amazon and it shows for the first time that the silicate weathering rate and atmospheric soil co2 consumption are higher in the andes than in the rest of the amazon basin the seasonal variations exhibit the significant role of runoff as a major factor controlling silicate weathering processes and show that the chemical erosion rates vary greatly from low discharge to high discharge the average weathering rate estimated for the whole amazon basin 15 m my is comparable to other estimations made for other tropical equatorial environments a comparison between physical and chemical weathering rates of silicate rocks for the amazon basin and for each tributary basin show that in the andes and in the amazon trough the soil thicknesses are decreasing whereas in the shield the soil profiles are deepening

evolving geometrical and material properties of fault zones in a damage rheology model we discuss numerical simulations of evolving fault zone structures in a 3 d lithospheric model with a seismogenic crust governed by a damage rheology that accounts for large strain associated with permanent brittle deformation results for the initial propagation of an existing narrow damage zone subjected to oblique loading exhibit strong asymmetry of the evolving damage with respect to the initial fault orientation and predict out of plane directions of the propagating damage zones the orientations of the simulated damage zones agree with analytical expectations based on fracture mechanics for the directions of wing cracks generated at the tips of a crack under mixed mode loading lithosphere scale numerical simulations for the long term evolution of a large strike slip fault zone produce initially a system of stepping en echelon segments associated with the asymmetric generation of new damage zones the simulated fault zone segments evolve with continuing deformation to a throughgoing localized structure large scale perturbation in the geometry of the moho interface together with the regional heat regime can reduce considerably the degree of localization of the fault zone structure and the associated deformation fields

earthquake cycle fault zones and seismicity patterns in a rheologically layered lithosphere we study the coupled evolution of earthquakes and faults in a model consisting of a seismogenic upper crust governed by damage rheology over a viscoelastic substrate the damage rheology has two types of functional coefficients 1 a generalized internal friction separating states associated with material degradation and healing and 2 damage rate coefficients for positive degradation and negative healing changes the evolving damage modifies the effective elastic properties of material in the upper crust as a function of the ongoing deformation this simulates the creation and healing of fault systems in the upper seismogenic zone in addition to the vertically averaged thin sheet approximation we introduce a green function for three dimensional elastic half space for the instantaneous component of deformation the formulation accounts in an internally consistent manner for evolving deformation fields evolving fault structures aseismic energy release and spatiotemporal seismicity patterns these developments allow us to simulate long histories of crustal deformation and to study the simultaneous evolution of regional earthquakes and faults for various model realizations to focus on basic features of a large strike slip fault system we first consider a simplified geometry of the seismogenic crust by prescribing initial conditions consisting of a narrow damage zone in an otherwise damage free plate for this configuration the model generates an earthquake cycle with distinct interseismic preseismic coseismic and postseismic periods model evolution during each period is controlled by a subset of physical properties which may be constrained by geophysical geodetic rock mechanics and seismological data in the more generic case with a random initial damage distribution the model generates large crustal faults and subsidiary branches with complex geometries the simulated statistics depend on the space time window of the observational domain the results indicate that long healing timescale h describing systems with relatively long memory leads to the development of geometrically regular fault systems and the characteristic frequency size earthquake distribution conversely short h relatively short memory leads to the development of a network of disordered fault systems and the gutenberg richter earthquake statistics for intermediate values of h the results exhibit alternating overall switching of response from periods of intense seismic activity and the characteristic earthquake distribution to periods of low seismic activity and gutenberg richter statistics

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

hybrid fracture and the transition from extension fracture to shear fracture fracture is a fundamental mechanism of material failure two basic types of brittle fractures are commonly observed in rock deformation experiments extension opening mode fractures and shear fractures for nearly half a century it has been hypothesized that extension and shear fractures represent end members of a continuous spectrum of brittle fracture types however observations of transitional fractures that display both opening and shear modes hybrids in naturally deformed rock have often remained ambiguous and a clear demonstration of hybrid fracture formation has not been provided by experiments here we present the results of triaxial extension experiments on carrara marble that show a continuous transition from extension fracture to shear fracture with an increase in compressive stress hybrid fractures form under mixed tensile and compressive stress states at acute angles to the maximum principal compressive stress fracture angles are greater than those observed for extension fractures and less than those observed for shear fractures fracture surfaces also display a progressive change from an extension to shear fracture morphology

the seismic cycle at subduction thrusts 2 dynamic implications of geodynamic simulations validated with laboratory models 1 the physics governing the seismic cycle at seismically active subduction zones remains poorly understood due to restricted direct observations in time and space to investigate subduction zone dynamics and associated interplate seismicity we validate a continuum visco elasto plastic numerical model with a new laboratory approach paper 1 the analogous laboratory setup includes a visco elastic gelatin wedge underthrusted by a rigid plate with defined velocity weakening and strengthening regions our geodynamic simulation approach includes velocity weakening friction to spontaneously generate a series of fast frictional instabilities that correspond to analog earthquakes a match between numerical and laboratory source parameters is obtained when velocity strengthening is applied in the aseismic regions to stabilize the rupture spontaneous evolution of absolute stresses leads to nucleation by coalescence of neighboring patches mainly occurring at evolving asperities near the seismogenic zone limits consequently a crack or occasionally even pulse like rupture propagates toward the opposite side of the seismogenic zone by increasing stresses ahead of its rupture front until it arrests on a barrier the resulting surface displacements qualitatively agree with geodetic observations and show landward and from near the downdip limit upward interseismic motions these are rebound and reversed coseismically this slip increases adjacent stresses which are relaxed postseismically by afterslip and thereby produce persistent seaward motions the wide range of observed physical phenomena including back propagation and repeated slip and the agreement with laboratory results demonstrate that visco elasto plastic geodynamic models with rate dependent friction form a new tool that can greatly contribute to our understanding of the seismic cycle at subduction zones

systematic receiver function analysis of the moho geometry in the southern california plate boundary region we investigate the geometry of the moho interface in the southern california region including the san andreas fault saf san jacinto fault zone sjfz elsinore fault ef and eastern california shear zone with systematic analysis of receiver functions the data set consists of 145 teleseismic events recorded at 188 broadband stations throughout the region the analysis utilizes a 3d velocity model associated with detailed double difference tomographic results for the seismogenic depth section around the saf sjfz and ef combined with a larger scale community model a 3d ray tracing algorithm is used to produce effective 1d velocity models along each source receiver teleseismic ray common conversion point ccp stacks are calculated using the set of velocity models extracted for each ray the ccp stacks are analyzed with volumetric plots maps of maximum ccp stack values and projections along profiles that cross major faults and other features of interest the results indicate that the moho geometry in the study area is very complex and characterized by large prominent undulations along the ne sw direction a zone of relatively deep moho 35 40 km with overall n s direction crosses the saf sjfz and ef a section of very shallow moho 10 km below and to the se of the salton trough likely associated with a young oceanic crust produces large moho offsets at its margins locations with significant changes of moho depth appear to be correlated with fault complexity in the brittle crust the observations also show vertical moho offsets of 8 km across the saf and sjfz close to cajon pass and sections with no clear moho phase underneath cajon pass and adjacent to the sjfz near anza likely produced by complex local velocity structures in the brittle upper crust these features are robust with respect to various parameters of the analysis procedure

fault trace complexity cumulative slip and the shape of the magnitude frequency distribution for strike slip faults a global survey summary we examine whether the shape of the magnitude frequency distribution for strike slip faults is described by the gutenburg richter relationship log n a bm or by the characteristic earthquake model by analysing a data set of faults from california mexico japan new zealand china and turkey for faults within regional seismic networks curves of the form log n yrpl a bm where n yr is the number of events per year equal to magnitude m are fit to the instrumental record of seismicity and geological data are used to estimate independently the size and recurrence rate of the largest expected earthquakes that would rupture the total length of the fault extrapolation of instrumentally derived curves to larger magnitudes agrees with geological estimates of the recurrence rate of the largest earthquakes for only four of the 22 faults if uncertainties in curve slope are considered and significantly underestimates the geological recurrence rates in the remaining cases also if we predict the seismicity of the faults as a function of fault length and slip rate and the predicted seismicity is distributed in accord with the gutenburg richter relationship we find the predicted recurrence rate to be greater than the observed recurrence rates of smaller earthquakes along most faults if individual fault zones satisfy the gutenburg richter relationship over the long term our observations imply that during the recurrence interval of the largest expected earthquakes the recurrence of lesser sized events is not steady but rather strongly clustered in time however if the instrumental records provide an estimate of the long term rate of small to moderate earthquakes along the faults our observations imply that the faults generally exhibit a magnitude frequency distribution consistent with the characteristic earthquake model also we observe that the geometrical complexity of strike slip faults is a decreasing function of cumulative strike slip offset the four faults we observe to be consistent with the gutenburgrichter relationship are among those characterized by the least amount of cumulative slip and greatest fault trace complexity we therefore suggest that the ratio of the recurrence rate of small to large earthquakes along a fault zone may decrease as slip accumulates and the fault becomes smoother

carbon fluxes pco2 and substrate weathering in a large northern river basin canada carbon isotope perspectives abstract isotopic composition of dissolved inorganic carbon 13 c dic in the ottawa river basin is about 8 and 16 for lowland carbonate and upland silicate tributaries respectively this suggests that 1 the source of dic to the ottawa river is soil respiration and carbonate weathering 2 exchange with the atmosphere is unidirectional or volumetrically unimportant and 3 in river respiration and photosynthesis are not significant influences on the river carbon budget accepting these constraints chemical and isotopic data are used to reconstitute soil pco2 for tributary catchments averages for upland silicate mixed and lowland carbonate basins are calculated to be roughly 2000 5000 and 30 000 ppm respectively these values are used as input to model the pathway of carbon through the watershed rain water to soil water to river water the flux of carbon from the ottawa river as dic is calculated to be 4 3 1010 mol c a utilizing carbon isotopes 75 and 25 of the ca2 mg2 flux is calculated to originate from carbonate and silicate weathering respectively and 61 of the dic is calculated to originate from organic respiration the latter represents some 6 of respired carbon in the basin assuming an average respiration rate of 0 5 mmol c m 2 h 1 based on a diffusion model co2 evasion to the atmosphere from the ottawa river and its tributaries is estimated to be 1 3 1010 mol c a or 30 of the dic flux

inferring paleostresses from natural fracture patterns a new method we introduce a method to infer the remote differential stress magnitude from the curvature of overlapping echelon fracture traces the curving paths of overlapping echelon cracks imply the predominance of local crack induced stresses over remote stresses during propagation nearly straight crack paths imply the controlling influence of a remote compressive crack parallel differential stress this method is used to interpret complex joint patterns mapped in sedimentary rock it is also applied to the problem of fracture pattern generation using computer models

the seismic cycle at subduction thrusts insights from seismo thermo mechanical models 1 the underestimation of the size of recent megathrust earthquakes illustrates our limited understanding of their spatiotemporal occurrence and governing physics to unravel their relation to associated subduction dynamics and long term deformation we developed a 2 d continuum viscoelastoplastic model that uses an eulerian lagrangian finite difference framework with similar on and off fault physics we extend the validation of this numerical tool to a realistic subduction zone setting that resembles southern chile the resulting quasi periodic pattern of quasi characteristic m8 m9 megathrust events compares quantitatively with observed recurrence and earthquake source parameters albeit at very slow coseismic speeds without any data fitting surface displacements agree with gps data recorded before and during the 2010 m8 8 maule earthquake including the presence of a second order flexural bulge these surface displacements show cycle to cycle variations of slip deficits which overall accommodate 5 of permanent internal shortening we find that thermally and stress driven creep governs a spontaneous conditionally stable downdip transition zone between temperatures of 350 c and 450 c ruptures initiate above it and below the forearc moho propagate within it interspersed by small intermittent events and arrest below it as ductile shearing relaxes stresses ruptures typically propagate upward along lithological boundaries and widen as pressures drop the main thrust is constrained to be weak due to fluid induced weakening required to sustain regular subduction and to generate events with natural characteristics fluid pressures of 75 99 of solid pressures the agreement with a range of seismological geodetic and geological observations demonstrates the validity and strength of this physically consistent seismo thermo mechanical approach

chemical weathering in the upper huang he yellow river draining the eastern qinghai tibet plateau we examined the fluvial geochemistry of the huang he yellow river in its headwaters to determine natural chemical weathering rates on the northeastern qinghai tibet plateau where anthropogenic impact is considered small qualitative treatment of the major element composition demonstrates the dominance of carbonate and evaporite dissolution most samples are supersaturated with respect to calcite dolomite and atmospheric co2 with moderate 0 710 0 715 87 sr 86 sr ratios while six out of 21 total samples have especially high concentrations of na ca mg cl and so4 from weathering of evaporites we used inversion model calculations to apportion the total dissolved cations to rain evaporite carbonate and silicate origin the samples are either carbonate or evaporite dominated but the relative contributions of the four sources vary widely among samples net co2 consumption rates by silicate weathering 6 120 10 3 mol km 2 yr are low and have a relative uncertainty of 40 we extended the inversion model calculation to literature data for rivers draining orogenic zones worldwide the ganges brahmaputra draining the himalayan front has higher co2 consumption rates 110 570 10 3 mol km 2 yr and more radiogenic 87 sr 86 sr 0 715 1 24 than the upper huang he but the rivers at higher latitudes are similar to or lower than the upper huang he in co2 uptake by silicate weathering in these orogenic zones silicate weathering rates are only weakly coupled with temperature and become independent of runoff above 800 mm yr copyright 2005 elsevier ltd

the co2 system in rivers of the australian victorian alps co2 evasion in relation to system metabolism and rock weathering on multi annual time scales abstract the patterns of dissolved inorganic c dic and aqueous co2 in rivers and estuaries sampled during summer and winter in the australian victorian alps were examined together with historical 1978 1990 geochemical data this study provides for the first time a multi annual coverage of the linkage between co2 release via wetland evasion and co2 consumption via combined carbonate and aluminosilicate weathering 13c values imply that carbonate weathering contributes 36 of the dic in the rivers although carbonates comprise less than 5 of the study area baseflow interflow flushing of respired c3 plant detritus accounts for 50 and atmospheric precipitation accounts for 14 of the dic the influence of in river respiration and photosynthesis on the dic concentrations is negligible river waters are supersaturated with co2 and evade 27 7 106 mol km2 a to 70 9 106 mol km2 a co2 to the atmosphere with the highest values in the low runoff rivers this is slightly higher than the global average reflecting higher gas transfer velocities due to high wind speeds evaded co2 is not balanced by co2 consumption via combined carbonate and aluminosilicate weathering which implies that chemical weathering does not significantly neutralize respiration derived h2co3 the results of this study have implications for global assessments of chemical weathering yields in river systems draining passive margin terrains as high respiration derived dic concentrations are not directly connected to high carbonate and aluminosilicate weathering rates

a global view of the molecular oxygen night airglow 1 the high resolution doppler imager on the upper atmosphere research satellite has observed the o2 atmospheric band nightglow at extremely high spatial resolution of 50 km in the horizontal over much of earth s surface these observations of the oxygen nightglow are shown to be a good surrogate for atomic oxygen outflow from the thermosphere and subsequent recombination in the upper mesosphere the distribution of enhanced airglow and recombination verify the previous observations that bright regions of the nightglow are associated with descending motion where the tides are transporting atomic oxygen out of the thermosphere and regions of decreased airglow are associated with ascending tidal motion the detailed observations of the global airglow at a scale of 100 km present a much more complex picture however the tidally enhanced regions are extremely structured with strong longitudinal and latitudinal variability in brightness and associated atomic oxygen recombination these structured regions are persistent on a timescale of a day or more with certain regions of the globe exhibiting enhanced airglow much of the time these regions are present over the entire night side of the globe but are strongly modulated by the ascending and descending tidal motions a theoretical study of these enhancements suggests that they are caused by the upward propagation of gravity waves which break in the high mesosphere and induce strong vertical motion in the atmosphere it is interesting that the primary cause of the increased transport of atomic oxygen is vertical motion rather than the conventional enhanced turbulence explanation these gravity waves are associated with wind shear and strong convective activity in the troposphere and often appear in certain preferred locations where convective activity is expected these observations have important implications for the basic processes by which momentum and energy are deposited in the upper mesosphere we suggest that the processes must be modeled as stochastic events that dance around the base of the thermosphere generally in climatologically preferred regions rather than the relatively uniform distribution of gravity wave forcings that is being used in general circulation models up to this time

brittle deformation and damage induced seismic wave anisotropy in rocks summary we study the relations between rock fracturing non linear deformation and damage and stress induced anisotropy of seismic waves by comparing theoretical predictions of a damage rheology model to results of laboratory experiments with granite samples the employed damage model provides a generalization of hookean elasticity to a non linear continuum mechanics framework of cracked media incorporating degradation and recovery of the effective elastic properties along with gradual accumulation of irreversible deformation beyond the elastic regime the model assumes isotropic distribution of local microcracks expressed in terms of a scalar damage variable but the non linear elastic response caused by the opening closure and evolution of the internal cracks is predicted to lead to seismic wave anisotropy we develop relations between the seismic wave anisotropy internal rock damage and stress field and test the viscoelastic damage rheology against sets of laboratory experiments with cylindrical granite samples the observed data include measurements of stress and strain in three loading cycles culminating in a final macroscopic failure together with measured wave velocities along and perpendicular to the axis of the cylinder using a single set of parameters the model fits well the overall evolution of the axial and transversal stress strain relations as well as the anisotropic elastic wave velocities during all cycles from the onset of fracturing in the first cycle until the macroscopic failure in the final cycle

chemical weathering and co2 consumption in the xijiang river basin south china monthly samples of riverine water were collected and analyzed for the concentrations of major ions ca2 mg2 k na hco3 so42 cl no3 dissolved silicon and total dissolved solids tds at wuzhou hydrological station located between the middle and lower reaches of the xijiang river xjr from march 2005 to april 2006 more frequent sampling and analysis were carried out during the catastrophic flooding in june 2005 stoichiometric analysis was applied for tracing sources of major ions and estimating co2 consumption from the chemical weathering of rocks the results demonstrate that the chemical weathering of carbonate and silicate rocks within the drainage basin is the main source of the dissolved chemical substances in the xjr some 81 20 of the riverine cations originated from the chemical weathering processes induced by carbonic acid 11 32 by sulfuric acid and the other 7 48 from the dissolution of gypsum and precipitates of sea salts within the drainage basin the co2 flux consumed by the rock chemical weathering within the xjr basin is 2 37 x 10 11 mol y 1 of which 0 64 x 10 11 mol y 1 results from silicate rock chemical weathering and 1 73 x 10 11 mol y 1 results from carbonate rock chemical weathering the co2 consumption comprises 0 38 x 10 11 mol during the 9 d catastrophic flooding the co2 consumption from rock chemical weathering in humid subtropical zones regulates atmospheric co2 level and constitutes a significant part of the global carbon budget the carbon sink potential of rock chemical weathering processes in the humid subtropical zones deserves extra attention c 2008 elsevier b v all rights reserved

gravity enhanced representation of measured geoid undulations using equivalent sources summary direct global positioning system measurement of geoid undulations on accurately levelled stations usually tens of kilometres apart can be interpolated by taking advantage of denser surveys of free air gravity anomalies covering the same area using either a spherical or a planar earth model a two layer equivalent source is constructed with the deepest masses located under the geoid stations and the shallower ones under the gravity stations in such a way that the effect of the masses fits simultaneously with different precisions the anomalous potential related to the geoid and its vertical gradient or gravity anomaly this poses a linear bayesian problem whose associated system of equations can be solved directly or by iterative procedures the ability of the described method to predict the geoid elevation over the gravity stations is assessed in a synthetic example and in the application to a real case a gravity enhanced geoid is mapped for an area of buenos aires province argentina where local features are put in evidence

temporal variation in the geometry of a strike slip fault zone examples from the dead sea transform abstract the location of the active fault strands along the dead sea transform fault zone dst changed through time in the western margins of dead sea basin the early activity began a few kilometers west of the preset shores and moved toward the center of the basin in four stages similar centerward migration of faulting is apparent in the hula valley north of the sea of galilee as well as in the negev and the sinai peninsula in the arava valley seismic surveys reveal a series of buried inactive basins whereas the current active strand is on their eastern margins in the central arava the centerward migration of activity was followed by outward migration with pleistocene faulting along nne trending faults nearly 50 km west of the center largely the faulting along the dst which began in the early middle miocene over a wide zone of up to 50 km became localized by the end of the miocene the subsidence of fault controlled basins which were active in the early stage stopped at the end of the miocene later during the plio pleistocene new faults were formed in the negev west of the main transform they indicate that another cycle has begun with the widening of the fault zone it is suggested that the localization of faulting goes on as long as there is no change in the stress field the stresses change because the geometry of the plates must change as they move and consequently the localization stage ends the fault zone is rearranged becomes wide and a new localization stage begins as slip accumulates it is hypothesized that alternating periods of widening and narrowing correlate to changes of the plate boundaries manifest in different euler poles

worldwide distribution of continental rock lithology implications for the atmospheric soil co2 uptake by continental weathering and alkalinity river transport to the oceans 1 the silicate rock weathering followed by the formation of carbonate rocks in the ocean transfers co2 from the atmosphere to the lithosphere this co2 uptake plays a major role in the regulation of atmospheric co2 concentrations at the geologic timescale and is mainly controlled by the chemical properties of rocks this leads us to develop the first world lithological map with a grid resolution of 1 1 this paper analyzes the spatial distribution of the six main rock types by latitude continents and ocean drainage basins and for 49 large river basins coupling our digital map with the gem co2 model we have also calculated the amount of atmospheric soil co2 consumed by rock weathering and alkalinity river transport to the ocean among all silicate rocks shales and basalts appear to have a significant influence on the amount of co2 uptake by chemical weathering

stationary planetary waves inferred from windii wind data taken within altitudes 90 120 km during 1991 96 abstract a climatology of stationary planetary waves spws in horizontal winds at latitudes 70 s 70 n and altitudes 90 120 km is obtained from wind imaging interferometer windii green line measurements in december january and march april of 1991 96 the observed solstitial spw fields are relatively stronger and dominated by zonal wavenumber 1 variations in contrast the equinoctial spw fields are weaker and characterized by zonal wavenumber 2 variations the zonal amplitude maxima of 10 25 m s 1 are generally centered at the midlatitudes of 35 40 in both hemispheres around 96 km with the eastward perturbation velocity maxima around 90 e for wavenumber 1 and 60 and 240 e for wavenumber 2 the meridional amplitude maxima are about 5 15 m s 1 and show more variabilities in their latitude height distributions the meridional phases indicated that eliassen palm ep fluxes were downward poleward for the winter maxima vertically varying poleward for the summer maxima and more variable during march apr

deformation and seismicity associated with continental rift zones propagating toward continental margins 1 we study the propagation of a continental rift and its interaction with a continental margin utilizing a 3 d lithospheric model with a seismogenic crust governed by a damage rheology a long standing problem in rift mechanics known as thetectonic force paradox is that the magnitude of the tectonic forces required for rifting are not large enough in the absence of basaltic magmatism our modeling results demonstrate that under moderate rift driving tectonic forces the rift propagation is feasible even in the absence of magmatism this is due to gradual weakening and long term memory of fractured rocks that lead to a significantly lower yielding stress than that of the surrounding intact rocks we show that the style rate and the associated seismicity pattern of the rift zone formation in the continental lithosphere depend not only on the applied tectonic forces but also on the rate of healing accounting for the memory effect provides a feasible solution for thetectonic force paradox our modeling results also demonstrate how the lithosphere structure affects the geometry of the propagating rift system toward a continental margin thinning of the crystalline crust leads to a decrease in the propagation rate and possibly to rift termination across the margin in such a case a new fault system is created perpendicular to the direction of the rift propagation these results reveal that the local lithosphere structure is one of the key factors controlling the geometry of the evolving rift system and seismicity pattern

δ13c pattern of dissolved inorganic carbon in a small granitic catchment the strengbach case study vosges mountains france abstract the transfers and origins of dissolved inorganic carbon dic were studied for a year in a soil spring stream system in the strengbach catchment vosges mountains france this 80 ha experimental research basin is located on the eastern side of the mountains at an altitude ranging from 883 to 1146 m a s l and is mainly covered by spruce 80 brown acid and podzolic soils developed on a granitic basement and as a result the dic originates solely from co2 generated by oxidation of soil organic matter the 13 c dic in catchment waters is highly variable from about 22 in the springs and piezometers to about 12 in the stream at the outlet of the catchment in the springs pronounced seasonal variations of 13 c dic exist with the dic in isotopic equilibrium with the soil co2 that has estimated 13 c of about 24 in winter and 20 in summer these seasonal variations reflect an isotopic fractionation that seems only induced by molecular diffusion of soil co2 in summer in stream water seasonal variations are small and the relatively heavy dic 12 on average is a result of isotopic equilibration of the aqueous co2 with atmospheric co2