a 6 year record of baroclinic transport variability of the antarctic circumpolar current at 140 e derived from expendable bathythermograph and altimeter measurements 1 repeat hydrographic sections across the antarctic circumpolar current are used to derive an empirical relationship between upper ocean temperature and the baroclinic transport stream function cross validation shows this relationship can be used to infer baroclinic transport above and relative to 2500 dbar from temperature measurements with an error of a few per cent the mean transport distribution derived from 31 austral summer expendable bathythermograph xbt sections over a 6 year period consists of westward flow immediately south of tasmania a broad band of strong eastward flow between 50 and 55 s and three cores of eastward flow south of 55 s by defining a second empirical relationship between surface dynamic height and cumulative transport a continuous time series of baroclinic transport is derived from altimeter measurements of sea surface height transports derived from altimetry in this way agree well with simultaneous in situ estimates root mean square error in net transport is 4 106 m3 s 1 suggesting sea level anomalies largely reflect baroclinic changes above 2500 dbar the 10 day sampling of the altimeter transport time series shows the irregular xbt sampling aliases variability at unresolved timescales the standard deviation of net transport above and relative to 2500 m is 4 3 106 m3 s 1 the variability in net transport is largest 2 7 106 m3 s 1 in the quasi annual band periods of 4 months to 1 5 years slightly smaller 2 3 106 m3 s 1 in the mesoscale band 1 5 years 1 5 106 m3 s 1 changes in transport are correlated with local changes in both wind stress and wind stress curl in the quasi annual and interannual bands but the transport time series is too short to draw significant conclusions

model for the origin of the yakutat block an accreting terrane in the northern gulf of alaska a composite oceanic and continental terrane the yakutat block is currently colliding with and accreting to north america in the northern gulf of alaska marine geophysical data indicate that the block has moved with the pacific plate during pliocene and quaternary time but are indeterminant about its previous movement history a model that explains some observed geologic and structural features of the block is that it originated as a result of subduction of the kula farallon spreading center beneath north america in this model the spreading center that formed the basaltic basement of the yakutat block was offset from a spreading center to the south by a left lateral transform fault 400 500 km long subduction of the northern spreading center about 45 m y ago sliced off part of the north america continental margin attached it to the kula plate and initiated northward movement of the composite terrane as the yakutat block during eocene and oligocene time migration of the southern spreading center toward north america truncated the yakutat block on the south and left a fossil fracture zone that is now seen as the transition fault the southern spreading center subducted about 25 m y ago and the yakutat block has since traveled with the pacific plate to southern alaska

exploiting coastal altimetry to improve the surface circulation scheme over the central mediterranean sea this work is the first study exploiting along track altimetry data to observe and monitor coastal ocean features over the transition area between the western and eastern mediterranean basins the relative performances of both the aviso and the x track research regional altimetric data sets are compared using in situ observations both products are cross validated with tide gauge records the altimeter derived geostrophic velocities are also compared with observations from a moored acoustic doppler current profiler results indicate the good potential of satellite altimetry to retrieve dynamic features over the area however x track shows a more homogenous data coverage than aviso with longer time series in the 50 km coastal band the seasonal evolution of the surface circulation is therefore analyzed by conjointly using x track data and remotely sensed sea surface temperature observations this combined data set clearly depicts different current regimes and bifurcations which allows us to propose a new seasonal circulation scheme for the central mediterranean the analysis shows variations of the path and temporal behavior of the main circulation features the atlantic tunisian current the atlantic ionian stream the atlantic libyan current and the sidra gyre the resulting bifurcating veins of these currents are also discussed and a new current branch is observed for the first time

small mesoscale features at a meandering upper ocean front in the western ionian sea mediterranean sea vertical motion and potential vorticity analysis abstract transient mesoscale and submesoscale processes such as small eddies and filaments could play a fundamental role in the marine ecosystem especially in oligotrophic seas like the mediterranean however very little is known about the biological and physical dynamics characterizing such structures in this work the 8 km horizontal resolution data collected during the symplex 1998 survey are analyzed to describe the physical dynamics of small mesoscale features along the atlantic ionian stream western ionian sea the data were optimally interpolated over a regular grid and used to compute the 3d ageostrophic circulation by solution of the q vector formulation of the omega equation the relative importance of stratification relative vorticity and twisting terms in the rossby ertel potential vorticity is thus examined along selected isopycnals together with the associated vertical motions and vortex stretching a surface cyclonic eddy 15 km of radius was observed near a meander of the atlanti

numerical simulation of the interannual variability of the mediterranean sea upper ocean circulation numerical simulations reveal that variations in wind stress and heat fluxes can induce significant interannual fluctuations in the circulation of the upper layers of the mediterranean from january 1980 to november 1988 the atmosphere shows changes in the structure and magnitude of the surface winds and in the air temperatures which induce modifications in the upper ocean structure and currents the model prediction of the interannual fluctuations of the sicily strait baroclinic westward volume transport is in agreement with observations and the variability is explained as a function of the wind curl forcing in the region the current anomalies persist for many months after a winter atmospheric anomalous disturbance has occurred over the basin the eastern mediterranean basin is the area where the interannual ocean response is most pronounced

geophysical insights into the transition fault debate propagating strike slip in response to stalling yakutat block subduction in the gulf of alaska on the basis of faulting mapped on seismic reflection and bathymetric data seismicity current plate motions and evidence that the yakutat block may be anomalously thick we propose a tectonic model for yakutat pacific interactions including the often debated transition fault to the east deformation associated with the queen charlotte fairweather fault system is extending offshore facilitating westward propagation of strike slip motion along the eastern segment of the transition fault to the west the oblique slip pamplona zone and transition faults merge at an embayment in the continental margin where a north south dextral strike slip fault within the pacific plate illuminated by the 1987 1992 earthquake swarm intersects the pacific yakutat tectonic boundary these fault patterns are consistent with modern plate motions and reflect a plate boundary reorganization that may be caused by resistance to subduction by the yakutat block a possible moderate sized oceanic plateau

seasonal variability of water transport through the straits of gibraltar sicily and corsica derived from a high resolution model of the mediterranean circulation abstract the variability of the water transport through three major straits of the mediterranean sea gibraltar sicily and corsica was investigated using a high resolution model this model of the mediterranean circulation was developed in the context of the mercator project the region of interest is the western mediterranean between the strait of gibraltar and the strait of sicily the major water masses and the winter convection in the gulf of lions were simulated the model reproduced the meso scale and large scale patterns of the circulation in very good agreement with recent observations the western and the eastern gyres of the alboran sea were observed but high interannual variability was noticed the algerian current splits into several branches at the longitude of the strait of sicily level forming the tyrrhenian branch and the atlantic ionian stream and the atlantic tunisian current in the eastern mediterranean the north current retroflexed north of the balearic islands and a dome structure was observed in the gulf of lions the cyclonic barotropic algerian gyre which was recently observed during the mater and elisa experiment was evidenced in the simulation from time series of 10 day mean transport the three straits presented a high variability at short time scales the transport was generally maximum in april for the strait of gibraltar in november for the strait of sicily and in january for the strait of corsica the amplitudes of the transport through the straits of gibraltar 0 11 sv and sicily 0 30 sv presented a weaker seasonal variability than that of the strait of corsica 0 70 sv the study of the relation between transport and wind forcing showed that the transport through the strait of gibraltar is dependent on local zonal wind over short time scales 70 which was not the case for the other straits less than 30 the maximum minimum of the transport occurred for an eastward westward wind stress in the strait an interannual event was noticed in november december 2001 which corresponded to a very low transport 0 3 sv which was characterised by a cyclonic circulation in the western alboran sea that circulation was also reproduced by the model for other periods than winter during the interannual simulation the transport through the strait of sicily is not influenced by local wind the wind stress curl of the northwestern mediterranean influenced the transport through the strait of corsica

the sicily channel surface circulation revisited using a neural clustering analysis of a high resolution simulation the sicily channel surface circulation is investigated by analyzing the outputs of a high resolution ocean model med12 forced during 46 years by the arpera atmospheric fields applying a neural network classifier we show that the surface circulation in the sicily channel can be decomposed into 8 modes characterizing the major patterns of that circulation particularly the algerian current separation at the entrance to the sicily channel the features of the atlantic tunisian current and of the atlantic ionian stream these modes reflect the variability of the circulation in space and time at seasonal and inter annual scales some modes preferably occur in winter whilst others are characteristic of summer the mode sequence presents an inter annual variability in good agreement with observations the topography of the sicily channel sill plays a major role in steering the circulation in particular the summer upwelling along the southern coast of sicily which is present in several modes could be explained by a large scale density forcing a combination of barotropic baroclinic double kelvin waves generated on both sides of the sill provides a mechanism for explaining the complexity of the surface circulation advecting the surface waters from the western mediterranean toward the eastern mediterranean the most salient features of which are the atlantic tunisian current the atlantic ionian stream and the tyrrhenian sicilian current which is a new feature highlighted by the present study

the transition from strike slip to oblique subduction in southeastern alaska from seismological studies abstract body waveform modeling of 11 moderate to large earthquakes within southeastern alaska has been incorporated with earthquake relocations and the results of previous seismicity studies to examine the transition from strike slip to oblique subduction in southeastern alaska in the sitka region of extreme southeastern alaska earthquakes indicate seismic slip is parallel to the direction of motion between north america and the pacific plate as the plate margin begins to bend to the west near cross sound and encounters the southeastern edge of the yakutat block partitioning of seismic slip is evident both onshore and offshore although the largest earthquakes magnitude 6 0 in this region have slip parallel to plate motion most moderate sized events have slip vectors rotated clockwise from plate motion offshore the 1973 cross sound sequence indicates that the southern end of the transition zone is seismogenic with the pacific plate being thrust beneath the yakutat block while onshore strike slip faulting has occurred along the fairweather border ranges and denali faults in the st elias region thrust faulting is occurring along and above the plate interface moderate sized events in the st elias show a mix of slip vector orientations in the pamplona zone slip vectors of offshore earthquakes and deformation directions determined onshore from gps studies show a counter clockwise rotation relative to plate motion suggesting that a change in strain field occurs just west of the st elias region

seismicity of the wrangell and aleutian wadati benioff zones and the north american plate along the trans alaska crustal transect chugach mountains and copper river basin southern alaska the configuration of the aleutian and wrangell wadati benioff zones in southern alaska between longitudes 142 w and 148 w is determined from regionally recorded earthquakes from 1971 to 1986 the earthquakes are located with a simple velocity model calibrated with seismic refraction measurements conducted for the trans alaska crustal transect tact west of the transect meridian approximately 145 20 w and beneath the chugach mountains shocks in the depth range 25 60 km compose the shallow part of the northwest to north dipping aleutian zone this zone can be traced updip and seaward beneath prince william sound east of the transect meridian and north of 61 n latitude the weakly active north northeast dipping wrangell zone extends to a depth of at least 100 km beneath the wrangell volcanoes and along strike for at least 150 km the two zones appear to be continuous at least in the depth range 20 45 km and may define adjacent limbs of a buckle in the subducted oceanic lithosphere north of 61 n focal mechanisms in the shallow aleutian zone are compatible with a uniform stress field characterized by in plane least compressive stress directed toward the steeply dipping deeper part of the aleutian zone north of cook inlet stress orientation in the wrangell zone is unresolved because of the low level of seismicity no focal mechanisms corresponding to slip on a gently northward dipping megathrust have been observed along the transect meridian a change of focal mechanism with depth near the top of the dipping seismic zone is inferred to reflect the interplate boundary beneath the chugach mountains this boundary coincides with a band of strong reflectors imaged by tact vertical seismic profiling the overriding plate appears to be aseismic beneath the northern chugach mountains but minor shallow seismicity occurs beneath the copper river basin first motion patterns for these shallow shocks suggest the most compressive stress within the overriding plate is oriented subhorizontally and approximately north south

collisional model for rapid fore arc block rotations arc curvature and episodic back arc rifting in subduction settings 1 we review geophysical and geological data from 23 active and ancient plate boundaries to document a compelling spatial and temporal relationship between collision plate boundary curvature rapid tectonic rotations and the occurrence of back arc rifting our observations support a conceptual model where the change from subduction to collision causes rapid fore arc rotation when viewed in a reference frame relative to the bounding tectonic plates leading to marked plate boundary curvature our global compilation reveals that most active back arc rifts are associated with rapidly rotating fore arcs and nearby collisions thus we propose that collision and rapid fore arc rotations play a major role in the evolution and kinematics of back arc basins we conduct numerical modeling to better understand the physical processes behind these observed rapid tectonic rotations at convergent margins our results suggest that the presence of an indentor or choke point in the subduction system e g collision can generate rapid rotation of the fore arc about a nearby pole and lead to back arc rifting the rate of fore arc rotation and back arc rifting depends on the incoming indentor velocity and can be greatly enhanced by slab rollback and the presence of a low viscosity back arc where viscosity of the back arc is low fore arc rotation dominates where back arc viscosity is high the formation of strike slip faults and tectonic escape dominates our observational and model derived results illustrate that shallow crustal forces produced by the entry of buoyant features into subduction zones are a fundamental mechanism for the generation of fore arc block rotations plate boundary curvature back arc rift evolution and tectonic escape in subduction systems rollback of the subducting slab within the mantle will certainly enhance the processes we describe but it is not the only driving force

inter annual variations of surface currents and transports in the sicily channel derived from coastal altimetry twenty year coastal altimetry data set x track is used for the first time to gain insight into the long term inter annual variations of the surface circulation in the sicily channel firstly a spectral along with a time space diagram analysis are applied to the monthly means of the x track geostrophic currents over the period 1993 2013 they reveal a regionally coherent current patterns from track to track with a marked inter annual variability that is unequally shared between the atlantic tunisian current and atlantic ionian stream inflows in the sicily channel and the bifurcation tyrrhenian current outflow northeast of sicily secondly an empirical altimetry based transport like technique is proposed to quantify volume budgets inside the closed boxes formed by the crossing of the altimetry tracks and coastlines over the study area a set of hydrographic measurements is used to validate the method the inferred altimetry transports give a well balanced mean eastward atlantic waters baroclinic flow of 0 4 sv and standard deviations of 0 2 sv on a yearly basis throughout the sicily channel and toward the ionian sea which is fairly coherent with those found in the literature furthermore the analysis allows to quantify the intrusions of atlantic waters over the tunisian shelf 0 12 0 1 sv and highlights two main modes of variability of the main surface waters path over the sicily channel through the bifurcation atlantic tunisian current and atlantic ionian stream systems some physical mechanisms are finally discussed with regards to changes in the observed currents and transports

tectonic drivers of the wrangell block insights on fore arc sliver processes from 3 d geodynamic models of alaska intracontinental shear zones can play a key role in understanding how plate convergence is manifested in the upper plate in regions of oblique subduction however the relative role of the driving forces from the subducting plate and the resisting force from within intracontinental shear zones is not well understood results from high resolution geographically referenced instantaneous 3d geodynamic models of flat slab subduction at the oblique convergent margin of alaska are presented these models investigate how viscosity and length of the denali fault intracontinental shear zone as well as coupling along the plate boundary interface modulate motion of the wrangell block forearc sliver and slip across the denali fault models with a weak denali fault 1017 pa s and strong plate coupling 1021 pa s were found to produce the fastest motions of the wrangell block 10 mm yr the 3d models predict along strike variation in offs et along the denali fault changing from dextral strike slip motion in the eastern segment to oblique convergence towards the fault apex models further show that the flat slab drives oblique motion of the wrangell block and contributes to 20 models with a short fault and 28 models with a long fault of the observed quaternary slip rates along the denali fault the 3d models provide insight into the general processes of forearc sliver mechanics and also offer a 3d framework for interpreting hazards in regions of flat slab subduction

new constraints on the motion of the fairweather fault alaska from gps observations 1 gps velocities from sites near to the fairweather fault in southern alaska are combined with line length data from geodetic surveys by the u s geological survey usgs to estimate the slip rate and locking depth of the fairweather fault using dislocation theory we perform a weighted least squares inversion of the geodetic data and obtain a best fitting slip rate of 45 6 2 0 mm yr and locking depth of 9 0 0 8 km the slip rate we estimate is one of the highest observed across any strike slip fault we also include the dalton creek segment of the denali fault in our model and estimate a slip rate of 3 8 1 4 mm yr for this section of the fault this is substantially lower than the rate observed for the denali fault segment to the northwest which ruptured in the november 3 2002 mw 7 9 denali fault earthquake

tectonic block motion and glacial isostatic adjustment in southeast alaska and adjacent canada constrained by gps measurements 1 we use data from campaign and continuous gps sites in southeast alaska and the neighboring region of canada to constrain a regional tectonic block model that estimates block angular velocities and derives a self consistent set of fault slip rates from the block motions present day tectonics in southeast alaska is strongly influenced by the collision of the yakutat block our model predicts a velocity of 50 3 0 8 mm a toward n22 9 0 6 w for that block our results suggest that the eastern edge of the yakutat block is deforming along this edge the fairweather fault accommodates a large portion of the pacific north america relative plate motion through 42 9 0 9 mm a of dextral slip further south along the queen charlotte fault our model predicts an average of 43 9 0 6 mm a of dextral slip and a southward increasing amount of transpression strain from the yakutat collision is transferred far to the east of the strike slip system this strain transfer causes the region north of glacier bay to undergo a clockwise rotation south of glacier bay and inboard of the queen charlotte fault a smaller but clearly defined clockwise rotation is observed the heterogeneous block motion north and south of glacier bay may indicate the area is undergoing internal deformation and could explain regional patterns of diffuse seismicity the northern cordillera of canada displays a small northeasterly motion our block model suggests that the entire southeastern alaska northwestern canada margin is mobile

high sedimentation rates and thrust fault modulation insights from ocean drilling offshore the st elias mountains southern alaska abstract the southern alaskan margin offshore the st elias mountains has experienced the highest recorded offshore sediment accumulation rates globally combined with high uplift rates active convergence and extensive temperate glaciation the margin provides a superb setting for evaluating competing influences of tectonic and surface processes on orogen development we correlate results from integrated ocean drilling program iodp expedition 341 sites u1420 and u1421 with regional seismic data to determine the spatial and temporal evolution of the pamplona zone fold thrust belt that forms the offshore st elias deformation front on the continental shelf our mapping shows that the pattern of active faulting changed from distributed across the shelf to localized away from the primary glacial depocenter over 300 780 kyrs following an order of magnitude increase in sediment accumulation rates simple coulomb stress calculations show that the suppression of faulting is partially controlled by the change in sediment accumulation rates which created a differential pore pressure regime between the underlying faulted strata and the overlying undeformed sediments

exhumation along the fairweather fault southeastern alaska based on low temperature thermochronometry 1 the southern alaskan syntaxis marks the spectacular junction between the 1000 km long pacific north america transform margin and the chugach st elias belt where subduction and terrane accretion drive rapid convergent deformation and rock uplift new low temperature thermochronometry reveals that intense orogenic deformation is not restricted to one side of the syntaxis but extends nearly 300 km south along the dextral fairweather fault apatite and zircon u th he ages as young as 0 9 and 2 0 ma suggest maximum exhumation rates of nearly 2 mm a in close proximity 0 5 mm a along the entire plate margin we estimate that long term rock uplift accommodates 3 mm a of fault normal convergence in this area this suggests that the fairweather fault is slightly transpressive and highly partitioned analogous to the central san andreas fault this convergence only accounts for 1 5 of the obliquity between pacific plate motion and the continental margin however implying the deficit is taken up by 1 2 cm a thrust sinistral motion along the offshore transition fault additionally thermochronometry shows a marked increase in bedrock cooling coincident with onset of heavy glaciation similar to what has been observed in other parts of the pacific northwest the tectonically active fairweather corridor is distinguished however by the magnitude of the acceleration and the depth of exhumation since pliocene climate change

altimetric signal and three dimensional structure of the sea in the channel of sicily the 1996 altimeter synoptic mesoscale plancton experiment alt symplex was specifically designed to perform in situ measurements simultaneous with the passage of topex poseidon t p and ers 2 over selected tracks in the central and eastern sicily channel this experiment made it possible to have for the first time a validation of altimetry with in situ data over the mediterranean where weak dynamics results in a modest sea elevation rarely exceeding 10 cm historical infrared and altimetric satellite data were first analyzed in order to study the variability of the circulation in the area the comparative and integrative analysis of simultaneous satellite data and in situ measurements permitted investigation of the relation between the altimeter derived surface topography and the three dimensional structure of the sea the pearson correlation coefficients between altimeter data and dynamic heights along track resulted to be 0 72 0 89 t p and 0 88 ers 2 when using conventional repeat track analysis for t p a correlation value of 0 87 was found for time differences computed basing on a collinear analysis technique this analysis also led to the identification of a strong barotropic component of the velocity field located near the sicilian continental shelf where it is responsible for approximately 60 of the signal

the western mediterranean deep water a proxy for climate change reconstructions of mediterranean ocean temperature fields back to 1950 show a proxy relationship between heat content changes in the north atlantic and the western mediterranean deep water wmdw formed in the gulf of lions in winter because of consistent air sea heat fluxes over these areas strongly correlated to the north atlantic oscillation nao

tidal and subtidal currents in the strait of sicily 1 current measurements from shipboard and moored instruments from the strait of sicily are examined to evaluate the importance of tidal and subtidal currents during summer 2000 the results show that the principal tidal components m2 k1 s2 and o1 are particularly important in the western shelf and sill region but are significantly less important over the eastern shelf and almost negligible in the central part of the strait there is a significant internal tide in the narrowest passage through the western sill the residual nontidal currents describe the main pathways and local structures of atlantic water as it crosses the strait the residual currents are compared with the geostrophic velocity calculated from simultaneous hydrographic measurements

hydrochemical performance and mineralogical evolution of a dispersed alkaline substrate das remediating the highly polluted acid mine drainage in the full scale passive treatment of mina esperanza sw spain acid mine drainage remediation is an unresolved matter in abandoned mining districts around the world development and implementation of passive treatment systems in these areas are commonly focused on engineering and water quality aspects neoformed mineral phases precipitated within the reactive material of these passive treatments account for the removal of pollutants but also can cause clogging and passivation of the reactive substrate after 20 months of operation and monitoring the limestone based passive treatment system implemented in mina esperanza sw spain was sampled to study the relationship between water chemistry mineral composition of the neoformed precipitates and treatment performance water chemical profiles show the existence of three precipitation zones controlled by fe al and zn hydrochemistry and also a migration with time of precipitation zones downward into the reactive material these precipitation zones were also confirmed by a mineral study performed on the solid samples where either schwertmannite and goethite or hydrobasaluminite and zn rich green rust were the mineral phases that controlled the metal removal in the three precipation fe al or zn zones iron and al precipitates were observed to play a critical role in the time evolution of the reactive material hydraulic conductivity furthermore al precipitates passivated to some extent the limestone grains by armoring although migration of the fe precipitation zone and al redissolution later activated the limestone grains a higher proportion of limestone in the reactive mixture and the addition of new reagents to the bottom section of the reactive material to enhance the reducing environment and to promote divalent metal removal are proposed on the basis of this hydrochemical and mineralogical study for a future design for the mina esperanza passive treatment system

exploiting the potential of an improved multimission altimetric data set over the coastal ocean until now most satellite altimetry studies of the coastal ocean have been based on along track data from a single mission whereas up to four missions were operative in 2002 2005 here to monitor the coastal ocean we have applied specialized corrections and dedicated processing strategies to compute a multimission data set at a mean distance of 32 km of the coast the resulting altimetric data set is compared with sea level data from three in situ stations over a coastal zone of the northwestern mediterranean the mean rms difference between this data set and the sea level stations is 2 9 cm against 3 7 cm when using the aviso altimetric product comparison of altimeter derived geostrophic velocities with a mooring also shows that the spatial and temporal variability of the surface current field is well reproduced the agreement with in situ measurements extends to intraseasonal time scales showing a significant improvement compared to previous studies in the 50 km coastal band

interannual variations of volume transport in the western labrador sea based on topex poseidon and woce data abstract the interannual variations of volume transport in the western labrador sea are estimated using six years of topex poseidon altimeter data and hydrographic data from a woce repeat section and a method based on the linear momentum equation in which the sea surface is the level of known motion the interannual variation of the total transport in spring summer has a range of 6 2 sv sv 106 m3 s 1 and is positively correlated with the fall winter north atlantic oscillation nao index and wind patterns in the northwest north atlantic the total transport anomaly is decomposed into a barotropic and a baroclinic component the interannual change of the barotropic transport is similar to that of the total transport and is positively correlated with the fall winter nao index the baroclinic transport anomaly in comparison has a smaller magnitude and the opposite sign the authors conjecture that the deepened icelandic low in high index years generates a strong cyclonic wind stress curl which in tur

evidence for past subduction earthquakes at a plate boundary with widespread upper plate faulting southern hikurangi margin new zealand abstract at the southern hikurangi margin new zealand we use salt marsh stratigraphy sedimentology micropaleontology and radiocarbon dating to document evidence of two earthquakes producing coseismic subsidence and in one case a tsunami over the past 1000 yrs the earthquake at 520 470 yrs before present b p produced 0 25 0 1 m of subsidence at big lagoon the earthquake at 880 800 yrs b p produced 0 45 0 1 m of subsidence at big lagoon and was accompanied by a tsunami that inundated 360 m inland with a probable height of 3 3 m distinguishing the effects of upper plate faulting from plate interface earthquakes is a significant challenge at this margin we use correlation with regional upper plate paleoearthquake chronologies and elastic dislocation modeling to determine that the most likely cause of the subsidence and tsunami events is subduction interface rupture although the older event may have been a synchronous subduction interface and upper plate fault rupture the southern hikurangi margin has had no significant m 6 5 documented subduction interface earthquakes in historic times and previous assumptions that this margin segment is prone to rupture in large to great earthquakes were based on seismic and geodetic evidence of strong contemporary plate coupling this is the first geologic evidence to confirm that the southern hikurangi margin ruptures in large earthquakes the relatively short time interval between the two subduction earthquakes 350 yrs is shorter than in current seismic hazard models online material historical accounts description of vertical deformation core names foraminifera census and abundance diatom census modern analog samples map of cores collected stratigraphic correlation diagram for all cores and detailed core logs

effect of the northward migrating mendocino triple junction on the eel river forearc basin california structural evolution offshore northern california the gorda plate is subducting obliquely beneath north america the resulting complicated tectonic setting forms the southern end of the cascadia subduction zone the southern cascadia subduction zone and overlying eel river forearc basin lie just north of the unstable mendocino triple junction the neogene strata of the eel river basin record structural deformation caused by the underthrusting of the gorda plate as well as deformation generated by northward migration and encroachment of the mendocino triple junction three distinct deformation regimes are present in the eel river forearc basin 1 along the western margin of the forearc basin and within the foreslope of the accretionary prism thrust faults and anticlines record pliocene pleistocene shortening caused by subduction of the gorda plate 2 the southern part of the basin rotated counterclockwise in the late pleistocene resulting in modern transpressional deformation offshore humboldt bay the rotation and deformation are caused by north south convergence across the boundary between the pacific plate and the southernmost part of the forearc basin at the triple junction 3 the northeastern margin of the eel river basin is deformed by high angle faults with a component of strike slip motion that may represent the incipient northward propagation of the pacific north american transform system north of the triple junction

the role of straits and channels in understanding the characteristics of mediterranean circulation abstract straits in the mediterranean sea form an important network from which one can determine the characteristics of the water exchange between all the constituent sub basins this includes the definition of water masses and water transport and their time variability from 1994 all the major straits in the mediterranean sea gibraltar sicily otranto balearic sea straits cretan arc straits and corsica were subject to long term observations as part of various research projects besides adding new elements to the knowledge of internal strait conditions the data sets collected allow us to propose a fairly consistent representation of the mediterranean circulation and budgets in key points within the basin the amplitude of the annual water transport measured at these straits was about 1 sv and it appears to be modulated by a significant low frequency and seasonal variability for the first time a seasonal component was identified at gibraltar thus raising new questions on the actual state of the mediterranean also the very likely existence of a significant interannual component was documented in the corsica channel this component was found to be related to the interannual variability of the north atlantic oscillation the observations in the cretan arc straits have provided a more comprehensive representation of the recent changes in the eastern mediterranean thermohaline cell it is noteworthy that the effects of these changes have been observed both in the otranto and sicily straits and are now affecting the adjacent sea regions the presence of a stream of modified atlantic water in the balearic sea channels indicates that part of the atlantic inflow may be diverted directly into the northern region of the western mediterranean finally data gathered in the sardinia channel indicate that the central mediterranean region plays a critical role in controlling exchanges between the eastern and the western mediterranean while it is emphasized that the tyrrhenian sea area plays a role in strongly modifying some of the water masses that contribute to the large scale basin circulation their mixing creates new water types which modify the currently known pattern and composition of the mediterranean circulation

the 1987 1992 gulf of alaska earthquakes abstract we present a study of the 1987 1992 gulf of alaska earthquake sequence using relocated seismicity data together with body wave analysis of selected larger events most of the sequence is located on a n s trending fault directly south of the yakataga seismic gap and consists of four main events of mw 7 2 7 8 7 7 and 6 8 and associated aftershocks the first earthquake is of left lateral strike slip type on an ene wsw trending fault the second event is a right lateral strike slip earthquake on the n s trending fault the fault plane of the third strike slip event was identified as an ene wsw trending fault located to the south of that for the first event in a previous study using body wave analysis we show that though the body wave study cannot unambiguously identify the fault plane the temporal development of the seismicity together with the pattern of aftershock distribution on the conjugate fault suggests that this event also occurred on the n s trending fault and is of right lateral type the seismicity on the conjugate fault is interpreted as being triggered by the increase of the shear stress in the direction of the normal to the fault plane due to the main shock the occurrence of the fourth main shock a right lateral strike slip event in 1992 which itself can be considered an aftershock of the 1987 1988 sequence with epicentres distributed along a n s trending fault favours this conclusion the first three events of the sequence have been described in earlier studies as having too short a rupture length for their seismic moment if the rupture lengths inferred from the aftershock zones in this study are used we find that this is not the case the events in the 1987 1992 sequence lie along magnetic anomaly 13 and related conjugate fracture zones indicating that the oceanic crust is rupturing along pre existing zones of weakness in response to plate boundary stresses at the southern end the seismic activity terminates near a seamount which rises 1 km above an otherwise relatively low relief ocean floor and close to a fracture zone perpendicular to the n s trend of the earthquake sequence suggesting that the n s striking rupture along the n s trending fault is terminated here by a barrier at the northern end the sequence terminates at the alaska trench near the yakataga seismic gap where there is a right lateral offset in the bathymetry along the transition fault this offset also being visible on the gravity map of the region thus this offset has the same right lateral sense as the n s trending strike slip fault planes of three of the main shocks and suggests that though there was no significant seismic activity in this region of the gulf of alaska since 1964 faulting here has been active in the past

mapping the megathrust beneath the northern gulf of alaska using wide angle seismic data in the northern gulf of alaska and prince william sound we have used wide angle seismic reflection refraction profiles earthquake studies and laboratory measurements of physical properties to determine the geometry of the prince william and yakutat terranes the aleutian megathrust and the subducting pacific plate in this complex region the yakutat terrane is underthrust beneath the prince william terrane and both terranes are interpreted to be underlain by the pacific plate wide angle seismic reflection refraction profiles recorded along five seismic lines are used to unravel this terrane geometry modeled velocities in the upper crust of the prince william terrane to 18 km depth agree closely with laboratory velocity measurements of orca group phyllites and quartzofeldspathic graywackes the chief components of the prince william terrane to hydrostatic pressures as high as 600 mpa 6 kbar a landward dipping reflector at depths of 16 24 km is interpreted as the base of the prince william terrane this reflector corresponds to the top of the wadati benioff zone seismicity and is interpreted as the megathrust immediately beneath the megathrust is a 4 km thick 6 9 km s refractor which we infer to be the source of a prominent magnetic anomaly and which is interpreted by us and previous workers to be gabbro in eocene age oceanic crust of the underthrust yakutat terrane wide angle seismic data magnetic anomaly data and tectonic reconstructions indicate that the yakutat terrane has been underthrust beneath the prince william terrane for at least a few hundred kilometers wide angle seismic data are consistent with a 9 to 10 landward dip of the subducting pacific plate beneath the outer shelf and slope distinctly different from the inferred average 3 to 4 dip of the overlying 6 9 km s refractor and the wadati benioff seismic zone beneath the inner shelf our preferred interpretation of the geophysical data is that one composite plate composed of the pacific plate of a fairly uniform thickness and the yakutat plate of varying thickness is subducting beneath southern alaska

coastal and mesoscale dynamics characterization using altimetry and gliders a case study in the balearic sea 1 dynamics along the continental slopes are difficult to observe given the wide spectrum of temporal and spatial variability of physical processes which occur coastal currents meanders eddies etc studying such complex dynamics requires the development of synergic approaches that use integrated observing systems in this context we present the results of an observational program conducted in the balearic sea combining coastal gliders and altimetry the objectives of this experiment are to study regional dynamics using new technologies such as gliders in synergy with satellite altimetry and to investigate the limitations and potential improvement to altimetric data sets in the coastal zone in this regard new methodologies have been developed to compute consistent altimetric and glider velocities and a novel technique to estimate absolute glider velocities combining surface glider geostrophic velocities with integrated currents estimated from the glider gps positioning has been applied in addition the altimetric velocity computation has been improved especially in the coastal zone using high frequency along track sampling associated with new filtering and editing techniques this approach proves efficient for homogenizing the physical contents of altimetry and glider surface currents percentage of standard deviation explained is 40 and characterizing regional dynamics in the balearic sea through a combined analysis of a high resolution observing system such as the appearance of anomalous intense mesoscale features missing in the classical circulation scheme of the balearic sea

transient eastern mediterranean deep waters in response to the massive dense water output of the aegean sea in the 1990s abstract we present a detailed account of the changing hydrography and the large scale circulation of the deep waters of the eastern mediterranean emed that resulted from the unique high volume influx of dense waters from the aegean sea during the 1990s and of the changes within the aegean that initiated the event the so called eastern mediterranean transient emt the analysis uses repeated hydrographic and transient tracer surveys of the emed in 1987 1991 1995 1999 and 2001 2002 hydrographic time series in the southern aegean and southern adriatic seas and further scattered data aegean outflow averaged nearly 3 10 6 m 3 s 1 between mid 1992 and late 1994 and was largest during 1993 when south and west of crete aegean influenced deep waters extended upwards to 400 m depth emt related aegean outflow prior to 1992 confined to the region around crete and to 1800 m depth wise amounted to about 3 of the total outflow outflow after 1994 up to 2001 2002 derived from the increasing inventory of the tracer cfc 12 contributed 20 to the total of 2 8 10 14 m 3 densities in the southern aegean sea deep waters rose by 0 2 kg m 3 between 1987 and 1993 and decreased more slowly thereafter the aegean waters delivered via the principal exit pathway in kasos strait east of crete propagated westward along the cretan slope such that in 1995 the highest densities were observed in the hellenic trench west of crete aegean influenced waters also crossed the east mediterranean ridge south of crete and from there expanded eastward into the southeastern levantine sea transfer into the ionian mostly followed the hellenic trench largely up to the trench s northern end at about 37 n from there the waters spread further west while mixing with the resident waters additional transfer occurred through the herodotus trough in the south levantine waters after 1994 consistently showed temperature salinity t s inversions in roughly 1000 1700 m depth with amplitudes decreasing in time the t s distributions in the ionian sea were more diverse one cause being added aegean outflow of relatively lower density through the antikithira strait west of crete spreading of the aegean influenced waters was quite swift such that by early 1995 the entire emed was affected and strong mixing is indicated by near linear t s relationships observed in various places referenced to 2000 and 3000 dbar the highest aegean generated densities observed during the event equaled those generated by adriatic sea outflow in the northern ionian sea prior to the emt a precarious balance between the two dense water source areas is thus indicated a feedback is proposed which helped triggering the change from a dominating adriatic source to the aegean source but at the same time supported the previous long year dominance of the adriatic the emed deep waters will remain transient for decades to come

earthquakes in the pamplona zone yakutat block south central alaska the pamplona zone is a region of complex deformation and moderate seismicity located within the yakutat block a region that has been relatively aseismic since a series of large m 7 8 earthquakes in 1899 in 1970 a sequence of moderate to large sized earthquakes occurred within the pamplona zone largest event of mw 6 7 together with a mw 6 1 event in 1958 these events are the only m 5 5 events known to have occurred in the pamplona region since 1900 thus these events give important information on internal deformational processes within the yakutat block waveform modeling of three earthquakes in april 1970 showed rupture complexity along low angle thrust faults focal depths indicate that two of the events occurred above the wrangell aleutian megathrust while the largest event may have occurred on the megathrust events in 1958 and february 1970 indicate that deformation within the western pamplona zone is occurring along high angle 60 faults with reverse oblique motion we believe the pamplona spur the easternmost part of the pamplona zone may have behaved as an asperity during the 1899 sequence the location of the spur may be influenced by a north south trending fault zone in the subducting pacific plate that appears to be responsible for the 1987 1992 gulf of alaska sequence occurring 50 to 200 km south of the pamplona zone

peeling oceanic crust in subduction zones thin slabs of oceanic pillow basalt formed at ridge axes with associated pelagic sediments are common features in ancient accretionary complexes estimates of the average thicknesses of scraped off basaltic sections of oceanic crust in accretionary prisms vary from a few tens of metres to 300 m with a mean thickness of 80 100 m in the complexes studied the permeability contrast within the uppermost part of the oceanic crust is an important factor governing the thickness of delaminated oceanic crust this mechanism is an effective means of separating oceanic crust altered at low temperatures from the remainder of the downgoing slab and thus controlling geochemical budgets in subduction zones

subsurface geostrophic velocities inference from altimeter data application to the sicily channel mediterranean sea 1 coupled pattern reconstruction cpr and multivariate empirical orthogonal function reconstruction meof r techniques have been applied to infer the vertical structure of the sea from surface integrated measurements in the sicily channel mediterranean sea the data used to train the methods are the ctd casts present in the medar medatlas climatology the independent test and validation data set consisted of topex poseidon sea level measurements and ctd profiles collected during the synoptic mesoscale plankton experiment symplex 1996 and 1998 cruises meof r was found to give the more accurate and promising results being able to discriminate and reconstruct the main processes that drive the variability inside the channel in particular the analysis of the covariance of steric heights temperature and salinity profiles confirmed that mesoscale processes are predominant in fact the first meof steric height pattern closely resembles the first baroclinic normal mode estimated from the mean stratification profile a critical discussion on the signals contributing to the sea level variability has been done before applying the meof r to altimetric data the steric contribution of the upper 300 dbar has then been estimated from topex poseidon measurements the effects of the adjustment of altimeter data with a synthetic mean dynamic topography have also been quantified

archean oceanic flake tectonics assuming that the archean mantle was hotter and the oceanic crust thicker than at present we estimate that the archean oceanic lithosphere had a sandwich rheology with the lower crust behaving as a soft ductile layer accordingly the archean oceanic lithosphere had a rheological structure similar to present day continental lithosphere but unlike present day oceanic lithosphere the thickness of the ductile layer is a decreasing function of age while its strength is an increasing function of age the buoyancy problem in archean subduction could be overcome by delamination of oceanic upper crust but mass balance calculation indicates that most archean oceanic crust must have been recycled where the right dynamic conditions existed for delamination oceanic flake tectonics may have been an important process leading to the preservation of oceanic upper crust in greenstone belts that are characteristic of archean terrains

mediterranean surface geostrophic circulation from satellite gravity and altimetry observations we present a data based approach to study the mean and the climatology of the surface geostrophic currents sgc for the mediterranean sea using satellite ocean surface altimetry observations for 22 years 1993 2014 in conjunction with the geoid solution derived from the space mission of goce gravity field and steady state ocean circulation explorer release 4 the resultant product is the mediterranean sgc velocity field that we denote by sgc goce alt given in spatial resolution of 1 4 circ and monthly time resolution it exhibits smaller scales and lower dynamic intensities in comparison with open oceans making the mediterranean sea a challenging test case for our satellite based analysis the mean sgc goce alt is largely consistent with previous findings but with additional circulation features in time and space we also compare our results with the sgc output from the regional hydrodynamic model of mercator that assimilates satellite altimetry satellite sea surface temperature and in situ observations the prominent sgc features agree well not only on the large and subbasin scales but also in the widespread mesoscale dynamics we find however comparatively lower intensities than the mercator model in general with differences that are on average around 7 cm s but might reach 13 cm s in some coastal areas

modeling the baroclinic circulation in the area of the sicily channel the role of stratification and energy diagnostics 1 aspects of the circulation of the sicily channel region are studied with a high resolution primitive equation sigma coordinate model this work is an attempt to study the process governing the purely baroclinic dynamics and its sensitivity to seasonal stratification thus no atmospheric forcing is used two numerical experiments are analyzed using as initial conditions diagnostic velocity fields derived from the winter and summer climatological hydrologies the quasi steady state is characterized by circulation patterns in the depth range of the modified atlantic water maw and the levantine intermediate water liw strongly controlled by mesoscale eddies and topography seasonal difference is found in the surface current which exhibits the major variability on the african side downstream of adventure bank and the ionian slope where the absolute maximum occurs the intermediate circulation instead does not show relevant seasonal differences liw enters through the two passages south of malta plateau and preferentially flows along the sicilian shelf edge exiting over the northern sill its pathway is strongly controlled by subsurface cyclonic and anticyclonic cells the results are in good agreement with observations an energy diagnostics is applied to model results and sheds important light on dynamical characteristics of the mesoscale eddy field and indicates seasonal differences in the energetic exchange with the mean flow the analysis of the mean mke and eddy eke kinetic energy the transfer terms between energy compartments and the eddy momentum flux divergence indicates how eddies are strongly energetic in summer and exchange energy more efficiently with the mean flow in the quasi steady state maw volume transport and mke and eke fluctuations are strongly correlated this result suggests that mesoscale motions can control up to 40 of volume transport variability

coupled stratigraphic and structural evolution of a glaciated orogenic wedge offshore st elias orogen alaska 1 the st elias orogen is the result of 10 myr of oblique convergence and flat slab subduction in the gulf of alaska between north america and the yakutat microplate extensive glaciation and a complex tectonic environment make this region a unique case study in which to examine the details of terrane accretion and the possible coupled influence of climate and tectonic drivers on the structural and topographic evolution of an orogenic wedge reflection seismic profiles across the offshore pamplona zone fold thrust belt the frontal st elias orogenic wedge provide constraints for quantifying pleistocene deformation recorded in the glaciomarine yakataga formation the total amount of pleistocene shortening observed varies from 3 to 5 mm yr compared to the current gps derived yakutat north america convergence rate across the st elias orogen of 45 mm yr growth strata and kinematic fold analysis allow comparison of relative timing of fault activity which reveals temporal and spatial shifting of active deformation during the glacial period faulting localized adjacent to the coastline and at the current submarine deformation front the abandoned currently inactive region is colocated with the major glacial depocenter in the region the bering trough these observations imply that glacial processes such as sediment loading and focused erosion during advance retreat cycles has a direct effect on the evolution of individual faults within the pamplona zone and the overall deformation pattern in the offshore st elias margin this information provides key constraints for understanding how climatic shifts may have affected the evolution of margin architecture during pleistocene glacial interglacial periods

exhumation rates in the st elias mountains alaska abstract reprocessing and interpretation of seismic profiles from the gulf of alaska in the vicinity of the st elias mountains indicate that over 3000 km 3 of sediment were deposited on the ocean shelf since the end of the last glacial epoch approximately 10 000 years ago this estimate of the sediment volume does not include material moved out of the region by long shore currents transportation from the shelf to deeper waters or material trapped in fiords and basins on and near land thus an estimated sedimentation rate offshore of 7 9 mm year and the average erosion rate of 5 1 mm year from the st elias mountains derived from the estimated sedimentation rate represent minimum estimates we infer that these estimated rates are not typical of the approximately 5 m y history of mountain building in the area but rather they represent the result of efficient erosion by glaciers during this interglacial period

a possible influence of the north atlantic oscillation on the circulation of the western mediterranean sea a current time series spanning from 1985 to 1996 in the corsica channel shows that seasonal and interannual variabilities are stable components of the circulation of the northern part of the western mediterranean sea for the first time these characteristics are related to the state of the north atlantic oscillation during winter we have found that this large scale control is mainly maintained through the air sea interaction processes which take place in the northern basin these results provide new elements for a consistent explanation of the major features of the basin circulation such as the seasonal increase of the boundary current and deep water formation

sensitivity of the sea circulation to the atmospheric forcing in the sicily channel abstract we investigate the sensitivity of the sea surface circulation in the sicily channel to surface winds using a 15 year long 1994 2008 air sea coupled numerical simulation analysis is based on the clustering of six main wind regimes over the sicily channel domain the analysis of the corresponding sea current clusters shows that sea circulation in this area is sensitive to surface wind patterns this wind modulates the strength of the two main branches of the sea circulation in the sicily channel i e the atlantic tunisian current and the atlantic ionian stream the modulation of these two currents depends on the wind regime and displays a strong seasonal variability it is also shown that the sea circulation in the sicily channel is strongly controlled by the thermohaline circulation and the bathymetry geostrophic current however the contribution to the total current of its ageostrophic component forced by the surface winds is significant with a correlation coefficient varying from 0 3 to 0 7

seismicity of the bering strait region evidence for a bering block newly compiled russian and u s seismological data support an independent bering block in motion relative to the north american plate this motion is likely to be driven by the westward extrusion of southwestern alaska resulting from compression in southern alaska due to subduction of the pacific plate and terrane accretion seismicity extends from central alaska through the bering strait and into chukotka in eastern chukotka several southwest trends are evident some of which continue through the koryak highlands to kamchatka the seismicity outlines the bering block which includes most of the bering sea chukchi peninsula seward peninsula and parts of western alaska focal mechanisms young basaltic volcanism and normal faults in western alaska and chukotka indicate that the bering strait is under northeast southwest extension this in conjunction with thrust faulting in the koryak highlands indicates that the bering block is rotating clockwise relative to the north american plate

the dynamics of the sicily strait a comprehensive study from observations and models abstract the dynamics of the sicily strait are investigated in a comprehensive study using recent in situ observations ocean general circulation model ogcm simulations and process model results in particular results of a very high resolution mediterranean model med16 developed in the context of the mercator project are described the circulation in the sicily strait can be described as a two layer exchange of atlantic water aw and eastern mediterranean outflow water eow the algerian current brings aw the upper layer eastwards and splits into two branches at the entrance to the sicily strait one flowing to the tyrrhenian sea the other into the sicily strait the later is composed of two streams referred to as the atlantic ionian stream ais and the atlantic tunisian current atc in winter the atc signature is more pronounced in summer the ais is associated with a number of well known semi permanent features including the intermittent northward extension of the ais called nais at the ionian shelf break which seems to be driven by the surface density contrast between waters of the sicilian and the ionian basins new intermittent patterns are shown by the med16 simulations for example an anticyclonic eddy called mca south of the malta channel and an anticyclonic gyre associated to the nais called naisa upwelling is well developed in august with temperature lower than 24 c along the western and southern coasts of sicily the seasonal transport of the aw through the strait has a maximum value 1 4 sv in winter and a minimum value at the end of summer 0 8 sv in the lower layer at the exit of the sicily strait the eow mainly composed of levantine intermediate water liw outflows into the tyrrhenian sea and veers to the right then as well known the liw flows along the northern coast of sicily before reaching the sardinia channel a new liw path from the sicily strait towards the sardinia channel is shown by the med16 model and is due to intermediate eddy shedding at the exit of the sicily strait the topography of the sill in the sicily strait plays a major role in the circulation a combination of barotropic baroclinic double kelvin waves on both side of the sill provides a mechanism for splitting the algerian current