the proportionality between relative plate velocity and seismicity in subduction zones the magnitude and rate of seismicity differ between subduction zones calculations of background seismicity rates based on a global model of subduction zone seismicity reveal a positive correlation between relative plate velocity and background seismicity yet only the seismically quieter zones seem capable of generating magnitude 9 earthquakes

historical evolution and extreme climate events during the last 400years on the rhone prodelta nw mediterranean abstract the rhone river is the most important source of freshwater and sediment to the western mediterranean sea deltaic lobes and littoral prisms compose the sedimentary units that make up the whole rhone subaqueous delta which reaches up to 50 m in thickness individual lobes that accompanied the retreat of the rhone during sea level rise and the subsequent westward then eastward shift of the main outlet display averaged sedimentation rates in excess of 1 cm yr 1 containing both continental and marine material during the industrial period most of the river flow was delivered through the pegoulier and roustan distributary channels which evolved under human influence within the prodeltas associated to these distributaries very expanded sedimentation rates 10 cm yr 1 allow the documentation of historical extreme climate events a 7 71 m long piston core rhs ks57 was retrieved from the distal prodelta 79 m water depth a multi proxy study was carried out using microfossil assemblages ostracods benthic foraminifera and coccoliths in combination with sedimentological and geochemical proxies our results show that 1 four different intervals i iv spanning a time range comprised between 1600 ad and present day have been differentiated from this multi proxy analysis they correspond to a different position of distributary channels each interval correlates with the different phases of channel avulsion induced by climate events or by human activity 2 the signature of extreme floods that can be identified by the punctuated occurrence of freshwater continental ostracods e g candona spp ilyocypris sp correlating with increases in grain size and or organic carbon content they correspond to decadal scale increased runoffs reported in historical archives our study demonstrates the relevance of benthic microfossil studies for reconstructing paleoenvironmental changes in transitional marine continental settings

coastal sea level trends from topex poseidon satellite altimetry and tide gauge data in the mediterranean sea during the 1990s a joint analysis of topex poseidon satellite altimetry and tide gauge data is used to estimate sea level trends along the mediterranean sea coast from 1993 january to 2002 february a generalized least squares gls method allows us to take into account the space time distribution of the data and their respective error budgets nearly optimal parameters of the covariance functions involved in the gls method are estimated at different scales of analysis using a trial and error method combined data time series are then reconstructed at 153 locations along the coast the basin wide averaged linear trend for the coastal area shows a sea level rise of 4 54 0 30 mm yr 1 compared to 4 28 0 30 mm yr 1 for the open ocean only i e a 0 26 0 16 mm yr 1 difference the error is smaller because the systematic error does not take part in the error budget which is quite significant at local scales the coastal linear trends ranges from 8 5 to 13 5 mm yr 1 which is much narrower than ranges found by other open sea studies 24 0 to 10 0 16 0 to 29 0 mm yr 1 however a detailed error budget shows that the largest estimation errors come from the spatial extrapolation of the sea level signal required when tide gauge and altimeter data are merged the second error source is the instrumental noise and the random noise generated by the littoral contamination on altimeter measurements and from the crustal motions that are contaminating the tide gauge signal at local scale it is estimated that 85 percent of the error on linear trends does not exceed 2 mm yr 1

spatial distribution of live benthic foraminifera in the rhone prodelta faunal response to a continental marine organic matter gradient abstract benthic foraminifera were collected in the rhone prodelta gulf of lions mediterranean sea an enriched zone with high organic matter content in june 2005 sediment cores were sampled at depths ranging from 20 to 100 m four distinct foraminiferal assemblages were determined in the study area reflecting the geographical distribution of the impact of river supply the living foraminiferal faunas present a typical picture with strongly impoverished faunas composed exclusively of stress tolerant taxa fursenkoina fusiformis bulimina aculeata leptohyalis scottii and adelosina longirostra in the immediate vicinity of the river mouth this assemblage is well adapted to a high input of continental organic matter and a minimum oxygen penetration depth into the sediment to the southwest under the main corridor followed by the river plume high organic input with a dominantly terrestrial signature more refractory may be stressful for many taxa which need organic matter of a more labile quality in this area nonion scaphum nonionella turgida and rectuvigerina phlegeri are present in low densities on the edge of this area these taxa show much higher densities a greater proportion of marine organic carbon could explain their increasing abundances in this area towards the east and towards the deepest stations in the outer part of the enriched zone biodiversity increases faunas at these stations have intermediate densities and contain a number of taxa cassidulina carinata epistominella vitrea valvulineria bradyana nonionella iridea bradyi at the deepest stations bolivina dilatata spathulata and textularia porrecta at the eastern stations that seem to benefit from more marine organic matter the comparison of geochemical measurements and foraminiferal data strongly suggests that the spatial distribution of foraminifera in the rhone prodelta is mainly governed by the quality and the quantity of organic matter reaching the sediment water interface since bottom waters are well oxygenated 215 260 mol l and oxygen penetration into the sediment is less than 1 cm at all stations benthic ecosystem oxygenation appears to have only a minor impact on regional differences in faunal distribution

interseismic coupling and seismic potential along the central andes subduction zone we use about two decades of geodetic measurements to characterize interseismic strain build up along the central andes subduction zone from lima peru to antofagasta chile these measurements are modeled assuming a 3 plate model nazca andean sliver and south america craton and spatially varying interseismic coupling isc on the nazca megathrust interface we also determine slip models of the 1996 m w 7 7 nazca the 2001 m w 8 4 arequipa the 2007 m w 8 0 pisco and the m w 7 7 tocopilla earthquakes we find that the data require a highly heterogeneous isc pattern and that overall areas with large seismic slip coincide with areas which remain locked in the interseismic period with high isc offshore lima where the isc is high a m w 8 6 8 8 earthquake occurred in 1746 this area ruptured again in a sequence of four m w 8 0 earthquakes in 1940 1966 1974 and 2007 but these events released only a small fraction of the elastic strain which has built up since 1746 so that enough elastic strain might be available there to generate a m w 8 5 earthquake the region where the nazca ridge subducts appears to be mostly creeping aseismically in the interseismic period low isc and seems to act as a permanent barrier as no large earthquake ruptured through it in the last 500 years in southern peru isc is relatively high and the deficit of moment accumulated since the m w 8 8 earthquake of 1868 is equivalent to a magnitude m w 8 4 earthquake two asperities separated by a subtle aseismic creeping patch are revealed there this aseismic patch may arrest some rupture as happened during the 2001 arequipa earthquake but the larger earthquakes of 1604 and 1868 were able to rupture through it in northern chile isc is very high and the rupture of the 2007 tocopilla earthquake has released only 4 of the elastic strain that has accumulated since 1877 the deficit of moment which has accumulated there is equivalent to a magnitude m w 8 7 earthquake this study thus provides elements to assess the location size and magnitude of future large megathurst earthquakes in the central andes subduction zone caveats of this study are that interseismic strain of the forearc is assumed time invariant and entirely elastic also a major source of uncertainty is due to fact that the available data place very little constraints on interseismic coupling at shallow depth near the trench except offshore lima where sea bottom geodetic measurements have been collected suggesting strong coupling

sources and exchanges of mercury in the waters of the northwestern mediterranean margin abstract ocean margins are focal regions in terms of mercury hg exchanges between the continent and the open sea the aim of this paper is to describe the distribution and partition of hg between the gaseous dissolved and particulate phases in the waters of the northwestern mediterranean nwm margin in order to assess the hg sources and exchanges within the continuum between the continental shelf gulf of lions and the open sea northern gyre mean standard deviation of total hg species hgt concentrations in unfiltered water samples were 1 52 1 00 pmol l 1 n 36 in the inner shelf 1 09 0 15 pmol l 1 n 30 along the slope and 1 10 0 13 pmol l 1 n 99 in the northern gyre the dissolved phase the hg from the open sea water is the largest hg input to the gulf of lions 5 7 kmol yr 1 whereas inputs from the riverine source account for 3 4 kmol yr 1 and atmospheric deposition for less than 0 5 kmol yr 1 the hg accumulated in the sediments of the shelf is 4 5 kmol yr 1 including 0 6 1 7 kmol yr 1 in the rhone prodelta sediments the evasion to the atmosphere represents a hg flux of 2 6 kmol yr 1

interseismic strain accumulation measured by gps in the seismic gap between constitucion and concepcion in chile the concepcion constitucion area 35 37 s in south central chile is very likely a mature seismic gap since no large subduction earthquake has occurred there since 1835 three campaigns of global positioning system gps measurements were carried out in this area in 1996 1999 and 2002 we observed a network of about 40 sites including two east west transects ranging from the coastal area to the argentina border and one north south profile along the coast our measurements are consistent with the nazca south america relative angular velocity 55 9 n 95 2 w 0 610 ma discussed by vigny et al 2008 this issue which predicts a convergence of 68 mm year oriented 79 n at the chilean trench near

long term sea level fluctuations driven by ocean basin dynamics earth9s long term sea level history is characterized by widespread continental flooding in the cretaceous period 145 to 65 million years ago followed by gradual regression of inland seas however published estimates of the late cretaceous sea level high differ by half an order of magnitude from 40 to 250 meters above the present level the low estimate is based on the stratigraphy of the new jersey margin by assimilating marine geophysical data into reconstructions of ancient ocean basins we model a late cretaceous sea level that is 170 85 to 270 meters higher than it is today we use a mantle convection model to suggest that new jersey subsided by 105 to 180 meters in the past 70 million years because of north america9s westward passage over the subducted farallon plate this mechanism reconciles new jersey margin based sea level estimates with ocean basin reconstructions

interplate coupling beneath ne japan inferred from three dimensional displacement field 1 the northeastern japan arc is located in a typical subduction zone and is a seismically active region where large interplate earthquakes have occurred repeatedly the nationwide gps network has made it possible to investigate the crustal deformation in unprecedented detail however vertical displacements are less accurate than the horizontal ones and have not been used to constrain interplate coupling models in this study gps carrier phase data are analyzed in order to estimate three components of site displacements the result indicates uplift along the japan sea coast and subsidence along the pacific ocean coast using the vertical site velocities together with the horizontal ones as the data for a geodetic inversion method a new model of interplate coupling is constructed to explain both the horizontal and vertical velocities for the interseismic period from 1997 to 2001 the model demonstrates strong coupling in the area off miyagi and in the area off aomori through the area off tokachi including the areas of asperities the downdip limit of the locked fault zone on the plate boundary has been estimated seismologically to be at a depth of 50 60 km in northeastern japan and the distribution of slip deficits derived in this study indicates that the transition zone extends down to a depth of about 100 km

using centroid time delays to characterize source durations and identify earthquakes with unique characteristics the relationship between m 0 and the rupture duration is often difficult to establish this is particularly true for large earthquakes for which the moment rate functions mrf generally have complicated shapes and the estimated durations can vary considerably depending on the methodology used to evaluate the mrf in this work we show that the centroid time delay c provides an alternative estimate of the source duration inverted mrfs often end gradually making the end of coseismic rupture difficult to detect in such cases when the rupture duration is not well defined the time delay c is a useful quantity to represent the first order temporal characteristics of the rupture process variations in stress parameter can be investigated by assuming a standard scaling relationship between the seismic moment m0m0 and c this simple scaling relationship can also be used to identify unusual earthquakes with unique source properties such as events involving complicated rupture processes or earthquakes characterized by unusual rupture velocities stress drops or aspect ratios

origin and pathways of winter intermediate water in the northwestern mediterranean sea using observations and numerical simulation received 25 june 2013 revised 31 october 2013 accepted 6 november 2013 published 6 december 2013 1 the study of water masses worldwide their formation spreading mixing and impact on general circulation is essential for a better understanding of the ocean circulation and variability in this paper the formation and main pathways of winter intermediate water wiw in the northwestern mediterranean sea nwmed are investigated during the winter spring 2011 using observations and numerical simulation the main results show that the wiw formed along the continental shelves of the gulf of lion and balearic sea circulates southward following five preferential pathways depending on the wiw formation site location and the oceanic conditions wiw joins the northeastern part of the balearic sea or flows along the continental shelves until joining the balearic current maximum of 0 33 sv in early april or further south until the ibiza channel entrance two additional trajectories contributing to water mass exchanges with the southern part of the western mediterranean sea bring the wiw through the ibiza and mallorca channels maxima of 0 26 sv in late march and 0 1 sv in early april respectively the circulation of wiw over the nwmed at 50 200 m depth its mixing and spreading over the western mediterranean sea reaching the south of the balearic islands the algero provencal basin the ligurian and the alboran seas suggest that the wiw may have an impact on the ocean circulation by eddy blocking effect exchange of water masses between north and south subbasins of western mediterranean sea through the ibiza channel or modification of the ocean stratification

earthquake size distribution in subduction zones linked to slab buoyancy some of the most devastating earthquakes are generated in subduction zones analysis of the stress state of subduction zones worldwide suggests that large earthquakes are generated more frequently where a young buoyant plate subducts

interplate coupling and transient slip along the subduction interface beneath oaxaca mexico summary we describe and model gps measurements of surface deformation from the oaxaca segment of the mexican subduction zone to characterize interseismic strain accumulation and episodic transient slip in this region and test seismologically based models of strain accumulation and release along subduction interfaces deformation measured from 2001 to 2007 within our dense 31 station gps array has consisted of 1 trench normal horizontal contraction at rates that decrease monotonically inland from the coast 2 rapid coastal subsidence that changes gradually to slow uplift at locations more than 100 km inland and 3 periods of transient slip that interrupt the otherwise steady deformation inverse modelling of transient station offsets in 2004 and 2006 indicates that transient slip along the subduction interface occurred downdip from the rupture limits of previous large earthquakes in this region in both 2004 and 2006 gps site velocities that are corrected for the effects of this transient slip vary significantly over distances of only tens of kilometres both along the coastline and inland implying that similar spatial variations occur in the degree of locking across the subduction interface deformation rates measured along the coast reach their maximum above the core of the rupture zone of the 1978 ms 7 8 shallow thrust earthquake and generally decrease outwards towards the edges of the rupture zone bounded value inverse modelling of the interseismic gps velocity field with a finite element mesh that simulates the study region indicates that much of the rupture zone of the 1978 shallow thrust earthquake is fully locked at the plate convergence rate but that this region is surrounded by weakly locked areas of the subduction interface which may slow or arrest the propagation of future earthquakes much of the deeper region of transient slip downdip from the seismogenic zone is also fully locked between the episodes of transient slip however the elastic energy that accumulated due to locking of this deeper transitional zone between 2002 and 2006 appears to have been mostly or completed released by the 2004 and early 2006 transient slip events the approximately balanced energy budget for the deeper zone of transient slip implies that this region is unlikely to contribute significant elastic energy to future earthquakes that originate along the seismogenic zone our results support a model in which seismic asperities coincide with regions of strong locking between earthquakes the potential elastic energy that has re accumulated since 1978 in the seismogenic zone is already sufficient to cause a repeat of the 1978 earthquake

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

satellite measurements reveal persistent small scale features in ocean winds four year averages of 25 kilometer resolution measurements of near surface wind speed and direction over the global ocean from the quikscat satellite radar scatterometer reveal the existence of surprisingly persistent small scale features in the dynamically and thermodynamically important curl and divergence of the wind stress air sea interaction over sea surface temperature fronts throughout the world ocean is evident in both the curl and divergence fields as are the influences of islands and coastal mountains ocean currents such as the gulf stream generate distinctive patterns in the curl field these previously unresolved features have important implications for oceanographic and air sea interaction research

tectonostratigraphic evolution of the eastern algerian margin and basin from seismic data and onshore offshore correlation abstract the eastern algerian basin part of the western mediterranean domain is a back arc basin resulting from the se drift of the lesser kabylia block gave rise to continental extension and birth of a new oceanic domain we aim here to define the structure and tectonostratigraphic evolution of this basin and the adjoining continental margin indeed the absence of wells and the lack of published mcs data kept this area mostly unknown the crustal architecture down to the moho and seismo stratigraphy of the sedimentary infill are detailed emphasizing particularly the pre messinian series by combining a new set of offshore deep penetrating seismic conventional mcs sections and wide angle seismic data because no well exist offshore we realized new field descriptions of the late oligocene and miocene deposits on land and propose onshore offshore extrapolation and age correlations the pre messinian series display four main units pmsu1 to 4 above which messinian units are consistent with stratigraphic models already proposed for the mediterranean basin the deep basin displays units as old as the omk oligo miocene kabyle series on land the basement is shaped by conjugate transcurrent faults striking n120 n40 forming a series of rhombic troughs resulting from transtensional tectonics the coeval e w extension and nw se stretching of the continental crust suggest a radial opening of the algerian basin during late oligocene lower miocene followed by a progressive uplift of the upper margin after the collision of lesser kabylia with africa besides steep slope of the eastern algerian margin downward flexure of the oceanic basin near the margin toe and growth of s dipping thrusts within the margin evidence a significant quaternary stress inversion overall this study highlights the complex stress evolution of the east algerian margin since oligocene times as evidenced by significant upward downward vertical motions and crustal extensional compressional successions we summarize this evolution into three main stages 1 rifting including sea floor spreading at late oligocene burdigalian in the context of back arc 2 collision between alkapeca blocks and africa at 17 ma and post rift sag basin infill till late tortonian to messinian and 3 inversion of the margin and development of flexural basins at quaternary times

faulting process of the august 8 1993 guam earthquake a thrust event in an otherwise weakly coupled subduction zone we study a large mw 7 7 earthquake that occurred on june 8 1993 slightly offshore and under the island of guam in the southern mariana island arc from a complete study of p and sh body waves a relocation of the aftershocks and the subevents of the main shock we propose a relatively simple model of the rupture process of this event we propose that this earthquake ruptured a shallow dipping thrust fault that corresponds to the subduction interface under guam like many other earthquakes this event started with a small foreshock and was followed by two large energy release events located to the northeast of the epicenter along the subduction zone the rupture process had a relatively short duration of about 32 s with a weak starting phase that lasted about 8 s seismic moments estimated from body waves surface waves and global positioning system gps are very similar of the order of 4 5 1020 n m the displacement field produced by our best model was compared to the gps measurements of coseismic slip obtained by beavan et al 1994 we find an excellent agreement both in displacement direction and magnitude between the predicted and observed gps displacements this appears to be then the largest earthquake to have occurred on a shallow dipping thrust fault in the mariana subduction zone during this century its occurrence requires a reassessment of the concept of seismic coupling in this subduction zone

shallow dynamic overshoot and energetic deep rupture in the 2011 mw 9 0 tohoku oki earthquake strong spatial variation of rupture characteristics in the moment magnitude mw 9 0 tohoku oki megathrust earthquake controlled both the strength of shaking and the size of the tsunami that followed finite source imaging reveals that the rupture consisted of a small initial phase deep rupture for up to 40 seconds extensive shallow rupture at 60 to 70 seconds and continuing deep rupture lasting more than 100 seconds a combination of a shallow dipping fault and a compliant hanging wall may have enabled large shallow slip near the trench normal faulting aftershocks in the area of high slip suggest dynamic overshoot on the fault despite prodigious total slip shallower parts of the rupture weakly radiated at high frequencies whereas deeper parts of the rupture radiated strongly at high frequencies

sediment dynamics during wet and dry storm events on the tet inner shelf sw gulf of lions abstract the importance of short term processes such as floods and storms on sediment delivery and reworking on the tet inner shelf was investigated the tet inner shelf is a small event dominated system located in the south western part of the gulf of lions the expected sedimentary scenario in this environment is that fluvial sediment should be deposited on the prodelta and later dispersed around the shelf and slope by wave and current reworking during storms this paper investigates differences in inner shelf sediment dynamics between storm events occurring during usual river discharges and those occurring during river floods waves current velocities near bottom water turbidity bottom sediment grain size and sea floor erosion accretion were concurrently measured at 28 m water depth on the tet inner shelf from november 2003 to march 2004 two major storms took place on 4 december 2003 and 21 february 2004 and two moderate storms occurred on 8 december 2003 and 14 march 2004 the two major storms displayed similar wave characteristics maximum significant wave height h s 7 m peak period t p 12 s and wave direction around 90 the main environmental differences during the two major storm events correspond to the amount of sediment discharged from the tet river about 2 10 4 t of sediment was delivered by the river during the 4 december flood wet storm and less than 5 10 2 t during the 21 february storm dry storm sediment dynamics were quite similar during the storm events resuspension caused by waves and sediment advection towards the southeast due to near bottom shelf currents were the dominant sedimentary processes the result was a bottom sediment erosion of several centimetres at the study site during both the wet and dry events the main differences between the wet and dry events arose after the storm immediately after the peak of the wet storm sediment supplied by the tet river and probably from other rivers was deposited around the river mouth a few days later during a moderate storm this unconsolidated sediment was resuspended transported offshore and deposited on the inner shelf in contrast a moderate storm which occurred some days after the dry february storm caused bottom erosion on the inner shelf because no fresh sediment was available on the shallower area the results from this study indicate that the tet inner shelf at 28 m water depth is mainly a bypass zone for sediment that is transported s se towards the middle outer shelf and slope although ephemeral sediment deposits may be favoured by the sediment supplied from flood events sediment transport across the shelf from the river to the slope follows a complex multi step pattern that needs to be addressed using a multi event approach

drainage evolution of the heihe river in western hexi corridor china derived from sedimentary and magnetostratigraphic results abstract the uplifting of the tibetan plateau has significantly changed the environment in surrounding areas by delivering abundant water and sediment the heihe river draining the qilian shan in the ne tibetan plateau acts as a dominant sediment routing system from the uplifted ne tibetan plateau to the hexi corridor as well as the badain jaran desert reconstructing the evolution of the heihe river could provide evidence for the birth of the badain jaran desert and enhance the understanding of sedimentary basin fill and the relationship between tectonism drainage evolution and environmental changes with this aim two parallel cores dwj and xkjd with depths of 140 and 68 2 m respectively were drilled in the floodplain of the heihe river the facies analysis of the sedimentary sequences from the drilling cores showed that the sedimentary environment changed from the lake system to a delta system and finally to a fluvial system at the depths of 133 3 and 68 m respectively the magnetostratigraphic results revealed ages of approximately 1 75 and 1 12 ma for the dwj and xkjd cores respectively and an age of approximately 1 1 ma for the transition from delta to fluvial environment in both the cores the change of the sedimentary environment at approximately 1 1 ma was caused by the formation of the integrated heihe river the integrated heihe river may have developed via mechanisms such as river capture and river diversion due to the uplifting of the north qilian shan and the longshou shan the present study suggested that the formation of large inland rivers such as the heihe river and the shiyang river in nw china played an important role in the evolution of the deserts and the loess plateau

the 1996 peru tsunamigenic earthquake broadband source process we investigate the spatio temporal complexity of moment release of the february 21 1996 peru earthquake mw 7 5 we use a non linear source tomographic technique based on simulated annealing to invert surface wave source spectra for the slip distribution on a gently dipping fault plane the spectra 5 65 mhz are obtained using an empirical green s function egf method applied to first and second orbit fundamental mode rayleigh waves spectra are well fit by a 110 km bilateral rupture subparallel to the trench updip of the hypocenter with a total moment of 2 0 1020 nm the non linear inversion reveals a 30 30 km major slip patch south the onset where rupture velocities attain 1 5 2 0 km s inversions of teleseismic broadband p and sh waves 10 500 mhz indicate little or no directivity consistent with the surface wave data the average source time functions for both the surface and body wave data are similar in shape and in duration 50 s part of the slip during the 1996 peru event occurred in a region of reduced background seismicity as was the case for the 1992 nicaragua slow event suggesting that the seismogenic potential of low seismicity regions near the trench should be globally reassessed

geodetic evidence for low coupling on the hellenic subduction plate interface we develop a block model for the aegean and surrounding areas constrained by global positioning system gps in order to investigate the degree of coupling on the hellenic subduction interface i e the fraction of the motion across the plate boundary accommodated by elastic strain accumulation we use previously published models and seismicity to define the geometry of the interface separating the down going nubian slab from the overriding aegean this model provides a good fit to the gps observations for the 200 000 km2 aegean block the wrms of the residual velocities is 1 4 mm yr for 80 gps velocity estimates approximately the 95 level of the gps velocity uncertainties we investigate the degree of coupling on the seismically active plate interface the hellenic trench splay fault believed to be the source of the 365 ad great crete earthquake and tsunami and the kephalonia transform fault by comparing the modeled gps residual velocity field for a range of coupling values the gps observations are almost insensitive to coupling on the kephalonia transform fault because of the vertical dip of the fault that creates interseismic deformation only close to the fault where few gps sites exist the absence of resolvable shortening of the leading edge of the aegean plate precludes coupling of more than 0 2 20 of the full nubia aegean convergence rate on the modeled plate interface because of the shallow dip of the plate interface and trench splay fault and high rate of convergence if these boundaries were fully coupled high elastic strain rates would be expected to extend well into the overriding aegean plate based on our preferred value for the degree of coupling 0 1 and assuming characteristic earthquake behavior we estimate a recurrence time for great earthquakes with slip similar to that for the 365 crete event of 5700 8300 yr consistent with the absence of subsequent great earthquakes on this segment of the subduction zone

origin and dynamics of mesoscale eddies in the catalan sea nw mediterranean insight from a numerical model study past observations and satellite sea surface temperature imagery indicate the presence of mesoscale anticyclonic eddies drifting along the catalan coast in september 2001 one of these anticyclonic eddies was surveyed over the shelf break during an oceanographic cruise which permitted the 3 d description of its structure in this work we investigate the origin and dynamics of such catalan eddies using a numerical circulation model of the northwest mediterranean at 3 km resolution driven by high resolution atmospheric analyses and compare model eddies with the observations in the catalan sea we identify two zones of eddy formation in the gulf of lions in front of the city of marseille and at the southeast of coast of roussillon from which anticyclonic eddies are observed to drift toward the catalan sea the hydrology and dynamics of the structures observed in the simulations are characterized sensitivity experiments and energy analysis are performed which allow us to identify the mechanisms associated with their generation properties of the eddy observed during the 2001 cruise at the catalan shelf break are found to compare well with model eddies generated at the southeast of the roussillon coast the model relates the origin of these eddies to the separation of the coastal current downstream from creus cape flow separation is linked to intense downwelling taking place in front of the roussillon coast when strong northwesterly winds events occur

alpine lee cyclogenesis influence on air sea heat exchanges and marine atmospheric boundary layer thermodynamics over the western mediterranean during a tramontane mistral event 1 data from a recent field campaign are used to analyze the nonstationary aspects of air sea heat exchanges and marine atmospheric boundary layer mabl thermodynamics over the gulf of lion gol in connection with synoptic forcing the data set includes measurements made from a wide range of platforms sea borne airborne and space borne as well as three dimensional atmospheric modeling the analysis focuses on the 24 march 1998 tramontane mistral event it is shown that the nonstationary nature of the wind regime over the gol was controlled by the multistage evolution of an alpine lee cyclone over the tyrrhenian sea between sardinia and continental italy in the early stage low at 1014 hpa the tramontane flow prevailed over the gol as the low deepened 1010 hpa the prevailing wind regime shifted to a well established mistral that peaked around 1200 utc in the afternoon the mistral was progressively disrupted by a strengthening outflow coming from the ligurian sea in response to the deepening low over the tyrrhenian sea 1008 hpa and the channelling induced by the presence of the apennine range italy and the alps in the evening the mistral was again well established over the gol as the depression continued to deepen 1002 hpa but moved to the southeast reducing the influence of outflow from the ligurian sea on the flow over the gol the air sea heat exchanges and the structure of the mabl over the gol were observed to differ significantly between the established mistral period and the disrupted mistral period in the latter period surface latent and sensible heat fluxes were reduced by a factor of 2 on average during that latter period air sea moisture exchanges were mainly driven by dynamics whereas during the former period both winds and vertical moisture gradients controlled moisture exchanges the mabl was shallower during the latter period 0 7 km instead of 1 2 km because of reduced surface turbulent heat fluxes and increased wind shear at the top of the mabl in connection with the outflow from the ligurian sea in the period of established mistral gravity waves above the mabl were observed to have an influence on the mabl structure in the perturbed mistral case this influence was not observed over the gol the ubiquitous presence of sheltered regions i e regions of reduced wind speed in the mabl in the lee of the three major mountain ranges surrounding the gol namely the pyrenees the massif central and the alps was shown to have an impact on surface turbulent heat fluxes the position of these sheltered regions which evolved with the synoptic conditions was the key to a correct interpretation of multiplatform surface turbulent flux measurements made over the gol on 24 march 1998

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

evidence for active subduction at the new guinea trench 1 recent seismic tomography imaging shows clear evidence for southwestward subduction along the entire length of the new guinea trench ngt in indonesia and papua new guinea viewed in conjunction with the occurrence of large mw 7 thrust earthquakes that are known to have occurred on the trench this confirms conclusions of earlier studies that the ngt is an active inter plate boundary the 650 km long slab is visible to a depth of about 300 km and subducts with a dip angle that varies from 30 at 136 e to 10 at 143 e the improved clarity of the seismic tomography in this region stems from the use of a more accurate data set of p and s wave arrival times and hypocentral locations

motion of continental slivers and creeping subduction in the northern andes regions of intense continental deformation termed continental slivers have been identified in chile bolivia and ecuador analyses of gps data now identify another large sliver in peru the inca sliver that is moving away from a neighbouring sliver in ecuador implying that moving continental slivers control the deformation of almost the entire andean mountain range

forms of hydraulic fractures in shallow fine grained formations hydraulic fractures have been created in fine grained formations at depths of 2 10 m to improve the performance of environmental remediation projects at dozens of locations and in a wide range of geologic conditions the effectiveness of a hydraulic fracture during remediation will depend primarily on its form that is its shape thickness orientation length width and location with respect to the borehole the forms of many hydraulic fractures have been determined by mapping exposures in excavations and by compiling split spoon sampling data these observations indicate that a typical hydraulic fracture at shallow depths is gently dipping slightly elongate in plan and slightly asymmetric with respect to the parent borehole shallow hydraulic fractures lift the ground surface to produce gentle domes and the pattern of uplift reflects the location and thickness of the fracture at depth the forms of hydraulic fractures created over a narrow range of depths at the same site are similar but the forms

physical characteristics and dynamics of the coastal latex09 eddy derived from in situ data and numerical modeling 1 we investigate the dynamics of a coastal anticyclonic eddy in the western part of the gulf of lion gol in the northwestern mediterranean sea during the latex campaign in the summer 2009 latex09 the sampling strategy combines sea surface temperature satellite imagery hull mounted acoustic doppler current profiler data conductivity temperature depth casts and drifter trajectories our measurements reveal an anticyclonic eddy latex09 eddy with a diameter of 23 km and maximum depth of 31 m centered at 3 34 e 42 33 n we use a high resolution three dimensional primitive equation numerical model to investigate its generation process and evolution the model is able to reproduce the observed eddy in particular its size and position the model results suggest that the latex09 eddy is induced by a large anticyclonic circulation in the northwestern part of the gol pushed and squeezed toward the coast by a meander of the northern current this represents a new generation mechanism that has not been reported before the post generation dynamics of the eddy is also captured by the model the collision of the latex09 eddy with cape creus results in a transient structure which is depicted by the trajectories of two lagrangian drifters during latex09 the transient structure and its advection lead to a transfer of mass and vorticity from the gol to the catalan shelf indicating the importance of mesoscale structures in modulating such exchanges in the region

impact of an intrusion by the northern current on the biogeochemistry in the eastern gulf of lion nw mediterranean abstract we present the results from the rhoma2011 leg2 campaign that took place in the eastern gulf of lion from 7 to 17 oct 2011 and combine them with remote sensing observations and results from a 3d coupled hydrodynamic biogeochemical model to study an intrusion event of the northern current nc onto the continental shelf in the gulf of lion nw mediterranean our analysis shows that during the intrusion the previously upwelled nutrient rich water present on the shelf is replaced by warmer and mostly oligotrophic nc water within a matter of 2 3 days this has a marked impact on the local biogeochemistry in the gulf with pre intrusion chl a concentrations in the surface layer of over 0 5 mg m 3 dropping to near the detection limit within less than 72 h the intrusion event leads to a dramatic albeit short lived regime shift in the limiting nutrient for primary production prior to the intrusion most of production on the shelf is nitrogen limited while the intrusion induces a shift to phosphorous limitation the relatively high frequency of occurrence of these intrusions in combination with their impact on the local ecosystem make them primary targets for future study

determination of earthquake energy release and ml using terrascope we estimated the energy radiated by earthquakes in southern california using on scale very broadband recordings from terrascope the method we used involves time integration of the squared ground motion velocity and empirical determination of the distance attenuation function and the station corrections the time integral is typically taken over a duration of 2 min after the p wave arrival the attenuation curve for the energy integral we obtained is given by q r cr n exp kr r 2 2 h ref 2 with c 0 49710 n 1 0322 k 0 0035 km 1 and h ref 8 km where is the epicentral distance a similar method was used to determine m l using terrascope data the station corrections for m l are determined such that the m l values determined from terrascope agree with those from the traditional optical wood anderson seismographs for 1 5 6 5 m l saturates the ratio e s m 0 m 0 seismic moment a measure of the average stress drop for six earthquakes the 1989 montebello earthquake m l 4 6 the 1989 pasadena earthquake m l 4 9 the 1990 upland earthquake m l 5 2 the 1991 sierra madre earthquake m l 5 8 the 1992 joshua tree earthquake m l 6 1 and the 1992 landers earthquake m w 7 3 are about 10 times larger than those of the others that include the aftershocks of the 1987 whittier narrows earthquake the sierra madre earthquake the joshua tree earthquake and the two earthquakes on the san jacinto fault the difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times the aftershocks which occurred on the fault plane where the mainshock slippage occurred had a very short time to heal hence a low stress drop the repeat time of the major earthquakes on the frontal fault systems in the transverse ranges in southern california is believed to be very long a few thousand years hence the events in the transverse ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times such as the san andreas fault and the san jacinto fault the observation that very high stress drop events occur in the transverse ranges and the los angeles basin has important implications for the regional seismic potential the occurrence of these high stress drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events characterization of earthquakes in terms of the e s m 0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the los angeles basin and the transverse ranges

the 1995 colima jalisco mexico earthquake mw 8 a study of the rupture process in this study we map rupture characteristics of the great shallow thrust earthquake of october 9 1995 which caused extensive damage to the coastal towns of colima and jalisco to isolate the earthquake rupture details we deconvolve surface waves with two empirical green s functions the aftershock of october 12 1995 mw 5 9 and the foreshock of october 6 1995 mw 5 8 from the corresponding mainshock records specifically we use a spectral water level deconvolution to obtain 80 apparent source time functions astf at 62 stations rayleigh and love waves durations of the astf as a function of azimuth indicate that the rupture propagated toward n70 w the duration of the source time function stf is around 62 s with a large pulse at 45 s to map the main characteristics of the rupture we use an inverse radon transform of the astfs assuming a ribbon fault model aligned in the direction of the rupture propagation our analysis indicates that the rupture initiated about 20 km offshore of manzanillo and propagated almost unilaterally for 150 km towards n70 w with an average rupture velocity of approximately 2 8 km s the earthquake was a composite of three significant subevents the largest occurred 45 s after the initiation of the rupture and was located about 100 km away this result is in good agreement with the inversion of deformation data measured with gps melbourne et al 1997

subduction of the woodlark basin at new britain trench solomon islands region abstract the woodlark basin located south of the solomon islands arc region is a young 5 ma oceanic basin that subducts beneath the new britain trench this region is one of only a few subduction zones in the world where it is possible to study a young plate subduction of several ma to obtain the image of the subducting slab at the western side of the woodlark basin a 40 day ocean bottom seismometer obs survey was conducted in 1998 to detect the micro seismic activity it was the first time such a survey had been performed in this location and over 600 hypocenters were located the seismic activity is concentrated at the 10 60 km depth range along the plate boundary the upper limit just about coincides with the leading edge of the accretionary wedge the upper limit boundary was identified as the up dip limit of the seismogenic zone whereas the down dip limit of the seismogenic zone was difficult to define the dip angle of the plate at the high seismicity zone was found to average about 30 using the cascadia subduction zone for comparison which is a typical example of a young plate subduction suggests that the subduction of the woodlark basin was differentiated by a high dip angle and rather landward location of the seismic front from the trench axis 30 km landward from the trench axis furthermore as pointed out by previous researchers the convergent margin of the solomon islands region is imposed with a high stress state probably due to the collision of the ontong java plateau and a rather rapid convergence rate 10 cm year the results of the high angle plate subduction and inner crust earthquakes beneath the shortland basin strongly support the high stress state the collision of the ontong java plateau the relatively rapid convergence rate and moderately cold slab as evidenced by low heat flow rather than the plate age may be dominantly responsible for the geometry of the seismogenic zone in the western part of the woodlark basin subduction zone

the seismic coupling of subduction zones revisited 1 the nature of seismic coupling for many of the world s subduction zones has been reevaluated geodetic estimates of seismic coupling obtained from gps measurements of upper plate deformation during the interseismic period are summarized we compared those with new estimates of seismic coupling obtained from seismological data the results show that with a few notable exceptions the two methods agree to within about 10 the seismological estimates have been greatly improved over those made 20 30 years ago because of an abundance of paleoseismological data that greatly extend the temporal record of great subduction earthquakes and by the occurrence in the intervening years of an unusual number of great and giant earthquakes that have filled in some of the most critical holes in the seismic record the data also again with a few notable exceptions support the frictional instability theory of seismic coupling and in particular the test of that theory made by scholz and campos 1995 overall the results support their prediction that high coupling occurs for subduction zones subjected to high normal forces with a switch to low coupling occurring fairly abruptly as the normal force decreases below a critical value there is also considerable variation of coupling within individual subduction zones earthquake asperities correlate with areas of high coupling and hence have a semblance of permanence but the rupture zones and asperity distributions of great earthquakes may differ greatly between seismic cycles because of differences in the phase of seismic flux accumulation

sand bodies at the shelf edge in the gulf of lions western mediterranean deglacial history and modern processes abstract the outer continental shelf of the gulf of lions is covered by thick mainly regressive sand deposits a combination of seismic sedimentological and geochronological methods allows us to demonstrate that a veneer of transgressive sand bodies few m to less than 1 m thick reworks these deposits they take the form of sand ridges and transverse dunes that formed at different periods in fact the low gradient outer shelf of the gulf of lions displays a complete record of deglacial history including not only transgressive deposits that formed during sea level rise but also bedforms that still evolve under episodic high energy events that occur under more highstand conditions core lithology 14 c dates and regional sea level curve suggest that the formation of the sand ridges was favoured during a period of deceleration of sea level rise such as during the younger dryas event the dunes are part of a mobile carpet here u160 the deposition of this marine sand veneer is possibly related to the interplay between different factors that trigger the turning on off for bottom currents sand deposition transport on the outer shelf in fact the sands appear to have been reworked intermittently due to high energy conditions in shallow water depth currents wave regime and wind driven circulation as well as they form current ridges superimposed to the transgressive deposits in the westernmost part of the studied area at the bourcart canyon s head

multiscale variability in the balearic sea an altimetric perspective 1 the present day availability of an 18 year record of 1 8 merged mediterranean sea sea level anomaly sla data enables a contemporary description of long term mesoscale activity in the balearic sea sla data from satellite altimetry are used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales within this complex and relatively understudied region in the western mediterranean wmed we find that the mean northern current along the iberian slope is strongest in autumn although higher variability in winter leads to stronger peaks in kinetic energy the balearic current which flows along the northern slopes of the balearic islands also has its maximum expression in autumn across the two balearic channels ibiza and mallorca key locations that partly regulate meridional exchange in the wmed observed seasonal variability in geostrophic velocity anomalies conforms rather well to prior descriptions suggesting cautious confidence in the use of the mediterranean merged altimeter product in nearshore regions circulation through the channels is maximum in winter the channel data support the hypothesis that the channel circulation may be hindered by the intermittent presence of the western intermediate water mass which sometimes forms in winter in the gulf of lions this is the first time that an analysis of variability in the balearic channels has been performed using altimetric data

apparent stress fault maturity and seismic hazard for normal fault earthquakes at subduction zones summary the behavior of apparent stress for normal fault earthquakes at subduction zones is derived by examining the apparent stress a es m 0 w here es is radiated energy and m 0 is seismic moment of all globally distributed shallow depth h 1m pa are also generally intraslab but occur where the lithosphere has just begun subduction beneath the overriding plate they usually occur in cold slabs near trenches where the direction of plate motion across the trench is oblique to the trench axis or where there are local contortions or geometrical complexities of the plate boundary lower a 1m pa i sassociated with events occurring at the outer rise or complex between the or and the trench axis as well as with intracrustal events occurring just landward of the trench the average apparent stress of intraslab normal fault earthquakes is considerably higher than the average apparent stress of interplate thrust fault earthquakes in turn the average a of strike slip earthquakes in intraoceanic environments is considerably higher than that of intraslab normal fault earthquakes the variation of average a with focal mechanism and tectonic regime suggests that the level of a is related to fault maturity lower stress drops are needed to rupture mature faults such as those found at plate interfaces that have been smoothed by large cumulative displacements from hundreds to thousands of kilometres in contrast immature faults such as those on which intraslab normal fault earthquakes generally occur are found in cold and intact lithosphere in which total fault displacement has been much less from hundreds of metres to a few kilometres also faults on which high a oceanic strike slip earthquakes occur are predominantly intraplate or at evolving ends of transforms at subduction zones earthquakes occurring on immature faults are likely to be more hazardous as they tend to generate higher amounts of radiated energy per unit of moment than earthquakes occurring on mature faults we have identified earthquake pairs in which an interplate thrust and an intraslab normal earthquake occurred remarkably close in space and time the intraslab normal member of each pair radiated anomalously high amounts of energy compared to its thrust fault counterpart these intraslab earthquakes probably ruptured intact slab mantle and are dramatic examples in which me an energy magnitude is shown to be a far better estimate of the potential for earthquake damage than mw this discovery may help explain why loss of life as a result of intraslab earthquakes was greater in the 20th century in latin america than the fatalities associated with interplate thrust events that represented much higher total moment release

radiated seismic energy and earthquake source duration variations from teleseismic source time functions for shallow subduction zone thrust earthquakes 1 earthquake source time functions deconvolved from teleseismic broadband p wave recordings are used to examine rupture variations for 417 underthrusting earthquakes located on the interplate interface in circum pacific subduction zones moment scaled duration of significant moment release varies with depth with longer duration events occurring in the shallowest 20 km of the megathrusts the source time functions are also used to estimate radiated seismic energy two estimates are obtained a simple scaled triangle substitution for the moment release history provides a minimum estimate while integration of the time function shape provides an estimate limited only by the bandwidth of the teleseismic deconvolutions while these energy calculations underestimate total energy they enable systematic comparisons of rupture process within and between subduction zones we do not find significant depth dependence for radiated energy overall but some regions do show mild trends of increasing energy seismic moment ratios e mo with increasing source depth that correspond to rupture duration variations in those regions the observations of longer rupture duration at shallow depth with moderate e mo may be due to heterogeneous friction and structural features on the shallow plate interface index terms 7215 seismology earthquake parameters 7230 seismology seismicity and seismotectonics 8164 tectonophysics stresses crust and lithosphere keywords radiated energy shallow subduction source parameters

global evaluation of large earthquake energy from 1997 through mid 2010 1 we develop an updated radiated seismic energy e catalog of global earthquakes with seismic moment m0 1019 nm mw 6 7 from 1997 through mid 2010 recording 342 events using 17849 seismograms station specific corrections and event duration dependent total p wave group calculations allow for improved e determinations for large and long duration earthquakes we find the global mean energy to moment ratio log10 e m0 4 59 0 36 robust deviations are found for thrust t 4 74 strike slip ss 4 44 and normal n 4 51 faulting events for two regions with recent energy deficient tsunami earthquakes tse we examine all large thrust earthquakes with m0 5 1017 nm mw 5 7 to identify a regional characterization in their relative radiated energy to moment ratio while thrust events along java indonesia the site of two tse events in 1994 and 2006 are comparable t jv 4 91 to the global thrust average events along the middle america trench mat the site of the 1992 nicaragua tse are consistently deficient t mat 5 15 along the mat a trend of increased deficiency in radiated energy to the southeast occurs in the direction of more rapid plate convergence global thrust mechanisms become increasingly deficient in radiated seismic energy at shallow depths with tse events representing the shallowest and most energetically deficient end member of the events in the study results suggest thrust events are highly variable but tend to increase in apparent stress from about 15 kpa near the surface to 2 mpa near 70 km depth

an apparent mechanism dependence of radiated seismic energy we develop an extension to the method of boatwright and choy 1986 for determining the radiated seismic energy es that accounts for factors that bias the estimate we apply our technique to 204 events worldwide during the period 1992 1999 and find that the apparent stress is on average largest for strike slip events 0 70 mpa while for reverse and normal events it is significantly smaller 0 15 and 0 25 mpa respectively these results support the mechanism dependence of es reported by choy and boatwright 1995 although we find that once likely sources of bias are accounted for the mechanism dependence is not as strong as found previously the source of the mechanism dependence is unclear but one possibility is that it reflects a mechanism dependent difference in the stress drop this hypothesis is suggested by the scaling of slip with width in large strike slip earthquakes and makes two predictions which could be used to test it the first is that the discrepancy should disappear for the very largest dip slip earthquakes as the length of the fault greatly exceeds the downdip extent the second is that the discrepancy ought to disappear for smaller earthquakes the first can not yet be tested due to a lack of recent very large dip slip earthquakes the second is supported by the lack of mechanism dependence to es for smaller earthquakes an alternative hypothesis is that the apparent mechanism dependence could result if faults are opaque during rupture blocking seismic radiation across them brune 1996 this could cause radiated seismic energy to be trapped preferentially in the crust near the source volume for dipping faults there remains however a large discrepancy between estimates of es obtained from teleseismic versus regional data this discrepancy indicates a problem with teleseismic and or regional estimates of the seismic energy and must be resolved before a definite conclusion can be drawn

modeling the deep convection in the northwestern mediterranean sea using an eddy permitting and an eddy resolving model case study of winter 1986 1987 1 in the northwestern mediterranean sea winter 1986 1987 was particularly cold inducing a strong open ocean convection event in order to investigate the impact of numerical models spatial resolution on the convection representation and the effects of deep convection on the northwestern mediterranean circulation we perform two numerical three dimensional simulations eddy permitting versus eddy resolving models are forced at the surface by the era40 atmospheric fluxes with a simple heat flux correction to better mimic the observed value we examine the characteristics of the deep convection mixed layer water masses characteristics convection zone and mesoscale structures and perform temporal analysis of this event in terms of kinetic energy buoyancy equilibrium and deep water dw evolution the convection characteristics are similarly represented on a global scale by both models and are in good agreement with observations except for the size of the convection region however the eddy resolving model better reproduces the mesoscale structures whose role in the dw formation mixing and transport is shown to be essential the boundary circulation and the overturning are enhanced during the convection event sixty six percent of the dw spreading is due to the bleeding effect into the catalan sea during the convection event whereas 33 is due to the mesoscale structures southwestward advection after the event sixty percent of the restratification with respect of the water column initial structure occurs before july 1987 and is due to light water advection afterward restratification is due to the mixing and is not complete before next year convection

earthquake mechanisms and active tectonics of the hellenic subduction zone summary we use improved focal mechanisms and centroid depth estimates of earthquakes combined with gps velocities to examine the tectonics of the hellenic subduction zone and in particular the processes occurring at both ends of the hellenic arc nubia aegean convergence is accommodated by shallowly dipping thrust faulting along the subduction zone interface as well as by steeper splay faults in the overriding material from a comparison of observed and expected seismic moment release over the last 100 yr combined with existing knowledge of the longer term documented historical record we confirm earlier suggestions that most 80 per cent of this convergence is accommodated aseismically that is that the subduction zone is uncoupled this conclusion is robust even allowing for rare very large earthquakes on splay faults such as that of ad 365 and also allowing for the contribution of small earthquakes the downgoing nubian plate deforms by arc parallel contraction at all depths from 200 km seaward of crete to at least 100 km within the subducting slab extensional t axes of earthquakes are aligned downdip within the descending slab suggesting that even if the aseismic prolongation of the slab has reached the 670 km mantle discontinuity it does not transmit stresses to shallower depths shallow thrust faulting earthquakes on the subduction interface show a divergence of slip vectors round the arc and gps measurements show that this is accommodated mainly by e w extension on normal faults in the overriding aegean material the eastern end of the subduction zone south of rhodes displays distributed deformation in the overriding material including a mixture of strike slip and splay thrust faulting and probably involves rotations about a vertical axes here slip on the interface itself is by thrust faulting with slip vectors oblique to the arc but parallel to the overall nubia aegean convergence there is no evidence for slip partitioning in the traditional sense in the west the subduction zone terminates in a distributed zone of parallel ne sw strike slip faults of which the most prominent is the kefalonia transform fault ktf a flexural gravity anomaly confirms that the deep bathymetric escarpment of the ktf is a lateral ramp formed as the ionian islands are emplaced sw onto the apulian lithosphere and enhanced by minor thrust faulting with slip vectors perpendicular to the scarp distributed parallel strike slip faults both sw and ne of mainland central greece terminate in e w graben in central greece which accommodate the overall ne sw shear by clockwise block rotation central greece therefore acts as a relay zone between the strike slip faulting of the ne aegean and the ionian islands western peloponnese

a sensitivity study of the general circulation of the western mediterranean sea part ii the response to atmospheric forcing abstract this paper investigates the influence of sea surface thermohaline fluxes and wind stress on the circulation of the western mediterranean sea using a high resolution 3d primitive equation model an 18 year experiment was forced with the daily output of a fine grid mesh numerical weather prediction model the major characteristics of the circulation are well reproduced the basin surface circulation is cyclonic over all of the basin the two anticyclonic alboran gyres are present the instabilities of the algerian current generate large anticyclonic eddies that invade the whole algerian basin the liguro provencal catalan current is well marked deep water convection down to the bottom only occurs during the first 3 years then winter intermediate water is produced the north south gradient of the atmospheric thermohaline fluxes induces a northward surface transport of water from the algerian basin into the liguro provencal basin this pattern can be associated with the balearic front sensitivity

on the nature of near inertial oscillations in the uppermost part of the ocean and a possible route toward hf radar probing of stratification abstractinertial band response of the upper ocean to changing wind is studied both theoretically and by analysis of observations in the northwestern mediterranean on the nontraditional f plane because of the horizontal component of the earth s rotation for waves of inertial band with frequencies slightly below the local inertial frequency f there is a waveguide in the mixed layer confined from below by the pycnocline it is argued that when the stratification is shallow these waves are most easily and strongly excited by varying winds as near inertial oscillations nios these motions have been overlooked in previous studies because they are absent under the traditional approximation the observations that employed buoys with thermistors adcps and two 16 3 mhz wellen radar wera hf radars were carried out in the gulf of lion in april june 2006 the observations support the theoretical picture a pronounced inertial band response occurs only in the presence of shallow stratification and is confined

last millennia sedimentary record on a micro tidal low accumulation prodelta tet nw mediterranean statistical sequential analysis was performed on a series of sediment cores collected from the tet prodelta in the gulf of lions northwestern mediterranean sea between october 2003 and october 2004 seabed changes during that period were correlated to hydrodynamic conditions waves and currents and river discharge low sediment supply prevents full preservation of new sediment strata on this low accumulation prodelta located on a microtidal storm dominated inner shelf severe meteorological events caused a rapid succession of erosion and deposition phases for example the december 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and or bioturbation until a new storm event eroded this layer a typical sedimentary sequence was observed for the secular deposits composed of a 10 cm thick sandy layer overlaying siltyclayey layers these characteristic features were used to analyse the last millennia sedimentary record of the tet prodelta the low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions no flood layer was found related to catastrophic flooding of the last century in the sedimentary record the little ice age 1550 1850 ad probably favoured the formation of a well developed muddy prodelta in the mouth of the tet river later on the decrease of sediment supply by rivers due to climate change and or human activities damming irrigation and the increase of the number of high energy storms reaching the coast induced a coarsening of the top sediment layer on this prodelta this modern change of the substrate is also observed in the composition of benthic biota found in the substrate

the rhone river plume in unsteady conditions numerical and experimental results surface current maps obtained in the plume of the rhome river by two vhf radars gave rise to comparisons with simulations produced by a primitive equation model two situations were investigated one in steady conditions the other with a variable wind the model gives a good estimation of current direction and velocity not only in the plume itself but also in the surrounding water the model reveals the mechanisms involved in the plume dilution and more generally in the renewal of surface water near the coast when the wind changes direction the sensitivity of the model results to the upper boundary condition for turbulent kinetic energy is also shown

rupture and variable coupling behavior of the mentawai segment of the sunda megathrust during the supercycle culmination of 1797 to 1833 we refer to periods of subduction strain accumulation beneath the mentawai islands sumatra as supercycles because each culminates in a series of partial ruptures of the megathrust in its final decades the finale of the previous supercycle comprised two giant earthquakes in 1797 and 1833 and whatever happened in between this behavior between two great ruptures has implications for how the megathrust will behave between its more recent partial failure during the m w 8 4 earthquake of 2007 and subsequent large ruptures we synthesize previously published coral microatoll records and a large new coral data set to constrain not only these two giant ruptures but also the intervening interseismic megathrust behavior we present detailed maps of coseismic uplift during the two earthquakes and of interseismic deformation during the periods 1755 1833 and 1950 2000 as well as models of the corresponding slip and coupling on the underlying megathrust the large magnitudes we derive m w 8 6 8 8 for 1797 and m w 8 8 8 9 for 1833 confirm that the 2007 earthquakes released only a fraction of the moment released during the previous rupture sequence whereas megathrust behavior leading up to the 1797 and 2007 earthquakes was similar and comparatively simple behavior between 1797 and 1833 was markedly different and more complex several patches of the megathrust became weakly coupled following the 1797 earthquake we conclude that while major earthquakes generally do not involve rupture of the entire mentawai segment they may significantly change the state of coupling on the megathrust for decades to follow influencing the progression of subsequent ruptures

nutrients and plankton spatial distributions induced by a coastal eddy in the gulf of lion insights from a numerical model a plankton functional types model forced by a hydrodynamic model is used in the present work to study the impacts of a coastal eddy on the distribution of nutrients and plankton in the western part of gulf of lion nw mediterranean sea this study based on a realistic simulation of the year 2001 focuses on a long life anticyclonic eddy detected during summer the studied anticyclonic eddy has some biogeochemical characteristics of those observed in the open ocean as for example the low productivity at their core and rising up of nutricline on their edges however the functioning and consequences of such coastal eddy on nutrients and plankton distributions are complicated by potential interactions with topography wind induced upwelling along the languedoc coast and nearby northern current nc especially the proximity of the southern edge of the eddy with the nc makes possible the exchanges of organic matter plankton at times during the eddy s life the coastal eddy thus transports organic matter from the coastal zone to the offshore domain the coupled model also suggests the importance of offshore to coastal transport by nc through a seeding process of the eddy in plankton at the beginning of its life a detailed biogeochemical functioning of the studied eddy all along its lifetime is proposed from the model results at the beginning the eddy mainly acts as a transporter of the plankton wind induced bloom occurring along the languedoc coast several days before the eddy set up at the same time the eddy shows upwards vertical velocities on its edges creating upwelling of nutrient enriched waters the process of eddy induced upwelling is notably enhanced on the eddy western side along the roussillon coast due to the shelf topography the around eddy advection and relative lower temperatures prevent the large development of phytoplankton along the roussillon coast and the eddy induced bloom is predicted to occur near the northwestern side of the eddy the eddy induced and wind induced blooms of phytoplankton then merge on the eastern side by advection and this process of aggregation may explain the persistent occurrence of a filament of high chlorophyll observed on the offshore edge of the eddy throughout the study period the changes in plankton composition due to a combination of top down and bottom up processes during the coast to offshore transport may explain the disappearance of the filament south of 43 n at the surface

global patterns of radiated seismic energy and apparent stress radiated energies from shallow earthquakes with magnitudes 5 8 that occurred between 1986 and 1991 are used to examine global patterns of energy release and apparent stress in contrast to traditional methods which have relied upon empirical formulas these energies are computed through direct spectral analysis of broadband seismic waveforms velocity squared spectra of body waves are integrated after they have been corrected for effects arising from depth phases frequency dependent attenuation and focal mechanism the least squares regression fit of energy es to surface wave magnitude ms for a global set of 397 earthquakes yields log es 4 4 1 5ms which implies that the gutenberg richter relationship overestimates the energies of earthquakes the least squares fit between es and seismic moment m0 is given by the relationship es 1 6 10 5 m0 which yields 0 47 mpa as the average global value of apparent stress however the regression lines of both es ms and es m0 yield poor empirical predictors for the actual energy radiated by any given earthquake the scatter of data is more than an order of magnitude about each of the regression lines on the other hand global variations between es and mo while large are not random when subsets of es m0 are plotted as a function of seismic region and faulting type the scatter in data is substantially reduced the es m0 fits for many seismic regions and tectonic environments are very distinctive and a characteristic apparent stress c can be derived the lowest apparent stresses 3 0 mpa are associated with strike slip earthquakes that occur at oceanic ridge ridge transforms and in intraplate environments seaward of island arcs intermediate values of apparent stress 1 5 a 3 0 mpa are associated with strike slip earthquakes at incipient or transitional plate boundaries in general the dominant mode of failure for a tectonic environment is associated with the faulting type that has the lowest apparent stress an energy magnitude me can complement moment magnitude mw in describing the size of an earthquake me being derived from velocity power spectra is a measure of seismic potential for damage mw being derived from the low frequency asymptote of displacement spectra is more physically related to the final static displacement of an earthquake when earthquake size is ranked by moment a list of the largest events is dominated by earthquakes with thrust mechanisms when earthquake size is ranked by energy the list of the largest events is dominated by strike slip earthquakes

on the mechanism of seismic decoupling and back arc spreading at subduction zones to address the problem of the great variability of the mechanical state of subduction zones we investigate the mechanics of back arc spreading and seismic decoupling back arc spreading is assumed to be due to rifting of the upper plate and hence occurs when trench normal tension reaches a critical value seismic decoupling is assumed to occur when the normal stress at the frictional interface is decreased by an amount sufficient to cross the friction stability transition two forces are important in this problem the first is a small component of the slab pull force which remains unbalanced by the subduction resistance and exerts a vertical suction force at the trench the second is a sea anchor force exerted on the slab that resists its lateral motion assumed to occur at the upper plate velocity both forces contribute to the coupling problem only the sea anchor force is responsible for back arc spreading the unbalanced slab pull force is determined from a force balance for subduction the sea anchor force is computed as the hydrodynamic resistance to the facewise translation of an elliptical disc through a viscous fluid the model predicts three regimes seismically coupled compressional arcs with advancing upper plates seismically decoupled extensional arcs with retreating upper plates and strongly extensional arcs which also have back arc spreading this model is applied in detail to the izu bonin marianas system it shows that back arc spreading occurs when the integrated tension in the upper plate exceeds a value of about 1 1013 n m 1 and requires a residual tension of about a third that to drive the back arc spreading once rifting is completed it shows why the plate interface near guam is seismically coupled while the plate boundary everywhere farther north is decoupled when applied globally it successfully predicts the state of seismic coupling and back arc spreading in more than 80 of the world s subduction zones of the remaining half can be seen to contain additional complications not included in the model about 10 of cases remain unexplained but some of these may have incorrectly determined seismic coupling coefficients

slab1 0 a three dimensional model of global subduction zone geometries 1 we describe and present a new model of global subduction zone geometries called slab1 0 an extension of previous efforts to constrain the two dimensional non planar geometry of subduction zones around the focus of large earthquakes slab1 0 describes the detailed non planar three dimensional geometry of approximately 85 of subduction zones worldwide while the model focuses on the detailed form of each slab from their trenches through the seismogenic zone where it combines data sets from active source and passive seismology it also continues to the limits of their seismic extent in the upper mid mantle providing a uniform approach to the definition of the entire seismically active slab geometry examples are shown for two well constrained global locations models for many other regions are available and can be freely downloaded in several formats from our new slab1 0 website http on doi gov d9arbs we describe improvements in our two dimensional geometry constraint inversion including the use of average active source seismic data profiles in the shallow trench regions where data are otherwise lacking derived from the interpolation between other active source seismic data along strike in the same subduction zone we include several analyses of the uncertainty and robustness of our three dimensional interpolation methods in addition we use the filtered subduction related earthquake data sets compiled to build slab1 0 in a reassessment of previous analyses of the deep limit of the thrust interface seismogenic zone for all subduction zones included in our global model thus far concluding that the width of these seismogenic zones is on average 30 larger than previous studies have suggested

global variations of stress drop for moderate to large earthquakes 1 we investigate the global variation of earthquake stress drops using spectra of about 2000 events of mb 5 5 between 1990 and 2007 we use an iterative least squares method to isolate source displacement spectra from travel path and receiver contributions based on a convolutional model the observed p wave source spectra are corrected with a globally averaged empirical correction spectrum and estimates of near source attenuation assuming a brune type source model we estimate corner frequencies and compute stress drops stress drop estimates for individual earthquakes range from about 0 3 to 50 mpa but the median stress drop of about 4 mpa does not vary with moment implying earthquake self similarity over the mw 5 2 to 8 3 range of our data a comparison of our results with previous studies confirms this observation over most of the instrumentally observable magnitude range while the absolute values of our estimated stress drops depend upon the assumed source model we identify relative regional variations of stress drop that are robust with respect to the processing parameters and modeling assumptions which includes an inherent assumption of constant rupture velocity we find a dependence of median stress drop on focal mechanism with a factor of 3 5 times higher stress drops for strike slip earthquakes and also find a factor of 2 times higher stress drops for intraplate earthquakes compared to interplate earthquakes

interplate seismogenic zones along the kuril japan trench inferred from gps data inversion stress accumulation between earthquakes results from slip that is insufficient to fully accommodate plate movement an inverse analysis of gps data from the kuril japan trench reveals a trench parallel belt of stress accumulation with six peaks in the depth range of 10 40 km suggesting potential source regions for future earthquakes in the subduction zones around japan where four plates interact with one another large earthquakes have occurred repeatedly1 these interplate earthquakes are part of the process of tectonic stress accumulation and release that is driven by relative plate motion2 3 4 stress accumulation between earthquakes results from slip deficit slip that is insufficient to fully accommodate plate movement for the prediction of large earthquakes it is therefore important to monitor the distribution of slip deficit on plate interfaces here we apply an inversion method based on bayesian modelling using direct and indirect prior information on the magnitude and distribution of fault slip5 to horizontal and vertical velocities from global positioning system data for the seismically calm period between 1996 and 2000 we obtain a precise distribution of slip deficit rates on the interface between the north american and pacific plates around japan which reveals a trench parallel belt of slip deficit with six peaks in the depth range of 10 40 km these peaks agree with the source regions of past large interplate earthquakes along the kuril japan trench we conclude that the slip deficit zones identified with our method are potential source regions of large earthquakes

interpretations of the jebar term abstract in diagnostic calculations of the ocean s circulation the so called jebar joint effect of baroclinicity and relief term may induce a significant depth average current field as has been noted in the oceanographic literature here we present two consistent interpretations of this term in the equation governing the vorticity of the depth averaged current a topographic vortex stretching term proportional to the dot product of depth averaged velocity and the depth gradient arises we show that jebar corrects this term by removing the contribution of the geostrophic flow referenced to the bottom which cannot generate topographic vortex stretching in the evolution equation for the vorticity of the depth integrated flow a bottom torque term is present we show that the jfbar term discussed above enters here as a contribution to the bottom torque emphasizing the role of jebar as a forcing term we also show that when a diagnostic calculation is formulated completely in terms of the transport str

the 1994 java tsunami earthquake slip over a subducting seamount on june 2 1994 a large subduction thrust earthquake ms 7 2 produced a devastating tsunami on the island of java this earthquake had a number of unusual characteristics it was the first recorded large thrust earthquake on the java subduction zone all of the aftershock mechanisms exhibit normal faulting no mechanisms are similar to the main shock also the large tsunami and the relatively low energy radiated by the main shock have led to suggestions that this earthquake might have involved slow shallow rupture near the trench similar to the 1992 nicaragua earthquake we first relocate the main shock and the aftershocks we then invert long period surface waves and broadband body waves to determine the depth and spatial distribution of the main shock slip a dip of 12 hypocenter depth of 16 km and moment of 3 5 l020 n m mw 7 6 give the best fit to the combined seismic data and are consistent with the plate interface geometry the source spectrum obtained from both body and surface waves has a single corner frequency between 10 and 20 mhz implying a stress drop of 0 3 mpa the main energy release was preceded by a small subevent lasting 12 s the main slip occurred at 20 km depth downdip and to the nw of the hypocenter this area of slip is collocated with a prominent high in the bathymetry that has been identified as a subducting seamount we interpret the java earthquake as slip over this subducting seamount which is a locked patch in an otherwise decoupled subduction zone we find no evidence for slow shallow rupture no thrust aftershocks are expected if the entire locked zone slipped during the main shock but extension of the subducting plate behind the seamount would promote normal faulting as observed it seems probable that such a source model could also explain the size and timing of the observed tsunami

along strike variability of rupture duration in subduction zone earthquakes 1 subduction zone earthquakes exhibit a wide spectrum of rupture times that reflect conditions on the megathrust fault tsunami earthquakes are examples of slower than expected ruptures that produce anomalously large tsunamis relative to the surface wave magnitude one model explaining tsunami earthquakes suggests slip within patches of low rigidity material at shallow depths heterogeneous fault conditions such as having patches of low rigidity material surrounded by higher strength material should produce heterogeneous earthquake rupture parameters here we investigate along strike variation in rupture duration for 427 shallow thrust earthquakes mw 5 0 7 0 in the peru chile alaska tonga kuril izu and java sumatra subduction zones to explore how heterogeneous seismic and tectonic characteristics such as differences in sediment type thickness and roughness of subducting bathymetry affect earthquake properties earthquake source parameters including rupture durations are estimated using multi station deconvolution of teleseismic p and sh waves to solve for earthquake source time functions and all events are relocated using additional depth phase information we classify events into shallow 26 km and deep 26 km and 61 km groups based on the overall mean depth and focus on the longest duration events with moment normalized rupture durations of 1 standard deviation above the mean duration for each group we find long duration events at all depths within the study regions except peru and chile we find no correlation with incoming sediment thickness or type and limited spatial correlation with regions of past tsunami earthquakes regions of observed afterslip and subducting bathymetric features

suspended sediment fluxes and transport processes in the gulf of lions submarine canyons the role of storms and dense water cascading contemporary suspended sediment transport was studied in seven submarine canyons of the gulf of lions gol current meters equipped with turbidity sensors were moored 4 m above bottom at 300 m depth in the canyon axis from november 2003 to may 2004 sediment transport events were monitored and studied in relation to forcing conditions there was a large flood in early december during which discharges from all of the coastal rivers increased by more than one order of magnitude a smaller flood of the rhone river occurred later in mid january followed by a persistent high river discharge that lasted until mid february there were also several e se storm events during the measurement period two of them causing large swell one in early december max hs 8 4 m coinciding with the major river flood andoneinlatefebruary maxhs 7m duringaperiodoflowerriverdischarge mostofthevariabilityindown canyoncurrentspeeds waslinkedtostrongdownwellinginducedbye sestormsandtocascadingofdenseshelfwaterinducedbynandnwwinds theintensity and timing of these processes strongly varied spatially eastern storms generated higher waves and induced stronger downwelling in the western than in the eastern sector of the gol shelf dense water cascading events were enhanced during eastern storms and they were also more intense in the western sector of the gol these events occurred frequently from january to may along the western canyons and from february to april along the eastern canyons from february to april they occurred simultaneously in all the canyons sediment transport was mainly down canyon and mostly concentrated during storm induced downwelling and dense water cascading events during the high river discharge season most of the newly supplied and resuspended sediment remained stored on theshelf however duringthelatefebruarystormandcascadingevent thestoredsedimentwasquicklyresuspendedandtransported mainly through the westernmost submarine canyon cap de creus following a flushing pattern later although minor storms and shelfdensewatercascadinghardlyincreasedsuspendedsedimentconcentrationswithinthecanyons theyinducedstrongnear bottom current velocities increasing down canyon sediment fluxes and generating small but significant sediment transport events most of the shelf canyon transfer took place during the late february storm and cascading event through the cap de creus canyon where the net suspended sediment flux was between one and two orders of magnitude higher than in the other canyons

sea surface transport in the western mediterranean sea a lagrangian perspective 2 we study the sea surface transport in the western mediterranean sea from a lagrangian point of view in particular the alboran and the north western subbasins the study is carried out through the analysis of 3 years of surface velocity model data through finite size lyapunov exponents residence time and virtual particle trajectories complementing the classical eulerian approach the spatiotemporal variability of the main transport processes is inferred from the empirical orthogonal function modes of the lyapunov exponents being the most relevant modes discussed and physically interpreted results indicate that some of the variability in the surface transport patterns in the western mediterranean can be explained by specific modes which provide an indication of connectivity among subbasins like the inflow of atlantic waters through the ibiza channel

the 17 july 2006 java tsunami earthquake the 17 july 2006 java earthquake involved thrust faulting in the java trench and excited a deadly tsunami 5 8 m that inundated the southern coast of java the earthquake s size estimates vary significantly with seismic wave period very long period signals 300 500 s indicate a seismic moment of 6 7 10 20 nm m w 7 8 m s 20 s 7 2 m b 1 s 6 2 while shaking intensities 3 10 hz were mmiv the large tsunami relative to ms characterizes this event as a tsunami earthquake like previous tsunami earthquakes the java event had an unusually low rupture speed of 1 0 1 5 km s and occurred near the up dip edge of the subduction zone thrust fault most large aftershocks involved normal faulting the rupture propagated 200 km along the trench with several pulses of shorter period seismic radiation superimposed on a smooth background rupture with an overall duration of 185 s

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

can observations of earthquake scaling constrain slip weakening summary we use observations of earthquake source parameters over a wide magnitude range m w 0 7 to place constraints on constitutive fault weakening the data suggest a scale dependence of apparent stress and stress drop both may increase slightly with earthquake size we show that this scale dependence need not imply any difference in fault zone properties for different sized earthquakes we select 30 earthquakes well recorded at 2 5 km depth at cajon pass california we use individual and empirical green s function spectral analysis to improve the resolution of source parameters including static stress drop and total slip s we also measure radiated energy e s w ecompare the cajon pass results with those from larger california earthquakes including aftershocks of the 1994 northridge earthquake and confirm the results of abercrombie 1995 e s m 0 where rigidity and both e s m 0 and increase as m 0 and s increases uncertainties remain large due to model assumptions and variations between possible models and earthquake scale independence is possible within the resolution assuming that the average trends are real we define a quantity g 2 es m 0 s 2w hich is the total energy dissipation in friction and fracture minus 1 s w here 1 is the final static stress if 1 d the dynamic shear strength during the last increments of seismic slip then g g the fracture energy in a slip weakening interpretation of dissipation

monte carlo slip inversion in the frequency domain application to the 1992 nicaragua slow earthquake the spatio temporal complexity of moment release of the 1992 nicaragua slow earthquake mw 7 7 is estimated by simulated annealing contrary to linearized inversions monte carlo techniques do not make assumptions about a priori features of the model in particular large variations in rupture velocities can be imaged relative spectra between the main shock and an empirical green s function were obtained from 4 44 mhz using first and second orbit fundamental mode rayleigh waves the spectra were inverted for the moment distribution on a 2d horizontal fault under the physical constraints of slip positivity and causality the non linear inversion revealed two main regions of slip one centered 20 km to the nw of the epicenter the other 160 km to the se but delayed by 70 s rupture velocities in the slipping patches were found to be low around 1 km s large amount of slip occurred trench ward of the epicenter accounting for the large tsunami excitation analysis of the slip distribution suggests that the slow and smooth nature of the 1992 nicaragua event may be related to the frictional properties at the plate interface

numerical high resolution air sea coupling over the gulf of lions during two tramontane mistral events 1 the near sea surface meteorological conditions associated with strong wind events over the mediterranean sea constitute a strong forcing on the ocean mixed layer the present study addresses the question of the sea surface scheme used in high resolution and short range atmospheric numerical modeling to represent the ocean mixed layer response under these severe mistral wind events in the gulf of lions area several slab ocean models have been used coupled with the weather research and forecasting wrf model and applied on two mistral cases 1 a slab model based on the transport divergence equation where the mixed layer evolution is only driven by the wind stress 2 a slab model where the temperature is the only prognostic variable and evolves according to the net surface heat flux and 3 a complete slab scheme from price 1981 the coupled simulations are also compared to two basic simulations one using a constant sea surface temperature sst field during all of the model integration and another using a 6 hourly update sea surface temperature reanalysis in this study we mainly focus on the slab model performances we identify the processes involved in the ocean mixed layer response under strong wind situations i e local and fast cooling and deepening the feedbacks of an interactive ocean mixed layer on the atmospheric simulation are also investigated

the fate of river organic carbon in coastal areas a study in the rhone river delta using multiple isotopic delta c 13 delta c 14 and organic tracers a significant fraction of the global carbon flux to the ocean occurs in river dominated ocean margins riomar although large uncertainties remain in the cycle of organic matter om in these syste

observation and modeling of the winter coastal oceanic circulation in the gulf of lion under wind conditions influenced by the continental orography fetch experiment 1 hydrological and currentmeter observations were collected on the continental shelf and slope of the gulf of lion during the fetch experiment 13 march to 15 april 1998 results from the first part of the cruise characterized by strong northern winds are presented the hydrological structures evidence well mixed water masses on the eastern and western ends of the shelf in the central part the situation is more complex with the influence of the rhone river s freshwater plume in the first 40 m of the water column and closer from the bottom with the confrontation of downwelled coastal cold water and upwelled warmer and saltier slope water current measurements show the path of the cyclonic circulation along the slope which is part of the general circulation of the western mediterranean and suggest the presence of large and temporary eddies on the shelf this oceanic circulation is simulated with a free surface three dimensional model using realistic forcing the model outputs are in agreement with the main hydrological and circulation patterns the results further indicate that coastal eddies are generated by the mesoscale structure of the wind field

scardec a new technique for the rapid determination of seismic moment magnitude focal mechanism and source time functions for large earthquakes using body wave deconvolution accurate and fast magnitude determination for large shallow earthquakes is of key importance for post seismic response and tsumami alert purposes when no local real time data are available which is today the case for most subduction earthquakes the first information comes from teleseismic body waves standard body wave methods give accurate magnitudes for earthquakes up to mw 7 7 5 for larger earthquakes the analysis is more complex because of the non validity of the point source approximation and of the interaction between direct and surface reflected phases the latter effect acts as a strong high pass filter which complicates the magnitude determination we here propose an automated deconvolutive approach which does not impose any simplifying assumptions about the rupture process thus being well adapted to large earthquakes we first determine the source duration based on the length of the high frequency 1 3 hz signal content the deconvolution of synthetic double couple point source signals depending on the four earthquake parameters strike dip rake and depth from the windowed real data body wave signals including p pcp pp sh and scs waves gives the apparent source time function stf we search the optimal combination of these four parameters that respects the physical features of any stf causality positivity and stability of the seismic moment at all stations once this combination is retrieved the integration of the stfs gives directly the moment magnitude we apply this new approach referred as the scardec method to most of the major subduction earthquakes in the period 1990 2010 magnitude differences between the global centroid moment tensor cmt and the scardec method may reach 0 2 but values are found consistent if we take into account that the global cmt solutions for large shallow earthquakes suffer from a known trade off between dip and seismic moment we show by modelling long period surface waves of these events that the source parameters retrieved using the scardec method explain the observed surface waves as well as the global cmt parameters thus confirming the existing trade off for some well instrumented earthquakes our results are also supported by independent studies based on local geodetic or strong motion data this study is mainly focused on moment determination however the scardec method also informs us about the focal mechanism and source depth and can be a starting point to study systematically the complexity of the stf

interpretation of the 1993 2001 and 2002 guam earthquakes as intraslab events by a simultaneous relocation of the mainshocks aftershocks and background earthquakes it has been unclear whether the 1993 2001 and 2002 guam earthquakes m w 7 8 7 0 and 7 1 respectively in the southern mariana subduction zone were interplate events or intraplate ones within the pacific slab we relocated their mainshocks aftershocks and numerous long term background earthquakes simultaneously with high relative accuracy using the modified joint hypocenter determination mjhd method as a result their mainshocks and three day aftershocks are clearly distributed within the background slab seismicity therefore we conclude that the 1993 2001 and 2002 guam earthquakes were not interplate events which scarcely occur in the mariana subduction zone but intraslab earthquakes within the subducted pacific plate the 1993 fault plane is inferred to be the near horizontal nodal plane of the mechanism solution though the 2001 and 2002 fault planes remain unknown the relocation of target events simultaneously with background earthquakes has turned out very effective for discriminating between large interplate and intraslab earthquakes in subduction zones

the 2010 mw 7 8 mentawai earthquake very shallow source of a rare tsunami earthquake determined from tsunami field survey and near field gps data 1 the mw 7 8 october 2010mentawai indonesia earthquake was a tsunami earthquake a rare type of earthquake that generates a tsunami much larger than expected based on the seismicmagnitude itproducedalocallydevastatingtsunami withrunupcommonlyinexcess of 6 m we examine this event using a combination of high rate gps data from instruments located on the nearby islands and a tsunami field survey the gps displacement time series are deficient in high frequency energy and show small coseismic displacements 16 m our modeling results show that the combination of the small gps displacements and large tsunami can only be explained by high fault slip at very shallow depths far from the islands and close to the oceanic trench inelastic uplift of trench sediments likely contributed to the size of the tsunami recent results for the 2011 mw 9 0 tohoko oki earthquake have also shown shallow fault slip but the results from our study which involves a smaller earthquake provide much stronger constraints on how shallow the rupture can be with the majority of slip for the mentawai earthquake occurring at depths of 6 km this result challenges the conventional wisdom that the shallow tips of subduction megathrusts are aseismic and therefore raises important questions both about the mechanical properties of the shallow fault zone and the potential seismic and tsunami hazard of this shallow region

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

gps derived coupling estimates for the central america subduction zone and volcanic arc faults el salvador honduras and nicaragua summary we invert gps velocities from 32 sites in el salvador honduras and nicaragua to estimate the rate of long term forearc motion and distributions of interseismic coupling across the middle america subduction zone offshore from these countries and faults in the salvadoran and nicaraguan volcanic arcs a 3 d finite element model is used to approximate the geometries of the subduction interface and strike slip faults in the volcanic arc and determine the elastic response to coupling across these faults the gps velocities are best fit by a model in which the forearc moves 14 16 mm yr 1 and has coupling of 85 100 per cent across faults in the volcanic arc in agreement with the high level of historic and recent earthquake activity in the volcanic arc our velocity inversion indicates that coupling across the potentially seismogenic areas of the subduction interface is remarkably weak averaging no more than 3 per cent of the plate convergence rate and with only two poorly resolved patches where coupling might be higher along the 550 km long segment we modelled our geodetic evidence for weak subduction coupling disagrees with a seismically derived coupling estimate of 60 10 per cent from a published analysis of earthquake damage back to 1690 but agrees with three other seismologic studies that infer weak subduction coupling from 20th century earthquakes most large historical earthquakes offshore from el salvador and western nicaragua may therefore have been intraslab normal faulting events similar to the m w 7 3 1982 and m w 7 7 2001 earthquakes offshore from el salvador alternatively the degree of coupling might vary with time the evidence for weak coupling indirectly supports a recently published hypothesis that much of the middle american forearc is escaping to the west or northwest away from the cocos ridge collision zone in costa rica such a hypothesis is particularly attractive for el salvador where there is little or no convergence obliquity to drive the observed trench parallel forearc motion

a numerical study of the effects of coastline geometry on wind induced upwelling in the gulf of lions an attempt is made to explain the fixed locations of coastal upwelling centers in the gulf of lions as a function of the coastline geometry alone the semi implicit numerical model based on two layer shallow water equations uses a spatial discretization with triangular finite elements vertical mixing is shown to play an important role in determining the final shape of the upwelling centers it is conjectured that an observed upwelling filament results from the straining and stretching of a coastal upwelling center by the observed anticyclonic circulation farther offshore

observing global ocean topostrophy 1 recent publications have evaluated topostrophy f v d where is f coriolis v is velocity and d is gradient of total depth as a means of comparing models circulations some results are striking comparing four global models two with modest grid size and two with fine grids merryfield and scott 2007 show that finer grid models are characterized by more positive especially at greater depths and higher latitudes among nine arctic ocean models holloway et al 2007 find in three of the models quite distinct from the other six a result shown to depend upon subgrid eddy parameterization from different choices of numerical method within the same model penduff et al 2007 show that improved numerical representations support more positive can these model results be compared with observations a global compilation has been prepared from 17120 current meter records spanning 83087 current meter months the compilation tends to confirm modeling progress achieved by finer resolution improved parameterizations and better representations a new characterization of global ocean circulation emerges with suggestive dynamical insights

tsunami hazard posed to new zealand by the kermadec and southern new hebrides subduction margins an assessment based on plate boundary kinematics interseismic coupling and historical seismicity we assess the tsunami hazard posed to new zealand by the kermadec and southern new hebrides subduction margins neither of these subduction zones has produced tsunami large enough to cause significant damage in new zealand over the past 150 years of well recorded history however as this time frame is short compared to the recurrence interval for major tsunamigenic earthquakes on many of the earth s subduction zones it should not be assumed that what has been observed so far is representative of the long term for each of these two subduction zones we present plate kinematic and fault locking results from block modelling of earthquake slip vector data and gps velocities the results are used to estimate the current rates of strain accumulation on the plate interfaces where large tsunamigenic earthquakes typically occur we also review data on the larger historical earthquakes that have occurred on these margins as well as the global cmt catalogue of events since 1976 using this information we have developed a set of scenarios for large earthquakes which have been used as initial conditions for the comcot tsunami code to estimate the subsequent tsunami propagation in the southwest pacific and from these the potential impact on new zealand has been evaluated our results demonstrate that there is a significant threat posed to the northland and coromandel regions of new zealand should a large earthquake m w 8 5 occur on the southern or middle regions of the kermadec trench and that a similarly large earthquake on the southern new hebrides trench has the potential to strongly impact on the far northern parts of new zealand close to the southern end of the submarine three kings ridge we propose logic trees for the magnitude frequency parameters of large earthquakes originating on each trench which are intended to form the basis for future probabilistic studies

evidence for non constant energy moment scaling from coda derived source spectra 1 we present two lines of evidence showing the ratio of seismically radiated energy er to seismic moment mo increases with increasing moment for crustal events spanning 5 orders in seismic moment this ratio often referred to as the scaled energy er m0 has been elusive and the subject of recent debate within the seismological community because significant frequency dependent corrections must be made to account for source and path heterogeneity it is not uncommon that energy estimates of the same event by different researchers have significantly different values to minimize some of the potential problems we used the regional coda methodology outlined by mayeda et al 2003 on 4 large earthquake sequences mw 7 4 and 7 2 izmit duzce mw 7 2 gulf of aqaba mw 7 3 landers and mw 7 2 hector mine this methodology has been shown to provide the lowest variance estimate of the source spectrum when compared against traditional direct wave estimates in our first approach we made energy estimates from coda derived spectra and observed that increases with increasing moment for 3 7 mw 7 4 in our second approach we used the simple idea outlined by prieto et al 2004 to directly test for self similarity under self similarity earthquake source spectra scaled by 3 should have the same shape to test this one needs very stable spectra either through spectral stacking of direct wave spectra or by the use of stable coda derived spectra for all sequences we found that the mainshocks and larger aftershocks had significantly different spectral shapes than the smaller events the scaled 3 spectra of the larger events represented an upper bound having larger amplitudes near the corner frequency in fact an 3 5 scaling moved the larger events closer to the mean of the spectral population though the spectral shape differences persisted these results strongly suggest that earthquakes are not scaling self similarly and that complexities in the rupture process such as variable slip velocity exist between small and large events

the fetch experiment an overview the flux etat de la mer et teledetection en conditions de fetch variable fetch was aimed at studying the physical processes associated with air sea exchanges and mesoscale oceanic circulation in a coastal region dominated by frequent strong offshore winds the experiment took place in march april 1998 in the northwestern mediterranean sea gulf of lion observations were collected with the r v l atalante with an air sea interaction spar asis buoy with waverider buoys and with research aircraft equipped for in situ and remote sensing measurements the present paper is an introduction to the following special section which groups 12 papers including this one presenting results on turbulent flux measurements at the ocean surface on the behavior of the marine atmospheric boundary layer on the ocean waves characteristics on the ocean circulation and on remote sensing of surface parameters this overview presents the background and objectives of fetch the experimental setup and operations and the dominant atmospheric and oceanic conditions and introduces the different papers of the special section

influence of depth focal mechanism and tectonic setting on the shape and duration of earthquake source time functions source time functions of 255 moderate to great earthquakes obtained from inversions of teleseismic body waves by tanioka and ruff 1997 and coworkers were compared in a systematic way they were scaled to remove the effect of moment and to allow the direct comparison and averaging of time function shape as well as duration time function durations picked by tanioka and ruff 1997 are proportional to the cube root of seismic moment if moments from the harvard centroid moment tensor catalog are used the average duration of scaled time functions is shorter and the average shape has a more abrupt termination for deeper events than shallower ones with a distinct change occurring at 40 km depth the complexity of the time functions as quantified by the number of subevents appears to decrease below 40 km depth furthermore among events shallower than 40 km the average duration of scaled time functions is shorter and their average shape has a more abrupt termination 1 for events with strike slip focal mechanisms compared to thrust events and 2 for the few thrust events associated with an intraplate setting compared to the majority associated with an interplate subduction boundary in each of these cases events in more technically and seismically active settings have a longer duration and a more gradual termination this can be interpreted in terms of lower stress drops and or slower rupture velocities at active plate boundaries suggesting that fault rheology depends on slip rate and may evolve as total fault slip accumulates furthermore differences in average time function shape and duration associated with different subduction zones suggest that differences exist in the rheology on the plate boundaries at the various subduction zones supporting data table is available via web browser or via anonymous ftp from ftp kosmos agu org directory append username anonymous password guest subdirectories in the ftp site are arranged by paper number information on seraching and submitting electronic supplements is found at http www agu org pubs esupp about html