a seiche hazard study for lake union seattle washington abstract large seismic waves can be a result of earthquakes on local regional or distant fault zones occasionally setting bodies of water into oscillation seismic seiching is a recurrent phenomenon in the state of washington and elsewhere e g berninghausen 1969 barberopoulou et al 2004 cassidy et al 2005 barberopoulou et al 2006 to investigate and characterize wave motion in lakes during strong ground shaking various scenarios of seiche generation are considered for lake union in seattle washington as subjected to a variety of ground motions both relatively simple harmonic and more complex earthquake excitation synthetic and real data are used in the modeling to isolate any effects resulting from a predominantly east west or north south motion or the contribution from parts of the shoreline ground motions are first separated into their horizontal components motions along latitude or longitude before they are combined this approach shows that long linear shorelines are the largest contributors to water wave heights depending on the shape of the lake enhanced wave heights can also be a result of focusing the wave motion in the lake is found to be predominantly east west even when the ground motions are in the north south direction the results of this study suggest that coastal structures can be vulnerable due to resonant excitation initiated from earthquakes on water bodies far from tsunamigenic sources

shallow water numerical models for the 1947 gisborne and 2011 tohoku oki tsunamis with kinematic seismic generation abstract traditionally the initialization of seismically generated tsunamis is done by setting the initial free surface deformation as identical to the final deformation of the sea floor however numerous effects are neglected through this method in particular the dynamics of the sea floor deformation here two temporal parameters characterizing the sea floor deformation are defined the rise time tr vertical motion and the rupture velocity vp horizontal motion these parameters have already been theoretically introduced by hammack 1973 and todorovska and trifunac 2001 respectively for a simplified and schematic motion of the sea floor using simultaneously both parameters a theoretical linear analysis developed in le gal et al 2017 showed a resonance phenomenon for which the amplitude of the generated wave becomes significantly larger than the amplitude of the sea floor deformation this phenomenon concerns deformation with small rise times and rupture velocities close to the linear long wave velocity g h the aim of the present study is to investigate the influence of a kinematic deformation using both parameters during historical tsunamis with numerical nonlinear shallow water simulations this work corroborates le gal et al s theoretical schematic analysis for this purpose two events are studied the march 1947 new zealand and the 2011 japan tsunamis

formation and spreading of red sea outflow water in the red sea hydrographic data chlorofluorocarbon 12 cfc 12 and sulfur hexafluoride sf6 measurements collected in march 2010 and september october 2011 in the red sea as well as an idealized numerical experiment are used to study the formation and spreading of red sea outflow water rsow in the red sea analysis of inert tracers potential vorticity distributions and model results confirm that rsow is formed through mixed layer deepening caused by sea surface buoyancy loss in winter in the northern red sea and reveal more details on rsow spreading rates pathways and vertical structure the southward spreading of rsow after its formation is identified as a layer with minimum potential vorticity and maximum cfc 12 and sf6 ventilation ages of seawater within the rsow layer calculated from the partial pressure of sf6 psf6 range from 2 years in the northern red sea to 15 years at 17 n the distribution of the tracer ages is in agreement with the model circulation field which shows a rapid transport of rsow from its formation region to the southern red sea where there are longer circulation pathways and hence longer residence time due to basin wide eddies the mean residence time of rsow within the red sea estimated from the psf6 age is 4 7 years this time scale is very close to the mean transit time 4 8 years for particles from the rsow formation region to reach the exit at the strait of bab el mandeb in the numerical experiment

origin of fine scale wind stress curl structures in the benguela and canary upwelling systems numerous studies have shown the primary importance of wind stress curl in coastal upwelling dynamics the main goal of this new analysis is to describe the quikscat surface wind stress curl at various scales in the benguela and canary upwelling systems the dominant spatial pattern is characterized by cyclonic curl near continental boundaries and anticyclonic curl offshore in association with equatorward alongshore upwelling favorable wind stress at a smaller scale we demonstrate the sensitivity of the quikscat wind stress curl to coastal processes related to sea surface temperature sst mesoscale fluctuations by presenting a linear relationship between the curl and crosswind sst gradients despite the spatial and temporal sensitivity of the underlying thermal coupling coefficient a local analysis of the fraction of the curl ascribed to sst variability shows that sst is a main driver of the wind stress curl variability and magnitude over the upwelling extension zone 100 300 km from the coast in both the canary and benguela systems closer to the shore the curl patterns derived from quikscat observations are only loosely related to sst wind interactions as a working hypothesis they can also be associated with the coastline geometry and orographic effects that are likely to play an important role in local cooling processes

enhanced turbulence and energy dissipation at ocean fronts the ocean surface boundary layer mediates air sea exchange in the classical paradigm and in current climate models its turbulence is driven by atmospheric forcing observations at a 1 kilometer wide front within the kuroshio current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude suggesting that the front rather than the atmospheric forcing supplied the energy for the turbulence the data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence the resulting boundary layer is stratified in contrast to the classically well mixed layer these effects will be strongest at the intense fronts found in the kuroshio current the gulf stream and the antarctic circumpolar current all of which are key players in the climate system

effects of rupture complexity on local tsunami inundation implications for probabilistic tsunami hazard assessment by example we investigated the influence of earthquake source complexity on the extent of inundation caused by the resulting tsunami we simulated 100 scenarios with collocated sources of variable slip on the hikurangi subduction interface in the vicinity of hawke s bay and poverty bay in new zealand and investigated the tsunami effects on the cities of napier and gisborne rupture complexity was found to have a first order effect on flow depth and inundation extent for local tsunami sources the position of individual asperities in the slip distribution on the rupture interface control to some extent how severe inundation will be however predicting inundation extent in detail from investigating the distribution of slip on the rupture interface proves difficult assuming uniform slip on the rupture interface in tsunami models can underestimate the potential impact and extent of inundation for example simulation of an mw 8 7 to mw 8 8 earthquake with uniform slip reproduced the area that could potentially be inundated by equivalent nonuniform slip events of mw 8 4 deaggregation to establish the contribution of different sources with different slip distributions to the probabilistic hazard cannot be performed based on magnitude considerations alone we propose two predictors for inundation severity based on the offshore tsunami wavefield using the linear wave equations in an attempt to keep costly simulations of full inundation to a minimum

on the role of the mesoscale circulation on an idealized coastal upwelling ecosystem 1 an idealized circulation model of coastal upwelling coupled to an ecosystem model has been built to address the impact of features such as eddies and filaments emerging from mesoscale dynamics on a marine ecosystem the model mimics coastal upwelling along an infinite straight coast with north south cyclic boundary conditions thanks to the parametrization of the geostrophic onshore flow in the thermocline the circulation captures the typical characteristics of a coastal upwelling region an equatorward coastal jet a poleward undercurrent along the continental slope and mesoscale eddies and filaments this eddying three dimensional simulation is compared to a two dimensional simulation using the averaged velocity field of the first simulation as velocity field this approach allows us to compare simulations having similar upwelling and nutrient input but differing in the nature of the flow an offshore spreading of the phytoplankton bloom is found in the eddying simulation the width of the productive coastal band is increased from 80 km to 200 km by the mesoscale activity a biogeochemical budget carried out in a 300 km wide coastal band provides evidence that mesoscale activity decreases the total phytoplankton content mainly by exporting a significant part of the surface phytoplankton below the euphotic layer in presence of mesoscale activity the downward and offshore export of phytoplankton zooplankton and detritus significantly contributes to total export of organic matter out of the surface coastal ocean whereas their contribution to export is weak in the two dimensional case

the summer circulation in the gulf of suez and its influence in the red sea thermohaline circulation abstractthe gulf of suez is accepted as an important location for red sea deep water formation but the circulation and exchange with the red sea around the year remains elusive a summer cruise in the area gives the opportunity to investigate features of the summertime hydrological structure and exchange with the red sea an inverse estuarine circulation and exchange with the red sea is evident the topographic patterns of the gulf play an important role in the circulation two sills one in midbasin and a second at the mouth of the gulf inhibit the bottom flow topographically trapping waters that were formed in the cold season although the water mass characteristics of the outflowing waters during the other seasons are not directly related to the deep waters they can influence the water column structure of the northern red sea a simple box model shows that their contribution can have a significant influence in the formation of the intermediate layer a hypersaline 40 6 psu but relatively warm 23

impact of a coastal trapped wave on the near coastal circulation of the peru upwelling system from glider data alongshore velocity data from a glider repetitive section off the coast of peru 14 s are used to study the cross shore structure and temporal variability of the peru current system during a 5 week period in april may 2010 besides providing substantial information on the surface frontal jet associated with the peru coastal current and the surfacing peru chile undercurrent that flows poleward trapped on the continental shelf and slope the glider data reveal the presence of an intense deep equatorward current which transports up to 2 5 sv the dynamics of this current are investigated using an eddy resolving regional model the variability of the vertically sheared alongshore flow is shown to be related to the passage of a poleward propagating coastal trapped wave likely of equatorial origin solutions from a two dimensional linear coastal wave model suggest that the alongshore current observed vertical structure is associated with the second and third baroclinic modes of the coastal trapped wave

renewal of deep water in the red sea during 1982 1987 between october 1982 and may 1983 the deep water in the northern red sea was ventilated through slope convection the deep water became cooler fresher and more oxygenated dense bottom water formed in the gulf of suez during winter cooling sank down the continental slope thereby entraining near surface and intermediate depth waters from the application of a one dimensional plume model a vertical transport of 0 58 106 m3 s 1 over a period of 7 months was estimated long term time series of atmospheric heat fluxes show that such a major convection event can occur every 4 7 years the corresponding renewal time of the red sea deep water is thus of the order of 40 90 years in agreement with previous estimates

seiche effects in lake tekapo new zealand in an mw8 2 alpine fault earthquake this study investigates the potential for seismic seiches in lake tekapo new zealand triggered by ground shaking from an mw8 2 alpine fault earthquake synthetic ground motions are used as a forcing boundary to drive lake water motions by further developing a tsunami simulation model comcot and coupling it with earthquake simulation model outputs our modelling results reveal that lake water oscillations are mobilised immediately by the ground movement and further amplified by cross lake seiches amplitudes of lake oscillations can reach up to 4 0 m in the lake s narrow southern arm over 1 0 m along the shore of lake tekapo township and about 1 5 2 5 m along many other parts of the lake shore large amplitude water oscillations quickly attenuate in the first 5 10 min after the earthquake due to their relatively short periods while long period oscillations continue for a long time albeit with much smaller amplitudes spectral analysis clearly reveals that the ground motions trigger both fundamental and higher modes in the lake whose oscillation periods are consistent with theoretical estimates we find that large amplitude lake water oscillations are better correlated with low frequency less energetic ground motion content than with high frequency large amplitude ground motions ground motion triggered lake oscillations are large enough to pose potential threat to tourists residents boats and infrastructure both in the lake water and onshore near the waterfront in contrast vertical co seismic displacements in the lake area the conventional mechanism for tsunami generation are too small to trigger tsunami waves of concern

satellite altimetry data reveal jet like dynamics of the humboldt current 1 satellite derived mean sea level anomalies were blended with mean dynamic topography to obtain seasonal climatologies of the eastern south pacific ocean s surface circulation with an emphasis on the humboldt current the humboldt current is confined to a narrow northward flowing jet like stream of about 350 km associated with maximum geostrophic velocities of more than 15 cm s 1 from 35 to 23 s the current streams closer to the coast in the south within 500 km but is found 500 km offshore in its northern section a bifurcation takes place at 23 s with a more coastal branch heading toward the coast of southern peru 15 s and an oceanic branch continuing in a north northwesterly direction the humboldt current intensifies by 3 cm s 1 in austral summer as compared to winter in contrast the humboldt current s coastal branch is stronger in austral winter by the same order of magnitude we attribute these distinct seasonal flow fields to the meridional movement of the south pacific anticyclone which includes a seasonal relocation of a strong wind stress curl nucleus from offshore central southern austral summer to central northern chile austral winter thus driving the humboldt current by means of seasonal sverdrup dynamics the geostrophic flow field in the eastern south pacific communicates colder and fresher sub antarctic surface water toward the tropics along the eastern rim of the subtropical gyre

modes of subsurface intermediate and deep water renewal in the red sea a linear box model of the red sea is presented the model which inverts hydrographic and 3he data for the main features of the width integrated circulation is able to describe a large part of the seasonal and annual mean circulation by combining and reconciling major elements of current theories of the red sea circulation available flow measurements and tracer data the model provides a unified conceptual framework for the understanding of the circulation of the red sea the model forms deep water in the extreme north in two modes as first suggested by cember 1988 the convective mode renews the bottom water at an annual mean rate of 0 04 sv in the winter the isopycnal mode water renews the uppermost part of the deep water mass it flows to the south along the bottom of the pycnocline at an annual mean rate of 0 02 0 04 sv a new feature in the model s near surface circulation scheme is the ventilation of the thermocline in the winter at a mean rate of 0 04 sv also from the extreme north there is also a middepth return flow to the north at an annual mean rate of 0 07 sv this flow has been suggested but never rigorously quantified before

wind forced modeling studies of currents meanders and eddies in the california current system this process oriented study of the california current system ccs uses a high resolution multilevel primitive equation ocean model on a plane to isolate the response of that eastern boundary oceanic regime to temporal and spatially varying wind forcing to study the generation evolution and maintenance of many of the observed features such as currents meanders and eddies in the ccs the model is forced from rest with seasonal climatological winds in response to the prevailing wind direction surface equatorward currents develop along with upwelling of cooler water along the coast and a poleward undercurrent baroclinic barotropic instabilities in the equatorward surface current and poleward undercurrent result in the generation of meanders near the coast as the meanders intensify cold upwelling filaments develop along the coast and subsequently extend farther offshore in time the meanders form both cyclonic and anticyclonic eddies which subsequently propagate farther offshore longer simulation times 3 4 years in which a quasi equilibrium state for the ccs is reached show a seasonal cycle in response to the wind forcing for the coastal currents upwelling and filaments the meanders and eddies however can be quasi permanent as well as seasonal features the quasi permanent features play a significant role in modifying coastal currents upwelling and filaments which leads to large temporal and spatial variability in the ccs in a sensitivity study the results from several numerical experiments are used to examine the dependence of the generation of the currents meanders and eddies on the type of coriolis parameterization wind forcing and coastline geometry both the meridional variability of plane and the alongshore component of the wind stress are shown to be key ingredients for generating realistic vertical and horizontal structures for the cores of the surface equatorward and the subsurface poleward currents with such structures the currents are baroclinically and barotropically unstable resulting in the generation of meanders filaments and eddies irregularities in the coastline geometry are shown to be important for anchoring upwelling and filaments as well as for enhancing the growth of meanders and eddies cyclonic eddies tend to form in the vicinity of capes while anticyclonic eddies tend to form in the coastal indentations between capes the region off cape blanco is identified as the location where the coastal equatorward flow off oregon leaves the coast to develop a meandering jet off california the results from these experiments support the hypothesis that wind forcing and coastline irregularities on a beta plane are important mechanisms for the generation of many of the observed features of the ccs

the low level jet off the west coast of subtropical south america structure and variability abstract the subtropical anticyclone over the southeast pacific drives low level southerly flow along the west coast of south america in turn the alongshore flow induces coastal upwelling that supports a wealth of fishery resources within this region satellite data marine reports and coastal observations indicate the existence of a southerly coastal jet i e a maximum of wind speed off central chile 26 36 s the mean features and variability of this southerly jet is documented in this work using 4 yr of satellite derived sea surface winds complemented by satellite derived cloud amount fields and atmospheric reanalysis furthermore analysis of in situ data and model results of a well defined jet event during october 2000 allows a preliminary description of the jet s three dimensional structure and a comparison with the northerly jet off the coast of california southerly jet events off central chile occur year round but they are more frequent during spring summer over 60 of the time the

tracer signals of the intermediate layer of the arabian sea in 1995 hydrographic and chlorofluorocarbon cfcs components f11 f12 measurements were carried out in the gulf of aden in the gulf of oman and in the arabian sea in the gulf of oman the f12 concentrations in the persian gulf outflow pgw at about 300m depth were significantly higher than in ambient surface water with saturations reaching 270 these high values could not be caused by air sea gas exchange the outflow was probably contaminated with oil and the lipophilic character of the cfcs could then lead to the observed supersaturations the intermediate f12 maximum decreased rapidly further east and south at the strait of bab el mandeb in the gulf of aden the red sea outflow rsw was saturated with f12 to about 65 at 400m depth and decreased to 50 while descending to 800m depth the low saturation is not surprising because the outflow contains deep and intermediate water masses from the red sea which were isolated from the surface for some time the tracer contributions to the arabian sea for indian central water icw and pgw are about equal while below 500m depth the rsw contribution greatly exceeds icw modeling the cfc budget of the arabian sea the inflow of icw north of 12 degrees n is estimated to be 1 6 sv depending mainly on the strength of the flow of red sea water into the arabian sea

on the sources formation and circulation of red sea deep water red sea deep water is renewed from sources in the far north of the red sea upwelling of deep water throughout the basin maintains the sharp pycnocline with its base near the depth of the sill at bab el mandeb before now deep water renewal was thought to occur mainly by means of convective deep water formation in the north which renews the bottom water and gives rise to a southward flowing bottom current carbon 14 and 3he data from the geosecs indian ocean expedition lead to the identification of an additional volumetrically larger mode of northern deep water formation in which new deep water is injected immediately beneath the pycnocline this mode of deep water formation to be called the isopycnal mode also gives rise to a southward flowing current in this case at the top of the deep water mass geosecs data also demonstrate the existence at intermediate depths in the deep water of a return flow to the north the surface history in the nuclear era of the 14c in the deep water source region was reconstructed by direct radiocarbon measurements on annual growth bands of corals calculation then shows that new deep water forms in the convective mode at a rate of 0 05 0 01 sverdrup sv expressed as if the flow were continuous and is due principally to processes occurring in the mouth of the gulf of suez the injection beneath the pycnocline of new deep water formed in the isopycnal mode is 0 11 0 02 sv this new deep water appears to originate mainly in the extreme open northern red sea the gulf of aqaba makes a modest but significant contribution to both modes the total deep water renewal rate is about 0 16 sv yielding a bulk deep water residence time of about 36 years oxygen consumption in the deep water shows approximately exponential decrease of consumption rate with depth as expected on geological and geophysical grounds hydrographically significant fluxes of heat and salt from the sea floor into the red sea deep water are discernible in the hydrography helium 3 flux from the sea floor into the deep water is about 69 1 stp year

the tattered curtain hypothesis revised coastal jets limit cross shelf larval transport exchange and retention of coastal waters modulate dispersal of marine larvae affecting marine ecosystem dynamics a hypothesis was put forward in the 1980s describing the coastal upwelling front as a tattered curtain that retains larvae this front was envisioned to be broken up by squirts and eddies hitting the coast under upwelling relaxation events here we revise this hypothesis by using an idealized ocean model of an eastern boundary upwelling current and an idealized particle larvae model appropriate for shelf spawning benthic species modeled larval settlement patterns were controlled by retention in the core of the upwelling jet bounded by regions of high velocity shear on the flanks of the jet squirts filaments poleward moving eddies and meanders modulated settlement patterns locally while dense packets moved equatorward within the upwelling jet correlation between settlement i e particles 20 40 d old 10 km from shore and wind was low for a lagged wind product r 0 33 and moderate for a 20 d integrated wind product r 0 62 we determined that it is not upwelling relaxation but sustained moderate upwelling that can result in a highly retentive jet that entrains larvae and acts as a barrier to cross shelf transport however the amount of retention is highly variable settlement was low after strong persistent upwelling completely tattered the jet jet cores in general should act as important retentive transport barriers across diverse coastal systems a view supported by dynamical theory modeling studies and larval recruitment observations

a spatial random field model to characterize complexity in earthquake slip 1 finite fault source inversions reveal the spatial complexity of earthquake slip over the fault plane we develop a stochastic characterization of earthquake slip complexity based on published finite source rupture models in which we model the distribution of slip as a spatial random field the model most consistent with the data follows a von karman autocorrelation function acf for which the correlation lengths a increase with source dimension for earthquakes with large fault aspect ratios we observe substantial differences of the correlation length in the along strike a x and downdip a z directions increasing correlation length with increasing magnitude can be understood using concepts of dynamic rupture propagation the power spectrum of the slip distribution can also be well described with a power law decay i e a fractal distribution in which the fractal dimension d remains scale invariant with a median value d 2 29 0 23 while the comer wave number k c which is inversely proportional to source size decreases with earthquake magnitude accounting for larger slip patches for large magnitude events our stochastic slip model can be used to generate realizations of scenario earthquakes for near source ground motion simulations

interannual variability of the subsurface eddy field in the southeast pacific the southeast pacific which encompasses the coasts of peru and chile is one of the world s most productive regions resulting principally from the upwelling of subsurface nutrient rich waters over the satellite altimetry era there have been numerous evidence that surface mesoscale eddies play an important role in the offshore transport of rich coastal waters but it has been only recently that few observational numerical studies have highlighted the importance of the subsurface eddies the eddy field variability is explored using the results of a high resolution model experiment from 1979 to 2012 the model results indicate an asymmetry of the surface and subsurface eddy fields while surface intensified cyclones are slightly more frequent than anticyclones the subsurface field is dominated by anticyclones intrathermoclineeddies ites triggered by the instability of the subsurface peru chile undercurrent pcuc composite maps are consistent with in situ observations ites are associated with maximum vorticity around 150 200 m depth warmer and more saline core characteristic of the equatorial subsurface water from the pcuc we find that the variability of the ites is significantly correlated with the enso equatorial signal during strong el nino events e g 1982 1998 we find that while the pcuc transport increases the volume of coastal waters transported by ites however decreases during those periods we find that the relaxation of the isopycnals along the coast during el nino events leads to weakened baroclinic instability and to a decrease of the ites transport

seasonal dynamics of the near surface alongshore flow off central chile 1 the seasonal cycle of the near surface circulation off central chile was analyzed using satellite altimetry and an oceanic model to evaluate the role of the wind stress curl on the circulation we performed two identical simulations except for the wind forcing the control run used long term monthly mean wind stress and the no curl run used a similar wind stress field but without curl the observed and modeled control run surface currents showed a strong seasonal cycle and a well defined equatorward flow with a jet like structure this jet develops during spring and summer consistent with the presence of a low level wind jet south of punta lavapie cape 37 s the equatorward surface current remains close to the coast after the flow passes this cape however it separates to become an offshore jet in contrast in the no curl simulation the separation at punta lavapie is not observed and the offshore jet farther north is not present demonstrating the importance of the wind stress curl on the dynamics of this flow although the offshore integrated sverdrup transport was similar to the model transport the offshore jet was not located where the wind stress curl was maximum instead the position of the jet followed approximately the zero wind stress curl which corresponds to the climatological location of the low level wind jet axis these results illustrate the importance of the offshore upwelling downwelling associated with curl driven ekman pumping which tilts isopycnals upward downward toward the east west of the wind jet forcing a northward flow through thermal wind balance

sensitivity of red sea circulation to monsoonal variability during the holocene an integrated data and modeling study received 20 october 2009 revised 6 march 2010 accepted 30 june 2010 published 4 november 2010 1 we used an oceanic general circulation model to evaluate the sensitivity of the hydrography and circulation of the red sea in response to reduced sea level and modified atmospheric conditions during the holocene with holocene sea level close to the modern level the red sea was sensitive to changes in atmospheric conditions and it only shows a relatively mild response to sea level change changes in the monsoon system influence the exchange flow through the strait of bab el mandab the meridional overturning circulation of the red sea and its hydrography forced by humid conditions the modeled red sea temperature increased by 1 5 c while when arid conditions were imposed the temperature decreased by 2 5 c similar heating and cooling events during the early and late holocene are seen in a sea surface temperature record from the northern red sea derived from the temperature sensitive tex86 molecular biomarker which suggests that humid conditions prevailed during the early holocene and more arid conditions prevailed during the late holocene the gradual decline in red sea temperature between these two time periods suggests a gradual decline in the summer monsoon strength this monsoon trend and the resulting changes in the red sea circulation are supported by the distribution of crenarchaea fossil lipids in red sea sediments from this period monsoon driven changes in the exchange flow through the strait of bab el mandab affected the crenarchaea population structure and therefore their molecular fossil distribution in the sediments of the red sea potentially provides an index for the summer monsoon strength during the holocene

modes of covariability between sea surface temperature and wind stress intraseasonal anomalies along the coast of peru from satellite observations 2000 2008 1 the tropical rainfall measuring mission microwave imager sea surface temperature sst and quikscat wind stress satellite data are used to investigate the intraseasonal upwelling variability along the coat of peru over the period 2000 2008 two regions of peak variance correspond to the central peru region pisco region 15 s and the northern peru region piura region 5 s a covariance analysis reveals a significant coherency between winds and sst anomalies off pisco consistent with ekman pumping and transport dynamics the upwelling cell consists in a meridionally extended fringe of colder warmer water extending as far as 250 km from the coast at 15 s in the piura region the intraseasonal covariability pattern is represented by two modes one relevant to the direct ekman dynamics and the other one associated with the remote forcing of intraseasonal oceanic kelvin wave two regimes of variability are evidenced a low period regime 10 25 days is the signature of ekman transport pumping dynamics and is remotely forced by the migratory atmospheric disturbances across the southeastern pacific anticyclone a high period regime 35 60 day band is associated with the combined forcing of oceanic equatorial kelvin waves and migratory atmospheric disturbances in the midlatitudes in particular the modes of covariability exhibit a prominent 50 day period energy peak it is shown that this period arises from the impact of the first two baroclinic modes kelvin wave with the second baroclinic mode kelvin wave being more influential on the piura region

major earthquakes occur regularly on an isolated plate boundary fault the scarcity of long geological records of major earthquakes on different types of faults makes testing hypotheses of regular versus random or clustered earthquake recurrence behavior difficult we provide a fault proximal major earthquake record spanning 8000 years on the strike slip alpine fault in new zealand cyclic stratigraphy at hokuri creek suggests that the fault ruptured to the surface 24 times and event ages yield a 0 33 coefficient of variation in recurrence interval we associate this near regular earthquake recurrence with a geometrically simple strike slip fault with high slip rate accommodating a high proportion of plate boundary motion that works in isolation from other faults we propose that it is valid to apply time dependent earthquake recurrence models for seismic hazard estimation to similar faults worldwide

water masses in the humboldt current system properties distribution and the nitrate deficit as a chemical water mass tracer for equatorial subsurface water off chile abstract three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern south pacific and their distributions oceanographic data were taken from the scorpio may june 1967 piquero may june 1969 and krill june 1974 cruises vertical sections of temperature salinity dissolved oxygen nitrate nitrite phosphate and silicate were used to analyze the water column structure five water masses were identified in the zone through t s diagrams subantarctic water subtropical water equatorial subsurface water antarctic intermediate water and pacific deep water their proportions in the sea water mixture are calculated using the mixing triangle method vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m several characteristic oceanographic features in the study area were analyzed the shallow salinity minimum displacement towards the equator the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south and the equatorward intermediate antarctic salinity minimum associated with a dissolved oxygen maximum the nitrate deficit generated in the denitrification area off peru and northern chile is proposed as a conservative chemical tracer for the equatorial subsurface waters off the coast of chile south of 25 s

norwegian seiches from the giant 2011 tohoku earthquake 1 seismic waves of the giant 2011 tohoku earthquake triggered seiches in western norwegian fjords the seiching began a half hour after the earthquake origin time the oscillations were noted by eyewitnesses and recorded by surveillance and cell phone cameras the observations show maximum trough to peak amplitudes of 1 0 1 5 m and periods of 67 100 s the water waves were not triggered from the arrival of the surface waves the timing inferred for other seiches instead the seiching began during the passage of horizontal s waves we reproduced the s wave trigger by means of a shallow water wave model calibrated previously to norwegian tides and storm surges the simulations which used the observed earthquake motion as forcing show water waves with periods and amplitudes similar to those in the film clips however the strongest horizontal ground oscillations with shorter periods 20 30 s did not contribute much to the formation of the seiches

local amplification of seismic waves from the denali earthquake and damaging seiches in lake union seattle washington 1 the mw7 9 denali alaska earthquake of 3 november 2002 caused minor damage to at least 20 houseboats in seattle washington by initiating water waves in lake union these water waves were likely initiated during the large amplitude seismic surface waves from this earthquake maps of spectral amplification recorded during the denali earthquake on the pacific northwest seismic network pnsn strong motion instruments show substantially increased shear and surface wave amplitudes coincident with the seattle basin because lake union is situated on the seattle basin the size of the water waves may have been increased by local amplification of the seismic waves by the basin complete hazard assessments require understanding the causes of these water waves during future earthquakes

cyclonic entrainment of preconditioned shelf waters into a frontal eddy the volume transport of nutrient rich continental shelf water into a cyclonic frontal eddy entrainment was examined from satellite observations a slocum glider and numerical simulation outputs within the frontal eddy parcels of water with temperature salinity signatures of the continental shelf 18 19 c and 35 5 respectively were recorded the distribution of patches of shelf water observed within the eddy was consistent with the spiral pattern shown within the numerical simulations a numerical dye tracer experiment showed that the surface waters 50 m depth of the frontal eddy are almost entirely 95 shelf waters particle tracking experiments showed that water was drawn into the eddy from over 4 of latitude 30 34 5 s consistent with the glider observations the modeled particles entrained into the eddy sunk relative to their initial position particles released south of 33 s where the waters are cooler and denser sunk 34 m deeper than their release position distance to the shelf was a critical factor in determining the volume of shelf water entrained into the eddy entrainment reduced to 0 23 sv when the eddy was furthest from the shelf compared to 0 61 sv when the eddy was within 10 km of the shelf from a biological perspective quantifying the entrainment of shelf water into frontal eddies is important as it is thought to play a significant role in providing an offshore nursery habitat for coastally spawned larval fish

finescale vertical structure of the upwelling system off southern peru as observed from glider data abstractthe upwelling system off southern peru has been observed using an autonomous underwater vehicle a slocum glider during october november 2008 nine cross front sections have been carried out across an intense upwelling cell near 14 s during almost two months profiles of temperature salinity and fluorescence were collected at less than 1 km resolution between the surface and 200 m depth estimates of alongshore absolute geostrophic velocities were inferred from the density field and the glider drift between two surfacings in the frontal region salinity and biogeochemical fields displayed cross shore submesoscale filamentary structures throughout the mission those features presented a width of 10 20 km a vertical extent of 150 m and appeared to propagate toward the shore they were steeper than isopycnals and kept an aspect ratio close to f n the inverse of the prandtl ratio these filamentary structures may be interpreted mainly as a manifestation of submesoscale turbulence through sti

seasonal overturning circulation in the red sea 1 model validation and summer circulation the overturning circulation in the red sea exhibits a distinct seasonally reversing pattern and is studied using high resolution mit general circulation model simulations in the first part of this study the vertical and horizontal structure of the summer overturning circulation and its dynamical mechanisms are presented from the model results the seasonal water exchange in the strait of bab el mandeb is successfully simulated and the structures of the intruding subsurface gulf of aden intermediate water are in good agreement with summer observations in 2011 the model results suggest that the summer overturning circulation is driven by the combined effect of the shoaling of the thermocline in the gulf of aden resulting from remote winds in the arabian sea and an upward surface slope from the red sea to the gulf of aden set up by local surface winds in the red sea in addition during late summer two processes associated respectively with latitudinally differential heating and increased salinity in the southern red sea act together to cause the reversal of the contrast of the vertical density structure and the cessation of the summer overturning circulation dynamically the subsurface northward pressure gradient force is mainly balanced by vertical viscosity resulting from the vertical shear and boundary friction in the strait of bab el mandeb unlike some previous studies the three layer summer exchange flows in the strait of bab el mandeb do not appear to be hydraulically controlled

oceanographic observations in chilean coastal waters between valdivia and concepcion 1 the physical oceanography of the biologically productive coastal waters of central chile 36 to 40 s is relatively unknown in december 1998 we made a short exploratory cruise between valdivia 40 s and concepcion 37 8 s taking temperature salinity oxygen and current velocity profiles coincident sea surface temperature and color measurements were obtained by satellite the results showed an area dominated by wind induced coastal upwelling river runoff intrusion of offshore eddies mixing and heating upwelling centers were found over the shelf at three locations inshore of mocha island off valdivia and off lavapie point at these centers equatorial subsurface water essw intrudes into the coastal waters sometimes affecting the surface waters since essw has characteristically low oxygen and high salinity values it is easily detected off valdivia runoff imparts stratification while farther north solar heating and reduced mixing may facilitate stratification in some areas even strong winds would not destroy the stratification imparted by the advection of buoyancy that occurs during the upwelling process strong equatorward currents 1 m s 1 in the form of an upwelling jet were found off lavapie point this is also the location of an intruding anticyclone elsewhere currents were mainly northward but highly variable because of intrusions from offshore eddies the sea surface temperature and ocean color images show a complex field of onshore and offshore intrusions combined with the effects of mixing on chlorophyll concentrations the residence time of upwelled water on the shelf is estimated to be less than 1 week

amplification of seismic waves by the seattle basin washington state recordings of the 1999 m w 7 6 chi chi taiwan earthquake two local earthquakes and five blasts show seismic wave amplification over a large sedimentary basin in the u s pacific northwest for weak ground motions from the chi chi earthquake the seattle basin amplified 0 2 to 0 8 hz waves by factors of 8 to 16 relative to bedrock sites west of the basin the amplification and peak frequency change during the chi chi coda the initial s wave arrivals 0 30 sec had maximum amplifications of 12 at 0 5 0 8 hz whereas later arrivals 35 65 sec reached amplifications of 16 at 0 3 0 5 hz analysis of local events in the 1 0 to 10 0 hz frequency range show fourfold amplifications for 1 0 hz weak ground motion over the seattle basin amplifications decrease as frequencies increase above 1 0 hz with frequencies above 7 hz showing lower amplitudes over the basin than at bedrock sites modeling shows that resonance in low impedance deposits forming the upper 550 m of the basin beneath our profile could cause most of the observed amplification and the larger amplification at later arrival times suggests surface waves also play a substantial role these results emphasize the importance of shallow deposits in determining ground motions over large basins

near simultaneous great earthquakes at tongan megathrust and outer rise in september 2009 the tsunami that struck the samoan and northern tongan islands in september 2009 was preceded by a magnitude 8 earthquake on the outer slope of the oceanic trench where the pacific plate bends as it enters the subduction zone this was initially thought to be the sole source of the tsunami but a more complex picture is emerging two groups report the occurrence of two earthquakes a triggered doublet at nearly the same time and place what is not clear is which triggered the other beavan et al use an analysis of global positioning system station displacements and tsunami models to show that the outer rise earthquake was accompanied possibly triggered by a near simultaneous mega thrust earthquake in the adjacent tonga subduction zone lay et al analyse the available seismic data and their model suggests that the outer rise event triggered megathrust faulting either way this dual strike suggests a mechanism for the occasional large tsunamis generated at the tonga subduction zone on 29 september 2009 a tsunami devastated the samoan and northern tongan islands it is shown here that an unusual earthquake sequence preceded this tsunami a magnitude 8 earthquake in the outer rise intraplate region occurred almost simultaneously with rupture of the shallow subduction interplate interface equivalent to a magnitude 8 earthquake the findings provide information on strain release mechanisms at subduction zones and a possible mechanism for the occasional large tsunamis generated at the tonga subduction zone the earth s largest earthquakes and tsunamis are usually caused by thrust faulting earthquakes on the shallow part of the subduction interface between two tectonic plates where stored elastic energy due to convergence between the plates is rapidly released1 2 the tsunami that devastated the samoan and northern tongan islands on 29 september 2009 was preceded by a globally recorded magnitude 8 normal faulting earthquake in the outer rise region where the pacific plate bends before entering the subduction zone preliminary interpretation suggested that this earthquake was the source of the tsunami3 here we show that the outer rise earthquake was accompanied by a nearly simultaneous rupture of the shallow subduction interface equivalent to a magnitude 8 earthquake that also contributed significantly to the tsunami the subduction interface event was probably a slow earthquake with a rise time of several minutes that triggered the outer rise event several minutes later however we cannot rule out the possibility that the normal fault ruptured first and dynamically triggered the subduction interface event our evidence comes from displacements of global positioning system stations and modelling of tsunami waves recorded by ocean bottom pressure sensors with support from seismic data and tsunami field observations evidence of the subduction earthquake in global seismic data is largely hidden because of the earthquake s slow rise time or because its ground motion is disguised by that of the normal faulting event earthquake doublets where subduction interface events trigger large outer rise earthquakes have been recorded previously4 but this is the first well documented example where the two events occur so closely in time and the triggering event might be a slow earthquake as well as providing information on strain release mechanisms at subduction zones earthquakes such as this provide a possible mechanism for the occasional large tsunamis generated at the tonga subduction zone5 where slip between the plates is predominantly aseismic6

front eddy influence on water column properties phytoplankton community structure and cross shelf exchange of diatom taxa in the shelf slope area off concepcion 36 37 s in eastern boundary current systems ebcss submesoscale to mesocale variability contributes to cross shore exchanges of water properties nutrients and plankton data from a short term summer survey and satellite time series january february 2014 were used to characterize submesoscale variability in oceanographic conditions and phytoplankton distribution across the coastal upwelling and coastal transition zones north of punta lavapie and to explore cross shelf exchanges of diatom taxa a thermo haline front frn 1 flanked by a mesoscale anticyclonic intrathermocline eddy ite 1 or mode water eddy persisted during the study period and the survey was undertaken during a wind relaxation event at the survey time ite 1 contributed to an onshore intrusion of warm oceanic waters southern section and an offshore advection of cold coastal waters northern section with the latter forming a cold high chlorophyll a filament in situ phytoplankton and diatom biomasses were highest at the surface in frn 1 and at the subsurface in ite 1 whereas values in the coastal zone were lower and dominated by smaller cells diatom species typical of the coastal zone and species dominant in oceanic waters were both found in the frn 1 and ite 1 interaction area suggesting that this mixture was the result of both offshore and onshore advection overall front eddy interactions in ebcss could enhance cross shelf exchanges of coastal and oceanic plankton as well as sustain phytoplankton growth in the slope area through localized upward injections of nutrients in the frontal zone combined with ite induced advection and vertical nutrient inputs to the surface layer

long period effects of the denali earthquake on water bodies in the puget lowland observations and modeling analysis of strong motion instrument recordings in seattle washington resulting from the 2002 m w 7 9 denali alaska earthquake reveals that amplification in the 0 2 to 1 0 hz frequency band is largely governed by the shallow sediments both inside and outside the sedimentary basins beneath the puget lowland sites above the deep sedimentary strata show additional seismic wave amplification in the 0 04 to 0 2 hz frequency range surface waves generated by the m w 7 9 denali alaska earthquake of 3 november 2002 produced pronounced water waves across washington state the largest water waves coincided with the area of largest seismic wave amplification underlain by the seattle basin in the current work we present reports that show lakes union and washington both located on the seattle basin are susceptible to large water waves generated by large local earthquakes and teleseisms a simple model of a water body is adopted to explain the generation of waves in water basins this model provides reasonable estimates for the water wave amplitudes in swimming pools during the denali earthquake but appears to underestimate the waves observed in lake union

late quaternary slip rates and slip partitioning on the alpine fault new zealand abstract published geological data on late quaternary offsets on the alpine fault new zealand have been assembled into a common format and analysed with respect to uncertainties uncertainties arise mainly from measurement of offset features relating apparent offsets to actual fault slip and dating the offset features despite the considerable uncertainties the data form a coherent set consistent with a relatively constant rate of strike slip of 27 5 mm year between milford sound and hokitika this rate represents 70 75 of the fault parallel interplate motion north of the confluence with the hope fault the rate drops substantially dip slip rates on the other hand show considerable variation along strike rising to a maximum of more than 10 mm year in the central section and decreasing to zero at the southern end partitioning of c 25 of the interplate slip on to structures east of the alpine fault occurs in the central section consistent with predictions from critical wedge models the partitioning of all the fault normal component of displacement on to other structures in the south may be related in part to a doubling in width of the deforming wedge to the east most probably however the fault normal displacement is mainly accommodated by underthrusting of the australian plate offshore due to a change in the nature of the crust from continental to oceanic

mesoscale variability and nutrient phytoplankton distributions off central southern chile during the upwelling season the influence of mesoscale eddies abstract mesoscale features are recurrently found in the coastal transition zone ctz off central southern chile 35 40 s a region characterized by seasonal wind driven coastal upwelling in this study oceanographic data from two consecutive cruises carried out during the upwelling season january 2009 were combined with satellite time series data in order to characterize the structure and evolution of mesoscale eddies and to explore their influence on phytoplankton structure and nutrient distribution in the context of organic carbon exchanges between the coastal upwelling zone and the ctz two coastally generated contiguous mesoscale eddies 2 months old were characterized a surface cyclonic eddy cc1 and a subsurface anticyclonic eddy aa1 the distributions of salinity and dissolved oxygen together with nutrients suggested that both eddies were sites of vertical injection of high nutrient concentrations from the equatorial subsurface water mass essw into the upper layer in the ctz in addition eddy aa1 in combination with an upwelling plume was involved in the offshore advection of nutrients from the core of the essw located in the coastal zone at shallow depths

intrathermocline eddies in the coastal transition zone off central chile 31 41 s 1 the three dimensional structure and the origin of mesoscale anticyclonic intrathermocline eddies ites in the coastal transition zone ctz off central chile 31 41 s were analyzed through the combination of data from oceanographic cruises and satellite altimetry and the application of an eddy resolving primitive equation ocean model coupled with a numerical experiment using a passive tracer in this region ites are represented by subsurface lenses 100 km diameter 500 m thickness or vertical extension of nearly homogeneous salinity 34 5 and oxygen deficient 1 0 ml l 1 waters properties which are linked to the equatorial subsurface water mass essw transported poleward by the peru chile undercurrent pcuc in the coastal band at least five to seven ites were observed simultaneously in the area between 31 and 38 s during winter cruises in 1997 and 2009 satellite data indicated that the ites identified from in situ data moved westward each at a mean speed of 2 km d 1 and transported a total volume of 1 106 m3 s 1 1 sv the lifespan of each ite ranged from a few months to 1 year model results indicate that ites become detached from the pcuc under summer upwelling conditions in the coastal zone

importance of the gulf of aqaba for the formation of bottom water in the red sea received 30 march 2000 revised 8 may 2001 accepted 13 september 2001 published 16 august 2002 1 conductivity temperature depth tracer and direct current measurements collected in the northern red sea in february and march 1999 are used to study the formation of deep and bottom water in that region historical data showed that open ocean convection in the red sea can contribute to the renewal of intermediate or deep water but cannot ventilate the bottom water the observations in 1999 showed no evidence for open ocean convection in the red sea during the winter 1998 1999 the overflow water from the gulf of aqaba was found to be the densest water mass in the northern red sea an anomaly of the chlorofluorocarbon component cfc 12 observed in the gulf of aqaba and at the bottom of the red sea suggests a strong contribution of this water mass to the renewal of bottom water in the red sea the cfc data obtained during this cruise are the first available for this region because of the new signal it is possible for the first time to subdivide the deep water column into deep and bottom water in the northern red sea the available data set also shows that the outflow water from the gulf of suez is not dense enough to reach down to the bottom of the red sea but was found about 250 m above the bottom index terms 4875 oceanography biological and chemical trace elements 4283 oceanography general water masses 4243 oceanography general marginal and semienclosed seas 4271 oceanography general physical and chemical properties of seawater keywords gulf of aqaba red sea formation of bottom water tracer oceanography cfc overflow

seasonal variability of alongshore winds and sea surface temperature fronts in eastern boundary current systems seven years of satellite observations 2003 2009 are used to describe variability in sea surface temperature sst fronts and in the alongshore component of ocean winds and to investigate their relations in four eastern boundary current systems ebcs the general patterns of sst frontal activity are remarkably similar in all ebcs with high frontal probabilities along the coast decreasing with distance from the coastline results from empirical orthogonal function decompositions reveal that the seasonal evolution of sst fronts and wind stress are significantly correlated with intensified upwelling favorable winds associated with an increase in frontal probabilities an offshore migration of the region of high frontal activity is observed during the period of upwelling favorable alongshore wind stress in ebcs in all regions the seasonal variability of frontal activity and wind stress is stronger at mid than at low latitudes the width of the region of high frontal activity is relatively broader in the california and benguela current systems and narrower in the canary and humboldt current systems the width of the band of high frontal activity may be influenced by multiple factors including wind forcing flow topography interactions and mesoscale dynamics while seasonal variability in frontal activity in the california current system acts to reinforce or weaken the average pattern they are substantially different in the canary current system where there is little overlap in the areas characterized by persistent and seasonally varying front activity

seasonal overturning circulation in the red sea 2 winter circulation author posting 0american geophysical union 2014 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 119 2014 2263 2289 doi 10 1002 2013jc009331

red sea during the last glacial maximum implications for sea level reconstruction the red sea is connected to the indian ocean via a narrow and shallow strait and exhibits a high sensitivity to atmospheric changes and a reduced sea level we used an ocean general circulation model to investigate the hydrography and circulation in the red sea in response to reduced sea level and modified atmospheric conditions occurring during the last glacial maximum lgm the model salinity shows high sensitivity to sea level reduction together with a mild atmospheric impact sea level reduction affects the stratification and alters the circulation pattern at the strait of bab el mandab which experiences a transition from a submaximal flow to a maximal flow the best correlation to reconstructed conditions during lgm exists when the water depth of the hanish sill the shallowest part in the strait of bab el mandab is 33 10 75 m which would be affected by a sea level lowering of approximately 105 m our results support the reconstructed maximum salinity of around 57 practical salinity units because of a simple model that takes into account mixing processes along the strait and comparison of the surface salinity gradient to reconstructions based on isotopic records from sedimentary cores the salinity and 18o are sensitive to the mixing process at the strait and the sensitivity increases as the sea level is further reduced a local relative sea level reduction of approximately 105 m is also in close agreement with the inference of the lgm low stand of the sea at the location of the sill based on the ice 5g vm2 model

hikurangi margin tsunami earthquake generated by slow seismic rupture over a subducted seamount abstract tsunami earthquakes generate much larger tsunami than their surface wave magnitude would suggest and are a problem for tsunami warning systems they are often not accompanied by intense or even strong ground shaking and hence do not provide a natural warning for self evacuation the lesser known 1947 offshore poverty bay and tolaga bay earthquakes along the east coast of the north island new zealand share many characteristics with other well known tsunami earthquakes including low amplitude shaking long durations and anomalously large tsunami however these two new zealand events are rare in that their source area has been imaged directly by long offset 2d seismic reflection profiles in this contribution we propose a source model for the 1947 offshore poverty bay tsunami earthquake recognising that the hypocentre occurs in a region where seismic reflection and magnetic data support the existence of a shallow m 7 earthquakes with complex low velocity rupture scenarios that enhance tsunami waves and their role in seismic hazard should not be under estimated

seismic attenuation structure of the seattle basin washington state from explosive source refraction data we used waveform data from the 1999 ships seismic hazard inves tigation of puget sound seismic refraction experiment to constrain the attenuation structure of the seattle basin washington state we inverted the spectral amplitudes of compressional and shear wave arrivals for source spectra site responses and one and two dimensional q 1 models at frequencies between 1 and 40 hz for p waves and 1 and 10 hz for s waves we also obtained q 1 models from t values calculated from the spectral slopes of p waves between 10 and 40 hz one dimen sional inversions show that qp at the surface is 22 at 1 hz 130 at 5 hz and 390 at 20 hz the corresponding values at 18 km depth are 100 440 and 1900 qs at the surface is 16 and 160 at 1 hz and 8 hz respectively increasing to 80 and 500 at 18 km depth the t inversion yields a qp model that is consistent with the amplitude inversions at 20 and 30 hz the basin geometry is clearly resolved in thet inversion but the amplitude inversions only imaged the basin structure after removing anom alously high amplitude shots near seattle when these shots are removed we infer that q 1 values may be 30 higher in the center of the basin than the one dimensional models predict we infer that seismic attenuation in the seattle basin will significantly reduce ground motions at frequencies at and above 1 hz partially countering amplification effects within the basin

multivariate reconstruction of missing data in sea surface temperature chlorophyll and wind satellite fields 1 an empirical orthogonal function based technique called data interpolating empirical orthogonal functions dineof is used in a multivariate approach to reconstruct missing data sea surface temperature sst chlorophyll a concentration and quikscat winds are used to assess the benefit of a multivariate reconstruction in particular the combination of sst plus chlorophyll sst plus lagged sst plus chlorophyll and sst plus lagged winds have been studied to assess the quality of the reconstructions the reconstructed sst and winds have been compared to in situ data the combination of sst plus chlorophyll as well as sst plus lagged sst plus chlorophyll significantly improves the results obtained by the reconstruction of sst alone all the experiments correctly represent the sst and an upwelling downwelling event in the west florida shelf reproduced by the reconstructed data is studied

high resolution seismic reflection imaging of growth folding and shallow faults beneath the southern puget lowland washington state abstract marine seismic reflection data from southern puget sound washington were collected to investigate the nature of shallow structures associated with the tacoma fault zone and the olympia structure growth folding and probable holocene surface deformation were imaged within the tacoma fault zone beneath case and carr inlets shallow faults near potential field anomalies associated with the olympia structure were imaged beneath budd and eld inlets beneath case inlet the tacoma fault zone includes an 350 m wide section of south dipping strata forming the upper part of a fold kink band coincident with the southern edge of an uplifted shoreline terrace an 2 m change in the depth of the water bottom onlapping postglacial sediments and increasing stratal dips with increasing depth are consistent with late pleistocene to holocene postglacial growth folding above a blind fault geologic data across a topographic lineament on nearby land indicate recent uplift of late holocene age profiles acquired in carr inlet 10 km to the east of case inlet showed late pleistocene or holocene faulting at one location with 3 to 4 m of vertical displacement south side up north of this fault the data show several other disruptions and reflector terminations that could mark faults within the broad tacoma fault zone seismic reflection profiles across part of the olympia structure beneath southern puget sound show two apparent faults about 160 m apart having 1 to 2 m of displacement of subhorizontal bedding directly beneath one of these faults a dipping reflector that may mark the base of a glacial channel shows the opposite sense of throw suggesting strike slip motion deeper seismic reflection profiles show disrupted strata beneath these faults but little apparent vertical offset consistent with strike slip faulting these faults and folds indicate that the tacoma fault and olympia structure include active structures with probable postglacial motion

observations and modeling of a pulsating density current 1 we investigate density current formation and flow in the northern gulf of eilat red sea using in situ observations and a high resolution nonhydrostatic general circulation model these density currents occur in relatively warm water 20 c and are probably the warmest in the world ocean we demonstrate the intrinsic nonlinearity of density currents by comparing two high resolution simulations forced by different heat flux this nonlinearity which is poorly represented in global models is shown here to affect the properties of simulated density currents such a bias in simulating density currents in global models may lead to significant biases on the larger scale global ocean circulation and water mass distribution