heat flux estimates for the western north atlantic part ii the upper ocean heat balance abstract the assimilation of temperature and altimetric velocity into a numerical model of the upper ocean mixed layer in part i allowed an analysis of the upper ocean heat budget for the western north atlantic ocean over the 2 5 year period of the geosat exact repeat mission november 1986 april 1989 the balance of terms varied regionally south of the gulf stream advection was relatively unimportant in the heat budget and the ocean responded passively to changes in surface flux within the gulf stream and to the north of it cooling of the upper ocean by advection was as large as 0 15 c day for periods of several weeks an analysis of the advection term showed that cooling by ekman transport was opposed by warming from the geostrophic currents of the gulf stream with cooling typically stronger by a factor of 2 because nonuniform ekman transport disrupted the normal alignment between isotherms and sea surface height contours there is a complex ocean atmosphere coupling in this region in addition to

the meandering gulf stream as seen by the geosat altimeter surface transport position and velocity variance from 73 to 46 w the surface geostrophic velocity field for the gulf stream region was analyzed for the position structure and surface transport of the gulf stream for 2 5 years of the geosat altimeter exact repeat mission synthetic data using a gaussian velocity profile were generated and fit to the sea surface residual heights to create a synthetic mean sea surface height field and profiles of absolute geostrophic currents most of cross track velocity variance was due to the meandering of the gulf stream rather than to rings or complicated velocity profiles which suggested that the simple model parameters are an efficient description of the gulf stream fluctuations an analysis of the model parameters and the actual geostrophic velocity profiles revealed two different flow regimes for the gulf stream connected by a narrow transition region coincident with the new england seamount chain the upstream region was characterized by relatively straight gulf stream paths long eulerian time scales and eastward propagating meanders the downstream region had more large meanders no consistent propagation direction and shorter eulerian time scales a 25 reduction in surface transport occurred in the transition region with a corresponding reduction in current speed and no change in gulf stream width a significant anomaly in surface transport near 69 w suggested the existence of small scale recirculation gyres there the highest variance empirical orthogonal functions of position and surface transport were significantly correlated with larger surface transports leading more northerly positions by a month

a limited area model of the gulf stream design initial experiments and model data intercomparison abstract a primitive equation n layer eddy resolving creation model has been applied to the gulf stream system from cape hatteras to cast of the grand banks 78 45 w 30 48 n within the limitations of the model realistic coastlines bottom topography and forcing functions have been used a two layer version of the model was driven by observed mean climatological wind forcing and mass transport prescribed at inflow outflow was determined by a radiation boundary condition and an integral constraint on the mass field in each layer specification of a deep western boundary current dwbc was included in some model runs six numerical experiments from a series of over fifty integrated to statistical equilibrium were selected for detailed description and intercomparison with observations the basic case consisted of a flat bottom regime driven by wind forcing only realistic inflow transport in the upper layer was then prescribed and two different outflow specifications at the eastern boundary were s

mean flow and variability in the kuroshio extension from geosat altimetry data using altimeter data from the geosat exact repeat mission erm we investigated the mean flow and temporal and spatial variations of the kuroshio extension in the region of 140 180 e and 30 40 n mean surface height profiles were estimated along individual tracks by assuming the velocity profile of the kuroshio extension to be gaussian shaped and by successively fitting this synthetic current s height profile to the residual height data using the mean profiles from ascending and descending tracks we derived the mean surface height field by an inverse method and obtained the absolute surface height fields for the first 2 5 years of the geosat erm both the mean and the instantaneous height fields thus derived compared well with the available hydrographic data and the sst patterns from the noaa satellites the mean surface height difference across the kuroshio extension attains its maximum around 146 e between the two quasi stationary meanders and its decrease thereafter is mainly due to large scale recirculations on the southern side of the kuroshio extension the ratio of the eddy kinetic energy over the mean kinetic energy has a nearly constant value of 1 5 2 0 along the kuroshio extension path propagation of mesoscale fluctuations in the height fields is generally westward except for the upstream region of the kuroshio extension effects of deep mean flow and baroclinic shear are found to be important in explaining the observed propagation speeds in the upstream region of 141 e and 154 e annual variations in the surface height difference across the kuroshio extension h have a september maximum with an average amplitude of 0 2m for large scale interannual fluctuations anomalies in h are found to be significantly correlated with those of the current axis positions a larger surface height difference corresponds to a more northerly position of the kuroshio extension the interannual changes in h are possibly related to the 86 87 enso event in the low latitude pacific ocean

on the role of heat flux in the gulf stream sargasso sea subtropical gyre system abstract in contrast with the traditional view of midlatitude circulation driven by winds in the ocean interior and regulated by friction along the western boundary it is hypothesized that some control can be attributed to surface cooling acting primarily in a recirculation region off the western boundary current several arguments suggests that this mechanism and the generation of eddies are the two major reactions of the midlatitude ocean under the action of the surface winds the theory is best described by tracing the journey of a water parcel around the subtropical gyre in the interior the anticyclonic wind stress pattern acts to decrease the parcel s potential vorticity pv in reaction the parcel first migrates south where the planetary vorticity is less then veers westward and participates in a western boundary jet where the relative vorticity is less instead of calling upon friction within the jet it is not difficult to conceive that pv restoration can be achieved by diabatic processes

interannual variability of the altimetry derived eddy field and surface circulation in the extratropical north atlantic ocean in 1993 2001 abstract the distribution of surface eddy kinetic energy eke depicts main oceanic surface circulation features the interannual variability of eke and associated geostrophic velocity anomalies in the north atlantic ocean were analyzed to describe the variations in oceanic currents between 1993 and 2002 the sea level anomaly maps of the combined topex poseidon ers 1 2 and topex poseidon alone satellite altimetry data were used to derive eke the study focused on the areas of the gulf stream extension gs north atlantic current nac azores current ac and the northeastern rockall channel and iceland basin and northwestern irminger basin and labrador sea north atlantic the interannual variability of the altimetry derived eke field in the gs extension area reflected the meridional displacements of the gs core described in earlier studies the interannual change of eke in the ac was characterized by high values in 1993 95 followed by lower eke in subsequent years the interannual variability of

surface climate variations over the north atlantic ocean during winter 1900 1989 abstract the low frequency variability of the surface climate over the north atlantic during winter is described using 90 years of weather observations from the comprehensive ocean atmosphere data set results are based on empirical orthogonal function analysis of four components of the climate system sea surface temperature sst air temperature wind and sea level pressure an important mode of variability of the wintertime surface climate over the north atlantic during this century is characterized by a dipole pattern in ssts and surface air temperatures with anomalies of one sign cast of newfoundland and anomalies of the opposite polarity off the southeast coast of the united states wind fluctuations occur locally over the regions of large surface temperature anomalies with stronger than normal winds overlying cooler than normal ssts this mode exhibits variability on quasi decadal and biennial time scales the decadal fluctuations are irregular in length averaging 9 years before 1945 and 1

contributions of wind forcing waves and surface heating to sea surface height observations in the pacific ocean the dominant processes affecting sea surface height ssh variability observed by the topex poseidon altimeter vary regionally in the pacific baroclinic rossby waves equatorially trapped kelvin waves steric response to seasonal heating and the response to wind stress curl forcing are all important the steric response to surface heating dominates seasonal ssh variability in the subpolar gyre and the eastern subtropical gyre south of the kuroshio extension and south of 20 n in the eastern pacific the dominant contribution to ssh is from near annual period rossby waves to quantify the wave energy observed ssh was assimilated into a kinematic model of westward propagating waves these waves account for 70 of ssh variance between 10 s and 10 n but only 30 between 10 n and 30 n although wave energy in the eastern pacific is correlated with ssh anomalies at the equator the much larger wave energy in the western pacific is correlated with wind stress curl suggesting that the rossby waves there are locally forced in addition to these planetary waves the ocean response to wind forcing via ekman pumping is observed in several places specifically in the north equatorial current a quasi steady topographic sverdrup balance is detectable over most of the north pacific at latitudes as low as 10 15 n as well as in the south pacific where it is seen north of 50 s the decomposition of the ssh signal into propagating waves an ekman pumping response and sverdrup transport is consistent with the results from an isopycnal numerical model

observations of atmosphere ocean coupling in midlatitude western boundary currents oceanographic fields derived from the geosat altimeter and atmospheric fields from the european centre for medium range weather forecasts ecmwf were examined for both the western north pacific ocean and the western north atlantic ocean to determine the nature of the coupling despite the short data records approximately 2 5 years correlation analyses of nonseasonal fluctuations showed similar relationships for both oceans correlations between the height difference across the jets surface transport and the path of the western boundary currents suggested that there is a structural change of the recirculation gyres associated with a path change with timescales of 5 9 months both wind stress and wind stress curl were clearly correlated with the surface transport and path in each ocean although net surface heat flux and wind stress were correlated there was no clear correlation between net surface heat flux from ecmwf and surface transport over the entire study region additional regional analyses of the north atlantic showed a consistent relationship between cooling sea surface temperature sst and surface transport west of 62 w anomalous cooling accompanied by cyclonic wind anomalies corresponds to a weaker sst gradient across the gulf stream and decreasing surface transport because the surface transport fluctuations to the west and east of 62 w in the western north atlantic are not correlated structural changes in the recirculation gyres which have their maximum variations east of 62 w may not be related to surface heat flux variations

a deep reflection seismic line across the northern rhine graben abstract two reflection seismic lines across the tertiary rhine graben in central europe were recorded in 1988 as a joint venture of the french ecors and the german dekorp deep seismic reflection programs in this paper the line across the northern graben is presented the main results are the asymmetry of the graben as documented by the sedimentary fill is accompanied by asymmetric features throughout the entire deep crystalline crust a thin 3 7 s twt reflective lower crust in the east a thick 5 5 s twt relatively transparent lower crust in the west total crustal thicknesses of 8 7 s twt in the east vs 10 5 s twt in the west provided a laterally homogeneous crust existed prior to rifting significant differences in upper and lower crustal thinning must be postulated extension occurred along localized shear zones that are located in the upper crust and at the crust mantle boundary the entire lower crustal layer acts as a decoupling zone

the jura mountains an active foreland fold and thrust belt abstract recently completed in situ stress measurements using the borehole slotter at 33 new test sites within the swiss and french jura mountains combined with previously published stress data allow a detailed description of the contemporary state of stress in this fold and thrust belt and the adjacent foreland five stress provinces can be recognized with two different general orientations of maximum horizontal stress sh 1 the central and southwest provinces with a nnw sse to nne ssw orientation 2 the east northwest and southeast provinces with an e w to nw se orientation stress magnitudes are in general higher in the southern than in the northern jura mountains characteristic of the northern jura is an e w trending zone of low stress magnitudes which can be traced from the bresse depression south of besancon to the eastern end of the jura northwest of zurich boundaries of stress provinces show poor agreement with boundaries of tectonic units in the jura in addition stress provinces extend beyond the boundaries of the jura mountains into their foreland furthermore palaeo stress orientations show large discrepancies with respect to the contemporary stress orientation these findings are considered to indicate a termination of jura thin skinned foreland tectonics which probably took place some time between 9 and 4 ma according to palaeontological and tectonic evidence it is suggested that a new style of tectonics has commenced in the jura mountains deforming both the basement directly below the jura fold and thrust belt and the cover rocks in a similar mode

large scale response of the ocean to atmospheric forcing at low frequencies estimates of the time dependent sea surface topography on large space 500 2500 km and time 30 days to 2 years scales from altimetry and tide gauge data are compared with estimates of the surface meteorological fields winds and pressure on the same scales the comparisons are made in the north pacific and north atlantic despite the obvious remaining high noise level in the sea surface topography there is a significant correlation between the atmosphere and the time varying ocean circulation these relations are quantified using simple multichannel regression models with no time lags typically 50 of the sea level variance can be described by the wind curl and divergence and the pressure field some areas produce classical static inverted barometer effects but others suggest an amplified response the motions are believed to characterize most of the water column

multiple equilibria and low frequency variability of the wind driven ocean circulation abstract the link between low frequency time dependent variability and the existence of multiple unstable steady state solutions in a reduced gravity quasigeostrophic ocean model for the midlatitude wind driven circulation is investigated it is shown that a sequence of successive symmetry breaking pitchfork bifurcations lead to multiple equilibria that differ from each other primarily in the elongation of the recirculation cell in the amount of meandering present in the intergyre jet and in a north south shift in the eastward jet the elongation of the recirculation cells and the meandering of the jet play compensating roles in the establishment of the global energy and vorticity balance the solutions also have distinct energy levels but general agreement between them and the bumps in a histogram of the total energy obtained from a 1200 yr time dependent simulation is not found nevertheless a substantial fraction of the variance 30 can be accounted for by four coherent structures that capture th

remote and local forcing in the brazil malvinas region origins of the seasonal variability observed in current meter data from the malvinas falkland current are sought in the wind field on both a regional and circumpolar scale a singular value decomposition of the covariance of the fields makes it possible to distinguish between a local and a remote source of variability the local mode is the result of changes in the wind stress curl around 408s causing an annual modulation transverse to the mean path of the current and thus contributes little to the variability in transport it seems likely that the wind stress curl drives the annual excursions of the brazil malvinas front and forces the retroflection of the malvinas current the remote mode features increased transport trailing negative wind stress curl anomalies at drake passage with a lag of 20 30 days repeating this analysis with the winds on a circumpolar domain suggests that this might be the regional manifestation of a more global feature associating globally negative wind stress curl anomalies north of 608s with increased transport this analysis also shows that the malvinas current transport is anticorrelated with the zonal wind stress hence with the antarctic circumpolar current although initially counterintuitive this is confirmed through coherence analyses with bottom pressure measurements at the south of drake passage these results are further assessed using a 5 yr series of transport in the malvinas current derived from topex poseidon altimeter data which is compared with the circumpolar averages of both zonal wind stress and wind stress curl coherences are largest with the wind stress curl at latitudes north of drake passage up to the subtropics and also indicate that it is most influential in the pacific sector it is suggested that the antarctic circumpolar current and the malvinas current respond differently to the wind forcing and that these two modes cohabit at drake passage while the barotropic variations of the former have been shown to respond to the zonally averaged wind stress the fluctuations of the latter at timescales of 100 200 days are more sverdrupian that is sensitive to the wind stress curl lag 20 days explaining why they fluctuate with opposite phase superimposed on this intraseasonal variability at shorter periods 70 days results from baroclinic shelf waves trapped along the edge of the patagonian plateau these propagate from drake passage and may originate from equatorial kelvin waves in the pacific

seismicity wedge beneath the upper rhine graben due to backwards alpine push abstract the distribution of hypocentres in the upper rhine graben area is re examined and discussed with respect to the present day tectonic framework most earthquakes occur within a n60 striking wedge located on top of a moho dome this wedge is limited by the surface and at depth by a plane which in the south of the dome coincides with the se dipping conrad discontinuity in depth the seismicity shows a normal distribution the maximums of which are located on a surface dipping 6 towards se parallel to the south eastward dipping conrad and moho this surface outcrops along the north western edge of the uplifted crystalline vosges and black forest the main shocks in earthquake swarms in the region often occur in the vicinity of this surface and along pre existing n s to ne sw variscan or tertiary faults and show focal mechanisms of strike slip in contrast part of the aftershocks show focal mechanisms of reverse faulting associated with se nw striking compression the seismic wedge and the north westward rising seismic surface suggest initiation of crustal ramp which starts at the south eastern rim of the conrad dome and which may become a thrust plane if se nw compression continues in the south eastern edge of the graben and above the south eastern ridge of the moho dome where evidences for extension have been found we identify clustering of hypocentres along a surface that strikes n150 parallel to the main compression and dipping towards ne dominant normal faulting mechanisms along this surface suggests initiation of a normal probably listric fault at depth the onset of the future fault plane is located on top of the nw se striking ridge of the lower crust and moho which act as a an indenter in addition to thrusting of the whole wedge towards nw increasing of nw se compression would lead to the formation of a half graben at the place of the present sierentz depression

seasonal and interannual variations in geostrophic velocity in the middle atlantic bight 1 more than 6 years of measurements from the topex poseidon t p altimeter are used to study the seasonal and interannual variations of the geostrophic velocity anomalies in the middle atlantic bight region geostrophic velocities from t p data are compared with the simultaneous low pass filtered current meter data the correlations are all above 95 significance for the three current meter observations at the 1000 m 2210 m and 2990 m isobaths the seasonal mean geostrophic currents from 63 75 w show coherent variations along isobaths with seasonal reversals toward the southwest during the winter and toward the northeast during the summer the eof analysis indicates that the seasonal reversals disappeared during 1996 this disruption is part of the intensification of the slope sea gyre and is related to the southward shift of the gulf stream which acts as the boundary between the subpolar and subtropical gyres the gulf stream moved farther south during 1996 1998 the variations in the gulf stream position may be caused by the wind stress wind stress curl change

stress tensor determination in france and neighbouring regions abstract the tectonic behaviour of different seismic regions of france is inferred from the properties of the local stress tensor obtained from focal mechanisms of regional earthquakes polarities of p wave arrivals for several earthquakes are used in the inversion of the stress tensor and individual focal mechanisms the principal axes and the shape of the tensor are closely related to the forces which generate seismic ruptures on pre existing faults we analyse 142 earthquakes of magnitude above 3 7 which occurred between 1965 and 1989 good results are obtained for some regions the northern alps and the southern end of the upper rhinegraben show a quasi compressive strike slip tectonic regime with a maximum stress axis oriented nw se the tectonic regime changes to an extensional strike slip type in the rhenish massif and the lower rhinegraben the direction of the minimum stress axis being nne ssw the central and western regions of france central and armorican massifs exhibit an extensional tectonic regime combined with strike slip faulting the minimum stress axis strikes in a ne sw direction a strongly non homogeneous stress field seems to be present in the southwestern alps and no unique stress tensor could be obtained for that region this problem is likely to be related to a rapid variation of the stress field in space which could be expected given the arc like geometry of the mountain range the pyrenean domain is unresolved due to lack of data and moreover existing focal mechanisms are globaly inconsistent nevertheless those mechanisms which are well constrained suggest a nnw sse to nw se direction of maximum stress in the western part of the pyrenees thus the stress field in france is fairly homogeneous at a regional scale for most of the territory except for the highly deformed belts

recirculation and seasonal change of the kuroshio from altimetry observations surface height fluctuations across an eastward flowing boundary current such as the gulf stream and the kuroshio can be caused by changes both in the upstream inflow and in the neighboring recirculation gyres clarifying these causes is important in understanding the time dependent nature of the boundary currents and their relationship to the surface wind and buoyancy forcing using satellite altimetry data to identify these causes however requires mean surface height field information which is not readily available from the altimetry observation owing to lack of accurate geoid data the present study presents a method to estimate the mean surface height profile across a boundary current system including recirculation gyres by combining altimetrically measured residual height data and historical hydrographic data applying this method to the kuroshio revealed that the absolute surface height profiles thus estimated agree well with the results from quarterly in situ hydrographic observations by separating the signals of the surface height fluctuations into those of the eastward flowing jet and the recirculation gyres we found that the seasonal cycle in the surface transport of the kuroshio which has a maximum in july and august is primarily due to the seasonal change in the intensity of the recirculation gyre south of the kuroshio

gulf stream velocity structure through inversion of hydrographic and acoustic doppler data near surface velocities from a shipborne acoustic doppler instrument are used together with conductivity temperature depth and o2 data to make estimates of geostrophic velocities off of cape hatteras the data set consists of two transects across the gulf stream at approximately 73 w and 71 w made by the r v endeavor in august 1982 an inversion technique is applied which makes use of both the acoustic doppler data and property conservation requirements the method produces estimates of the absolute flow field across the two sections with formal errors of 1 2 cm s at the time of the observations the net gulf stream transports are estimated to be 116 2 109 kg s at 73 w and 161 4 109 kg s at 71 w a southwestward deep western boundary current transport is estimated at 4 1 109 kg s taken together with recent gulf stream transport estimates of similar accuracy made in june 1982 the results are in general larger than historical transport estimates in this region

interdecadal variations in north atlantic sea surface temperature and associated atmospheric conditions abstract evidence is presented for a distinct pattern of ocean atmosphere relationship associated with interdecadal variability in the north atlantic region using a century of surface marine observations it is shown that middle and high latitude sea surface temperature sst display a long term fluctuation with negative anomalies before 1920 and during the 1970s and 1980s positive sst conditions prevailed from about 1930 to 1960 the pattern of interdecadal sst variability is constructed by subtracting the average field during 15 cold years from that during a similar interval of warm years the early century warming and the more recent cooling display a similar spatial pattern in both cases the pattern is basin scale and largely of one polarity with maxima in the vicinity of iceland in the labrador sea and northeast of bermuda the corresponding differences in surface atmospheric conditions are determined by averaging and subtracting in the same manner fields of sea level pressure slp and surf

interseismic re strengthening and stabilization of carbonate faults by non dieterich healing under hydrothermal conditions abstract friction experiments consisting of a velocity stepping stage a slide hold slide shs stage and a second velocity stepping stage have been performed to study the frictional healing behavior of carbonate fault gouge and the effects of healing on the velocity dependence of friction at 20 140 c and at 50 mpa effective normal stress dry experiments show classical dieterich healing characterized by a transient peak in friction after each hold period with no effects of shs testing on steady state friction or velocity dependence by contrast the wet tests show 1 an increase in apparent steady state friction upon re sliding after a hold period and 2 a pronounced increase in the velocity dependence parameter a b after the shs stage while the first of these non dieterich type healing effects has been observed in previous hydrothermal experiments on simulated quartz gouges it has not been reported previously for carbonate gouges the observed effect of shs testing on a b has never been reported our findings suggest that under in situ hydrothermal conditions interseismic fluid assisted deformation processes such as pressure solution can significantly promote fault re strengthening in carbonates and can cause slip stabilization if the results are applicable to active faults in carbonate terrains they have important implications for understanding how the extent of the seismogenic zone and how earthquake magnitude and aftershock distributions may evolve with repeated cycles of natural seismicity and interseismic healing

structure and tertiary tectonic history of the mulhouse high upper rhine graben block faulting modified by changes in the alpine stress regime 1 the mulhouse high horst is situated in the southernmost upper rhine graben and changes in its tectonic history record the interaction with the adjacent alpine front recently released seismic data show that the mulhouse high consists of the sierentz and the altkirch tilted blocks separated by the ferrette fault zone with a throw of several hundred meters during the eocene early rupelian main rifting phase the mulhouse high was the elevated flank of the dannemarie basin with sedimentation affected by the nearby southern boundary of the rhine graben the miocene jura compression extended into the mulhouse high creating a series of semiparallel buried folds with no evidence for thin skin tectonics the change to a nw se regional compressive stress reactivated the main graben faults as wrench faults it also resulted in transpression on the ne sw trending faults particularly the northern segment of the illfurth fault zone consequently the northern part of the mulhouse high was uplifted strike slip motion along the ferrette fault zone is shown to be small

variability in the deep western boundary current local versus remote forcing 1 horizontal velocity temperature and salinity measurements from the line w array for the period 2004 2008 show large changes in the water mass structure and circulation of the deep western boundary current dwbc fluctuations in the flow with periods from 10 to 60 days are bottom intensified signals most likely associated with topographic rossby waves trw a fraction 15 of the dwbc transport variability is caused by gulf stream rings and meanders these flow anomalies are surface intensified and fluctuate at frequencies lower than the trw interannual variability in the velocity field appears to be related to changes in the hydrographic properties the dominant mode of variability is characterized by an overall freshening cooling a potential vorticity pv increase in the deep labrador sea water dlsw and a pv decrease in the overflow water ow the variability in the flow associated with these property changes is not spatially homogeneous offshore water depths larger than 3500 m changes in the velocity are in phase with pv changes in the ow a decrease in the ow pv is accompanied by an increase in the southward negative transport conversely variations of the inshore flow are in phase with changes in the dlsw pv increasing pv and decreasing transport this trend true for most of the record reverses after the winter of 2007 2008 a sudden decrease of the dlsw pv is observed with a corresponding intensification of the flow in the inner dwbc as well as a northward shift in the gulf stream axis

tertiary tectonics of the dannemarie basin upper rhine graben and regional implications recently released seismic reflection data together with previous seismic and well data are used to describe the development of the dannemarie basin in the sw end of the upper rhine graben the dannemarie basin was formed during the main rifting phase of the upper rhine graben as an asymmetrical graben trending ne sw post rift tectonism shifted the depocenter southward and changed the overall shape of the basin miocene jura compression did not result in the formation of folds as in the adjacent mulhouse horst strike slip faulting was dominant in the post rift period and new faults were created most notably the north trending and transpressional belfort fault the boundary of the dannemarie basin with the vosges mountains is part of a restraining bend which may account for the uplift of the southernmost part of the vosges mountains

anatomy and kinematics of oblique continental rifting revealed a three dimensional case study of the southeast upper rhine graben germany the upper rhine graben is a north northeast trending small displacement crustal scale rift of tertiary age retrodeformation of its southeastern part demonstrates that it is a product of sinistral oblique rifting early extension was toward 80 later the major stretching axis changed to a 60 direction the modeling results suggest that the eastern main border fault developed first and that faulting later propagated into the evolving graben interior considerable along strike variations in heave throw and displacement are evident displacement partitioning causes warping of the rift floor with a 30 35 km wavelength we consider this to be a characteristic of oblique rifting contact deformation of the wall rocks to the major faults may have caused widespread smaller scale faulting and brecciation and may be the location of later movements close spatial coincidence of the depth projections of some of the faults studied and the hypocenters of recent small earthquakes indicates continuing activity of the fault system apparently three fault segments in the freiburg area are currently active and may be an increased earthquake risk

gulf stream surface transport and statistics at 69 w from the geosat altimeter geosat altimeter height measurements for the gulf stream for three subtracks from the exact repeat mission were processed to remove the geoid and mean gulf stream height a gaussian model for the gulf stream velocity profile was used to predict the form of the residual height profiles seen by geosat and the mean height profile using estimates of the width and position derived from the height residuals estimates of the maximum surface velocity and the surface transport were obtained by a least squares fit of the synthetic height profiles to the data location statistics from the geosat data were in good agreement with values obtained from infrared images of the gulf stream maximum surface velocities were typically between 1 2 and 2 0 m s 1 the time series showed that surface transport is correlated primarily with the magnitude of the surface velocities although an anomalously large increase in surface transport in the winter of 1987 1988 was caused by an increase in the width of the gulf stream an analysis of the average annual signal in transport showed maximum values in the late fall and minimum transport in the late spring maximum minimum surface transport generally occurred when the gulf stream was north south of its mean position

kinematic evolution of a tectonic wedge above a flat lying decollement the alpine foreland at the interface between the jura mountains northern alps and the upper rhine graben we estimate strain rates of three parameters that describe the buildup of a tectonic wedge jura front france the uplift rate on frontal ramps decreases with the slip on the ramps and the coeval increase of vertical loads the migration rate of the tip of the sole thrust appears to be episodic and faster than the translation rate of the backstop the long term tilting rate appears to be constant whereas the short term rate is slightly slower we propose a model of wedge growth that proceeds without underthrusting in a prefractured medium the wedge would activate the frontal ramp with a weaker frictional resistance than the forward decollement an instantaneous forward jump of the deformation front would occur when the resistance on the ramp equals the resistance of the frontal decollement this model differs from those proposed for accretionary zones and relates to the backstop of a single tapered orogenic belt

estimating present day displacement fields and tectonic deformation in active mountain belts an example from the chartreuse massif and the southern jura mountains western alps abstract determination of relative movements between the alpine foreland and the external crystalline massif is a key point for the understanding of the present day tectonics of the western alps in this study we try to test the continuity of the present day tectonics with the mio pliocene deformation in particular we will test if the present day displacements are localized along the thrusts of the jura mountains or along a blind thrust in the bas dauphine molasse basin definition of relative movements is achieved by several methods including a comparison of two high precision leveling networks to estimate vertical displacements horizontal deformation measurements performed by triangulation triangulation and triangulation gps comparison in situ stress measurements performed in the different tectonic units and geomorphologic observations that constrain the location and the magnitude of the quaternary deformation comparison of leveling data demonstrates 1 an uplift of the southern bas dauphine molasse basin relative to its northern part 0 8 mm year also revealed by geomorphologic analysis 2 a significant uplift of the most external jurassian anticlines 0 8 to 2 mm year also recorded by the deformation of a paleo river bed and 3 an important uplift up to 2 mm year of the subalpine massifs the horizontal strain estimated from comparison of horizontal geodetic data triangulation gps shows 1 a nw se directed shortening between the eastern chartreuse massif and the bas dauphine molasses basin approximately 3 mm year 2 an e w directed shortening in the jura mountains approximately 4 3 mm year and 3 a dextral strike slip motion consistent with focal mechanisms along a nne ssw direction between the eastern chartreuse massif and the eastern belledonne massif these data reveal a present day strain partitioning between the belledonne external crystalline massif and the bas dauphine molasses basin the westward motion of the subalpine massifs is partitioned along two southern jurassian thrust folds and a dextral nne ssw strike slip shear zone between the chartreuse massif and the belledonne massif this strain partitioning is also accompanied by a stress partitioning between the alpine foreland and the external crystalline massifs

the upper rhenish shield basement vosges upper rhinegraben and schwarzwald main structural features deduced from magnetic gravimetric and geological data abstract interpretation of magnetic and gravimetric data and correlations with geological observations on outcrops and in boreholes have enabled the construction of a geological sketch map of the pre westphalian basement in the area of the upper rhenish shield the map demonstrates the contrast between the heavy and magnetic saxothuringian characterized by palaeozoic units metamorphosed to varying degrees and intruded by early carboniferous basites and the lighter moldanubian consisting mainly of gneisses and granites geological structures and tectonic features are recorded beneath the mesozoic and cenozoic cover the present picture of the basement is mainly the result of late visean early namurian structural features represented by a linear arrangement of magmatic bodies and the distribution of strike slip and thrust faults the major structural features are the e w vittel lalaye lubine baden baden fault that marks the border between saxothuringian and moldanubian the n35 left lateral wrench fault system running along the present rhinegraben the n60 grain of the northern vosges and the saar basin and the s verging crustal thrusts of moldanubian

plio pleistocene transpressional reactivation of paleozoic and paleogene structures in the rhine bresse transform zone northern switzerland and eastern france pliocene to recent uplift and shortening in the southern rhinegraben is documented by deformation of pliocene fluvial gravels deposited on a nearly planar surface as well as by progressive deflection and capture of rivers this deformation is suggested to result from thick skinned tectonic movements as evidenced by ob servations on seismic records which demonstrate a spatial coincidence between en chelon anticlines at the surface and faults located in the crystalline basement these findings contradict the often invoked thin skinned tectonism in the recent tectonic history of the rhine graben in particular the transfer zone between the rhinegraben and the bressegraben is very suitable for reactivation under the present day stress field thick skinned reactivation of faults in the basement is also expressed by focal plane mechanisms of recent earth quakes showing strike slip rather than reverse faulting characteristics this is of importance for the densely populated and industrialised southern rhinegraben pre viously affected by large earthquakes in historical times e g basel 1356

new insight in the tectonics of the southern rhine graben jura region using local earthquake seismology 1 a new seismic data set was acquired using a dense temporary network of mobile seismic stations it is combined with existing seismological data for the southern rhine graben the data yielded some new focal mechanisms and allowed for a detailed local earthquake tomography these methods give new insight in the structure of the crust and stress conditions in the area by combining the tomography with the earthquake hypocenter locations and focal mechanisms some of the structures in the p wave velocity model are interpreted as active faults the eastern boundary fault zone of the graben is found to be activated in a left lateral strike slip sense the southern continuation of these faults is formed by variscan structures in the basement a change in orientation of the graben axis between the main graben and its southern end have played a role during the development of the system this difference in orientation caused the development of the dannemarie and allschwil subbasins during a late stage of the opening of the rhine graben this study shows evidence for active faulting in the basement underneath the detachment of the jura mountains these faults which are interpreted as reactivated permo carboniferous troughs coincide with the frontal thrusts of the jura mountains it might be that these structures in the basement have influence on the detachment tectonics in the region

seismic reflection evidence for thick skinned tectonics in the northern jura newly released seismic reflection data from the northern jura mountains and southern rhine graben provide the first high quality subsurface images from this area these throw light on the details of the fault patterns in the area and show that the ferrette and le glaserberg jura structures are largely the result of thrust faulting however the faults differ in their nature from those usually assumed in jura tectonics they are not low angle thrusts converging on a decollement zone in triassic evaporites they appear instead to be high angle faults that cross the entire sedimentary section indicating that thick skinned tectonics prevailed in this part of the jura embryonic jura folds can be seen on the images from the nearby mulhouse horst folds that are not supported by thickened triassic evaporites the existence of recent earthquake activity taken together with the prevalence of thick skinned tectonics suggests that occasional large earthquakes cannot be ruled out in this area

the wind driven circulation quasi geostrophic simulations and theory for nonsymmetric winds abstract simulations of the wind driven ocean circulation carded out with an eddy resolving quasi geostrophic numerical model and symmetric idealized wind forcing have a large scale structure that is predicted wen by the steady nonlinear theory of rhines and young the sharp jet and inertial recirculation am often confined weft inside the region of closed hyperbolic characteristics defined by that theory and hence do not affect the sverdrup dynamics part of the gyre the characteristics make possible simple predictions about the development of the circulation including time dependence and eddy stirring by tilting the line of vanishing ekman pumping away from the east west orientation as it is tilted in the north atlantic and less so the north pacific we explore a family of circulations as the tilt of the wind held is increased characteristics originating at the eastern boundary begin to thread through the energetic region occupied by the free jet then extensive new branches of eddy driven f

thrust tectonics a mechanistic view from the west and central alps abstract two modern models of thin skinned thrust tectonics by elliott 1976 and chapple 1978 are reviewed and found to be of restricted application following possible variations of surface and basal slope and based on published alpine cross sections eight elementary two dimensional mechanical models are set up these include the possibility of a weak basal layer a common feature of alpine thrust sheets and an externally applied subhorizontal compression six of these have two variants depending on if the maximum shear stress in the sheet attains the yield stress in which case there is permanent deformation and the sheet changes shape perhaps to that of a different elementary model the long ignored analysis by goguel 1948 of stresses in a relaxed plastic material at depth below an inclined surface is outlined stress components resulting from this analysis are used together with supplementary stresses derived by hafner 1951 to represent an externally applied subhorizontal compression to suggest ways in which decollement possibilities of the models can be investigated some specific examples are considered

gulf stream variability and ocean atmosphere interactions abstract time series of gulf stream position derived from the topex poseidon altimeter from october 1992 to november 1998 are used to investigate the lead and lag relation between the gulf stream path as it leaves the continental shelf and the changes in sea level pressure surface wind stress and sea surface temperature sst as given by the ncep reanalysis the dominant signal is a northward southward displacement of gulf stream axis 11 to 18 months after the north atlantic oscillation nao reaches positive negative extrema a sst warming cooling peaking north of the gulf stream is also seen to precede the latitudinal shifts but it is a part of the large scale sst anomaly tripole that is generated by the nao fluctuations there is no evidence that the gulf stream shifts have a direct impact onto the large scale atmospheric circulation a fast passive response of the gulf stream to nao forcing is also suggested by a corresponding analysis of the yearly mean gulf stream position estimated from

seismic refraction investigation of the black forest abstract within the framework of site surveys of the deep continental drilling program ktb deep seismic sounding experiments were carried out in the black forest southwest germany in august 1984 these site surveys comprised seismic refraction as well as seismic reflection measurements this paper will concentrate on the interpretation of the refraction data which were observed along a 240 km long line approximately following the morphological axis of the black forest in a n s direction and extending in the south into the swiss molasse basin from the available seismic refraction data a detailed velocity depth model of the crust and uppermost mantle was derived a clear phase refracted in the basement with a velocity of 5 9 km s is observed for all shots this phase is followed by a reflection from the upper boundary of a low velocity zone this zone is very accentuated under the northern and central black forest and is characterized by a velocity decrease from 6 2 to 5 4 km s between depths of about 8 and 14 km towards the south the velocity inversion gradually loses its intensity under the center of the southern black forest velocities of about 6 km s prevail throughout the upper crust the lower crust which starts at the lower boundary of the low velocity zone shows a very complicated response in the record sections due to long reverberations between travel times of 1 5 3 5 s reduced by 6 0 km s at an epicentral distance of approximately 30 70 km a classical phase correlation is not possible based on a combined interpretation of near angle and wide angle reflection data the lower crust is characterized by a stack of thin layers with alternating high and low velocities the average velocity of the laminated zone is 6 7 km s the reflection from the moho at a depth of 25 26 km is the most prominent phase at epicentral distances greater than 60 km

eddy mean flow interactions in the along stream development of a western boundary current jet an idealized model study a theoretical study on the role of eddy mean flow interactions in the time mean dynamics of a zonally evolving unstable strongly inertial jet in a configuration and parameter regime that is relevant to oceanic western boundary current wbc jets is described progress is made by diagnosing the eddy effect on the time mean circulation examining the mechanism that permits the eddies to drive the time mean recirculation gyres and exploring the dependence of the eddy effect on system parameters it is found that the nature of the eddy mean flow interactions in this idealized configuration is critically dependent on along stream position in particular relative to the along stream evolving stability properties of the time mean jet just after separation from the western boundary eddies act to stabilize the jet through downgradient fluxes of potential vorticity pv downstream of where the time mean jet has through the effect of the eddies been stabilized eddies act to drive the time mean recirculations through the mechanism of an upgradient pv flux this upgradient flux is permitted by an eddy enstrophy convergence downstream of jet stabilization which results from the generation of eddies in the upstream region where the jet is unstable the advection of that eddy activity along stream by the jet and the dissipation of the eddies in the region downstream of jet stabilization it is in this region of eddy decay that eddies drive the time mean recirculations through the mechanism of nonlinear eddy rectification resulting from the radiation of waves from a localized region it is found that similar mechanisms operate in both barotropic and baroclinic configurations although differences in the background pv gradient on which the eddies act implies that the recirculation driving mechanism is more effective in the baroclinic case this study highlights the important roles that eddies play in the idealized wbc jet dynamics considered here of stabilizing the jet and driving the flanking recirculations in the absence of eddy terms the magnitude of the upper ocean jet transport would be significantly less and the abyssal ocean recirculations and their significant enhancement to the jet transport would be missing altogether

does atmospheric cooling drive the gulf stream recirculation abstract a two layer model for the recirculation is studied initially a narrow jet of the upper layer moves eastward with the lower layer remaining stagnant att 0 cold air flows over the narrow front region all the moving water in the upper layer sinks to the lower layer with the momentum vertically well mixed within the lower layer thus cooling creates an unbalanced eastward jet in the second layer and an unbalanced pressure field at a vertical density front after the geostrophic adjustment a high pressure center south of the front and a low pressure center north of the front are established these pressure centers drive a much stronger barotropic eastward current slightly north of the pressure center and slow westward return flow in the far field both south and north of the front thus cooling over a narrow stream can intensify an eastward jet and create recirculation gyres both north and south of the stream

the variscan tectonic inheritance of the upper rhine graben evidence of reactivations in the lias late eocene oligocene up to the recent processing of gravity and magnetic maps shows that the basement of the upper rhine graben area is characterized by a series of ne sw trending discontinuities and elongated structures identified in outcrops in the vosges black forest and the odenwald mountains they form a 40 km wide n30 40 striking sinistral wrench zone that in the visean shifted the variscan and pre variscan structures by at least 43 km to the ne wrenching was associated with emplacement of several generations of plutonic bodies emplaced in the time range 340 325 ma the sub vertical ne sw trending discontinuities in the basement acted as zones of weakness susceptible to reactivation by subsequent tectonism the first reactivation marked by mineralizations and palaeomagnetic overprinting along ne sw faults of the vosges mountains results from the liassic nw se extension contemporaneous with the break up of pangea the major reactivation occurred during the late eocene n s compression and the early middle oligocene e w extension the ne sw striking basement discontinuities were successively reactivated as sinistral strike slip faults and as oblique normal faults elongated depocenters appear to form in association with reactivated variscan wrench faults some of the recent earthquakes are located on ne sw striking variscan fault zones and show sinistral strike slip focal mechanisms with the same direction suggesting also present reactivation

effects of healing on the seismogenic potential of carbonate fault rocks experiments on samples from the longmenshan fault sichuan china fault slip and healing history may crucially affect the fault seismogenic potential in the earthquake nucleation regime here we report direct shear friction tests on simulated gouges derived from a carbonate fault breccia and from a clay carbonate fault core gouge retrieved from a surface exposure of the longmenshan fault zone lfz which hosted the 2008 wenchuan earthquake the experiments were conducted under dry and hydrothermal conditions at temperatures up to 140 c at an effective normal stress of 50 mpa and involved sequential velocity stepping vs slide hold slide shs and velocity stepping stages dry tests performed on breccia derived samples showed no dependence of quasi steady state friction ss on shs or vs history and a log linear relation between transient peak healing pk and hold time or classical dieterich type healing behavior by contrast all experiments conducted under hydrothermal conditions were characterized by non dieterich healing behavior this included 1 an increase in ss upon resliding after a hold period and 2 an increase in friction rate parameter a b after shs testing comparison with previous results suggests that the healing behavior seen in our wet tests may be attributed to solution transfer processes occurring during hold periods our findings imply that the shallow portions of faults with carbonate clay rich cores e g the lfz can heal much faster than previously recognized while the upper limit of the seismogenic zone may migrate to deeper levels during interseismic periods these effects have important implications for understanding the seismic cycle in tectonically active carbonate terrains

ventilation of the north atlantic and north pacific subduction versus obduction abstract ventilation in the north atlantic and north pacific is examined by analyzing the levitus climatological data and the hellerman and rosenstein wind stress data ventilation between the permanent pycnocline and the overlying seasonal pycnocline and mixed layer consists of two physical processes subduction and obduction subduction takes place mainly in the subtropical basin where surface water is irreversibly transferred into the permanent pycnocline below obduction takes place in the subpolar basin where water from the permanent pycnocline is irreversibly transferred into the mixed layer above veatilation in the north atlantic and north pacific can be clarified into four physically different regions the subductive region the obductive region the ambiductive region where both subduction and obduction take place and the insulated region where neither subduction nor obduction occurs although the total subduction rates in these two oceans are comparable the total obduction rates are considera

frictional properties and slip stability of active faults within carbonate evaporite sequences the role of dolomite and anhydrite seismological observations show that many destructive earthquakes nucleate within or propagate through thick sequences of carbonates and evaporites for example along the apennines range italy carbonate and evaporite sequences are present at hypocentral depths for recent major earthquakes 5 0 mw 6 3 however little is known about the frictional properties of these rocks which are dominated by dolomite and anhydrite and differ from typical quartzofeldspathic rocks here we report on laboratory experiments designed to illuminate friction constitutive properties and associated microstructures of anhydrite and dolomite fault rocks we performed frictional sliding experiments on powdered samples for a range of normal stresses n from 10 to 150 mpa and sliding velocities from 1 to 300 m s experiments employed the double direct shear configuration and were conducted both dry at room temperature and water saturated at 75 c under true triaxial stresses at 25 c sliding friction is 0 65 for all samples and conditions studied at 75 c samples develop cohesive strength and sliding friction ranges from 0 4 to 0 5 for n from 10 to 35 mpa velocity step tests were used to assess rate state frictional behavior at 25 c the slip behavior is velocity strengthening neutral for all samples microstructural observations indicate localized deformation on r1 riedel and incipient y shear planes with marked grain size reduction at 75 c and larger strain we find that rate state friction behavior correlates with velocity dependent layer dilation and compaction and this is associated with the development of through going y shear planes we conclude that elevated temperature strain and the presence of pore fluids enhance shear localization into continuous y shear planes which could promote frictional instability at seismogenic depth within dolomite anhydrite sequences

determining the mean gulf stream and its recirculations through combining hydrographic and altimetric data the altimetric data from the first 2 5 year geosat exact repeat mission were used to estimate the mean sea surface height ssh field in the region of the gulf stream and its recirculation gyres assuming the instantaneous surface velocity field is composed of an eastward flowing jet and two westward recirculating flows we used the time varying surface data from the altimeter to determine the shape of the along track mean ssh profiles and the historical hydrographic data to constrain the net ssh difference across the gulf stream system the two dimensional mean ssh field was determined by objectively mapping the mean height profiles along the ascending and descending tracks the ssh jump across the mean gulf stream has a maximum of 1 15m around 65 w and drops to an almost constant 0 9m downstream of the new england seamount chain nesc while the ssh jump associated with the mean northern recirculating flow is mostly uniform we found that the gulf stream s southern recirculation has two local gyres that are separated by the nesc an attempt was then made to estimate the mean deep circulation in this region by comparing the mean ssh field derived from the altimetry data and the surface dynamic height field based on the historical hydrographic data despite the large uncertainties the mean deep flow pattern thus estimated agrees favorably with the overall circulation pattern from the long term current meter observations like the well defined northern recirculation gyre we found that a continuous southward flow exists along 57 5 w which follows closely along the deep layer potential vorticity contours to the south of the gulf stream the deep circulation consists of two separated recirculation gyres the recirculation gyre to the east of the nesc appears to be trapped around the corner rise

monitoring gulf stream transport by radar altimeter and inverted echo sounders abstract profiles of the gulf stream sea surface height ssh from the geosat altimeter were compared with thermocline depth measurements from inverted echo sounders ies for a period of about 19 months the correlation between ssh anomalies and thermocline depth anomalies at about 68 w was 0 92 to distinguish between agreement in the location of the gulf stream jet and agreement in the strength of the jet separate comparisons were made for jet location and the ssh difference across the gulf stream based on an error function fit to each geosat and ies profile the correlation between the jet centers from the two types of measurements was 0 97 and the correlation between the amplitudes of the error functions was 0 76 although the altimeter measures surface geostrophic velocity the high degree of vertical correlation in the gulf stream velocity profiles allows the altimeter to monitor transport fluctuations as well as changes in jet position based on this assessment of the accuracy of the altimeter

graben inversion in nature and experiments the inversion of crustal scale basement grabens is studied here through laboratory experiments on small scale models and available oil industry seismic lines from the southern north sea two basic configurations are considered first both the basement and the sedimentary cover are brittle and inversion does not involve any potential decollement between them second the basement and sedimentary cover are separated by a weak ductile layer e g salt which can allow decollement of the cover during both extension and later compression and inversion the second configuration is more complicated and can lead to a large variety of geological structures laboratory experiments were carried out on brittle ductile models built with sand to represent brittle layers basement and sedimentary cover and silicone putty to simulate the decollement layer between basement and cover a mechanically based classification of inversion structures is proposed the effects of some crucial parameters are investigated including obliquity between the direction of shortening and normal faults as well as strength profiles and the presence or absence of salt diapirs the experimental investigation leads to the following conclusions 1 the inversion of the graben by reactivation of normal faults implies that the angle between the direction of compression and the graben is less than 45 2 if there is a superficial decollement e g basement cover interface inversion initiates low dipping thrust faults in the cover localized at graben borders 3 salt diapirs or salt walls localized along the graben borders in the cover are preferential sites for the development of thrust faults and 4 when the cover is decoupled from the basement by a decollement layer inversion induced deformation in the cover which is partitioned between thrust faults along the graben borders and strike slip faults within the graben trending oblique to the graben borders experimental results are compared with field examples in particular from the southern north sea

contourites and their relevance for mass wasting along the mid norwegian margin between about 12 and 4 3 ma slope parallel bottom currents dominated the neogene sedimentation on the slope of the mid norwegian margin and large scale sediment bodies accumulated to thicknesses up to 1000 m these bedforms are morphologically classified as sheeted and elongated mounded contourite drifts an increase in sediment supply from about 4 to 3 ma due to onshore uplift and glaciation resulted in a massive influx of downslope derived material onto the continental margin only on the voring plateau was contourite sedimentation little affected by this change in sedimentary style during the last 0 5 my contouritic deposits occurred also in the storegga area as 100 150 m thick infill drifts inside the scars of two palaeo slides r and s holocene post slide deposits in the scar of the storegga slide 8 2 ka have the typical morphological features and distribution of contourite drifts with the upslope limit at the lower base of the warm northward flowing north atlantic current at 500 700 m depth and the downslope limit at depths of approximately 1200 m detailed chronostratigraphy of the post slide sediments show relatively constant high sedimentation rates in the order of 1 2 m ky during the last 8000 years this is equivalent to the estimated rates for the older infill drifts the infill drifts consist mainly of clays with silty and sandy lamina and represents marine and glaciomarine conditions the main influence of contourite drifts on slope stability relates to their physical properties forming a more sensitive and brittle deposit than the glacial deposits and their exposure to downslope sedimentation in addition the potential for build up of excess pore pressure due to rapid loading from subsequent glacial depositions their seabed smoothing effect and great lateral extent make the contourite drift deposits particularly important for slope instability in this region

the 2005 heidelberg and speyer earthquakes and their relationship to active tectonics in the central upper rhine graben we determine the source parameters of three minor earthquakes in the upper rhine graben urg a cenozoic rift using waveforms from permanent and temporary seismological stations two shallow thrust faulting events m l 2 4 and 1 5 occurred on the rift shoulder just south of heidelberg in march 2005 they indicate a possible movement along the sediment crystalline interface due to tectonic loading from the near by odenwald in february 2005 an earthquake with a normal faulting mechanism occurred north of speyer this event m l 2 8 had an unusual depth of about 22 km and a similar deep normal faulting event occurred there in 1972 m l 3 2 other lower crustal events without fault plane solutions are known from 1981 and 1983 at such a depth inside the lower crust ductile behaviour instead of brittle faulting is commonly assumed and used for geodynamic modelling based on the newly available fault plane solutions we can confirm the brittle extensional regime in the upper and lower crust in the central to northern urg indicated in earlier studies

spatial variations of earthquake occurrence and coseismic deformation in the upper rhine graben central europe abstract seismic activity in the densely populated upper rhine graben urg is an aspect in the public political and industrial decision making process the spatial analysis of magnitude frequency distributions provides valuable information about local seismicity patterns and regional seismic hazard assessment and can be used also as a proxy for coseismic deformation to explore the seismo tectonic setting of the urg we combine five instrumental and one historic earthquake bulletins to obtain for the first time a consistent database for events with local magnitudes m l 2 0 in the whole urg and use it for the determination of magnitude frequencies the data processing results in a dataset with 274 poisson distributed instrumentally recorded earthquakes within the urg between 01 1971 and 02 2012 and 34 historic events since the year 1250 our analysis reveals significant b value variations along the urg that allow us to differentiate four distinct sections i iv with significant differences in earthquake magnitude distributions i basel region in the swiss france german border region b 0 83 ii region between mulhouse and freiburg in the southern urg b 1 42 iii central urg b 0 93 and iv northern urg b 1 06 high b values and thus a relatively low amount of high magnitude events in the freiburg section are possibly a consequence of strongly segmented small scale structures that are not able to accumulate high stresses we use the obtained magnitude frequency distributions and representative source mechanisms for each section to determine coseismic displacement rates a maximum horizontal displacement rate of 41 m a around basel is found whereas only 8 m a are derived for the central and northern urg a comparison with geodetic and geological constraints implies that the coseismic displacement rates cover less than 10 of the overall displacement rates suggesting a high amount of aseismic deformation in the urg

stress inversion and basement cover stress transmission across weak layers in the paris basin france we investigate the source of non purely gravitational horizontal stresses in the paris basin a nowadays tectonically quiet intracratonic basin in its eastern border of which outstandingly dense stress measurements are available based on a synthesis of published data the stress state in the basin is first shown to be very close to the one that may be extrapolated for the underlying basement in terms of principal stress orientations and horizontal to vertical stress ratios this is in favour of a mechanical coupling between the basement and its sedimentary cover which may seem contradictory to the presence of several weak rock layers in the basin fill e g an argillite layer that was shown to bear low deviatoric stresses and salt layers that are implicated in a major decollement elsewhere to unravel this apparent contradiction a 3d numerical modelling is performed following a rigorous inverse problem approach to determine the long term elastic properties of both the basement and the basin rocks the objective is to find the set of elastic constants that provides the best fit between the calculated stress state in the basin and the in situ data by assuming that the stress state in the basement is known this methodology provides a realistic set of mechanical parameters in agreement with previous studies which leads to the conclusion that the horizontal stresses in the basin constitute its mechanical response to the stresses that developed in the underlying basement during and since the last tectonic event alpine phase the fact that horizontal stresses could be transmitted across the weak horizons contrary to what may be expected at first glance is explained both by the geometry of the basin and the fact that over the long term the stiffnesses of the various sedimentary rocks are only slightly different from each other

seismicity of the northern upper rhine graben constraints on the present day stress field from focal mechanisms abstract we present new results for the microseismic activity in the northern upper rhine graben by analyzing seismogram recordings from two temporary networks of up to 13 broad band stations in combination with data from permanent stations previous studies have mainly focused on the southern and intermediate sections of the upper rhine graben where the station coverage by regional networks is more dense between october 2010 and september 2013 we recorded 56 earthquakes that occurred within the immediate vicinity of the northern upper rhine graben with local magnitudes ranging from 0 5 to 3 2 the majority of the hypocenters are located beneath the eastern graben shoulder and in the graben itself while activity observed along the western graben shoulder is lower a further active region is located along the southern rim of the taunus mountains to the northwest of the study area the seismicity extends to a depth of 25 km the hypocentral depth distribution exhibits a pronounced peak of seismic energy release in the depth range between 12 and 18 km fault plane solutions for a total of 58 earthquakes including data from previous recordings were derived from p polarities and sv p amplitude ratios this new data set more than quadruples the number of available data for regional stress field analysis the majority of the focal mechanisms show predominantly strike slip movements only a few events are of reverse or normal faulting type t axis trends are oriented ne sw the calculated focal mechanisms presented in this study confirm that the area is in transtension however in contrast to previous studies a stronger strike slip component is identified we also derived the azimuths of the principal stress axes by inverting the fault plane solutions and calculated the direction of the maximum horizontal stress which is mainly oriented n135 e

variability in the slope water and its relation to the gulf stream path 1 sea surface temperature sst and sea surface height ssh data for 1993 2007 for the north atlantic are combined with hydrographic data at 69w to investigate the relation between the gulf stream gs position and the slope water properties sst anomalies north of the gs are correlated with changes in its path the lag of this correlation is such that positive temperature anomalies precede northward shifts of the gs and suggests that sst anomalies move westward with speeds of several cm s eof analysis of the sst and ssh fields shows that cooling and strengthening of the sw flow are in phase over the slope water which is mirrored in the vertical structure of these fields at 69w indicating larger transports in the deep western boundary current lead to southward shifts of the mean gs path this relation between the slope water and the gs path provides some predictability for the latter