sequence of thrusting within a thick skinned tectonic wedge evidence from40ar 39ar and rb sr ages from the austroalpine nappe complex of the eastern alps the sequence of thrusting within a regional scale alpine thick skinned tectonic wedge has been constrained by rb sr and 40ar 39ar dating of whole rock constituent white mica and biotite from structural units of the austroalpine nappe complex eastern alps austria preservation of variscan and pre variscan isotopic signatures in pre alpine basement units indicates a non penetrative metamorphic alpine overprint alpine nappe assembly and accompanying ductile deformation occurred during maintenance of lower greenschist facies metamorphic conditions c 300 450 c analyses from greenschist facies metamorphic mylonites and penetratively ductile deformed cover sequences display decreasing 40ar 39ar plateau ages structurally downward thrusting and accompanied ductile deformation commenced at c 100 90 ma in the uppermost structural levels footwall fault propagation effected internal deformation and out of sequence thrusting within intermediate structural levels at c 95 80 ma this was contemporaneous wit

midshelf to surfzone coupled roms swan model data comparison of waves currents and temperature diagnosis of subtidal forcings and response abstracta coupled wave and circulation model that includes tide wind buoyancy and wave processes is necessary to investigate tracer exchange in the shelf region here a coupled regional ocean model system roms simulating waves nearshore swan model resolving midshelf to the surfzone region of the san pedro bay california is compared to observations from the 2006 huntington beach experiment waves are well modeled and surfzone cross and alongshore velocities are reasonably well modeled modeled and observed rotary velocity spectra compare well in subtidal and tidal bands and temperature spectra compare well in the subtidal band observed and modeled mid and inner shelf subtidal velocity ellipses and temperature variability determined from the first vertical complex eof ceof mode have similar vertical structure although the modeled subtidal velocity vertical shear and stratification are weaker than observed the ratio of stratification to shear is similar suggesting model vertical mixing i

west florida continental shelf response to upwelling favorable wind forcing 2 dynamics dynamics analyses are presented for the west florida continental shelf response to upwelling favorable alongshore or offshore winds using a three dimensional time dependent primitive equation model these analyses complement the kinematics analyses of li and weisberg 1999 results are provided on four topics 1 the response evolutions to quasi steady states 2 the across shelf distributions of the vertically integrated alongshore and across shelf momentum balances 3 the three dimensional structures of the terms composing the momentum balance closures and 4 the model sensitivity to vertical friction parameterization the response evolution starts with a local wind driven acceleration and it transitions over the inner shelf into a primary balance between the pressure gradient coriolis and vertical friction terms thus the inner shelf spin up takes a classical ekman geostrophic route the middle shelf takes longer because it also depends on coastal boundary effects notably the partial closure of the domain in the south by the florida keys the outer shelf never achieves a steady state because of topographic wave effects coastline and isobath geometries result in fully three dimensional flow fields thus a two dimensional model that ignores alongshore variations cannot account for the results obtained the inner shelf is the transition region between ekman and ekman geostrophic balances where the surface slope results from mass adjustments through overlapping surface and bottom ekman layers across the inner shelf the vertically integrated momentum balance shows a gradual trade off between the coriolis pressure gradient and bottom friction terms and with the inner shelf frictionally determined its scale is sensitive to vertical friction parameterization

aseismic slip during the 1996 earthquake swarm in and around the onikobe geothermal area ne japan abstract in august 1996 an earthquake swarm including 4 earthquakes of magnitudes greater than 5 occurred in and around the onikobe geothermal area northeast japan while earlier studies detected ground displacements by l band jers radar interferograms there remained certain puzzling discrepancies between the observations and the predictions from a seismologically inferred model and no satisfactory models have yet been proposed here by identifying that a steep gradient in the radar line of sight changes exists in seismicity gaps to the east and west of the torage area just to the north of the onikobe caldera we propose two aseismic reverse faults which turn out to contribute to a local topographic growth as well as explaining the pre existing discrepancies another significant signal is detected in a region in which no large earthquakes occurred we account for this signal by another aseismic fault this fault adds to another evidence for the recent hypothesis that aseismic fault motion drives earthquake swarm

aseismic strike slip associated with the 2007 dike intrusion episode in tanzania abstract in july 2007 an earthquake swarm initiated in northern tanzania near lake natron and lasted for about two months mt oldoinyo lengai located to the southwest of the swarm began to erupt effusively about a month prior to the swarm and increased its eruption intensity on september when the swarm almost ceased several previous studies have already reported the crustal deformation signals associated with the swarm using interferometric synthetic aperture radar insar however nearly all the published data are based on the c band envisat asar images acquired only from the descending path we use the l band alos palsar images acquired from both ascending and descending paths which allow us to examine the deformation signals in more detail in addition to the insar data we employ the offset tracking technique to detect the signals along the azimuth direction using insar and offset tracking data we obtain the full 3d displacement fields associated with the episode besides the horizontal extension and subsidence signals due to the dike intrusion as already reported the inferred full 3d displacements further indicate that the subsiding zone was horizontally moving by 48 cm toward ssw to explain the displacements we performed fault source modeling assuming an elastic half space the fault slip distribution indicates that the contribution of the strike slip component is about 20 of total moment release because almost all the focal mechanisms of earthquakes during the 2007 event indicate nearly pure normal faulting aseismic strike slip must have been responsible for the horizontal movement of the subsiding zone the strike slip at the shallowest depths suggests the presence of transtensive stress which seems to be reasonable to generate the relay zones that are widely observed in the east african rift we also confirmed that the stress changes due to the dike intrusion were consistent with the inferred fault slip distributions

a description of subtidal pressure field observations on the northern california continental shelf during the coastal ocean dynamics experiment during the coastal ocean dynamics experiment code along the northern california continental shelf in the spring and summer of 1981 and 1982 the first comprehensive effort to obtain all of the observations necessary to infer pressure fluctuations throughout the water column was made this is a description of the subtidal fluctuations in measured bottom pressure internal pressures inferred from moored conductivity and temperature observations and the water column total pressure anomalies computed from a combination of the two components the pressure field during code 2 april july 1982 is found to be more energetic than that in code 1 april july 1981 with more than 70 total pressure variance concentrated at frequencies of less than 15 days 1 the spatial structure of the pressure fluctuation field is characterized by coastal intensification and a tendency for poleward phase propagation like the pressures most of the code across shelf pressure difference variance is found at the lower frequencies with more than 60 of the total across shelf pressure difference variance at frequencies of less than 15 days 1 the code across shelf pressure differences are found to be in geostrophic balance with both alongshelf currents and the total alongshelf transport the alongshelf pressure difference variance is generally found to be concentrated at the lower frequencies much like that of the across shelf pressure differences most of the pressure and pressure difference variance is found to be highly coherent with wind stress the 20 day band pressure variability is apparently related to the response of the pressure field during so called relaxation events the barotropic component of the alongshelf geostrophic transport i e across shelf pressure difference has been found to be almost perfectly coherent with regional wind stress y and to propagate poleward within the code region at the same rate as y and the alongshelf pressure gradient is very important in accelerating the alongshelf flow the 5 day band pressure variability in the code region appears to result from local wind stress fluctuations the alongshelf pressure gradient was found to be of secondary importance relative to the wind in accelerating the alongshelf flow

extension in compressional orogenic belts the eastern alps extension in the eastern alps encompasses the following 1 extension accompanying simple shear crustal stacking subhorizontal stretching occurs along flat lying foliations and regionally consistent stretching lineations with associated high strains on a local scale stretching results from extrusion of ductile sediments squeezed between rigid basement blocks basement blocks during thrust sheet imbrication the overall geometric effect is crustal thickening 2 classical extensional tectonics extension first occurs as a consequence of accretion and underthrusting of continental and oceanic material and represents gravitational adjustment of an unstable orogenic wedge extension then occurs as a consequence of terminal continental collision and is accommodated by lateral extrusion of crustal of crustal blocks the overall geometric effect is crustal thinning extension is generally oriented subparallel to the strike of the orogen

west florida shelf response to upwelling favorable wind forcing kinematics the barotropic responses of the west florida continental shelf to idealized upwelling favorable alongshore and offshore wind stresses are studied using the three dimensional time dependent primitive equation princeton ocean model pom when forced with uniform winds the shelf circulation evolves quickly to a quasi steady state a southeastward alongshore wind lowers sea level along the coast and drives a southeastward coastal jet with a relatively weak northwestward return flow farther offshore a southwestward offshore wind lowers sea level along the west florida coast and raises sea level along the panhandle coast two independent circulation gyres are set up in association with these regionally different sea level distributions an anticyclonic gyre off the west florida coast consisting of a southeastward coastal jet and a broad return flow over the middle shelf and a cyclonic gyre off the panhandle coast consisting of a strong northwestward coastal jet and an adjacent narrow southeastward undercurrent these gyres are separated by the big bend region in both cases alongshore and offshore wind forcing the circulations are fully three dimensional with opposing surface and bottom boundary layer flows accounting for the across shelf transports the shapes of the coastline and the isobaths are important determinants of the shelf wide responses several locally maximum upwelling regions are identified for geometrical reasons these include the panhandle coast south of apalachicola bay the west florida coast south of tampa bay along the florida keys and at the shelf break where topographic rossby waves are evident

seasonal circulation over the catalan inner shelf northwest mediterranean sea 1 this study characterizes the seasonal cycle of the catalan inner shelf circulation using observations and complementary numerical results the relation between seasonal circulation and forcing mechanisms is explored through the depth averaged momentum balance for the period between may 2010 and april 2011 when velocity observations were partially available the monthly mean along shelf flow is mainly controlled by the along shelf pressure gradient and by surface and bottom stresses during summer fall and winter the along shelf momentum balance is dominated by the barotropic pressure gradient and local winds during spring both wind stress and pressure gradient act in the same direction and are compensated by bottom stress in the cross shelf direction the dominant forces are in geostrophic balance consistent with dynamic altimetry data

imaging magma transport during the 1997 seismic swarm off the izu peninsula japan the spatio temporal evolution of a propagating magma filled crack was estimated from inversion of global positioning system gps data tiltmeters and leveling the dike opened at a maximum rate of 50 millimeters per day and had a peak magma flux of 2 x 10 6 cubic meters per day although the spatial resolution was limited slow upward propagation was resolved during the 9 day long intrusion in contrast the earthquakes migrated rapidly upward during the first 12 hours of the swarm and nearly all of the seismic energy was released in the first 2 days comparison of inversion results with accurate hypocenter locations will lead to improved understanding of magma transport through the brittle crust and of the causes of volcanic seismicity

crustal earthquake bursts in california and japan their patterns and relation to volcanoes 1 we analyze 153 bursts of earthquakes in southern california and japan the burst patterns are similar in southern california and japan they fill a spectrum between swarm like sequences without obvious mainshocks and mainshocks with omori law abiding aftershocks in agreement with our previous work the swarm like sequences in japan have more events are more voluminous and tend to expand with time when compared to mainshock aftershock type sequences in both regions we find that the sequences starting with their largest events tend to be much shorter in duration bursts within 50 km of volcanoes are similar in character to those elsewhere except they tend to have longer duration we hypothesize that swarminess is a proxy for fluid pressure redistribution and or aseismic slip driving the seismicity bursts and conversely the mainshock aftershock style sequences have end member behavior that results solely from a cascade of elastic failures the complexity of the spatial seismicity distribution does not correlate with the style of swarm observed indicating that fluid conditions and composition are likely more influential than geometry in determining the patterns we observe

simple shear experiments on calcite rocks rheology and microfabric ideal simple shearing of carrara marble and solnhofen limestone was achieved by inserting calcite rock slices into sandstone cylinders precut at 35 the experiments covered a wide range in temperatures 25 900 c at confining pressures of 200 and 250 mpa and at strain rates between 10 3 and 10 5 s 1 shear strains of up 2 7 were achieved the stress strain data for simple shear favourably compare with predictions on the basis of existing flow laws established in coaxial testing this comparison demonstrates that the simple shear experiments covered most of the previously established flow regimes for calcite rocks at the highest temperatures carrara marble exhibited substantial work softening after high shear strains a complete texture analysis was carried out with the u stage and a texture goniometer the following four distinct microfabric regimes were found 1 twinning regime an oblique c axis maximum deflected from the pole to the flattening plane towards 1 and against the imposed sense of shear results directly from e twinning extensive twinning some grains are completely twinned rapidly rotates the c axes into near parallelism with 1 this regime was observed for carrara marble deformed at temperatures below 700 c and for solnhofen limestone at room temperature 2 intracrystalline slip regime three c axis maxima were observed in both rock types at more elevated temperatures and in the absence of twinning these c axis orientations result from an alignment of slip planes and slip directions into parallelism with the shear zone boundary and the shear direction respectively this finding supports the idea of an orientation for easy slip resulting from simple shearing in addition to r and f glide basal glide is inferred to have been operative 3 grain boundary sliding regime a great circle distribution of c axes approximately perpendicular to the direction of finite shortening is observed this texture is weaker compared to the other regimes it is interpreted to result from minor contributions of f slip towards total strain this regime is restricted to fine grained solnhofen limestone deformed at the highest temperatures 4 grain boundary migration regime only in carrara marble deformed at the highest temperatures is there substantial grain boundary migration recrystallization the texture consists of a dominant c axis maximum oriented perpendicular to the shear zone boundary this single maximum corresponds to an orientation for easy slip for basal slip grain boundary migration assists rapid lattice reorientation and leads to geometrical work softening quantitative analysis of grain boundary surface orientations gave the following results within the twinning and the intracrystalline slip regimes the characteristic grain shape is elliptical for both rock types the strain ellipses derived from this analysis closely correspond to the known finite strain at the lowest temperatures at intermediate temperatures and especially in carrara marble there is a consistent trend for the aspect ratios to indicate too little flattening and for the angles between the long axis of the strain ellipse and the shear zone boundary to be too small in the absence of grain boundary migration recrystallization this finding indicates minor translations of grains with respect to one another grain boundary sliding or translations accommodated in the mantle regions of grains at the highest temperatures where extensive grain boundary migration occurs in carrara marble grain boundary migration regime two preferred orientations of grain boundaries are observed 1 parallel to the shear zone boundary and 2 parallel to an oblique direction deflected 20 away from the normal to the shear zone boundary in the sense of the imposed shear the same pattern of grain boundary alignment is observed in solnhofen limestone deformed in the grain boundary sliding regime the geological applications of this experimental work are discussed in terms of calcite tectonites in particular and sheared rocks in general

dynamics of the summer shelf circulation and transient upwelling off ningaloo reef western australia received 19 july 2012 revised 21 january 2013 accepted 25 january 2013 published 11 march 2013 1 the shelf circulation off ningaloo reef near the north west cape of western australia is driven by complex interactions between the southward flowing leeuwin current and wind driven currents that episodically reverse the coastal flow toward the north the presence of these northward equatorward wind driven currents is thought to make this section of coast one of the few locations along western australia to experience periodic coastal upwelling we used a combination of field observations and numerical modeling to investigate the summer circulation and upwelling dynamics along ningaloo reef we analyzed current and temperature profiles from moorings at four sites across the shelf and used two regional ocean modeling system roms sub models 1 a coarser model of northwestern australia forced by a global ocean model and 2 a nested fine scale model of the ningaloo region this nesting significantly improved model skill as it included the offshore mesoscale dynamics that strongly influenced the shelf circulation off ningaloo the field observations revealed several northward flow reversals accompanied by cooling of the coastal waters adjacent to ningaloo which were associated with strong northward wind events analysis of the coastal heat budget revealed that cooling events were primarily driven by upwelling whereas warming of coastal waters during relaxation events resulted mostly from along shelf advection of warm water from the north due to the combined effects of its relatively steep 1 50 slope shelf and strong summer stratification upwelled water was sourced from the interior of the water column likely influencing the sources and fluxes of nutrients to ningaloo reef

momentum balances on the north carolina inner shelf four months of moored current pressure temperature conductivity wave and wind observations on the north carolina shelf indicate three dynamically distinct regions the surf zone the inner shelf between the surf zone and the 13 m isobath and the midshelf in the surf zone the along shelf momentum balance is between the cross shelf gradient of the wave radiation stress and the bottom stress the linear drag coefficient in the surf zone is about 10 times larger than seaward of the surf zone on the inner shelf the along shelf momentum balance is also frictional the along shelf wind stress and pressure gradient are balanced by bottom stress in the cross shelf momentum balance the pressure gradient is the superposition of roughly equal contributions from the coriolis force geostrophy and wave setdown from shoaling unbroken surface gravity waves at midshelf the along shelf momentum balance is less frictional and hence flow accelerations are important the cross shelf momentum balance is predominantly geostrophic because the greater depth and smaller bottom slope at midshelf reduce the importance of wave setdown the cross shelf density gradient is in thermal wind balance with the vertical shear in the along shelf flow in depths as shallow as 10 m the dominant along shelf momentum balances provide a simple estimate of the depth averaged along shelf current in terms of the measured forcing i e wind stress wave radiation stress divergence and along shelf pressure gradient that reproduces accurately the observed cross shelf variation of the depth averaged along shelf current between the surf zone and midshelf

shelf circulation induced by an orographic wind jet the dynamical response to cross shelf wind jet episodes is investigated the study area is located at the northern margin of the ebro shelf in the northwestern nw mediterranean sea where episodes of strong northwesterly wind occur in this case the wind is channeled through the ebro valley and intensifies upon reaching the sea resulting in a wind jet the wind jet response in terms of water circulation and vertical density structure is investigated using a numerical model the numerical outputs agree with water current observations from a high frequency radar additionally temperature sea level and wind measurements are also used for the skill assessment of the model for the wind jet episodes the numerical results show a well defined two layer circulation in the cross shelf direction with the surface currents in the direction of the wind this pattern is consistent with sea level set down due to the wind effect the comparison of the vertical structure response for different episodes revealed that the increase of stratification leads to an onshore displacement of the transition from inner shelf to mid shelf in general the cross shelf momentum balance during a wind jet episode exhibits a balance between the frictional terms and the pressure gradient in shallow waters shifting to a balance between the coriolis force and the wind stress terms in deeper waters

along shelf current variability on the catalan inner shelf nw mediterranean 1 we examine the circulation over the inner shelf of the catalan sea using observations of currents obtained from three acoustic doppler current profilers two at 24 m and one at 50 m during march april 2011 the along shelf current fluctuations during that period are mainly controlled by local wind stress on short time scales and by remote pressure gradients on synoptic time scales different forcing mechanisms are involved in the along shelf momentum balance during storm conditions wind stress sea level gradients and the nonlinear terms dominate the balance during weak wind conditions the momentum balance is controlled by the pressure gradient while during periods of moderate wind in the presence of considerable stratification the balance is established between the coriolis and wind stress terms vertical variations of velocity are affected by the strong observed density gradient the increased vertical shear is accompanied by the development of stratified conditions due to local heating when the wind is not able to counteract and break stratification the occasional influence of the besos river plume is observed in time scales of hours to days in a limited area in near the city of barcelona the area affected by the plume depends on the vertical extent of the fresher layer the fast river discharge peak and the relaxation of cross shore velocities after northeast storm events this contribution provides a first interpretation of the inner shelf dynamics in the catalan sea

coastal water circulation patterns around the northern channel islands and point conception california abstract the northern channel islands in california host multiple marine protected areas containing kelp forest ecosystems little is known about the water circulation onshore of the 20 m isobath we use water velocity recorded at 21 sites near the 15 m isobath at the islands and mainland during 1999 2012 to describe the water circulation on time scales of days to months the mean circulation is eastward or weak at the islands but poleward along the mainland speeds 0 10 cm s 1 the subinertial frequency along shelf flow is surface intensified and reverses direction on time scales of days in summer the flow becomes more poleward throughout the region the mean cross shelf flow profiles are strikingly similar at most sites with flow speeds 1 2 cm s 1 the mean flow near bottom in the vicinity of the kelp forests is offshore the time varying two layered response to wind is stronger up to 6 cm s 1 the flushing time of the shelf onshore of the 15 m isobath is short at most 2 dy at a few sites exposed to the prevailing wind up to 60 of the velocity variance is predictable from wind measured in the santa barbara channel in the lee of point conception or at the islands however regional wind explains little of the velocity variance during weak winds the velocity at some mainland but not island sites responds to pressure gradients measured along the mainland coast these pressure gradients are associated with local wind relaxations at pt conception not with remotely generated coastal trapped waves

momentum balances on the inner continental shelf at martha s vineyard coastal observatory 1 the subtidal depth average momentum balances in 12 m and 27 m water depth are investigated using observations from 2001 to 2007 of water velocity temperature and density bottom pressure surface gravity waves and wind stress in the fluctuating across shelf momentum budget the dominant terms are surface wind stress pressure gradient and coriolis acceleration the balance is a combination of 1 the geostrophic balance expected at midshelf sites and 2 the coastal setup and setdown balance driven by the across shelf wind stress expected where surface and bottom boundary layers overlap at the 12 m site the estimated wave radiation stress gradient due to surface gravity wave shoaling is also large but is uncorrelated with the observed pressure gradient a simple model suggests the wave radiation stress gradient is balanced by an across shelf pressure gradient with a spatial scale too small to resolve with this mooring array in the fluctuating along shelf momentum balance the dominant terms are surface wind stress pressure gradient and bottom stress at the shallower site but the other estimated terms are not negligible our results support the grant and madsen 1986 formulation for wave induced bottom stress the fluctuating along shelf pressure gradient is mainly a local sea level response to wind forcing not a remotely generated pressure gradient a strong correlation between along shelf velocity and along shelf wind stress at the shallower site is captured by a simple steady model of imbalance between wind stress and pressure gradient balanced by linear bottom drag

circulation on the continental shelf of the southeastern united states part i subtidal response to wind and gulf stream forcing during winter abstract subtidal current and sea level response to wind and gulf stream forcing are investigated for the south atlantic bight shelf during winter conditions low frequency flow variability in the outer shelf results primarily from wavelike meanders and eddies in the gulf stream front that occur in a 2 day to 2 week period band current meter derived vertically integrated momentum balances indicated that these large amplitude flow events are in approximate geostrophic balance with baroclinic pressure gradients induced by northward propagating gulf stream disturbances low frequency flow at midshelf is primarily a local ekman response to wind forcing cross shelf momentum balance for the total water column is between the along shelf geostrophic current and the cross shelf barotropic pressure gradient resulting from wind induced sea level changes at the coast this balance holds for both mean and fluctuating parts of the flow with the along shelf barotropic current lagging sea level by 6 to 12 hours and al

subinertial currents on the southern califoinia shelf abstract subinertial currents on the southern california shelf are investigated using observations from a current meter array deployed near san diego during the summer fall and winter of 1978 79 this region is characterized by weak winds order 1 2 m s 1 and thus other driving mechanisms for the subinertial currents may be important a simplified depth averaged longshore momentum equation consisting of a balance between current accelerations the adjusted sea level asl gradient and the wind and bottom stress is examined the asl gradient is estimated using sea level and atmospheric pressure observations separated by 350 km a linear parameterization of the bottom stress is used with a drag coefficient of 5 10 4 m s 1 during fall and winter the first order balance of terms in the longshore momentum equation over the inner shelf 15 m depth is between the wind and bottom stress over the outer shelf 60 m the primary balance is between the asl gradient and the bottom stress at midshelf 30 m bo

tomographic imaging of seismic velocity structure in and around the onikobe volcanic area northeastern japan implications for fluid distribution abstract we estimated three dimensional p vp and s wave velocity vs and vp vs structures in and around the onikobe volcanic area northeastern japan by local travel time tomography we used travel time data from source and receiver pairs located within and outside the study area which plays an important role in obtaining the optimum ray coverage and in elucidating the deeper structure more accurately detailed information on deeper structures is essential for imaging the complete volcanic system from the magmatic source zone through areas of shallow hydrothermal circulation more than 50 000 travel time data for the p waves and 35 000 for the s waves were used to image the velocity structure our results show the following dominant features 1 two conduits in the upper crust with low vp and low vs indicative of h2o rich fluid pathways one lying beneath naruko volcano the other beneath the focal area of the 1962 northern miyagi earthquake m6 5 2 an underlying broad region in the lower crust with low vp low vs and high vp vs suggestive of a zone of partial melt from which the fluids in 1 are derived and 3 low vp vs areas near the surface of the sanzugawa and onikobe calderas suggesting a diffuse vapor saturated cap

wind modulated buoyancy circulation over the texas louisiana shelf this numerical investigation examines buoyancy driven circulation on the texas louisiana shelf modulated by seasonal winds in wintertime with downcoast in the direction of kelvin wave propagation wind forcing the mississippi atchafalaya river plume exhibits a bottom advected pattern the plume is fairly wide and the horizontal density gradients span almost across the entire shelf inshore of 50 m within the plume vertical shear of alongshore flow is in thermal wind balance with the cross shore density gradient and the shear causes a slight reversal of alongshore flow near the bottom an alongshore flow estimated by the thermal wind relation along with an assumption of zero bottom velocity generally well agrees with the actual flow near the surface in regions deeper than 20 m in spring and summer the thermal wind balance derived flow deviates from the actual alongshore flow and an ekman flow driven by strong onshore wind makes the major contribution to the deviation besides the summertime upcoast wind component transforms the plume to a surface advected state resulting in reduced cross shore density gradients and increasing the relative importance of wind driven barotropic alongshore flow which contributes to the remaining deviation

the spatial structure of tidal and mean circulation over the inner shelf south of martha s vineyard massachusetts abstractthe spatial structure of the tidal and background circulation over the inner shelf south of martha s vineyard massachusetts was investigated using observations from a high resolution high frequency coastal radar system paired with satellite ssts and in situ adcp velocities maximum tidal velocities for the dominant semidiurnal constituent increased from 5 to 35 cm s 1 over the 20 km wide domain with phase variations up to 60 a northeastward jet along the eastern edge and a recirculation region inshore dominated the annually averaged surface currents along with a separate along shelf jet offshore owing in part to this variable circulation the spatial structure of seasonal sst anomalies had implications for the local heat balance cooling owing to the advective heat flux divergence was large enough to offset more than half of the seasonal heat gain owing to surface heat flux tidal stresses were the largest terms in the mean along and across shelf momentum equations in the area of the reci

complex mean circulation over the inner shelf south of martha s vineyard revealed by observations and a high resolution model 1 inner shelf circulation is governed by the interaction between tides baroclinic forcing winds waves and frictional losses the mean circulation ultimately governs exchange between the coast and ocean in some cases oscillatory tidal currents interact with bathymetric features to generate a tidally rectified flow recent observational and modeling efforts in an overlapping domain centered on the martha s vineyard coastal observatory mvco provided an opportunity to investigate the spatial and temporal complexity of circulation on the inner shelf adcp and surface radar observations revealed a mean circulation pattern that was highly variable in the alongshore and cross shore directions nested modeling incrementally improved representation of the mean circulation as grid resolution increased and indicated tidal rectification as the generation mechanism of a counter clockwise gyre near the mvco the loss of model skill with decreasing resolution is attributed to insufficient representation of the bathymetric gradients h h which is important for representing nonlinear interactions between currents and bathymetry the modeled momentum balance was characterized by large spatial variability of the pressure gradient and horizontal advection terms over short distances suggesting that observed inner shelf momentum balances may be confounded given the available observational and modeling data this work defines the spatially variable mean circulation and its formation mechanism tidal rectification and illustrates the importance of model resolution for resolving circulation and constituent exchange near the coast the results of this study have implications for future observational and modeling studies near the mvco and other inner shelf locations with alongshore bathymetric variability

earthquake potential along the northern hayward fault california the hayward fault slips in large earthquakes and by aseismic creep observed along its surface trace dislocation models of the surface deformation adjacent to the hayward fault measured with the global positioning system and interferometric synthetic aperture radar favor creep at 7 millimeters per year to the bottom of the seismogenic zone along a 20 kilometer long northern fault segment microearthquakes with the same waveform repeatedly occur at 4 to 10 kilometer depths and indicate deep creep at 5 to 7 millimeters per year the difference between current creep rates and the long term slip rate of 10 millimeters per year can be reconciled in a mechanical model of a freely slipping northern hayward fault adjacent to the locked 1868 earthquake rupture which broke the southern 40 to 50 kilometers of the fault the potential for a major independent earthquake of the northern hayward fault might be less than previously thought

long term observations of turbulent reynolds stresses over the inner continental shelf abstractin situ observations of turbulent momentum flux or reynolds stresses were estimated from a 10 yr acoustic doppler current profiler adcp record of inner shelf velocities at the martha s vineyard coastal observatory mvco using recently developed analysis techniques that account for wave induced biases these observations were used to examine the vertical structure of stress and turbulent mixing in the coastal ocean during tidal wave and wind driven circulation by conditionally averaging the dataset by the level of forcing or stratification present bottom intensified stresses were found during tidally driven flow having estimated eddy viscosities as high as 1 10 2 m 2 s 1 during slack water an assessment of the mean low wave low wind stress results quantified the magnitude of an unmeasured body force responsible for the mean circulation present in the absence of wind and wave forcing during weak stratification and isolated wind forcing downwind stresses matched the observed wind st

ocean currents along a nearshore frontal zone on the continental shelf of the southeastern united states abstract river and estuarine discharges mix to form a frontal zone along a 400 km length of the coast of the south eastern united states the frontal width extends from the coast outward 10 20 km two ships anchored across the frontal zone during autumn obtained simultaneous hourly profiles of currents and density for five consecutive tidal cycles the frontal zone contained a baroclinic coastal current flowing southward the flow was strongly convergent more water entered on the coastal side than exited on the seaward side much of the inflow was apparently turned southward thus the frontal zone acted as a dynamic barrier that inhibited the advection of mixed river discharge farther offshore a thermal wind relationship suitably predicted vertical shear through the frontal zone bottom friction seemed to play only a secondary role data suggest that the baroclinic coastal current was modified by the presence of a barotropic current seaward of the frontal zone the force responsible for the barotrop

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

wind driven currents on the west florida shelf abstract three weeks of current meter wind and sea level data off cedar key florida are analyzed currents and sea level are found to be coherent with alongshore wind stress in the synoptic band 0 05 0 25 cycle per day and to lag it by approximately half a day little coherence is found with cross shelf wind stress at the inshore mooring 22 m depth currents are nearly barotropic for these winter 1978 data a linear parameterization of bottom stress in the barotropic alongshore current leads to a bottom friction parameter r of 0 01 0 02 cm s 1 using coastal wind stress no significant steady alongshore slope is found during this short interval the dominant momentum balance in the alongshore direction is between wind and bottom stress the offshore frictional length scale csanady 1978 is estimated to be 75 100 km which implies a seaward extent to a depth of about 30 m at the offshore mooring 44 m depth there is vertical shear between the currents at 9 and 39 m the upper cross shelf compon

mg metasomatism and formation conditions of mg chlorite muscovite quartzphyllites leucophyllites of the eastern alps w hungary and their relations to alpine whiteschists the lower austroalpine orthogneiss micachist complex of the sopron fertorakos area of w hungary contains mg chlorite muscovite quartzphyllites leuco phyllite and mg chlorite bearing kyanite quartzites whose chemical compositions differ greatly from their surrounding rocks formation of leucophyllites took place in shear zones and was associated with depletion in alkalies and iron and enrichment of magnesium and h2o mg zonation of relict igneous muscovites of leucophyllites and changes in the whole rock chemical compositions suggest mg metasomatism material gains and losses have been assessed using the composition volume relationship approach proceeding from metagranite through transition rocks to leucophyllites mgo h2o feo and alkalies show continuously increasing dispersion in isocon plots with mg enrichment even in sheared gneiss not in contact with leucophyllite the metasomatic processes that formed the mg rich rocks may be similar to those responsible for the formation of high pressure whiteschists in the central and western alps the geochemical characteristics of the dora maira whiteschists italy and their country gneisses are very similar to those of the sopron leucophyllites supporting the theory that mg metasomatism produced the whiteschist chemistry on the basis of oxygen isotope compositions of relict igneous muscovites the precursor granitic rock had a 18o value around 13 proving its crustal anatectic origin the leucophyllites have whole rock oxygen isotope compositions around 8 5 which is in conflict with the theory of an mg rich sedimentary protolith rather the low 18o values reflect fluid rock interaction with a low 18o fluid quartz mineral oxygen isotope fractionations yield a metamorphic temperature of 560 30 c which agrees with earlier estimates from mineral stabilities silicon contents of phengites correspond to a metamorphic pressure of 13 gpa at this temperature indicating eclogite facies metamorphism the fluids in equilibrium with leucophyllites had oxygen isotope compositions around 7 9 similar to those calculated for the ultrahigh pressure dora maira whiteschists 7 6 further supporting the genetic link between the leucophyllites and whiteschists hydrogen isotope compositions of mixed white mica chlorite samples from leucophyllites range from 40 to 35 correlating with chlorite contents the calculated endmember chlorite and white mica have d values of 30 and 40 respectively the similar d values of the white micas in leucophyllites gneisses and metagranites suggest an overall equilibration with respect to h isotopes the calculated d value of the fluid is approximately 0 suggesting a seawater origin this conclusion was also reached for the dora maira whiteschists a possible fluid source that satisfies both metasomatic and isotopic data is dehydration of hydrothermally altered oceanic crust the mafic ultramafic complex of the alpine penninic unit underlying the austroalpine nappes is a likely candidate the subduction and subsequent dehydration of the ophiolite series would supply the mg rich fluids whose migration brought about the metasomatic alteration of the overlying gneiss micaschist complexes

kinematics of cretaceous nappe tectonics in the austroalpine basement of the koralpe region eastern austria krohe a 1987 kinematics of cretaceous nappe tectonics in the austroalpine basement of the koralpe region eastern austria tectonophysicz 136 171 196 the austroalpine basement of the koralpe area austria was affected by penetrative ductile deformation in the cretaceous three metamorphic events have been established ht lp metamorphism of unknown age a hercynian mt mp metamorphism and a cretaceous eo alpine mt mp metamorphism in the koralpe area cretaceous rb sr cooling ages of muscovite indicate temperatures of at least 500 o c during the eo alpine event the most intense deformation occurred along intracrustal shear zones plattengneis north to northeast directed thrusting is indicated by an inverted metamorphic gradient regional transposition of an older foliation s c fabrics and oblique quartz fabrics after development of high temperature mylonites low angle normal shear zones low temperature mylonites cut the uppermost parts of the austroalpine basement and indicate an extensional tectonic setting at about 85 to 90 ma s c and quartz fabrics indicate downdip movements of the hanging wall towards the northeast intracrystalline a slip in quartz caused strong preferred lattice orientation in high and low temperature mylonites during the e alpine deformation the basal a slip system is more pronounced at lower temperatures whereas a prism a system predominates at higher temperatures the overall kinematic history of the austroalpine nappe complex in the study area suggests a model in which an intracrustal south over north imbrication took place in an early stage of eo alpine collision these movements were outlasted by sinistral strike slip movement possibly due to oblique collision along irregular margins of the austroalpine and brianpnnais complexes the collision imbrication process resulted in crustal thickening isostatic uplift and thus extension of the higher parts of the crust low angle normal faulting initiated sedimentation in the intramontane c tic gosau basins of late cretaceous age

plate boundary kinematics in the alps motion in the arosa suture zone the arosa zone forms a melange complex along the penninic austroalpine boundary and belongs to the main alpine suture zone accretion and plate collision occurred during cretaceous and lower tertiary time a mixture of ophiolitic rocks and pelagic sediments is imbricated with flysch and blocks of austroalpine continental derivation we present a description of deformation structures an analysis of strain and a kinematic interpretation based on structural work deformation histories of imbricates show a translation path that was west directed between ca 110 and 50 ma and north directed thereafter the kinematics of the arosa zone agrees with the recently deduced displacement history of the austroalpine units in the eastern alps during the cretaceous orogeny this calls for a predominantly top to the west imbrication of austroalpine and penninic units and is in contradiction to what is inferred in most models of the eastern alps a direct relation between the deformation along the austroalpine margin and relative plate motion existed

field observations of wave driven setdown and setup wave driven setdown and setup observed for 3 months on a cross shore transect between the shoreline and 5 m water depth on a barred beach are compared with a theoretical balance between cross shore gradients of the mean water level and the wave radiation stress the observed setdown the depression of the mean water level seaward of the surf zone is predicted well when radiation stress gradients are estimated from the observations using linear theory at each location along the transect the observed setdown also agrees with analytical predictions based on offshore wave observations and the assumption of linear dissipationless normally incident waves shoaling on alongshore homogeneous bathymetry the observed setup the superelevation of the mean water level owing to wave breaking is predicted accurately in the outer and middle surf zone but is increasingly underpredicted as the shoreline is approached similar to previous field studies setup at a fixed cross shore location increases with increasing offshore wave height and is sensitive to tidal fluctuations in the local water depth and to bathymetric changes numerical simulations and the observations suggest that setup near the shoreline depends on the bathymetry of the entire surf zone and increases with decreasing surf zone beach slope defined as the ratio of the surf zone averaged water depth to the surf zone width a new empirical formula for shoreline setup on nonplanar beaches incorporates this dependence

alongshore momentum balance analysis on a cuspate foreland 1 nearshore measurements of waves and currents off cape hatteras north carolina u s a are used to investigate depth averaged subtidal circulation and alongshore momentum balances in the surf and inner shelf region around a cuspate foreland data were collected on both sides of the cape representing shorefaces with contrasting shoreline orientation north south vs northwest southeast subjected to the same wind forcing in the nearshore the subtidal flow is aligned with the local coastline orientation while at the cape point the flow is along the existing submerged shoal suggesting that cape associated shoals may act as an extension of the coastline alongshore momentum balance analysis incorporating wave current interaction by including vortex and stokes coriolis forces reveals that in deep waters surface and bottom stress are almost in balance in shallower waters the balance is complex as nonlinear advection and vortex force become important furthermore linearized momentum balance analysis suggests that the vortex force can be of the same order as wind and wave forcing farther southwest of cape hatteras point wind and wave forcing alone fail to fully explain subtidal flow variability and it is shown that alongshore pressure gradient as a response to the wind forcing can close the momentum balance adjacent tide gauge data suggest that the magnitude of pressure gradient depends on the relative orientation of local coastline to the wind vector and in a depth averaged sense the pressure gradient generation due to change in coastline orientation even at km length scale is analogous to the effect of alongshore variable winds on a straight coastline

rift parallel block like motion of the graben floor during the 2005 2010 afar rifting episode abstract crustal deformations associated with rifting episodes are often explained by both normal faulting and tensile opening in an elastic body suggesting no significant rift parallel displacements in this study using alos palsar pixel offset and multiple aperture interferometry mai data we detected 1 m of northwestward block like cumulative horizontal motion in the graben floor during the latter half of the 2005 2010 afar rifting episode ethiopia this horizontal block like motion can be explained by additional shallower strike slip on normal fault surfaces which was presumably aseismic due to the very small number of strike slip earthquakes and a significant gap between seismic and geodetic moment releases we conclude that the rift parallel movement can be interpreted by the strain accommodation of plate oblique spreading associated with dike intrusions as has been demonstrated for the 2014 bar arbunga dike intrusion episode although we do not propose direct evidence for the plate oblique spreading the complicated tectonic setting caused by the rotation of the danakil block and the upwelling plume beneath the afar triple junction may be drivers of the rift parallel motion associated with the afar dike intrusion

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

interplay of seismic and aseismic deformations during earthquake swarms an experimental approach observations of earthquake swarms and slow propagating ruptures on related faults suggest a close relation between the two phenomena earthquakes are the signature of fast unstable ruptures initiated on localized asperities while slow aseismic deformations are experienced on large stable segments of the fault plane the spatial proximity and the temporal coincidence of both fault mechanical responses highlight the variability of fault rheology however the mechanism relating earthquakes and aseismic processes is still elusive due to the difficulty of imaging these phenomena of large spatiotemporal variability at depth here we present laboratory experiments that explore in great detail the deformation processes of heterogeneous interfaces in the brittle creep regime we track the evolution of an interfacial crack over 7 orders of magnitude in time and 5 orders of magnitude in space using optical and acoustic sensors we explore the response of the system to slow transient loads and show that slow deformation episodes are systematically accompanied by acoustic emissions due to local fracture energy disorder features of acoustic emission activities and deformation rate distributions of our experimental system are similar to those in natural faults on the basis of an activation energy model we link our results to the rate and state friction model and suggest an active role of local creep deformation in driving the seismic activity of earthquake swarms

observations and a model of undertow over the inner continental shelf abstract onshore volume transport stokes drift due to surface gravity waves propagating toward the beach can result in a compensating eulerian offshore flow in the surf zone referred to as undertow observed offshore flows indicate that wave driven undertow extends well offshore of the surf zone over the inner shelves of martha s vineyard massachusetts and north carolina theoretical estimates of the wave driven offshore transport from linear wave theory and observed wave characteristics account for 50 or more of the observed offshore transport variance in water depths between 5 and 12 m and reproduce the observed dependence on wave height and water depth during weak winds wave driven cross shelf velocity profiles over the inner shelf have maximum offshore flow 1 6 cm s 1 and vertical shear near the surface and weak flow and shear in the lower half of the water column the observed offshore flow profiles do not resemble the parabolic profiles with maximum flow at middepth observed within the su

palaeostress estimation using calcite twinning experimental calibration and application to nature abstract by means of high temperature deformation experiments on calcite rocks of different grain sizes we have established the relationships between differential stress and twinning incidence twin density and volume fraction and the way that these relationships depend on grain size both twinning incidence and volume fraction increase with grain size at a constant level of differential stress log twin density is proportional to stress but is independent of grain size at a given grain size volume fraction of twinning increases non linearly with differential stress twinning activity measured by twinning incidence increases linearly with stress the behaviour of each of these parameters is independent of temperature strain and strain rate these relationships can be used as a basis for the estimation of palaeostress values in naturally deformed calcite rocks this is illustrated by a study of twinning activity in limestones close to thrust faults in the cantabrian zone of the variscan orogenic belt in northwestern spain high peak differential stresses were measured ranging from 150 to 250 mpa using the turner dynamic analysis technique however it is clear that shear stresses resolved parallel to the fault planes were very low the attainment of high stress differences when the resistance to faulting was low is attributed either to bending forces induced during the motion of the non planar surfaces relative to each other or to the stress peak being attained prior to the localization of deformation onto the fault surfaces

distorted drainage basins as markers of crustal strain east of the himalaya extensive lithospheric deformation on the eastern margin of the india eurasia collision has brought three major rivers into exceptionally close proximity for over 300 km the salween mekong and yangtze rivers are only tens of kilometers apart 10 times closer than rivers of comparable length elsewhere in the world we view deeply incised river valleys as displacement markers that move with the underlying crust over time scales of at least tens of millions of years accordingly the close spacing of these major rivers and their nearly parallel trends reflect the large crustal strains near the eastern himalayan syntaxis these river characteristics are consistent with two primary phases of deformation in this tectonic setting ne sw shortening of 0 5 oriented radially from the eastern syntaxis followed by dextral shear strain of 6 1 along a north trending zone pervasive shearing of this magnitude throughout the 150 km wide region of anomalous drainage would account for 1000 km of northward motion of india relative to southern china directly east of this region another 1000 km of northward motion is likely to have been accommodated by pervasive shearing through a zone hundreds of kilometers wide finally we draw attention to the remarkable accord between the arcuate paths of each of the three great rivers in the broader southeastern tibet region and small circles that curve around the eastern himalayan syntaxis

deformation induced resetting of rb sr and 40ar 39ar mineral systems in a low grade polymetamorphic terrane eastern alps austria a paradox in dating metamorphic events in low grade polymetamorphic terranes is exemplified by the eastern lower austroalpine nappes of the eastern alps here the last metamorphic event best recorded in post variscan cover rocks is dated as late cretaceous in age c 80 85 ma by white mica rb sr and 40 ar 39 ar systems within the underlying polymetamorphic basement 40 ar 39 ar and rb sr ages of phengitic white mica record only early and or late variscan ages 375 270 ma indicating that the alpine greenschist facies metamorphic overprint virtually caused no rejuvenation of variscan mineral ages based on these results the timing of a penetrative ductile top to wnw simple shear deformation recorded within both basement and cover rocks was contradictory deformation within the post variscan cover rocks had to be alpine in age whereas phengite 40 ar 39 ar ages from basement mylonites yield variscan ages to date this deformation directly we isolated different mineral size fractions 63 30 and 30 10 m from highly strained shearbands within the wechsel basement nappe a resulting rb sr errorchron pointed to an upper cretaceous age c 85 ma for the deformation consistent with the timing of alpine metamorphism in the cover rocks coarser grained white mica 150 300 im from similar basement mylonites do not reflect any alpine overprint of either k ar and or rb sr systems it follows that dynamic re and or neocrystallization induced by ductile deformation within the shearbands was the dominant process by which the rb sr system locally virtually re equilibrated this is valid even for overprinting metamorphic conditions below the temperatures required for ar diffusional loss in phengitic white mica c 40 ar 39 ar should be considered with caution

aseismic deformation of a fold and thrust belt imaged by synthetic aperture radar interferometry near shahdad southeast iran at depth many fold and thrust belts are composed of a gently dipping basal thrust fault and steeply dipping shallower splay faults that terminate beneath folds at the surface movement on these buried faults is difficult to observe but synthetic aperture radar sar interferometry has imaged slip on at least 600 km 2 of the shahdad basal thrust and splay fault network in southeast iran approximately 70 mm of thrust motion on the 88 dipping shahdad basal thrust occurred 8 30 km to the east of the 14 march 1998 fandoqa earthquake mw 5 6 6 that involved 1 6 m of oblique strike slip and normal slip displacement on a steeply dipping fault that earthquake transferred stress to the shahdad basal thrust and associated splays triggering slip either immediately or in the following six months modeling shows that to produce the observed surface deformation the shahdad faults must have accommodated a nearly complete release of the shear stress increase this could be due to either low friction on the faults or deformation throughout a wedge of material that is everywhere close to failure the anomalously small magnitude of displacement on the shahdad basal thrust and splay faults compared to the area of slip suggests a slip mechanism that is likely aseismic

aseismic creep along the san andreas fault northwest of parkfield ca measured by radar interferometry ers 1 radar images acquired 14 months apart studied by differential radar interferometry show the wide area distribution of aseismic creep along the fault segment northwest of parkfield california a sharp discontinuity in the interferometric phase of less than 2 cm equivalent line of sight displacement extends over 80 km in the differential interferogram coincident with the mapped trace of the active san andreas fault and consistent with the expected and measured fault motion although patterns of strain associated with the transition from locked to creeping are not clearly identifiable a decrease in creep displacement from northwest to southeast along the fault is visible the observations are in agreement with a model of elastic deformation constrained by in situ data that supports a maximum expected deformation signature of 10 mm across the image

west florida shelf response to local wind forcing april 1998 we compare west florida shelf velocity and sea level data with a model simulation for april 1998 responses for three upwelling and three downwelling favorable wind events are documented along shelf jets accompanied by oppositely directed upper and lower layer across shelf flows with connecting vertical velocity comprise the fully three dimensional inner shelf responses which are sensitive to stratification with an initial density field representative of april 1998 the model simulates velocity and sea level variations in general agreement with the observations whereas substantial mismatches occur without stratification despite the winds being the primary motive agent for the inner shelf the stratification dependence requires that model density fields be maintained through a combination of adequate initial conditions surface offshore and land derived buoyancy inputs and data assimilation dynamical analyses define the inner shelf as the region where the surface and bottom boundary layers are important in the momentum balance kinematically this is where surface ekman layer divergence fed by the bottom ekman layer convergence or conversely sets up the across shelf pressure gradient stratification causes a response asymmetry wherein the offshore scale and magnitude of the upwelling responses are larger than those for the downwelling responses this asymmetry is attributed to thermal wind effects across the bottom ekman layer buoyancy torque by isopycnals bending into the bottom adds constructively destructively with planetary vorticity tilting under upwelling downwelling favorable winds and this may have important implications for nutrients and other material property distributions on the shelf

nonplanar fault source modeling of the 2008 mw 6 9 iwate miyagi inland earthquake in northeast japan we use crustal deformation data sets acquired by the phased array type l band synthetic aperture radar palsar and the japanese nationwide global positioning system gps earth observation network geonet to develop a fault source model for the 2008 iwate miyagi inland earthquake m w 6 9 that occurred on 14 june 2008 in northeastern honshu japan the palsar data include interferometric synthetic aperture radar insar range offset and azimuth offset acquired from both ascending and descending paths the range and azimuth offset data are the only quantitative deformation signals around the epicenter and exhibit complicated signals that were not detected by the gps data we refine our preliminary model by using green s functions from triangular dislocation elements to represent nonplanar fault geometries although a single segment model can well explain the gps data it generates significant misfit residuals in the offset data thus both west dipping and east dipping segments are necessary as also suggested from aftershock distribution data the moment magnitudes of the west dipping and east dipping faults are 6 53 and 6 76 respectively and the total sum 6 87 is almost identical to the seismological moment magnitude this result suggests that both segments contributed equally to the total seismic moment demonstrating a complex rupture process of the inland earthquake

on the longshelf structure and dynamics of subtidal currents on the eastern united states continental shelf abstract strong correlations were observed among subtidal longshelf currents from the middle atlantic bight mab to the georges bank region a distance spanning 615 km the longshelf current consisted predominantly of wind forced motions and freely propagating events which together accounted for 75 90 of the longshelf current energy much stronger longshelf currents were observed in the mab than on georges bank the mab georges bank energy ratio for wind forced currents on the 60 m isobath was 20 the ratio for freely propagating events was 3 the magnitudes of many of the terms in the vertically integrated wind driven momentum equations were estimated from observations of current pressure and surface stress and from calculations of bottom stress the cross shelf momentum balance was geostrophic surface and bottom stress the longshelf pressure gradient and the coriolis force on the cross shelf flow were important terms in the longshelf momentum balance an analytic model of wind forced current w

an alongshore momentum budget over a fringing tropical fore reef author s arzeno isabella b collignon audric merrifield mark giddings sarah n pawlak geno

postseismic mantle relaxation in the central nevada seismic belt holocene acceleration of deformation and postseismic relaxation are two hypotheses to explain the present day deformation in the central nevada seismic belt cnsb discriminating between these two mechanisms is critical for understanding the dynamics and seismic potential of the basin and range province interferometric synthetic aperture radar detected a broad area of uplift 2 to 3 millimeters per year that can be explained by postseismic mantle relaxation after a sequence of large crustal earthquakes from 1915 to 1954 the results lead to a broad agreement between geologic and geodetic strain indicators and support a model of a rigid basin and range between the cnsb and the wasatch fault

the impact of storms and stratification on sediment transport in the rhine region of freshwater influence we present measurements of along and across shore sediment transport in a region of the dutch coast 10 km north of the rhine river mouth this section of the coast is characterized by strong vertical density stratification because it is within the midfield region of the rhine region of freshwater influence where processes typical of the far field such as tidal straining are modified by the passage of distinct freshwater lenses at the surface the experiment captured two storms and a wide range of wind wave tidal and stratification conditions we focus primarily on the mechanisms leading to cross shore sediment flux at a mooring location in 12 m of water which are responsible for the exchange of sediment between the nearshore and the inner shelf net transport during storms was directed offshore and influenced by cross shelf winds while net transport during spring tides was determined by the mean state of stratification tidal straining dominated during neap tides however cross shore transport was negligible due to small sediment concentrations the passage of freshwater lenses manifested as strong pulses of offshore transport primarily during spring tides we observe that both barotropic and baroclinic processes are relevant for cross shore transport at depth and since transport rates due to these competing processes were similar the net transport direction will be determined by the frequency and sequencing of these modes of transport based on our observations we find that wind and wave driven transport during storms tends move fine sediment offshore while calmer more stratified conditions move it back onshore

surf zone longshore currents and random waves field data and models abstract analytic and numerical models for longshore currents generated by obliquely incident random waves am compared with field observations five days of observations were selected during which the waves were narrow banded in both frequency and direction in keeping with model assumptions the extensive measurements included radiation stress and wave directional spectra in 9 m depth and a closely spaced array of current and pressure sensors on a line perpendicular to shore the longshore current models are based on balancing the gradient of the radiation stress with the alongshore bed shear and reynold s stresses assuming stationary wave conditions and straight and parallel bottom contours the spatial variation of wave height required to determine the gradient of the radiation stress is modeled using linear random wave theory given hrms in 9 m depth the model predicts hrms at shoreward locations with an average error of less than 9 using a nonlinear bottom shear stress formulation and the meas

multiply deformed terrains problems of correlation abstract the best tools available for carrying out a structural analysis in a complex area are overprinting style and patterns of orientation unfortunately all have limitations which are reviewed briefly and discussed in areas of continuous unfaulted outcrop the deformational history can be established purely on the basis of overprinting but even in such areas there can be problems since not all overprinting relationships are unambiguous most fold interference patterns are reliable overprinting relationships based on foliations however are commonly unreliable and various examples are cited and discussed even in areas where the sequence of deformational events can be established their temporal significance is unclear since the methods applied only determine local relative timing and absolute relationships must vary in space and time across an orogen

structural evolution of an antiformal window the scheiblingkirchen window eastern alps austria abstract the scheiblingkirchen window a lower austroalpine tectonic window at the eastern margin of the eastern alps austria was formed during late cretaceous continent continent collision structural investigations including structural mapping microstructural studies and texture analysis revealed a decompression related three stage tectonic history of lower austroalpine units during the formation of the scheiblingkirchen window 1 intra lower austroalpine nappe stacking was by top to the n out of sequence thrusting of the kirchberg fold nappe over the wechsel nappe under lower greenschist facies metamorphic conditions the structural expression of the stacking event d1 comprises a penetrative foliation containing a n s trending stretching lineation isoclinal recumbent folds trending subparallel to the stretching lineation and ultramylonites quartz and calcite microstructures indicate that dynamic recrystallization processes accompanied deformation their commonly moderately developed lattice preferred orientation record dominant slip on the prism and rhomb planes parallel to a 2 subsequent exhumation of previously stacked rocks is related to the formation of foliation parallel mylonitic shear zones within an e w extensional regime d2 microstructures and textures suggest similar deformation temperatures during thrusting and extension 3 a superimposed phase of nw se oriented horizontal shortening d3 was accommodated by large and small scale upright folding of the area around ne sw trending axes and by backthrusting leading to the antiformal doming of the scheiblingkirchen window subsequent subvertical flattening resulting from the shortening phase led to the formation of ne sw trending outcrop scale open recumbent folds low temperature deformation conditions as inferred from the low degree of recrystallization of quartz and calcite aggregates and the dominance of glide on the basal planes point to a cooling related deformation event

field observations of wave setup wave setup is assumed to be a balance between the cross shore convergence of the onshore flux of momentum wave radiation stress sxx in the surfzone and a cross shore pressure gradient oceanic observations between the 2 and 8 m isobaths near duck north carolina provide a test of the wave setup balance without assuming that wave height in the surfzone is proportional to water depth analysis of data from a cross shore array of 11 pressure gauges and 10 sonar altimeters deployed during the fall of 1994 indicates the wave setup balance holds to at least the accuracy of the pressure measurements a few centimeters the correlation between the two terms in the setup balance is 0 93 and the linear regression slope is 1 05 0 19 accurate estimates of the cross shore pressure gradient require density measurements to adjust pressure measurements taken at different depths to the same level the assumption that pressure and bathymetry are linear between the 2 and 8 m isobaths or the more common assumption that the height of normally incident shallow water waves is proportional to the water depth introduces errors of up to 6 cm for the conditions considered here given this assumption 3 5 years of data from pressure gauges in 2 and 8 m of water indicate that the wave setup balance is valid for a wide range of conditions correlation 0 71 and regression slope 0 98 0 08

active salt tectonics in the needles district canyonlands utah as detected by interferometric synthetic aperture radar and point target analysis 1992 2002 1 the needles district in canyonlands national park utah is known for its well exposed array of extensional faults which are thought to be produced by gravity driven extension and downward flexure of a thin sandstone plate into the colorado river canyon in response to dissolution and flow of underlying evaporites halite and gypsum owing to a lack of precise geodetic data however it remains uncertain if and to what extent those extensional faults are currently deforming in this study we use synthetic aperture radar sar data to search for ongoing decadal ground displacements by applying both a stacking interferometric sar insar analysis and interferometric point target analysis ipta our results show that most of the needles district is indeed undergoing deformation now at a maximum rate of 2 3 mm year away from the satellite looking roughly westward with an incidence angle of about 20 also we identify a localized region along the riverbank that is uplifting at a rate of 2 3 mm year we estimate the measurement precision to be better than 0 8 mm year except along the riverbank where the errors are probably higher than this by analyzing residual signals and carrying out a signal recovery experiment using synthetic two dimensional correlated noise the deforming region is almost totally bounded by the colorado river canyon to the west and north a rapidly subsiding east west trending graben to the south and a relatively sharp to very diffuse deformation gradient to the east we observe deformation patterns that were previously undetected these include an area in the southwestern part of the deforming region that is deforming at higher rates than anywhere else in the needles but that has little surface extensional faulting rates of deformation are lower but still clearly significant further north in a region of spectacularly exposed fault blocks that have been previously studied in considerable detail

ocean currents and sea surface heights estimated across the west florida shelf abstract the across shelf structures of the ocean circulation and the associated sea surface height ssh variability are examined on the west florida shelf wfs for the 3 yr interval from september 1998 to december 2001 five sets of characteristic circulation patterns are extracted from 2 day low pass filtered data using the self organizing map extreme upwelling and downwelling structures with strong currents asymmetric upwelling and downwelling structures with moderate currents and a set of transitional structures with weak currents the temporal variations of these structures are coherent with the local winds on synoptic weather time scales on seasonal time scales they are related to both the local winds and the water density variations the circulation is predominantly upwelling during autumn to spring months october april and downwelling during summer months june september coastal sea level fluctuations are related to both the dynamical responses of the inner shelf circulation to meteorol

slow earthquake in afghanistan detected by insar 1 the chaman fault system forms a prominent 900 km long left lateral transform plate boundary between the indian and eurasian plates in afghanistan and pakistan here we show satellite radar interferometry data that revealed an afterslip or slow earthquake signal following an earthquake of magnitude 5 0 this slow slip episode lasted for more than a year and accompanied a widespread creep signal that occurred at least 50 km along the fault we detected no surface slip before the earthquake during the 1 5 years sampled by our data this finding of long lasting widespread afterslip demonstrates that the plate motion along the chaman fault is accommodated by slow slip episodes following moderate earthquakes and suggests that a potential for magnitude 7 class earthquakes was significantly reduced the duration and moment release of the detected afterslip do not fit the recently proposed scaling law for slow earthquakes

response of south carolina continental shelf waters to wind and gulf stream forcing during winter of 1986 the south carolina shelf water response to strong winter atmospheric forcing and gulf stream variations over the slope is discussed with the aid of a comprehensive set of atmospheric and oceanic observations made during project gale genesis of atlantic lows experiment a mixed response is observed to wind and gulf stream forcing subtidal variability of inner and middle shelf waters is primarily a barotropic forced response to coherent synoptic scale alongshore winds this response is not trapped over the shelf as has been found for other wide non equatorial shelves but is also significant at the shelf edge possibly because of the comparable widths of the shelf and slope the outer shelf also shows a significant gulf stream influence the gulf stream appears to have two preferred position modes either onshore with the stream flowing over the charleston bump and along the shelf break or offshore when the stream can be located up to 100 km east of the shelf break transition between the two states is rapid subtidal variability in the outer shelf is dominated by weekly period frontal eddies and meanders when the stream is in an onshore mode and by persistent southward flow when the stream is offshore this southward flow is produced by enlarged cyclonic eddies with upwelled centers located over the slope between the offshore stream and the shelf edge sometimes referred to as the charleston gyre positive mean alongshore sea level slopes at the shelf edge due to the persistence of the cyclonic gyres are geostrophically balanced by mean onshore flow which transports upwelled waters onto the shelf enhancing the biological productivity of the area relative to other regions of the south atlantic bight

coefficients for sea surface wind stress heat flux and wind profiles as a function of wind speed and temperature surface layer coefficients for wind profiles wind stress and heat flux in typical open sea conditions are briefly reviewed businger dyer flux gradient relationships and a charnock wind stress formula fit the empirical data and are dimensionally consistent these have been solved by an iterative method and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data

alongshore momentum balances in the nearshore the one dimensional time averaged over many wave periods along shore momentum balance between forcing by wind and breaking waves and the bottom stress is examined with field observations spanning a wide range of con ditions on a barred beach near bottom horizontal currents were measured for 2 months at 15 locations along a cross shore transect extending 750 m from the shoreline to 8 m water depth the hourly averaged bottom stress was estimated from observed currents using a quadratic drag law the wave radiation stress was estimated in 8 m depth from an array of pressure sensors and the wind stress was estimated from an anemometer at the seaward end of a nearby pier the combined wind and wave forcing integrated over the entire cross shore transect is balanced by the integrated bottom stress the wind stress contributes about one third of the forcing over the transect analysis of the momentum balances in different cross shore regions shows that in the surf zone wave forcing is much larger than wind forcing and that the bottom drag coefficient is larger in the surf zone than farther seaward consistent with earlier studies

volcanic subsidence triggered by the 2011 tohoku earthquake in japan the 2011 tohoku earthquake caused high levels of crustal deformation in japan analysis of satellite radar and gps data show that the earthquake caused nearby volcanic regions to subside instantaneously creating elliptical depressions that are parallel to the direction of quake induced crustal extension

silent slip on the cascadia subduction interface sensor arrays based on the global positioning system permit increasingly precise continuous monitoring of deformation in earth9s crust in his perspective thatcher highlights the report by dragert et al who have analyzed data from one such array and have detected a silent aseismic slip event in a subduction zone such events would normally be expected to be associated with recent earthquake activity much remains to be learned about earthquake stress buildup but thanks to gps and other technologies our understanding of earthquakes is rapidly expanding