systematic comparisons of earthquake source models determined using insar and seismic data abstract robust earthquake source parameters e g location seismic moment fault geometry are essential for reliable seismic hazard assessment and the investigation of large scale tectonics they are routinely estimated using a variety of data and techniques such as seismic data and more recently interferometric synthetic aperture radar insar comparisons between these two datasets are frequently made although not usually in a comprehensive way this review compares source parameters from global and regional seismic catalogues with those from a recent database of insar parameters which has been expanded with 18 additional source models for this study we show that moment magnitude mw estimates agree well between the two datasets with a trend for thrust events modelled using insar to have slightly larger mw estimates earthquake locations determined using insar agree well with those reported in regional catalogues with a median difference of 6 3 km between them which is smaller than for global seismic catalogues we also investigate the consistency of source parameters and source directivity by comparing isc hypocentres with gcmt and icmt centroid locations for earthquakes with mw 6 5 in some cases the source directivity is qualitatively comparable with previous studies especially when comparing isc and icmt locations the average difference between insar determined depths and those in the ehb catalogue is reduced if a layered half space is used in the inversion of insar data overall faulting geometry strike dip and rake angles remain in good agreement with values from the gcmt catalogue and any large discrepancies can be attributed to tradeoffs between parameters with continued investment in satellites for radar interferometry insar is a valuable technique for the estimation of earthquake source parameters the observed trends and discrepancies between insar and seismically determined source parameters are the result of issues with the data different inversion techniques and the assumed earth structure model

early diagenesis in deep sea turbidites the imprint of paleo oxidation zones sediment cores up to 35 m long have been recovered from turbidite sequences in the madiera abyssal plain and the southern nares abyssal plain detailed geochemical analyses of these sediments si al fe mn ca organic and inorganic carbon and associate pore waters nitrate ammonia silicate fe2 mn2 and alkalinity provide representative profiles of both steady state and nonsteady state diagenetic reactions initiated by oxidation and reduction processes models demonstrate that chemical transport in the pore water system is diffusion dominated over periods of a few thousands of years to several hundreds of thousands of years mn and fe mobilized in the subsurface mildly reducing sediments are precipitated as easily reducible oxyhydroxides in the near surface oxidized sediments nonsteady state profiles show the influence of episodic and rapid turbidite deposition and the imprint of oxidation zones that developed as the result of oxygen diffusion into the upper portions of turbidites during intervals of slow pelagic deposition the time required for development of oxidation zones between turbidites ranges from 2 0 to 15 ka in the madeira abyssal plain and from 0 2 to 2 4 ka in the southern nares abyssal plain paleo oxidation zones can be recognized in old turbidites by distinct changes in color between lower and upper portions of the deposit in the basal unoxidized portion of the turbidite the sediments are characteristically dark green gray or brown in the paleo oxidized zone the sediments are pale green blue or yellowish brown these zones in both the madeira and southern nares abyssal plains contain distinctly less organic c and carbonate in the paleo oxidized zone as compared with the unoxidized sediments depletion of carbonate content in the oxidized zones in the southern nares abyssal plain is particularly significant in that as much as 80 of the initial carbonates have been lost also the relative amounts of weak acid soluble fe and mn are generally less in the paleo oxidized zones due to the initial oxidation of metal carbonate and metal hydroxide forms to easily reducible oxide forms which are then subsequently solubilized under the mildly reducing conditions at depth in the sediment column

radar interferometric mapping of deformation in the year after the landers earthquake although the 1992 landers california earthquake sequence occurred in an area well sampled by geodetic networks1 3 the postseismic deformation in the months following the earthquake has been measured at only 15 geodetic stations4 another shortcoming in the geodetic coverage occurs west of the primary rupture where the existing geodetic observations suggest but cannot resolve sympathetic slip on secondary faults1 such measurements which are needed to place the landers earthquake sequence in the context of a recurring seismic cycle in california can be obtained with the dense spatial coverage provided by satellite radar interferometry5 9 here we present radar maps of the surface deformation field which reveal features that would otherwise have been poorly sampled particularly if the earthquake had occurred in a less accessible area we see triggered slip at the level of several centimetres as far as 100 km from the primary rupture and can resolve the geodetic signal of at least one small magnitude 5 aftershock the amount of surface slip following the main shock is less than a decimetre and is consistent with an exponential decay time of several months for the postseismic deformation

authigenic uranium relationship to oxygen penetration depth and organic carbon rain we have measured u in benthic incubation chambers sediment pore waters and in sediments along the california continental margin sedimentary u uptake rates based on a combination of sediment pore water profiles and benthic incubation chambers generally agree with those predicted from sediment accumulation rate data this agreement supports the view that most of the continental margin sedimentary u is delivered by diffusion across the seawater sediment boundary the average rate of authigenic u accumulation for all the sites examined here is 0 2 nmol cm 2 y 1 which is consistent with published global estimates of sedimentary u uptake in addition the accumulation rate of u in sediments exhibits a nonlinear relationship with the oxygen penetration depth and a linear relationship with the organic carbon rain rate these relationships highlight the potential utility for the u accumulation rate as a proxy for these processes

mobility of mo u as and sb within modern turbidites modern turbidites uranium molybdenum arsenic antimony we present and discuss porewaters and sediment data of mn fe mo u as and sb within four recent turbidites from the capbreton canyon sw france the deposition of turbidites on continental margins exerts strong influence on the fate of trace metals causing trace metal migration and or immobilization the down core distribution of the elements here depends entirely of ongoing diagenetic processes rather than the diffusion of o2 the persistence of fe mn oxides under anoxic conditions led to anoxic reoxidation of numerous species as nh4 reduced s compounds and trace metals metal oxides thus control the immobilization of mo and as in the solid phase and the remobilization of u and sb to the porewaters although the low sulphide production prevents anoxic authigenesis of mo and as reducing conditions below each horizon rich in mn fe oxides resulted in u and sb accumulation the exact mechanisms of sb immobilization are not known but it is most certainly different from that of as the profile shapes of mn and u were used to estimate the age of the turbidite deposits which cannot be determined by conventional radionuclide methods our interpretations however depend on calculations of diffusion coefficient particularly for u a simple diffusive model applied to mn suggested that the age of the latest deposit noted t1 was 22 months this date is close to the time elapsed between the core sampling and the last known turbiditic event in the capbreton canyon i e martin storm 18 months using the u data set and depending on diffusion coefficients used the estimated ages of the deeper layers were 4 7 yr for t2 and 7 5 14 yr for t3 the reliability and precision of this new approach to date sediments at short timescales is limited by the ignorance of a precise value for u diffusion coefficient reducing uncertainty on u diffusion coefficient will greatly support application of the proposed approach

shallow seismic source parameter determination using intermediate period surface wave amplitude spectra summary estimating reliable depths for shallow seismic sources is important in both seismo tectonic studies and in seismic discrimination studies surface wave excitation is sensitive to source depth especially at intermediate and short periods owing to the approximate exponential decay of surface wave displacements with depth a new method is presented here to retrieve earthquake source parameters from regional and teleseismic intermediate period 100 15s fundamental mode surface wave recordings this method makes use of advances in mapping globaldispersiontoallowhigherfrequencysurfacewaverecordingsatregionalandteleseismic distances to be used with more confidence than in previous studies and hence improve the resolution of depth estimates synthetic amplitude spectra are generated using surface wave theory combined with a great circle path approximation and a grid of double couple sources are compared with the data source parameters producing the best fitting amplitude spectra are identified by minimizing the least squares misfit in logarithmic amplitude space the f test is used to search the solution space for statistically acceptable parameters and the ranges of these variables are used to place constraints on the best fitting source estimates of focal mechanism depth and scalar seismic moment are determined for 20 small to moderate sized 4 3 mw 6 4 earthquakes these earthquakes are situated across a wide range of geographic and tectonic locations and describe a range of faulting styles over the depth range 4 29km for the larger earthquakes comparisons with other studies are favourable however existing source determination procedures such as the cmt technique cannot be performed for the smaller events by reducing the magnitude threshold at which robust source parameters can be determined the accuracy especially at shallow depths of seismo tectonic studies seismic hazard assessments and seismic discrimination investigations can be improved by the application of this methodology

late cenozoic extension in sw bulgaria a synthesis abstract southwest bulgaria forms the northern margin of the aegean extensional province since the early pliocene c 4 ma this region has accommodated southward or sse extension at several millimetres per year superimposed on c 400 m of post early pliocene regional uplift this sense of deformation superseded earlier extension oriented ene wsw which is estimated to have begun in the early late miocene c 10 9 ma and lasted until c 4 ma the regional topography is dominated by nnw sse striking grabens and normal fault escarpments relics from this time normal faults that are now active cut across these older structures although in some localities normal faults that were oriented obliquely to the earlier extension have remained active also oblique to the modern extension sense it is suggested that this present phase of extension relates to the modern sense of deformation throughout the aegean region and to the modern geometry of the north anatolian fault zone nafz which is independently inferred to have existed since c 4 ma the earlier ene wsw extension is inferred to have involved two phases the first predating the nafz and the second synkinematic with its initial phase of slip during c 7 4 ma when its geometry and the overall sense of deformation in the aegean region were different from at present some previous studies have inferred that sw bulgaria experienced large scale extension on low angle normal faults in the mid miocene or earlier however the limited evidence in support of this view is open to other interpretations and after due consideration can be discounted

redox reactions and carbonate preservation in deep sea sediments abstract geochemical analyses of long sediment cores in turbidite sequences from two abyssal plains in the north atlantic have provided evidence for a relationship between post depositional oxic decay of organic matter and the dissolution of carbonates palaeo oxidation zones in the upper part of individual turbidites were initially identified by distinct colour changes in the sediments these zones were found to have distinctly lower amounts of organic carbon carbonate minerals and labile metals such as fe mn ni and zn as compared with the underlying unoxidized parts of the same turbidite it appears that the initial oxidation of organic matter by oxygen results in an undersaturation of the pore water with respect to carbonates while at the same time some metals are precipitated as easily reducible and soluble oxyhydroxides after burial under suboxic conditions the palaeo oxidation zones are subjected to mildly reducing pore waters that leach the oxyhydroxides resulting in a depletion in labile metal contents in the palaeo oxidized zones it is important that these characteristics be identified in the sedimentary record as the result of diagenetic processes and not as a reflection of primary production in palaeo oceans

recurrent uranium relocations in distal turbidites emplaced in pelagic conditions abstract the sediments of the madeira abyssal plain east of great meteor seamount are dominated by distal turbidite deposition while the turbidites exhibit a wide compositional range 25 80 caco3 individual examples can be correlated over a wide area and are relatively homogenous organic c oxidation by bottom water oxygen proceeds from the turbidite tops downwards after emplacement in pelagic conditions and the progress of this oxidation front is marked by a sharp colour contrast in the sediments wilson et al 1985 in turbidites with corg 0 5 redistribution of authigenic u occurs to form a concentration peak 4 9 ppm u just below the oxidation front or colour change several tens g u cm2 may be mobilised and in all examples studied 60 of the remobilised u is relocated into the peak following burial by subsequent turbidites such u concentration peaks are persistent as relict indicators of their extinct oxidation fronts for at least 2 105 years in the case of thin turbidites where labile corg is almost exhausted the u peaks may be located in underlying sedimentary units because of their relationship to the oxidation front a redox mechanism for u peak formation is suggested from these data rather than a complexation with organic matter

metal accumulation rates in northwest atlantic pelagic sediments measurements of 230th 87sr86sr and twenty four metals were made on cores from the nares abyssal plain the sediment is characterized by slowly accumulating 0 3 0 7 g cm2 103 yr pelagic red clays and rapidly deposited grey clays transported by turbidity currents despite their colour differences and the enrichment of mn fe cu co ni zn v and to a lesser degree the rare earths in the red clays sr isotope evidence demonstrates that the clays have the same terrigenous origin the excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated the fluxes obtained are in the ranges 20 50 mol cm2 103 yr for mn and fe 0 1 0 4 mol cm2 103 yr for cu co ni zn v sr and ce 10 20 nmol cm2 103 yr for la and nd and 0 5 3 nmol cm2 103 yr for sm eu gd dy er and yb authigenic fluxes of y nb cr zr rb u and th were not resolvable fluxes appear to be near constant on the plain but comparison with other areas shows that they are quite variable both between and within ocean basins the chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter element comparisons and from differences in fluxes between atlantic and pacific red clays corresponding to the oceanic reactivities of the elements

a comparison of sediment accumulation chronologies by the radiocarbon and 230thexcess methods abstract four northeast atlantic cores which exhibited well correlated linear progressions of conventional radiocarbon age with depth were analysed to provide 230 th excess profiling data the current evaluation of marine radiocarbon data suggests that conventional radiocarbon ages consistently underestimate true time this deficit progressively increases from 4 to 22 ky bp as a result steady state sediment accumulation rate models based on conventional radiocarbon ages are expected to be in error by up to 17 dependent on the period over which the estimates are made when proxy timescales from the radiocarbon and 230 th excess data for the four cores are compared over periods between 0 11 5 and 0 18 2 ky bp the trend of cumulative time derived from the 230 th excess profiling data is shown to be consistent with the expected trend of conventional radiocarbon age vs the best current estimate of true time this agreement supports the use of 230 th excess as a tracer for detailed estimates of changing deep sea sediment accumulation fluxes

contribution of radar interferometry to a two step inversion of the kinematic process of the 1992 landers earthquake we study the rupture process of the 1992 landers earthquake to limit the trade off between slip amplitude and rupture time that affects solutions using only seismological data we adopt a two step approach we first constrain the slip distribution and its uncertainty by independent geodetic data to recover in the second step the temporal details of the rupture propagation the first step consists of an inversion of interferometric data and global positioning system measurements both independently and together to constrain slip distribution on a three segment fault model along both strike and dip direction we use a genetic algorithm to test the uniqueness of the solution and a least squares formulation to find the model which best fits the data we conclude from the results of these geodetic inversions that interferometric data are rich enough to access the slip distribution in the case of the landers earthquake since the surface deformations are more sensitive to shallow slip in our configuration the slip amplitude is better resolved near the surface than at depth the resulting slip distribution is in agreement with geological observations at the surface and confirms the heterogeneous nature of the landers earthquake most of the slip occurs at shallow depths on the homestead valley fault second segment with a maximum value of around 7 m another high slip zone is observed on the johnson valley fault first segment at 8 km depth in the second step we invert strong motion data with the a priori final slip amplitude and its uncertainty deduced from geodetic data to constrain the time history of the rupture process this second step emphasizes a strong variation of the temporal development of the earthquake fast rupture front velocities appear within high slip zones and the rupture slows when it encounters a resistance along the fault on average the rupture front propagates with velocities close to the s wave velocity and terminates about 20 s after initiation the large variations in both slip amplitude and rupture velocity suggest that the rupture process is better described by successively breaking asperities than by a pulse propagating with constant velocity

the environmental seismic intensity scale esi 2007 in greece addition of new events and its relationship with magnitude in greece and the mediterranean preliminary attenuation relationships abstract the environmental seismic intensity esi scale has been officially released in 2007 and is based on the quantification of earthquake environmental effects due to its quantitative nature the scale improves the process of assessing macroseismic intensities particularly in the epicentral area of those cases in which sole traditional intensity scales prove to be ineffective following a large number of publications that applied this relatively newly established scale there is some need for parametrization this is because this intensity scale can offer new insights to seismic hazard assessment and has the potential to reduce the uncertainties that stem from traditional macroseismic scales this study has three main goals firstly to enrich and compile an esi 2007 database from earthquakes in greece by adding 4 new events secondly to extract a relationship between magnitude and the esi 2007 for greece and the mediterranean thirdly to offer a preliminary estimate of how the intensity attenuates with distance after developing a code in python language to assist this process the esi 2007 scale was applied in the 1995 ms 6 6 kozani grevena earthquake the 1978 mw 6 5 thessaloniki earthquake the historic 1894 atalanti earthquake sequence m 6 4 and m 6 8 and the 365ad event in crete m 8 4 these events were selected because they have well documented and extensive co seismic effects including primary and secondary surface ruptures rockfalls landslides and liquefaction phenomena for the kozani earthquake extracted results were correlated with sar interferograms in order to provide a complete and high spatial resolution of the ground deformation both the kozani grevena and the thessaloniki events produced a maximum intensity ix on the esi 2007 scale the atalanti earthquake produced a maximum intensity x and the 365ad crete earthquake a maximum intensity xii overall the esi 2007 scale compares fairly well with the traditional macroseismic scales except for some villages in the kozani grevena epicentral area where due to the poor quality of buildings existing scales overestimated the intensity by one degree compared to the esi 2007 it is interesting to note that both for greece and the mediterranean area a strong correlation exists between mw and the esi 2007 scale in particular the following relationships between the mw and the esi scale have been extracted i for greece io esi 2007 3 1427 exp 0 1643mw and ii for the mediterranean io esi 2007 3 3543exp 0 1557mw however more events and more data regarding the intensity distributions are required to establish the intensity attenuation with distance

the 1995 kozani grevena northern greece earthquake revisited an improved faulting model from synthetic aperture radar interferometry summary previously geodetic data associated with earthquakes have been widely modelled using coplanar rectangular dislocations in an elastic half space however such models appear inadequate when complex geometries such as variations in strike and dip or multiple fault segments are involved here we revisit the 1995 m s 6 6 kozani grevena earthquake and use synthetic aperture radar sar interferometric measurements tectonic observations and seismological data to constrain a fault model with a realistic geometry we undertake a critical analysis of all available sar data including characterization of atmospheric artefacts these are partially removed and the possibility that such effects are misidentified as secondary faulting is examined three well correlated interferograms provide an accurate and complete description of the ground deformation field associated with the event to take into account the complexity of the fault system activated during the earthquake we construct a 3 d fault model composed of triangular elements that is geometrically more consistent with surface ruptures than those of previous studies using first trial and error and then iterative inversion we explore the ranges of geometric parameters that can explain the data we obtain an average final model and its standard deviation with small slip amplitude at the surface consistent with the field observations and with slip as large as 2 5 m at depth this model is compared with those previously published we conclude that an antithetic fault is not required to explain the sar data

depth localization of denitrification in a deep sea sediment from the madeira abyssal plain1 sediments of the madeira abyssal plain are dominated by alternate sequences of pelagic sediment and turbidites composed of relatively organic rich material transported from the continental margin after the deposition of a turbidite and resumption of pelagic sedimentation the zones of o2 and no3 respiration progress slowly into the turbidite from above the oxidation front is characterized by depletion of o2 and no3 at almost identical depths data are presented to show that no3 respiration denitrification within such a turbidite is localized in a very small depth interval at the oxidation front

authigenic uranium in atlantic sediments of the last glacial stage a diagenetic phenomenon cores from three different atlantic localities equatorial cape verde rise and porcupine abyssal plain are shown to have anomalous high u contents 5 8 ppm total in sediments laid down during the last glacial stage 12 24 ky bp radiocarbon data demonstrate that the sediments hosting the peak u levels were accumulated at rates similar to those immediately above and below all the cores exhibit maximum mn levels characteristic colour changes and maximum u levels in the same sequence with increasing depth in core on the evidence of the similarities between the cores and pore water u data from a porcupine abyssal plain site it is proposed that the authigenic u enrichments are syndiagenetic and possibly active no correlation is observed between sediment authigenic u and corg contents the source of enrichment is bottom water u which has diffused downwards into the sediments to be sorbed at a particular redox level located 10 30 cm below the oxic post oxic boundary marked by the colour change the magnitude of the enrichments is caused by the persistence of this boundary at a particular level as a result of the decrease in mean sediment accumulation rate between the last glacial stage 5 2 up to at least 19 1 cm ky 1 and the holocene 2 2 4 1 cm ky 1 similar accumulation rate contrasts are expected to be widespread in the atlantic and the implications for previous reported work particularly from the mid atlantic ridge are discussed

post depositional migration of elements during diagenesis in brown clay and turbidite sequences in the north east atlantic abstract two cores from a ne atlantic pelagic clay area of low accumulation rate each contain a single turbidite with different age thickness and composition diagenesis following introduction of exotic turbidite material into the pelagic clay sequence has resulted in distinctive colour changes the diagenetic process is thought to be driven by bacterially mediated organic oxidation and compositional differences in the turbidites and clays allow examination of the effects on metal concentrations of this process in one core a long turbidite section emplaced 330 000 years ago is overlain by clay organic oxidation has apparently proceeded from the turbidite top downwards and has maintained a u concentration peak below the oxidation front marked by a colour change the u source is believed to be u initially associated with the organic matter in the oxidised section of the turbidite vanadium and cu behave similarly but upward migration of the redox sensitive metals mn and ni is also seen in the second core an 8 cm turbidite section was emplaced about 170 000 years ago in a clay column in this case organic consumption now appears complete but evidence for diagenetic effects is found in a 16 cm compositional alteration halo of the underlying pelagic clay fe ii has been enriched and the hydrogenous component of mn co ni and cu removed from the pelagic clay to form the halo

concentration vertical flux and remineralization of particulate uranium in seawater abstract concentrations and fluxes of particulate u were measured throughout the water column at several locations in the atlantic and pacific oceans with in situ filtration systems and sediment traps the results indicate that dissolved u is fixed to particles in surface seawater organic matter appears to be the carrier phase formation of particulate authigenic u below the surface waters could not be detected authigenic u is remineralized within the bathypelagic layers at the open ocean sites studied in the panama basin an upwelling area with high biological productivity remineralization of authigenic u in the deep water column was not observed the rate of remineralization of authigenic u in the deep sea is insufficient to produce a measurable concentration gradient between surface and deep waters within the mixing time of the oceans formation of authigenic u in the water column in areas such as the panama basin is not a significant sink for u on an ocean wide basis

integrating high precision aftershock locations and geodetic observations to model coseismic deformation associated with the 1995 kozani grevena earthquake greece 1 we integrate high precision aftershock locations with geodetic inverse modeling to create a more complete kinematic model for the kozani grevena earthquake sequence using the double difference algorithm we have improved relative hypocentral locations by a factor of 7 and thus imaged the details of the fault network associated with the seismic sequence the interpreted fault network consists of multiple segments including 1 a master normal fault that strikes nearly due west and dips toward the north at 43 extending from 6 to 15 km depth 2 an upper segment that connects the top of the seismicity to the observed surface ruptures and dips 70 3 hanging wall antithetic faults 4 a more steeply dipping southwest striking linking structure at the southwest end of the rupture and 5 a separate south dipping segment at the southwestern end of the aftershock cluster the imaged fault segment dimensions orientations and geometric relationships are consistent with regional fault patterns using slip inversion on triangular dislocation patches we calculate variable slip on the imaged three dimensional fault network that best fits the surface displacements observed by satellite interferometric synthetic aperture radar insar in our preferred model we find that the majority of slip occurred at depth on the west and southwest striking segments by comparing these results to a planar fault model derived solely from the insar data using nonlinear inversion methods we demonstrate that the three dimensional model improves the fit to the geodetic data while incorporating the observations of surface rupturing and aftershock distributions

changes in redox conditions in deep sea sediments of the subarctic north pacific ocean possible evidence for the presence of north pacific deep water cores of upper quaternary and holocene sediment from the subarctic north pacific north of about 48 n contain one or more layers of oxidized brown sediment interbedded within predominantly reduced green sediment the brown layers are enriched in several trace elements especially mn mo ni and co relative to the green layers where multiple oxidized layers are present the intensity of the brown coloration and the magnitude of trace element enrichment often decrease with depth suggesting that the oxidized layers are unstable and are being chemically reduced at depth the oxidized layers represent a change in redox conditions between the north pacific red clay province and the subarctic biosiliceous green clay province the redox change may have been caused by an increase in supply of dissolved oxygen to bottom waters during glacial interglacial transitions as the result of the periodic formation of a seasonal bottom water mass in the northeastern pacific ocean

the behaviour of manganese in atlantic carbonate sediments abstract manganese porewater and solid phase data are considered from two different atlantic carbonate sediments both with good geochemical characterisation the first case is a continuously accumulated alternating pelagic marl carbonate ooze where there is a correlation in post oxic conditions between mn ii porewater levels and an acetate leachable mn fraction of the sediment this leachable mn appears to have an association with calcite and in this example the leached residue mn content approximates to that of shale in the second case a very recent compositionally homogeneous calcareous turbidite is underlain by mn oxyhydroxide at the former sediment surface which is now acting as a source of mn ii by reduction sorption of mn by the turbidite sediment and shale like leached residue mn levels in anoxic conditions are again observed as mn ii diffuses towards present oxic conditions although no unique equilibrium is achieved similar older buried turbidites have concentration decreases in solid phase mn content preserved from bottom to top as relict evidence that this process has occurred in these turbidites 54 64 of the total mn is leachable by the acetate method and therefore presumed to be sorbed by calcite the oldest example has persisted for 125 kyr it is suggested that the slow breakdown of metastable mn oxyhydroxide and sorption of mn ii to calcite surfaces are important controls on the behaviour of mn in pelagic carbonates in mildly reducing conditions where accumulation fluctuations occur these processes act together with accumulation to limit overall mn migration and to prevent the large mn enrichments seen near the sediment surface in more reducing environments

the displacement field of the landers earthquake mapped by radar interferometry geodetic data obtained by ground or space based techniques can be used to infer the distribution of slip on a fault that has ruptured in an earthquake although most geodetic techniques require a surveyed network to be in place before the earthquake1 3 satellite images when collected at regular intervals can capture co seismic displacements without advance knowledge of the earthquake s location synthetic aperture radar sar interferometry first introduced4 in 1974 for topographic mapping5 8 can also be used to detect changes in the ground surface by removing the signal from the topography9 10 here we use sar interferometry to capture the movements produced by the 1992 earthquake in landers california11 we construct an interferogram by combining topographic information with sar images obtained by the ers 1 satellite before and after the earthquake the observed changes in range from the ground surface to the satellite agree well with the slip measured in the field with the displacements measured by surveying and with the results of an elastic dislocation model as a geodetic tool the sar interferogram provides a denser spatial sampling 100 m per pixel than surveying methods1 3 and a better precision 3 cm than previous space imaging techniques12 13

global compilation of interferometric synthetic aperture radar earthquake source models 1 comparisons with seismic catalogs 1 while many earthquakes have now been studied using interferometric synthetic aperture radar insar data a full assessment of the quality and additional value of insar source parameters compared to seismological techniques is still lacking we compile a catalog of source models obtained using insar and estimate the corresponding centroid moment tensor cmt parameters we refer to this compilation as the icmt archive we compare source parameters from over 70 insar studies of 57 global earthquakes with those in the global cmt gcmt international seismological centre isc and engdahl hilst buland ehb seismic catalogs we find an overall good agreement between fault strike dip and rake values in the gcmt and icmt archives likewise the differences in seismic moment between these two archives are relatively small and we do not find support for previously suggested trends of insar leading to larger moments than seismic data however epicentral locations show substantial discrepancies which are larger for the gcmt median differences of 21 km than for the ehb and isc catalogs median differences of 10 km since insar data have a high spatial resolution and thus should map epicentral locations accurately this allows us to obtain a first independent estimate of epicentral location errors in the seismic catalogs earthquake depths from insar are systematically shallower than those in the ehb catalog with a median of differences of 5 km while this trend may be partly due to unmodeled crustal complexity it is also compatible with the observation that the rupture of crustal earthquakes tends to propagate upward in the seismogenic layer

magnetic measurements used to identify paleoxidation fronts in deep sea sediments from the madeira abyssal plain we describe the results of rock magnetic measurements of a sediment core from the madeira abyssal plain which contains multiple turbidites previous studies of trace element e g u concentration and observations of sediment color changes have shown that turbidite emplacement has resulted in reductive diagenesis and the formation of paleoxidation fronts we show that variations in sediment lithology and postdepositional sedimentary processes can be characterized very sensitively using magnetic measurements low concentrations of magnetic minerals occur in turbidites with a high organic content reflecting the destruction of magnetic material via the process of reductive diagenesis in addition fossil redox fronts are readily identified by rock magnetic properties

integrating high precision aftershock locations and geodetic observations to model coseismic deformation associated with the 1995 kozani grevena earthquake greece kinematic model of the kozani earthquake

assessing the role of stress transfer on aftershock locations 1 the influence of the static stress changes caused by the mw 6 5 kozani grevena greece earthquake of 13 may 1995 on aftershock locations is investigated a three fault rupture model for the main shock aftershock relocations and fault plane solutions for the aftershocks is available we have developed a testing method which tests whether the proportions of aftershocks located inside areas determined by a selected criterion on the static stress change could be attained if there were no effect of the stress change due to the main shock on aftershock locations the areas of stress change are determined at the focus of every aftershock the analysis is performed separately for areas defined by a positive stress change greater than or equal to 0 1 0 3 1 0 5 0 and 10 0 bar and by a negative change less than or equal to 0 1 0 3 1 0 5 0 and 10 0 bar the tests have confidently indicated a rise in probability to locate aftershocks inside areas of positive static stress change which supports the hypothesis on the triggering effect in these areas the analysis has not evidenced the existence of stress shadows inside areas of larger negative stress change on the contrary the tests have indicated a significant increase of the probability of event location in the areas of a change less than or equal to 5 0 and 10 0 bar for areas of larger absolute stress change this probability increases regardless of the sign of the change though distinctly more in areas of positive than of negative change

active diagenetic formation of metal rich layers in n e atlantic sediments sediment cores from the porcupine abyssal plain exhibit an indurated layer 0 5 3 cm thick at depths of approximately 50 cm this is some 15 20 cm below the glacial holocene transition as interpreted by radiocarbon dating and the palaeontological criteria of ruddiman and mcintyre 1981 the layer is forming currently at the oxic post oxic boundary in the sediments as revealed by pore water data o2 and no 3 are present in solution above the layer while fe2 mn2 po3 4 and nh 4 are present in solution below and all these species show concentration gradients indicating fluxes into the layer these data are consistent with the hypothesis for the initiation and sustained formation of such layers proposed by wilsonet al 1986a b the elements mn ni co fe p v cu zn and u are all enriched to varying degrees in the vicinity of the layer some differential stratification of these elements in the vertical consistent with a redox control is observed at one site with a 0 5 cm layer with mn ni and co above fe p v and cu in the layer and u below at another site the metal rich layer has higher fe and p concentrations and is more indurated here all enrichments except co are contained within a single layer sample 3 cm thick

early diagenesis in an organic rich turbidite and pelagic clay sequence from the cape verde abyssal plain ne atlantic magnetic and geochemical signals abstract processes of early diagenesis in sediments from the cape verde abyssal plain are investigated using the complimentary techniques of environmental magnetism and solid phase geochemistry the sequence captured by a 2 m long box core comprises an organic rich turbidite derived from the nw african continental margin emplaced ca 330 ka bp overlain by brown pelagic clay diagenesis in the pelagic clay mainly involves slow in situ oxidation of the iron oxide phases present which mossbauer effect data suggest are detrital haematite and magnetite possibly maghaemitised in the turbidite diagenesis has proceeded in two stages the first involving suboxic reductive processes following depletion of porewater o2 and the second involving oxidative processes associated with the slow descent of an oxidation front through the bed due to diffusion of o2 from the overlying seawater carbonate free magnetic parameters interparametric quotients and remanence acquisition demagnetisation and coercivity measurements of the core reveal that significant depletion of detrital ferrimagnetic iron fe2 fe3 oxide grains like titano magnetite has occurred within the turbidite during suboxic diagenesis and confirm previous suggestions that reductive dissolution of such components is a grain size selective process however the higher oxidation state fe3 canted antiferromagnetic iron oxide grains like haematite and goethite are much less susceptible to reductive diagenesis remobilisation of transition metal ions from below the oxidation front in the turbidite has led to authigenic precipitation of ferrimagnetic fe mn micronodules in a distinct layer immediately overlying the front and above this a further interval of mn enriched diagenetic laminae however within the suboxic organic rich zone of the turbidite well below the oxidation front there is clear evidence for the presence of a significant concentration of fine single domain ferrimagnetic iron oxide grains which are most probably associated with a population of live magnetotactic bacteria between this zone and the oxidation front there is a transitional interval in which the number of live magnetotactic bacteria declines rapidly and fossil magnetosomes in the sediment are being reductively dissolved progressively up sequence these results are broadly similar though differing in some respects to magnetic and geochemical studies of hemipelagic and high productivity pelagic sediments in which mn and fe redox boundaries have been recognised and further illustrate the value of environmental magnetic parameters for characterising early diagenetic processes in sediments of this kind

postdepositional enrichment of uranium in sediment from the bering sea abstract deep sea sediments were collected from the northern north pacific and the bering sea and separated into hcl soluble and hcl insoluble fractions these sediments were analyzed for their uranium and thorium concentrations and 234 u 238 u activity ratios by alphaspectrometry the mean concentration of total uranium in the oxic northern north pacific sediment was relatively low 1 25 ppm and showed little variation with sediment depth the concentration of total uranium in the surface sediment of the bering sea basin was also low 0 85 ppm similar to those of the northern north pacific sediment but it was higher 2 36 ppm in the strongly reducing sediment below 40 cm this increase in uranium concentration with depth is ascribed to higher quantities of hcl soluble uranium it is suggested that uranium diffuses through interstitial water and is postdepositionally precipitated during early diagenesis in the subsurface reducing environment a postdepositional precipitation rate of uranium in the bering sea basin sediment was estimated to be 28 g cm 2 103 yr 1 in the reducing bering sea basin sediment the concentration of total uranium in the layers enriched in manganese carbonate was 1 68 ppm which was slightly less than that of the other normal deep layer this depletion of uranium may be due to dilution with volcanic material of coarser texture

comparative behavior of authigenic re u and mo during reoxidation and subsequent long term burial in marine sediments the trace element re is enriched in mildly reducing suboxic sediments close to or slightly later in the redox sequence than u and before reduction of mo in more reducing sulfidic sediments this work investigates the behavior of authigenic re during oxidation and long term burial in the sediments of several turbidites from the madeira abyssal plain exposure to bottom water o2 clearly remobilizes authigenic re as found in previous work but reimmobilization occurs in reducing sediments below the oxidation front over a depth range of 0 5 3 m the large spread of the re burndown peak must be kinetically controlled perhaps influenced by the corg content once reimmobilized however the authigenic re signal remains immobile for at least 3 4 myr authigenic u in contrast consistently forms peaks 0 5 m broad whereas authigenic mo is lost on oxidation and does not appear to be refixed unless authigenic pyrite is formed these results imply that any paleoenvironmental significance of authigenic re will be compromised in low sedimentation rate environments 10 cm kyr where there is significant exposure of authigenic re to bottom water o2 however authigenic re records from rapidly accumulating continental margin sediments with much less exposure to bottom water o2 still offer considerable potential as high fidelity recorders of past reducing conditions

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

rock magnetic characterization of early redoxomorphic diagenesis in turbiditic sediments from the madeira abyssal plain rock magnetic measurements of two sediment cores from the madeira abyssal plain map north atlantic are used to investigate post depositional changes in the concentration grain size and composition of magnetic minerals in the sediments that have occurred within organic rich turbidite horizons the changes are associated with an initial stage of suboxic reductive diagenesis following depletion of porewater o2 and a later stage of oxidative diagenesis associated with the slow descent of an oxidation front through the sediment as a result of diffusion of o2 from the overlying sea water the turbidites are of late quaternary age 18o stages 1 3 and derive both from different sites on the nw african continental margin and from the flanks of the canary islands thus the turbidites are variable compositionally especially in terms of carbonate detrital magnetic mineral and organic carbon content diagenetic changes in these sediments have been identified using solid phase geochemical data u mn corg and caco3 reported previously in more than one study rock magnetic parameters of the sediments when expressed on a carbonate free basis reveal that significant depletion of detrital ferrimagnetic iron fe2 fe3 oxide grains has occurred within organic rich turbidites during redoxomorphic diagenesis normalized quotients of magnetic parameters also show that reductive diagenesis is a ferrimagnetic grain size selective process but it has a minimal effect on the canted antiferromagnetic fe3 oxides in the sediment such components if present therefore become relatively enriched in magnetic assemblages as the ferrimagnetic grains are dissolved progressively and bulk magnetic concentration is thus depleted there is clear evidence in both cores for the existence of ultrafine ferrimagnetic grains at depth within the suboxic zone of the organic rich turbidites beneath both active and fossil oxidation fronts these grains are most probably associated with populations of live magnetotactic bacteria which commonly inhabit such organic rich horizons and play a part in the chain of bacterially mediated reactions normally associated with suboxic diagenesis these results show that simple and rapid rock magnetic techniques can be used to characterize early diagenetic processes involving iron phases in deep sea sediments at least as effectively as more laborious time consuming and sample destructive geochemical measurements

early diagenesis in north atlantic abyssal plain sediments characterized by rock magnetic and geochemical indices processes of early diagenesis are investigated in a sequence of late quaternary turbiditic sediments from the madeira abyssal plain map west of the nw african continental margin in three sediment cores from this region solid phase geochemical indices of redox sensitive ion mobilization are compared with rock magnetic parameters as proxies for diagenesis characterization the mud dominated distal turbidites are emplaced mainly as a result of glacio eustatic changes in sea level and derive both from different sites on the nw african margin and from the flanks of the canary islands thus the turbidites are of variable composition especially in terms of carbonate detrital magnetic mineral and organic carbon content within organic rich 0 5 corg turbidite horizons remineralization of organic detritus proceeds in two stages the initial stage involves suboxic reductive diagenesis following depletion of pore water o2 while the later stage involves oxidative diagenesis associated with the slow descent of an oxidation front through the sediment due to diffusion of o2 from the overlying seawater rock magnetic parameters of these sediments when expressed on a carbonate free basis reveal that significant depletion of detrital ferrimagnetic iron fe2 fe3 oxide grains has occurred within the organic rich turbidites during suboxic diagenesis normalized quotients of magnetic parameters and remanence coercivity profiles of selected samples also show that reductive diagenesis is a ferrimagnetic grain size selective process but it has a minimal effect on the canted antiferromagnetic fe3 oxides in the sediment such components if present therefore become relatively enriched in magnetic assemblages as the ferrimagnetic grains are progressively dissolved in all three cores studied however there is clear evidence for the presence of ultrafine ferrimagnetic iron oxide grains at depth within the suboxic zones of organic rich turbidites beneath both active and fossil oxidation fronts these grains are probably associated with populations of live magnetotactic bacteria which inhabit such organic rich horizons and which form a link in the chain of bacterially mediated reactions normally associated with suboxic diagenesis these results comply with previous observations made in studies of suboxic diagenesis in hemipelagic sediments and demonstrate the value of rapid and non destructive rock magnetic measurements for illuminating redoxomorphic processes of diagenesis involving transformation of iron phases in deep sea sediments

the kozani grevena greece earthquake of 13 may 1995 revisited from a detailed seismological study the kozani earthquake m s 6 6 of 13 may 1995 is the strongest event of the decade in greece and occurred in a region of low seismic activity using regional data and the strong motion record at the kozani station we relocate the mainshock at 40 183 n and 21 660 e beneath the vourinos massif at a depth of 14 2 km we also compute a focal mechanism by body waveform modeling at te leseismic distance which confirms a normal mechanism the most likely plane strikes 240 1 n and dips 40 1 nwithacentroidd epthof 11 1 km modeling of the strong motion record at kozani confirms that nucleation started at the eastern termination of the bottom of the fault six days after the mainshock we installed a network of 40 portable seismological stations for one week around the epicentral region several thousand aftershocks were recorded among which we locate 622 with a precision better than 1 km we compute 181 focal mechanisms that mostly show normal faulting the aftershock seismicity is restricted between 5 and 15 km depth and defines a plane dipping north at an angle of about 35 consistent with the mainshock mechanism seismic activity with the same pattern of normal fault mechanisms is also seen on an antithetic fault connected to the main one at 12 km depth which cuts the ground surface north of the vourinos ophiolite massif in the siatista valley these results suggest two possibilities for the active fault plane either it is the deskati fault that is flat and dips with a constant angle and therefore the surface breaks are secondary features or more likely it is the paleohori fault that is new of listric shape and located ahead of the deskati fault which was not active during the earthquake

a new geochemical classification of sedimentary environments because of the relative constancy of ph in most subaqueous sediments and the general lack of measurability of eh these parameters are not practically useful for classifying sedimentary environments in their place a new classification is offered which derived from studies of modern sediments is based on the presence or absence of dissolved oxygen and dissolved sulfide in the sediments at the time of authigenic mineral formation sedimentary environments are first of all divided into oxic and anoxic depending upon the presence or absence of measurable dissolved oxygen anoxic environments in turn are divided into sulfidic and non sulfidic depending upon the presence of measurable dissolved sulfide anoxic nonsulfidic environments are further divided into postoxic or resulting from oxygen removal without sulfate reduction weakly reducing and methanic or resulting from complete sulfate reduction with consequent methane formation strongly reducing the environments are shown to succeed one another during early diagenesis in the order oxic post oxic sulfidic methanic iron and manganese minerals characteristic and stable in each environment are listed and discussed so that they may be used to distinguish the environments when studying the ancient geological record

the anatomy of the 2009 l aquila normal fault system central italy imaged by high resolution foreshock and aftershock locations 1 on 6 april 01 32 utc 2009 a mw 6 1 normal faulting earthquake struck the axial area of the abruzzo region in central italy we study the geometry of fault segments using high resolution foreshock and aftershock locations two main sw dipping segments the l aquila and campotosto faults forming an en echelon system 40 km long nw trending the 16 km long l aquila fault shows a planar geometry with constant dip 48 through the entire upper crust down to 10 km depth the campotosto fault activated by three events with 5 0 mw 5 2 shows a striking listric geometry composed by planar segments with different dips along depth rather than a smoothly curving single fault surface the investigation of the spatiotemporal evolution of foreshock activity within the crustal volume where the subsequent l aquila main shock nucleated allows us to image the progressive activation of the main fault plane from the beginning of 2009 the foreshocks activated the deepest portion of the fault until a week before the main shock when the largest foreshock mw 4 0 triggered a minor antithetic segment seismicity jumped back to the main plane a few hours before the main shock secondary synthetic and antithetic fault segments are present both on the hanging and footwall of the system the stress tensor obtained by inverting focal mechanisms of the largest events reveals a ne trending extension and the majority of the aftershocks are kinematically consistent deviations from the dominant extensional strain pattern are observed for those earthquakes activating minor structures

evidence from authigenic uranium for increased productivity of the glacial subantarctic ocean authigenic uranium is precipitated in reducing sediments and therefore responds both to changes in particulate organic carbon flux to the sediment and to changes in the oxygen concentration of bottom waters by examining a large number of cores over a wide latitudinal and depth range in the atlantic sector of the southern ocean we hope to distinguish between a predominantly productivity driven authigenic u signal and a circulation or sediment focusing signal we find little to no authigenic u in holocene sediments throughout the south atlantic ocean glacial sediments north of 40 s lack authigenic u whereas sediments from the subantarctic zone show substantial enrichments in authigenic u relative to the holocene up to 5 3 ppm the widespread distribution of glacial u enrichment even in cores with no glacial interglacial change in mass accumulation rate implies that u deposition was not caused by an increased supply of organic carbon via sediment focusing authigenic u and organic carbon in a shallow core 1000 m from the subantarctic region show the same glacial increase found in the deep cores because this site was well ventilated during the last glacial maximum its record provides further evidence that increased glacial productivity of the subantarctic region contributed to the high concentrations of authigenic u found in the glacial sections of deep cores

geodetic investigation of the 13 may 1995 kozani grevena greece earthquake the ms 6 6 13 may 1995 kozani grevena earthquake struck a region of low historical seismic activity which includes a 10 year old triangulation network in northern greece after the earthquake monuments from this network were occupied with gps to measure co seismic displacements inversion of the co seismic displacement field to yield a source mechanism is achieved by use of a hybrid simplex monte carlo method which requires no a priori constraints the model focal mechanism agrees well with the global cmt solution and locally observed aftershocks but implies a significantly higher scalar moment than do seismological or sar interferometry studies and has a longer fault length than the model based on sar interferometry

accumulation rates of th 230 pa 231 and some transition metals on the bermuda rise abstract measurements of 238u 234u 230th 232th 231pa mn fe co ni cu and zn were made on 23 samples from core gpc 5 a 29 m giant piston core from a water depth of 4583 m on the northeastern bermuda rise 33 41 2 n 57 36 9 w this area is characterized by rapid deposition of sediment transported by abyssal currents unsupported 230th and 231pa are present throughout the core but because of large variations in the sedimentation rate show marked departures from exponential decay with depth the trend with depth of the 231 pa ex 230 th ex ratio is consistent with the average accumulation rate of 36 cm 1000 y reported earlier on the basis of radiocarbon dating and caco3 stratigraphy when expressed on a carbonate free basis concentrations of mn co ni cu zn 230thex and 231paex all show cyclic variations positively correlated with those of caco3 the correlations can be explained by a model in which all of these constituents including caco3 are supplied to the sediments from the water column at a constant rate concentration variations are controlled mainly by varying inputs of terrigenous detritus with low inputs occurring during interglacials and high inputs during glacials relationships between the metal and 230thex concentrations permit estimates of the rates at which the metals are removed to the sediment by scavenging from the water column the results in g cm2 1000 y are 4300 1100 for mn 46 16 for ni and 76 26 for cu these rates are somewhat larger than ocean wide averages estimated by other methods and the absolute rate of 230th accumulation in gpc 5 averages about nine times higher than production in the overlying water column this part of the bermuda rise and similar bottom current deposits may act as important accumulators of elements scavenged from seawater

mudstones of the tanqua basin south africa an analysis of lateral and stratigraphic variations within mudstones and a comparison of mudstones within and between turbidite fans permian deep water mudstones in the tanqua basin south africa have been studied using geochemical and spectral gamma ray techniques the mudstones occur as thick sequences between sand rich submarine fans but also occur as thinner mud rich units within each fan the interfan mudstones are interpreted to have accumulated during transgression and the consequent period of relatively high sea level while the submarine fans and their intrafan mudstones were deposited during regression and relatively low sea level geochemical analyses revealed systematic differences between interfan and intrafan mudstones because the two types of mudstones have slightly different source lithologies differences between the two types of mudstone suggest that changes in relative sea level played a role in controlling exposure of sediment source areas there are geochemical signals that display systematic stratigraphic trends within both interfan and intrafan mudstones these are best explained by gradual denudation exposure and weathering of different lithologies within a single sediment source area both interfan and intrafan mudstones have uniform geochemical signals along the flow direction except for the relative amount of uranium it is most likely that the basinward increase in uranium in the mudstones is the result of reduced clastic dilution of uranium bearing pelagic fallout

global compilation of interferometric synthetic aperture radar earthquake source models 2 effects of 3 d earth structure 1 we carry out long period surface wave centroid moment tensor cmt inversions using various global tomographic models and two different forward modeling techniques for 32 large earthquakes previously studied using interferometric synthetic aperture radar insar data since insar methods provide an alternative and independent way of locating and characterizing shallow continental earthquakes comparisons of our source parameters with those from insar are a novel way to assess limitations in the insar models as well as the effects of inaccurate wave propagation formulations and or 3 d earth structure on earthquake source determinations we show that comparing insar results with our seismic solutions is valuable to identify inaccuracies in the earthquake slip distribution retrieved using insar moreover we find that using more accurate formulations together with the best fitting earth models substantially reduces biases and differences between moment magnitude and fault strike determined using insar and seismic data as expected for long period surface wave source inversions for shallow earthquakes the fault dip and rake angles are difficult to constrain but we show that when using the best fitting earth models differences to insar estimates are reduced moreover spurious deviations from a pure double couple earthquake mechanism are on average smaller for the best fitting earth models and the more accurate formulation of wave propagation there are large differences between insar epicentral locations and those obtained in this study and on average no clear improvements to the global cmt locations are achieved this suggests that higher resolution earth models are necessary to further refine long period cmt epicentral locations

the 1995 grevena northern greece earthquake fault model constrained with tectonic observations and sar interferometry after the 1995 grevena ms 6 6 event in northern greece we mapped the earthquake fault break in detail the surface break is small 8 12 km long 4 cm slip compared to the moment release of the event however the morphologic and tectonic study of the active faults in the field and using the spot satellite imagery suggests that the earthquake ruptured part of a much larger fault system including interconnecting segments we used sar interferometry of the satellite ers 1 imagery to characterize the coseismic displacement field this shows a kidney shaped zone of subsidence reaching 30 cm flanked by an uplift zone reaching 5 cm we reproduce this field using dislocations in an elastic half space and our observations of the fault system this requires 1 m slip from 4 to 15 km depth on a main normal fault segment dipping nnw our preliminary model includes significant ne dipping scissors faulting at the eastern end of the rupture clearly seen in the interferograms

structural control on fault geometry example of the grevena ms 6 6 normal faulting earthquake in this paper we present a three dimensional velocity structure of the kozani grevena region a relatively low seismicity area of the western margin of the internal hellenides which was struck by a ms 6 6 earthquake on may 13 1995 p wave arrival times from 656 aftershocks are inverted to resolve the velocity structure of the upper 12 km of the crust the 1995 ruptured fault dheskati fault lies at the southeastern end of a 35 km long normal fault the servia fault the crustal heterogeneities identified by tomography help to constrain the geometry and structure of the 1995 fault and the rupture evolution during the mainshock the aftershocks and the velocity structure define a fault dipping 35 toward nw which from 5 km depth splays upward into two nearly parallel shallow faults the slip during the mainshock and the aftershocks all were concentrated along the deeper portion of the fault while the limited slip observed at the surface occurred on the northern of the two shallower splays the paleochori fault it appears that the lithological heterogeneities of the shallow crust are responsible for the splaying of the main fault upward our work stresses the importance of crustal structure in determining fault geometry and segmentation and rupture evolution

uranium and thorium isotope concentrations in foraminiferal calcite abstract uranium and thorium isotope activities were measured by isotope dilution alpha spectrometry in four late pleistocene and holocene foraminiferal calcite samples sample cleaning methods were utilized to separate calcite tests from contaminating clay and surface oxide coatings the maximum concentration of lattice bound uranium is 0 023 ppm 10 10 9 moles u mole ca consistent with the lowest reported value 0 025 ppm 1 230th 234u activity ratios in samples cleaned as described above are much greater than one indicating that the cleaning methods used do not effectively remove230th from the surfaces of the calcite the upper limit for lattice bound232th is 0 039 ppm 17 10 9 moles th mole ca

estimating slip distribution for the izmit mainshock from coseismic gps ers 1 radarsat and spot measurements we use four geodetic satellite systems global positioning system gps european remote sensing ers radarsat and satellite pour l9observation de la terre spot to measure the permanent deformation field produced by the izmit earthquake of 17 august 1999 we emphasize measurements from interferometric analysis of synthetic aperture radar sar images acquired by ers and radarsat and their geodetic uncertainties the primary seismological use of these data is to determine earthquake source parameters such as the distribution of slip and the fault geometry after accounting for one month9s postseismic deformation tropospheric delay and orbital gradients we use these data to estimate the distribution of slip at the time of the izmit mainshock the different data sets resolve different aspects of the distribution of slip at depth although these estimates agree to first order with those derived from surface faulting teleseismic recordings and strong motion careful comparison reveals differences of 40 in seismic moment we assume smooth parameterization for the fault geometry and a standard elastic dislocation model the root mean square residual scatter is 25 mm and 11 mm for the ers and radarsat range changes respectively our estimate of the moment from a joint inversion of the four geodetic data sets is m 0 1 84 10 20 n m a moment magnitude of m w 7 50 these values are lower than other estimates using more realistic layered earth models given the differences between the various models we conclude that the real errors in the estimated slip distributions are at the level of 1 m the prudent geophysical conclusion is that coseismic slip during the izmit earthquake tapers gradually from approximately 2 m under the hersek delta to 1 m at a point 10 km west of it we infer that the yalova segment west of the hersek delta may remain capable of significant slip in a future earthquake

the use of foraminifera as a record of the past neodymium isotope composition of seawater 1 we present new isotopic data for sedimentary planktonic foraminifera as well as for potential water column and sedimentary sources of neodymium nd which confirm that the isotopic composition of the foraminifera is the same as surface seawater and very different from deep water and sedimentary nd the faithfulness with which sedimentary foraminifera record the isotopic signature of surface seawater nd is difficult to explain given their variable and high nd ca ratios ratios that are often sedimentary foraminifera ratios that are often much higher than is plausible for direct incorporation within the calcite structure we present further data that demonstrate a similarly large range in nd ca ratios in plankton tow foraminifera a range that may be controlled by redox conditions in the water column cleaning experiments reveal in common with earlier work that large amounts of nd are released by cleaning with both hydrazine and diethylene triamine penta acetic acid but that the nd released at each step is of surface origin while further detailed studies are required to verify the exact location of the surface isotopic signature and the key controls on foraminiferal nd isotope systematics these new data place the use of planktonic foraminifera as recorders of surface water nd isotope ratios and thus of variations in the past supply of nd to the oceans from the continents via weathering and erosion on a reasonably sure footing

measurement of interseismic strain accumulation across the north anatolian fault by satellite radar interferometry in recent years interseismic crustal velocities and strains have been determined for a number of tectonically active areas through repeated measurements using the global positioning system the terrain in such areas is often remote and difficult and the density of gps measurements relatively sparse in principle satellite radar interferometry can be used to make millimetric precision measurements of surface displacement over large surface areas in practice the small crustal deformation signal is dominated over short time intervals by errors due to atmospheric topographic and orbital effects here we show that these effects can be overcome by stacking multiple interferograms after screening for atmospheric anomalies effectively creating a new interferogram that covers a longer time interval in this way we have isolated a 70 km wide region of crustal deformation across the eastern end of the north anatolian fault turkey the distribution of deformation is consistent with slip of 17 32 mm yr below 5 33 km on the extension of the surface fault at depth if the gps determined slip rate of 24 1 mm yr is accepted the locking depth is constrained to 18 6 km

poroelastic rebound along the landers 1992 earthquake surface rupture maps of surface displacement following the 1992 landers california earthquake generated by interferometric processing of ers 1 synthetic aperture radar sar images reveal effects of various postseismic deformation processes along the 1992 surface rupture the large scale pattern of the postseismic displacement field includes large lobes mostly visible on the west side of the fault comparable in shape with the lobes observed in the coseismic displacement field this pattern and the steep displacement gradient observed near the emerson camp rock fault cannot be simply explained by afterslip on deep sections of the 1992 rupture models show that horizontal slip occurring on a buried dislocation in a poisson s material produces a characteristic quadripole pattern in the surface displacement field with several centimeters of vertical motion at distances of 10 20 km from the fault yet this pattern is not observed in the postseismic interferograms as previously proposed to explain local strain in the fault step overs peltzer et al 1996b we argue that poroelastic rebound caused by pore fluid flow may also occur over greater distances from the fault compensating the vertical ground shift produced by fault afterslip such a rebound is explained by the gradual change of the crustal rocks poisson s ratio value from undrained coseismic to drained postseismic conditions as pore pressure gradients produced by the earthquake dissipate using the poisson s ratio values of 0 27 and 0 31 for the drained and undrained crustal rocks respectively elastic dislocation models show that the combined contributions of afterslip on deep sections of the fault and poroelastic rebound can account for the range change observed in the sar data and the horizontal displacement measured at global positioning system gps sites along a 60 km long transect across the emerson fault savage and svarc 1997 using a detailed surface slip distribution on the homestead valley kickapoo and johnson valley faults we modeled the poroelastic rebound in the homestead valley pull apart a poisson s ratio value of 0 35 for the undrained gouge rocks in the fault zone is required to account for the observed surface uplift in the 3 5 years following the earthquake this large value implies a seismic velocity ratio vp vs of 2 1 consistent with the observed low vs values of fault zone guided waves at shallow depth li et al 1997 the sar data also reveal postseismic creep along shallow patches of the eureka peak and burnt mountain faults with a characteristic decay time of 0 8 years coseismic dilatant hardening locking process followed by post seismic pore pressure controlled fault creep provide a plausible mechanism to account for the decay time of the observed slip rate along this section of the fault

seismological constraints on the down dip shape of normal faults this work forms part of the nerc and esrc funded project earthquakes without frontiers and was partially supported by the nerc large grant looking inside the continents from space

tropospheric corrections of sar interferograms with strong topography application to etna the accuracy of spaceborne geodetic techniques including sar interferometry is limited by the time and spatial variation and altitude dependance of the propagation delay of electomagnetic waves in the lower troposphere particularly in mountainous areas in this paper we use a 1d model developed for tropospheric corrections of gps and doris measurements to correct sar data the differential tropospheric delay is computed at each pixel of the interferogram from ground temperature humidity and pressure using two empirical parameters calibrated from several radio soundings acquired in various latitude and climate conditions it is shown that with such a model given the 3300 meters topography of etna tropospheric variations can generate up to 4 phase rotations between the top and the bottom of the volcano in 16 out of the 20 interferograms processed with images acquired between august 1992 and october 1993 correction of the tropospheric effect reduces the number of fringes associated with the 1991 93 eruption from previous estimates the remaining deformation is consistant with a deforming source located at a depth of 14 1 km during the second half of the eruption the subsidence rate at the top of the volcano is roughly stable at 13 3 mm month these values are in good agreement with tiltmeter data collected on etna during the same period and with the estimated volume of erupted material no significant deformation can be observed during the last month of eruption inflation of the volcano seems to resume immediately after the end of the eruption at a rate of 3 mm month

interlaboratory comparison study of mg ca and sr ca measurements in planktonic foraminifera for paleoceanographic research thirteen laboratories from the usa and europe participated in an intercomparison study of mg ca and sr ca measurements in foraminifera the study included five planktonic species from surface sediments from different geographical regions and water depths each of the laboratories followed their own cleaning and analytical procedures and had no specific information about the samples analysis of solutions of known mg ca and sr ca ratios showed that the intralaboratory instrumental precision is better than 0 5 for both mg ca and sr ca measurements regardless whether icp oes or icp ms is used the interlaboratory precision on the analysis of standard solutions was about 1 5 and 0 9 for mg ca and sr ca measurements respectively these are equivalent to mg ca based temperature repeatability and reproducibility on the analysis of solutions of 0 2 c and 0 5 c respectively the analysis of foraminifera suggests an interlaboratory variance of about 8 rsd for mg ca measurements which translates to reproducibility of about 2 3 c the relatively large range in the reproducibility of foraminiferal analysis is primarily due to relatively poor intralaboratory repeatability about 1 2 c and a bias about 1 c due to the application of different cleaning methods by different laboratories improving the consistency of cleaning methods among laboratories will therefore likely lead to better reproducibility even more importantly the results of this study highlight the need for standards calibration among laboratories as a first step toward improving interlaboratory compatibility

estimation of an earthquake focal mechanism from a satellite radar interferogram application to the december 4 1992 landers aftershock using the interferometric fringes generated by the phase difference between a pair of synthetic aperture radar sar images acquired by the ers 1 satellite we estimate the focal mechanism of a small shallow thrust earthquake the inversion procedure is an iterative linearized least squares algorithm based on a standard elastic dislocation formulation for coseismic displacements our preferred estimate is a thrust focal mechanism with its hypocenter at n34 35 0 4 km w116 91 0 2 km 2 6 0 3 km depth on a plane dipping southward beneath the san bernardino mountains with a moment magnitude mw of 5 4 the strike dip and rake are n106 e 7 28 4 and 93 4 respectively on a fault 3 1 0 5 km wide and 2 9 0 4 km long the precision of these estimates is competitive with seismological determinations

climatic control of turbidite deposition on the madeira abyssal plain studies of sedimentation in the southwestern part of the madeira abyssal plain have revealed sequences of turbidites correlatable over thousands of square kilometres turbidites are sediments transported by turbidity currents and represent rapidly accumulated sedimentary units1 in this case in the distal part of the flow they are very fine grained and homogeneous occasionally with silty bases individual turbidites are separated by thin pelagic units which alternate from oozes to pelagic clays a stratigraphy for these pelagic units has been produced from combining coccolith distributions and lithological changes which enables comparison to cores containing only pelagic sediments from outside the turbidite province these comparisons show that turbidity currents cause no significant erosion in the area the major turbidites occur between lithological alternations which reflect global climate changes associated with glaciations and related eustatic sea level fluctuations turbidites have been linked with eustacy on previous occasions but only with low stands of sea level2 3 our work shows that turbidites are more likely to occur during regressions and transgressions rather than in the quiet periods between

early organic diagenesis the significance of progressive subsurface oxidation fronts in pelagic sediments abstract porewater and solid phase geochemical data at two contrasting ne atlantic stations are reported station 10552 on the cape verde abyssal plain is a site of slow pelagic accumulation ca 0 4 cm kyr 1 molecular oxygen is present in the sediment column to at least 2 m and probably much deeper labile organic carbon is almost totally consumed in the upper few centimetres of the sediment by contrast at station 10554 on the madeira abyssal plain the pelagic sequence has been interrupted by the occasional deposition of organic rich turbidites porewater oxygen and nitrate profiles show that subsurface organic metabolism of the organic carbon associated with the uppermost turbidite layer is a significant fraction of the overall metabolism in the sediment column this metabolism occurs at a relatively thin reaction front which progresses deeper into the turbidite with time this phenomenon exerts a controlling influence on the present nutrient profile and redox succession in a less extreme form substrate distributions of this latter type are not uncommon in atlantic sediments a model has been developed which is controlled by both oxygen and nitrate data this model permits a vertical profile of metabolic activity to be derived and also gives estimates of the reaction rate constants and solid phase mixing rates at these two contrasting stations about 30 of the total activity at station 10554 is located within the turbidite at the deepening reaction front this is a non steady state condition in fact it is found that the integrated metabolic activity at the two stations is not dissimilar ca 1 2 10 13 moles cm 2 sec 1 the striking differences in redox profile are therefore primarily attributable to differences in the distribution of metabolic activity within the column

the updip and downdip limits to great subduction earthquakes thermal and structural models of cascadia south alaska sw japan and chile this study examines thermal and structural controls of the updip and downdip rupture limits of great subduction thrust earthquakes data on past great earthquake seismic limits have been compiled for four continental subduction zones cascadia sw japan south alaska and chile these limits have then been compared to the predictions of several models for what constrains great earthquake rupture temperatures on the subduction thrusts have been estimated by finite element numerical models the landward limits of the observed updip aseismic zones correspond to the position where the thrust temperature reaches about 100 c that is depths of about 2 to 10 km for the subduction zones studied this temperature agrees with the dehydration of stable sliding smectite clays to illite chlorite the temperatures in this region are controlled mainly by the thickness of sediment on the incoming crust and by the crustal age and thus heat flow the downdip limits correspond to the depth on the thrust where either 1 the temperature reaches about 350 c which corresponds to thermally activated stable sliding behavior for crustal rocks with a transition to 450 c or 2 about 40 km depth if 350 c is reached at greater depth depths of about 40 km approximately correspond to the intersection of the thrust with the continental forearc moho and this downdip limit may be a consequence of stable sliding serpentinite or talc and other hydrated forearc mantle rocks the primary temperature controls on the downdip region are the age of the subducting oceanic plate and the thrust dip profile secondary control comes from the thickness of incoming sediment the convergence rate and the radioactive heat generation in the overlying forearc the 100 c updip limit occurs near the trench for young subducting plates with a thick sediment section such as cascadia 6 8 ma and up to 80 km landward for older oceanic crust such as south alaska 50 ma the 350 c downdip thermal limit is applicable for young oceanic plates e g cascadia and nankai whereas the forearc mantle limit applies for older plates e g south alaska and chile except near the chile rise for the margins studied that have experienced great earthquakes there is generally good agreement between the postulated thermal and moho limits and the rupture or seismogenic zone as defined by the distribution of aftershocks and by waveform tsunami and dislocation modeling the downdip limit of the interseismic locked zone from dislocation modeling is also in agreement with these limits

mixing and cycling of uranium thorium and 210pb in puget sound sediments abstract activity profiles of excess 234 th excess 210 pb 232 th 230 th 234 u and 238 u and 228 232 th ratios determined in eight box cores of sediment from six sites in central puget sound provide new insights into the dynamic nature of solid phase mixing in surface sediments the exchange of 228 ra and other soluble species across the sediment water interface and the cycling of u th and 210 pb in this coastal zone comparison of excess 234 th inventories in sediments with its production rate in the overlying water column indicates a mean residence time of at most 14 days for particles in the central puget sound water column surface sediment horizons with excess 234 th have no excess 228 th which might be used to ascertain sediment accumulation rates over the past decade instead deficiencies of 228 th due to loss of soluble 228 ra from pore water to the overlying water persist to 20 30 cm revealing that exchange of soluble chemicals between pore and overlying waters reaches these depths in the extensively bioturbated sediments of puget sound solid phase u isotope concentrations tend to increase by up to a factor of two with depth in sediments as a result of dissolved u being biologically pumped down into sediments where it is partially removed when conditions become mildly reducing 232 th and 230 th activities and 230 232 th ratios are constant with depth in sediments indicating constant detrital phase compositions and essentially no authigenic 230 th steady state 210 pb depositional activities in and fluxes to puget sound sediments average only about onehalf those for sediments of the open washington coast north of the columbia river mouth primarily because of a much lower supply of dissolved 210 pb in sea waters adverting into puget sound excess 234 th profiles in sediments reveal much more detail about the depth dependency dynamic nature and recent history of solid phase mixing processes than excess 210 pb profiles at least six of eight 234 th profiles show that mixing within the 210 pb defined surface mixed layer is depth dependent in three profiles 234 th derived mixing rates are fastest several centimeters below the sediment water interface indicating greater macro benthic activity at these depths depth dependent mixing coefficients derived from the best fit of a four layer advection diffusion decay model to the 234 th data are consistent with 210 pb profiles determined for the same sediments strongly suggesting that 234 th and 210 pb are mixed equivalently and in a multilayered manner

mobility of authigenic rhenium silver and selenium during postdepositional oxidation in marine sediments sedimentary records of redox sensitive trace elements hold significant potential as indicators of paleoceanographic environmental conditions records of re can reveal the intensity of past reducing conditions in sediments at the time of deposition whereas records of ag may record the magnitude of past diatom fluxes to the seafloor confidence in paleoenvironmental reconstruction from records of either metal however requires it to have experienced negligible redistribution since deposition this study examines diagenetic rearrangements of re and ag that occur in response to exposure to bottom water o2 in environments of low sedimentation rate including madeira abyssal plain turbidites and eastern mediterranean basin sapropels authigenic re was remobilized quantitatively by oxidation but poorly retained by the underlying sediments all records are consistent with previous work demonstrating that only a limited reimmobilization of re occurs preferentially in corg rich reducing sediments silver was also mobilized quantitatively by oxidation but it was subsequently immobilized more efficiently in all cases as sharp peaks immediately into anoxic conditions below active oxidation fronts and these peaks remain immobile in anoxic conditions during long term burial comparison of ag s and se records from various cores suggests that ag is likely to have been immobilized as a selenide a mechanism previously proposed for hg in similar situations mercone et al 1999 coexisting narrow peaks of ag and hg with se offer a means of assessing whether oxidative burndown has ever occurred at the top of corg and sulfide rich sedimentary units although these results suggest that caution must be used when inferring paleoenvironmental information from records of ag and re in cores with low sediment accumulation rates 5 cm ka 1 they should not affect the promise that authigenic ag and re records hold for paleoenvironmental reconstruction in sediments with higher accumulation rates and where anoxic conditions have been maintained continuously

rapid subsidence over oil fields measured by sar interferometry the lost hills and belridge oilfields are in the san joaquin valley california the major oil reservoir is high porosity and low permeability diatomite extraction of large volumes from shallow depths causes reduction in pore pressure and subsequent compaction forming a surface subsidence bowl we measure this subsidence from space using interferometric analysis of sar synthetic aperture radar data collected by the european space agency remote sensing satellites ers 1 and ers 2 maximum subsidence rates are as high as 40 mm in 35 days or 400 mm yr measured from interferograms with time separations ranging from one day to 26 months the 8 and 26 month interferograms contain areas where the subsidence gradient exceeds the measurement possible with ers sar but shows increased detail in areas of less rapid subsidence synoptic mapping of subsidence distribution from satellite data powerfully complements ground based techniques permits measurements where access is difficult and aids identification of underlying causes

early diagenesis of marine organic matter alteration of the carbon isotopic composition in two distal carbonate turbidites labelled a and e from the madeira abyssal plain oxidation of organic matter om has been accompanied by a reduction in hydrogen index hi and change in the isotopic composition of carbon since the emplacement of turbidite 0 5 ka ago 35 of the om in the upper part has been oxidised by oxygen and nitrate diffusing from sea water into the sediment there is an accompanying decrease of 0 3 in 13c om and a decrease of 25 in hi turbidite e was emplaced about 73 ka and was exposed to bottom water for 12 3 ka before being buried beneath later turbidites during exposure oxygen and nitrate diffused into its upper part and oxidised 50 of the toc without an accompanying change in isotopic composition further oxidation of the more refactory organic components decreased toc by a further 25 and decreased 13c by 2 5 oxidation also reduced hi by 50 from originally low values unless corrected for the isotopic changes accompanying extended oxic and suboxic degradation of organic matter in sediments will give rise to erroneous estimates of marine terrestrial om ratios

coseismic and early post seismic slip associated with the 1999 izmit earthquake turkey from sar interferometry and tectonic field observations summary we use combined tectonic field observations and sar data to determine an improved model of the slip associated with the 1999 izmit earthquake which ruptured the north anatolian fault at the eastern end of the sea of marmara the leading goal is to understand the main features of the coseismic and post seismic deformation which are captured together in the sar data to achieve this we make a critical analysis of the ers1 2 sar data which allows atmospheric effects to be identified and removed we also use detailed field mapping and measurements of the earthquake surface rupture dislocations in elastic half space and a forward modelling strategy allow us to obtain a slip model by steps a trial and error approach is combined with conventional inversion techniques to determine the slip in the different regions of the fault the sar data are well explained with three main zones of high slip along the fault releasing a total moment of 2 3 10 20 nm mw 7 6 which is higher than the seismological estimates 1 7 2 0 10 20 n m the inhomogeneous slip distribution correlates with fault segments identified at the surface the izmit rupture appears to have extended 30 km west of the hersek peninsula into the sea of marmara with slip tapering fro m2mt ozero the western end of the rupture is located 40 km sse from istanbul we show that some features seen near to mudurnu and gevye and previously interpreted as slip on secondary faults are explained mostly as atmospheric effects correlated with the topography using our approach and the available gps data we obtain a slip model that represents the coseismic slip alone which suggests that the moment release during the main shock was 1 9 10 20 nm mw 7 5 consistent with the seismological estimates we conclude that the sar data include the effects of 2 m of fast after slip during the month following the main shock within a zone of the fault located 12 24 km below the epicentral region near the hypocentre at a depth of 18 km the fault appears to have experienced dynamic slip of 1 m associated with the main shock followed by 2 m of rapidly decelerating post seismic shear during the following month we suggest that the distribution of heterogeneous slip and loading along the different fault segments may be important factors controlling the propagation of large earthquake ruptures along the north anatolian fault

redox dynamics in the chesapeake bay the effect on sediment water uranium exchange the effect of seasonal variations in productivity and redox dynamics on the sediment water exchange of uranium was investigated on a twelve cruise time series in the chesapeake bay the deep waters of the bay undergo seasonal anoxia in response to high primary productivity and water column stratification from late spring to early fall dissolved oxygen was used to monitor water column redox conditions and dissolved iron manganese and sulfide were measured to monitor sediment redox conditions dissolved 238u was measured in the water column and sediment porewaters to monitor water column sediment exchange uranium incorporation in bay sediments results from two distinct processes productivity dependent scavenging from the water column and redox dependent cycling of uranium between sediments and bottomwater uranium is removed from surface waters of the bay by scavenging with biodetritus during periods of high primary productivity bottomwater and sediment redox conditions determine whether this particle bound uranium is buried or released to overlying water particulate uranium is released to bottomwaters and porewaters during the degradation of biodetritus and oxidation of authigenic uranium low oxygen in bottomwaters in the summer results in minimal exchange of uranium between the sediments and bottomwater due to the stability of reduced u iv high bottomwater oxygen concentrations associated with bay turnover in the fall results in release of authigenic uranium by oxidation to the soluble vi form enrichment of uranium in fall bottomwater suggests that authigenic uranium is very labile when exposed to oxic environmental conditions this process is enhanced by physical mixing when anoxic sediments are resuspended into the oxic bottomwaters