on the relationship between southern ocean overturning and acc transport the eddy field in the southern ocean offsets the impact of strengthening winds on the meridional overturning circulation and antarctic circumpolar current acc transport there is widespread belief that the sensitivities of the overturning and acc transport are dynamically linked with limitation of the acc transport response implying limitation of the overturning response here an idealized numerical model is employed to investigate the response of the large scale circulation in the southern ocean to wind stress perturbations at eddy permitting to eddy resolving scales significant differences are observed between the sensitivities and the resolution dependence of the overturning and acc transport indicating that they are controlled by distinct dynamical mechanisms the modeled overturning is significantly more sensitive to change than the acc transport with the possible implication that the southern ocean overturning may increase in response to future wind stress changes without measurable changes in the acc transport it is hypothesized that the dynamical distinction between the zonal and meridional transport sensitivities is derived from the depth dependence of the extent of cancellation between the ekman and eddy induced transports

accurate relocation of izmit earthquake mw 7 4 1999 aftershocks in cinarcik basin using double difference method 1 we relocated part of the aftershock activity in cinarcik basin and surrounding areas that are associated with the 1999 izmit earthquake mw 7 4 double difference relocation algorithm is used to relocate the aftershocks the data set was obtained from a temporary seismic network deployed 10 days after the main shock by cooperation between bogazici university kandilli observatory and earthquake research institute lgit grenoble and ipgp paris for a better station coverage additional data set was obtained from a network operated by tubitak marmara research center differential travel times were calculated using both arrival time readings and waveform cross correlation method we relocated 1145 of the aftershocks and interpreted the results with emphasis on the yalova and tuzla cluster located within the marmara sea the results show better focused seismicity patterns for the yalova cluster providing clear evidence for the proposed models we present a revised location of the 1963 cinarcik earthquake which took place in area of yalova cluster finally we propose that the activity of tuzla cluster represents a parallel subsidiary fault of the main marmara fault

cave pearls the integrated product of abiogenic and biogenic processes abstract cave pearls up to 8 cm long collected from dried out rimstone pools in old man village cave on grand cayman british west indies have nuclei e g bone that are encased by laminated cortices these laminae are composed of trigonal prismatic calcite crystals calcite crystal bushes or particulate calcite that is formed of filamentous microbes four morphotypes spores seven morphotypes extracellular polymers eps disorganized and organized calcite fiber crystals and detrital calcite grains syntaxial overgrowths modified many of the fiber crystals and the trigonal calcite crystals thin laterally discontinuous growth lines are formed of micrite that may have been precipitated in a microbial mat growth of the cave pearls involved abiogenic and biogenic processes the trigonal calcite crystals and crystal bushes probably formed abiogenically whereas the particulate calcite laminae appear to have formed as microbes trapped and bound detrital grains to the surfaces of the cave pearls and indirectly mediated precipitation of the fiber crystals water flow into the rimstone pools which was linked to local rainfall controlled the influx of detrital grains water chemistry and microbe growth into the pools and hence the growth of the cave pearls periods of low water influx led to stagnation of pool waters that seemed to trigger periods of rapid abiogenic calcite precipitation and curtail microbial colonization high flow rates slowed abiogenic calcite precipitation promoted microbe growth and fed detrital materials into the pools despite the lightless environment of the cave the evidence clearly shows that the microbes and their associated eps played a critical role in the growth and development of the cave pearls

topographic enhancement of eddy efficiency in baroclinic equilibration abstractthe processes that determine the depth of the southern ocean thermocline are considered in existing conceptual frameworks the thermocline depth is determined by competition between the mean and eddy heat transport with a contribution from the interaction with the stratification in the enclosed portion of the ocean using numerical simulations this study examines the equilibration of an idealized circumpolar current with and without topography the authors find that eddies are much more efficient when topography is present leading to a shallower thermocline than in the flat case a simple quasigeostrophic analytical model shows that the topographically induced standing wave increases the effective eddy diffusivity by increasing the local buoyancy gradients and lengthening the buoyancy contours across which the eddies transport heat in addition to this local heat flux intensification transient eddy heat fluxes are suppressed away from the topography especially upstream indicating that local

seven years of postseismic deformation following the 1999 m 7 4 and m 7 2 izmit duzce turkey earthquake sequence 1 we report the results of nearly 7 years of postseismic deformation measurements using continuously recorded and survey mode gps observations for the 1999 izmit duzce earthquake sequence resolvable time dependent postseismic changes to the preearthquake interseismic velocity field extend at least as far as the continuous gps station in ankara 200 km southeast of the izmit rupture seven years after the earthquake sequence the relative postseismic velocity across the north anatolian fault naf reaches 10 12 mm a roughly 50 of the steady state interseismic rate with the highest postseismic velocities within 40 km of the coseismic ruptures we use a sequence of logarithmic time functions to fit gps site motions up to three logarithmic terms with decay constants of 1 150 and 3500 days are necessary to fit all the transient motion observed at the continuous gps stations the first term is required for the component of site motion parallel to the naf at near field sites strongly implicating rapid shallow afterslip the intermediate and longer term postseismic velocity components reflect more broadly distributed strain with a symmetric double couple pattern suggestive of either localized deep afterslip or viscoelastic relaxation of the upper mantle and or lower crust in two areas including the marmara sea this pattern is superimposed on north south extension centered on the naf we speculate that this extension may result from aseismic dip slip along coseismically weakened faults driven by the background tectonic stress

a barotropic model of eddy saturation abstracteddy saturation refers to a regime in which the total volume transport of an oceanic current is insensitive to the wind stress strength baroclinicity is currently believed to be the key to

the role of mesoscale eddies in the rectification of the southern ocean response to climate change abstract simulations from a fine resolution global coupled model the geophysical fluid dynamics laboratory climate model version 2 4 cm2 4 are presented and the results are compared with a coarse version of the same coupled model cm2 1 under idealized climate change scenarios a particular focus is given to the dynamical response of the southern ocean and the role played by the eddies parameterized or permitted in setting the residual circulation and meridional density structure compared to the case in which eddies are parameterized and consistent with recent observational and idealized modeling studies the eddy permitting integrations of cm2 4 show that eddy activity is greatly energized with increasing mechanical and buoyancy forcings buffering the ocean to atmospheric changes and the magnitude of the residual oceanic circulation response is thus greatly reduced although compensation is far from being perfect changes in poleward eddy fluxes partially compensate for the enhanced equatorward

mean antarctic circumpolar current transport measured in drake passage the antarctic circumpolar current is an important component of the global climate system connecting the major ocean basins as it flows eastward around antarctica yet due to the paucity of data it remains unclear how much water is transported by the current between 2007 and 2011 flow through drake passage was continuously monitored with a line of moored instrumentation with unprecedented horizontal and temporal resolution annual mean near bottom currents are remarkably stable from year to year the mean depth independent or barotropic transport determined from the near bottom current meter records was 45 6 sv with an uncertainty of 8 9 sv summing the mean barotropic transport with the mean baroclinic transport relative to zero at the seafloor of 127 7 sv gives a total transport through drake passage of 173 3 sv this new measurement is 30 larger than the canonical value often used as the benchmark for global circulation and climate models

on the transport and angular momentum balance of channel models of the antarctic circumpolar current abstract angular momentum balances are discussed both in general as well as in the context of simple channel models of the antarctic circumpolar current acc particular emphasis is placed on the close relationship between the angular momentum balance and the meridional circulation it is found that topographic form drag is established very early in the integration whereas interfacial form drag can take much longer to develop restrictions on the geostrophic portion of the meridional circulation imposed by zonally reconnecting potential vorticity contours in the upper ocean allow derivation of an estimate for the steady state transport the estimate assumes there to be little or no circumpolar flow at great depth an assumption that stems from the belief that the band of zonally reconnecting geostrophic contours in the southern ocean does not extend to the ocean floor the predicted transport is proportional to the strength of the stratification and compares favorably with numerical results in the lite

eddy saturation of equilibrated circumpolar currents abstractthis study uses a sector configuration of an ocean general circulation model to examine the sensitivity of circumpolar transport and meridional overturning to changes in southern ocean wind stress and global diapycnal mixing at eddy permitting and finer resolution the sensitivity of circumpolar transport to forcing magnitude is drastically reduced at sufficiently high resolution there is little or no sensitivity of circumpolar transport to wind stress even in the limit of no wind in contrast the meridional overturning circulation continues to vary with southern ocean wind stress but with reduced sensitivity in the limit of high wind stress both the circumpolar transport and meridional overturning continue to vary with diapycnal diffusivity at all model resolutions the circumpolar transport becomes less sensitive to changes in diapycnal diffusivity at higher resolution although sensitivity always remains in contrast the overturning circulation is more sensitive to change in diapycnal

on the dynamics of wind driven circumpolar currents the factors controlling the transport of the antarctic circumpolar current acc have recently been a topic of heated debate at the latitudes of drake passage potential vorticity contours are uninterrupted by coastlines and large amplitude flows are possible even with weak forcing and dissipation the relationship between the dynamics of circumpolar currents and inertial recirculations in closed basins is discussed in previous studies sverdrup balance and baroclinic adjustment theories have both been proposed as theories of the acc transport these theories predict the circumpolar transport as various simple functions of the surface wind stress a series of experiments is performed with a simple channel model with different wind strengths and different idealized basin geometries to investigate the relationship between wind strength and circumpolar transport the results show that baroclinic adjustment theories do predict transport in the special case of a periodic channel with no topographic variations or when the wind forcing is very weak more generally the transport is determined by a complex interplay between wind forcing eddy fluxes and topographic effects there is no support for the idea that sverdrup balance determines the transport through drake passage

holocene slip rate of the north anatolian fault beneath the sea of marmara abstract the north anatolian fault naf is a major continental transform system that extends e w across turkey for over 1600 km separating the anatolian and eurasian plates a portion of its northern branch runs below the sea of marmara this portion constitutes a seismic gap because the last destructive earthquakes occurred at the western 1912 ganos earthquake m 7 4 and eastern 1999 izmit and duzce earthquakes m w 7 4 7 2 edges of the marmara basin it is likely that fault ruptures will fill this gap in the next decades this region of the north anatolian fault is critical to our understanding of fault interactions stress buildup during seismic cycle and seismic hazard in the istanbul area we obtained high resolution acoustic images of the naf in the floor of the eastern marmara sea gulf of izmit and measured fault related offsets of 14 c dated subseafloor channels and paleoshorelines the resulting average slip rate on the fault is 10 mm year for the last 10 kyr this is less than half the total anatolia eurasia relative motion estimated at 24 mm year for the last 10 years from satellite geodetic measurements we conclude that either much of the strike slip motion along this branch of the naf did not occur on the main fault segment or the slip rate increased recently or both these results affect kinematic models of the naf and assessments of seismic hazard for the city of istanbul and the surrounding region

seafloor gas seeps and sediment failures triggered by the august 17 1999 earthquake in the eastern part of the gulf of izmit sea of marmara nw turkey abstract on august 17 1999 a major earthquake mw 7 4 occurred affecting a large area in northwestern turkey a 150 km long section of the north anatolian fault ruptured from the entrance of the gulf of izmit to golyaka in the east during the earthquake we utilized high resolution shallow seismic data acquired during a post earthquake cruise to find evidence of gas seeps gas charged sediments and sediment failure in the eastern izmit basin of the gulf of izmit the data showed anomalies that suggest the presence of increased gas in the gulf after the earthquake five major zones of offshore mass movement were found in the study area comparison of data collected before and after the earthquake indicates that the apparent amount of gas increased after the earthquake and the mass movement has a causative relationship to the august 17 1999 earthquake therefore we conclude that the seismic event presence of increased gas and the offshore mass movements in the study area are interrelated

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

loss of primary texture and geochemical signatures in speleothems due to diagenesis evidences from castanar cave spain geochemical signals from speleothems are commonly used in the investigation of palaeoenvironments in most cases however little attention is paid to whether or not these signals are primary or altered by diagenesis the speleothems of the castanar cave caceres spain which are initially formed of calcite or aragonite have undergone a variety of meteoric diagenetic processes such as micritization and neomorphism inversion that collectively modify their primary features textures mineralogy geochemical signals the mean 13c and 18o values of the aragonites in the cave are 8 66 and 4 64 respectively whereas the primary calcites have mean 13c and 18o values of 9 99 and 5 77 respectively following the diagenetic process of micritization the aragonite isotopic signals averaged 7 63 13c and 4 74 18o and the calcite micrite signals 9 53 13c and 5 21 18o where inversion took place some secondary calcites after the aragonite show preserved aragonite whereas others do not the secondary calcites without aragonite relics show isotopic values slightly higher than those of the primary calcite due to the inheritance of the aragonite signal where aragonite relics are preserved the isotopic signatures are very similar to those of the aragonite micrite in addition the stable isotopic values and sr and mg contents of the speleothems became also modified by micritization and or inversion these diagenetic processes were driven by the changes in composition of the cave waters over time and space but also in the case of aragonite by its initial unstable mineralogy the present results highlight how important diagenesis is in caves and how the initial features of cave minerals may be lost these changes alter the geochemical signals shown by speleothems which may have an impact on the interpretation of the results obtained in palaeoenvironmental studies

the active main marmara fault abstract this paper presents selections from and a synthesis of a high resolution bathymetric sparker and deep towed seismic reflection data set recently acquired by the french ifremer r v le suroit in an e w deep trough that forms the northern half of the sea of marmara in nw turkey it includes the first high resolution complete bathymetric map of this area a single throughgoing dextral strike slip fault system which is the western continuation of the northern branch of the north anatolian fault cuts this trough lengthwise and joins the 1999 8 17 kocaeli earthquake fault with the 1912 8 09 arkoy murefte earthquake fault both of which display strike slip offset in its eastern one fourth the structure follows closely the northern margin of the deep trough whereas in the west it hugs its southern margin the eastern one fourth of the structure has a minor component of its displacement distributed across the deep trough owing to a possible original bend in the course of the dextral structure the present course of the north anatolian fault in the sea of marmara originated some 2 105 a ago by cutting across the older basin fabric generated by a dominant nne ssw extension before it began taking up major motion in the pliocene

surface rupture and slip distribution along the karadere segment of the 17 august 1999 izmit and the western section of the 12 november 1999 duzce turkey earthquakes on 17 august 1999 the mw 7 5 i zmit turkey earthquake produced surface rupture in excess of 120 km and perhaps as much as 200 km with up to 5 m of dextral slip along a western portion of the north anatolian fault zone the 12 november 1999 mw 7 1 duzce turkey earthquake produced a 40 km long sur face rupture including 9 km of rupture overlap with the eastern end of the august event our mapping focused on the 40 km long karadere rupture segment the east ernmost segment of the august event as well as on the western 20 km of the no vember rupture maximum dextral slip along the karadere segment is approximately 1 5 m and the average slip on this segment is close to 1 m although slip along the karadere segment is considerably less than that on segments to the west this segment is of particular interest for three reasons 1 the western boundary of the karadere segment is defined by the most striking structural discontinuity along the entire au gust surface rupture i e a 5 km wide zone of no surface rupture as well as a 25 change in trend from e w to ene and such a discontinuity may have important implications for rupture dynamics 2 surface rupture terminates at the east end of the karadere rupture segment at a 1 5 to 3 km wide extensional step over at eften lake and 3 the 12 november 1999 duzce earthquake reruptured the easternmost 9 km of the karadere segment raising interesting questions about rupture dynamics and interactions between events on adjacent fault segments the details of the 17 august 1999 and l2 november 1999 surface rupture traces suggest that rupture may have partially propagated across the eften lake extensional step over although this step over seems to have acted as an effective barrier to rupture propagation

global prediction of abyssal hill root mean square heights from small scale altimetric gravity variability 1 abyssal hills which are pervasive landforms on the seafloor of the earth s oceans represent a potential tectonic record of the history of mid ocean ridge spreading however the most detailed global maps of the seafloor derived from the satellite altimetry based gravity field cannot be used to deterministically characterize such small scale 10 km morphology nevertheless the small scale variability of the gravity field can be related to the statistical properties of abyssal hill morphology using the upward continuation formulation in this paper i construct a global prediction of abyssal hill root mean square rms heights from the small scale variability of the altimetric gravity field the abyssal hill related component of the gravity field is derived by first masking distinct features such as seamounts mid ocean ridges and continental margins and then applying a newly designed adaptive directional filter algorithm to remove fracture zone discontinuity fabric a noise field is derived empirically by correlating the rms variability of the small scale gravity field to the altimetric noise field in regions of very low relief and the noise variance is subtracted from the small scale gravity variance suites of synthetically derived abyssal hill formed gravity fields are generated as a function of water depth basement rms heights and sediment thickness and used to predict abyssal hill seafloor rms heights from corrected small scale gravity rms height the resulting global prediction of abyssal hill rms heights is validated qualitatively by comparing against expected variations in abyssal hill morphology and quantitatively by comparing against actual measurements of rms heights although there is scatter the prediction appears unbiased

pore fluid chemistry of the north anatolian fault zone in the sea of marmara a diversity of sources and processes as part of the 2007 marnaut cruise in the sea of marmara an investigation of the pore fluid chemistry of sites along the main marmara fault zone was conducted the goal was to define the spatial relationship between active faults and fluid outlets and to determine the sources and evolution of the fluids sites included basin bounding transtensional faults and strike slip faults cutting through the topographic highs the basin pore fluids are dominated by simple mixing of bottom water with a brackish low density pleistocene lake marmara end member that is advecting buoyantly and or diffusing from a relatively shallow depth this mix is overprinted by shallow redox reactions and carbonate precipitation the ridge sites are more complex with evidence for deep sourced fluids including thermogenic gas and evidence for both silicate and carbonate diagenetic processes one site on the western high displayed two mound structures that appear to be chemoherms atop a deep seated fluid conduit the fluids being expelled are brines of up to twice seawater salinity with an exotic fluid chemistry extremely high in li sr and ba oil globules were observed both at the surface and in cores and type ii gas hydrates of thermogenic origin were recovered hydrate formation near the seafloor contributes to increase brine concentration but cannot explain their chemical composition which appears to be influenced by diagenetic reactions at temperatures of 75 c 150 c hence a potential source for fluids at this site is the water associated with the reservoir from which the gas and oil is seeping which has been shown to be related to the thrace basin hydrocarbon system our work shows that submerged continental transform plate boundaries can be hydrologically active and exhibit a diversity of sources and processes

possible worst case tsunami scenarios around the marmara sea from combined earthquake and landslide sources this study evaluates tsunami hazards in the marmara sea from possible worst case tsunami scenarios that are from submarine earthquakes and landslides in terms of fault generated tsunamis seismic ruptures can propagate along the north anatolian fault naf which has produced historical tsunamis in the marmara sea based on the past studies which consider fault generated tsunamis and landslide generated tsunamis individually future scenarios are expected to generate tsunamis and submarine landslides could be triggered by seismic motion in addition to these past studies numerical modeling has been applied to tsunami generation and propagation from combined earthquake and landslide sources in this study tsunami hazards are evaluated from both individual and combined cases of submarine earthquakes and landslides through numerical tsunami simulations with a grid size of 90 m for bathymetry and topography data for the entire marmara sea region and validated with historical observations from the 1509 and 1894 earthquakes this study implements tunami model with a two layer model to conduct numerical tsunami simulations and the numerical results show that the maximum tsunami height could reach 4 0 m along istanbul shores for a full submarine rupture of the naf with a fault slip of 5 0 m in the eastern and western basins of the marmara sea the maximum tsunami height for landslide generated tsunamis from small medium and large of initial landslide volumes 0 15 0 6 and 1 5 km3 respectively could reach 3 5 6 0 and 8 0 m respectively along istanbul shores possible tsunamis from submarine landslides could be significantly higher than those from earthquakes depending on the landslide volume significantly these combined earthquake and landslide sources only result in higher tsunami amplitudes for small volumes significantly because of amplification within the same tsunami amplitude scale 3 0 4 0 m waveforms from all the coasts around the marmara sea indicate that other residential areas might have had a high risk of tsunami hazards from submarine landslides which can generate higher tsunami amplitudes and shorter arrival times compared to istanbul

interdecadal variability of the southern ocean the intrinsic variability of the antarctic circumpolar current is investigated using an idealized wind driven model the model uses three quasigeostrophic layers with steady wind stress forcing and no diabatic effects despite the idealized nature of the model the simulations display a robust mode of low frequency variability in the flow it is demonstrated that this variability is dependent upon the explicit simulation of the dynamics of mesoscale eddies as such the variability is sensitive to stratification horizontal viscosity bottom stress and topography the energetic balance of the variability is diagnosed and a driving mechanism is proposed that involves positive feedback between the generation of eddies through baroclinic instability and the dynamics of the mean circulation

submarine fault scarps in the sea of marmara pull apart north anatolian fault implications for seismic hazard in istanbul earthquake scarps associated with recent historical events have been found on the floor of the sea of marmara along the north anatolian fault naf the marmarascarps cruise using an unmanned submersible rov provides direct observations to study the fine scale morphology and geology of those scarps their distribution and geometry the observations are consistent with the diversity of fault mechanisms and the fault segmentation within the north marmara extensional step over between the strike slip ganos and izmit faults smaller strike slip segments and pull apart basins alternate within the main step over commonly combining strike slip and extension rapid sedimentation rates of 1 3 mm yr appear to compete with normal faulting components of up to 6 mm yr at the pull apart margins in spite of the fast sedimentation rates the submarine scarps are preserved and accumulate relief sets of youthful earthquake scarps extend offshore from the ganos and izmit faults on land into the sea of marmara our observations suggest that they correspond to the submarine ruptures of the 1999 izmit mw 7 4 and the 1912 ganos ms 7 4 earthquakes while the 1999 rupture ends at the immediate eastern entrance of the extensional cinarcik basin the 1912 rupture appears to have crossed the ganos restraining bend into the sea of marmara floor for 60 km with a right lateral slip of 5 m ending in the central basin step over from the gulf of saros to marmara the total 1912 rupture length is probably about 140 km not 50 km as previously thought the direct observations of submarine scarps in marmara are critical to defining barriers that have arrested past earthquakes as well as defining a possible segmentation of the contemporary state of loading incorporating the submarine scarp evidence modifies substantially our understanding of the current state of loading along the naf next to istanbul coulomb stress modeling shows a zone of maximum loading with at least 4 5 m of slip deficit encompassing the strike slip segment 70 km long between the cinarcik and central basins that segment alone would be capable of generating a large magnitude earthquake mw 7 2 other segments in marmara appear less loaded

sensitivity of the overturning circulation in the southern ocean to decadal changes in wind forcing abstractthe sensitivity of the overturning circulation in the southern ocean to the recent decadal strengthening of the overlying winds is being discussed intensely with some works attributing an inferred saturation of the southern ocean co2 sink to an intensification of the overturning circulation while others have argued that this circulation is insensitive to changes in winds fundamental to reconciling these diverse views is to understand properly the role of eddies in counteracting the directly wind forced changes in overturning here the authors use novel theoretical considerations and fine resolution ocean models to develop a new scaling for the sensitivity of eddy induced mixing to changes in winds and they demonstrate that changes in southern ocean overturning in response to recent and future changes in wind stress forcing are likely to be substantial even in the presence of a decadally varying eddy field this result has significant implications for the ocean s role in the carbon cycle and

an exploration of the role of transient eddies in determining the transport of a zonally reentrant current the meridional ekman transport in a zonally reentrant channel may be balanced by diabatic circulations standing eddies associated with topography or by lagrangian mean eddy mass fluxes a simple model is used to explore the interaction between these mechanisms a key assumption of this study is that diabatic forcing in the poleward edge of the channel acts to create lighter fluid as is the case with net freshwater fluxes into the southern ocean for weak wind forcing or strong diabatic constraint a simple scaling argument accurately predicts the level of baroclinic shear however given our understanding of the relative magnitudes of ekman flux and deep upwelling this is not the appropriate parameter range for the antarctic circumpolar current with stronger wind stresses eddies are prominent with baroclinic instability initially developing in the vicinity of large topography arguments have been advanced by a number of authors that baroclinic instability should limit the velocity shear leading to a stiff upper limit on the transport of the current however in the simulations presented here baroclinic instability is largely confined to the region of topographic highs and the approach to a current that is independent of the wind stress occurs gradually several recent parameterizations of transient eddy fluxes do not reproduce key features of the observed behavior

fluid flow deformation rates and the submarine record of major earthquakes in the sea of marmara along the north anatolian fault system abstract the submerged portions of the north anatolian fault naf in the sea of marmara and the ne aegean sea are sites of large magnitude earthquakes that leave diagnostic geological signatures in the sedimentary record in the form of mass wasting deposits turbidites and fluid and gas escape features this is due to the interplay of seismic shaking mass and turbidity flows sediment resuspension and fluids circulation in relatively small sub basins with a complex paleo oceanography steep slopes high rates of deformation and diffuse fault controlled gas and fluid seeps to unravel the complex interrelations of these phenomena during earthquake cycles we carried out paleoseismological studies at several key locations here we report results of these studies carried out onboard the r v urania over a decade starting soon after the mw 7 4 1999 izmit earthquake our work included high resolution mapping of active faults through multibeam bathymetry and high resolution seismic reflection profiles multi parameter analysis of sediment cores as well as seafloor observations using sensors mounted on remotely operated vehicles rov the main objectives were to map active faults determine slip rates and earthquake recurrence times along major fault strands and assess connections between fault deformation and fluid activity we mapped fault geometry in the gulfs of izmit gemlik and saros showing the trans tensive nature of these depressions the average slip rates for the last 10 ka was found to be 10 mm y in the gulfs of izmit and saros at the eastern and the western ends of the naf northern strand and 3 4 mm yr in the gulf of gemlik along the middle strand of the naf these rates integrated over 10 ka of naf activity are smaller than those determined by the gps geodetic measurements submarine paleoseismological studies in the gulf of izmit detected the sedimentary records of earthquakes for the last 2 4 ka suggesting an average recurrence time of 300 years for major events multisensor observations and monitoring of the seafloor have shown widespread emissions of gas and fluids along the submerged part of the naf associated with reduced black sediments we investigated their possible connection with the earthquake cycle

anatomy of the antarctic circumpolar current volume transports through drake passage the 20 year october 1992 to august 2013 observation based volume transport time series of the antarctic circumpolar current acc through drake passage dp across the jason altimeter track 104 is analyzed to better understand the acc transport variability and its potential causes the time series of three transport components total tt barotropic bt and baroclinic bc referenced to 3000 m present energetic intraseasonal fluctuations with a salient spectral peak at 50 and 36 days with the largest least variance being associated with the bt bc component low frequency variations are much less energetic with a significant variance limited to the annual and biannual timescales and show a nonstationary intermittent link with the southern annular mode and the nino 3 4 index for interannual timescales the region around 57 s in the yaghan basin appears to be a strategic point for a practical monitoring of the acc transport as the whole track tt is significantly correlated with the local tt r 5 0 53 and bt r 5 0 69 around 57 s these local bt and tt variations are associated with a well defined tripole pattern in altimetric sea level anomaly sla there is evidence that the tripole pattern associated with bt is locally generated when the bc associated mesoscale slas which have propagated eastward from an upstream area of dp cross the shackleton fracture zone to penetrate into the yaghan basin barotropic basin modes excited within the yaghan basin are discussed as a plausible mechanism for the observed energy containing intra seasonal spectral peaks found in the transport variability

the role of closed gyres in setting the zonal transport of the antarctic circumpolar current abstracteddy permitting simulations are used to show that basinlike gyres can be observed in the large scale barotropic flow of a wind driven channel with a meridional topographic ridge this is confirmed using both two layer quasigeostrophic and 25 level primitive equation models at high horizontal resolution comparing results from simulations with and without the topographic ridge it is shown that the zonal baroclinic transport in the channel increases with increasing wind stress when the bottom topography is flat but not when there is a meridional ridge the saturation of transport for increasing wind occurs in conjunction with the development of recirculating gyres in the large scale barotropic streamfunction this suggests that the total circulation can be thought of as a superposition of a gyre mode which has zero circumpolar transport and a free circumpolar mode which contains all of the transport basinlike gyres arise in the channel because the topography steers the barotropic streamlines a

eddy saturation of the southern ocean a baroclinic versus barotropic perspective eddy saturation is the regime in which the total time mean volume transport of an oceanic current is relatively insensitive to the wind stress forcing and is often invoked as a dynamical descript

modelling tectonic deformation along the north anatolian fault in the sea of marmara abstract using analogue techniques we attempted to model the complex tectonic deformation pattern observed along the north anatolian fault in the sea of marmara from morpho bathymetry and seismic reflection images in particular this paper focuses on the so called cinarcik segment of the fault connecting the eastern izmit segment which entirely ruptured during the mw 7 4 1999 earthquake to the western segment of the central high the cinarcik segment potentially loaded after the izmit earthquake is expected to rupture during an earthquake occurring in the near future possibly the next decades with a high potential to affect the istanbul metropolitan area our analysis suggests that the development of the observed structures accommodating strike slip transtensional and transpressional deformations could be explained by changes in the geometry of fault segments within a right lateral strike slip tectonic regime tectonic deformations were reproduced in the analogue model by imposing a small about 10 and sharp difference in the relative orientations of the strike slip segments at the edges of a major releasing bend in the model slower strain accumulation occurs along the analogue of the cinarcik segment than along the analogue of the izmit segment of the fault this would predict a delay for earthquakes triggered by stress transfer between the izmit and cinarcik segments the model further predicts that most of the deformation in the cinarcik basin is controlled by the sharp changes in the geometry of the fault itself

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

petrography and environmental controls on the formation of phanerozoic marine carbonate hardgrounds early marine seafloor lithification of carbonate sediments leads to the formation of hardgrounds and is known from rocks as old as the proterozoic hardground surfaces however are more commonly recorded in the phanerozoic sedimentological archive while ecological studies of hardground biota abound the environmental and physico chemical parameters leading to the development of seafloor lithification remain in many cases poorly understood and documented this paper reviews published evidence on the petrography mineralogy and geochemistry of phanerozoic carbonate hardgrounds within a process oriented context of their environmental controls hardgrounds typically develop in warm and shallow agitated tropical waters that are saturated with respect to caco3 but are also reported from hemi pelagic to bathyal realms and from cool water temperate settings a range of early marine cement types are documented from present day hardgrounds whereas preserved cement fabrics and related mineralogies are less diverse in early phanerozoic hardgrounds carbonate hardgrounds are widespread during calcite sea periods e g ordovician and cretaceous as opposed to some preservation bias ancient aragonite seas e g permian and triassic obviously the relation between seawater chemistry and hardground abundance and attributes is not an easy one here the concept of aragonite versus calcite seas serves as a first order template for the sake of a structured discussion whereas modern aragonite mode oceans document a significant diversity in spatial and bathymetric seawater properties this spatio temporal complexity is perhaps reflected in the scarce record of calcite sea hardgrounds from the devonian or paleogene rock record contrasted by the abundance in aragonite holocene and recent seas holocene hardgrounds allow for the direct assessment of rates of and reasons for early subaquatic lithification and in most cases escaped subsequent non marine diagenetic overprint conversely studies of ancient hardgrounds are often biased by early biological and mechanical erosion the degree of diagenetic overprint and tectonic to orogenic processes the formation distribution and physical properties of hardgrounds depend on the global climatic context greenhouse icehouse modes on sea level changes on ocean stratification on the spatial extent of epicontinental seas and carbonate depositional environments and on the spatially different mineralogies and rates of carbonate production the fabrics and mineralogies of early hardgrounds cement seem to substantially hinge on variations in atmospheric co2 thus the application of lessons from modern to ancient hardground case examples is not straightforward a holistic model explaining the full variability of controls on submarine hardground formation and their cement petrography throughout the phanerozoic is as yet lacking a more critical view on secular changes in hardground formation patterns is clearly needed future work should rely on the combination of sedimentological stratigraphic palaeoecological petrographic and geochemical approaches specific emphasis should be given to time intervals triassic carboniferous cambrian etc where the bulk of reported case studies is at best scarce

persistent anomalies blocking and variations in atmospheric predictability abstract we consider regimes of low frequency variability in large scale atmospheric dynamics the model used for the study of these regimes is the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography twenty five modes are retained in a spherical harmonics expansion of the streamfunction solutions are studied as a function of the nondimensional intensity of the forcing and dissipation multiple stationary solutions are obtained as a result of nonlinear interaction between waves mean flow and orography the number of modes retained in the analysis permits these multiple equilibria to appear for realistic values of the forcing the equilibria exhibit blocked and zonal flow patterns bearing a marked resemblance to synoptically defined zonal and blocked northern hemisphere midlatitude flows wave wave interactions influence strongly the stability properties of the equilibria and the time evolution of nonequilibrium solutions time depe

paleoseismic history and slip rate along the sapanca akyazi segment of the 1999 izmit earthquake rupture m w 7 4 of the north anatolian fault turkey abstract the sapanca akyazi segment sas is located on western part of the north anatolian fault naf of turkey it was ruptured together with four other segments during the 17th august 1999 izmit earthquake mw 7 4 which caused 145 km long surface rupture in the east marmara region we conducted geomorphological investigations and 2d 3d paleoseismic trenching at 3 different sites near the sakarya river along the sas to obtain new data for the timing of past earthquakes and slip rate of this section of the naf detailed investigations using ground penetrating radar on the western bank of the sakarya river reveal 18 5 0 5 m of right lateral cumulative offset of an alluvial terrace dated as 850 11 years bp using optically stimulated luminescence the analysis of trench data from the three different sites of the sas indicates the occurrence of four surface rupturing past earthquakes including the 1999 izmit earthquake according to the radiocarbon dating these paleo earthquakes can be correlated with the 1719 ce 1567 ce and 1037 ce historical earthquakes and suggest an average recurrence period between 273 and 322 years the total dextral offset the age of trench units and the terrace deposits together suggest a 22 3 mm yr slip rate for this portion of the naf

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

sea level changes and depositional environments in the izmit gulf eastern marmara sea during the late glacial holocene period abstract offshore and onshore stratigraphic studies together with high resolution shallow seismic reflection profiling and multibeam bathymetric mapping were carried out in the western and central part of the izmit gulf these studies indicate that the izmit gulf was a lacustrine environment as part of the marmara lake during the late glaciation and early deglaciation until 12 kyr bp when the marmara basin was inundated by the mediterranean waters correlation of 14 c dated onshore and offshore stratigraphic units in the western izmit gulf indicates that generally coarse late glacial sediments overlie a marked erosional surface formed during the low water level of the marmara lake these coarse sediments are succeeded by 10 4 7 kyr bp old transgressive and by late holocene post transgression mud units the bathymetry and sub bottom chirp profiles clearly show that the paleoshoreline of the gulf was located at 85 m having been controlled by the bedrock sill depth of the canakkale strait another paleoshoreline observed at 65 m on the northern margin of the western izmit and karamursel basins was probably formed during the younger dryas sea level stillstand the shelf areas during this time were colonized by bioherms which were subsequently drowned and disappeared after a further rise of the sea level the presence of a 65 m marine paleoshoreline in the karamursel basin indicates that the sill restricting this basin to the west was much deeper than its present 55 m level and was located further south the golcuk basin restricted by a 38 m sill to its west was probably not flooded by marine waters until 9 kyr bp

sedimentary earthquake records in the izmit gulf sea of marmara turkey abstract sedimentary earthquake records of the last 2400 a including that of the devastating 17 august 1999 izmit earthquake mw 7 4 were studied in cores from the 210 m deep central karamursel basin of the izmit gulf in the eastern sea of marmara using laser grain size physical properties stable o and c isotopes and xrf core scanner analyses and dated by radionuclide and radiocarbon methods the earthquake records are represented by turbidite homogenite mass flow units thu that commonly contain a basal coarse layer a middle laminated silt layer and an overlying homogeneous mud layer the coarse basal part has a sharp and sometimes scoured lower boundary and includes multiple coarse sand silt layers or laminae showing normal size grading multiple coarse layers and occasional bi directional cross bedding suggest deposition from a bed load during water column oscillations or seiche effect the grain size characteristics of the overlaying laminated silt and the homogeneous mud units indicate deposition from weak oscillating currents and homogeneous suspension respectively high mn value just below the base of thus suggests diagenetic enrichment at oxic anoxic redox boundary before the mass flow event sharp decrease in mn with very low values within the thus suggests transient redox conditions following the mass flow variable geochemical compositions of the basal coarse layers indicate different sediment sources for different thus eight sedimentary earthquake records observed in the last 2400 a in the izmit gulf can be confidently correlated with the historical earthquakes of 1999 1509 ad ms 7 2 1296 ad i vii 865 ad i viii 740 ad i viii 268 ad i viii 358 ad i ix and 427 bc this gives an earthquake recurrence time of ca 300 a with the interval between consecutive events ranging from 90 to 695 a

living stained deep sea foraminifera from the sea of marmara a preliminary study abstract in this preliminary study we investigate living stained foraminifera from the sea of marmara we focus on the faunal composition and geochemical signatures trace elements carbon and oxygen stable isotopes in foraminiferal tests at two deep sea sites 329 and 1240 m depth respectively documented by rov observations and sampling both study areas are heterogeneous including bacterial mats and carbonate concretions proximal to cold seeps and consist of dysoxic bottom water o2

interpretation of recent southern hemisphere climate change climate variability in the high latitude southern hemisphere sh is dominated by the sh annular mode a large scale pattern of variability characterized by fluctuations in the strength of the circumpolar vortex we present evidence that recent trends in the sh tropospheric circulation can be interpreted as a bias toward the high index polarity of this pattern with stronger westerly flow encircling the polar cap it is argued that the largest and most significant tropospheric trends can be traced to recent trends in the lower stratospheric polar vortex which are due largely to photochemical ozone losses during the summer fall season the trend toward stronger circumpolar flow has contributed substantially to the observed warming over the antarctic peninsula and patagonia and to the cooling over eastern antarctica and the antarctic plateau

seismic imaging of the 1999 izmit turkey rupture inferred from the near fault recordings we use near fault accelerograms to infer the space time history of rupture on the fault during the izmit earthquake the records show that the ground displacement and velocity near the fault were surprisingly simple rupture propagated toward the west at a velocity of about 3 km s and toward the east at a remarkably high average velocity of 4 7 km s over a distance of about 45 km before decelerating to about 3 1 km s on the eastern segment slip on the fault is particularly large down to a depth of 20 km on the central portion of the fault where it reaches about 7 m slip is large also below 10 km on the eastern fault segment and this may have contributed to the loading of shear stress on the duzce fault on the western fault segment large slip seems confined to shallow depths

basin and channel contributions to a model antarctic circumpolar current the idea that basinlike dynamics may play a major role in determining the antarctic circumpolar current acc transport is revisited a simple analytic model is developed to describe the relationship between the wind stress and transport at very low wind stress a nonzero minimum is predicted this is followed by two distinct dynamical regimes for stronger forcing 1 a stommel regime in which transport increases linearly with forcing strength and 2 a saturation regime in which the transport levels off the baroclinic structure of the sverdrup flux into the drake passage latitude band is central to the analytic model and the geometry of characteristics or geostrophic contours is key to predicting the transition between the two regimes a robustness analysis is performed using an eddy permitting quasigeostrophic model in idealized geometries many simulations were carried out in large domains across a range of forcing strengths the simulations agree qualitatively with the analytic model with two main discrepancies being related to zonal jet structures and to a western boundary inertial recirculation eddy fluxes associated with zonal jets modify the baroclinic structure and lower the saturation transport value inertial effects increase the transport although this effect is mainly limited to smaller domains

seismicity of the sea of marmara turkey since 1500 summary we use the earthquake history of the last 500 years to help evaluate the tectonic and hazard contexts of the1999 earthquakes at izmit and dzce in westernturkey the 20th century has been unusually active but over the 500 year period the seismic moment release can account for the known right lateral shear velocity across the marmara region observed by gps two areas of known late quaternary faulting stand out as unusually quiet over this period the northwest shore of the sea of marmara and the southern branch of the north anatolian fault system between bursa and mudurnu

time dependent distributed afterslip on and deep below the izmit earthquake rupture surface deformation transients measured with the global positioning system during the 87 days between the 17 august 1999 izmit earthquake and the 12 november 1999 duzce earthquake indicate rapidly decaying aseismic fault slip on and well below the coseismic rupture elastic model inversions for time dependent distributed fault slip using a network inversion filter approach show that afterslip was highest between and below the regions of maximum coseismic slip and propa gated downward to or even below the base of the crust maximum afterslip rates decayed from greater than 2 m yr immediately after the i zmit earthquake to about 1 2 m yr just prior to the duzce earthquake maximum afterslip occurred below the eastern karadere rupture segment and near the i zmit hypocenter afterslip in the upper 16 km decayed more rapidly than that below the seismogenic zone these observations are consistent with a phase of rapid aseismic fault slip concentrated near the base of the seismogenic zone continued loading from the rapid deep afterslip along the eastern rupture zone is a plausible mechanism that helped trigger the nearby mw 7 2 12 november duzce earthquake

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

surface fault breaks aftershock distribution and rupture process of the 17 august 1999 izmit turkey earthquake the results obtained from field studies of surface fault breaks on land aftershock studies and analysis of complex teleseismic body waves of the 17 august 1999 izmit earthquake m w 7 4 indicate that the northern strand of the north anatolian fault zone had been ruptured between 29 1 e and 31 1 e with a maximum total fault rupture length of about 200 km the 12 november 1999 duzce earthquake m w 7 2 extended the surface fault break an additional 41 km to the east alignment of the aftershocks delineates the fault rupture on land and extends it to the west of the hersek delta well into the marmara sea to 29 1 e longitude we have identified six fault rupture segments two of them are located to the west of the hersek delta and four are located to the east rupture process analysis suggests two stages of rupture separated in space and time with an estimated total scalar seismic moment of 2 42 1020 n m the first stage initiated at the epicenter near izmit and propagated asymmetrically first eastward and then westward with a total scalar moment of 1 6 1020 n m showing predominantly right lateral strike slip faulting followed by a minor subevent extending the rupture further east the second stage took place at the western and eastern ends of the source area rupturing two segments within the marmara sea west of the hersek delta and two segments between akyazi and golyaka the rupture process analysis indicates that six fault segments were ruptured during the mainshock four of them on land and two within the marmara sea the major moment release of 1 2 1020 n m is found on the 64 km long sapanca segments located between the easternmost tip of the gulf of izmit and akyazi with an estimated maximum slip of 5 3 m the moment release on the golcuk segment with a length of 30 km is about 3 7 1019 n m and the estimated slip on this segment is 4 1 m rupture process analysis suggests two 20 km long segments between akyazi and golyaka striking n70 e the scalar moment releases on these segments are 2 7 1019 and 1 9 1019 n m with estimated offsets of 2 2 and 1 6 m respectively the last two subevents took place to the west of the hersek delta on the yalova segment and within the marmara sea with estimated offsets of 1 3 and 1 0 m respectively manuscript received 20 august 2000

relationships between colour and diagenesis in the aragonite calcite speleothems in basajaun etxea cave spain abstract basajaun etxea cave north spain contains a wide morphological and colour variety of speleothems most of them are composed of aragonite but calcite speleothems are also found their most common colour is white but there are also pink green and turquoise speleothems in different areas of the cave mg rich dissolution waters from the cave s crystalline dolostone and magnesite host rock favour aragonite precipitation and drive important diagenetic changes in this paper we will discuss how diagenesis modifies speleothem texture mineralogy and geochemistry causing significant changes in the colour we also discuss how speleothems that have undergone diagenesis may also be useful indictors of paleoclimatic conditions our work shows that diagenesis changes the colour of the speleothems because of the mobility of the chromophore elements during this process along with this elemental alteration comes the loss of the primary isotopic signals of speleothems detailed petrological studies of speleothems should precede their analysis for palaeoclimatic reconstruction so that influence of areas affected by diagenesis can be eliminated in addition diagenetic signals also contain valuable information on the changes of the waters within the cave and the overall evolution of speleothems and the cave itself

coseismic and postseismic fault slip for the 17 august 1999 m 7 5 izmit turkey earthquake we use global positioning system gps observations and elastic half space models to estimate the distribution of coseismic and postseismic slip along the izmit earthquake rupture our results indicate that large coseismic slip reaching 5 7 meters is confined to the upper 10 kilometers of the crust correlates with structurally distinct fault segments and is relatively low near the hypocenter continued surface deformation during the first 75 days after the earthquake indicates an aseismic fault slip of as much as 0 43 meters on and below the coseismic rupture these observations are consistent with a transition from unstable episodic large earthquakes to stable fault creep sliding at the base of the seismogenic zone

rupture processes of the 1999 august 17 izmit and november 12 duzce turkey earthquakes summary we derive the rupture history of the 1999 august 17 izmit mw 7 4 and 1999 november 12 duzce mw 7 1 earthquakes in turkey from teleseismic body waves using broad band data of the global seismograph network aftershock locations and mapped surface breaks the centroid solutions indicate strike slip mechanisms for both events the izmit earthquake was characterized by rupture propagating predominantly eastwards it consisted of a main rupture lasting about 25 s followed within 1 min by two more events of mw 6 9 and mw 7 0 with the teleseismic data we could not resolve the westward extent of rupture into the marmara sea however an upper bound of the seismic moment release west of the epicentre of the izmit event is estimated to be 1 9 1019 n m the duzce earthquake lasted about 14 s and was characterized by a bilateral mode of rupture in excellent agreement with mapped surface breaks and aftershock locations

kinematic analysis of secondary faults within a distributed shear zone reveals fault linkage and increased seismic hazard abstract complex multifault earthquake ruptures involving secondary faults emphasize the necessity to characterize their seismogenic potential better and study their relationship with major faults to improve the seismic hazard assessment of a region high resolution geophysical data were interpreted to make a detailed characterization of the averroes fault and the north averroes faults which are poorly known secondary right lateral strike slip faults located in the central part of the alboran sea western mediterranean these faults appear to have evolved since the pliocene as part of a distributed dextral strike slip shear zone in response to local strain engendered by the diverging movement of the carboneras fault to the north and the yusuf and alboran ridge faults to the south in addition the architecture of these faults suggests that the averroes fault may eventually link with the yusuf fault thus leading to a higher seismogenic potential therefore these secondary faults represent a hitherto unrecognized seismogenic hazard since they could produce earthquakes up to moment magnitude mw 7 6 our results highlight the importance of the role played by secondary faults in a specific kinematic framework their reciprocal linkage and their mechanical relationship with the main faults could lead to future complex fault ruptures this information could improve fault source and earthquake models used in seismic and tsunami hazard assessment in this and similar regions

lateral offsets on surveyed cultural features resulting from the 1999 izmit and duzce earthquakes turkey surveys of offset linear cultural features that cross the surface ruptures of the 17 august and 12 november 1999 earthquakes on the north anatolian fault in turkey yield slip values as large as or larger than those recorded by near field measurements in the same areas immediately after the earthquake using long linear alignments of trees fence lines walls and canals we demonstrate as much as a 2 m increase in observed slip over the initial field measurements on an average we observed about 15 of the total lateral slip as off fault deformation with values ranging from 0 to 40 of the total slip part of this lateral deformation is accom modated by bending or drag in a zone as much as 30 m in width although usually the zone varies between 5 and 20 m in width this supports the idea that substantial nonbrittle off fault deformation is associated with ruptures in areas of alluvial fill alternatively there may have been substantial afterslip although none has been recognized on postearthquake repaired structures our observations suggest that post earthquake measurements of fault slip using tape measures on offset geomorphic features may underestimate the actual amount of slip in that event where the non linearity of the offset feature does not allow recognition of the warping surveys of multiple tree lines within groves of poplar trees planted in straight lines across the fault prior to the earthquake show surprisingly large lateral varia tions in one grove slip increases by nearly 1 8 m or 35 of the maximum measured value over a lateral distance of nearly 100 m this and other observations along the 1999 ruptures suggest that the lateral variability of slip observed from displaced geomorphic features in many earthquakes of the past may represent a combination of 1 actual differences in slip at the surface and 2 the difficulty in recognizing distributed nonbrittle deformation

joint inversion of insar gps teleseismic and strong motion data for the spatial and temporal distribution of earthquake slip application to the 1999 izmit mainshock the space time distribution of slip of the 17 august 1999 izmit earthquake is investigated by inverting synthetic aperture radar sar interferometry and global positioning system gps data together with teleseismic broadband and near field strong motion records surface offsets are used as an added constraint special emphasis is given to analysis of the resolution of the different data sets we use a four segment finite fault model and a nonlinear inversion scheme allowing slip to vary in amplitude direction and duration as well as variable rupture velocity from the inversion of synthetic data we find that the best spatial resolution can be expected in the upper half of the fault model above 12 km where coverage of the interferometric sar data is good western half of the rupture and near the gps and strong motion stations teleseismic data are found to have a lower resolution that is more evenly distributed over the fault model the joint inversion of all the data sets has an increased resolving power compared with the separate inversions and gives a more robust description of the space and time distribution of slip our study shows the importance of resolution tests in evaluating the reliability of earthquake kinematic models and it confirms that an excellent fit of a single kind of data does not necessarily imply a good retrieval of the kinematic properties of an earthquake the izmit rupture which is almost pure right lateral strike slip faulting is dominated by the bilateral breaking of a central asperity located between 29 7 e about 10 km west of the city of golcuk and 30 4 e eastern margin of sapanka lake with slip reaching 6 8 m in the depth range 6 12 km the western termination of the rupture is found near the city of yalova but large slip ends around 29 7 e about 10 km east of hersek delta a second area of large slip is required by all the data sets further east toward the city of duzce between 30 7 e and 31 1 e karadere and duzce faults this eastern slip zone which is separated from the main central asperity by an area of greatly reduced slip is less well constrained by the data however a strong motion station near the city of duzce helps to locate a high slip patch near 31 1 e in the depth range 6 12 km the total seismic moment resulting from the joint inversion is 2 4 1027 dyne cm most of the energy release occurred in a short time less than 15 sec corresponding to the bilateral breaking of the central asperity rupture propagation is relatively uniform and fast toward the west with a rupture velocity close to 3 5 km sec propagation of large slip toward the east is initially slower but it accelerates during a short time interval about 10 sec after rupture nucleation eastward progression then slows down to less than 2 km sec after 15 sec and rupture almost vanishes in amplitude ca 20 sec after initiation rupture propagation then proceeds on the easternmost karadere and duzce fault segments east of 30 7 e from 22 to ca 50 sec supershear rupture propagation is not required for modeling the waveforms considered in this study the hypocenter of the duzce earthquake which occurred 3 months later 12 november 1999 m w 7 2 is located in the immediate vicinity of the easternmost slip patch of the izmit earthquake manuscript received 28 july 2000

source rupture process of the kocaeli turkey earthquake of august 17 1999 obtained by joint inversion of near field data and teleseismic data the rupture process of the 1999 turkey earthquake is examined using both near field strong motion data and teleseismic body wave data the derived source parameters are as follows strike dip slip 268 86 180 nearly pure strike slip the seismic moment mo 1 7 1020 nm mw 7 4 the source duration 20 sec the fault length 70 km the fault width 15 km the rupture process is characterized by an asymmetric bilateral rupture propagation and smooth slip it consists of two major fault segments a rupture propagating to the west and a second rupture propagating to the east the maximum dislocation and the maximum dislocation velocity are 6 3 m and 2 7 m s respectively both found at the former segment the average dislocation is about 4 m the extent of the coseismic rupture suggests that a considerable part of the anticipated seismic gap remains unruptured

dynamic models of earthquakes on the north anatolian fault zone under the sea of marmara effect of hypocenter location 1 we perform three dimensional spontaneous dynamic rupture models of potential earthquakes on the geometrically complex north anatolian fault zone nafz under the marmara sea turkey the nafz south of the city of istanbul consists of a large scale extensional stepover with right lateral strike slip segments linked by an oblique normal segment we find that earthquakes nucleating near the stepover do not propagate across the entire fault system due to the statically unfavorable stress field on the oblique fault and lead to moderate size events only however earthquakes initiating a significant distance from the stepover cause significant dynamic unclamping of the oblique fault and thus generate large through going ruptures dynamic unclamping also produces supershear rupture propagation in the vicinity of fault discontinuities the results emphasize that estimations of earthquake size rupture propagation and slip distribution cannot be decoupled from the location of the hypocenter and the orientation of the geometrically complex fault system within the tectonic stress field

geological slip rates along the north anatolian fault in the marmara region 1 reliable piercing points on both sides of the sea of marmara enabled us to obtain an estimate of the slip rate over time scales of 10 15 ka on different fault strands of the north anatolian fault naf system we analyzed geomorphic features in the gulfs of izmit gemlik sea of marmara and saros ne aegean sea which were passively displaced by the naf strands after their abandonment related to the post glacial sea level rise results for the main northern strand consistently similar on both sides of the marmara pull apart are in the order of 10 mm yr about one half of that expected from geodetic measurements and accepted plate tectonic models in the southern branch of the naf the estimated rate of 4 mm yr is only slightly higher than that given by geodetic models our findings have implications for both neo tectonic reconstructions of the submerged portion of the naf system and fault interactions and seismic hazard estimates in the marmara region they suggest that either the total anatolia eurasia plate motion is more diffuse than previously reported or geodetic data are not representative of the geological time scale deformations moreover they suggest that a significant amount of stress is accommodated along the southern strand of the naf system on which the last large m 7 earthquakes dates back to 1419 1855 and 1863 ad

vertical structure and transport of the antarctic circumpolar current in drake passage from direct velocity observations 1 the structure of the antarctic circumpolar current acc in drake passage is examined using 4 5 years of shipboard acoustic doppler current profiler adcp velocity data the extended 1000 m depth range available from the 38 khz adcp allows us to investigate the vertical structure of the current the mean observed current varies slowly with depth while eddy kinetic energy and shear variance exhibit strong depth dependence objectively mapped streamlines are self similar with depth consistent with an equivalent barotropic structure vertical wavenumber spectra of observed currents and current shear reveal intermediate wavenumber anisotropy and rotation indicative of downward energy propagation above 500 m and upward propagation below 500 m the mean observed transport of the acc in the upper 1000 m is estimated at 95 2 sv or 71 of the canonical total transport of 134 sv mean current speeds in the acc jets remain quite strong at 1000 m 10 20 cm s 1 vertical structure functions to describe the current and extrapolate below 1000 m are explored with the aid of full depth profiles from lowered adcp and a 3 year mean from the southern ocean state estimate sose a number of functions including an exponential are nearly equally good fits to the observations explaining 75 of the variance fits to an exponentially decaying function can be extrapolated to give an estimate of 154 38 sv for the full depth transport

influence of wind stress wind stress curl and bottom friction on the transport of a model antarctic circumpolar current abstracteddy permitting simulations of a wind driven quasigeostrophic model in an idealized southern ocean setting are used to attempt to describe what sets the wind driven circumpolar transport of the antarctic circumpolar current acc for weak forcing the transport is well described as a linear sum of channel and basin components the authors main focus is on stronger forcing in this regime an eddy driven recirculation appears in the abyssal layer and all time mean circumpolar streamlines are found to stem from a sverdrup like interior the sverdrup flux into drake passage latitudes can then be thought of as the sum of one part that feeds the circumpolar current and another that is associated with the recirculation the relative fractions of this partitioning depend on the bottom drag the midchannel wind stress and the wind stress curl increasing the strength of the bottom drag reduces the recirculation and increases circumpolar transport increasing a zero curl eastward wind stress reduces th

rapid growth and recrystallization of cave pearls in an underground limestone mine abstract an underground limestone mine in quincy illinois contains cave pearls forming in splash pools to better examine cave pearl growth seeds of different composition were placed in two pools and left for either 8 or 22 months the resulting cave pearls accumulated 1 to 6 mm of low mg calcite with growth rates of 0 4 to 5 5 mm yr these pearls are composed of 1 thinly laminated alternations of micrite and microspar mainly on the bases 2 dendrite crystals mainly on the top and sides and 3 equant calcite spar that crosscuts earlier formed laminations x ray diffraction and microprobe analysis shows that all three fabrics are low mg calcite with no detectable compositional differences scanning electron microscopy reveals fossil exopolymeric substances eps and fossil microbes but they are widely scattered the micrite microspar laminae range from 50 m thick the 8 month cave pearls contain approximately 100 couplets and the 22 month pearls contain 50 150 couplets therefore individual couplets are forming in days to weeks this does not correlate with any known climate signal and their origin remains a mystery the dendrite layers are thicker than the micrite microspar laminated areas with growth rates up to 5 5 mm year attributable to rapid co2 degassing assisted by the mine ventilation the equant calcite spar tends to start within microspar laminae and then extends as a triangular reaction front up to 1 5 mm into overlying laminae obliterating the original fabric this recrystallization fabric is mainly but not only within the laminated layers and starts in as little as 1 to 2 months after laminae precipitation ostwald ripening aggrading neomorphism is the likely drive for this recrystallization as the outer layers of the pearl continue to grow during recrystallization of the interior this rapid recrystallization from calcite to calcite has significant ramifications for the use of speleothems for paleoclimate studies and for the rate of early carbonate diagenesis

north anatolian fault in the gulf of izmit turkey rapid vertical motion in response to minor bends of a nonvertical continental transform 1 the catastrophic rupture of the north anatolian fault east of the marmara sea on 17 august 1999 highlighted a need for mapping the underwater extension of that continental transform a new bathymetric map of izmit gulf indicates that the fault follows the axis of the gulf with a few minor bends submerged shorelines and shelf breaks that formed during the last glacial maximum provide markers to quantify vertical deformation variable tilting of these horizons reveals that vertical deformation is highest just south of the fault a correlation between vertical deformation of the southern fault block and distance to fault bends can be accounted for by a fault dipping steeply to the south hence subsidence uplift of the southern hanging wall block would be expected where the fault strikes at a slightly transtensional transpressional orientation to relative plate motion subsidence reaches about 8 mm yr west of the town of golcuk and might be accommodated in 1 2 m subsidence events during large earthquakes that scenario is compatible with the tsunami runups and the coseismic subsidence of the southern shore that occurred in 1999 seafloor morphology also suggests that earthquakes are accompanied by widespread gas and fluid release the periphery of the deepest basin displays a hummocky texture diagnostic of sediment fluidization and mud volcanoes occur west of hersek peninsula that might be activated by earthquakes finally the backscatter imagery reveals a series of lineaments midway through the gulf that are interpreted as products of the 1999 surface rupture the seafloor is undisturbed farther west suggesting that surface slip decreased to an insignificant level beyond hersek possibly the stress shadow from the 10 july 1894 earthquake which was felt strongly along the western izmit gulf contributed to arrest the 1999 surface rupture

role of residual overturning for the sensitivity of southern ocean isopycnal slopes to changes in wind forcing abstractthe antarctic circumpolar current plays a central role in the ventilation of heat and carbon in the global ocean in particular the isopycnal slopes determine where each water mass outcrop

gas emissions and active tectonics within the submerged section of the north anatolian fault zone in the sea of marmara the submerged section of the north anatolian fault within the marmara sea was investigated using acoustic techniques and submersible dives most gas emissions in the water column were found near the surface expression of known active faults gas emissions are unevenly distributed the linear fault segment crossing the central high and forming a seismic gap as it has not ruptured since 1766 based on historical seismicity exhibits relatively less gas emissions than the adjacent segments in the eastern sea of marmara active gas emissions are also found above a buried transtensional fault zone which displayed micro seismic activity after the 1999 events remarkably this zone of gas emission extends westward all along the southern edge of cinarcik basin well beyond the zone where 1999 aftershocks were observed the long term monitoring of gas seeps could hence be highly valuable for the understanding of the evolution of the fluid fault coupling processes during the earthquake cycle within the marmara sea

internal precipitation of microcrystalline carbonate a fundamental problem for sedimentologists abstract recent studies of submarine lithification have shown that microcrystalline carbonate or carbonate mud traditionally thought to represent ooze deposited in quiet water commonly forms as an internal precipitate below the sediment water interface this internally precipitated micrite alters the mud grain ratio of pre existing sedimentary deposits and invalidates classifications that relate the amount of micrite matrix in limestones to the degree of water energy associated with the environment of deposition

the seismic activity of the marmara sea region over the last 2000 years we examined the seismicity of the region of the sea of marmara in northwest turkey over the last 2000 yr using the historical record of the region we found no evidence for truly large earthquakes of a size comparable to those in the north anatolian fault zone in the marmara basin events are smaller in keeping with the known fault segmentation of the basin over the last 2000 yr seismic mo ment release accounted for the known right lateral shear velocity across the marmara region observed by global positioning system measurements its average rate is relatively constant and varies between 1 6 and 2 4 cm yr the long term seismicity in the marmara sea region shows that large earthquakes are less frequent than pre dicted from the 100 yr long instrumental period

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

estimates of seismic potential in the marmara sea region from block models of secular deformation constrained by global positioning system measurements we model the geodetically observed secular velocity field in north western turkey with a block model that accounts for recoverable elastic strain ac cumulation the block model allows us to estimate internally consistent fault slip rates and locking depths the northern strand of the north anatolian fault zone nafz carries approximately four times as much right lateral motion 24 mm yr as does the southern strand in the marmara sea region the data show strain accu mulation to be highly localized we find that a straight fault geometry with a shallow locking depth of 6 7 km fits the observed global positioning system velocities better than does a stepped fault geometry that follows the northern and eastern edges of the sea this shallow locking depth suggests that the moment release associated with an earthquake on these faults should be smaller by a factor of 2 3 than previously inferred assuming a locking depth of 15 km online material an updated version of velocity field data

influence of releasing step overs on surface fault rupture and fault segmentation examples from the 17 august 1999 izmit earthquake on the north anatolian fault turkey the 17 august 1999 izmit earthquake broke four distinct structural segments of the north anatolian fault from east to west the karadere sakarya sapanca and golcuk fault segments these segments are separated from one another and the adjoining yalova and duzce fault segments to the west and east respectively by distinct right releasing step over and or gaps in the fault trace these include from east to west the eften lake step over 2 4 km wide akyazi gap 6 13 km long sapanca step over 1 2 km wide golcuk step over 1 2 km wide and karamursel step over 4 5 km wide the earthquake nucleated within or near the golcuk step over with bilateral rupture propagation to the west and east to the west about 4 5 5 m of surface rupture up to 7 m of subsurface rupture on the golcuk segment was mostly if not entirely arrested by the 4 to 5 km wide karamursel step over to the east about 3 4 m of surface rupture about 4 m of subsurface rupture propagated through the 1 to 2 km wide sapanca step over triggering up to 4 5 5 5 m of surface rupture up to 5 6 m of subsurface rupture on the sakarya segment rupture on the sakarya segment stepped across the akyazi gap triggering 1 1 5 m of rupture on the karadere segment rupture on the karadere segment was arrested by the 2 to 4 km wide eften lake step over modeling of the transient stress field associated with the rupture propagation agrees well with the field observations the modeled fault rupture of 5 m on the golcuk segment appears to decrease the transient stress on the eastern tip of the adjoining yalova segment across the 4 to 5 km wide karamursel step over even if we allow rupture on the golcuk segment to extend along the entire southern margin of the step over our model shows that regardless of the amount of slip in a generic sense it is difficult to increase stress on the tip of an adjoining fault segment across a 5 km wide step over on the other hand fault rupture of 3 m on the western tip of the sapanca fault segment significantly increases the transient stress on the adjoining sakarya segment across the 1 to 2 km wide sapanca step over allowing rupture propagation across the basin an evaluation of 30 historical strike slip earthquakes involving 59 step over basins supports our field observations and stress modeling of the izmit fault rupture historical strike slip events with small to large displacements usually propagate through step overs less than 1 2 km wide with increasing displacement larger and larger step overs can be ruptured through the empirical data generally show a ratio ranging from 2 1 to 1 1 between step over width in kilometers and strike slip displacement in meters for a through going rupture however step overs of 4 to 5 km width appear to always arrest fault rupture regardless of the amount of displacement these results therefore provide important constraints for evaluating the probability of multisegment ruptures on segmented strike slip faults manuscript received 20 august 2000

geometry slip distribution and kinematics of surface rupture on the sakarya fault segment during the 17 august 1999 izmit turkey earthquake the m w 7 4 17 august 1999 izmit earthquake ruptured five major fault segments of the dextral north anatolian fault zone the 26 km long n86 w trending sakarya fault segment sfs extends from the sapanca releasing step over in the west to near the town of akyazi in the east the sfs emerges from lake sapanca as two distinct fault traces that rejoin to traverse the adapazari plain to akyazi offsets were measured across 88 cultural and natural features that cross the fault such as roads cornfield rows rows of trees walls rails field margins ditches vehicle ruts a dike and ground cracks the maximum displacement observed for the izmit earthquake 5 1 m was encountered on this segment dextral displacement for the sfs rises from less than 1 m at lake sapanca to greater than 5 m near arifiye only 3 km away average slip decreases uniformly to the east from arifiye until the fault steps left from sagir to kazanci to the n75 w 6 km long akyazi strand where slip drops to less than 1 m the akyazi strand passes eastward into the akyazi bend which consists of a high angle bend 18 29 between the sakarya and karadere fault segments a 6 km gap in surface rupture and high aftershock energy release complex structural geometries exist between the izmit duzce and 1967 mudurnu fault segments that have arrested surface ruptures on timescales ranging from 30 sec to 88 days to 32 yr the largest of these step overs may have acted as a rupture segmentation boundary in previous earthquake cycles manuscript received 10 july 2000

pore water geochemistry at two seismogenic areas in the sea of marmara within the sea of marmara the highly active north anatolian fault naf is responsible for major earthquakes mw 7 and acts as a pathway for fluid migration from deep sources to the seafloor this work reports on pore water geochemistry from three sediment cores collected in the gulfs of izmit and gemlik along the northern and the middle strands of the naf respectively the resulting data set shows that anaerobic oxidation of methane aom is the major process responsible for sulfate depletion in the shallow sediment in the gulf of gemlik depth concentration profiles of both sulfate and alkalinity exhibit a kink type profile the sulfate methane transition zone smtz is located at moderate depth in the area in the gulf of izmit the low concentrations observed near the seawater sediment interface for sulfate calcium strontium and magnesium result from rapid geochemical processes aom and carbonate precipitation occurring in the uppermost part of the sedimentary column and sustained by free methane accumulation barite dissolution and carbonate recrystallization have also been identified at deeper depth at the easternmost basin of the gulf of izmit this is supported by the profile of the strontium isotope ratios 87sr 86sr as a function of depth which exhibits negative anomalies compared to the modern seawater value the strontium isotopic signature also shows that these carbonates had precipitated during the reconnection of the sea of marmara with the mediterranean sea finally a first attempt to interpret the sulfate profiles observed in the light of the seismic activity at both sites is presented we propose the hypothesis that seismic activity in the areas is responsible for the transient sulfate profile and that the very shallow smtz depths observed in the gulf of izmit is likely due to episodic release of significant amount of methane

how far did the surface rupture of the 1999 izmit earthquake reach in sea of marmara an open problem concerning the mw 7 4 1999 izmit earthquake along the north anatolian fault naf system is the apparent conflict between estimates of strike slip deformation based on field and remote sensing data this is due to the fact that the main strand of the naf west of the epicenter lies below the sea of marmara seismological evidence and models based on synthetic aperture radar interferometry suggest that coseismic and early postseismic displacement accumulated after the earthquake could have reached the western end of the izmit gulf and possibly the southern edge of the cinarcik basin tapering off along the northern coast of the armutlu peninsula more than 60 km from the epicenter this scenario is not confirmed by onshore field observations that point toward a termination of the surface rupture around 30 km to the east these discrepancies convey high uncertainties in the estimate of the tectonic load produced by the izmit earthquake on the adjacent fault segment toward istanbul we analyzed data from different sources including high resolution marine geophysical surveys and two nautile dives along the fault controlled canyon that connects izmit cinarcik basins our observations suggest that the surface rupture of the 1999 izmit earthquake propagated through the shallow gulf but did not reach the deep marmara basins in fact along the slope between cinarcik and the western end of the izmit gulf we do not observe fault related ruptures affecting the sea floor but rather a series of active gas seeps and black patches that mark the presence of known active faults our findings have implications for seismic risk assessment in the highly populated region of istanbul both for the estimate of tectonic load transferred to the next fault segments and the location of the next earthquake citation gasperini l a polonia g bortoluzzi p henry x le pichon m tryon n cagatay and l