controls on turbulent mixing in a strongly stratified and sheared tidal river plume abstractconsiderable effort has been made to parameterize turbulent kinetic energy tke dissipation rate e and mixing in buoyant plumes and stratified shear flows here a parameterization based on kunze et al is examined which estimates e as the amount of energy contained in an unstable shear layer ri ric that must be dissipated to increase the richardson number ri n2 s2 to a critical value ric within a turbulent decay time scale observations from the tidal columbia river plume are used to quantitatively assess the relevant parameters controlling e over a range of tidal and river discharge forcings observed e is found to be characterized by kunze et al s form within a factor of 2 while exhibiting slightly decreased skill near ri ric observed dissipation rates are compared to estimates from a constant interfacial drag formulation that neglects the direct effects of stratification this is found to be appropriate in energetic regimes when the bulk averaged richardson number rib is less than

wave breaking in dense plumes sinking dense plumes are important in many oceanographic settings notably the polar formation of deep and bottom waters the dense water sources feeding such plumes are commonly affected by tidal modulation leading to plume variability on short time scales in a simple unsteady theory of one dimensional plumes based on conservation equations for volume momentum and buoyancy this plume variability is manifested as waves that travel down the resulting current using numerical techniques applied to the hyperbolic conservation equations this study investigates the novel concept that these waves may break as they travel down the plumes triggering intense local mixing between the dense fluid and surrounding ocean the results demonstrate that the waves break at geophysically relevant distances from the plume source the location of wave breaking is very sensitive to plume drag from the seabed the properties of the dense source and the amplitude and period of the source modulation to the extent that the simple model represents the real world these results suggest that wave breaking originating from the tidal modulation of dense plumes could lead to a strong and previously unexplored source of local deep ocean mixing

deformation structures from splay and decollement faults in the nankai accretionary prism sw japan iodp nantroseize expedition 316 evidence for slow and rapid slip in fault rocks

reservoir turbidity current modeling with a two dimensional layer averaged model abstracta two dimensional layer averaged model is developed and verified to simulate turbidity current characteristics and its sluicing in reservoirs the governing equations consist of mass and momentum conservation laws for the turbidity current mixture equations for the sediment transport and bed dynamics and auxiliary relations for the interactions among clear water turbidity current and bed a finite volume unstructured polygonal mesh method is adopted so that reservoirs with complex terrains may be simulated special algorithms are developed to capture the turbidity current front movement through a clear water bed and to simulate turbidity current sluicing through reservoir outlets the developed model has been tested and verified with both conservative and nonconservative turbidity currents ranging from simple to complex reservoir terrains case studies presented include a lock exchange turbidity current with large eddy simulation and direct numerical simulation results a laboratory test of

interaction between an inclined gravity current and a pycnocline in a two layer stratification a series of laboratory experiments were conducted to investigate the characteristics of a dense gravity current flowing down an inclined slope into a quiescent two layer stratification the presence of the pycnocline causes the gravity current to split and intrude into the ambient at two distinct levels of neutral buoyancy as opposed to the classical description of gravity currents in stratified media as being either a pure underflow or interflow the splitting behaviour is observed to be dependent on the richardson number ri unicode stix x1d70c of the gravity current formulated as the ratio of the excess density and the ambient stratification for low ri unicode stix x1d70c underflow is more dominant while at higher ri unicode stix x1d70c interflow is more dominant as ri unicode stix x1d70c increases however we find that the splitting behaviour eventually becomes independent of ri unicode stix x1d70c additionally we have also identified two different types of waves that form on the pycnocline in response to the intrusion of the gravity current an underflow dominated regime causes a pycnocline displacement where the speed of the wave crest is locked to the gravity current whereas an interflow dominated regime launches an internal wave that moves much faster than the gravity current head or interfacial intrusion

mixing and entrainment in the red sea outflow plume part i plume structure when the salty and heavy water of the red sea exits from the strait of bab el mandeb it continues downslope into the gulf of aden mainly along two channels the 130 km long northern channel nc is topographically confined and is typically only 5 km wide in it the red sea plume shows unanticipated patterns of vertical structure turbulent mixing and entrainment above the seafloor a 25 120 m thick weakly stratified layer shows little dilution along the channel hence this bottom layer undergoes only weak entrainment in contrast a 35 285 m thick interfacial layer shows stronger entrainment and is shown in a companion paper to undergo vigorous turbulent mixing it is thus the interface that exhibits the bulk of entrainment of the red sea plume in the nc the interfacial layer also carries most of the overall plume transport increasingly so with downstream distance the southern channel sc is wider than the nc and is accessed from the latter by a sill about 33 m above the floor of the nc entrainment into the bottom layer of the sc is diagnosed to be strong near the entry into the sc such that the near bottom density and salinity are smaller in the sc than in the nc at the same distance from bab el mandeb in comparison with winter conditions the authors encountered weaker outflow with shallower equilibration depths during the summer cruise bulk froude numbers computed for the whole plume varied within the range 0 2 1 local maxima occurred in relatively steep channel sections and coincided with locations of significant entrainment

paleochannel sands as conduits for hydrocarbon leakage across faults an example from the wilmington oil field california this article evaluates the impact of a submarine channel sand in the western wilmington oil field california on hydrocarbon accumulation and leakage across boundary faults the wilmington field is in a broad anticline broken into 10 fault blocks by normal faults the coarse grained channel deposit named t4 is identified in fault blocks i through iii within the tar zone a lower pliocene turbidite deposit and the shallowest productive zone in the area the channel deposit incised into three sand units t2 t5 and t7 evidences of tilted oil water contacts owc owc cutting structure depth contours scattered oil traces and fault seal analysis all indicate that the channel deposit is responsible for hydrocarbon leakage across the boundary faults the leakage occurs in the three channel incised sand units t2 t5 and t7 in fault block i hydrocarbons in the three sands charge the channel sand at the structural culmination and then leak across the eastern boundary wilmington fault into the wet s sand directly above the tar zone on the hanging wall block in fault block iia hydrocarbons from the t5 and t7 sands pool in the channel sand on the north flank and leak across the eastern boundary ford fault into the s sand on the hanging wall block this leakage across faults caused depletion of almost all hydrocarbon accumulations in the three channel incised sands in fault block i the leakage also raised owcs on the north flank in fault block iia resulting in tilted owcs in the two channel incised sand intervals

a regional modeling study of the entraining mediterranean outflow 1 we have evaluated a regional scale simulation of the mediterranean outflow by comparison with field data obtained in the 1988 gulf of cadiz expedition our ocean model is based upon the hybrid coordinate ocean model hycom and includes the richardson number dependent entrainment parameterization of xu et al 2006 given realistic topography and sufficient resolution the model reproduces naturally the major observed features of the mediterranean outflow in the gulf of cadiz the downstream evolution of temperature salinity and velocity profiles the mean path and the spreading of the outflow plume and most importantly the localized strong entrainment that has been observed to occur just west of the strait of gibraltar as in all numerical solutions there is some sensitivity to horizontal and vertical resolution when the resolution is made coarser the simulated currents are less vigorous and there is consequently less entrainment our richardson number dependent entrainment parameterization is therefore not recommended for direct application in coarse resolution climate models we have used the high resolution regional model to investigate the response of the mediterranean outflow to a change in the freshwater balance over the mediterranean basin the results are found in close agreement with the marginal sea boundary condition msbc a more saline and dense mediterranean deep water generates a significantly greater volume transport of the mediterranean product water having only very slightly greater salinity

descent and modification of the overflow plume in the denmark strait bulk properties of the denmark strait overflow dso plume observed in velocity and hydrography surveys undertaken in 1997 and 1998 are described despite the presence of considerable short term variability it is found that the pathway and evolution of the plume density anomaly are remarkably steady bottom stress measurements show that the pathway of the plume core matches well with a rate of descent controlled by friction the estimated entrainment rate diagnosed from the rate of plume dilution with distance shows a marked increase in entrainment at approximately 125 km from the sill leading to a net dilution consistent with previous reports of a doubling of overflow transport measured by current meter arrays the entrainment rate increase is likely related to the increased topographic slopes in the region compounded by a decrease in interface stratification as the plume is diluted and enters a denser background

seismic slip recorded by fluidized ultracataclastic veins formed in a coseismic shear zone during the 2008 mw 7 9 wenchuan earthquake dark aphanitic material occurs as a thin w 7 9 wenchuan china earthquake it also forms injection veins in a 5 cm wide coseismic shear zone within the longmen shan thrust belt powder x ray diffraction data and microstructural analysis indicate that the veins contain little or no glassy material and are composed of fine grained fragments set in an ultrafine grained matrix all sourced from the country rock of interbedded siltstone and mudstone on the basis of x ray diffraction and mesostructural and microstructural features it is concluded that these veins are ultracataclastic veins generated by coseismic comminution with little melting accompanied by rapid fluidization in the coseismic shear zone during the 2008 wenchuan earthquake the findings support earlier suggestions that 1 ultracataclastic veins that resemble pseudotachylyte veins in appearance can be generated by crushing and rapid injection accompanied by fluidization of fine grained material during seismic faulting with little or no melting and 2 ultracataclastic veins formed in this way may record seismic slip events in seismogenic fault zones acting as earthquake fossils in much the same way as pseudotachylyte veins

a numerical investigation of the dynamics and structure of hyperpycnal river plumes on sloping continental shelves 1 a 3 d hydrodynamic model regional ocean modeling system is used to investigate the dynamics and structure of hyperpycnal river plumes over sloping continental shelves the focus is on the plume s response to varying slopes and settling velocities ws the idealized model is configured to represent small mountainous river systems during a flood event a hyperpycnal sediment concentration of 60 g l is specified at the river mouth such that the sediment freshwater mixture is denser than the seawater causing the plumes to traverse the shelves as undercurrents a realistic range of shelf slope of 0 001 0 03 is chosen the settling velocity is varied based on river s carrying capacity the model derived velocity profiles and the entrainment rate compare favorably against prior laboratory experiments both cross shore and alongshore momentum balances are primarily between gravitational forcing and bottom friction but the coriolis deflection is significant at the plume core in the alongshore momentum budget i e ekman balance as the slope increases and settling velocity decreases hyperpycnal plumes transition from depositional to autosuspending regime an estimate of critical slope governed by a dimensionless parameter ws3 qb qb is buoyancy input reasonably captures the regime transition in the depositional regime the plume s runout cross shore penetration scales with advective distance increasing slopes and discharge enhance the gravitational forcing and plume velocity leading to an increase in runout in contrast increasing settling velocity shortens the vertical settling time thereby reducing the plume s horizontal footprint for the range of parameters considered the runout of depositional plumes is confined within 15 km from the mouth whereas the penetration of autosuspending plumes is essentially unlimited

co seismic ground shortening structures produced by the 2008 mw 7 9 wenchuan earthquake china abstract we observed ground shortening structures produced by the 2008 m w 7 9 wenchuan earthquake along the 285 km long wenchuan co seismic surface rupture zone the structures are characterized by co seismic thrusting and folding structures that include thrust fault scarps flexure slip folds and mole tracks fold structures are generally developed within alluvial deposits river channel deposits and sealed road surfaces mainly restricted to within a

hydraulic properties of a low permeable rupture zone on the yingxiu beichuan fault activated during the wenchuan earthquake china implications for fluid conduction fault sealing and dynamic weakening mechanisms abstract fluid transport properties of fault rocks are crucial parameters that affect earthquake nucleation and rupture propagation in this study we examined the internal structure mineral composition and fluid transport properties of fault rocks collected from two shallow boreholes penetrating a granitic rupture zone on the yingxiu beichuan fault ybf that was activated during the 2008 wenchuan earthquake fluid transport properties were measured using water as pore fluid at effective pressures p e ranging from 10 mpa to 165 mpa permeabilities of fault rocks exhibit a wide variation from 2 1 10 22 m 2 to 4 6 10 17 m 2 strongly depending on rock types and overburden pressure specifically at p e of 165 mpa the damage zone samples have permeabilities from 5 0 10 21 m 2 to 1 2 10 17 m 2 and the fault gouges are between 2 1 10 22 m 2 and 3 1 10 19 m 2 thus the ybf consists of a low permeability fault core acting as fluid barrier and surrounding high permeability damage zones acting as fluid conduits combining the structural and compositional results and transport data together we propose that the interplay between cataclasis and fluid rock interactions controls the hydraulic properties and their response to the fault zone evolution it is noteworthy that we measured extremely low permeabilities but high porosities and high specific storages for the gouges the cemented cataclasites which are inferred to be equivalent to the rocks in which the wenchuan earthquake nucleated also have low permeabilities suggesting the fault zone is a potential area for fluid storage and capable of generating high pore pressure at depths according to our laboratory data we found fluid pressurization could occur at depths below 2 7 km we suggest thermal pressurization has played an important role in causing the dynamic weakening of the wenchuan earthquake

structural analysis of coseismic normal fault zones of the 2011 mw 6 6 fukushima earthquake northeast japan the 2011 m w 6 6 fukushima earthquake occurred in iwaki city 250 km southwest of the epicenter of the 2011 m w 9 0 tohoku japan earthquake and produced two subparallel 15 23 km long surface rupture zones with distinct displacements along two pre existing normal faults the shionohira and yunodake faults which strike north northwest south southeast and northwest southeast both dipping southwest respectively field investigations and structural analysis of the coseismic shear zones developed within the shionohira and yunodake fault zones reveal that 1 the coseismic shear zones consist of a fault core that includes a narrow fault gouge zone of 10 cm in width generally 1 5 cm a fault breccia zone of 50 cm in width and a damage zone of 5 50 m in width that is composed of cataclastic rocks fractures and subsidiary faults 2 the foliations characterized by s c fabrics developed in the shear zones indicate a dominantly normal fault slip sense consistent with that observed along the coseismic surface ruptures and 3 veinlet cataclastic rocks composed of unconsolidated fault gouges and fine grained materials occur as simple discrete veinlets and multiple cross cutting interconnected networks of veinlets these newly documented structural characteristics for two coseismic fault shear zones and associated cataclastic rocks indicate that the locations of coseismic slip zones associated with the 2011 fukushima earthquake were controlled by pre existing fault shear zones central to the shionohira and yunodake faults which have repeatedly moved as seismogenic normal faults since the timing of formation of associated cataclastic rocks our results demonstrate that the structural analyses of coseismic shear fault zones provide a powerful tool to study the nature and active faulting history of seismological faults

cold outflow from the faroe bank channel abstract the exchange of water between the norwegian sea and the north atlantic around the faroe islands was investigated in 1987 and 1988 combining ctd data with shipborne acoustic doppler current profiler adcp measurements tests were devised to assess the accuracy of the adcp measurements and the results are described it is found that estimating a reference velocity for geostrophic measurements is limited by the presence of tides of order 10 cm s 1 in the outflow of cold water from the faroe bank channel which reaches speeds of nearly 1 m s 1 the error is acceptably small but strong time dependent components are revealed the discharge of cold water is traced 75 km beyond the sill of this channel and changes in potential temperature salinity and potential vorticity on an isopycnal surface are attributed to intense mixing an effective diffusivity near 100 cm2 s 1 is derived and k h instability demonstrated as a plausible source of the turbulent energy six current meter moorings were deployed from

focal mechanism of prehistoric earthquakes deduced from pseudotachylyte fabric fault pseudotachylytes form by frictional melting during seismic slip and therefore are widely interpreted as earthquake fossils rapid movement along a rupture surface typically forms a pseudotachylyte generation vein the thickness of which increases with earthquake magnitude the direction and sense of seismic slip cannot always be determined due to the generally complex geometry of pseudotachylyte veins here we show for the first time that the orientation of the magnetic fabric of fault pseudotachylytes indicates both direction and sense of seismic slip the magnetic fabric acquired in a manner similar to that of other magmas arises in this case from the asymmetric preferred orientation of paramagnetic grains during viscous shear of the friction melt this kinematic information coupled with fault plane orientation and generation vein thickness provides new and critical insight for the earthquake focal mechanism the magnetic fabric of pseudotachylytes therefore not only constitutes a valuable kinematic criterion for these fault rocks but also could expand our knowledge of prehistoric seismic events

oscillating dense plumes abstractthe flow of dense polar shelf waters down continental slopes is a critical component of the global ocean circulation recent observations suggest that such plumes can be heavily impacted by tidal variability and many of the world s important dense water sources are located in tidally active areas tides affect the source of dense water by modulating the location of hydrographic gradients and control the subsequent plume mixing and flow path in an effort to separate these effects dense plumes are modeled here by extending a classical one dimensional plume model to two unsteady scenarios in which the plume path is fixed the first case features a pulsed release of dense water into a stagnant ambient and the model predicts that gravity waves propagate down the plume advective waves in plume density travel with the mean velocity of the current and thus have a wavelength of the product of plume velocity and the oscillation period p the second case is of a steady sourced plume flowing through

active tectonics of the beichuan and pengguan faults at the eastern margin of the tibetan plateau the steep high relief eastern margin of the tibetan plateau has undergone rapid cenozoic cooling and denudation yet shows little evidence for large magnitude shortening or accommodation generation in the foreland basin we address this paradox by using a variety of geomorphic observations to place constraints on the kinematics and slip rates of several large faults that parallel the plateau margin the beichuan and pengguan faults are active dominantly dextral slip structures that can be traced continuously for up to 200 km along the plateau margin both faults offset fluvial fill terraces that yield inheritance corrected cosmogenic 10be exposure ages of 15 kyr indicating latest pleistocene activity the pengguan fault appears to have been active in the holocene at two sites along strike latest quaternary apparent throw rates on both faults are variable along strike but are typically 1 mm yr 1 rates of strike slip displacement are likely to be several times higher probably 1 10 mm yr 1 but remain poorly constrained late quaternary folding and dextral strike slip has also occurred along the western margin of the sichuan basin particularly associated with the present day mountain front these observations support models for the formation and maintenance of the eastern plateau margin that do not involve major upper crustal shortening they also suggest that activity on the margin parallel faults in eastern tibet may represent a significant seismic hazard to the densely populated sichuan basin

injection veins of crushing originated pseudotachylyte and fault gouge formed during seismic faulting this paper describes the injection veins of crushing originated pseudotachylyte and fault gouge formed along the iida matsukawa fault in granitic cataclasite southern nagano prefecture central japan the pseudotachylyte which shows a dense and aphanitic appearances and fault gouge occur as simple veins fault vein along the main fault plane and as complex network veins injection vein in the neighboring cataclasite locally the injection veins of pseudotachylyte and fault gouge can be traced back to the fault veins powder x ray diffraction patterns and petrological analysis indicate that both of the pseudotachylyte and fault gouge consist entirely of fine grained angular clasts and that the pseudotachylytes and fault gouges have a similar x ray diffraction patterns with that of the host granite the similarity of chemical compositions and distribution patterns of grain size also show that the injection veins of pseudotachylyte and fault gouge have the same source material as that of fault veins field occurrences and petrological characteristics strongly suggest that the injection veins of pseudotachylyte and fault gouge formed during seismic faulting by a rapid intrusion and fluidization of crushed fine grained materials generated in the shear zone in a gas solid fluid system

spatial variability of turbulent mixing in the abyssal ocean ocean microstructure data show that turbulent mixing in the deep brazil basin of the south atlantic ocean is weak at all depths above smooth abyssal plains and the south american continental rise the diapycnal diffusivity there was estimated to be less than or approximately equal to 0 1 x 10 4 meters squared per second in contrast mixing rates are large throughout the water column above the rough mid atlantic ridge and the diffusivity deduced for the bottom most 150 meters exceeds 5 x 10 4 meters squared per second such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry

structural analysis of the right lateral strike slip qingchuan fault northeastern segment of the longmen shan thrust belt central china abstract the eastern margin of the tibetan plateau is marked by the longmen shan thrust belt lstb which is dominated by thrust faults and thrust related fold structures that is home to the 2008 mw 7 9 thrusting type wenchuan earthquake although previous works demonstrated that the seismogenic fault for the earthquake changed coseismic slip sense from thrust dominated slip in the central and southeastern segments of the lstb to right lateral strike slip dominated displacement along the qingchuan fault northeastern segment of the lstb the related structures and current activity of the qingchuan fault remains unclear topographic analyses of 0 5 m resolution worldview imagery and digital elevation model dem data field investigations and structural analysis of the fault zone reveal that i stream channels and late pleistocene holocene terrace risers and alluvial fans are systematically offset dextrally along the qingchuan fault ii foliations developed in the fault zone indicate a right lateral strike slip dominated displacement and iii geological evidence and seismic data show that the qingchuan fault is currently active as the main seismogenic fault dominated by a right lateral strike slip with an average slip rate of ca 3 5 mm yr our results demonstrate that the spatial change in slip sense along the lstb from thrust dominated in the central and southwestern sectors to right lateral strike slip dominated in the northeastern sector is mainly caused by a change in the orientation of fault geometry from ne sw to ene wsw along the lstb

physical properties of surface outcrop cataclastic fault rocks alpine fault new zealand 1 we present a unified analysis of physical properties of cataclastic fault rocks collected from surface exposures of the central alpine fault at gaunt creek and waikukupa river new zealand friction experiments on fault gouge and intact samples of cataclasite were conducted at 30 33 mpa effective normal stress n using a double direct shear configuration and controlled pore fluid pressure in a true triaxial pressure vessel samples from a scarp outcrop on the southwest bank of gaunt creek display 1 an increase in fault normal permeability k 7 45 10 20 m2 to k 1 15 10 16 m2 2 a transition from frictionally weak 0 44 fault gouge to frictionally strong 0 50 0 55 cataclasite 3 a change in friction rate dependence a b from solely velocity strengthening to velocity strengthening and weakening and 4 an increase in the rate of frictional healing with increasing distance from the footwall fluvioglacial gravels contact at gaunt creek alteration of the primary clay minerals chlorite and illite muscovite to smectite kaolinite and goethite accompanies an increase in friction coefficient 0 31 to 0 44 and fault perpendicular permeability k 3 10 10 20 m2 to k 7 45 10 20 m2 comminution of frictionally strong 0 51 0 57 cataclasites forms weaker 0 31 0 50 foliated cataclasites and fault gouges with behaviors associated with aseismic creep at low strain rates combined with published evidence of large magnitude mw 8 surface ruptures on the alpine fault petrological observations indicate that shear failure involved frictional sliding within previously formed velocity strengthening fault gouge

mixing and entrainment in developing stratified currents the spatially developing region of a steady downslope current in transition from a hydraulically controlled arrested wedge flow is examined through a set of laboratory experiments the mixing and entrainment mechanisms at the shear interface are explored with the use of imaging techniques the initial unstable accelerating region characterized by rapid development low shear layer richardson numbers and high entrainment rates is limited by the effects of stratification which suppress the large scale overturning a subsequent high richardson number region is characterized by weak entrainment and the collapse of turbulence from the initial region the flow approaches a quasi stable state as the mixed layer draws energy from the accelerating density current observed large scale structure is attributed to an instability of the marginally unstable shear layer entrainment rates are calculated within each region for the various slopes considered and estimates for the extent of the transition regions are obtained

meso and microstructural analysis of coseismic shear zone of the 1999 mw 7 6 chi chi earthquake taiwan the surface rupture of the 1999 m w 7 6 chi chi taiwan earthquake was controlled primarily by the pre existing chelungpu fault zone which is distributed in a wide zone of up to 60 m although the main coseismic slip is localized in a narrow shear zone of 0 3 cm the chelungpu fault zone is composed of cataclasite fault breccia and gouge zones that are well observed in both the fault outcrops and the drill cores taken throughout the fault zone the foliations developed in the cataclasite and fault breccia zones are oriented parallel to that of the fault gouge zone where the main coseismic slip occurred the structural analyses of the shear zone and fault rocks show that the chelungpu fault zone has slipped as a thrust fault with a significant left lateral slip component since its formation in the pleistocene this oblique thrust motion is caused by the southeast northwest oblique convergence between the philippine sea plate and the eurasian plate

characteristics of the fault related rocks fault zones and the principal slip zone in the wenchuan earthquake fault scientific drilling project hole 1 wfsd 1 abstract scientific drilling in active faults after a large earthquake is ideal to study earthquake mechanisms the wenchuan earthquake fault scientific drilling project wfsd is an extremely rapid response to the 2008 ms 8 0 wenchuan earthquake which happened along the longmenshan fault eastern margin of the tibetan plateau in order to better understand the fault mechanism and the physical and chemical characteristics of the rocks the wfsd project will eventually drill 5 boreholes along the two main faults this paper focuses on the first hole wfsd 1 which started just 178 days after the earthquake down to a final depth of 1201 15 m petrological and structural analyses of the cores allowed the identification of fault related rocks in the yingxiu beichuan fault fault gouge cataclasite and fault breccia and the principle slip zone psz location of the wenchuan earthquake was determined we found 12 fault zones in the entire core profile with at least 10 including the yingxiu beichuan fault zone with a multiple cores structure and minimum width of 100 m the co seismic slip plane of the wenchuan earthquake at depth corresponding to the yingxiu beichuan fault zone at the outcrop as well as its psz was expected to be located at the bottom of the fault zone at 759 m depth instead it was found at 590 m depth with 1 cm wide fresh fault gouge as determined by logging data such as temperature natural gamma ray p wave velocity and resistivity combined with the fresh appearance magnetic susceptibility and microstructure of the gouge the wenchuan earthquake slip plane has a dip angle of 65 showing the high angle thrust feature the distribution of fault gouge with several meters thick the location of the wenchuan earthquake s psz and the thickness of fresh gouge all imply a correlation between the width of the fault zone and the number of seismic events

pseudotachylyte and fluid alteration at seismogenic depths glacier lakes and granite pass faults central sierra nevada usa we present evidence for ancient seismicity in the form of tectonic pseudotachylyte and coeval cyclic hydrothermal alteration and cataclasis along fault zones exhumed from 2 4 to 6 0 km in the central sierra nevada ca the glacier lakes fault glf and granite pass fault gpf are exhumed left lateral to left lateral oblique strike slip faults with up to 125 m of left lateral separation exposed in mesozoic granite and granodiorite plutons precipitation of epidote along fault slip surfaces chloritization of biotite saussurite and sericite alteration of plagioclase and quartz and calcite filled veins are present in the glf and gpf zones one difficulty encountered in studying exhumed fault zones is providing convincing evidence for a frictional melt origin of pseudotachylyte rocks in the field may preserve convincing evidence for frictional melt i e aphanitic dark injection structures that are later shown to be related to cataclasis or injection of hydrothermal fluids another challenge results from the low preservation potential of several of the microscopic features that are convincing evidence of a frictional melt origin microlites amygdules and glassy matrix here we test the usefulness of grain shape and nearest neighbor distribution analysis of pseudotachylyte and cataclasites from the glf and gpf to discriminate between these fault rocks and to determine a frictional melt origin for pseudotachylyte fabric analyses of the clasts within the pseudotachylytes examined are more circular and exhibit a random nearest neighbor clast distribution relative to adjacent cataclasites with increased comminution and melting the mean clast circularity increases and the nearest neighbor distances approach a random distribution we conclude that this observed pattern can be applied to other fault zones as an indicator of a frictional melt origin for fault related rocks mutually cross cutting zones of hydrothermal alteration and calcite deformation twins constrain the ambient temperature conditions in the fault zone to between 170 and 320 c during pseudotachylyte formation based on previous thermochronologic studies the temperature conditions of the country rock during faulting were between 110 and 220 c the overlapping to elevated temperatures in the fault zone can be explained by 1 infiltration of hydrothermal fluids into the fault zone or 2 residual elevated temperatures as a result of frictional heating in the fault zone during seismic slip

cyclogenesis in the denmark strait overflow plume a densely spaced hydrographic survey of the northern irminger basin together with satellite tracked near surface drifters confirm the intense mesoscale variability within and above the denmark strait overflow in particular the drifters show distinct cyclonic vortices over the downslope edge of the outflow plume growing perturbations such as these can be attributed to the baroclinic instability of a density current a primitive equation model with periodic boundaries is used to simulate the destabilization of an idealized dense filament on a continental slope that resembles the northeastern irminger basin unstable waves evolve rapidly if the initial temperature profile is perturbed with a sinusoidal anomaly that exceeds a certain cutoff wavelength as the waves grow to large amplitudes isolated eddies of both signs develop anticyclones form initially within the dense filament and are rich in overflow water in contrast cyclones form initially with their center in the ambient water but wrap outflow water around their center thus containing a mixture of both water types the nonlinear advection of waters that were originally located within the front between both water masses contributes most significantly to the stronger intensification of the cyclones in comparison with anticyclones the frontal waters carry positive relative vorticity into the center of the cyclone the process bears therefore some resemblance to atmospheric frontal cyclogenesis after saturation there is a bottom jet of overflow water that is confined by counterrotating eddies anticyclones upslope and cyclones downslope of the overflow core the parameter dependence of the maximum growth rate is studied and the implications of eddy induced mixing for the water mass modification is discussed

amorphous material formed by the mechanochemical effect in natural pseudotachylyte of crushing origin a case study of the iida matsukawa fault nagano prefecture central japan abstract pseudotachylytes from the iida matsukawa fault central japan iida pseudotachylytes are described down to the nanometer scale using high resolution electron microscopy scanning electron microscopy analyses of chemical compositions and mercury intrusion porosimetry the pseudotachylyte matrix chiefly consists of nanoscale particles and elongated submicron fragments with biotite composition amorphous material of several tens of nanometers in size is also observed despite the absence of melt textures lattice fringe images reveal that the amorphous phase coexists with lattice distortion in deformed biotite fragments that are several hundreds of nanometers in size the presence of these submicrostructures indicates that the amorphous material formed by mechanical stress during the comminution process that is via the mechanochemical effect we conclude that amorphous material does not always provide evidence of the rapid cooling of melt in pseudotachylyte the amorphous materials present in the iida pseudotachylyte resulted from the mechanochemical effect due to both shear stress and normal stress during the comminution process that accompanied fault motion

co seismic thrusting rupture and slip distribution produced by the 2008 mw 7 9 wenchuan earthquake china field investigations reveal that the mw 7 9 wenchuan china earthquake of 12 may 2008 produced a 285 km long surface rupture zone with dominantly thrusting slip accompanied by a right lateral component along the central northern segments of the zone and left lateral component along the southern segment along the longmen shan thrust belt eastern margin of the tibetan plateau the co seismic ruptures mainly occurred along the pre existing yingxiu beichuan guanxian anxian and qingchuan faults which are the main faults of the longmen shan thrust belt the displacements measured in the field are approximately 0 5 6 5 m in the vertical typically 1 3 m accompanied by an average left lateral component of 2 m along the 50 km long southernmost segment of the rupture zone and an average right lateral component of 1 m along the 150 km long central northern segments the maximum thrust slip amount is estimated to be 10 m accompanied by 9 m of shortening across the rupture zone this finding is consistent with estimates based on seismic data the rupture length and maximum vertical displacement are the largest among all intracontinental thrust type earthquakes reported to date our findings demonstrate that i the wenchuan earthquake occurred upon pre existing active faults of the longmen shan thrust belt thereby controlling the spatial distribution of co seismic surface rupture and displacement and the rupture processes of the earthquake ii the long rupture length and large thrusting slip resulted from compressive stress associated with eastward extrusion of the tibet plateau as it accommodates the ongoing penetration of the indian plate into the eurasian plate and iii present day shortening strain upon the eastern margin of the tibetan plateau is mostly released by seismic slip along thrust faults within the longmen shan thrust belt

when do marginal seas and topographic sills modify the ocean density structure 1 we ask what effect marginal seas at high latitudes have on the abyssal densities and stratification of the oceans although marginal seas are not necessary for the formation of dense abyssal waters topographic sills tend to restrict exchange flows and increase density differences laboratory experiments with a steady state large scale overturning circulation forced by a gradient in surface temperatures or heat fluxes show that a marginal sea and topographic sill influence the abyssal density when the sill depth is less than twice the oceanic thermocline depth the overflow over shallow sills interacts directly with the surrounding thermocline stratification decreasing the abyssal density relative to an ocean with no marginal sea and increasing the density difference between the sea and the ocean experiments show that the effect of the sill depends on the surface boundary conditions and indicate a larger response for conditions approaching a prescribed distribution of temperature rather than of heat flux application of the results to the north atlantic circulation suggests that the greenland scotland ridge is shallow enough to lead to a significant reduction of the density of north atlantic deep water and this is consistent with the conclusions from an analysis of water mass properties the greenland scotland ridge is therefore likely to have a significant effect on the density structure and heat transport in the global oceans

a study of three dimensional gravity currents on a uniform slope received 23 march 2001 and in revised form 3 april 2001 in many geophysical environmental and industrial situations a nite volume of fluid with a density dierent to the ambient is released on a sloping boundary this leads to the formation of a gravity current travelling up down and across the slope we present novel laboratory experiments in which the dense fluid spreads both downslope and initially up slope and laterally across the slope the position shape and dilution of the current are determined through video and conductivity measurements for moderate slopes 5 to 20 the entrainment coecient for dierent slopes is calculated from the experimental results and is found to depend very little on the slope the value agrees well with previously published values for entrainment into gravity currents on a horizontal surface the experimental measurements are compared with previous shallow water models and with a new wedge integral model developed and presented here it is concluded that these simplied models do not capture all the signicant features of the flow in the models the current takes the form of a wedge which travels down the slope but the experiments show the formation of a more complicated current it is found that the wedge integral model over predicts the length and width of the gravity current but gives fair agreement with the measured densities in the head the initial stages of the flow during which time the wedge shape develops are studied it is found that although the influence of the slope is seen relatively quickly for moderate slopes the time taken for the wedge to develop is much longer the implications of these ndings for safety analysis are briefly discussed

longmen shan fold thrust belt and its relation to the western sichuan basin in central china new insights from hydrocarbon exploration the longmen shan fold thrust belt is one of the key regions of demonstrable mesozoic cenozoic tectonic evolution in china and the sichuan basin was the first natural gas producing area in china in this article the structural features of the longmen shan belt are presented using both seismic profiles and field data the complex structures of the northeast trending longmen shan fold thrust belt and its foreland in the western sichuan basin are formed by southeast directed thrusting several eastward verging rootless thrust sheets and imbricates of cambrian triassic rocks have been recognized in the northern longmen shan belt evidence suggests that the northern longmen shan belt experienced at least two major periods of deformation in the late triassic and cenozoic however the southern longmen shan belt is represented by the basement involved thrust structures and klippen and its major periods of deformation were in the latest cretaceous early cenozoic sedimentary features in the western sichuan basin reflect a two phase flexural loading history and illustrate that the late triassic foreland basin extends along the foredeep of the entire length of the longmen shan belt but the uppermost cretaceous paleogene rejuvenated foreland basin is restricted in the southern part of the western sichuan basin structural geometries suggest that prospective traps are mainly developed in the frontal zone of the longmen shan fold thrust belt and in the southern part of the western sichuan basin one of the major contributions of this article is finding preexisting paleozoic rift basins under the cenozoic thin skinned thrust belts which represent a new potential hydrocarbon play

glassy pseudotachylyte veins from the fuyun fault zone northwest china glassy pseudotachylytes occur in granitic mylonites from the fuyun fault zone northwest china powder x ray diffraction data indicate that the fine grained matrices of the fuyun pseudotachylytes vary from almost crystalline to complete glass a few to 90 wt glass powder x ray diffraction patterns also indicate that clasts in the glass type pseudotachylyte veins mostly consist of quartz grains microlites displaying quenched or rapid cooling textures vesicles and amygdules flow structures and rounded fragments are also common in the fuyun pseudotachylytes the average bulk chemical compositions of these pseudotachylytes are similar to those of the host rocks but the glass matrix has a low sio2 component which is 5 15 wt lower than that of the host rocks the pseudotachylytes contain 2 3 wt water h2o using experimental data which relate the solubility of water to pressure approximately 400 bars lithostatic pressure corresponding to approximately 1 5 km depth of pseudotachylyte formation is estimated a minimum temperature estimate of 1450 c can be estimated due to the presence of the pure sio2 glass the x ray diffraction and chemical data indicate that the fuyun pseudotachylytes formed during seismic faulting at shallow depths by selective melting under water saturated conditions rather than by total melting or by crushing of the host rocks along fault surfaces

tides of the northwestern ross sea and their impact on dense outflows of antarctic bottom water abstract moored and depth profile measurements of hydrography and currents during the 2003 2005 antarctic slope anslope program on the shelf slope region near drygalski trough sill in the northwest ross sea have revealed an energetic benthic outflow of cold dense antarctic bottom water aabw produced near the shelf break this outflow couples dense water production processes on the continental shelf to ventilation of the global deep ocean we use time series of bottom pressure and currents on the anslope moorings and a high resolution three dimensional primitive equation numerical model to explore the hypothesis that the tidal currents near the shelf break have a significant impact on outflow volume transport and hydrographic properties tidal currents exceed 1 m s 1 at spring tide over the outer shelf and upper slope tidal advection at spring tide carries water parcels 20 km across slope during a half tidal cycle sufficient to advect water from northern drygalski trough across the sill to the shelf break or similarly from the shelf break 500 m water depth down to the 1600 m isobath a tidally rectified lagrangian mean flow of order 0 05 0 1 m s 1 over the outer shelf and upper slope accompanies the spring tide thickness and water mass properties of the benthic layer over the sill and upper slope exhibit pronounced tidal cycles due to advection of hydrographic gradients and to energetic mixing that can extend more than halfway up from the seabed to the ocean surface maximum parameterized diapycnal diffusivity in the benthic layer at spring tides approaches 1 m 2 s 1 the addition of tides has a profound effect on time averaged outflows of aabw primarily through an increase in benthic layer thickness during spring tide downslope volume fluxes of aabw over the slope averaged over a tidal cycle are 2 5 times larger at spring tide than at neap indicating a need to include the effect of tides in large scale ocean models attempting to represent shelf water contributions to the global ocean circulation

thermal pressurization and fluidization of pulverized cataclastic rocks formed in seismogenic fault zones abstract vein networks of pseudotachylytes and ultracataclastic rocks are composed mainly of ultrafine to fine grained materials including fault gouge and microbreccia and are widely considered indicators of past seismic faulting events i show that such vein networks of pseudotachylyte with both melt and crush origins as well as ultracataclastic rocks form by the rapid injection of ultrafine to fine grained material sourced from pulverized ultracataclastic rocks in seismogenic fault zones under thermal pressurization and fluidization during seismic events the thermal expansion of seismic slip zones caused by frictional heating results in the rapid fluidization of ultrafine to fine grained materials along with expanded fluids and gases e g water vapor and melt that are injected under pressure into fracture void spaces within fault zones in a gas solid liquid system during large earthquakes i propose that the thermal expansion of water vapor and ultrafine to fine grained materials caused by frictional heating in the fault slip zone is the main mechanism responsible for the dramatic increase in pore pressure that results in the dynamic coseismic weakening of faults

intense mixing of the faroe bank channel overflow 1 the continuous swift flow of cold water across the sill of the faroe bank channel the deepest passage from the nordic seas to the north atlantic ocean forms a bottom attached dense plume overflow the amount and distribution of entrainment and mixing that the overflow encounters during its descent influence the ventilation of the deep north atlantic however remain poorly known due to lack of direct measurements using the first direct turbulence measurements we describe the dynamic properties and mixing of the overflow plume as it descends toward the iceland basin the vigorously turbulent plume is associated with intense mixing and enhanced turbulent dissipation near the bottom and at the plume ambient interface but with a quiescent core our measurements show a pronounced transverse circulation consistent with rotating plume dynamics a strong lateral variability in entrainment velocity and a vertical structure composed of order 100 m thick stratified interface and comparably thick well mixed bottom boundary layer with significant transport and entrainment

increasing reserves in a mature giant wilmington field los angeles basin part ii improving heavy oil production through advanced reservoir characterization and innovative thermal technologies enhanced recovery of low gravity oil from unconsolidated high porosity high permeability sands in the supergiant wilmington field began in the early 1960s despite nearly four decades of production postprimary recoveries have been generally low due to reservoir heterogeneity and operational problems in particular steamflooding has yielded poor results because of elevated steam oil ratios early steam breakthrough and consequent premature equipment failure a multidiscipline effort to address these problems and improve recovery is underway as part of the u s department of energy class iii slope and basin clastic reservoir oil recovery field demonstration initiative in the fault block iia portion of wilmington field this effort has focused on several main objectives those objectives discussed in this paper include 1 three dimensional geologic modeling to rigorously define important relationships 2 rock typing and rock log modeling to improve reservoir characterization 3 testing the feasibility of using horizontal wells in steamflood operations at wilmington and 4 employing a novel low cost completion technique applicable to unconsolidated formations to date significant levels of success have been achieved with regard to all these objectives when complete the project at wilmington field should have wide ranging application to similar reservoirs throughout southern california and elsewhere

gravity current dynamics and entrainment a process study based on observations in the arkona basin abstract a 19 h time series of dissipation stratification and horizontal velocities has been obtained for a dense gravity current flowing into the arkona basin in the western baltic sea the observations are compared with one dimensional quasi steady theory in which the gravity component in the flow direction is balanced by bottom friction while that in the cross flow direction is balanced by the coriolis force the observations deviate from the theory in that the bottom shear stress is more than 2 times as large as that required to balance the gravity several reasons for this discrepancy are discussed a 1d turbulence model is also compared with the observations profiles of velocity stratification and dissipation rates generally show similar variations with depth as the observations although the observed dissipation rates are somewhat larger than the modeled and the modeled transverse velocities are much larger than the observed subsequently the model is used to investigate the variation of t

structural analysis of a previously unknown active fault that triggered the 2013 mw 5 8 awajishima earthquake southwest japan the m w 5 8 awajishima earthquake occurred on 13 april 2013 in southwest awaji island 25 km southwest of the epicenter of the 1996 m w 6 8 kobe earthquake southwest japan analyses of aerial photographs and 3d perspective images field investigations and structural analysis of fault rocks reveal that 1 a previously undocumented fault here called the yamada fault strikes northwest southeast and dips southwest at 86 along a topographic lineament at the geological boundary between mesozoic granitic rocks and the late pliocene quaternary osaka group composed of interbedded sandstone and mudstone 2 the main shear zone of the yamada fault consists of a fault core with a 10 cm wide zone of fault gouge generally 1 5 cm a fault breccia zone of 100 cm wide and a damage zone of 10 50 m wide composed of cataclastic rocks and fractures 3 foliations characterized by s c fabrics that have developed in the shear zone indicate a dominantly thrust fault sense consistent with that revealed by the focal mechanism and 4 coseismic surface ruptures occurred locally along the main trace of the yamada fault consisting of numerous short fissures ranging in length from centimeters to several meters and concentrated in a zone 5 m wide our findings show that the newly identified yamada fault is an active fault and that it is probably the fault on which the 2013 m w 5 8 awajishima earthquake occurred therefore it is necessary to construct a fault model to better understand the deformation characteristics of the seismogenic source fault and for reassessing the seismic hazards on the densely populated awaji island of southwest japan

application of a transient reduced gravity plume model to the denmark strait overflow a hydrostatic reduced gravity two dimensional primitive equation numerical model for the simulation of transient bottom arrested gravity plumes was developed by adopting an algorithm from a wadden sea model a model that simulates the wetting and drying of mud flats sand banks etc with a movable lateral boundary the vertically integrated nonlinear rotational model accounts for the dissipation of momentum due to bottom friction and for the entrainment of water mass properties from a spatially structured but stagnant ambient water body it predicts the temporal and spatial evolution of the flow field and the water mass modification within a gravity plume that descends on an arbitrary topography previous model investigations considered a laterally integrated streamtube whereas our model resolves the plume horizontally in the streamtube approach it was assumed that the plume descends in a stationary almost geostrophic balance modified only by bottom drag and entrainment the results of this model demonstrate that this balance may be disturbed whenever the plume encounters topographic disturbances which for the initial intruding phase in particular accounts for its highly transient character the model results are in good agreement with theoretical and laboratory investigations and with observations as is demonstrated by some basic test experiments an application to the overflow of dense water through the denmark strait is presented

mediterranean outflow mixing and dynamics the mediterranean sea produces a salty dense outflow that is strongly modified by entrainment as it first begins to descend the continental slope in the eastern gulf of cadiz the current accelerates to 1 3 meters per second which raises the internal froude number above 1 and is intensely turbulent through its full thickness the outflow loses about half of its density anomaly and roughly doubles its volume transport as it entrains less saline north atlantic central water within 100 kilometers downstream the current is turned by the coriolis force until it flows nearly parallel to topography in a damped geostrophic balance the mixed mediterranean outflow continues westward slowly descending the continental slope until it becomes neutrally buoyant in the thermocline where it becomes an important water mass

satellite interferometric observations of displacements associated with seasonal groundwater in the los angeles basin 1 the newport inglewood fault zone nifz displays interferometric synthetic aperture radar sar phase features along most of its length having amplitudes of up to 60 mm however interpretation in terms of right lateral shallow slip along the fault fails to match the range of geologic estimates of slip recently bawden et al 2001 proposed that these phase features as well as a broader deformation pattern in the los angeles basin are due to vertical motion related to annual variations in the elevation of the water table we confirm this hypothesis through the analysis of a longer span of data consisting of 26 sar images collected by the ers 1 and ers 2 spacecraft between june 1992 and june 2000 moreover we use continuous gps measurements from 1995 to the present to establish the amplitude and phase of the vertical deformation the los angeles basin becomes most inflated one quarter of the way through the year which is consistent with water table measurements as well as with the end of the rainy season when the aquifer should be at a maximum the spatial pattern of the amplitude of the annual signal derived from continuous gps measurements is consistent with the shape of the interferometric fringes gps sites both near the nifz and in a 20 by 40 km zone within the basin also show significant n s annual variations that may be related to the differential expansion across the fault since these horizontal signals have peak to trough amplitudes of 6 mm they mask the smaller tectonic signals and need to be taken into account when interpreting gps time series of site position moreover since the groundwater signal appears to have a long term vertical trend which varies in sign depending on location it will be difficult to distinguish interseismic tectonic slip along the nifz and within the affected areas in the basin

contained density currents with high volume of release contained density currents with high volume of release reflect against the boundaries of the reception environment commonly leading to oscillatory flow these flows exist in sediment clarifiers compromising their operations and deposited signatures of contained turbidity currents are found as part of the infill of sedimentary basins for operation of the former and interpretation of the latter it is essential to understand the dynamic processes of these flows six lock exchange experiments with different initial densities were made in a horizontal flume where the volume of the saline mixture in the lock was equivalent to the volume of the ambient fluid a further two tests with a repeated initial density were made one with high volume of release and very long duration and another with low volume of release firstly the movement of the current is discussed including the oscillations within the experimental tank involving the density current and an upper layer counter current it is shown that the cyclic behaviour is self similar with the reduced gravity of the initial density in the lock secondly entrainment and water mixing processes are characterized the time evolution of mixing is characterized qualitatively by analysing the background potential energy of the density distributions to show that mixing occurs even in the earlier stages of the current and mainly within the first cycle of the oscillation quantified analysis reveals that in currents with high volume of release entrainment discharge is one order of magnitude higher mainly due to the larger interface between the ambient fluid and the current a model for the evolution of the mixing process is proposed for density currents with high volume of release finally the dynamics of the head of the current is analysed the entrainment in the head when compared to the entrainment in the remainder body of the flows is less important for the configuration with a larger lock

reconstruction of seismic faulting by high velocity friction experiments an example of the 1995 kobe earthquake 1 high velocity friction experiments on a fault gouge collected from the nojima fault activated during the 1995 kobe earthquake showed that the friction coefficient decreased from 0 63 to 0 18 over a slip weakening distance dc at high slip rates of 1 m s the dramatic drop in friction coefficient of more than 0 3 is consistent with that for the kobe earthquake estimated from seismological observations experimentally determined dc becomes 5 m at a higher normal stress of 1 85 mpa close to the order of magnitude of seismologically determined dc of 0 5 to 1 m the difference in dc is not significant because the fracture energy consumed during frictional slip is the same order of 106 n m for both cases here we show that frictional behavior of a fault during an earthquake can be predicted by conducting high velocity friction experiments

a new parameterization for entrainment in overflows abstract dense overflows entrain surrounding waters at specific locations for example sills and constrictions but also along the descent over the continental slope the amount of entrainment dictates the final properties of these overflows and thus is of fundamental importance to the understanding of the formation of deep water masses even when resolving the overflows coarse resolution global circulation and climate models cannot resolve the entrainment processes that are often parameterized a new empirical parameterization is suggested obtained using an oceanic and laboratory dataset which includes two novel aspects first the parameterization depends on both the froude number fr and reynolds number of the flow second it takes into account subcritical fr 1 entrainment a weak but nonzero entrainment can change the final density and consequently the depth and location of important water masses in the open ocean this is especially true when the dense current follows a long path over

increasing reserves in a mature giant wilmington field los angeles basin part 1 reservoir characterization to identify bypassed oil with estimated reserves of over 2 8 billion bbl oil the supergiant wilmington field is the largest productive area in the los angeles basin one of the world s most prolific petroleum provinces similar to most other fields in the basin wilmington produces from thick sequences of upper miocene pliocene slope and basin floor turbidites ranging from well indurated to unconsolidated in character due to a range of factors enhanced recovery in these reservoirs has been incomplete or inefficient with the result that a substantial remaining resource exists to help devise improved methods for exploiting this resource the u s department of energy has included portions of wilmington field in its class 3 slope and basin clastic reservoirs oil recovery field demonstration program at present two projects are underway one aimed at identifying bypassed pay and the other project aimed at improving tertiary recovery operations both projects have employed advanced reservoir characterization techniques and have demonstrated considerable success results of this work should have wide application to slope and basin clastic reservoirs elsewhere part 1 of the following two part paper presents a summary of work completed thus far

mixing in flows down gentle slopes into stratified environments observations of the flow of dense fluid into uniformly density stratified environments down plane slopes with small inclination to the horizontal 20 are described and a quantitative model for such flows is presented in these experiments the dense fluid is released at the top of the slope for a finite period of time the resulting downslope gravity current or downflow has uniform thickness with a distinct upper boundary until it approaches its level of neutral density where the fluid leaves the proximity of the slope turbulent transfers of mass and momentum occur across the upper boundary causing a continuous loss of fluid from the downflow in most cases and associated loss of momentum the flow may be characterized by the local values of the richardson number ri the reynolds number re generally large and of m qn 3 g 2 where q is the two dimensional volume flux n the buoyancy frequency and g the negative buoyancy of the dense fluid the model for the downflow describes the turbulent transfers in terms of entrainment detrainment and drag coefficients e e e d and k respectively and the observations enable the determination of these coefficients in terms of the local values of m and ri the model may be regarded as an extension of that ellison turner 1959 to stratified environments describing the consequent substantial changes in mixing and distribution of the inflow it permits the modelling of the bulk properties of these flows in geophysical situations including shallow and deep flows in the ocean

mixing and entrainment in the red sea outflow plume part ii turbulence characteristics abstract south of the strait of bab el mandeb saline red sea water flows downslope into the gulf of aden mainly along the narrow 130 km long northern channel nc and the shorter and wider southern channel sc in the nc the red sea plume simultaneously exhibited weak entrainment into a 35 120 m thick weakly stratified bottom layer while a 35 285 m thick interfacial layer above showed signs of vigorous mixing overturns up to 30 m thick and extensive zones of gradient richardson numbers below 1 4 turbulent overturning scales or thorpe scales are extracted from regular ctd profiles and equated to ozmidov scales on this basis interfacial mixing is quantified in terms of estimated turbulent dissipation rates vertical turbulent salt flux and interfacial stress even though these estimates are subject to significant uncertainty they demonstrate the intensity of mixing during strong winter outflow in terms of eddy diffusivities k on the order of 10 2 m2 s 1 the large k occur in strong strati

pathways of river water to the surface layers of stratified reservoirs this study uses tracer experiments to characterize the fate of a cold plunging river into a mediterranean reservoir under different stratification conditions three tracer experiments in lake beznar spain demonstrate that a significant fraction of the inflow may be quickly entrained into the surface mixed layer sml rather than flowing to lower depths we observe that a fraction and possibly all of river inflow entrains into the sml when the density current forms intrusions at the top of the metalimnetic layer intrusions near the base of the sml form due to lighter interfacial fluid at the top of the density current with intermediate properties between river reservior water when there is sufficient dilution of the cold inflow and abrupt density changes at the base of the sml consequently a layer of fluid splits from the denser part of the current and intrudes just below the sml while any remaining fluid flows to lower depths we parameterize this splitting behavior in terms of the transition richardson number ri12 2 1 0 1 where 0 1 and 2 are densities of the inflow the sml and the metalimnetic layer underneath respectively and is the total dilution through the plunge zone and subsequent entrainment splitting occurs when ri12 1 consistent with previous laboratory experiments we use this theory to predict the seasonal fate of river water during the stratification of lake beznar and identify the conditions that favor the formation of intrusions near the base of the sml

how entraining density currents influence the stratification in a one dimensional ocean basin abstract the sensitivity of ocean stratification to the vertical distribution of plume entrainment is analyzed a large ocean basin supplied by dense water from an adjoining marginal sea is considered the dense water flows into the ocean basin as an entraining density current and interleaves at the bottom or at the level of neutral density where it deposits a mixture of marginal sea and basin water as the basin water i e old plume water is entrained and re circulated in the plume a stratification develops in the basin the mixture deposited at the bottom hence contains an increasing fraction of marginal sea water and the basin density increases with depth as well as with time a stationary solution in which diffusion of buoyancy from above is important is approached asymptotically in time non diffusive solutions to the initial transient adjustment as well as the diffusive asymptotic state have been studied in four different parameterizations of plume entrainment it is shown that in the transient regime the basin stratification and plume density are highly sensitive to how mixing is parameterized the stationary diffusive solution that is approached asymptotically in time is less sensitive to parameterization but depends strongly on basin topography source water density and buoyancy flux at the surface

structure and variability of the denmark strait overflow model and observations we report on a combined modeling and observational effort to understand the denmark strait overflow dso four cruises over the course of 3 years mapped hydrographic properties and velocity fields with high spatial resolution the observations reveal the mean path of the dense water as well as the presence of strong barotropic flows energetic variability and strong bottom friction and entrainment a regional sigma coordinate numerical model of interbasin exchange using realistic bottom topography and an overflow forced only by an upstream reservoir of dense fluid is compared with the observations and used to further investigate these processes the model successfully reproduces the volume transport of dense water at the sill as well as the 1000 m descent of the dense water in the first 200 km from the sill and the intense eddies generated at 1 3 day intervals hydraulic control of the mean flow is indicated by a region supercritical to long gravity waves in the dense layer located approximately 100 km downstream of the sill in both model and observations in addition despite the differences in surface forcing both model and observations exhibit similar transitions from mostly barotropic flow at the sill to a bottom trapped baroclinic flow downstream indicating the dominant role of the overflow in determining the full water column dynamics

numerical investigation of split flows by gravity currents into two layered stratified water bodies the behavior of a two dimensional 2 d gravity current impinging upon a density step in a two layered stratified basin is analyzed using a high resolution reynolds averaged navier stokes model the gravity current splits at the density step and the portion of the buoyancy flux becoming an interflow is largely controlled by the vertical distribution of velocity and density within the gravity current and the magnitude of the density step between the two ambient layers this is in agreement with recent laboratory observations the strongest changes in the ambient density profiles occur as a result of the impingement of supercritical currents with strong density contrasts for which a large portion of the gravity current detaches from the bottom and becomes an interflow we characterize the current partition process in the simulated experiments using the densimetric froude number of the current fr across the density step upstream and downstream when underflows are formed more supercritical currents are observed downstream of the density step compared to upstream fru frd which indicates lower mixing between the current and ambient water after the impingement due to the significant stripping of interfacial material at the density step

coseismic magnetization of fault pseudotachylytes 1 thermal demagnetization experiments fault pseudotachylytes form by quenching of silicate liquids produced through coseismic frictional melting here we show that in natural pseudotachylytes the main carrier of magnetic remanence blocked in during cooling of the frictional melt is fine grained magnetite this confirms previous studies on friction melt experiments stoichiometric magnetite produced during earthquakes by the breakdown of ferromagnesian silicates records the ambient magnetic field during seismic slip we find that most fault pseudotachylytes exposed in the santa rosa mountains southern california a classic pseudotachylyte locality acquired their natural remanent magnetization nrm upon cooling of the frictional melt through the range of magnetization blocking temperatures of the magnetite grains and this primarily constitutes a thermal remanent magnetization nrm intensities typical of most pseudotachylyte veins range from 1 to 60 10 4 am2 kg a few specimens however contain magnetizations significantly higher than that caused by the earth s field as well as magnetization directions that are highly variable over short distances other magnetization processes possibly related to coseismic electric currents may be involved during the seismogenic process to control nrm acquisition

entrainment in a dense current flowing down a rough sloping bottom in a rotating fluid abstractdense oceanic overflows descend over the rough topography of the continental slope entraining and mixing with surrounding waters the associated dilution dictates the fate of these currents and thus is of fundamental importance to the formation of deep water masses the entrainment in a dense current flowing down a sloping bottom in a rotating homogeneous fluid is investigated using laboratory experiments focusing on the influence of the bottom roughness on the flow dynamics the roughness is idealized by an array of vertical rigid cylinders and both their spacing and height are varied as well as the inclination of the sloping bottom the presence of the roughness is generally observed to decelerate the dense current with a consequent reduction of the froude number when compared to the smooth bottom configuration however the dilution of the dense current due to mixing with the ambient fluid is enhanced by the roughness elements especially for low froude numbers when the entrainment due to s

dynamics of rotating shallow gravity currents passing through a channel part i observation of transverse structure abstract a detailed dataset describing a quasi stationary bottom gravity current approximately 10 m thick and 10 km wide passing through a channel like constriction in the western baltic sea is presented the data include full depth synoptic and highly resolved transects of stratification and turbulence parameters as well as detailed velocity transects across the gravity current at different down channel locations the velocity data reveal a persistent transverse circulation creating a characteristic wedge shaped density structure in the interface a strong asymmetry was also found in the interior of the gravity current where the evolution of a dynamically significant transverse density gradient to the right of the down channel flow was observed spectral analysis of the near bottom velocities showed a surprisingly strong contribution to the bottom stress from low frequency motions with periods up to 30 min that are possibly related to internal wave effects cross channel transects of shear microst

permeability and borehole stoneley waves comparison between experiment and theory we performed laboratory experiments to evaluate theoretical models of borehole stoneley wave propagation in permeable materials a berea sandstone and synthetic samples made of cemented glass beads were saturated with silicone oils we measured both velocity and attenuation over a frequency band from 10 khz to 90 khz our theoretical modeling incorporated biot theory and deresiewicz skalak boundary conditions into a cylindrical geometry and included frequency dependent permeability by varying the viscosity of the saturating pore fluid we were able to study both low frequency and high frequency regions of biot theory as well as the intermediate transition zone in both low frequency and high frequency regions of the theory we obtained excellent agreement between experimental observations and theoretical predictions velocity and attenuation 1 q are frequency dependent especially at low frequencies also at low frequencies velocity decreases and attenuation increases with increasing fluid mobility permeability viscosity more complicated behavior is observed at high frequencies these results support recent observations from the oil field suggesting that stoneley wave velocity and attenuation may be indicative of formation permeability

topographic influence on overflow dynamics idealized numerical simulations and the faroe bank channel overflow 1 properties of the north atlantic deep water nadw depend on mixing that occurs in the denmark strait ds and the faroe bank channel fbc overflow regions how the sill s topography in those regions may affect mixing processes and downstream variability is thus investigated using a high resolution terrain following ocean model model results agree with observations that show enhanced mixing and entrainment downstream from the sill however mixing seems to occur over a longer distance downstream from the fbc sill and more abruptly downstream from the ds sill sensitivity experiments with various fbc sill widths demonstrate that the narrow sill is responsible for the enhanced mixing the downstream flow variability eddy propagation and deep water properties are affected by sill width and background stratification similar to the laboratory overflow experiments of cenedese et al 2004 three distinct mixing regimes characterized by the froude number are identified in the fbc simulations a steady subcritical flow regime upstream from the sill a supercritical wave like flow regime downstream from the sill and an irregular eddy dominated regime farther away from the sill satellite altimeter data near the fbc show cyclonic anomalies propagating along the northern slope of the channel resembling the surface eddies associated with the overflow variability in the model a cross channel circulation over the fbc sill driven by frictional bottom boundary layers resulted in convergence divergence zones near the southern northern slopes and pinching spreading of isotherms across the channel similar to the observation based mechanism proposed by johnson and sanford 1992

fault rocks within the blueschist metabasalts of the diamante terranova unit southern italy potential fossil record of intermediate depth subduction earthquakess vitale et al fault rocks within blueschist metabasalts

fault rock injections record paleo earthquakes fault rocks such as pseudotachylyte melt or granular gouge are sometimes injected into cracks off a fault surface the width to height ratio of the injection veins is a direct measure of the shear strain in the wall rock required to accommodate the injection so the aspect ratios preserve a record of the overpressure opening the cracks and injecting melt or fluidized granular material from the fault zone we measured the aspect ratios for 201 pseudotachylyte injections and 29 granular injections they have aspect ratios of 0 2 0 177 0 025 and 0 227 0 077 respectively within 99 confidence these are significantly proportionally wider than the aspect ratios of ordinary dikes from 10 4 to 10 3 the injection aspect ratios exceed the usual limit of elastic strain in the wallrock 1 so we infer that the injection veins were accommodated by permanent deformation by microcracking and slip on foliation surfaces in the host rock which is difficult to detect observationally the fully elastic model therefore offers an upper bound on the stress required to open these injection veins 10 8 210 10 pa with higher pressures in stiffer host rock lithologies these overpressures cannot be achieved by expansion of the fault rock fluids during melting or gouge fluidization mechanisms as the pressure along the fault is limited to 10 7

mixing and spreading of the mediterranean outflow abstract hydrographic and current profiler data taken during the 1988 gulf of cadiz expedition have been analyzed to diagnose the mixing spreading and descent of the mediterranean outflow the s properties and the thickness and width of the outflow were similar to that seen in earlier surveys the transport of pure mediterranean water i e water with s 38 4 psu was estimated to be about 0 4 106 m3 s 1 which is lower than historical estimates most of which were indirect but comparable to other recent estimates made from direct velocity observations the outflow transport estimated at the west end of the strait of gibraltar was about 0 7 106 m3 s 1 of mixed water and the transport increased to about 1 9 106 m3 s 1 within the eastern gulf of cadiz this increase in transport occurred by entrainment of fresher north atlantic central water and the salinity anomaly of the outflow was consequently reduced the velocity weighted salinity decreased to 36 7 psu within 60 km of the strait and decre

internal structure of the wenchuan earthquake fault zone revealed by surface outcrop and wfsd 1 drilling core investigation abstract fault zones record a series of faulting events that have occurred under different physical conditions during their evolution therefore it is essential to understand the internal structures of fault zones in order to better understand the mechanical behavior of faults the internal structure of the wenchuan earthquake fault zone that prevailed at the bajiaomiao outcrop and in the wfsd 1drilling cores located along the southern segment of the yingxiu beichuan surface rupture in the hongkou area is described in details in this paper based on field surveys x ray diffraction analysis microstructure and analysis of the drilling cores an 240 m wide fault zone was confirmed as the yingxiu beichuan fault zone ybf at the bajiaomiao outcrop corresponding to the 100 m fault zone in the wfsd 1 drilling cores fault rocks including fault breccia fault gouge and cataclasite were identified in both the outcrop and drilling cores while pseudotachylyte was only present at the outcrop two different types of gouge veins formed by thermal pressurization and fluidization respectively are observed in this area the ybf possesses the characteristics of a multiple core model and consists of 5 different fault rock units from top to bottom these are cataclasite zone black fault gouge breccia zone gray fault breccia zone dark gray fault breccia zone and black fault gouge breccia zone outcrop investigation and drilling core research show that the slip zone of the wenchuan earthquake does not completely follow the ancient fault slip zone the wenchuan earthquake fault is a high angle thrust fault which crosses the ybf obliquely the multi layered fault rocks displayed in the research area might indicate that the ybf comes from the long term fault activity and evolution over the last 15 10 ma

intensified turbulent mixing in the boundary current system of southern greenland 10 4 m 2 s 1 commonly occur in the dwbc these diffusivities estimated with an internal wave strain based parameterisation are independently confirmed by budgets of density and dissolved o2 moderate mixing rates 10 4 m 2 s 1 over the dwbc path between denmark strait and cape farewell 1000 km drive a similar net increase in volume transport by diapycnal entrainment to the more intense 10 3 m 2 s 1 localised mixing rates found near the denmark strait overflow sill therefore turbulent mixing associated with the dwbc south of denmark strait is instrumental in establishing the magnitude of the north atlantic meridional overturning circulation elevated mixing rates are also seen in the east and west greenland currents this may be significant in preconditioning seasonal restratification of the intermediate layers of the irminger and labrador basins citation lauderdale j m s bacon a c naveira garabato and n p holliday 2008 intensified turbulent mixing in the boundary current system of southern greenland geophys res lett 35 l04611

amorphous material in safod core samples san andreas fault evidence for crush origin pseudotachylytes 1 several types of amorphous material in ultracataclastic core samples recovered from 3194 m and 3294 m depth of the main bore hole of the san andreas fault observatory at depth are identified and described with transmission electron microscopy and scanning electron microscopy we observed 1 amorphous material on a slickenside surface 2 glassy bands contained in an ultracataclastic matrix and 3 amorphous rims surrounding quartz or feldspar clasts chemical analyses of the amorphous material reveal that silica content is slightly enriched or similar as in the adjacent matrix we suggest that all amorphous material was formed by comminution of clasts crush origin pseudotachylytes rather than by melting melt origin pseudotachylytes the observed amorphous phases may act as lubricating layers that reduce friction in the san andreas fault

field evidence of rupture of the qingchuan fault during the 2008 mw7 9 wenchuan earthquake northeastern segment of the longmen shan thrust belt china abstract although many studies of the 2008 mw 7 9 wenchuan earthquake have described the ground deformation features rupture mechanism and structural features of the seismogenic fault zone associated with this event debate remains concerning the total length of the co seismic surface rupture zone and whether the earthquake ruptured the qingchuan fault in the northeastern segment of the longmen shan thrust belt lstb china in this paper we present new field evidence that the qingchuan fault was ruptured by the 2008 wenchuan earthquake and that the total length of the co seismic surface rupture zone is up to 285 300 km field investigations reveal that the earthquake produced a 60 km long surface rupture zone along the pre existing qingchuan fault with the offset being mainly right lateral strike slip and a distinct component of vertical slip co seismic surface ruptures are characterized by faults and extensional cracks field measurements indicate co seismic right lateral strike slip displacements along the qingchuan fault of 0 3 0 6 m and vertical offsets of 0 2 0 5 m which differs to the displacements observed along the central and southwestern segments of the wenchuan surface rupture zone in the displacement amount and sense the change in slip sense from thrust dominated slip in the central and southwestern segments of the lstb to right lateral strike slip dominated displacement along the qingchuan fault northeastern segment of the lstb reflects a change in the orientation of compressive stress along the lstb associated with eastward extrusion of the tibetan plateau as it accommodates the ongoing penetration of the indian plate into the eurasian plate

numerical simulation of the red sea outflow using hycom and comparison with redsox observations abstract the outflow of warm salty and dense water from the red sea into the western gulf of aden is numerically simulated using the hybrid coordinate ocean model hycom the pathways of the modeled overflow temperature salinity velocity profiles from stations and across sections and transport estimates are compared to those observed during the 2001 red sea outflow experiment as in nature the simulated outflow is funneled into two narrow channels along the seafloor the results from the three dimensional simulations show a favorable agreement with the observed temperature and salinity profiles along the channels the volume transport of the modeled overflow increases with the increasing distance from the southern exit of the bab el mandeb strait due to entrainment of ambient fluid such that the modeled transport shows a reasonable agreement with that estimated from the observations the initial propagation speed of the outflow is found to be smaller than the estimated interfacial wave speed the

magnetic properties of fault rocks from the yingxiu beichuan fault constraints on temperature rise within the shallow slip zone during the 2008 wenchuan earthquake and their implications abstract rock magnetic measurements were conducted on fault rocks from the dagou village outcrop at shuiguan town pingwu county sichuan province china which is located on the yingxiu beichuan fault the main fault ruptured in the 2008 wenchuan m s 8 0 earthquake results revealed that magnetic behavior of fault gouge is possibly dominated by paramagnetic siderite and lepidocrocite as well as pyrrhotite thermomagnetic analysis indicated that these fe bearing minerals are readily decomposed once temperature over 250 400 c and form newly ferrimagnetic magnetite maghemite that would increase the magnetization of fault rocks consequently the paramagnetic nature and relatively low magnetization of fresh fault gouge suggest that the shallow fault plane has not been subjected to thermal event over 250 400 c during the wenchuan earthquake this inference can be confirmed by a kinetic model analysis these findings proposed that thermal pressurization was not likely to occur during the wenchuan earthquake at least at the shallow part of slip zone onset of an elastohydrodynamic lubrication mechanism was alternatively discussed using a model in which fault zone containing viscous gouge results indicated that the lubrication pressure could reach up to 30 2 mpa which can widen the gap between the fault surfaces and reduce the area of asperity contact this prediction well matches the reported injection veins within the coseismic shear zone and the largest ground motions associated with lower predominant frequencies and large stress drop during the wenchuan earthquake

entrainment and turbulence in saline underflow in lake ogawara under certain tidal conditions a saline underflow originating in the pacific ocean moves into lake ogawara japan the underflow consists of a uniform saline bottom layer that is slightly warmer than the ambient and an interfacial shear layer in which the velocity and density are decreased within the experimental area the underflow is confined to a channel approximately 1 km wide and is essentially two dimensional the underflow had a bulk richardson number defined in terms of the mean properties between 1 and 2 the rate of entrainment into the bottom layer was calculated using two distinct methods the first method used the change in the maximum salinity of the underflow measured at two stations along the path of the underflow to infer the amount of ambient water entrained the second method made direct measurements of vertical mass fluxes with a profiler the agreement between the two methods was excellent the measured entrainment coefficients were consistent with the derived entrainment law the turbulent structure of the flow was mapped for a 3 h quasi steady period of the flow turbulence is predominantly generated on the bottom boundary and is transported vertically to the density interface where it leads to mixing

dynamics of rotating shallow gravity currents passing through a channel part ii analysis abstract the physics of frictional control for channelized rotating gravity currents are analyzed using an extensive dataset including hydrographic current and microstructure measurements from the western baltic sea rotational effects in these gravity currents characterized by ekman numbers of the order of one and subcritical froude numbers induce a complex transverse circulation that strongly affects the internal dynamics the key component of this circulation is a geostrophically balanced transverse jet in the interface that modifies the entrainment process by i laterally draining the interface and ii providing additional interfacial shear comparable to the down channel shear the recirculation of mixed interfacial fluid into the interior distorts the internal density structure of the gravity current and creates a thermal wind shear in the interior that is comparable to the observed shear using a theoretical model this effect is shown to be responsible for the three layer structure of the tr

the production of north atlantic deep water sources rates and pathways updating an earlier account by dickson et al 1990 this paper reviews the initial development phase of north atlantic deep water nadw production from the points where the dense inflows from nordic seas cross the greenland scotland ridge to the point off south greenland where the buildup of new production appears almost complete in particular three long term current meter arrays totaling 91 instruments and set at 160 km intervals south from the denmark strait sill are used to validate earlier short term arrays by others and in combination with these earlier arrays to describe the downstream evolution of mean speed depth and entrainment the variability of the overflow current in space and time and the likely contribution of the other three main constituents of nadw production at densities greater than 27 8 from the points of overflow 5 6 sv the transport within this range increases by entrainment and confluence with other contributory streams to around 13 3 sv at cape farewell while recirculating elements prevent us from determining the net southgoing transport a nadw transport of this order appears consistent with recent estimates of net abyssal flow passing south through the north and south atlantic

hydraulics and mixing in a laterally divergent channel of a highly stratified estuary author posting american geophysical union 2017 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in journal of geophysical research oceans 122 2017 4743 4760 doi 10 1002 2016jc012455

dynamic weakening of serpentinite gouges and bare surfaces at seismic slip rates to investigate differences in the frictional behavior between initially bare rock surfaces of serpentinite and powdered serpentinite gouge at subseismic to seismic slip rates we conducted single velocity step and multiple velocity step friction experiments on an antigorite rich and lizardite rich serpentinite at slip rates v from 0 003 m s to 6 5 m s sliding displacements up to 1 6 m and normal stresses n up to 22 mpa for gouge and 97 mpa for bare surfaces nominal steady state friction values nss in gouge at v 1 m s are larger than in bare surfaces for all n tested and demonstrate a strong n dependence nss decreased from 0 51 at 4 0 mpa to 0 39 at 22 4 mpa conversely nss values for bare surfaces remained 0 1 with increasing n and v additionally the velocity at the onset of frictional weakening and the amount of slip prior to weakening were orders of magnitude larger in gouge than in bare surfaces extrapolation of the normal stress dependence for nss suggests that the behavior of antigorite gouge approaches that of bare surfaces at n 60 mpa x ray diffraction revealed dehydration reaction products in samples that frictionally weakened microstructural analysis revealed highly localized slip zones with melt like textures in some cases gouge experiments and in all bare surfaces experiments for v 1 m s one dimensional thermal modeling indicates that flash heating causes frictional weakening in both bare surfaces and gouge friction values for gouge decrease at higher velocities and after longer displacements than bare surfaces because strain is more distributed