balancing rare earth element distributions in the northwestern mediterranean sea abstract elemental concentrations of rare earth elements ree and isotopic compositions of neodymium end have been measured in three water column profiles in the north western mediterranean sea clear enrichments of ree are observed when comparing to adjacent atlantic waters suggesting ree inputs along the circulation in this area for the first time relative proportions of external sources including submarine groundwater discharges sgd have been quantified for the studied area atmospheric deposition is estimated to be the most important external source for all the ree with an average contribution of 44 followed by diffusion from porewaters which provide a 30 dissolved riverine fluxes account for 11 sgd for 10 and dissolution of remobilized surface sediments the remaining 6 mass balances accounting for seawater transport and identified external sources have been delineated for the three main water masses modified atlantic waters levantine intermediate waters and western mediterranean deep waters they show that the balances of ree in this area are dominated by seawater mass mixing superimposed on this hydrography ree vertical profiles are affected by external sources and biogeochemical cycling dissolved ree are correctly balanced in deep waters whereas substantial missing fluxes are identified in the surface and intermediate water masses additional net lree outputs and hree inputs are required in the surface waters while net output fluxes for all the ree are missing at intermediate waters the most likely process suggested here is an active reversible scavenging consistent with a stronger adsorption of lree compared to hree in the particular case of the redox sensitive cerium the most plausible mechanism to explain the net output missing fluxes is ce 3 removal by particle scavenging via oxidation to insoluble ce 4 estimated ce oxidation rates of 0 33 d 1 in surface waters agree well with previously published values exchange fluxes derived from the isotopic nd mass balance indicate higher nd scavenging in surface compared to intermediate waters

combination of precise leveling and insar data to constrain source parameters of the mw 6 5 26 december 2003 bam earthquake we used new precise leveling data acquired 40 days after the bam earthquake in combination with radar interferometry observations from both ascending and descending orbits to investigate static deformation associated with the 2003 bam earthquake we invert this geodetic data set to gain insight into the fault geometry and slip distribution of the rupture the best fitting dislocation model is a steeply east dipping right lateral strike slip fault that has a size of 11 by 8 km and strikes n2 w we find that such smooth geometry fits available geodetic data better than previously proposed models for this earthquake our distributed slip model indicates a maximum strike slip of 3 m occurring about 3 to 5 km deep the slip magnitude and depth of faulting taper to the north where the fault approaches the bam city inclusion of crustal layering increases the amount of maximum slip inferred at depth by about 4

surface ruptures and building damage of the 2003 bam iran earthquake mapped by satellite synthetic aperture radar interferometric correlation 1 we use the interferometric correlation from envisat synthetic aperture radar sar images to map the details of the surface ruptures related to the 26 december 2003 earthquake that devastated bam iran the main strike slip fault rupture south of the city of bam has a series of four segments with left steps shown by a narrow line of low correlation in the coseismic interferogram this also has a clear expression in the field because of the net extension across the fault just south of the city limits the surface strain becomes distributed over a width of about 500 m probably because of a thicker layer of soft sedimentary material another fault north of bam shows offset and low correlation over a wider zone in the interferograms but it has no discrete surface rupture possibly because of a net shortening across this fault taking the difference between the interferometric correlation for an interval including the earthquake and an interval before the earthquake separates the changes due to the earthquake from other effects in the partially vegetated city of bam we map the damage to buildings by measuring the change from high correlation to low correlation where buildings were destroyed by the earthquake

methodology of hydrogeological characterization of deep carbonate aquifers as potential reservoirs of groundwater case of study the jurassic aquifer of el maestrazgo castellon spain a methodology for the characterization of deep carbonate aquifers has been developed and applied to el maestrazgo jurassic aquifer in castellon spain characterization of these aquifer formations located at more than 300 m deep consisted of a previous phase of compilation analysis and synthesis of the existing information about the area followed by a coordinated combination of different speciality studies geology stratigraphy structural analysis hydrogeology hydrochemistry geophysics and remote sensing geological studies included geological mapping definition of stratigraphical units and facies and structural analysis the aim of the hydrogeology study was to define aquifer formations recharge area aquifer points inventory and groundwater flow directions for the establishment of piezometric and water quality observation nets special techniques were applied like thermal infrared aerial images and the evaluation of submarine groundwater discharge by means of natural radium isotopes hydrochemical techniques including majority elements characterization and stable isotopes 18o 2h and 3h determination allowed classifying hydrochemical facies and establishing a renewal pattern for water within the system geophysics was useful in determining the aquifer geometry the features of the basement and the petrophysical characteristics of the geological formations preliminary results show an important tectonic complexity and the possibilities for groundwater uses in the area of study

the succoth cu ni pd deposit a new taxite hosted magmatic sulphide system in the west musgrave province western australia abstract the succoth cu ni pd deposit is large taxite hosted magmatic sulphide deposit located in the west musgrave province of western australia mineralisation consists of disseminated matrix and massive cu fe sulphides and lesser ni fe sulphides hosted within a mafic intrusive body the intrusive was emplaced within a sequence of earlier proterozoic mafic intrusives and meta volcanics during the giles event 1085 1040 ma and subsequently ductile deformed and strongly overprinted by hydrous alteration phases predominantly amphiboles an igneous architecture is presented based on contact and xenolithic relationships and internal fractionation trends in existing diamond drill holes and the silicate and sulphide mineralogy of the host and wall rock units are detailed sulphide geochemistry and stable isotope data are interpreted to reflect modifications to the magmatic signature of the mineralised intrusion as a consequence of wall rock contamination and hydrothermal overprinting genetic implications of different pge chemistry between disseminated and massive sulphides in the system are discussed

evidence for rapid fault healing derived from temporal changes in s wave splitting 1 tadokoro et al 1999 had made an s wave splitting analysis on the nojima fault zone that ruptured during the 1995 hyogo ken nanbu earthquake for a period 9 12 months after the mainshock the direction of faster shear wave polarization had been parallel to the fault strike suggesting fractures of shear fault origin in this study we made an additional s wave splitting analysis for a period 33 45 months after the mainshock and detected the rotation of that is the direction was parallel to the regional maximum horizontal compressional stress which is oblique to the fault strike this temporal change suggests that all the fractures of shear fault origin had completely healed and cracks of tectonic stress origin recovered between the two periods this is strong evidence for rapid fault healing which completed within 33 months after the mainshock

shear wave splitting in the upper mantle wedge above the tonga subduction zone summary intermediate period seismograms of shear waves from deep earthquakes are examined for shear wave splitting diagnostic of seismic velocity anisotropy in the upper mantle wedge between the subducting tonga slab and stations in the fiji islands earthquakes with near vertical incidence angles are selected to minimize complications of converted phases and the free surface horizontal component seismograms for 25 deep earthquakes recorded at station lak on the lau ridge show splitting of up to 0 9 s with an average of 0 45 0 25 s between fast and slow s wave components anisotropy in the upper mantle is the most likely cause of the splitting the ese orientation of the fast velocity direction at station lak corresponds to an axis of symmetry of the anisotropic mantle and is approximately perpendicular to magnetic lineations in the lau basin and the northeastern portion of the south iiji basin the observations are consistent with a model of flow alignment of olivine 100 and orthopyroxene 001 axes parallel to the direction of basin extension seismograms for eight deep earthquakes at station sva on viti levu show up to 1 0 s splitting with an average of 0 65 0 29 s and a weak nne preferred orientation of fast velocity polarizations of shear wave particle motions corrected for anisotropy are within 36 5 26 of polarixations predicted for nine moment tensor solutions the magnitude of shearwave splitting and estimates of the thickness of the lithosphere in the fiji region imply that the anisotropy cannot be contained in the lithosphere alone either the anisotropy is distributed in both the lithosphere and asthenosphere or the asthenosphere alone is anisotropic

mapping stress and structurally controlled crustal shear velocity anisotropy in california we present shear velocity anisotropy data from crustal earthquakes in california and demonstrate that it is often possible to discriminate structural anisotropy polarization of the shear waves along the fabric of major active faults from stress induced anisotropy polarization parallel to the maximum horizontal compressive stress stress directions from seismic stations located near but not on the san andreas fault indicate that the maximum horizontal compressive stress is at a high angle to the strike of the fault in contrast seismic stations located directly on one of the major faults indicate that shear deformation has significantly altered the elastic properties of the crust inducing shear wave polarizations parallel to the fault plane

ediacaran and cambrian paleosols from central australia abstract ediacaran to cambrian red sandstones of the northern territory including arumbera sandstone and grant bluff and central mount stuart formations have been reexamined and sampled in order to reconstruct paleoenvironments from sedimentary facies and paleosols sedimentary facies include green gray calcareous sandstone member iii of arumbera sandstone only red siltstone with calcareous nodules also only member iii and also non calcareous red green siltstone interbedded red siltstone and sandstone and trough bedded sandstone the green gray facies has diverse and distinctive cambrian marine trace fossils not found in the red beds which have instead an assemblage of problematic body fossils including arumberia noffkarkys hallidaya ernietta trepassia and dickinsonia the red facies are interpreted as fluvial paleochannels trough cross bedded fluvial levees interbedded siltstone and sandstone poorly drained floodplain red green siltstone and well drained floodplain or low terrace calcareous nodular the carbonate nodules have micritic replacive fabrics and a significant positive correlation of 13c and 18o characteristic of pedogenic carbonate of calcid soils other red beds have pseudomorphous sand crystals after gypsum like those of gypsid soils individual red beds show negative strain and mass transfer for cationic bases typical of soils as well as gradational alteration down from fossiliferous tops characteristic of soils their varied degree of pedogenic differentiation is identified as psamment aquent and ochrept paleosols phosphorus depletion in the paleosols is evidence that organisms lived in the paleosols and were not introduced by transient marine incursions the problematic quilted fossils arumberia noffkarkys and hallidaya formed a distinctive inland terrestrial polsterland during the ediacaran and early cambrian

precambrian tectonics and the physicochemical evolution of the continental crust i the gabbro eclogite transition revisited abstract we report the first occurrence of retrograde eclogite shear zones cutting proterozoic granulites from australia the musgrave range granulites were metamorphosed at about 12 kbar pressure and 850 900 c the granulites then cooled isobarically and developed a variety of lower temperature mineral reaction coronas typical of garnet granulites these rocks are cut by a major shear zone the davenport shear in which lower temperature fine grained eclogite developed this demonstrates that mafic rocks in the deep crust can cool down into the thermodynamic stability field of eclogite without undergoing transformation to eclogite we agree with harte et al 1981 that rocks lacking a fluid phase in stable tectonic regions are unlikely to maintain local equilibrium at ambient geotherm conditions until depths well within the upper mantle are reached it is proposed that many isobaric high pressure granulites could have cooled down into the eclogite field before their later excavation to the surface and did not transform to an eclogite mineralogy the inability of the lower crust to transform into eclogite by retrograde reaction has important implications for the seismic petrologic and geochemical character of the lower crust the continental moho cannot be caused by the gabbro eclogite transition preservation of relatively low density high temperature granulite and gabbroic mineral assemblages in the lower continental crust prohibits major recycling of lower crust back into the mantle once it is removed from active plate boundaries however in island arcs with magmatically thickened crust mafic rocks at a depth of 60 to 70 km will be in the eclogite stability field at high enough temperatures 800 900 c for eclogite to rapidly form and sink back into the mantle this could result in a net accreted crust of broadly andesitic composition in contrast later growth of continental crust by basalt underplating in stabilised shield regions will not result in subsequent eclogite formation and lower crustal recycling back into the mantle will not occur thus estimates of the average composition of the continental crust which are based on a mass balance of plate margin basaltic input from the mantle will not be adequate

shear wave polarizations near the north anatolian fault i evidence for anisotropy induced shear wave splitting summary the turkish dilatancy projects tdp1 in 1979 and tdp2 in 1980 recorded small earthquakes near the north anatolian fault with closely spaced networks of three component seismometers in order to investigate the possibility of diagnosing dilatancy from its effects of shear wave propagation this paper examines the polarizations of shear wavetrains recorded in the shear wave window immediately above the earthquake foci abrupt changes in the orientation and or ellipticity of the shear wave polarizations are almost always observed during the first few cycles following the initial shear wave arrival on each seismogram the horizontal projections of the polarizations of the first shear wave arrivals at any given station show nearly parallel alignments with approximately the same orientations at each of the recording sites with one exception it is difficult to explain this uniform alignment over a wide area in terms of scattering at the irregular surface topography or by earthquake focal mechanisms we demonstrate that the shear wave splitting is likely to be the result of anisotropy in the region above the earthquake foci which could produce polarizations displaying the observed alignments the temporal change of the azimuth of alignment observed at one locality between 1979 and 1980 may be due to the release of a local stress anomaly by a very near earthquake

observation and modelling of fault zone fracture seismic anisotropy i p sv and sh travel times summary three component vsp borehole seismograms taken in the vicinity of an active normal fault in california show strong systematic shear wave splitting that increases with proximity to the fault using cerven s method of characteristics for ray tracing in anisotropic heterogeneous media and hudson s formulation of elastic constants for media bearing aligned fractures we have fitted a suite of p sv and sh hanging wall and foot wall travel times with a simple model of aligned fractures flanking the fault zone the dominant fracture set is best modelled as parallel to the fault plane and increasing in density with approach to the fault the increase in fracture density is non uniform power law or gaussian with respect to distance to the fault although the hanging wall and the foot wall rock are petrologically the same unit the fracture halo is more intense and extensive in the hanging wall than in the foot wall upon approach to the fault plane the fracture density or fracture density gradient becomes too great for the seismic response to be computed by hudson cerven procedures the maximum fracture density that can be modelled is about 0 08 within this 25 m fracture domain it appears more useful to model the fault and near field fractures as a low velocity waveguide we observe production of trapped waves within the confines of the intense fracture interval

3 d velocity structure of the 2003 bam earthquake area se iran existence of a low poisson s ratio layer and its relation to heavy damage abstract to understand the generation mechanism of the bam earthquake mw 6 6 we studied three dimensional v p v s and poisson s ratio structures in the bam area by using the seismic tomography method we inverted accurate arrival times of 19490 p waves and 19015 s waves from 2396 aftershocks recorded by a temporal high sensitivity seismic network the 3 d velocity structure of the seismogenic region was well resolved to a depth of 14 km with significant velocity variations of up to 5 the general pattern of aftershock distribution was relocated by using the 3 d structure to delineate a source fault for a length of approximately 20 km along a line 4 5 km west of the known geological bam fault this source fault dips steeply westward and strikes a nearly north south line the main shallow cluster of aftershocks south of the city of bam is distributed just under the minor surface ruptures in the desert the 3 d velocity structure shows a thick layer of high v s and low minimum 0 20 at a depth range of 2 6 km the deeper layer with a thickness of about 2 km appears to have a low v s and high maximum 0 28 from 6 km depth beneath bam to a depth of 9 km south of the city the inferred increase of poisson s ratio from 2 to 10 km in depth may be associated with a change from rigid and sio 2 rich rock to more mafic rock including the probable existence of fluids the main seismic gap of aftershock distribution at the depth range of 2 to 7 km coincides well with the large slip zone in the shallow thick layer of high v s and low the large slip propagating mainly in the shallow rigid layer may be one of the main reasons why the bam area suffered heavy damage

swas a shear wave analysis system for semi automatic measurement of shear wave splitting above small earthquakes the complexity of shear wave arrivals above small earthquakes makes the polarisations and time delays of shear wave splitting above small earthquakes difficult to measure we report a semi automatic shear wave analysis system swas that appears to combine the benefits of both visual and automatic techniques initially swas automatically estimates shear wave polarisations and picks shear wave arrivals by an expert system which provides sufficiently accurate initial measurements for visual adjustment swas then allows easy comparison and adjustment of picks between screen images of original seismograms seismograms rotated into anisotropic polarisations and polarisation diagrams hodograms with immediate plotting in various standard or non standard configurations this speeds up visual measurements by well over an order of magnitude and typically allows records of almost all small earthquakes m 1 0 to be reliably measured for shear wave splitting polarisations and time delays swas was developed and tested for data from the sil seismic network in iceland

transgressive regressive cycles and jurassic palaeogeography of northeast iberia abstract a correlation and sequence stratigraphy study of jurassic successions has been carried out in the main sedimentary basins of northeast iberia i e asturias basque cantabrian and iberian basins based on the identification of transgressive regressive cycles the development and palaeogeographic evolution of the epicontinental carbonate platforms of northeast iberia were largely controlled by major tectonic activity at three main intervals at the beginning of the jurassic in the lower middle jurassic transition and during the uppermost jurassic respectively during early jurassic times northeast iberia was the site of a single and large carbonate ramp opened to the north this carbonate ramp suffered a progressive drowning evolving from an inner to hemipelagic ramp systems with the local development of suboxic environments in the deepest areas located to the north during the middle jurassic different open carbonate platforms were formed including the development of swells in intermediate areas during the upper jurassic the outer ramp areas were progressively moving to the east iberian basin and the ammonite faunas showing a markedly tethyan affinity thereafter three first order t r cycles bounded by major discontinuities associated with significant time gaps are identified they extend respectively from the latest rhaetian to the early aalenian from the middle aalenian to the early oxfordian and from the early oxfordian to the late berriasian major transgressive peaks occurred at the middle toarcian bifrons zone at the late bajocian upper niortense and garantiana zones and at the mid kimmeridgian divisum zone each of the first order cycles includes four second order t r cycles cycles 1 1 1 4 are identified in the northern basins cycles 2 1 2 4 display some differences in age of transgressive peaks from one basin to another cycles 3 1 3 4 are mainly identified in the iberian basin the correlation with other separated boreal and thethysian basins demonstrates that the number and age of t r cycles varies from one basin to another and are mainly controlled by the local or regional tectonic development the transgressive peaks may reflect episodes of eustatic rise during the jurassic however their different age from one basin to another is explained by different subsidence evolution

strong motion and teleseismic waveform inversions for the source process of the 2003 bam iran earthquake the bam earthquake m w 6 5 occurred on 26 december 2003 in southeastern iran causing a major disaster in the city of bam a remarkable vertical peak ground acceleration value of 988 cm s2 and two horizontal pulses were recorded inside the damaged city previous analyses showed that the earthquake was caused by a subsurface rupture on an unknown strike slip fault in this study we attempt to determine the precise fault location and source process of the 2003 bam earthquake by performing a multiple time window linear waveform inversion of teleseismic and strong motion data both individually and jointly we examined the general features of the fault location and the source process by analyzing the teleseismic displacement waveforms and determined the precise features and fault geometry by inverting the three components of strong motion velocity records the final estimate of the source process of the 2003 bam earthquake was determined by joint inversion of the datasets our results show that a single fault model characterized by the appropriate location of the hypocenter rake angle variations and the rayleigh like speed of the rupture front can satisfactorily explain the three components of the strong motion records at bam station

diffusion geospeedometry in natural and experimental shear zones abstract a new method for determining the timescales of ductile deformation utilizes diffusion profiles around oriented mineral inclusions this geospeedometer was tested with rutile needle inclusions in mylonitized quartz grains because they are sensitive to the kinematics of deformation and behave as diffusion couples that can be either a source or sink for ti diffusion in the host quartz the method was applied to experimental samples in which the time temperature conditions are known and to natural samples in which the time temperature conditions are determined using independent geochronometers and geothermometers in our experimental quartzite rutile needles become included in quartz during isostatic annealing rotate into the elongation direction of shearing during imposed deformation and act as a source of ti for the surrounding undersaturated quartz diffusion modeling of ti enrichment halos yields appropriate trends in experiment duration in a natural quartzite mylonite from the extensional detachment zone of the pioneer core complex idaho usa quartz grains are densely and pervasively rutilated titanium depletion halos in quartz around lineated and boudinaged rutile needles indicate that rutile exsolved during deformation by estimating temperature from quartz microstructures and ti in quartz thermometry diffusion modeling results suggest that ductile deformation in the shear zone lasted 5 10 myr consistent with geologic and thermochronologic data defining exhumation of the complex considering structural offsets across the detachment extrapolating our lab derived diffusivities to the conditions of natural samples equates to strain rates of 1 10 12 s 1 tests of geospeedometry in both naturally and experimentally deformed rutilated quartz samples indicate that this method can provide reliable information on shear zone longevity and strain rate directly from the phase controlling the rheological behavior of deformation

indication of high pore fluid pressures in a seismically active fault zone summary polarisations of seismic shear wave splitting observed above small earthquakes in iceland are typically approximately ne to sw parallel to the direction of maximum horizontal stress in contrast the polarisations of shear waves at three new stations sited over the husav ik flatey fault a major seismically active transform fault in northern iceland are approximately nw to se orthogonal to the stress aligned polarisations elsewhere modelling suggests that these 90 flips in polarisations are caused by propagation through cracks containing fluids at high pore fluid pressures within one or two mpa of the critical stress these observations suggest that high pore fluid pressures which play a key role in earthquake source mechanisms can be monitored by analysing shear wave splitting above seismically active fault planes

calcium diffusivity in alumino silicate garnets an experimental and atem study concentration gradients in calcium are common in metamorphic or magmatic garnets and can be used to determine the timescales of geological processes however the kinetics of ca diffusion in garnet is poorly constrained and experimental studies have to date yielded widely varying diffusion coefficients in this paper we describe a new method for generating diffusion profiles in garnet we incorporated polished and compositionally homogeneous garnet seeds in a finely ground powder of clinopyroxene and garnet during the experiments 1 3 gpa 1 050 1 250 c and o2 the graphite o2 buffer the mineral powder partially melted recrystallized and formed a 10 50 m wide overgrowth zone of compositionally distinct garnet around the seeds long duration experiments generated measurable relaxation profiles at these seed overgrowth interfaces we performed analytical transmission electron microscope traverses across the interfaces in each experiment thirteen usable compositional profiles were obtained with characteristic distances of diffusion ranging from 300 to 1 000 nm from these profiles ca fe mg interdiffusion coefficients were retrieved using an analytical solution for the diffusion equation and the data were cast in an arrhenius relation linear regression of the data yields an activation energy q ca fe mg equal to 188 48 kj mol 1 and a frequency factor d 0 equal to 6 6 10 14 m2 s 1 within the compositional range studied the composition of garnet has no major effect on the ca fe mg interdiffusion coefficient the very slow diffusion rate of ca is in agreement with natural observations indicating that ca diffuses more slowly than fe and mg the ca diffusion coefficients derived from this study are not model dependent and can be used to determine the durations of geological events from ca relaxation profiles in natural garnets

damage patterns stress rotations and pore fluid pressures in strike slip fault zones 1 active faults unfavorably oriented with respect to the regional maximum compressive stress have been labeled as weak the seismic hazards posed by these faults make understanding this apparent weakness a priority stress rotations in these fault zones together with an increase in mean stress could enable high pore fluid pressures to weaken a fault zone such a model requires a foundation in the physics and mechanics of damage this paper presents a new model for stress rotations in fault zones by combining the effective medium theory with anisotropic poroelasticity this approach enables the quantitative characterization of crack damage and the prediction of progressive changes in the elastic properties of rocks across the fault zone the processes of fault growth and wear will lead to distinct patterns of crack damage with different effects on the elastic properties elevated pore fluid pressures have long been known to change the effective normal and shear stresses of anisotropic rocks and this work incorporates these effects into a multilayer fault zone model it is shown that high pore fluid pressures in the anisotropic rocks of the core zone can generate large stress rotations i e more fault parallel and increases in mean stress sufficient to weaken the fault stress rotations in the damage zones of unfavorably oriented faults tend to be away from the fault i e more fault normal for likely combinations of damage patterns and pore fluid pressure

the 2003 bam se iran earthquake precise source parameters from satellite radar interferometry summary differential radar interferometry provided high quality near field deformation data for the 2003 bam earthquake and therefore strong constraints on its source parameters the ruptured fault segments could be clearly detected by using a sobel edge filter on the phase unwrapped deformation field the estimated total rupture length is about 24 km more than 80 per cent of the seismic moment was released from its southern segment of about 13 km where the slip reached a maximum of up to 270 cm resulting in a stress drop of at least 6 mpa in addition optical remote sensing data show that the bam fault is not a single fault but consists of a 4 5 km wide fault system with the known main branch running between the city of bam and baravat the fault ruptured by the bam earthquake appears to continue the nw branch of this fault system from bam city southwards based on these results we suggest that the bam earthquake ruptured a hidden or new fault and that in this process an unusually strong asperity was involved

stress directions and shear wave anisotropy observations from local earthquakes in southeastern sicily italy the spatial distribution of 414 earthquakes 1 0 m l 4 6 recorded from 1994 to 2002 in southeastern sicily italy has been analyzed the seismicity generally coincides with mapped plio quaternary faults including the north north west south southeast striking offshore fault system which is the most important tectonic structure of the area for the best located events we computed 70 focal mechanisms by combining p wave polarities with s wave polarizations a predom inance of strike slip and normal faults was observed focal mechanisms were then inverted for stress tensor parameters by using the algorithm of gephart and forsyth the results highlighted a region governed mainly by a north northwest south south east to northwest southeast compressional stress regime moreover anisotropy anal ysis of shear waves showed a polarization of fast s waves coherently aligned with this stress direction a finer scale analysis of the stress tensor evidenced three regions characterized by slightly differing orientation of the greatest principal stress axis r1 the eastern sector displays a nearly horizontal r1 trending northwest southeast the central sector is affected by a low dip north northwest south southeast r1 whereas in the western sector a north northwest south southeast oriented r1 with a higher dip angle was detected finally the comparison of the spatial distribution of seismicity occurring during 1994 2002 with locations of previous instrumental earthquakes and larger m 5 0 historical events showed that the seismicity patterns are persistent

seismic versus aseismic deformation in iran inferred from earthquakes and geodetic data summary a combined analysis of the geodetic strain rate field and the strain rate field deduced from the seismicity allows us to define the style of deformation and to distinguish seismic from aseismic deformation we perform this analysis in iran where the present day tectonics results from the north south convergence between the plates of arabia to the south and eurasia to the north the data consist of velocities measured with a gps network of 28 benchmarks and of instrumental and historical earthquake catalogues the axes of the seismic strain rate tensor have similar orientations to those deduced from the gps velocity field this indicates that the seismicity can be used to improve gps information on the style and the orientation of the deformation comparison of seismic and geodetic strain rates indicates that highly strained zones experience mainly aseismic deformation in southern iran and seismic deformation in northern iran a large contrast is observed between the zagros less than 5 per cent seismic deformation and the alborz kopet dag regions more than 30 100 per cent seismic deformation the distribution of the seismic geodetic ratio correlates with the distribution of large earthquakes intensive low magnitude seismicity is observed in the zagros whereas the largest earthquakes occur in northern iran the contrast of seismic deformation between the zagros and peri caspian mountains is confirmed considering 300 or 1000 yr of seismicity rather than 100 or 200 yr

a decade of shear wave splitting in the earth s crust what does it mean what use can we make of it and what should we do next it is 10 years since shear wave splitting throught to be diagnostic of some form of seismic anisotropy was first positively identified in the earth s crust from the beginning it was argued that the splitting was probably associated with the presence of stress aligned cracks inclusions in the crust and that this would provide the opportunity for monitoring the in situ geometry of cracks and stress in a variety of different circumstances and in a variety of different applications

deformation of granitoids at low metamorphic grade i reactions and grain size reduction abstract deformation and chemical reaction in granitoids at greenschist facies conditions were investigated in samples from three shear zones two from the alps corvatsch granodiorite and aiguilles rouges granite switzerland and one from eastern australia wyangala granite when examined by light and electron microscopy all show similar features of deformation that progressed from coarse parent rock through to fine grained mylonite quartz deformed plastically while both k feldspar and plagioclase fractured and recrystallized in conjunction with chemical change which had as its end point an assemblage albite quartz white mica caal silicates k feldspar and calcic plagioclase depending on fluid chemistry from the parent rock were unstable at low metamorphic grades in the presence of aqueous fluid since ca bearing plagioclase was not stable in these environments myrmekite did not replace k feldspar in any of the rocks examined recrystallization of feldspar which should perhaps be termed neocrystallization was initiated predominantly at clast margins or along microfractures that are marked by fluid inclusions and twin offsets in old feldspar grains particularly in plagioclases dislocations exist in wall like structures that are commonly associated with voids suggesting origins in microfractures these dislocations had severely limited mobility and subgrain rotation does not appear to have contributed to recrystallization we conclude that recrystallization mainly occurred via a classical nucleation mechanism with minor contributions from twin boundary migration we argue that the 450 550 c lower limit for recrystallization of feldspar referenced throughout the literature is not applicable to the rock systems under investigation and should be discarded as a universal limit microfracturing microboudinage and reaction are seen as the prerequisites for mylonite formation from coarse grained granitic rocks at low metamorphic grades see part ii of this paper neocrystallization fluid access and nucleation appear to have accompanied or immediately followed the first deformation increments and were primarily responsible for continued grain size reduction transgranular fracture was comparatively important only at the onset of deformation since the formation of shear zones in granitoids commonly takes place under conditions of low metamorphic grade in the presence of aqueous fluids in the earth s crust breakdown reactions and nucleation recrystallization in feldspars may be important influences upon localization of deformation in granitoids

mesozoic extensional tectonics stratigraphy and crustal evolution during the alpine cycle of the eastern iberian basin abstract sequence stratigraphy subsidence analysis and the integration of the basin fill data allow to the identification of four successive evolutionary stages in the basins of the eastern iberian margin during mesozoic extension 1 triassic rift late permian hettangian 2 early and middle jurassic postrift sinemurian oxfordian 3 late jurassic and early cretaceous rift kimmeridgian middle albian and 4 late cretaceous postrift late albian maastrichtian the present day crustal structure of the eastern iberian range and evidence of its evolution are deduced from the analysis of a new gravity map and other geophysical data a regional gravity low along the iberian range is interpreted in terms of crustal thickening beneath the orogen as a result of the collision between the ebro block and the iberian plate during the paleogene the boundary between these blocks coincides with a magnetic lineament that is interpreted as an inherited signature of the thinning that occurred during mesozoic extension a geodynamic scenario for the crustal evolution of the eastern part of the iberian peninsula based on the evaluation of mesozoic extensional tectonics and an analysis of the available geophysical data includes three main successive evolutionary stages 1 1 mesozoic crustal thinning 2 2 paleogene crustal thickening 3 3 neogene crustal thinning based on new geological and geophysical arguments this study offers an alternative and a more complete geodynamic history of the eastern iberian basins related to the evolution of the iberian plate and the central north atlantic

seismic trapped modes in the oroville and san andreas fault zones three component borehole seismic profiling of the recently active oroville california normal fault and microearthquake event recording with a near fault three component borehole seismometer on the san andreas fault at parkfield california have shown numerous instances of pronounced dispersive wave trains following the shear wave arrivals these wave trains are interpreted as fault zone trapped seismic modes parkfield earthquakes exciting trapped modes have been located as deep as 10 kilometers as shallow as 4 kilometers and extend 12 kilometers along the fault on either side of the recording station selected oroville and parkfield wave forms are modeled as the fundamental and first higher trapped sh modes of a narrow low velocity layer at the fault modeling results suggest that the oroville fault zone is 18 meters wide at depth and has a shear wave velocity of 1 kilometer per second whereas at parkfield the fault gouge is 100 to 150 meters wide and has a shear wave velocity of 1 1 to 1 8 kilometers per second these low velocity layers are probably the rupture planes on which earthquakes occur

s wave anisotropy in the aftershock region of the 2003 bam iran earthquake mw 6 5 abstract the 2003 bam earthquake mw 6 5 occurred in the southeastern iran on december 26 2003 we studied s wave anisotropy using the aftershock data observed at 5 stations in and around the aftershock region the fast polarization direction of shear wave splitting at the stations near the aftershock region is almost ne sw which corresponds to the maximum compressive stress trend the p axis of the main shock it is suggested that the inferred anisotropy might be caused by a systematic alignment of cracks resulting from the present day stress field the fast direction at the station just above the fault zone shows ew direction normal to the fault strike the fault normal alignment of cracks introduces a significant reduction of shear stress of the fault which suggests a high stress drop and large slip asperity another possible explanation for different result at the station from that of other stations is the effect of inhomogeneous velocity structure in and around the fault damaged zone the delay time of the split s waves ranges between 20 and 100 ms large delay time area is found in the shallower part of the fault zone with high aftershock activity assuming a uniform distribution of anisotropy inside and outside the aftershock region we estimated that the crack densities are 0 013 inside and 0 004 outside the aftershock region it may show more intense cracks within the high active region of aftershocks

s wave splitting in the aftershock region of the 1995 hyogo ken nanbu earthquake the 1995 hyogo ken nanbu earthquake kobe earthquake m7 2 occurred on january 17 1995 a temporary aftershock observation was carried out by the geophysical research group organized by universities for prediction seismology in 1995 from october 1995 to january 1996 a dense seismic network was deployed in and around the aftershock region and some seismic stations were set directly on the active fault traces we analyze the s wave splitting in and around the aftershock region of the hyogo ken nanbu earthquake we detect a spatial variation of s wave splitting which can be related to crack orientations in an area where a large earthquake has occurred at stations more than 1 km away from the hyogo ken nanbu earthquake fault zone the leading shear wave polarization directions lspd are found to be parallel to the axis of the regional maximum horizontal compressional stress e w suggesting that cracks caused by regional tectonic stress exist in the area however at stations within 500 m of the earthquake fault zones the lspds are parallel to the fault strikes n45 50 e this suggests that new fractures were produced parallel to the faults by shear faulting of the hyogo ken nanbu earthquake and resulted in s wave splitting along the earthquake fault zone nevertheless shear fault origin anisotropy was not evident at stations on the active faults which ruptured in 1596 this implies that healing processes have already closed the fractures produced by shear faulting in 1596 therefore we can expect that s wave splitting can be a useful tool for monitoring healing processes of active faults

large volumes of anhydrous pseudotachylyte in the woodroffe thrust eastern musgrave ranges australia a mylonitic thrust zone at least 1 5 km thick forms a sharp contact between granulite and amphibolite facies gneisses in the eastern musgrave ranges central australia the thrust dips gently to the south and is interpreted as an extension of the woodroffe thrust which was formed about 550 ma ago mylonites at the base of the thrust grade upwards into ultramylonites which pass abruptly into a pseudotachylyte bearing zone approximately 1 km thick containing approximately 4 of pseudotachylyte veining the orientation of the veins appears to be random pseudotachylytes occur only in the granulite facies rocks and their precursors are felsic pyroxene and or garnet granofelses rotated blocks of ultramylonite are present in some of the pseudotachylytes and some pseudotachylyte veins have been plastically deformed suggesting nearly contemporaneous semiductile and brittle behaviour the matrix of the pseudotachylyte shows spectacular examples of igneous quench microstructures especially skeletal and dendritic crystals of plagioclase and feathery pyroxene dendrites also present are glass devitrification microstructures spherulites evidence of liquid flow and partly melted residual grains with former glassy rims showing different optical properties from those of the surrounding isotropic material these features confirm that the pseudotachylyte formed by melting in anhydrous conditions the matrix of the pseudotachylyte veins is less siliceous than the host rocks owing to non equilibrium melting of pyroxene garnet and plagioclase the igneous assemblages of the melt notably the crystallization of pigeonite are consistent with rapid cooling from very high temperature 1000 c melting and quenching is probably due to very local short lived rises in temperature accompanied by dilation

source fault structure of the 2003 bam earthquake southeastern iran inferred from the aftershock distribution and its relation to the heavily damaged area existence of the arg e bam fault proposed 1 we investigate the hypocenter distribution of aftershocks of the december 26 2003 bam earthquake mw 6 5 by using a temporal seismic network the hypocenters distribute linearly over about 20 km in parallel with a line 3 5 km west of the geological bam fault and extend from the south of bam city to the heavily damaged area in the eastern part of the city including the historical mud brick citadel arg e bam based on the hypocenter distribution we propose a schematic 3 d structural model of a new fault that we have named the arg e bam fault we suggest that the bam earthquake occurred not in the bam fault but in the arg e bam fault bam city is located just above northern part of the arg e bam fault and also on the rupture propagation direction from the asperity this may be one of the main reasons why eastern part of bam city suffered the heaviest damage

geometry of a large scale low angle midcrustal thrust woodroffe thrust central australia the musgrave block in central australia exposes numerous large scale mylonitic shear zones developed during the intracontinental petermann orogeny around 560 520 ma the most prominent structure is the crustal scale over 600 km long e w trending woodroffe thrust which is broadly undulate but generally dips shallowly to moderately to the south and shows an approximately top to north sense of movement the estimated metamorphic conditions of mylonitization indicate a regional variation from predominantly midcrustal circa 520 620 c and 0 8 1 1 gpa to lower crustal 650 c and 1 0 1 3 gpa levels in the direction of thrusting which is also reflected in the distribution of preserved deformation microstructures this variation in metamorphic conditions is consistent with a south dipping thrust plane but is only small implying that a 60 km long n s segment of the woodroffe thrust was originally shallowly dipping at an average estimated angle of 6 the reconstructed geometry suggests that basement cored thick skinned midcrustal thrusts can be very shallowly dipping on a scale of many tens of kilometers in the direction of movement such a geometry would require the rocks along the thrust to be weak but field observations e g large volumes of syntectonic pseudotachylyte argue for a strong behavior at least transiently localization on a low angle near planar structure that crosscuts lithological layers requires a weak precursor such as a seismic rupture in the middle to lower crust if this was a single event the intracontinental earthquake must have been large with the rupture extending laterally over hundreds of kilometers

fabric related velocity anisotropy and shear wave splitting in rocks from the santa rosa mylonite zone california the directional dependence of p and s wave velocities have been measured at pressures up to 600 mpa and temperatures up to 700 c in rocks from the santa rosa mylonite zone southern california during tectonism these were progressively deformed from granodiorite protolith to mylonite and ultimately phyllonite the mineralogical and chemical composition of protolith and mylonite is nearly identical thus these rocks provide excellent material for documenting the effect of microstructural and textural changes on rock anisotropy velocity anisotropy increases significantly with the degree of deformation whereas average velocities and densities do not change at low pressure 50 mpa the velocity anisotropy ranges from 1 7 in granodiorite up to 19 in phyllonite and is due to both oriented microfractures and crystallographic preferred orientation at high pressure 600 mpa the residual anisotropy up to 12 is mainly due to preferred mineral orientation in particular of biotite significant shear wave splitting is measured parallel to the foliation plane and shows a good correlation with the biotite texture these observations confirm that oriented microcracks and preferred orientation of minerals should be taken into account in the interpretation of seismic reflection and refraction data in terranes with deformed rocks

the intraplate character of supercontinent tectonics abstract for several decades geoscientists have recognised intraplate tectonic activity far from plate margins both from modern and ancient examples this apparent disconnect with the drivers of plate tectonics does not necessarily imply unconnected processes but rather an uncertainty in understanding exactly how these systems operate are the driving forces derived locally or do they propagate from plate margins how do these forces interact with a complex tectonic inheritance to generate the observed tectonism furthermore what novel approaches have been applied to understand these processes here we review the general literature and the contents of this special issue to develop some partial answers to these questions key observations include the critical importance of local lithospheric heterogeneities as a control on the mode of orogenesis and also the role of locally derived forces from mantle upwelling or from depositing thick piles of magmatic or sedimentary rocks these processes happen within the overarching tectonic setting provided by far field plate margins which show intimate links in both time and observed processes with many intraplate regions these insights would not be possible without a growing arsenal of geological geophysical and numerical methods that can be applied to intraplate regions and this is reflected in the varied approaches within the issue we envisage that this special issue will provide a stimulus for further progress in understanding intraplate tectonics

diffusion creep in feldspar aggregates experimental evidence a combination of mechanical and microstructural results for experimentally deformed albite aggregates of 2 10 m grain size indicates a regime of grain boundary diffusion creep that depends upon the presence of water temperature and strain rate at 900 c and 10 5 s 1 deformation occurs dominantly by recrystallization accommodated dislocation creep when the aggregates contain 0 2 wt water but by grain boundary diffusion creep when the aggregates contain 0 9 wt water experiments at other temperatures and strain rates indicate that fine grained aggregates with added water may go directly from cataclastic flow to grain boundary diffusion creep with increasing temperature or decreasing strain rate bypassing the field of dislocation creep microstructural evidence for grain boundary diffusion creep in the wet fine grained aggregates includes the development of rectangular grains rather than polygonal grains grain growth a very low average dislocation density open grain boundaries including pores and channels and the presence of overgrowths of a different composition on grains in a two plagioclase an1 and an79 aggregate additional evidence for diffusion creep in the wet fine grained aggregates is indicated by their similar microstructures and strengths when deformed at 600 and 1500 mpa in contrast dry feldspar aggregates deforming by dislocation creep show an increase in strength and a transition to semi brittle behavior at lower confining pressures grain boundary diffusion creep of feldspars may be common in naturally deformed rocks due to the ease of grain size reduction by both cataclasis and dynamic recrystallization

the nature and origin of the barrovian metamorphism scotland 40ar 39ar apparent age patterns and the duration of metamorphism in the biotite zone abstract a geochronological traverse across the barrovian metamorphic series scotland shows 40 ar 39 ar apparent age spectra that reflect the influence of progressive metamorphism during the grampian orogenic episode the lowest grade units of the barrovian metamorphic series retain pre grampian detrital ages as components of their white mica 40 ar 39 ar apparent age spectra these relict ages are progressively obliterated in the direction of increasing metamorphic grade with a grampian age 40 ar 39 ar step heating plateau first occurring in the biotite zone the microstructure at this point shows only limited recrystallization suggesting loss of argon mainly by diffusion forward modelling of argon diffusion from white mica grains was therefore carried out for various thermal histories and grain sizes to match 40 ar 39 ar step heating apparent age spectra patterns preserved within the biotite zone of the barrovian metamorphic series the results imply a thermal duration of between 1 and 10 ma for barrovian metamorphism in the biotite zone such short time scales for metamorphism place a limit on length scales for the heat sources responsible mid crustal extensional ductile shear zones that crop out in the ne of the grampian terrane once focused narrow grampian age heat sources e g magmas hot fluids shear heating that drove a brief thermal episode resulting in the barrovian metamorphism supplementary material 40 ar 39 ar data tables and plots including 1 data from analyses on flux monitors and plots used for j factor determination and 2 data from analyses on unknowns and 40 ar 39 ar step heating spectra and inverse isochron plots for each unknown are available at http www geolsoc org uk sup18442

transient and periodic brittle deformation of eclogites during intermediate depth subduction abstract brecciated eclogite clasts from the monviso ophiolite in the western alps fossil subduction zone preserve healed fractures within garnet crystals these fractures are divided into two distinct populations based on chemical and textural criteria diffusion modeling on profiles across fractures identifies a characteristic diffusive timescale for each population with a mean calculated difference between population timescales of 2 myr we interpret this relative difference in diffusional timescales to represent the maximum period between individual fracturing events during prograde subduction at eclogite facies p t conditions the period between the two distinct fracturing events is likely controlled by transient fluid pressure and or strain rate increases during prograde subduction an increase in pore fluid pressure may be related to the dehydration of adjacent portions of the down going plate during prograde subduction while an increase in strain rate may be related to seismicity at shallower depths in the subducting slab the absolute duration for diffusion as constrained by diffusion modeling implies extremely short timescales near peak p t conditions this suggests that the subducting slab potentially experienced multiple periods of seismic activity immediately prior to detachment and subsequent exhumation from intermediate depths the presence of similar healed fractures in garnets from eclogites is relatively common in the rock record implying that similar transient and periodic processes may be relatively common during subduction worldwide and through time

constraints from diffusion profiles on the duration of high strain deformation in thickened crust diffusion profiles in garnet are used to determine the duration of movement on shear zones in the musgrave block central australia grenville age granulites were overprinted at depths of 40 km by high strain zones during the intracratonic petermann orogeny ca 550 ma ago in these zones quartzofeldspathic mylonites contain garnet from the early granulite facies event that developed compositional gradients during the high pressure overprint the diffusion of ca into garnet is linked with the release of ca in plagioclase the only calcic mineral in the rock during neocrystallization of sodic feldspar during high strain deformation available diffusion data on garnet directly define the duration of high strain deformation at eclogite facies our results indicate that the integrated time scales of movement in individual high strain zones were short lived between 0 07 ma and 1 4 ma and that wide shear zones were active longer than narrow ones in addition we find that relict k feldspar in one of the narrow eclogite facies shear zones yields a 40 ar 39 ar age that is partially reset indicating that the thermal event was also short lived these short time scales support the hypothesis that shear heating was the dominant source of heat for the eclogite facies overprint

assembly of proterozoic australia implications of a revised pole for the 1070 ma alcurra dyke swarm central australia summary the pole position for the late mesoproterozoic alcurra formerly kulgera dyke swarm ads musgrave block central australia has been revised by adding new data from two more dykes a palaeomagnetic fold test is positive at the 99 percent confidence level and the pole position is latitude 2 8 s longitude 80 4 e dp 7 2 dm 10 7 new 40ar 39ar determinations on single biotite grains from country rock gneiss 20 cm from the contact with an alcurra dyke yield ages from 1068 2 ma to 1085 2 ma 2 in addition 40ar 39ar determinations on two samples of aggregates of very fine grained biotite from the mesostasis of a stuart dyke sd arunta inlier northern territory yield ages of 1059 2 and 1066 3 ma 2 these new ages are in agreement with those of the 1070 ma warakurna large igneous province west central australia indicating that both the ads and sd belong to that suite palaeomagnetic poles determined by others for the ads and sd are indistinguishable from each other but cannot be presently combined as a single pole because the published information on the sd is incomplete an analysis of the palaeogeography implied by the dispersed palaeomagnetic poles from members of the extended warakurna suite shows that the present relationships between the major precambrian cratons west north and south australian which constitute australia west of the tasman line are inconsistent with the inferred relationship at 1070 ma nor is it apparent that internal deformations within the separate cratons are the cause of the dispersion our findings imply that these major australian cratons must have finally assembled sometime after 1070 ma

thermal history and differential exhumation across the eastern musgrave province south australia insights from low temperature thermochronology abstract multi method geo and thermochronological data obtained for palaeo and mesoproterozoic granitoids traversing the main structural architecture of the eastern musgrave province within south australia reveal multiphase cooling histories apatite u pb dating on six samples yield consistent ages of 1075 1025 ma suggesting a thermal reset coinciding with mantle derived magmatism of the greater warakurna large igneous province 1080 1040 ma apatite fission track aft analysis indicate that four discrete thermal events affected the study area inducing cooling through the aft partial annealing zone 60 120 c supported by apatite and zircon u th sm he data late neoproterozoic cooling from deep crustal levels to temperatures the results highlight a complex phanerozoic thermal history for the eastern musgraves and help to elucidate the poorly appreciated tectonic evolution of inland australia this study further demonstrates how high density sample transects across structural architecture can assess the relative crustal level and associated preservation of the thermal history record within fault reactivated terranes

assessing the role of submarine groundwater discharge as a source of sr to the mediterranean sea abstract submarine groundwater discharge sgd has been identified as an important source of sr to the ocean and the sgd driven sr flux to the global ocean has been recently re evaluated beck et al 2013 however the uncertainty of this value is still high because of the uncertainties related to the determination of sgd flow rates and the paucity of 87 sr 86 sr data in sgd end members as carbonates have high sr concentrations and are subjected to intense heightened weathering they might significantly influence the sgd input of sr to the ocean here we present data on sr concentrations and 87 sr 86 sr ratios in three carbonate dominated sites of the western area of the mediterranean sea a semi enclosed basin characterized by abundant coastal carbonates the 87 sr 86 sr ratios in groundwater were lower compared to modern seawater 0 70916 as expected for areas dominated by carbonate lithologies concentrations of sr and 87 sr 86 sr ratios in groundwater showed conservative mixing in the studied subterranean estuaries by using sgd flow rates reported in the literature for the study areas a flow weighted fresh sgd end member characterized by a sr concentration of 27 30 m and a 87 sr 86 sr ratio of 0 707834 0 708020 was calculated for the eastern coast of the iberian peninsula integrating these sr data with literature data i e values of sr concentration and 87 sr 86 sr ratio from other lithologies as well as sgd flow rates we also calculated the fresh sgd driven sr flux to the entire mediterranean sea obtaining a value of 0 34 0 83 10 9 mol y 1 with a 87 sr 86 sr of 0 7081 0 7086 thus for the entire mediterranean basin sgd is globally a source of sr less radiogenic compared to seawater the sgd sr flux to the mediterranean sea represents 5 6 of the sgd sr flux to the global ocean and the mediterranean sgd end member has higher sr concentration 5 12 m than the global sgd end member 2 9 m this confirms the significant role of carbonate lithologies on sgd driven sr fluxes to seawater the fresh sgd driven sr flux to the mediterranean sea is about 20 50 of the riverine sr input and significantly higher than the input through atmospheric dust deposition therefore sgd should be considered as an important continental source of sr to the basin

the source motion of 2003 bam iran earthquake constrained by satellite and ground based geodetic data summary the interpretation of coseismic surface deformation measurements through inversion techniques is of major importance to understand the mechanical behaviour of a seismic fault dense geodetic data sets in the vicinity of the ruptured fault provide unique constraints on detailed fault geometry and slip distribution at depth making them complementary to seismological data bam earthquake mw 6 6 2003 december 26 induced surface deformation has been precisely mapped by envisat asar interferometry and by subpixel correlation techniques applied to spot 5 and asar amplitude images these oblique and horizontal estimations of deformation have been completed with one levelling profile along the main road crossing the rupture from west to east we process these data separately and jointly in a two step inversion technique within the elastic half space theory framework our objective is to determine the dislocation model at depth that satisfies simultaneously all the geodetic constraints also we estimate the relative contribution of each geodetic data set to this inversion process we first use a stochastic direct approach called neighbourhood algorithm in order to estimate the average characteristics of the rupture and their relative uncertainty constraining in this way the geometry of the ruptured fault we then linearize the inverse problem and compute the slip distribution on the fault using a standard weighted least square technique assuming the solution is smooth to some degree at each step we discuss the optimal models their stability as well as the relative influence of each data set on the derived models parameters our preferred model reveals a shallow dislocation on a quasi vertical fault slightly dipping towards east the slip vector has a strike slip component as high as 2 m while the dip slip component seems negligible however the estimation of the resolution matrices emphasizes the fact that the details of deep fault slip distribution remain out of the scope of this ill conditioned inverse problem yet our preferred model suggests a main dislocation limited at depth between 1 and 6 km by contrast the aftershocks observed in the months following the earthquake are located just beneath the estimated main shock

fault zone waves observed at the southern joshua tree earthquake rupture zone waveform and spectral characteristics of several aftershocks of the m 6 1 22 april 1992 joshua tree earthquake recorded at stations just north of the indio hills in the coachella valley can be interpreted in terms of waves propagating within narrow low velocity high attenuation vertical zones evidence for our interpretation consists of 1 emergent p arrivals prior to and opposite in polarity to the impulsive direct phase these arrivals can be modeled as headwaves indicative of a transfault velocity contrast 2 spectral peaks in the s wave train that can be interpreted as internally reflected low velocity fault zone wave energy and 3 spatial selectivity of event station pairs at which these data are observed suggesting a long narrow geologic structure the observed waveforms are modeled using the analytical solution of ben zion and aki 1990 for a plane parallel layered fault zone structure synthetic waveform fits to the observed data indicate the presence of ns trending vertical fault zone layers characterized by a thickness of 50 to 100 m a velocity decrease of 10 to 15 relative to the surrounding rock and a p wave quality factor in the range 25 to 50

duration of high pressure metamorphism and cooling during the intraplate petermann orogeny abstract the ediacaran cambrian petermann orogeny central australia is an exceptional example of intraplate orogenesis it involved sub eclogite facies metamorphism and extreme basin inversion during the exhumation of musgrave province basement from beneath the formerly contiguous centralian superbasin sensitive high resolution ion microprobe shrimp u pb geochronology of zircon titanite and rutile along with ti in zircon thermometry from meta igneous samples have been used to determine the timing and duration of high pressure metamorphism and subsequent cooling associated with this orogenic event peak metamorphic temperatures of 720 760 c were attained at 544 7 ma u pb zircon subsequent cooling to 600 660 c by 521 ma occurred at a rate of 2 6 7 0 c myr 1 as recorded by the closure of pb diffusion in titanite further cooling to 585 560 c by 498 472 ma occurred at a rate of 0 9 4 8 c myr 1 as recorded by pb closure in rutile the duration of tectonism was long lived 40 myr across the central and western parts of the orogenic system and deformation occurred in a comparatively warm and weak portion of crust characterised by regional thermal gradients of 17 26 c km 1 this proposed duration of tectonism is much longer than that permitted by a shear heating mechanism which requires an exceptionally short duration of tectonism and additionally an overall cold lithosphere characterised by geothermal gradients of 9 c km 1

compositional changes of minerals associated with dynamic recrystallizatin the rate of compositional and isotopic exchange between minerals may be enhanced significantly if the rock is deformed simultaneously the enhanced exchange rate may result from a reduction in grain size shorter distance for volume diffusion dissolution and growth of grains by diffusion creep pressure solution or the movement of high angle grain boundaries through strained grains during recrystallization in the dislocation creep regime the migration of high angle grain boundaries provides high diffusivity paths for the rapid exchange of components during recrystallization the operation of the latter process has been demonstrated by deforming aggregates consisting of two plagioclases an1 and an79 at 900 c 1 gpa confining pressure and a strain rate of 2x10 6s 1 the polygonal recrystallized grains were analyzed using an analytical transmission electron microscope and have a variable but often intermediate composition at the conditions of these experiments the volume interdiffusion rate of nasi caal is too slow to produce any observable chemical change and microstructural chemical relations indicate that the contribution from diffusion creep was insignificant except for initially fine grained 2 10 m aggregates these results indicate that strain induced recrystallization can be an effective mechanism for enhancing the kinetics of metamorphic reactions and for resetting the isotope systematics of minerals such as feldspars pyroxenes and amphiboles

intracratonic strike slip partitioned transpression and the formation and exhumation of eclogite facies rocks an example from the musgrave block central australia mountain belts developed in an intracratonic setting during the neoproterozoic in the center of australia mesoproterozoic granulite and amphibolite facies gneisses of the musgrave block were overprinted during the petermann orogeny 550 ma with zones of high strain concentrated along broadly east west trending shear zones these zones formed under eclogite facies t 650 c and p 12 kbars to greenschist facies conditions and may form part of a strike slip related crustal scale flower type structure granulite facies gneisses preserve ages older than 700 ma suggesting that these rocks did not experience temperatures greater than 350 c at 550 ma for these rocks not to have been thermally equilibrated to temperatures of 350 c at a depth of 12 kbars requires either an extraordinarily low geothermal gradient 9 c km 1 or if the geothermal gradient was more typical 20 c km 1 then transport to that depth and subsequent exhumation occurring in a short time interval 40 myr

cation diffusion kinetics in aluminosilicate garnets and geological applications the compositional properties of garnet probably preserve the most extensive records of the pressure temperature time p t t history of metamorphic rocks there are a number of cation exchange and discontinuous reactions involving garnet that have been extensively used to decipher the p t conditions or p t paths of the host rocks as these were buried and exhumed e g ganguly and saxena 1987 spear 1993 however as metamorphic garnets commonly show compositional zoning the choice of composition within a zoned garnet to retrieve peak metamorphic conditions requires consideration of its diffusion kinetic properties dasgupta et al 2004 2009 as does the issue of whether the peak condition is at all preserved in the compositional property of a garnet of a given grain size e g spear 1991 ganguly and tirone 1999 tirone and ganguly 2010 diffusion kinetic modeling of the major element compositional zonings of garnets leads to important constraints on the time scales of metamorphic processes such as heating and cooling rates e g florence and spear 1993 ganguly et al 2000 faryad and chakraborty 2005 augue and baxter 2007 from which one may infer the burial and exhumation rates respectively e g ganguly et al 2000 faryad and chakraborty 2005 and time scales of deformation camacho et al 2009 in addition the presence of garnet in the source region of a basaltic magma imparts a characteristic signature often referred to as the garnet signature to its rare earth element ree pattern in addition to providing an important constraint on the depth of the source region of a basaltic magma since garnet is stable below 50 km depth in the earth s interior e g saxena and eriksson 1983 the ree pattern of basaltic magma with garnet signature is often used to infer

evidence for shear heating musgrave block central australia the phenomenon of shear heating is generally difficult to recognise from petrologic evidence alone establishing that shear zones attain higher temperatures than the surrounding country rocks requires independent evidence for temperature gradients in the musgrave block central australia there is a clear spatial association between shear zones and interpreted elevated temperatures eclogite facies shear zones that formed at 550 ma record temperatures of 650 700 c outside the high pressure shear zones minerals with low closure temperatures such as biotite 450 c in the 40ar 39ar and rb sr systems preserve ages 800 ma suggesting that these rocks did not experience temperatures greater than about 450 c at 550 ma for any extended period thus the shear zones record temperatures that are 200 c higher than the surrounding country rocks simple calculations show that the combination of relatively high shear stresses 100 mpa and high strain rates 10 11 s 1 for short durations 1 ma can account for the observed apparent temperature variations the evidence indicates that shear heating is the dominant mechanism for localised temperature increases in the shear zones while the country rock remained at relatively lower temperatures

three orders of regional sea level changes control facies and stacking patterns of shallow platform carbonates in the maestrat basin tithonian berriasian ne spain middle tithonian berriasian shallow platform carbonates of the maestrat basin salzedella and montanejos sections ne spain are stacked in sequence stratigraphic units of different orders higher order sequences parasequences and subunits have a shallowing or deepening shallowing evolution they have been related to the short term eccentricity and precession cycles major facies changes and stacking pattern of parasequences reveal the presence of two 2nd order sequences the lower sequence is middle tithonian mid early berriasian in age the upper sequence extends up to the mid late berriasian it is suggested that local subsidence changes along with regional sea level changes controlled the long term evolution of accommodation in the maestrat basin facies evolution stacking pattern and sharp lithological changes have allowed the definition of five 3rd order sequences in the lower sequence in montanejos the transgressive deposits are characterised by the progressive absence of the restricted lagoon facies and the presence of deepening upward intervals in the parasequences the highstand deposits display an increase in siliciclastics and a progressive predominance of restricted lagoon facies some of the 3rd order sequence boundaries match the sequence boundaries identified in other european basins and may be related to sea level falls induced by the long term eccentricity cycle enhanced during periods of long term loss of accommodation

isotopic dating of strain fringe increments duration and rates of deformation in shear zones the time scales over which deformation in the earth9s crust remains localized in shear zones are poorly known as are the associated strain rates we have determined the longevity and rates of deformation using rubidium strontium rb sr microsampling dating of increments of fibrous strain fringes from a pyrenean shear zone the fibers grew quasi continuously through a protracted deformation history between 87 and 50 million years ago over a period comparable to that of an orogeny during a short interval between 66 and 62 million years a rise in strain rate from 1 1 10 15 to 7 7 10 15 seconds 1 occurred this acceleration correlates with an abrupt change in fiber growth direction and a stress field inversion from gravitational collapse to renewed horizontal crustal shortening

timing and exhumation of eclogite facies shear zones musgrave block central australia timing constraints on shear zones can provide an insight into the kinematic and exhumation evolution of metamorphic belts in the musgrave block central australia granulite facies gneisses have been affected to varying degrees by mylonitic deformation some of which attained eclogite facies the davenport shear zone is a dominant strike slip system that formed at eclogite facies conditions t 650 c and p 12 0 kbar sm nd mineral isochrons obtained from equilibrated high pressure assemblages as well as 40ar 39ar data show that the eclogite and greenschist facies high strain overprints were coeval at c 550 ma mylonitic processes do not appear to have reset the u pb system in zircon but may have partially disturbed it the thermal gradient in the musgrave block crust at c 550 ma was c 16 c km 1 and at c 535 ma was c 18 c km 1 based on p t estimates of eclogite and greenschist facies shear zones respectively these estimates are similar to present day geothermal gradients in many stable continental shield areas suggesting that the region did not undergo a significant transient perturbation of the geotherm therefore in the musgrave block cooling subsequent to eclogite facies metamorphism appears to have been controlled by exhumation rather than by the removal of a heat source estimated exhumation rates in the range 0 2 to 1 5 mm year 1 are comparable with other orogenic belts rather than cratonic areas elsewhere

orientation of the stress field surrounding the creeping section of the san andreas fault evidence for a narrow mechanically weak fault zone we determine how the orientations of the principal stresses change with distance from the creeping section of the san andreas fault saf our data are 2392 earthquake focal mechanisms which are grouped according to distance from the saf into 33 bins parallel to fault strike the width of the bins are dictated by the spatial organization and density of the seismicity only events with m 1 5 depth 2 km and well constrained focal mechanisms are used the focal mechanisms are inverted simultaneously for the orientations and relative amplitudes of the principal stresses using two different inversion programs a bootstrap resampling method provides confidence limits on the stress orientations our general result is that the maximum horizontal compression lies mostly at high angles to the saf except in a narrow zone on the fault no wider than 1 3 km in which it appears to lie at a smaller angle 45 from the fault strike in particular the maximum horizontal compression lies at a high angle to the saf trend immediately adjacent to the fault this stress state is most readily interpreted as due to a narrow mechanically weak saf in this region the narrowness of this zone contrasts with the region wider than 20 30 km of rotated stresses found surrounding the saf in southern california hardebeck and hauksson 1999 suggestive of different mechanical behaviors of the saf in these two regions this approach may provide a way to define the width of the mechanically weak part of faults

quantifying groundwater discharge from different sources into a mediterranean wetland by using 222rn and ra isotopes summary groundwater discharge constitutes the main water inflow of many coastal wetlands despite the potential of ra isotopes and 222rn as tracers of groundwater discharge the use of these radionuclides to quantify the groundwater inflow in coastal wetlands has been only scarcely addressed in the literature the main goal of this study is to evaluate the use of 222rn and ra isotopes to estimate the contribution of distinct groundwater sources into a mediterranean coastal wetland the peniscola marsh castello spain the peniscola marsh is a small shallow wetland nourished by groundwater coming from four different flowpaths i a deep flow from the regional carbonate aquifer of el maestrat ii a shallow flow and iii an intermediate flow both from the irta range and the detritic vinaros peniscola aquifer and iv seawater intrusion data on 226ra 222rn and salinity obtained in summer 2007 revealed that the deep groundwater contribution was 15 of the total water inflow whereas the shallow and intermediate flow paths represented 32 and 48 respectively seawater accounted only for the remaining 5 inputs to the wetland ra isotopes also allowed estimating the marsh water age in 1 2 days both the groundwater contributions derived from 222rn measurements and the ra derived marsh water age agreed well with the direct measurements obtained using propeller flow meters evidencing the effectiveness of the used methods an interannual comparison between the estimated groundwater inflow and the precipitation revealed that shallow groundwater flows respond to local precipitation whereas the deep groundwater flow from the carbonate aquifer is dominated by a constant baseflow

anisotropy in the shallow crust observed around the san andreas fault before and after the 2004 m 6 0 parkfield earthquake local seismic arrays were deployed at two locations along the san an dreas fault saf near parkfield california before and after the 2004 m 6 0 parkfield earthquake using local earthquakes we determine the anisotropic field within 1 2 km of the main trace of the saf at the two array locations separated by 12 km the initial array near the safod site was deployed for six weeks in october and november 2003 and the second array located near the town of parkfield was de ployed for 3 months following the 28 september 2004 m 6 0 parkfield earthquake we find the fast shear wave polarization direction nearly fault parallel n40w for stations on the main fault trace and within 100 m to the southwest of the saf at both array locations these fault parallel measurements span the 100 to 150 m wide zone of pervasive cracking and damage interpreted from fault zone trapped waves associated with the main fault core li et al 2004 2006 outside of this zone the fast orientations are scattered with some preference for orientations near n10e roughly parallel to the regional maximum horizontal compressive stress direction rh in addition fast directions are preferentially oriented parallel to a northern branch of the saf recorded on stations in the 2004 parkfield deployment the measured anisotropy is likely due to a combination of stress aligned micro cracks away from the fault and shear fabric within the highly evolved fault core the majority of our measurements are taken outside of the main fault core and we es timate the density of microcracks from the measured delay times apparent crack densities are approximately 3 with large scatter the data suggest weak depth dependence to the measured delay times for source depths between 2 and 7 km below 7 km source depth the delay times do not correlate with depth suggesting higher confining pressure is forcing the microcracks to close no coseismic variation in the anisotropic parameters is observed suggesting little to no influence on measured splitting due to the 2004 m 6 0 parkfield earthquake however the premainshock and postmainshock data presented here are from arrays separated by 12 km limiting our sensitivity to small temporal changes in anisotropy

methodological study of submarine groundwater discharge from a karstic aquifer in the western mediterranean sea summary a multiproxy approach of complementary techniques is applied to localise and quantify submarine groundwater discharge sgd from el maestrazgo jurassic aquifer an example of widespread carbonate coastal aquifer of the western mediterranean sea castellon spain unconventional water resources are critical in this area where highly populated resorts have been developed the aquifer has two main features of particular interest a karstic system with a deep saturated zone reaching 450 m and with no significant surface discharge occurring within the continental area on the other hand sgd can alter the condition of coastal marine environments reducing salinities and providing nutrients that can cause eutrophication and algal blooms the applied combined techniques make it possible to detect groundwater outflows using airborne thermal infrared tir images to monitor physico chemical anomalies in the sea and to quantify the submarine groundwater discharges by means of direct measurements and radium isotopic analyses three main coastal areas affected by sgd and a submarine spring located at 3 km from the coast which seems to be associated with tectonic discontinuities were localised the calculated fresh sgd from ra isotopes 375 mm 3 y 1 is in agreement with the mean aquifer recharge obtained by hydrogeological methods 394 mm 3 y 1

development of magnetic and elastic anisotropies in slates during progressive deformation abstract magnetic and elastic anisotropies were investigated in rocks of the nizk jesenik mountains northeast bohemian massif ranging in lithology from almost unmetamorphosed sediments through slate to phyllite and showing a range of structural styles from sedimentary through spaced and slaty cleavage to metamorphic schistosity in unmetamorphosed and undeformed sedimentary rocks both the anisotropies display close relationships to the sedimentary fabric during the development of the spaced and slaty cleavage they are gradually re oriented into the attitudes of the deformational fabrics and in the rocks with metamorphic schistosity they are fully related to the deformational fabric elements which can be oriented in a very different way from the original sedimentary structures the magnetic anisotropy is mostly due to the preferred orientation of phyllosilicates generated during very weak regional metamorphism and subordinately due to the preferred orientation of magnetite the elastic anisotropy is probably controlled by the preferred orientation of phyllosilicates and by the existence of oriented systems of microcracks

rates of fe mg mn and ca diffusion in garnet extraction of the thermal and chemical histories preserved by modified compositional zoning in garnet is compromised by large uncertainties in experimentally determined diffusion coefficients for principal divalent cations some of this uncertainty derives from long down temperature extrapolations but much of it arises from an inability to account accurately for large variations in diffusivity as a function of garnet composition numerical simulation of stranded diffusion profiles in partially resorbed natural garnets constrains diffusivities at low temperature and reveals a systematic dependence of diffusion rates on host garnet composition a comprehensive model incorporating a simple compositional dependence allows accurate prediction of diffusion rates for fe mg mn and ca for nearly all garnet compositions across the full range of geologically relevant temperatures pressures and oxygen fugacities

laboratory seismic measurements an aid in the interpretation of seismic field data this contribution reports data and evidence from laboratory measurements of compressional and shear wave velocities and mineralogical microstructural and chemical analyses in crustal rocks that may provide an aid to understanding and interpreting geophysical data it is shown that the correlation of laboratory seismic data with stratigraphic field data can provide the necessary data base for constructing a seismic model of the earth s crust in a particular geological area

a review of shear wave splitting in the crack critical crust summary over the last 15 years it has become established that crack induced stress aligned shear wave splitting with azimuthal anisotropy is an inherent characteristic of almost all rocks in the crust this means that most in situ rocks are pervaded by fluid saturated microcracks and consequently are highly compliant the evolution of such stress aligned fluid saturated grain boundary cracks and pore throats in response to changing conditions can be calculated in some cases with great accuracy using anisotropic poro elasticity ape ape is tightly constrained with no free parameters yet dynamic modelling with ape currently matches a wide range of phenomena concerning anisotropy stress shear waves and cracks in particular ape has allowed the anisotropic response of a reservoir to injection to be calculated predicted with hindsight and the time and magnitude of an earthquake to be correctly stress forecast the reason for this calculability and predictability is that the microcracks in the crust are so closely spaced that they form critical systems this crack critical crust leads to a new style of geophysics that has profound implications for almost all aspects of pre fracturing deformation of the crust and for solid earth geophysics and geology we review past present and speculate about the future of shear wave splitting in the crack critical crust shear wave splitting is seen to be a dynamic measure of the deformation of the rock mass there is some good news and some bad news for conventional geophysics many accepted phenomena are no longer valid at high spatial and temporal resolution a major effect is that the detailed crack geometry changes with time and varies from place to place in response to very small previously negligible changes however at least in some circumstances the behaviour of the rock in the highly complex inhomogeneous earth may be calculated and the response predicted opening the way to possible control by feedback the need is to devise ways to exploit these new opportunities in the crack critical crust recent observations from the smsites project at husavik in northern iceland gathered while this review was being written display the extraordinarily sensitivity of in situ rock to small changes at great distances the effects are far too large to occur in a conventional elastic brittle crust and their presence confirms the highly compliant nature of the crack critical crust

the burning heart the proterozoic geology and geological evolution of the west musgrave region central australia the musgrave province is one of the most geodynamically significant of australia s proterozoic orogenic belts lying at the intersection of the continent s three cratonic elements the west north and south australian cratons while remoteness and cultural sensitivity have slowed geological research into this region recent collaborative programs in western australia the west musgrave province have done much to address this this focus review provides a synthesis of this and previous work investigating the mesoproterozoic to neoproterozoic geological evolution of the province the musgrave province is a mesoproterozoic to neoproterozoic belt dominated by granites formed and deformed during several major events a cryptic juvenile basement is exposed mainly in the east musgrave province as c 1600 1550 ma orthogneiss and in the west musgrave province as isolated outcrops of granulite facies metagranites of the c 1575 ma warlawurru supersuite zircon hf isotopic data suggest an earlier major juvenile crust forming event at c 1950 1900 ma there is however no evidence that the province evolved over archean crust the c 1600 1550 ma period probably involved evolution within a primitive arc setting perhaps developed on c 1950 1900 ma oceanic or oceanic arc crust voluminous calc alkaline plutonism was accompanied by clastic and volcaniclastic basin formation during the 1345 1293 ma mount west orogeny this stage traced the evolution of a continental arc reflecting the final amalgamation of the combined north and west australian craton with the south australian craton the intervening c 1400 ma primitive crust the madura province on which the proto musgrave province had evolved was consumed during amalgamation the thickened crust resulting from this accretion was drastically thinned at the beginning of the c 1220 1150 ma musgrave orogeny as this central part of the new combined craton entered an extraordinary period of high heat flow characterised by c 100 m y of ultrahigh temperature metamorphism and high temperature anhydrous alkali calcic magmatism sourced from mash chambers developed at the base of the thinned crust the ridged cratonic architecture and a massive accumulation of high radiogenic heat producing granites within the mid crust perpetuated a thin crustal regime voluminous magmatism was again triggered during the c 1090 1040 ma giles event with the evolution of the magmatism dominated ngaanyatjarra rift this event was likely initiated through renewed movement along translithospheric faults that intersected the thermally perturbed musgrave province pinned at a cratonic junction mantle derived bimodal magmatism extended more or less continuously for 50 m y producing one of the world s largest layered mafic intrusions and supervolcano sized additions of juvenile felsic crust in the form of alkali calcic to alkali a type rhyolite deposits together the albany fraser orogen which developed over the southern margin of the west australian craton and the musgrave province mark the preserved edge of the north and west australian craton these two belts show remarkable chronological links between c 1345 and 1150 ma but contrasting histories before and after that period their period of shared evolution reflects collision and accretion of the south australian craton but their tectonic setting and basement geology throughout that event were very different